Insights · HVAC Manufacturing — Electronics & PCB

PCB and Electronics Assembly HVAC Duct Guide — SMT, Reflow, Wave Solder, Coating, EMS Box-Build

A complete engineer-led Australian guide to HVAC ductwork for printed-circuit-board assembly, surface-mount technology, wave and selective solder, conformal coating booths, aqueous and solvent cleaning, AOI and X-ray inspection, BGA rework, cable assembly and EMS box-build to IPC-A-610 Class 3. Covers ESD-controlled environments to IEC 61340-5-1, NFPA 33 coating booths, NFPA 86 reflow enclosures, NFPA 660 combustible-dust collection from FR-4 routing, AS 1668.2 mechanical ventilation, AS 4254 duct construction, AS 1530.4 fire-rated penetrations and ISO 14644 cleanroom integration for medical and RF assembly. Written for the Australian electronics manufacturing market — Codan, DroneShield, BAE Systems Australia, Cochlear, ResMed, Mektronics, Resitech, Tritium and the wider EMS contract sector.

By · Published · 38 min read · Reviewed by SBKJ QA & Engineering

Why PCB and electronics assembly HVAC is its own discipline

Walk a modern surface-mount line in Australia — Codan at Mawson Lakes, DroneShield in Sydney, Mektronics at Box Hill (a short drive from our own engineering office), or any of the larger EMS contract houses — and the first thing you notice is the air. It is dry but not parched. It is cool but not cold. It is filtered but not sterile. It is balanced against the reflow oven exhaust, the wave solder fume hood, the conformal coating booth, the FR-4 routing dust collector, and the AOI inspection room all at once. Take any of those branches out of balance and you see the result on the next IPC-A-610 inspection report: a tombstoning event in Q3, a coating bubble where solvent flashed off too fast, a BGA solder ball void rate creeping up after a Friday afternoon humidity excursion.

PCB and electronics assembly HVAC is not general industrial ventilation with a few exhaust hoods added. It is a parallel set of process-critical air systems running simultaneously: an ESD-controlled comfort environment for the assembly hall, a high-temperature flux-laden exhaust system for the reflow and wave solder gallery, a flammable-vapour rated exhaust system for the coating booths, a combustible-dust deflagration-protected collection system for the depanel and routing area, a cleanroom-grade supply for any medical or RF subassembly, and a stress-chamber ventilation system for the final test bay. Every one of those systems answers to a different Australian or international standard and every one of them has to drop into the same building envelope without disturbing the others.

This guide is built for two readers. The first is the EMS plant manager or process engineer who is briefing a mechanical contractor for a new line, an expansion or a recommissioning. The second is the consulting mechanical engineer who is sizing the AHU, laying out the duct routes and selecting fume extraction equipment. The numbers, the standards and the construction methods here are the same ones we use when our duct-machinery customers — sheet-metal contractors who serve the Australian electronics manufacturing sector — ask us how to translate an IPC-A-610 acceptability target into a manufacturable duct package and an air balance that holds for the life of the plant.

The Australian electronics manufacturing landscape

Before we get to the duct, it pays to map the Australian electronics manufacturing landscape, because the HVAC requirements differ sharply between segments. Australia does not have a TSMC-class wafer fab and never will. What it does have is a tier of high-mix, low-to-medium-volume PCB assembly and box-build operations serving defence, medical, telecom, mining technology, energy storage and instrumentation. The HVAC requirements for these plants are not semiconductor-class — they are far more practical — but they are demanding enough that getting them wrong costs you yield, certification and operator health.

The defence and aerospace electronics segment in Australia is anchored by BAE Systems Australia at Edinburgh Parks SA (Nulka decoy electronics, JORN over-the-horizon radar processing, JSF F-35 mission-system assemblies), Thales Australia at Lithgow NSW and Garden Island NSW (combat-system and sensor electronics), Saab Australia at Mawson Lakes SA (combat management system processors), Lockheed Martin Australia in Melbourne, Northrop Grumman Australia, L3Harris Australia, Raytheon Australia in Adelaide, Leidos Australia, and the sovereign cyber-defence specialist Penten in Canberra. Codan (ASX:CDA, Mawson Lakes SA) and DroneShield (ASX:DRO, Sydney) sit alongside this group with substantial PCB and RF assembly capacity. Electro Optic Systems (ASX:EOS, Mt Stromlo ACT) and Quickstep (ASX:QHL, Bankstown NSW) round out the defence electronics segment. These plants run to IPC-A-610 Class 3 routinely and to MIL-STD where required. The HVAC implications are tight ESD control, low VOC residuals in the air path, traceable filter change-outs, and in some cases TEMPEST-class shielding that interacts with duct penetrations through screened rooms.

The medical electronics segment is dominated by Cochlear (ASX:COH, Macquarie Park NSW — implantable hearing electronics produced in an ISO Class 7 cleanroom), ResMed (ASX:RMD and NYSE:RMD, Bella Vista NSW — CPAP and ventilator PCB and box-build), Compumedics (ASX:CMP, Abbotsford VIC — sleep diagnostics electronics), Nanosonics (ASX:NAN, Macquarie Park — trophon medical electronics), Optiscan Imaging (ASX:OIL), Universal Biosensors (ASX:UBI, Rowville VIC), Imricor Medical (now operating from Tullamarine), and the medical technology arm of Telstra Health. These plants run to IPC-A-610 Class 3 and to ISO 13485 medical-device quality, with HVAC packages that include ISO 14644 Class 7 or Class 8 cleanroom integration, ASHRAE Standard 170 where the line sits inside an integrated medical device manufacturing envelope, and tight microbial control on supply air where the device is implantable.

The telecom, audio and networking segment includes Audinate (ASX:AD8, Sydney — Dante audio networking silicon and reference boards), Vocus Communications (telecom infrastructure electronics), and the Australian operations of the global telecom electronics manufacturers. The clean energy and EV segment includes Tritium (ASX:DCFC, Murarrie QLD — Veefil DC fast charger electronics) and Schneider Electric Australia (Macquarie Park and Mascot — power electronics and switchgear PCB). The contract EMS sector — the bread-and-butter of Australian PCB assembly volume — runs through Mektronics at Box Hill VIC (almost a neighbour to the SBKJ engineering office in Box Hill North), Electromold in Melbourne, ROCC Computers and Megatron Engineering in Sydney, Resitech Industries in Brisbane, the Australian EMS Group, and Sapio Group.

What this landscape tells you is that the Australian EMS plant is typically 1,500 to 8,000 square metres of factory floor, one or two SMT lines, a wave solder and a selective solder, one to four conformal coating booths, a PCB router and depanel area, an AOI and X-ray room, a battery and final-test area, and a box-build floor. The HVAC package that serves it has to do everything in this guide simultaneously, in a building envelope that was rarely purpose-built for electronics — most are former general manufacturing or warehouse shells. That constraint, more than anything else, drives the duct decisions that follow.

The eight-zone HVAC plan

Walk into a well-laid-out EMS plant and the HVAC zones tell you what each space does. The eight zones, with their characteristic conditions, are the foundation of every duct package we have specified in this sector:

  1. Incoming goods and stencil store — 22 plus or minus 3 degrees Celsius, 30-60 percent RH, 6 ACH. Holds reels of components on MSL (moisture sensitivity level) baking schedules, stencil-frame storage, and dry boxes for J-STD-033 floor life management. Pressure neutral or slightly positive against the loading dock.
  2. SMT line hall (ESD-controlled EPA) — 22 plus or minus 2 degrees Celsius, 45 plus or minus 5 percent RH, 8-15 ACH, plus 15 Pa positive against goods inwards and box-build floor. The core IEC 61340-5-1 ESD-protected area.
  3. Reflow and wave solder gallery — 24 plus or minus 3 degrees Celsius (the radiant load from the ovens raises ambient), 40-55 percent RH, exhaust-dominated with 600-1,800 m3/h per oven going out to a dedicated stack or fume filter.
  4. Conformal coating room (NFPA 33 Class I Division 2 or AS/NZS 60079 Zone 2) — 22 plus or minus 3 degrees Celsius, 45 plus or minus 10 percent RH, 12-20 ACH, 5 Pa negative against the SMT hall, with booth face velocity 0.5 m/s and stack discharge above the roofline.
  5. Aqueous and solvent cleaning bay — 22 plus or minus 3 degrees Celsius, vapour-exhaust dominated, with the solvent degreaser room classified per AS/NZS 60079 if a vapour zone exists.
  6. PCB depanel, routing and rework room — 22 plus or minus 3 degrees Celsius, dust-collection dominated, with a dedicated explosion-rated cartridge collector on FR-4 dust per AS 3957 and NFPA 660.
  7. AOI and X-ray inspection room — 22 plus or minus 1 degree Celsius (tighter than the main hall for camera thermal stability), 45 plus or minus 5 percent RH, ESD-controlled, with X-ray cabinet ozone vent to atmosphere.
  8. Box-build and final test floor — 22 plus or minus 3 degrees Celsius, 45 plus or minus 10 percent RH, 6-10 ACH, ESD-controlled where ESDS components are exposed during assembly, with environmental stress chamber heat rejection ducted to atmosphere.

Each zone has its own supply branch off the main AHU, its own return path, and where process exhaust applies, its own dedicated stack. The duct material follows the zone: galvanised steel everywhere except the medical EMS cleanroom branches (304 stainless), the solvent vapour degreaser return (316L for chloride resistance), and the FR-4 dust collection (bonded galvanised with continuous earthing). The cross-zone interlocks — pressure cascade, fire damper coordination, smoke control zoning — are where the integration work happens.

Australian standards that apply, and how they layer

The standards stack for an Australian PCB and electronics assembly plant is denser than most industrial categories. The HVAC engineer has to reconcile mechanical ventilation codes (AS 1668.2), ductwork construction codes (AS 4254), fire and smoke codes (AS 1530.4, AS 1668.1), electronics acceptability standards (IPC-A-610, IPC-A-600, IPC-2221), ESD control (IEC 61340-5-1, IPC-9203), cleanroom standards where they apply (ISO 14644), and a series of NFPA codes that the Australian industry treats as deemed-to-satisfy when no equivalent AS standard exists (NFPA 33 for coating booths, NFPA 86 for reflow ovens, NFPA 660 for combustible dust, NFPA 75 for IT equipment rooms, NFPA 855 for battery storage).

AS 1668.2 is the baseline. It sets the minimum mechanical ventilation rate for general working spaces and includes prescriptive provisions for industrial buildings, exhaust systems, kitchens, car parks, and similar. For an electronics assembly hall, the AS 1668.2 minimum is 10 L/s per person plus 0.35 L/s per square metre floor area — but on every real EMS project we have seen, the process exhaust budget plus 10-15 percent pressurisation allowance dominates, and AS 1668.2 becomes a fallback minimum rather than the design driver. AS 1668.2 Section 4 governs the routing and termination of contaminant exhaust stacks, including the minimum stack height above the roof and the offset from intake louvres.

AS 4254 sets the construction standard for the duct itself — sheet metal gauge, joint type, hanger spacing, sealant class, and leakage class. For an EMS plant we recommend Class C leakage as a minimum, which limits leak rate to 0.5 L/s per square metre of duct surface area at 250 Pa. Class C is the practical limit for transverse joints made on an automatic duct line (SBAL-V or SBAL-III), and it is well within reach for a competent shop running an SBSF stitchwelder or an SBFB lock-former on TDF flanges. For solvent and coating booth exhaust duct that runs hot and condensing, Class B (0.25 L/s per square metre) is achievable on welded longitudinal seams from an SBTF spiral tubeformer.

AS 1530.4 governs fire-rated penetrations and fire dampers. Where the duct crosses a fire-rated wall — typically the solvent storage room boundary, the battery storage boundary, the conformal coating booth boundary, and any zone separating the SMT hall from the dust collector enclosure — a fire damper or smoke damper rated to match the wall FRL must be installed. AS 1668.1 then governs smoke control where the building is required to have a smoke-management system (typical for plants over 3,000 square metres open floor area).

IPC-A-610 is the global acceptability standard for electronic assemblies. It defines Class 1 (general electronic products), Class 2 (dedicated service electronic products — most commercial and industrial), and Class 3 (high-performance electronic products — life-support, defence, aerospace, medical implantable). Class 3 imposes tighter limits on solder joint quality, cleanliness, conformal coating coverage, and through-hole barrel fill. The HVAC implications are real: Class 3 acceptance requires controlled humidity to prevent moisture-related defects, low VOC residuals to prevent coating adhesion failures, and reproducible reflow profiles that depend on stable ambient temperature in the gallery. Most Australian EMS work for defence and medical customers runs to Class 3.

IPC-A-600 is the parallel acceptability standard for bare PCBs (laminate, copper, solder mask, drill quality, plating). IPC-2221 is the generic PCB design standard, including environmental requirements for design margin. Both feed into the HVAC spec through MSL and J-STD-033 floor life management — components and PCBs absorb moisture from humid air and release it as steam during reflow, causing delamination, popcorning and BGA voids if not baked out properly.

IPC-9203 aligns with IEC 61340-5-1 on ESD protection. The two together define the Electrostatic Protected Area (EPA) — a continuous physical zone within which all surfaces, garments, tools and air conditions are controlled to keep ESD events below the susceptibility threshold of the components being handled. The most common Class 0 target is 100 V or less of human body model discharge. The HVAC contribution to ESD control is humidity — at 40 percent RH and above, surface conductivity on common materials is high enough that walking voltages and triboelectric charging fall below the Class 0 threshold; below 30 percent RH, even ionisation-augmented EPA flooring struggles to keep walking voltages within limits. This is why the SMT hall humidity band is specified as 45 plus or minus 5 percent — 40 percent at the lower bound is the ESD floor, 50 percent at the upper bound is the MSL ceiling, and the centre setpoint gives the controls a working band.

ISO 14644 applies where flexible-circuit assembly, RF and microwave PCB work, medical implantable electronics or high-reliability defence assembly is performed in a classified cleanroom. ISO 14644 Class 7 (10,000 particles at 0.5 micrometres per cubic foot legacy equivalent) is the common Australian medical EMS class — Cochlear and high-grade ResMed lines run here. ISO Class 8 is used for less critical assembly that still needs better particle control than a general factory floor. HEPA filter classes follow EN 1822 — H13 (99.95 percent at MPPS) for most ISO 7/8 work, H14 (99.995 percent) for tighter applications.

ASHRAE Standard 170 governs ventilation of healthcare facilities. It applies to PCB and electronics assembly lines only where the line sits inside an integrated medical device manufacturing facility that also contains patient-care or compounded-product space. In Australia, the relevant medical EMS operations are mostly assembled separately from clinical space, but where they share envelopes — some of the larger ResMed and Cochlear sites do — ASHRAE 170 governs the boundary.

ASHRAE Applications Handbook Chapter 18 (Clean Spaces) is the global engineering reference for cleanroom HVAC design, including PCB and electronics cleanrooms. We treat it as a primary design reference for any ISO 7 or ISO 8 line we specify in Australia, alongside the local AS 1668.2 requirements.

NFPA 75 covers information technology equipment rooms — relevant to EMS where the plant operates an on-site data centre or large server rack room for ERP, MES and production controls. The fire suppression integration (typically clean-agent FK-5-1-12 / Novec 1230, sometimes inert-gas) interacts with HVAC through dampered isolation of the IT room from general extract.

NFPA 86 covers ovens and furnaces — directly applicable to the SMT reflow oven and the through-hole convection oven if present. NFPA 86 mandates pre-purge cycles before light-off, excess-temperature trips, controlled-cooling provisions on shutdown, and ventilation rates that prevent flammable atmospheres inside the oven. The duct system from the oven exhaust to the stack is downstream of the oven enclosure and not directly governed by NFPA 86, but the interlock between oven exhaust fan VFD and oven controller is.

NFPA 33 covers spray application of flammable and combustible materials — directly applicable to every conformal coating booth, urethane potting booth and spray-cleaning station. NFPA 33 prescribes booth construction, ventilation rate, electrical area classification (Class I Division 2 in the booth and within 1 metre of the opening), interlocks between booth fan and spray gun trigger, and the requirement that exhaust duct discharge to atmosphere and not be reused. In Australia we cross-reference NFPA 33 with AS/NZS 60079 hazardous-area classification.

NFPA 660 (which absorbed NFPA 484, NFPA 654, NFPA 655, NFPA 664 and NFPA 61 into a consolidated combustible dust standard in 2024) governs FR-4 PCB routing and depanel dust. It mandates dust hazard analysis (DHA), determination of minimum explosive concentration (MEC), provision of deflagration vents or chemical isolation suppression on the dust collector, bonding and earthing of all duct, and isolation of the collector from the production space. In Australia we cross-reference with AS 3957 (electrical installations in coal handling, which is the closest current AS for combustible dust general practice).

NFPA 855 covers stationary energy storage systems — applicable to battery pack assembly, cell test chambers and large UPS battery installations. AS/NZS 5139 is the Australian parallel. Both require dedicated extract on the battery room, toxic-gas monitoring (CO, HF, HCN for lithium fires), and thermal runaway venting.

ESD-controlled assembly hall: holding 22 °C and 45 %RH year-round

The single biggest HVAC line item in any EMS plant is the SMT assembly hall, because it is where the largest air volume meets the tightest condition tolerance. The target — 22 plus or minus 2 degrees Celsius dry bulb, 45 plus or minus 5 percent relative humidity, year-round — sounds modest until you consider what year-round means in Melbourne, in Sydney, in Adelaide, in Brisbane, in Perth, in Darwin. Outdoor design conditions for these capitals range from a winter dry-bulb low of 2 degrees Celsius (Melbourne, Canberra) to a summer 1-percent dry-bulb of 38 degrees Celsius (Adelaide) and a summer wet-bulb extreme that reaches 28 degrees Celsius in Brisbane and Darwin. The makeup air has to be tempered from any of those conditions back to 22 degrees and 45 percent RH before it enters the SMT hall.

The mechanical design that delivers this typically uses a four-stage AHU: outside-air mixing box with motorised dampers, pre-filter (G4) and bag filter (F7 to F9), pre-heat coil (steam or hot water), cooling coil (chilled water at 6/12 degrees Celsius for sensible cooling, supplemented by a low-temperature loop at minus 5/0 degrees Celsius for deep dehumidification in summer), reheat coil (hot water or electric for humidity control independent of cooling), and a steam or evaporative humidifier for the dry-winter season. The hall is divided into two or three supply zones, each with its own VAV terminal and reheat, so that the upstream end of the line (paste printer, AOI before reflow) can be held tighter than the downstream end (post-reflow AOI, in-circuit test).

The return strategy in the SMT hall matters more than most general industrial designs. Ceiling return through high-side wall grilles is the default, with a few low-side returns for the heavier-than-air solvent residuals near the wave solder and the cleaning bay. Where the hall is part of an ISO 8 cleanroom for medical EMS, the return goes through floor-level wall grilles at the perimeter to maintain a top-down displacement flow that sweeps particles off the operator and away from the workpiece.

The supply duct itself is conventional galvanised steel to AS 4254, Class C leakage, with TDF flanges or transverse drive cleats on every 1.2 metre section. The SBKJ SBAL-V auto duct line produces this duct directly from 0.5 to 1.5 mm coil at up to 1500 mm coil width, finishing at 16 metres per minute. For most Australian EMS plants the duct work is 0.7 mm to 1.0 mm coil for trunks and 0.5 mm to 0.7 mm for branches and small fittings. A 5,000 square metre EMS plant typically takes 3,500 to 6,000 metres of supply, return and exhaust duct combined — work that one SBAL-V line completes in eight to twelve production days assuming single-shift operation.

For very large operations and tight programmes, the SBAL-III line gives 14 metres per minute output with a smaller power footprint (15.7 kW versus 87 kW on the V). For prototype shops and short-run EMS contractors, the SBAL-II at 18 metres per minute and 5.5 kW is the budget option that still delivers Class C duct on 0.5 to 1.2 mm coil.

Solder reflow oven exhaust: lead-free chemistry, flux condensation, NFPA 86

The reflow oven is the loudest single voice in the EMS plant HVAC conversation, because its exhaust carries the broadest mix of contaminants of any single process source. A nitrogen-flooded SAC305 (Sn96.5Ag3.0Cu0.5) reflow profile peaks at 245 to 260 degrees Celsius, soaks above 217 degrees (the SAC305 liquidus) for 45 to 75 seconds, and runs the board through 8 to 12 individual zones in a 4 to 6 metre tunnel. Every zone has its own exhaust port; manufacturers (Heller, BTU, Rehm, Vitronics-Soltec, ERSA) typically provide between three and six exhaust ports on a production-grade oven, sized for 250 to 400 cubic metres per hour each at 50 to 150 pascals negative static.

The contaminants in the exhaust are mostly flux pyrolysis products. Modern no-clean fluxes use ester carriers and rosin or rosin-modified resin systems with mild activators; their pyrolysis products are aldehydes, low-molecular-weight organic acids, and a condensable resin fraction that wants to plate out on cool duct surfaces. The classic legacy hazard — leaded solder fume, lead aerosol from SnPb 63/37 — is largely absent from current lead-free production, but the Safe Work Australia workplace exposure standards (WES) for the components still apply: solder rosin fume at 0.1 milligrams per cubic metre (acid mist of flux activator), lead at 0.05 mg/m3 for any remaining SnPb line (defence, some medical, some legacy industrial), formaldehyde at 1 ppm, and total VOC managed by EPA Victoria operating licence conditions on stack emissions where applicable.

The duct from each oven exhaust port to the building stack is 150 to 200 mm galvanised round, sloped at 1:50 minimum back to the oven so that condensed flux drains rather than collects at low points. At every 90-degree elbow we specify a clean-out drop pot with a removable end cap — typically 200 mm by 200 mm by 300 mm deep, with a drain plug at the bottom and a viewport. Flux condensate is sticky, conductive when warm, and resistive when cold; a missed drop pot becomes a charred deposit inside two months of production and a fire risk in twelve.

From the oven the duct runs to one of three terminations. The first is a roof-mounted flux-removal filter — the dominant suppliers in Australia are Plymovent (SCS-series), Purex (4000i and 6000i benchtop and roof-mount), and BOFA (AD-series and Universal series). These units use a multi-stage filter train: a metal mesh impactor for the heavy condensable fraction, a pleated F7-F9 main filter for the aerosol, and a chemisorption stage (typically activated carbon impregnated with caustic) for the acid gas residual. Filter change-out runs 30 to 90 days under heavy production. The unit either discharges to atmosphere through a small roof stack or recirculates to the assembly hall after the carbon stage if local air-quality permits allow.

The second termination is a direct roof discharge — the duct runs through a fire-damper-protected wall penetration, up a vertical riser, and out a roof stack with a weather cowl. Stack height is set by AS 1668.2 Section 4 — minimum 1.0 metre above any roofline within 8 metres, minimum 3.0 metres above any outdoor air intake within 8 metres horizontal. Stack discharge velocity should exceed 7.5 m/s to prevent downwash into adjacent air intakes.

The third termination, used on larger plants and where local permits require it, is a regenerative thermal oxidiser (RTO) or catalytic oxidiser that destroys the VOC and condensable fraction at 800 degrees Celsius before stack discharge. RTOs are common on lines processing 50,000 boards a week or more; smaller plants use filter packs because the RTO capital and operating cost is hard to justify.

The duct itself is galvanised steel — the temperature, even at the oven outlet, is below 200 degrees Celsius (the oven internal peak is 260, but the exhaust port dilutes with cooling air to about 120-180), well within the temperature rating of Z275 hot-dip galvanised coil. Stainless is sometimes used on the first 2-3 metres downstream of the oven if condensate corrosion is a concern (modern fluxes with chlorinated activators are aggressive), but most plants run galvanised for the full length and accept a periodic duct cleaning. SBKJ supplies both the galvanised SBAL-V duct line for the standard run and the SBTF spiral tubeformer with stainless option for the few metres of hot section where stainless is specified.

Wave solder pot extract and lead-free dross

Wave solder still has a place in Australian EMS even as more boards move to surface-mount-only construction, because through-hole connectors (D-sub, board-to-wire, high-current power terminals) remain in defence, automotive electronics and industrial controls. A modern wave solder machine — Pillarhouse, ERSA Powerflow, Vitronics-Soltec MR Series, Speedline Electrovert OmniMax — runs a SAC305 bath at 260 to 270 degrees Celsius with a no-clean foam flux or a water-soluble flux applied by spray or foam fluxer, a pre-heater section, the primary wave (or wave plus chip wave), and a finger conveyor.

The fume load on a wave solder is concentrated above the pot itself and above the fluxer. Pot exhaust is dominated by flux pyrolysis (similar to reflow but more concentrated because the pot temperature is higher and the residence time longer); fluxer exhaust adds the spray-flux carrier solvent if the flux is solvent-based (most no-clean fluxes today use isopropanol IPA as the carrier, with a Safe Work Australia WES of 400 ppm).

Standard practice is a sloped capture hood directly above the pot, sized for 0.4 m/s capture velocity at the pot lip, ducted to a 200 to 250 mm galvanised steel exhaust riser. The hood is angled forward 15-20 degrees to catch the natural thermal plume from the pot. A parallel local extract at 100 to 150 mm runs from the fluxer enclosure. Both ducts merge into a manifold either above the line or at roof level, then run to a wave-solder-rated fume filter (Plymovent MDB, Purex Alpha, BOFA AD2000) or to a direct roof discharge.

Dross is the third extract. Lead-free dross — predominantly tin oxide with traces of copper and silver from the SAC305 alloy — forms on the pot surface during normal operation and is skimmed mechanically or by automated dross paddle. The skimming operation lifts a cloud of fine oxide particles and unreacted flux residue. A low-volume local extract at 100 mm duct, 100-150 m3/h, at the dross collection pan keeps operator exposure below the lead WES (0.05 mg/m3) on any remaining SnPb operation and below the rosin WES (0.1 mg/m3) on lead-free.

Total wave solder fume budget on a typical Australian EMS line is 400 to 800 m3/h. For a plant with two wave solder machines and one selective solder, budget 1,500 to 2,500 m3/h of wave-segment exhaust before the conformal coating booths and the routing dust collector are added.

Selective solder machines (ERSA Versaflow, Pillarhouse Jade, Vitronics Soltec Cheetah) use a small wettable nozzle in place of the wave and selectively solder through-hole pins one at a time, with the rest of the board protected. Their fume load per machine is one-third to one-half of a full wave solder — typically 200 to 400 m3/h — captured at a localised hood directly above the nozzle and the flux drop point.

Conformal coating spray booths under NFPA 33 and AS/NZS 60079

Conformal coating is the protective layer applied over a finished PCB assembly to seal it against humidity, salt fog, dust, chemical attack and incidental electrical contact. The four main coating chemistries — acrylic (AR), polyurethane (UR), silicone (SR) and parylene (XY) — each carry their own application and ventilation requirements. AR and UR are solvent-based (typically xylene, toluene or proprietary aromatic-aliphatic blends), SR is moisture-cure or peroxide-cure with limited solvent, and XY is a vapour-deposited polymer applied in a vacuum chamber rather than a spray booth.

The spray-applied coatings (AR, UR and most SR) are regulated under NFPA 33 (Spray Application Using Flammable or Combustible Materials), with the Australian parallel in AS 4114 (spray booths) and AS/NZS 60079 hazardous-area classification. NFPA 33 mandates: a booth with a captured exhaust airflow that yields 0.5 m/s minimum face velocity at the operator opening; electrical equipment within the booth and within 1 metre of the opening rated for Class I Division 2 (or Zone 2 under IEC); interlock between booth exhaust fan and spray gun air supply so the gun cannot operate if the fan is off; non-combustible booth construction; and exhaust discharge to atmosphere without recirculation.

For a 1.5 m by 1.0 m booth opening, the minimum exhaust airflow is 2,700 m3/h. Most production booths run 3,000 to 5,000 m3/h to give margin and to ensure capture velocity at the workpiece (not just at the opening) exceeds the 0.4-0.6 m/s recommended in IPC-CC-830 for spray application. The exhaust duct is 304 stainless or unlined galvanised steel — stainless if the chemistry includes chlorinated activators, galvanised for most acrylic and urethane systems. The duct is sloped 1:100 back to a solvent-condensate drain pot at the building penetration.

The duct discharges to a roof stack via a fire damper at the wall penetration (AS 1530.4 FRL matching the wall rating, typically -/120/- for a coating booth boundary), and either directly to atmosphere or through a vapour abatement unit. For low-volume operations (one booth, 3,000 m3/h, modest VOC load) direct discharge is acceptable in most Australian jurisdictions subject to EPA licence conditions. For larger operations a UV-cure abatement, a thermal oxidiser, or an activated-carbon adsorber is used to bring stack VOC concentration below the licence limit (typically 50 mg/m3 total VOC for new operations under EPA Victoria, with site-specific tighter limits in residential-adjacent zones).

Parylene CVD coating is a different system. Parylene N, C, D and HT are vapour-phase polymers deposited at room temperature on the workpiece in a vacuum chamber. The HVAC requirement is not booth ventilation but rather process vacuum-pump exhaust — the dimer monomer that feeds the process is benign, but the vacuum pump oil can collect organic residuals and the pump exhaust needs to vent to atmosphere through a dedicated 50-100 mm line, not back into the room. Parylene equipment suppliers (Para Tech, SCS, Plasma Parylene Systems) provide their own pump exhaust manifold; the building HVAC contractor extends it to a roof discharge.

Operator-zone solvent vapour control inside the coating room follows NFPA 33's general ventilation requirement of at least 4 ACH outside the booth envelope. For the 80-160 square metre coating room typical of an Australian EMS plant, this is 1,200 to 2,400 m3/h of general extract on top of the booth exhausts. Pressure cascade keeps the coating room at 5 to 10 Pa negative against the SMT hall so that solvent vapour does not migrate back to the assembly line.

Underfill epoxy cure and adhesive cure exhausts

Underfill is the epoxy applied beneath BGA, CSP and flip-chip packages to redistribute thermal stress and prevent solder ball fatigue. The epoxy is dispensed at the edge of the package and capillary-wicks beneath, then cured in a benchtop or inline oven at 150-165 degrees Celsius for 30-60 minutes. The cure releases low concentrations of amine, aldehyde and phenolic curing agents into the air.

An underfill cure oven needs a 100 to 150 mm local exhaust ducted into the main reflow exhaust manifold or to a dedicated roof discharge, 100-200 m3/h. The exhaust is similar in chemistry to the reflow oven exhaust but lower in volume — most plants share a stack between the reflow and underfill exhausts after isolation by a backdraught damper to prevent cross-contamination during downtime.

The same approach applies to staking adhesive cure ovens, board-mount cure ovens for SMT adhesives, and any thermal cure step in the EMS flow. Each gets a local extract sized to its volume and chemistry, manifolded into the main solder-fume exhaust where possible.

Aqueous and solvent cleaning extract

Post-solder cleaning is required on any board that uses a no-clean flux residue removal pathway, a water-soluble flux, or has critical low-impedance regions where flux residue would degrade SIR (surface insulation resistance). The two main cleaning approaches in Australian EMS are aqueous spray-in-air machines (DI water plus a saponifier) and solvent vapour degreasers (modified alcohol or HFE-based, non-ozone-depleting).

An aqueous cleaner — Aqueous Technologies Trident, PBT Works Super Swash, Austin American Hydrojet — uses a heated DI water bath with 1-5 percent saponifier (alkaline detergent) at 60-70 degrees Celsius, sprayed through nozzle arrays at 0.5 to 2 megapascal pressure. The boards run through a wash section, a rinse section (more DI), and a drying section (hot air at 90-110 degrees Celsius). The HVAC implications are a 5,000 to 8,000 m3/h general capture hood at the inlet and outlet of the machine — water mist and a small fraction of saponifier carry into the room air. A mist eliminator is fitted before the duct enters the building service zone. The duct is 304 stainless or fibreglass-reinforced plastic (FRP) — the saponifier is mildly alkaline and the mist is corrosive to mild steel even with hot-dip galvanising.

A solvent vapour degreaser — Branson, Crest Ultrasonics, Baron-Blakeslee, Brulin — uses modified alcohol or HFE-7100 / HFE-7200 solvent (non-ozone-depleting, low global warming potential) in a Class III closed-loop machine. Class III refers to the EPA equipment classification for vapour degreasers with refrigerated freeboard, hoist controls, automated cycle and minimal solvent loss. The machine itself is a sealed loop with low ventilation makeup; what needs ventilation is the room around it, classified per AS/NZS 60079 if a vapour zone exists.

For a typical solvent degreaser room — 30 to 80 square metres, one machine, ancillary parts wash — the ventilation rate is 6 ACH general extract, with a low-level extract at 200 mm above floor level to capture vapour that is heavier than air. The extract duct on the low-level run is 316L stainless steel, because solvent residuals can attack zinc coatings over time and chlorinated decomposition products from accidental thermal decomposition (above 250 degrees Celsius) form HCl. The duct discharges to a roof stack above the building roofline, with the inlet positioned more than 8 metres from any outside-air intake. EPA licence conditions apply on the stack — most modern HFE solvents meet the licence without additional abatement, but a charcoal adsorber is added if the licence limit is tight.

Plasma cleaning is a third option used on high-reliability and medical assembly. A plasma cleaner (Nordson March, PVA TePla, Diener) generates a low-pressure plasma in argon, oxygen or argon-oxygen mix that removes organic residues from the board surface. The plasma chamber is under vacuum, so the HVAC requirement is a vacuum pump exhaust manifold to roof discharge, similar to the parylene system. Most plasma units exhaust through a 25-50 mm dedicated line to a roof stack.

PCB drilling, routing and depanel: FR-4 dust under NFPA 660

FR-4 (flame-retardant grade 4) is the glass-cloth epoxy laminate that makes up over 90 percent of rigid PCBs by volume. Mechanical drilling, CNC routing and depanelling generate FR-4 dust at 0.1 to 100 micrometres particle size. The dust is a combustible-dust hazard under NFPA 660 and AS 3957: the epoxy resin component sustains a deflagration at airborne concentrations above the minimum explosive concentration (MEC) of approximately 30 to 50 grams per cubic metre, with a Kst (deflagration index) typically in the 100 to 200 bar metres per second range — a Class St 1 dust.

Capture is by close-couple local exhaust at each drill spindle or router head. The transport velocity in the capture duct must be 25-30 m/s minimum to prevent dust dropout in the duct itself, which would create a fuel layer for a secondary deflagration if a primary event occurred in the collector. Duct material is bonded steel — galvanised on most installations, stainless where corrosive coolant is used. Aluminium duct is forbidden in dust deflagration zones because of the incendive-sparking risk if a particle of magnesium or steel strikes the aluminium wall during a transient overpressure event.

The duct manifolds from the individual drill heads converge on a dedicated cyclone pre-separator (typically a high-efficiency cyclone with 1.5 to 2.0 metre diameter), then a cartridge dust collector (Donaldson Torit, Camfil GS, Nederman MFP, Imperial Systems CMAXX). The collector is rated for combustible dust service with one of three deflagration protection schemes:

  • Deflagration venting — a rupture panel on the collector body releases an internal deflagration to atmosphere along a vent line to an external safe location. Vent area is sized by NFPA 68 calculations against the collector volume, vessel strength and Kst. Indoor venting requires a flameless vent (Fike, IEP Technologies, REMBE) that quenches the flame and discharges only cool overpressure gases.
  • Chemical isolation suppression — pressure detectors in the duct trigger isolation valves and a chemical suppressant discharge that quenches the deflagration before it propagates back upstream. NFPA 69 governs the design. More complex than venting but allows indoor collector placement.
  • Inerting — nitrogen blanketing inside the collector keeps oxygen below the limiting oxygen concentration (LOC) for the dust. Common on aluminium and magnesium dust, less common on FR-4 because the LOC is achievable but the operating cost of continuous nitrogen is high.

The duct from the collector to the production area must be isolated by a backdraught damper or a fast-acting isolation valve so that a deflagration cannot propagate upstream into the production zone. NFPA 660 also requires that all duct be bonded to a continuous earth, that flexible plastic hose is not used (only earthed metal flex), and that the collector is located outside the production building or in a separate dust-collector enclosure with explosion-relief venting to a safe outdoor location.

For an Australian EMS plant with one inline depanel router and two standalone drilling stations, the dust collection budget is typically 3,000 to 6,000 m3/h at the collector, with 75 to 125 mm steel duct at each capture point. The collector itself is typically a 5 to 15 kW unit, with a Kst-matched deflagration vent and a continuous monitoring of pressure differential across the cartridges. The duct package from SBKJ for this run is SBTF spiral tubeformer round duct (galvanised) for the trunk, SBEM elbow former for the bends, and SBAL-V branch ducts where rectangular cross-section is needed at junctions.

Reel-to-reel SMT line ESD shielding and air supply

The reel-to-reel SMT placement section — Yamaha YSM, Panasonic NPM, ASM SIPLACE, JUKI, Mycronic — is the most ESD-sensitive part of the line because components are picked from tape-and-reel feeders at high speed, exposed briefly during placement, and re-encapsulated by the next operation only after the full board passes through. Each placement head moves at up to 2 metres per second, and the tribocharging on the polyester tape and the nozzle tip alone can generate hundreds of volts of static if humidity is below the EPA limit.

The HVAC contribution to ESD control on the placement section is twofold. First, the humidity at the placement bench must be at or above 40 percent RH — the lower bound of the SMT hall envelope. Second, the supply air must not be a source of triboelectric charging itself. Conditioned air delivered at 4-6 m/s through a galvanised supply duct does not generate significant static, but air delivered through a long run of plastic flexible duct can carry a charge. Our recommendation is no plastic flex within 5 metres of the placement zone — all final duct sections are bonded steel.

Where the placement zone is fully ESD-controlled (defence and medical EMS), the supply diffuser is a HEPA-filtered terminal grille with a metal frame bonded to the building earth, mounted directly above the line. The terminal velocity is held below 0.45 m/s at the workpiece to prevent component sweep — a high-velocity supply jet can lift 0201 and 0402 chip resistors off the pickup point.

AOI, X-ray and inspection room HVAC

Automated optical inspection (AOI) and X-ray inspection are the two main electronic-assembly inspection technologies in Australian EMS. AOI uses high-resolution cameras with structured lighting to check solder joint geometry, component presence, polarity, and surface defects. X-ray uses a tube source (typically 70-160 kV) with a flat-panel detector to image hidden joints under BGAs and bottom-terminated components.

Both technologies are temperature-sensitive. The AOI camera thermal drift over a 5-degree-Celsius ambient swing can shift the reported solder fillet height by 10-15 micrometres, which is enough to cause a false fail on a Class 3 acceptance limit. The X-ray tube anode life and image quality are similarly temperature-sensitive. For these reasons the inspection room is held at 22 plus or minus 1 degree Celsius (tighter than the main hall's plus or minus 2), with 45 plus or minus 5 percent RH and 8-10 ACH.

The X-ray cabinet itself is shielded against radiation leakage by lead-lined steel and a safety-interlocked door. The interior of the cabinet is at room temperature and the only HVAC requirement is a small (50-100 m3/h) extract from inside the cabinet to atmosphere to vent any ozone formed by X-ray ionisation of room air. This vent is a 50 mm steel duct to a dedicated roof outlet — it must not connect to any other building system, because the ozone-laden air is mildly oxidising and the X-ray cabinet pressure relationship is independent of room ventilation.

Where the AOI and X-ray room is part of an ISO 8 cleanroom for medical EMS, the room has its own supply duct branch with H13 HEPA at the terminal grille, a pressure differential of +5 Pa against the SMT hall, and a return through low-side wall grilles. Air change rate goes up to 20-25 ACH in the cleanroom version.

BGA rework station and bench-top extracts

BGA rework is the localised re-soldering of a single ball-grid-array package. The rework station — Ersa IR/PL550, Martin Expert series, ZeroTouch, Air-Vac Onyx29 — applies infrared or hot-air heating to the top of the package while a bottom heater pre-warms the board. Peak top-side temperature reaches 230 to 260 degrees Celsius, similar to a reflow zone, but the local fume load is concentrated above the package rather than distributed along an oven tunnel.

Each rework station needs a 150 mm flexible local extract arm rated 200-300 m3/h, ducted into the main solder-fume system or to a benchtop Plymovent Phv, Purex 400i or BOFA V200 benchtop unit. The arm hood is positioned 15-30 centimetres above the package being reworked. The bench-top fume filter typically runs a pre-filter, F8 main filter and activated-carbon stage, with a 90-180 day filter change.

Cable assembly, heat-shrink and adhesive-lined sleeve work generates a similar low-grade fume that benefits from local extract. A typical cable assembly bench has a 100 mm fume arm at 150-200 m3/h, ducted to a small bench filter. The setpoint on the hot air gun used for heat-shrink is typically 250-300 degrees Celsius — keep it below 300 to avoid HCl release from any PVC sleeving in the workflow.

Battery pack assembly and cell-test chamber HVAC

The battery segment of an EMS plant has grown substantially over the past five years, driven by Australian operations in EV charging (Tritium), portable medical electronics (ResMed, Cochlear), defence batteries (Codan-class radio packs), and energy storage. Battery pack assembly typically involves cell handling (18650, 21700 cylindrical or pouch cells), welding (laser or resistance), busbar attachment, BMS PCB integration, and thermal management.

NFPA 855 (USA) and AS/NZS 5139 (Australia) both govern the HVAC requirements. The battery assembly area and the cell-test chamber are separated from the main SMT hall by a fire-rated boundary (typically -/120/- minimum, often -/180/- for larger installations). Inside the boundary the ventilation rate is 15 ACH minimum, ducted to a separate roof stack that does not share with the main reflow exhaust. A toxic-gas detection system (CO, HF, HCN, CO2) is interlocked to the exhaust fan VFD so that detection of a thermal runaway event triggers an emergency high-flow extract.

The cell-test chamber itself — typically a thermal-cycle chamber with cells under charge-discharge profiles — is its own enclosure with a dedicated 100-200 mm extract to atmosphere. The duct is galvanised steel for general service, with a fire damper rated to the boundary FRL. For lithium-ion cell test, an early-warning gas detection on the chamber outlet duct (off-gas detection of electrolyte vapour) is increasingly specified.

Final test chamber temperature/humidity stress HVAC

Final test environmental stress screening (ESS), burn-in and HALT/HASS (highly accelerated life testing and stress screening) chambers cycle the finished assembly across temperature and humidity profiles. Typical ranges are minus 40 to plus 85 degrees Celsius for commercial-grade ESS, minus 55 to plus 125 degrees Celsius for defence and aerospace, and 10 to 95 percent RH for humidity profiles. Chamber sizes range from 0.5 cubic metres bench-top to 10 cubic metres walk-in.

The HVAC implication is heat rejection. A 1.5 cubic metre chamber running at minus 40 degrees Celsius rejects 5-12 kW of compressor heat to the chamber room. A walk-in 10 cubic metre chamber rejects 20-50 kW. If multiple chambers operate simultaneously the rejected heat load on the chamber room can exceed 100 kW — enough to lift room temperature by 5-10 degrees Celsius if not handled.

Our standard solution is a dedicated chamber room with 6-10 ACH extract and a tempered makeup air supply that absorbs the chamber heat rejection without disturbing the main SMT hall HVAC. The chamber room is held at 22-26 degrees Celsius — slightly warmer than the SMT hall is acceptable because no PCB assembly is performed in the chamber room. The exhaust duct from the chamber room is galvanised steel, 6-10 ACH sized, discharging through a roof stack.

Where the chambers are humidity-cycling and the chamber drain or chamber breathing port can release residual moisture into the room, a small (50-100 m3/h) local extract at the chamber back panel is added to prevent humidity drift in the chamber room.

Material selection: galvanised, 304 stainless, 316L stainless, FRP

Material selection across the eight-zone EMS HVAC plan follows a simple decision tree:

  • Hot-dip galvanised steel (Z275) — the default for almost every supply duct, return duct, general exhaust and standard process exhaust. AS 4254 Class C construction. SBKJ SBAL-V, SBAL-III and SBAL-II auto duct lines produce this directly from 0.5 to 1.5 mm coil.
  • 304 stainless steel — used on critical medical EMS cleanroom supply branches downstream of the final HEPA, on the first 2-3 metres of reflow exhaust where flux condensation is heavy, on aqueous cleaner extract where saponifier mist would corrode galvanising, and on conformal coating booth exhaust where solvent condensate is present. SBKJ SBTF spiral tubeformer and SBAL-V (with stainless coil change) both produce 304 duct.
  • 316L stainless steel — used on the solvent vapour degreaser return path where chlorinated decomposition products may form, on coastal-site duct exposed to salt air (Sydney, Brisbane, Perth coastal facilities), and on any acid scrubber inlet (rare in standard EMS but applicable in some advanced cleaning chemistries).
  • Fibreglass-reinforced plastic (FRP) — used on aqueous cleaner extract downstream of the mist eliminator where stainless would still be expensive, and on the cooler section of solvent exhaust where temperature is below 80 degrees Celsius and chemistry compatibility is verified. Not produced on SBKJ machines — purchased from FRP duct specialists and integrated by the contractor.

Aluminium duct is rejected on three grounds: (1) in dust deflagration zones it is incendive against steel and forbidden under NFPA 660 and AS 3957; (2) it does not survive saponifier or alkaline cleaner exposure; (3) it is more expensive per kilogramme than galvanised steel without the corrosion resistance of stainless. PVC and PVC-coated duct are rejected on outgassing grounds anywhere in the SMT hall supply or any medical EMS branch — phthalate plasticiser release can deposit on cool PCB surfaces and degrade coating adhesion.

Duct construction class is set by leakage. AS 4254 Class C (less than 0.5 L/s per m2 at 250 Pa) is the minimum for the SMT hall and all production zones. Class B (less than 0.25 L/s per m2 at 500 Pa) is specified on conformal coating exhaust, solvent extract and any duct where leakage would mean fume into the production space. Class A (less than 0.125 L/s per m2 at 1000 Pa) is reserved for ISO 7 medical cleanroom supply duct.

Pressure cascade across the eight zones

The pressure cascade across the EMS plant is one of the most underspecified elements of the HVAC package. Done well, it prevents contamination migration between zones, holds the SMT hall ESD environment, and gives the building a stable relationship with outdoor ambient even as doors open and exhausts cycle. Done badly, the conformal coating room dumps solvent into the SMT hall every time the door opens, the FR-4 router dust collector pulls clean air from the box-build floor, and the medical cleanroom de-pressurises every time the wave solder extract fan starts.

Our recommended pressure cascade for an Australian EMS plant, in pascals relative to the building exterior at zero datum:

  • Medical EMS cleanroom (ISO 7) — +25 Pa
  • Medical EMS gowning — +15 Pa
  • SMT line hall — +15 Pa
  • Reflow and wave solder gallery — +10 Pa (slightly positive against ambient, slightly negative against the main hall)
  • Box-build floor — +5 Pa
  • Incoming goods and stencil store — 0 Pa
  • AOI and X-ray room — +20 Pa (positive against the main hall to prevent particle entry)
  • Aqueous cleaning bay — -10 Pa
  • Solvent degreaser room — -15 Pa (negative against everything else)
  • Conformal coating room — -10 Pa
  • FR-4 router and dust collector room — -15 Pa
  • Battery pack assembly and cell-test room — -10 Pa

The cascade is held by sizing the supply and return flows in each zone with a deliberate offset. A zone targeted for +15 Pa receives 8-12 percent more supply than return; a zone targeted for -10 Pa receives 8-12 percent less supply than return (with the balance made up by air drawn from adjacent zones through door undercuts, transfer grilles or pass-through interlocks). Differential pressure transmitters at each boundary feed the building management system and trigger alarms if any boundary drifts more than 5 Pa from setpoint.

SBKJ duct machinery for an EMS plant package

Translating the eight-zone HVAC plan into a duct package that an Australian sheet-metal contractor can fabricate efficiently is where SBKJ's machinery line earns its place in the EMS supply chain. Our customers are the contractors — they build the duct in their shop and install it on the EMS plant site. The machinery they need to do the job in the timeframe a typical EMS commissioning programme allows (12-20 weeks from contract to first piece on site) is the same machinery we recommend for any high-mix, medium-volume duct production:

  • SBAL-V auto duct line — the production-grade rectangular duct line. 16 metres per minute finished duct output, 87 kW total connected power, 0.5 to 1.5 mm coil thickness, up to 1500 mm coil width. Produces TDF-flanged, Pittsburgh-seamed or snap-locked rectangular duct directly from coil with full inline notching, cleating, slitting and seaming. The line of choice for a contractor producing 100+ tonnes of EMS duct per year.
  • SBAL-III auto duct line — the medium-output line. 14 m/min, 15.7 kW, 0.5 to 1.2 mm coil. Same TDF and Pittsburgh capability as the V at a lower power footprint. The line of choice for contractors with intermittent EMS work mixed with general HVAC fabrication.
  • SBAL-II auto duct line — the prototype and short-run line. 18 m/min, 5.5 kW, 0.5 to 1.2 mm coil. Compact footprint, ideal for an EMS contractor doing 20-50 tonnes per year mixed with manual fabrication.
  • SBTF-1500C, SBTF-1602 and SBTF-2020 spiral tubeformers — for round spiral duct on solvent exhaust risers, dust collection trunks, parylene vacuum lines, and any application where round geometry is preferred over rectangular. Coil width 1500 / 1602 / 2020 mm available; both galvanised and stainless coil supported.
  • SBEM-1250 elbow former — produces formed elbows in matching diameter to the spiral tubeformer output, eliminating the need for fabricated mitred elbows on round duct. Faster, cleaner and more consistent than welded mitred construction.
  • SBSF-1525 stitchwelder — 2.5 kW resistance stitchwelder for transverse joint sealing on rectangular duct. Used where solid welded transverse joints are required (high-leakage-class duct, hot solvent exhaust, pressurised supply).
  • SBFB-1500 lockformer — 7.5 kW, 1.20 m/min, Pittsburgh-seam and TDF-flange forming line for shop fabrication of fittings, transitions and short-run sections that do not justify the SBAL line setup.
  • SBHF horizontal flanger — auxiliary flange forming for TDF and angle-flange joint preparation.
  • SBPC1500 plasma cutting table — for fitting, transition and custom-blank cutting from coil and sheet.
  • SBLR-600 and SBLR-600A laser welders — 7.6 m/min laser longitudinal seam welding for stainless duct on medical EMS cleanroom branches and any duct that requires Class A leakage.

A typical Australian EMS contractor's machinery package for a 5,000 to 8,000 square metre EMS plant fit-out is an SBAL-V or SBAL-III for the rectangular run, an SBTF-1500C for the spiral runs, an SBEM-1250 for the elbows, an SBSF-1525 or SBFB-1500 for the seaming, and an SBPC1500 for cutting. The package produces every duct section in the eight-zone plan from coil to finished part in a single shop pass.

Duct support, vibration isolation and structural coordination

Ductwork above the SMT line cannot transmit motor or fan vibration into the conveyor, the stencil printer, the placement machines or the reflow oven. Modern SMT placement machines hold sub-100-micrometre placement accuracy; floor or ceiling vibration at the placement head above approximately 100 micrometres per second velocity in the 1-100 Hz band starts to degrade placement accuracy and increase rework rate.

Our standard practice for an SMT hall duct package is:

  • Duct hangers on 25 mm EPDM neoprene-free isolators wherever the duct passes within 5 metres of an SMT placement machine or stencil printer.
  • Flexible duct connectors (EPDM, 75-150 mm wide) at every fan inlet and outlet, including the AHU, the reflow exhaust fan, the wave solder fan, the dust collector fan and the coating booth fan.
  • Independent duct hangers from the building primary structure, not from the SMT line support steel.
  • Fan tip speed below 30 m/s on supply fans, below 35 m/s on exhaust fans.
  • Floor vibration verification at commissioning, with measurements below 100 micrometres per second velocity in the 1-100 Hz band at the placement machine foot.

Hanger spacing per AS 4254 Section 7 is 3.0 metres on 0.5-0.8 mm duct, 2.4 metres on 1.0-1.5 mm duct, and 2.0 metres on insulated duct over 600 mm in the long dimension. Hanger rod diameter is M10 for duct under 750 mm and M12 for duct above. Bracing against seismic loads follows AS 1170.4 where the plant is in a Category 2 or higher seismic zone — most of Australia is Category 1 or 2, but some EMS plants in inland NSW and SA fall in higher categories and require seismic restraint on every fan, every AHU and every duct trunk above 600 mm.

Commissioning, balancing, leak testing and ESD audit

The commissioning sequence for an EMS plant HVAC package follows a fixed order:

  1. Mechanical completion — every duct section installed, every fan rotational checked, every damper actuator stroked.
  2. Leak testing — AS 4254 Annex E pressurisation test on each duct trunk. Class C target less than 0.5 L/s per m2 at 250 Pa. Class B target less than 0.25 L/s per m2 at 500 Pa. Document with calibrated flow meter and pressure gauge for each tested section.
  3. Initial balancing — TAB (test, adjust, balance) contractor sets each diffuser and grille to plus or minus 10 percent of design airflow per AS 1668.2 commissioning. Issue a balancing report.
  4. Pressure cascade verification — measure differential pressure across every zone boundary with a calibrated manometer. Adjust supply or return offsets until all boundaries are within plus or minus 3 Pa of setpoint.
  5. Process exhaust verification — measure capture velocity at the reflow oven, wave solder hood, coating booth, dust collector capture points and AOI extract. Verify each is at or above the design value.
  6. Fume filter commissioning — Plymovent, Purex or BOFA commissioning per supplier protocol, including filter loading verification and pressure drop baseline.
  7. Dust collector commissioning — verify Kst-matched deflagration vent, isolation valve operation, and earthing continuity. Sample dust for actual Kst, MEC and MIE if not previously characterised.
  8. HEPA leak testing (medical EMS branches) — IEST-RP-CC034 polydisperse aerosol challenge on each HEPA filter and frame seal. Maximum permitted penetration 0.01 percent for H13 and 0.005 percent for H14.
  9. Particle count verification (medical EMS) — ISO 14644-3 particle count at 0.5 and 5 micrometre channels. Pass criterion is 95th percentile UCL below the class limit, measured under at-rest and operational conditions.
  10. Temperature and humidity stability test — log SMT hall conditions over 7 consecutive days, including a hot day, a cold day and a normal day. Verify temperature stays within 22 plus or minus 2 degrees Celsius and humidity within 45 plus or minus 5 percent RH at all times.
  11. ESD audit — IEC 61340-5-1 walking voltage test, point-to-point floor resistance, work surface resistance, operator garment resistance, ionisation discharge time. Document an EPA audit report and issue a certificate of EPA compliance.
  12. Stack emission sampling — where required by the EPA operating licence, sample the reflow exhaust stack, wave solder stack, coating booth stack and dust collector vent for VOC, particulate and any site-specific contaminants. Issue an emission compliance report.
  13. QA dossier handover — final dossier includes all of the above plus AS 4254 construction certificates, mill certificates for stainless on critical branches, fire damper certificates per AS 1530.4, AHU commissioning report, sequence-of-operations documentation, BMS point list and as-built drawings.

Total commissioning time for a 5,000 to 8,000 square metre EMS plant is typically 4 to 8 weeks from mechanical completion to certificate of practical completion. The longer end of the range applies where medical EMS cleanroom particle count verification requires extended stability runs and where stack emission permits require multi-week sampling for licence approval.

Energy, recovery and operating cost

An Australian EMS plant typically spends 18-30 percent of its operating energy bill on HVAC — fans, chillers, humidifiers and reheat. The breakdown on a representative 5,000 square metre, two-line SMT plant in Melbourne:

  • SMT hall AHU (chilled water cooling, humidification, reheat) — 65,000 to 95,000 kWh/year per 1,000 m2 of hall
  • Reflow exhaust fan plus filter pack — 8,000 to 14,000 kWh/year per oven
  • Wave solder exhaust — 4,000 to 7,000 kWh/year per machine
  • Conformal coating booth fans — 6,000 to 12,000 kWh/year per booth
  • Dust collector fan plus cartridge change-out — 12,000 to 22,000 kWh/year per collector
  • Solvent and aqueous cleaner extract — 5,000 to 10,000 kWh/year per machine
  • Chamber room ventilation — 8,000 to 15,000 kWh/year for a 4-chamber bank

Heat recovery from the reflow exhaust to the makeup air supply is technically feasible with a stainless plate exchanger or a glycol run-around coil. The trade-off is flux deposition on the recovery surface, which reduces effectiveness and increases maintenance. We recommend recovery only on plants running more than 3 reflow ovens at consistent production volume, with annual chemical cleaning of the recovery coil. Payback on a glycol run-around coil for a single oven is rarely under 7 years; for 3 ovens at high duty it is 3-4 years.

Free cooling from outside air is highly attractive in Melbourne, Adelaide, Canberra and Hobart for 4-6 months of the year, when ambient dry-bulb temperature is below 18 degrees Celsius and ambient dew point allows direct supply to the SMT hall without dehumidification. A four-stage AHU with full economiser dampers and a high-efficiency mixing box captures this saving and can reduce annual chiller runtime by 35-50 percent on a Melbourne plant.

Lead time, cost and procurement

Lead time on an Australian EMS plant HVAC package, from contract to practical completion, runs 16-28 weeks. Breakdown:

  • Engineering design and shop drawings — 4-6 weeks
  • Long-lead AHU, chillers and fume filters — 8-14 weeks (AHU from Aerotech or Air Change; chillers from Trane/Carrier/Daikin; fume filters from Plymovent/Purex/BOFA via Australian distributors)
  • Duct fabrication — 4-8 weeks (depends on contractor's machinery capacity; an SBAL-V-equipped contractor fabricates a 5,000 m2 plant's duct in 2-3 weeks)
  • Installation — 6-10 weeks
  • Commissioning — 4-8 weeks

Total installed cost for the HVAC mechanical package on a 5,000 to 8,000 square metre Australian EMS plant ranges from AUD 1.8 million to AUD 4.5 million, depending on whether medical EMS cleanroom space is included, the number and complexity of fume extract systems, and whether the existing building shell provides the structural and electrical capacity to support the load. Duct fabrication and installation alone is typically 18-28 percent of this total. The balance is AHU, chillers, fume filters, controls, fire protection integration and commissioning.

Procurement strategy on the duct portion is straightforward where the contractor has an SBAL-V or SBAL-III line. Coil is sourced from BlueScope (galvanised) or Atlas Steels/Vulcan Steel (stainless), the line produces every section from coil to finished part, and installation runs in parallel with AHU procurement so the duct does not become the critical path. Contractors without an automatic line typically subcontract the rectangular duct to an SBAL-equipped fabricator or fall back to manual fabrication with significant lead-time penalty.

Common failure modes and what to avoid

From commissioning experience across EMS sites, the recurrent failure modes are:

  • SMT hall humidity drift below 35 percent RH in winter — caused by undersized humidifier capacity. Specify steam or evaporative humidification at 1.2 times peak winter latent load to give margin. Verify with a 7-day winter logging run before signing off commissioning.
  • Reflow flux deposition in horizontal duct sections — caused by inadequate slope back to the oven. Verify 1:50 minimum slope on every horizontal run. Install drop pots at every elbow.
  • Wave solder fume migration to SMT hall — caused by insufficient pressure cascade between the wave gallery and the main hall. Verify minus 5 Pa across the boundary at commissioning and on a quarterly basis thereafter.
  • Coating booth back-draught when adjacent door opens — caused by inadequate booth exhaust margin. Specify booth exhaust at 1.3 times NFPA 33 minimum to absorb door-opening transients.
  • FR-4 dust collector deflagration vent missing or wrongly sized — caused by procurement of standard industrial collector instead of combustible-dust-rated model. Verify Kst-matched NFPA 68 vent area or NFPA 69 isolation suppression on every cartridge collector handling FR-4 dust.
  • Medical EMS HEPA frame leakage — caused by inadequate frame flatness or wrong gasket type. Specify gel-seal HEPA frames, verify frame flatness within 0.5 mm before installation, scan-test every filter and frame at commissioning per IEST-RP-CC034.
  • Battery room exhaust shared with general extract — never acceptable under NFPA 855 or AS/NZS 5139. The battery room must have a dedicated stack with toxic-gas detection on the discharge.
  • X-ray cabinet ozone vent connected to general return — never acceptable. The cabinet vent goes direct to atmosphere through a dedicated 50 mm duct.
  • Solvent degreaser room ventilation taken high-level only — modified alcohol and HFE vapours are heavier than air. Specify a low-level extract at 200 mm above floor in addition to high-level general extract.

Avoid these and you avoid most of the post-commissioning rework that haunts EMS HVAC packages.

What an EMS contractor should ask before quoting

If you are a sheet-metal contractor or an HVAC consultant pricing an Australian EMS plant package for the first time, the questions to ask the customer before quoting are:

  1. What is the production volume per shift? Boards per hour drives reflow throughput, wave solder duty and total fume load.
  2. Is the line lead-free SAC305 only, or is there a parallel SnPb line for legacy defence work? The latter changes the WES targets on the operator-zone monitoring.
  3. Is conformal coating in-house or subcontracted? If in-house, how many booths, what chemistry (AR, UR, SR, parylene), and is the coating room already classified per AS/NZS 60079?
  4. Is PCB depanel and routing in-house? If yes, what router model, what spindle count, what FR-4 grade? Specify the dust collector before the duct.
  5. Is there a medical EMS or RF assembly line that requires ISO 7 or ISO 8 classification? If yes, ASHRAE 170 may apply and HEPA filtration is required.
  6. Is battery pack assembly or cell test included? If yes, NFPA 855 / AS/NZS 5139 applies and a dedicated extract is needed.
  7. Where is the plant geographically? Outdoor design conditions vary substantially across Australia and affect AHU sizing.
  8. Is the building purpose-built or a retrofit? Retrofits typically need additional structural and electrical work and have lower ceiling heights that constrain duct routing.
  9. What is the EPA operating licence condition on stack emissions? VOC limits, particulate limits and odour conditions all flow into the abatement specification.
  10. What is the commissioning programme? Tight programmes (under 16 weeks) typically force parallel duct fabrication and AHU procurement and put a premium on contractors with automatic duct lines.

Answer those before quoting and you have the basis for a fixed-price package that holds through delivery.

Related SBKJ insights and where to go next

This guide sits inside a wider SBKJ engineering library. For deeper detail on adjacent topics, see:

FAQ

What HVAC conditions are required for an ESD-controlled SMT assembly hall?

An IEC 61340-5-1 compliant Electrostatic Protected Area for surface-mount and through-hole PCB assembly is held at 22 plus or minus 2 degrees Celsius dry bulb and 45 plus or minus 5 percent relative humidity year-round. The lower humidity bound (40 percent RH) is set by ESD physics — below 40 percent RH walking voltages exceed the 100 V Class 0 limit. The upper bound (55 percent RH) is set by moisture sensitivity of unsealed components and by solder-paste tack life. Air change rate is 8-15 ACH in conventional SMT halls and 20-30 ACH where the hall is also ISO 7 or ISO 8 cleanroom-classified.

How is solder fume extracted from a lead-free SMT reflow oven?

A SAC305 reflow oven runs at 245-260 degrees Celsius peak and discharges flux pyrolysis products, aldehydes and laminate outgassing. Manufacturer recommendations specify 250-400 cubic metres per hour per exhaust port at 50-150 pascals negative static, ducted in 150-200 mm galvanised steel with a flux drop pot at every elbow and a sloped riser back to the oven. The duct discharges to a Plymovent SCS, Purex 4000i or BOFA AD-series filter or to a roof stack. NFPA 86 governs the oven enclosure.

What ventilation does a conformal coating spray booth need?

A conformal coating booth is regulated under NFPA 33 and AS/NZS 60079. Booth face velocity is 0.5 m/s minimum across the operator opening, 0.4-0.6 m/s capture at the workpiece. A 1.5 m by 1.0 m opening needs 2,700 cubic metres per hour minimum. The exhaust duct is 304 stainless or unlined galvanised, sloped to a solvent drain pot, with a fire damper at the building envelope. Class I Division 2 electrical applies inside the booth and within 1 metre of the opening.

How is wave solder extract designed for a lead-free plant?

A wave solder machine at SAC305 260-270 degrees Celsius needs a sloped capture hood above the pot at 0.4 m/s capture velocity, ducted in 200-250 mm galvanised steel to a fume filter (Plymovent MDB, Purex Alpha, BOFA AD2000) or roof discharge. A parallel 100-150 mm extract is added at the dross pan. Total wave solder fume budget is 400-800 cubic metres per hour. Operator-zone solder fume must stay below the Safe Work Australia WES of 0.1 mg/m3.

What HVAC class is needed for a medical PCB cleanroom?

Implantable medical electronics (Cochlear-class), RF and microwave PCB assembly, and flexible-circuit lamination typically operate at ISO 14644 Class 7 with 20-30 ACH through H13 or H14 HEPA filtration. The duct is 304 stainless on supply downstream of the final HEPA, galvanised on returns and exhaust. Pressure cascade is +15 Pa production to +5 Pa gowning to 0 Pa ambient. ASHRAE Standard 170 applies where the line is part of an integrated medical device facility.

How is PCB drilling and routing dust handled?

FR-4 glass-epoxy PCB dust is combustible under NFPA 660 and AS 3957. Capture is by close-couple local exhaust at each drill head at 25-30 m/s transport velocity in 75-125 mm bonded steel duct, ducted to a cyclone pre-separator and an explosion-rated cartridge collector with deflagration vent or chemical isolation suppression. The duct is earthed continuously, with no flexible plastic hose. Aluminium duct is forbidden because of incendive sparking risk.

What duct machinery does SBKJ recommend for an EMS plant?

For an Australian EMS plant SBKJ recommends an SBAL-V or SBAL-III auto duct line for galvanised supply duct (16 m/min and 14 m/min respectively, up to 1500 mm coil width), an SBTF-1500C or SBTF-1602 spiral tubeformer for round exhaust and dust collection risers, an SBEM-1250 elbow former for fittings, and an SBSF-1525 stitchwelder or SBFB-1500 lock-former for transverse joints. Medical EMS cleanroom branches are produced in 304 stainless; 316L is reserved for the solvent degreaser return path.

What is the typical HVAC cost for an Australian EMS plant?

Total installed HVAC mechanical package cost for a 5,000-8,000 square metre Australian EMS plant ranges AUD 1.8-4.5 million depending on medical EMS cleanroom inclusion, fume extract complexity and building shell condition. Duct fabrication and installation is 18-28 percent of this total. Lead time from contract to practical completion is 16-28 weeks.

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