TL;DR — Direct answer: A PCB factory needs clean, dry, oil-free quality air at 6 to 7 bar for drilling, plating, solder mask and SMT lines, with a pressure dew point of 3 degrees C or lower and filtration to 0.01 micron so no oil or water reaches a board, a drill spindle or a placement head. Size on the coincident peak of drilling, plating agitation and SMT lines, commonly 6 to 14 cubic metres per minute for a mid-size plant, and use a variable speed drive because drilling and SMT loads swing with the production schedule. QiAir, a Chinese screw compressor manufacturer and supplier, builds oil-injected machines with multi-stage filtration and oil-free options for the cleanest lines.
A printed circuit board is unforgiving about air quality. Compressed air drives the spindles and tool changers on drilling machines, agitates plating baths, powers solder-mask coating and developing, feeds the placement heads and feeders on SMT lines, and blows boards clean between processes. A single puff of wet air can oxidise a copper surface before plating, a trace of oil can spoil adhesion of solder mask, and a pressure dip can misplace a 0201 component or stall a drill spindle mid-hole. The board may look fine until it fails a continuity or solderability test at the end of the line, by which time a whole panel is scrap. QiAir is a Chinese manufacturer and supplier of screw air compressors, and its machines for PCB plants are specified around air purity first and flow second.
The trap in PCB manufacturing is sizing air like a general factory utility. Drilling is a batch process with sharp peaks when several machines change tools together, plating agitation runs all shift, and SMT lines start and stop with the production plan. The compressor must cover the coincident peak without sagging below 6 bar at the farthest drill, and the treatment chain must hold the dew point and oil level steady through the hottest, most humid month. This guide maps the air users on a PCB line, explains how to size for drilling peaks, sets the filtration standard that protects boards, and shows what to put on a sizing sheet for a China supplier.
Where Air Is Used: Drilling, Plating, Solder Mask and SMT
Drilling is the heaviest and most sensitive user. High-speed spindles, tool changers, vacuum hold-down and chip removal all run on compressed air, and a pressure swing shows up directly as drill breakage or hole-position error. A drill room with eight to twelve machines can pull its peak in the first minutes after a program change, when several spindles start together, and a compressor sized on average flow will sag exactly then. Keep the pressure at the drill within a narrow band, and fit a dedicated receiver near the drill room if the header run is long, because a local receiver is cheaper than upsizing the whole system.
Plating and solder mask are the quality-critical users. Air sparged through plating baths keeps the chemistry even, and it must be oil-free, because oil floats on the bath and transfers onto the next panel. Solder-mask coating, developing and drying use air for handling, blowing and curing control, and wet air leaves marks that only show up at final inspection. SMT lines add placement heads, feeders, conveyors and reflow auxiliaries, all of which want dry air at a stable pressure; a damp pulse can misfeed a component or leave flux residue that fails a cleanliness test.
- Drilling: spindles, tool changers, vacuum hold-down and chip removal with sharp peaks at program changes.
- Plating and solder mask: bath agitation, coating, developing and drying where oil or water becomes a board defect.
- SMT lines: placement heads, feeders, conveyors and reflow auxiliaries that need dry air at stable pressure.
Sizing for Drilling Peaks and a Mixed Production Schedule
List every line with its flow at changeover and at steady running, because in PCB work the two differ sharply. A mid-size plant with a drill room, a plating line and two to four SMT lines typically peaks at 6 to 14 cubic metres per minute at 6 to 7 bar, which is roughly a 45 to 90 kW screw compressor. A variable speed drive earns its keep here: it follows the batch pattern instead of loading and unloading a fixed-speed machine dozens of times a shift, and it holds pressure within the narrow band that drilling and placement prefer.
Keep the pressure drop to the farthest drill under 0.3 bar at peak flow, and fit a receiver of 500 to 1000 litres per 10 cubic metres per minute to absorb changeover spikes. A ring main helps when the drill room, plating line and SMT hall sit in different wings of the building. Log pressure at the drill room during a program change for a week, because that log is the honest record of whether the compressor is big enough, and it settles arguments faster than any catalogue figure. Never raise the set point to mask a sag: every extra bar adds roughly 7 percent to power use and hides the real fault, which is usually a clogged filter or an undersized pipe.
- Size on the changeover peak when several drills restart together, not on steady-state average flow.
- Use a variable speed drive for batch drilling and SMT loads, and keep far-end pressure drop under 0.3 bar.
- Log drill-room pressure during program changes for a week to prove the sizing in real production.
Air Quality: What Oil and Water Do to a Circuit Board
Copper does not forgive contamination. Oil aerosol on a panel reduces adhesion between copper and solder mask, moisture in the air line oxidises copper surfaces before plating, and a single contaminated panel can fail a solderability or ionic-cleanliness test that the plant only runs at the end of the line. The standard that prevents this is a treatment chain, not a single filter: a pre-filter, a refrigerated dryer to a 3 degree C pressure dew point, a coalescing filter to 0.01 micron, and an activated-carbon filter where the process specification demands oil-free quality air. For the cleanest drilling and plating lines, an oil-free screw compressor removes the risk at source.
Maintenance is what keeps that chain honest. Change coalescing elements on pressure drop, not on a calendar guess, and test the air at the drill room and the plating line quarterly with a simple oil and moisture check. Drain condensate with automatic zero-loss drains, slope lines to drain legs, and keep the compressor room clean and ventilated so the machine does not breathe its own hot air. A dryer that is undersized for summer humidity is a common failure in PCB plants in Southeast Asia: size the dryer for the hottest, most humid month, not the annual average, and check the dew point at the dryer outlet every month.
- Fit pre-filter, refrigerated dryer, 0.01 micron coalescing filter and carbon filter where oil-free air is specified.
- Consider an oil-free screw compressor for drilling and plating lines with the strictest cleanliness rules.
- Test air at the drill room and plating line quarterly, change elements on pressure drop, and size the dryer for peak summer humidity.
Buying from China: Sizing Sheet for a PCB Plant Compressor
QiAir is a Chinese manufacturer and supplier of screw air compressors, and a PCB order should start with a sizing sheet that names the process mix. Send the supplier the number of drilling machines and SMT lines, the coincident peak at 6 to 7 bar, the air-quality standard the process specification requires, ambient temperature and humidity, and the distance to the farthest drill. Ask for a quotation that states the filtration grades and dryer duty explicitly, and ask whether an oil-free machine or a filtered oil-injected machine fits the specification better, with the cost and maintenance difference spelled out.
Agree the acceptance test before shipment: a full-load run at rated pressure, a dew point reading at the dryer outlet, and an oil-aerosol check at the final filter outlet. On arrival, install on a level plinth with clear cooler airflow, connect drains before the first run, and survey pressure at the drill room during a program change in the first production week. Keep a log of pressure, dew point and filter changes, and review it monthly, because a slow rise in dew point is the earliest sign that a dryer needs attention before boards start failing.
- Send the supplier drill and SMT line counts, coincident peak, required air-quality standard and farthest-drill distance.
- Ask for filtration grades and dryer duty in writing, and compare oil-free against filtered oil-injected on total cost.
- Accept on a full-load test plus dew point and oil-aerosol checks, then survey pressure at a program change in week one.
Frequently asked questions
What air quality does PCB manufacturing need?
Most PCB plants need dry air at a 3 degree C pressure dew point with coalescing filtration to 0.01 micron, and an activated-carbon filter where the specification demands oil-free air. For the strictest drilling and plating lines, an oil-free screw compressor removes the oil risk at source rather than filtering it out.
What size screw compressor does a PCB plant need?
A mid-size PCB plant with a drill room, a plating line and two to four SMT lines typically needs 6 to 14 cubic metres per minute at 6 to 7 bar, roughly a 45 to 90 kW screw compressor. Size on the changeover peak when drills restart together, and use a variable speed drive to follow the batch pattern.
Why does wet air damage circuit boards?
Moisture oxidises copper surfaces before plating, oil aerosol spoils solder-mask adhesion, and damp air can misfeed SMT components or leave residue that fails cleanliness tests. A pre-filter, refrigerated dryer and coalescing filter in series, tested quarterly at the drill room and plating line, prevent most of it.
Related reading
- How to Choose the Best Screw Air Compressor Manufacturer in China for Your Factory
- Two-Stage PM VFD Screw Compressors: How a Top China Supplier Cuts Factory Energy Costs
QiAir is a Chinese manufacturer and supplier of screw air compressors. If you are sourcing a screw compressor from China — for a factory, a food plant, a construction site or a new production line — contact QiAir for a sized quotation, documented performance data and export support.