Compressed Air for Electronics Manufacturing – Air Compressor Manufacturers

Electronics manufacturing's requirements for compressed air cleanliness rank among the absolute strictest in the industrial sector. This industry's air quality requirements and other manufacturing are simply not on the same level. Oil content 0.01 mg/m³, dew point -40°F, particles Class 1. These three parameters written clearly in bid documents. Can't meet them, don't bother bidding.

0.01 mg/m³

Oil Content

-40°F

Dew Point

Class 1

Particles

Oil-Free Machine vs Oil Removal Filter Debate

Do electronics factories use oil-free machines or oil-flooded machines with oil removal filters? This question has been argued for years.

Oil-Flooded Machines

Argument for oil-flooded machines is straightforward: cheap. Same output capacity, oil-flooded screw is one-third or more cheaper than oil-free screw. Add three-stage oil removal filtration downstream, coarse filter, precision filter, activated carbon, total investment still saves money. Plus oil-flooded machines are mature technology. Low failure rate. Simple maintenance. Any random compressor repair tech can handle it.

Oil-Free Machines

Argument for oil-free machines is also plenty compelling: risk. Oil separator element has a lifespan. Normal use, three to four thousand hours and it should be changed. Problem is many factories don't change on schedule, or change to cheap knockoff elements. Once oil separator element ruptures, massive oil mist blasts downstream. Oil removal filters behind it simply can't handle this kind of shock load.

A Taiwanese chip packaging factory, had an incident in 2019. Oil separator element broke without anyone noticing. Didn't get found until wire bond defect rate spiked on the packaging line. Whole line shut down four days for cleaning. Batch of wafers scrapped. Customer claim amount was enough to buy a dozen oil-free machines.

Oil-free compressor — Water-lubricated and dry oil-free screw compressors for electronics applications

From technical standpoint, oil-free machines really are the safer choice. Water-lubricated screw machine compression chamber only has water. Dry oil-free screw machine, screw surfaces have Teflon coating, no lubricating fluid at all. Eliminates oil contamination possibility at source. Atlas Copco AQ series and Gardner Denver Ultima are water-lubricated representatives. Ingersoll Rand Sierra and Sullair DSP are dry oil-free representatives. Electronics factory installed base for all of these is quite large.

Water-lubricated machines have one hassle: water quality management. Machine has conductivity requirements for water. Too high affects bearings. Need water treatment system. Northern factories in winter also need freeze protection. Shutdown must drain water completely. Dry oil-free machines don't have these worries. But discharge temperature is high. Energy efficiency slightly worse than water-lubricated. Electricity cost year after year is also cost.

Which to choose depends on specific situation. Small volume, tight budget, just doing general electronics assembly, oil-flooded machine with good aftertreatment can get by. But elements must be changed on schedule. Don't skimp on that money. Chip packaging, optical components, medical electronics, these high-end applications, get oil-free machines no question. Oil contamination incident costs are too enormous.

Dew Point Parameter

-40°F pressure dew point is standard requirement for electronics factories. Chip fabs want -94°F. Refrigerated dryers can't reach these numbers. Must use desiccant dryers.

Desiccant dryer regeneration method affects operating cost. Heatless regeneration simplest. Two towers alternating operation. Regeneration uses product air for purging. Air consumption around 15%. A compressor producing 350 CFM paired with heatless desiccant dryer, equals 53 CFM of air purely wasted on regeneration. When volume is small, doesn't matter. Volume gets big, this bill is substantial. Micro-heated regeneration adds heater. Air consumption drops to around 7%. Blower heated regeneration can push air consumption below 2%. Equipment expensive. But large factories doing long-term math figure it's worth it.

On adsorbent, activated alumina is cheap. Doing -40°F no problem. Going to -94°F, it struggles. Molecular sieve is expensive but stronger water absorption capability, can reach lower dew point. Some manufacturers make composite bed layers. Alumina on bottom, molecular sieve on top. A compromise approach.

Adsorbent's worst enemy is oil. Gets contaminated with oil and it's poisoned. Adsorption capability drops dramatically. Regeneration can't recover it. Can only replace the entire bed. So the oil removal filter in front of desiccant dryer is absolutely critical. This money can't be saved. Seen a factory where desiccant dryer used two years and dew point started climbing. No matter how they adjusted, couldn't fix it. Finally discovered upstream oil removal wasn't done well. Adsorbent was poisoned. Replacing one bed of molecular sieve, several thousand dollars. Plus downtime. Painful lesson.

On whether -40°F is over-design, some engineers think shop temp is 70-something degrees, piping won't go below this temperature either. Dew point at -4°F already absolutely no condensation. Why chase -40°F. This reasoning has some merit. But misses one point: electronics manufacturing fears more than just liquid water. Solder paste printing is humidity sensitive. High relative humidity causes voids in soldering. Wafer must be baked to remove moisture before molding. If blowing air is humid, baking was for nothing. So -40°F wasn't randomly picked. It's a number arrived at after stepping in plenty of pitfalls.

SMT Production Line Air Source Issues

Pick and place machine is the SMT line's highest air consumer and most demanding equipment.

Nozzle system uses compressed air to create vacuum to pick up components. Orifice diameter fractions of a millimeter. Too many particles and it clogs. Clogged means either can't pick up or picks up and places inaccurately. Throw rate climbs steadily. Panasonic, Fuji, ASM pick and place machine manuals all write inlet air requirements. Particles, oil content, dew point. Three parameters, none can be sloppy.

Many factories' approach is SMT shop has its own dedicated air line. Splits off right after the dryer. Filtration grade one level higher than general shop. Some factories go further. Install a small filter at each pick and place machine air inlet. Called POU filter. Prevents pipe secondary contamination.

Secondary contamination issue frequently gets overlooked. From treatment system to use point, how many pipes, elbows, valves, fittings does air pass through? All these spots can harbor filth. Especially old factories. Piping used over ten years. Inner wall condition, nobody can say for sure. No matter how clean the main line treatment is, reaching the endpoint might still carry dirty stuff in. POU filter elements aren't expensive. Few bucks each. Install one for peace of mind.

Piping Material Selection

Carbon steel pipe is banned in electronics factories. Carbon steel rusts. Iron rust particles ride the airflow. Filters can't catch all of it. Will continuously contaminate downstream equipment. Old factories doing air source upgrades, first thing is replace the piping.

Stainless steel pipe is standard. 304 grade sufficient for general applications. 316 has better corrosion resistance. Highest cleanliness requirement locations use electropolished stainless steel pipe. Inner wall roughness Ra below 16 microinches. Shiny as a mirror. Dirt can't adhere.

Installation matters more than material selection. Stainless steel pipe welding needs TIG, with argon purge inside the pipe. Otherwise weld seam oxidizes. Inside is all weld spatter. No amount of blowing cleans it out. Weld one joint, inspect one joint. Endoscope goes in to look. Problem found, rework immediately.

After installation do a blowout. High flow air pushes out residual debris inside pipe. End point checked with white silk cloth. Some construction crews aren't careful. Blowout done as formality. Acceptance inspection isn't thorough either. After commissioning, problems start showing up.

Aluminum alloy quick-connect piping has been used more and more in recent years. Advantage is fast installation. No welding needed. Later modifications convenient. Joints sealed with O-rings. Gas-tightness is decent. Cleanliness slightly lower than welded stainless steel. General electronics assembly factory, it's good enough. Chip factories still mainly welded stainless steel.

Filter Configuration

Multi-stage filtration is standard practice. Coarse to fine, one stage at a time. First stage coarse filter with cyclone separator catches liquid water and large particles. Second stage precision filter does 0.3 to 1 micron. Third stage ultra-precision filter does 0.01 micron. Fourth stage activated carbon adsorbs gaseous oil molecules.

Elements need to be changed on time. Everyone understands this principle. Executing it, many factories can't manage. Some factories use elements until differential gauge goes red before changing. Some factories don't even have differential gauges, going purely by feel. Element clogged, resistance big, compressor energy consumption rises. That's the mild version. Clogged too badly, element gets punctured by differential pressure. Everything that should have been caught runs downstream. Filter equals not installed. Few hundred bucks per element. Saving this money really isn't worth it.

Chip Packaging Special Requirements

Chip packaging compressed air requirements approach wafer fabrication levels.

Wire bonding process. Gold wire diameter 0.8-1.2 mil. Bond head driven by cylinder runs back and forth between chip and lead frame. Anything dirty enters the cylinder, motion precision can't be guaranteed. Bond position offset, bond strength insufficient, both are batch defects. Mold encapsulation, lead trimming, test sorting, back-end processes have relatively relaxed requirements. But still higher than general electronics assembly.

Packaging factory air source systems are often independently designed. Separate from general shop. Piping uses electropolished stainless steel. Terminal filters use 0.01 micron or even higher grade. Some factories add inline particle counters before critical equipment. Real-time monitoring air cleanliness. Exceeds limit, alarm triggers.

Particle counters aren't cheap. Small factories can't justify buying them. Use white silk cloth visual inspection instead. White silk cloth catches particles visible to the naked eye. Submicron level, can't see at all. Accuracy is pure luck. If you can afford it, get online monitoring equipment. Dew point meter, particle counter, oil content detector. Problem happens, you find it immediately. Much easier than after-the-fact investigation.

Cleanroom Air Supply

Cleanrooms need positive pressure maintained. Must continuously supply makeup air. This air can't just be randomly tapped from shop piping. Cleanliness must match cleanroom classification.

Proper approach is cleanroom supply air gets its own dedicated piping. Splits off from dryer outlet. Piping standard higher than general shop. Some factories cut corners. Cleanroom inside and outside share one piping system. Only difference is cleanroom equipment inlets have one extra terminal filter. This approach can work. But terminal filter burden is heavy. Elements changed frequently. Long-term cost may not actually save. And if one day someone forgets to change the element, cleanroom air quality has no guarantee.

Static Electricity Hassle

Compressed air with dew point below -40°F, relative humidity typically under 10%. Blowing it out inevitably carries static. Static damage to electronic components is sometimes latent. Doesn't test abnormal leaving factory. Problems show up after some use.

Dealing with static, several approaches: install ionizer bars or ion guns at use points, blow air and eliminate charge simultaneously. Use anti-static material for air hoses and fittings. Equipment properly grounded. Some factories within process allowance make dew point not so extreme. -40°F is enough, don't chase -94°F. Leave a little humidity to help static dissipate. This depends on specific process. Can't generalize.