2.3 Compressed Air Standards (ISO 8573)

Compressed air is the "Fourth Utility," but unlike electricity or water, you manufacture it on-site. If your air quality fails, you are injecting pollution directly into your precision equipment.

Pneumatic actuators in pick-and-place heads and screen printers operate at highmillisecond speeds with tight tolerances.speeds. Contaminants in(water, theoil, compressed air supplydust) cause Stiction—the friction that kills repeatability. A 0.1-second valve stiction,delay nozzleturns clogging,a andperfect oilplacement depositioninto ona optics.skewed Thisdefect.

chapter

The mandates compliance with ISO 8573-1 airStandard purity(Class classes.

1.2.1)

The

Do not ask for "Clean Dry Air." That is a subjective wish.

Demand ISO 8573-1 Class 1.2.11. Standard 

Electronics manufacturing requires air thatThis is dry,the oil-free,engineering anddefinition particle-free.of "clean" for electronics.

• Particulates1. Solids (Class 1):

  • Limit: < 100 particles (0.1 – 0.5 micronµm) sizeper limits. Filters must capture dust to prevent abrasive wear on solenoids.m³.
  • The Risk: SMT vacuum nozzles have internal filters with 10 µm mesh. Class 1 particulates pass right through and grind against the solenoid spool, causing premature wear.

  2. Water (Class 2):

  • Limit: Pressure Dew Point (PDP) must be ≤ -40°C.
    • Why:The Physics: WaterAs vapor condenses ascompressed air expands inat the machinepoint tools.of Liquiduse, waterit cools rapidly (Joule-Thomson effect). If the dew point is not low enough, invisible vapor turns into liquid water.
    • Consequence: Water washes away lubricantsthe "lifetime grease" inside pneumatic cylinders, leading to rust and rusts internal components.seizure.

  • 3. Oil (Class 1):

    • Limit: Total oilOil contentContent ≤ 0.01 mg/m³.
    • The "Silent Killer": Oil mist coatsatomizes at the exhaust port of the machine. It settles on optical sensors and camera lenses, causingslowly blinding the machine's vision systemsystem.
    • Control: failures.Use Oil-Free compressors. If using oil-injected screw compressors, active carbon towers are mandatory.

    Nitrogen (N2) Generation

    Nitrogen is an expensive necessity for Reflow, Wave, and Selective Soldering. It displaces Oxygen to prevent oxidation, widening the process window for wetting, especially with OSP (Organic Solderability Preservative) finishes.

    
    

    Purity Standard (EMS Requirement):

    • Target:

      For soldering processes requiring inert atmospheres (to reduce oxidation and improve wetting):

      • Purity: 99.99% (4N).
      • Context: minimumThis forpurity OSPis finishes;sufficient 99.999%to prevent oxidation on copper pads and component terminations during the thermal spike. Higher purity (5N) is unnecessary cost for waferstandard bumping.SMT/Through-hole assembly.

      Process Control Logic:

      • If Reflow O2 ppm > 1000 -> Then Stop the conveyor. Solder joints will exhibit "Grapeing" or Head-in-Pillow defects.
      • O2 Monitoring:If OxygenN2 sensorstank pressure < 4 bar -> Then Alarm immediately. Low pressure allows air ingress into the oven tunnel.

      Pro-Tip: Leaks are money evaporating. Install flow meters on the main N2 line. If flow exists when production is idle (weekend), you have a leak. Find it.

      Filtration Architecture

      You cannot filter a problem away at the end of the pipe. You must treat it in thestages.

      reflow
      1. Compressor tunnelRoom: mustWater activelySeparator control-> N2Refrigerant injectionDryer -> Coalescing Filter.
      2. Point of Use (Machine): Desiccant Dryer (to maintainhit <-40°C) 1000-> PPMActive O2Carbon concentration.(Oil) -> Dust Filter.

    Final Checklist

    UtilityParameter	StandardSpecification (ISO 8573)	Impact ofCritical Failure Mode
    Air Particulates	ISO Class 1 (0.1 – 0.5 µm)	CloggedValve Vacuum/ NozzlesCylinder abrasion
    AirWater Moisture(Dew Point)	ISO Class 2 (≤ -40°C PDP)C)	Rusted SolenoidsRust / StictionLubricant Washout
    AirOil OilContent	ISO Class 1 (Oil≤ Free)0.01 mg/m³)	ContaminatedLens/Sensor Vision SystemsFogging
    NitrogenN2 Purity	99.99% (4N)	Oxidation / Poor Wetting
    Filter Service	>Based 99.99%on Purity∆P (Pressure Drop)	Poor Wetting / Head-in-PillowLogged