6.2 Preventive Maintenance (PM) Planning

FacilityPreventive downtimeMaintenance is productionnot downtime.a suggestion; it is a rigid contract between Engineering and Operations. In high-precision electronics manufacturing, facility systems are not passive infrastructure but active process variables. A failure5% drop in compressed air filtrationpressure haltscan cause a pick-and-place nozzles;nozzle to drop a lapseBGA incomponent. ESDWe grounddo maintenancenot compromisesmaintain component integrity invisiblesystems to visual"look inspection.good"; Thiswe chaptermaintain mandatesthem to stabilize the preventive maintenance (PM) schedules and technical actions required to guarantee system reliability andmanufacturing process stability.window.

Electrical Distribution & UPS

UnplannedDirty power interruptionscorrupts andlogic. "dirty"Voltage powersags cause logic resets inunexplainable SMT equipmentresets and corrupt reflowserver profiles.databases.

Maintenance

Thermographic focusesInspection on(IR thermal integrity and backup reliability.

Scan)

• ThermographicFrequency: InspectionAnnual.
• Action:: Conduct infrared (IR) scanning ofScan all distribution panels, switchgear,panels and bus ducts annually.
  • Mandate: Investigate and re-torque any connection showing aunder >5 40% load.
  • If Delta T is > 5˚C rise(above overambient) ambient-> orThen Schedule torque verification within 48 hours.
  • If Delta T is >2 20˚C variance-> betweenThen phases.Immediate Shutdown and Repair.

  UPS Battery Health

  • Frequency: Quarterly.
  • UPSMeasure: Systems:
    • BatteryInternal Impedance: Measure internal impedance of individualevery batteryblock.
    • If blocks quarterly. Replace entire strings if impedanceImpedance deviates > 30% from baseline.baseline -> Then Replace the entire string.
    • TransferPhysics: Test:Mixing Verify static bypass switch operationnew and offlineold transferbatteries speedsdestroys annuallythe tonew ensureones via unequal charging currents.<10ms transition.
  • Grounding: Inspect main earthing pits and bonding cables annually. Clean oxidation from busbars and retighten mechanical lugs to maintain low-impedance paths.

  Compressed Air Systems (ISO 8573 Class 1.4.1)

  Pneumatic systemstools require energy, not water. Moisture acts as a solvent, washing away internal lubrication in SMTsolenoid linesvalves (solenoids,and vacuum generators) require air that is mechanically clean and dry. Maintenance prevents oil carryover and moisture saturation.generators.

  Filtration Logic

  • FiltrationMonitor::
     Differential Pressure (∆P).
    • Pre/Post FiltersIf: Monitor∆P differential pressure gauges weekly. Replace elements immediately if differential pressure exceeds> 0.7 bar (10 psi) or every-> 6Then monthsReplace filter element immediately.
    • Constraint: Never bypass a clogged filter "just to keep running." This injects contaminants downstream that require weeks to purge.

    Oil Analysis,

    whichever
    • Frequency: comes first.Quarterly.
    • Auto-Drains: Test zero-loss drains on receiver tanks and dryers weekly to ensure condensate ejection is functional.
  • Refrigerated Dryers:
    • Condenser Coils: Clean condenser fins monthly using compressed air to prevent high-pressure trips.
    • Refrigerant: Check sight glass for moisture indication and refrigerant levels monthly.
  • CompressorTest:: SampleTotal oilAcid quarterly for total acid numberNumber (TAN) and particulateParticle count.Count.
  • Rule: Change oil and air/oil separators based on hourschemistry, runnot (typicallyjust hours. Acidic oil eats air-end bearings.4,000 – 8,000 hours).

  Pro-Tip: Verify "Zero-Loss" drains actually work. A stuck open drain wastes $2,000/year in energy. A stuck closed drain floods the dryer.

  HVAC Hardware MaintenanceIntegrity

  WhileThe setpointsBuilding areManagement coveredSystem in(BMS) Environmentalcontrols Control,the setpoint, but the hardware mustdelivers bethe maintained to hold those targets without oscillation.reality.

  Fan Belts & Drives

  • Air Handlers (AHU)Action::
    • Belts: Check drive belt tension monthly.
    • If Replacebelt is "glazed" or cracked -> Then Replace.
    • Risk: Slipping belts showing cracking or glazing. Improper tension causes fan speed fluctuation andcause airflow instability.oscillation, disrupting the laminar flow required in cleanrooms.

    Sensor Calibration

    • Frequency: Annual.
    • CoilsStandard:: ChemicallyNIST-Traceable clean evaporator and condenser coils semi-annually to maintain heat transfer efficiency.
    reference.
  • SensorsIf: Calibrate wall-mounted temperature and humidity sensors annually against a NIST-traceable reference standard.
    • Drift Limit: Recalibrate or replace sensors driftingis >2% RH0.5˚C or >0.5 C2% RH. -> Then Replace sensor. Do not use software offsets to "mask" the error.

  • Steam Humidifiers

    • Action:: Inspect steam cylinders monthly.monthly Replacefor cylinderscale.
    • If when scale buildupScale covers > 50% of electrodes or-> amperageThen drawReplace dropscylinder.
    • Logic: belowScale specification.acts as an insulator, preventing the current required to boil water, leading to low-humidity alarms.

    ESD Infrastructure Upkeep

    StaticThe controlESD systemsfloor degradeis withan wearelectrical andcomponent, dirtnot accumulation.just a surface to walk on.

    Flooring Maintenance

    • ESD Flooring:
      • Deep CleanChemicals:: ScrubUse floorsonly quarterly with ESD-specificSpecific neutral cleaner. cleaners.
      • Do notProhibition: Never use standard waxfloor orwax. sealers,It whichcreates createan insulative layers.dielectric layer (infinite resistance), rendering the conductive floor useless.
      • Surface RepairRepair:: Patch gouges or cracks immediately with conductiveConductive epoxyEpoxy, tonot maintainstandard the equipotential plane.filler.

    • Ionizers (Overhead & Benchtop):

      • Emitter PinsAction:: Clean emitter pointspins monthly.
      • Physics: Silicon dust accumulates on overheadthe needle tips ("Fuzzy Needles"), insulating the high-voltage emitter and benchtop ionizers monthly. Oxidized or blunted pins reducestopping ion output and offset balance.
      • Fan Filters: Clean foam intake filters on ionizing blowers monthly to prevent dust recirculation onto PCBA surfaces.
      production.

    Final Checklist

    SystemParameter	MaintenanceMetric Action	Frequency/ Rule	Critical Failure LimitState
    PowerElectrical Panel	IR ScanHotspot Panels	AnnuallyLimit	>5< 5˚C Rise rise over ambient
    PowerUPS Batteries	UPSImpedance Battery Impedance	QuarterlyDeviation	>< 30% deviation
    Air Filters	ReplaceMax Particulate Filters	6 Months∆P	>0.7 bar (10 psi) diff. pressure
    Air Drains	TestFunction Auto-DrainsCheck	Weekly	Blocked/Stuck Open
    HVAC Sensors	CalibrateMax Temp/RH Sensors	AnnuallyDrift	>2% RH / 0.5˚C drift
    HVAC	Tension Fan Belts	Monthly	Slippage/Glazing
    ESD Floor	CleanCleaning Ionizer Pins	Monthly	Visible Oxidation
    ESD	Deep Clean Floor	QuarterlyAgent	No Wax/SealerWax / ESD Only
    Ionizers	Emitter Status	Clean / Sharp
    PM Scheduling	Trigger	Usage (Hours) > Calendar