7.2 Power Quality & Grounding

Modern SMT equipment and test instrumentation require "clean" power to operate within tolerance. Electrical noise, voltage sags, and ground loops are invisible drivers of "No Trouble Found" (NTF) test failures and erratic machine behavior. This section defines the electrical architecture required to isolate sensitive logic from heavy inductive loads.

7.22.1 CompressedThe AirSingle StandardsPoint Ground (ISOStar 8573)Topology) 

To prevent ground loops—where current flows between two equipment grounds due to potential differences—the facility must utilize a Single Point Ground architecture.

• Why it matters:Requirement: DirtyAll airSMT destroyslines expensiveand pneumaticTest valvesRacks inmust pick-and-placereference machines.a central earth ground bar. Daisy-chaining grounds between machines is prohibited.
• The Standard:Impedance: AdoptingResistance ISOto 8573-1earth Classground must be < 1.0 Ohm.

7.2.12 Uninterruptible Power Supply (UPS) Strategy

Sudden power loss causes catastrophic failures in thermal processing equipment.

• Reflow Ovens: (orMust similar)have sufficient UPS capacity to keep the conveyor belt moving for SMT15-20 lines.minutes.
  • Particulates:Failure Mode: FiltrationIf requirements.
  • Water:the Dewbelt pointstops requirementswhile the oven is hot, FR4 substrates inside the tunnel will carbonize (Dryersburn), areand mandatory;the wateroven inheater lineselements ruinsmay actuators).
  • Oil:warp Oil-freedue compressorsto vs.lack filtration.of airflow.
• PC Control: Pick-and-place PCs must have UPS to allow for a graceful software shutdown, preventing corruption of placement programs and databases.

Final Checklist

Utility	Requirement	Criticality
Equipment Ground	Star Topology (< 1 Ohm)	High (Prevents Test Noise)
Reflow Backup	UPS for Conveyor Drive	Critical (Prevents Fire/Damage)
Voltage Stability	± 5% of Nominal	Medium (Machine Uptime)
Harmonics	THD < 5%	Medium (Motor longevity)