7. Process control & metrics: monitoring
Relying solely on final end-of-line yield metrics is a lagging indicator; by the time the reported yield drops, the scrap has accumulated and the financial impact is already realized. To thrive in high-reliability manufacturing, we must monitor and react to leading indicators in real-time using
In this chapter, we detail the daily application of formal control charts (X-bar/R, p-charts) to relentlessly monitor all defined Critical-to-Quality parameters. By clearly differentiating between inherent common cause variation and assignable special cause variation, Engineering and Production teams are empowered to safely intervene and correct the equipment before a drifting process shifts out of its required specification limits.
- 7.1 Statistical process control: cₚ & cₚₖ
SPC is the financial difference between merely inspecting quality **in** at the end of the line (reactive waste) and actively building quality **in** at each step (proactive engineering). Inspection o...
- 7.2 Operational metrics: FPY, RTY, CoQ & review cadence
In high-volume, high-reliability manufacturing, standard end-of-line "Yield" is a lagging metric. A production line reporting a 99% Output Yield can still be financially unviable if 40% of those units...
- 7.3 Test process quality: ICT/FCT & retest limits
Testing is an appraisal process designed to verify the hardware. A test station does not fix poor quality; it merely identifies functional units while segregating failures. In high-reliability EMS, on...
- 7.4 Layered process audits
End-of-line inspection checks the physical product; LPAs check the underlying **process**. A seemingly perfect product built by an undocumented process introduces significant risk in the field. **Laye...