Consigned Kits against Turnkey Purchasing on the Same Board
Split procurement saves component markup fees on high-cost ICs but demands strict kit audits, overage management, and clear contract defect attribution rules.
Cpk Transfer Efficiency
Process Capability
Statistical capability indices quantify how consistently a stencil printing process deposits solder paste onto printed circuit board pads relative to specified volume tolerances. SMT solder paste deposition determines solder joint quality and requires tight statistical control. Cpk transfer efficiency measures the process capability index of deposit volume divided by theoretical stencil aperture volume across an entire production run.
A value above 1.33 confirms that the printing process operates predictably within defined upper and lower volume limits.
Statistical Method
Automated solder paste inspection systems measure deposit height, area, and volume for every PCB pad after stencil printing. The calculation evaluates the difference between the mean transfer efficiency and the nearest specification limit, divided by three times the standard deviation. A low standard deviation indicates high process stability.
If solder paste viscosity changes due to ambient temperature shifts, the mean transfer efficiency drifts toward the specification limit, lowering the capability index.
Control Limit
Stencil apertures for fine-pitch surface mount devices require consistent paste release to prevent bridging and solder starve defects. Process engineers use the index to validate stencil foil coatings and squeegee blade parameters before approving full volume production. Cpk transfer efficiency applies only to the solder paste deposition phase and does not evaluate component placement accuracy or reflow thermal profiles.