Solder Ball Removal and Acceptance Criteria A solder ball is a small sphere of alloy on the board surface that is not part of a joint, and the question it raises is whether it can move. A ball that is held by the mask is a cosmetic defect and one…
Solder Paste Jetting: Preparation, Placement and Process Control Jetting deposits solder paste without a stencil, driving small dots of material from a nozzle onto the pad at high speed. The appeal is obvious: no foil to order, no squeegee pressure to tune, no paste left on a stencil web. The…
Selective Soldering Nozzle Geometry and Maintenance Selective soldering exists to join the through hole components that reflow cannot reach, without the thermal and mechanical exposure of a wave solder pot. The nozzle is the tool that delivers heat and alloy to one joint at a time, and its geometry decides…
Production Sample Retention Policy Sample retention is the practice of keeping a unit from a build so that a question asked months later can be answered by examining the product rather than by rebuilding it. It is inexpensive, it is frequently omitted and it is disproportionately valuable when a customer…
Defect Code: Defect Coding Scheme Design A defect coding scheme is the difference between data and a list. With a consistent structure, the codes support a pareto, a trend and a root cause analysis; without one, the records accumulate as free text that nobody can aggregate. The scheme does not…
Inspection Lighting and Magnification Choices An inspector finds what the light shows and the magnification resolves. Both are equipment decisions, and both are usually made once and then left as they were installed, which is why a defect that is visible under one light becomes invisible under another. What the…
Pick and Place Machine Maintenance Schedule A placement machine is a set of mechanical axes, a set of feeders and a vision system, and each of them drifts. Maintenance is the schedule that keeps the drift inside the tolerance the placement accuracy depends on, and the schedule is set from…
Solder Joint Thermal Fatigue and Its Drivers A solder joint fails in thermal fatigue when the strain from a temperature change accumulates faster than the alloy can accommodate it. The drivers are the geometry, the materials and the cycle itself, and the four are usually examined together because the effect…
Line Stop Escalation and Recovery A line stop is a decision as much as an event. Continuing to build while a problem is unresolved produces suspect product that has to be sorted later; stopping the line loses output and may lose the shift. The framework that makes the decision consistent…
Surface Finish Thickness Measurement on PCB A surface finish is specified as a thickness because the thickness is what provides the protection during storage and what forms the joint during assembly. Measuring it is easy with the right instrument and misleading with the wrong one. What the Thickness Provides The…
