Fine Lines in High Yield (Part CXXVI): Troubleshooting the PWB Fabrication Process

摘要

Process engineers in charge of increasing the overall yield of a PWB fabrication process need the tools to track yield trends and to assign probable cause to defect types. Without such tools any process change intended to improve yields would be a stab in the dark. The effectiveness to improve yields of any process change could not be measured. "Yield by AOI" inspection is a common way to track innerlayer yields. Basically, the AOI compares the actual board with a perfect board ("golden board") and applies programmed pass/fail criteria to any observed deviation ("event") of the actual circuit pattern from the perfect pattern to distinguish between good boards and scrap.