Original Date: 06/05/2006
Revision Date: / /
Best Practice : Optical Feedback System
Rockwell Collins’ Coralville facility developed a novel feedback mechanism using downstream inspection data to provide nearly real-time feedback to upstream processes, enabling a significant reduction in defects.
Rockwell Collins’ Coralville facility developed a novel method of improving production-line yield by using an optical inspection machine. The Coralville plant is part of an overall improvement strategy to reduce waste and defects in the production of printed circuit boards (PCBs). The process has led to many benefits that will bring Rockwell Collins closer to reduced cost and higher quality for its customers.
Production of PCBs using high-speed pick-and-place machines prior to recent improvements was prone to defects. Typically, manual and visual inspection are relied upon to find defects. Data shows that about 20% of all visual inspections can miss something, leading to errors being moved downstream in the production process. To correct these defects, the boards were sent in batches to another area to be reworked, leading to more bottlenecks. The data to track and report the defects was cumbersome at best – all of which created delays and a reactive response to solving the problems.
The Optical Feedback System (OFS) – a novel new application – was developed that addresses many of the often- seen board problems (i.e., electrical solder shorts, solder tombstones, unsoldered or missing parts, and misaligned or rotated parts). As the circuit card assemblies are processed through the system, each is optically inspected for defects. This data is fed into a database that is available to the upstream operators in almost real time, which enables the operators to make adjustments to eliminate those errors. This information adds to the experience and knowledge of the operators and engineers and can be utilized for a host of reasons. Users of the OFS Viewer system can see representations of the product as well as trend data of past populations of PCBs. Design engineers can study the effects of certain parts and part-placement variables while process engineers can use the data to improve processes and machine yields.
The benefits to this improvement were immediate. Data tracking the defects per million over the last eight years indicates a reduction of more than 70%. The move away from batch and queue toward true one-piece flow made possible by the new inspection feedback system has reduced throughput time by almost 50%.
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