IN A PERFECT world, design and manufacturing teams work together to minimize defect opportunities prior to releasing a PCB assembly into production. Lessons learned over time are incorporated in design philosophy and the product and associated processes continually improved as a result. The muda, a Japanese word associated with the Toyota Production System concept of waste reduction, is eliminated prior to production start. In EMS, that is not always the case. The sheer variety of products, speed of product or engineering change order (ECO) release, or vendor-related quality issues enable defects and associated muda to slip in. While a proactive approach to minimizing defect opportunities is ideal, EMS companies also need to have a strategy for quickly identifying and eliminating the inevitable defects.
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The first step is identifying which PCBs are the main drivers of defects. At SigmaTron International's Elk Grove Village (IL) facility, a custom defect data management system has been integrated into the company's proprietary iScore Product Management System to help in achieving this goal.
Every nonconformance found in production and test is entered into this program. The assembly number, shop order number and the product's unique serial number are embedded in a 2D barcode. The user scans the product barcode and enters a specific code number to identify the defect found, the area in the product routing where the defect was found, the location of the defect per the boards' component reference location, and a brief comment, if needed.
The system is set up to alert management and supervisors to defect trends occurring within a 24-hour period on products. The system generates an email defect alert when the same defect at the same location on a product has been entered into the system at 3, 5, 10 and 20 time intervals. This permits immediate corrective action to take place.
Defect reports can be generated at will for any date range, defect type, or product assembly number for analysis. The quality and production management team...