Wave Solder Process Improvement Project Example

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In today’s high-tech world, almost any household gadget has some basic electronics circuitry built into it – refrigerator, coffee maker, oven, toothbrush, vacuum cleaner, toaster or alarm system. In this case study, a Six Sigma team improves a manufacturing process whose purpose is to "glue" – via a process called soldering – electrical components to a circuit board.

In the current process, 100 percent of all final printed circuit boards (PCBs) are functionally tested. Through this testing, 99.9 percent of solder defects are detected and subsequently reworked, fixed or scrapped. Because nearly all solder defects are addressed before products reach the customer, these defects do not represent a significant customer concern. They are, however, quite costly to the company.

Due to an unacceptably high level of solder defects, the company spends $500,000 annually on the poor performance of the wave soldering process, including excessive operating costs, poor quality rework, reduced yield and extra labor.

The manufacturing leaders tasked a Six Sigma project team to improve the performance of the process to reduce defects and consequently reduce the need for and dependency on indirect quality support personnel called the "solder specialists." Additionally, and most importantly, they requested that we implement proper performance controls to ensure ongoing process capability. Two relevant project metrics were defined to support the initiative: wave solder rolled throughput yield and number of supporting indirect personnel. If our team could improve the process, reduction in labor costs would yield $300,000 in annual cost savings.

This project utilized both Lean and Six Sigma tools and demonstrated the complementary nature of the two methodologies. Reworking of PCBs and inefficient use of production personnel are examples of waste that can and should be eliminated under the directive of Lean. Six Sigma helps by improving the process to allow for this waste elimination.

Through the DMAIC improvement project, the team reduced solder defects by 92 percent and saved the company $300,000 annually.