SMT007 Magazine

SMT-June2019

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64 SMT007 MAGAZINE I JUNE 2019 In this column, I will discuss why zero defect may be a desirable goal but not realistic. I will share some industry data to prove my point, and you can use that data to benchmark defect levels in your products. I will also address the choices we make about selecting components that have a big impact on the level of defects you should expect. I do want to make one thing clear. It may be unrealistic to have zero defect in products right after reflow, but we do need zero defect in products that we ship to the customer. That is the very basic reason for inspection, test, and repair even though they are non-value- added process steps, but they are necessary steps. After all, you don't want your custom- ers to discover those defects at their site or in the field. In next month's column, I will talk about bad and good defects. Yes, there are bad and not-as-bad defects even though all defects are unacceptable. Heads up: Almost all companies have bad defects in their products. They can escape despite the rigorous test and inspection regimes you may have. Why Do We Not Have Zero Defect? Most companies attempt to achieve higher yield in SMT products through trial and error at considerable expense and frustration. Even though we have been manufacturing SMT products in high volume for more than three decades, less than 10% of companies have first-pass yield of more than 90%. That means 90% of companies have much lower first-pass yield. I am using 1985 as the baseline for high-vol- ume motherboard production. Some of you may remember the first serious PCs with Intel 286—a very fast 6-MHz processor. It cost me USD $5,000 with a 20% Intel employee dis- count. I do acknowledge that I went overboard Benchmarking Defect Levels in Your Products SMT Solver by Ray Prasad, RAY PRASAD CONSULTANCY GROUP

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