Improving SMT Yield and Reducing Defects: A Rauland Case Study

Estimated reading time: 6 minutes

Figure 3: The cost calculator considers the costs of rework, both simple and complex, the cost of wiper paper, and the cost of the solvent.

Crow's line could now run 24 print cycles before cleaning. Their AOI and ATE tests saw no reduction in quality. With a faster screen printer, a faster SMT line and a cleaner process, Crow maintained improved quality while running faster.

The Numbers

Crow thought he had found the trifecta—softer wiper paper, engineered solvents and a nanocoating. As a result, Crow delivered terrific results for Rauland: SMT-related defects were reduced by over 50%; throughput was increased by over 20%, and the company saved $1 million per year for three SMT lines. First pass yield went from 80% to 99%. The line had a 79% reduction in under-stencil wiping as the interval went from five prints per wipe to 24 prints per wipe.

Using the downloadable cost of ownership calculator Shea created for Aculon, Crow could demonstrate to management the result of his process improvement program. In calculating savings, the cost calculator considers the costs of rework, both simple and complex, the cost of wiper paper, and the cost of the solvent. Using the calculator, Crow could determine that the cost per board for simple rework was $2.30 per board compared with $34.50 per board for the cost of complex rework. In addition, the cost of paper was just $0.03 per board and the cost of solvent was $0.02 per board.

By combining the rework savings along with the reduction in paper and solvent used due to less under-stencil wiping, the annual savings demonstrated from using the calculator were considerable. In addition, as Crow’s team was not changing wiper rolls as often, he was getting an extra 52 hours—over a full shift week—of additional production a year. For his investment, Crow produced an additional 5,000 boards a year. With approximately 200 stencils at a cost of $25 an application, a total investment across all stencils is about $5,000—to save $395,000.

Crow's management recognized the magnificent work by giving him a bonus and promotion. So, what can we say, but, 'Well done Jimmy!' Here's to a job well done.

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