Читать книгу Design for Excellence in Electronics Manufacturing - Cheryl Tulkoff - Страница 47

The old, traditional Western approach to reliability growth and modeling used a design‐build‐text‐fix (DBTF) cycle. This was essentially a trial‐and‐error approach where the product was designed, prototypes were tested, failures/defects were discovered, corrections were made in the design, more prototypes were made, etc. Traditional OEMs spent almost 75% of product‐development costs on this approach (Allen and Jarman 1999). Shortcomings of this approach include:

 Design issues are often not well defined.

 Early build methods do not match final processes.

 Testing doesn't equal actual customer usage.

 Improving fault detection catches more problems but causes more rework.

 Problems are found too late for effective corrective action; quick fixes are often used.

 Testing more parts and more/longer tests are “seen as the only way” to increase reliability.

 OEMs cannot afford the time or money to test to high reliability.

In DBTF‐based product development and validation process, reliability growth continued well into production and the field and was a highly reactive process. Using this approach, design engineers worked independently, then transferred designs either “over the wall” to the next department or external to the company. Eventually, manufacturing had to assemble a product not designed for its processes. Since it was too late to make changes, manufacturing struggled to meet yield, quality, cost, and delivery targets. This required trial‐and‐error crisis management, followed by launch delays, and then quality and reliability issues. This approach has fallen out of favor and been replaced by a combination of concurrent engineering and reliability physics modeling approaches. The newer approaches have the goal of simultaneously optimizing the design across all the DfX disciplines.