Model-Based Design Used by Industry for Long Time

As a counterpoint to Terry’s post from Wednesday, many parts of our industry have used “model-based-design” at least since the early ‘80s — it just was not called that. And it has been formalized in IPC documents for some time. The first industry document urging this approach was IPC-SM-785, published in November 1992. This was followed by IPC-D-279, published July 1997, which directly urged utilization of “Design-for-Reliability” (DfR) procedures — ”model-based-design” is just a new verbiage for what was called “Design-for-ilities” like “Design-for-Reliability” (DfR), “Design-for-Manufacturability” (DfM), “Design-for-Testability” (DfT), etc. and which has been bunched together as DfX— ”Design-for-Excellence.”

The models in these documents, as well as most other models, do not need validation per se, because in most cases they were developed from extensive data bases. What they do need is the determination as to the limits of their applicability. The need for recognizing, and documenting, these limits comes as the result of the temptation to use models in situations for which they were not developed, simply because no other model is available.

Indeed, it is rare, that model limitations are stated as “Caveats” with an explanation for the reasons of these limitations. It is certainly true that the situations for which the models may be misapplied did not even exist at the time of the development of the model.

I will present a webinar titled “Solder Joint Reliability for Pb-Free Solders” on September 17, 2009, and a workshop “Fundamentals in Solder Joint Reliability” on September 24 at IPC Midwest, in which I will present new models for the most common Pb-free solders based on available accelerated reliability data.

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