This is just an Excerpt from a larger document, click here to view the entire document.Manufacturing Emulation
Procedures are required today to not only procure acceptable parts and materials, but also to ensure that the process steps from shipping to assembly do not destroy good components. It is not enough to qualify components to a standard qualification procedure (i.e., MIL-STD-883, TM5004 & TM5005) because some current assembly processes impose greater stress than those used previously. A classic example is surface mount technology, which uses soldering processes (i.e., vapor phase, infrared heating) that provide a very fast temperature transition to 220°C, creating a thermal shock which is greater than that used for component verification testing. This is exemplified by the use of plastic surface mount packages which, in some cases, have resulted in the "popcorneffect." This refers to a phenomena in which moisture is absorbed by the plastic encapsulant material and, upon exposure to the soldering thermal shock, the moisture vaporizes, causing the package to delaminate or crack due to the resulting high internal pressures.
In order to determine if components will perform reliably after exposure to handling and assembly stresses, a preconditioning procedure emulating these processes should be developed and applied.
