The selection of the proper resin system for a molded PWB or electronic package must take into account considerably more parameters than simply the cost of and the ability of the polymer to fill the tooling. Molding of an electronic package is only the initial step in a multi stage sequence to produce a functional PWB or interconnect device.

It is of extreme importance that a manufacturer of molded electronic packages understand not only the fabrication properties of a resin, but also those mechanical, thermal, and chemical requirements of the circuit application and assembly operations.

A specific circuitry application process will usually require a specific set of substrate characteristics. These performance characteristics may relate to platability, thermal stability, modulus, compressive strength, or even adhesive bondability for a given procedure. The substrate requirements for several popular circuit application methods is reviewed.

Assembly presents perhaps the most demanding area of resin performance in electronic package or PWB fabrication. The thermal stresses encountered in wave soldering and vapor phase reflow will quickly differentiate among current engineering resin offerings. The importance of controlled moisture absorption and high temperature modulus retention is explored in addition to end use environmental factors which can be of special concern.