Reliability, Thermal and Thermomechanical Characteristics of Polymer‐on‐metal Multilayer Boards

Wiring requirements and thermomechanical factors related to the design and fabrication of Polymer‐on‐metal constraining core PWBs are discussed. The necessity of small plated‐through‐holes for high‐density surface mount design is shown. Typical MLB constructions are shown with techniques for increasing wiring density. A design methodology for the POM construction is defined. The thermomechanical properties of copper‐Invar‐copper and the interactions of the MLB are described. The reliability of small PTHs is measured over a wide range of module constructions. Sixteen mil. diameter PTHs are reliable if the MLB thickness is kept below 0·040 inch. Through‐substrate PTHs make reliable side‐to‐side interconnections.