SMT manufacturing parameters and their impact on system reliability

Producible electronic assembly using Surface Mount Technology (SMT) includes several issues which, when addressed concurrently, result in a product which can be expected to perform throughout an extended life. This paper focuses on SMT manufacturing parameters and their impact on system reliability. The data illustrate how the use of fatigue life projections can provide insight into the correct materials and processes selection and what the resultant impact on system reliability will be. Galaxy Microsystems have undertaken several programs, both commercial and military, to implement SMT as a new technology. These programs required that the designs be compatible with several printed wiring board (PWB) technologies, utilize a complex mixture of packaging approaches and be assembled using different manufacturing flows. For example, three designs resulted in 14 layer PWBs populated with standard SMT parts, fine pitch quad flat packs (QFPs) and pin grid arrays (PGAs). The paper describes the relationships between the critical parameters and the life cycle of the hardware delivered to the customer. A depot repair process that can accommodate this overall parametric mix while simultaneously reducing the impact on solder joint fatigue is also discussed