SMT—Wave Soldering, Adhesives and Mixed Technology

With the increased functional density requirements of military avionics it is impossible to meet these demands without utilising Surface Mount Technology. The Electronics Manufacturing Technology Group at Boeing Military Airplanes is working to meet SMT design requirements through research and development of processes, materials and equipment for all variations of SMT. Basic processes have been established for both 100% SMT and mixed technology. However, the Group continues to advance its capabilities by evaluating and improving all aspects of SMT manufacturing. A description of the initial thrust into Type III SMT as well as subsequent development is given. This includes a description of the evaluation of Surface Mount Component (SMC) attach adhesives comparing the adhesive used initially with others available by examining the various criteria involved in selecting the appropriate one for a given process. Also, a discussion follows of factors involved in determination of Mil‐spec. passive SMCs which are compatible with wave soldering. Included in the evaluation of passive SMCs is a comparison of the compatibility of the wave solder system in use with the component industry's recommended temperature profiles through an analysis based on in‐house testing to determine the actual component endurance to solder system heating. Throughout this discussion emphasis is placed on a systematic guided approach to examining process development.