SMT Adhesives: Evaluating the Material's Critical Parameters

Category: Adhesives and Dispensing
Post Date: July 20, 2004
Author(s): Steven J. Beckman, Rick Labbee, Suzzette Cowan of Lockheed Martin Commercial Electronics and Frank Murch, Douglass Dixon, and Steve Marongelli of Universal Instruments

Description
The use of adhesives in the SMT process is often overlooked. Adhesives are largely viewed as a temporary process to hold components on the board until the solder joint is formed. The yield improvements that can be made in dispensing and through the correct selection of adhesives can be dramatic. When Lockheed identified adhesives and dispensing as a key area for process improvement the methods for evaluation and the critical parameters were largely undocumented and poorly understood. Lockheed evaluated the information and resources available in the industry and identified Universal Instrument's process abilities and laboratory as a key resource. Universal Instruments and Lockheed jointly studied the process as a whole and the effects of various process and material parameters at Universal Instrument's facilities in New York and Lockheed's facility in New Hampshire. This report describes the test regimen we used to evaluate commercial adhesives and make selections from a basis of sound engineering principles. The two companies studied three broad categories of SMT epoxy performance: dispense capability, mechanical strength and environmental robustness. Each of these areas produced results that improved overall yield and process stability.

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