Ph.D. Thesis Defense by Ruijun Chen

(Dr. Daniel Baldwin, advisor)

"Fixturing Analysis and Synthesis for Flexible Circuit Board Assembly"


The proposed research investigates fixturing technologies for flexible circuit board assembly. Flexible circuit and thin flexible circuit board assembly technologies are some of fastest developing technologies in the electronic manufacturing industry. However, state-of-the-art Surface Mount Technology (SMT) equipment utilizes tooling designed to handle rigid circuit board assemblies. Thin flexible circuit boards such as PC Cards and flex circuits pose a major problem for SMT assembly requiring specially engineering dedicated tooling to fixture the substrates during assembly. The problem lies in the associated nature of the flexible substrate when subjected forces.  During solder paste printing and component placement, thin flex circuit boards experience forces normal to the board that result in in-plane transverse displacements and normal deflections.  The solder reflow process further complicates the issue due to the thermo-mechanical warpage induced during the thermal excursion. The proposed research seeks to develop underlying theories and analysis methodologies for optimizing assembly fixturing of thin flexible circuit boards. The first step is to develop a mathematical model tailored for predicting in-plane transverse displacements and normal deflections of thin flexible substrates subject to normal typical assembly. The second step is to theoretically investigate the locating principle, called network-locating principle, and optimization algorithm for determining the optimum fixturing configuration of thin flexible substrate assemblies by applying finite element analysis and mathematical programming technique. The final step of this work will be to demonstrate the design of optimum fixturing configurations on SMT and/or Flip Chip assembly equipment for a series of thin flexible substrate assemblies as case studies.  The primary contribution of this research is to establish a locating principle for optimal fixturing system design of flexible substrate assembly based on the large deflection plate model specially tailored from von Karman plate theory and other analysis techniques.