Testing methodology for reflow soldering process compatibility evaluation of surface mount technology

Surface Mount Technology (SMT) is one of the most significant developments in the electronics manufacturing industry. The reflow soldering process for surface mount technology is quite different from the traditional wave soldering. A viable testing method for evaluating the SMT reflow soldering process is critically needed, especially now, with the lead-free solder alloys currently being required in the manufacturing industry.;This study proposes a new concept; reflow soldering process compatibility (RSPC), and a test methodology for RSPC evaluation. RSPC is a comprehensive measure of how well the process parameters work together. These parameters include surface finishes, surface conditions, solder alloys, flux types and reflow temperature profiles. Each of these parameters can be controlled in the proposed RSPC test to provide the evaluations of different combinations of test conditions. The purpose of RSPC test is to identify the process combination that is best for a particular set of manufacturing requirements.;RSPC tests are recommended in production, whenever the process parameters need to be changed. These tests can help decide what could be the best combination for the new manufacturing process without stopping and trying different combinations on the production line. This will considerably reduce the cost and time for process changes.;Summary of original contributions to technology. A new concept, reflow soldering process compatibility (RSPC), is introduced this dissertation.;A feasible test methodology for evaluating RSPC, and a quantitative index to measure RSPC called process compatibility index (PCI) are proposed.;PCI is computed by combining two measurable quantities, molten solder spreading coverage and rate. Offset printing technique on the test surface enables the test equipment to monitor the molten solder spreading on the test surface.;The molten solder spreading images are filtered and analyzed sequentially to give the solder spreading coverage and rate, by utilizing the image processing and digital filter algorithms.;The PCI is calculated and reported by the software, and the test procedures are automated by implementing the image processing and digital filter algorithms using C++ and object-oriented design.;The PCI test results for five different surface finishes under different steam age conditions using tin-lead or lead-free solder pastes with no-clean flux are presented in this study. Several hundred of proof-of-principle experiments have been conducted.