The communications industry has gone through an evolutionary change in the past decade. Products are becoming increasingly complex due to the need for higher bandwidth and increased speed. Increased functionality of products has resulted in highly complex Printed Circuit Assemblies (PCAs), particularly with a large number of Ball Grid Array (BGA) packages. These PCAs are subject to multiple assembly process steps and testing procedures. Many of these processes, if not controlled carefully, induce a variety of stresses on the assemblies. These stresses induce failures at the solder joint level that may be detected during the test process or worse, result in failures in the field. This study provides a detailed root cause analysis of intermittent failures on one BGA package. Analysis includes a) Printed Circuit Board (PCB) design review, b) PCB fabrication process review, c) incoming PCB inspection including warpage measurements, d) assembly process study and e) test process evaluation. The results of the study indicate that In-Circuit Test (ICT), used to isolate manufacturing related defects on PCAs, causes some amount of stress on the solder joints due to the mechanical nature of the test. In some instances, lack of very critical controls can cause excessive localized stress, which leads to premature solder joint failures. Thorough review of the test probe density and ICT fixture design can prevent the occurrence of these failures.
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