Surface Mount International Conference Proceedings


Authors: Leo Anderson
Company: IBM,
Date Published: 9/10/1996   Conference: Surface Mount International

Abstract: As Plastic Ball Grid Array (PBGA) components proliferate, card assembly questions arise about the robustness of the second level (module to circuit card) attachment process. Attachment processes are subject to variation from many sources and the acceptance of a new component may depend on its sensitivity to process variation. Components that exhibit high initial attachment solder joint yields will likely be adopted more quickly than lower yielding components. Other questions surface about the long term reliability of the solder joint between the ball and the card pad after the module is attached to a card. This paper addresses process sensitivity aspects of the second level attach process and solder joint reliability questions. These questions were addressed in two different assembly builds at IBM in Austin during the development of IBM’s PBGA capability. Each of these major assembly builds was composed of smaller builds that come late with the different assembly processes available. Table 1 describes the card and module content of the designed experiment build, the first major assembly build. Included in the table is a matrix of testing that was applied to these assemblies, The second major build was assembled under optimum process conditions. After assembly, forced reworks were performed on selected sites. Some sites were reworked once and others were reworked twice. After rework all the cards were subjected to Accelerated Thermal Cycle (ATC) testing. Table 2 describes the build content which includes the number of forced reworks of cards from each of the assembly processes.

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