Type 225L PBGAs with eutectic balls are specially processed and assembled to determine the effect of ballcoplanarity on solder joint formation. A mathematical model is developed to predict the formation and shape of the joints as a function of the initial ball volume, coplanarity, and other part and process variables. The model-predicted values are in very good agreement with the observed ones. A method is also developed for characterizing the effect of PCB warpage, and sag during assembly reflow, on joint formation. The overall methodology may be used to set package coplanarity specifications that ensure acceptable solder joints.

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation.ABSTRACT -A no-clean mass reflow process for 396-pin, 324-pin and 225-pin over moulded plastic pad array carriers (OMPACs) or plastic ball grid array (BGA) is presented. Emphasis is placed on the OMPAC assembly parameters such as the design, material and process of the packages and printed circuit board (PCB), solder paste, stencil design, printing technology, pick and place, mass re-flow and inspection. Furthermore, cross-sections and the 'popcorn' effect of the OMPAC assembly are provided and discussed.

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