SMTA International Conference Proceedings


Author: Peter Borgesen
Company: Universal Instruments
Date Published: 9/12/1999   Conference: SMTA International

Abstract: The attachment of a flip chip of moderate size and pitch to an organic substrate has lost much of its mystique in recent years. A small but increasing number of companies, including several contract manufacturers, are establishing flip chip capabilities. This can, in fact, be done in a step by step fashion and with moderate investments in facilities, equipment and training. Still, since only the few can afford to simply remain conservative in today’s market, implementation of the technology will require an ongoing optimization supported by a sizable R&D organization.

Overall cost, yields and reliability are sensitive to a multitude of materials, design and process parameters and their interactions. Assembly yields depend, among other, on design, placement accuracy, substrate pad and solder mask tolerances, ball height statistics, substrate warpage, and fluxing technique. Assembly reliability varies with encapsulant and flux type, chip passivation, solder joint number and distribution, solder mask surface morphology and chemistry, laminate chemistry, substrate rigidity and pad metallurgy, and various process parameters in a rather complex fashion. All of this is exacerbated by a trend towards larger die, finer pitches and smaller standoffs, as well as the continuous development of new, improved and/or alternative materials. Observed dependencies can, however, apparently be rationalized and generalized on the basis of an understanding of the underlying mechanisms.

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