Journal of SMT Article


Authors: Ahmer Syed and Tony Panczak et al.
Company: Amkor Technologies
Date Published: 4/1/1999   Volume: 12-2

Abstract: ChipArray* is a near chip size, laminate-based ball grid array (BGA) package offered by Amkor Technologies. The package is available in various sizes and lead counts. This paper deals with the solder joint reliability of this package when mounted on the motherboard. Accelerated thermal cycle test data as well as life prediction results are presented, encompassing the effect of die size, ball count, and ball pitch. Solder joint reliability is compared with the requirements for various end-use applications and accelerated test conditions.

While chip scale and near chip scale packages offer the advantage of small size and increased packaging density, the solder joint reliability of these packages can become a concern for some applications. Although smaller package size reduces the DNP (distance from neutral point) effect, the relatively large chip-to-package area ratio causes the effective CTE of the package to be closer to that of silicon, thus resulting in greater CTE mismatch with the motherboard.

Higher densities are also driving the ball pitch down, which in turn results in smaller pads and smaller solder balls connecting the package to the motherboard. These factors cause reduction in fatigue life so that a package may not be able to meet 2nd level reliability requirements.

This paper investigates these factors for the ChipArray package. Thermal cycle test data is presented for a 0.5 and a 0.8mm pitch package for two test conditions and motherboard thicknesses. Since it becomes cost prohibitive and impractical to study the effect of a number of different design variables through tests, the effect of package size, die size, motherboard thickness, substrate thickness, and test conditions are quantified using a life prediction approach.

*ChipArray is a trademark of Amkor Technologies

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