Date of Award

Fall 1995

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Civil Engineering

First Advisor

Heinrich, Stephen M.

Second Advisor

Wenzel, Thomas H.

Third Advisor

Nigro, N. J.

Abstract

A strain model is developed based on the elastic beam theory to estimate the maximum shear strain in an array of solder joints in a uniform Ball Grid Array (BGA) electronic package subjected to a thermal loading. An assumption of parabolic variation for the cross-sectional area and second moment of area is introduced to facilitate the evaluation of the integrals in the flexibility coefficients. Closed-form expressions for joint lateral stiffness and maximum shear strain are derived for the case of no warping of component or substrate of the package. These results are compared with the results obtained for a joint shape based on a circular-arc profile using a numerical approach. A parametric study on the sensitivity of maximum shear strain to Poisson's ratio of solder, joint slenderness, joint shape, and pad dimensions is performed for the case of no warping. The determination of optimal solder volume based on minimizing the maximum shear strain is explored.

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