Damage Boundary Curves: A Computational (FEM) Approach

Abstract

As the mechanical, thermal, and electrical demands on 2nd and 3rd level electronic packages increase, so does the need for early dynamic analysis of the proposed design. Estimating effect of dynamic transients (shock inputs) is of primary concern and the current topic of discussion. The computational determination of a damage boundary curve/s (DBC) for a proposed 2nd/3rd level package may seem a formidable task. With the experienced use of the finite element method (FEM), engineering insight, and some relatively simple mechanical testing, the task can be reasonably accomplished. This is not to say that every failure mechanism can be foreseen, predicted or modeled, but some failures can be avoided during qualification testing. The proposed method of DBC determination requires some initial ideas related to where failures may occur due to transient inputs. Failures may include a given maximum stress level, strain, deflection of a particular point or the force at a riveted connection. These suspect areas of failure will tend to guide the modeling technique. Models must be constructed not only to address the specific areas of concern but also to reasonably represent the overall dynamics of the package. Examples of this technique will be presented, each with varying degrees of verification.