MODELS FOR RAPID ASSESSMENT OF LEADLESS COMPONENT FAILURES DURING PRINTED WIRING BOARD BENDING

Abstract

The proliferation of leadless ceramic chip components has caused their failure to become a critical issue in the electronics industry. The majority of these failures are due to mechanical loads applied to the printed wiring board during assembly. The intentions of this dissertation are to demonstrate the relationship between printed wiring board flexure and the failure of leadless ceramic chip components and to develop a methodology for rapidly assessing the risk of these types of failures. To achieve this objective, closed form structural engineering based equations have been developed for calculating the loads at the critical location within the surface mount package when the underlying printed wiring board is subjected to bending. These loads are then used to calculate the stresses in the component. Validation of these stress results was done by comparing them to those of finite element models. Failure predictions using these stresses and a probabilistic failure model were then made and compared to published experimental results. The developed methodology was then physically validated with mechanical testing and field case studies. This research identifies the physical mechanism that initiates failure in ceramic bodies attached to a glass fiber/epoxy matrix composite in a non-compliant manner, assesses the response of the mechanism to various geometries and mechanical loading conditions, and develops an analytical model that allows the user to assess risk during the design phase and to determine the root cause of field failures.