Drop Damage of Smart Mobile Phone Module:Weakest Link Damage or Cumulative Shock Damage?

Abstract

It is not unusual for the portable devices to be accidentally dropped onto hard floors due to inadvertent handling in the course of using these devices. Therefore, almost manufacturers are make an effort to protect damage of product from drop impact and perform a various pre-test in the development process. However, failure mechanisms to successfully describe test data have not been fully covered yet. In this article, we propose a discriminating procedure of selecting the model best describes drop impact durability of smart mobile phone (SMP) displays based on two candidate failure mechanisms: weakest link failure and cumulative damage failure. The weakest link theory provides a theoretical basis on a Weibull distribution and the cumulative shock theory on a inverse Gaussian distribution. We introduce the ratio of the maximum likelihood (RML) to discriminate between Weibull and inverse Gaussian distributions, and get the asymptotic distribution of the logarithm of the RML. Based on the asymptotic distribution of the RML, the probability of correct selection is computed. The proposed method is applied to drop impact test results on SMP displays made of organic light emitting diodes (OLEDs) to uncover their plausible failure mechanisms.