Test Methodology for Impact Testing of Portable Electronic Products

Abstract

This paper introduces a test methodology to examine the durability of surface mount interconnects under impact loading when a portable electronic product is dropped. Conventional testing approaches that consider loading (total impact energy, orientation and number of impacts) as the governing criterion for failure, typically report difficulties in correlating with impact durability under field conditions. This study considers damage accumulated in the interconnects in terms of local flexural strain, strain rate and acceleration. The advantage is that the results are less dependant on structure and loading, because damage is quantified in terms of specimen response rather than the loading. An instrumented, repeatable impact test setup is developed. The test matrix covers the design space in terms of specimen styles, impact orientation, loading and boundary conditions. The entire test matrix is replicated twice for proof of consistency of the test data. A finite element model of the transient impact is developed. Results indicate that number of impacts to failure is a good damage metric for constrained impacts. The same damage metric may not be applicable for unconstrained (free) impacts because the strain signatures are more complex. A comparative analysis of the experimental and numerical data indicates a good correlation between the two. The end goal is to develop a consistent, accurate and generic methodology for ranking the impact durability of different surface mount interconnects technologies.

A review of board level solder joints for mobile applications

“…7b). Varghese et al [32,33] of CALCE delivered the impact using a steel ball attached to a string (Fig. 7c).…”

“…Varghese et al [32,33] of CALCE proposed a fatigue damage model that takes into account the bending mode and the stress amplitude. Discrete wavelet transform techniques were used to decompose the time history response of the PCB obtained from impact bending tests (Fig.…”

“…(a) Impact bending test setup by Hitachi[29,30], (b) Motorola[31], and (c) CALCE[32,33]. Near half-sine response of PCB subjected to impact bending[30] (Courtesy of JSME Int.…”

Electronic Components for High-g Hardened Packaging

“…PWB flexure is a primary cause of electronic product failures (9). Therefore, the product should be designed so that impacts or shocks to the exposed portions of the product result in minimal deformation of the internal PWBs.…”

Test methodology for durability estimation of surface mount interconnects under drop testing conditions

“…Tests conducted by Yu et al [7] and Juso et al [8] indicated that the number of cycles to failure decreased as the PWA strain and strain rate increased. Varghese and Dasgupta [9] ran impact tests on PWAs in the in-plane and out-of-plane orientations and showed that the number of impacts to failure decreased with increasing PWA strain. The failure site for both impact orientations was the interfacial intermetallic layer.…”