Reliability analysis of an ACA attached flex-on-board assembly for industrial application

Abstract

Purpose

The purpose of this paper is to examine the long-term reliability of an anisotropic conductive adhesive (ACA) attached polyethylene terephthalate (PET) flex-on-board (FOB) assembly for industrial application used in harsh environments. In addition, the possibility of reducing reliability testing time was studied.

Design/methodology/approach

A−40/+125°C thermal cycling test with 5- and 14-minute soak times was used to study the reliability. To study the functionality of the FOB assembly during testing, a real-time resistance measurement was used together with a 90° peel strength test. Failure analysis was performed on samples using scanning electron microscopy and cross sectioning.

Findings

No failures or noticeable increase in the measured resistance values were seen during testing. The peel strength, however, decreased significantly with both soak times used. The highest drop in the mechanical strength occurred at the start of the temperature cycling tests. The time spent at the high temperature extreme seemed to have a greater impact on the peel strength than the number of temperature cycles. The failure mode of peel tested samples changed due to temperature cycling from interfacial delamination to cohesive failure. The temperature cycling was also observed to induce voiding inside the adhesive.

Originality/value

The paper illustrates the applicability of ACA attached PET flex in high reliability industrial applications. Additionally, testing methods for high reliability adhesive interconnections are discussed. Especially, the effect of temperature cycling soak time on peel test results and reliability testing time is studied.

Citation

Kiilunen, J. and Frisk, L. (2014), "Reliability analysis of an ACA attached flex-on-board assembly for industrial application", Soldering & Surface Mount Technology, Vol. 26 No. 2, pp. 62-70. https://doi.org/10.1108/SSMT-03-2013-0007