Reliability of ACA bonded flip chip joints on LCP and PI substrates

Abstract

Purpose

The purpose of this study is to investigate the reliability of flip chip joints made with anisotropic conductive adhesives (ACA) on flexible polyimide (PI) and liquid crystal polymer (LCP) substrates.

Design/methodology/approach

Six test series using two ACAs and an LCP substrate were made with varying bonding pressure. The ACAs had the same matrix and conductive particles. To lower the CTE of one of the adhesives silica had been added to it. The reliability of the test series was studied in a temperature cycling test. The purpose of these test series was to find the optimal bonding pressure for both the adhesives used. According to the results from these initial tests, further test series were made with both LCP and PI substrates. The reliability of these test samples was studied using a temperature cycling test and a constant humidity test. The adhesion strength of the joints was studied before testing.

Findings

Both substrates had excellent reliability during the temperature cycling test. However, the reliability of the PI substrates during the constant humidity test was markedly lower than that of the LCP substrates. Additionally, the adhesion strength of the adhesives on to PI substrates was clearly less.

Originality/value

The work shows how the substrate material used affects the reliability of flip chip joints. In addition, the work shows how the addition of silica to the ACA matrix affects the reliability of the joints.

Citation

Frisk, L. and Cumini, A. (2006), "Reliability of ACA bonded flip chip joints on LCP and PI substrates", Soldering & Surface Mount Technology, Vol. 18 No. 4, pp. 12-20. https://doi.org/10.1108/09540910610717866