Effect of substrate material and thickness on reliability of ACA bonded flip chip joints

Abstract

Purpose

The purpose of this paper is to investigate the effect of substrate material and thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive adhesives (ACA).

Design/methodology/approach

Four test lots are assembled using three different substrates. Two of the substrates are made of FR‐4. The thicknesses of these substrates are 600 and 100 μm. The third substrate is made of liquid crystal polymers (LCP) and is flexible. With the thicker FR‐4 substrate two test lots are assembled using both normal and two‐step bonding profiles to study how the bonding profile affects the deformation of the substrate. Four different bonding pressures are used to study the effect of pressure on reliability and the failure mechanism of the ACA joints. The reliability of the test samples is studied using a temperature cycling test.

Findings

The reliability of the test lot with the LCP substrate is considerably better than that of the test lots with the FR‐4 substrates. Additionally, the thinner FR‐4 substrate has better reliability than the thicker FR‐4 substrate. The failure mechanisms found varied among the test lots. The effect of the two‐step bonding process on the deformation of the substrate is found to be minor compared with the effect of the glass fibres.

Originality/value

The work shows that the thermal cycling reliability of ACA flip chip joints is markedly influenced by the thickness and material of the substrate. It is also seen that the substrate used influences the failure mechanisms formed during thermal cycling testing.

Citation

Frisk, L. and Cumini, A. (2009), "Effect of substrate material and thickness on reliability of ACA bonded flip chip joints", Soldering & Surface Mount Technology, Vol. 21 No. 3, pp. 16-23. https://doi.org/10.1108/09540910910970376