Effect of bonding pressure on reliability of flip chip joints on flexible and rigid substrates

In this study the effect of bonding pressure on the reliability of adhesive flip chip joints was evaluated. Two different substrates were used: rigid FR-4 board and flexible liquid crystal polymer (LCP) board. The reliability of the test samples was studied in a temperature cycling test, carried out between temperatures of -40 °C and 125 °C. To determine the exact time of a failure the resistance of each test sample was measured using continuous real-time measurement. A clear difference between different substrates was observed in the test. Cross sections of the samples were made in order to analyse the failure mechanisms.