To achieve good reliability and high performance flip chip interconnection, process parameters and materials used in the flip chip process must be optimised. In this paper reliability of Sn37Pb solder bumped flip chips on an FR5 board, using different fluxes and underfill materials, are tested in a temperature cycling test. Also the contact pad geometry used on the FR5 board had a great influence on the reliability of the joint. The solder bumps were grown on the wellknown TiWAu under bump metallurgy UBM1 with an extra layer of nickel UBM2 which gives a reliable and high performance solder joint.
Microelectronics International – Emerald Publishing
Published: Apr 1, 2000