Effects of Printed Circuit Board Materials on Lead-free Interconnect Durability

Abstract

This study investigates the effects of printed circuit board (PCB) material on interconnect durability of lead free assemblies. The assemblies involve soldering various packages (array and peripheral) on to FR4, high glass transition temperature (Tg) FR4 and Polyimide (PI) printed circuit boards using Sn3Ag0.5Cu solder alloy. The glass transition temperature of these materials ranges from 130°C to 230°C. Thermomechanical properties, such as elastic modulus and thermal expansion coefficients, of the board materials vary considerably. These properties have a direct impact on the interconnect durability. In this paper, thermomechanical properties are experimentally determined and used for solder joint durability simulation. Two kinds of environmental loadings are simulated: temperature cycling and random vibration loading. The results show that PI board provides a better solder joint durability than FR4 and high TgFR4 under temperature cycling conditions. PI assembly has better durability than FR4 assembly under random vibration. The paper also presents the effect of temperature on the vibration response of the FR4 printed circuit board assemblies. The understanding of these changes can contribute to the study on interconnect durability under combined temperature cycling and vibration loading conditions.