Characterization of the material properties of two FR4 printed circuit board laminates

Most printed circuit boards are based on a laminate of weaved glass fiber cloth and epoxy. These laminates have so-called viscoelastic material properties. This means that properties such as elasticity and thermal expansion drastically change above a certain temperature, called the glass transition temperature. When selecting a laminate, the temperature range of the soldering process and the end application must therefore be taken into account. The objective of this work has been to increase our knowledge on laminates used in printed circuit boards by characterizing two FR4 laminates. This was done by measuring the storage and loss modulus, glass transition temperature, coefficient of thermal expansion and flexural strength. The effect of a typical soldering process was also investigated. The result was detailed material properties for the two laminates and an increased knowledge related to printed circuit board laminates in general. The work reported here was done as part of a summer internship.