Effect of Moisture on Dielectric Properties of CSP Board-Level Underfill

摘要

Using accelerated aging conditions to predict the reliability of a device is standard practice in the electronics world. Accelerated aging specifications are driven by the end use application and life expectancy of the device. OEMs supplying portable devices commonly require drop resistance,thermal cycling stability,and long term electrical stability. With each generation,OEMs are increasing the device level reliability requirements to reflect the consumer’s on-the-go lifestyle. Since the early 1990’s,OEMs have successfully employed underfill adhesives to achieve the desired mechanical integrity. Recently,OEMs have been implementing more challenging conditions for so-called “damp heat” accelerated aging tests. Underfills are expected to retard moisture ingress,maintain their interfacial integrity,and retain their functionality in the device. Achieving these CTF parameters is realized via appropriate material chemistry and material properties. This paper will assess the changes in an underfill’s dielectric properties as a function of residence time at 65°C/90%RH and 85°C/85%RH. Additionally,the effect of damp heat conditioning on the glass transition temperature (T_g) and adhesion strength will be discussed.