Measurement Technique of In-Plane Thermal Resistance of PCB

Nowadays, thermal design of electrical packages is a key issue for the development of electronics. One of the most important thermal design is the estimation of temperature distribution on Printed Circuit Board (PCB). However, estimated temperature distribution by Computational Fluid Dynamics (CFD) analysis has not enough accuracy because of unknown in-plane thermal conductivity of PCB. PCB has complex wiring pattern and the effect of copper wire on heat diffusion has not been investigated. In this study, we developed measurement technique of thermal resistance of PCB without and with in-plane heat diffusion effect. Measured PCB consists of Glass-Epoxy of 1.6 mm thickness and various copper wiring patterns of 35 μm thickness. Measurement results showed that thermal resistance without inplane heat diffusion effect was not dependent on the wiring patterns. On the other hand, thermal resistance including in-plane heat diffusion effect became smaller with increasing the amount of copper. Further, we compared the experimental results with the results of Thermal Network Method (TNM).