Standards Development

Scope

This part of IEC 6xxxx specifies methods for measuring the thermal conductivity of circuit boards such as FR-1, FR-4, CEM-3 and multilayer circuit boards made of polymer composites.

This document applies to circuit boards made of polymer composites with thermal conductivities from 0,1 W/m·K to 10 W/m·K and thicknesses from 0,5 mm to 3,0 mm.

The measurement methods referred to in this document are the steady -state method and the laser flash method, which have already been standardised. This document describes the sample preparation method, the measurement conditions and the measurement procedures.

This document states that for circuit boards with polymer composites, the steady -state method is the only way to evaluate the true value and that the value obtained by the laser flash method is an apparent value. 

Purpose

In the thermal design of circuit board heat-dissipation type, it is extremely important to accurately determine the thermal conductivity of the circuit board. However, printed circuit boards are often polymer composites, and their microstructure makes them heterogeneous and anisotropic, making it difficult to accurately measure their thermal conductivities. Currently, an internationally standardised steady-state method, the laser flash method, is used to measure the thermal conductivity of materials. The steady-state method can measure the thermal conductivity of composites but requires greater sample thickness for greater accuracy. The laser flash method is often used because of its small sample size, short measurement time and convenience. However, due to its measurement principle, this method is suitable for homogeneous materials, and when measuring heterogeneous composites, the accuracy of the thermal conductivity obtained may become poor.

This part of IEC 6xxxx specifies methods for measuring the in-plane and thickness thermal conductivities of circuit boards with polymer composites using the steady -state and laser flash methods.