Meaning
A material property of a printed circuit board substrate defines the temperature range where the cured polymer resin transitions from a rigid, glassy state to a flexible, rubbery state. Process engineers monitor the substrate resin glass transition temperature to ensure that the board can withstand the high-temperature reflow cycles used during automated assembly. Crossing this threshold causes a rapid increase in the rate of thermal expansion of the board material.
This mechanical shift puts significant stress on the copper vias and surface-mount solder joints.
Thermal Stress
Exceeding this critical temperature during operation or assembly can cause the laminate to delaminate or the internal copper circuits to fracture. A high substrate resin glass transition temperature protects the board from physical deformation during double-sided reflow processes. It is a critical specification for multi-layer boards that undergo multiple high-heat steps.
Soldering Reliability
Lead-free soldering requires reflow temperatures that can easily exceed the transition point of standard epoxy resins. Specifying a substrate material with a high substrate resin glass transition temperature ensures that the board remains dimensionally stable during assembly. This stability prevents the warping that leads to misaligned components.
Material Selection
Selecting the correct resin ensures that the completed assembly can operate reliably in high-temperature environments.
