We test per IPC TM 650 188.8.131.52.
This test is used to determine the thermal reliability during assembly and rework processes of PWBs. In addition, it can be used to down select laminate choices for a given application. The information obtained from this test is typically more useful than the Tg test alone can provide in helping to choose the correct material.
In this test, the sample is enclosed in a furnace chamber where the temperature is controlled to ramp at 10°C per minute to preset isotherm and then stays at temperature for set time. When an event occurs, cracking, moisture release, stress relaxation, or decomposition, a sudden movement of the sample surface will be detected.