Trelic’s picture of the week – 2/2017

Can you guess what does this picture represent?

The small pieces are various kinds of material samples measured with thermomechanical analyser (TMA).

TMA is a thermal analysis technique used for material characterization. It can be used to measure several material parameters. TMA measures dimensional changes of a sample while it is heated. As a result, parameters such as coefficient of thermal expansion (CTE) and glass-transition temperature (Tg) can be determined. While Tg can be measured with several techniques, TMA is one of the few possibilities to measure CTE. And, it is crucial to know the CTE of your materials if they are used in environments with varying temperatures to avoid unexpected failures!

How is the measurement done in practise? A small piece (smaller than 1cm x 1cm x 1cm) of material is placed under TMA probe, which lightly presses the sample while it is heated, as shown in the Figure below. Are your materials in films form? No problem, film samples can also be measured with another kind of probe.

Which kinds of materials are in the cup? The brownish and yellowish samples are epoxies – those tend to become darker while heated. Additionally, some of them have been aged at humid conditions to study their long-term stability. The clear materials are optical silicones. The silver coloured materials are silver epoxies (ICAs), which can be used as thermally and electrically conductive adhesives. The nice pink one is die attach adhesive.