Three images obtained from a light emitting diode are shown above. On the left is the topography, middle DC thermal image and left the AC thermal image (amplitude). Little contrast is seen between the different areas on the surface. Below are shown the results of localised TMA both inside and outside of the circular feature that can be seen in all three images.

It can be seen that all parts of the device show similar expansion on heating. The images of a second LED are shown below.

The types of images are the same as for the first LED shown above. In the topography image in particular, the results of damage can be seen that was occasioned by the removal on a gold contact wire. This time there is significant thermal contrast between the circular feature and the surroundings. The localised TMA results are shown below.

Again there are significant differences between the ‘lighter’ circular feature and the ‘darker’ surrounding material. The first LED did not fail while the second one did. The explanation is believed to be the thermal stresses induced by these differences in thermal expansion coefficient.