X-Ray images of Raytheon 320 x 240 BST sensor

[Fraser]

I thought it would be interesting to X-Ray image one of the Raytheon 320 x 240 pixel thermal imaging sensors that I have on my bench at the moment. I was hoping that the ROIC might show up but silicon is pretty transparent to X-Ray so it was no surprise that I could not see it with a quick X-Ray in full Auto mode. It may be possible if I mess around with manual settings but no time for that at the moment.

The images may surprise you. Likely not what most people would expect to see inside this ceramic package. More on this with the X-Ray images. For starters and to set the scene, I attach pictures of the BST sensor so that you can see what it looks like on the outside.

Fraser

[Fraser]

OK, now the X-Ray images......

[Fraser]

Some close-ups.....

[Fraser]

So what is the snake like shape covering the sensor ?

The BST sensor is a ceramic package that contains the sensor array, Read Out IC and the temperature stabiliser. The temperature stabiliser takes the form of a Peltier element. I suggest that what we can see snaking around the sensor area is the Peltier element that is made up of individual junctions within each of the visible rectangles.

The rear of the ceramic package is thermally bonded to the heat-sink via a thermally conductive pad.

Sorry you cannot see the actual BST pixels, they are just too small and low density to image easily with my MX20 X-Ray machine.

Fraser

[helius]

The serpentine track is just a heater, right? Or does it detect temperature gradients across the package?

[Fraser]

The shape you see is a collection of Peltier junctions used to stabilise the temperature of the sensor die at around 32 Degrees C.
Temperature sensors on the sensor die (normally at least two) feed into the closed loop temperature stabiliser circuit to maintain the correct die temperature.

Fraser