The ARM Cortex-M0 based VA10800 microcontroller has been qualified and is rated for operation at 200˚C. The device uses a plastic package that is ductile, small, lightweight and very cost-effective. High temperature plastic packages for integrated circuits are still not common, but are becoming more widespread in use as there is a demand for high reliability and cost-effective alternatives to costly ceramic packaging.
Despite the qualification being completed, the device was subjected to additional testing of 4000 hours at 200˚C and 2000 hours at 225˚C in a temperature controlled oven. Upon completion of this testing, we de-processed the devices by grinding the package back to the pad / bond interface to assess the Cu-Al (Copper – Aluminum) bond after prolonged exposure to high temperature. Our objective was to look for any possible damage from voids, cracks, oxidation or corrosion.
The photo shown is a 1000X magnification of the pad / bond interface. No ill effects were observed. An intermetallic growth is observed (the thin darker region above the copper pad) that has strengthened the bond.
These devices are destined for use in the most unforgiving environments in downhole drilling, aerospace and high temperature industrial applications. This type of testing and ongoing study of the silicon and packaging is important to ensure that VORAGO microcontrollers can operate in environments that other products can’t handle.