# Temperature and flash corruption in microcontrollers

I'm repairing quite the pricey device, where a strain gauge failed. It's a pressurized device, and the strain gauge measures the internal pressure by means of it. The crux of the matter is that the strain gauge goes on a small metal cylinder epoxied to the PCB itself.

To install a new one, I will need to use hot curing resin, but I want to avoid having to remove the metal cylinder to reduce risks of damage and potential surprises. This means baking the whole PCB, MCU included, which worries me a lot since I have no clue whether it could become corrupted and I can't reprogram it.

I have 3 options for hot curing with Adhesive A:

• 1 hour at 190 °C
• 3 hours at 170 °C
• 6 hours at 160 °C

And other 3 with Adhesive B:

• 30 minutes at 200 °C
• 1 hour a 180 °C
• 3 hours a 150 °C.

Now, the max storage temperature I saw in the datasheets of some ICs on the board is 125 °C which is what is deterring me from attempting this.

I found this question that basically asks the same, but I'm looking for a more formal resource if anyone has one.

I'm also thinking if there's a possibility of insulating the rest of the PCB since the topology allows it.

Thank you very much in advance.

• I did some one-off tests where we needed to operate an MCU (from Microchip) at $180^\circ\text{C}$. We had to write data into EEROM, too, while depending upon the code running in flash memory. Way out of spec. But we were consistently successful running for 3-4 hours in that situation. (Threw away the parts and replaced them with new ones before the next cycle of testing, of course, since there was no way we'd trust them later.) Metal migration is an issue. Ask IC designers about it and they can provide predictions to help, if you ask. That's what I did. You are on iffy ground.
– jonk
Nov 9 '19 at 2:31
• Any chance you could selectively cool the MCU during curing? Nov 9 '19 at 4:20
• @jonk thanks a lot! I thought so. Nov 10 '19 at 16:01