I have a LED-ring PCB, relatively new, that we sent through a few temperature cycle tests (-50 to +85*C), and it now shows signs of the solder-mask coming off some of the copper traces.
The LEDs weren't powered during the temperature cycle tests, and the tests were not oriented at the PCB but rather the weatherproofing of its enclosure. The PCB is mounted in an aluminum+glass enclosure (aluminum acting as heatsink) to be installed outdoors in the ground, so it'll be exposed to harsh temperatures.
The images show the slight damage to the traces on the bottom and the top of the PCB. A multimeter test confirms that the copper trace is exposed on some of the positions.
I am trying to understand if the soldermask coming off is
- a natural occurrence when dealing with PCBs getting hot or cold?
- a case of a low-quality soldermask (ordered from seeedstudio, who as far as I can see don't offer any soldermask options)?
- a sign of too-high-current on too slim traces?
If it's the first (typical temperature issue) would a conformal coating help to just keep the traces insulated (they do sit on top of aluminum)?
Material: FR4 TG130
PCB Thickness: 0.8mm
Power track width: 0.4mm (max 1A current)
Default track width: 0.25mm (max 0.25A current)