Hi

Im planning a pcb with a temperature and humidity sensor on it and I'm wondering if aluminum pcbs will have good corrosion resistance in a humid enviroment. A google search didnt turn up any info. Anyone got any experience on this?

Thanks

 

Normally, resistance to humidity is achieved by plating the traces (no exposed copper). This can even be with solder. In extreme cases a conformal coating is applied to the board. I don't know of any reason to be concerned about FR4 and humidity, did you want to use aluminum for some other reason?

 

Normally, resistance to humidity is achieved by plating the traces (no exposed copper). This can even be with solder. In extreme cases a conformal coating is applied to the board. I don't know of any reason to be concerned about FR4 and humidity, did you want to use aluminum for some other reason?

Thanks for your response. There is no purticular reason for the aluminum no.

I have had corrosion issue on FR4 with LeadFree HASL-RoHS on a previous project. The enviroment for that board should have been low moisture but its possible that water dripped on it at some point, but I cant be sure, that board corroded badly at the th pins which I guess points more to poor quality solder. So im looking at what other options I have because this board with the sensor will be in a high humidity enviroment.

 

I'm wondering if aluminum pcbs will have good corrosion resistance in a humid enviroment

Who makes PCBs with aluminum instead of copper?

Conformal coatings are probably the easiest solution.

 

Aluminum is a common substrate for high power LED modules.
As for moisture affecting FR4 boards, apparently they can absorb moisture through the edges.
https://hackaday.com/2021/05/17/soil-moisture-sensors-how-do-they-work/
I got a couple of those sensors, but I guess I'll be dipping them in conformal coating a few times before putting them to use.

 

One more thing, aluminum PCBs are very hard to work with. You will need a hot plate to preheat or reflow to solder the components.

Conformal coating is the standard practice for things that have to handle moisture.

 

Aluminum is typically anodized (or coated) to avoid corrosion.

 

PCBs with copper on the outside and aluminum inside are commonly used in LED lamps to carry the heat away from the die. The aluminum is not typically used to conduct electricity, only as a heat spreader.

Anodized aluminum is an insulator.

Getting down to your problem - humidity on the PCB is usually solved by (for the third time in this thread) a conformal waterproof coating. This complicates repair but can be dealt with.