[SOLVED] Routing DC signals, isolated by solder mask only ?!?

[elektr0]

Hello,

we have a three layer PCB process and I am wondering if I can route DC signals on the bottom layer, which is screwed to the mechanical housing (GND) and is isolated by standard solder mask only (I guess 1 micron ?). What do you think ? Thank you for your help.

Regards
-e

 

[FvM]

Although surely stronger than 1 µm, the solder mask isn't intended as electrical isolation.

Isn't it possible to place spacers between PCB and housing, e.g. nylon washers?

 

[Terminator3]

I had similar problem, for solution used piece of kapton adhesive tape in that area.

 

[elektr0]

Thank you very much. The main problem is I cannot accept more height, but adhesive or <5mil nylon washers might work.
I will try ... Thanks -e

 

[biff44]

1 mil of kapton, so long as there are no sharp protruding ends sticking out, will withstand hundreds of volts. But in general, it is a poor engineering design to do so. why not add another board layer and be done with it?

I suppose if you were stuck, you could add a non-conductive coating to what the board is mounting too, in addition to the kapton. Mabe anodize the aluminum surface, etc.

5 mil washers will do NOTHING if the board flexes under vibration or if the board warps.

 

[D.A.(Tony)Stewart]

Thank you very much. The main problem is I cannot accept more height, but adhesive or <5mil nylon washers might work.
I will try ... Thanks -e

If you need heatsink properties, use 3M thermal adhesive tape with perfect smooth surface ( no burrs)
If you need Strong electromechanical insulation, use Polyamide tape (KAPTON) < best.

 

[Warpspeed]

I would not trust washers, the board may bow downwards, and as its height critical I would go for a very thin sheet of insulating "stuff".

My choice would be thin sheet mylar.
Excellent insulating properties, very tough, and very heat resistant.