Which type washer for best electrical connection?

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Subject:		Which type washer for best electrical connection?
From:		Finn Lassen (finn.lassen@verizon.net)
Date:		Sat Apr 20 - 4:06 PM

I'm redoing the engine controller installation in my RV-4 to ensure 
better ground paths for noise reduction.

Moving from (cheaper and lightweight plastic box) to cast alum box. 5 oz 
increase, ouch!

I had been using star washers under screw heads and between PCB (ground) 
and spacers and to air frame.

Now I'm wondering what is the best choice of washer. Perhaps 
ribbed/serrated is better -- won't damage PCB ground traces and better 
contact?

I think this picture best shows the ones I have:

https://www.jugenheimersupplies.com/ecomm_images/items/large/ribbedwasher.jpg

The other question is whether I should put washers between bottom of box 
and the RV-4 side skin it's being mounted to.

I know I being anal here but figure might as well do everything I can 
can to get good paths.

Finn