On 7/30/2016 11:43 AM, Rich Osman lists@... [Homebrew_PCBs] wrote: > > On 7/30/2016 10:34 AM, alan00463@... [Homebrew_PCBs] wrote: >> >> In searching for a vendor of Liquid-Tin I ran across >> this waterproofing spray: >> http://bamtech.com/product/acrylic-coating/ >> >> Since I live in the RustBelt and know what oxidized >> copper looks like, I wonder if I should use this on >> my PCB to keep the copper from contacting moist air? >> > Some protection will be smart. >> >> >> My PCB will be used outside in a plastic box. The >> plastic box will be waterproof, but not airtight. >> I am guessing the Liquid Tin and leaded solder ap- >> plied to the traces will prevent oxidation. I just >> > No, tin will just change the type of oxide. Tin oxidizes too. Hello-- Worse yet, tin can grow conductive whiskers that can cause short circuits and intermittents: http://nepp.nasa.gov/whisker/reference/tech_papers/2012-Panashchenko-IPC-Art-of-Metal-Whisker-Appreciation.pdf There's information on what conformal coatings NASA found that would resist whisker growth. The waterproof box will collect moisture inside due to infiltration of moist air and temperature cycling. About all one can do is to create an air- and water-tight box that has a moisture-accumulating dryer cartridge venting the box. You'd have to periodically replace the cartridge. 73-- Brad AA1IP
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Re: [Homebrew_PCBs] Preventing oxidation of copper outdoors
2016-07-30 by Brad Thompson