Corrosive PCB potting compound? - Page 1
Forum section: electronics / projects

author: 13hm13
author_rank: Frequent Contributor
timestamp: April 12, 2014, 12:23:12 pm
content: Is PCB potting compound (sometime time called glue) corrosive (or can it become corrosive over time)?In a recent elec. troubleshooting video of a subwoofer ....... the blogger noted that one reason for poor performance was a corroded zener diode (see video @10:30) that has " corrosive glue" on it.I think the potting / glue compound is resin-based but not sure.

author: con-f-use
author_rank: Unknown
timestamp: April 12, 2014, 12:29:24 pm
content: In professional electronics the compound is specifically selected to be long-term stable, non-conductive and non-corrosive. In some (cheap) manufacturers miss-use silicone glues that contain acidic solvents.

author: 13hm13
author_rank: Frequent Contributor
timestamp: April 12, 2014, 01:04:53 pm
content: Quote from: con-f-use on April 12, 2014, 12:29:24 pmVelodyne (manuf. of the subwoofer in the above troubleshooting video) is fairly reputable brand and not inexpensive dept. store gear. At least that used to be the case up to about decade back when I stopped following the audio industry.Anyway, can you (or anyone) give some examples (brands / manufs.) of "glue" that are "safe" and and brands to avoid?Thx!

author: Fsck
author_rank: Super Contributor
timestamp: April 12, 2014, 01:13:48 pm
content: Quote from: con-f-use on April 12, 2014, 12:29:24 pm^this. It should never be corrosive or conductive (under it's specified conditions). Stability, however, tends to be dependent (usually on cost or extreme environmental factors).however, looking at that board, it looks like there are contaminants all over the board (quick glance at video), all nighter + crappy eyesight = it sort of looks like there's flux residue on the board so it could be that.Quote from: 13hm13 on April 12, 2014, 01:04:53 pmdo you want glue or do you want conformal coating or do you want potting compound? Brand matters less than the correct choice of substance for the effect desired.glue is designed to attach components together mechanically (sometimes, also exploiting for some electrical/thermal conductivity).potting compound is (typically) designed to fill up a large amount of volume to completely isolate anything exposed inside from each other, airborne contaminants, moisture and mechanical resistance.conformal coating is (typically) designed to cover up something (electrical) with some isolating/insulating properties, similar to potting compound but as in the name, it's a *coating*.

author: mariush
author_rank: Super Contributor
timestamp: April 12, 2014, 01:44:43 pm
content: That glue/compound (normally white or cream in color) they used is basically made with a bad formula which dries out in time and with heat and becomes conductive and corrosive in time.See this pdf :http://cdr.cz/sites/default/files/Bad_glue.pdfQuoteQuote

author: 13hm13
author_rank: Frequent Contributor
timestamp: April 12, 2014, 03:04:03 pm
content: It's funny ... the brand in the OP was Velodyne (one of the better subwoofer brands -- not a cheapie and has a good reputation for performance). And mariush mentioned SonyBroadcastVTRs! Sony high-$ pro gear?!So ... the bad stuff is kinda randomly used. Or the estimated life use of the product -- before it's ready for scrap -- meant it was disposed of long before the glue became an issue (or at least out of warranty).Not many manufs. "engineer" for dumpster-diving YouTube bloggers and eBay junkies

author: mariush
author_rank: Super Contributor
timestamp: April 12, 2014, 03:18:00 pm
content: That Velodyne uses Capxon capacitors - no company that cares about quality would use those. They probably just bought a design or allowed the Chinese company assembling the boards select the parts.