Black Goop used on PCBs - Page 1
Forum section: electronics / beginners

author: peps1
author_rank: Regular Contributor
timestamp: August 09, 2015, 10:59:12 pm
content: Was just wondering what the black shiny goop you find on some PCBs is actually made of?

author: microbug
author_rank: Frequent Contributor
timestamp: August 09, 2015, 11:18:48 pm
content: What do you mean specifically? Solid black blobs found on a PCB (particularly one from a cheap product) are likely chip on board ICs. The black substance is made from epoxy glue.

author: peps1
author_rank: Regular Contributor
timestamp: August 09, 2015, 11:29:53 pm
content: This type of potting compound, that seems really viscous.

author: Mephitus
author_rank: Regular Contributor
timestamp: August 09, 2015, 11:50:30 pm
content: As a rough guess, it looks like a silastic (silicone) based potting material.

author: John Coloccia
author_rank: Super Contributor
timestamp: August 10, 2015, 12:47:45 am
content: Just what EEVBlog needs...a Klon thread. LOLLots of different things. Some people use black epoxy...some black silicone based material as mentioned. You can even use a black hot glue stick. Potting and conformal coat does have a purpose, but as you already know it's being used in this case to try and obscure the circuit. Black epoxy is probably the most difficult to defeat, though I wouldn't know. I've never gooped. Seems very amateurish to me. I couldn't imagine ever giving a customer a piece of gear that I've purposely made impossible to repair and/or modify. Meh.

author: NeverDie
author_rank: Regular Contributor
timestamp: August 10, 2015, 01:22:45 am
content: What about the glob of something on the module on the left?Is that likely a "chip on board IC" that you're referring to? Is that an unpackaged die somehow mounted directly to the board, and so the blob stuck on it afterward becomes like an after-the-fact cheap packaging?

author: peps1
author_rank: Regular Contributor
timestamp: August 10, 2015, 01:46:42 am
content: Quote from: John Coloccia on August 10, 2015, 12:47:45 amMan, that made me spit tea all over my keyboard!Quote from: John Coloccia on August 10, 2015, 12:47:45 amI totally agree, my interest is purely a quest for knowledge then any plans to goop tube screamer clones and Joyo pedals!

author: sleemanj
author_rank: Super Contributor
timestamp: August 10, 2015, 05:16:23 am
content: Quote from: NeverDie on August 10, 2015, 01:22:45 amYes that is a chip on board exactly as you described. Die is glued to the board, then the (gold) bond wires are attached from the die to pads on the board, then a blob of epoxy is slapped on top of it.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 10, 2015, 05:45:57 am
content: Just for the sake of completenesshttps://learn.sparkfun.com/tutorials/how-chip-on-boards-are-madeQuote

author: john_p_wi
author_rank: Regular Contributor
timestamp: August 10, 2015, 05:55:57 pm
content: Quote from: John Coloccia on August 10, 2015, 12:47:45 am+1 BTW, clearly following in the gooping mystique created by Dumble...

author: Jeroen3
author_rank: Super Contributor
timestamp: August 10, 2015, 06:27:46 pm
content: Some enviroments require potting. Water, oil, dust or sand. Sometimes heat. You can make your product a lot more durable.For diy, you use two-component epoxy. Doesn't fully harden, it stays rubberish. It also only lasts 5 to 7 years before drying out and cracking. If used in environments where it is a bit hot.If you outsource it, they use polyurethane. Turns into a solid black block. Still a bit flexible, lasts ages.You can pot top-down into a enclosure, but also using molds.http://www.purtec.nl/im_el16.jpgYou decrease the repairability figure to 0, removing it requires heat and scratching tools. Only usefull if there is enough time available and money to gain.

author: old gregg
author_rank: Regular Contributor
timestamp: August 10, 2015, 10:06:02 pm
content: QuoteAs you ask, in guitar pedal is more about hiding the "uber-original idea of cloning old circuits as million other do already" than nothing else. Last time I checked, the "Vertex gate" was very funny as well.QuoteYep Chip on board. No die, direct on the circuit board. The goop is here to protect the all mess.