Does this brown glue mean the component is failed? - Page 1
Forum section: electronics / general

author: Steve1984
author_rank: Newbie
timestamp: November 29, 2017, 02:08:06 am
content: Hi,I have a malfunctioning controller and when I opened it up I noticed this brown glue or flux substance on the ribbon header pin. I was wondering if the brown goo is a glue or if it is a result from the component being damaged?Any help would be great.

author: ataradov
author_rank: Super Contributor
timestamp: November 29, 2017, 02:29:25 am
content: That looks like it was done intentionally. May be they needed to fix that connector in place?Does it feel hard? Does the stringy part break easily?

author: Cubdriver
author_rank: Unknown
timestamp: November 29, 2017, 02:43:54 am
content: That looks like glue to me.-Pat

author: TerraHertz
author_rank: Super Contributor
timestamp: November 29, 2017, 03:22:58 am
content: It's glue. Used to stop things like connectors from vibrating loose.However there's a commonly used variety of brown glue, that becomes acidic and electrically conductive as it ages. It's a death sentence for electronics when used on PCBs because it corrodes everything after a few years, and also shorts out PCB traces and pads.Your brown glue doesn't look quite like the death-glue, which is an opaque sh*t-brown color. Yours is kind of translucent.But I notice it's across pins of what looks like a membrane keypad flex connector. Such keypads tend to use fairly high impedance signals, so some slightly conductive glue might stop it working. I'd advise removing the glue by scraping with the tip of a modelling knife.Is that a microwave oven controller? Or thermostat? What is it doing wrong?

author: abraxa
author_rank: Frequent Contributor
timestamp: November 29, 2017, 06:46:36 am
content: Quote from: TerraHertz on November 29, 2017, 03:22:58 amAlso, the connector has exposed silver contact surfaces, which corrode. You don't say how it's broken but if it's the key pad then this could be the cause. In that case, you can pull out the flex cable, clean it (ash should work) and put it back in carefully, making sure you don't break the fragile silver traces from accidentally bending the cable.

author: martinator
author_rank: Contributor
timestamp: November 29, 2017, 07:07:09 am
content: It's a sort of contact adhesive.It's used to hold some components down while they go through the wave soldering machine.Those headers would fall over or float out of the holes without the glue.There's probably a small blob under the electrolytic caps too.Sometimes you see power supply caps with silicone or 'hot snot' on them. It is a common mistake in most cases to infer that it is done for vibration damping or rigidity although one could call that a secondary feature.

author: TerraHertz
author_rank: Super Contributor
timestamp: November 29, 2017, 10:21:26 pm
content: Quote from: martinator on November 29, 2017, 07:07:09 amIt's a common mistake to rely on assumptions, without making a close visual examination first.Observe that the glue in question in the photo, is on both the 90 degree pin header AND the flex-membrane connector plugged onto the header. The flex-connector cannot have been attached when the board went through wave soldering, therefore the glue was applied afterwards, once the PCB was installed and the flex-connector plugged in.