Newb Question: What is that white compound?

[Greensold]

I recently opened up a PSU from a "popular computer manufacturer" because the fan had gone bad.

I noticed that most (maybe all) of the caps had a hard white compound on top of them. It looked like epoxy to me, but one of my coworkers said it keeps the caps cool.

I find that hard to believe since I've never seen it before, and in one spot the top of a transistor (mounted sideways) was connected to the side of a large cap with the stuff. That was the only spot where the compound wasn't just a standalone glob on top of a cap.

If it does keep the caps cool, why isn't every cap covered with the stuff?

Enlighten me please.

[Galvanized]

Re: Newb Question: What is that white compound?

It's silicone and it's used to stabilize the bits during handling and shipment.

Welcome to badcaps. Please do look around. The PSU pics thread will show most all units use the goop.

[gonzo0815]

Re: Newb Question: What is that white compound?

It avoids noise too, thus most mfk do a lot in.

[UraBahn]

Re: Newb Question: What is that white compound?

But it certainly won't keep the caps cool. In fact, having too much of that glue (that's the white goop) in the PSU will restrict airflow and cause things to heat up considerably. I'm not saying that glue is a bad thing in PSU (far from it actually) but having too much can't be good.

I'd personally be concerned if I opened up my PSU and found the insides smothered with glue. I'd take that as a sign that the manufacturer used cheap or underrated parts, and compensated for the resulting heavy component/coil vibration by dumping lbs of glue into it.

Of course I'm wrong on so many things... Damn the conspiracy theorist in me.

[PeteS in CA]

Re: Newb Question: What is that white compound?

The goop is used to stabilized taller and heavier components against shock and vibration. If the caps or inductor cores are being worked really hard, the insulating effect of the goop would make me nervous.

[jonnyGURU]

Re: Newb Question: What is that white compound?

It must have been a PSU used in a porno.

[Tom41]

Re: Newb Question: What is that white compound?

I've seen PSUs where the cap tops are covered with glue. This begs the question, what would happen if the caps were to vent? It's as bad as gluing the vents shut, and could cause the caps to fail from the bottom or even the sides!

One failed PSU I saw had the caps covered with glue. The internal temperature was so high that the glue had turned back into a semi-solid substance, and at the same time the cap underneath had vented - leaving a large bubble in the glue (which then hardened again)!

[Greensold]

Re: Newb Question: What is that white compound?

Thanks for the replies everyone. It was very informative.

Sounds like the silicone doesn't do much for the heat in the caps, so it's probably good that we're deciding to get a replacement PSU (We didn't have a replacement fan of that size anyway). The fan had gone bad and the computer was shutting down from overheating (and there's no temp sensor inside the PSU), so I imagine the caps were getting pretty hot.

[larrymoencurly]

Re: Newb Question: What is that white compound?

If it's glossy and white, it's silicone rubber, but if it's semi-glossy or flat white, like the stuff found in Delta and Newton PSUs, it's something else that dissolves with lacquer thinner or carburetor spray.

Why do Channel Well Antecs have that yellow sealer/glue that turns brown and brittle in a matter of months. CWT knows it's bad because they use silicone rubber on some of the caps.