thermal grease, question

[JC@]

I really hate that white stuff, but today I opened a solid state fender amp and instead of the white thing it had something very similar to vaseline. Translucid, and if you rub it between your fingers it disappears just like vaseline. The amp is 13 yo with no repairs, so this thing works for sure.

What is it?

[52 Bill]

It's just a different type of silicon grease. Back in the sixties that type was all I ever saw, but was replaced by the white type as standard. Someone (maybe Zenith) used to include a little ketchup type packet of the stuff with every power transistor that you bought. And you are right, it is a lot easier to clean up.

[JC@]

It's just a different type of silicon grease. Back in the sixties that type was all I ever saw, but was replaced by the white type as standard. Someone (maybe Zenith) used to include a little ketchup type packet of the stuff with every power transistor that you bought. And you are right, it is a lot easier to clean up.

Oh, I see. Thanks, I will do some google.
At the end of the day, sometimes I have the chest of my pullover full of solder blobs and traces of that white stuff..

[Enzo]

Yes, the stuff has a homing system that will seek out and find you. I cannot come near the stuff without getting it all over me.

[Paleo Pete]

I cannot come near the stuff without getting it all over me.

I've been working on computers for 10 years, the same white thermal compound is used for CPUs. Arctic silver is the better type [brand], silver in color, and spreads even worse. Both manage to get all over everything you touch. I think it's factory trained to spread itself to anything and everything possible. I haven't seen the clear stuff, but suspected it was just a different type of thermal coompound...

[JC@]

I've been doing some research and it is not something easy to find.
In fact I haven't. Now that I know it does exist...
Maybe the white one is better, but I don't care. I also noticed that the clear one remains clean and "fresh" over the years. The white one seems to get "rubbery" with time

[JC@]

Well this is what I found after some reserch:
source->encyclocentral.com/2897-Greases.html

Petroleum jellies, such as Vaseline, are also sometimes called greases, and are commonly used for lubricating food-handling equipment. Greases In elucidates that Thermal grease (also called Thermal compound or Thermal paste) is a substance used to help the conduction of heat between two (usually metal) surfaces. In electronics, it is often used to aid the thermal dissipation of components via a heatsink. Today, thermal grease is produced by many companies. There are several types of thermal grease: 1) Silicone-based thermal grease has moderate thermal conductivity, is usually white, and is often shipped with CPU heatsinks. 2) Ceramic-based thermal grease contains ceramic particles suspended in other thermally conductive ingredients. Ceramic thermal grease conducts heat better than most silicone greases, but poorer than metal greases. 3) Metal-based thermal grease contains metal particles (usually silver) and other conductive ingredients. Metal thermal grease has a better thermal conductivity (and is more expensive than silicone-based grease). Thermal grease''s primary purpose in electronics is to substitute for the constructional imperfections of a heatsink''s surface. When applied in appropriate quantities, it fills the tiny pits and grooves (particularly on today''s CPUs that have a complicated surface), thereby increasing the amount of surface-to-surface contact with the CPU die. The most important parameter of the thermal grease is the thermal conductivity, measured in watts per metre-kelvin (W/(m·K)). The typical silicon/zinc oxide thermal compound has thermal conductivity between 0.7 and 0.9 W/(m·K). The compound must also be smooth, easy enough to apply in a really thin layer.

So what Fender used in this amp could be just vaseline, and that's what I will use from now on

[52 Bill]

Great, and I'm stuck with a lifetime supply, pint size can of the white Wakefield stuff. Maybe I can use it as sun block.

[Enzo]

Nah, on hot days, smear yourself with it and lean up against a large aluminum wall.

[savage]

I have a can of dielectric silicon, clear grease like stuff. I don't know how thermally conductive it is though. It's great for protecting joins in automotive wiring, You can likely get it at any auto parts store.

[JC@]

I have a can of dielectric silicon, clear grease like stuff. I don't know how thermally conductive it is though. It's great for protecting joins in automotive wiring, You can likely get it at any auto parts store.

I remember that kind of product, I may still have a tube somewhere.
Krafft I think was it's brand name.

[Enzo]

Remember the point of greasing the thing at all is to transfer heat better. It is not like a lubricant or something. We don't want to grease it just for the sake of greasing it.

[Paleo Pete]

I have a can of dielectric silicon, clear grease like stuff...It's great for protecting joins in automotive wiring

I get that in small plastic squeeze packs, it's electrically conductive and mostly used to prevent corrosion on automotive connections, especially ignition systems. I don't think it would work as thermal compound at all, that's not its intended use.

I've been explaining a very condensed version of what JC posted for computer repair purposes for several years. Thermal compound is intended to fill the tiny, often microscopic, pits and surface variations and eliminate air pockets, which inhibit heat transfer. When used on CPU's it should be applied in a very thin layer, a dab just over the size of a pinhead will do a P-IV CPU. Some overclockers or just cooling fanatics also lap their CPU and heatsink for flatter surfaces and even better heat transfer. But as the article quoted pointed out, a thin layer is the objective, usually.

The composition of the thermal compound does make a difference too, I've pulled a CPU and removed the white stuff, then replaced it with Arctic Silver and dropped the CPU temp 10° F. I don't think it would be usable for electronics though, it's at least nominally conductive.

[JC@]

Well, maybe this doesn't deserve such a long thread.
The point to me is that I really hate the white silicon thing because it spreads allover... fingers, cleaning rags, cables, chassis, clothes... silicon is what I hate, and if it is white, more. And as stated, it is not the best heat transfer component in a compound.

So I think I will go a little step down in heat transfer capabilities, and use just vaseline from now on. With the mica spacers and a very thin vaseline layer (in case it really was), this fender amp has been happy for quite a few years.

So applying just a little is also the trick maybe. I've seen those large support/heatsink aluminum blocks in ss amps muffled up with a thick plaster of the white silicon stuff.

Plus, it gets semi-dry / rubbery with time.
Plus in such a mess, it is possible that a tiny solder blob or something gets between the heatsink and the component making close contact a joke.

[52 Bill]

My bench also occasionally serves as a guitar repair bench. Using the white stuff lets me see where it has gotten to, as silicon can be problematic for refinishing jobs.