heat sink compound 340 dow corning

[indianajo]

I tacked an order for dow corning 340 heat sink compound onto an order since they suggested it. My tube of WP8033 is 40 years old and the GC 10-8109 silicon heat sink compound is 30 years old. I use this on mica washers. Newark didn't even sell TO-3P or TO247 silicon wafers, as of Thursday. Everything was gold "phase change pad .107 deg C/W". If I order berquist from digikey it cost $6 more freight & takes 2 days longer. Besides digikey never offers me close outs & I got the 14 weird ECB pattern BD140 transistors I needed today for $.024 each.
So the tube comes in and the MSDS says the active compound is zinc oxide. Should I even bother to keep this, just throw it away? I thought heat sink compound was beryllium oxide in paste? No MSDS on the old stuff. I always wash my hands as if it were beryllium.

 

[Elvee]

Zinc oxide is the normal filler for standard thermal pastes, and fortunately, you cannot find BeO ones: in its unsintered condition, the stuff is incredibly dangerous, and it would take much more than washing your hands to be half-safe.

Even when sintered, small chips and debris caused by shocks and abrasion remain highly hasardous.

There are however better materials than zinc oxide: magnesium oxide, aluminum oxide come to mind, but there are also ceramic materials.

You can easily make your own, better performance paste: mix silicone grease or oil with magnesium oxide (heavy): it will be extremely cheap and completely safe (magnesium oxide is a food supplement).
You can also make thermal glue if you use RTV silicone as a substitute for grease.
You can make a small quantity, and adjust the proportion of filler to suit the application: more filler=lower thermal resistance, more silicone=easier compound to spread and work with

 

[JonSnell Electronic]

Most thermal pastes are dangerous.
Here is a few that are better than most.
Buy thermal paste online from RS Components

 

[Elvee]

There is a difference between dangerous and DANGEROUS.

Silicones and ordinary light-metal oxides can cause relatively mild problems, just like about anything, but BeO is in a different league.

Here is an excerpt from the description (found here for example: Berryllium (Be) - Chemical properties, Health and Environmental effects ):

Beryllium is not an element that is crucial for humans; in fact it is one of the most toxic chemicals we know. It is a metal that can be very harmful when humans breathe it in, because it can damage the lungs and cause pneumonia.

The most commonly known effect of beryllium is called berylliosis, a dangerous and persistent lung disorder that can also damage other organs, such as the heart. In about 20% of all cases people die of this disease. Breathing in beryllium in the workplace is what causes berylliosis. People that have weakened immune systems are most susceptible to this disease

Read more: Berryllium (Be) - Chemical properties, Health and Environmental effects

 

[indianajo]

Most thermal pastes are dangerous.
Here is a few that are better than most.
Buy thermal paste online from RS Components

I'm not shipping stuff across the Atlantic. I don't know what the WP & GC compounds I'd been using for 40 years was, MSDS weren't invented in 1975. The labels say "silicon heat sink compound" which is non-informative as any consumer product. The stuff I scrape off heat sinks of dead amps is probably more dangerous than anything new, since the oil is always dried out.

 

[avtech]

The GC seems to still be in production for $10 per Oz:

https://www.newark.com/gc-electronics/10-8109/thermal-grease-tube-1fl-oz/dp/00Z581

Between that and the Dow 340, the thermal conductivity is equally poor at 0.67 and 0.7 W/m-K:
http://www.farnell.com/datasheets/2057594.pdf
https://www.spacematdb.com/spacemat/manudatasheets/DC 340.pdf

If you've been happy with the GC compound, then you should be similarly happy with the Dow Corning.

My tube of WP8033 is 40 years old and the GC 10-8109 silicon heat sink compound is 30 years old.

We won't mention about shelf life, eh.. 😉