Some exciting things are happening in the M.O.A.N. prototype lab*! Our research staff** is working tirelessly to give you tomorrows products today!

- Work on the "nameless" class A amp is expected to resume shortly!

- Testing of a new thermal insulation coating for flat package transistors is scheduled for next weekend***!

- Performance charts are being worked up on the new YYZ thermal compound! Closely monitored stress testing and long term testing of this miracle product is now complete!

And much more!





* my basement
** me, basically
*** or next available day off.

You joker , you realize "M.O.A.N" is "circulating" ? I've seen it mentioned in numerous places already !!
Thanks for printer tips , I am hunting EBAY for one.
OS

M.O.A.N...Like the sound of sweet music, let it drift where it may!

That printer should be easy to find - I saw many of them in my travels and they are a few years old now so you may get one for low bucks.

You should get a slab of directional heat conducting carbon, to go with the coating.
Could be a match made in heaven.

Magura

Hi Magura,
The coating I'm testing is waterbased polyurethane applied in one dip coat and cured for a week. It is my belief that this will effectively isolate the package electrically from the heatsink (acting in the same way as a silpad or mica washer) but as it is so thin, would markedly improve thermal transfer.
I'm going to get some pics on here soon.

It is thinner, but will the parasitic capacitance be larger? I get the feeling that many CFPs are unstable simply because of the capacitance between the collector and heatsink.

- keantoken

Hi Kean,
Interesting point, have you done any sims that support this?
I look at this as a real boon for output stage devices, where efficient heat transfer is critical. Considering a typical (non CFP) output stage the backplate (collector) is (usually) at rail potential and the heatsink at ground, the capacitance will actually aid in decoupling and bypass, so a good thing and no effect on stability.
Another large benefit is the ease of assembly after the devices are coated and cured, especially using my YYZ heatsink compound ($5 paraffin / silicone stick lubricant).

BTW, here's the test subject - an MJW21196 that has been single dipped in undiluted waterbased polyurethane and has now cured for 5 days.

I have recently made some tests that shows higher parasitic capacitance, using thinner isolators.
I have turned my attention towards relatively thick Al oxide insulators, as the parasitic capacitance was easily measurable with the Kapton insulators.

The reason I mentioned carbon heat spreaders, was to increase the uniformity of the thermal performance of the devices. The carbon does increase the uniformity dramatically.

Magura

John looking at your "drippings" the coating is not uniform. Anodising is not conductive and the transistor can be bolted directly onto an anodised heatsink. Magura, I tend to agree with John's opinion regarding capacitance. The capacitance change would be rather minute since the base is relatively small and the distance to the heatsink and collector tab does not matter much as it is only edge effect that could account for change.

Hey Nico,
The coating is very uniform actually - that pic was taken about an hour after it was dipped and there is a trick of the light making it look uneven. It is supremely flat.
I haven't gotten around to testing it yet but I believe it will be a total success.

I thought about anodizing but this beats nearly everything else for speed and ease of application. Once coated and cured it's ready to be mounted.