Transistor torture...(or gruesome murder anyway)

Glue them back together and sell them on E-BAY for half price. Under not tested and as is.;-)

"Tim Wanker Williams"

..... Phil

Sil-pads are indeed garbage. They usually have thetas around twice datasheet specs. You pay a dollar for a premiun sil-pad, and it reduces the value of your mosfet by 10:1.

But Phyllis loves sil-pads, so you will have to endure her wrath.

You can usually squeeze them edgewise in a vise and shatter the plastic off.

ftp://jjlarkin.lmi.net/ExFets.jpg

Speaking of which, yesterday I blew up a Murata sip dc/dc converter, and hacked it open to see what's inside. It's potted with some semi-hard, sort of gritty epoxy, so by the time I x-actoed my way in I'd destroyed enough stuff to make analysis difficult. Anybody know of a way to dissolve epoxy? The substrate is ceramic, so it will survive.

Looks like a classic 2-transistor push-pull oscillator, tiny toroid, and a dual-diode half-bridge rectifier, but I can't make out the details. Runs around 60 KHz. These dc/dc bricks are handy gadgets.

Blowing up/dissecting stuff is fun.

John

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I use to disolve epoxy seals with methylene chloride.. nasty stuff. Worked in a fume hood and put everything in a sealed container so it wouldn't evaporate. Took a few days and the epoxy would soften up... then added a bit of heat and I could pop the seals open.

"Blowing up/dissecting stuff is fun."

A yup,

George H.

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Warm it to ~200=BAF, and it gets soft. You can pick it away with a needle, heating as needed to keep it soft.

Works great.

James Arthur

You might try carburetor cleaner? In which case you could get a wide-mouth can with a basket to dunk parts that you can reseal for less fumes (with the parts dunked in it) at an auto parts store. California version is different than elsewhere, per one set of MSDS I looked at, but either seems worth a try.

I recalled it having the aforementioned methylene chloride, but that was missing from the MSDS's I happened to find for the current stuff - perhaps some brands still use it, but if something else will work, might be just as well. When I had all 4 carbs form a 140 corvair soaking, I had tinfoil over them and used a fume hood and still was not overly happy about it - nasty stuff.

One brand of commercial epoxy solvent ("Attack") seems to be mostly methylene chloride (based on some mentions, have not found an MSDS for it), so there's an indicator that that may be the stuff you want. In which case, all due caution, it is unpleasant stuff.

That's the hard way. Hot sulfuric acid is easier. Or, bake in a kiln and dust after cooling with a camel hair brush...

You should have local suppliers who can remove the epoxy for a reasonable fee (like $50 or something). They use nasty stuff like hot spray nitric acid, so it's worth outsourcing. The key search word is "decapsulate".

Best regards, Spehro Pefhany

Is this a new Impulse LED design?

At Signetics, to get inside standard epoxy package ICs, we used IRFNA and a hot plate (don't ask temperature, do not remember); use DRY acetone as a wash to get the bubbling glop off. Milled into the package to near die first to decrease time; also the acid eventually dissolves the metals.

When I needed a die photo in a hurry (back when I ran a thick film hybrid line), I'd simply run the plastic package thru our firing furnace (~1100°C, IIRC). It'd emerge from the other end, looking intact, though now white in color. Turned out the plastic became ash, which was easily brushed away ;-) ...Jim Thompson

When I was destroying 1206 resistors recently, with 1 ms 60-watt pulses, we looked at one with our IR viewer. It looked just like a pulsing LED, with a big blob of illumination between the end caps. I think that a properly designed thinfilm on the right substrate can make microsecond thermal flashes.

John

I've used lacquer thinner to dissolve epoxy, but it works rather slowly, and I'm not sure about different formulas of epoxy. It does work slowly on the stuff from the handyman store.

Jim

Depends on your definition of hard, doesn't it? :-) Hot acid scares me.

OTOH, dipping a part in boiling water is pretty benign.

Epoxy gets crumbly (like a gum eraser) when so warmed. That, then picking away the crumbs with a dental pick had it clean in no time.

(This was for epoxy used to encapsulate / pot. Dunno if, fer instance, IC packages would respond as well.)

-- Cheers, James Arthur