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Old 5th October 2012, 06:24 PM   #21
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Putting one in a vise crosswise is by far the most reasonable approach. If not on the first try, in the next few one of them will show you the die surface neatly, minus bond wires. If you're trying to save the wiring or trying to transplant the die, oh well, but for ID, especially since you have a pile, mechanical is the best way to go.
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Old 6th October 2012, 12:08 AM   #22
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Tried several on mechanical, vise crush from the sides.

The die is not left in good condition that I can see. Nothing that can be identified one way or the other as die (A) or die (B)...

Over the weekend I can try much higher magnification and try to see what is going on in terms of seeing the surface of the die. No luck thus far.

Also the die has seemed to be partially destroyed when the plastic is de-laminated, thus far.

_-_-bear

Looks like a lost cause thus far. Paypal may save me some $$, we'll see.

PS. now that I know where the die is inside the thing, I may try some jewelers saws to hack most of the way on all sides, and then try a gentle wedge or a crush at that point, hopefully not destroying the die quite so well
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Old 6th October 2012, 03:07 AM   #23
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The same device from different sources can have very different dies. Most companies made a small number of die styles which became many different devices by varying the doping levels and test sorting. eg the basic dies from Fairchild and Motorola looked very different
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Old 6th October 2012, 03:28 AM   #24
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What about heat? The die should withstand far more than the package.
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Old 6th October 2012, 03:46 AM   #25
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Some heat is a good idea.

I guess the layer of conformal coating over encapsulated power dies does't exist in the signal packages. So the epoxy is bonded directly to the die.

Enough heat would probably make some really smelly smoke. If they're copper leaded and you put a good heat sink on the collector you might be able to torch it crumbly without harming the die.

Last edited by Andrew Eckhardt; 6th October 2012 at 03:52 AM.
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Old 7th October 2012, 12:52 AM   #26
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davidsrsb, there is only *one* source for this part: Toshiba.
So there should be only one die.

As far as assembly plants, I dunno that answer.
They could all use different stuff inside the black package.

I will have at another one or two tomorrow and see if I can manage to get it to open without destroying the die...

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Old 12th October 2012, 01:26 PM   #27
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Are they labeled "Toshiba"? If so, contact Toshiba and tell them you suspect you have some counterfit parts. They might offer to decap them to check if you are willing to tell them exactly where these parts were purchased. Counterfit parts are a hot topic among semiconductor makers nowadays.
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Old 12th October 2012, 01:54 PM   #28
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Good thought, but Toshiba oddly enough did not actually put a logo or label on their jfets! Also Toshiba has stopped production on this part. They are dropping their entire JFET line it would seem. Plus communicating with these companies is an exercise in futility. And, I would expect that they are acutely aware of pirating and counterfeiting in asia.

Looks like a lost cause.

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Old 27th October 2012, 06:46 AM   #29
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The curves show that they don't match the original manufacturer's. Isn't that enough to reject and retrun the batch to the supplier?

Assuming you succeed in disassmbling the case and the die doesn't look the same as the original, then what?
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Old 27th October 2012, 07:03 PM   #30
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this may be of some value....a year ago I accidently asked for too much current through a Fairchild TO-92 jfet, and it let out a very small hint of smoke. It appeared mostly normal. but a loop revealed a short crack in the epoxy. A small amount of squeeze in a vise was applied and it cracked nicely into it's original pieces.
It even still had one of the wires from the legs to the die attached. I looked at it at 8 power, and it seemed to be in mostly in original condition, meaning the die had not burned up or melted. I believe it was something like 3 - 5 times the rated curent, not a total short.

If you have enough samples, maybe try to overheat it some from the inside to loosen it up a bit, before trying the crush.
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