Semisouth JFET's: What are they good for? - Page 11 - diyAudio
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Old 18th October 2009, 02:28 PM   #101
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Quote:
Originally Posted by Magura View Post
Hey, since you're the "push 'em over the edge" expert here.

How would you go about soldering a device that gets so hot?

I did some playing around with pushing devices real hard, back then, the only solution I found, was to crimp instead of solder.


Magura

EDIT: And you might as well spill the beans. How do we get that plastic casing off, without damaging the fet?
It have been done before
Look at the attachment... please notice publicaton date
Take care
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Old 18th October 2009, 02:40 PM   #102
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Choky, you're bad....

The rest of you guys are scaring me....
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Old 18th October 2009, 03:23 PM   #103
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Maybe the temp fluctuation could be handled, by adding some thermal mass?
Magura
Yes, I agree. I was working with bare die mounted to Kapton film only at the die pads. We would typically have several times the mass in copper soldered to the back of the die in a mounted leadframe situation.
BTW, die are typically soldered (Die Bonded) using a "silver solder" type paste that goes liquidous at about 450C.
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Old 18th October 2009, 03:30 PM   #104
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Yes, I agree. I was working with bare die mounted to Kapton film only at the die pads. We would typically have several times the mass in copper soldered to the back of the die in a mounted leadframe situation.
BTW, die are typically soldered (Die Bonded) using a "silver solder" type paste that goes liquidous at about 450C.
Hmm, so the magic number is 175.

I see a cube filled with oil in my future

I have been working with high temp adhesives in another project recently, so bonding a JFET to a piece of carbon, and dumping it in such a cube, should be an interesting experiment.

Do you know if the phase change of the fluoinert is 100% reversible, or do I have to consider loss?

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Old 18th October 2009, 03:43 PM   #105
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If by "100% reversible" you mean actuall loss of material? My set-up had a cooling unit that kept the fluid a 65C and a condesing coil setup at the top to cool and reclaim all the gasous vapor. The unit would typically be almost sealed but when we open the lid we would incure some loss. flourinert was $350-550 a gallon then (1994)
BTW, if you actually burn or epose florinert to flame it will produce a fatally poison gas
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Old 13th December 2009, 12:43 AM   #106
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Hey, anyone got any ideas yet?
I have a dozen of these critters in the mail. I will probably try these with the BA-1 variant, it seems the most flexible.

Any advice on trying to match these things?
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Old 13th December 2009, 12:51 AM   #107
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Hey, anyone got any ideas yet?
I have a dozen of these critters in the mail. I will probably try these with the BA-1 variant, it seems the most flexible.

Any advice on trying to match these things?
Plug them into a wall outlet and match by how much they dim the lights?
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Old 13th December 2009, 01:01 AM   #108
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Yep, my HP bench supply can't do a 1000V. Just wondering if this needs any special attention compared to older NP matching articles. I mean VGS @ 24v at 1A? Just trying to avoid mounting them to a heatsink to match.
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Old 13th December 2009, 01:18 AM   #109
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I would think Nelson's matching technique would work fine...

You could always hook them up to a heat sink and match them to the wattage draw they'll encounter in the actual circuit.
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Old 13th December 2009, 08:59 AM   #110
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Originally Posted by Tea-Bag View Post
Hey, anyone got any ideas yet?
I have a dozen of these critters in the mail. I will probably try these with the BA-1 variant, it seems the most flexible.

Any advice on trying to match these things?
Did you get the 125 or the 120 variant ?

I have been told, that the 120 variant is within tighter tolerances withing each batch, thus easier to get good matches.


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