How Easy is it to cook Transistors - share your transistor baking story....

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mac

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Jun 5, 2009
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Location
Sunshine Coast, Australia
How easy is it to cook a V reg.
I appear to just have cooked a 7915 reg by soldering on really short legs (I cut them down to fit my heatsink arrangement).....

Is this a normal thing?

I thought they would take some pretty high temps??


Mac
 
I can't answer your question, but since building the EQN and EZ1290 where this is the only way to do it, I have made it my custom to solder transistors and v regs with the heat sink already attached. Just figured that the soldering is when they really need a headsink most.
Also the usual tricks - solder one leg, then do a few other components, then the next leg.
If I am doing a layer of transistors I might do all the emitters, check my email, solder all the bases, etc.
 
maybe just a dud one straight out of the box??

Is the quality or reliability of these components getting worse over the last few years. I have had two dud ones in the last few weeks, and I presumed I might be to blame.

Beyond V regs, isnt it easy to cook small signal transistors with soldering, like BC107's and the like?


Mac
 
Due to the nature of modern manufacturing if anything the failure rate or DOA parts are near zero.

If you are getting a high percentage of faulty parts DOA, either they are being mishandled, or were not prime parts to start with.

Regarding soldering, most modern through hole parts are designed to literally sit in a molten solder pool for several seconds so perhaps if you're using some unconventional higher than ordinary temperature iron damage could occur, but most irons intended for electronic soldering should be easily tolerated by modern components.

JR
 
Perhaps you electrocuted it?
If you f.e. held it by the metal handle with pliers and held the soldering iron with another hand, some static charge could occur.

Or was it already mounted to a heatsink?

 
Sometimes I use a 60W iron for soldering/desoldering and never cooked a semiconductor. If you did it you must have sat on it for a very long time.
 
When I was about 10 years old, I heard that a transistor can be used as an amplifier and that more power supply voltage the better, so in my infinite wisdom I connected 240V AC from the wall socket across the C-E and the output of my cassette recorder across the B-E and also connected a speaker in there somewhere. I then switched on the 240V and the transistor instantly went poof, some smoke came out of it and I didn't hear any sound from the speaker.

I don't think the heat did it, one thinks 240V across the collecter to emitter might have been a bit too much!

 
I souped-up a PC motherboard with an un-approved CPU. It worked fine, but the CPU power regulator looked floppy. It was running SO hot that it melted the solder around its legs. Yet it worked for most of an hour, and after I re-mounted the device on a bigger heatsink it ran for years.

Somewhat different than your case. This was a simple transistor, not a complex IC. The design of its driver tolerated great leakage, the main reason transistors go out-of-spec above rated temps.

Still I doubt that any "electronics soldering iron" will swiftly ruin modern Silicon.

Why are you sure it is dead? Not just mis-wired?
 
Some years ago I clumsily unsoldered some IC opamps in order to install sockets for better opamps (the usual novice's way of trying to "mod" stuff without actually know what you're doing - or what the circuit is doing for that matter). Those were quad opamps mostly, and it took me quite a while and lots and lots of heat to unsolder all their legs. Yet, to my surprise, those opamps still worked fine afterwards.
 
always learning..

I thought it would be easy to cook them when soldering, but as evidenced by all here obviously not. I was rigging up an elaoborate heat sink arrangement and had to trim the legs down on a brand new device, so when it didnt work, I presumed I cooked it with heat.

Must have been a dud one out of the box, or somehow it shorted or something else. I replaced it with another one from the same batch and it works fine.

Mac
 
mac said:
was rigging up an elaoborate heat sink arrangement and had to trim the legs down on a brand new device, so when it didnt work, I presumed I cooked it with heat.

Must have been a dud one out of the box

There also the possibility you broke one of the legs while trimming and bending them for the heatsink. I've managed this in the past with a TO220 package. The legs are wide and prone to breaking off when bent with heatsink installation related activities.. Leg just about stays in the slot, but really it's disconnected from the actual IC. Try yanking one of the legs and the disconnected one will come off with ease. Lesson learned: don't bend directly from the IC, grip the legs with something protecting the IC so the roots won't bend.
 
One time I made a nice transistor appetizer, some bc134's baked them for about 40 minutes at 600 makes a nice dish. With white wine of course;-)
 
only time i've ever cooked a transistor (and my thumb.  idiocy was pervasive that day) was for a school project.  perf boarded a divider circuit to short (and thus brake) the dc generator of a wind turbine above a threshold voltage.  forgot the heatsink in testing, got a nice round plastic blob.  that was my smoky reminder to always check the bench for leftover parts before firing things up.  also, DON'T TOUCH HOT STUFF  ;).
 
I cooked several about three weeks ago. Was troubleshooting an old LA-4 when after a chain of events beginning with one transistor in the Wavetek power supply I managed to take out six transistors and send way too much current through two resistors. Lots of smoke and cool noises.

No audio components were harmed during the making of this film.
 
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