3 diodes busted because of a heat gun ??

norbyx · Jun 23, 2013

There is no other sense, I mount everything and it works no problem but as soon as I use the heat gun to shrink the tubing on the diodes connections it just kills the diode. Already busted 2 diodes because of this. What do you guys use to shrink the tube on the diodes leads.???

Speedy78 · Jun 23, 2013

A heat gun at 250 degrees F. How long do you hold it on the heat shrink? It is really quick to shrink and you shouldnt need to hold it on there. I also shrink the leads in a module while its ina bench type heat sink to help draw away any unwanted heat but I have done it with just the module before.

Pi R Squared · Jun 23, 2013

You can use your soldering iron for that. No need for a heat gun.

norbyx · Jun 23, 2013

Speedy78 said:
A heat gun at 250 degrees F. How long do you hold it on the heat shrink? It is really quick to shrink and you shouldnt need to hold it on there. I also shrink the leads in a module while its ina bench type heat sink to help draw away any unwanted heat but I have done it with just the module before.

Well I don't know if my heat gun is just 250F I think more like 250 C, since if I hold it close enough to a circuit it will melt the soldering lead. I will never do it again, fortunately the diodes that got busted were cheap (one was $10 and the other 15), but I know for sure that next time I will ether use a lighter or my iron.

Speedy78 · Jun 23, 2013

Maybe mine is C to. Im not sure. Either way the heat shri k melts faster than the diode can absorb any damiging amoubt of heat. I would rule out a heat gun. Its what most of use use. How far away are yoy from the leads and how long is it exposed to the heat gun? A lighter will apply to much heat and actually melt it. Unless tou do a quick sweeping motion (which is what I do with the heat gun) Try putting the module in a heat sink when you do it. Soldering the leads should transfer more heat to the diode case than the heat gun. Have you tested the diode after soldering? Do you use flux? With flux the solder flows really fast and helps avoide long exposures of heat on the pins.

LaZeRz · Jun 23, 2013

I use short bursts from a hairdryer or hold my iron a miimetre away from the heat shrink. That way you greatly reduce the risk of damaging your diode.

IsaacT · Jun 23, 2013

Make sure and point the heat perpendicular to the leads so the heat is not pointed at the diode.

daguin · Jun 23, 2013

I have used a heat gun on, literally, hundreds of diodes
If it is the gun, maybe your gun is producing/leaking static
Have you tried another gun?

Peace,
dave

djQUAN · Jun 23, 2013

A lighter can also deposit soot on the diode window, which is definitely not good.

lasersbee · Jun 23, 2013

Speedy78 said:
A heat gun at 250 degrees F. How long do you hold it on the heat shrink? It is really quick to shrink and you shouldnt need to hold it on there. I also shrink the leads in a module while its ina bench type heat sink to help draw away any unwanted heat but I have done it with just the module before.

I just tested my Heat gun and at maximum output it
hits 350 C (572 F).
You need to use a lower setting if your heat gun
has settings or not hold the heat to the area for
too long. You only want to direct the heat on the
Heat Shrink if possible.

When I do heat shrinking in a plastic box I use a
heat shield that only allows the heat to pass onto
the heat shrink to protect the plastic from melting or
getting warped.

Like Dave said you may also have a very electrically
noisy heat gun transmitting high EMF spikes. A little
less likely but possible. IIRC you use 220VAC where
you live.

Jerry

djQUAN · Jun 23, 2013

BTW, how do you use the heat gun to the heatshrink? do you keep it still until it shrinks completely or do you sweep it back and forth axially (to the wire) while turning it until it shrinks tightly? I always do the latter.

grainde · Jun 23, 2013

As others have mentioned just use the soldering iron and quickly touch it to the heat shrink. Works imediately and I have never killed diode, well this way...

BTW my iron is usually set around 180 C - dont know error here though...:beer:

scumbagatheist · Jun 23, 2013

This is all very good advice! You should rep everyone above.
I used to use the soldering iron method, but it seemed a bit slow to me.

I use one of those meth-head favored cigar lighters...the torch like, piezo driven ones.
The heat is very accurately directed directly at my shrink tubing, and only takes a second, maybe two, to shrink it up. I usually do this once the diode is heatsinked, but it's not necessary, as the shrinking happens so fast and cools to the air faster than it moves into the diode module.

I don't have any theories to offer with regard to the heat gun. Just well wishes with regard to your future diodes.

grainde · Jun 23, 2013

Ah Scumbag reminded me of something. When ever I do any soldering to a diode I make sure I have the diode, not only in a (pref copper) module, but in a heat sink too! Maybe not essential, but I prefer to err on the side of caution! :beer:

norbyx · Jun 23, 2013

Thanks for all the info. I sure got the idea on what I can be doing wrong, I won't use the heat gun for my next build and if it all works than I have nothing else to blaim.

I know that the lasers worked just before I used the heat gun to sink the tube on the diode (I tested everything before closing up the host). The diode was installed in the aluminum heatsink before using the heat gun.

Anyhow I shall see what happens. BTW we use 110V here.

+1 Rep to all (if I can).

Meatball · Jun 23, 2013

If you use a heat gun, use a small nozzle so the heat can be properly focused onto the target.

If you use a light, use a butane one for a clean flame, one without all the soot.

If you use a soldering iron, keep the iron just below the target and let the heat naturally convect upwards underneath the target.

3 diodes busted because of a heat gun ??

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