recovering parts

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kmagers
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recovering parts

Post by kmagers » Sat Nov 09, 2002 2:53 pm

has any one used a paint striping gun to strip
parts for reuse it's amazing with a little practice you can get almost anything of boards
i recently got about 60$ worth of plcc and dip
sockets off some boards

Dean Huster
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Re: recovering parts

Post by Dean Huster » Sat Nov 09, 2002 5:00 pm

Well, I've not used the mongo heat guns, but I use my Ungar heat gun all the time for stripping a board of SMT parts. I try to pull thru-hole parts first using "normal" desoldering techniques. Then I start at one corner with the heat gun, working my way across the board while pointing the gun in the direction I'm going. I use tweezers to lift the parts off and grab the diodes first, then the transistors, then the ICs and finally the resistors and capacitors. I figure that's a good "order-of-heat-vulnerabilty".<p>By keeping the heat gun pointed in the direction I'm going, the board gets preheated and component removal is undelayed.<p>I try to keep the board grounded and use a wrist strap and keep a grounded wet sponge on the bench where I can place ESD sensitive devices to cool off (they'd melt into most other ESD pads).<p>So far, I haven't discovered any damage from this gross method of desoldering SMT components, but I don't use it on thru-hole parts. Those DO tend to be destroyed before they're ready to remove, especially if they're electrolytic caps and you're dealing with a nasty ground plane.<p>I also made some special tweezers that I can connect to my DMM or digital capacitance meter for faster sorting of resistors and caps as they both pick up the component from either end and connect to the meter for a reading -- one tool for both jobs, reading and pick/place.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

kmagers
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Re: recovering parts

Post by kmagers » Sat Nov 09, 2002 5:14 pm

love idea of the tweezers got to make some i know
the paint gun put out some heat but that just takes getting used to just enough to get it loose
i made a set of test probes for my dmm out of mechanical pencils the ones that the ends screw on gut them use a strait pin solder a test lead on and hot glue or epoxy the pin in the end makes
a ultra fine test probe for smt stuff i was going
to send that tip in it poptronics but hear it is
some of the best probes i have :}

bodgy
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Re: recovering parts

Post by bodgy » Sat Nov 09, 2002 8:27 pm

Pick up a BGA infra red soldering machine - use that as a desolderer for PLCC stuff.<p>Leave it too long and you'll see your nice 4 layer board do a surfing impression as well as PTH components falling out.<p>It's quite spectacular I tell you.<p>
bodgy
On a clear disk you can seek forever.

Dimbulb
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Re: recovering parts

Post by Dimbulb » Sat Nov 09, 2002 8:51 pm

I am concerned about lead fumes. Good ventilation is prefered like outside with a breeze.
I like using an old toaster oven (my econo reflow)but sometimes I use two pencil soldering irons warming then tapping the circuit board on a block knocking the parts free. I have used a propane torch but I burnt alot of parts this way. More often I use a temp controlled pencil iron a fine file a tip tinner and cleaner and damp sponge and fine wick and a squeege bulb.<p>I have used my heat gun less but it's not like a really nice heat gun. For (smt) small parts a magnifying light and tweezers make the tiny world almost manageable. I am not happy with size 603 and 805 smt but the 1206 are kind of nice once you adjust the board design for surface mount. You can insert a thin wire under an IC then use it to pry each pin by warming and pulling the wire. I use this because I worry about over heating the part beyond it's die temperature.
Using heat sinks takes more time but you can set a block of aluminum or brass on the IC and wick up as much as you can safely and hopefully it will pry up with a tiny straight slot screwdriver one plink at a time.

kmagers
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Re: recovering parts

Post by kmagers » Sat Nov 09, 2002 9:40 pm

you would not beleive what can come off with some
practice and with out destroying them i just put the board in my vise heat on the oposite side of
the part lift up with tweezers or pic the trick
is to get it just hot enough to melt the solder
some parts a glued down or the plated thru holes
are so tight it seems they jak hammered them in
those just simply won't come out

Dean Huster
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Re: recovering parts

Post by Dean Huster » Sun Nov 10, 2002 2:14 pm

Some SMT manufacturing processes DO glue the components in place before soldering and they are a bit more difficult. ICs are more robust to heat than you may think, but that is why I keep the wet, grounded cellulose sponge at hand -- it takes care of ESD and cools the part down.<p>Yeah, Joe, the propane torch does get a little too hot for this application, however, you may have more success by working carefully from the back side of a board if the SMT parts are mounted on the "component side" only.<p>Lead fumes? Well, I've been an intense solderer and desolderer since 1962, holding solder in my mouth, working with it until my fingertips were gray, inhaling that sweet aroma of vaporized flux ... and have yet to notice any ill effects and certainly none related to lead poisoning.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

Dimbulb
Posts: 324
Joined: Sun Oct 13, 2002 1:01 am

Re: recovering parts

Post by Dimbulb » Mon Nov 11, 2002 3:57 pm

Thanks Dean that good info, I will remember that trick sponge cooler and heat from opposite side.<p>I won't say you're getting lead poison but right on top for cancer causing. Follow-up studies done on children that bite wood painted with lead paint is proving more significant.Study showed that kids that played in an empty lot in San Francisco where painters dumped paint sanding dust is VERY conclusive that the children had lead poisoning in significant levels. Interesting the location of the lead was found calcified in thier upper leg bones. Since this study I am more careful. I catch myself with a resistor in my mouth once in awhile. I hope somebody does'nt use a propane torch on a pcb in a small room without ventilation.

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