Heatgun for scavenging parts off pc boards

[diydidi]

Hi all.
A friend recently gave me some boards from medical machines to butcher and strip for spare parts.
Will a heatgun, the type used for stripping old paint off, work for this?? If so, what would be a good wattage??

[soundguruman]

heat destroys electronics parts

[J M Fahey]

A heat gun is too slow, you will burn your parts by the time solder melts ..... *if* it melts at all.
Unless those boards have a couple expensive ICs which you happen to *need* (VERY unlikely), it's not worth it.
Besides, parts will have very short leg stubs which will make reusing them almost impossible.
It *might* be interesting to save some relay, or switches, "mechanical" stuff like that.
Parts that cost a couple cents, such as resistors or small diodes, are more expensive to recover than to buy new, plus many will be damaged.

[Jazz P Bass]

heat destroys electronics parts

So the 'preheat' cycle on a wave solder process uses what? Ice?
"General guidelines are to get a topside or preheat temperature of the assembly to approximately 140-160 C for the topside of the assembly, ramping linearly the preheat settings are commonly set at 200-210C."
Set up for lead-free wave soldering

[J M Fahey]

Dear jpb: in this case I can't correct sgm because he's basically right.
In general lines, heat damages parts, more specifically molten solder temperatures and above.
And "pre-heat" *is* limited , not by chance, to a safe value , those 140/160ºC you mention.
And it's done to stay less time at the *real* damaging molten soldering temperature.
jm2c

[Jazz P Bass]

Back to the original OP's question: I researched the 'Paint Remover' guns.
Wow!
They can run anywhere from 800 F to 1200 F.
Yikes!

[R.G.]

For soldering or desoldering without damaging stuff, the rule is to get in quickly with high heat, melt it locally before the heat has time to conduct away to the sensitive stuff, then get out. The thermal pathways and the delay to getting through them act as a self-heatsink.

I've removed parts from PCBs with a propane torch and a modified wide-flame tip. Works much better than a silly heat gun. Scorches the PCB, but then, the board is expendable if you're looking to save the parts. If you're saving the PCB, clip the parts off the component side and remove the leads one at a time. Rework is easy if either the board or the part is disposable. The truly difficult task is when you have to have both the part and the PCB be usable after you remove it.

[kg]

generally speaking the only stuff i scavenge is line power stuff... cords, bushings, dpdt switches, pilot lights, etc. sometimes power trannies.

power supplies can have some useful caps and bridges, but it doesn't sound like you got those.

[Mark Hammer]

If it's a double-sided board, it may well be much more trouble than it's worth. And this is coming from a guy who still has germanium transistors from the radio I bought with my summer earnings in 1965.

[jrfrond]

Wave-soldering temperatures and times for both preheat and solder bath are closely-controlled and monitored, not just haphazardly shot out of a gun at random temperatures for random time periods.

If you want to try this, I suggest that you suspend the PCB upside-down, paint the bottom surface with RMA paste flux, and then heat in a WELL-VENTILATED area. Heavier parts SHOULD just fall out of the board by their own weight, unless they are crimped first, which is highly-likely.