Desoldering wattage and tip size for tight multilayer vias

The heatsinking effect of planes can be a real issue. I use a 140W Weller soldering gun for motherboard capacitor replacement, it's the only thing I've found that puts down enough heat to remove the caps without ripping up traces.

Indeed. I neglected to mention that I cranked up the wattage with a variac to about 90W but that is nowhere near what you use ;)

Michael

msg Inscribed thus:

Hot air preheating works wonders. I use a hot air paint stripper gun to preheat an area first before then desoldering the cap. Usually they come out of the board quite cleanly but some manufacturers bend the leads after insertion into the pcb, which can be a pain.

That's a great idea, I'll have to give it a try next time. Just have to be careful not to overdo it and cause SMT parts to drop off the board.

My tool for that is a dart with a bolt exchanged for the flight. Without heating, excavate around the solder with the dart until you can lever the pin up. But then I continue on , using the hot-air only. Another recently discovered aid for this process. I saw a plumber using some woven glass mat to protect a cupboard before soldering. As I had plenty of GRP grade woven mat I glued together 4 bits of sheet of that , using contact adhesive (discolours but holds together on hot air heating). Cut a hole to match the area of interest and lightly clamp the mat to the board , mounted in a vice with protected jaws.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

James Sweet wrote in news:Lye1k.2159$Yx.1418 @trndny08:

I have built dams out of paper to protect nearby parts from the hot air. Held the paper on the board with alligator clips.

Works fine. Also a good temperature indicator. If the paper chars too much, your air is too hot.

caveat: I was playing with an old pcb, stripping it of parts with my hot air gun. One of the electrolytic caps got caught in the guns nozzle.

Before I could shake it out, BANG. Small jet of flames. Shell of cap flying across the room.

In other words "avoid overheating electrolytics, they can explode."

I wouldn't even attempt to do this without a temperature controlled soldering station. You need a lot of power, but with no temperature control, you're likely to over heat the board and lift traces. It's also critical to have a clean properly tinned tip. Andy Cuffe

snipped-for-privacy@gmail.com

I have one, but it doesn't provide enough heat. 140W gun works great, haven't damaged a board yet, I've been soldering for a long time though.

Having a Weller miniature iron with 80 watts is sure nice. Sometimes I combine heats from the 3 outputs. Desolder, solderer, and hot air. I have used 2 irons before. For the rough things sometimes I also use a Bic lighter against the iron for a afterburner effect. The RS 250 watt gun, then the torch.

I got so tired of watching the game last night, I got to the point I just wanted anybody to win so it was all over....

greg

Lets go Pens

Wimp! ;-)

James Sweet Inscribed thus:

I have found that often SMT parts are glued down and are a right pig to get off the board, particularly if its a part that you want to salvage !

Often yes, but when you want it to stay on the board, it'll fall right off! Don't ask me how I know that :)