Desoldering?

[Ark42]

Desoldering is hard, any tips? I found if you melt a fresh blob of solder over the lead it can help conduct heat down, but it can still be hard to melt all of the solder enough to pull out the old cap. Either the motherboard spreads the heat out too much or the solder Epox used on my board doesn't melt at as low a temp as the 60/40 rosin solder I have to resolder things back on with.

[kc8adu]

you need a hotter iron.
the heat is getting soaked up by the inner ground traces.
dont pull the caps out till the solder is completely melted all the way through or you will pull out the through hole and ruin the board!

[Ark42]

What? I got a 15W when people were telling me 5-10W would be enough and I wouldn't want to damage the board with excessive heat. Radioshack's least amount of Watts was 15 so I get that one, and now you're telling me it can't even melt the solder because the board is too big?
Anybody know where I can get a replacement tip that is 1mm wide diameter and about 5mm or so long, just a straight cylinder, not a cone shape, so I can just stick the whole tip into the hole?

[kc8adu]

a 15w iron wont do squat on a mobo.
i use a temp controlled station or a 60w iron with a wide tip that will heat both leads at once.

[Ark42]

I got the 45W radioshack iron with the built-in bulb sucker thing today. While it does make removing the caps a ton easier, I still can't get the holes clear of solder enough to put new ones in...

[Ark42]

The 45W really made things easier. I managed to finally replace the 5 bulging caps on one of my 8K7A boards. Having never soldering before this, I was surprised when the thing actually booted back into windows without any issues when I put the computer back together.
I found that soldering is pretty easy, and desoldering is not so bad either. But if the hole gets filled with solder after a cap is removed it becomes a nightmare to clean the hole in preparation for a new cap. I eventually got out a sowing needle and just picked away at the hole until it was clear for one particularly stubborn hole.

[kc8adu]

now you have experiance for the next job.

[Ark42]

I'm really thinking there has to be an easier way to clean holes. I spent all frickin day picking at these holes with all kinds of things from paperclips, pieces of wire, thumbtacks, needles, etc. I tried adding a blob of fresh solder and using the bulb and vacuum to suck away solder from the hole, but the center of the hole stays solid no matter what I do. I have not tried a drill yet, but I'm thinking of finding a bit that is 1mm or smaller and using it next time.

[clsk]

just a question....do you have to clean the holes? i think im the most ghetto...i use my 2$ iron i got at a discout store and instead of cleaning the solder out of the holes i just cut the contacts of the new capacitor to size place it over the 2 holes and just do the reverse of taking it out...heat up 1 hole while pushing it in then the other and repeate...i also dont have any solder around, i did 3 motherboards like this, and havent had a problem (yet)

[Ark42]

People told me to try that, but it did not work. I tried tinning the leads of the cap and heating the lead with the iron, and also heating the back of the hole with the iron, trying to push the cap leads through the solder, but the solder stays solid and thus the cap can't push through. I think when the old cap is there, its lead helps draw heat around the solder, melts it just long enough to pull the cap out, but then I can never re-melt that piece of solder in the center. Say the hole is 1mm wide and 6mm deep, I can clean out the top 2mm or so from either side using the iron and sucker, but the 2mm in the center of the hole stays there. I don't have the problem on all the holes, but I am thinking maybe the ones I do have the problem with are the ones with big green pads around them, drawing away all the heat. Maybe I'm just not patient enough, but after holding the iron on the hole for a full minute and not melting the solder, I give up because I don't want to damage the board.

[Fatal0E]

I do the same as clsk, just heat the holes and stick the cap in, done 4 boards now, minimal problems.

[Ark42]

With my boards, I dont think that would work. I tried heating the hole and sticking the new cap in (I did not cut the leads) but it did not go in at all. The solder in the very center of the hole would stay solid no matter what I tried.

[alwayzamd]

Solder Braid

Have you tried the copper solder removal braid? I think that stuff works great. It soaks up the solder like a spunge. You just put the braid over the hole that still has solder in it. Then put your iron tip over the braid, and it soaks up the solder. Works for me - just my two cents.

T.J.

[Ark42]

I got a few boards changed since that post.
My tool of choice for both desoldering and solding the new caps on is the 40W desoldering iron from radioshack with the built-in solder-sucker bulb thing.
I like it because the tip is a cone with a hole, not a point, and you can put it around a lead sticking out the back of the board to more easily desolder things.
I use it to solder new caps on as well for the same reason - I found if you cut the leads to near the proper length, its a lot easier to force them through holes without even trying to clean out the old solder first. The shape of the desoldering iron really helps in this process too.

[Kako]

I'm also having trouble cleaning out the center of the holes from the solder. I bought the desoldering tool from Radio Shack, and it works great, as long as the cap is still in place. But the center of the hole is just stuborn. I don't even think its clean solder anymore, that its probably picked up a bit of filth from time after time of trying to melt it away. The recommendation that the leads be cut to close to appropriate size during installation, I'll try and do that. I just don't want to waste a cap destroying it in the process of putting it in. Any other recommendations for removing that stubborn piece of solder?

[Topcat]

Reheat the hole with the iron, add a little fresh solder to reflow and melt the old, and then poke a needle or dental pick through it with the iron still applied. Remove the iron leaving the pick in the hole. When the solder hardens, gently spin the pick (the solder won't adhere to stainless steel) to break it loose, and pull it out. Scrape any remaining solder boogers away with an exact-o knife or fingernail, and viola! A clean open hole!

Good Luck!

[kc8adu]

seems you are still not getting enough heat if the suction doesnt get the hole clear.
i use a heat gun to preheat stubborn ones and it does the trick.

[ncdave]

moby solder sucker

Any other recommendations for removing that stubborn piece of solder?

Don't call this a "recommendation," but, for your amusement, and with apologies to Tim "The Toolman" Taylor, here are a couple of photos of my solution:
http://www.burtonsys.com/BP6_desoldering1.jpg
http://www.burtonsys.com/BP6_desoldering2.jpg
Yes, they are hooked "in series," with the bags removed for extra power. (Removing the beater-brush or belt might also help a bit.) They made a most impressive roar, lemme tell you! Note that the power cords snake off in different directions, because I plugged them into different circuits, so that they wouldn't trip a breaker.

I tried to improve the design with a ball valve in place of the clamped hose...
http://www.burtonsys.com/soldersucker5.jpg
...but no joy: it leaked the slightest smidgen, which made it impossible to fill the desoldering tip with molten solder. I need an SPDT "Y-valve" rather than a simple SPST on/off valve, so that I can switch the tip back and forth between atmosphere and vacuum, but I can't seem to find such a valve. :-( Does anyone know where I could get one?

Other variations are possible, too:
http://www.burtonsys.com/soldersucker2.jpg
http://www.burtonsys.com/soldersucker1.jpg

Really, I think TopCat's dental pick or sewing needle is a better solution for those stubborn little holes.

-Dave

[kdr9232]

quick way

take large dikes and cut cap in two, use rubbing achole to clean up mess and reuse the old legs, solder two old legs for quick fix. its quicker exspecially if
you dont have a good soldering station.

[(In)Sanity]

Best way I've found to clean the holes is to use a good heat iron and about 6 or so inches of copper phone wire, the solid stuff. You strip the wire off just before your going to use it, heat the hole and push it through. It will pull all the solder with it leaving a nice clean hole. You can reuse the same wire many times before you'll need a new one. This works far better then the desoldering braid. If you can't get the solder hot enough to push through, add a little more solder to the hole.

Also another idea.

These guys sell drills smaller then anything you can get at a hardware store.

http://www.drillbitcity.com/