Problem, broken legs.

[RobotHamster]

I tried to recap the logic board of my 2nd hand iMac. The problem found here
https://www.badcaps.net/forum/showthread.php?t=26694

So I removed both capacitors following the main FAQ and when I go to clear the holes, I find a snag. One of the two caps came away freely but on the other, it seems that I simply snapped the legs without removing them leaving the holes plugged by each leg. Now I cannot remove them using the sewing needle method. It seems that the soldering iron I have is too weak (only 40W) and I cannot melt the solder enough to push the old legs through it.

Any suggestions other than getting a higher power iron?

[Gariarto]

Re: Problem, broken legs.

Any suggestions other than getting a higher power iron?

Add more molten 60/40 or similar lead bearing solder to the blocked holes to hold heat at the site. The new solder should readily mingle into the old and allow you to push those busted pieces through. Once out, wick away the excess. Be gentle around those traces with heating for an extended time.
Good luck.

[RobotHamster]

Re: Problem, broken legs.

Is that lead as in metal lead or power lead? Sorry I I'm kind of a soldering noob.

[RobotHamster]

Re: Problem, broken legs.

Got the problem sorted. At the time I didn't understand the suggestion well enough so I used the solder that I have which is about 99% Tin, 1% copper.

But it worked after I left it there for about 2 hours and the holes are now clear of all obstructions, although i'm not too sure about the traces so i'll have to be careful when fitting the new caps.

Thanks again mate.

[Gariarto]

Re: Problem, broken legs.

You are quite welcome ! I'm pleased you got a result. I was talking about regular flux core, wire solder, and by extended time I was thinking around a minute ! I should have been more specific, sorry. Take a read through this for a clearer picture of soldering. http://en.wikipedia.org/wiki/Soldering Plus there's a large number of online video tutorials on Youtube that will help.

[mariushm]

Re: Problem, broken legs.

Ok, you used solder wire that's mostly Sn and 1% copper. This is really not a good soldering wire to fix things, mostly because the temperature the solder becomes "liquid" at is much higher, above 210c

When you repair something, you want to use solder that has lead it it, because it melts at much lower temperature, about 180c, so when it combines with the lead free solder on the components, the overall temperature required to get the solder liquid drops down close to that 180c.

Now, wherever you have those large planes of copper on the board like you have on the second picture for example, that large copper surface will act like a mini heatsink and cool down the solder tip of your iron.

You need an iron that has a large heat reserve or is powerful enough to keep its temperature up.

If you use solder that has to go above 210c to go liquid, on an area like that one with lots of copper, your iron needs to be capable of staying at around 300-350c just to make the solder liquid.

Some cheap irons can't manage that.

With leaded solder, it's usually possible to do stuff with solder irons that can only do 220-250c at the tip.

Also, flux is important.. most solder for electronics has some flux in it but solders like the one you have 99% Sn/1% Cu may not have flux at all.

Flux is basically like a weak acid - when your solder tip heats the solder wire, the flux inside it splashes on the surface that you try to solder and removes a thin layer of oxides and other impurities that prevent the solder iron tip from heating the surface that you want to solder or desolder.

So if you plan to do more soldering in the future, it's really recommended to get some good 60/40 or 63/37 (Sn 60 / Pb 40 or Sn 63 / Pb 37) solder wire, with no-clean flux or mildly activated flux - rosin fluxes, water based fluxes, SOME mildly activated fluxes have to cleaned off the board with isopropyl alcohol (some people use acetone but it's not always a good idea) after soldering because if you leave them, they may in time continue to corrode the metal and weaken the solder or destroy traces.