# Soldering Techniques



## AlbertMC2 (Jul 15, 2010)

Hi

Sometimes I have to remove and replace leaking capacitors off motherboards (among other components). I can solder them back on but sometimes, especially with older motherboards, I struggle to desolder (unsolder?) them.
The solder starts meting but then gets almost sticky. When this happens only a very little section of the solder that is keeping the component in place actually melts, in fact it is so bad that it seems it is only the solder that is in direct contact with the soldering iron. 
Even if you add new solder to the joint, the new solder just doesn't seem to melt/mix with the solder already on the board. It seems to coat it but then the underlying solder still has the same problem.
My soldering workstation goes from 30W to 120W. But no matter what I choose it doesn't make a difference.
What am I missing? Do I need something extra or is my soldering workstation not good enough?


----------



## Basementgeek (Feb 7, 2005)

Are you roughing the old Solder connection up any after you remove the old solder?

BG


----------



## AlbertMC2 (Jul 15, 2010)

"Roughing the old Solder" meaning scrape it? Then yes I have tried scraping it with a knife to "clean" it thinking there was maybe an old film of something on it. Yet it doesn't make a difference. The solder is still sticky and I just cannot remove it easily. I though maybe the manufacturer used special solder or something. 
When this happens I always end up cutting the solder away as much as possible. Then the little that is left is small enough that it will melt and I can pull the damaged component out of the PCB if I am quick enough. Sometimes if I want a 2nd hand component from a PCB that I know is damaged I end up breaking the PCB and cutting it away from the component. Drastic but effective.

I do not know all the different soldering equipment, solder and techniques. All I have in my arsenal is my soldering workstation, solder and a solder sucker/pump.


----------



## Done_Fishin (Oct 10, 2006)

Motherbods are multi layer and most capacitors sit between voltage rails that tend to be massive areas of copper surrounding the soldered pins. This area of copper acts like a heatsink sucking all the heat from the soldering iron and leaving the tip at a temperature almost that of the melting point of solder. 

I use desoldering equipment which is temperature controlled and adjustable .. when I find that the board leaves the tip cold I up the temperature sometimes as much as 400 degrees C. 

I always use a good 50 watt iron just to treat the solder with a fresh coat of solder before trying to suck out the old. Sometimes though even with the equipment I have I just cannot get ONE of the through-plated holes to open up .. so I ensure that the longest lead on the new capacitor is the one that goes through the open hole, and use the extra hot desoldering pistol on the other hole with the leg ready to penetrate from above whilst applying gentle pressure so that the leg feeds through as the hole "melts" .. you need to be very careful though that you don't disconnect the through plating from the connection to the layer. Patience here is a must. Likewise when desoldering I leave the desoldering tool to warm up the board whilst gently wriggling the capacitor until I can feel that the leg is free and the heat has gone through the whole board before hitting the vacuum control to suck out the solder.

Practice and patience are a must .. it is very difficult to remove solder from capacitors on motherboards as you have found out and the better the soldering iron you have in terms of heat and wattage the better.


----------



## octaneman (May 13, 2009)

On older boards the solder has lead in it making stick to the components the newer solders are lead free as per the new environmental standards. Personaly I prefer the lead type solders it makes a better joint. On stubborn joints I apply a little flux on it set my iron to 500°F to spread the heat out evenly, its a bit more time consuming but you can pull out the capacitors one leg at a time.


----------



## Laxer (Dec 28, 2010)

60W iron + a solder wick is what I use...

Sometimes I need to apply some newer solder to get it all off...


----------



## Done_Fishin (Oct 10, 2006)

Laxer said:


> Sometimes I need to apply some newer solder to get it all off...


:laugh: over and over again til you get the via's clear .. I've tried all methods and several different (desoldering) irons .. :smile:


----------



## WereBo (Apr 5, 2008)

Quite often, changing the soldering-iron 'bit' to the next size up helps a lot, it holds it's heat longer before the rest of the surrounding metal can draw it away :wink:


----------



## DonaldG (Aug 23, 2007)

For £2.16 get a "Solder Sucker". See this one at Amazon UK. Worth their weight in gold. Save time, frustration and helps to alleviate damage to components & PCBs.


----------



## Done_Fishin (Oct 10, 2006)

Whilst quite right with the majority of Soldering jobs Donald, unfortunately they are not very useful when removing capacitors from Motherboards .. and an extyra tip here for those that use them frequently ... use a short length of silicon tubing at the tip to avoid melting it and not jarring the soldering iron across the board when you press the plunger & it flies.


----------



## DonaldG (Aug 23, 2007)

From my servicing of replacing capacitors, resistors, ICs, and a host of other components (not surface mount) applying the soldering tip to the component lead and when solder melted, quickly place the nozzle of the sucker and fire. This, I have found often removes the solder on the solder side but also cleans out the via hole on PTH (plated through holes) boards.

A sucker is also very useful for removing overloaded solder on a solder pad when attempting to replace old oxidised stuff with fresh fluxed stuff.

I have never had problems using a solder sucker in dismounting capacitors, large or small.


----------

