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My desoldering iron wont work on some pc boards Answered

I have a radioshack 45 watt desoldering iron, and it wont work correctly on the pc boards out of a sony television, it will melt and suck up some of the solder, but not all of it so I can't get the parts such and sockets and such out correctly.  However it works perfectly on a pc boards out of things such as power supplies. It wouldnt even work right after i put a brand new tip on it. Any ideas? thanks in advance.

10 Replies

jeff-oBest Answer (author)2010-01-29

The board you're trying to remove parts from likely has one or more ground planes.  Ground planes in a multilayer board tend to soak up a tremendous amount of heat, which makes it difficult to solder and desolder components.

First try adding some fresh solder to the joint from which you've removed most of the solder.  Old solder doesn't tend to flow very well.  Then, try sucking it out again.

The next thing to try, if possible, is to heat the lead from one side with a soldering iron, and heat it on the other side with a desoldering iron.  This added heat may allow the joint to go completely molten, allowing it to be sucked out.

You can also try pre-heating the whole board in an oven, but I don't recommend doing this in an oven you also use for food.

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lemonie (author)2010-01-28

You are having problems with the boards not the iron. If the solder is melting then your iron works. You are not pulling the components out of the board (whilst it is molten) in the right way. Or do you expect them to just fall-out?


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mathews (author)2010-01-28

Put a blob of solder on the end of a soldering iron, and then try to melt it.

Is it a desolder iron with suction? Hold it in your other hand and use at the same time as the iron, or if you have one, a normal solder sucker.

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Doctor What (author)2010-01-27

 This happens.  If the desoldering iron doesn't work right, use a desoldering braid (also called a desoldering wick), to get the remainder.  The braid uses "capillary action" to suck up the solder into the braid of copper wires.  

It's cheap and easy.

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frollard (author)Doctor What2010-01-27

I think framistan has the right stuff to get the sucker actually working - but this is the easiest idea using good cheap solder wick:

http://www.dealextreme.com/details.dx/sku.6252  <or etc.

I have that stuff and its top notch for the price.

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seandogue (author)2010-01-27

It's quite possible the solder has oxidized, especially if it's an old TV. I've found that when harvesting from  older electronics, I sometimes have to use sacrifical solder to aid the process. That is, I have to add fresh solder to dilute the oxides to the point where the heat can penetrate the entire void properly, thereby allowing me to drawing *all of the solder off the junction.

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framistan (author)2010-01-27

Using a desoldering tool requires some trick TECHNIQUES learned from experience.  It is not easy to teach experience over a keyboard... but let me try.....

TIP #1...   APPLY MORE HEAT.  If solder sucker is not sucking then you are NOT HEATING the joint enough.  Apply a 2nd solder iron to add more heat or use a BIGGER iron.  Usually this problem occurs when trying to unsolder larger pins or large components connected to heatsinks. 

TIP #2.....  You SUCKED too soon.  Let the junction heat up real hot before sucking the solder.

TIP #3....   If your first attempt didn't work... then you will likely need to RESOLDER the junction and try sucking junction AGAIN.. This time heat it up HOTTER before sucking. 

TIP #4.... The tip of the iron must not have BLACK CHARCOAL look to it.  Tip must be silvery clean and tinned.  Use wet sponge to keep tip clean or if tip is VERY carboned-up... you might need to use some radioshack TIP CLEANER stuff.  (only a couple bucks... dont be cheap BUY ONEj).  If tip still doesn't clean up... you may need to wire-brush or knife-scrape the tip lightly and RE-TIN with solder.  

TIP *5.... you may need to heat BOTH sides of the pc board at the same time with 2 soldering irons to get enough heat to melt the solder.  

All of this takes PRACTICE and Patience.... then you will  get it.  Too much heating of the pc board will eventually damage the board.  You will discover it is better to heat the junction ONCE REAL HOT and succeed.... rather than to heat it SIX TIMES and fail... and have damaged board.   

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