De-solder braid

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HowardKennitby | 15:07 Fri 30th Mar 2012 | Electronics
6 Answers
Hello all

Does anyone know if copper de-solder braid goes 'off' as it gets old?
I am trying to remove some components from a circuit board and the braid I have is not picking up the solder very well. It is probably about 2 years old.




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Yes. The copper will get a film of verdigris on itself over time. As plumbers know, copper has to be clean to take solder. You could try dipping the braid in flux.
Question Author
Thanks for that.
I had a feeling that would be it. I have to go to Maplin tomorrow anyway so will get some new stuff.
copper can aquire several different surface coatings depending on what kind of atmospheric pollutants it is exposed to. Dilute hydrochloric acid should clean it up, Sanilav toilet cleaner solution should work too as it is in effect dilute suphuric acid. after cleaning wash in rainwater or distilled water.
Some desolder braid is rubbish in the first place. Get a good quality product.

I would not even consider using jomifl's suggest as some acid residue would remain and possibly damage the board. Acid is a plumber's soldering resource not something for an electronics tech.

A powerful soldering iron is required to get enough heat into the braid and joint very quickly to get the solder flowing. The braid really sucks the heat away and the solder follows the heat so it is essential the braid is hotter than the joint.

The main problem with many PCBs is they have plated-through holes. These tend to hold the solder very well due to the capilliary action of the lead in the hole. They also transfer more heat into the board because of the greater contact area.

If the iron is too low powered it may take to long to heat the solder and damage the bond between the pad and the board. The pad comes off and may take a substantial piece of track with it. This takes considerable skill to repair especially with the fine tracks on high density boards that sometimes have tracks between the pads where chips are mounted.

Generally the best solution is to cut the legs of the components and remove them with small fine nose pliers while melting the joint. Then it is easier to remove the residual solder but often it helps to use a resistor lead or similar to help push out the solder remaining in the hole. A blast of compressed air through the hole while the solder is flowing also works. Even blowing can do it but don't burn your lips.

However it is very easy to damage the board when removing the component lead by pulling the plating right out of the hole with the lead. This is especailly common if the lead has been cut such that the end has been squeezed and is wider than the hole.

With a double sided board this damage can be recoved by soldering both sides but may be a real problem in a multilayer board.
Also check if the product is rated RoHS. This stands for Reduction of Hazardous Substances and among other things means the solder is lead free.

This requires a considerably higher temperature to melt the solder and it is much more difficult to get the solder to wet anything, including braid.
Beso, washing does work for removing contaminants from non porous surfaces surfaces. Incidentally neve use acetic acid curing silicone rubber near delicate circuitry especially in confined spaces as the acetic acid vapour will destroy it.

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