• Daniel Wright

Wicked!


When it comes to de-soldering with wick, convention dictates using a soldering iron tip with a flat head. This seems to work for most people, but not me. I’ve practised and practised this method for years and the results are mixed. In the early days I lifted and ripped a lot of pads or ended up picking strands of copper wire out of solder blobs with tweezers. I just couldn’t get the hang of moving the wick and not the tip and even when I appeared to do it correctly, it was still messy.

Eventually, my technique improved enough to be considered passable but I was never entirely comfortable with it and I still made stupid mistakes.


So over the course of a couple of weeks, I decided to change everything through a process of experimentation and elimination.


Changing Flux


As a throwback to teaching myself 'through hole soldering' years ago, I was still using a liquid flux that was okay for soldering large components but I’m not sure it was suitable for de-soldering and removing surface mounted micro components. Using it was just laziness on my part because it was a familiar product that could be dispensed from a bottle with a fine nozzle and the amount was easy to control. The problem is liquid solder burns too quickly, so I always added more and ended up with a burnt, sticky mess that hindered rather than aided de-soldering. It had the opposite effect of facilitating heat transfer from tip to wick and it no longer acted as a lubricant. It can also be a nightmare to clean up.


The flux I eventually settled on, was a yellow paste with the worst user reviews of all the fluxes in the entire history of fluxes! It sells as ‘Advanced Quality ZJ-18' (whatever that means) and the entire world of know it all solder snobbery hates it with a passion. According to the reviews, it’s so evil, even whispering the name will kill a board and corrode every solder joint and component within a 100 mile radius!


As it turned out, it improved my de-soldering success to mistake ratio quite considerably and I’m yet to see any evidence of the much feared joint corrosion. As far as I can tell, that would only occur without proper cleaning and poorly flowed solder joints.



I also completely ignored the know it all's and tried blag AMTECH flux from a syringe. Once again, it did the job better than any of the other highly recommended fluxes. I'm sure the real thing would be preferable but getting hold of it quickly in the UK is nigh on impossible and the price is a bit on the steep side, especially as there's no guarantee it will be genuine.


Changing Wick

I hate de-solder wick. It’s stupid and messy and it hates me right back! In an ideal world I would be earning enough from board level repairs to justify buying a decent quality de-soldering station, but I’m not. So I have to put up with copper braid and make the best of it.

I originally made the mistake of using the same wick I used when removing solder from through hole PCB’s. It was far too wide and harder to control and it tended to spread and splay when the smaller soldering iron tip was pressed down too firmly. This led to all sorts of mishaps and my attempts to correct them often led to even bigger mistakes!

I had more success with 3 mm and 2 mm width wicks because It's much easier to control movement with a smaller braid. It's also less likely to spread and more suited to smaller pads. The various brands I tried were pretty much same as same as. The one I finally settled on (and highly recommend) is 1.5 mm Goot Wick. Unlike all of the other wicks I’ve tried, Goot Wick is double layered braid. It allows for perfect control, sucks up the solder like a mudfunking leech and the double layer makes it less likely to spread when the tip is firmly pressed down. Most people would probably use a 2 or 3 mm wick for board work but I find the 1.5 much easier to manoeuvre.


Changing Tip

When I first started soldering and removing surface mount PCB components, I watched hundreds of instructional videos and most of them made it look easy. The generally accepted wisdom being - the best way to clean solder pads with wick is to use a flat soldering tip of a similar width to the braid. This made perfect sense because I already did it on through hole PCB’s. However, at a micro soldering level I never quiet got the hang of it. I progressed beyond destroying pads but not far enough to be 100% confident in my abilities. I was fine replacing an 8 pin mosfet on a 2 year old HP laptop board but not so much the delicate LCD screen connector on an immaculate 2016 MacBook Pro.



Eventually, I decided to try something different. I had seen several people de-solder with wick using curved tips but I didn’t have a similar tip to fit my Iron. So I decided to make one myself. I took a finely pointed tip while it was hot and bent it with pliers to form a curve. I gave it a try and a few minor tweaks later, it was perfect. Applying it to the braid from the curved elbow down and slightly rolling it back and forth appears to provide very even heat distribution. The wick absorbs the solder more effectively and it definitely holds the braid in place better. It's also much easier to control when lifting the iron and wick from the pad at the same time. An added benefit is the natural curl that forms as the braid absorbs solder, making it easier to push and pull over the pads.

Since I made these changes, the whole process feels more comfortable and natural. I now find de-soldering with copper braid far less stressful and my mishaps are few and far between. Now when I make mistakes, I know they are down to me and not the tools I'm using.


Defy Convention


The moral of this story is conventions are great, but only if they work for you. Sometimes you need to ignore the advice of ‘Internet experts’ and try something different. It’s the only way to be certain of whether the problem is you, the tools you are using or your method of application. I’ve started to believe that soldering is as much art as it is a science. It may be governed by a set of static physical principles, but the application of those principles is open to interpretation. In this case, the aim is to remove old solder from a PCB without destroying the pads. Experience has taught me that the way to achieve this successfully is not necessarily set in stone.

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