A Guide to Desoldering

Desoldering is a process in which the solder and components are removed from a work-piece for the purpose of replacement, repair, troubleshooting, salvage, etc. just like soldering, desoldering is also a very simple process and it too requires a soldering iron.

While many are a pro at both soldering and desoldering, there are others who are only trying to learn the basics. For beginners desoldering can be a little tricky. To make it easier for novices I have created this ultimate step-by-step guide to desoldering.

Step 1: Get Your Equipment Ready

Before getting started, make sure that you have all the necessary equipment ready on your workbench so that your work can be done in an orderly manner. listed below are the tools that required for desoldering.

Soldering Iron

Soldering iron will produce the heat that will be used to melt the solder. Soldering irons with power ranging between 15W and 30W are perfect for most electronics or printed circuit board desoldering. Anything higher than that may damage either the board or the component. Soldering guns are not recommended for this purpose as they have a very high wattage and most of them generate their heat by carrying an electrical current within a wire. Due to this, the wire of the gun carries an irregular voltage that can damage components and circuits.

Cleaning Sponge

A good cleaning sponge is required for cleaning the tip. Make sure that your sponge is properly wet. You can also use a wire sponge as a substitute.

Solder

Solder is a very important accessory. It’s an alloy made from the mixture of different types of metals. There are many sorts of solder available in the market with different metal composition. If you are a beginner go for a lead-based solder. Lead-free solders need high heat melting temperatures; hence the soldering iron must be designed to be used with lead-free if you are going to use this solder type. However, there are also other choices like the flux-cored solders.

Solder Remover

A solder-removing device is a vital tool for desoldering. You must choose a device according to your personal opinion as well as experience. Given below are some of the most preferred solder removing devices.

Manual Solder Sucker

A manual solder sucker works well for removing through holes components selectively from a PCB. However, cheaper and smaller units don’t work very well. The manual solder suckers are handy and compact but they fail to work as well because of the smaller cylinder and limited stroke length.

Solder Wick

Solder wick has no moving parts like the soldering sucker. It looks like a braid of thread used in oil lamps, only it’s made of copper that will soak up the liquid solder when placed over it. One thing to remember about a solder wick is that it’s not reusable, and because it is expendable, the solder wick is less versatile.

Desoldering machine

This is your ultimate option in case you repair a lot of boards and you are much more into desoldering. It’s generally a soldering iron that has a hole in the center of the tip, which is connected directly to a vacuum pump. When you hold the up the iron to any soldered lead, it simply sucks the solder right up. It’s just like the manual sucker, but automatic and more efficient.

Hot Air Rework System

A hot air rework station with variable temperature settings is a perfect tool if you have to desolder several surface mount components at one time.  The system has different tips for desoldering different types of components. a regular hot air gun can also be used,  but you must be careful as it can damage the board and other components.

Tweezers

Heated tweezers work great for removing surface mount components selectively.  Once the tweezers get up to the specific temperature you can use it to simply pluck up the old solder or components off the work-piece.

Compressed Air

You can use a soldering iron to heat up the joint that needs to be desoldered and use a can of compressed air to blow away the hot solder. This process is quite messy, so I would recommend doing this only on a work-piece that you are salvaging components from as you can end up soldering the parts where you don’t need it.

You’ll also need other accessories such as cleaning cloth for cleaning the board, a small flat-tip screwdriver and alligator clip, pliers, Isopropyl Alcohol as a cleaner and a toothbrush.

Step 2: Preparation

Soldering iron

Now that you have got all the necessary tools ready, it’s time to get started. First of all turn the soldering iron on and set the temperature.  Wait around three minutes for the iron to get hot.

Wet the cleaning sponge and then clean the soldering iron tip by rubbing it back and forth with the wet sponge. Repeat the process until the entire tip has been cleaned. Some smoke will appear while doing that, and you need not worry because that is normal as the sponge is wet.

Work-piece

Assume that you are working on a circuit board.  Determine the terminals for the component that needs to be removed. Now put some isopropyl alcohol on a toothbrush and gently clean the terminals to be removed. Make sure that only the soldered side terminals of the board is cleaned and not anything else on the component side. Just ensure that the varnish, grease,  or glue, if any, is removed from the joint before heating the component. Not doing this can shorten the tip life.

Heat applied during the process can possibly cause damage to sensitive components like the integrated circuits or transistors. Clip a metal alligator clip between the terminal and the component you are going to desolder, in order to dissipate some amount of heat.

Step 3: Desolder

As different solder remover uses a different mechanism to desolder, I have noted down the process for the solder removing tools that I have mentioned above.

Manual Solder Sucker

First, heat the terminal using a soldering iron until the old solder on the terminal melts. at the same time push the terminal slightly with the soldering iron tip to free the parts while the solder melts.

Now press the end of the solder sucker until it clicks into place. It will compress a spring, and latch the pump in the depressed position.  After the solder has melted, touch the tip of the pump without applying pressure, to the solder and push the button to release the spring, making the piston shoot back rapidly. This will create a vacuum which will pull up the melted solder into the sucker. And finally, empty the solder sucker into the trash.

Tips

  • Since pushing the terminal with the soldering iron can wear the tip down, it’s recommended to use an old iron tip if you have one.
  • As the solder can harden quickly, work on only one terminal at a time and always keep the pump ready.
  • Desoldering machines work with the same mechanism.

Solder Wick

First, unwind some inches of solder wick from the coil. If the wick does not contain flux on it, apply some flux to the part of the wick that you’ll use. Now put the braid over the component that you want to desolder and place the hot soldering iron tip against the braid over the component. After a few seconds, the solder will flow off the component and onto the braid. Finally, remove the braid and the component.

Tips

  • Choose a wick smaller than the solder pad on the circuit board or of the same size, and slightly broader than your soldering iron tip.
  • Don’t hold the braid with hot solder directly on your hands.
  • Melting a bit of new solder on the soldered component can help melt the old solder.

Hot Air Rework System

Heat the existing soldered terminal using the soldering iron until the old solder has melted. Then vacuum up the melted solder using the vacuum nozzle or a desoldering pump on your rework station.

Tweezers

Each pincer on the heat tweezers is basically a soldering iron itself. All you need to do is simply pinch each pin on a surface-mounted component to melt the solder and pull off the part that needs to be removed.

Compressed Air

Heat the component with a soldering iron to melt the solder. Turn the can of compressed air upside-down and spray the air against the joints. When the melted solder is sprayed away, wrench off the components that must be removed, by using a pair of pliers.

Step 4: Clean up

After you are done with the desoldering, there might be some brown resin or residue stuck on the solder pad. You can use a commercial resin cleaner to remove it, or very carefully scrape it away with a tiny, flat-head screwdriver or by using a steel wool. Also, give a finishing touch by cleaning the area with an isopropyl alcohol dampened toothbrush.

Conclusion

Desoldering can be pretty tricky, and many people have their own methods to cleanly extracting components from a circuit board. Apart from these techniques, there are much more. If you know the right way, you’ll find it quite easy. I would only recommend you to keep experimenting.

Edward
 

Click Here to Leave a Comment Below 0 comments

Leave a Reply: