How To Solder
Soldering is defined as "the joining of metals by a fusion of alloys which have relatively low melting points". In other words, you use a metal that has a low melting point to adhere the surfaces to be soldered together. Soldering is more like gluing with molten metal than anything else. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and developed with practice.
This document attempts to teach soldering through a few simple steps. Tips and tricks are also provided at the end.
How To Solder
Step 1:EquipmentSoldering requires two main things: a soldering iron and solder. Soldering irons are the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and you risk damaging either the component or the board. Note that you should not use so-called soldering guns. These are very high wattage and generate most of their heat by passing an electrical current through a wire. Because of this, the wire carries a stray voltage that could damage circuits and components. The choice of solder is also important. One of the things to remember is to never use acid core solder. Acid core solder will corrode component leads, board traces and form conductive paths between components. The best solder for electronics work is a thin rosin core solder. I prefer a thickness of 0.75mm, but other thicknesses will also work. Just remember not to get anything too thick.Remember that when soldering, the rosin in the solder releases fumes. These fumes are harmful to your eyes and lungs. Therefore, always work in a well ventilated area. Hot solder is also dangerous. Be sure not to let is splash around because it will burn you almost instantly. Eye protection is also advised.
Step 2:Surface Preparation:A clean surface is very important if you want a strong, low resistance joint. All surfaces to be soldered should be cleaned with steel wool and some sort of solvent. Laquer thinner works well. Some people like to use sand paper, but I think that it is all too easy to sand right through circuit board traces, so steel wool is my preference. Don't neglect to clean component leads, as they may have a built up of glue from packaging and rust from improper storage.
Step 3:Component PlacementAfter the component and board have been cleaned, you are ready to place the component on the board. Bend the leads as necessary and insert the component through the proper holes on the board. To hold the part in place while you are soldering, you may want to bend the leads on the bottom of the board at a 45 degree angle. Once you are sure that the component is properly placed, you can more on to the next step.
Step 4:Apply HeatApply a very small amount of solder to the tip of the iron. This helps conduct the heat to the component and board, but it is not the solder that will make up the joint. Now you are ready to actually heat the component and board. Lay the iron tip so that it rests against both the component lead and the board. Normally, it takes one or two seconds to heat the component up enough to solder, but larger components and larger soldering pads on the board can increase the time.
Step 5:Apply Solder And Remove HeatOnce the component lead and solder pad has heated up, you are ready to apply solder. Touch the tip of the strand of solder to the component lead and solder pad, but not the tip of the iron. If everything is hot enough, the solder should flow freely around the lead and pad. Once the surface of the pad is completely coated, you can stop adding solder and remove the soldering iron (in that order). Don't move the joint for a few seconds to allow the solder to cool. If you do move the joint, you will get what's called a "cold joint". This will be discussed shortly.
Step 6:CleanupAfter you have made all the solder joints, you may wish to clean with steel wool or solvent to remove all the left over rosin. You may also wish to coat the bottom of the board with laquer. This will prevent oxidation and keep it nice and shiny.
Cold Solder Joints
A cold joint is a joint in which the solder does not make good contact with the component lead or printed circuit board pad. Cold joints occur when the component lead or solder pad moves before the solder is completely cooled. Cold joints make a really bad electrical connection and can prevent your circuit from working.
Cold joints can be recognized by a characteristic grainy, dull gray colour, and can be easily fixed. This is done by first removing the old solder with a desoldering tool or simply by heating it up and flicking it off with the iron. Once the old solder is off, you can resolder the joint, making sure to keep it still as it cools.
Tips and TricksSoldering is something that needs to be practiced. These tips should help you become successful so you can stop practicing and get down to some serious building.
- Use heatsinks. Heatsinks are a must for the leads of sensitive components such as ICs and transistors. If you don't have a clip on heatsink, then a pair of pliers is a good substitute.
- Keep the iron tip clean. A clean iron tip means better heat conduction and a better joint. Use a wet sponge to clean the tip between joints.
- Double check joints. It is a good idea to check all solder joints with an ohm meter after they are cooled. If the joint measures any more than a few tenths of an ohm, then it may be a good idea to resolder it.
- Use the proper iron. Remember that bigger joints will take longer to heat up with an 30W iron than with a 150W iron. While 30W is good for printed circuit boards and the like, higher wattages are great when soldering to a heavy metal chassis.
- Solder small parts first. Solder resistors, jumper leads, diodes and any other small parts before you solder larger parts like capacitors and transistors. This makes assembly much easier.
Step 1:
EquipmentDesoldering requires two main things: a soldering iron and a device to remove solder. Soldering irons are the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and you risk damaging either the component or the board. Note that you should not use so-called soldering guns. These are very high wattage and generate most of their heat by passing an electrical current through a wire. Because of this, the wire carries a stray voltage that could damage circuits and components. The choice of your solder removing device is also important. There are two main ones; vacuum pumps (solder suckers) and solder wick. They both do the same thing, so what you use will depend on your personal opinion or experiences. I suggest keeping both on hand though, as you may find that each works well in different situations. Solder suckers usually look like large syringes. There is a spring loaded plunger, and a button to release it. The plunger is pushed down. When you want to suck up the solder, you position the nozzle over the molten solder and hit the button. The plunger moves up, creating a vacuum and sucking up the solder. Solder wick, on the other hand, has no moving parts. It looks like wick used in oil lamps, except that it is made of copper. To use it, you put the wick over the joint and heat it. One thing to note about solder wick is that it is expensive, and because it is expendable, a solder sucker may be a better choice if you plan to do a lot of desoldering. I personally prefer to use a sucker to remove most of the solder, then finish up with the wick.Remember that when desoldering, the resin in the solder and the coating on the board may releases fumes. These fumes are harmful to your eyes and lungs. Therefore, always work in a well ventilated area. Hot solder is also dangerous. Be sure not to let it splash around because it will burn you almost instantly. Eye protection is also advised.
Step 2:
Surface PreparationThere isn't really too much to worry about when removing solder. Just make sure to get any grease, varnish or glue off the joint before you start heating. If you don't, you will probably foul the tip of your soldering iron pretty quickly.
Step 3:
Apply HeatLay the iron tip so that it rests against both the component lead and the board. Normally, it takes one or two seconds to heat the component up enough to solder, but larger components and larger soldering pads on the board can increase the time.
Step 4:
Remove SolderSolder SuckerPush down the plunger so it locks into place. Usually, you will feel or hear a click. If the tool has been used before, a small "plug" of solder may be pushed out of the nozzle. Once the solder sucker is cocked, put the nozzle into the molten solder and press the button. The plunger will pop up quickly take the solder with it. This should remove most, if not all, the solder from the joint. Don't worry if the tip softens a little, but don't melt it. You may need to repeat this step a few times in order to get all the solder.Solder WickYou will probably want to heat the wick first. Before applying any heat to the joint, lay the wick over it and put the tip of the iron on the wick. It will take a second or two to heat up, but once it is hot you will feel the wick slide. You should also see the solder flow into it. You probably won't have to repeat this step. Once a section of wick is filled with solder, it is used up and must be replaced. Since the wick comes on a spool, all you need to do is cut off the used sections and take some more off the spool.
Step 5:
Clean UpYou may wish to clean the solder pad and surrounding pad to remove any resin and left over solder. There are commercial products available to take off the resin, but 000 steel wool works well of you are careful.
Damaged Solder Pads
Occasionally , you may damage a solder pad in your efforts. Usually, this just involves lifting the pad from the board, but not actually separating the traces. If this is the case, then it should be fine if you just leave it. If this is not the case and you actually break the trace, you will need to use a small piece of wire to connect the pad to where it is supposed to go. Just follow the trace until you find a suitable location for soldering. Usually, this is the next closest solder joint. Then, jumper the wire between the two points.
Tips and Tricks
Desoldering is just like soldering in that it is something that needs to be practiced. These tips should help you become successful quickly.
- Use heatsinks. Heatsinks are a must for the leads of sensitive components such as ICs and transistors. If you don't have a clip on heatsink, then a pair of pliers is a good substitute.
- Keep the iron tip clean. A clean iron tip means better heat conduction. Use a wet sponge to clean the tip between joints.
- Check the pads. Use a continuity tester to check to make sure you did not damage the pad or trace when you removed the solder. If you did, then follow the steps above to fix it.
- Use the proper iron. Remember that bigger joints will take longer to heat up with a 30W iron than with a 150W iron. While 30W is good for printed circuit boards and the like, higher wattages are great when desoldering heavy connections, such as those to a chassis.
- both a solder sucker and solder wick. Use a solder sucker to remove the majority of the solder, then follow up with the wick to finish things up..
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