Constructors Corner.
Anyone can solder, all you need is a little practice and a basic understanding in the theory of the process, even Denise (2W0BDX) learned after saying 'I can't do that!'. It is not difficult, but does require care and attention if you are going to achieve good results every time.
Your 'work bench' is important, it needs to be large enough for you to work comfortably, without being cramped, and have space for the hot iron well away from your hands and elbows.
Things to consider are light, the more the better, ventilation, the fumes from the flux in the solder can be irritating or even harmful over a long time, and access to properly earthed mains power.
Ok I know you and I may look foolish with goggles on while soldering but if a small piece of molten metal were heading for my eye I don't care how daft I look as long as I can still see afterwards!
For bending the leads on components and holding nuts while you tighten bolts.
For component leads what you are looking for is 'flush cutting' pliers rather than the traditional 'diagonal cutting' pliers.
Flush cutting pliers are used for cutting wire and trimming leads on the soldered side of a circuit board.
Larger cutting pliers can be used for cable etc.
You will need screwdrivers to suit the work you are doing - Always use the correct size and type of screwdriver for the screw, a damaged screw head is as useful as a soldering iron made of ice!
For example, a 'Stanley' knife, with a razor-sharp blade, can be used for stripping wires and trimming things.
For checking voltages, resistances, continuity, and current. A digital multimeter with an 'audible continuity feature' is great.
For examining circuit board traces and solder connections.
If you can, you should solder under magnification using a magnifying work lamp, but you can start with a hand magnifier or loupe.
'Helping Hands' are also a useful addition, they generally have 2 croc clips and a magnifier so 'helping' by holding small items in place while letting you see the work and leaving both your hands free.
Wires with alligator clips on the ends for making temporary connections.
That's so easy to say, but there's so much choice!
When you're working on a printed circuit board you need to apply a precise amount of heat for a reasonably precise amount of time to a very precise area, so care is needed in selecting the right tool but when dealing with, for example, a PL259 you need a lot of heat in a small area and a 15 Watt pencil iron just won't do!
Your beginner's tool kit should include a 15 to 30 Watt soldering pencil with a fine chisel tip and at least one spare tip.
You will need a much heavier iron (100+ Watts) (NOT a soldering 'gun' the don't have the mass to hold the heat) if you are going to work with some types of large connectors, PL259 etc, but don't try to use it on a circuit board as it will cause damage.
Ultimately you may want to invest in a 'soldering station,' but please buy one with temperature control rather than wattage control.
Try soldering without it!
It's traditional to start out with a caution that you must use rosin core solder and never acid core solder, but in practice acid core solder is so hard to find that the warning is almost superfluous however if you are buying a separate flux ensure that it is not acid based (most plumbers types are) as the acid will rot your wire, circuit board, plug, in fact just about any metal it comes in contact with!
There are three factors to consider:
For now, let's leave it with a recommendation that you start with 60/40 (60% tin, 40% lead) rosin core solder or one of the newer lead free solders with a diameter of around .03 inch. This will be fine for almost any kit or project and there's no point in departing from it until you have a particular reason to do so.
Note:
Lead Free solders melt at a higher temperature than Lead based types.
Lead based and Lead Free types should not be mixed, the same iron can be used IF you change the tip.
You will make mistakes - everyone does. Also there will be times when you want to remove a component for testing, or to substitute a different value. The only practical way to 'unsolder' a connection is with solder wick or a sucker.
Now you have prepared your work area correctly ensuring that it is well ventilated and nobody can accidentally touch the hot soldering iron we can start.
The 4 key factors affecting the quality of a soldered joint are:
Firstly, and without exception, all parts - including the iron tip itself - must be clean and free from contamination. Solder just will not "take" to dirty parts! Old components or copper board can be notoriously difficult to solder, because of the layer of oxidation which builds up. This forms a barrier that the molten solder will not bond with and this will soon be evident because the solder will "bead" into globules, going everywhere except where you need it. Another side effect of having dirty surfaces is the tendency for people to want to apply more heat in an attempt to "force the solder to take". This will often do more harm than good because it may not be possible to burn off the contaminants, also the residue left by burnt contaminants becomes yet another contaminant!, anyway the component may be overheated causing damage. In the case of semiconductors, temperature is quite critical and they may be harmed by applying such excessive heat.
Before using the iron to make a joint, it should be "tinned", this is coating with solder, by applying a few millimetres of solder to the hot iron, then wiping on a damp sponge. This prepares it for use. You should always do this immediately with a new bit, anyway.
Personally, I always re-apply a very small amount of solder again, mainly to improve the thermal contact between the iron and the joint, so that the solder will flow more readily and easily. It's sometimes better to tin larger parts as well before making the joint itself, but it isn't generally necessary with printed circuit board work.
A worthwhile product is Weller's Tip Tinner & Cleaner, a small 15 gram tin of paste onto which you dab a hot iron - the product cleans and tins the iron ready for use. There are alternative makes, but this is one I have used in the past to good effect.
Normal electronics grade solder used to, usually, be 60% lead - 40% tin, nowadays it is a lead free solder that is used in production, there is more than one type of lead free solder and a whole website could be written about the different types and their benefits/drawbacks! I'm not going into that here, I only mention it so you are aware of it.
Whichever type you use, electronics solder already contains cores of "flux" which helps the molten solder to flow more easily over the joint.
Flux removes oxides which arise during heating, and is seen as a brown fluid bubbling away on the joint.
The next step to successful soldering is to ensure that the temperature of all the parts is raised to roughly the same level before applying solder.
Imagine, for instance, trying to solder a resistor into place on a printed circuit board: it's far better to heat both the copper p.c.b. and the resistor lead at the same time before applying solder, so that the solder will flow much more readily over the joint.
Heating one part but not the other leads to a less satisfactory joint (if at all!), so ensure that the iron is in contact with all the components first, before touching the solder to it. The melting point of most tin/lead solder is in the region of 188°C (370°F) and the iron tip temperature is typically 330-350°C (626°-662°F).
Next, the joint should be heated with the bit for just the right amount of time - during which a short length of solder is applied to the joint. Do not use the iron to carry molten solder over to the joint!
Excessive time will damage the component and perhaps the circuit board copper foil too!
Heat the joint with the tip of the iron, then continue heating whilst applying solder to the joint (I usually apply the solder to the side of the joint furthest away from the iron, this ensures that the whole joint is at the right temperature), then remove solder and the iron and allow the joint to cool. This should take only a few seconds, with experience.
The heating period depends on the temperature of your iron and size of the joint - and larger parts need more heat than smaller ones - but some parts (semiconductor diodes, transistors and i.c.s), are sensitive to heat and should not be heated for more than a few seconds. Novices sometimes buy a small clip-on heat-shunt, which resembles a pair of aluminium tweezers. In the case of, say, a transistor, the shunt is attached to one of the leads near to the transistor's body. Any excess heat then diverts up the heat shunt instead of into the transistor junction, thereby saving the device from over-heating. Beginners find them reassuring until they've gained more experience (also cheaper than several boxes of the same components!).
The final step to a successful solder joint is to apply an appropriate amount of solder. Too much solder is an unnecessary waste and may cause short circuits with adjacent joints. Too little and it may not support the component properly, or may not form fully a working joint.
How much to apply, only really comes with practice. A few millimetres is enough for an "average" joint. A quality solder joint uses minimal solder - just enough to "fill" the area between the elements. You don't need to cover the connection with a ball of solder. A quality connection will appear smooth and shiny as opposed to dull as the solder flows into the gaps.
Here we can see a poor solder joint.
It was caused, in this instance, by not heating
the component sufficently before applying the solder.
We can see where the heat was from the build up of
solder to the right of the component lead.
Here we can see a better solder joint.
The lead is fully surrounded with solder
and there are no holes.
Soldering is quite simple if you observe a few simple rules:
OK, that's it. The process is actually much simpler that it sounds. If you are new to soldering, take the time to practice on some scrap cables, pc boards and terminals until you feel confident. I bought some inexpensive (under £10) kits from the local Maplin store (other stores available) for Denise to practice on and she did really well.
It is a good idea to build a kit and see (or hear) it work as it builds confidence quickly. If it doesn't work first time, check everything and try again, on printed circuit boards, and especially ICs, it is very common to accidentally form a solder bridge. This is when a connection of solder forms between two adjacent pins. Many hours have been dedicated to troubleshooting and many components destroyed as well as a result of this "minor" error. I would suggest that at the end of each component soldering you stop to visually inspect that connection. Look for both 'dry' joints (dull looking) and bridges, and don't be shy about using a magnifying glass to examine each connection in detail, I use a 10x jewellers loupe, that gets really close! Checking is a valuable investment with a payback in both trouble free start up and long term reliability.
If it still doesn't work take it to your local club and ask someone to check it. Don't be afraid, we all have to learn sometime!