Real modders do it all themselves. Phil Chia shows how to banish the silvery blob and flex your flux.
This is part of a short series that we're going to run on getting a bit more into the hardcore side of things -- namely electronics. Perhaps the most valuable skill that a modder can have up his/her sleeve is that of soldering. Of course, most people are just happy to leave their mods at the odd hole or Molex connection to hook up a CCFL or a fan, but truly hard-core modders will appreciate that there are just some mods that you can't get by mail-order!
For instance, my trusty HAL10,000 Xeon rig that comes with me to LAN sessions gets tons of Chi-Chi points primarily because it's got home-rolled mods that simply aren't on the market (Like my PiMP patented 4.5" TFT case status monitor).
But more importantly, soldering makes stuff reliable. It's estimated that as much as 80% of electrical failure (non SMD system) can be attributed to faulty soldering, or to no soldering. Wherever possible, wires and circuits should be soldered together, not just reliant on mechanical connection (twisting, bonding, heat-shrinking).
But just the thought of dealing with molten lead and poisonous fumes can be off-putting to most. With a little bit of direction and know-how, we'll show you how to make more reliable mods and how to make some of your own custom circuits in the next few issues.
Why soldering?
Soldering is the basis of all of our modern circuitry, because it's been proven over the decades to be reliable and efficient (read, cheap!). Soldering makes a sound electrical and mechanical joint between components. Electronic soldering is based on 60/40 soldering, so called because the solder alloy contains 60% tin (Sn), 40% lead (Pb). This alloy's composition is ideal as it bonds to copper easily and offers good corrosion resistance whilst still being able to melt at a relatively low temperature. 60/40 solder melts at about 180°C, but it's often best to use at about 210-250°C. Corrosion resistance is especially important, considering that most electronic circuits use copper which notoriously oxidizes rapidly into non-conducting oxides and sulphate-salts.
Solder is also available with other alloys, but the next most common is the more expensive Sn62/Pb36/Ag2. It's similar to normal 60/40, but has the addition of 2% silver which makes it a better conducting solder for resistance critical applications, such as building high-end hi-fi or sensitive lab equipment. Straying too far away from 60/40 though isn't too good an idea as it means using different temperatures and different techniques.
SolderElectronic solder also contains flux which acts as a sort of a wetting agent to help clean and prepare the surface so that the molten solder can stick to the parts. It's important to use electronic solder, as there's also 60/40 craft solder that doesn't contain flux. Also there is acid based or corrosive flux that is often found in hardware stores. Never use these types of solder on electronics, as the flux will slowly eat through your circuits.
Although not strictly absolutely necessary, soldering without flux does increase your chances of creating a cold joints (see later in the article).
A couple of warnings first though. Firstly, lead is toxic. Handling solder with bare hands probably won't result in lead poisoning, but chewing on it is probably not a good idea. It's also good practice to wash your hands before you handle any foodstuffs... then again, it's good practice to wash your hands before you eat anyway! Also, at proper soldering temperatures, the flux will tend to burn off creating flux fumes. This stuff is toxic, corrosive, and pretty irritating to the airways, so work in a well ventilated area. If you suffer from asthma, it's a good idea to put a small desk fan next to your work area to blow fumes away from you. Don't over kill this, because if you whack a hurricane fan on your desk, you'll cool the solder before it's had a chance to melt! I use a nice 200mm fan salvaged from a DEC server. Finally, your soldering iron's going to be hot; at least 250°C, so for goodness sakes, protect your bench surface, and don't solder stuff in a cluttered environment with papers everywhere! I use a rubber cutting mat because I prefer the non-slip surface, but covering your bench-top with 4 layers of aluminium foil with 4 sheets of broadsheet newspaper underneath works pretty well.
Also, try to work in an area with no carpets (soldering iron scorch marks are unforgiving), and no kids/pets running around. Finally, never leave a hot iron unattended.
ABOVE: Solder comes in different forms. At the top is solder paste, used with surface mounted circuits. So toxic, you need gloves to use it (hence the bag). Next below is 1mm and 0.71mm solder. Below that is 0.25cm and 1.5cm desoldering braid.
Solder also comes in a variety of gauges, however for most hand-soldering use, I've found that 0.71mm (22swg) is the most useful. 1mm (18swg) is probably the largest gauge that one would use. I wouldn't advocate the use of 'hardware supply' solders (2-4mm) unless you're actually tinning a circuit board (more on this in a later article).
The ironChoosing the right soldering iron is critical to successful soldering. Irons can vary from the budget hobbyist $20 special, all the way up to $400 for the top of the line ESD IEEE certified, digital temperature controlled workstations.
SMD tong irons are specialised for surface mounting work found in most computer peripherals. SMD circuits will be covered in a future article. Soldering guns are not suitable for electronic use.
One of the most important things to look for is the wattage. Wattage doesn't relate to temperature; it merely means that the iron has a lot more in 'reserve' when tackling big jobs. When dealing with large components (capacitors, heavy gauge wires) or even special low resistance, wide-track circuits, the track or components that you're trying to solder can actually draw away the heat from the join point, and it subsequently takes longer to get the joint up to melting temperature. This is one of the most common causes of component failure as instead of heating just the joint briefly, the entire component is exposed to the heat of the iron. Exposing an IC or a capacitor to 150°C for anything more than a second or two usually results in a fried component. Worst case, it can result in exploding capacitors when you test your circuit.
Most beginner irons, such as my old-faithful Weller SP15D have 15W elements. Ok for small jobs and beginners, however for more general-purpose use, look towards a minimum of 25W. Larger 80W irons can be a bit of overkill and usually, their huge bits aren't suitable for fine electronics use.
Anatomy of an iron
Issue: 107 | December, 2009