The Gutzy Guide to Soldering
I have been seeking to wind down my activities on geekhack recently since I have largely determined what is suitable for me. I’m no longer interested in conventional keyboards and am merely awaiting for Samwisekoi, Dorkvader, Acidfire and Wcass to produce the things I do want. (As well as some other people to do the necessary casings.) But it seems this forum has magneticism, and I keep being drawn back. I can’t extricate myself from the little world of geeks! Now a newbie has requested advice on soldering, and I have decided to write a guide of my own.
Please be aware that this is intended to be a practical guide for people who do not intend to take exams and get certified. This is a hand holding, spoon feeding guide for noobs, written by one of geekhack’s least competent and most inept modder. I have done plenty of reading, so I know some of the theory, but I know most noobs aren’t going to invest that much time in reading and they want useful info right from the start. So I’m going to give them that.
To a pro, most of what I say may be a joke. But it’s what worked for me or what I found right after many painful and expensive experiences, and so I’m going to share what I have.
What’s my competence? Over 10,000 solder joints either soldered or desoldered on dozens of keyboards of varying ages and quality with under 20 pads lifted and under 10 traces damaged. Quite a number of small repairs successfully done. A few hundred SIP sockets and LEDs soldered or desoldered. I’ve seen at least 50 different keyboard PCBs by now. New stuff like Ducky Shine 3, Filco Majestouch 2 bluetooth, all the way to Qtronix and Cherry keyboard PCBs over 20 years old. I don’t think this is a great record or anything, but it shows I am not coming in with the experience of only having done 84 solder joints on a brand new GH40.
I will assume that the reader knows nothing and doesn’t really want to spend hours knowing everything. He just wants to be able to build his keyboard quickly and painlessly. He doesn’t care about professional quality; he just needs something serviceable and usable without spending too much money and time. You are expecting to use your keyboard at home and in the office, and not in outer space or extreme environments.
Since I can’t cover everything and really don’t have time to answer questions, I hope that other people can step in and offer their views and experiences in the areas that I don’t cover.
The Gutzy Guide to Soldering
ONE: Your workplace and tools
You need a nice flat table, stable and resilient and capable of enduring burns. Didn’t I say this was a spoon feeding guide? I don’t want you to burn a hole in your table or set it on fire the minute you drop your soldering iron. Needless to say, please have common sense and do not cover it with newspaper when you solder. Use something more durable and less flammable. Do not walk away with the soldering iron turned on.
Some of you geeks have very nice glass tables. I suggest you find some plywood or other tough, sacrificial material to cover your table if you do not want to damage it by accident. Solder does splatter at times so I suggest not having that prized HHKB with $500 of keycaps sitting nearby.
Gloves. Again, common sense please, cotton/hemp/fabric gloves not rubber that melts and sticks to your skin when you touch the soldering iron by accident.
Dry rags or heavy cotton napkins to clean your soldering iron which you need to do so every 5-10 joints. I really do not recommend a wet sponge, as it will cause rust on your soldering iron.
A metal stand to keep your soldering iron tip from touching anything else. Many cheap soldering irons don’t come with a stand. Beware! (I use a flat biscuit tin to hold the iron in addition to the stand.)
A solder sucker in case you make mistakes. You WILL make mistakes.
A little metal (or non flammable) pan to hold solder bits if you have to desolder something. I use a biscuit tin cover usually.
Solder wick when you make a mistake and have to desolder.
0.4mm or 0.6mm roisin core solder wire. If you are in Europe or some place where leaded solder is banned, try your best to buy leaded solder from Taobao and ship it to your country. You’re a noob, don’t go for unleaded solder if you can!
A note on the purchase: you don’t need a lot of solder to do one keyboard. You can just buy the smallest spool they have available. However, due to quality concerns, you should buy at least two small spools from different sellers, made by different companies. That way you lower the chance of running into solder wire that does not work. Sometimes it happens. Nothing you can do about it.
It’s not a question of saving money. It’s a question of getting leaded solder from the (less developed) countries where it is still not banned. Unleaded is harder to work with.
Soldering iron. You can just get any cheap one, but best to buy two because they often fail. You don’t need much power. Even 20, 30W soldering irons will work with leaded solder. Remember that the keyboard is a precision instrument and the solder joints you need to make are smaller than the more industrial applications that use powerful soldering irons. Most 60W and above tips are too big for keyboard use. Also try not to use 40W tips for soldering or desoldering LEDs or diodes. These are also too powerful and are more likely to lift pads. Small sharp tips are better. The large majority of all pads that I have ever lifted are LED or diode pads, because they are small and more vulnerable.
If you are soldering a teensy, I very strongly suggest leaded solder and a 20W or sufficiently small and sharp tip. Teensy is teeny weeny and a big pain to solder. And if you choose to brave it and use unleaded solder, better pray you don’t make a mistake, because desoldering a Teensy mistake is very hard.
Stanley has a wedge shaped tip that I have found superior to conventional sharp tips, but I can’t find a local replacement in Singapore and did not desire to incur huge shipping costs to get a similar tip from the US. Those CONUS people should find it much cheaper with practically everything shipped free CONUS. If you are buying a soldering iron online and already expect to do quite some soldering, I suggest buying a couple of tips as well. Tips oxidize and can no longer be used, no matter how you try to take care of them. If you take care, a tip can last 10 keyboards. But eventually it will die. I’ve changed 6 tips in the course of several dozen keyboards/ PCBs. Along the way I did some Brasso-ing until even that failed to produce a reliable tip.
XXX
TWO Your soldering iron
The main thing to remember with the soldering iron is that while it is a simple tool, keeping it useful and in tip (pun intended) top condition is not so simple.
The iron must be kept clean and rust free. The way to do so is to keep cleaning it and tinning the tip. So you must constantly clean the iron on your rags, then apply solder to the tip to form a thin layer so that the tip is shiny (this is called tinning). That’s right, before you even solder your first joint, you must first solder your soldering iron! The solder that adheres to the tip will keep the tip from rusting, and also help to conduct heat. Because the temperatures are high, rust forms quickly – literally in seconds. So you must always have a layer of solder protecting the iron tip underneath.
The more black the tip is, the worst it is. You will end up having impurities and rust that makes it hard to transmit heat or transmits heat unevenly and in an unexpected manner (eg causing solder to ball up on your soldering iron tip). Whenever you find this happening with your soldering, STOP ALL WORK and let the iron cool down. You must restore the tip to shiny status first. Otherwise you are not just wasting your time, you may be overheating the pad, depositing impurities on your pad, or cause damage that is hard to fix.
Be obsessed with cleaning your tip and tinning it ALL THE TIME. When you have finished soldering, always make sure your iron has a shiny tip of freshly coated solder when you put is away. That way it won’t rust.
At this point I’m not even talking to you about the solder pad or the keyboard. These can take care of themselves. Pay attention to your soldering iron tip first!
If your soldering iron is new and in good shape, DO NOT use sandpaper on it or anything rough. Many irons come with a thin protective covering that is easy to wear off.
However, if your soldering iron starts to perform badly, it will have lost whatever protective covering it once had. Turn it off and let it cool down. Then you can go ahead and attack the rust with your favourite instruments – sandpaper, steel wool, brasso, whatever works for you to remove all the rust. Then once the rust is off, tin the iron again so that you have a thin layer of tin (solder) covering the iron tip.
As my experiences have taught me, do all these even before you attempt to solder your first joint. A perfectly working tip is essential for all soldering!
XXX
THREE Soldering your first joint
All soldering (and desoldering) must be done quickly. Do not panic and fumble as the iron is hot and dangerous – but do not tarry. Take the soldering iron, press it against the pad at an angle that touches both the pad and the component to be soldered (eg the switch contacts or the legs of the leds). Make sure you heat both; otherwise the solder will only adhere to the thing that you heated. Then bring the solder wire over and touch the area that you want soldered. The wire should melt all over both the pad and the component. If it melts over only one part, that means you have heated them unevenly and need to adjust the position if your soldering iron.
A good solder point looks like one of Hershey’s kisses. Most of you readers are CONUS; don’t you dare tell me you don’t know what I am talking about! Do not create balls, mushrooms, or anything else on your solder pad. It means the joint was poorly formed and there may be air pockets or poor contact underneath. You don’t want your keyboard to suddenly fail a week later because some solder joint broke after a few days of usage.
Now how much time do all these take place in? Within 2 seconds. Don’t go for a third second. If you can solder within one second, even better. Most of my best solder joints were done within 1 second. The joints that took two or more tries to do, that took more time to do, were often inferior joints!
Do remember that every few solder joints you should re-tin the tip on your iron. That ensures you have fresh, clean solder that can act as a good bridge to transmit heat to your pads and contacts.
Intimidated? Get out your ancient computer or something with a PCB. Instead of throwing it away, do some practicing on it. That way you don’t need to use your precious keyboard as a sacrificial victim.
XXX
FOUR Flux and other things
Some of you will have read about things like flux and PCB cleaning fluids and what not. I agree they all have their use, and I have used them before in situations where they were needed. But you don’t need them unless there are complications – such as a dirty PCB or non-working solder wick when you are desoldering. If you are just soldering a brand new Poker keyboard after which you no longer want to solder anything ever again, don’t bother with these other things.
XXX
FIVE Reworking
Sometimes in the course of soldering you notice a joint is poor. Such as forming a ball, mushroom, etc like mentioned above. What do you do? You can reflow the solder, by heating the joint again until the solder has melted and moved to form a better looking joint.
If this doesn’t work within 3 seconds, STOP. Do not heat the pad for too long. If there is still poor contact, it may be because of 2 reasons. 1) Impurities have gotten in 2) the pad is damaged eg a corner has been lifted which explains the inability of the solder to form that nice Hershey’s kiss on top of the PCB.
Often when that happens the only solution is to remove the solder and try again.
If the pad is clearly damaged and no longer able to offer contact for forming a suitable joint, you will have to grab a wire and make your own trace. This will be the subject of another post, preferably by someone who has more experience than me. (I have fixed only about 10 traces and generally my soldering was not very nice looking so I prefer more experienced people to offer their views.)
XXX
SIX Desoldering
Don’t be afraid to desolder. This is one of the most important things to remember. In the course of soldering, you will always come across times when you made a poor solder joint. Don’t court future trouble with that joint. Take out your solder sucker and get to work. Sometimes an ugly joint will work for weeks until you have that all important project and are typing up a storm – then it will assert itself!
Desoldering is always more troublesome than soldering. The main problem is with heating the pad and with removing the solder effectively. To avoid heating the pad too long in one spot I suggest moving the soldering iron a bit over the joint. This spreads the heat around also. Then, move the tip to one side (but still in contact with the solder joint), place the solder sucker totally over the pad, and press the button to suck up the solder.
If not all the solder gets sucked up, you might find it better to resolder and try again. It is often easier to remove a moderate bit of solder, than a tiny amount of solder.
Always remember, never more than 3 seconds of continuous heating on any solder pad. Preferably 2 seconds or less. It takes practice, so try it out with your sacrificial PCB first if you like.
If a joint is ugly and blackish it means there are impurities that will make desoldering hard. You can use cleaning agents of course, but in general, isopropyl alcohol with a toothbrush is sufficient to clean most nasties off the solder joint and the surrounding area. Remember, this is a guide for noobs who aren’t going to invest heavily in soldering equipment. I’m looking for simplicity and cost effectiveness here.
XXX
SEVEN Aftercare
After all your soldering is done, always remember to clean the tip of the soldering iron and add fresh solder to it before you turn off the iron. By doing so, you are covering the tip and protecting it against rust whilst in storage. Never put away your soldering iron without tinning the tip. Your iron should always have a shiny tip, regardless of whether you are using it!
XXX
That’s all I have to say for now. Hopefully this guide will be useful to most newbies. If you find it useful, you can always ask the mods to make this a sticky or something. Or maybe over time it will generate some discussion and in future the accumulated wisdom could be turned into a better entry.