Get ready ! In this article you will discover a lot of theory and practical advice about welding. Then, we will also mention how to solder some specials and tricky components!
We will also take a look at the needed equipment to start welding in the perfect condition.
hand soldering tools
In fact, you can start quickly and affordably with a few gear. So we go, still in a DIY spirit, we’ve separate the list into 3 sections. The essentials, the comforts and those for the pros.
You will soon realize that the more you prototype and the more you will want to equip yourself. This make the experience so much funny and enjoyable!
- Your kit / prototype, with the components to place on your PCB.
- A soldering iron. There are all very different and it can be hard to identify the one you are looking for. For small budgets we offer this iron from the Japanese brand, Goot. It will be very useful and efficient for some kits from time to time.
- Tin! There are 2 major family of tin. The ones with 60% tin and 40% lead and the others with 95%-99% of tin + copper and/or silver. The first one is the easiest to weld but the worst for the environment. If you have a really bad iron, go for it (but, I never suggested that …). Otherwise with a good iron like the ones we propose, use unleaded tin !
- Cutting pliers! You’ll be able to make it with a big electrician’s pliers. But you may twist your beautiful welds by going a bit too wide! A small and dedicated plier, with the good shape will allow you to preserve your job and make it much easier.
- What to strip a cable. It can be a cutter, a lighter, your teeth, all the tools found by MacGyver … Or simply, a wire stripper.
- A table of course! Be careful the tin provided create small splashes of flux. It stains and sticks …
- A tip cleaner, and not a wet sponge! No more temperature shocks, we clean our iron tip in a metal sponge to get this perfect result.
comfort material, for lovers of tinkering
- The third hand! This tool helps you to hold a component, some cables, a PCB … This is what we all dream about, a 3rd hand !
- A rotating PCB holder. The holy Grail for a few bucks. The PCB is held in a vice and can be turned on itself to place components and weld. On the other hand at this price, the tool is quite strong. For an everyday use we have some much more advanced equipment. Like the one we use in our productions. But for some kits, you can go for it!
- A soldering iron stand, to avoid to see the iron falling on that table …
- A desoldering pump! And yes stupid things happen quickly. With this one you can easily empty a pad, filled of unwanted tin!
- Some tin plated desoldering wick! By heating it up on a pad it will suck the tin by capillarity. It is much more efficient than the pump if you want to remove a component, but it requires some technique. The pump is still super nice to empty a pad when you start.
- A tip refresher. This is optional for those who use lead but for those with unleaded tin it becomes almost vital! We dip the hot tip in this paste to refurbish it. At the office, we use it every day. Several times a day…
- A soldering station! This is more for those who want to play the game seriously! The Goot brand also offers stations that we use every day to solder our PCBs by hand. The result is just bluffing! We weld much faster and much better. The tip last several months. While it is used almost 8 hours a day, 5 days a week. On the small irons, the tip is wicked part and you have to replace it quite often. It is also the most important part for a good quality of solder joint.
- A fume extractor. When we just do a kit from time to time, we can open the windows and then, we avoid putting the nose in the smoke. This could be fine for a short time period, and still can be dangerous. Because it is true that it is strongly inadvisable to inhale these fumes which are very irritating but fortunately not carcinogenic.
- A tin reel dispenser, a nice small luxury. We pull the wire and he will come by itself to your joint. You will see when you have made many projects, you will dream about it!
If you want you can skip the theory and go straight to the practice. But if you are curious, there is plenty to learn here.
what is a solder joint?
The component leg is made of copper and the manufacturer has added a tinning (tin covering the copper). It’s the same for the PAD, the hole on the PCB which hosts this component. Over time, oxygen and moisture in the air attack this coating and oxidize it! I.e. a layer of another composition is added on the surface. And there, no luck, if we want our signal goes from the leg component to the pad, with such insulation it’s going to be complicated! Then anyway, the solder will not hold on for a long time.
So we have a quick fix, the FLUX. It is a chemical product that in our case, is integrated into the tin wire. He will strip (de-oxidize) the pads to make them clean and welcoming for the tin. To work well, it is necessary to pre-heat the surfaces between 130 and 150°C in order to activate the flux and to be able to clean the surface.
the different alloys
Once the card has preheated and the flux is acting, we need to take care of our alloy! Either tin + lead for hobbyists or tin + copper for those who follow the RoHs ecological standard!
The first alloy has a melting temperature close to 183°C and the second requires at least 227°C! We understand better why the lead-free solder is more difficult! It requires more heat.
Then, the chemical agents are different and they attack more the tip of the soldering iron. Then, we must learn how to maintain it.
let’s make our first solder joint!
The 4 steps:
- Put the iron to preheat the solder joint
- Add some tin gradually to prevent a temperature shock
- Reset tin when the gasket is filled with tin
- Remove the iron along the component leg to create a beautiful, perfect dome
That sounds very easy like that though it takes a little practice to get a good result.
the different solder joint
In analog electronics, poor welding can lead to multiple problems. And they can sometimes be difficult to detect! The worst part of all this is that a bad solder is getting worse over time. So it’ll be worse and worse and hard to detect! So take the time to make beautiful welds and be sure of the result. We will have a PCB that can last more than a decade!
You managed to make a beautiful dome welding as in this example?
Did tin came through the PCB to create a 2nd dome?
the different leads cutting
The cutting of the legs of the components is essential. If left as is, it may be that the legs are touching each other, creating short circuits!
So we will take our cutter and come cut the exceeding part of the lead at the top level of the “volcano” created by tin.
Be careful not to cut too short or too long! In the first case you risk to damage the solder joint, which would age prematurely. In the second case, it may damage the cables around, or create false contacts with the box or other areas of the PCB.
Obviously the welding is better with a quality material and in good condition. It had to happen to you to try to weld with a carbonized tip, then the tin does not catch and it’s hell!
my morning routine
- When I start the iron, I find it very useful to “wake it up”. Once it’s hot, I plunge the iron into the tip renovator to restore its youthful glow!
- Then I put a lot of tin on the iron until a ball is formed. Then, I rub the tip on the tip cleaner to strip it. I am finally ready to weld.
- When welding unleaded at a station, avoid putting it thoroughly, thinking that it will work better! Personally I like working at a maximum of 380 ° C.
- When I stop welding for a few minutes, I lower the temperature of the iron, or even turn it off.
- Every 5 to 10 welds, I rub the tip on its cleaner to turn tin dragging over and no longer flows.
- Every 3h I like to put a little bit of tip renovator. Then, it goes again… fresher!
- When the tip is too carbonized or it starts to darken every 10min, it is useless to fight. It is impossible to recover it in a sustainable way, so you have to get rid of it and replace it!
- In the evening before switching off, we clean and then renovate the tip. The next morning it is like new!
for specific components
Come on, the last step to succeed all your projects!
potentiometers and switches
You really lucky, at first we decided to wire them by hand!
Then finally, we had some good heart. We thought it would be nice if you come back to see us the next time we release a kit!
So we found a supplier who has knobs and switches that are soldered directly on the PCB!
To solder them, there’s nothing simpler!
- You return the board
- You put the switch or the pot
- On the same side you put a little tin on the metal reinforcements on the sides of the component so that it holds all alone.
- Then you flip it again
- You cut all the legs cleanly by being careful not to burn a component around with your iron
- You redo the welding you had done on the other side at first so that it is perfect!
Usually a LED is in a through hole format, which has the same legs as an electrolytic capacitor. For the purposes of our design we have been using for some years a slightly more recent LED technology. It is white and sends more lumens than the previous one but it consumes a lot of current! The only format that exists for this LED is in SMD for Surface Mounted Devices. It requires a particular welding technique and a couple of equipment. So we have a method to share with you which save time and avoid having lots of equipment!
The different steps :
- Put some tin on the positive leg (the one on the top of the PCB)
- With needle-nose pliers, preferably angled, catches the SMD LED.
- Attention LED has a polarity. You can identify the +, it is the side where there is a setback on the top.
- In one hand you hold the LED and in the other you come back to heat your tin pie.
- You put the “+” side on the tin. Too bad for the quality of welding the goal is only to focus on the location of the LED.
- You remove the iron.
- Once well cooled you pass on the “-” and you make a nice weld by catching the 3 legs to make a nice pie nice. Enjoy! It’s the only time it will happen!
- Once fully cooled you come back on the “+” and you remake us a nice weld.
You will notice at the bottom of your PCB that there are 2 places to come weld pins. They will maintain your footswitch and communicate between the main board and the 3PDT.Again it is an “optimized” method that avoids wiring but it generates a bit of welding technique.
- For this technique we will weld a pin approximately then we will return to better weld.
- So you have to hold your pins on one side and weld on the other. Beware if your finger is below you’ll burn you by conduction. It stings! We must therefore put it on the farthest one at the opposite of the one you are soldering.
- Once this pine is welded you can do the others cleanly.
- Then you come back on the first pin to make it better.