I wanted to write down some tips and experiences from building Amiga hardware – Could be interesting if you are getting into this hobby of building hardware kits and wonder what you need.
Use the right tools and hardware
I think the most important thing is to use the right tools. Without the right tools it can be very difficult doing even the simplest tasks.
Use the right soldering iron for the job
I use a hobby grade solder iron that lets me set the temperature for the solder iron. I only use non leaded soldering lead so I run 380 degrees celsius usually. If the PCB I am soldering on has a large ground area I run 400+ degrees celsius on that area, otherwise lead wont flow. Using a cheap soldering iron that is connected directly to power is a bad idea. I actually tried using one, it was impossible to get a good result with it so I consider this a must have.
Cleaning the tip
I found out I needed some way of cleaning the tip. I use a Weller tip activator to get it back to a good working condition when it has been used for a long time.
I have also used those copper rags you can dip the tip in to clean it off. I have one but have not used it that much.
Keep in mind there is a correct process in how you operate the soldering iron. I don’t know if I am using the correct process, but I am very satisfied with the process I am following. I wet the tip of the soldering iron with lead, apply tip to component to solder it to PCB and then do not wipe the tip clean, waiting until I want to wet the tip again before cleaning it. If you clean it off and let it sit, it will oxidize and you will need to clean it harder before applying fresh solder to it.
Use the right tip, or the one that works for you
I also use hoof tips exclusively (almost), I have a really large hoof tip that holds heat well and a smaller hoof tip for most of my soldering. I like the flat surface and it is perfect to heat up passives such as capacitors and resistors by holding it flat against the edge of the part.
But again, there is the correct tool for every application, it is impossible to solder a PLCC socket with a 7 mm hoof tip, then it is better to use a 0.5 mm pointy tip. Some people only use pointy tips, so its best to find out for yourself what resonates with you.
Use a silicone soldering mat
Buying a silicone soldering mat was one of the best investments I made. A silicone mat protects the work table from heat as it is very heat resistant. The soldering mat is also ESD friendly and prevents static build up under your PCB. I consider this one a must have, I just wished I got a 100% flat mat, I do not use or need the pockets in the mat to keep small components.
Use good tweezers that are meant to be used for soldering
I prefer to use thin, straight and long tweezers. Not all tweezers are made the same and while there are some really expensive tweezers on the market I am perfectly fine with the ESD tweezers I got from AliExpress. Tweezers for stamps can be used on larger components, using them with surface mounted smaller components is a real pain though.
Using flux when soldering surface mounted components
I use sticky flux when soldering surface mounted parts. Sticky flux helps the solder lead spread out and makes for a solid connection. Sticky flux also helps keeping small components on the PCB when you need to place more than at a time. You do not really need lots of flux, a tiny dab on each solder point is enough.
For surface mounted parts using flux is a must. My experience is that the more flux you add, the more you need to clean it off. For through hole parts I rarely use flux at all. Most YouTube tutorials claims more flux is always better. I do not always agree with this, in some cases it is a good idea to use flux, but I rarely need a lot of flux, a tiny dab is enough.
When doing fine pitched ICs with drag soldering or other techniques, flux is a must, and that is one application where more flux is usually better than less as it helps the flux flow.
Use smaller solder lead for smaller surface mounted components
Soldering lead comes in many sizes. I found that using a 0.35 mm soldering lead is perfect for small sized surface mounted components (0603 and up). Especially when soldering fine legged ICs it is easy to run into problems with thicker soldering lead. But for soldering a Zorro or ISA slot to a PCB, it is better to use a 1 mm soldering lead otherwise it will take three times the amount of time to solder them. So my combo consists of one 0.35 mm roll and one 1 mm roll of lead.
Use fresh solder and fresh desoldering wick
I once put a damp soldering spunge in a box together with my soldering equipment. It took less than a week for the dampness to spread throughout the box. What surprised me was that the roll of solder I had in the box did not work as good anymore. The solder did not want to spread out as easely and did not want to melt as good as before. It could have been a bad batch of solder, or it could have been the dampness of the spunge oxidizing the solder. If soldering lead is difficult to work with I just get a new roll.
The same happened with a roll of soldering wick I had. It would never absorb soldering lead, no matter what I tried. The reason for that was that the soldering wick had dried out, the flux in it had evaporated and the copper oxidized. I got some new desoldering wick and the improvement was like night and day.
Cleaning the PCB
One of the most difficult areas to grasp IMHO is how you should clean the PCB if you do not have an ultrasonic cleaner. There are thousands of recommendations and techniques. I first looked for a product that could solve my problems. There are cleaners in spray bottles you can buy, I bought one called Flux off, but it makes even worse mess after been applied.
Using flux leaves a sticky mess that can be difficult to get off a PCB. I have by trial and error found a way that leaves a clean motherboard that is not sticky.
The process for cleaning the PCB from flux I am using are these.
For SMC components such as resistors and capacitors
- I solder the component to the PCB, for example a 0805 surface mounted resistor.
- I spray the component area on the PCB with IPA isopropanol that I have filled a small spray bottle with.
- Then I wipe the area throughly with a micro fiber cloth.
- If needed I repeat step 2 and 3 again untill I am happy with the result.
For surface mounted ICs
- I solder the component to the PCB
- I spray the area with IPA
- I wipe the area with a microfiber cloth
- If needed I dip a tops in IPA and clean areas where flux got stuck on the legs.
- If needed I scrub legs soaked in IPA with a toothbrus.
For through hole components
This is where things get interesting. I took me a many tries before I got this working. It is still not perfect, but leaves a reasonable result with little mess.
- I solder the through hole component to the PCB such as a ISA slot
- Keep in mind, I dont use flux, but the larger 1 mm solder lead has more flux in it and it will spread out leaving a sticky mess around the pins
- I spray the bottom area generously with IPA
- Before the IPA dries off I brush the legs with a toothbrush to loosen up the flux
- Then I repeat 3 and 4 a second time
- Then I spray the area with generous amount of IPA again
- And finally I agressively scrub the bottom PCB with a micro fiber cloth. Expect the micro fiber cloth to get ripped
- I repeat step 6 and 7 again
- The micro fiber cloth will get stuck and leave parts of it in the through hole legs, but these can be peeled off by hand
(I am grounded when I am scrubbing the PCB with the microfiber, I am always grounded when handling the PCBs)
Hot air rework station
A hot air rework station is not a must have, but it can help a lot with removing components from a PCB. I have made lots of errors when building hardware. While there are techniques for removing parts without a hot air rework station, in some cases it is just so much easier to use hot air. The hot air station can be difficult to get a hang of, especially if it is a cheap one.
I think the main problem is calibration, often I have to run full fan speed and 450 degrees celcius to get results. If the air really is 450 degrees celcious is anyones guess.
Cheaper ones are good for desoldering stuff but they lack the horse power of a professional unit. If you just want to remove some passives or Amiga PLCC chips its fine though but the learning curve IMHO was steep. Most tutorials on YouTube are made with pro machines, a pro machine can easely handle larger desoldering jobs that a cheaper machine wont handle. A cheaper machine will just melt the PCB or component.
Learn how to desolder and clean parts
When I was new at building hardware projects I did not even know how to clear out a through hole that accidentily was flooded with solder. I did not knew that you could desolder a DB25 port with just solder and a copper wire. The scope in this article is unfortunately too narrow to go into different techniques in desoldering parts from a PCB. There is however a lot of well made videos around the topic on YouTube. The main technique centers around flooding components with solder and letting it fall off the PCB or be removed by hand with a plier while the solder holding it to the PCB is liquid.
Cleaning out a through hole is as easy as applying flux and letting the solder wick absorb the solder lead. In some cases that is unnecessary as you can just as easely just heat the leg of the component up as you let it slide into the flooded hole.
Tripple check everything
It goes without saying, and I have learnt this the hard way, tripple check EVERYTHING. From component placement, BOM to documentation. If something does not make sense, do not solder it. Do not assume things, make sure you know before commiting to soldering down a component or ordering a component that is not exactly the correct part.
Typical things that go wrong
Here is a list of errors I have made.
Cold solder joints
This was the most common error I made in the beginning. It was more common for me to do this error on small 0805 resistor nets but it happened to SMD capacitors and resistors too. Error was often just a visual error, component looked liked it was properly soldered but solder had fail to make connection with the PCB so one side of the component was floating.
Wrong part soldered
Either a part was soldered to the wrong location or the BOM specified a different part than I used. It is best to tripple check before soldering parts so you are sure you are soldering to the right location.
Broken PCB trace
I have gotten PCBs with broken traces and I have messed up traces myself. One time I was cutting off legs of through hole connectors and cut too deep resulting in the through hole lifting off the PCB. Most of these errors can be fixed by a jumper cable soldered over the cut of the trace.
Surface mounted PLCC socket not soldered correctly
The infamous surface mounted PLCC socket can often scare the most seasoned electronics builder. One option is to cut off the bottom plate but that can lead to a weak connection in the socket. I have experienced this myself, thus I chose 3M sockets because they can be soldered by hand with a small solder tip and a lot of patience without cutting off the inner part.
PCB not cleaned properly
I have finished PCB projects that did not function correctly during the first test run. After washing it around the ICs with IPA, it would run fine.