Dear followers and the rest of the world!
Today, you will get two blog posts! This post is unfortunately not about composites but about small part of the amazing world of soldering.
Many readers might not know what soldering is but Wikipedia has an article about soldering which is quite informative. There are many ways to solder but I’m only going to tell you about the soldering process for MUSCAT.
You might know that the MUSCAT experiment has two PCBs in each free falling unit (FFU) which we identify by naming them top and bottom PCBs. We start with soldering the bottom PCBs which are more complicated to solder than the top ones. In the figure above you can see one side of the bottom PCB. As you can see it is a green board with some small places where it is shiny, some are golden and other look like silver (but are actually tin and lead blend) which are called soldering pads. The long lines however are not soldering pads, they are just lines that carry the signals. In space soldering one does not want to have gold plated pads since they can cause short circuits when it suffers some mechanical stresses, e.g. thermally induced stresses, which basically means that it can destroy our experiment. For this reason we pre-tin the pads. But we can’t use pure tin because the same thing happens if it is pure and that is why we use a 63/37 (Sn/Pb) tin-lead blend for the actual soldering of the components, but for pre-tin purposes I use 60/40 (Sn/Pb) blend. What we do is that we use flux which removes oxide and then I apply the tin blend to the pad with a soldering iron. When the gold film gets heated with the tin blend the tin sucks it up and they blend together. Next I use soldering wick to clean the tin/gold blend away. The soldering wick is a braid of copper with flux in it so it sucks up all the tin and gold when heated with a soldering iron. So far I have pretined Doc, Sleepy and half of Dopey and one third of Sneezy so I only need to finish Dopey, Sneezy and Bashful and then all the PCBs are ready for soldering.
Next step is soldering the components on to the PCB. But first one needs to practice. I have been practicing for at least two weeks now and finally today I went on to soldering components on to the PCBs we are going to use. First we solder the 3.3 V voltage regulator and then we solder all the capacitors, then all the resistors and so on. Today I soldered 6 capacitors on to Sleepy (one of our PCB) and it took me an hour, but fortunately I am not alone doing the soldering, Marcus Lindh soldered about 39 capacitors on Doc (another of our PCB) yesterday in an hour and Markus Fjällid was also soldering this evening but it is not confirmed how many capacitors he solders in an hour, but he is quite quick at it. But as they say, practice makes perfect so probably at the end of the soldering phase I will manage to solder around 40 capacitors in an hour with high quality, but we will see.
Unfortunately I do not have pictures of my soldering today (because my phones memory was full) but so that you can get a better idea of what I was doing today I have included links to some cool youtube videos I found that show how to surface mount various things.
The first one shows what I was doing today, i.e. soldering a capacitor, although this person does not apply extra flux as I do and I also use another method, i.e. first I place the component on the pad, place a holder on top of it so that it will not move and then I apply flux. Finally I use the soldering iron and tin connect the capacitor to the pad. This guy makes it look so easy that I am thinking about if I should practice more in order to become good at this method.
The next video is a tutorial on how to solder and I think it is quite good and shows well what I am going to be doing for the next few weeks.
Then I found this and I thought it was quite cool and I wish we could just place all our capacitors on the board and it would just melt like that so I decided to share it with you:
I hope you enjoyed this post. Take care!