DIY SMT soldering station

SMT soldering

While beeing an electronics enthusiast for ages now, I had a longer period where I’d only repair stuff and solder the odd circuit when I couldn’t find a ready-to-go product. The availability of microcontroller boards resulted in me getting involved in soldering again, but as I grew older the parts grew smaller. Soldering SMT isn’t that easy without a proper soldering station and although I could afford buying a professional one, I started to search the internet for some ideas for a Do-It-Yourself one.

I was happily surpised when I found Martin Kumm’s post and realised that this could be what I was thinking of. Martin had a kit with the needed parts, which I bought right away.

In the meantime, I’d seen a guy soldering together a GPS+GLONASS Geiger Counter in dead bug style. This video made clear to me how important a good soldering flux is. I wanted a NC (No Clean) one and after some reading about fakes, I bought AMTECH NC-559-AS from TME (I’m neither affiliated with them, nor do I get paid in any way to promote this flux. You are invited to buy whatever suits you!) and used my old Weller station with a fine tip to solder Martin’s kit together.

To use the controller you need an Arduino and a power supply. I had the first lying around, but had to buy a 12V, 5A power supply with a 2.1mm round connector. You can also recycle one from an old laptop as long as it delivers 12-15 Volts and at least 5 Ampere.

Which handpiece?

When I had all needed parts together, the soldering station worked perfectly out of the box, but I did not like the 3.5 mm stereo cable. I felt the handle should be longer and the cable softer… That set me searching for a WMXP handpiece, which I found for ~125 Euro (no link here, since it was a one time offer). The handpiece was exactly as I had imagined it, but I could not find a round connector for it. Weller probably uses an own creation, so I had to cut it off and use one of the shelf. I tried to find out which wire is what, but had to realise that only the power lines for the tip where directly available. Knowing from Martin’s post that RT-x tips have a built-in temperature sensor, I forced myself to disassembly the handpiece alltogether. You can see the results in the pictures below.

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I assume that there is some kind of signal processing done there and if I understood the descriptions correctly, also some sensor to put the soldering tip into stand-by when not moved. I couldn’t find more information, so I just removed all wires except for the power ones and one for the temperature sensor. To use that, I had to cut one connection on the printed circuit, just to be sure the other electronics will not interfere with “my” soldering station. By the way: the handpiece is put together of two cylinders with a fine thread…

Some soldering work later, the handpiece worked perfectly and I was satisfied with the overall feeling.

Housing

Without a housing the soldering station wouldn’t last long. I chose a housing from Fischer Electronic sold at Reichelt. You need to buy 2 pieces of KOH-4160 and one DPL 4-4. I also bought four case feet (GF 15) or else the case would be scratched in short time.

I did the holes taking measure with a caliper and drilling and filling one after the other. The Arduino board was fixed using a piece of aluminium sheet and 3 screws (I used Blu Tack to place the nuts). I think I didn’t do a bad job:

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And a look inside:

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To do …

Martin’s circuit allows to use a push button for a stand-by modus. I’m looking for a good handpiece holder and as soon as I have one, I’ll put it on top of the left part of the case and connect it with a button. The idea is that when you put the handpiece in the holder, the additional weight pushes the button and the tip goes to stand-by at 100°C. I’m still searching, but haven’t found anything suitable for a reasonable price.

Costs so far

Kit                                   30 Euro
RT 4 soldering tip     22 Euro
Handpiece                125 Euro
Housing                       34 Euro
Arduino Uno clone  17 Euro
Power supply            16 Euro
Sum                            222 Euro

 

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