As I had already written in the first part, only now did the whole thing begin to take on greater proportions.

I had presented my little project in the Forum64.de.

 

Mein Betrag im Forum64.de
My contribution in Forum64.de

 

And for me very unexpectedly, my small handicraft action met with lively interest. So far I was used to it that maybe one or two people liked my handicrafts, but nobody else really noticed it.

The question was asked whether I could make a collective order. A phenomenon that can be found very often in this forum and that I have made use of from time to time.

But initiate a collective order yourself? That made me sweat a little. But well, why not? First of all, I started a thread for one month, and added a small survey, how the resonance would be. Roughly I had estimated the costs, and it should not become actually more expensive than 20, - euro, at least if there would be enough.

Umfrage im Forum64.de
Poll in Forum64.de

Since I knew that many people didn't like SMD soldering so much, I had offered to solder at least the processor and the other IC.

The resonance had more than surprised me. But it turned out that a lot of people are afraid to solder anything with SMD. I had chosen extra large SMD components in the 0805 format, but even that seems to have overwhelmed most of them.

So I considered what the alternative would be. To solder 80 kits by hand, I honestly waved off. So the whole thing had to be optimized.

So far I had soldered only one or two boards for me. The whole effort with stencil and reflow system was not worth it for me. I had experimented with it a long time ago, but it wasn't worth the effort to solder a PCB. There I was faster when soldering by hand.

Since I had made very good experiences with the vapor phase soldering (I had already reported about it), I decided for it, because it goes substantially faster and simpler, than with the Reflow furnace.

Since I didn't want to print the small 17×55 PCBs with solder paste individually, I had a panel with 6 PCBs made for the test.

Ein sogenanntes Panel, worauf sich mehrere trennbare Platinen befinden
A so-called panel, on which several separable boards are located

I also ordered a so-called stencil to go with it. A stencil is a template, similar to screen printing. These are cut with a laser into a thin sheet metal. Wherever soldering is to take place later, holes have been drilled.

Gut ist das Muster der Platine in diesem Stencil zu erkennen
The pattern of the board can be seen well in this stencil

In order to get reproducible results, it is best to build a small frame. Beta-Layout offers a suitable set for this purpose. Then you insert the appropriate board into it and bring the stencil congruently over it. The easiest way is to attach the stencil to one side with crepe tape. So you can open the stencil and exchange the board for a new one and start a small serial production.

Das Panel in einem Rahmen befestigt
The panel mounted in a frame

Now the stencil comes over it.

Das Stencil liegt Deckungsgleich über dem Panel
The stencil lies congruently over the panel.

And now it's getting exciting. After the soldering paste has been warmed up to room temperature (normally the soldering paste is kept in the refrigerator because of its shelf life) it is first stirred well. Then apply a thin layer to the stencil. Anyone who has ever taken pictures with the screen printing process will be familiar with the whole thing.

 

And basically, it's nothing else. The sieve and the template are replaced by the stencil. The color here is the solder paste. Then you take a squeegee and spread the paste evenly and slowly over the stencil.

Then carefully lift off the stencil, or in this case fold it upwards. And already the board is completely coated with solder paste at the corresponding solder points.

Man sieht fein den grauen Belag auf den Lötpunkten.
You can see the grey coating on the solder pads.

Now the board can be equipped with the components.

Bauteil für Bauteil nimmt die Platine Gestalt an.
Component by component, the circuit board takes shape.

Once the board is completely assembled, it is soldered using the reflow process. I use vapor phase soldering, also called condensation soldering. This is the most gentle process available for reflow. And actually also the simplest and fastest. It is often used in industry for sensitive components.

 

The circuit boards are ready. Here already separated from the panel and with the USB plug provided, which I soldered then completely normally by hand. Because only SMD can be soldered reasonably in the reflow procedure.

The whole process took a good hour, whereas the assembly takes most of the time. The soldering itself is finished in 5 minutes. But I think the work was worth it, and I think I have found the right way to get many SMD boards quickly and cleanly manufactured with half the effort.

 

Translated with www.deepl.com/translator

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