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How to get boards and solder parts? #10

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PeckTonium opened this issue Aug 17, 2017 · 1 comment
Open

How to get boards and solder parts? #10

PeckTonium opened this issue Aug 17, 2017 · 1 comment

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@PeckTonium
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PeckTonium commented Aug 17, 2017

I hope this isn't too noob-ish, but I'm not sure how exactly to use what you have in github to get me a few of these things.

The boards have to be ordered from somewhere, I believe...that's not a home-made pcb. SMD soldering is kinda scary too...not sure if my wife is going to like me baking chips in the oven. So, do you have suggestions/advice on this, or are you going to sell pre-built ones?

@valerionew
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valerionew commented Aug 17, 2017

I'll try to answer your fabrication questions, and some questions from the omega forum post (i don't know if you are the same person or not 😁) .
First of all:
I strongly encourage anyone who has any basic electronic soldering experience, to get the boards from wherever they want and solder his own. It's much more satisfying and, if you've never done SMD before, you'll have a chance to learn it.
Why do i say so? Because this board has a very few parts, big SMD pads and reasonably big components. Once you learn SMD soldering, they are even easier to solder than through hole parts. Don't feel uncomfortable, SMD parts are great.

Boards

The easiest thing is to just get it from OSHPark. They have good prices, deliver three boards and the shipping is free worldwide. I've already uploaded my v1.0 design on their website, so that you can order it with just a few clicks.
Again, i have to remember you that the v1.0 is not tested yet, so proceed at your own risk.
Here is the link.

Soldering

So, what you need to get started?

  • A soldering iron. I use the Hakko FX-888D with the tip that comes with it, but that's upon your preferences and your budget. A cheaper Chinese iron will also do the job.
  • Solder. I use Sn60Pb40 solder, and i recommend you to do the same. I prefer 0.5 mm, but you can go with whatever you want, i suggest to stay in the 0.4-0.75 range.
  • Some flux. I use it in a felt tip dispensing pen, but again, you can use whatever you prefer.
  • Solder wick. I use whatever i can find, not really a problem.
  • Fine tweezers, if possible ESD safe. I use the Vetus ESD-11, but you can use whatever you want.
  • Patience! A lot of that! After all, you are learning something new

That's all you need. Given that you already have a soldering iron, the other things are cheap. Patience is free.
About the method, these are the steps i do for a 2 pin component:

  1. Put some flux on the pads. No skimping with that
  2. Heat one pad with your iron and put some solder on it. You'll learn the right amount with the time, but don't worry, you'll have the chance to remove the excess with the wick after (or before, if you prefer) you've soldered the part.
  3. Grab the part with the tweezers, reheat the pad and place the component. Don't be too quick or solder won't stick to the part. Hold the part with the tweezers until the solder becomes solid. Then release.
  4. Solder the other pin, adding some solder.
  5. Inspect. Check, by eyes or with a magnifying glass, that there is a joint between each pad and the component.

That's it. For ICs and parts with more pins i usually solder one pad first, make sure that the alignment is correct, then solder the diagonally opposite pin, then all the others, but the steps are basically the same.
Same rule as THT soldering applies: lower profile parts first.

Parts

For the passives you can basically pick whatever you want, as long as they are the same value, same package, and same tolerance. All those specs and quantities are shown in the table in the README file.

The only two ICs here are U1 and U2.

U1 is USBLC6-2SC6. This is a TVS and diode protection array, specifically designed for USB ESD protection. It is not strictly necessary, but given that it's a very cheap part and provides additional protection, why not use it. Moreover, the docks from omega use a similar protection too. However, if you aren't going to use it short pad 1 with pad 6, and pad 3 with pad 4. DON'T short pad 2 and pad 5. That would be a short on the power supply

U2 is just a basic 1117-3.3v. A linear 3.3v regulator. You can pick a 1117 3.3v or even another linear regulator, as long as it has the same package, the same footprint, and it's capable of supplying at least 500mA.

There is a 1206 PTC fuse, anything from 1A to 1.5A should be good.

Connector choice is critical to this project. I've indicated the exact part that i've used. If you can't find them you have two choices:

  1. Pick another part. You can go to whatever supplier, shop or distributor and find a part that would fit mechanically in the pins. Make sure to check the distance between the mechanical mounting pins and the electrical pins. Also check the pinout, they are not always the same, especially in RJ45 connectors..
    In USB and RJ45 connectors, the distance from the last pin in the back, and the back of the connector is critical: it should be no more than what is in the parts that i've indicated, or the two polarized capacitors won't fit. If the RJ45 part has LED pins, they can be cut before soldering, so no big deal.
  2. Modify the board. You can download the KiCad files and modify the footprints in order to fit your particular connector. Again, check the pinout.

Then, pick two parts of 1x16 2mm female header, and you are done.

I hope i've answered all the questions, if you have more please ask.

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