Week 04

Electronics production.

The task this week was to make PCBs, milling and soldering.This week I worked with Caroline as we could work in couples.


Led Badge & USB to FTDI

The firt thing to do was to dowload the already designed PCB files that Fab Academy provided us (one LED badge and an USB to FTDI. For each PCB we will have 2 files, one for the trace in which you use a 1/64" endmill, and another one for the interior in which you should use a 1/32" endmill. These are not to be confused as the end mills are really fragile and they could be broken easily.


rml file

This file is to be prepared in Mods according to the specific machine you will use to mill your PCB board. In this case, we were to use a CNC Roland SRM-20 so the configurations are somehow pre-loaded but you still need to adjust some other things. Also very important is to invert the file if needed as the "black" part is the one that's going to be taken out. We made this mistake with one of our boards and we noticed it until it was already cut wrongly.

mods

Milling

To prepare the machine the first step is to set the x, y & z origin points. For x & y, movig the spindle over where you want the corner of your PCB and the z origin was a little bit tricky for us, we thought we had it but ended up breaking an endmill. So the correct steps were to lower the z coordinate really slowly (step x10) until the endmill touches the bed, then unscrew it being carfeul not to drop it. After that, you place it back barely touching the bed and screwing it back tight enough and set the z origin. For each endmill you need to re do this process but don't touch the x & y origin points.

The next step is to upload the file and run it starting with a speed of 40% and then increase it if everythings is correct.

We wanted to mill 3 different boards, the first one being the FabTinyISP, which came out perfect while we encountered some problems with the USB and LED boards. With the USB one the traces were too thin so I tried to solder normally, but they ended up coming off. Apparently this result was due to the endmill being to 'long' while cutting, causing an extra circular movement that cutted a little bit more than what's needed.

milling
mods

Soldering

After running both files (traces and interior) your PCB is done and it's time for soldering. For each board you have a list of components which you look for in the lab. This is literally your 'shopping list'. Be careful as most of the components are really small so it is recommended to glue them besides each component's name and avoid confusion.

Once you're ready with all your components you can start. Soldering is mostly about patience and precision, but of course as you get used to it you can get better at it. You need to be careful with the temperature and the technique because it needs to be almost perfect. Also, there are some 'tricks' to undo a mistake so you don't ruin your board. I did not get to finish my board but I did had to cut the same board twice because of the traces mistake.

list
list
Files

PCB files

Student

Elsa Garduño

Date

02.26.2020

Category

Fab Academy

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