Peter Perez's Fab Academy Portfolio

Week 04: Electronics Production

Week 4's Goals:

Group Assignment

Sending a PCB to mill in a mill shop

If you follow youtube there are many different PCB milling houses that you can send your designs to and get them milled for a few dollars a board. If you have the time and a well prototyped board you definiely can send your things there and have a great repeatable and much easier to solder product. But learning the milling process allows for great leaps in prototyping. Considering I had not learned how to design a board yet I used the Quentorres board supplied to us to order.

Originally I tried to upload the Quentorres to pcbway but for some reason I was having difficulty so instead I went to jlcpcb and had a much easier time of it!

Step One: Download the gerber files for your circuit. If you are in KiCAD you need to export them, but since we are using QuenTorres we just download it from the site.

The files should look something like this:

Step Two: Zip up the folder with the gerber files. JLC only accepts .zip files so just make sure to compress all into a zip and upload it onto the website.

You will then be given a ton of options!

Here I kept it all default, but I was very tempted to change the color of the board to a purple since it was closest to Moonlighter Pink.

You can even order a stencil to make your soldering easier but I opted out of that.. Probably should have purchased it.

After that you can choose a lead time, I kept it standard. But for 5 boards it would be $2. I ordered 10

After about a week or so I received my boards in the mail. The quality was much better than I expected and will definitely be ordering again.

Characterizing PCB Mill

As said below we used the Discontinued Bantam Tools PCB Mill for our PCB milling.

To upload the files onto the program you need to extract the Gerber files just from wherever you sourced them. Then you use the bantam tools PCB Milling Software that looks a little like this:

Once the program opens you have to set up the board size that you are using. I have found it is VERY important to measure out the boards exactly as there are many manufacturing differences between one and the other.

When the board settings are in you have to upload the gerber files and it is very important to pick 3 specific files to get a good board those are the: F_Cu file or the front copper. The Edge_Cuts which determines the edge of the board and the PTH file which has all the drills through the board!

For these boards we used two different end mills: the 1/64" and 1/32" flat end mills. These came out with excellent definitition even for small gaps between parts on the board.

This software is excellent because it automatically has all the settings for each of the mills you are working with. Down to the frequency of the spinning, the movelment of the bit and more. I can say however with small bits like this it is incredibly nervewracking to let it go through as they are expensive and break super easily.

Once those settings are in you can set the depth of your cuts. This is something we struggled with initially.

In this case a depth of .15 mm always worked for the boards we were working with.

Well I thought this would be easy...

Milling a Circuit

This week we were tasked with milling a circuit. Last week's class held a lot of warnings from Neil that had to do with the work being done. Millings bits would break, specifications are precise, etc. And honestly all of the above happened and more.

Keeping it simple I decided to work on the same circuit that was proposed to us:

The QuenTorres Microcontroller Development Board

The files were given to us so we decided to go for a run. In the lab at the Moonlighter we had a Bantam Tools PCB milling machine. Actually a discontinued model but I will say when it gets working it does the job well. It mills beautifully and autoprobes so you dont have to worry about offsets (mostly) among other things.

The idea was to use the png images to the Bantam Tools cutter and then cut the board, easy peasy. But we ran into our first issue right there, the Bantam tools software does not take pngs, it takes svg files. This made us convert the images to svg's in Illustrator. There may be easier programs but that is the one we knew.

The process to do this conversion is pretty simple.

If you do not follow this process while using the tool you will get an image like below. Milling out EVERYTHING

If you do it right you will get an image like this:

Yay the traces are there and we can send it to the mill! Which we did and ended up with a pretty good product, except there was one issue, we were missing the holes.

We followed the same process as before to alter the holes image but there was an issue, it created a file created holes, but not in the right position. So we had to play with tools inside of the Bantam software to move it to where it went as best as we could. As you can see, this did not work well

This led to a lot of trial and error eventually having us to try to open the Gerber file. Which worked beautifully.

The Difficulties of Milling

From here we thought it would be a done deal. Click mill, change tools, let it work. We were very wrong. Unfortunately we ended up breaking 5 mill tools and cutting a bit into our board due to characterizing our machine a bit too late.

After all the tries you see above we finally got a good product and started milling the ones we needed for the lab

We cleaned the chip with soap and water and got to soldering

Big Hands Small Solder

I was experienced in soldering but this was the first time I used surface mount parts by hand. And I will say I had the hardest time getting them on. And spoiler, I will be remaking this board soon because I do not like how it turned out.

The biggest issue was that I melted one of the leads off in this section.

But luckily the circuit works!

Things I learned