# I DONT KNOW HOW BUT I MADE A PCB

2024-03-23

Last December I made a bold move to buy a ticket to iDKHOW's show in
Detroit. The show is on April 5th.

I've heard of fans giving out handmade souvenirs on shows like this. In my
mind I have a PCB with the band logo on it. The logo happens to be super
regular shapes like lines and arcs. As long as I don't do it for profit,
I'm fine. So I imagine I'd be at the show just handing them out to people.

## Step 0: What do I make and how?

First idea: blinking LEDs like my previous PCB, [Blobcat](blobcat-pcb.md).

Too many parts, too much soldering. No time for that when I've got 18
credits of courses.

Second idea: a coil that harvests power from your phone's NFC and light an
LED. 

Much less soldering but physics is too hard. I can't even prove it's
feasible.

Third idea: just a logo and nothing else.

Really easy to design but a waste of money if I pay a factory. But there's
another option.

There's a Bantam machine at my uni that any student can use as long as
they passed a quiz. The Bantam is basically a computerized milling
machine. Instead of dissolving copper with chemicals like they do in
factories, it mechanically etches off copper with a drill bit.

A common drill bit is 1/32 inch, or about 0.8 mm. This means I can't do
fine traces. Not a problem.

## Step 1: Design PCB

I created a PCB with KiCad with only two useful layers:

- F.Cu (front copper, where my design goes)
- Edge.Cuts (board outline and holes)

To minimize milling time, I need to maximize copper and minimize etching.
So I fiddled around a bit and found such a design that looks ok:

![KiCad PCB design measuring 36×26 mm with
a hole](img/idkhow-pcb/kicad_pcb.png)

The red curves and pale red solid fill are copper and between them is
where the drill bit goes.

## Step 2: Use the Bantam

On 2024-03-20 at 18:00, I checked in at the machine shop. My friend guided
me through the process and gave me his drill bit. The drill bit is
carbide, but brittle at high speeds.

![Bantam machine drilling an FR-1 board. My thumb rests on the emergency
stop button.](img/idkhow-pcb/bantam.jpg)

The drill bit rotates at a nerve-wrecking speed and copper shreds splashed
everywhere (in the protective window, ofc). Each board took 9 minutes in
the machine, plus some extra where I recalibrated the spindle. I had
enough material for 9 of them, so it took around 2 hours.

![Nine PCBs laid in a grid](img/idkhow-pcb/product.jpg)

Note that #9 has a defect. Part of the trace wasn't etched deep enough.
I sanded all of them but went too hard on #2 (row 2, column 1). It's kinda
scratchy and I don't wanna risk sanding off everything. So I'm claiming it
as my own and using it as a keyfob.

![Seven PCBs laid in a stack and another one in
front](img/idkhow-pcb/stack.jpg)

Overall, this was really cool. I enjoy abusing public resources for my
useless projects, and I will do it again.

## Pre-show update

2024-03-31 update: I was reminded there's a line in the opening track
"DOWNSIDE":

> And when I die I'll get those cold copper kisses on my eyes

Therefore, I am from now on calling them "cold copper kisses".

Despite the name, it is highly recommended that you do not kiss it.