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diff --git a/docs/projects/idkhow-pcb.md b/docs/projects/idkhow-pcb.md new file mode 100644 index 0000000..adc21bf --- /dev/null +++ b/docs/projects/idkhow-pcb.md @@ -0,0 +1,91 @@ +# 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. |