For quick 2 or 4 layer prototypes, I often use PCB Pool in Ireland, both because the board quality is quite good and because they include a free laser cut stencil with every proto order. One of the nice little touches they’ve added in recent years is that you can request photos of your PCB as it goes through the different manufacturing stages. Click through to see some photos from a weekend project I’ve been working on.
It’s an LPC11U24/LPC11U37/LPC1347 MCU combined with either an AT86RF212 or AT86RF230/1 using Akiba’s excellent Chibi wireless stack, and is designed to fit inside these weather-proof enclosures. It’s just a prototype platform for me to test some new MCUs out, but I kept the power input flexible since I want to try to include a small solar cell beneath the transparent cover of those enclosures, combined with a supercap to see how long I can power this thing with no battery at all (though there is a backup CR1220 on the bottom layer).
I’m working on a longer blog post on this board and a lot of interesting things I learned … but until the PCBs get here later this week, I thought these photos might be interesting to look at.
Resist before copper removal
Stripped PCB (pre solder mask)
Solder mask and silk screen (before pads are tinned using the selected method … ENIG, etc.)
After this the pads will get tinned, and the board will be routed with a CNC router, stuffed in a box, and on my doorstep 24 hours later!
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Back in 1982, I was doing a university internship at the Kollmorgen Multiwire company in Glen Head, NY. They were affiliated with the Photocircuits corp, at the time, one of the biggest PCB manufacturers in USA.
One of my most vivid memories was a wet-process tech warning me, as we walked through the gold-plating line, “If you smell almonds, hold your breath and get out of the building immediately!”
The plating baths contained lots of rude chemicals, including lots of cyanide salts of Gold, whose fumes smell like almonds.
They have long since closed their doors, and rumor has it that they are now a vacant Superfund site, but that’s another story
Anyway, Multiwire is a really interesting technology for making high-density and/or controlled-impedance PCBs.
Basically, a special CNC machine “wrote” insulated wires right into an adhesive layer on a flat PCB substrate. Following several more processes, the panels were drilled, drilling right through the wire. Connections from the wires to the plated hole barrels were accomplished using a method similar to making plated-through holes.
The machines were modified Excellon drilling machines, and the original ones used 5-bit punched paper tape to store and read-back the CNC G-codes. In a concession to Modern (!) Technology, the paper-tape units were replaced by a PDP-8 mini (about the size of a dorm-fridge) computer. Programs were stored on 12″ floppy disks.