#pcb etch

[tinkerpit]

Process Change

When I did my first few PCBs, I was using paper from a Dell catalog, printing with my little HP LaserJet 1018, and then ironing it onto the copper clad board with the clothes iron.  The board then went to the storage container marked "acid" that originally contained hydrochloric acid and hydrogen peroxide, but now contains cupric chloride.  The whole process from start to finish would take about half an hour or so.  Well, my wife wanted the iron back.

Ok, really, I wanted finer traces.  I was getting really good results with the iron + catalog paper, but the removal of the paper sometimes damaged traces.  And the inaccuracy of the iron would overheat and squish some traces, making them wider, and destroying the gap between traces.

So I did a quick search for other methods, and came across Pulsar's products (www.pcbfx.com).  I was skeptical, and a bit unhappy about the costs, but I figured "what the hell" and purchased the transfer paper.  The paper by itself, not so useful.  It's hard to get the right temperature and pressure with the iron and half the time the traces would lift right off the board.  I was so irritated, I switched back to catalog paper for a few more boards.

Well, around Christmas, I bought the laminator Pulsar recommended (Apache AL13P from Amazon).  And then I fixed it because it was broken already and I didn't want to send it back and wait for a replacement.  Now we're in business. This works great.  It works great with the standard 1/16" thick board, not just the 1/32" thick board Pulsar recommends.

So that is my new process, no more print to catalog paper and hand iron it.  Now we print to the Dextrin paper, run it through the laminator at 375F half a dozen times, drop it in water to float the paper off, and away we go.  So when you see 10 mil traces with 10 mil gaps, you'll know it wasn't done with magazine/catalog paper and a hand iron.  The process still takes about half an hour or so, but I'm getting finer detail in my results.

[tinkerpit]

My first PCB

I have done a few protoboards with the lovely point-to-point wiring.  My intelligent motor control board (not pictured below) is a lovely example.

This (as you may know) is my custom programming board for Atmel ATmega and ATtiny processors.  It's actually a very simple circuit overall, so I figured, what better to try a PCB with.

My chosen chemicals: peroxide and hydrochloric acid.  They're cheap and they work.  My transfer method: paper from a dell catalog.  My chosen design software: Fritzing.  I like Fritzing, it works fairly well.  The breadboard view is virtually un-usable once you hit a certain component density, but the PCB view works nicely.  Anyway, I created the circuit, printed it, ironed it onto the board, and then etched the board.

I think it came out really nice for my first try.  Ok, so now I dunk it into some tinning compound and then take it to the drill press.  A drunken monkey could have gotten straighter lines, but whatever, the holes are drilled.

Shiny.  Alright, looking good.  Now the fun part, desoldering all the parts off the old board.  I didn't need to.  Aside from the ZIF socket, I have plenty of spare parts.  But I don't like wasting them.

So with my reclaimed parts, I set about putting everything onto the new board.  You'll notice the power jack is smaller, I screwed up there.  Fritzing defaulted to a 3.5mm jack and I didn't catch it until the design was done.  I didn't feel like moving everything around to accommodate the larger jack, so I just used a 3.5mm jack instead.  Also, some of the "silkscreen" rubbed off while working with the board.  I repaired with permanent marker where I felt like it.

Overall, I think my first PCB came out nicely.  You can see how the drunken monkey drilling caused some things to go on a little crooked, but nothing terrible.  But to solve this problem in the future, I may need to come up with a small scale CNC drillpress.  There are a few extra components, but for the most part, it's the same board, just much cleaner.