Friday, 19 February 2010

Ah! That's the way to do it!

Last night, I got round to making a couple of PCBs with the LaserPrinter method, using a couple of tips scavenged off the comments and interweb.
From PCB
I printed onto some sticker backing paper from some laserprinter address labels I had around. The first sheet, which was completely sticker-free, was a bit thin and bendy and got jammed up in the rollers and didn't print properly. After retrieving the sheet (and extracting a cat toy from the inside of my LaserPrinter), I removed a few stickers from the centre of a new sheet of stickers, so it was thicker and stiffer.
This printed perfectly.

I then taped on my cleaned copper board (Cif and green scourer again) and put it through a cheap home laminator machine.

This worked really really well. The toner transferred perfectly to the copper, and the sticker paper was left completely clean. It seems to have bonded well to the copper, so I will have a go at etching the boards soon.
From PCB
I re-printed my temperature controller PCB board. Since I only had a PDF of the circuit diagram, I had to mirror it before printing. Last time, I used a command-line utility and a converter - but this converted the tracks into a low-res jpg, which worked but was certainly not the best quality.
This time, I printed out the PDF version and measured the printed PCB (49mm). I then zoomed in, so the tracks were filling the whole screen (in the PDF reader) and took a screenshot. This screenshot can be cropped to the edge marks, and flipped in GIMP, and GIMP offers specific print options to print out at exact sizes - i.e. the size measured earlier. This worked well (apart from a minature mouse pointer appearing on my PCB tracks!)

Single Sided Makerbot Stepper Driver board
From PCB
I've been trying to get hold of the Stepper driver board for a little while, but while waiting I thought I'd try and make a single-sided version of the PCB that was easier to etch at home.
First task was getting to grips with Eagle, and downloading the .brd files from the RepRap repository. The biggest problem with the mix of through hole and surface mount components is that the pads end up on both sides of the board - the through hole pads are on the bottom, and surface mount on the top.
I loaded up Eagle and mirrored the through hole components onto the other side of the board. The plugs are now pointing downwards (not ideal) but at least the pads are now on the top side. Rotating the connectors by 180 degrees helped match the tracks to the existing routes.
This left lots of messy tracks on the board, but a bit of work tidied them up. I then went to work moving via's (that would now have to be wire links) and moving the via points so they are not underneath the surface mount components, as I'd have to through-hole solder them. I'm no circuit board designer, so I went with moving the components as little as possible, and re-routed the tracks to avoid or shorten the vias where I could. Straightening the vias helped avoid crossing wires, and some of the connectors could be connected directly.

I printed off the PCB and transferred it to the copper. If it etches well, and I can drill some holes without ripping all of the tiny tracks off the board, it might be worth getting some components to build up a version.

[Edit - here are the eagle board files for anyone who's interested. Probably there will be later versions that might actually work.]

3 comments:

Krafter said...

I like the single sided stepper board.

One question though. Don't you need a pad under the driver chip to assist with cooling?

-- Chris

BodgeIt said...

Hey. its looking good.. I just used the green scourer didnt use Jif..

My first atempt on my ss stepper I used Paintshop pro to make multiple images .. big mistake! Afte hours of etching I tryed to fit the chip.. it was a tad too small had to re do the whole thing,... this time i used the KiCad print to print it..

I have tried sever makes of lable now the best ones seem to be the cheap ones from a pound shop.
They seem to be on a waxy type paper. where as the expensive lables its like a plastic coating.
And is not so good.

Have been buliding the board to night testing tomorow.. what chip are you using thou its square?

The PSP board was 34.5mm x 44mm.

The correct one was:

37.5mm x 48.5mm.

Renoir said...

The scaling can be an issue. I usually print out on paper, and then press a chip socket through to check the alignment of pins and pads. If they match, I know the scale is right before printing onto the backing paper.

I bought some cheap labels from the local stationary shop, and they're on nice waxy paper. At least you can re-use it once you've found a good sheet.

The stepper driver is the one from the makerbot driver. I'm no electronics whizz, I just borrowed their design and re-arranged it .

I know that the stepper driver chips can get hot - I was going to add some big heatsinks to the top (maybe memory heatsinks, I've got lots of PC hardware lying about)