Showing posts with label PCB. Show all posts
Showing posts with label PCB. Show all posts

Thursday, December 20, 2012

2-Layered PCB with a Laser? Nah, Toner Transfer

I tried using the laser to remove some spray paint, and... I declare it a dud. Two major factors stymied this process for me for the moment:
  1. I didn't have the right spray paint (matte black) nor the right environment (dry and warm) for the paint I did have. What I did get to stick to the copper had a very uneven surface.
  2. The laser is... finicky. I can't tell if the layers were wildly inconsistent, if the paint behaved differently as it dried, or if maybe the laser had trouble, not liking the cold temperature or moist environment. I never can tell if it's about to give up.
Impatient as usual, I used my regular method: laser printer toner transfer. Determined to make a 2-sided board work, I spent a while aligning corner crop marks and pre-taping the paper with the toner before laminating it to the copper. The toner transfer worked beautifully-- perfect result laminating it ten times (5 up, 5 down), but the top-bottom alignment, while close, may not be close enough. At this point it's etched (see photo) and drilled, but there are still bridges and the misalignment will make assembly an adventure.

Looking at guides online, (especially the tutorial at An Engineer's Life which so many people are linking to today,) it does seem like most people use a photographic process and abandon toner transfer when they go for double-sided and SMD. Before going that route, I want to take toner transfer further though-- I've had such good results so far, the only issue is top-bottom alignment. The biggest sources of alignment error:
  1. Top-bottom alignment of printed out patterns. A light box, some magnets, and tape should do the trick-- I need to see the registration targets better. Update: lightbox on the way from B&H.
  2. The laminator binds and jerks sometimes, which could distort the pattern slightly. It's hard to tell without sending through a test image, but it seems like time to take apart the laminator and see about modding it to separate the rollers a hair.
I'm happy with a slightly lower level of quality with toner transfer because it's a simpler process with fewer (and cheaper) expendables that can also transfer labeling to the top and bottom after etching.

Monday, December 17, 2012

Laser for PCB Prototyping?

I've had a great time working on circuit designs in Eagle the last week or so-- after my surgery, my sciatic pain is mostly gone and I'm able to concentrate again! Still, I'm mostly confined to the neighborhood and can't lift or bend or exert myself for another few weeks, so I'm happily plugging away at a few projects, the main one of which is my latest coffee grinder timer.

The timer PCB's odd shape was dictated by the enclosure's design, resulting in a 100mm x 74mm board. It needed to be double-sided, but traces were made wide and vias were kept to a minimum in the interest of home prototyping. I've had great success with toner transfer in the past, but not for 2-sided boards, and not for anything large.

A PCB-production process I've wondered about is using a laser engraver to remove an etch-resistant layer on copper before normal etching. The best and most successful example I've found is on Instructables: "Custom PCB Prototyping using a Laser Cutter," where the author uses flat black Krylon indoor/outdoor paint as the resist.

The example (at right) shows a single-sided board, but I'm primarily interested in using the process for excellent top-bottom registration. Before attempting the large board, I will first try some small pieces with test shapes, then I'll try a double-sided ATmega32u4 breakout board (my own design), then Grinder Timer 5. Stay tuned...

Friday, June 11, 2010

DorkbotPDX PCB Order: Boards and Boards and...

After missing the May 17 deadline, I was able to get two boards in for the May 31 DorkbotPDX PCB order. That order has taken longer than previous ones though, since the fab house quoted a much higher price than for previous orders. Fortunately, Laen was able to find a different manufacturer for the panel and stick with the $5/square inch (for three boards *shipped*) pricing structure-- woohoo!!

I submitted a 3-digit 7-segment display board (using an SAA1064) and an Arduino-compatible board with curvy traces and optional everything (including 3.3V operation).

The next deadline is this Monday, June 14 at 8AM, so tweak your designs this weekend and get your .brd or gerber files in!!

Thursday, April 8, 2010

Minimalduino v.89 Delivered

Three copies of my latest Minimalduino design (V .89) arrived today, fabricated in the DorkbotPDX circuit board order. I built one with all components and it works perfectly, with the exception of the 3.3V regulator having a different pinout than the 75LXX part I used in Eagle-- oops...

A SparkFun protoshield and Adafruit motor shield fit on top fine, but with very little (read: "zero") clearance over the tall capacitors I used-- they'll get some tape on top, and the next revision will use shorter caps or orient them sideways. Excited to work with my first factory-made board, I shot and posted some build pictures with a few notes.

To correct in the next revision:
  • Fix 3.3V regulator (MCP1700-330) pinout,
  • Lay out for wider/shorter or horizontal voltage regulator caps for better shield vertical clearance.
To add/improve in the next revision:
  • 5V/3.3V switchable with a jumper on three pins (though it will limit power),
  • Top pad and through holes under 7805 for better heat dissipation,
  • Credits (CC, author names) on bottom silk screen,
  • Optional resettable fuse?
  • Optional on/off switch or jumper pins?
  • Try to reduce the number and length of jumpers.

Monday, March 29, 2010

Minimalduino: Three, Please!

I got the latest version (.89) of my Minimalduino board to Laen at DorkbotPDX before the deadline this morning-- looking forward to getting three copies of it!

I met all of the specs I laid out in my original post, except there are no TX/RX LEDs and no SPI header. Keeping it exactly the same size as the Diecimila/Duemilanove meant more (and longer) jumpers than I wanted, but I like the layout over all, and the jumpers won't matter for the DorkbotPDX order since those will be 2-sided boards.

My favorite features are the button type options (top or side), power connection options (barrel or screw terminals, plus .1" separated pins), I2C header, and extra standoff mount-- the three Diecimila/Duemilanove standoff mounts never seemed adequate to me.

Sunday, January 3, 2010


I reworked the one-layer board to got everything routed nicely in two layers, and etched it last night with the layers very well aligned! Now to get flux-- without it, the vias need their own little lead, which is quite a pain. I'll build it out today and test it, then look at board house prices for making a minimal order, seeing how many I'd have to order to get the price down to $10/kit (with no extras). I wonder about rebuilding it in KiCad though-- I've about had it with EAGLE's inefficient UI.

Mute-tater lives!

I've been working on the mutetater program and board, and have it mostly sorted out, including the bulk of the mounting details. I etched a small 1-sided board to hold my old Arduino Mini, with transistors rigged like the TV-B-Gone v1.2, and headers for four LEDs, a button, ftdi programming cable, and 5V power. I'm using a Bodhilabs "VPack" with a single cr2032 to get 5V, and its header works nicely for mounting a power switch. It all fits in the foam potato, so now to figure out the button and LED mounting.

Thursday, April 9, 2009

BrewTroller Brewing Control System

Excellent project out today: BrewTroller - Brewing Control System. Starting with the Sanguino layout, Jeremiah Dillingham built out a custom 1-sided board with a great interface-- rotary encoder and character LCD display. Nice use of RJ11 connectors for temperature sensor input, plus a 6-pin rotary encoder header and screw terminals for other connections. (via Hacked Gadgets)