Monday, January 22, 2007

 

Laser-etched PCB

Someone is experimenting with using a laser to etch PBCs. Looks like they're taking a copper-clad board, painting it black and using a high-powered laser to vaporize the copper.

It looks like the laser is mounted on the X axis and the head just contains a mirror to redirect the beam.



(link to flickr album)

Comments:
this is really cool. i can definitely forsee a day when we'd want to have a laser head attachment... its one of the things i'm going to play with once i get mine assembled.

however, that being said, i think that we're much better off taking the pcb router approach for a variety of reasons.

1. its a no brainer and obvious step to do routing / milling in general. the project will be stronger if there is a symbiosis between additive and subtractive manufacturing.

2. pcb routing will allow us to do things like drilling holes at fabtime whereas with laser you'd have to manually drill them later.

3. lasers / mirrors are expensive / moderately dangerous. a $50 rotary tool and a diamond bit and you're ready to do circuit boards.

anywho... fun stuff.
 
They are using the laser to vaporise unwanted resist, not to vaporise the copper directly.

This solves the problem of getting the artwork onto the PCB, but not the greater problem of the use of toxic etchants like ferric chloride, and proper disposal of the waste products.

I've been thinking on this since the article about etching with electrolysis was posted. I think its possible to make a precision etch head with that technique.

My current thinking is to place a tub of saturated sodium chloride beneath an XY axis. The head consists of a plastic tube. Inside the tube is a copper wire serving as negative electrode. Outside the tube is a carbon rod which provides the positive charge to the copper. When the tube is in contact with the copper, etching can only take place in the area enclosed by the tube. This should allow a PCB to be etched.

Further thoughts - this should also work on brass. A small enough head, a brass sheet - gears?

It may also be able to run in reverse - precision electroplating. It would be worth looking at whether objects can be fabricated by electroplating layers in much the same manner as FDM deposits layers of plastic.
 
pt is Phillipe Terrone, the editor of make (makezine.com)

It wasn't until I started reading that I realized he was using the laser to burn off the resist. Which is still cool, but rather like using a bridgeport mill to nip the top off your boiled egg.

A large fraction of the industrial lasers out there are C02 Lasers, which have all their power in the infrared, around
9.4 and 10.6 micrometers. These are great at cutting paper, wood, or what have you, and do a good job on almost all metals. C02 Lasers don't work on copper, however, which reflects all the IR light away, rather than absorbing it.
Refs:
http://en.wikipedia.org/wiki/CO2_laser
http://www.repairfaq.org/sam/lasersam.htm

If you're making PCBs at home, you'll have more luck with PCB routing with your repstrap and a machine controller like emc (linuxcnc.org)
or using an inkjet or laser printer to put down your resist, either directly onto the PCB (in some versions), or via a transfer onto coated paper or transparency.
Refs:
http://tech.groups.yahoo.com/group/Homebrew_PCBs_Archives/
or lots of other links, via google.

Andrew, did you see this:
http://steampunkworkshop.com/electro-mach.shtml
http://steampunkworkshop.com/electro-mach2.shtml
via
Brass Googles Steampunk Blog.
http://ccgi.firewyre.force9.co.uk/brassgoggles/?p=317#comments

I see RepRaps having laser heads eventually to do Selective Laser Sintering
http://en.wikipedia.org/wiki/Selective_laser_sintering
and general fabrication-related mayhem.
 
//They are using the laser to vaporise unwanted resist, not to vaporise the copper directly.//

Aha! I missed that bit. That seems slightly saner but not nearly as cool.
 
I think we're better off re-approaching the whole circuit board thing... and sticking with the reprap as it is...

We can create the 'board' itself... we can (in theory) lay the circuits inside that board (and make them 3 dimensional)... We've got a couple leads/ideas on being able to build resistance into the pathways themselves (forget about using resistors, the pathways are all resistors, most are just '0' resistance...)

Once we get all that squared away, I'm sure it won't be much of a leap to making capacitors... and really... how far does that leave us from primitive (but functional) processors/chips?

It's time to take a step back and throw away what's out there... it's time to reinvent the circuit board!

At the very least, a sheet of non-conductive material, with the pathways 'plotted' onto it by a reprap...
 
The only key advantage I see with the laser approach (Other than being able to say "Activate the laserrr!") is that there is no evil bending forces generated by cutting heads removing material.

So maybe in that way that could fit well with some of the ongoing reprap concepts.
 
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