Homebrew PCBs

Hi, Craig.

The vector plotting reminds me of pen plotters - pen-down would be laser-on; pen-up would be laser-off.  I don't think that's part of the G-code or Gerber instruction set, though.

The round spot may take some non-spherical optics.  Think astigmatism.

As for the rest - very cool.
Donald

----- Original Message -----
From: "designer_craig" <cs6061@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, November 13, 2009 2:21:00 PM GMT -05:00 US/Canada Eastern
Subject: [Homebrew_PCBs] Re: Making PCB using these new 405nm LASER Diodes

I had the same idea last spring and purchased a 405nm laser diode with holder/lense and some Riston film off ebay.  I added a heat sink to the holder and have driven it up to 110ma.  At that power level it will burn through paper, so I have no doubts that it should harden the photo resist. I did some initial crude calculations based on the Riston data and estimated diode power that led me to believe it would be possible to write a .001" dia spot at 80"/sec.

My initial plan is not to raster scan the board but to vector draw the pattern using my Bridgeport mill that is currently being converted to CNC. I will need to write some code to convert the Gerber photo plot file to a G-Code file to drive the mill.  These files are very similar, the Gerber format being an offshoot of the G-code format. Since I plann on using a fixed spot size, wide traces will need multiple passes as will donuts etc. This all has to be coded in the conversion program.  

Currently I am working on the mill's CNC conversion and have not done any testing on the direct exposure part of the project. It will be a couple of months before the mill is ready for PCB testing.

Issues to be resolved:
1.Is the exposure of photo resist linear ie. is high power UV for a short time the same as low power UV for a longer time.

2.Code to make multiple passes for trace and shape widths from the point gerber data.

3.How to get a .001" dia round spot.  The laser diode output is not round. How to measure the spot dia.

4.How long will it take to expose a 3'x5" board?

Craig