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Subject: Re: [Homebrew_PCBs] Re: laser ablation of paint on copper clad

From: Camillus <camillus_blockx@...>
Date: 2014-12-09

why using the paint, this should also work with the presensitised clad boards. If you use a UV laser in the right wavelengt of the photoresist. I have being pondeingr over this myself, but never though to have a suitable beam that can be controlled in width from let say 0.1 to 0.5 mm. I was even thinking of making my boards myself, by submerging the board completely in UV cureable photoresist, and then centrifuge it with high speed, so that the centrifugal force would make the layer of resist so equal as possibe. A brushless motor from old drive would be good for this, just have to make a reliable holder to keep the board from flying away...LOL.
 If you have more information about laser control, specialy the focus part, then please would you care to send it to me or post it here?

thanks.

Camillus

On 12/9/2014 7:25:07 AM, Howard Chester howard.chester@... [Homebrew_PCBs] <homebrew_pcbs@yahoogroups.com> wrote:

 

Jeff posted,
>I’m mentally exploring the idea of spray painting copper clad with spraypaint and drawing traces in the paint >with a laser.  After the laser,the board is then placed in etchant and the copper exposed by the laseris >etched away.   I understand this is possible with 20W CO2 lasers byYoutube videos but has anyone >explored this with a laser diode?  Is the abundant ebay 445nm, 1W laser or the 808nm, 3W laser up for >the taskpaint ablation?
 
>Jeff

Hello Jeff,
Just a few words of my musings...
Why not try to replace the high power LASER with a 400nm Ultra Violet Soild State Laser Diode combined with a CD/DVD optic sled unit to expose a UV resist PCB?

A few advantages;-
1) Lower power equals safer working enviroment
2) Ease of use, the CD/DVD has a constant correcting focus control loop. This would probably allow tracks in the sub mm range(0.2mm?). As the visable red dot shining through the prism bounces back from the PCB, mixing the nearly invisible UV beam on the opposite side of the prism assembly by delivering the beam via a short lenght of cladded fiber through the unpopulated side of the prism.
3) A secondry advantage of the visible red dot is easy and accurate registration when doing double sided PCB's.
4) By tapping into the beam control(constant amplitude loop that monitors the reflected beam power to compensate for impurities on CD/DVD's  (analog available at the red laser diode Anode-Cathode as a varying Current through  the red Diode)) would allow for a "Resist thickness vs stepping motor delay"  as well as slaving the UV LASER drive current.
5) Modern Micro-stepping Motor drive IC's would maximise the resolution of the optics, unless you use the optics of the "sled" control. In which case the resolution could be in the micro/nano meter range.
6) Cost, a UV LASER Diode module costs about 45 Bucks vs BIG bucks for a large LASER, Drive Electronics and the delivery optics.

 have pondered this concept for a while now but declining health has force my early retirement and as such, my access to the nessessary engineering tools.

As stated, just my musings...
Good-luck with you project, chester




























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