Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

On 12/10/2014 1:46:29 AM, Slavko Kocjancic eslavko@... [Homebrew_PCBs] <homebrew_pcbs@yahoogroups.com> wrote:

 

Using photoresist and 20mW 405nm laser works nice.
I use cheap ebay laser and got spot under 0.08mm in one direction and 0.1 in other (spot is oval not round.)
Now I wait to get stronger laser to crank up speed. Now I need aprox 15minutes for 100x160mm board raster scanned. I do try to implement solder resist too but need 10x more power. (I slow down scanning 10 times and paint solidify) but that's inpractical. Hope that with new laser I got solder resist curing under 10 minutes and photoresist sensitizing undef 5 minutes (speed of mechanic is limiting factor and laser driver too as frequency approach 1MHz.)

Slavko.


On 10. 12. 2014 06:43, 'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs] wrote:

I think there are two options to achieve a small spot size.  The first is a collimating lens.  The second is a fiber laser which is just a laser diode sold with a fiber attached.  I think both will achieve a spot size about 0.1mm (0.004”).  Can someone comment if this is correct?  Lenses are fiber lasers are sold on Ebay.  A microscope objective also works for a collimating lens.

 

I would like to avoid photoresist because –

No developing step

No preheating the developer

No developer required

No photoresist required

Quality of traces improves with no overdeveloping some areas and underdeveloping others

Cost is lower

No photoresist film application step – the most error producing step in the whole board making process from my experience

No laminator required for applying the photoresist

No modifying laminators for the correct photoresist application temperature

No guessing how good the photoresist is from age since the last time you used it

 

Jeff

 

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, December 09, 2014 12:57 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: laser ablation of paint on copper clad

 

 

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 spray paint 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 laser is >etched away.   I understand this is possible with 20W CO2 lasers by Youtube 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 task paint 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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