Homebrew PCBs

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\u201d).  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 \u2013
>
> 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 \u2013 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@...
>     <mailto:howard.chester@...> [Homebrew_PCBs]
>     <homebrew_pcbs@yahoogroups.com
>     <mailto:homebrew_pcbs@yahoogroups.com>> wrote:
>
>     Jeff posted,
>
>     >I\u2019m 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
>
> ------------------------------------------------------------------------
>
> <http://www.avast.com/>
>
> 	
>
> This email has been checked for viruses by Avast antivirus software.
> www.avast.com <http://www.avast.com/>
>
>
>
>