Homebrew_PCBs

Anyone knows where to order an UV Collimator?
I'm working to replace the mill on a CNC Milling Machine with a .0254mm UV beam, on presensitivized PCB.
Cristian

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G'day
I haven't tried it myself but I one saw reference to using the eggcrate
diffuser for flourescent lights and painting it matt black to eliminate
reflections.

There was a light loss involved of about 25% I think.

Cheers
Brian

-------Original Message-------

From: Homebrew_PCBs@yahoogroups.com
Date: 05/02/05 14:49:49
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] collimator help

Anyone knows where to order an UV Collimator?
I'm working to replace the mill on a CNC Milling Machine with a .0254mm UV
beam, on presensitivized PCB.
Cristian

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I gather that you're using the CNC table to move a board under a UV source, much like a Gerber plotter. Years ago this was called 'direct imaging.' The object was to eliminate photo tools (artwork). I spent a lot of time working with UV lasers and other techniques. They worked, but they were too slow for commercial applications. We had to expose an 18" x 24" board in 30 seconds. Fortunately you don't suffer from that requirement. In the last few years laser diodes that emit at 370 to 375 nm have become available. Great columination, but low power.

You'll need a bright UV source that radiates around 365 nm. There are UV sources intended to be mounted in forced air heating systems to kill microbes, spores, etc. that would be fine for this application. They are continuous duty lamps, but they need LOTS of cooling air. The easiest way to get columniation is to move the lamp further away. You might consider putting a parabolic reflector behind the lamp to increase the intensity. I'd just use a piece of PVC or aluminum pipe, about 18" long, painted black inside. Put your pinhole at one end, and the lamp housing at the other. Make sure you have good light traps to prevent stray UV light from escaping. This is going to be a long exposure and stray light will expose photoresist. You might consider a light shield at the end of the pipe to shield the board. Set the pinhole as close to the board as you possibly can - a couple thousandths of an inch max if you want to do really fine lines.

I'd also consider using a larger pinhole. You're probably going to have to give the photo resist a 10 second exposure. With a .025mm pinhole that will mean a head speed of .0025 mm per second. For a typical small board with 50% of the area exposed you might be looking at 2500 sq mm to expose. You may want to check the math, but I come out with an exposure time a bit longer than a year. If you go with a .125 mm pinhole you get down to 50 hours - still long, but at least reasonable.

----- Original Message -----
From: Cristian C
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, May 02, 2005 12:49 AM
Subject: [Homebrew_PCBs] collimator help


Anyone knows where to order an UV Collimator?
I'm working to replace the mill on a CNC Milling Machine with a .0254mm UV beam, on presensitivized PCB.
Cristian



[Non-text portions of this message have been removed]

I think he means he wants to collimate a UV laser beam.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Brian Clancy" <bclancy1@b...>
wrote:

> G'day
> I haven't tried it myself but I one saw reference to using the eggcrate
> diffuser for flourescent lights and painting it matt black to eliminate
> reflections.
>
> There was a light loss involved of about 25% I think.
>
> Cheers
> Brian
>
> -------Original Message-------
>
> From: Homebrew_PCBs@yahoogroups.com
> Date: 05/02/05 14:49:49
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] collimator help
>
> Anyone knows where to order an UV Collimator?
> I'm working to replace the mill on a CNC Milling Machine with a

.0254mm UV

> beam, on presensitivized PCB.
> Cristian
>

laser beams are almost perfectly columinated. You just have to control dot size. The simplest technique would be to use a pinhole just a bit smaller than the circuit trace you want to create and just trace the circuit. That would get the job done in a reasonable time period. A 0.025 mm dot size would be appropriate for a raster scan technique. I think a .15mm dot size would do just about any board you want and with a 10 second exposure the speed would be about 90 mm per minute. That would image a small board in a reasonable time period.

----- Original Message -----
From: Steve
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, May 02, 2005 11:00 AM
Subject: [Homebrew_PCBs] Re: collimator help


I think he means he wants to collimate a UV laser beam.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Brian Clancy" <bclancy1@b...>
wrote:
> G'day
> I haven't tried it myself but I one saw reference to using the eggcrate
> diffuser for flourescent lights and painting it matt black to eliminate
> reflections.
>
> There was a light loss involved of about 25% I think.
>
> Cheers
> Brian
>
> -------Original Message-------
>
> From: Homebrew_PCBs@yahoogroups.com
> Date: 05/02/05 14:49:49
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] collimator help
>
> Anyone knows where to order an UV Collimator?
> I'm working to replace the mill on a CNC Milling Machine with a
.0254mm UV
> beam, on presensitivized PCB.
> Cristian
>





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[Non-text portions of this message have been removed]

I want to collimate a 30 degree UV Led Array made by Nichia.

Steve <alienrelics@...> wrote:I think he means he wants to collimate a UV laser beam.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Brian Clancy" <bclancy1@b...>
wrote:

> G'day
> I haven't tried it myself but I one saw reference to using the eggcrate
> diffuser for flourescent lights and painting it matt black to eliminate
> reflections.
>
> There was a light loss involved of about 25% I think.
>
> Cheers
> Brian
>
> -------Original Message-------
>
> From: Homebrew_PCBs@yahoogroups.com
> Date: 05/02/05 14:49:49
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] collimator help
>
> Anyone knows where to order an UV Collimator?
> I'm working to replace the mill on a CNC Milling Machine with a

.0254mm UV

> beam, on presensitivized PCB.
> Cristian
>

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No way, UV lasers are too weak.
Lens collimator source is what I'm asking for.
Thanks.

"Earl T. Hackett, Jr." <hacketet@...> wrote:
laser beams are almost perfectly columinated. You just have to control dot size. The simplest technique would be to use a pinhole just a bit smaller than the circuit trace you want to create and just trace the circuit. That would get the job done in a reasonable time period. A 0.025 mm dot size would be appropriate for a raster scan technique. I think a .15mm dot size would do just about any board you want and with a 10 second exposure the speed would be about 90 mm per minute. That would image a small board in a reasonable time period.

----- Original Message -----
From: Steve
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, May 02, 2005 11:00 AM
Subject: [Homebrew_PCBs] Re: collimator help


I think he means he wants to collimate a UV laser beam.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Brian Clancy" <bclancy1@b...>
wrote:
> G'day
> I haven't tried it myself but I one saw reference to using the eggcrate
> diffuser for flourescent lights and painting it matt black to eliminate
> reflections.
>
> There was a light loss involved of about 25% I think.
>
> Cheers
> Brian
>
> -------Original Message-------
>
> From: Homebrew_PCBs@yahoogroups.com
> Date: 05/02/05 14:49:49
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] collimator help
>
> Anyone knows where to order an UV Collimator?
> I'm working to replace the mill on a CNC Milling Machine with a
.0254mm UV
> beam, on presensitivized PCB.
> Cristian
>





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[Non-text portions of this message have been removed]

No way, UV lasers are too weak.
Lens collimator source is what I'm asking for.
Thanks.

"Earl T. Hackett, Jr." <hacketet@...> wrote:
laser beams are almost perfectly columinated. You just have to control dot size. The simplest technique would be to use a pinhole just a bit smaller than the circuit trace you want to create and just trace the circuit. That would get the job done in a reasonable time period. A 0.025 mm dot size would be appropriate for a raster scan technique. I think a .15mm dot size would do just about any board you want and with a 10 second exposure the speed would be about 90 mm per minute. That would image a small board in a reasonable time period.

----- Original Message -----
From: Steve
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, May 02, 2005 11:00 AM
Subject: [Homebrew_PCBs] Re: collimator help


I think he means he wants to collimate a UV laser beam.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Brian Clancy" <bclancy1@b...>
wrote:
> G'day
> I haven't tried it myself but I one saw reference to using the eggcrate
> diffuser for flourescent lights and painting it matt black to eliminate
> reflections.
>
> There was a light loss involved of about 25% I think.
>
> Cheers
> Brian
>
> -------Original Message-------
>
> From: Homebrew_PCBs@yahoogroups.com
> Date: 05/02/05 14:49:49
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] collimator help
>
> Anyone knows where to order an UV Collimator?
> I'm working to replace the mill on a CNC Milling Machine with a
.0254mm UV
> beam, on presensitivized PCB.
> Cristian
>





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