[REQ] PCB by LASER

[blip]

80W is a lot of power. Can it cut through the copper layer too?

Indeed mine is slow, but very cheap.

The 5W laser head can be found here: http://www.optlasers.com

I did not understand. Can you cut the epoxy layer with your 80W CO2 laser?

[Ichan]

No, 80W CO2 laser can not cut any metal.

CO2 laser for metal cutting application usually in KW range, 150W and above plus oxygen can cut trough thin steel sheet, but not other metal. To cut metal the trend now is using Fiber Laser, currently still too expensive - note that "fiber coupled laser" is not the same with "fiber laser".

80W CO2 can cut epoxy but not the glass fiber inside the pcb substrate.

That 5W optlaser is a blue laser diode module, for spending $500 i think better play with 35W CO2 glass tube - but you will have to rebuild your machine, look at HERE.

-ichan

[blip]

Thanks for the info. Many people may be interested in your experience and in these numbers. I was thinking of installing a CO2 laser in my CNC, but this info you gave me made me rethink.

I've just posted some results on using PCBGcode with Eagle and on finding a good focus position:

http://gabuleu.blogspot.fr

Your comments are welcome.

Posted on: January 01, 2016, 11:23:42 23:23 - Automerged
Which fiber they use to generate such power, do you know? I did my masters in optics. Fiber lasers can be built with the right fibres and the right pumping...

[Vineyards]

I was thinking of fitting my A4 size mini CNC with a laser head.
Are you painting a PCB with ink and etching that with a low power laser head? If that is the case:
1- What is a suitable wattage range?
2- How long does it take to finish a Eurocard PCB?
3- Do you need to use a coolant?
4- Are there any fumes or hazard risks involved?
Thanks in advance.

Posted on: January 02, 2016, 01:01:23 01:01 - Automerged

That 5W optlaser is a blue laser diode module, for spending $500 i think better play with 35W CO2 glass tube - but you will have to rebuild your machine, look at
-ichan

What about the costs of a compressor and a CO2 feeder?

[blip]

Vineyards:

Hi. I use a 0.5W 808nm laser diode. I bought the parts on EBay and assembled the rest myself. Earlier blog posts show parts list and some details.

The example board I showed on the blog takes around 15min to plot with the laser. I do not know about the Eurocard PCB. Mine is 35mm x 18mm approx.

I use no coolant. Maybe a small fan around would be nice. Nothing else.

You can see some smoke coming out of the paint where the laser hits. I do not believe it to be hazardous, but the room where the CNC is installed has a constant breeze flowing. I do not see any trouble.

Ichan:
About a CO2 laser tube, I have a question. When you install it on a CNC, do you use the collimated beam to cut or do you focus it with a lens in the end of the optical circuit?


Posted on: January 02, 2016, 02:59:53 02:59 - Automerged
PS: I tried to focus the laser beam on a PCB while it was being chemically etched. What I found? The spot where the light was focused remained clean, copper like. Everything around was coloured brown, green, etc, due to the reaction. Does the light inhibits salt formation on the focal spot?

[Ichan]

Glass tube is not ideal to be mounted on z axis of cnc router style mechanism because of:
- big size and heavy, 35 watt will have about 70cm length.
- glass is fragile
- need water cooling circulation
- high voltage about 18KV DC

There are samples on the internet people who mount the tube vertically on the Z axis (so no mirrors required), but the most common mechanism is light high speed X-Y gantry mechanism, Z axis usually not needed. The tube positioned outside of the mechanism where the laser beam delivered to the cutting point by several mirrors. The beam comes out the tube is in several mm diameter size, it will need to be focused by lens just before the cutting point.

What to buy for small glass tube laser system:
- laser tube + mounting bracket
- laser power supply
- 2 or 3 mirrors + mounting bracket
- focus lens + mounting bracket (laser head)
- small aquarium water pump + tubing
- optionally a small air compressor for air assist to cut thicker material

I saw all available on the site i gave the laser tube link before, i have no other intention but just use it as reference - i myself bought related things directly from china.

-ichan

[blip]

Ichan,

Glass may be transparent to IR light, but I know it absorbs UV. That may be why few Watts on UV wavelength may do a lot more damage to glass than many more Watts of IR.

[Ichan]

Hi Blip, i am seeking for UV laser source for some time - do you know one?

I believe LPKF pcb laser machine use UV laser.

-ichan

[blip]

Ichan, the highest power I could find for a NEW laser diode at 405nm on EBay was this:

http://www.ebay.com/itm/Sony-SLD3237VF-405nm-400mW-Violet-Laser-Diode-5-6mm-Brand-new-1-pcs-/231573723017?hash=item35eade9789:g:O9IAAOSwNSxVY8ec

There are some units available at 900mW, but they seem to have been taken from  other devices.

But if we go to a slightly longer wavelength, in the blue violet region, there are those 5W LDs at 445nm. I'll try to find the soda lime glass absorption spectrum at 445nm to compare it to 405nm.



Posted on: January 04, 2016, 01:12:24 01:12 - Automerged
Found this:

http://3dprinter.wdfiles.com/local--files/dlp-projectors-optics/Borofloat-vs-soda-glass_transmission.gif

It would be amazing if we could deliver power at wavelengths up to 320nm.

Posted on: January 04, 2016, 01:18:52 01:18 - Automerged
I could not find a borosilicate glass transmission/absorption spectrum over 5microns. The ones I found suggest that it is opaque above 5000nm, which means glass is absorbing all the light from your CO2 laser source.  In this case deep UV 300nm lasers will not do any better than the CO2 laser you've got.

So how does LPKF cuts the board? They use a pulsed source?

[blip]

You may like this:

http://www.rofin.com/en/markets/glass-industry/laser-cutting/

[vern]

cutting metal with a CO2 Laser is not easy, see attached absorbtion spectrum
Since a CO2 Laser is around 10um, most metals are highly reflective in that area. Because of the long wavelength the focus spot is also bigger than with shorter wavelength.
That is why laser cutting machines have a very high output in the kW range. They are used because they are relatively cheap, compared to Fiber or other lasers.
Fiber lasers are around 0,925um where the absorbtion of copper is a little better. But since the wavelength is 1/10th of CO2, the focus spot is also 10 times smaller, so the energy per area is a lot higher.
But below 500nm absorbtion of copper is very good, an UV Diode with several watts is a better solution than a high power CO2 laser.
(always wear safety goggles!)

[crunx]

My two cents:

- Using a relatively low power laser to "burn"/evaporate a resist may be a good idea, as such resist is basically just paint. And ordinary etching should be thereafter rather easy to control.

- Engraving the metal directly with a high power laser is NOT easy: First, you need a lot of power, and secondly, there is a high propability of burning/carbonizing the base material (such as epoxy/glass fiber in FR4). See below about my experiences:

In my current work location in a consulting company doing development work and prototyping, they have a big, heavy, and expensive laser system capable of cutting metal and also producing for example prototype flexible circuit boards. The first time I requested the proto-shop for a small flex board, they had to fine-tune and experiment a while before the copper was cleanly cut without burning the base material. So it was NOT easy even for a professional with a lot of experience, and a very expensive machinery! (And the result was not astonishingly clean-edged, but still useful for a not too demanding flexible board)

[Vineyards]

I tried to focus the laser beam on a PCB while it was being chemically etched. What I found? The spot where the light was focused remained clean, copper like. Everything around was coloured brown, green, etc, due to the reaction. Does the light inhibits salt formation on the focal spot?

In my opinion, the heated spot causes a constant water outflux preventing metal from contacting water and the chemicals dissolved in it. In other words there is a heat jacket and a positive pressure. The surrounding area is also heated more than the rest of the board. Heat accelerates reaction. One would expect the presence of a globular heat zone causing a roughly circular imprint on the plane (that is the PCB). Different colors you see are caused by a very complex chain of reactions between FeCl3 and the copper on the PCB whoch continues until all the Fe in the etchant is consumed after which point it becomes pretty useless. There are however a series of reactions involving chlorine, NaCl as well as other minerals and impurities in water.