What spot size can I get from a 405/445nm laser diode

I am building a cnc machine to engrave pc boards using laser etching of black paint.
I am at the stage of ordering the diode and can not decide between a 900mw 405nm or a 2 watt 455nm diode with a 3 element glass lens or a G2 lens on either.
Ideal would be to get to a 0.1mm/.004 inch.
What spot size and speed can I get out of each of these combinations?

Thanks for your help
George

... with 300mW@405nm diodes and focal distance of 30mm I'm measuring 0.03mm spot diameters.

With 2W445nm and the same optical setup the spot size is around 0.05mm.

The 'effective' spot size can be slightly bigger for heat/energy-transfer or 'overshooting' when using sensible materials ...

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Viktor
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Thanks Vicktor
I understand the 3 element lens has 30% less power but a smaller spot size than the single element G2
What are you using?
What would be the difference in speed between these two diodes.

George

Edited 1 time(s). Last edit at 03/22/2016 07:21PM by george4657.

Hi George,

I'm using this housings with standard collimator lenses from lasertack - [lasertack.com]

The more power, the faster can be engraved - but I'm mostly engraving with only 30-50mm/s max. speed to prevent mechanical oszillations ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hi George,

I have a laerdiod engraver and use it to create pcbs by burning black paint.
It works very well.
I have tried the M140 diode - works well but i have e tendency to overload them.
I am now using the NDB7875 3W, works better and very good focus.
I think I used the G2 lense, I have the glass lense as well.
I can't measure the spot size, but I have no problem to create 0.2 mm
tracks and clearances, a qfp with 0.5 mm pitch is no problem,
I engrave paint on pcbs at around 2 min/cm2.
It is a tradeoff of how clean the laser with burn and the speed.
There is always some burned paint layer left, it is easy to
remove after a minute in the etch bath. The slower speed,
the easier and better.