With a room full of Uv / Co2 lasers juxtaposed to my office, here's a few
pennies of my thoughts:
Co2 lasers do excel in the cutting of specific materials. They are used to
cut steel, hobby stuff such as model airplane balsa wood parts, plastics,
glass, etc... However, with pcb's my choice would be to use Uv at a low
power. Sometimes I'm called upon to cut board features with the Uv laser.
The Uv will get me through the metals and the dielectric, versus only
dielectric with the Co2, at lower power levels. Steel lasers may use upward
of 150W+, while pcb lasers are usually system limited to 3 - 20 or so watts.
Large steel cutting lasers may feed material without a bed or platen, while
a pcb laser drill / router will have a vacuum table to hold the board.
Throwing high power pulses on your platen can damage work-piece board
surfaces due to reflection, and can damage the platen itself. Therefore
lower power pulses are used. With a 15 - 20um Uv beam and a mere .5 - 1 watt
of power, the cut is so small you need to use a scope to see it. As the
laminates are a woven epoxy glass, the epoxy, with a higher absorption rate
will ablate before the glass fiber bundles or any metals. Yes there will be
some charring, but less with Uv. I would cut through the epoxy and a good
portion of the glass bundles, similar to a score operation. The board
feature would then just need a bend to break off.
My choice of lasers depend on the difference of material properties, mostly
due to the fact that the Uv laser works more in a bond breakage type
mechanism, versus the melting / burning ablation mechanism of a Co2 laser.
Consideration is also given to beam collimation / shaping and type for the
application. Experimenting with different lasers on a particular material is
the only way to prove the results. I've cut tempered glass & plastics on a
Co2 with clean results. Some plastics produce a frosted appearance on the
cut edge, while others will produce a melted / mirror like surface. Most of
the charring that occurs on board material is the ablation of the epoxies,
as the glass cloth cuts fairly clean. Under a scope you would see the 'ball'
end lenses created on the tips of the cut glass fibers with a Co2, versus a
'sheared' appearance with the Uv.
Dave Simonik
CNC Laser / Mechanical Tech.
Sanmina SCI Corp.
Owego NY Division
-----Original Message-----
From: Atkinson, Neil [mailto:[log in to unmask]]
Sent: Wednesday, April 27, 2005 4:49 AM
To: [log in to unmask]
Subject: Re: Laser Cut PCBs
Thanks Mike,
Actually we are looking at CO2 laser on FR1 material.
The laminate discolours and leaves a small amount of 'soot' on the cut edge.
Neil
-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]]
Sent: 27 April 2005 09:43
To: 'TechNet E-Mail Forum'; 'Atkinson, Neil'
Subject: RE: [TN] Laser Cut PCBs
I've been out of this a while but so far as I recall
Assuming a CO2 laser and FR4, theoretically if it is correctly tuned/focused
it should give a big enough instant enough whack that the laminate is
vaporised before it burns. In practice you are likely to get a little
discoloration (no charring), you can reduce this by going for a perforation
rather than a continuous cut as this reduces rate of heat input leading to
local overheating. If you are looking at the high frequency funny stuff
laminates with random weaves, then it is possible to make continuous cuts on
some of these OK, [but there are too many types to remember now which
specifically].
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Atkinson, Neil
Sent: Tuesday, April 26, 2005 6:10 PM
To: [log in to unmask]
Subject: [TN] Laser Cut PCBs
We are looking to use lasers to de-panel assembled PCBs, the initial results
look very good apart from a slight burning (obviously) on the edge of the
laminate. The burn is just on the surface in most cases but can discolour
the laminate up to 1/4 mm into the PCB in the worst case.
Does anyone have experience of this? What reliability issues can you
foresee?
By the way - Petrol (Gas) is currently almost $7 a gallon in the UK!
Many thanks,
Neil
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