For those who are curious, here is one table of TEA-mode laser pulse characteristics. Note the lower average power to get megawatt peak pulses about 1/6 uS wide: Pulse Energy (J) 5 4 2 0.4 0.15 Max. Average Power (W) 60 60 60 60 75 Max. Repetition Rate (pps) 12 15 30 150 500
Beam Size (H x V, mm) at laser 25 x 25, 25 x 25, 12 x 16, 11 x 14, 8 x 9 Note: Specifications apply to operation in both the 10 μm and 9 μm wavelength ranges On Thu, Aug 28, 2014 at 6:46 AM, Doug Ausmus <[email protected]> wrote: > UV laser for copper, IR laser for circuit board substrate material. > > Some laser machining 101: > > When ablating (not cutting), you need short, high-energy pulses.. not > average watts. This means you can do a lot with low "watts" as long as > those average watts are concentrated in very short, very high strength > pulses. Different lasing approaches can create differently-profiled pulse > energy (time vs. energy) with a given average "wattage". > > I've seen very powerful and fast copper ablation with LED excited UV > lasers running less than 5 watts, generating a pulse train above 50 KHz. > Similarly, a tea-mode laser pulsing at 500 Hz with a continuous power of > 75W very effectively "cuts" fiberglass circuit board substrates. > > Note that tea-mode lasers typically use a flowing-gas chamber and very > high voltage capacitive discharge to cause a laser pulse to form, shaped > with a very high peak energy for a very short time. In other words, the > pulses "hit very hard". These are usually expensive lasers to buy and > operate, but they work quite well. I just wish they could cycle faster. > > Using an engraving laser can work (maybe), but is sub-optimal. Copper can > be used in making mirrors for IR lasers, so you can see why IR lasers don't > even touch copper very well. > > To find the proper laser for a given material, you must look at the light > absorption curve vs light wavelength. As mentioned by others, heat > dissipation of the material and damage of material by the heat-zone must > also be considered when looking at choosing a wavelength and power. You > can't always "go faster" by "going more powerful". > > Lenses and mirrors must be carefully chosen to reduce heat build-up and > keep your beam optimal. Pre-lens beam diameter is critical for lasing tiny > features (bigger beam entering the lens can allow a smaller final spot > size, one of several reasons you will find beam-expanders involved) and > lens focal length is important for depth vs focus vs spot size vs optics > protection issues. And masking (pre-lens) can help shape and manage beam > modes at the expense of final power at the substrate. > > Hope this was informative, if not actually useful. > :-) > > > > On Thu, Aug 28, 2014 at 2:33 AM, Mike Payson <[email protected]> > wrote: > >> There is no inherent difference between a laser cutter and a laser >> engraver, the main difference is one of setting expectations. If a laser >> can engrave a given material, it can generally cut that material also-- >> *provided >> the piece is thin enough*. Generally with laser cutters that are priced >> in the range that hobbyists can afford (even well-funded hobbyists) that >> generally means metal is out. I think you can cut very thin (<1mm or so) >> stainless on a high-powered (~150W) small CO2, but generally any other >> metal can't be done on small machines. >> >> Copper in particular is hard to laser cut, even on very expensive >> machines. It is the worst possible combination for laser cutting: It is >> both highly reflective and it dissipates heat very well (aluminum is also >> hard to laser cut for the same reasons). Our laser cutter at work can cut >> 3/8" stainless steel and plain steel, but it can barely make a mark on >> 1/32" copper (I haven't tried anything thinner than that yet). >> >> >> On Thu, Aug 28, 2014 at 3:36 AM, Kenny <[email protected]> wrote: >> >>> My understanding is that an engraver is like a cutter with less output >>> power. Enough power to leave a mark, but not much more. The level of >>> precision probably isn't implied in either case. >>> >>> If you are looking at engravers on Ebay, they are probably low power CO2 >>> which can't engrave copper. There are IR and UV lasers designed for >>> prototyping PCBs, but they cost somewhere in the $60k range to get >>> started. >>> >>> There are other options for using a CO2 engraver, I suppose. Like >>> painting on a chemical resist layer that can be engraved off, leaving >>> exposed copper to be consumed by your favorite acid. >>> >>> http://www.instructables.com/id/Double-sided-PCBs-with-a-laser-cutter/ >>> >>> >>> -- >>> Kenny >>> >>> -+---+++-++-++++--+------+-+-++--++--+-+-++--+++-++----+-++-+++---+----+--+----+ >>> >>> >>> >>> On Wed, 2014-08-27 at 22:15 -0700, benjamin barber wrote: >>> > Question: is a laser engraver a smaller and more precise version of a >>> > laser cutter? >>> > >>> > Question: can a laser engraver be used to manufacture PCBs? >>> >>> _______________________________________________ >>> dorkbotpdx-blabber mailing list >>> [email protected] >>> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >>> >> >> >> >> -- >> www.MakersToolWorks.com - Tools for Makers >> >> _______________________________________________ >> dorkbotpdx-blabber mailing list >> [email protected] >> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >> > >
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