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Vaporizing Wax

Savage

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I would like to try using wax as a resist for etching PCB's. To do SMD's I would need to be able to burn lines in the wax with a resolution of 100 microns or possibly less.

Ebay has some cheap 808nm 300mW laser diodes that I was thinking about trying. My questions are; would it be possible to achieve the resolution I need with this LD and if so would it require a collimator? I can mount the LD at whatever height I need above the board.
 

DrSid

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You will need some kind of optics if that is what you ask. Diodes themselves radiate in about 30 degree cone, it has to be focused into point. It would be good to get specially designed lens for laser focusing. The lens should also have anti-reflection coating tuned for the working wavelength. I guess glass lens for red pointers would work at 808 pretty well. The 100microns should be no problem. Well it depends on distance .. further you focus, bigger the spot. If you are talking about few cm distance, it should be fine.
What are you planing to move the laser with ? Is 808nm best wavelength for the wax ?
 
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Hiemal

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Eerrrrm, how would wax etch copper? Also, how are you planning to move the laser? It'll need be rather precise; it almost sounds like you want a sort of laser engraver setup or something.
 

Savage

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I figured that I'd probably need some way to focus the beam - even if the LD were close to the part.

As to moving the laser, I'll be using a microcontrolled stepper.

And, from what little info i could find on regular paraffin wax it looks like the optimal wavelength is around 700 nm so it seems to me that an 808 nm @ 300 mW should do the job.
 

Savage

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Wax doesn't etch copper. i want to use it as a resist - which is a shield that protects selected areas of copper from being etched by the etchant.

Moving - microcontrolled stepper motor.

An engraving setup is probably very close to what i want.
 

MadEye

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That really sounds interesting. Is this your idea or are already people doing it that way?

I always etched my PCBs with laser printer toner as resist (the noobs way :D) and now trying to switch to UV exposure (280 LEDs on 15*20cm :>) with pre-coated PCBs.

But I think to get sharp contours you will need more then 300mW because I cant imagine the wax will immediately vaporize and melt first... And if it starts melting the liquid spot will spread pretty fast. But a high powered pulsed laser should work I guess, maybe some CO2 tube? ;)

Though it would be really cool if you try it that way and show us how far you get with this power.
 
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DrSid

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I tried removing paint from beer cans with 1.5W 445nm .. and it works rather fast. As for wax, hard to say ..
 

Savage

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I saw something online from a guy who tried it but failed. I'm not sure why he failed. There are also articles about ppl trying to use wax paper to apply toner.

The reason i wanted to try removing wax is to reduce making pcb's to a two step process. Print, etch. no toners, transparencies, UV, etc.
 
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I have not tried anything with wax, but if you point a red laser at a 'white' candle,
yes it absorbs it, but it wont melt, let alone burn anything..
The same thing can be observed if you point a red laser at your finger..
A large area will light up red like a beacon, where 445nm or even 532 green
will not. If there is enough power, it begins to burn away skin.

Unless you are using wax with a dark pigment, I would suggest 445nm.. Not
only can you control the output in case you need more, but the dot
will be easier to get to a smaller point.

445nm burns most materials you put in its way. Even solder can be melted..
and copper heated.

http://laserpointerforums.com/f42/soldering-light-1-55w-445nm-l-s-e-r-73206.html

You also may want to consider that there may be residue left over which
will still impede the etchant from performing its task.

Should you decide to use a visible wavelength like 445nm, I can set you
up with a machined 'head' with variable power control and the optics
to get a super fine point, as well as eye protection.

PM me if interested :beer:
 

Savage

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I tried removing paint from beer cans with 1.5W 445nm .. and it works rather fast. As for wax, hard to say ..
if the beam is .1 mm i figure i can probably get a lot of energy into a very small spot. the idea is to vaporize the plastic. if the temp is high enough (400-500F) the wax will instantly go to a vapor state.

i think the trick will be to remove wax without the adjacent material melting and flowing into the groove. it might be possible to fire a fast pulse that will transfer enough energy to the target area to vaporize the wax very quickly. i'm hoping if it's fast enough it'll carry the extra heat away before it diffuses into the surrounding material.

If the wax won't melt cleanly at room temp one possibility might be to preheat the pcb so that the wax is close to melting. that way the amount of energy required to vaporize would be lower.
 

Savage

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I have not tried anything with wax, but if you point a red laser at a 'white' candle,
yes it absorbs it, but it wont melt, let alone burn anything..
The same thing can be observed if you point a red laser at your finger..
A large area will light up red like a beacon, where 445nm or even 532 green
will not. If there is enough power, it begins to burn away skin.
for thick material i'm not surprised that the beam would diffuse. however, i figure that i will likely be firing the laser at a film 50 microns or less. i'm hoping that the beam will pass thru the wax and be reflected back by the copper before it has a chance to diffuse.

Unless you are using wax with a dark pigment, I would suggest 445nm.. Not only can you control the output in case you need more, but the dot will be easier to get to a smaller point.
pigment is an option as long as it doesn't interfere with the etchant.

i read somewhere that shorter wavelengths were easier to focus and was considering that as an option.

You also may want to consider that there may be residue left over which will still impede the etchant from performing its task.
yes, i have considered that. if it does become a problem i have a couple of ideas that may help. one would be to increase the energy transfer either by slowing the burn down or increasing the wattage.

Should you decide to use a visible wavelength like 445nm, I can set you
up with a machined 'head' with variable power control and the optics
to get a super fine point, as well as eye protection.

PM me if interested :beer:
this is something i may be interested in. i've got a couple of machined lenses. not sure how effective they'll be. i'm currently exploring options but i'll definately keep you in mind. thanks.
 




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