Making PCB's with a CNC
Philldapill
Posts: 1,283
I'm making a CNC machine that I'm hoping will have the precision and accuracy I need. Assuming it will work and I'm able to etch out circuit boards like it's nothing, is there a cheap way to apply solder resist/mask to the board? I'm hoping to be able to solder these TINY chips that only have 0.5mm clearance between pins and I bet it's going to be awfully hard to prevent solder briges without any solder mask. Any pointers on where to get it and how to apply? I think I've seen something where you make a stencil of the places you want the copper exposed, and somehow apply solder mask to everything else...
Comments
If you're going to reflow solder (with an oven for example), then you're probably going to need a stencil. When you make your schematic, you make a solder mask layer, the Gerber for that layer can be used with a laser cutter to make a stencil out of piece of mylar or plastic sheet. You use a squeegie to apply solder paste.
A fab house can usually make stencils. There are small mom & pop companies with laser cutters that make stencils too - I've run across them on the Web before - but don't have any URLs.
There are tutorials about this at Sparkfun. Try this link:
www.sparkfun.com/commerce/hdr.php?p=tutorials
Scroll down the page and you'll see the surface mount soldering and stencil links.
Unless you're going to do production level builds, I would try to stick to parts with wider pin pitch and hand solder them. That way with your CNC you completely independent of any fab houses for boards or stencils.
I don't know how a stencil would behave with a CNC PCB. The lands might stick up too much compared with an etched board. Hmmm...
Regards,
David
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Good luck!
Since i have been using such machines for a long time do not save on mechanics!
And the milling tools are not that cheep.
My first CNC was a ISEL type, actually i have a older LPKF milling unit,
but it happens that things are not going as they should and mostly it is because of details!
Saluti Joerg
I use an LPKF too, and we purchased a kit to make solder mask. It was a thin amber colored plastic that you cut-out the exposed copper areas, then you put it on top, put the whole thing in a press, then put the press in an oven. There is a heat activated glue on the plastic.
We only used it a couple times because it is too much of a pain. If you have a part with 0.5mm pitch there isn't going to be any (or hardly any) mask between the pins anyway.
Bean.
P.S. I am sell an LPKF on ebay right now. But you must pick it up in Shiremanstown PA 17011. Item # 300202499731
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www.iElectronicDesigns.com
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I may be missing the point here, but why do you want to use a CNC machine to produce PCB's? Wouldn't etching them using photo sensitive boards and oxidizing solution (Sodium persulfate, NOT sodium hydroxide as I stated before!) be far easier, cheaper, faster and better generally? And if you are doing it on a hobby basis, soldering 0.5mm pitch IC pins by hand is straight forward. Just wondering
Cheers,
Shane.
Post Edited (Shane De Catania) : 3/3/2008 11:27:32 PM GMT
I use a laser printer to print my artwork on transparency material and then expose the·board with a flourescent lamp.· The chemicals are easy to get a hold of from places like http://www.web-tronics.com/·and the whole process only takes about an hour from start to completed etching.··You can get a great yield with 10mil spacing, but anything more complicated·should probably be·sent to the board house.
Can you post a link to the kit you where useing?
Also, You mentioned a long time back a guy that you recommended for doing Gerber files. I have two left feet when it comes to getting board schematic layed out for the manufactures and could definately use some help.
Post Edited (bambino) : 3/5/2008 2:45:20 AM GMT
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
With the CNC you cannot make PTH, so a board with 0.5 mm pitch and more than a few components may not be that useful. Another possibility is to use a small adapter board from TQFP-64 or TQFP-100 to 2.54 mm raster and solder that to your board. You get many of those adapters for few € and make your board with the CNC avoiding the fine pitch. Just a thought. I'd love to have one CNC to make the cases and keys for my calculators, though [noparse]:)[/noparse]
Good luck !
One thing that's extremely important in a CNC machine that cuts away the copper from a circuit board is precision height registration. You mentioned in another post that keeping a precise height with your home-built CNC is proving difficult. This is going to be a major problem for you, I fear, unless you can figure out a way to solve it. You might consider a method that self-registers the tool height relative to the board with some kind of spring-loaded follower that rides on the board's surface. Otherwise, you'll be victim to the inexactness of both your machine (even with software calibration) and whatever means you use to secure the board to the platen.
The mechanical precision of machines like the LPKF is one of the things that makes them so expensive. I'm sorry to have to say it, but trying to achieve the necessary precision with slides cut from HDPE on a radial arm saw will likely be an exercise in frustration.
-Phil
For those who have an interest in cnc mechanical milling, there's a new place that
focuses on it here...
http://www.millpcbs.com/
Video of milling a double sided board...
http://www.millpcbs.com/phpbb3/viewtopic.php?f=12&t=11&p=44#p44
Phil from pminmo.com has been having great success with very fine trace
milling...
http://www.millpcbs.com/index.php?page=finished-result
All with a very cheap machine.
Just thought I'd mention it.
John
You said, "All with a very cheap machine". How cheap and where can you buy them. I tried to join the MillPCBs forum as there's no info on the machines on the main site, but the registration process requires moderator approval and that could be pending for a while. Can you make any recommendations?
How do you plate through the via holes? Is it even possible? I know this is less of an issue these days with SMT, but it still comes up.
David
This is why god created ebay, search THK, IKO, Daedal, parker, linear stage, xy stage, linear bearing. Eventually you can get bargains with a better spec than you will find on the LPKF machines, and I'm not kidding.
The best bargains are mislabeled ones, I saw small linear stages with ball screws and thk linear bearings being sold as stepper motors!
Graham
There is no control over the speed or distance.
There is a "foot" around the bit that rides on the PCB. So it must be flat with no componets or anything on it.
Bean.
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www.iElectronicDesigns.com
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He has a small MDF machine I was making several months ago. I put
that machine on a "back burner" until someone who had the time to
demonstrate that a cheap machine could do a good job milling circuit
boards. I don't mill boards myself...I do very fine jewelry designs.
Milling PCBs is different. That machine was $375.
Phil is now showing the how's and why's of doing that PCB milling.
I only mention it as I know there are many people who have thought
about it, tried it, wondered about it....and now his site will explain
how to actually do it. It's apparently not as complicated as I'd
originally thought. It seems a key thing is a $25 aluminum tooling
plate from ebay.
Those interested should ask him questions and decide if they have
a use for it. If there was any interest....after someone familiarizes
themselves with the process and setup, then I could make a few
more of those machines. Or they could make their own.
The good thing is now there's someone with hands on experience,
that knows what he's doing, that's ready, willing and able to help
and advise, and can show solid examples and techniques...
I've seen some Extremely Impressive examples...But I'll let him
show you himself...[noparse]:)[/noparse]
John
Forgot about the thru-hole plating...[noparse];)[/noparse]
I'm not familiar with that process myself. But it
comes up fairly often here...
http://tech.groups.yahoo.com/group/Homebrew_PCBs/
HTH
John
David
He's topped everything today....I'm Truly Amazed at what he can do with a
very inexpensive MDF machine...
WELL worth a look for anyone interested in milling proto's...[noparse];)[/noparse]
http://www.millpcbs.com/phpbb3/viewtopic.php?f=12&t=11&p=55#p55
Unbelievable!
[noparse]:)[/noparse]
John
Edit: I don't think the MillPCBs machine shown in his videos is the V90 as shown in the attached file. His is a moving table machine, not a gantry. See my follow-up post(s) below.
Regards, David
Post Edited (Drone) : 4/2/2008 11:48:34 AM GMT
Rgds,
David
They should make some form of tubular rivet for prototyping, pushed in the hole, expanded a little with pointed rods from each side and then soldered. For SMT it's mainly for vias anyway but if they are under chips wire doesn't work so well.
Well it turns out the fellow doing the fine-pitch PCBs on MillPCBs is none other than the fellow that sells the Fireballcnc machines. Indeed the PCB examples were made by a F90 machine, which pre-dated the M90 and was in-kind replaced by the V90 gantry machine. The F90 used may be seen at this link: http://www.fireballcnc.com/group1/F90/[url=http://. The F90 seems to be a smaller movable table machine. As the supplie says:<br><br>"The older M90 is no longer made. The F90 replaced it by being easier to align and highly adjustable. I haven't made any in a while, but I could make some if someone wanted them. I started making the gantry style V90 machines because more people with general-purpose uses were interested in the much larger cutting area."<br><br>The F90, unpainted is priced at $375 USD plus shipping. The full post is publicly readable at:<br><br>]. The F90 seems to be a smaller movable table machine. As the supplie says:
"The older M90 is no longer made. The F90 replaced it by being easier to align and highly adjustable. I haven't made any in a while, but I could make some if someone wanted them. I started making the gantry style V90 machines because more people with general-purpose uses were interested in the much larger cutting area."
The F90, unpainted is priced at $375 USD plus shipping. The full post is publicly readable at:
[/url]http://forums.parallax.com/forums/default.aspx?f=25&m=254578&r=r
Again, I seem to be getting the impression from the CNC community that a tight moving table machine is required for fine-pitch PCB manufacture. Very interesting subject. I'll continue to follow it.
Regards, David
Phil and I are not the same person....
He makes electronic stuff....I make inexpensive
cnc machines.
[noparse]:)[/noparse]
John
My sincere apologies.
I'm getting the impression this subject of fine-pitch PCB milling takes a lot of work to get right. Perhaps it's pushing the machines to their limit.
Regards, David
Yes, it is certainly a lot to absorb...[noparse];)[/noparse]
And it does take very careful attention and practice.
Phil *is* pushing the limits of what should be expected from
what amounts to a Home-built machine.
But I think he also recommends that there's really no
need to go as fine as he's getting. Point being, a cheap
machine is Very capable of making Highly,Highly useful
circuit boards for one-offs, prototypes, as well as
mechanical things like stand-offs, enclosures...even 3D
ones...panels...custom bezels, knobs, and unlimited or
unimagined parts for use in the electronics field.
We're not but a few years away from a cnc machine
being almost a necessity in most any small shop or
R&D environment.
They're very useful in general...[noparse]:)[/noparse]
John
I have done boards with my (home built) router and it was a whole load of fun (I am not being sarcastic)· watching the tracks form always put a smile on my face.
I never did small surface mount stuff with it though, I know guys are achieving great results these days.· These days I use a modified printer for my boards, the results are great, and it is easy to use (not so easy to mod in the first place) [noparse]:)[/noparse] Link to it in action if anybody is·interested :
http://www.youtube.com/watch?v=FkHpjzOhzxA
The thing I miss by not using the CNC Router is having to drill the holes by hand, instead of the machine doing it, can't have everything I suppose.
Graham mentioned a tubular rivet for via's, I am sure I have actually seen this exact method used, the rivets just happen to fit inside one of those clutch pencil's so you don't have to buy the applicator.· I will try to find the link.
Cheers.
Russell.
Edit: I just checked the catalog... they do not seem to have it anymore (the Proxxon CNC)
Post Edited (Ale) : 4/3/2008 12:02:24 PM GMT
CNC is the way to go, I love what epineh and crew is doing with direct printing.· But I'm done with the nasty etchants and then drilling the copper by hand for through holes.
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Phil
Too many interests, too many projects, not enough time!!!
Visit my website http://PMinMO.com
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