Which bits to use for PCB milling?

Page 1 of 10 1234 ... LastLast
Results 1 to 12 of 110

Thread: Which bits to use for PCB milling?

  1. #1
    Registered
    Join Date
    Jul 2012
    Location
    Danmark
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Which bits to use for PCB milling?

    Hi all,

    ... so I set up my CNC for my first PCB milling today and was successful drilling the holes, however, milling the actual traces was much less of a success ...

    Using a 10 degr. 0.1 mm V-bit the result overall looked like the PCB I was supposed to mill but unfortunately not much more than that. And the V-shape bit clearly had changed its end shape when the milling was completed.

    Which brings me to my reason for posting here .. I hope someone here have some good experience on milling PCBs and may advice on:

    - which mills to use for carving high-precision PCBs with traces down to 0.2mm widths and similar trace spacings? V-bit mills or regular low-diameter end mills? And which metal types/coatings are particularly useful for this?

    - which rpms and feeds to use for a successful milling?

    - how much may the Z-axis depth be increased per pass?


    I would much appreciate some advice on this - and if possible a link to a calculator of some kind that may help estimate these values for various bit sizes.

    Cheers & thanks,

    Jesper

    A P.S.: I guess part of successful CNC milling is using good end mills ... might one of you have a suggestion for a good end mill vendor in Europe?

    Similar Threads:
    Last edited by evalon; 08-30-2018 at 11:32 AM.


  2. #2
    Registered CitizenOfDreams's Avatar
    Join Date
    Nov 2012
    Location
    USA
    Posts
    541
    Downloads
    4
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    10-degree bits have very fragile tips, they break if you look at them sideways. 30 to 60 degrees work much better for PCBs.
    Regular end mills are pretty much out of question. Your two options are:
    - V-bits and pyramid bits off eBay - cheap but functional.
    - Specialized PCB bits (such as PreciseBits) - supposedly better than V-tips but $10 to $15 a piece.

    RPMs and feeds: depending on the machine and spindle you have. My "sweet spot" is 8 000 RPM and 150mm/min; yours can be totally different.

    Depth of cut: I use a single pass at 0.05mm. Depending on the copper thickness you may have to cut deeper and/or make multiple passes.



  3. #3
    Registered
    Join Date
    Jul 2012
    Location
    Danmark
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi C-O-D ... & thanks for your feedback.

    The thing - which I should have written, my apology - is that I will make quite special PCBs. Likely up to 0.5 mm copper thickness and still with 0.2mm - 0.25 mm spacings between some of the tracks. And I also need these tracks to be very reasonably impedance matched. So a higher angle degree V-bit or the like is less than optimal if another option may be available ... Which is what I somehow hope to find ..

    Cheers - Jesper



  4. #4
    Registered CitizenOfDreams's Avatar
    Join Date
    Nov 2012
    Location
    USA
    Posts
    541
    Downloads
    4
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Wow. What are you making, high power strip filters? RF amplifiers?

    A 10-degree V-cutter may work, but definitely not in one pass. Probably not even in five passes.

    I have not tried cutting such thick copper, but I would try a stub 0.2mm mill like this one:

    eBay




  5. #5
    Gold Member
    Join Date
    Apr 2013
    Location
    Sweden
    Posts
    1834
    Downloads
    2
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Quote Originally Posted by evalon View Post
    Likely up to 0.5 mm copper thickness and still with 0.2mm - 0.25 mm spacings between some of the tracks.
    Wow...

    Normal PCB has 35µm (0.03500000mm) copper layer, some heavy duty electronics use 70µm layer, but that's not very common, so whatever you plan to do it must be very special because I have never heard about PCB with 500µm copper layer. To me that sounds like you missed a zero after the decimal point or is not a PCB but copper plate. Sorry, I can't help you with this sort of PCB, I only use standard PCB with 35µm copper layers and on those I am using 22k RPM, 30 degree V-bit with 0.2mm tip. It works well, but I would not use it on PCB with 500µm copper layer.





  6. #6
    Registered
    Join Date
    Jul 2012
    Location
    Danmark
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi both ... well, I am doing something where I need the GND level to be very firm for a wide range of frequencies. And I am also interested in trying out what happens when using such a thick PCB copper layer. Regarding the PCB laminate I intend to start out with thinner copper layers (175um) and then move up in size if I can make it work. PCB laminates are not readily available with such thick copper - as you A-camera mention - but I have some PCB prepreg and will try to make the PCB myself in due time.

    I think I will try with another V-bit and also the 0.2 mm endmill that CitizenOfDreams linked to.

    Thanks again for your replies ;-)

    Jesper



  7. #7
    Registered CitizenOfDreams's Avatar
    Join Date
    Nov 2012
    Location
    USA
    Posts
    541
    Downloads
    4
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Quote Originally Posted by evalon View Post
    And I am also interested in trying out what happens when using such a thick PCB copper layer.
    Well, I can tell you the first thing that would happen: you will buy a preheater and the most powerful soldering iron you can find.



  8. #8
    Registered
    Join Date
    Nov 2012
    Location
    Romania
    Posts
    123
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    If you're indeed working with multi-hundred micron copper layers I'm afraid not much of anyone's PCB milling experience will apply. No idea what kind of tool would work for you, although a 0.1mm tip 10 degree v-bit is certainly quite fragile even for normal PCB work. Also, expecting your traces to come out exactly as wide as designed is not realistic with a V-bit; you might get the results you're looking for in time if you experiment enough, but typical modest machines just can't control milling depth that precisely. Regarding milling bits in the EU, these are the ones I know of (no affiliation with any of them), I think all of them carry PCB-specific bits: Sorotec.de, FrezyCNC.eu, VHF.de

    Last edited by blinkenlight; 08-31-2018 at 01:46 PM. Reason: fixing mangled links


  9. #9
    Registered
    Join Date
    Nov 2013
    Posts
    62
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi,
    I use a double sided PCB blank with 12oz copper, that is 420um or 0.42mm. I can confirm that its not easy to do. Tapered engraving bits are hopeless.
    I'm using 0.5mm two flute uncoated endmills made by Kyocera Tycom and supplied to me by drillman1 on Ebay. The last lot I got were on special for only
    $2.65 US each so I got 30, wish I'd bought more.

    They are fragile and its taken a while and quite a few tools to work out a good strategy for using them. First in order to get them to last you must avoid cutting
    the underlying fiberglass as much as possible. The Autoleveller software utility improved my results not just with this heavy copper board but ordinary board as
    well. The second thing I do is use flood coolant. Just water with water soluable oil but it increases the tool life from about 1/2 to 1 hour to over 10 hours and
    a marked increase in cut quality.

    Craig



  10. #10
    Registered
    Join Date
    Nov 2013
    Posts
    62
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi,
    should add what cutting parameters:

    I spin the 0.5mm tools at 24000 rpm, I'd spin them faster if my spindle would go faster.

    On a full width slotting pass, WITH COOLANT, I will go only half depth, ie 0.21mm cut depth at 100mm/min plunge and 200mm/min slotting.
    The second pass using the same toolpath, ie cutting too full depth is done at the same parameters, 100mm/min plunge and 200mm/min slotting
    to 0.45mm deep. That is to say through the copper (0.42mm) and a fraction more (0.03mm) into the fiberglass to be sure of isolation.

    Subsequent toolpaths are done at 50% stepover ie 0.25mm at 200mm/min plunge and 400mm/min cutting.

    Craig



  11. #11
    Registered
    Join Date
    Nov 2013
    Posts
    62
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi,
    I should emphasize the flood coolant. If you try, particularly the first full width slotting type tool paths without flood coolant to remove the copper chips from the cut zone
    you will break the tool for sure.

    I have found that the flood cooling to be the difference between success and failure. Its more about removing chips than cooling. I have just one modest jet of coolant
    directed at the cutzone. I think I would get even better results if I had three smaller but higher pressure jets directed at the zone. I would need a different pump
    so haven't tried it.

    Craig



  12. #12
    Registered
    Join Date
    Nov 2013
    Posts
    62
    Downloads
    0
    Uploads
    0

    Default Re: Which bits to use for PCB milling?

    Hi,
    re-reading your post and you say that you are trying to end up with 0.2mm to 0.25mm between traces. That would require endmills of
    0.2mm and they are too fragile especially if you are cutting 500um deep. That would be a 100% width cut, ie full width slotting which is always a challenging
    toolpath but at 250% deep!

    My heavy copper boards have a SOIC with 0.6mm between the IC pin pads, ergo I can use 0.5mm endmills. I am glad I do not have to go any finer than that.

    You may have seen that there are companies that make these heavy copper boards. It seems that military customers are prepared to pay the premium.
    They use a combination of etching, plating and isolation routing. The cost of borads of that description complete with plated through holes is about $1000US/sq foot.
    One company published design rules and they specify that the minimum distance between tracks be at least 0.4mm or at least the thickness of the copper. In my
    case with 0.42mm copper if I got them to make the boards they would have a minimum spacing of 0.42mm.

    I think you will have to review your design requirements with regard to either copper thickness OR minimum practical spacing.

    Craig



Page 1 of 10 1234 ... LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Which bits to use for PCB milling?

Which bits to use for PCB milling?