is my fr2 actually fr4?

Discussion in 'General Electronics Chat' started by gregtomko, Jun 18, 2012.

  1. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    I bought some circuit board material sold as fr2 so I would not dull my milling bits. I think it is actually fr4. It looks like fiberglass, as you can see the woven cross hatch pattern, which looks exactly like fiberglass. Is there a way to tell for sure, short of dulling my brand new carbide bit? I tried breaking a piece of the board apart to extract a fiber, but after a half hour with a pair of pliers all I could manage to do was crumble it into little bits. I thought if I could get a fiber out I could see if it burns or melts, but no such luck so far. Thanks in advance for any help.
     
  2. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    I tried burning a small thin section of the material. The resin burned off, but the cloth inside remained even after glowing orange for 30 seconds over the flame. I am not sure if the cotton cloth could be somehow that flame retardant, but it seems unlikely. I will see tomorrow if the piece will now dissolve in sulfuric acid. Supposedly that will be the final determination, if what I have read about fiber analysis is true. From what I can tell after an hour or so researching, phenolic actually appears similar to fiberglass, so just looking at the board won't tell you either way, but I am not certain about that. Any insights would be greatly appreciated.
     
  3. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    The sulfuric acid did not dissolve the cloth, so it looks like it is glass fiber. This makes it unusable for my pcb mill. Does anyone know where I could find a supplier for small quantities of real phenolic fr2 board material? I am looking for somewhere in the range of 300 to 500 square inches, in both double and single sided copper. Thanks again if anyone can help.
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    wouldn´t fr1 be better available? It seems to be similar.
     
  5. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    Yes that would be acceptable also, but I haven't had any luck finding a supplier for small quantities of anything except fr4.
     
  6. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    Also I should mention, a supplier in north America would be the best for me, I am in New York.
     
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    EBay can be your friend:

    Single Sided.

    Double Sided.

    Stuff I order from China typically gets to me in NY in under 2 weeks, even those places that have free shipping.
     
  8. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    Those are actually the exact boards I purchased, and they are fiberglass reinforced, no question about it. They are NOT fr2, at least not the ones I received. Although their shipping was pretty good, it took 11 days.
     
    Last edited: Jun 20, 2012
  9. ErnieM

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    Apr 24, 2011
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    I bow to your superior expertise and curse that damn Chinaman!
     
  10. kubeek

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    Sep 20, 2005
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    Can you tell me where exactly does it say that FR2 needs to be made of cotton cloth? Isn´t the FR class more about the resin which binds it and what temperature it withstands? At least that is all I could find about it.
     
  11. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    You may be right about that. Looks like I spoke too soon. It is strange that someone would manufacture a board with a higher cost substrate than necessary, but certainly not impossible. Thanks for the heads up on that one!
     
  12. ErnieM

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  13. gregtomko

    Thread Starter Member

    Sep 29, 2008
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    I have been making circuit boards by hand with perf board for years. I now have a CNC mill and have been dulling my carbide bits on glass reinforced boards. It works, and it is still very economical for prototypes, but if I could find a source for phenolic paper boards It would cut my tool bit costs ten fold. I am sure there are other hobbyists who are in the same situation. If anyone knows where to source such material we would all benefit. Thanks for all your help!
     
    Last edited: Jun 22, 2012
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