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PCB Material

Twisted PairTwisted Pair Posts: 177
edited 2007-07-23 03:07 in General Discussion
Looking for the Green in color,·flame resistant PCB material for making my own boards. Any suggestions for a supplier ? Thanks for your Help.



Twisted Pair....

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-07-19 00:37
    The green color that you see on printed circuit boards comes from the soldermask that's added after the boards are etched. The natural color for unetched fire-retardant fiberglass (FR4) is a translucent off-white.

    -Phil
  • Twisted PairTwisted Pair Posts: 177
    edited 2007-07-19 00:50
    Hello Phil,
    Is the green soldermask available to the public and does it add any more fire protection to the FR4 board ? I've been using Radio Shack boards. After the board is etched and populated, I spray it with a product called final coat. This spray is clear and more like a lacquer. Thanks for your help....

    Twisted Pair....
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-07-19 02:11
    Application of a soldermask is not something usually undertaken by hobbyists, and I know of no available products for doing this outside of a production environment. Fire-retardancy is a property of the FR4 itself. I'd be more concerned with substances that you add to it that might promote combustion, such as the plastics used in IC packaging, connector housings, and the like. I'm not sure about the flammability of the various Fine-L-Kote products, which are designed to protect against moisture and corrosion.

    You need to be aware that "fire-retardant" only means "will not support combustion". It doesn't mean "will not be damaged by heat". Some fire-retardant substances can still melt or reduce to ash without actually catching fire.

    -Phil
  • Twisted PairTwisted Pair Posts: 177
    edited 2007-07-19 11:56
    Ok Phil,

    Thank you for the help. I'll look around for the FR4 board materials....

    Twisted Pair....
  • pwillardpwillard Posts: 321
    edited 2007-07-20 01:35
    You can look into what's called "conformal coatings". The only ones I've seen for sale are clear however. MG Chemicals has a product that is available through MOUSER that is specifically designed to coat PC boards. Circuit Works has a small PEN designed for PC board repair that applies a green tinted conformal coating to match underlying coating after a repair.
  • ForrestForrest Posts: 1,341
    edited 2007-07-20 03:24
    We're discussing two different products here.

    Soldermask (available in green, red, black, blue and other colors) is always applied by the board manufacturer at the end of the PC board manufacturing process. It's usually made of epoxy, acrylic or a combination of the two. LPI (liquid photoimageable) is the most common type - it's printed in an UV exposure machine (3KW to 10KW UV lamps), developed in an aqueous developer and then exposed to additional UV and/or thermal energy (oven). As you can see, it's not the type of process you can duplicated at home. It's primary purpose to cover all circuitry except holes/SMT pads to prevent bridging during soldering - making it easier to assemble defect free boards. Here's a popular company who makes soldermask www.taiyo-america.com/

    Conformal coating (typically clear) is applied AFTER assembling and testing the circuit board. Conformal coating is available in urethane, silicone or parylene. The first two are available in spray cans, followed by a low temperature bake. They can also be air dried - though some of the urethane formulations require 1-4 weeks to dry at room temperature. This process could easily be done at home. The primary purpose of conformal coating is to protect the board from the elements - moisture, grime, etc. Here's a popular company who makes conformal coating www.humiseal.com/
  • Steve JoblinSteve Joblin Posts: 784
    edited 2007-07-21 13:42
    Check out Pulsar (http://www.pulsarprofx.com/PCB/a_Pages/1_Menu/overview.html)· I think they offer the product(s) you are looking for.
  • ForrestForrest Posts: 1,341
    edited 2007-07-21 13:58
    I checked Pulsar's web site - they only offer green spray paint that can be soldered thru. This isn't the same as soldermask - which CAN'T be soldered thru.

    According to Pulsar:

    "Available at R/C type hobby stores or direct through Testors Corporation. Product #1601.

    Note: This Testor product is only a transparent acrylic spray paint. It does not act as real solder mask."
  • Twisted PairTwisted Pair Posts: 177
    edited 2007-07-22 15:34
    Ok, Here is what I understand from all the great post. The green color of the boards are from a Soldermask applied by manufactures who have spent tens of thousands of dollars for the equipment to do this and is not a suitable process for the home hobbyist who makes their own PCB's. The issue of protecting the board is still a concern so the only logical choice for me would be a conformal spray coating. I have been using a product called Fine-L-Kote which is a Silicone conformal spray coating that can be air dried and Soldered Thru. The manufacture claims that the Thermal Shock Range is from -46F to above 390F. Impressive for a inexpensive spray can that doesn't take up much storage space, and except for shaking the can, is ready to be used. So the moral of the story is,,,, if you are making your own PCB's, use a conformal spray coating that suits your purpose.

    Twisted Pair....
  • ForrestForrest Posts: 1,341
    edited 2007-07-22 17:36
    Yes, I think you've got it.

    Silicone conformal coatings works great for protecting against moisture, but isn't suitable for solvent resistance - you can easily wipe it off with Acetone. If you want moisture and solvent resistance - get a urethane conformal coating.
  • Twisted PairTwisted Pair Posts: 177
    edited 2007-07-22 20:58
    I will check into the Urethane coating for the best of both world's. Thank you for the Soldermask and Conformal coating Education. Any supplier suggestions for the FR4 board material ?


    Twisted Pair....
  • ForrestForrest Posts: 1,341
    edited 2007-07-22 21:49
    I don't build that many boards - so I still buy FR4 and Prototyping boards from Radio Shack. Most of the Radio Shack's NOT loacated in shopping malls still stock this stuff www.radioshack.com/family/index.jsp?categoryId=2032265&cp=2032058.2032230
  • Twisted PairTwisted Pair Posts: 177
    edited 2007-07-23 03:07
    Roger that....Thanks for your help Forrest....




    Twisted Pair....
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