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Resistor colour coatings - not the marking bands

Discussion in 'Electronic Design' started by Jumbaliah, Jul 24, 2003.

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  1. Jumbaliah

    Jumbaliah Guest

    I was looking at some junked boards the otherday and noticed some of
    the resistors ( through hole, appeared to be 1/4W) had different
    colours for their coatings. They weren't the usual tan or beige
    colour. I thought the colours might have something to do with the
    tolerance but from reading the marking bands they appeared to be 5%.
    Some had a red coating others had a blue (blue = Metal film?) coating.
    I've come across the light green/aqua ones before but I assumed it
    was just a different manufactuer. I have some blue metal film
    resistors but they have 5 marking bands. All the ones on this board
    have only 4 marking bands. Anyone know the reason?

  2. The blue ones with five bands are 1% tolerance units. They have 3 digits, 1
    multiplier, and one tolerance band.


    Chip Shults
    My robotics, space and CGI web page -
  3. Jumbaliah

    Jumbaliah Guest

    Thanks for the explanation but I'm more concerned with the reason
    behind the different 'coating' colours and not the bands. Everytime I
    search for things about resistor coatings I get descriptions like: red
    means 2 grey means 8... etc. The closest I've come is finding some
    companies that make the coating material used by Yageo and others to
    cover the resister during manufacturing. There must be a reason
    behind using these different colours.

  4. Okay, I didn't understand exactly what you wanted the first time around.
    For the most part, resistor body colors have little meaning. Some represent
    the temperature coefficient of the resistor, others mean nothing at all.
    However, blue and white resistors usually mean non-flammable, and fusible, in
    that order. If you run across a blue or white resistor, you should not replace
    it with a standard type of resistor. Doing so can increase the risk of fire in
    some applications.
    Blue resistors are non-flammable and will not burn if they overheat. They
    will simply char or become open. White resistors will open when exposed to
    sudden increases of temperature, or extremes of temperature.
    Usually, you will see these in precision, aerospace, or defense hardware.
    Often these resistors are used in medical applications. Because of their cost,
    they are usually 1% tolerance or better, and that explains why so many 5-band or
    1% tolerance resistors are blue.


    Chip Shults
    My robotics, space and CGI web page -
  5. I believe Philips (now BC Components) used the body colour to indicate
    the resistor "family" - metal film, carbon film, high voltage, etc...
  6. Jumbaliah

    Jumbaliah Guest

    Thanks to those who replied. I looked at Yageo's sheets for their
    different resistor families. Here's what the sheets say:

    "Professional and flame proof type":
    The FC0207 are coated with layers of green
    color flame-proof lacquer.

    "Professional type miniature style (MF)":
    The resistors are coated with multilayers of
    blue color lacquer.

    "Carbon Film resisters":
    The resistors are coated with layers of tan
    color lacquer.

    "Flameproof wire wound":
    The KNP/NKN series are coated with
    layers of green color flame-proof lacquer.

    "metal oxide film resistors":
    The normal style & the miniature style of RSF
    series are coated with layers of gray and pink
    colors flame-proof lacquer respectively.

    Too bad they didn't have red listed, unless their 'pink' is my red. I
    wish their datasheets had colour pictures instead of grainy black and
    white. Then I'd be able to tell.

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