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Trimming SIP resistors — Parallax Forums

Trimming SIP resistors

LevLev Posts: 182
edited 2013-03-19 15:57 in General Discussion
I sometimes trim SIP resistor arrays to fewer pins using a pair of diagonal cutters. They cut cleanly, and testing shows the resistance from common to each remaining pin is not immediately affected. Is this a common accepted practice, or could it somehow damage the resistor and the damage not be evident until later? I haven't been able to find any info on this from any authoritative source on the web.

Comments

  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2013-03-19 11:08
    Lev wrote: »
    I sometimes trim SIP resistor arrays to fewer pins using a pair of diagonal cutters. They cut cleanly, and testing shows the resistance from common to each remaining pin is not immediately affected. Is this a common accepted practice, or could it somehow damage the resistor and the damage not be evident until later? I haven't been able to find any info on this from any authoritative source on the web.

    Although I have seen other people do it as well I would try to avoid it. I would never do this for a finished design or project. If I saw that on a production product it would make me question the rest of the device. If you are building a prototype then I suppose you could get away with it but instead just leave the other pins unconnected.

    Just my opinion.
  • LeonLeon Posts: 7,620
    edited 2013-03-19 11:17
    I sometimes make my own by mounting resistors vertically.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-03-19 11:34
    If you must do this, cut close to the first pin you want to remove, file it down the rest of the way, and cover the wound with epoxy. The reason for cutting too long, then filing, is that sidecutters produce a tremendous sideways force impulse on whatever they're cutting, which could damage anything proximal to the cut. Think about what flies off -- and how fast -- when you cut a piece of thick wire.

    -Phil
  • RDL2004RDL2004 Posts: 2,554
    edited 2013-03-19 11:51
    Even when trimming leads on normal resistors and other components you should grip the lead in a pair of needle-nose pliers (or similar) between the cut point and the body of the component, in order to avoid damage to the internal connections due to mechanical shock.
  • Mark_TMark_T Posts: 1,981
    edited 2013-03-19 15:57
    Diamond wheel cutting would be preferable - you still lose the conformal coating and open the internal metalization up
    to the elements.
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