Tricky Repair of Power Driver for CNC Machine

tricky-power-driver-repair

Designing and building something from scratch is one thing. But repairing fried electronics is a much different type of dark art. This video from [Mike’s Electric Stuff] is from more than a year ago, but we didn’t think you’d mind since what he accomplishes in it is so impressive. He’s got a burnt out pick and place hybrid power module which isn’t going to fix itself.

The power module construction includes a part that has chip-on-board-style MOSFETs and the circuitry that goes with them enclosed in a black plastic housing. It’s kind of like a submodule was encapsulated using the same plastic as integrated circuits. After cracking it open it appears the bonding wire has burnt away. [Mike] connects a jumper wire to one of the board traces in order to use an external MOSFET. This is much easier said than done since the module substrate is ceramic designed to dissipate heat. We’re amused by his technique of melting the jumper into the plastic housing to protect it from the heat sink that goes over the package. In the end he gets his CNC running again. This may not be the best long-term fix but he just needed to continue running until a proper replacement part arrives.

Oh, one more thing: the Metcal vacuum desolderer he uses in the video… do want!

[Thanks Buddy via Reddit]

24 thoughts on “Tricky Repair of Power Driver for CNC Machine

    1. Most cereamics are bad at conducting heat, but there are those especially engineered to do it good. Like in peltier modules.

    2. You can create thermally conductive ceramics using silicon carbide or aluminum nitride among other things.

      You just hear more about ceramics being used for insulation.

    3. They are certainly not as good as metal, but they can be better than other electrical insulators, if you load them with enough metal oxides.

      1. Technecally correct yes. CNC stands for computer numberical control it doesn’t matter if it is a pick and place a mill or a laser cutter, so yes they are correct.

    1. Yes, you need to protect the wire from syncing with the heat. If the heat is really hot and the wire syncs with the hotness of the heat, the wire too will be hot. And hot wiring a CNC may be a crime in some contries.

      Cool fix though :)

  1. This is what it is like to have the proper tools. And you can get a lot of the real bench and rework tools on the used market. I love my hot air rework so I can do BGA and other large PITA devices without resorting to hokey methods.

        1. That said, the Metcal tips are also the perfect temperature to dig parts out of potting. Hot enough to get the potting to a jello like consistency, but not hot enough to burn the potting plastic. (and yes, clean the tips ASAP if you do this.)

  2. Heat sink, not heat sync. It’s the opposite of a heat source, not a synchronizer of heat.

    – Rich Grise, Self-appointed Chief
    Internet Syntax Police

  3. Metcal vacuum desolderers – suck. no pun intended. Having used plently of solder suckers, including the metcal and cordless plunger types, They all tend to go unused and wick wins out. They just never work as well as good solder wick does. From getting clogged up after a joint or two to tips erroding and loosing vacuum almost as fast. I did myself a favor forever ago and got rid of the metcal and freed up bench space and a power port on my metcal supply for a second pencil.

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