Reusing A Wire Bonded Chip

We will all at some point have opened up a device to investigate its internal workings, and encountered a blob of resin on the PCB concealing an integrated circuit. It’s usually a cost thing, the manufacturer has sourced the chip as bare silicon rather than in encapsulated form, and it has been bonded to the board with its connections made directly using fine wires. The whole fragile component is then hidden by a protective layer of resin.

Normally these chips are off-limits to we experimenters because they can not be removed from the board without damage, and we have no information such as a part number about their function. Today though we have a rare example of a wire bonded chip being reused courtesy of Reddit user [BarockObongle], who has incorporated the controller from a multi-game joystick into his handheld NES project by cutting a square of PCB containing the chip, and soldering lengths of wire to the PCB tracks.

Of course, he’s in the rare position of knowing the function of the chip in question, and having a ready application for it. But it’s probable that few of us have considered the possibility of taking a resin blob from its original board and using it in a different way, so even though this is quite a straightforward piece of work it is sufficiently unusual to be worth a look. Sadly we don’t have the rest of the build to see it in context, it would be nice to think we’ll be able to feature it when it is completed.

If you are interested in what goes on underneath the blob, have a look at SparkFun’s explanation. Or charge your laser.

 

37 thoughts on “Reusing A Wire Bonded Chip

      1. +1

        Could only do a little better if the bonding wires (Enamel stuff seen above) were tinned after stripping.

        Tip:
        Use a hot iron even if the max temperature is, maybe, needed…
        Tin Iron,
        Put iron on enamel wire to heat it,
        Force a blob formation with fresh solder until the enamel cooks off….
        practice until exactly the wanted length of to be solder coated area is stripped and the rest unburnt.

  1. May years ago in an issue of Popular Electronics there was an article on enabling the memory and constant functions available, but unused, in a common chip used in many handheld calculators. A few wires and a couple of added momentary switches.

    By chance I happened to own the exact model of calculator featured in the article. “Nice! This will be easy!”

    Nope. While the make and model were the same, the insides were totally different. Where the calc in the article had a PCB with the various chips and other components, mine contained nothing but the number pad and the LED display, with a blobbed chip mounted directly to the back of the display. If that blobbed chip contained the memory and other functions there was no way to get at them. :(

    Probably saved the manufacturer a ton of $ and I bet they didn’t lower the price. I’d picked it up at a yard sale for cheap.

    1. I recall an electronics magazine (Radio-Electronics?) years ago had an article about converting a calculator into a capacitance tester. IIRC, it used the calculator’s clock to time the discharge of the capacitor. I didn’t try it, I didn’t want to mess up a good calculator, (cheap $1 calculators were unheard of then).

  2. I’ve sometimes thought about using a calculator as the ALU of a homebrew computer, but then I think of the complexity of the interface, and how slow calculators seem to work… & go do something more worthwhile, but I’m glad reusing a blob chip is possible!

    1. I couldn’t bring myself to take one apart! I wonder if anyone has programmed games on it. I’d try Bulls and Cows, since the commercial game Mastermind was based on it and came out the year before the calculator.

  3. I did something similar to this for a while for Crazy Clocks, except that instead of trying to use the CoB, I was trying to disable it and replace it with something else.

    I used to have a video on YouTube showing the retrofit process that used to include modifying the original controller board and tacking wires on to a replacement. Nowadays I just replace the whole board with a physical clone that has the replacement circuit on it.

  4. The blob chips are the lowest form of life on the totem pole. Someplace to the left of consumer grade. Why would you spend what looks like a good amount of time and energy retrofitting a very low grade part into one of your designs?

  5. Aside from the awful, awful solder joints (I can do better and I’m no wizard, Harry!) — that perfboard he’s using is from the late great Radio Shack. I don’t think they still sell those… :(

  6. This was me, done years ago when I didn’t know how to solder correctly and only had a cheap chinese iron that came with one of those wood engraving kits. This thing did work (surprisingly) but I ended up using a different controller board for layout/space reasons. Also this wasnt originally my idea, I got the idea from the benheck forums.

    1. Dude, I’ve had a cheap Chinese iron before… specifically an ATTEN 937B rebrand. I’ve also had “curtain burner” (non-temperature-controlled) irons — a /very/ cheap Weller and a couple nasty Radio Shack jobs (they all sucked — sorry, even the Weller… although, in all fairness, it was the $7 model). I don’t think I’ve /ever/ seen soldering that’s that bad… by me or by anyone else. That work is not the fault of that iron unless you were heating it literally with tongs and a bonfire.

      I’m glad to hear you’ve improved, though… TBH, good soldering is not a super easy thing to come by. I fully admit I’m still learning… a good iron, though, is /at least/ half of one’s skill… my current iron is a very used Hakko 926, and it’s a dang sight better than that ATTEN, which it replaced. I’d love to have a /brand new/ Hakko, but that’s not something I can pay for. Meh. The one I’ve got is amazing.

    2. Yes, it looked like someone wanting to do something before soldering skills had developed.

      The first projects I built were done with the iron from a woodburning kit, since we had it. I didn’t know how to solder (in retrospect, at the time I didn’t know better), and the woodburning iron was not good for the task. I hadn’t even grasped the concept of “tinning the iron”. Those first projects never worked, I didn’t have enough knowledge t the time to troubleshoot. Lots of other issues, the substituted transistors might not have been suitable, or even have the same pinouts, and the coil might have been too different. So the soldering didn’t matter at that point, incredibly messy.

      But it only got better.

      Michael

      1. I was once called to solder a connector back to a laptop. The guy before me tried but had gotten so much PLA on the iron that it didn’t even solder anymore. I spent 15 minutes cleaning up and then retinning the iron, and then it took me 1 minute to resolder the connector.

        1. Some irons’ tips just seemingly re-coat themselves with an oxide layer and soot…. Long after cleaning them of the plastic!

          Annoyingly, (Before some “TUPE” issue lost half our workforce to a now sued company, pronounced 2p BTW) people at work would use other peoples’ irons as smoldering irons to melt plastic. I had two irons labeled up, “Plastic ONLY”, and, “Metal-SOLDER ONLY” Yet the solder only iron would always be used by someone to melt plastic!

  7. Oh come on.. like any of us just sprung into existence already possessing a perfect ability to solder.

    I remember my first soldering project.. a kit transistor AM radio. I couldn’t get it to work. I revisited it years later with experience under my belt and re-soldered every single joint. That was it, after that it worked just fine!

    Anyway.. that kit of mine was probably late 70s, early 80s vintage Rat Shack. It had solder pads that today would be considered to be HUGE. He was soldering to thin little traces that were never meant to be soldered where he had to rub off the solder mask. And yet it worked! Not bad for a beginner!

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