Modifying Surface Mount to Fit Through-Hole Board

Discussion in 'The Projects Forum' started by C64, Mar 22, 2015.

  1. C64

    Thread Starter New Member

    Mar 22, 2015
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    Hello, new guy with a question here. I sell games online (board, card, video, etc.), and as part of my business I spend a lot of my spare time cleaning and restoring old cartridge games. Many older carts use a volatile SRAM chip to store saved game states (non-volatile memory chips being prohibitively expensive at the time), and to power them a coin cell battery is soldered onto the circuit board.

    It's impressive how long those old nickel-cadmium batteries last (I find functional batteries all the time in 25+ year old NES carts), but eventually they all die and need to be replaced. The simple solution is to just solder a new battery directly onto the board, and it's cheap & easy to buy them in bulk with leads already attached, but I'd like to start replacing them with battery holders instead so that the next person who needs to swap out the battery won't need to break out his or her soldering iron to do it. The main problem with that solution is finding a battery holder with a low enough profile to fit inside the plastic cartridge shell, but since pretty much all console game carts use CR2032 batteries* I only need to find one design works.

    Anyway, I finally found a holder that seems to fit everywhere I need it to fit, but it's a surface mount component. Would it be possible to modify these to work with a through-hole board, preferably without raising its profile? Or if someone can point me to a through-hole version of this holder, that would be pretty great, too.

    * Games for portable systems use the smaller CR2016 variety, but good luck finding a battery holder that will fit inside a Game Boy Color cartridge. Which is too bad, because some of the later Pokemon games drain power like crazy (they kept track of things like calendar dates and time of day to trigger certain events and whatnot) -- their save batteries start to die after just a few years, not decades.
     
  2. praondevou

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  3. Marcus2012

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    Feb 22, 2015
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  4. djsfantasi

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    You could even solder L shaped bits of wire or component leads to the tabs. If you could solder to the top of the tabs, you wouldn't raise the profile at all.
     
  5. #12

    Expert

    Nov 30, 2010
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    Battery soldering tips:
    Damage the surface with a worn out diamond fingernail file.
    Go in hot and fast with an over-sized soldering iron to tin the damaged surface of the battery.
    Wait for everything to cool completely.
    Tin a bit of wire and tack that on quickly.
     
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  6. djsfantasi

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    Who's soldering to a battery? Were talking about soldering to a battery holder...
     
  7. #12

    Expert

    Nov 30, 2010
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    Completely missed? :oops: Oh well. At least I labeled the procedure correctly. :D
     
  8. C64

    Thread Starter New Member

    Mar 22, 2015
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    Yep, definitely too big. There's only about 6mm of clearance between the board and the plastic case inside a Genesis cartridge, so any design that involves a long spring clip over the top of the coin cell is going to be too big to fit. From the sizing I've done so far with various samples it seems like all the black socket-style holders are pretty chunky, profile-wise.
     
  9. Marcus2012

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    Feb 22, 2015
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    Ahh that sucks :( Must be squeezed right in there then lol. I'm not sure how big the solder points are for the SMD one from the photo but if you can get away with drilling a 1mm hole through it you could drop a terminal pin through from the topside, solder the head and then solder the underside. The solder point under the battery has a depression so it might accommodate the head of the pin.

    These are the kind of terminal pin in mean

    PCB Terminal Pins for Vero Boards
     
  10. C64

    Thread Starter New Member

    Mar 22, 2015
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    Thanks! I've ordered samples from a couple of other electronic component suppliers like Keystone (the samples they sent me were awful quality -- the lowest-profile design they sent me shattered into pieces in my hand when I tried to remove the battery I'd slotted into it to test the fit), and for some reason I thought I'd ordered some from Digikey as well but now I'm thinking that maybe I just browsed their inventory late one night and somehow managed to remember that as having ordered from them as well. They've got a couple of designs that could work -- I'm particularly curious to measure the profile on their snapdragon holders once the top piece has been snapped into place.
     
  11. C64

    Thread Starter New Member

    Mar 22, 2015
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    That's an interesting idea, but I'm not sure drilling 1mm holes would end well. The positive lead is 3mm wide by 2mm long, and the negative is 2mm wide by 5mm long, and the metal is pretty cheap and thin. I experimented with a more direct approach by bending the tabs down and trimming them with some flush cutters until they were thin enough to slide into the holes, but they snapped off before they bent anywhere near far enough. You win this round, Taiwan.
     
  12. Søren

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  13. DickCappels

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    Aug 21, 2008
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    Soldering to coin cells is dangerous. The heat can and often cause pressure to build up to the point of the battery exploding. Besides, the purpose of this thread is for the next person to change the battery to be able to do so without soldering.


    These are about US 15¢ each and in stock at Electronic Source in Bangkok.
    [​IMG]
    http://www.es.co.th/tabs.asp?keyword=battery+holder
     
  14. C64

    Thread Starter New Member

    Mar 22, 2015
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    Shipping included, my order of sample battery holders from Digi-Key totals exactly $6.66. Here's hoping the factories in hell know how to produce a quality product.
     
  15. Søren

    Senior Member

    Sep 2, 2006
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    They should be extremely heat resistant in the very least then :D
     
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  16. C64

    Thread Starter New Member

    Mar 22, 2015
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    Okay, so the CR2032 battery holders I ordered from Digi-Key look great and are beautifully low profile (especially the snapdragon holders, which are just a touch under 5mm), but they all have depressingly large footprints -- too large for my purposes. After some further experimentation, it's looking more and more like my caveman solution of taking a surface mount holder and just bending the tabs down and trimming them up to fit in the board is going to be the way to go, especially with the ridiculously tiny amount of space I have to work with inside a SEGA Genesis cartridge. Also, the standard distance between the holes on almost every circuit board I've come across is ~1.95mm, and as luck would have it that's exactly the distance between the leads on the surface mount holders once the tabs have been bent down, whereas on the snapdragon holders I mentioned it's closer to ~2.75mm.

    I still need to figure out how to attach a battery holder to the board on Genesis carts produced by Electronic Arts, though. As an up-yours to SEGA's licensing fees, EA decided to manufacture a cartridge of their own design for their games. The EA carts are a different shape (more height, less width), they have a few millimeters roomier inside, they have an obnoxious yellow plastic tab on one side that makes it difficult (but not impossible) to open the carts and remove the circuit board without breaking the tab off, but more importantly for our purposes here the holes on their circuit boards for the battery leads are only ~1.65mm apart. As I said, there's more room inside to work with (the factory-installed batteries on the boards I've opened up are already up to 7mm off the board), so there's some wiggle room here, but I'm wondering if anyone has some tips on modifying a battery holder to fit a narrower set of holes on a board without raising its profile too much.
     
  17. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    What about using a coin cell that they use in computers to keep power for the bios ??
    [​IMG]
     
  18. C64

    Thread Starter New Member

    Mar 22, 2015
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    Interesting. Do you happen to know what the holder looks like inside that black shrink wrap by any chance?
     
  19. Søren

    Senior Member

    Sep 2, 2006
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