Repairing the PICqueño32 dev-board prototype

In a previous video we soldered the PICqueno32 prototype. There was a big mistake though, we used the wrong PIC32 chip. In this video the old chip comes off and the new chip goes on.

For the swap we used a flux sample sent by Farnell. It was fantastic! Here’s the webpage if you want to pick one up. We also tested a new soldering iron cleaning gadget.

Grab your own PICqueno prototype PCB from the free PCB store.

Don’t miss:

  • Farnell’s absurdly large shipping tray for 2 ICs
  • Flux and soldering iron tip cleaner review
  • Now in 1080p quality!

A three camera setup is on the way. More videos soon.

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16 Comments

  1. Nice video. I just started watching your posts after I got the Open Logic Sniffer and listened to you on a podcast.

    I’m working on two boards that I’m making multiples of. I was applying solder paste by hand, placing components, and then using a hot plate to reflow it all. After that, I’d go around with the braid and wick off the bridges.

    I decided to get some Kapton stencils to speed up the process. I tested it on the larger PCB first. It worked great. Out of 6 PCBs I made, I only got 2 bridges. It really sped up the application and almost eliminated the wicking process.

    Then I moved to my second board. This one has very fine pitch TSOP chips. I can’t seem to do it without bridges. In fact, I still end up with bridges even after I’ve wicked it all with the braid. With a loupe, I can’t see any bridges, but the continuity test proves there are some left.

    I’d love to hear any suggestions you have about any of this. Are Kapton stencils the way to go? Should I start using the hot air for the fine pitch chips? I’m definitely not the best, and neither is my equipment, but both my skills and my tool supply are growing. I’m happy to take recommendations.

    1. One thing that saves you is patience :) keep wicking and resoldering untill no bridges are left.

      Something you could try is hot-air and flux to re-flow the solder, suppose you have a hot-air station off course. Or you could use your iron to scrape off the excess solder, for some reason i can’t work with the solder wick :(

      1. I’ll definitely keep plugging away with the wick. Out of 5 (of the TSOP) boards I’ve assembled, I have 1 working. The others still have bridges. I’m fairly patient, but I also know that this process will never fly if I want to make any quantity. That’s why I’m looking for suggestions. Thanks!

      2. Thanks for the feedback and suggestions everyone. I’m not a great solderer, one goal of these videos is to show that anyone can try this stuff. Even if, like me, you shake like a leaf and don’t have 1337 reflow skills.

        @flavor – be sure to use lots of flux, it will help the solder flow better and prevent bridges.

        @bearmos & rsdio – I sometimes do the add more solder to make it easier to take off, agreed.

        My wick is pre-fluxed, so I don’t usually add more. More flux does help get more mileage out of the wick if I do a ton of cleanup.

        You certainly don’t need to add flux to remove a chip, and it’s a heck of a lot less smokey and gross if you don’t. I personally feel it helps. It makes the solder flow better when melting, and keeps things cleaner when you pop the chip off. Though I could totally be wrong, I just like to use lots of flux everywhere. I have a saying about it, but it’s not work safe ;)

    2. A couple of suggestions for the solder wick: use flux to wet the actual wick (951 works fine for me, just about anything should help), and don’t be afraid to add more solder. One of the biggest mistakes made when taking chips off is thinking that it’s a sin to add solder – by adding a dab here and there you’ll actually help the heat transfer better to the solder you’re trying to take off.

      If you’re getting solder bridge during reflow, then I’m guessing you either have too much paste, too “sloppy” of a paste application, or your footprints are a bit large – it’s probably too much paste though. You might try using a thinner stencil (the thickness of the stencil determines how much solder paste goes down onto the board – sorry if this is blatantly obvious). Also check to make sure that after the paste is applied, you’ve got nice clean lines that are on the lands.

      1. Thanks again. I read up on it. I finally got up to 4 of 5 of my boards working. I know there are bridges on the last one (from ringing pins out), I have no idea where the actual bridges are. That board is almost shot from all my messing around, now. If/When I get a hot air station, I’ll probably just reclaim the chips from that one.

        Anyway, after reading, I’m hoping that the next time I try to reflow it goes better.

    3. Thanks guys!

      I got a bunch of bridges off by adding some solder and wicking the whole new blob off. By the end of the evening, I had flux everywhere and one working board (out of 4).

      I don’t have a hot air station, but I’m hoping to get the one Ian recommended sometime soon. My birthday is at the end of the month. :) Then, I’d probably just pull up the chip and start over.

      I don’t know what I’m doing wrong with the stencil, but I feel like I must be getting way too much solder on there. The stencil holes are so close together, though. When I apply the solder paste and pull up the stencil, it doesn’t appear like there’s just solder on the pads. It’s between them, too. On top of that, when I place the TSOP40 chip, I can never get it right when I drop it. I have to nudge it a bit. I assume any nudging will smear the solder paste across/between pads.

      It’s very annoying. There has to be a better way.

  2. Heh. I got the XC9572XL to put on the CPLD board I got from one of your free PCB posts in an absurdly large tray from Farnell; meant to post pictures of it at the time.

  3. Oh well, I’m saved in the very last moment! I was about hit the checkout button for my components order for the PICqueño and other proyects and… well, I could change the PIC32…..64 for the 128 version on time!. My PICqueño will be ready veeeery soon!

    PS. Farnell also sent me things in big packages!. I had an enormous moisture barrier bag with a decent size box inside for two XC2C64’s

  4. arrow also has a habit of sending QFP’s in trays. when you get something like a single IC in a tray, all of the sudden the min orders start to make sense…

  5. I don’t think I’ve ever actually added flux before taking a chip off with hot air. Do you notice a difference? Its never even crossed my mind, but I feel like I’m missing out now. . .

    1. Seems to me like you would not need any flux to take a chip off. Flux is supposed to clean surfaces so that metal joining is facilitated. I see nothing to indicate that flux would help separate metal surfaces that have already been joined.

      When using a desoldering iron, flux might improve the heat transfer so that you can melt the old solder faster, but this is equivalent to adding a little solder to help remove all of the solder. The multi-core Ersin solder that I used for years has rosin that seems to help melt existing solder.

      I must admit that I do not use flux or wick nor do I try to hand-solder TSSOP.

      As for the soldering iron cleaner, I think you’re doing it wrong. You’re not supposed to wipe the tip across the top of the ball – that’s surely how you get molten metal sprayed all over your workbench and electronics. Instead, it’s intended for you to stab the tip straight down into the ball of steel wool so that any solder spray goes down into the holder. Try it that way and see how you like it. I purchased the same soldering iron cleaner from VetCo, and when I got to the counter an old gentleman explained to me how to use it correctly. I admit that I’m spoiled by living in a place with several PCB fab houses, SMD assembly shops, and various electronics supply and even 3D printing facilities.

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