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Ramblings of an insane Microsolderer AKA BAD hair day

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  • Ramblings of an insane Microsolderer AKA BAD hair day

    Sage IC with dull pads. Dull pads are a sign of oxidation. Solder will not take to an oxidised surface. How to remove the oxidation? Load the IC up with flux. Load up the iron tip(3mm-4mm tip!) with fresh solder. Run over the pads. I did this and all the dull pads turned shiny. And all the ads took solder, except one. It's pad was shiny but it remained flat. I don't know why.

    Bits chipped of the edges of the IC. I still pincer the ICs too tightly. And this is indirectly because I attack the IC too aggressively with the brush in my isopropyl bath trying to remove all traces of flux and black flakes. The black flakes troll me. I don't know whether they're coming off the tip of the iron or the IC. I don't know whether they're a symptom of abuse or whether they're 'normal'. I don't know whether they're coming off an iron tip that's on it's way out or a sign that the IC is breaking down(from too many goes).

    Reballing stencils, solder paste, flux and uneven balls. Often I blame dried out solder paste.
    Old solder paste, dried out solder paste - I'm not sure what the difference is? All the same to me. Adding fresh flux and mixing in thoroughly with my spatula seems to resolve the problem, sometimes.
    My biggest fear ... uneven balls. After my first reball attempt when I discover some balls are noticeably flatter than others. I apply another batch of solder paste to the stencil in an attempt to bring the flat balls up but,before long... big blobs...the solders balls are rearing their ugly heads over the TOP of the stencil hole lip! I bring in the tip of my soldering iron to remove the extension... it always takes off too much. Downward slide. I end up removing ALL the solder balls and starting all over again.... like Bill Murray in groundhog day. And at the end of all this I feel like a nomad that's been roaming the desert, aimlessly for days. OK Off to bed. I guess there's always tomorrow!



  • #2
    It's a brand new day. Still thinking about the oxidation on the Sage IC yesterday . Really got trolled on that one and wasted a huge wad of time exercising 'solutions' that didn't address the issue.
    (1) Cleaning my QianLi 3D stencil within an inch of it's life
    (2) Scrubbing my IC with isopropyl like I'm trying to clean off a child's dirty neck(within an inch of it's life and pincering so hard bits break off the edges and it'll never work again anyway!)
    (3) Assuming my solder paste had dried out and mixing in (too much?) flux.

    And of course repeated useless attempts of removing the balls and starting over again, again and again. All reflex reactions and getting nowhere.

    How did the oxidation happen in the first place? It would be nice to know but it doesn't really matter. The most important thing is to identify what went wrong, fix it quickly and move on!

    Lesson learnt. You can really make hell for yourself when you don't clearly identify the issue and address it!

    Comment


    • #3
      all of this is because of your paste. You need fresh paste that is very dry.

      Comment


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        Before attempting to reball check your paste. Make sure it nicely beads up into balls with heat.

    • #4
      Hello Jessa
      Thank you. That was the vital piece of information I needed to hear. After reading your response I spent much of yesterday contacting electronics businesses asking them to confirm the batch dates of their solder paste. One electronics business had unopened solder pastes stored in their fridge with batch dates as early as 2015. I am assuming that the maximum expected shelf life of solder paste is 6 months and storing it in the fridge at 4 degrees celcius only guarantees this, The batch dates of all their other tubes were over six months so today I left the shop with a single 10cc tube(which they had stored in the fridge) with a batch date of January 2020. I now see I am going to have an issue getting guaranteed fresh solder paste, even from reputable suppliers.

      https://www.indium.com/blog/solder-p...shelf-life.php

      Comment


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        Don't worry about those dates---we use solder paste that is a couple of years old. Just make sure that it beads up and works like expected. Some fresh solder paste is crap and ancient stuff works fine. There is no guarantee--use your own eyes rather than rely on dates. Does it bead up without leaving little baby balls everywhere? If so---good to go. If you're struggling and dont see why---try fresh paste.

      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        Remember--Fresh paste is great--but you must dry it out before using it.

    • #5
      Thanks for that clarification. That would mean some pastes actually come fresh loaded up with too much flux?But just want to be sure I understand. That also implies cracking open the paste and for the first time leaving it exposed to open air for a few hours? Finally to be able to dry it out ...that's something you can't do with paste that comes in a syringe so I guess that also means to (always?)buy one's paste in small jars, keep one out (and store a few more in the fridge).. Several years go I remember buying 250g jar, only using about thirty grams and throwing the rest out 2 years later.

      Comment


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        All stored pastes have too much flux for reballing straight out of the jar. You need to dry a pea sized drop of paste in a paper towel before using it to reball. Never leave paste in the jar "out in the open"

    • #6
      Ah now I think I get it. Drying out in this case really means wiping off/absorbing the excess flux into a paper towel. And when, in order to address, when maybe one has added too much flux, to address older dried out paste(assuming the balls haven't reacted with the activator) it should work just as well.

      Comment


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        Ehhh...."adding flux" makes me worried. Not for reballing. You want it as dry as you can make it. Super dry. If your paste is "dried out" meaning---the parent container is contaminated or left open, then throw it away and start with fresh paste. Take some out and close the jar. Fresh pliable even good quality paste----then dry it out---then reball.

    • #7
      Ok thanks I think that I now understand that too much flux in the solder paste causes problems..... when reballing with a stencil I apply the solder paste(which I now understand needs to be 'dried' out) with my finger, gently wipe off the excess(as not to force the paste thru and beyond the holes
      and, before I apply hot air, syringe out a decent blob of amtech flux on top (like icing on a cake). I did this based on an early ipad rehab video. I'm assuming adding the flux on top is still valid?

      Comment


      • #8
        No flux. Dry paste. No flux.

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        • #9
          Ok No flux. Thanks.
          I found in my case spreading the flux out on a paper tended to pick up paper fibres so used a lint free Kimwipe instead. Anyway...
          Here's what I did..please see pictures attached




          Attached Files

          Comment


          • #10
            Picture 1 SAGE after cleaining off the balls
            Picture 2 Fresh flux straight out of the tube
            Picture 3 Drying the solder paste out on a Kimtech lint free wipe (I spread it out to lose some of the flux)
            Picture 4 After spreading the dried out paste into the stencil
            Picture 5 SAGE the result after hot air 360 degrees 100L 8mm nozzle for 20seconds

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            • #11
              Oh yes and I did not ice it over witha blob of fresh flux.

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              • #12
                Woops I meant to sy Fresh SOLDER paste fresh out of the tube not flux

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                • #13
                  seems like it worked--great job. Your paste still seems pretty wet. We would have failed that as "not dry" at PBRS, but if it works for you then great. There are no hard and fast rules. Microsoldering is more art than science.

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