Cleaning Question - White residue after cleaning...

Discussion in 'General Electronics Chat' started by bob332, Apr 8, 2011.

  1. bob332

    bob332 Thread Starter Member

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    i have noticed after cleaning boards w/ 91% ISP that there is a white residue on the components and slight haze on the board. my process is to clean the board before hand w/ 91% ISP, not handle components by any leads and most of the time i am placing them by tweezers as they are smd (qfn, tqfp, 0402, 0603, etc) and to only touch the board on the sides, not near any contacts. to clean, i use a new toothbrush, pour the ISP on the new toothbrush and then go over the solder joints. the boards work excellent, and i have no electrical issue w/ the soldering technique and am always trying to refine it to get it better, but this cleaning is bothering me. guess i get a little anal about my projects...

    i use this solder:

    http://www.mouser.com/Search/ProductDetail.aspx?R=4894-227Gvirtualkey59020000virtualkey590-4894-227G

    &

    http://parts.digikey.com/1/parts/955917-solder-paste-no-clean-63-37-5cc-smd291ax.html

    any way i can have a clean board w/ no white residue/haze would be greatly appreciated, and hopefully w/ easily accessible household/drugstore items :)

    thanks,
    bob

    edit - the board needs to be dry after the cleaning as it will be exposed and not 'sealed up' at all, but not rain, just outdoor weather that one would be in flying radio controlled models around the globe
    Last edited: Apr 9, 2011
  2. R!f@@

    R!f@@ AAC Fanatic!

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    Try Spraying contact cleaner..it works for me...get's rid of that white haze stuff and leaves a protective yet dust collecting oily layer.

    This is what I get here.
  3. bob332

    bob332 Thread Starter Member

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    man, i should have mentioned the board needs to be dry as it will be exposed and not sealed up. not rain, but weather you would expect when flying radio controlled models around the globe.
  4. R!f@@

    R!f@@ AAC Fanatic!

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    Then get Plastic coating type of spray.
    It will insulate from dust and humidity.

    Clean the board with Acetone, let it dry and then spray a protective coating.

    Sgt mentioned it to me...Conformal Coating or something
  5. bob332

    bob332 Thread Starter Member

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    will acetone take of the silkscreen info?

    appreciate the info :)
  6. R!f@@

    R!f@@ AAC Fanatic!

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    Nope..Acetone just cleans, it's harmless....but stay away from it's vapor

    I use Acetone in a Paint spray gun. Pretty easy to wash Motherboards but it does not deal with the type of flux I have.
  7. bob332

    bob332 Thread Starter Member

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    thanks, will give it a try. any issue going over the boards i cleaned w/ ISP? just want to make sure no ill effects would strike my boards.
  8. jpanhalt

    jpanhalt E-book Developer

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    Caution: acetone is not harmless. It will melt or soften many different plastics, including polystyrenes, acrylics, PVC, and ABS. It way also affect the printing on the board. It will cause most enamel paints to crinkle or be removed. Acetone is a major component in many paint removers.

    I use absolute ethanol to clean my boards. Isopropyl alcohol (IPA) which is what you used also works well. Water in your IPA may cause the incomplete removal of excess flux. Or, if the board had a solder mask on it, the milky residue may be from slightly dissolving that masking material. As the IPA evaporates, it leaves behind a little water, which may be what is causing the coating to become a little milky, like when a cold drink is set on a lacquered surface. A little bit of water can make a huge difference in the solvent properties of alcohols, including IPA and ethanol.

    My suggestions:
    1) If the IPA was fresh and truly 91%, I would either just leave the residue or try water to remove it. After water, re-rinsing with IPA will help dry it.
    2) The residue is probably harmless.
    3) If you coat with a conformal coating to protect from moisture, the slight haziness will probably disappear. Commercial conformal coatings are essentially clear, acrylic lacquers. Some have a dye added for color.

    John
  9. R!f@@

    R!f@@ AAC Fanatic!

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    John....not to disagree but. What you say does not happen, ever since you mentioned Acetone, I went and bought it and I use High pressure to spray and wash away dirt.
    It does a pretty good job, It haven't obviously damaged any of my boards. If it had I would not recommend it.

    I use it instead of thinner cause it does not leave any residue.

    Or could it be that what I get here is not actually Acetone?
    and one more thing, our Thinner is more powerful than the Acetone I bought.
  10. kubeek

    kubeek AAC Fanatic!

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    you could use 100% isp, that should not have any residue.
  11. jpanhalt

    jpanhalt E-book Developer

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    @ R!f@@: You have never used IPA or a combination of IPA followed by acetone in the Maldives. So, it is hard for me to understand the basis for your recommendation that acetone will remove residue from IPA cleaning.

    Acetone and alcohols have distinctly different solvent properties. In fact, I usually add a little acetone to my ethanol wash because it enhances the cleaning a little, but it is not necessary. When I am cleaning any board with cheap plastic components or optical components (e.g., an IRED) on it, I will use just the ethanol, or I am very careful where I get the ethanol-acetone mixture. It is important to note that solvent damage to plastics may not be immediately obvious. The damage, such as crazing, may not become evident until much later, sometimes even years.

    I can't comment on whether you actually have acetone or whether it is a mixture of acetone, water, and other solvents. We also don't know what sort of plastics were on the boards you cleaned with it. Contact time is very important. If the time is very brief, damage to susceptible plastics will probably be minimal.

    In general, I think plain IPA (91% or purer) or ethanol are the best cleaners to use. Various propellants may be added to aerosol versions, but they probably have minimal effect on the cleaning function. I find an old toothbrush is a useful helper. The bristles are chemically resistant and they don't shed.

    John
  12. bob332

    bob332 Thread Starter Member

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    later today i will go pick up some new IPA - where do i get the stronger than 91% stuff? drugstore? hardware store? this will rule out 'old' IPA or anything else. also a new toothbrush will be used.
  13. jpanhalt

    jpanhalt E-book Developer

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    91% is the water azeotrope of IPA. Anything with less water needs to be dehydrated by a method other than simple binary distillation. It may be hard to find.

    If you are in a hot and humid part of the world, what you are seeing may be due to more than one factor. One is blushing from condensation of atmospheric water onto the slightly cooler, softened coating (if you have ever sprayed a fast-drying lacquer or paint you know what blushing is). Another factor may be an insoluble residue from the flux. If it it soluble in acetone on a test area, it is probably organic and a more anhydrous alcohol will work better. If it is not soluble in acetone, then I would try water or not worry about it.

    Got to run now. I need to read up on what is added to activate rosin fluxes.

    John
  14. bob332

    bob332 Thread Starter Member

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    i am in AZ :) will at least get new IPA and see how that does. maybe find some ethanol too at the local hardware store.

    appreciate the info, thanks
  15. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    I have to agree with Jpanhalt here. I have a LOT of experience with Acetone, it is almost a universal solvent. It will melt many, many plastics, not good enough to use as a glue, but you will see the crinkling after you are done.

    We had an operator in a clean room who used acetone for cleaning. The result was damage to a lot of equipment, labels removed, Plexiglas fogged, you name it.

    Isopropyl can be bought off the shelf at 97% purity. Don't use the 70% isopropyl, as it has other chemicals (such as lanolin). It can also cause damage to labels, but overall is much gentler.

    There is always everclear. Expensive, but pure ethanol.
  16. R!f@@

    R!f@@ AAC Fanatic!

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    How can I find ethanol?
  17. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    A lot of hardware stores sell it as a cleaning agent, but it is denatured. Denatured means they deliberately add poisons to prevent people from drinking it. It is still very pure though.

    You can also buy it from pharmacies, it is also denatured. It comes in the polypropylene bottles that is used for isopropyl alcohol.

    Ethanol is a good fuel for making alcohol burners. I used them to make glassware during my chemistry experimentation phase. It makes a nice hot smokeless blue flame, unlike isopropyl.

    Everclear is drinking alcohol, sold at liquor stores. It is as pure as they can make it cheaply, around 99%. It also burns a clean blue, used for many specialty drinks that are lit on fire in dark bars. I remember one I had that was named an "Orgy". You blow the flame out of course, and don't spill it!
  18. BillB3857

    BillB3857 Senior Member

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    I have also experienced the white hazing of a board after cleaning with 99% IPA. It usually shows up when drying off with an air hose. I found that using a heat gun to drive off the moisture restores the board to a very clean and clear appearance.
  19. unorthodox

    unorthodox New Member

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    be careful acetone melts some plastics
  20. unorthodox

    unorthodox New Member

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    and for cleaning use servisol 10
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