Cleaning PCB's and IC chips pins

Discussion in 'General Electronics Chat' started by relicmarks, May 11, 2008.

  1. relicmarks

    relicmarks Thread Starter Active Member

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    What do you guys use to Clean PCB soldering ? cause i can't get the ROSIN off the PCB's boards what do you guys use?

    I have used MEK with a acid brush to remove the ROSIN off the PCB if this ok or right?

    What else can i use please?

    HOw do you guys clean dirtry IC chip pins that are very dirty ?

    I use a Brass Wire brush to remove the dirt off of the IC chip pins , but it bent the IC chip pins alot

    How can i prevent the IC chips pin from bending while cleaning?

    Or What do you guys use to clean dirty IC chip pins?

    I use steel wool after to polish up the IC chip pins is this good?
  2. SgtWookie

    SgtWookie Expert

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    I use isopropyl alcohol with acid brushes for cleaning flux. You can find 91% isopropyl if you look around. The common drugstore variety is 70%, of which 30% is water. The 91% is much better. Isopropyl alcohol absorbs moisture out of the air, and burns with a nearly invisible flame. For both of those reasons, you should keep it covered unless you're actually using it. Avoid contact with your skin, as the 91% will dry your skin out.

    MEK is pretty dangerous stuff.

    I use muriatic acid for cleaning corrosion from component leads. It's actually a very dilute hydrochloric acid solution that is available from pool supply stores. You do not want to breathe the fumes, get it on your skin or clothes, nor use it in an enclosed area. It will etch concrete surfaces. I use a fan to keep the fumes blowing away from me, work on a plastic-top bench, wear rubber gloves, and keep a bucket of water and a hose ready in case of spills/splashes. I put my components in a throw-away plastic container that has a lid, add the muriatic acid, put the lid on and agitate it a bit for 30 seconds or so. Then I rinse the components very thoroughly with plenty of water, and dry them with an isopropyl alcohol rinse.

    I wouldn't recommend steel wool, as it is flammable, will easily cause short circuits, and microscopic bits of the steel wool will become embedded in the soft metal of the pins, later causing corrosion. Instead, I have a few 3M Scotchbrite(tm) pads that you can find in your grocery store's cleaning section. They do a nice job of stripping off corrosion from things like resistor/capacitor/diode leads, and won't cause problems.
  3. relicmarks

    relicmarks Thread Starter Active Member

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    3M Scotchbrite(tm) pads ?

    So do i use 3M Scotchbrite(tm) pads or isopropyl alcohol 91% on the IC pins too? with a acid brush?
  4. relicmarks

    relicmarks Thread Starter Active Member

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    MEK is pretty dangerous stuff.

    What can it do wrong to the PCB or components using MEK?
  5. thingmaker3

    thingmaker3 Retired Moderator

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  6. relicmarks

    relicmarks Thread Starter Active Member

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    so what should i use then?
  7. thingmaker3

    thingmaker3 Retired Moderator

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    Try using Sgt Wookie's recommendation. It has worked wonders for me for decades.
  8. relicmarks

    relicmarks Thread Starter Active Member

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    To use 3M Scotchbrite with a acidbrush on the IC chip pins?
  9. thingmaker3

    thingmaker3 Retired Moderator

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    91% Isopropyl Alcohol.
  10. relicmarks

    relicmarks Thread Starter Active Member

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    ok i'll try it thanks
  11. SgtWookie

    SgtWookie Expert

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    3M puts out several different kinds of items under the Scotchbrite brand. I usually get a 3-pack of the green wool-like pads. The package looks like this:
    [​IMG]
    3M calls them "heavy duty scour pads".
    There's a similar version in blue called "multi-purpose scour pads" that would also work; they're not as aggressive. They would likely be better for components with thin leads.

    I don't use the Scotchbrite pads on ICs. It would be far too easy to bend the pins. I use the muriatic acid bath (for new old stock) as I previously described. It is a somewhat hazardous procedure, but I believe I've already detailed the important points. It really works great for parts that have corroded tin or silver plating on them. You don't want to leave the parts in there for more than a minute though. The exposed metal surfaces will be etched, which would be lousy for cleaning silverwear, but is perfect for soldering.

    Prior to soldering, everything gets a brush-over with isopropyl alcohol and thorough drying, away from the soldering station. Because it burns with a nearly invisible flame and also will dry your skin, isopropyl alcohol is still a mildly hazardous chemical to work with. However, having the components absolutely clean and dry makes them very easy to solder correctly the first time.

    Clean components don't need flux. Flux is used to cause impurities to float to the surface of the molten solder. But if the board, components, solder, and soldering iron are all spotlessly clean, there isn't a need for flux - or a clean-up afterwards.

    Many soldering difficulties are caused by handling the parts (including the solder itself) prior to soldering. Perspiration and "finger oils" get on the component leads, contaminating them. You can avoid contaminating the leads by wearing rubber gloves, finger cots, or simply wash your hands before handling components, and wash the board and components prior to soldering.

    MEK isn't hazardous to the parts, it's hazardous to people. It's one of those nasty chemicals that will "get you" if you breathe too much of it, get it on your skin, or whatever. It doesn't have much of a smell, which makes it more dangerous because you may not realize how much of it you've breathed. It's very flammable. It eats it's way through a lot of things. I only use it if I have to. It's one of those "chemicals of a last resort", definitely not a first choice.
  12. Dave

    Dave Retired Moderator

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    I concur with this assessment, MEK is evil stuff. When I worked in the aerospace industry we used MEK for cleaning all and everything because of it potency - removing thiokol was nothing to MEK! I started getting blotchy skin and headaches from just being in its presence, and eventually stopped using it. From speaking to my ex-colleagues who still work in the aerospace industry it has now been completely removed from usage.

    It most certainly works for cleaning PCBs, IC chips and just about anything else you can throw at it, but it is not very good for you by any stretch of the imagination.

    Dave
  13. techroomt

    techroomt Senior Member

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    there are commercially available flux remover products. i use the spray version with acid brushes for agitation. are the ic's you're cleaning installed or not-installed (or socketed), that they are bending leads?
  14. roddefig

    roddefig Active Member

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    I second the Isopropyl and Scotch-Brite pads recommendation. I also use Flux-Away, it comes in a spray bottle and washes the flux right off. I think you can order it out of Digi-Key.
  15. jpanhalt

    jpanhalt E-book Developer

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    Rosin flux is composed mainly of abietic acid (http://en.wikipedia.org/wiki/Abietic_acid) and related compounds plus activators. Wikipedia lists it as being soluble in alcohols, acetone and ethers. It is also soluble in other ketones (e.g., MEK) as noted previously in this thread.

    Clearly, isopropyl alcohol (IPA) will clean the residue. However, the more water in the IPA, the less effective it becomes. 91% works, as previously noted. I have no firsthand experience with 100% IPA. If you want to demonstrate the effect of water. Take the used IPA after cleaning several boards and add water slowly. It should become cloudy with very little additional water.

    I use 100% ethyl alcohol. Denatured alcohol, which is essentially 100% ethyl alcohol with small amounts of denaturants added, is readily available and inexpensive. I also add a little acetone, but that is not necessary for it to work. While I don't have firsthand experience with IPA, I can say that ethyl alcohol requires almost no scrubbing. A dip in the solution, very light rubbing with a toothbrush, and a quick wipe or blow-off with compressed air is all that is required. I have found it cleans under the chips.

    John
  16. John Luciani

    John Luciani Active Member

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    I have been using water soluble flux (Kester 2331-ZX) and a solder with water
    soluble flux (Kester 24-6337-6422). I clean the board within an hour of assembly
    with hot water and an acid brush.

    (* jcl *)
  17. thingmaker3

    thingmaker3 Retired Moderator

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    The MSDS for one of the commercial flux removal products list the ingredients as isopropanol and toluene. Mix runs anywhere from 30/60 to 60/30.
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