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Do I need to invest in an ultrasonic cleaner? — Parallax Forums

Do I need to invest in an ultrasonic cleaner?

TotalPCBNoobTotalPCBNoob Posts: 1
edited 2013-08-30 13:01 in General Discussion
I own a small repair business and I regularly come across dirty PCBs from consumer electronics devices. I am just launching into this and don't really know what I'm doing. One project I'm working on right now is a small PCB that does not power on the device. It has components on both sides (components meaning, ICs, diodes, thermoplastic soldered parts, etc). My goal is to try to get it to power on again. After the PCB cleaning I intend to reflow it, but I'm not completely sure how to do that right either.

I attempted cleaning this PCB by submerging it in a solution of 99.9% isopropyl alcohol and gently wiping it on both sides with a Q tip. I let it dry for a day, then came back to it, and I noticed that it had white crusty corrosion and was still dirty in other places as well. It has what looks like a yellowish tarnish color in places, and now the board is also warped a little bit. Did the IPA cause this warping? By warping, I mean that the board is bending upwards in the middle, in a concave manner.

I'm wondering if it would make sense for me to invest the required $200-$400 in an ultrasonic cleaner at this point. Would the ultrasonic cleaner get rid of the crusty white corrosion, yellow tarnish, and other problems? Would my PCB come out completely clean? Is there any danger of an ultrasonic cleaner doing damage to my PCB? Ultimately, as I said above, my goal is to get this PCB to power on again. What do you guys think? I'd especially appreciate the advice of someone who is in the business of cleaning PCBs professionally. Thanks.

Comments

  • xanaduxanadu Posts: 3,347
    edited 2013-08-29 12:53
    IPA always makes that white residue, don't use it. Get canned PCB cleaner to prep a board and use a soft brush. Ultrasonic is probably better for after a reflow but I've never used one so idk...

    If you're fixing boards with BGAs (xbox, laptops, etc) on them be prepared to completely remove and reflow using a solder stencil or most of your repairs will be temporary.
  • PublisonPublison Posts: 12,366
    edited 2013-08-29 13:29
    xanadu wrote: »
    Get canned PCB cleaner to prep a board and use a soft brush.

    Most canned PCB cleaner use IPA as a solvent. We used to use a freon based solvent back in the 80's that has been banned.
  • PublisonPublison Posts: 12,366
    edited 2013-08-29 13:40
    TotalPCBNoob wrote: »
    I own a small repair business and I regularly come across dirty PCBs from consumer electronics devices. I am just launching into this and don't really know what I'm doing. One project I'm working on right now is a small PCB that does not power on the device. It has components on both sides (components meaning, ICs, diodes, thermoplastic soldered parts, etc). My goal is to try to get it to power on again. After the PCB cleaning I intend to reflow it, but I'm not completely sure how to do that right either.

    I attempted cleaning this PCB by submerging it in a solution of 99.9% isopropyl alcohol and gently wiping it on both sides with a Q tip. I let it dry for a day, then came back to it, and I noticed that it had white crusty corrosion and was still dirty in other places as well. It has what looks like a yellowish tarnish color in places, and now the board is also warped a little bit. Did the IPA cause this warping? By warping, I mean that the board is bending upwards in the middle, in a concave manner.

    I'm wondering if it would make sense for me to invest the required $200-$400 in an ultrasonic cleaner at this point. Would the ultrasonic cleaner get rid of the crusty white corrosion, yellow tarnish, and other problems? Would my PCB come out completely clean? Is there any danger of an ultrasonic cleaner doing damage to my PCB? Ultimately, as I said above, my goal is to get this PCB to power on again. What do you guys think? I'd especially appreciate the advice of someone who is in the business of cleaning PCBs professionally. Thanks.

    Immersing in alcohol should not produce any warping unless heat was applied afterwards.

    To clean a board, use a brush, a 1" or 2" chip brush with the bristles cut down to 1" to scrub, not lightly. Immerse or cover the board in clean alcohol. Wash the board in water if components will take it. Dry in oven at 125 degrees for an hour.

    Works for me.

    If you invested in a ultrasonic cleaner, you would still need a solvent. Isopropyl Alcohol is still the best.
  • GadgetmanGadgetman Posts: 2,436
    edited 2013-08-29 13:53
    Never EVER use Alcohol or other easily flammable liquids in an ultrasonic cleaner!

    Who can spell 'fuel air explosion'?
    Or just airborne carcinogens.

    I've never used mine to clean PCBs, only car parts so far...
    (Industrial unit, HBM 'GL Series' 2.5L, 50W, all around stainless steel)
    15 minutes with clean water at 45degree Celsius water stripped the paint off of the brackets holding the gasoline injectors to the HP reservoir...

    I have no idea what the silly little 'jewelry cleaner' models can do, though.
  • PublisonPublison Posts: 12,366
    edited 2013-08-29 14:02
    Gadgetman wrote: »
    Never EVER use Alcohol or other easily flammable liquids in an ultrasonic cleaner!

    OK. Use a venting hood to the outside. We always did that. Should have included that little bit of info. :)
  • RDL2004RDL2004 Posts: 2,554
    edited 2013-08-29 14:27
    Quality solvents are just that, solvent. IPA should have nothing in it to leave residue. More than likely any remaining residue is gunk that was dissolved in the cleaning process and not completely rinsed off.

    Personally, I like to use the dishwasher followed by a thorough rinse in distilled water. Dry for several days and/or bake at 150F. Items with lots of nooks and crannies will benefit from a blowing off with low pressure air before drying.
  • xanaduxanadu Posts: 3,347
    edited 2013-08-29 15:03
    The IPA leaves the residue because it can't dissolve it. It also ruins your IPA bath unless you filter it. I used IPA for many motherboards until one day switching to PCB cleaner. Canned PCB cleaner is way cheaper and leaves no residue. All you need is $20 to get a can and a soft brush. Anything else will have pros and cons, canned is versatile and low cost which for someone starting out leaves more money for a reflow oven :)
  • RDL2004RDL2004 Posts: 2,554
    edited 2013-08-29 15:15
    All I said was that the residue shouldn't be from the IPA if it's of any decent quality. Pour a small puddle of IPA on a clean piece of glass and see what's left after it evaporates. There should be pretty much nothing left.

    What exactly is in this PCB cleaner you use? I'm guessing it's just a blend of slightly better solvents. IPA is not really all that good as far as solvents go.
  • xanaduxanadu Posts: 3,347
    edited 2013-08-29 15:51
    The residue is some chemical on the board from its original manufacture. Alcohol breaks it free but can't break it down. I've read a few theories and it boils down to it can be a number of chemicals in the solder as well as flux.

    The stuff I use is called Misty, it is the safest for plastics. I replacing traditional electrolytic caps with the plastic plug in the bottom so that matters to me. There is another brand that is not safe for plastics but worked better on burnt flux, I got it at Frys but can't find it on their site now.
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-08-29 17:47
    The "white residue" you are seeing is what happens to many no-clean fluxes when IPA is introduced to them for cleaning. Most no-clean fluxes can only be properly cleaned using IPA alone if the flux residue has only been on the boards for less than 24 hours because the residue crystallizes over time and becomes very hard. There are also many no-clean fluxes that do not leave a white residue when IPA is introduced regardless of the age of the residue. Obviously, unless you built the boards, you won't know this until you attempt cleaning.

    Using an ultrasonic cleaner for PCBs is a valid solution, but not preferred for many reasons. If you do choose to use an ultrasonic cleaner, you can use a solution of IPA and deionized water (distilled water can be substituted at home) in a 50/50 mix. However, the proper method would be to use an appropriate cleaning agent from Zestron or the like. At work, we have systems made by Aqueous Technologies (not ultrasonic, FYI) and we use either straight de-ionized (DI) water or a DI water/solvent solution. We use solvents from Zestron.

    Canned cleaning agents are still available and still used very often. In my opinion, the best products in this category are those from MicroCare. Plus, they are usually easy to source.

    Another cause of the residue turning white is inadequate temperature of the cleaning solution. The solution in an ultrasonic system should be above 135F for proper performance. Our wash systems at work vary from 140-160 depending on the profiles and depending on if we are using pure DI water or DI water with an added saponifier that is designed to break down our types of no-clean fluxes.

    Here are a few more links for additional information:
    http://www.ipcoutlook.org/mart/50350D.shtml
    http://www.circuitnet.com/experts/73284.shtml
    http://www.circuitnet.com/experts/68860.shtml

    P.S. Been in the PCB manufacturing industry for 22 years and have been personally responsible for 6 different wash systems. The latest craze is cleaning no-clean PCBs. The trick is remembering that there is no such they as a no-clean flux. Only no-clean processes. Many of the products we wash at work were manufactured with a "no-clean" paste or wave flux, but even though the flux residue is acceptable if left on the board, we remove it based upon customer, cosmetic, or conformal coating requirements.
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2013-08-30 12:09
    Andrew,

    I've heard that one should not use an ultrasonic cleaning procedure on boards that carry a tuning fork crystal, i.e. a 32kHz. Is that really a concern in your experience? That is an explicit warning in the data sheet for the real time clock chip that I use, one with embedded crystal (ISL12020MIRZ). I'd think that would be a problem only if the cleaner operating frequency is near the crystal resonant frequency. I've also heard that automotive and jewelry cleaning systems use a much lower frequency (~40kHz) than electronic systems, which may be above 100 kHz.
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-08-30 13:00
    Tracy, I have not heard that specifically, but I can completely see how that would be of a concern. I checked a datasheet for an Abracon crystal that we use and it does not list any cleaning precautions. However, Abracon has a "recommended handling" guide on their website that does specifically state "Ultrasonic cleaning should be avoided due to the risk of damage to the crystal element." It is probably safe to assume that all other crystal manufacturers would have a similar precaution.

    ps. another example of how assuming the datasheet gives you everything you need to know is a bad habit.......
  • GenetixGenetix Posts: 1,754
    edited 2013-08-30 13:01
    In the medical device industry we ultrasonically clean parts in IPA all the time.
    If you are cleaning PCBs then you need Chem-Wipes or something similar to soak up all the dissolved flux or it will just redeposit on the board as white powder. Older solder was Rosin Core but newer solders have No Clean flux. Rosin flux takes some effort to remove.
    You need to be careful though because some items like switches and piezos can be messed up if you get flux residue inside them.
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