Favorite way to apply rosin flux? And cleaning leftover? - Page 1
Forum section: electronics / beginners

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 23, 2018, 06:58:56 am
content: So I was considering getting a bottle of this rosin flux (MG Chemicals Liquid Rosin Flux, for Leaded and Lead Free Solder, 125 ml Bottle):https://www.amazon.com/gp/product/B005DNR01Q/However it seems like there are many options for applying it. Pens, bottles, syringes, brushes, etc.What would you recommend? Do I need to purchase any additional cleaning tools in case I use too much flux, or after doing flux + solder + iron and there's still a little flux left?

author: GreyWoolfe
author_rank: Unknown
timestamp: July 23, 2018, 11:41:33 am
content: I have a squeeze bottle with a syringe and a bottle with a brush, similar to a nail polish bottle, these are cheap and cheerful on eBay. For cleaning, I have alcohol swabs, Q-tips and alcohol, and for stubborn residue, an old toothbrush. By the way, I use the same flux.

author: exe
author_rank: Unknown
timestamp: July 23, 2018, 05:37:50 pm
content: Quote from: blueskull on July 23, 2018, 07:10:52 amWhat about 10x cheaper Chinese cleaners? I saw them working reasonably well (on youtube)...Frankly, I won't be bothered with this, as the residue is not conductive anyway.Quote from: blueskull on July 23, 2018, 07:10:52 amIdk, some tens of picoamps can be measured relatively cheaply (like using µCurrent or a DIY meter). Of course an electrometer would be nicer. Old keithelys start from like $300 on ebay. I bought µCurrent for this purpose, but haven't had time to check its performance. Also don't have high-value resistors(Don't know how to measure femtofarads)

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 23, 2018, 10:24:27 pm
content: I am considering using these nail polish bottlesNakpunar 6 pcs Oblong Empty Glass Nail Polish Bottles with Brush, Cap and Mixing Agitator balls:https://www.amazon.com/gp/product/B075QHD6MT/to hold this flux(MG Chemicals Liquid Rosin Flux, for Leaded and Lead Free Solder, 125 ml Bottle):https://www.amazon.com/gp/product/B005DNR01Q/Would this work? Do the brushes stay workable or do they gum up over time? Wondering if I should stick with a flux pen instead, assuming that minimizing exposure to air keeps it working longer.

author: GreyWoolfe
author_rank: Unknown
timestamp: July 23, 2018, 10:42:43 pm
content: Quote from: AnyNameWillDo on July 23, 2018, 10:24:27 pmYou won't need the agitator balls. I bought the bottles about 6 months ago and I am only using 1 right now. The brush is still very supple. Just be careful to clean the threads of flux when done or it will glue the cap closed.You getfor the flux.

author: Ian.M
author_rank: Super Contributor
timestamp: July 24, 2018, 12:16:23 am
content: A little bottle like that on the bench *will* get knocked over, usually when you are reaching for it to wet the brush with more flux or put the cap back on. If you dont want a nasty sticky flux spill, its worth making a wide base from a block of hardwood - if its wider than the height of the bottle, the chances of a spill are much reduced, but to make it easy to fit the bottle in a hole in the base, you really need to get a round bottle. If at any stage the brush or cap starts to get too crusty wash it with IPA and wipe with paper towel.If applying flux before placing components, a refillable wedge tip marker pen (about 5mm nib) is useful as it offers more control than a bottle + brush, but it s nib will wear badly on the edges of component leads if you use it for fluxing already soldered joints.

author: Relayer
author_rank: Contributor
timestamp: July 24, 2018, 01:37:41 am
content: Hello AnyNameWillDo,I use Acetone (Nail Polish Remover) to get off heavy flux using an old toothbrush.It cleans it quite fast, and I've never had the solder-mask or print on a PCB thatgot smeared or leeched off.I then give it a clean with Isopropyl alcohol to get rid of any residue.Using alcohol alone on heavy fluxed areas will take you ages to remove.You will find that the toothbrushes or any other brush will eventually gum up, butsoaking them in acetone overnight cleans them reasonably.Furthering Ian.M's suggestion, you can purchase a dispenser like the one shown below:DispenserEven if you knock it over, the only thing you'll spill is what's already in the upper bowl.They are excellent for that reason. The liquid will also keep, provided you keep the lidclosed, it will never evaporate away.Regards,Relayer

author: helius
author_rank: Super Contributor
timestamp: July 24, 2018, 02:32:21 am
content: I prefer to use mixtures like MG Chemicals 4050A or 4140, but 99% isopropyl will work in a pinch. Rosin flux will wash off with isopropyl just fine if the correct technique is used. If the flux is very burnt then the mixtures are more effective.Avoid using acetone willy-nilly since it melts plastic and will totally remove markings on ICs.Brushes aren't very absorbent. Instead of brushing directly on the board, use a paper towel wet with flux remover and brush over it.

author: Ian.M
author_rank: Super Contributor
timestamp: July 24, 2018, 02:56:02 am
content: My experience is: Acetone melts toothbrushes.Take a natural bristle acid brush and cut it down to 1/2" if you ever need something to scrub with that will stand up to Acetone.

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 24, 2018, 02:58:56 am
content: Quote from: helius on July 24, 2018, 02:32:21 amReading this reminded me of a video I saw recently where I think this technique is used (1 min 8 sec mark and 1 min 54 sec mark):

author: David Hess
author_rank: Super Contributor
timestamp: July 24, 2018, 03:20:41 am
content: I like using little bottles which have a brush attached to the cap or dipping the solder wire into the flux just before soldering. I do not like oiler type bottles for flux; they get plugged up too easily.For cleaning touch up work if necessary, I use cotton swabs and whatever flux thinner is suitable. Just isopropyl alcohol works but 50/50 IPA/toluene (a common flux thinner), 50/50 IPA/acetone, or lacquer thinner is even better.These dispensing bottlesare nice for cleaning liquids but a little expensive.

author: helius
author_rank: Super Contributor
timestamp: July 24, 2018, 04:17:28 am
content: Quote from: AnyNameWillDo on July 24, 2018, 02:58:56 amSure. The idea is that the towel has a much larger area, and as solvent evaporates from its top surface, it can draw dissolved residue up from the bottom like a wick. It's important for there to be some way to transport residue away from the board or you are just moving it around. You can also use a spray-flush after brushing, by tilting the board at an angle and spraying so that the dirty solvent runs off. Yet another way is to place the board in a tray with solvent (isopropyl alcohol or ethyl lactate but beware of the latter's incompatibility with acrylic), and agitate so that the soils fall to the bottom of the tray. If the dirty solvent dries in place, you are back to where you started with residues stuck to the board.You can use regular paper towels, but in the video Kimwipes (non-linting woven towels) are used.

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 24, 2018, 04:22:43 am
content: Picking up these as well:RAM-PRO 12 Flexible Horsehair Bristle Tin/Metal Tubular Ferrule Handle Acid/Flux Brushes for Home/School/Shop/Garage:https://www.amazon.com/gp/product/B01LXC1VBE/2 Needle Tip Bottle Liquid Flux Dispenser Oil Solvent Applicator Dropper 0.7 Oz:https://www.amazon.com/Needle-Dispenser-Solvent-Applicator-Dropper/dp/B00UG08QDC/Kimberly-Clark Kimtech Science Kimwipes Delicate Task Disposable Wiper:https://www.amazon.com/gp/product/B008UB6IKC/I *think* this should be enough to experiment with. Can either use the needle-bottle to squirt flux directly, or use the pre-fluxed brush from the nail polish bottle. For cleanup, the kimwipes + separate brush + alcohol.My normal/usual paper towels are kinda linty so I'm hesitant to use those but I'll probably give them a shot either way.

author: rbm
author_rank: Regular Contributor
timestamp: July 24, 2018, 05:53:43 am
content: I use a Weller FD2 bottle with 0.010" needle. I find this gauge needle ideal for dispensing exactly the right amount of liquid flux on the board for SMD work down to 0805. The Weller captures the needle with the cap and prevents the needle from dislodging from the spout as you use it. The problem with the dispenser bottle product you linked to is that the needle depends on friction to remain secured to the spout. There's no luer lock or captured cap. What I find happens with the Weller bottle I have is the needle plugs up easily after a while when I stop using the dispenser, and I'm required to soak the needle tip in IPA to loosen the rosin plug. This soaking operation could be a problem with those bottles you're considering.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 24, 2018, 04:28:13 pm
content: For through hole components I prefer old school paste flux. I just “dip” the leads in the flux before I solder them. It out a little flux on the lead that then get scraped off by the hole in the PCB when you insert the component. This puts a little flux right on the pad where you want it.

author: Bassman59
author_rank: Super Contributor
timestamp: July 25, 2018, 12:20:25 am
content: Quote from: AnyNameWillDo on July 23, 2018, 06:58:56 amDo yourself a favor and use "tack flux." It doesn't run all over the board and is easy to apply.Something likethis.

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 25, 2018, 02:46:03 am
content: Quote from: Bassman59 on July 25, 2018, 12:20:25 amDoes it matter that this is no-clean flux whereas I am using rosin-core solder?

author: exe
author_rank: Unknown
timestamp: July 25, 2018, 06:54:06 am
content: Quote from: Bassman59 on July 25, 2018, 12:20:25 amIt is water-soluble, not for beginners, imho. It must be cleaned well (or it will cause corrosion and other problems), which not always possible without proper tools. Particularly, cleaning under smd parts, which may require an ultrasonic cleaner.

author: helius
author_rank: Super Contributor
timestamp: July 25, 2018, 03:55:27 pm
content: "Water washable no-clean" looks like a mistake, as water-soluble fluxes cannot ever be left without cleaning. That is a REL0 no-clean flux that would normally be cleaned, if necessary, with isopropyl alcohol. Any rosin-based flux residue can be cleaned in aqueous systemswith the addition of saponifiers, but that is not special to this product.

author: AnyNameWillDo
author_rank: Regular Contributor
timestamp: July 25, 2018, 04:24:54 pm
content: Stick to rosin-core solder, rosin flux?

author: David Hess
author_rank: Super Contributor
timestamp: July 25, 2018, 07:41:35 pm
content: I have a spool of solder which has the organic "water clean" flux and it is definitely not worth using except in a production environment. The same largely goes for "no clean" rosin flux which works acceptably on new parts and boards but it less satisfactory for rework and prototyping.

author: helius
author_rank: Super Contributor
timestamp: July 25, 2018, 09:28:30 pm
content: I agree, rosin based (mildly activated) fluxes in the ROM0 category are better to work with.https://www.pillarhouse.co.uk/technology/choosing-flux-technical-article

author: KL27x
author_rank: Super Contributor
timestamp: July 25, 2018, 10:01:06 pm
content: I use a syringe applicator. A box of 100 syringes can be had for something like $20.00. Add 100 black plastic twist caps. Then you need 20 or so tapered plastic needles, because they eventually wear out (from twisting them off the empty syringe with pliers; rosin is good glue).Lately, I stuff some Q tip cotton or whatnot into the back of the plastic needle and cut the tip to the size and angle I want. (In the past I was more fancy pants, threading some cotton string/twine through the needle with a knot and melting/squeezing the tip to lock it in. That's overkill.) The cotton is to prevent squirts and drips.I fill 5 to 10 syringes at a time, using a modified plunger that doesn't stick in the rubber gasket too tight. Cap them off, remove the plunger, and put these reloads into a cup at my bench. When my syringe runs out, I remove the needle and the plunger and transfer them to the next syringe.If unused for a long while, the tip will dry out, but pressing on the plunger will get it working again in short order. I clip the syringe point down onto the side of my microscope in a little HDPE spring clip mount where I can retrieve and replace it without looking away from the microscope.