Flux ?? - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 01, 2016, 05:54:58 am
content: I have been working with smd now and I wanted to see what company and style(Liquid or paste) of flux do you use ??Thanks

author: GreyWoolfe
author_rank: Unknown
timestamp: January 01, 2016, 01:01:15 pm
content: MG Chemicals liquid RA rosin flux served up in either a squeeze bottle with an 18 gauge needle or a syringe with a slightly smaller needle for smaller pad applications.

author: nanofrog
author_rank: Super Contributor
timestamp: January 01, 2016, 05:54:39 pm
content: I use Kester 186 or 1544 in a refillable brush pen (Bonkote BON-102*). Plenty of other ways to dispense it if you prefer, such as a needle bottle, squeeze type brush bottle (example), nail polish type of brush bottle, dip a small brush into a cap full of flux, refillable felt tip pens (ITW/Chemtronics CW7000), ...Kester doesn't sell bottles smaller than 1 gallon though (disposable pens are alotmore expensive), so getting small quantities of liquid usually means taking a gamble on eBay sources. I've found one for 186 (RMA that's near RA in performance; seller =Dickie's Garage Sale), and got the 1544 (RA) from Skycraft Surplus on my last trip to Orlando.So MG Chemicals 835 RA better fits the hobbyist market as they offer 125ml and 1qt containers.Another member reminded me that it tends to be tackier than Kester when done soldering, which makes it a little tougher to clean (also creates a desire to clean it). But it can be left on the board if you wish in most cases, and above all, it's performance is excellent.Kleen Strip brand Denatured Alcohol is a good flux cleaner (50/50 mix of ethanol & methanol along with a little bittering agent to make it unpalatable), and if it happens to be a little under-powered, you can add a little xylene to increase its aggressiveness (~20% by volume), or even acetone (more aggressive yet, but be careful with plastics; do a spot test first). Not only does this work, it's easy to find locally (i.e. Home Depot), and inexpensive as well.*I wouldn't recommend buying these from eBay or similar sites as they're highly counterfeited (price is usually a huge clue, but not foolproof). You may get lucky with a counterfeit (one the valve assy. actually works), but worst case, you can remove the guts and still be able to use it. Just without the volume control valve, so you can over-dispense if you're not careful. It will also be more prone to dripping,/spilling with the valve removed, so keep the brush end upright when not in use if you find yourself in this situation (price of a few bucks is very tempting).

author: KL27x
author_rank: Super Contributor
timestamp: January 02, 2016, 06:44:27 am
content: QuoteI have some rosin paste flux. I thought it would be handy for sticking leads and pin headers into the can. It turns out to be not as useful as I thought it would be. It's mostly forgotten. Liquid RA, and "solid RA" are what I use the most. By that, I mean liquid RA with all the solvent boiled off. It's not really a solid, though. It's amorphous, like glass. There's not an actual phase change between solid and liquid.I have used Alpha Metals, Kester, and MG. I don't see a big diff.QuoteI'm not sure that I agree with this. All RA I have used is extremely tacky. And when thoroughly dried and at room temp, completely non-tacky. I have had no problem leaving MG RA on the pcb, because when it's dry, it's a complete non issue. If you live in the tropics, maybe a different story. MG might be a little thicker than the other two I've used, though. If you let the other two kinds of rosin dry out some, they start acting like fresh MG. Maybe more a matter of having less solvent to start with.Rosin flux is "Clean it if you want. No problem. Don't clean. No problem."The peculiar property of being tacky when dissolved in solvent and/or hot and non-tacky (and quite solid) when dried out and at room-temp can be a useful property when taken advantage of.I have only ever tried one kind of MG "no clean." AFAIC, it should be called "never clean." If you try to clean the board with common solvents like alcohol or acetone, you'll find out why. Rosin is very easy to clean off the board, if you care to.

author: Armxnian
author_rank: Regular Contributor
timestamp: January 02, 2016, 08:00:05 am
content: Quote from: GreyWoolfe on January 01, 2016, 01:01:15 pmThis. Just clean it after you're done as it's sticky and doesn't look very professional if kept on.

author: KL27x
author_rank: Super Contributor
timestamp: January 02, 2016, 10:05:23 pm
content: ^Don't be so hasty.If you can stop playing with your boards for a day and actually still be able to sleep, you may find that there's nothing significant to see and nothing to feel the next day.The no clean will leave a transparent hard residue, immediately. The rosin flux will leave a translucent amber hard residue the next day. Unless your pcb soldermask is white, you might not even be able to see it unless you scrutinize the board. And unless you are going way overboard, there won't be enough to interfere with inspection at any point. The major difference to me is that you can easily clean off the rosin immediately, the next day, or years later, no problem. I often completely coat my toner transfer boards with a layer of rosin flux and never clean it off.While reworking a circuit board years down the road, you might need to wipe an IC or area of the board to see better. You might use a Q tip dipped in alcohol. If the board was made with no clean, you may be rewarded with a load of white shmegma that doesn't dissolve, along with the aggravation of brushing the board for several minutes to mechanically remove this residue.

author: Armxnian
author_rank: Regular Contributor
timestamp: January 02, 2016, 10:41:01 pm
content: Right, instead of cleaning it after you're done and avoiding any potential problems, wait until it bothers you so you have to go back and clean it... sound advice my friend.

author: KL27x
author_rank: Super Contributor
timestamp: January 02, 2016, 10:43:03 pm
content: It only bothers me if I am reworking a spot and the FRESH residue that I just added with solder wire or additional liquid flux is temporarily obscuring my vision on a stubborn connection, lol, such as when trying to solder to a scraped trace or some other fine rework. Or, say, pulling a shorted no lead chip and cleaning off the pads, I may wipe the pads to inspect them before refluxing them. This was going to happen even if the board was spic an span to begin with. This is why I like rosin, because it doesn't react badly to alchohol, if I do want to clean the board at any point.Also, there's a saying, if it isn't broken, don't fix it? I don't know what problems you are fixing by cleaning off the harmless residue. You mentioned esthetics and stickiness. One problem goes away by itself. The other becomes extremely minimal.If the esthetics still don't meet your standards, then the residue is almost as easy to clean later as it ever was. Sound advice? Meh. It's not going to hurt your board to try it and see for yourself. I have been soldering for decades, and this is stuff I have learned only fairly recently, due to taking on more of the assembly process in my own operations. Who'd a thought I could keep a 4"x4" board covered in a thick layer of dried (extra sticky MG) rosin flux on my bench in a 200 square foot lab that is the home of two cats, and there is not a hair to be found stuck in the rosin? I wouldn't have. I am fairly impressed by this fact. I thought this info might be new to someone else. If you are picking up some sort of attitude from my post, maybe you can try to ignore it. And maybe there will still be something useful left.

author: Armxnian
author_rank: Regular Contributor
timestamp: January 03, 2016, 10:12:06 am
content: Quote from: KL27x on January 02, 2016, 10:43:03 pmIt gets really annoying really fast when everyone on every forum argues for the sake of arguing, and on top of that responds with posts that defy any logic like yours.You say the stickiness of RA flux doesn't bother you. Who in reality solders a single capacitor and finishes with the board? You will work on it for longer periods of time, and then will need to wash your hands and everything else that accidentally comes in contact. Do I really need to explain this to you?You say RA flux residue is not noticeable except on white PCBs. That is false. The only color of pcb that would require you to look for the residue would be black, as it counteracts any translucent properties of the amber residue.Go read this thread and educate yourself:https://www.eevblog.com/forum/suggestions/myth-busting-solder-flux-cleaning-with-isopropanol-alcohol/Leaving RA flux on a board will not cause your work to disentigrate over night. Doesn't mean you shouldn't spend two seconds cleaning it to avoid any future problems and make your work look professional.

author: KL27x
author_rank: Super Contributor
timestamp: January 03, 2016, 12:02:12 pm
content: Sure. You make a lot of good points, and you're right!Sorry I couldn't help. I probably have different needs than most hobbyists. Doing mostly SMD and low speed digital stuff. And lately doing large batches of boards. And hands? Heck, after assembling several square yards of boards, I have to wipe down my entire bench.I keep a jug of sawdust at my bench, which comes in handy after particularly egregious exposure to liquid rosin. (But that's rarely necessary. It's primarily there for cleaning up my hands after using silicone or linseed oil or for spills.) But the amazing thing is after a few hours, the boards are tack-free.That link was good reading!*For some reason when I press probes into my rosin residue a mm apart, my DMM ohm meter doesn't register anything, at all. And a lot of the cathode tube tele's I've seen have visible rosin all over the board, and we know those things only lasted for decades. I've never done any RF work, personally, though. And I have read from several sources that RA shouldn't be left on the board, but rosin and RMA are ok. I guess I don't care, yet. RA has been easier to buy, and my boards don't care.Rosin is a barrier against air and water. Corrosion requires oxidation by air and moisture. It's quite possible that it's better to leave the residue on, intact, than to remove only the rosin with alcohol. The potentially corrosive bits in the RA embed in the surface of the metals and are not removable with alcohol. Unless you're cleaning your boards with stuff you can't buy at the grocerty store and which you wouldn't want to take a bath in, you are not actually removing the embedded halides/chlorides. But you are exposing your contaminated joints to air.