Flux questions - Page 1
Forum section: electronics / projects

author: Chasm
author_rank: Regular Contributor
timestamp: February 23, 2011, 04:04:11 pm
content: Flux... Flux is actually simple.For most applications no clean type flux should be right. Maybe in the more paste form instead of the usual fluid variant.But why are flux pens so damn expensive?About 10 Euro a each in Germany, practically regardless of brand and flux.That's a lot of money for usually 10ml of flux especially if you take the prices for large containers of the same flux into account. Am I missing something?

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 23, 2011, 04:22:09 pm
content: maybe the pen alone is expensive? and of course you have to pay more /ml for smaller quantity compared to large container.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: February 23, 2011, 05:55:37 pm
content: Quote from: Chasm on February 23, 2011, 04:04:11 pmWell it's all to do with the inherent difficulties of tapping the flux capacitor for it's electrolyte.

author: Chasm
author_rank: Regular Contributor
timestamp: February 23, 2011, 06:58:43 pm
content: Quote from: Mechatrommer on February 23, 2011, 04:22:09 pmNot really, it's more or less a cheap felt pen. Ok, the tip is a bit different so that it does not get clogged too fast.The fun part is that you usually can get a gallon container of the very same brand flux for the price of a handful of 10ml flux pens.But then I don't need that much and it is not supposed to keep well either.Ordering from china is a possibility, but then you never know what flux it actually is. Water soluble instead of no clean under a qfn or similar chip that you can't really clean would be annoying.Quote from: FreeThinker on February 23, 2011, 05:55:37 pm*g* Probably I should pay the distributor a visit. I always wanted to see a flux capacitor in real life.Actually they are near a company I visit once in a while, with some luck that should take care of shipping cost.

author: Unknown
author_rank: Unknown
timestamp: February 23, 2011, 10:52:57 pm
content: I find flux pens frustrating, the tip falls apart after fluxing a few soldered components, especially THT. It's because you need to apply some pressure for the flux to flow.There are refillable flux pens but meh...same issue.You can use these bottles filled with flux from a bigger container. Careful, flux expires. You can dispense it drop by drop.Then there are these bottles:That you can use with a paint brush.Paste-type flux from a syringe is also useful sometimes as it doesnt spead everywhere and helps keep the component in place.

author: Chasm
author_rank: Regular Contributor
timestamp: February 24, 2011, 12:46:49 am
content: Got a similar container and brush for rosin flux. That works but sticks a lot.Still looking for a cheap pump dispenser that actually closes tightly.Oh, never buy them at the electronics companies, they charge about 200% pervert surcharge compared to nail studio suppliers and the same again compared to ebay .

author: Lance
author_rank: Frequent Contributor
timestamp: February 24, 2011, 05:15:57 pm
content: What's the difference between RMA and water soluble flux? A video I watched on soldering QFN devices said it was better to use that kind of flux as opposed to water soluble.

author: Unknown
author_rank: Unknown
timestamp: February 24, 2011, 05:50:27 pm
content: Main difference for hobby use is that WS flux is more aggressive than rosin based fluxes. This makes it ideal in applications with high level of oxidisation.Residues from WS fluxes are active in room temp and continue eating away on the joint after soldering. They are also hygroscopic meaning they will absorb moisture from the air. WS flux must be cleaned off the board in a short amount of time.At home I would recommend arosin based flux like 'No clean' RMA or RA. Variations exist within this category. It is a shame not to clean off flux residues from your board even though not strictly necessary with a particular flux.Instead of trying to generalise and find the best flux, read the datasheets of the solder/flux that is available to you (Farnell RS etc), they will recommend a cleaning procedure. Dont use WS fluxes at home, especially with SMT components.

author: qno
author_rank: Frequent Contributor
timestamp: February 25, 2011, 08:50:37 am
content: We used to buy Flux spray until i found out that it was only Ammonium chloride dissolved in water.about a teespoon/liter is fine.

author: Lance
author_rank: Frequent Contributor
timestamp: February 25, 2011, 05:35:59 pm
content: Quote from: Alex on February 24, 2011, 05:50:27 pmWhat kind of flux do you usually find in flux core solder then? Also, if you're applying your own flux I guess you don't need to use flux core solder?

author: Unknown
author_rank: Unknown
timestamp: February 25, 2011, 08:22:31 pm
content: Quote from: Lance on February 25, 2011, 05:35:59 pmYou can buy it with various kinds of flux, look in the catalog of a solder manufacturer like Kester. RA, RMA and no-clean are the most common.Quote from: Lance on February 25, 2011, 05:35:59 pmExtra flux is often used because flux will burn of on the soldering tip, so if you apply solder to the tip to drag-solder some SMT component, the flux is likely burned off before you touch the tip to the component. This is where additional flux applied to the component legs/PCB comes in handy. The flux is not used because applying flux from a bottle is so much more convenient than flux in the solder, so the solder usually also has a flux core. These fluxes should be compatible, according to the solder/flux manufacturers, although I've never had an issue with this.

author: Lance
author_rank: Frequent Contributor
timestamp: February 25, 2011, 10:33:03 pm
content: Okay then. Which companies are good to go to for flux, and those little dispenser bottles? All my solder is Kester stuff.