Flux -- questions/observations

[GiskardReventlov]

I have not done a lot of soldering and I've relied on the flux in the solder. But after watching videos I see that the pros use flux, one proclaiming "that you can never use too much". 

So I don't know anything about flux and looked on digikey but saw expensive flux so I passed. At radioshack I picked up 2oz. rosin soldering flux, non-spill paste.

The contents WW Gum Rosin, Diethylene Glycol Dibutyl, Dymerex Rosin.
Products of decompisition: CO, CO2 and aldehydes

Is this stuff good enough? If not, what's a good, cheap flux to get?

Edit: changed "pros use solder" to "pros use flux"

[mariush]

Get no clean flux or rma flux. 

It's not expensive for the amount you get:

http://www.digikey.com/product-detail/en/CW8400/CW8400-ND/768491
http://www.digikey.com/product-detail/en/760089/82-145-ND/2498943

This  will also work but you should clean the flux after soldering with isopropyl alcohol : http://www.digikey.com/product-detail/en/835-P/473-1033-ND/949475

No clean flux can be left on the board without problems. Rosin mildly activated (RMA) can usually be left on board but it wouldn't hurt to clean. Rosin Activated (RA) should be cleaned with isopropyl alcohol.

Water clean flux should be avoided.

I don't know what type of flux that is, but it's dubious, based strictly on ingredients.


Good solder will have a certain percent of flux in it, but it never hurts to use additional flux especially on more oxidized leads and pads (or old boards).

And if anyone stumbled upon this thread, here's some explanations about flux and solder (there's a whole series and this is just part 1, a bit outdated videos but information is still valid):

[Vgkid]

This is the RS flux I use, it works pretty good. It will take me a while to use it up

[GiskardReventlov]

I thought those pen fluxes were too small. I will try one and compare to this RS flux.

Will have a look at video too.

I don't know what type of flux that is, but it's dubious, based strictly on ingredients.

I looked at MSDS for the above mentioned and they all seem to be toxic.  Which ingredient(s) look dubious in the RS flux and why?

[tx8]

To know for sure weather your flux is corossive and needs to be avoided you should know the ISO or DIN or IPC standard it complys with. No clean flux will have eg. 1.1.3  "rma" will have a 2.1.3 but to add some confusion: 2.2.3 is again less corossive. On the german wiki page there is a nice overview to convert DIN to ISO. To me the old norm seems to be much clearer as the corrosiveness is linear to the number while the iso number jumps back and forth. My fluitin .4mm wire has a F-SW-32 core  and i have some RMA 2.2.3 (look at the figure on the wiki page its supposed to be non corossive - green but also corossive - yellow  )

http://de.wikipedia.org/wiki/Flussmittel_%28L%C3%B6ten%29#Alte_DIN_8511

[IanB]

So I don't know anything about flux and looked on digikey but saw expensive flux so I passed. At radioshack I picked up 2oz. rosin soldering flux, non-spill paste.

The contents WW Gum Rosin, Diethylene Glycol Dibutyl, Dymerex Rosin.
Products of decompisition: CO, CO2 and aldehydes

Is this stuff good enough? If not, what's a good, cheap flux to get?

What you have there from RS is rosin paste flux. It is perfectly fine for through hole soldering.

For SMD soldering you will often see people using liquid flux with an applicator that allows them to put a few drops in just the right place. The liquid flux is basically the same stuff as the paste flux except dissolved in a solvent that evaporates with the heat of the iron.

Flux pens contain liquid flux with an easy to use applicator. It's worth having one of those as well as paste flux.

Typical usage is to poke wires and component leads into paste flux and use a flux pen on circuit boards.

[sleemanj]

You're a hobbiest right, don't need specific composition and properties and such...

The RMA-223-UV flux gels on ebay etc in 10CC syringes, yeah, they work pretty good. Despite the label, they are absolutely not "Amtech" and are absolutely not "Made in USA", but that doesn't mean they don't work.

You can also get flux paste in tubs on ebay (or DX, or Ali or ...), just do not believe the weight on the label, it's not right by a long shot, assume you'll get maybe 75% at best, but the flux itself, well, it's flux, no problem, works like flux works.  I note that dx.com are good about putting a more correct weight in the product title (but the label is still wrong).

Flux pens are on ebay too, coming from china don't believe "Kester" being written on the label for a moment, but probably it works just fine (disclaimer: I dont' use flux pens).

So in short, just grab a couple types of ebay for a couple bucks.  It will work.

You could even , get some rosin off ebay (exactly same stuff used to "rosin up your bow"), grate, dissolve.  The active ingredient in flux is rosin.

Do NOT get plumbers flux, that's acidic, no good for electronics.

And here's a couple of good old fashioned flux-offs :-)

[tx8]

 they are absolutely not "Amtech" and are absolutely not "Made in USA"

they also comwe with a ROHS sticker and a warning about the ingredients to include lead an cause birth defects... 


btw. this is more worthy looking at than the wiki info i posted earlier: http://www.sos.sk/a_info/resource/pdf/ine/Fluxes_EN.pdf

[nctnico]

One of my observations with flux in a spray-can: after 10 years they start to leak at the bottom of the can. I have had this problem with 2 different brands so far.

[Legion]

And if anyone stumbled upon this thread, here's some explanations about flux and solder (there's a whole series and this is just part 1, a bit outdated videos but information is still valid):

That video is great.

[zapta]

I have had good results with this tacky flux

http://www.digikey.com/product-detail/en/SMD291/SMD291-ND/355201

It works better IMO than the liquid/pen kinds because they stay were to want them to be. For cleaning I use Isopropyl alcohol.

[GiskardReventlov]

I have had good results with this tacky flux

Looks like a good product but it says it ships with an ice pack. So I guess it has to be kept cold and that's too finicky for me. I'm sure to forget keeping it cold.

[GiskardReventlov]

What you have there from RS is rosin paste flux. It is perfectly fine for through hole soldering.

This is helpful.

For SMD soldering you will often see people using liquid flux with an applicator that allows them to put a few drops in just the right place. The liquid flux is basically the same stuff as the paste flux except dissolved in a solvent that evaporates with the heat of the iron.

I've looked at a lot of SMD soldering/reflow stuff and it's not something I want to do. But I think it's inevitable.

Flux pens contain liquid flux with an easy to use applicator. It's worth having one of those as well as paste flux.

Typical usage is to poke wires and component leads into paste flux and use a flux pen on circuit boards.

I'm going to get a flux pen.

[GiskardReventlov]

To know for sure weather your flux is corossive and needs to be avoided you should know the ISO or DIN or IPC standard it complys with.

I will try to track this down.  I believe these kinds of things (i.e. crazy standards) are a symptom of too many lawyers.  It's a shell game to avoid blame. Or maybe a better way to think of it is fear of standing up and taking ownership for your product.  If we don't stand behind our products we'll obfuscate anyway we can.

[GiskardReventlov]

You're a hobbiest right, don't need specific composition and properties and such...

I am  hobbiest, and I think the flux I have is fine, which means I know nothing about composition/properties of flux.

The RMA-223-UV flux gels on ebay etc in 10CC syringes, yeah, they work pretty good. Despite the label, they are absolutely not "Amtech" and are absolutely not "Made in USA", but that doesn't mean they don't work.

I like to limit my exposure to questionable tools/parts/etc.

Homemade sounds interesting but for now I'll just buy it.
Will check those vids.

[ion]

You could even , get some rosin off ebay (exactly same stuff used to "rosin up your bow"), grate, dissolve.  The active ingredient in flux is rosin.

I've been using DIY flux for the last few months and I can say it works great as a flux.  Bit of a pain to clean though if you want your board to look nice.

[GiskardReventlov]

This is the RS flux I use, it works pretty good. It will take me a while to use it up

Yes it will last me a long time too, especially considering I relied on the flux in my solder.

[poorchava]

I love to use diy rosin flux. It works really great, but has one significant downside: it's sticky as hell when the solvent vaporises.

It makes your pcb, tools and everything else sticky. I think that the concentration of 20-80% mentioned in the flux-off video is is way over the top.

For soldering stuff to factory made pcbs I use RF800 flux. According to MSDS it's typically <2.5% Rosin and <2.5% Succinic acid and the rest is IPA. It's almost non-sticky and gives you very nice joints. It's also very thin (due to being mostly IPA) so one drop will get everywhere it needs for most components. The downside is that everytime you touch the pcb with your iron most of the flux will evaporate and you need to apply more. It doesn't work well for heavily oxidized or contaminated suraces (eg. stranded wires, homemade pcbs etc).

[mrflibble]

I love to use diy rosin flux. It works really great, but has one significant downside: it's sticky as hell when the solvent vaporises.

It makes your pcb, tools and everything else sticky. I think that the concentration of 20-80% mentioned in the flux-off video is is way over the top.

Over the top indeed.  What ratio do you use by the way?

That dangerous protoype vid does give me an idea to test adding some rose glycerin. The glycerin content in there seems to do the trick for faster curing of acetic silicone sealant, so with a bit of luck it does it's job in flux as well.

[poorchava]

no idea, last batch i made like 5 years ago (300ml jar). IIRC i just eyeballed it to be half of 40g package and topped off the jar with ipa.