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Author Topic: Flux and Solder for Smd Hand Soldering  (Read 3286 times)
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diamadiss
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« on: October 23, 2012, 11:51:24 23:51 »

Hello,
can anyone suggest me a flux and solder in gel form, like these at the video below, to buy?

http://www.youtube.com/watch?v=5uiroWBkdFY&feature=related
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CocaCola
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« Reply #1 on: October 24, 2012, 02:42:26 02:42 »

As of late I have been using the Chip Quik flux, item #4, my supplier had it at a reasonable cost and highlighted it for sale one week so I gave it a try and was happy...

http://www.chipquik.com/products.html

There are plenty of other 'gel' fluxes out there, but beware of stuff you find cheap on the web, especially if it comes from Asia....  Get your flux from a reputable supplier, because believe it or not there is a thriving counterfeit flux market in China, with a lot of companies trying to pass off cheap no name garbage and junk (some doesn't even work) as legit name brand stuff, with near identical name brand counterfeit packaging that is hard to identify...

I'm sure the likes of Kester make some great fluxes as well, but sometimes it's hard to find them in 'hobbyist' size portions...  For this you can sometimes find a guy on Ebay (pay attention to feedback) that is repackaging Kester flux in smaller sizes...  I get my Kester no clean smd liquid flux this way, just can't at this time justify purchasing it by the gallon, as it last for a long time and I can pay a little extra and get a few ounces in a nice squeeze bottle on Ebay...

If you are talking about the 'solder paste' ground solder mixed in flux, then for that I get the cheap stuff from China as the US stuff is again in larger portions and costly...  Also note that the stuff is supposed to be kept on ice, so you will likely need to pay overnight shipping and dry ice if you order it from a legit US supplier...  Most Asian supplier ignore keeping it on ice, and just ship it...  On the other hand you can get little vials of it from China for a few bucks that work just fine, glue syringes to make dispensing easier are again not all that hard to source if you choose, personally I just get veterinary syringes and cut the point off...

Here is a source for cheap solder paste that I use...
 
*** Edit link removed as they are no longer have the stuff I have used in stock, so I can't recommend any off hand...
Check Ebay for 'solder paste' ignore the plethora of fluxes that pop up and look for the ones mixed with solder,  read feedback...

For example here is one of the 'repackers' of name brand stuff

http://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Disp-Pak-/230838562964?pt=LH_DefaultDomain_0&hash=item35bf0cf094

Sometimes you might find adding a little isopropyl alcohol to thin it down beneficial for hobby use as it ages, or a little extra flux mixed it sometimes helps as it ages as well...

Also if you watch Ebay you can sometimes find expired (not kept on ice) solder paste, I picked up a few pound tube years ago for next to nothing and regardless of it being 5 years expired it still works fine, just not as smooth and creamy...
« Last Edit: October 24, 2012, 02:57:47 02:57 by CocaCola » Logged
bigtoy
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« Reply #2 on: October 25, 2012, 06:49:22 06:49 »

For hand soldering prototype and hobby boards, I use a rosin-based flux easily found at any supplier (rosin is not "no clean" but I don't clean it off because it's not corrosive or conductive), along with leaded solder (gasp!). Makes for easy soldering. Certainly not RoHS-compliant, but for easy and reliable hand soldering, it's great.
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Langley
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« Reply #3 on: October 28, 2012, 12:18:02 00:18 »

If hobby quality solder paste is what you're looking for, I've used both of these with good success in the past year. For home SMD projects I argue strongly for "leaded" paste as it seems more forgiving of oxidized/contaminated boards and parts, though I'm sure the flux greatly influences that, too.

https://www.sparkfun.com/products/10448

http://dx.com/p/mechanics-soldering-paste-50g-7952

The 3.36USD DealExtreme container looked nearly identical to the 9.95USD SparkFun version, but took ~3 weeks to arrive in the U.S. (this might've been what CocaCola edited from his post, though(?), as it's currently showing "Item is temporarily sold out")

They do show a couple of other similarly cheap options in stock, however.
http://dx.com/s/solder+paste
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flo0319
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« Reply #4 on: October 28, 2012, 01:08:04 01:08 »

I suggest you to make a flux by your self : rosin + acetone (or other solvent with fast evaporation) . You can use a brush to put this solution over pads and pins and after you have soldered,you can clean with acetone(or other solvent). Cheap, clean and easy.
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Ichan
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« Reply #5 on: October 28, 2012, 09:20:47 21:20 »

The secret of the video provided is not only about the flux, more important is the soldering tip - it is special for Drag Soldering.

-ichan
« Last Edit: October 28, 2012, 09:28:38 21:28 by Ichan » Logged

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CocaCola
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« Reply #6 on: October 29, 2012, 07:06:50 19:06 »

The 3.36USD DealExtreme container looked nearly identical to the 9.95USD SparkFun version, but took ~3 weeks to arrive in the U.S. (this might've been what CocaCola edited from his post, though(?), as it's currently showing "Item is temporarily sold out")

That is what I edited out, I have used the dx cheap stuff for just about everything, it's cheap and works well...  You can find the same stuff on Ebay if you dig around...   I just hesitate to recommend something that I have not personally used because as I said there is a thriving market on 'bootleg' soldering supplies in Asia you just never know what you will get...

Sparkfun is a good alternative, the same stuff but with a middleman markup, but as you said no wait time and the Sparkfun guys are really good at shipping fast and offering support if you need it...

Quote
The secret of the video provided is not only about the flux, more important is the soldering tip - it is special for Drag Soldering.

A lot of the really depends on your skill set, I do just about all my soldering with a .5mm chisel tip...  I can do the drag soldering and everything else in that video with the same tip, yeah it might not work as well but it does work...  I'm not saying that the larger more specialized tip doesn't make it easier, it does but I'm too lazy to deal with swapping out my tips all the time...
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Pacific13
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« Reply #7 on: October 30, 2012, 07:59:10 19:59 »

Confirm that the DX solder past work very well. I use generaly http://dx.com/p/lodestar-soldering-paste-50g-4711?item=3
and when it begin to be dry (out of freeser) I mix it with rosin http://dx.com/p/solder-soldering-paste-flux-grease-10cc-117099?item=2 I obtain a very good paste which I used with a plastic stencil made with my CNC. Very usefull for personnal use.
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Tech_n
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« Reply #8 on: November 08, 2012, 08:17:45 20:17 »

The dx pastes are very thick, so they are good for stencils, but not for dispensing from a syringe. Attempt to dilute it with flux, gel or some cheap paste lead to very bad results. As the mixture heats up, the diluent will dissolve and the paste blob will melt like ice and flow away like ice melts. I spent many hours experimenting with this.

Dilution with any solvent is even worse. The solvent will evaporate when reflowing and the paste will pop and splatter over the whole board.

A simple flux pen is easily made from an (refillable) whiteboard marker. Take it apart, wash the most of the dye out with some alcohol and fill with a mixture of rosin or some paste flux in isopropanol. I used this for some time, but its only good for frequent usage as the tip will dry out pretty fast.
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CocaCola
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« Reply #9 on: November 08, 2012, 08:44:48 20:44 »

The dx pastes are very thick, so they are good for stencils, but not for dispensing from a syringe. Attempt to dilute it with flux, gel or some cheap paste lead to very bad results. As the mixture heats up, the diluent will dissolve and the paste blob will melt like ice and flow away like ice melts. I spent many hours experimenting with this.

Can't say I have experienced any such negative results...  I have cut the DX paste (as well as other paste) with liquid rosin flux to make it more 'sticky' with fine results, short of the fact that it then leaves a heavier flux residue...  I have also cut it with 99% isopropyl to thin it out, this has worked well also, especially with a cut of both rosin flux and isopropyl...  But, my preferred choice of cutting liquid is Kester 951 no clean flux, I have found it works quite well as a primary cutting liquid... 

Quote
Dilution with any solvent is even worse. The solvent will evaporate when reflowing and the paste will pop and splatter over the whole board.

Hmm, I have done 1000s of boards and never experienced this...  But, if you are having this issue it appears you might be heating it up too fast and not giving the solvent enough time to evaporate slowly, instead forcing it to a boil...  Try a slower initial heating profile or let the board sit out after component placement for a few minutes to let the solvent evaporate prior to putting it in the oven...
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« Reply #10 on: November 08, 2012, 09:36:14 21:36 »

Can't say I have experienced any such negative results...  I have cut the DX paste (as well as other paste) with liquid rosin flux to make it more 'sticky' with fine results, short of the fact that it then leaves a heavier flux residue...  I have also cut it with 99% isopropyl to thin it out, this has worked well also, especially with a cut of both rosin flux and isopropyl...  But, my preferred choice of cutting liquid is Kester 951 no clean flux, I have found it works quite well as a primary cutting liquid... 


Maybe i had a bad batch of flux. I used some chinese "AMTECH" flux. The diluted paste was very hard to put through the needle. The mixture had a good consistency, but afer heating, no drying was observed, insead the flux melted and the tin spheres flowed away with it.
I heated very slowly with hot air, after about an hour when the paste was applied.

My bad experince cant be generalized, though.

I had only to populate some board, and after not much succesfully application of paste with a syringe i gave up and soldered the 0603 stuff with an iron.
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CocaCola
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« Reply #11 on: November 08, 2012, 10:47:33 22:47 »

Maybe i had a bad batch of flux. I used some chinese "AMTECH" flux.

As I stated in my previous post "there is a thriving counterfeit flux market in China" and a lot of that stuff might as well be KY jelly or tap water because it sure isn't legitimate flux...  The stuff you used was probably a horrible low quality flux cut with water to start with and you simply compounded the issue of this additional water, that had no business being there in the first place...

Personally I'm not a fan of applying with a syringe in most cases, if my part count is so low that I can't justify having a plastic stencil cut, I just hand solder with an iron...  There are a few exceptions like when you are doing that one off package that has a hidden thermal pad on the bottom, where the syringe comes in handy, but even with those I just use the paste for the thermal pad and actually set the part with the iron first before reflowing the thermal pad...
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pl4tonas
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« Reply #12 on: November 09, 2012, 08:18:29 08:18 »

Another one source for cheap soldering paste and also some other stuff.

http://www.ledsee.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=500&category_id=28&option=com_virtuemart&Itemid=1
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Pacific13
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« Reply #13 on: November 09, 2012, 07:30:04 19:30 »

I agreed that the use of syringe with the mixture using rosin (also chinese) is not easy. In fact, and it is certainely due to this mixture, the paste don't adhere on the pad although it was well cleaned with isopropyl.On the other hand it is difficult to obtain a product sufficently liquid to flow in the needle I will try, as stated to add isopropyl. I have not done any testing yet as I was not sure of the paste constistency. I read that some are made with water and other with a chemical binder.
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« Reply #14 on: November 18, 2012, 06:40:50 18:40 »

I'm using almit t435 flux. It is liquid. You can get it in a small bottles with a brush to apply. Works great.
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« Reply #15 on: December 24, 2012, 10:35:19 22:35 »

I've recently bought SMD291NL syringe. Actually, I tried it today, I have to say that the iron temperature should be below 300, otherwise bad flames will arise and burn your nose. Also, movement should be fast. This flux is not real liquid, it feels like paste.

I have a question, after I use it, should I use the cap that closes the syringe, or I just can leave the needle attached?
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« Reply #16 on: December 25, 2012, 12:02:54 00:02 »

I have a question, after I use it, should I use the cap that closes the syringe, or I just can leave the needle attached?
I would leave the needle attached, It would not harm to seal the needle, with say a blob from your hot glue stick, so you can pull it off, & reseal it, with the same blob.
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