Most appropriate solder paste for home/hobby use

[mark03]

I am finally ready to discard my four-year-old (!) solder paste and buy some new.  I apply with an ordinary syringe and disposable plastic dispensing tips, no stencil.  Any opinions on the best choice of [tin-lead] paste for home use?

Criteria:

* Long shelf life.  This is by far the most important to me, as I never manage to use all of the paste before it goes bad.  It's also a given that I will use the paste well beyond its spec'ed shelf life, but presumably a longer official shelf life would translate into a longer "hobby-useful" shelf life.

* Low viscosity.  With my last paste (FCT NC676) it was difficult to get the tiny bead I wanted out of the syringe, without also risking blockages at the tip, even when the paste was fresh.  The lower the viscosity the better.

* Clean-up.  I have a choice of no-clean or water-soluble, but only have experience with the no-clean.  Is it easy to clean the water-soluble stuff with a gentle toothbrush?

I have a local source for FCT pastes.  NC676 is what I used last:
https://fctsolder.com/wp-content/uploads/2017/03/NC676.pdf
There is also WS159:
https://fctsolder.com/wp-content/uploads/2017/03/WS159.pdf

Their web site makes it sound like the water-soluble WS159 might have a longer shelf life, but the actual data sheets have identical boilerplate text   The WS159 is also listed as having a higher viscosity.

Suggestions?  Thanks.

[rstofer]

I just can't get excited about the $16 it costs for a syringe full of solder paste.  When it gets too hard to push through the needle, I buy another one.  When it comes to boards that I will reflow, some small portion of $16 is just chump change.

http://www.howardelectronics.com/soldering/soldering-accessories/solder-paste-and-flux/qualitek/p615d-013-8840i-qi-qualitek-sn63-37-solder-paste/

[tooki]

I use the syringe of 63/37 solder paste from MG Chemicals that I bought on Amazon. I keep it in the fridge.

Anyway, I strongly advise against water-soluble. If for any reason you fail to flawlessly remove every trace of the flux residues, then you risk corrosion down the line. (Water soluble fluxes are acids that are corrosive at room temperature. No-clean and rosin fluxes are also acids, but which are only active at soldering temperatures.)

[mark03]

I just can't get excited about the $16 it costs for a syringe full of solder paste.

This is already progress.  I was not aware of *any* mail-order source which would condescend to ship paste in a non-refrigerated, non-express manner.  The usual problem is that shipping costs more than the paste itself.  Looks like $3 USPS is an option for Howard Electronics

[Bud]

CML Supply, Kester EP256 

https://www.cmlsupply.com/kester-ep256-lead-solder-paste-63-37-syringe-dispenser/

[helius]

Are you using a manual plunger to dispense from the syringe?
There are dispensing systems that run on compressed air, and some that use a DC motor. It is much easier to get a controlled bead with these, even if the viscosity is high.
https://www.eevblog.com/forum/reviews/dm-dispenser-now-available/
https://www.eevblog.com/forum/reviews/solder-pasteflux-manual-syringe-applicator/
https://www.i-extruder.com/en/

[tooki]

Don't open paste mask on BGA pads. Spray some liquid flux before stencil printing, then solder the BGAs without paste, it is recommended when you don't have confident on BGA solder paste printing.
This only works for ENIG and tin plated boards for apparent reason, any warping can cause big trouble for this, and less available flux makes silver boards unusable.

What? Can you reword all that? It doesn't make sense, though I can tell it's useful advice, whatever it is!

[tooki]

Oh, gotcha. But why would anyone even think to apply solder paste to a BGA?? The whole point of the balls is that they alone provide the solder. Flux, of course, is critical since it’s a reflow operation.

[TheDane]

Chip Quik has a two part solder paste solution.
https://www.digikey.com/en/product-highlight/c/chip-quik/patent-pending-two-part-mix-solder-paste

It has a long shelf life (24 months), and comes in various sizes and compositions.

I do not know how well it mixes with other fluxes, to 're-flow' the paste.

[SimonD]

What about the GC10 Henkel / Loctite ?
I hear good words in the forum ...

[tooki]

What about the GC10 Henkel / Loctite ?
I hear good words in the forum ...

Given that Henkel bought Multicore (which has a stellar reputation) and has been little by little rebranding the Multicore products as Loctite, I’d expect it to be top-notch.

[helius]

BGA balls are designed to have a certain stand off height for inspection and stress relief. With insufficient solder, you will have the parts witting on less solder, hence shorter distance for mechanical stress buffering.

Yes. BGA mounting normally uses both paste stencil printing and solder ball positioning. See this video of a combination stencil and ball machine from Japan:

[tooki]

Ignoring reballing of salvaged BGAs, I thought that virgin BGAs came with solder balls attached, and that then they were simply fluxed and reflowed to the PCB. Are you saying that virgin BGAs get solder paste on the PCB, too?

[wraper]

Ignoring reballing of salvaged BGAs, I thought that virgin BGAs came with solder balls attached, and that then they were simply fluxed and reflowed to the PCB. Are you saying that virgin BGAs get solder paste on the PCB, too?

Usually small amount of paste is applied to the pads. Some BGA chips actually have metal coated polymer core balls instead of simple solder balls and they require solder paste.

[Corporate666]

CML Supply, Kester EP256 

https://www.cmlsupply.com/kester-ep256-lead-solder-paste-63-37-syringe-dispenser/

Buy this.

I have used various different leaded (and some lead free) solder pastes from AIM, Sparkle, Chipquick, Loctite/Henkel and others - and nothing comes close in my experience to EP256.  EP means Easy Profile and it is aptly named.  It is SO forgiving. 

I have pasted boards that sat around for three, four or five days before components got placed on them - no problem.  I've had jars of the solder paste sitting around for months unrefrigerated that performs the same as brand new product.  It has almost no residue, parts reflow and center perfectly on pads, I never have issues with tombstoning, and it has a great consistency that is great for either silkscreening or syringe dispensing.