Quality solder paste available in small quantities

[Emil]

Can anyone recomend a good quality no-clean solder paste which is available in small quantities? Either with lead or lead free.

I have checked Mouser (where I prefer to get my components) and googled, but it's hard to find any solder paste from reputable brand which is available in small quantities without expensive shipping. Most are either 500g jars or 12 packs of syringes.

I have tried SolderMax lead free solder which I found on eBay from a UK seller. It works fine when doing one or two boards (30 components on each), but if doing anymore the paste will be dry/not sticky when placing the last components.

I have also tried Mechanic (leaded) solder, also from eBay. That seemed to work well, but I never tried doing several boards at once so I don't know if it has the same problem with drying.

How long working time should I expect from a good solder paste?

[nanofrog]

Amtech.
They sell small syringes, usually 35g, and larger ones at 100g. Don't see working time being a problem if you're not exceeding a few hours or so IMHO (days OTOH...), and storage time is 6mo when kept in the refrigerator (1 mo. at room temp). Do be careful on where you source it though, as there are fakes out there. Best to buy from an authorized distributor if you can. Unfortunately, Mouser isn't one, but there are sources in Europe (distributor list).

ChipQuik would be a second brand to check out.

A third would be ZephPaste (Zephyrtronics), and has a 1yr shelf life in the fridge (6mo. at room temp). FWIW, Mouser carries it here in the US, so you may not even have to go anywhere else to get it than you're already using. 

Hope this helps.

[echen1024]

I use Multicore from Digi-Key.

[Emil]

I couldn't find ZephPaste at mouser.com. I have tried searching and browsing by category. Do you have a link?

I might buy ChipQuick because they have flat rate $10 shipping worldwide. Both ChipQuick and ZephPaste have longer shelf life at room temperature than most other brands (6 months at room temperature, 1 year refridgerated.)

[nanofrog]

I couldn't find ZephPaste at mouser.com. I have tried searching and browsing by category. Do you have a link?

I might buy ChipQuick because they have flat rate $10 shipping worldwide. Both ChipQuick and ZephPaste have longer shelf life at room temperature than most other brands (6 months at room temperature, 1 year refridgerated.)

Not finding it on the US site either now. 

At this point, I'd go for the ChipQuik.

[Corporate666]

Kester "easy profile" 256 is by FAR the best I have used, and I have used many different kinds, including AIM, Star and many many others.

I have abused this stuff in ways that would shock some people - not refrigerating it (ever), leaving a tub of it on a desk and using the same tub over the course of 6 or 8 months, or a year.  Or two years.  Pasting boards that don't get placed for 2, 3 or 5 days.  Scraping the left over paste off the stencil and back into the tub.  And much more - it always reflows beautifully every time.

Nothing else has even come close to being as good and as reliable despite the abuse you give it... I also rarely get tombstoning and components center very nicely.  It's available in small syringes as well as 500g jars. 

[georges80]

Yep, I use Kester easy profile 256 as well. Great solder paste with a good flux concentration. I store it in a ziplock bag in the fridge (syringes). In the US I purchase it from a small place that has excellent pricing versus many of the other 'stores'.

cheers,
george.

[nanofrog]

Kester "easy profile" 256 ... It's available in small syringes...

Kester easy profile 256 ... I store it in a ziplock bag in the fridge (syringes).

Kester only shows it in 500g jars, 600g cartridge, 750g cassette, and a 1400g cartridge (here). Only aware of Kester selling R276 in 35g syringes. 

So where are you guys getting it? CML Supply (repacking it)? 

[alank2]

Can you water rinse EP256?  I know it is no clean, but I like to clean off any flux residue if possible with a water rinse.

[georges80]

Yes, CML re-packages EP256 into syringes which is why that sell the smaller syringes. I've bought from them over the past few years and never had quality issues.

Ultrasonic washer with plain water does a pretty good job of removing any of the flux. IPA if there's any further issue.

cheers,
george.

[zapta]

Ultrasonic washer with plain water does a pretty good job of removing any of the flux. IPA if there's any further issue.

cheers,
george.

How does this work, you put the board in the water and turn on the ultrasonic?  I never mixed water and electronics but it may worth a try. Anything to watch for?  Do you dry it later? Any component type to avoid?

[georges80]

Washing boards is what assembly houses do all the time....

I used compressed air (compressor in the garage) to blow/dry after ultrasonic washing. I run my washer 5 minutes if I've used one of the 'must wash' activated fluxes. I don't wash for the no-clean flux. EP256 flux residue is very minor and no-clean.

Most components (even switches and trimpots etc) are already rated for washing, but check the datasheets if you have concerns.

cheers,
george.

[Corporate666]

Kester "easy profile" 256 ... It's available in small syringes...

Kester easy profile 256 ... I store it in a ziplock bag in the fridge (syringes).

Kester only shows it in 500g jars, 600g cartridge, 750g cassette, and a 1400g cartridge (here). Only aware of Kester selling R276 in 35g syringes. 

So where are you guys getting it? CML Supply (repacking it)? 

I actually don't buy it in syringes, but I did a Google search on Kester EP256 and saw syringes, so I figured that would work for your "small quantity" requirement.  I just checked after reading your post and it looks like it is indeed CML repackaging it.  $13 and change on eBay though, pretty good deal.

[scientist]

Doesn't ultrasonic vibration fatigue solder joints?

This stuff is good: http://www.digikey.com/product-detail/en/SMD291AX/SMD291AX-ND/1160002

[Kjelt]

Doesn't ultrasonic vibration fatigue solder joints?

If you take some precautions (see below) there is not much problem, if you use a cheap low frequency US cleaner you can damage components esp. crystals and wirebonds inside ic's what I have read. But there seems to be opposing sides to this.

Research by B.P. Richards et al at GEC Marconi and the EMPF Laboratory suggests four parameters for the safe cleaning of PCBs using ultrasonic technology:
1.The ultrasonic frequency should be 40 kHz or higher. The lower the frequency the more aggressive the ultrasonic cavitation becomes.
2."Sweep" or "Alternating" frequency technology be used to prevent "hot spots" in the cleaning bath.
3.The "Power Density" should be 10 watts per liter or less (referred to as Low Power Density). The higher the power density the stronger the "scrubbing" action (the electrical output of the ultrasonic generator(s) divided by the total liters of cleaning solution in the bath).
4.The ultrasonic wash cycle should be 10 minutes or less.

[nanofrog]

I actually don't buy it in syringes, but I did a Google search on Kester EP256 and saw syringes, so I figured that would work for your "small quantity" requirement.  I just checked after reading your post and it looks like it is indeed CML repackaging it.  $13 and change on eBay though, pretty good deal.

OP is in Europe, so I don't think CML (or their eBay store) would be of much help in his case.

Certainly worth going for CML's repacked syringes though for US members IMHO. Cheaper than ChipQuik ($20 for 35g @ mouser) or ZephPaste ($15.49 for 12g) to top it off for a top quality product (prices for 63/37 no-clean).

[Emil]

I actually don't buy it in syringes, but I did a Google search on Kester EP256 and saw syringes, so I figured that would work for your "small quantity" requirement.  I just checked after reading your post and it looks like it is indeed CML repackaging it.  $13 and change on eBay though, pretty good deal.

OP is in Europe, so I don't think CML (or their eBay store) would be of much help in his case.

Certainly worth going for CML's repacked syringes though for US members IMHO. Cheaper than ChipQuik ($20 for 35g @ mouser) or ZephPaste ($15.49 for 12g) to top it off for a top quality product (prices for 63/37 no-clean).

Actually CML (http://www.cmlsupply.com) looks good. $12.99 for 35g + $10.95 shipping to Norway.

[Emil]

Kester "easy profile" 256 is by FAR the best I have used, and I have used many different kinds, including AIM, Star and many many others.

I have abused this stuff in ways that would shock some people - not refrigerating it (ever), leaving a tub of it on a desk and using the same tub over the course of 6 or 8 months, or a year.  Or two years.  Pasting boards that don't get placed for 2, 3 or 5 days.  Scraping the left over paste off the stencil and back into the tub.  And much more - it always reflows beautifully every time.

The issue I have with the paste I use now is that it will dry after stenciling the boards so that after >1 hour the paste is no longer sticky. When I place a component on the dry paste it can easily move around, so the boards need to be handled very carefully until reflowed. The solder joints still turned out fine.

When you place the boards after several days, is the paste still sticky?

[Kjelt]

What's wrong with:
1)stencil X (X depending on size how many can be done within an hour) boards
2)put left over paste back in jar, clean stencil and squeegee a bit with some IPA (not thoroughly), blow extreme small holes in stencil clean with pressured air
3)place the components on the X stencilled boards
4)reflow the boards
return to 1) if time left

That's how I do it after I had a lot of stencilled boards to clean from paste because something else came in between unexpectedly.

[Emil]

What's wrong with:
1)stencil X (X depending on size how many can be done within an hour) boards
2)put left over paste back in jar, clean stencil and squeegee a bit with some IPA (not thoroughly), blow extreme small holes in stencil clean with pressured air
3)place the components on the X stencilled boards
4)reflow the boards
return to 1) if time left

That's how I do it after I had a lot of stencilled boards to clean from paste because something else came in between unexpectedly.

Nothing wrong with that, that's how I do it now. But I think it would be more efficient if I could do a few more boards at once and it would be nice to have more time in case something comes up while placing components.

[nanofrog]

I actually don't buy it in syringes, but I did a Google search on Kester EP256 and saw syringes, so I figured that would work for your "small quantity" requirement.  I just checked after reading your post and it looks like it is indeed CML repackaging it.  $13 and change on eBay though, pretty good deal.

OP is in Europe, so I don't think CML (or their eBay store) would be of much help in his case.

Certainly worth going for CML's repacked syringes though for US members IMHO. Cheaper than ChipQuik ($20 for 35g @ mouser) or ZephPaste ($15.49 for 12g) to top it off for a top quality product (prices for 63/37 no-clean).

Actually CML (http://www.cmlsupply.com) looks good. $12.99 for 35g + $10.95 shipping to Norway.

Nice. 

Didn't look to see if they did international shipping directly, as their eBay store was limited to US shipping.

[Corporate666]

The issue I have with the paste I use now is that it will dry after stenciling the boards so that after >1 hour the paste is no longer sticky. When I place a component on the dry paste it can easily move around, so the boards need to be handled very carefully until reflowed. The solder joints still turned out fine.

When you place the boards after several days, is the paste still sticky?

We pick and place all our boards, and I have placed boards a week after pasting with EP256 and they place fine.  I mostly use PLCC LED's, SOIC-8's, SOT's, SOD-123, and 0805 and 1206 passives.  I would say a week is about the outer limit of what you would ever want to push it to though.  After maybe 24-48 hours, the paste does take on a more peanut-butter like consistency vs. when it's fresh, but I've never had problems with parts not sticking.  I don't have a fully automated line either, so we have someone loading PCB's into and out of the pick and place and into PCB carriers, so it's probably not as gentle as if it was a fully automated line. 

And when I say I leave the pasted boards for a few days - I don't mean in the fridge, I mean in open air in a PCB carrier next to the pick and place.


For those wondering why I would be so cruel to my PCB's, it's not that we are intentionally brutal... but stuff happens... people call in sick, a pick-and-place nozzle gets damaged and I need to wait for parts, or sometimes we just don't get a batch of boards done as quickly as we hoped before a long weekend and such. 

I've used lots and lots of other pastes and nothing else comes close to EP256 in terms of staying tacky over time.



Speaking of which - anyone know a good way to remove dried on paste from PCB's?  I probably have a couple of hundred boards (no idea what paste is on there, probably another brand) that were pasted and never placed.  It was when we needed to wait a few weeks for the P&P to be repaired.  The paste on there is like concrete now.  I wonder if soaking in IPA and/or ultrasonic would remove it?  I hate to toss the boards, but it's not worth spending the labor having someone sit and clean them all by hand - would take forever, and little blobs of dried paste end up in all the holes and vias. 

[nanofrog]

Speaking of which - anyone know a good way to remove dried on paste from PCB's?

Take a sample board, and soak in IPA to see if it will work (no idea of the paste, so can't help past this). Keep an eye on it to see if/when the paste swells/changes appearance (i.e. texture). Other solvents, such as acetone, will speed it up, but there's the potential to damage the PCB (i.e. silkscreen or solder mask).

Expect it may take some scrubbing though, potentially pushing labor to the point it's not worth it (dishwasher might be an alternative if the pressure is sufficient). But at least you find out on a single/few boards rather than a bunch of them (waste a bunch of time & money before finding out salvaging them is a bust).

[Kjelt]

Just a thought: Ultrasonic clean them with IPA / fluxremover mixture? If you stack the pcb's vertically in the tank, the relatively heavy lead balls have to drop off eventually.

[theatrus]

I can vouch for the Kester pastes. I'm still using a 4 year old tub of lead free (refrigerated) no clean for prototypes with no issues. Other paste I've had always ended up with issues when old.