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Best Lead Solder Paste? — Parallax Forums

Best Lead Solder Paste?

SRLMSRLM Posts: 5,045
edited 2013-11-06 21:52 in General Discussion
I'm looking for some lead solder paste in a jar to use with a stencil. Has anybody compared the various pastes out there and can recommend a good paste?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-11-02 18:33
    Easy: Zephpaste. It comes in a syringe, but you can still use it with a stencil. The worst? Probably Kester.

    -Phil
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2013-11-02 18:45
    I had a run around with this paste http://www.digikey.com/product-search/en?x=-987&y=-73&lang=en&site=us&KeyWords=SMD291AX250T5-ND because I wanted fine pitch paste. However, no amount of heat would properly flow the joint. So I tried the water soluble version, it was much superior, and nice to clean. http://www.digikey.com/product-search/en?x=-987&y=-73&lang=en&site=us&KeyWords=SMD4300AX10T5-ND

    Haven't had good luck with kester either. Part of the problem is that a lot of paste out there is T3, which is rated for 20 mil pitch and larger.
  • tonyp12tonyp12 Posts: 1,951
    edited 2013-11-02 20:20
    As I don't the like the idea of lead poising I switched to lead free, I had good results with this one:
    http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=SMD291SNL10-ND&formaction=on&x=1&y=9
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-11-03 00:25
    For no-clean, lead paste, I only trust Kester EP-256. I have tried a few others over the years, but the EP-256 always gives positive results with little effort. I have been using it at home and at work (at two separate contract manufacturers) for about 11 years.

    Phil, I am curious, what concerns make you give Kester the worst rating?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-11-03 00:42
    WBA Consulting wrote:
    Phil, I am curious, what concerns make you give Kester the worst rating?
    Shelf life. I've thrown out more of it than I've ever had a chance to use. When it's fresh, it's okay. But the stuff just turns to concrete in short order, even when refrigerated. By contrast, I've had a syringe of Zephpaste well past it's expiration date, and it still performs like the day I acquired it.

    -Phil
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-11-05 14:49
    Ok, that's interesting. The batch of Kester EP-256 I just finished up using at home expired in 2009 and it printed and reflowed as if it was new.
  • JonnyMacJonnyMac Posts: 9,107
    edited 2013-11-05 15:37
    I've had a syringe of Zephpaste well past it's expiration date, and it still performs like the day I acquired it.

    Yep. Good stuff.
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2013-11-05 15:40
    To those who say it performs well after the date, have you tried the classic test, spread a thin layer on something, reflow, then look real close, preferably with a magnifier. The problems I see are really small solder balls that don't stay with the main part. You can't see this unless you look with magnification.
  • SRLMSRLM Posts: 5,045
    edited 2013-11-05 20:34
    I like Zephpaste, but I'm looking for a bit more paste. Plus, I haven't had such a good experience on my last order (delay of weeks, wrong contents, no replies on emails).

    Thanks everyone for the information. I didn't know about the paste size.

    My previous paste was the EP-256 that I purchased in November of last year. I don't know if it was the paste or something else, but when I tried using it in July for a design with the same components as in November I had many more troubles. It might be the paste, it might not, but I think I'll explore the market some.

    I don't have the old paste to experiment with anymore: I had to give it away since I moved more than a few hours drive away.
  • SRLMSRLM Posts: 5,045
    edited 2013-11-06 16:09
    Well, after looking around some more I came up with a shortlist of 3 products, all lead free and no clean:

    Kester NXG33 - http://www.kester.com/products/product/NXG33-Solder-Paste/
    SMTSolderPaste.com - http://www.smtsolderpaste.com/product-info.php?lead-free-no-clean-type4-500g-jar-product-page-pid33.html
    ChipQuik - http://www.digikey.com/product-detail/en/SMD291SNL250T5/SMD291SNL250T5-ND/3645044

    On the surface the ChipQuik is the best fit: a nice T5 paste. But when I look at the datasheet I see a lack of care there, which makes me think that maybe the same sloppiness is applied to the paste.

    Between the Kester and the SMTSolderPaste.com pastes I selected the Kester. I know that Kester seems to be a controversial choice. I selected it because the company seems stable, and they have a nice website. There's probably a better method of determining choice, but I don't know enough about the market and the product to make a more informed decision.

    In any case, I'll report back on how it goes. I think I'll need to insulate my oven extra well so that it can more easily reach the 235C temperature requirements.
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-11-06 17:15
    SRLM, NXG33 is a good choice. I currently use NXG1 as my standard lead-free no-clean. What format did you order? Jar, syringe, or cartridge? I think that may be part of the variance. I do not use paste in syringes, only in jars, and mix it thoroughly before use.
  • SRLMSRLM Posts: 5,045
    edited 2013-11-06 17:26
    WBA Consulting wrote: »
    SRLM, NXG33 is a good choice. I currently use NXG1 as my standard lead-free no-clean. What format did you order? Jar, syringe, or cartridge? I think that may be part of the variance. I do not use paste in syringes, only in jars, and mix it thoroughly before use.

    I got it in a jar from Techni-Tool (source). Do you let the paste sit at room temperature for a few hours before use? After stenciling, do you put the unused paste back in the jar?
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2013-11-06 21:52
    Yes, let the paste rise to room temperature on it's own. I usually stir it after two hours to see how it's doing. (most solderpaste manufacturers recommend 18-24 hours at room temperature before use)

    If the paste has been out of the jar for less than 30 minutes, I will put it straight back in the jar. Any longer than that, I put it into another jar, but will still re-use it. If you let the paste dry out and put it back into the jar, it will balance out with "wetter paste" in the jar and "freshen up", but over time, repeating that will render the whole jar of paste dryer each time you use. (hopefully that makes sense).

    I always "work" the paste before printing boards for parts. I do this by setting up one board with the stencil, and then work the paste back and forth across the stencil a few times to get a really nice bead rolling on my squeegee (which happens to be a plastic putty knife with a very straight edge). I pull that board and and clean it off, clean my stencil apertures, and then start printing boards. Having a worked bead to print with makes a big difference in the quality of the "bricks" of solderpaste lef on the board.

    On the Kester website, they have a knowledge base category and if you click on "Solderpaste", there are a few really good PDFs with some standard handling tips.
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