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I’ve recently acquired a modified T962A reflow oven and have been experimenting with profiles. I’ve had to really ramp up the peak temperature and time at peak temperature to even have any chance at melting and flowing the solder paste.

In the attached pictures I believe the solder paste is burnt. How can this be avoided? As mentioned I had to really increase peak temperature, even with longer soak times and temperatures to get any sort of reflow.

EDIT: Here's a link to the solder paste in question. We've only had it for a few weeks and it's been stored within the recommended temperature range.

Burnt solder joint

Burnt solder joint

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    \$\begingroup\$ Oxidation issues from storage \$\endgroup\$
    – D.A.S.
    Commented Jun 8, 2019 at 12:33
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    \$\begingroup\$ Is that proper solder paste, with actual granulated solder in it, or just solder flux paste? What does it look like when it's still in the tub/syringe/whatever - greyish & opaque, brownish & translucent, something else? \$\endgroup\$
    – brhans
    Commented Jun 8, 2019 at 12:47
  • \$\begingroup\$ Very informative article. instructables.com/id/T962A-SMD-Reflow-Oven-FixHack \$\endgroup\$
    – Peter Smith
    Commented Jun 8, 2019 at 15:52
  • \$\begingroup\$ As others suspect what is pictured is not solder paste at all, but merely flux, you're apparently trying to solder parts with nothing but the HASL finish of the board to provide solder(!) If this is more than a simple mistake of using the wrong supplies, you'll need to edit the actual identity, specs, age, and storage confitions of your paste into the question. \$\endgroup\$
    – Chris Stratton
    Commented Jun 8, 2019 at 15:58
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    \$\begingroup\$ That looks like the "no clean" residue that is left after the reflow cycle. Are you finding the parts are attached well and making good contact? \$\endgroup\$
    – CrossRoads
    Commented Jun 10, 2019 at 12:46

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Is the solder paste old? It has a shelf life of only about 6 months if kept refrigerated.

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  • \$\begingroup\$ This is more of a request for clarification than an "answer" - it's also likely not relevant in the situation pictured, which does not appear to be of a solder paste at all. \$\endgroup\$
    – Chris Stratton
    Commented Jun 8, 2019 at 16:00
  • \$\begingroup\$ The solder paste is only a few weeks old (well, we've had it for a few weeks bought directly from RS) and has been stored within the recommended temperature range. \$\endgroup\$
    – amitchone
    Commented Jun 10, 2019 at 12:07

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