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0402 packages - absolutely tiny. I'm wondering if it's possible to reflow solder them using a hotplate/skillet or toaster oven. Does anyone have any experience with doing this?

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Not a big problem, although rather more fussy about the right amount of paste and more prone to tombstoning than 0603's. Much more viable with a stencil than with dispensed paste.

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    \$\begingroup\$ What is "tombstoning"? \$\endgroup\$
    – Thomas O
    Nov 6 '10 at 16:02
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    \$\begingroup\$ If the solder paste and/or heat is not distributed evenly on the two pads, then one will melt first, tilting the component. The other pad never joins, and so the component sits perpendicular to the board, with only one pad attached, looking like a tombstone. \$\endgroup\$ Nov 6 '10 at 16:07
  • \$\begingroup\$ Always a hilarious effect. I have a friend who hand solders 0201. He uses a microscope, but it can be done. \$\endgroup\$
    – Kortuk
    Nov 6 '10 at 17:01
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    \$\begingroup\$ Here's an example of tombstoning - flickr.com/photos/mightyohm/5051676871/in/photostream \$\endgroup\$ Nov 6 '10 at 23:49
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    \$\begingroup\$ An even more clear example of tombstoning \$\endgroup\$
    – stevenvh
    Aug 5 '11 at 13:43
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While it is entirely possible to reflow them, hand soldering 0402s is not too hard with practice.

(Use a fine tipped iron, a magnifying glass and plenty of flux).

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  • \$\begingroup\$ I prefer a hot air tool and a good pair of tweezers. A fine-tipped iron helps with after-the-fact touch-up. \$\endgroup\$ Jan 22 '11 at 4:02
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There's nothing wrong with hand-soldering 0402 or even 0201 with practice. 0402 I can do without an inspection microscope, but 0201 is getting too small to do without one. Then again, I also solder 0.5mm TSSOP and TQFP packages without a magnifier or microscope. Just need to take your time, use flux and relax.

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I have no expirience in manual dispense, but I know the automatic and semiautomatic paste printing. Talking of how much manual effort is involved, consider this. When you are using oven for reflow step, then there are no hands involved. So the limit is defined only by 2 factors. Proper amount and type of solder and thermal profile.

Component placement is not critical, because reflow is automatically aligning components with wet forces. The geometry of footprints and solder masks is not manual either, just follow the specified footprint for each component. Thermal profile is easy to achieve with measurement, timing etc. For simple components (not a bga or 100 pin) the geometry of paste is not critical.

So limit is in accuracy of amount of paste dispensed on a pad. For manual dispense, I'd recommend create a syringe with some screw pusher and calibrate the amount of paste per angle of screw rotation. This must work for any sizes.

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