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By DaveAK
#199711
I've just completed my first reflow board and I'm very happy with the results. It's just a small board with 3 TSSOPS and half a dozen 0603 caps. I used a hotplate with a piece of 3/8" aluminum plate to spread the heat. All went well but I did end up with three tiny bridges. Two on one chip and one on another. I used a 4mil steel stencil from OSH Stencils.

So what's the best way to remedy these? Exacto knife? Hot air rework? The knife I have, rework tools I don't (yet).

And what's the best way to prevent bridges in future projects? Placing the components isn't easy for me and I wonder if my hands aren't steady enough. Could I be smearing the paste trying to get the chips in place? The next project uses QFN parts and I'm worried that bridging will be more difficult to correct.

Any advice, tips or tricks would be greatly appreciated!
By lyndon
#199718
In my experience, bridging is most frequently due to too much paste being applied. Best way to clean up most bridges on small pitch components is with solder wick. Rubbing some flux on the wick helps too.
By DaveAK
#199719
Would a 3mil stencil have been a better choice do you think? I don't seem to do a great job with solder wick, but I've never tried it with flux. I probably just need to practice some more, and maybe get some better tools.
By lyndon
#199730
Possibly, a thicker stencil will hold more paste. I also use the OSH Stencils default thickness. I don't remember what that is, but it works fine with my 64-TQFP devices. I have never tried QFNs.

The "trick" I learned with wick was to use extra flux and make sure the tip of the iron is well tinned, with extra solder even, to get good heat transfer.
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