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New 0402 LED version

A project log for reDOT_smart

smart miniature (DIP6) 5x7 LED Matrix

AlexAlex 03/27/2017 at 20:107 Comments

Soldering the 0201 on double sided populated boards was a fail (see last log). But here is the solution: 0402 LEDs. The board will be with 300x390 mil a little bit bigger than the old one (300x340). But hope that the 0402 LEDs are easier to solder. And they are much cheaper also.

Discussions

Yann Guidon / YGDES wrote 03/27/2017 at 20:28 point

Is there a way to prevent the parts from falling ?

In the industry, I think they use different pastes with higher liquidus temperature for the bottom.

Can you try a temperature-resistant conformal coating before flipping the board ?

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davedarko wrote 03/27/2017 at 20:43 point

I thought they would glue the parts down first.

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Yann Guidon / YGDES wrote 03/27/2017 at 20:45 point

that's for the old, vintage parts likes 1206 or at most 0603...

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AVR (lordKiCAD) wrote 03/27/2017 at 20:47 point

yeah, today's process's rely on capilary action of the paste and pad surface

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K.C. Lee wrote 03/27/2017 at 20:58 point

They glue down the parts on the bottom side while wave soldering for through hole parts. The solder surface tension for small light parts should be sticky enough on a second pass of the reflow.

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Alex wrote 03/28/2017 at 09:27 point

As far as I know, is it all based on surface tension. As already written here. But in my mnual process this is not enough. I think I move it it much when soldering the second side. 

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Alex wrote 03/28/2017 at 09:29 point

some kind of coating or gluing could work if the coating/glue is heat resistant. But i am quite happy now with this 0402 version. So far didi not had that issue with 0402 LEDs. 

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