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How to reduce solder joint voids of LED without using vacuum reflow?

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SMTA-Rogers

#82491

How to reduce solder joint voids of LED without using vacuum reflow? | 6 May, 2019

Hello! Do you have a better stencil design to reduce the large area of solder joint voids? Or is there a suggested way to set the reflow profile? Or are there other process improvements to make the solder joint at the LED pad less than 10% per void? Thanks a lot.

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#82493

How to reduce solder joint voids of LED without using vacuum reflow? | 6 May, 2019

There are quite a few papers out there on the subject. Just enter "SMT void reduction" into google or other search engine and take your pick.

That said, slow ramp rates and paste volume reduction are a good place to start. Although I haven't tried it specifically to reduce voiding, I would think that a stencil thickness reduction might work better than an aperture reduction, assuming the actual volume reduction was the same.

There are also several "low void" pastes out there.

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#82500

How to reduce solder joint voids of LED without using vacuum reflow? | 7 May, 2019

I have personally never seen a reflow profile change reduce voids. We have invited "experts" in to demonstrate this claim. They were unable to.

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#82501

How to reduce solder joint voids of LED without using vacuum reflow? | 7 May, 2019

Probably just means you started out with an optimal profile.

I suspect that not everyone does. ;)

It seems like we did have some luck with profile adjustments in one instance with some QFN's with a large thermal pad. Like I said, though, the profile was basically trash to begin with.

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#82519

How to reduce solder joint voids of LED without using vacuum reflow? | 9 May, 2019

Hi, You can work on improving stencil design, having the perfect profile and other process improvements but it may be the paste itself letting you down. We have put a lot of work into developing our solder pastes to significantly reduce voiding. Your supplier should be able to help with choosing the correct paste for your application.

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