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BGA flux dipping process

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BGA flux dipping process | 1 June, 2009

i need some inputs regarding this process. is this really eliminates voids and other solderability issues on BGA's?

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BGA flux dipping process | 2 June, 2009

Early on when we started looking at BGAs we tried dipping. We've done it in production for a couple decades with flipchips. Dip fluxing BGAs worked fine in the lab but we ended up starting production with screen printed flux for cycle time reasons. We abandoned it for paste print pretty quickly when we started getting head in pillow defects - we needed the paste to help make up the gap when BGAs warp.

That was years ago when large BGAs and 1 mm pitch were common. Maybe smaller BGAs are less prone to warping and flux would work out OK, but cycle times requirements would prevent us from doing it on most of our lines.

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BGA flux dipping process | 2 June, 2009

thanks for the inputs. we are planning to run on fuji nxt i think cycle time will not be an issue.

i still have another question if we can still use the same reflow profile for paste? or do we need to create another profile?

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BGA flux dipping process | 2 June, 2009

We have been doing BGA's for years now, and I would suggest updating your profile and place a thermal couple on the BGA, keep in mind the bigger the part the more heat it will need, We stencil print all of BGA's from simple bga's to complex ones, your stencil provider if they know what they ware doing will be able to work with you on the stencil thickness. (DEK Rules), I also place BGA's without solder paste. Heres the most important trick to BGA's BAKE them first, they hold more moisture than any part i have seen. Hope this helps.

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BGA flux dipping process | 4 June, 2009

For low volume work and repair, just use a brush dipped in tacky flux to apply flux to the ball array.

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BGA flux dipping process | 15 June, 2009

IMHO I would suggest that if you are using flux only during a BGA placement on a small run, that you first tin the pads with your soldering iron, then level the pads back out with wick. Accomplishes two things; adds a little metal to the joint to make up for some warpage, and can help eliminate the head in pillow effect as well, since you are soldering the BGA sphere to the solder already on the pad. Naturally, this is already the case in a rework situation, where the BGA is being replaced. `Hege

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BGA flux dipping process | 16 June, 2009


If your using NXT to place these BGA's then you must be doing large runs.

BGA's are the most easy part to place, and don't worry about them. Just stencil paste down for them as any other component. But we use 1:1 reduction on our stencil, so we don't get paste release issues. Also, we use electroform stencils, as DEK make them cheap, and they are so much nicer than any other type of stencil we have used so far.

Don't know why you would want to use just flux, on such an fast line, when pasting them will be ok.


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