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BGA APATURE

MRMAINT

#26261

BGA APATURE | 5 November, 2003

HAS ANYONE EVER USED SQUARE APATURES ON A STENCIL FOR BGA'S IF SO WHAT IS THE REASONING BEHIND IT.

THANKS

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#26262

BGA APATURE | 5 November, 2003

I just did a bga job with square aperture's, the reasoning is for enhanced print release and additional paste volume. Be careful of the edge to edge clearance between the stencil openings, I don't recommend going below a 8 mil clearance, you could be setting yourself up for a bridging problem. Hope this helps!!!

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Stephen

#26273

BGA APATURE | 5 November, 2003

Make sure that the side of the square is the diameter of the pad, That is that the circle is inside the square not that the square is inside the circle. normally the aperatures are smaller than the pad to get gasketing. In this case the idea is to get more paste. Where I am now we use round aperatures and round pads. In the past I used square aperatures on the round BGA pads and round aperatures on square 0603 or 0402 pads.

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#26274

BGA APATURE | 5 November, 2003

I also have used square apps on the BGA's, this also allows for a bit more play in alignment of the ball to pad,

I am interested in the reasons why to use round apps on 0603's and 0402's ???

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Gabriele

#26294

BGA APATURE | 7 November, 2003

we experimented round pad for 0402, it improves chip self alignment and reduce tomb stone effects. On 0603, half round shape also gave guud results.

G

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