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BGA SOLDER BALL to SURFACE PAD size relationship

Robert Hutton-Squire

#4845

BGA SOLDER BALL to SURFACE PAD size relationship | 24 February, 2000

Hi, - any suggestions welcome...

I have a 484 pin ALTERA fineline BGA - ball pitch 1mm (40) - ball size 0.48mm (18.9)

What would you recommend for... 1. Surface pad size for the balls of this BGA device? 2. Stencil thickness/type and hole aperture and good printing?

Thanks, - Robert

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JAX

#4846

Re: BGA SOLDER BALL to SURFACE PAD size relationship | 24 February, 2000

Robert, Here's my recommendation's: Solder paste opening on screen should equal the solder mask opening on board. Stencil thickness at .008" but this should not be your main concern as stencil thickness should be determined by the fine pitch that are located on the board ( unless you have step down's ) That's just my opinion, I could be wrong!

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RDR

#4847

Re: BGA SOLDER BALL to SURFACE PAD size relationship | 24 February, 2000

#4848

Re: BGA SOLDER BALL to SURFACE PAD size relationship | 24 February, 2000

Robert: Ah, opinions are like mothers, everyone has one. Here's mine:

1 Goto the Altera site, get a copy of "AN 114," follow it. Generally, manufacturers are closer to the requirements of their components than others are. 2 Metal showing on the board pad SB the same size and shape as the metal showing on the BGA interposer. That'll give you balanced forces between the top and the bottom of the ball. No "torquing" for you laddie. 3 Type of mask / ball interface (SMD versus NSMD) SB the same on the BGA and the board. That'll give you balanced forces between the top and the bottom of the ball. 4 With a 0.006 inch thick stencil, assuming you have 0.025 inch pitch or less components on your board as well as the BGA, the BGA aperture SB the same size and shape as the metal showing on the pad.

Good luck and happy opinuating to all,

Dave F

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