Presumably the balls are too close together to get a track through to 
the centre? Why don't you ask the manufacturer how you're supposed to do it?

It might make them come up with a better layout next around (this wasn't 
made by my company I hope?).

Regards,



Upton, Shawn wrote:
> I am looking at a part with 0.2mm balls on the bottom, in a 3x3 pattern.
> I need to get a trace to the center ball, but one of the outer balls is
> not in use.  I'm thinking of just running  the trace under the solder
> ball and counting on the soldermask to prevent the ball from attaching
> to the PCB.  Good/bad?  I'm a bit worried that when the solderballs
> reflow, the lack of a pad under the unused solderball might cause that
> side of the part to sit higher, as there wasn't a pad to wick away that
> solder.
>   
Eric Christison Msc
Mechanical Engineer
Home Personal, Communication Sector
Imaging Division

STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom

Tel:	+44 (0)131 336 6165
Fax:	+ 44 (0)131 336 6001

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