eMMC NC Pad Removal

[jebin]

Hi Robert,
I have a eMMC Pitch is 0.508mm (Package - P-WFBGA153-1113-0.50) BGA fanout due to higher PCB price i want to use through hole Vias. Can i remove few of NC Pads Footprint from the PCB? if i remove the NC Pads any assembly or performance related issues will arise in the feature?

Jebin

[Paul van Avesaath]

actually that seems a good idea.. never done it.. i dont think that it would be a problem. you should double check with your manufacturer..
normally you make a full footprint, but if you would specifically to that part only than i kind of like the idea... just be sure you will not use the footprint for other parts.. also you probably should remove the NC pins of the schematic symbol too otherwise altium notices the difference in pin count..

[jebin]

Hi Paul,
Thanks for the replay.

Jebin

[robertferanec]

I have never done it. I am not really sure how the solder would behave (you know, when you melt down the ball and then press the chip down to PCB with solder mask).

[Paul van Avesaath]

normally when heating "the balls" would stay on the pad of the BGA, becuase there is no footprint pad and thus no added solder paste to make the connections. you might want to double check with manufacturing before doing this.. but still i like the idea.. those Emmc chips are way to small for normal rouintg.. and if they would just implement the connection pins on the outside.. but noooooooo.. they have to make it hard for us... sometimes i think that people who design chip packages should have at least some knowledge of PCB layout.. anywasy that was my rant for the day... let me know if you have tryed it and if it works.. (note: Make sure that if you have a via beneath the floating ball has solder resist on there.. )

[robertferanec]

normally when heating "the balls" would stay on the pad of the BGA, becuase there is no footprint pad and thus no added solder paste to make the connections

It will probably stay connected to the BGA pin, I am only wondering if it stays 100% centered and will not have intentions to flow on side and merge with neighbor pad.

[jebin]

I have posted same query to eMMC manufacturer they suggested that not to remove pads and draw traces. The reason behind is, if i do that it will create a parasitic capacitance this will affect the signal quality of the SDIO data lines and especially near to the internal regulator section.

[robertferanec]

jebin thank you for sharing their suggestions.

[Paul van Avesaath]

well that is kind of weird though.. since the pads will not be connected to GND, but left floating. (at least for my Emmc MTFC8GAKAJCN-4MIT)
also suggesting to connect it through a wire, kind of sucks.. because to connect the inner of the 3 rows you need a 2mil line or something..
why they can't just move the SDIO connections to the outside ring or inside ring beats me...