nrf51822-ceaa package PCB questions

Question

Hi, 
 I am currently designing a PCB to accept the BGA version of the nrf51822. 
 The Altium reference designs for the CEAA package (BGA) all include vias directly in the BGA pads, which is normally not suitable for reliable manufacture as solder can flow down the via during the assembly process and compromise electrical connectivity between the pad and component. 
 Is this an error, or for some reason is it advisable to have vias in the pads for this particular package? 
 As a secondary question, is there any reason not to use the package over the VQFN version? I read in the datasheets that there is an optical vulnerability, but is there any other reasons that the BGA package would not be production ready? 
 Thank you,
Jamie

Ole Morten · Accepted Answer

Sorry for the delay in answering. You're right that the problem with solder flowing down the via is avoided by filling the vias before soldering. 
 The CSP package is most definitely production-ready, and from a pure technical perspective there isn't any particular reason to not use it, except for the light-sensitivity as you say. This can for example be avoided by putting epoxy or similar over it. 
 In addition, you will often need a 4-layer PCB with finer resolution to be able to fully use all I/Os, so it might increase the cost of the hardware design. The CSP chip itself may also be more expensive than the QFN variant, but this is something you should check with your distributor.

nrf51822-ceaa package PCB questions

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