Optimizing PCB space with footprint size

Question

Hi, 
 looking to nRF52832 reference PCB designs I've noticed that BOM contains different element sizes for different packages. Such, most of capacitors for QFN48 have 0402 footprint, when WLCSP suggests 0201. The same for crystals. So I'm thinking about saving some space with smaller packages. 
 It's reasonable to avoid extra work recalculating the matching network and keep it intact. Also, replacing the 32MHz crystal (which itself is of the same footprint) capacitors won't really change anything: 
 
 But how about other elements? Would it be safe to follow WLCSP BOM as a packaging guideline? 
 Also, for my understanding moving them won't affect RF performance, right? 
 Thanks!

Kaja · Accepted Answer

Hi Mike, first: our reference design is with a 1.6 mm thick FR4 pcb. Changing the competent size of the component in the radio matching network, will most likely require that you tune the components values, but this is something that you usually have to do anyway, if you don't follow the reference design 1:1. The components you have listed in the answer, will not effect the RF performance. My best tips: Send us your design files, so that we can give you a proper review and advice, when you are done with the schematic and/or layout. We can also assist you on tuning matching network for the radio and antenna. Best regards, Kaja

Optimizing PCB space with footprint size

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