I am hoping to build an Arduino Nano type board with its own switching supply on board....


The chip is an SY8120l 4.2-18v Input - 500kHZ. You can make out the inductor placed on the bottom side (blue pads)
Would the circuit present problems with surrounding traces. Or is it even acceptable to have this contained in such a way?
DATASHEET: https://datasheet.lcsc.com/lcsc/2001171834_Silergy-Corp-SY8120IABC_C479076.pdf

Also some smps tend to have a low efficiency at very low currents (microamps). If the efficiency gets so bad like 1%, is it then
better to find a different solution? The datasheet on presents down to 10mA so can somebody with smps knowledge confirm
the characteristics of smps chips operating at low power consumption?

TIA

 

Keep an eye out. I saw mention of an extremely low power boost circuit but deleted the (spam) email before following up the link. If wrist watches can use boost converters for years at a time, or months at a time 50 years ago, you should be able to come up satisfactory solution.