a spiral inductor

This is a 3-layer spiral inductor with copper conductor and
polyimide dielectric .

My question is :
How is the quality factor when I put this spiral inducor in top layer
or in bottom layer ???

it is good to put the inductor in the top layer , the metal in the top layer is a thick metal which give a low seise resistance which will improve the quality factor

also the capacitance between the inductor and the substrate is less which is good also

Hi,

I am nto quite sure what type of spiral inductor you are talking about, but also thing it is in general better to place the inductor on the top layer.

1. Parasitic capacitance to ground is lower, self resonance is higher
2. Current induced in ground is smaller. It impacts the inductance value, it will be lower if the inductor is closer to the ground.
3. From 1. and 2. , Q factor of inductor on the top layer will be greater and operating frequency range higher

flyhigh