I know it is a bit late to make suggestions, but here is an idea for you guys:

In my work, I have done a bit of research on PCB trace inductors. From your description it seems like you have a coil of 4mmx2mm side cross section with 0.1mm thick wire plus winding and compression errors. Without the errors this makes about 800 turns, and in reality it could be a bit less.

800 turns passing 100mA is 80 ampere turns within your 11mmx2mm space. I will use this as my target field strength.

If you go with standard spec PCBs, track width is 8mil minimum, or 0.15mm, and can carry roughly 0.45A at this minimum trace width. The spacing minimum is also 0.15, making each wire 0.3mm.

Assuming you get an 8 layer PCB, 2mm thick:

4mm/0.3mm= 14 wires per layer x8layers = 112 turns x0.45A per turn = 50.4 Ampere turns within the same space.

This is a comparable value to what you have, the only catch would be you might need an amplifier to match the impedance (but that can be as simple as a couple of transistors or Op amp).


Personally, I like the idea of using a PCB because it offers a reliable source for custom inductors and transformers which is not dependent on your parts being available to order. It also ensures a pretty reproducible, rugged and reliable result (no flimsy wires). In your case, I remember you guys compaining about a coil manufacturer being unreliable and having to wind your own inductors, so I could really see it working for you.




- UD