Minimizing parasitic capacitance in set-up

[jto2]

Hello,

I'm running an experiment with a MEMS variable capacitor device. I want to minimize the parasitic capacitance of the electrical connections and wires. What kind of wires should I make my connections with? Stranded wires, solid wires, coax cables? My devices have 50pF or less capacitance, so my measurements will be off if there is a lot of stray capacitance from the set-up.

Thanks

[fromm8]

Hello John,

Is your variable capacitor differential or not?

Regards

Frank R. 

[jto2]

When I'm characterizing the capacitor, one end of the capacitor is to ground. When I'm using the variable capacitor in other set-ups, it's differential.

[fromm8]

Hi john, sorry for aask you again before give an answer but, I would like to know first what kind of "MEMS variable capacitor device" you have, do you have a model number or its name?

Regards

Frank R.

[jto2]

It's made from a series of interdigitated electrodes fabricated on doped silicon. I fabricate them myself in a clean room as part of my grad school research. After fabricating the devices, I mount them with epoxy to a custom made PCB. I use gold wire bonds to make electrical connections from the MEMS to the PCB.

I have the option of using coax connections to the PCB because I have SMA edge connectors. I could also just solder a male pin head, and connect wires that way. I don't have pictures now, but if it is unclear what I an saying, I could provide some.

Thanks for the help,
John

[fromm8]

John,

The truth is that I do not see a big difference between these options if you are talking about parasitic capacitance. This cable is going to be part of your connection to a different device, this is not part of your PCB (where it is a big deal), so I really do not see a difference. However if you have the option of using coax connections to the PCB, go ahead.

Regards

Frank R.