Capacitor dissipation

I want to build a wireless charger for my wireless mouse. I found a nice writeup here.

**broken link removed**

The author used mica caps, but they are expensive.

The question is can I use a film capacitor in place of the mica one or do I need to worry about the dissipation factor in the cap running at 125KHz. ?

Film capacitors should work fine at 125kHz as long as the voltage rating is adequate.

You could try a film cap, with the circuit supply initially at a reduced voltage. Switch off and immediately test for warming of the cap. If no problem, repeat with successively higher supply voltages.