Re: Flex Circuits?

[TQuiroz]

Hi Bob,   I did one flex board about a year ago for a pulse discharge circuit using some custom surface-mount thyristors. We chose Kapton flex boards because we were working at 15kV and we needed to achieve high dielectric separation in a small area. The fact that the board was flexible was an added bonus. A few things I remember: Kapton (polyimide) comes in standard stock thicknesses of 1-mil intervals up to 5 mils. Pretty much all you can do on a rigid board can be done on a flex board. Dielectric strength is about 7kV per mil (25.4um), but goes down to 2.5kV at 300C. For board layout, flex circuits require special consideration. Make traces with round corners. Sharp turns create break points when flexing the board. When using surface-mount components, use footprints with rounded copper and solder-mask features. Oh, yes, my first 5 prototypes came about $2000 (including NREs and electrical test), but then again this was (still is) an Army project. We used Flex Circuits Technologies (www.flexctech.com) out of Minneapolis.   Tony