I have a flex circuit application which requires low trace to trace leakage current (< 10 nA @ 10 V (1 G ohm), 75 C, low humidity). Layer to layer leakage measures ~3 nA. The construction is 4 layer with 7 mil lines and spaces. The critical traces are ~14 inches long and not guarded.  This translates to a required resistivity of ~2E12 ohms/square for the adhesive system. Samples of this design show lot to lot variation from 3 nA to 300 nA @ 10 V.

Does anyone have a flex process optimized for high insulation resistance?

Thanks,

Wes Melander
Agilent Technologies

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