A face-to-face chip stacking 7kV RMS digital isolator for automotive and industrial motor drive applications

A face-to-face chip stacking isolator structure, which makes it easy to enhance the insulation voltage, is proposed. Transmitter (Tx) and receiver (Rx) chips, each of which has a coil, are stacked and communicate through a magnetic coupling of the coils. The die attach film sandwiched by the two chips not only bonds the chips but also enhances the insulation voltage by taking advantage of its thickness. With test chips, the breakdown voltage of 7kV RMS is demonstrated and >20-year lifetime with a working voltage of 1.5kV is estimated by extrapolation of time-dependent dielectric breakdown results.