Preparation method of power module

The invention provides a preparation method of a power module. The method comprises the steps that a substrate is provided, a first conductive area, a second conductive area, a third conductive area and a plurality of signal connection areas are arranged on the substrate, the first conductive area comprises a positive electrode connection area, the second conductive area comprises an alternating current connection area, and the third conductive area comprises a negative electrode connection area; connecting the plurality of upper and lower bridge chips to the first and second conductive regions, respectively; respectively connecting the front surfaces of the upper bridge chips and the front surfaces of the lower bridge chips to the second conductive region and the third conductive region through independent metal sheets; the grid electrodes of the upper bridge chips and the grid electrodes of the lower bridge chips are correspondingly connected to a signal connection area through electric leads; and performin