A vehicle power module assembly including an array of frames each defining a passthrough and step is provided. The frames may be stacked such that the passthroughs are in at least partial registration with one another and the steps align to define an inlet manifold having first and second chambers extending a length of the array. The chambers may be partially open to one another such that the steps influence a momentum of coolant traveling from the first to the second chamber. A pair of endplates may be disposed on either end of the array and configured to retain the frames therebetween. Each of the frames may further define a pair of channels and may be arranged with one another to define a power stage cavity therebetween. A power stage may be disposed within the power stage cavity.