A three-dimensional grid array interposer includes first and second arrays of electrical terminals arranged in grid-like patterns having grid pitches of (X1,Y1) and (X2,Y2), where each electrical terminal of the first array corresponds to an electrical terminal of the second array, forming a corresponding pair of electrical terminals. The interposer also includes a plurality of stacked substrates, each substrate having a first surface, a second surface, a first edge, and a second edge, with each substrate having a row of electrical terminals of the first array along the first surface at the first edge and a row of electrical terminals of the second array along the first surface at its second edge, with a trace running along the first surface between each electrical terminal of each corresponding pair of electrical terminals. Spacers can be used to provide desired space transformation.