Abstract: Electronic systems utilizing a plurality of integrated circuit packages having a stackable heat sink assembly is formed by press-fit assembly of two or more identical fin layers. Each fin layer is formed using powdered metallurgy and has a button-like projection extending from its bottom surface and a recess opening in its top surface. The button-like projection and recess opening are sized and shaped such that an interference fit is formed when the buttonlike projection of one fin layer is pressed into the recess of another fin layer. The use of an adaptor to increase or decrease the effective size of the button-like projection of the bottom-most fin layer is described. Relieving gases that may be entrapped in the recess during assembly is described. Circular, elliptical and polygonal shapes (outlines) for the fin layers are described.