A self-similarity heat sink (SSHS) exhibits better overall performance than a conventional heat sink whereas although serious flow maldistribution still occurs. A modification to a conventional SSHS is proposed to overcome this disadvantage and obtain a more uniform heat transfer. Straight fins on the cover plate were replaced by zigzag fins to form a smaller incidence angle of fluid from the inlet manifold to the overflow channels, and the inlet manifold with constant cross-section was changed to a tapered inlet manifold to restrict excess flow to the downstream end of the inlet manifold. Numerical analysis was subsequently conducted to verify the modification. The results showed that the modification scheme successfully addressed the disadvantage of flow maldistribution of the original SSHS. Effects of the incidence angle on flow and heat transfer inside a single unit were analyzed at flow rates of 0.58-1.73 kg/h. The optimal incidence angle was found to be in the range of 20 degrees-25 degrees. For an entire SSHS with this optimal design, uniformity in flow distribution and heat transfer was significantly improved compared with original design, although the pressure drop increased slightly.