In some embodiments as in FIG. 9, circle 142 is also drawn according to simulation or experiment results. The radius of circle 142 may be small, and hence some of openings 158 that are outside of corner regions 160 are also outside of circle 142. Accordingly, as shown in FIG. 6, some of openings 158 (marked as 158″) that are outside of the circle 142 are also elongated openings 158A, while the openings 158 that are outside of corner regions 160, but inside circle 142, are non-elongated openings 158B.

FIGS. 12A and 12B illustrate the top views of some exemplary elongated openings 158A and the respective metal pad 150 (also refer to FIG. 1) that are underlying and in contact with the elongated openings 158A. In accordance with some embodiments, metal pad 150 has a non-elongated shape such as a circle (as shown in FIG. 12A), a square, a hexagon, an octagon, or the like. In alternative embodiments, as shown in FIG. 12B, metal pad 150 may also have an elongated shape that fits the shape of the respective elongated opening 158A. Furthermore, the long axis of metal pad 150 may be parallel to, and may overlap, the long axis of the respective elongated opening 158A. By designing metal pad 150 to be elongated, the reliability of the respective package may be further improved.