These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
a)-4(c) is a plan view of various shapes and sizes of pads in different embodiments of the present invention.
It is noted that the drawings of the invention are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
The following paragraphs discuss the comparative studies of different embodiments of the present invention with reference to conventional round shaped electrical interconnect pads illustrating the difference in packing density.
Implementation of the invention can take the form of any one of the embodiments illustrated in
a) illustrates a hexagonal pad with a conventional round electrical interconnect pad (hereafter simply referred to as round pad) inscribed therein. Results from a comparison study set out in Table 1(a) shows that the hexagonal pad is approximately 10% greater in area than the conventional round pad.
For example, the round pad area at round pad spacing of approximately 0.50 nm is approximately 0.196 nm2 while the hexagonal pad area at hexagonal pad spacing of approximately 0.50 mm is approximately 0.217 mm2. This difference in area is approximately 10%. As the pad spacing decreases from approximately 0.50 nm to approximately 0.10 nm, the additional area from hexagonal pads remain at approximately 10% greater than conventional round pads. With a greater area, the electrical contact surface is increased which improves the connectivity of devices to chip carrier 34 (in
b) illustrates a hexagonal pad with conventional round pad where the total area of both pads is the same. The result of a comparative study between the two types of pad is shown in Table 1(b).
From Table 1(b), where the area of the hexagonal pads are comparably constant with the area of conventional round pads, the spacing between the hexagonal pads is comparatively greater than the spacing of conventional round pads. For example, at pad area of approximately 0.196 mm2, the spacing between conventional round pads is approximately 0.50 mm while hexagonal pads of the same area have a spacing of approximately 0.524 mm. The result also shows that the percentage increase in spacing between hexagonal pads increases as the spacing becomes smaller. For example, at a pad area of approximately 0.196 mm2, where round pad spacing is approximately 0.50 mm and where the spacing between hexagonal pads is approximately 0.524 mm, the percentage increase in the spacing comparing hexagonal pads to conventional round pads is approximately 4.8%. At the area of approximately 0.63 mm2, where the spacing between hexagonally shaped pads is approximately 0.143 mm and the spacing of round shaped conventional pads is approximately 0.10 mm, the percentage increase in spacing of hexagonal pads as compared to round pads is at approximately 42.9%. The trend shown in Table 1(b) suggests that hexagonally shaped pads can be packed in an array at a higher density than round shaped conventional pads.
c) illustrates an embodiment where a hexagonal pad is inscribed in a conventional round pad.
Table 1(c) shows the results of a comparative study of the characteristics of the two types of pads. The hexagonal pad has a smaller area than the conventional round pad by a percentage of approximately 17.3%. The smaller area affords greater spacing between the hexagonal pads. For example, comparing hexagonal pad of area at approximately 0.162 mm2 and round pad area at approximately 0.196 mm2, the spacing between round pads is approximately 0.50 mm while the spacing between hexagonal pads is approximately 0.567 mm. This comparative increase in spacing progresses with increase in hexagonal pad area. For example, comparing a hexagonal pad with an area of approximately 0.162 mm2 to a hexagonal pad with an area of approximately 0.526 mm2, the percentage increase in spacing is from approximately 13.4% to approximately 120.6%. This indicates that a slight decrease in pad area will produce a significantly larger spacing between pads. This increased spacing reduces the risk of shorting between pads, or can be used for surface wiring as compared to the use of conventional round pads.
Returning to
The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of the invention as defined by the accompanying claims.