1. Field of the Invention
The present invention relates generally to semiconductor package technology and, more particularly, to a chip-on-board (COB) package having a flip-chip assembly structure and to a manufacturing method thereof.
2. Description of the Related Art
An integrated circuit (IC) card, in which an IC chip is contained, can substitute for a conventional magnetic card. Generally, the IC chip is assembled in the form of typical COB package and then embedded in the IC card.
FIG. 1 shows, in a cross-sectional view, a conventional COB package used for the IC card. Referring to FIG. 1, the COB package 10 mounts in a card body 9 through one surface of the card body 9. Conductive patterns such as metal patterns 11 formed on the COB package 10 and exposed outside the card body 9 act as contact terminals of the IC card.
The metal patterns 11 are formed on an outer surface 12a of a thin, non-conductive film 12. An IC chip 13 is attached on an inner surface 12b of the non-conductive film 12. The non-conductive film 12 has several holes 12c formed near the IC chip 13. Metal wires 14 electrically couple the IC chip 13 to the metal patterns 11 through the holes 12c in the non-conductive film 12. The IC chip 13 and the metal wires 14 are encapsulated in a mold resin 15 provided on the inner surface 12b of the non-conductive film 12. The mold resin 15 may protect and fix the IC chip 13 and the metal wires 14.
A typical package assembly process may be used to manufacture the aforementioned conventional COB package 10. Therefore, mass-productivity may be a merit of the conventional COB package 10. However, the IC card can be very thin, e.g., less than one millimeter thick, and can be inherently flexible. The conventional COB package 10 may tend to be affected by external force. In the conventional COB package 10, an active surface 13a of the IC chip 13 faces toward the inside of the card body 9 while the metal patterns 11 face toward the outside of the card body 9. This makes the length of the metal wire 14 relatively longer. Often, poorer electrical connections arise from longer metal wires 14 in spite of protection by the mold resin 15.
FIG. 2 shows in cross-section another conventional COB package used for the IC card. COB package 20 has a flip chip assembly structure instead of the metal wires and the mold resin as discussed above.
Referring to FIG. 2, an active surface 23a of an IC chip 23 faces toward a non-conductive film 22. Conductive bumps such as metal bumps 24 are formed on the active surface 23a of the IC chip 23, and second metal patterns 21a are formed on an inner surface 22b of the non-conductive film 22. The second metal patterns 21a are electrically coupled through interconnection vias 21b to first metal patterns 21 formed on an outer surface 22a of the non-conductive film 22. The metal bumps 24 are mechanically joined to the second metal patterns 21a, providing electrical paths between the IC chip 23 and the first metal patterns 21.
Metal bumps 24 provide relatively shorter and more reliable electrical paths. The above-discussed flip chip assembly structure may not only have less possibility of poor electrical connections, but also may have no need of the mold resin. Conventional COB package 20, however, necessarily requires the second metal patterns 21a on the inner surface 22b of the non-conductive film 22. This represents greater production cost in comparison with the previous example using the metal wires.
The first and second metal patterns 21 and 21a may be formed from metal plates, which are bonded to both surfaces 22a and 22b of the non-conductive film 22 and then patterned by selective etching in a photolithographic process. Therefore, using the second metal patterns 21a as well as the metal bumps 24 may incur relatively higher production cost in comparison with using the metal wires. The process of forming the second metal patterns 21a may be carried out separately from the process of forming the first metal patterns 21. As a result, this conventional COB package 20 may have no significant advantage in its manufacturing method.