In the field of integrated circuits, the use of plastic molded packages for providing mechanical and environmental protection for the integrated circuit chips has become commonplace. Such plastic molded packages are primarily beneficial due to their low cost of manufacture relative to ceramic encapsulated packages, particularly in avoiding the high cost of the piece parts of ceramic encapsulated packages.
Complementary metal-oxide-semiconductor (CMOS) technology for the design and fabrication of integrated circuits has also become more popular in recent years, due to the very low level of standby power dissipation in circuits fabricated according to this technology. Low power CMOS integrated circuits have enabled the widespread use of battery power in modern electronic systems, whether as backup or as primary power, as the operating life of the batteries in powering these low power circuits can be quite long.
Implementation of battery-powered integrated circuits into electronic systems, even as backup power, requires an additional degree of complexity in the system design and manufacture. As such, it has been desirable for some time to integrally package an electrical cell, or battery, within the integrated circuit package. Copending application Ser. No. 07/995,665, filed Dec. 21, 1992, entitled "Surface Mountable Integrated Circuit Package with Integrated Battery Mount" assigned to SGS-Thomson Microelectronics, Inc. and incorporated herein by this reference, describes an integrated circuit package of the surface-mountable type within which a battery is mounted to leads that extend from the side of an internal package body, with a housing attached to the package over the battery. Gaps between the housing and the internal package body provide thermal insulation of the battery from the package body, so that the circuit may be subjected to solder reflow mounting to a circuit board in the conventional sense for surface mountable packages, while insulating the battery from the high soldering temperatures.
By way of further background, it is desirable and customary in the art to test each integrated circuit in a fully functional manner, so that the integrated circuit customer can receive lots of the packaged circuit that are substantially free of defects. In many cases, however, integrated circuits having a battery backup mode cannot have their backup functionality tested with the actual battery with which they will be installed, but instead can only be tested in a circumstantial manner with an external battery source. Furthermore, while prior hybrid package techniques that include a battery with the integrated circuit are known, such prior techniques require high cost ceramic piece parts (such as headers, lids and the like), and thus are not suitable for use with high quantity commodity circuits such as random access memories, which are to be sold in highly price-competitive markets.
It is therefore an object of the present invention to provide a molded integrated circuit package within which both an integrated circuit and a battery power source are molded.
It is a further object of the present invention to provide such a package which enables complete functional testing of the integrated circuit, including the functionality of its battery backup capability.
It is a further object of the present invention to provide such a package which includes an inner package for the integrated circuit chip itself, so that assembly of the circuit and battery package may be done with a reduced risk that the integrated circuit chip will be damaged.
Other objects and advantages of the present invention will be apparent to those of ordinary skill in the art having reference to the following specification together with the drawings.