Integrated circuit device are conventionally enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection between the integrated circuit device and printed circuit boards. FIG. 1 is a cross sectional view of an inexpensive, conventional molded plastic package 1 known as a plastic dual in line package ("p-dip"). The elements of package 10 include an integrated circuit device 12, adhesive material (not shown) to attach integrated circuit device 12 to die pad 17, bond wires 13 that electrically connect bonding pads 14 on integrated circuit device 12 to individual leads 15 of the leadframe, and an adhesive plastic encapsulant material which covers the other components and forms package body 16.
In FIG. 1, molding compound (a.k.a., encapsulant material) is molded above and below device 12, leads 15 and die pad 17 to form package body 16. The peripheral sides 18 of package body 16 are sloped to facilitate release from the mold used to make the package. Leads 15 extend from package body 16. There are a variety of well-known alternative styles for the finishing the leads of such a package, including PLCC and gull wing styles.
Further background information concerning conventional plastic integrated circuit packages and leadframes is contained in chapter 8 of the book Microelectronics Packaging Handbook (1989), which was edited by R. Tummala and E. Rymaszewski, and is published by Van Nostrand Reinhold, 115 Fifth Avenue, New York, N.Y.
The operation of certain types of optical integrated circuit devices, such as erasable programmable read-only memory devices ("EPROM"), charge coupled devices ("CCD"), and camera-type devices require that light be applied to a light-sensitive cell on a surface of the device. For such devices, standard p-dip packages cannot be used. FIG. 2 is an example of a conventional molded package 20 for an optical integrated circuit device 23.
Package 20 includes some of the same features as package 10 of FIG. 1, so the same reference numbers will be used in FIG. 2. Package 20 of FIG. 2 includes leads 15 and die pad 17, upon which optical integrated circuit device 23 rests. Bond wires 13 extend between individual bonding pads 14 on optical device 23 and an individual lead 15. Encapsulant material is molded above and below the leadframe to form package body 25.
Below leads 15, package 20 of FIG. 2 is the same as package 10 of FIG. 1. Above leads 15, however, package 20 is modified to accommodate optical integrated circuit device 23. In particular, a portion of molded package body 25, namely, support structure 21, is formed on and above portions of leads 15. Support structure 21, which is integral with package body 25 and formed of the same material, surrounds optical device 23 and supports an optically clear plastic or glass cover 27 above optical device 23. Cover 19 transmits light to a light sensitive cell 24 on optical device 23.
Package 20 of FIG. 2 has two significant drawbacks. First, it is difficult to make. Second, it is expensive. Accordingly, there is a need for an inexpensive, easy-to-make package for optical integrated circuit devices.