1. Field of the Invention
This invention relates in general to improved carriers for electronic devices and, more particularly, to improved carriers for holding semiconductor die in a stacked relationship.
2. Background Art
Many electronic devices, particularly semiconductor devices, are manufactured in wafer form and then cut apart into individual die. The good die are picked out and the balance discarded. The good die are then bonded into individual packages or mounted directly onto ceramic or plastic circuit boards and/or tapes. It is frequently the case that wafer fabrication is carried out in one manufacturing location while die bonding and other assembly operations are carried out in a geographically separated location, sometimes even by a different company. Accordingly, large number of semiconductor die must be transported over large distances between the wafer manufacturing locations and the assembly locations. Since the semiconductor die are both fragile and expensive, the development of reliable and convenient shipping and handling containers is a matter of great commercial significance. These shipping and handling containers are generally referred to as die carriers.
Two general types of die carriers have been used in the prior art. The first involves a plastic tray which contains a large number of shallow depressions, much like an egg crate with flat bottomed compartments. One die is placed in each compartment and the plastic tray is covered with a lid. The die are generally loose within the compartment so that some jostling of the die takes place during handling and shipment. This jostling can result in chipping, scratching, or other defects. The second die carrier scheme utilizes an adhesive coated plastic tape or other tacky surface to which the die are stuck. The sticky or tacky-tape usually forms the bottom of a shallow dish. Once the die are in place, a protective cover is provided. Compartments are not needed with the tacky-tape type of container and, in general, the die do not move relative to the container during handling and shipment.
These prior art methods have a number of deficiencies, for example:
(1) the volumetric efficiency of these packing arrangements is poor. The die are separated laterally within the carrier, and even though the carriers may be stacked one upon the other the number of die per unit volume is low.
(2) the tacky-tape cannot be reused and must be discarded after shipment.
(3) the egg crate carriers, even though reusable, are bulky and expensive to ship back to the point of origin;
(4) these prior art carriers are difficult and/or expensive to mate with automated assembly equipment. The lateral separation of the die in the carriers requires that either the carrier or the die pick-up arm be repositioned as each die is removed. Thus, an additional two-dimensional translational motion must be provided in the handling and assembly equipment in addition to that ordinarily required for the loading, unloading, and assembly operations themselves. A further complication with respect to automated assembly is that neither the egg crate carrier nor the sticky tape carrier provides a reliable positional reference or die-to-die spacing. As a consequence the handling and assembly equipment must be able to accommodate a substantial variation in the individual die positions during loading, unloading, and assembly. This increases the cost of such equipment. Thus, a need continues to exist for improved handling and shipping containers for electronic devices, particularly semiconductor die carriers, which overcome these and other deficiencies of the prior art.
Accordingly, it is an object of the present invention to provide an improved handling and shipping container for electronic devices, especially an improved carrier for semiconductor devices, which is rugged, easily shipped, and inexpensive to manufacture and use.
It is a further object of the present invention to provide an improved carrier for electronic devices, which holds the devices firmly but gently during shipment to avoid jostling and which is completely reuseable.
It is an additional object of the present invention to provide an improved carrier for electronic devices which has a large and variable capacity, which is compact, and which has a high volumetric efficiency.
It is a further objective of the present invention to provide an improved carrier for electronic devices which is easy to load and unload, and which is particularly adapted for use with automated loading and unloading equipment, and with automated assembly equipment.