This invention relates generally to semiconductors and, more particularly, to an apparatus for processing semiconductor lead frames, including single semiconductor packages. The invention also relates to a method of processing semiconductor lead frames, including single semiconductor packages.
Integrated circuit chips are currently utilized in a wide variety of applications including computers, automobiles, video cassette recorders (VCR's), stereos, etc. After integrated circuit chips are manufactured, they are mounted to lead frames for further processing before they can be utilized for a specific application. The integrated circuit chips are mounted to lead frames by bonding the lead wires of the lead frame to the terminals of the integrated circuit. Then, each integrated circuit chip and its associated lead wires are encapsulated in a housing by a molding operation. The lead frames are then subjected to a multi-step process to create individual integrated circuits or "packages" for specific applications.
One step in this process consists of punching out and removing the portions of the frame, called dam bars, which initially provide support for the leads of the lead frame. The dam bars are removed to electrically isolate the frame leads from each other. Generally, this process is accomplished with a die machine. Prior to the dam bar step, small lateral projections on the sides of the molded housing, called flashing, which are created by the molding operation, must be removed. The flashing must be removed to prevent them from jamming the die machine during the dam bar step. This step is called deflash. The leads of the lead frame must then be cut to a constant length. This step is called trimming. Next, the leads of the lead frame are formed by cutting the tie-bars which connect adjacent leads and bending the leads to the desired configuration. Since the leads must conform to very strict tolerances after forming, the angles and dimensions of the formed leads are checked. This step is called checking. Finally the molded resin body is cut from the lead frame, or singulated, to provide an individual semiconductor product which is placed in a package or holder. The single semiconductor product must also be marked with a product number and a product name. If any mistakes occur in the processing of the lead frame, it may be possible to reprocess the lead frame in order to correct these mistakes. This step is called lead conditioning. Some of these steps are generally shown in U.S. Pat. No. 5,038,453, U.S. Pat. No. 4,885,837, and U.S. Pat. No. 4,627,159.
The standard apparatus used for manufacturing semiconductor lead frames includes a linear track along which are positioned a plurality of stations housing tools for accomplishing the steps of the multi-step process described above. As the lead frame travels along the track, the tools at the stations interact with the lead frame to accomplish a specific task of this process. This type of apparatus has proven to work; however, there are many disadvantages of such a system. It is difficult to increase productivity because only one or two packages on the lead frame can be processed at any one time at a station. If a linear machine were to be modified to process more packages at each station, such as processing the whole lead frame simultaneously at each station, the length of the machine would be too large. Also, if it is desired to perform a different task at a station, it is necessary to replace the whole die, which is time consuming and expensive, since the die accounts for a large percentage of the cost of the machine. In order to avoid replacing the dies to perform a different task at a station, dies which perform all of the desired tasks can be installed along the track. However, this also results in a machine which is too large. The dies at each station must also be replaced if it is desired to use the apparatus to process lead frames with different pitch distances between packages. Therefore, there is a need for an apparatus for processing lead frames which has an increased processing yield which occupies a minimum amount of space. There is also a need for an apparatus for processing lead frames which can be quickly and inexpensively retooled to perform different processing steps at each station and to process different types and lengths of lead frames. In this connection, there is a need for such an apparatus which can process a single semiconductor package.