Mercury process gold ballbond removal apparatus

Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...

Reexamination Certificate

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C134S002000, C134S010000, C134S016000, C134S018000, C134S021000, C134S026000, C134S028000, C134S032000, C134S034000, C134S036000, C134S041000, C134S042000, C134S061000, C134S076000, C134S083000, C134S111000

Reexamination Certificate

active

06294028

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus and method for reducing the risk of environmental contamination by toxic chemicals, and, in particular, to an apparatus and method for reducing the risk of environmental contamination by mercury and mercury salts used during the removal of gold ballbonds from the pads of a semiconductor device.
2. Description of Related Art
In the course of the failure analysis of semiconductor devices, one of the first steps involves the removal of the gold ball bonds that are used to connect the pads of the semiconductor device to the module leads. It is well known that gold will dissolve in liquid mercury and the technique is used to remove the gold ball bonds from semiconductor pads. For example, in U.S. Pat. No. 5,424,254, a semiconductor chip is laid down to float in an agitated mercury bath to remove gold ball bond connections. Generally, the technique involves black waxing the semiconductor device to a glass slide which is then dipped into a beaker of mercury, then into a beaker of nitric acid, then in a beaker of water, and then rinsed under a spigot in a sink. This process can be carried out manually, or more commonly by an automated carrier transfer system. In U.S Pat. No. 5,429,642, a method and apparatus is disclosed for transferring wafers from one processing station to another in a clean room or on a clean bench, to be dipped into a chemical liquid at each station.
During the gold ball bond removal process, when the dipped slide is removed from the mercury bath, particles of mercury remain attached to the slide and semiconductor device and are carried over into the nitric acid bath. These residual particles are dissolved in the nitric acid bath. The nitric acid is then removed from the slide and device by the water rinse. During the water rinse, it is possible for dissolved mercury to precipitate out as liquid mercury. It is also possible, that during movement of the slide from bath to bath, mercury particles, acid containing mercury salts, or water containing mercury salts, will spill or drip from the slide and down onto the work space or area. For health and environmental reasons, liquid mercury and liquids containing mercury salts cannot be allowed to remain on equipment or be flushed down industrial drains. While the automated transfer system reduces the risk of direct human contact with mercury or other toxic liquids, the containment of contaminants and spillage during the gold ball bond connection removal process and preventing contaminants from being introduced into an industrial waste line remains a problem.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an apparatus and method which will reduce mercury contamination of the environment during the gold ball bond removal process.
Another object of the invention is to provide a method and apparatus to contain mercury spillage during carry over between processing tanks during the gold ball bond removal process.
Yet another object of the invention is to provide a method and apparatus to reduce the risk of environmental contamination and the discharge of mercury and mercury salts into industrial waste lines during the gold ball bond removal process.
Still another purpose of the invention is to provide an apparatus for gold ball bond connection removal which is self-contained, compact in size, efficient and yet environmentally safe.
Yet another purpose of the invention is to provide a self-contained, compact, environmentally safe system for use with toxic chemicals and liquids.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
SUMMARY OF THE INVENTION
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a self-contained wet processing system for toxic materials comprising an enclosure having a plurality of stations contained within the enclosure, each station capable of containing a chemical liquid or water. There is at least one workpiece handler in the enclosure adapted to move workpieces through the enclosure from station to station. In the preferred embodiment, at least one station in the enclosure contains a toxic liquid such as mercury, a first decontamination station containing a first decontaminating liquid such as acid and a second decontaminating station containing a rinse liquid, such as water. The first decontamination station receives and decontaminates a contaminated workpiece, and includes a contaminant separator. The second decontamination station is for receiving a partially decontaminated workpiece for further decontamination and is adapted to render the workpiece safe for human handling.
It is preferred that the enclosure be comprised of an upper and lower chamber, the upper and lower chambers being separated by a partition which seals the upper chamber from said lower chamber. It is also preferred that the partition comprise an integrally formed flat plate having a plurality of openings integrally formed therein, each opening being in the form of a container having a sidewall and a base. Each container defines one of the stations capable of containing a chemical liquid or water.
In the preferred embodiment, the toxic liquid station is adapted to receive a removable tank. Preferably, the removable tank is made of glass and has a mouth, a base and a sidewall, and a flange extending horizontally outward from the top of the sidewall around the mouth of the removable tank. The flange may be adapted to be received in a recess integrally formed in the partition around the opening of the toxic liquid station.
In another preferred aspect, both the first and second decontamination station bases have at least one opening integrally formed therein for draining the decontamination station. One of the sidewalls of both the first and second decontamination station may have at least one opening integrally formed therein for filling the station with decontamination liquid. The opening in the sidewall of the decontamination station may also be used to re-circulate the decontamination liquid.
In the preferred embodiment, the first decontamination station drain is connected to a first pump for directing the first decontamination liquid through a first filter to remove contaminants and back to the first decontamination station or out to a first waste line. It is also preferred that the second decontamination station drain be connected to a second pump for directing the second decontamination liquid through a second filter to remove contaminants and out to a second waste line.
In the preferred embodiment, the upper chamber is a molded glass enclosure to allow viewing of the workpiece handler and workpiece during processing. The upper chamber may also have an environmentally sealable door to allow for loading the workpiece onto the workpiece handler.
It is preferred that the workpiece handler comprises a transport mechanism adapted to hold a slide having at least one semiconductor chip mounted thereon. The workpiece handler is preferably adapted to move in an X direction to position the slide over one of the stations and in a Y direction for lowering the slide into one of the stations. In the preferred embodiment, the workpiece handler is further adapted to move said slide in a reciprocating rotational movement to dislodge the toxic substance into the station.
In another preferred embodiment, the present invention relates to an environmental containment system for removing gold ball bonds on the pads of a semiconductor device. The containment system comprises a self-contained enclosure having a lower and upper chamber, a partition between the lower and upper chamber which seals the upper chamber from the lower chamber. Th

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