Metal working – Method of mechanical manufacture – Work holding
Reexamination Certificate
1999-05-04
2003-01-14
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Work holding
C269S021000, C029S743000, C156S345420
Reexamination Certificate
active
06505395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for removal of a carrier film from the bottom surface of semiconductor dice and other electronic devices. Particularly, the apparatus of the present invention reduces the surface area of the adhesive film which remains in contact with a die during removal. The present invention also relates to a method for removing semiconductor dice and other electronic devices from carrier film.
2. Background of Related Art
Several apparatus and methods are known for removing semiconductors and other electronic devices from adhesive carriers such as film. Some such methods involve degrading the adhesive properties of the carrier. Some devices employ needles, pistons, or other mechanisms which apply an upward force to push the die off of the carrier. Other devices utilize a vacuum to pull a die from a carrier. Many known apparatus and methods for removing a die from a carrier cause damage to a significant quantity of dice.
U.S. Pat. No. 4,778,326, issued in the names of Althouse et al., discloses a method and apparatus for transporting semiconductor dice which is commonly referred to as a “gel pack” or “die-pac.” The semiconductor dice are loaded onto and adhere to a flat, thin, flexible silicone film, which is attached to a carrier base. The carrier base has recesses formed therein, into which the silicone film may be pulled as a vacuum is applied beneath the film. As the film is pulled into the recesses, the area of the silicone film which contacts the dice is reduced, thereby reducing the magnitude of the adherence by which the dice are attached to the film. The dice may then be easily removed with a vacuum tip.
As mentioned above, the predominant use of gel packs is to transport dice. No semiconductor fabrication processes are performed while dice are on a gel pack. Use of gel packs is somewhat undesirable because the silicone of the films tends to contaminate dice by leaving a silicone residue thereon.
U.S. Pat. No. 5,590,787, issued in the name of Hodges, discloses another diepac device for transporting semiconductor dice. The device of the '787 patent includes a UV sensitive adhesive and permits the penetration of electromagnetic radiation, such as ultraviolet light, therethrough.
Techniques which utilize carrier films having ultraviolet light (UV) degradable adhesives thereon or other degradable adhesives are also well known in the art. The area of film attached to a die which has been selected for further manufacture is irradiated with the appropriate degradative source to remove the die from the film. Although the use of UV radiation and similar methods are desirable from the standpoint that they are unlikely to damage the die, the adhesives and carrier films required for such devices and processes are very expensive. UV-release carrier tapes have also been employed to a limited extent with gallium arsenide dice.
U.S. Pat. Nos. 4,990,051 and 4,850,780, each of which issued in the names of Safabakhah et al., each describe an apparatus for removing a die from an adhesive carrier film. That apparatus concurrently applies a vacuum to the exposed surface of the die and a chuck to the film on the opposite surface of the die. The vacuum collett is moved away from the chuck, which facilitates a pre-peel of a small area of the film from the periphery of the die. A piston disposed coaxially within the chuck is then forced against the carrier film to stretch the film and further reduce the area of the film which adheres to the die, thereby facilitating removal of the die from the film.
Some other apparatus for removing dice from a carrier film include a plunge-up piston which has a cap thereon to raise a selected die in relation to the adjacent dice on the film. This process is referred to as “tenting” the film. A needle disposed within the cap is actuated to contact the die from below and push it from the carrier film as a vacuum tip positioned above the die pulls the selected die away from the film.
Such tenting processes for removing dice from film are undesirable for several reasons. First, tenting sometimes creates an air bubble under the die, which tends to tilt the die, preventing the vacuum tip from obtaining a good hold on the die. In such cases, the vacuum tip will likely drop the selected die, damaging and/or contaminating the die. Second, in many such apparatus, the needles which push the selected die from the film have pointed ends, which tend to score the bottom surface of the die. Dice which have been scored in such a manner tend to subsequently fail mechanically at the location where they have been scored. Third, as the film is tented, the edges of other dice which are adjacent to the selected die may be chipped, causing damage to the circuitry on their active surfaces, with consequential failure.
U.S. Pat. No. 4,915,565, issued in the names of Bond et al., discloses an apparatus for removing a selected die from a wafer having an array of dice which is attached to a carrier film. In the apparatus of the '565 patent, the dice are positioned beneath the film during removal of each selected die. A head having an array of needles protruding therefrom is positioned over the film opposite a selected die. In operation, the head plunges toward the film, the needles penetrating the carrier film and dislodging the die from the film. The dislodged die then falls into a receptacle. U.S. Pat. No. 4,759,675, issued in the names of Bond et al., discloses the same die removal device.
The sole use of needles to remove a selected die from a carrier film makes the removal device of the '565 and '675 patents undesirable. The adhesive forces of the film to the die necessitate a large amount of force for removing the die therefrom. Further, the orientation of the plunge head relative to the die requires that the die suffer some impact when falling into a receptacle, increasing the likelihood of damage to the die.
U.S. Pat. No. 4,285,433, issued in the names of Garrett, Sr. et al., describes another method and apparatus for selecting and removing singulated dice from a wafer. The apparatus includes an adhesive film which is attached to the bottom of the carrier film supporting the dice. The adhesive film with adhered carrier film is pulled away from the dice through a slot. U.S. Pat. No. 4,607,744, issued in the name of Pak, discloses a similar method and device which removes carrier film from dice with a take-up drum which pulls a free end of the carrier film. The carrier film is pulled around a separator edge into a slot, the dice then passing over the separator edge and onto a conveyer which transports the dice away from the separator edge.
The amount of force applied to the dice as the carrier film is pulled downward through such a slot or separator edge while the dice proceed in a different direction of travel may be sufficient to break or damage the dice. Further, the processes of the '433 and '744 patents are undesirable in that they do not permit automated removal of selected dice from an array of dice including failed dice and die fragments, as well as functional dice.
As dice become thinner and are fabricated with larger surface areas (which adhere to a greater area of the carrier film), the likelihood of their being damaged by each of the foregoing mechanical removal processes increases.
Thus, an apparatus is needed for removing disposable carrier tape or film from semiconductor dice and other electronic devices which exerts little or no impact on a die, reduces the area of carrier tape or film adhered to a die before removal of the die, and utilizes an inexpensive yet effective carrier tape or film.
SUMMARY OF THE INVENTION
In contrast to the deficiencies exhibited by the prior art, the low-stress die removal system of the present invention addresses each of the foregoing needs. The apparatus is useful with many disposable carrier tapes or films known and used in the art. The apparatus also exerts little, if any, impact on the die. The apparatus of the present in
Farnworth Warren M.
Smith Rockwell
Cozart Jermie E.
Hughes S. Thomas
TraskBritt
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