Abrading – Abrading process – With critical nonabrading work treating
Reexamination Certificate
2000-04-10
2002-04-02
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
With critical nonabrading work treating
C125S023020, C083S746000
Reexamination Certificate
active
06364751
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the semiconductor technology field. More specifically, the present invention relates to a method for singling, i.e., dicing or separating, semiconductor components. Each of the components which are to be separated comprise at least one semiconductor chip which are mounted on a common carrier substrate. The semiconductor chips may be partly or completely surrounded by an encapsulation compound. The components are separated by severing the carrier substrate, if appropriate additionally by severing parts of the encapsulation compound on the carrier substrate. The finished components may in principle be in any desired arrangement, such as for example a ball grid array, a pin grid array, or the like.
The present invention furthermore comprises a singling device for separating semiconductor components.
In the production of semiconductor components, semiconductor chips are generally arranged on a carrier substrate, for example a carrier tape, a leadframe or a ceramic substrate, during the mounting operation. The entire configuration of the semiconductor chips on the carrier substrate can then be processed further and, if appropriate, encapsulated by an encapsulation compound. In a final step, the individual semiconductor components are detached from the overall assembly on the carrier substrate. This process is generally referred to as singling, separating, or dicing. For this purpose, the carrier substrate is severed around the semiconductor chip or around the semiconductor component, so that an individual semiconductor component is formed.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a singling method and a singling device for semiconductor components, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which enables the singling of semiconductor components to take place as efficiently and as gently as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of singling semiconductor components each formed with at least one semiconductor chip mounted on a common carrier substrate, which comprises:
bending a carrier substrate carrying a plurality of semiconductor chips to form a convexly curved surface; and
severing the carrier substrate beginning from the convexly curved surface, produced in the bending step, and singling individual semiconductor components.
In accordance with an added feature of the invention, prior to the severing step, the carrier substrate is placed on a curved base in an area of the carrier substrate to be severed, and the carrier substrate is caused to become connected to the base in a form-fitting manner by generating a vacuum between the base and the carrier substrate, i.e., the substrate is aspirated onto the base.
In accordance with an alternative feature of the invention, the carrier substrate is first freely suspended, at least in an area to be severed, and then pressure-exerting elements are pressed onto a surface of the carrier substrate. In a preferred embodiment of the invention, the pressure-exerting elements are pressure rollers.
In other words, there is provision for the carrier substrate to be bent at least in that area of the carrier substrate which is to be severed. The resultant curvature of the carrier substrate places one of the surfaces of the substrate under tensile stress. The severing of the carrier substrate then begins from this surface, which has acquired a convex curvature as a result of the bending. It is thus ensured that there is scarcely any material warpage caused by displacement of the material of the carrier substrate during the severing operation, and consequently the surface remains free of defects. The severing operation itself is also facilitated, since it is possible to use a lower mechanical pressure, resulting in more gentle severing of the carrier substrate.
The bending of the carrier substrate can be achieved in various ways. For example, it is possible for the carrier substrate, at least in the area which is to be severed, to be placed on a curved base prior to the severing operation. The carrier substrate can then be sucked onto the base in a form-fitting manner due to the generation of a vacuum between the base and the carrier substrate and can thus be connected to the surface of the base. This may, for example, be achieved by means of a suitable vacuum arrangement which is coupled to the surface of the base.
As an alternative, it is also possible for the carrier substrate, prior to the severing operation, to be suspended freely at least in the area which is to be severed. It is then possible for pressure-exerting elements to be pressed onto the surface of the carrier substrate from one side of the carrier substrate in the area which is to be severed, so that the carrier substrate is bent toward the opposite surface of the carrier substrate. The pressure-exerting elements used may, for example, be rollers. However, the carrier substrate may also be guided so as to slide over corresponding pressure-exerting elements.
In principle, various processes can be used to sever the carrier substrate, such as for example abrasive parting. Preferably, however, a cutting process is used. Ideally, a saw with a cutting blade made from hardened metal, i.e., carbide metal or sintered carbide, or ceramic can be used for this process.
Saw blades whose materials and shape have been adapted to the specific requirements involved in processing semiconductors are already known from U.S. Pat. No. 5,702,492. However, those saw blades from the prior art are designed for working on semiconductor wafers, not for separating semiconductor components from an overall assembly on a carrier substrate. During parting of components, such saw blades generally result in cut edges which are not clean, owing to contamination or “fraying” of the cut edges.
The number and position of severing operations carried out on the carrier substrate are selected according to the size of the semiconductor components and the distances between the individual semiconductor chips or semiconductor components and the distances between the semiconductor chips and the edge of the carrier substrate. Consequently, at least one severing of the carrier substrate is carried out between in each case two components or semiconductor chips. Depending on the nature and size of the carrier substrate, it may also be necessary to sever the carrier substrate between the components and the edge of the carrier substrate. However, it is also possible for two severing operations, which are spaced apart from one another, of the carrier substrate to be carried out at least between some of the components. This is useful in particular in those areas in which the distance between the components is relatively great and it would be desirable to achieve semiconductor components which are as small as possible. If two severing operations are carried out between the components, instead of only one, the resulting size of the semiconductor components is reduced accordingly. Ideally, the two severing operations are carried out simultaneously, in order to make the time required for this process step as short as possible.
In accordance with another feature of the invention, therefore, the severing step comprises cutting the carrier substrate along at least one line between in each case two components.
In accordance with again another feature of the invention, the severing step further comprises severing the carrier substrate also between the components and an edge of the carrier substrate.
In accordance with a further feature of the invention, the carrier is severed along two spaced-apart lines severing the carrier substrate between at least some of the components. The two-line severing may be staggered in time or it may be effected simultaneously.
With the above and other objects in view there is also provided, in accordance with the invention, a singling device for separati
Pohl Jens
Winderl Johann
Wutz Oliver
Hail III Joseph J.
Ojini Anthony
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