Stone working – Sawing – Reciprocating
Patent
1990-09-04
1992-03-31
Rachuba, M.
Stone working
Sawing
Reciprocating
125 1602, 125 2301, 5116577, 511658, 511659, B28D 106
Patent
active
050998200
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an abrasion-type splitting unit for splitting ingots made of hard material. This invention more particularly concerns cutting machines used in the electronics and the photoelectric cell industries for splitting an ingot of silicon, germanium or glass into a multiplicity of thin wafers.
DISCUSSION OF BACKGROUND MATERIAL
Cutting machines usually comprise at least two drums, also called wire guides, having on their cylindrical surfaces a series of circular grooves with the pitch adapted to the desired splitting. These wire guides are arranged in a horizontal plane, starting from a given vertical plane. A steel wire is wound around these wire guides to provide at least one horizontal set of cutting wires composed of a series of strands of steel wire parallel to one another. This wire may be set in motion by rotation of the wire guides. Also, the set of cutting wires is wet by an abrasive liquid, such as a suspension of particles of silicon carbide in water or oil. The ingot to be split is pushed against the set of wires from below by a plate. Abrasive particles carried by the liquid, which liquid is carried by the wire, thus produce a splitting or cutting effect.
Research ia now directed to optimizing the cutting quality obtained under mass production conditions. By cutting quality is meant exact planarity of the surfaces with a minimum of induced mechanical damage. Mass production considerations are, for example the rate of war of the wire, the possibility of recovering abrasive and/or a high product rate such as 2000 wafers per 80 cm ingot. Achieving an optimum cutting quality depends on a combination of parameters, such as the wire diameter which is of the order of 0.2 mm, the quality of the abrasive, the force with which the ingot is pressed against the set of wires which is currently set at about 50 g/line, the speed of the wire set at about 3 m/s and the wire tension which is preferably set to a value of the order of 2.5 kg (i.e. 26N).
Known splitting units or machines usually comprise a vertical front part from which two or three wire guide cylinder-s project perpendicularly, i.e. horizontally towards the front. In the same vertical plane are also arranged at different locations a supply coil of cutting wire, a take up coil and a wire tensioning device, for example, employing a lever arm, before winding about the wire guides. For example, reference can be made to the machines described in U.S. Pat. No. 3,478,732, U.S. Pat. No. 3,525,324 and FR 2 254 948. In the latter, an ingot to be cut is placed on an arm 60 also projecting from the front vertical plane. These wire guides and support plate are arranged in cantilever fashion and, because of the inherent elasticity of the steel of which they are made, forces acting between the set of wires and the ingot during cutting are transferred to the wire guides and to the supporting arms, necessarily producing a deflection of these components towards the right or left respectively, depending on the direction of motion of the wires.
In the machines described in FR 2,330510 and U.S. Pat. No. 4,640,259 and the actuator moving the ingot-supporting plate acts along an axis passing through the center of gravity of the ingot. However, in these machines the means for vertically guiding the actuator still remain insufficient to prevent any vibration and/or flexion of this arm, and hence of the plate during sawing.
It can readily be understood that because o: quality is affected in the following ways : conditions:
Moreover, known splitting units also suffer from the following defects: crystalline ingot necessary so that cutting by abrasion takes place following the planes of crystallization, constraints before and during sawing which enables such data to be integrated in a program loaded in electronic data processing means automatically controlling motion of the different mobile components of the splitting unit.
SUMMARY OF THE INVENTION
The object of this invention is to solve the problem set out above by
REFERENCES:
patent: 3032026 (1962-05-01), Raabe
patent: 4160439 (1979-07-01), Piat
patent: 4640259 (1987-02-01), Shimizu
patent: 4826127 (1989-05-01), Koblischek et al.
Copy of International Search Report and Annex.
Photec Industrie S.A.
Rachuba M.
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