Wire Saw Cooling Circuits for Wafer Flatness
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Solution Overview
Problem
Existing methods for slicing wafers using wire saws face challenges in preventing axial relative movement between the workpiece and the wire sections due to temperature changes, leading to curved wafer cross-sections and warp, which is not adequately addressed by controlling the temperature of wire guide rolls and fixed bearings simultaneously.
Innovation Solution
Independent cooling circuits are established for the wire guide rolls and their fixed bearings, with predefinition curves coordinating the coolant temperature and flow rate to manage temperature changes independently, ensuring minimal axial displacement and maintaining straight cuts during the sawing operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wire guide rolls and fixed bearings are cooled simultaneously using a common cooling system, then temperature control is simplified, but axial relative movement between workpiece and wire sections cannot be sufficiently reduced
Solution Approach 1:
The cooling system is segmented into two independent circuits: one for cooling wire guide rolls and another for cooling fixed bearings. This segmentation allows separate temperature control of each component, enabling precise compensation of thermal expansions independently, thereby reducing axial relative movement and improving wafer geometric precision.
Solution Approach 2:
Different cooling strategies are applied to different locations: wire guide rolls receive cooling through one circuit while fixed bearings receive cooling through another circuit. This local differentiation allows each component to be cooled according to its specific thermal characteristics and functional requirements, optimizing overall system precision.
2Temperature
If cooling water temperature and flow rate are increased to reduce thermal expansion, then temperature stability improves, but energy consumption increases
Solution Approach 1:
The cooling system uses dynamic control where coolant temperature and flow rate are adjusted in real-time based on the sawing progress and thermal conditions. Predefinition curves guide the cooling parameters through different phases of the sawing operation, ensuring optimal temperature stability while minimizing energy consumption by avoiding excessive cooling when not needed.
Solution Approach 2:
Cooling parameters are predetermined using predefinition curves that specify the optimal cooling water temperature and flow rate at different stages of the sawing operation. This preliminary planning allows the system to apply cooling proactively rather than reactively, maintaining temperature stability efficiently without wasting energy.
3Shape
If axial displacement of wire guide rolls is regulated to match workpiece displacement, then wafer curvature is reduced, but control system complexity increases
Solution Approach 1:
The system regulates axial displacement by changing thermal parameters (temperature) of the wire guide rolls and fixed bearings through independent cooling circuits. By controlling thermal expansion/contraction parameters, the system indirectly controls axial displacement and maintains wafer flatness without requiring complex mechanical displacement control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces axial relative movement to less than 20 μm, ensuring flat and plane-parallel wafer surfaces by independently controlling the temperature of the wire guide rolls and fixed bearings, thereby improving the geometry of sliced wafers.
Implementation Method 1
The wire guide rolls and the fixed bearings of the wire guide rolls are cooled independently of one another
Implementation Method 2
coolant temperature and flow rate to manage temperature changes
Implementation Method 3
changes in the length of the workpiece and of the wire guide rolls are mentioned in US 2010/0089377 A1, said changes being attributed to changes in temperature and an associated thermal expansion or thermal contraction
Data Source
AI summary
A method for slicing wafers from a workpiece includes providing wire guide rolls that each have a grooved coating with a specific thickness, providing a fixed bearing respectively associated with each wire guide roll and providing a sawing wire including wire sections disposed in a parallel fashion. The wire sections are tensioned between the wire guide rolls and are moved relative to the workpiece so as to perform a sawing operation. The wire guide rolls cooled and the fixed bearings are cooled independently of the wire guide rolls.