Cemented Carbide Grain Control for Precise PCB Drilling
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Solution Overview
Problem
The increased hardness of printed circuit boards due to improved heat resistance leads to wear of drill cutting edges, resulting in deteriorated precision during hole formation in fine processing.
Innovation Solution
A cemented carbide with specific composition and grain size distribution, including tungsten carbide grains and cobalt, is used to create a cutting tool with improved hardness, wear resistance, and fracture resistance, maintaining sharpness and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fine-grain cemented carbide with WC grains of less than or equal to 1 μm is used, then manufacturing precision is improved, but reliability deteriorates due to wear of cutting edges
Solution Approach 1:
The patent changes the grain size parameter of tungsten carbide from conventional ≤1 μm to a specific range of 1.0-2.0 μm, and adjusts the binder phase composition by adding boron to cobalt. This parameter change resolves the contradiction by achieving both improved reliability (reduced wear) and maintained manufacturing precision through the optimized grain size range and binder composition
Solution Approach 2:
The patent creates a composite binder phase consisting of cobalt and boron, where boron forms boride compounds that enhance wear resistance. This composite material approach allows the cutting tool to maintain sharpness and precision while significantly improving reliability against cutting edge wear during fine processing of hard materials
2Temperature
If heat resistance of printed circuit board is improved, then temperature resistance is improved, but manufacturing precision deteriorates due to increased hardness
Solution Approach 1:
The patent adjusts the WC grain size parameter to 1.0-2.0 μm and modifies the binder phase composition with boron addition, enabling the cutting tool to effectively process heat-resistant materials with improved hardness while maintaining excellent hole formation precision
Solution Approach 2:
The optimized cemented carbide composition extends tool life significantly, allowing the cutting tool to process numerous heat-resistant printed circuit boards before requiring replacement, thereby maintaining precision across multiple operations
Data Source
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AI summary
A cemented carbide consists of: a first phase consisting of a plurality of tungsten carbide grains; and a second phase including cobalt, wherein the cemented carbide includes more than or equal to 78 volume% and less than 100 volume% of the first phase, and more than 0 volume% and less than or equal to 22 volume% of the second phase, an average value of equivalent circle diameters of the tungsten carbide grains is more than or equal to 0.5 µm and less than or equal to 1.2 µm, on number basis, the tungsten carbide grains include less than or equal to 13% of first tungsten carbide grains each having an equivalent circle diameter of less than or equal to 0.3 µm, on number basis, the tungsten carbide grains include less than or equal to 12% of second tungsten carbide grains each having an equivalent circle diameter of more than 1.3 µm, in a histogram indicating a distribution of the equivalent circle diameters of the tungsten carbide grains, Fmax/Fmin is less than or equal to 7.0, Fmax/Fmin being a ratio of a maximum frequency Fmax to a minimum frequency Fmin, classes on a horizontal axis of the histogram represent the equivalent circle diameters of the tungsten carbide grains, and an interval of each of the classes is 0.1 µm, frequencies on a vertical axis of the histogram represent, on number basis, percentages of tungsten carbide grains belonging to the respective classes with respect to all the tungsten carbide grains, the maximum frequency Fmax is a maximum frequency in a first range in which the equivalent circle diameters are more than 0.3 µm and less than or equal to 1.3 µm, the minimum frequency Fmin is a minimum frequency in the first range, and a content ratio of cobalt in the cemented carbide is more than 0 mass% and less than or equal to 10 mass%.