Cemented Carbide Grain Control for Longer PCB Drill Life
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Solution Overview
Problem
The increased heat resistance requirements of printed circuit boards due to 5G technology have made them difficult to cut, leading to a reduced tool life for drills using fine-grain cemented carbide, particularly in fine processing applications.
Innovation Solution
A cemented carbide composition with specific ranges for hard phase and binder phase content, grain sizes, and distribution characteristics, including a uniform dispersion of the binder phase, is developed to enhance hardness, abrasion resistance, chipping resistance, and tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fine-grain cemented carbide is used for small-diameter drills, then drilling capability for printed circuit boards is achieved, but tool life is reduced due to increased heat resistance of PCBs
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size distribution parameters of the hard phase and binder phase. The hard phase grain size is controlled at 0.15 μm or less with specific distribution characteristics (N1 value), while the binder phase grain size is controlled at 0.10 μm or less with D10/D90 ratio of 0.23 or more. These parameter optimizations enable the cemented carbide to maintain both drilling capability for heat-resistant PCBs and extended tool life.
Solution Approach 2:
The patent employs composite material principles by creating a multi-phase cemented carbide structure consisting of hard phase (tungsten carbide), binder phase (cobalt), and optionally grain growth inhibitor phase. This composite structure with specifically controlled grain size distributions of each phase provides synergistic effects that simultaneously achieve the required hardness for drilling heat-resistant PCBs and toughness for extended tool life.
2Reliability
If binder phase grain size is reduced to improve uniformity and dispersion, then chipping resistance improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the binder phase grain size at 0.10 μm or less with a specific D10/D90 ratio of 0.23 or more. This parameter control achieves uniform dispersion and fine grain structure that improves chipping resistance while maintaining manufacturability through controlled sintering processes.
Data Source
Figure 1
AI summary
A cemented carbide consisting of: a hard phase consisting of a plurality of tungsten carbide grains; and a binder phase comprising cobalt, wherein a content of the hard phase in the cemented carbide is 91.5 mass% or more and 97 mass% or less, a content of the cobalt in the cemented carbide is 3 mass% or more and 8.5 mass% or less, the hard phase has an average grain size of 0.15 µm or more and 0.50 µm or less, the binder phase has an average grain size of 0.10 µm or more and 0.25 µm or less, in a histogram showing a grain size distribution of the hard phase, a number N1 is 7 or more and 10 or less, wherein N1 is the number of classes having a frequency of 50% or more of the maximum frequency Fmax, the classes on the horizontal axis of the histogram represent the grain sizes of the hard phase, and the classes are 0.05 µm intervals, the frequencies on the vertical axis of the histogram represent percentages, on number basis, of the hard phases falling within the respective classes, the percentages based on all of the hard phases, and the binder phase has a ratio of a 10% cumulative grain size D10 on area basis to a 90% cumulative grain size D90 on area basis, D10/D90, of 0.23 or more.