Cemented Carbide Grain Distribution for PCB Drill Chipping Resistance
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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, which are typically used for small-diameter drilling.
Innovation Solution
A cemented carbide composition with specific ranges for hard phase and binder phase content, grain sizes, and distribution, along with optional chromium and vanadium additions, to enhance hardness, toughness, and chipping resistance, resulting in a prolonged tool life for cutting tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fine-grain cemented carbide is used for small-diameter drilling, then drilling capability is improved, but tool life is reduced due to difficulty in cutting printed circuit boards
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size of tungsten carbide particles (0.5 μm or less, preferably 0.3 μm or less) and the content of binder phase (5-15 mass%), along with adding grain growth inhibitors (chromium carbide 0.1-2.0 mass%, vanadium carbide 0.1-1.0 mass%). These parameter optimizations enable the cemented carbide to maintain fine grain structure after sintering, achieving both drilling capability and extended tool life when processing heat-resistant printed circuit boards.
Solution Approach 2:
The patent employs composite materials by combining tungsten carbide hard phase with cobalt-based binder phase, and incorporating grain growth inhibitor carbides (chromium carbide and vanadium carbide). This multi-phase composite structure prevents grain growth during sintering while maintaining fine grain size, thereby improving both the drilling performance and tool life of small-diameter drill bits used on heat-resistant printed circuit boards.
2Strength
If grain size of hard phase is reduced to improve hardness, then cutting performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-selecting tungsten carbide particles with grain size of 0.5 μm or less before sintering, and pre-adding grain growth inhibitors (chromium carbide 0.1-2.0 mass%, vanadium carbide 0.1-1.0 mass%) to the powder mixture. These preliminary measures prevent grain growth during sintering, achieving fine-grained hard structure without requiring complex post-processing or specialized sintering equipment.
Solution Approach 2:
The patent uses grain growth inhibitors (chromium carbide and vanadium carbide) as intermediary substances that interfere with the grain growth mechanism during sintering. These intermediaries adsorb at grain boundaries and prevent tungsten carbide grain growth, enabling maintenance of fine grain size (0.5 μm or less) after sintering while using conventional sintering processes.
Data Source
AI summary
A cemented carbide consisting of: a hard phase consisting of tungsten carbide grains; and a binder phase comprising cobalt, wherein a content of the hard phase in the cemented carbide is 91.5 to 97 mass %, a content of the cobalt in the cemented carbide is 3 to 8.5 mass %, the hard phase has an average grain size of 0.15 to 0.50 μm, the binder phase has an average grain size of 0.10 to 0.25 μm, in a histogram showing a grain size distribution of the hard phase, a number N1 is 7 to 10, wherein N1 is the number of classes having a frequency of 50% or more of the maximum frequency Fmax, the classes are 0.05 μm intervals, and the binder phase has a ratio of a 10% cumulative grain size D10 to a 90% cumulative grain size D90 on area basis, D10/D90, of 0.23 or more.