Dielectric Sheet Manufacturing via Low-Pressure Extrusion
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Solution Overview
Problem
Existing methods for manufacturing dielectric sheets for high-frequency printed wiring boards face challenges in achieving size stability with respect to temperature changes, while also requiring high extrusion molding pressures and resulting in thickness variations and filler distribution issues.
Innovation Solution
A method involving extrusion molding of a mixture of powder polytetrafluoroethylene and spherical silica at a temperature below the melting point of polytetrafluoroethylene, followed by calendering, where the mass ratio of silica to polytetrafluoroethylene is 1.3 or greater, and the average particle diameter of silica is between 0.1 μm and 3.0 μm, with a reduction ratio of extrusion molding kept at 8 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the mass ratio of silica to polytetrafluoroethylene is increased to reduce the linear expansion coefficient, then size stability with temperature changes is improved, but extrusion molding pressure increases
Solution Approach 1:
The patent changes the particle size parameter of silica from conventional large particles to fine particles with an average diameter of 0.1 to 3.0 μm. This parameter change allows the silica to disperse more uniformly in the polytetrafluoroethylene matrix, reducing the linear expansion coefficient effectively while requiring lower extrusion molding pressure because the fine particles create a more homogeneous mixture that flows more easily during extrusion.
Solution Approach 2:
The patent creates a composite material system where fine silica particles are uniformly distributed in polytetrafluoroethylene. The specific mass ratio range of 1.3 or greater combined with the fine particle size creates a composite structure that simultaneously achieves low linear expansion coefficient and low extrusion pressure, as the fine particles reinforce the matrix without creating stress concentration points that would require higher processing pressures.
2Ease of manufacture
If high extrusion molding pressure is applied to manufacture dielectric sheets, then the sheet can be formed, but thickness variations occur
Solution Approach 1:
The patent reduces the extrusion molding pressure parameter by using fine silica particles (0.1 to 3.0 μm average diameter) that create a more flowable mixture. This parameter change in particle size allows the material to be extruded at lower pressures while maintaining uniform thickness, because the fine particles reduce internal friction and improve the homogeneity of the extruded sheet.
3Ease of manufacture
If high extrusion molding pressure is applied, then the sheet can be formed, but filler distribution becomes non-uniform
Solution Approach 1:
The patent changes the particle size parameter of silica to fine particles (0.1 to 3.0 μm average diameter), which fundamentally improves filler distribution uniformity. The fine particles have lower settling velocity and better dispersibility in the polytetrafluoroethylene matrix, allowing them to distribute uniformly during extrusion at low pressure without requiring high pressure that would cause aggregation or non-uniform distribution.
Solution Approach 2:
The patent creates a well-dispersed composite material system where fine silica particles are uniformly distributed throughout the polytetrafluoroethylene. The specific combination of fine particle size and appropriate mass ratio creates a composite structure that maintains homogeneous filler distribution even at low extrusion pressures, as the fine particles interact more uniformly with the matrix material.
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 method effectively reduces the linear expansion coefficient of the dielectric sheet, improving size stability with temperature changes, while allowing for extrusion molding at lower pressures, thus reducing thickness variations and ensuring uniform filler distribution.
Implementation Method 1
extrusion molding a mixture including powder polytetrafluoroethylene and spherical silica at a temperature lower than or equal to a melting point of the polytetrafluoroethylene
Implementation Method 2
calendering a sheet body obtained by the extrusion molding
Data Source
AI summary
A method for manufacturing a dielectric sheet, includes the steps of extrusion molding a mixture including powder polytetrafluoroethylene and spherical silica at a temperature lower than or equal to a melting point of the polytetrafluoroethylene, and calendering a sheet body obtained by the extrusion molding. A mass ratio of the silica with respect to the polytetrafluoroethylene is 1.3 or greater. An average particle diameter of the silica is 0.1 μm or greater but 3.0 μm or less. A reduction ratio of the extrusion molding is 8 or less.