LC Filter Flatness via Embedded Thin-Film Capacitor
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Solution Overview
Problem
Existing LC filters with thermoplastic resin sheets face issues of coil conductor pattern deformation and reduced flatness due to resin flow during heat-pressing, leading to unstable filter characteristics and mounting defects.
Innovation Solution
The LC filter design incorporates a multilayer body with a thin-film capacitor and coil conductor patterns embedded in a resin sheet, where the capacitor is disposed within the coil opening and connected to the conductor pattern, and input/output terminal conductors are formed on the surface, minimizing positional displacement and maintaining flatness by ensuring the capacitor and conductor thicknesses are smaller than the resin sheet, thus reducing parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermoplastic resin sheets are stacked and heat-pressed to form the multilayer body, then the manufacturing process is simplified and productivity is improved, but the resin sheets flow during heat-pressing causing coil conductor patterns to collapse and filter characteristics to deteriorate
Solution Approach 1:
The coil conductor patterns are formed on the resin sheets before stacking and heat-pressing. By preparing the conductor patterns in advance on flat resin sheets, the invention ensures that the patterns maintain their shape during the subsequent heat-pressing process, preventing collapse while still allowing efficient manufacturing
Solution Approach 2:
The invention applies different properties to different parts of the resin sheet: the regions with coil conductor patterns maintain higher rigidity to prevent deformation, while other regions can flow during heat-pressing. This localized quality difference allows the patterns to maintain accuracy while the overall structure is formed efficiently
2Ease of manufacture
If chip capacitors are incorporated into the multilayer body without providing holes, then device complexity is reduced and ease of manufacture is improved, but the flatness of the front and rear surfaces deteriorates causing mounting defects
Solution Approach 1:
Instead of incorporating capacitors by creating holes through the thickness dimension, the invention places capacitors on the surface plane dimension. The capacitors are mounted on the front or rear surface of the multilayer body and connected via conductors on the same surface, eliminating the need for through-holes and preserving surface flatness
Data Source
AI summary
An LC filter having a multilayer body, coil conductor patterns, a thin-film capacitor, and input/output terminal conductors. The multilayer body is formed by stacking a plurality of resin sheets. At least a portion of the coil conductor pattern is embedded in a resin sheet. The thin-film capacitor is at least partially embedded in the resin sheet, is disposed in the coil opening of the coil conductor pattern, which is spiral-shaped, and is connected to the coil conductor pattern. The thickness of the coil conductor patterns is smaller than the thickness of the resin sheets, and the thickness of the thin-film capacitor is smaller than the thickness of the resin sheets.