Multilayer Substrate Layout for Low-Loss High-Frequency Signal Lines
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Solution Overview
Problem
Existing laminated substrates for high-speed transmission experience increased skin resistance and transmission loss due to roughening of copper foil surfaces, which is necessary for adhesive force, especially in high-frequency applications.
Innovation Solution
The multilayer substrates are designed with signal lines and ground electrodes that partially contact hollow portions, where the thickness of these components is reduced through etching to minimize roughening, and anti-corrosion layers are applied to reduce oxidization, maintaining high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the copper foil surface is roughened to improve adhesive force, then the adhesive force of the copper foil is improved, but the skin resistance is increased and transmission loss is increased
Solution Approach 1:
The invention applies different surface qualities to different regions of the copper foil. The signal line portions are kept smooth to minimize skin resistance and transmission loss, while the ground electrode portions are roughened to ensure adequate adhesive force. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Strength
If the copper foil surface is roughened to improve adhesive force, then the adhesive force of the copper foil is improved, but the skin resistance is increased
Solution Approach 1:
The invention differentiates surface treatment between signal lines and ground electrodes. Signal lines maintain smooth surfaces to preserve high-frequency characteristics and minimize skin effect, while ground electrodes receive roughening treatment for adequate adhesion. This local quality approach prevents the degradation of high-frequency performance while ensuring mechanical reliability.
3Loss of energy
If the thickness of the signal line is reduced to minimize roughening effects, then the skin resistance is reduced and transmission loss is reduced, but the mechanical strength is reduced
Solution Approach 1:
The invention creates a dual-structure where signal lines have reduced thickness and smooth surfaces to minimize transmission loss, while ground electrodes maintain adequate thickness and roughened surfaces for mechanical strength and adhesion. The ground electrodes serve as both mechanical support and electrical reference, compensating for the reduced mechanical strength of the thinner signal lines.
Data Source
AI summary
A multilayer substrate includes conductor layer-formed resin layers each including a conductor layer on a resin layer, a first conductor layer-formed resin layer in which a first conductor layer is on one principal surface, and a second conductor layer-formed resin layer in which a second conductor layer is on one principal surface. At least a portion of the first conductor layer is a signal line. At least a portion of the second conductor layer is a ground electrode. A hollow portion in which a resin of the resin layer of a region of the first conductor layer-formed resin layer including a portion overlapped by the signal line is absent and to which the signal line is exposed, is provided. A thickness of the signal line in the hollow portion is smaller than a thickness of the first conductor layer at a portion other than in the hollow portion.