Circuit Substrate with Homogeneous Dielectric Constant
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Solution Overview
Problem
Current copper-clad laminate materials exhibit inhomogeneity in dielectric constant due to the microstructural differences in warp-wise and weft-wise directions, leading to signal time delay issues during high-speed signal transmission, which is challenging to address with existing methods.
Innovation Solution
A process involving pre-treating glass fabrics with a varnish having a dielectric constant close to that of the glass fabrics, followed by oven-drying and main-glue-dipping, to achieve a bonding sheet with reduced resin content and improved homogeneity, resulting in a circuit substrate with minimal warp-wise and weft-wise differences in dielectric constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass fabrics are used as reinforcing materials in copper-clad laminates, then the mechanical strength and structural integrity are improved, but the dielectric constant becomes inhomogeneous in warp-wise and weft-wise directions due to weaving structure
Solution Approach 1:
The patent divides the impregnation process into two distinct stages: pre-impregnation with a first resin composition followed by main impregnation with a second resin composition. This segmentation allows different resin systems to address different aspects of the problem - the first resin fills gaps in the glass fabric weave to improve homogeneity, while the second resin provides the primary bonding and mechanical strength, resolving the contradiction between structural integrity and dielectric uniformity.
Solution Approach 2:
The patent employs a composite resin system where two different resin compositions are used in sequence. The first resin composition (e.g., epoxy resin) and second resin composition (e.g., polyphenyl ether resin or liquid crystal polymer) have complementary properties that together achieve both mechanical strength and dielectric homogeneity, demonstrating the composite materials principle to resolve the contradiction between strength and compositional stability.
2Stability of the object's composition
If fiber-opening extent of glass fabrics is increased to improve homogeneity, then weft-wise homogeneousness is achieved, but warp-wise direction remains looser and complete fiber-opening homogeneity cannot be reached
Solution Approach 1:
The patent applies preliminary action by performing pre-impregnation with the first resin composition before the main impregnation step. This preliminary resin application fills the gap portions of the glass fabric weave structure in advance, creating a more uniform substrate that prepares the material for subsequent main impregnation and achieves complete homogeneity in both warp and weft directions.
Solution Approach 2:
The patent applies local quality by using the first resin composition specifically to fill the gap portions of the glass fabric weave where homogeneity is deficient. This targeted approach addresses the local inhomogeneity in the warp-wise direction without affecting the already homogeneous weft-wise direction, achieving complete planar homogeneity through localized treatment.
3Speed
If transmission rate is increased to higher levels (above 10 Gbps), then data transmission capability is improved, but signal time delay becomes a significant problem affecting signal integrity
Solution Approach 1:
The patent applies parameter changes by modifying the dielectric constant and loss tangent parameters of the laminate through the dual-resin impregnation system. By optimizing the composition and distribution of the two resin systems, the patent achieves lower and more uniform dielectric parameters that enable high-speed transmission (above 10 Gbps) while minimizing signal time delay and maintaining signal integrity.
4Ease of manufacture
If conventional one-step impregnation method is used, then the production process remains simple, but the resin content cannot be optimized to achieve both low dielectric constant and high homogeneity
Solution Approach 1:
The patent segments the impregnation process into two distinct steps with different resin compositions, each optimized for specific functions. The first resin composition targets gap filling and homogeneity improvement, while the second provides bonding and mechanical properties. This segmentation allows precise control over resin content and distribution, achieving optimal dielectric characteristics while maintaining a relatively simple production process that can be integrated into existing manufacturing lines.
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
The solution effectively reduces signal time delay and enhances the interlaminar bonding force, maintaining the production process simplicity and cost-effectiveness of conventional copper-clad plates while improving dielectric performance.
Implementation Method 1
pre-glue-dipping the glass fabric in the pre-treating varnish, and oven-drying solvent to obtain a pre-treated glass fabric
Implementation Method 2
laminated and hot-pressed
Data Source
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Figure 4~5
AI summary
The present invention relates to a process for preparing a bonding sheet for composing circuit substrate, comprising pre-treating glass fabrics with a pre-treating varnish having a same or close dielectric constant (DK) to glass fabrics being used. The present invention further relates to bonding sheets prepared by the process, as well as circuit substrate. The process for preparing circuit substrate of the invention, which has a lower cost, does not need to upgrade or adjust the equipments. The circuit substrates prepared thereby have less warp-wise and weft-wise difference in dielectric constant, and thus can effectively solve the problem of signal time delay.