Dual-Layer Conductive Via for LTCC Signal Loss
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Solution Overview
Problem
Conventional multilayer ceramic substrates experience signal loss and reduced electrical conductivity in the radio frequency band due to the mismatch in sintering shrinkage initiation periods between silver (Ag) via electrodes and low-temperature co-fired ceramics (LTCC), which leads to voids and cracks, and the addition of glass to match sintering behavior results in poorer conductivity.
Innovation Solution
A dual-layer conductive via structure is implemented, where the outer peripheral portion is formed with high-purity Ag metal and the inner peripheral portion is filled with a material having a higher shrinkage initiation temperature, such as silicon oxide or glass, to match the sintering shrinkage ratio with the LTCC, ensuring minimal voids and enhanced electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If glass is added to Ag powder to match sintering shrinkage initiation period with LTCC, then sintering behavior matching is improved, but electrical conductivity deteriorates
Solution Approach 1:
The conductive via is divided into two distinct layers: an outer peripheral portion made of Ag powder with glass for sintering matching, and an inner peripheral portion made of pure Ag powder for high conductivity. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
Different regions of the conductive via are assigned different material compositions tailored to their functional requirements. The outer layer uses Ag powder with glass content optimized for sintering behavior, while the inner layer uses pure Ag powder optimized for electrical conductivity, creating local quality variations throughout the via structure.
2Reliability
If pure Ag is used for via electrode, then electrical conductivity is improved, but sintering shrinkage matching with LTCC deteriorates
Solution Approach 1:
The conductive via is divided into two distinct layers: an outer peripheral portion made of Ag powder with glass for sintering matching, and an inner peripheral portion made of pure Ag powder for high conductivity. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
The outer peripheral portion uses a composite material of Ag powder and glass powder, combining the high conductivity of Ag with the sintering-matching properties of glass. This composite structure enables simultaneous achievement of electrical conductivity and sintering behavior compatibility.
3Strength
If glass content in via paste is increased to prevent voids and cracks, then structural integrity is improved, but electrical conductivity deteriorates
Solution Approach 1:
The conductive via is divided into two distinct layers: an outer peripheral portion made of Ag powder with glass for sintering matching, and an inner peripheral portion made of pure Ag powder for high conductivity. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
Different regions of the conductive via are assigned different material compositions tailored to their functional requirements. The outer layer uses Ag powder with glass content optimized for sintering behavior, while the inner layer uses pure Ag powder optimized for electrical conductivity, creating local quality variations throughout the via structure.
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 configuration maintains high electrical conductivity comparable to pure Ag vias while preventing signal loss by matching the sintering shrinkage initiation periods, thereby reducing AC electrical resistance and ensuring reliable signal transmission in the radio frequency band.
Implementation Method 1
the outer peripheral portion formed along an inner wall of a via hole extending through the dielectric layers and formed of a first conductive material containing a metal
Implementation Method 2
the inner peripheral portion filled in the outer peripheral portion and formed of a second conductive material having a shrinkage initiation temperature higher than a shrinkage initiation temperature of the first conductive material
Implementation Method 3
matching of the sintering shrinkage ratio
Data Source
AI summary
There is provided a multilayer ceramic substrate including a conductive via of a dual-layer structure capable of preventing loss in electrical conductivity and signal. The multilayer ceramic substrate includes: a plurality of dielectric layers; and a circuit pattern part formed on at least a portion of the dielectric layers, the circuit pattern part including at least one conductive via and conductive pattern, wherein the at least one conductive via comprises an outer peripheral portion and an inner peripheral portion, the outer peripheral portion formed along an inner wall of a via hole extending through the dielectric layers and formed of a first conductive material containing a metal, and the inner peripheral portion filled in the outer peripheral portion and formed of a second conductive material having a shrinkage initiation temperature higher than a shrinkage initiation temperature of the first conductive material.