Ceramic Wiring Board Interface Structure for Thin High-Bonding Boards

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Solution Overview

Problem

Existing ceramic wiring boards face challenges in achieving high toughness and bonding strength between the ceramic sinter and the metallic wiring, especially when the boards are thin and subjected to thermal expansion coefficient differences.

Innovation Solution

A ceramic wiring board is designed with a ceramic sinter containing alumina and zirconia as main components, along with manganese oxide and silica as auxiliary components. The wiring, made of molybdenum as a main component, is positioned within the ceramic sinter, and the zirconia crystal phase includes first and second crystal grains, with the second grains growing larger and entering recesses of the wiring at the interface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the ceramic wiring board is made thin to reduce size, then the compactness is improved, but the toughness and bonding strength between ceramic sinter and metallic wiring deteriorate

Engineering Contradiction:

Improveboard thicknessVSAvoidbonding strength

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent applies local quality by creating a specific microstructure at the interface between ceramic sinter and metallic wiring. Large grain-sized zirconia crystal phases are concentrated at this interface region, forming a localized zone with enhanced mechanical properties that provides strong bonding and toughness specifically where needed, while the rest of the board can remain thin for compactness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining alumina and zirconia in specific proportions (alumina: 70-90 wt%, zirconia: 10-30 wt%) to create a ceramic sinter with optimized properties. The zirconia phase, particularly the large grain-sized crystals at the interface, acts as a reinforcement that enhances bonding strength and toughness even in thin board configurations.

Inventive Principle:

Principle #40Composite materials

2Strength

If the ratio of large grain-sized zirconia crystals at the interface is increased to improve bonding strength, then the bonding strength between ceramic sinter and metallic wiring is improved, but the dielectric constant increases

Engineering Contradiction:

Improvebonding strengthVSAvoiddielectric constant

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent localizes the high zirconia content specifically at the interface region between ceramic sinter and metallic wiring, rather than uniformly distributing it throughout the entire ceramic sinter. This localized concentration of large grain-sized zirconia crystals provides the necessary bonding strength at the critical interface while keeping the overall dielectric constant of the board within acceptable ranges (7.0-8.5).

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent carefully controls the zirconia content parameter within a specific range (10-30 wt%) and adjusts the grain size distribution parameter to optimize the balance between bonding strength and dielectric constant. By controlling these parameters, the patent achieves bonding strength improvement while limiting the increase in dielectric constant to an acceptable range.

Inventive Principle:

Principle #35Parameter changes

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 enhances the toughness and bonding strength of the ceramic wiring board, reducing the likelihood of separation due to thermal expansion differences, even when the board is thin.

Implementation Method 1

The zirconia crystal phase includes first crystal grains and second crystal grains having a larger grain size than the first crystal grains. The second crystal grains positioned at an interface between the ceramic sinter and the wiring include the second crystal grains entering a recess of the wiring.

Methodology Applied

Scientific EffectGrain growth:

Implementation Method 2

reducing the likelihood of separation due to thermal expansion differences

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20250203768A1Ceramic wiring board, electronic device, and electronic module

Publication Date: 2025.06.19 KYOCERA CORP

AI summary

To provide a ceramic wiring board that may be thin, but have higher toughness, and have high connection strength to a wiring, an electronic device, and an electronic module. A ceramic wiring board (21) includes a ceramic sinter (211) containing an alumina crystal phase and a zirconia crystal phase as main components and containing manganese oxide and silica as auxiliary components, and a wiring (212) positioned in at least one of a surface or an inside of the ceramic sinter (211) and containing molybdenum as a main component. The zirconia crystal phase includes first crystal grains (211a) and second crystal grains (211b) having a larger grain size than the first crystal grains (211a), and the second crystal grains (211b) positioned at an interface between the ceramic sinter (211) and the wiring (212) include the second crystal grains entering a recess of the wiring (212).