Cu External Electrode Multilayer Ceramic Capacitor Hydrogen Management
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Solution Overview
Problem
Multilayer ceramic capacitors using base metals like Ni for internal electrodes face insulation resistance deterioration due to hydrogen absorption and emission, especially under high-temperature high-humidity conditions, which affects the reliability of the capacitors.
Innovation Solution
A multilayer ceramic capacitor design with a Cu-containing external electrode and a protective layer of Cu2O at the joining portion between the external electrode and plating layer, along with an Ni-plating and Sn-plating layer configuration, is implemented to reduce hydrogen absorption and diffusion, ensuring reliable insulation resistance by controlling hydrogen emission during heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If base metal (Ni) is used for internal electrodes to reduce cost, then material cost is reduced, but hydrogen absorption increases causing insulation resistance deterioration
Solution Approach 1:
A Cu-containing external electrode main body is introduced as an intermediary layer between the Ni internal electrode and the plating layer. This Cu-based external electrode acts as a mediator that suppresses hydrogen emission and prevents hydrogen from reaching the dielectric layer, thereby resolving the contradiction between using low-cost Ni and maintaining high insulation resistance
Solution Approach 2:
The invention changes the material parameter of the external electrode from traditional plating materials to Cu-containing material. This parameter change enables the external electrode to effectively suppress hydrogen emission through its inherent properties, solving the reliability issue while maintaining cost-effectiveness
2Reliability
If Ni-plating is applied to external electrodes to prevent solder dissolution, then solder resistance is improved, but hydrogen is generated and occluded into internal electrodes causing insulation resistance deterioration
Solution Approach 1:
The Cu-containing external electrode main body serves as an intermediary between the Ni-plating layer and the dielectric layer. It mediates hydrogen by suppressing hydrogen emission and preventing hydrogen generated during electroplating from reaching and damaging the dielectric layer
Solution Approach 2:
The harmful function of hydrogen generation is extracted and isolated from the system by using Cu as the external electrode base material, which inherently suppresses hydrogen emission. This separates the beneficial solder protection function from the harmful hydrogen generation effect
3Reliability
If Sn-plating is applied onto Ni-plating to improve soldering performance, then soldering performance is improved, but hydrogen is generated during electroplating that diffuses to dielectric layer causing insulation resistance deterioration
Solution Approach 1:
The Cu-containing external electrode main body acts as a protective intermediary layer between the Sn-plating/Ni-plating system and the dielectric layer. It mediates the hydrogen issue by suppressing hydrogen emission and preventing hydrogen diffusion to the dielectric, allowing the use of Sn-plating for improved soldering performance without the harmful effects
4Reliability
If hydrogen is emitted from internal electrodes under high-temperature high-humidity conditions, then hydrogen emission occurs causing insulation resistance deterioration, but using Cu-containing external electrode suppresses hydrogen emission
Solution Approach 1:
The Cu-containing external electrode main body serves as a thermal and hydrogen management intermediary. Under high-temperature high-humidity conditions, it mediates hydrogen behavior by suppressing hydrogen emission from the internal electrodes, preventing hydrogen damage to the dielectric layer while maintaining stable capacitor performance
Solution Approach 2:
The invention changes the external electrode material parameter to Cu-containing composition, which fundamentally alters the hydrogen emission characteristics under high-temperature high-humidity conditions. This parameter change enables stable performance by suppressing hydrogen emission during thermal stress
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 design effectively suppresses hydrogen diffusion to the dielectric layers, preventing insulation resistance deterioration and enhancing the reliability of the multilayer ceramic capacitors by reducing the quantity of hydrogen present, as demonstrated by specific hydrogen generation ratios and improved performance in high-temperature high-humidity tests.
Implementation Method 1
base metal such as Ni rather than noble metal such as Ag or Pd is often used as material of an internal electrode... some base metals such as Ni used as constituting material for internal electrodes and external electrodes including a plating layer have a high ability to absorb hydrogen
Implementation Method 2
the absorbed hydrogen is emitted to some extent depending on a temperature condition... the absorbed hydrogen is emitted and diffused to the dielectric layer
Implementation Method 3
a chemical reaction in a plating step generates hydrogen and the hydrogen is occluded into an internal electrode
Implementation Method 4
when heat is applied to the layered body after the external electrode is removed therefrom, and a quantity of hydrogen generated from the layered body is measured
Data Source
AI summary
A multilayer ceramic capacitor that includes a layered body in which dielectric layers and internal electrode layers are layered alternately, an external electrode on a surface of the layered body and a plating layer on a surface of the external electrode. The external electrode contains Cu, and a protective layer containing Cu2O is provided at a joining portion between the external electrode and the plating layer. When heat is applied to the layered body after the external electrode is removed, a ratio of an arithmetic mean value Xa of a quantity of hydrogen generated per unit temperature in a range higher than or equal to 350° C. with respect to an arithmetic mean value Y of a quantity of hydrogen generated per unit temperature in a range higher than or equal to 230° C. and lower than or equal to 250° C. (Xa/Y) is less than or equal to 0.66.