Multilayer Ceramic Device External Electrode Crack Prevention
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Solution Overview
Problem
Multilayer ceramic electronic devices often experience cracks during the manufacturing process, particularly due to mismatched shrinkage between the ceramic body and external electrodes, leading to electrical contact failures and plating defects.
Innovation Solution
The use of ceramic grains in the external electrodes, with a glass layer covering the first external electrode formed by co-firing with the ceramic body, and a second external electrode containing glass, which is baked separately, helps to suppress cracks by reducing stress and ensuring strong bonding between the electrodes and the ceramic body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal paste is applied and baked after firing the ceramic body (post-attached external electrodes), then the external electrodes can be formed with good electrical contact, but cracks may occur in the ceramic body due to shrinkage mismatch
Solution Approach 1:
The patent applies metal paste to the ceramic green sheet before firing, allowing the external electrode to be formed simultaneously with the ceramic body. This preliminary action ensures that both the ceramic and metal electrode undergo the same shrinkage process together, preventing crack formation while maintaining good electrical contact.
Solution Approach 2:
The patent combines the ceramic body formation and external electrode formation into a single simultaneous firing process. By merging these two processes, the shrinkage of the ceramic and metal electrode occurs together, eliminating the shrinkage mismatch that causes cracks.
2Strength
If metal paste is applied to unfired ceramic body and fired simultaneously (co-fired external electrodes), then the shrinkage mismatch is reduced, but cracks may still occur due to stress during firing
Solution Approach 1:
The patent modifies the metal paste composition by adding glass powder and ceramic powder to create a composite paste. This changes the physical and chemical parameters of the paste, enabling it to form a buffer layer that absorbs thermal stress and prevents crack formation during the simultaneous firing process.
Solution Approach 2:
The patent uses a composite metal paste containing metal powder, glass powder, and ceramic powder. This composite material combines the electrical conductivity of metal with the crack-resistant properties of glass and ceramic, creating an external electrode that is both conductive and resistant to firing-induced cracks.
3Reliability
If thick metal paste is used to ensure good electrical contact, then electrical conductivity improves, but stress during firing increases leading to more cracks
Solution Approach 1:
The patent uses a composite paste with metal powder, glass powder, and ceramic powder. The glass and ceramic components create a more compliant, stress-absorbing matrix that allows for adequate electrode thickness without generating excessive stress during firing, thus preventing cracks while maintaining conductivity.
Solution Approach 2:
The patent changes the compositional parameters of the paste by incorporating glass and ceramic powders in specific proportions. This modifies the mechanical properties of the dried and fired paste, reducing its brittleness and stress generation during firing, allowing thicker applications without crack formation.
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 effectively prevents cracks, maintains electrical contact, and reduces the risk of plating defects, allowing for a more reliable and durable multilayer ceramic electronic device.
Implementation Method 1
mismatched shrinkage between the ceramic body and external electrodes
Implementation Method 2
mismatched shrinkage between the ceramic body and external electrodes
Implementation Method 3
a metal paste is applied to an unfired ceramic body and the ceramic body and the metal paste are fired at the same time
Implementation Method 4
ensuring strong bonding between the electrodes and the ceramic body
Data Source
AI summary
A multilayer ceramic electronic device includes a multilayer chip having a plurality of internal electrode layers that face each other and a plurality of dielectric layers, each of which is sandwiched by two of the plurality of internal electrode layers, one end of at least one of the plurality of internal electrode layers being exposed at a side face of the multilayer chip, a first external electrode that is provided on the side face of the multilayer chip, is in contact with at least one of the each end of the plurality of internal electrode layers, and includes ceramic grains, and a second external electrode that is provided on the first external electrode, has a glass, and has a main component that is a same metal as that of the first external electrode.