MLCC Electrode and Bump Layout for Crack-Free Ultrasonic Joining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ultrasonic joining of multilayer ceramic capacitors can cause cracks due to stress concentration on the side and end surfaces, as existing methods do not effectively distribute stress during the joining process.
Innovation Solution
The multilayer ceramic capacitors are designed with first and second outer electrodes only on the principal surfaces, featuring bumps made of Au, Cu, or Al, which are strategically positioned to reduce stress concentration by increasing the contact area with the holder, thereby minimizing the occurrence of cracks during ultrasonic joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic joining is performed on multilayer ceramic capacitors with conventional outer electrode structures, then electrical connection is achieved, but cracks occur due to stress concentration on side and end surfaces
Solution Approach 1:
The patent removes outer electrodes from the second principal surface and reduces their coverage on the first principal surface, extracting the problematic elements that cause stress concentration. This selective removal prevents cracks while maintaining necessary electrical connections through strategically positioned bumps and reduced outer electrode areas.
Solution Approach 2:
The patent applies different electrode configurations to different surfaces: the first principal surface has outer electrodes with bumps for electrical connection, while the second principal surface has no outer electrodes to prevent stress concentration. This local differentiation optimizes both bonding reliability and crack prevention in respective areas.
2Reliability
If outer electrodes are provided on all surfaces of the capacitor body, then electrical connectivity is improved, but stress concentration during ultrasonic joining increases causing cracks
Solution Approach 1:
The patent extracts outer electrodes from the second principal surface entirely and reduces them on the first principal surface to specific regions where bumps are positioned. This removal eliminates the harmful stress concentration effect while preserving electrical connectivity through the remaining strategic electrode-bump configuration.
Solution Approach 2:
The patent creates non-uniform electrode distribution: full outer electrode coverage with bumps on the first principal surface for electrical connection, and no outer electrodes on the second principal surface to minimize stress. This local quality variation resolves the contradiction between electrical connectivity and stress reduction.
3Strength
If bumps with sufficient thickness are provided for ultrasonic joining, then bonding strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the bump structure with the outer electrode formation process, where bumps are created as protrusions from the outer electrode material itself rather than as separate components. This integration achieves sufficient joining strength through material continuity while simplifying manufacturing by eliminating additional bump fabrication steps.
Solution Approach 2:
The outer electrode material serves multiple functions: it provides electrical connection, forms the bump structure for ultrasonic joining, and eliminates the need for separate bump materials. This multi-functionality achieves strong bonding while reducing manufacturing complexity by consolidating materials and processes.
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 reduces or prevents the occurrence of cracks during ultrasonic joining by distributing stress more evenly, ensuring reliable bonding without damage to the capacitor surfaces.
Implementation Method 1
the holder is subjected to ultrasonic vibration while pressing the semiconductor device against the wiring component, thus transmitting the ultrasonic vibration to the bump and joining the electrode of the semiconductor device to the wiring component
Implementation Method 2
The ultrasonic joining is affected less by heat because metals are brought into solid-phase joining under the melting points
Data Source
AI summary
A multilayer ceramic capacitor includes a capacitor body including dielectric layers, first and second inner electrodes, first and second principal surfaces, first and second side surfaces, and first and second end surfaces, first and second outer electrodes on at least the first principal surface and respectively electrically coupled to the first and second inner electrodes, and first and second bumps on a surface on a first principal surface side of the capacitor body and including one of Au, Cu, or Al. The outer electrodes are not on the second principal surface of the capacitor body. The first and second outer electrode respectively include first and second metal layers in contact with the first and second bumps and made of the same material. Thicknesses of the first and second bumps in the first direction are equal to or greater than about 4.5 μm.