Ceramic Capacitor Electrode Geometry to Suppress Tombstoning
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Solution Overview
Problem
The tombstone phenomenon occurs during the mounting of multi-layer ceramic capacitors, where solder wets and spreads on one external electrode, causing the component to rise due to surface tension, leading to potential mounting failures.
Innovation Solution
The ceramic electronic component features external electrodes with Ni plating layers and rounded inner end portions, where the ratio of thickness t2 to t1 is set to 0.4 or more, inhibiting the tombstone phenomenon by steepening the outer surface inclination of the inner end portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the multi-layer ceramic capacitor is reduced in size and weight, then the mounting space is reduced and integration is improved, but the tombstone phenomenon occurs more frequently during mounting
Solution Approach 1:
The patent applies local quality by creating a specific rounded inner end portion shape at the inner end of the external electrode. This localized geometric modification (with radius R1 and R2) concentrates the anti-tombstone effect at the critical solder joint area without affecting the overall component size, allowing small capacitors to resist the tombstone phenomenon effectively
Solution Approach 2:
The patent changes the geometric parameters of the external electrode's inner end portion, specifically defining rounded corners with radii R1 and R2 that satisfy specific relationships (R1 ≥ 0.05mm, R2 ≥ 0.05mm, and R1/R2 ≥ 0.5). This parameter optimization creates an ideal solder wetting surface that prevents uneven solder distribution and the resulting tombstone effect in miniaturized components
2Reliability
If the end surfaces of the ceramic body are made recessed to flatten external electrodes, then the tombstone phenomenon is suppressed, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the rounded inner end portions during the external electrode formation process itself, rather than requiring subsequent mechanical processing. The rounding is created during the plating or screen printing stage, integrating the anti-tombstone feature into the base manufacturing flow without adding separate recessing operations
Solution Approach 2:
The patent replaces the traditional recessed flat surface with a rounded inner end portion geometry. The curved surface with specified radii R1 and R2 provides the necessary surface characteristics to prevent tombstone phenomenon while being more easily formed through standard plating or printing processes compared to creating precise recesses
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 suppresses the occurrence of the tombstone phenomenon, reducing the likelihood of mounting failures even in small, lightweight configurations, and ensures reliable electrical connection and physical fixation on the mounting substrate.
Implementation Method 1
the multi-layer ceramic capacitor rises up due to the surface tension of the solder acting on the one of the external electrodes
Implementation Method 2
The multi-layer ceramic capacitor is mounted by soldering its pair of external electrodes to a pair of terminals of a mounting substrate
Data Source
AI summary
A ceramic electronic component includes: a ceramic body including main surfaces perpendicular to a first axis and end surfaces perpendicular to a second axis; and external electrodes covering the end surfaces and extending from the end surfaces to the main surfaces. The external electrode includes a surface layer portion including a Sn plating layer, and an inner layer portion including a Ni plating layer adjacent to the Sn plating layer and including rounded inner end portions on the main surfaces. In a cross-section perpendicular to a third axis, a ratio t2/t1 is 0.4 or more, where t2 is a thickness in the first axis direction of a portion where an inclination of a tangent line of an outer surface of the inner end portion to each main surface is 45°, and t1 is a maximum thickness in the first axis direction of the inner layer portion on each main surface.