Ceramic Capacitor Electrode Plating for Tombstone Suppression
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Solution Overview
Problem
The tombstone phenomenon occurs during the mounting of multi-layer ceramic capacitors, where solder surface tension causes the components to rise, leading to mounting failures, especially in densely packed electronic circuits with reduced size and height.
Innovation Solution
The ceramic electronic component features external electrodes with Ni plating layers having a steep inclination, defined by a thickness ratio t2/t1 of 0.4 or more, which suppresses the tombstone phenomenon by enhancing solder wettability and preventing the component from rising during the reflow mounting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size and height of the multi-layer ceramic capacitor are reduced, then the mounting space is saved and integration is improved, but the tombstone phenomenon becomes more likely to occur during mounting
Solution Approach 1:
The patent applies local quality by creating a specific rounded shape at the inner end portion of the external electrode where it contacts the solder. This localized geometric modification (with radius R1 and R2) concentrates the effect on the critical mounting interface while leaving the rest of the capacitor structure unchanged, thereby suppressing the tombstone phenomenon without increasing overall size.
Solution Approach 2:
The patent changes the geometric parameters of the external electrode's inner end portion by defining specific radius values (R1 and R2) that create a rounded profile. This parameter modification alters how the solder interacts with the electrode surface, preventing the tombstone effect during reflow mounting while maintaining the reduced size and height of the capacitor.
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:
Instead of making the ceramic body end surfaces recessed to flatten the external electrodes, the patent inverts the approach by maintaining flat ceramic surfaces and creating the rounded profile directly on the external electrode metal layers. This reverses the conventional method and simplifies the manufacturing process while achieving the same tombstone suppression effect.
Solution Approach 2:
The rounded shape of the external electrode's inner end portion is formed during the electrode fabrication process itself, before mounting. This preliminary shaping action ensures that when solder is applied and heated, the pre-formed geometry already provides the necessary tombstone suppression, eliminating the need for additional post-processing steps.
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 the occurrence of mounting failures by ensuring the ceramic components maintain a stable posture on the substrate, even in compact designs, by controlling the shape and inclination of the inner end portions of the external electrodes.
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
solder wets and spreads antecedently on one of the pair of external electrodes
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.