Multilayer Ceramic Capacitor Electrode Layout for Tombstone Prevention
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Solution Overview
Problem
The tombstone phenomenon occurs in multilayer ceramic capacitors during reflow soldering due to imbalances in tensile forces applied by solder, causing one external electrode to rise, which is attributed to variations in solder wetting, area, amount, temperature, and mounting position.
Innovation Solution
The multilayer ceramic capacitors feature external electrodes with thickest portions off-center in the width direction toward the side surfaces, which are thicker in the length direction, and positioned closer to the mounting surface to reduce the occurrence of the tombstone phenomenon by altering the distribution of tensile forces during soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If external electrodes are made with uniform thickness at the center, then manufacturing is simple, but tombstone phenomenon occurs during soldering due to uneven tensile force distribution
Solution Approach 1:
The external electrodes are designed with asymmetric thickness distribution, where the thickest portion is positioned off-center toward one of the side surfaces rather than at the center. This asymmetric geometry creates a moment that counteracts the uneven tensile forces during soldering, preventing the tombstone phenomenon while maintaining manufacturing simplicity through a single-layer electrode structure
Solution Approach 2:
The external electrodes have non-uniform thickness with a specific region (thickest portion) having greater thickness than other regions. This local variation in quality is strategically positioned to optimize the stress distribution during soldering, addressing the mounting stability issue without requiring complex overall structural changes
2Stability of the object's composition
If external electrodes are positioned symmetrically, then structural balance is maintained, but tombstone phenomenon occurs due to imbalances in solder wetting, area, amount, and temperature
Solution Approach 1:
The patent intentionally introduces asymmetry in the external electrode design by positioning the thickest portion off-center. This asymmetric feature compensates for the various imbalances (solder wetting, area, amount, temperature) that occur during the soldering process, thereby preventing the tombstone phenomenon while maintaining overall structural functionality
3Manufacturing precision
If thickest portion of external electrode is at the center, then manufacturing precision is easier to control, but tombstone phenomenon occurs due to uneven tensile force distribution during soldering
Solution Approach 1:
The external electrodes are designed with a localized thickest portion positioned off-center toward one of the side surfaces. This local variation in thickness creates a moment arm that counteracts the uneven tensile forces during soldering, preventing the tombstone phenomenon while maintaining manufacturing precision through controlled local geometry rather than requiring complex overall thickness variations
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including internal electrode layers and dielectric layers that are alternately laminated, main surfaces opposite to each other in a lamination direction, end surfaces opposite to each other in a length direction that intersects with the lamination direction, and side surfaces opposite to each other in a width direction that intersects with the lamination direction and the length direction, and external electrodes on the end surfaces. Each of the external electrodes includes a thickest portion at a position off-center in the width direction toward either one of the side surfaces, and the thickest portion is thicker in the length direction than a remainder of the external electrode.