Multilayer Capacitor Cover Layers Phosphor Sintering
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Solution Overview
Problem
Multilayer ceramic capacitors face reliability issues due to cracking at the connection between the active region and the cover layers, caused by differences in sintering properties, which can lead to reduced capacitance and increased pore formation.
Innovation Solution
Incorporating a phosphor (P) in the ceramic composition of the cover layers, with a content of 1 to 2 wt % based on the total weight of the ceramic powder, to minimize the difference in sintering properties between the active region and the cover layers, thereby reducing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the stacking number of dielectric layers is increased to achieve higher capacity, then the capacitance increases, but the difference in sintering properties between the active region and cover layer increases, leading to cracks
Solution Approach 1:
The patent applies local quality by adding phosphor specifically to the cover layer composition (0.1-5 wt% P2O5) while keeping the active region composition different. This creates localized compositional differences that tailor sintering behavior to specific regions, allowing the cover layer to compensate for thermal stress during sintering and preventing cracks at the active region-cover layer interface, thus resolving the contradiction between high capacitance and crack resistance
2Quantity of substance
If more dielectric layers are stacked using high-k dielectric materials to increase capacity, then the capacitance increases, but stress occurs during sintering causing cracks in the connection portion
Solution Approach 1:
The patent changes the compositional parameters of the cover layer by incorporating phosphor (0.1-5 wt% P2O5), which modifies the sintering characteristics including shrinkage rate and thermal expansion properties. This parameter change allows the cover layer to better match the active region during sintering, reducing thermal stress and preventing structural failure while maintaining high capacitance through multiple dielectric layers
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
The use of phosphor in the cover layers enhances the sintering properties, reducing the frequency of cracks and improving the reliability of the multilayer capacitor by controlling grain growth and minimizing the difference in shrinkage between the active region and the cover layers.
Implementation Method 1
a difference in sintering properties between an active region and a cover layer in a capacitor body may be increased. Thus, after a capacitor body is sintered, a portion thereof connecting the active region and the cover may be cracked due to stress that occurs due to the difference in sintering properties
Data Source
AI summary
A multilayer capacitor includes a capacitor body having an active region and cover layers disposed on upper and lower surfaces of the active region. The active region includes a plurality of dielectric layers and first and second internal electrodes alternately disposed with the plurality of dielectric layers interposed therebetween. The first and second internal electrodes are respectively exposed to opposite surfaces of the capacitor body. First and second external electrodes electrically are connected to the exposed portions of the first and second internal electrodes on the capacitor body, respectively. A phosphor (P) is dispersed among a non-phosphor material in the cover layers of the capacitor body. In some examples, the phosphor (P) has a content of 1 to 2 wt %, based on a total weight of a ceramic powder of the cover layers not including the phosphor (P).