Laminated Ceramic Capacitor Low-Temperature Sintering
Solution Overview
Problem
Existing laminated ceramic capacitors face challenges in achieving high dielectric constant, longevity, and X7R temperature characteristics when sintered at low temperatures, particularly below 1030°C, and when dielectric ceramic layers are thinned to 2 μm or less, as previous solutions either require high-temperature sintering or are insufficient in ensuring reliability.
Innovation Solution
A laminated ceramic capacitor design featuring dielectric ceramic layers with primary phase grains of BaTiO3, secondary phase grains containing rare earth elements, and a grain boundary phase with boron and lithium, using copper or copper alloy internal electrodes, and specifying grain size distribution and secondary phase abundance to ensure sintering at low temperatures while maintaining high dielectric constant and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copper or copper alloy is used as internal electrodes to replace nickel, then cost is reduced and sintering temperature can be lowered, but it becomes difficult to achieve sufficient dielectric characteristics and longevity when sintered at low temperatures
Solution Approach 1:
The patent modifies the dielectric ceramic composition by adjusting the Ba/Ti ratio to 1.000≦A/B≦1.035 and adding specific amounts of rare earth elements (0.05≦a≦0.75 mol%) and MnO (0.25≦b≦2.0 mol%) to enable low-temperature sintering while maintaining reliability. This parameter optimization allows copper internal electrodes to be sintered at 1030°C or below without sacrificing longevity or dielectric characteristics.
Solution Approach 2:
The patent creates a composite dielectric ceramic system combining BaTiO3 with multiple auxiliary components including rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y), MnO, and other metals (B, Li, Si, V, Mo, Cu, Ca, Sr). This composite material approach enables simultaneous achievement of low-temperature sintering capability and high reliability with copper internal electrodes.
2Volume of moving object
If dielectric ceramic layers are thinned to reduce capacitor size, then compactness is improved, but achieving high dielectric constant and longevity becomes more difficult
Solution Approach 1:
The patent optimizes the grain size distribution parameters (D20, D50, D95, CV value) to control the microstructure of thinned dielectric layers. By maintaining specific grain size relationships even in ultra-thin layers (2 μm or less), the patent achieves both compactness and high dielectric constant with excellent longevity.
Solution Approach 2:
The patent creates a controlled non-uniform grain size distribution within the dielectric layer, where finer grains dominate but a specific distribution pattern is maintained. This local structural optimization ensures that even at 2 μm thickness, the layer achieves sufficient dielectric constant and longevity through optimized grain boundary characteristics.
3Reliability
If grain size is reduced to increase grain boundaries for better longevity, then reliability is improved, but dielectric constant may decrease
Solution Approach 1:
The patent precisely controls the grain size distribution parameters (D20≦D50×70%, D50≦t/4, D95≦t/2, CV value) to achieve an optimal balance. This parameter optimization ensures sufficient grain boundaries for longevity while maintaining adequate grain volume for high dielectric constant, resolving the trade-off between reliability and dielectric performance.
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 solution achieves a high dielectric constant of 1800 or more, X7R temperature characteristics, and longevity exceeding 100 hours under high-temperature load, even when sintered at 1030°C or below and with dielectric ceramic layers reduced to 2 μm or less, ensuring reliable performance.
Implementation Method 1
a laminated ceramic capacitor having a dielectric constant of 2000 or more
Implementation Method 2
sintered at low temperature... sintering to be implemented at 1030° C. or preferably 1000° C. or below
Data Source
AI summary
A laminated ceramic capacitor has multiple layered dielectric ceramic layers of a dielectric ceramic constituted by primary phase grains whose primary component is BaTiO3, secondary phase grains containing at least Re (Re represents at least one of Eu, Gd, Dy, Ho, Er, Yb, and Y), Ba, and Ti, and grain boundary phase containing at least one of B and Li or both; and internal electrodes which are made of Cu or Cu alloy. When a thickness of the dielectric ceramic layer is given by t, and when grain sizes at cumulative 20%, cumulative 50%, and cumulative 95% points of a cumulative count distribution of the primary phase grains are given by D20, D50, and D95, respectively, D20≦D50×70%, D50≦t/4, D95≦t/2, and CV value ((standard deviation between D20 and D95)/D50)<40% are satisfied.