Thin Film Capacitor Non-Uniform Electrode Stress Distribution
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Solution Overview
Problem
Thin film capacitors embedded in electronic circuit boards often experience nonuniform stress during the press process, leading to cracks in the dielectric layer and compromised humidity load reliability.
Innovation Solution
A thin film capacitor design with specific electrode and dielectric layer structures, including regions with varying distances and thermal expansion coefficients, is implemented to distribute stress uniformly and enhance humidity resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a thin film capacitor is embedded in an electronic circuit board through hot press curing, then the capacitor can be mounted in small spaces and reduced height is achieved, but nonuniform stress is applied to the dielectric layer causing cracks and deteriorating humidity load reliability
Solution Approach 1:
The electrode layers are designed with non-uniform thickness, creating regions with maximum distance (B and T regions) from the boundary surface. This local variation in electrode thickness compensates for the nonuniform stress distribution during hot press curing, preventing dielectric layer cracks while maintaining the embedded capacitor's space-saving advantage
Solution Approach 2:
The patent changes the physical parameter of electrode thickness from uniform to non-uniform. By controlling the distance between the boundary surface and electrode layer surface to satisfy specific equations (60%≤(SHb/S) and 60%≤(SHt/S)), the electrode structure adapts to stress distribution, preventing cracks and improving humidity load reliability during embedding
2Ease of manufacture
If uniform electrode layers are used in thin film capacitors, then manufacturing is simplified, but nonuniform stress during pressing causes dielectric layer cracking
Solution Approach 1:
Instead of uniform electrode thickness, the patent implements local quality variations with maximum distance regions (B and T) positioned strategically. This local thickening compensates for stress concentration points in the dielectric layer during pressing, preventing cracks while remaining compatible with standard manufacturing processes
Solution Approach 2:
The non-uniform electrode layer structure is prepared in advance during capacitor fabrication, creating predetermined stress-compensation regions (B and T regions) before the embedding process. This preliminary structural adjustment ensures the dielectric layer can withstand subsequent hot press curing without cracking
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 design prevents dielectric layer cracking and significantly improves humidity load reliability, allowing for effective embedding in electronic circuit boards while maintaining mechanical strength and capacity.
Implementation Method 1
a thermal expansion coefficient of a material constituting a face exposed toward a direction perpendicular to the boundary surface, in the one or more regions B, is designated as αHb, a thermal expansion coefficient of a material constituting a face exposed toward a direction perpendicular to the boundary surface, in the one or more regions T, is designated as αHt, and a thermal expansion coefficient of the dielectric layer is designated as αd
Data Source
AI summary
In a thin film capacitor, a first electrode layer 1 has one or more regions B in which a distance Hb between a boundary surface I of the first electrode layer 1 and a dielectric layer 2, and a surface of the first electrode layer 1, becomes maximum, and an outer layer 12 has one or more regions T in which a distance Ht between the boundary surface I and a surface of the outer layer 12 becomes maximum, as well as one or more regions t in which the distance Ht between the boundary surface I and the surface of the outer layer 12 does not become maximum. A projected area SHb, a projected area SHt, and a projected area S, satisfy equations (1) and (2):60%≤(SHb/S) (1);60%≤(SHt/S) (2).