Niobium Solid Electrolytic Capacitor Stress Relief Surface Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid electrolytic capacitors with niobium oxide dielectric material are prone to increased leakage current after heat-treatment processes like reflow soldering due to instability and stress-induced cracks at the anode-dielectric interface.
Innovation Solution
A solid electrolytic capacitor design featuring a surface layer of crystalline niobium oxide between a niobium base body and an amorphous niobium oxide dielectric layer, which relieves stress and prevents cracks during heat-treatment, reducing leakage current and equivalent series resistance (ESR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If amorphous niobium oxide is used as dielectric material, then capacitance is increased, but leakage current increases after heat-treatment
Solution Approach 1:
The anode is divided into two distinct layers: a base body layer and a surface layer with different material compositions and structures. This segmentation allows each layer to perform its specific function - the base body provides mechanical support while the surface layer provides stress relief and prevents crack formation during heat-treatment, thereby reducing leakage current while maintaining high capacitance.
Solution Approach 2:
The surface layer is designed with specific local properties (crystalline structure, specific thickness ratio between 0.05 and 1.5 times the dielectric layer thickness) that differ from the base body. This local quality enhancement at the critical interface region provides stress relief and prevents crack propagation, solving the leakage current problem without compromising the overall capacitance provided by the amorphous dielectric layer.
2Stability of the object's composition
If niobium nitride region is formed in dielectric layer, then resistance to heat-treatment is improved, but leakage current still increases
Solution Approach 1:
The surface layer acts as an intermediary structure between the base body and the dielectric layer. It provides the necessary stress relief and crack prevention functionality that the niobium nitride region alone could not achieve. This intermediary layer with its specific crystalline structure and thickness ratio effectively bridges the mechanical properties of the base body and dielectric layer, preventing interface cracks and reducing leakage current.
3Strength
If surface layer thickness is increased, then stress relief is improved, but equivalent series resistance increases
Solution Approach 1:
The thickness ratio of the surface layer to the dielectric layer is precisely controlled within the range of 0.05 to 1.5 times. This parameter optimization ensures that the surface layer is thick enough to provide adequate stress relief and prevent crack formation, yet thin enough to minimize its impact on the equivalent series resistance. The crystalline structure of the surface layer also contributes to low resistance while providing mechanical strength.
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 effectively reduces leakage current and ESR by controlling the thickness ratio of the surface layer to dielectric layer, maintaining capacitance stability during heat-treatment processes.
Implementation Method 1
the stress by expansion and shrinkage of its base body and dielectric layer during heat-treatment process
Implementation Method 2
a surface layer that includes crystalline niobium oxide which is formed between the base body that includes niobium, and a dielectric layer that includes amorphous niobium oxide
Implementation Method 3
Dielectric layer 102 is made of amorphous niobium oxide and formed by anodic oxidation on the anode 101 to cover the anode 101
Data Source
AI summary
An anode includes a base body of a sintered porous material of niobium particles, a surface layer made of crystalline niobium oxide formed on the base body, and an anode lead having partly buried in base body 1a. A dielectric layer containing amorphous niobium oxide is formed by anodic oxidation on the cathode. An electrolyte layer made of polypyrrole is formed on the dielectric layer and a cathode is formed on the electrolyte layer. A conductive adhesive layer and cathode terminal are formed on an upper surface of the cathode. The anode lead exposed from the base body is connected to an anode terminal by welding. In addition, a mold resin is formed to cover the second conductive layer, the cathode terminal and the anode terminal so as to expose cathode terminal and an end of anode terminal.