Flexible Varistor Terminations for Bending and Thermal Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multilayer ceramic varistors are prone to mechanical and thermal stress, leading to damage or failure when subjected to bending or thermal fluctuations, as they can fracture or become disconnected from substrates, compromising their ability to protect sensitive electronic components from voltage spikes and current surges.
Innovation Solution
A varistor design featuring a monolithic body with compliant external terminals made of conductive polymeric compositions, including polymers and dispersed conductive particles, which provide flexibility and improved electrical conductivity, reducing stress and enhancing durability by incorporating a conductive polymeric composition in the external terminals and using plating techniques for secure connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer ceramic varistors are used with rigid terminals, then electrical connectivity is achieved, but mechanical stress causes fracture or disconnection during bending or thermal cycling
Solution Approach 1:
The patent applies this principle by using a conductive polymer composition as the external terminal material. The conductive polymer provides flexible, compliant terminations that can bend and flex with the substrate without fracturing, unlike rigid ceramic terminals. This flexible terminal structure absorbs mechanical stress and maintains electrical connectivity during board flexing and thermal cycling.
Solution Approach 2:
The patent applies this principle by creating a composite terminal structure consisting of a conductive polymer composition. The conductive polymer combines the flexibility of polymers with the electrical conductivity of conductive particles, creating a material that is both mechanically compliant and electrically conductive, thus resolving the contradiction between rigidity for connectivity and flexibility for stress resistance.
2Ease of manufacture
If conventional rigid terminals are used, then manufacturing is simplified, but thermal expansion causes damage during temperature fluctuations
Solution Approach 1:
The patent applies this principle by changing the material parameter of the terminal from rigid ceramic to conductive polymer. The conductive polymer has different thermal expansion properties that are more compatible with the substrate, reducing thermal stress during temperature cycling. The material parameter change from rigid to compliant resolves the thermal expansion compatibility issue while maintaining manufacturability through established polymer deposition techniques.
3Reliability
If compliant conductive polymer terminals are used, then mechanical flexibility and thermal durability are improved, but electrical conductivity must be maintained
Solution Approach 1:
The patent applies this principle by formulating a conductive polymer composition that combines a polymer matrix with dispersed conductive particles. The polymer provides mechanical compliance and flexibility, while the conductive particles (such as metal particles or carbon-based materials) provide electrical conductivity. This composite structure simultaneously achieves both requirements: mechanical flexibility for stress resistance and electrical conductivity for signal transmission.
Solution Approach 2:
The conductive polymer acts as an intermediary material between the rigid ceramic body and the flexible substrate. It mediates the mechanical stress and thermal expansion differences, providing a compliant interface that protects the rigid ceramic from fracture while maintaining electrical connectivity to the substrate.
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 varistor exhibits enhanced mechanical and thermal durability, maintaining performance under significant bending and temperature cycling without substantial degradation, effectively diverting voltage spikes and current surges, and sustaining repetitive electrostatic discharge strikes.
Implementation Method 1
At least one of the first external terminal or the second external terminal can include a conductive polymeric composition
Implementation Method 2
A varistor design featuring a monolithic body with compliant external terminals made of conductive polymeric compositions, including polymers and dispersed conductive particles, which provide flexibility and improved electrical conductivity, reducing stress
Implementation Method 3
using plating techniques for secure connections
Data Source
AI summary
A varistor can include a monolithic body including a plurality of dielectric layers stacked in a Z-direction that is perpendicular to a longitudinal direction. The monolithic body can have a first end and a second end that is spaced apart from the first end in the longitudinal direction. A first external terminal can be disposed along the first end. A second external terminal can be disposed along the second end. A first plurality of electrodes can be connected with the first external terminal and can extend from the first end towards the second end of the monolithic body. A second plurality of electrodes can be connected with the second external terminal and can extend from the second end towards the first end of the monolithic body. At least one of the first external terminal or the second external terminal can include a conductive polymeric composition.