Chip Resistor Electrode Structure for Thermal Stress Absorption
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Solution Overview
Problem
Conventional chip resistors experience thermal stress peeling due to rigid solder joints, which are not effectively absorbed by the solder material, leading to potential conduction failure.
Innovation Solution
The chip resistor design includes back surface electrodes made of a synthetic resin with thick first electrode portions and multiple second electrode portions, allowing for flexibility to absorb thermal stress, preventing peeling by setting the first electrode portion's height greater than the second portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength solder is used to increase joint strength, then the solder joint becomes rigid with high Young's modulus, but the thermal stress cannot be absorbed and is transmitted to the back surface electrode causing peeling
Solution Approach 1:
The patent changes the material parameter of the back surface electrode from conventional rigid materials to a synthetic resin material with conductive particles that exhibits flexibility. This parameter change allows the electrode to absorb thermal stress through elastic deformation, preventing stress transmission to the insulating substrate while maintaining electrical conductivity through the embedded conductive particles.
Solution Approach 2:
The back surface electrode is constructed as a composite material consisting of a synthetic resin matrix combined with conductive particles. This composite structure provides both the flexibility needed to absorb thermal stress and the electrical conductivity required for signal transmission, resolving the contradiction between mechanical compliance and electrical functionality.
2Reliability
If the back surface electrode is made thick to increase solder joint thickness and relieve thermal stress, then the thermal stress can be absorbed, but the electrode structure becomes complex with multiple layers
Solution Approach 1:
The patent employs a flexible synthetic resin material for the back surface electrode that can deform elastically under thermal stress. This flexible electrode structure absorbs thermal stress through its inherent material properties rather than requiring increased thickness or multi-layer construction, thereby maintaining structural simplicity while achieving reliable thermal shock resistance.
3Reliability
If conventional sintered silver electrodes are used, then good electrical conductivity is achieved, but the rigid structure transmits thermal stress causing peeling from the insulating substrate
Solution Approach 1:
The back surface electrode is constructed as a composite material consisting of a synthetic resin matrix combined with conductive particles. This composite structure provides both the flexibility needed to absorb thermal stress and the electrical conductivity required for signal transmission, resolving the contradiction between mechanical compliance and electrical functionality.
Solution Approach 2:
The synthetic resin material acts as an intermediary between the solder joint and the insulating substrate, absorbing thermal stress through its flexibility and preventing stress transmission to the substrate. The conductive particles within the resin maintain the electrical conduction function, making the resin an effective mediator that provides both mechanical compliance and electrical functionality.
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 provides high thermal shock resistance by absorbing thermal stress through the flexible resin material, preventing peeling and ensuring reliable electrical connection.
Implementation Method 1
the flexibility of the solder (Young's modulus)... the hardness of solder (Young's modulus) varies depending on the composition of its solder material... a joint portion of the chip resistor mounted using a high-strength solder is rigid due to its material
Data Source
AI summary
A chip resistor according to the present invention includes an insulating substrate, a pair of back surface electrodes, a pair of top surface electrodes, a resistor, and a pair of end face electrodes. The back surface electrode includes the first electrode portion located inwardly and away from the end face of the insulating substrate, and the two second electrode portions arranged on two portions, respectively, in the short direction of the insulating substrate with the cutout portion, which is positioned between the end face of the insulating substrate and the first electrode portion, being interposed therebetween, and the maximum height of the first electrode portion is set to be more than the maximum height of the second electrode portions.