Chip Resistor Back Electrode Layout for Heat and Bonding Reliability
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Solution Overview
Problem
Existing chip resistors face challenges in efficiently dissipating heat and maintaining bonding strength with circuit boards, particularly under temperature cycles, due to limitations in back surface electrode design and area ratio.
Innovation Solution
The chip resistor design includes an insulating substrate with a resistor layer, first and second electrodes, and back surface electrodes with increased lengths and area ratios, which enhance heat dissipation and bonding strength by optimizing the contact area and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the back surface electrode area ratio is increased to improve heat dissipation and bonding strength, then the bonding strength and heat dissipation improve, but the device complexity increases
Solution Approach 1:
The back surface electrode is segmented into multiple independent electrodes (first back surface electrode and second back surface electrode) positioned at different locations. This segmentation allows each electrode to independently bond with corresponding land patterns on the circuit board, distributing the bonding stress and improving overall bonding strength without requiring a single large complex electrode structure
Solution Approach 2:
The patent applies different electrode configurations to different local areas of the back surface. The first back surface electrode is positioned to overlap with the first land pattern while the second back surface electrode overlaps with the second land pattern. This local optimization ensures that each electrode provides maximum bonding strength at its specific location, improving overall bonding performance without increasing global complexity
2Loss of energy
If the back surface electrode length is increased to improve heat dissipation, then the heat dissipation efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The heat dissipation function is segmented across multiple back surface electrodes rather than relying on a single large electrode. This allows the total effective heat dissipation area to be increased while maintaining manageable dimensions for each individual electrode, reducing the precision requirements for manufacturing each electrode while achieving cumulative heat dissipation improvement
Solution Approach 2:
The patent utilizes the planar dimension of the back surface by positioning multiple electrodes at different locations rather than extending a single electrode in one dimension. This dimensional distribution increases the total heat dissipation area while keeping each electrode within manufacturable size limits, reducing precision requirements
3Reliability
If the back surface electrode area ratio is increased to reduce thermal stress, then the temperature cycle reliability improves, but the device complexity increases
Solution Approach 1:
The stress distribution function is achieved through segmentation into multiple back surface electrodes positioned at different locations on the insulating substrate. Each electrode independently shares the thermal stress load during temperature cycles, reducing the stress concentration on any single electrode and improving overall reliability without requiring a single large complex electrode structure
Solution Approach 2:
The patent optimizes thermal stress resistance locally by positioning electrodes to overlap with land patterns at specific locations. This local optimization ensures that stress is distributed across multiple bonding points, improving temperature cycle reliability while maintaining a relatively simple overall electrode configuration
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
This design improves the short-time overload characteristics and temperature cycle reliability of the chip resistor by efficiently dissipating heat and increasing the bonding strength with circuit boards, thereby reducing the occurrence of cracks in bonding members.
Implementation Method 1
a ratio of a sum of a first area of the first back surface electrode and a second area of the second back surface electrode to an area of the back surface is 31% or more... efficiently dissipating heat... reducing thermal stress
Data Source
AI summary
A chip resistor includes: an insulating substrate having a front surface, a back surface on an opposite side of the insulating substrate from the front surface, a first end surface connected to the front surface and the back surface, and a second end surface on an opposite side of the insulating substrate from the first end surface; a resistor layer disposed over the front surface; a first electrode connected to the resistor layer; and a second electrode connected to the resistor layer, wherein the first end surface and the second end surface are spaced apart from each other in a direction in which the first electrode and the second electrode are spaced apart from each other, and wherein the first electrode includes a first back surface electrode disposed over the back surface and electrically connected to the resistor layer.