Chip Resistor Barrier Layer Anti-Corrosion Design
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Solution Overview
Problem
Conventional chip resistors are susceptible to corrosion from sour and corrosive gases, leading to changes in resistance value and potential open-circuit failures due to gas penetration through interfaces between protective coats and plated layers.
Innovation Solution
The introduction of barrier layers on the main upper electrodes, which are covered by the first protective coat and in turn by the second protective coat, along with plated layers, effectively prevents gas penetration and corrosion, using materials like nickel, palladium, or gold for the barrier layers and tin for the plated layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective coats and plated layers are used, then the chip resistor can be manufactured with standard processes, but corrosive gases penetrate through interfaces causing silver sulfide or copper sulfide formation and resistance value changes
Solution Approach 1:
A barrier layer made of corrosion-resistant material (such as nickel, palladium, or platinum) is introduced between the main upper electrode (silver or copper) and the protective coat system. This intermediary barrier layer prevents corrosive gases from directly contacting and reacting with the silver or copper, thereby blocking the formation of silver sulfide or copper sulfide and maintaining resistance value stability.
Solution Approach 2:
The protective system is constructed as a composite structure consisting of multiple layers: the barrier layer (corrosion-resistant material), the first protective coat (cuttable insulating material), the second protective coat (insulating material), and plated layers (nickel and tin). This composite structure combines the corrosion resistance of the barrier layer with the protective and mechanical properties of the coating system, providing comprehensive protection against corrosive environments.
2Reliability
If barrier layers are added to prevent corrosion, then anti-sulfuration and anti-corrosion protection is achieved, but the device structure becomes more complex
Solution Approach 1:
The protective system is segmented into distinct functional layers: the barrier layer for corrosion protection, the first protective coat for mechanical protection and cuttability, the second protective coat for additional insulation and protection, and plated layers for surface finish and solderability. Each layer performs its specific function, allowing the system to achieve comprehensive protection while maintaining manufacturing feasibility through standardized segment-based processes.
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 barrier layers provide anti-sulfuration and anti-corrosion protection, preventing changes in resistance value and open-circuit failures, ensuring the chip resistor's reliability in corrosive environments.
Implementation Method 1
forming two barrier layers on the main upper electrodes, wherein the barrier layers cover part of the first protective coat
Implementation Method 2
The first plated layers 18 are nickel layers, and each first plated layer 18 covers the main upper electrode 12, the bottom electrode 13, and the side electrode 17. The second plated layers 19 are tin layers, and each second plated layer 19 covers the first plated layer 18. The second plated layers 19 and the first plated layers 18 are formed by electroplating.
Data Source
AI summary
The present invention relates to a chip resistor and method for making the same. The chip resistor includes a substrate, a pair of bottom electrodes, a resistive film, a pair of main upper electrodes, a first protective coat, a pair of barrier layers, a second protective coat, a pair of side electrodes and at least one plated layer. The first protective coat is disposed over the resistive film, and covers part of the main upper electrodes. The barrier layers are disposed on the main upper electrodes, and cover part of the first protective coat. The second protective coat is disposed on the first protective coat, and covers part of the barrier layers. The plated layers cover the barrier layers, the bottom electrodes and the side electrodes. As a result, the chip resistor features high corrosion resistance.