Chip Resistor Palladium Silver Electrode Design
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Solution Overview
Problem
Chip resistors face issues with initial resistance values being higher than desired due to variations in printing and sintering conditions, leading to defective products and potential disconnection due to silver diffusion from front electrodes into resistive elements, affecting TCR characteristics and causing separation phenomena.
Innovation Solution
The use of front electrodes with 1-5 wt% palladium and balance silver, and auxiliary electrodes with 15-30 wt% palladium and a lower resistivity metal like gold, to increase resistance value changes and prevent silver diffusion-induced disconnections, while ensuring electrical continuity and stable resistance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If another resistive paste is printed and sintered to lower the initial resistance value, then the resistance value can be adjusted to target value, but silver diffusion from front electrodes into resistive element increases causing separation phenomenon and disconnection
Solution Approach 1:
A barrier electrode layer is introduced between the front electrode and the resistive element to prevent direct contact and silver diffusion. This intermediary layer acts as a diffusion barrier while maintaining electrical conductivity, allowing resistance adjustment through repeated sintering without causing separation or disconnection of the front electrode from the resistive element.
Solution Approach 2:
The front electrode is constructed as a composite structure with multiple layers having different functions: a lower resistivity layer for electrical conductivity and a higher melting point layer for diffusion barrier properties. This composite material approach enables the electrode to simultaneously provide low resistance and prevent silver diffusion into the resistive element during repeated sintering processes.
2Manufacturing precision
If repeated sintering is performed to lower resistance value, then resistance adjustment is achieved, but TCR characteristics deteriorate due to silver diffusion
Solution Approach 1:
The barrier electrode layer serves as a mediator that prevents silver atoms from diffusing from the front electrode into the resistive element during repeated sintering. This maintains the compositional stability and TCR characteristics of the resistive element while allowing the resistance value to be adjusted through the repeated sintering process.
Solution Approach 2:
The front electrode material composition is changed to include metals with higher melting points and lower diffusivity. This parameter change in material properties enables the electrode to withstand repeated high-temperature sintering cycles without significant silver diffusion, thereby maintaining the TCR characteristics of the resistive element while achieving resistance value adjustment.
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 configuration allows for effective lowering of initial resistance values, preventing disconnections and improving yield rates by securing electrical continuity and maintaining accurate resistance measurements, even with variations in probe positions during trimming.
Implementation Method 1
a resistive paste is printed and sintered on one surface of the aggregate substrate to thereby form a number of resistive elements
Implementation Method 2
laser light is applied to the resistive element to form the trimming groove therein while probes are brought into contact with the pair of front electrodes
Implementation Method 3
an amount of silver of the front electrodes diffused into the resistive element increases
Data Source
AI summary
The invention is to provide a chip resistor suitable for lowering an initial resistance value. A chip resistor 1 according to the present invention is provided with: an insulating substrate 2; a pair of front electrodes 3 which are provided on a front surface of the insulating substrate 2 so as to face each other with a predetermined interval therebetween; a resistive element 4 which is provided so as to bridge the front electrodes 3; a pair of auxiliary electrodes 5 which are provided so as to cover the front electrodes 3 and overlap end portions of the resistive element 4; and the like. The chip resistor 1 is configured such that: the front electrodes 3 are formed of a material which contains 1 to 5 wt % Pd and the balance Ag; and the auxiliary electrodes 5 are formed of a material which contains 15 to 30 wt % Pd and a metal material (e.g. Au) lower in resistivity than Pd and the balance Ag.