Lead-Free Thick Film Resistor Composition for Stable Resistance
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Solution Overview
Problem
Conventional thick film resistor compositions face challenges in achieving a resistance temperature coefficient close to zero and stable noise characteristics, particularly due to the use of lead-based components and variations in ruthenium oxide particle size and glass composition, which affect the resistance value and temperature coefficient stability.
Innovation Solution
A lead-free thick film resistor composition incorporating ruthenium oxide powder with specific crystallite and specific surface area characteristics, combined with a glass powder containing SiO2, B2O3, and RO, and amorphous silica powder, to control the resistance temperature coefficient and reduce current noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead oxide is used in glass powder to lower softening point and improve chemical durability, then glass transition temperature and chemical resistance are improved, but environmental pollution and health hazards increase
Solution Approach 1:
The invention extracts and removes the harmful lead oxide component from the glass powder composition while retaining the essential functions of lowering softening point and improving chemical durability through alternative oxide combinations (B2O3, SiO2, Al2O3, ZnO, etc.)
Solution Approach 2:
The invention uses a composite glass powder system comprising multiple oxide components (SiO2 30-70 wt%, B2O3 10-40 wt%, Al2O3 5-20 wt%, ZnO 5-20 wt%, and other metal oxides 1-10 wt%) that work synergistically to achieve the desired softening point (600-800°C) and chemical durability without lead content
2Manufacturing precision
If the proportion of ruthenium-based conductive particles is increased to achieve low resistance value, then resistance value decreases, but resistance temperature coefficient becomes positive and stability deteriorates
Solution Approach 1:
The invention changes the particle size parameters of ruthenium oxide, specifically controlling the average particle diameter to 0.5-5 μm and the proportion of fine particles (0.1-0.5 μm) to 20-80%, which optimizes both resistance value and temperature coefficient stability
Solution Approach 2:
The invention creates a composite conductive phase by combining ruthenium oxide particles with specific glass powder matrices, where the glass composition (containing B2O3, SiO2, Al2O3, ZnO) interacts with the conductive particles to stabilize the resistance temperature coefficient while maintaining low resistance values
3Adaptability or versatility
If glass powder with wide softening point range is used to adjust resistance value, then resistance value control is improved, but resistance temperature coefficient stability deteriorates
Solution Approach 1:
The invention changes the compositional parameters of the glass powder to a specific multi-oxide system with controlled ratios (SiO2 30-70 wt%, B2O3 10-40 wt%, Al2O3 5-20 wt%, ZnO 5-20 wt%, and other metal oxides 1-10 wt%), which provides both wide resistance value adjustability and stable temperature coefficient characteristics
Solution Approach 2:
The invention assigns different functional roles to specific glass components: B2O3 for softening point control, SiO2 for chemical durability, Al2O3 for structural stability, and ZnO for temperature coefficient stabilization, creating localized functional zones within the glass matrix
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 composition effectively adjusts the resistance temperature coefficient to near zero and improves noise characteristics, achieving stable electric properties even in high resistance ranges, while avoiding the use of lead components.
Implementation Method 1
The paste used to form the thick film resistor may be composed of a ruthenium-based conductive particle represented by ruthenium oxide
Implementation Method 2
glass having a softening point lower than the firing temperature of the paste for the thick film resistor was generally used
Implementation Method 3
thick film resistors, such as chip resistors, hybrid ICs, or resistance networks, are formed by printing and firing a paste for a thick film resistor on a ceramic substrate
Data Source
AI summary
A composition for a thick film resistor includes a ruthenium oxide powder, a glass powder, and a silica powder, wherein the composition does not include a lead component, wherein the glass powder contains SiO2, B2O3, and RO (where R represents one or more alkaline earth elements selected from Ca, Sr, and Ba), wherein when a total content of the SiO2, the B2O3, and the RO is 100 parts by mass, the glass powder contains 10 parts by mass to 50 parts by mass of the SiO2, 8 parts by mass to 30 parts by mass of the B2O3, and 40 parts by mass to 65 parts by mass of the RO, wherein the silica powder is an amorphous silica powder having a specific surface area of not less than 60 m2/g and not more than 300 m2/g, and wherein when a total content of the ruthenium oxide powder and the glass powder is 100 parts by weight, the composition for the thick film resistor contains 1 to 12 parts by mass of the silica powder.