LTCC Thick Film Conductor Composition for Resistivity Stability
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Solution Overview
Problem
Existing thick film conductor compositions for Low Temperature Co-fired Ceramic (LTCC) multilayer ceramic circuits face issues such as resistivity variation, conductor sinking, and water entrapment leading to structural instability in microwave and high-frequency applications.
Innovation Solution
A thick film composition comprising 30-98% finely divided noble metals, 0.2-20% refractory glass with specific viscosity, and 0.1-5% inorganic binders like metal oxides, dispersed in an organic medium, which are immiscible with remnant glasses, ensuring superior refire stability and optimal interface bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high-melting refractory glasses are incorporated to reduce resistivity variation, then resistivity stability is improved, but miscibility with remnant glasses deteriorates causing interface bonding issues
Solution Approach 1:
The patent changes the chemical composition parameters of the glass phase by incorporating specific amounts of metal oxides (Al2O3: 1-10 wt%, ZnO: 1-5 wt%, B2O3: 1-5 wt%) and non-metal oxides (SiO2: 5-20 wt%, P2O5: 1-5 wt%) to achieve optimal balance between resistivity stability and glass miscibility. This parameter optimization resolves the contradiction by finding the precise compositional window where both requirements are satisfied.
Solution Approach 2:
The patent creates a composite glass system combining multiple oxide components (refractory oxides like Al2O3 and ZnO with network formers like SiO2 and B2O3) to achieve synergistic effects. This composite approach allows the glass phase to simultaneously provide high-temperature stability for resistivity control and appropriate chemical reactivity for interface bonding with remnant glasses in the LTCC substrate.
2Quantity of substance
If metal oxide and non-metal oxide binder materials are added to increase densification, then conductor density is improved, but crystalline material growth into the conductor increases changing resistivity
Solution Approach 1:
The patent precisely controls the total oxide content (5-20 wt%) and the ratio between different oxide types to optimize densification while preventing excessive crystal growth. By adjusting these parameters, the glass phase provides sufficient binding and densification without allowing harmful crystalline phases to form and disrupt the conductor's resistivity.
Solution Approach 2:
The patent creates local chemical environments within the conductor composite where metal oxides promote densification at the particle interfaces while non-metal oxides maintain a glassy matrix that prevents widespread crystalline growth. This spatial differentiation of oxide functions allows simultaneous achievement of high density and resistivity stability.
3Ease of manufacture
If conventional thick film compositions are used for multilayer integration, then manufacturing flexibility is improved, but water entrapment occurs leading to structural instability
Solution Approach 1:
The patent modifies the chemical composition of the glass phase by incorporating specific oxide combinations that alter the glass transition temperature and viscosity characteristics. These parameter changes enable the glass matrix to more effectively bind and encapsulate volatile components, preventing water entrapment and subsequent structural instability during the co-firing process while maintaining multilayer manufacturing flexibility.
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 provides stable electrical performance with minimal resistivity variation and reduced risk of structural instability upon repeated firing, enhancing the reliability of LTCC devices in high-frequency applications.
Implementation Method 1
one or more refractory glass compositions with a specific viscosity (log n) in the range of 6-7.6 at the firing temperature of said circuit
Implementation Method 2
said glass compositions are immiscible or partially miscible with remnant glasses present in the low temperature co-fired ceramic substrate glasses at the firing conditions
Implementation Method 3
dispersed in (c) organic medium
Data Source
AI summary
The present invention is directed to a thick film composition for use in low temperature co-fired ceramic circuits comprising, based on weight percent total thick film composition: (a) 30-98 weight percent finely divided particles selected from noble metals, alloys of noble metals and mixtures thereof; (b) one or more selected inorganic binders and/or mixtures thereof, and dispersed in (c) organic medium, and wherein said glass compositions are immiscible or partially miscible with remnant glasses present in the low temperature co-fired ceramic substrate glasses at the firing conditions.The present invention is further directed to methods of forming multilayer circuits utilizing the above composition and the use of the composition in high frequency applications (including microwave applications).