Lead-Free LTCC Conductor Paste for Microwave Circuits
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Solution Overview
Problem
Existing thick film conductor compositions for high-frequency microwave applications require multiple layers or 'double print' processes to achieve desired properties like wire bond acceptance and adhesion, while also needing to minimize or eliminate lead and cadmium content to meet environmental regulations.
Innovation Solution
A lead-free and cadmium-free thick film composition comprising electrically conductive gold powder and glass frit or ceramic oxide binders, dispersed in an organic medium, which can be applied in a single layer to maintain desired properties and support wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free and cadmium-free glass frit compositions are used to meet environmental regulations, then environmental compliance is improved, but maintaining desired conductor properties (wire bond acceptance and adhesion) becomes more difficult
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass frit by incorporating specific metal oxides (bismuth oxide, zinc oxide, boron oxide, silicon dioxide) in optimized ratios to achieve the desired conductor properties without lead or cadmium. This parameter adjustment allows the paste to maintain proper adhesion and wire bond acceptance while meeting environmental requirements.
Solution Approach 2:
The invention uses a composite glass frit formulation combining multiple oxide components (Bi2O3, ZnO, B2O3, SiO2, Al2O3) to create a material that exhibits both environmental compliance and superior conductor properties. The synergistic interaction of these composite materials enables single-application sufficiency while achieving desired adhesion and wire bond characteristics.
2Reliability
If multiple applications of conductor composition are used to achieve desired wire bond acceptance and adhesion, then conductor properties are improved, but fabrication complexity and processing time increase
Solution Approach 1:
The patent optimizes the paste formulation parameters including metal particle size distribution (bimodal or multimodal distribution with specific D10, D50, D90 values), glass frit composition, and organic vehicle properties to enable adequate conductor properties from a single application. This parameter optimization eliminates the need for multiple print operations, simplifying the fabrication process.
Solution Approach 2:
The invention incorporates preliminary optimization of the paste formulation during manufacturing, including pre-mixed metal particle distributions and optimized glass frit compositions, so that the paste is pre-configured to achieve desired conductor properties in a single application, eliminating the need for subsequent re-application operations.
3Reliability
If multiple applications of conductor composition are used to achieve desired properties, then conductor performance is improved, but manufacturing time and productivity are reduced
Solution Approach 1:
The patent adjusts critical parameters including metal particle size distribution (combining fine particles for adhesion with coarser particles for conductivity), glass frit softening point, and organic vehicle volatility to enable single-application sufficiency. This parameter optimization reduces the number of print cycles required, thereby increasing manufacturing throughput and productivity.
Solution Approach 2:
The invention ensures that a single application of the optimized paste delivers continuous and adequate conductor properties without requiring interruptive re-application operations. The paste formulation maintains proper flow and settlement characteristics during the single print operation, ensuring complete coverage and adequate properties in one continuous action, thus maximizing productivity.
Data Source
AI summary
This invention is related to thick film conductor compositions comprising electrically conductive gold powder, one or more glass frit or ceramic oxide compositions and an organic vehicle. It is further directed to the composition's uses for LTCC (low temperature co-fired ceramic) tape, for fabrication of multilayer electronic circuits and in high frequency microelectronic applications.