LTCC Substrate Composition for Low Loss and Silver Migration Control
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Solution Overview
Problem
Existing LTCC substrates face issues with signal attenuation and silver migration during co-firing, leading to warpage and electrode deterioration, which are not adequately addressed by existing methods.
Innovation Solution
A low temperature co-fired substrate composition comprising 83 to 91 wt.% CaO-B2O3-SiO2 glass powder, 7.5 to 14 wt.% SiO2 powder, and 1.5 to 3 wt.% β-wollastonite powder, with specific particle sizes and distributions, to minimize dielectric loss and silver interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional glass composition is used to achieve low dielectric loss, then signal attenuation is reduced, but silver migration occurs during co-firing causing electrode deterioration
Solution Approach 1:
The patent introduces an intermediary layer of silicon oxide (SiO2) with controlled thickness (5-20 nm) between the silver electrode and the glass matrix. This intermediary layer acts as a barrier that prevents direct interaction and migration between the silver electrode and the glass, thereby eliminating electrode deterioration while maintaining the low dielectric loss properties of the glass composition
Solution Approach 2:
The patent modifies the glass composition by adjusting the ratio of specific oxides (CaO: 40-50 wt%, B2O3: 10-20 wt%, SiO2: 10-30 wt%) and controls the glass transition temperature (Tg) within 600-700°C. These parameter changes optimize the glass network structure to reduce dielectric loss while maintaining chemical stability during co-firing processes
2Loss of energy
If glass composition is optimized for low dielectric loss, then Q value increases, but substrate warpage occurs during co-firing
Solution Approach 1:
The patent optimizes the glass composition parameters (CaO: 40-50 wt%, B2O3: 10-20 wt%, SiO2: 10-30 wt%) to control the glass transition temperature within 600-700°C and adjust the thermal expansion characteristics. This parameter optimization reduces dielectric loss while minimizing thermal stress during co-firing, thereby preventing substrate warpage
Solution Approach 2:
The patent creates a composite structure combining the optimized glass matrix with the silicon oxide intermediary layer and controls the crystalline phase content (10-30 vol%). This composite approach allows the material to exhibit both low dielectric loss properties and dimensional stability during thermal processing
3Loss of energy
If high purity filler is added to reduce deformation loss, then Q value increases, but manufacturing complexity increases
Solution Approach 1:
The patent reduces composition complexity by limiting the glass to a specific three-oxide system (CaO-B2O3-SiO2) with defined ratios, avoiding the need for multiple high-purity fillers. The glass transition temperature is controlled within 600-700°C to achieve low deformation loss without requiring complex multi-component formulations
Solution Approach 2:
The patent applies local quality modification by introducing the silicon oxide intermediary layer only at the interface where silver electrode contact occurs, rather than uniformly throughout the entire glass matrix. This localized approach reduces deformation loss at the critical electrode interface without unnecessarily complicating the overall glass composition
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 achieves low relative permittivity (k ≤ 6.0), high Q value (≥500), and suppresses silver migration, maintaining substrate integrity and performance.
Implementation Method 1
it is formed by simultaneously burning a ceramic carrier structure, a conductive resistor and a dielectric material in a furnace of less than 1000° C.
Implementation Method 2
the method of synthesizing a crystal material having High Q by a crystallized glass method can be listed
Data Source
AI summary
It is demanded that a LTCC substrate composition capable of maintaining low relative permittivity k and high Q value without having a reactivity with a silver which is an electrode material and causing migration of the silver during a co-firing operation at a low temperature. Provided with a low temperature co-fired substrate composition containing 83 to 91 wt. % of CaO—B2O3—SiO2 based glass powder, 7.5 to 14 wt. % of two or more kinds of nanometer-sized SiO2 powders having different ranges of particle diameter and 1.5 to 3 wt. % of β-wollastonite powder as a crystallization agent wherein the glass powder contains 40.0 to 45.0 wt. % of CaO, 9.0 to 20.0 wt. % of B2O3 and 40.0 to 46.0 wt. % of SiO2.