Non-ferrous Lead Frame MLCC for Low ESL and ESR
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Solution Overview
Problem
Multi-Layer Ceramic Capacitors (MLCCs) face challenges in miniaturization due to limitations in increasing capacitance without increasing size, managing thermal issues, and maintaining mechanical robustness, especially when subjected to tensile stresses on non-rigid substrates, while existing lead frame materials like Ni/Fe alloys have electrical disadvantages.
Innovation Solution
The use of non-ferrous lead frame materials, such as phosphor bronze, with a higher coefficient of thermal expansion than the ceramic, which improves mechanical robustness and reduces Electrical Series Resistance (ESR) and Electrical Series Inductance (ESL), allowing for increased capacitance density and efficient operation in harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ni/Fe alloy lead frames are used to ensure mechanical robustness and CTE matching, then mechanical strength and thermal expansion compatibility are improved, but electrical performance deteriorates due to higher ESR and ESL
Solution Approach 1:
The patent changes the material parameters of the lead frame from ferrous (Ni/Fe alloy) to non-ferrous materials, specifically adjusting the coefficient of thermal expansion to be higher than the ceramic while maintaining mechanical robustness. This parameter change resolves the contradiction by selecting materials that simultaneously achieve both mechanical strength and lower electrical resistance.
Solution Approach 2:
The patent employs composite material strategies by combining non-ferrous materials with specific CTE properties to create lead frames that integrate both mechanical robustness and electrical performance. The use of non-ferrous alloys represents a composite approach to material selection that balances multiple competing requirements.
2Volume of moving object
If capacitor size is reduced to meet miniaturization requirements, then device compactness is improved, but electrical performance deteriorates due to increased ESR and ESL
Solution Approach 1:
The patent changes the lead frame material parameters to non-ferrous materials with higher CTE than ceramic, which enables smaller capacitor designs to maintain lower ESR and ESL. This material parameter change allows miniaturization without the usual penalty of increased electrical losses.
3Quantity of substance
If class 2 ferroelectric dielectric materials are used to achieve high capacitance, then capacitance density is improved, but energy loss increases due to domain wall heat loss
Solution Approach 1:
The patent extracts or removes the source of domain wall heat loss by using non-ferrous lead frame materials that do not interact magnetically with the ferroelectric domains. This extraction of the harmful magnetic interaction reduces energy loss while preserving the high capacitance benefits of class 2 dielectrics.
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 non-ferrous lead frames, particularly phosphor bronze, enhance electrical performance by reducing ESR and ESL, improving mechanical robustness, and enabling capacitors to withstand board flexure and thermal cycling without catastrophic failures, leading to lower operating temperatures and increased reliability.
Implementation Method 1
The use of non-ferrous lead frame materials, such as phosphor bronze, with a higher coefficient of thermal expansion than the ceramic, which improves mechanical robustness and reduces Electrical Series Resistance (ESR) and Electrical Series Inductance (ESL)
Implementation Method 2
The use of non-ferrous lead frame materials, such as phosphor bronze, with a higher coefficient of thermal expansion than the ceramic, which improves mechanical robustness
Data Source
Figure 1~1D
Figure 2~3
Figure 4
AI summary
A multi-layered ceramic capacitor with at least one chip and with first base metal plates in a parallel spaced apart relationship and second base metal plates in a parallel spaced apart relationship wherein the first plates and second plates are interleaved. A dielectric is between the first base metal plates and said second base metal plates and the dielectric has a first coefficient of thermal expansion. A first termination is in electrical contact with the first plates and a second termination is in electrical contact with the second plates. Lead frames are attached to, and in electrical contact with, the terminations wherein the lead frames have a second coefficient of thermal expansion and the second coefficient of thermal expansion is higher than said first coefficient of thermal expansion. The lead frame is a non-ferrous material.