Thin-Film Capacitor Lead Conductor Stress Management
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Solution Overview
Problem
Thin-film capacitors face issues with vertical stress concentration on outer connecting terminals like bumps, leading to potential separation of electrode layers and reduced reliability due to differences in thermal expansion coefficients between substrates, and have a small equivalent series resistance (ESR) that increases impedance at specific frequencies.
Innovation Solution
A thin-film capacitor design with a substrate, capacitor unit, protective layer, lead conductor, and outer connecting terminal where the outer connecting terminal is separated from the connecting part, allowing stress absorption by the protective layer and adjustable ESR through the length, thickness, and material of the wiring part, which can also reduce equivalent series inductance (ESL) by sharing a single outer connecting terminal among multiple connecting parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer connecting terminal is directly connected to the connecting part, then the electrical connection is direct and simple, but stress is directly applied to the electrode layers causing separation and reduced reliability
Solution Approach 1:
The patent introduces a protective layer as an intermediary between the outer connecting terminal and the electrode layers. This protective layer absorbs stress generated during mounting and thermal cycling, preventing direct stress transmission to the electrode layers and dielectric film, thereby maintaining reliability without significantly increasing structural complexity.
2Reliability
If the ESR is kept small for general performance, then low impedance is achieved, but impedance increases at specific frequencies due to small ESR
Solution Approach 1:
The patent changes the ESR parameter from a fixed small value to an adjustable value within a specific range (0.01Ω to 10Ω). By controlling the ESR to be within this range, the capacitor maintains low impedance for general performance while avoiding the impedance increase at specific frequencies that occurs with very small ESR values, thus achieving performance stability.
3Productivity
If a single outer connecting terminal is shared among multiple connecting parts, then ESL is reduced and space is saved, but the terminal structure becomes more complex
Solution Approach 1:
The patent merges multiple connecting parts into a single outer connecting terminal structure. This shared terminal reduces the overall number of components, saves mounting space, and reduces equivalent series inductance (ESL) by providing a common reference point for multiple capacitor elements, while the protective layer simplifies the overall structure rather than complicating it.
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
This design prevents stress from being directly applied to the electrode layers, reduces the risk of separation, and allows for flexible adjustment of ESR and ESL, enhancing the reliability and performance of the thin-film capacitor.
Implementation Method 1
a protective insulating layer 106 of resin material, such as polyimide, is provided for absorbing mechanical stress from the bumps 108a and 108b
Implementation Method 2
adjustable ESR through the length, thickness, and material of the wiring part
Implementation Method 3
reduce equivalent series inductance (ESL) by sharing a single outer connecting terminal among multiple connecting parts
Data Source
AI summary
A thin-film capacitor and a method for making the thin-film capacitor having a structure that can prevent vertical stress acting on outer connecting terminals, such as bumps, from concentrating on electrode layers, and capable of easily increasing the equivalent series resistance to a desired value. The thin-film capacitor includes a substrate, a capacitor unit disposed above the substrate and composed of at least one dielectric thin film and two electrode layers, a protective layer covering at least part of the capacitor unit, a lead conductor electrically connected to one of the electrode layers of the capacitor unit, and a bump disposed above the lead conductor. The lead conductor includes a connecting part disposed in an opening in the protective layer and electrically connected to one of the electrode layers of the capacitor unit, and a wiring part extending over the protective layer. The bump is disposed above the wiring part.