Thin Film Capacitor Layout for Low-ESR Embedded Substrates
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Solution Overview
Problem
Existing thin film capacitors face issues such as increased ESR and ESL due to long electrode line lengths, difficulty in separating electrodes leading to short circuits, and increased thickness due to support structures, which hinder their integration into miniaturized circuit boards.
Innovation Solution
A thin film capacitor design featuring a metal foil with one roughened main surface, a dielectric film with openings exposing the metal foil, and electrode layers positioned to minimize electrode length and prevent short circuits, along with a manufacturing method that forms insulating members and electrode layers to optimize capacitor structure and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a side surface electrode structure is used, then terminal electrodes can be disposed on the same plane, but the line length of the electrode increases, causing increased ESR and ESL
Solution Approach 1:
The invention transitions from a side surface electrode structure to a planar electrode structure where both terminal electrodes are disposed on the same plane through the metal foil surface. This dimensional reorganization allows direct access to both electrodes without routing through side surfaces, thereby reducing electrode line length and minimizing ESR and ESL while maintaining the desired electrode arrangement.
2Area of moving object
If a metal substrate is made entirely porous, then surface area is increased for electrode formation, but it becomes difficult to separate the lower electrode and upper electrode, increasing short circuit risk
Solution Approach 1:
The invention applies local quality by making only the main surface of the metal foil porous to increase surface area for electrode formation, while keeping the back surface non-porous. This localized porosity allows sufficient surface area for capacitance without compromising the structural integrity needed for electrode separation, thereby reducing short circuit risk while maintaining high surface area benefits.
3Ease of operation
If terminal electrodes are disposed on both surfaces of a metal substrate, then electrode access is provided, but the structure prevents access from one side and increases overall thickness
Solution Approach 1:
The invention merges both terminal electrode accesses onto the same plane of the metal foil surface. By forming both first and second terminal electrodes on the same surface through the porous metal foil structure, the invention eliminates the need for back-side access, thereby reducing overall capacitor thickness while maintaining ease of operation for both terminal connections.
4Reliability
If many laminated ceramic chip capacitors are mounted on circuit board surface, then required decoupling capacitance is ensured, but mounting space becomes insufficient due to miniaturization
Solution Approach 1:
The invention employs a thin film capacitor structure with a metal foil substrate that can be embedded within the circuit board. This thin film approach replaces bulky laminated ceramic chip capacitors, significantly reducing the mounting area required while maintaining the necessary decoupling capacitance functionality. The flexible thin film structure allows integration into miniaturized circuit board designs.
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 proposed design allows for the placement of terminal electrodes on the same plane without side surface electrodes, reduces stress on the outer peripheral area through a step-like shape, and enhances adhesion and reliability when embedded in multilayer substrates.
Implementation Method 1
a metal foil having one roughened main surface
Implementation Method 2
a dielectric film covering the one main surface of the metal foil
Data Source
AI summary
A thin film capacitor includes: a metal foil having a roughened upper surface; a dielectric film covering the upper surface of the metal foil and having an opening through which the metal foil is partly exposed; a first electrode layer contacting the metal foil through the opening; a second electrode layer contacting the dielectric film without contacting the metal foil; and an insulating member provided on the upper surface of the metal foil to surround the first and second electrode layers. The metal foil has an outer peripheral area which is positioned outside an area surrounded by the insulating member and which is not covered with the first and second electrode layers. A height of the electrode layer is equal to or higher than a height of the insulating member. This makes the outer peripheral portion of the thin film capacitor have a step-like shape.