Thin Film Capacitor Tapered Dielectric Hole Design

Solution Overview

Problem

Thin film capacitors with through holes in dielectric layers face issues of insufficient dielectric breakdown voltage and local stress concentration, leading to reduced capacitance and potential cracks or peeling when mounted in circuit boards.

Innovation Solution

A thin film capacitor design featuring a through hole with a first tapered surface having a large taper angle and a second tapered surface with a smaller taper angle, positioned closer to the center, which prevents local stress concentration and ensures a sufficient area for the upper electrode layer, while a manufacturing method involving wet etching forms these surfaces to achieve both reliability and capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the dielectric layer has a wide tapered surface (small taper angle), then the upper electrode layer can be disposed on the tapered surface, but the area of the upper electrode layer decreases to reduce capacitance

Engineering Contradiction:

Improvedielectric breakdown voltageVSAvoidcapacitance

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The tapered surface is divided into two distinct segments: a first tapered surface with a larger taper angle and a second tapered surface with a smaller taper angle. This segmentation allows different regions to serve different functions - the first surface provides mechanical stress relief while the second surface ensures sufficient dielectric breakdown voltage and electrode area

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the through hole are given different taper angles according to their specific functional requirements. The first tapered surface (closer to the opening) has a larger angle for stress distribution, while the second tapered surface (closer to the center) has a smaller angle for maintaining dielectric strength and electrode area

Inventive Principle:

Principle #3Local quality

2Reliability

If the taper angle is large to prevent stress concentration, then cracks or peeling may occur in the dielectric layer during mounting

Engineering Contradiction:

Improveresistance to cracks and peelingVSAvoidupper electrode layer area

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The tapered surface is divided into two distinct segments: a first tapered surface with a larger taper angle and a second tapered surface with a smaller taper angle. This segmentation allows different regions to serve different functions - the first surface provides mechanical stress relief while the second surface ensures sufficient dielectric breakdown voltage and electrode area

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the through hole are given different taper angles according to their specific functional requirements. The first tapered surface (closer to the opening) has a larger angle for stress distribution, while the second tapered surface (closer to the center) has a smaller angle for maintaining dielectric strength and electrode area

Inventive Principle:

Principle #3Local quality

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 design effectively prevents cracks and peeling during mounting, ensuring a reliable and sufficient upper electrode area, while maintaining capacitance by dispersing stress through the tapered surfaces and controlling the taper angles.

Implementation Method 1

The third step is performed by wet etching such that the inner wall surface of the through hole formed in the dielectric layer has a first tapered surface and a second tapered surface

Methodology Applied

Scientific EffectWet etching:

Data Source

PatentUS11676767B2Thin film capacitor having a dielectric layer having a through hole whose inner surface has first and second tapered surfaces, circuit board incorporating the same, and thin film capacitor manufacturing method

Publication Date: 2023.06.13 TDK CORP

AI summary

Disclosed herein a thin film capacitor that includes a lower electrode layer, an upper electrode layer, and a dielectric layer disposed between the lower electrode layer and the upper electrode layer. The dielectric layer has a through hole. An inner wall surface of the through hole has a first tapered surface and a second tapered surface surrounded by the first tapered surface. The first and second tapered surfaces are not covered with the upper electrode layer and have respective first and second taper angles with respect to a surface of the lower electrode layer. The second taper angle is smaller than the first taper angle.