Through-Glass Via Profile for High-Frequency Wiring Reliability
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Solution Overview
Problem
Existing techniques for forming through electrodes in glass substrates fail to consider the side surface roughness and thermal stress, leading to poor transmission characteristics and reliability issues, especially in high-frequency bands and under thermal cycling, due to the dispersion roughness and CTE mismatch between glass and conductive materials.
Innovation Solution
A glass substrate design with controlled side surface angles (4° to 7° and −7° to −15°) and minimal angle differences, combined with smooth side surfaces (dispersion roughness ≤1,000 nm and unevenness width ≤1,500 nm), to enhance transmission characteristics and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional through hole formation techniques are used, then through electrodes can be formed in glass substrates, but the side surface roughness becomes too high (dispersion roughness ≥1,000 nm, PV ≥1,500 nm), degrading transmission characteristics in high frequency bands
Solution Approach 1:
The patent applies parameter changes by precisely controlling the side surface angle parameters of the through hole. Specifically, it sets the side surface angle in the range of 4° to 7° in the upper portion (0-10% from first surface) and -7° to -15° in the lower portion (10-100% from first surface), with the angle difference between left and right sides being 1.0° or less. This precise parameter control achieves smooth side surfaces with dispersion roughness of 1,000 nm or less and PV of 1,500 nm or less, thereby improving transmission characteristics in high frequency bands while maintaining manufacturability
2Reliability
If through holes are formed with conventional shapes, then through electrodes can be created, but the wiring layers break at the interface between through electrodes and wiring layers under thermal stress due to CTE mismatch between glass and conductive materials
Solution Approach 1:
The patent applies parameter changes by optimizing the side surface angle parameters to reduce thermal stress concentration. By controlling the side surface angle to be 4° to 7° in the upper portion and -7° to -15° in the lower portion with minimal angle difference (1.0° or less), the through hole shape better accommodates thermal expansion differences between glass and conductive materials, preventing wiring layer breakage at the interface during thermal cycling
Solution Approach 2:
The patent applies beforehand cushioning by designing the through hole shape in advance to compensate for thermal stress effects. The specific side surface angle parameters (4° to 7° in upper portion, -7° to -15° in lower portion) are predetermined to cushion against the CTE mismatch between glass and conductive materials, preventing wiring layer failure before thermal stress can cause damage
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 solution provides glass substrates with improved transmission characteristics and high reliability, suitable for high-frequency applications and thermal stress resistance, by minimizing side surface roughness and angle variations.
Implementation Method 1
a first step of irradiating a portion of the glass substrate with a laser, the portion being where the through hole is to be formed
Data Source
AI summary
A glass substrate having a first surface and a second surface, including one through hole, a side surface of the through hole being such that: a side surface angle is in a range of 4° to 7° inclusive at a distance in a range from 0% or more to less than 10% from the first surface, and a difference between an inclination angle of the left side surface and an inclination angle of the right side surface is 1.0° or less; and a side surface angle is in a range of −7° to −15° inclusive at a distance in a range from 10% to 100% inclusive from the first surface, and a difference between an inclination angle of the left side surface and an inclination angle of the right side surface is 1.0° or less.