Ceramic Substrate Void Control for Arc Discharge Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ceramic substrates, such as silicon nitride and aluminum nitride substrates, exhibit insufficient long-term reliability in insulative properties due to the mismatch between withstand voltage test conditions and practical electric fields, leading to issues with arc discharge and dielectric breakdown, especially when high switching frequencies and power densities are involved.
Innovation Solution
A ceramic substrate design that ensures a ratio of arc discharge voltage to dielectric breakdown voltage (A/B) of not less than 0.3, with controlled void distribution and specific void characteristics, including a 90 µm × 120 µm region with limited void counts and sizes, to enhance long-term reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional withstand voltage test conditions are used (high voltage of about 9 kV), then dielectric strength can be measured, but the test conditions greatly deviate from practical electric fields (practical voltage is about 1 kV) and cannot accurately predict long-term reliability
Solution Approach 1:
The patent introduces a new evaluation parameter - the ratio of arc discharge voltage to dielectric breakdown voltage (A/B ratio). This parameter transforms the evaluation from absolute voltage values measured under extreme test conditions to a relative ratio that reflects practical operating conditions. By measuring arc discharge voltage at a controlled voltage increase rate of 200 V/s and comparing it to dielectric breakdown voltage, the patent creates an evaluation metric that better correlates with long-term reliability under practical electric fields of about 1 kV, resolving the contradiction between measurement accuracy and reliability prediction.
2Power
If high voltage is applied in withstand voltage test, then dielectric breakdown voltage can be determined, but arc discharge occurs at voltages much higher than practical operating voltages, making the test inappropriate for predicting long-term reliability
Solution Approach 1:
The patent applies preliminary action by detecting arc discharge phenomena at lower voltage levels (200 V/s increase rate) before reaching the dielectric breakdown point. This preliminary detection of arc discharge voltage serves as an early warning indicator of potential reliability issues, allowing evaluation of long-term reliability without subjecting the ceramic substrate to extreme breakdown conditions. The arc discharge voltage measured this way provides predictive value for practical operating conditions at about 1 kV.
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 designed ceramic substrate maintains excellent insulative properties even at high switching frequencies and power densities, suppressing arc discharge and ensuring long-term reliability by maintaining a high arc discharge voltage relative to dielectric breakdown voltage.
Implementation Method 1
the arc discharge voltage A (kV) is measured when an arc discharge is detected when applying an AC voltage of 50 Hz or 60 Hz between a front surface and a back surface of the ceramic substrate
Implementation Method 2
the dielectric breakdown voltage B (kV) between the front surface and the back surface is measured according to IEC 672-2
Data Source
Figure 1~3
Figure 4
AI summary
A ceramic substrate according to one embodiment is characterized in that the ratio A/B of an arc discharge voltage A to a dielectric breakdown voltage B is at least 0.3, in a case where a 50 Hz or 60 Hz alternating-current voltage is applied between the front surface and the rear surface of the ceramic substrate at a voltage rise speed of 200 V/s, and the arc discharge voltage A (kV) obtained by detecting an arc discharge is measured and the dielectric breakdown voltage B (kV) between the front surface and the rear surface is measured in accordance with IEC 672-2. In any cross-section of the ceramic substrate, it is preferable that there be a 90 µm × 120 µm region in which the number of first voids having a surface area of less than 1 µm2 is within the range of 30 to 500, and the number of second voids having a surface area of at least 1 µm2 is within the range of 0 to 30.