Circuit Substrate With Thick Copper Board And Brazed Bonding Layer
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Solution Overview
Problem
Circuit substrates with thick copper circuit boards face challenges in maintaining high TCT reliability and flexibility, as thickness exceeding 0.7 mm can reduce thermal expansion coefficient, making it difficult to mount semiconductor elements and achieve high cooling effects while maintaining a compact design.
Innovation Solution
A circuit substrate configuration using a ceramic substrate bonded with a copper circuit board and an active metal brazing layer, where the copper circuit board has an interior angle of 85° to 95° in cross-section, and a bonding layer with Ag, Cu, and Ti, allowing for a thick copper circuit board thickness of 0.7 mm or more, and a diffusion region with Ti, Ag, and Cu, to enhance bonding strength and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the copper circuit board is thickened to enhance cooling effect, then the cooling performance is improved, but the TCT reliability is reduced due to high thermal expansion coefficient
Solution Approach 1:
The invention changes the physical parameters of the copper circuit board by controlling its thickness to be 0.7 mm or more while optimizing the interior angle to 85°-95°. This parameter optimization allows the copper board to provide sufficient cooling effect through increased thickness while the specific angle range prevents excessive thermal expansion issues that would compromise TCT reliability.
Solution Approach 2:
The invention creates a composite structure by bonding the copper circuit board to a ceramic substrate with a bonding layer. This composite design allows the copper board to provide cooling while the ceramic substrate and bonding layer compensate for thermal expansion differences, maintaining TCT reliability even with thicker copper boards.
2Area of stationary object
If the copper circuit board is made large to secure space for semiconductor element mounting, then the mounting space is sufficient, but the degree of freedom in circuit design is reduced
Solution Approach 1:
The invention utilizes the vertical dimension by setting the copper circuit board thickness to 0.7 mm or more, allowing semiconductor elements to be mounted on the surface while the thickness provides cooling capacity. This dimensional approach eliminates the need to increase planar area for cooling purposes, preserving circuit design freedom.
Solution Approach 2:
By optimizing the interior angle to 85°-95°, the invention creates an efficient geometric configuration that maximizes the use of available space. This angular optimization allows compact mounting arrangements without requiring excessive board area, maintaining design flexibility.
3Reliability
If the copper circuit board is etched to form broad base shape, then the TCT reliability is improved, but the manufacturing cost increases and waste water disposal affects environment
Solution Approach 1:
The invention replaces expensive and environmentally harmful chemical etching processes with a mechanical forming approach. The copper circuit board is formed with the required 85°-95° interior angle through pressing or rolling during manufacturing, eliminating the need for costly chemical solutions and waste water treatment while achieving the same reliability benefits.
Solution Approach 2:
The invention substitutes chemical etching with mechanical forming methods. The copper board geometry is established through mechanical pressing or rolling processes that create the optimal interior angle directly during manufacturing, replacing the chemical dissolution process with a purely mechanical approach that is both cheaper and environmentally friendly.
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 configuration enhances TCT reliability, allows for high current and voltage applications, and supports the mounting of high-output semiconductor elements with improved cooling effects and compact design, while reducing environmental impact by eliminating the need for etching processes.
Implementation Method 1
a bonding layer which bonds the copper circuit board and the ceramic substrate to each other
Implementation Method 2
a diffusion region with Ti, Ag, and Cu
Implementation Method 3
it is necessary to heighten a cooling effect of a circuit substrate by thickening the copper circuit board
Data Source
Figure 1~2
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Figure 5
AI summary
Provided is a circuit substrate having a high TCT reliability and having a high degree of freedom in circuit design. The circuit substrate includes: a ceramic substrate; a copper circuit board which is provided on at least either one of a first surface and a second surface of the ceramic substrate and which has a thickness T (mm) of 0.7 mm or more, an angle θ of 85° or more to 95° or less of an interior angle in a cross section, and a semiconductor element mounting portion of 25 mm2 or more provided in a surface; and a bonding layer bonding the ceramic substrate and the copper circuit board. The bonding layer has a protruding portion protruding outside the copper circuit board, provided in a manner to creep up along a side surface of the copper circuit board, and having a protruding amount W1 of 0.1 mm or more to 1.0 mm or less and a creeping-up amount W2 of 0.05T (mm) or more to 0.6T (mm) or less.