Insulating Circuit Board Bonding with Curved Pressing Surfaces
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Solution Overview
Problem
Existing methods for manufacturing power module substrate boards face challenges in uniformly applying load during solid phase diffusion bonding, leading to bonding defects at the inner edge parts of copper layers, particularly where the circuit layers are separated by gaps.
Innovation Solution
The method involves forming convex curved surfaces on support boards that contact the copper boards, ensuring even load distribution by using carbon material sheets with a curvature radius between 8000 mm and 60000 mm, facilitating uniform bonding through solid phase diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pressing boards with guide posts are used for solid phase diffusion bonding, then the bonding process can be performed with a simple structure, but the load distribution becomes uneven causing bonding defects at inner edge parts
Solution Approach 1:
The pressing board is designed with a convex curved surface instead of a flat surface. This curvature allows the pressing board to contact multiple copper boards simultaneously, distributing the load evenly across the bonding surface including inner edge parts that were previously insufficiently pressed. The curved surface geometry transforms the point contact into area contact, ensuring uniform intermetallic compound layer formation throughout the bonding region.
2Device complexity
If guide posts are positioned outside the ceramic substrate board, then the pressing structure remains simple, but sufficient load cannot be applied to inner edge parts of copper layers
Solution Approach 1:
The convex curved surface of the pressing board enables it to span across the ceramic substrate board and contact copper boards at inner edge parts. This geometric modification allows the pressing force to be distributed to previously inaccessible regions without adding complex positioning mechanisms or guide posts inside the substrate area.
3Ease of manufacture
If flat pressing boards are used, then the bonding device is simple to manufacture, but bonding defects occur due to insufficient load on inner edge parts
Solution Approach 1:
The convex curved surface can be manufactured using conventional forming processes such as CNC machining, molding, or grinding. While slightly more complex than a flat surface, the manufacturing process remains straightforward and does not require advanced fabrication techniques. The curvature radius can be optimized to balance manufacturing ease with bonding performance.
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 approach prevents bonding defects by ensuring a sufficient thickness of intermetallic compound layers at the edge parts, maintaining a uniform load across the copper circuit layers, thereby enhancing the bonding quality.
Implementation Method 1
pressing the laminate in a lamination direction by moving the support boards to a facing direction and heating in this pressing state, so as to bond the copper boards on the aluminum circuit layers by solid phase diffusion
Implementation Method 2
heating in this pressing state, so as to bond the copper boards on the aluminum circuit layers by solid phase diffusion
Data Source
Figure 1
Figure 2~3A
Figure 3B~3D
AI summary
Steps of forming aluminum circuit layers forming an aluminum circuit layers on one surface of a ceramic substrate and forming copper circuit layers are included; the copper circuit layers are formed by laminating copper boards for the circuit layers on the respective aluminum circuit layers, arranging the laminate between a pair of support boards having a convex curved surface at least on one surface so as to face to each other, moving the support boards in a facing direction to press the laminate in a lamination direction, and heating in this pressing state so that the copper boards for the circuit layers are bonded on the aluminum circuit layers respectively by solid phase diffusion; and in the step of forming the copper circuit layers, the support boards are arranged so that either one of the convex curved surface is in contact with the adjacent copper boards for the circuit layers in the laminate.