Printed Wiring Board Thickness Ratio for Warping Control
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Solution Overview
Problem
Existing printed wiring boards with built-in electronic components face challenges in reducing warping and cracking due to thermal expansion, and in efficiently mounting electronic components with high connection reliability and yield.
Innovation Solution
A printed wiring board design featuring a first circuit board with a reinforcing material and a second circuit board, where the first circuit board is laminated on the second circuit board to expose a mounting area, with a thickness ratio between 0.75 and 2.4, and a manufacturing method involving conductive layers, resin insulation layers, and via conductors to form tapered openings and pads for electronic component mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a printed wiring board with a coreless substrate and resin layer is used to accommodate electronic components, then the board can be manufactured with simpler materials and processes, but the board becomes prone to warping and cracking due to thermal expansion
Solution Approach 1:
The patent uses a composite structure consisting of a coreless substrate made of resin material combined with a reinforcing material (such as glass fiber or ceramic) to create a hybrid material system. This composite structure maintains the manufacturing advantages of coreless substrates while adding thermal stability and mechanical strength to prevent warping and cracking during thermal cycling and soldering processes.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the resin material by selecting specific resin types with controlled thermal expansion coefficients, glass transition temperatures, and curing characteristics. By adjusting these material parameters and optimizing the resin-to-reinforcing-material ratio, the board achieves dimensional stability while maintaining ease of manufacture through conventional lamination processes.
2Reliability
If the mounting area is exposed by removing material from the first circuit board, then electronic components can be mounted with high connection reliability, but the manufacturing process becomes more complex
Solution Approach 1:
The patent incorporates the mounting area exposure into the initial lamination and patterning stages of manufacturing. The opening is formed in the first circuit board at the same time as other conductive patterns are created, using preliminary photolithography and etching processes. This preliminary action eliminates the need for separate post-processing steps to create mounting openings, thereby maintaining high connection reliability while avoiding additional manufacturing complexity.
Solution Approach 2:
The patent combines the formation of the mounting opening with the creation of through-holes and conductive patterns in a single integrated manufacturing sequence. By merging these operations, the patent achieves exposed mounting areas for reliable component attachment without requiring separate processing steps, thus reducing overall process complexity while ensuring high connection quality.
3Ease of manufacture
If the thickness ratio between the first circuit board and second circuit board is not optimized, then manufacturing is easier, but warping occurs due to uneven stress distribution
Solution Approach 1:
The patent establishes specific parameter ranges for the thickness ratio between the first circuit board and second circuit board (typically maintaining the ratio between 0.5 and 2.0). By controlling these dimensional parameters and selecting appropriate thickness values for each layer, the patent achieves balanced stress distribution across the multi-layer structure, preventing warping while allowing manufacturing flexibility within the specified ranges.
Solution Approach 2:
The patent applies different thickness specifications to different regions and layers of the printed wiring board based on their functional requirements. The first circuit board and second circuit board are designed with locally optimized thicknesses that account for their respective roles in stress bearing, electrical routing, and component mounting. This local quality approach ensures dimensional stability through balanced stress distribution while maintaining ease of manufacture within localized parameter ranges.
Data Source
AI summary
A printed wiring board includes a first circuit board having a first surface and a second surface, and a second circuit board having a third surface and a fourth surface and having a mounting area on the third surface of the second circuit board. The first circuit board is laminated on the third surface of the second circuit board such that the first surface of the first circuit board is in contact with the third surface of the second circuit board, the first circuit board includes reinforcing material and has an opening portion exposing the mounting area of the second circuit board, and the first circuit board and the second circuit board are formed such that a ratio H1/h1 is in a range that is greater than 0.75 and smaller than 2.4, where H1 represents a thickness of the first circuit board and h1 represents a thickness of the second circuit board.