Composite Wiring Board Layout for Low-Warpage Millimeter-Wave Radar
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Solution Overview
Problem
Conventional wiring boards for millimeter wave radar in the automotive industry face warpage issues due to the low storage modulus of organic resin, leading to attenuation of transmission signals and degradation of antenna characteristics.
Innovation Solution
A wiring board design featuring an insulating layer composed of organic resin with inorganic particles, a first metal layer on one surface, and a second metal layer on the opposite surface, with specific thickness and coverage ratios, and a higher organic resin ratio on one surface, reducing warpage and enhancing antenna characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an insulating layer mainly composed of organic resin is used, then low dielectric loss is achieved, but warpage occurs due to low storage modulus
Solution Approach 1:
The insulating layer is formed as a composite material combining organic resin with inorganic particles (silica, alumina, or titania). This composite structure maintains the low dielectric loss properties of the organic resin while the inorganic particles provide enhanced storage modulus to suppress warpage, directly resolving the contradiction between energy loss and compositional stability.
Solution Approach 2:
The patent creates non-uniform distribution of organic resin and inorganic particles within the insulating layer. The surface parts have different organic resin ratios compared to the interior, with the first surface part having higher organic resin content than the second surface part. This local quality variation optimizes both dielectric performance and warpage control in different regions.
2Stability of the object's composition
If the insulating layer thickness is increased to reduce warpage, then storage modulus effect improves, but transmission loss increases
Solution Approach 1:
The patent optimizes the thickness parameter of the insulating layer to a specific range of 75 μm to 1000 μm. This parameter change balances the competing requirements: sufficient thickness to provide adequate storage modulus effect for warpage suppression, while remaining thin enough to minimize dielectric loss and maintain good transmission characteristics for millimeter wave signals.
Solution Approach 2:
By creating different organic resin ratios at different locations within the insulating layer, the patent achieves localized optimization where the composition varies to balance warpage suppression and transmission loss reduction throughout the structure.
3Reliability
If metal layer coverage is increased to improve grounding, then antenna characteristics improve, but warpage increases due to higher weight
Solution Approach 1:
The patent applies different coverage ratios for different metal layers: the first metal layer has coverage of 5% to 25% while the second metal layer has coverage of 85% or more. This localized differentiation allows the second metal layer to provide extensive grounding for antenna performance while the first metal layer's reduced coverage minimizes additional weight and warpage-inducing forces.
Data Source
AI summary
A wiring board includes an insulating layer comprising organic resin with inorganic particles, a first metal layer on a first surface, and a second metal layer disposed on a second surface. The insulating layer has a thickness of 75-1000 μm and a storage modulus of 4 GPa-7 GPa. The first metal layer has a thickness of 1.5-10 μm and a coverage of 5%-25%. The second metal layer has a thickness of 3-10 μm or 25-100 μm and a coverage of 85% or more. A surface part of the insulating layer on the first metal layer side has a higher ratio of organic resin than a surface part of the insulating layer on the second metal layer side.