Asymmetric PCB Layer Stack for Thermal Warping Control
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Solution Overview
Problem
Conventional printed circuit boards face challenges in achieving high mechanical dimensional stability while maintaining a small thickness, especially under temperature fluctuations, which hinders further miniaturization in electronic assemblies.
Innovation Solution
A printed circuit board with an asymmetrical layered composite structure, featuring a dielectric layer with a Young's modulus between 1 and 20 GPa and a coefficient of thermal expansion between 0 and 17 ppm/K, which allows for high mechanical stability without warping, even at small thicknesses, achieved by using a dielectric material with specific mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the printed circuit board thickness is reduced to enable miniaturization, then the installation space is reduced, but the mechanical dimensional stability deteriorates and warping occurs under temperature fluctuations
Solution Approach 1:
The patent applies asymmetry by creating a layered composite structure that is deliberately free of a plane of symmetry along the z-axis. This asymmetric stacking of dielectric and metallic layers with specific thickness ratios optimizes the balance between mechanical stability and thermal expansion compensation, enabling thin board design without warping
Solution Approach 2:
The patent changes material parameters by specifying a dielectric material with a Young's modulus between 1-20 GPa and a coefficient of thermal expansion between 0-17 ppm/K. These parameter ranges are carefully selected to achieve the optimal balance between flexibility for stress absorption and rigidity for dimensional stability
2Strength
If conventional dielectric materials with high rigidity are used to maintain mechanical stability, then the board can support structural integrity, but thermally induced mechanical loads increase causing warping
Solution Approach 1:
The patent changes the rigidity parameter by limiting the Young's modulus to 1-20 GPa, which is lower than conventional rigid dielectric materials. This reduced rigidity allows the material to flex and absorb thermal expansion stresses, converting harmful thermally induced loads into manageable elastic deformations
Solution Approach 2:
The patent utilizes thermal expansion principles by selecting a dielectric material with a low coefficient of thermal expansion (0-17 ppm/K). This matches the thermal expansion characteristics of common electronic components, reducing differential expansion and the resulting mechanical stresses during temperature cycles
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 solution enables the construction of significantly thinner circuit boards with equivalent mechanical stability to traditional designs, enhancing miniaturization capabilities and reducing thermally induced mechanical loads, as demonstrated by withstanding multiple reflow cycles without damage.
Implementation Method 1
a dielectric material having (i) a Young's modulus E ranging between 1 and 20 GPa and (ii) a coefficient of thermal expansion along the x-axis and along the y-axis ranging between 0 and 17 ppm/K
Implementation Method 2
a dielectric material having (i) a Young's modulus E ranging between 1 and 20 GPa
Data Source
Figure 1(A)~1(C)
Figure 2(A)~2(C)
Figure 3(A)~3(C)
AI summary
The invention relates to a circuit board (200) having a layer structure with at least one dielectric layer (114) which has a planar extension parallel to an xy-plane that extends via an x-axis and a perpendicular y-axis, and has a layer thickness along a z-axis that is perpendicular to the x-axis and the y-axis, and with at least one metal layer (136) that is applied in a planar manner to the dielectric layer, wherein the layer composite is free from a symmetry plane along the z-axis, said symmetry plane being oriented in parallel to the xy-plane, and the dielectric layer (114) has a dielectric material which has an elastic modulus E in the region between 1 and 20 GPa, and has a thermal expansion coefficient in the region between 0 and 17 ppm/K along the x-axis and along the y-axis. The invention also relates to a method for producing a circuit board (200) of this type. The invention further relates to a method for producing a circuit board structure having two asymmetric circuit boards, and a method for producing two processed asymmetric circuit boards (500a, 500b) from a larger circuit board structure (505).