Metal Foil Protrusions for PCB Signal Loss and Peel Strength
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Solution Overview
Problem
Conventional PCBs face a contradiction in reducing high-frequency signal transmission loss and maintaining peeling strength between metal foils and dielectric layers, as lower surface roughness is required for signal loss reduction but higher roughness is needed for peeling strength, making it difficult to achieve both simultaneously.
Innovation Solution
A metal foil with protrusions having a limiting part with a circumscribed circle diameter smaller than the skin depth and a larger surface area above the limiting part is used, which reduces high-frequency signal loss while enhancing peeling strength by increasing the contact area with the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the surface roughness of the metal foil is reduced to minimize high-frequency signal transmission loss, then the signal transmission loss is reduced, but the peeling strength between the metal foil and the dielectric layer decreases
Solution Approach 1:
The invention applies local quality by creating protrusions with specific microscopic morphology (limiting part with diameter smaller than skin depth and larger surface area above) at localized positions on the metal foil surface. This allows different regions to serve different functions: the limiting part minimizes signal loss by being smaller than the current flow depth, while the larger upper surface area enhances peeling strength through increased bonding contact area with the dielectric layer.
2Strength
If the surface roughness of the metal foil is increased to enhance peeling strength between the metal foil and dielectric layer, then the peeling strength is improved, but the high-frequency signal transmission loss increases
Solution Approach 1:
The invention applies parameter changes by precisely controlling the morphology parameters of the protrusions on the metal foil surface. The limiting part has a circumscribed circle diameter specifically designed to be smaller than the skin depth, while the upper portion has a larger surface area. This parameter optimization allows the surface to provide sufficient bonding area for peeling strength without creating excessive roughness that would increase signal transmission loss.
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 effectively reduces high-frequency signal transmission loss and improves peeling strength between the metal foil and dielectric layer, enabling the manufacture of high-density, fine-line high-frequency circuit boards without layer delamination.
Implementation Method 1
The intrinsic reason thereof is that the high-frequency signal current flows in a thinner surface layer of the metal surface of the transmission line. Herein, the higher the signal frequency is, the smaller the depth of current flowing in the signal transmission line of the metal foil is.
Implementation Method 2
The signal transmission line of the copper foil layer is attached to the resin layer through the surface roughness to produce binding force with the dielectric layer. As the signal transmission line becomes thinner and thinner, about this aspect, the article 'Non-Classical Conductor Losses due to Copper Foil Roughness and Treatment' points out that: the adhesion between the copper foil and the dielectric layer is related to the roughness of the copper foil.
Data Source
AI summary
The disclosure discloses a metal foil, a metal foil with a carrier, a copper-clad laminate and a Printed Circuit Board. Herein, a plurality of protrusions are distributed on one face of the metal foil, and the protrusions have the follow microscopic morphology: the lower half part of the protrusion connected with the one face of the metal foil is provided with a limiting part, and the diameter of a circumscribed circle of the cross section of the limiting part is smaller than the skin depth of the metal foil; and the surface area of the part of the protrusion above the limiting part is larger than the surface area of other parts of the protrusion.