Separable Metal Foil Burying for Wiring Board Adhesion
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Solution Overview
Problem
Existing methods for manufacturing high-density wiring boards face challenges in thinning the board thickness and maintaining adhesion between the build-up section and the supporting substrate, leading to reduced fabrication yield due to plating solution infiltration at the boundary between copper foils.
Innovation Solution
A method involving a separable metal foil composed of a first and second metal foil, where the second metal foil is larger and thicker than the first, is used to bury the foil into the supporting substrate, shielding the boundary from external environments and preventing plating solution infiltration, thereby ensuring strong adhesion and high producibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrathin copper foil with carrier copper foil and supporting substrate have the same size, then the copper foil can be fully supported, but the boundary between carrier copper foil and ultrathin copper foil is exposed causing plating solution infiltration
Solution Approach 1:
The patent applies local quality by making the carrier copper foil larger than the ultrathin copper foil, creating a localized coverage where the carrier foil extends beyond the product forming region. This local extension ensures the boundary is covered while maintaining proper support in the product area.
Solution Approach 2:
The patent implements preliminary action by having the carrier copper foil extend beyond the ultrathin copper foil before the plating process begins. This pre-positioning prevents plating solution infiltration from the start, avoiding adhesion problems rather than correcting them afterward.
2Strength
If core substrate with thickness of 0.2 to 2.0 mm is used, then structural strength is maintained, but the entire thickness of wiring board cannot be thinned
Solution Approach 1:
The patent extracts and removes the traditional core substrate from the wiring board structure. By eliminating this thick supporting layer and using a thin supporting substrate instead, the overall board thickness is reduced while maintaining necessary strength through alternative support mechanisms.
Solution Approach 2:
The patent changes the thickness parameter of the supporting substrate from the conventional 0.2-2.0 mm core substrate thickness to a much thinner dimension. This parameter change enables thinning of the entire wiring board while the build-up section provides the necessary structural support.
3Ease of manufacture
If build-up section is separated from supporting substrate, then the wiring board can be manufactured, but adhesion is weakened causing peeling and reduced fabrication yield
Solution Approach 1:
The patent introduces the carrier copper foil as an intermediary element between the ultrathin copper foil and the supporting substrate. This intermediary layer provides a secure attachment point during manufacturing while enabling clean separation afterward, maintaining adhesion integrity throughout the process.
Solution Approach 2:
The patent segments the metal foil structure into distinct functional layers: the ultrathin copper foil for conductivity, the carrier copper foil for support and adhesion, and the supporting substrate for structural base. This segmentation allows each layer to perform its specific function optimally while maintaining strong inter-layer adhesion.
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 enhances the adhesion between the build-up section and the supporting substrate, preventing peeling and improving the fabrication yield of the wiring board by shielding the boundary from plating solution infiltration.
Implementation Method 1
fixing a lower surface and a side surface of the separable metal foil to the supporting substrate by pressing the separable metal foil against an upper surface of the product forming region
Implementation Method 2
a boundary between the carrier copper foil and the ultrathin copper foil is exposed outside... a plating solution for forming a wiring conductor occasionally infiltrates both the carrier copper foil and the ultrathin copper foil through the boundary therebetween
Implementation Method 3
separable metal foil which is composed of a first metal foil and a second metal foil that are separably adhered to each other
Implementation Method 4
forming the wiring conductor layer on a lower surface of the build-up section by removing a part of the second metal foil fixed to the build-up section through etching
Data Source
AI summary
A method for manufacturing a wiring board according to the present invention includes the steps of preparing a supporting substrate having a product forming region and a marginal region; preparing a separable metal foil whose area is larger than that of the product forming region and is smaller than that of the supporting substrate; fixing the separable metal foil to the supporting substrate by burying into the supporting substrate; forming a build-up section on the buried separable metal foil; integrally cutting out the supporting substrate, the separable metal foil and the build-up section; obtaining a laminated body for wiring board composed of the second metal foil and the build-up section by separating the first metal foil and the second metal foil; and forming the wiring conductor layer by removing a part of the second metal foil.