Multilayer PCB Adhesion via Tin-Sn Silane Coating
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Solution Overview
Problem
Existing multilayer printed wiring boards face challenges in achieving strong adhesiveness between conductive circuits and interlayer resin insulation layers, as well as between conductive circuits and via conductors, which affects electrical connectivity and reliability.
Innovation Solution
A multilayer printed wiring board design that includes a metal layer containing Sn on the surface of conductive circuits, a silane coupling agent coating film, and direct connection of via conductors to the conductive circuits, enhancing adhesiveness through chemical bonding between the metal layer, coupling agent, and resin insulation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a copper conductive circuit is directly connected to interlayer resin insulation layers, then the manufacturing process is simple, but the adhesiveness between the conductive circuit and insulation layers is insufficient
Solution Approach 1:
The patent applies composite materials by forming a metal layer containing Sn (tin) on the copper conductive circuit surface, and then forming a silane coupling agent coating film on the metal layer. This multi-layer composite structure (copper + Sn-containing metal layer + silane coupling agent film) provides both strong adhesion to the interlayer resin insulation layer and good electrical conductivity, resolving the contradiction between simplicity and adhesiveness.
Solution Approach 2:
The patent uses a silane coupling agent coating film as an intermediary between the metal layer and the interlayer resin insulation layer. This coupling agent film chemically bonds to both the metal surface and the resin, acting as a mediator that significantly enhances the adhesiveness between the conductive circuit and the insulation layer without requiring direct contact between copper and resin.
2Strength
If the surface of conductive circuit is roughened to improve adhesiveness, then the adhesion strength increases, but the electrical resistance increases
Solution Approach 1:
The patent changes the surface parameters of the conductive circuit by forming a metal layer containing Sn on the copper surface, and then forming a silane coupling agent coating film. This controlled parameter change (adding layers with specific thicknesses and compositions) provides adequate adhesion strength while maintaining smooth surfaces that minimize electrical resistance, unlike roughening which increases resistance.
Solution Approach 2:
The patent uses a composite structure of copper conductive circuit + Sn-containing metal layer + silane coupling agent coating film. This composite approach provides both adhesion enhancement (through the coupling agent) and electrical conductivity (through the smooth metal layers), avoiding the electrical resistance penalty associated with surface roughening.
3Strength
If a metal film made of copper-tin alloy is formed on the conductive circuit to enhance adhesiveness, then the adhesion improves, but the manufacturing complexity increases
Solution Approach 1:
The patent forms a composite structure with a metal layer containing Sn on the copper conductive circuit, followed by a silane coupling agent coating film. While this adds manufacturing steps, the use of standard plating and coating processes makes the implementation feasible, and the significant adhesion improvement justifies the additional manufacturing complexity.
Solution Approach 2:
The silane coupling agent coating film serves as an intermediary layer that chemically bonds to both the Sn-containing metal layer and the interlayer resin insulation layer. This mediator enables strong adhesion through chemical bonding mechanisms, making the enhanced adhesiveness achievable through a systematic manufacturing process despite the increased complexity.
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 solution improves the peel strength and electrical connectivity between conductive circuits and interlayer resin insulation layers, reducing electrical resistance and ensuring reliable connections, while maintaining excellent signal transmission characteristics.
Implementation Method 1
enhancing adhesiveness through chemical bonding between the metal layer, coupling agent, and resin insulation layers
Implementation Method 2
A multilayer printed wiring board design that includes a metal layer containing Sn on the surface of conductive circuits, a silane coupling agent coating film, and direct connection of via conductors to the conductive circuits, enhancing adhesiveness through chemical bonding
Data Source
AI summary
A multilayer printed wiring board including a first interlayer resin insulation layer, a first conductive circuit formed on the first interlayer resin insulation layer, a second interlayer resin insulation layer formed on the first interlayer resin insulation layer and the first conductive circuit and having an opening portion exposing a portion of the first conductive circuit, a second conductive circuit formed on the second interlayer resin insulation layer, a via conductor formed in the opening portion of the second interlayer resin insulation layer and connecting the first conductive circuit and the second conductive circuit, and a coating layer having a metal layer and a coating film and formed between the first conductive circuit and the second interlayer resin insulation layer. The metal layer is formed on the surface of the first conductive circuit and the coating film is formed on the metal layer.