Wiring Substrate with Copper Tin Alloy Layer for Fine Pitch Reliability
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Solution Overview
Problem
The existing methods for forming fine wiring layers on wiring substrates with a pitch of 10 μm or less face challenges such as electric short-circuits and transmission loss of high-frequency signals due to surface unevenness caused by the desmear process, which complicates the adhesion of wiring layers on insulating resin layers.
Innovation Solution
A method involving the sequential formation of a copper tin alloy layer, a copper layer, and a coupling agent layer on an insulating resin layer, followed by the deposition of a seed layer and metal plating layer, allowing for the formation of wiring layers using electroplating with the metal plating layer as a mask, while maintaining a smooth surface to prevent residue and unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the desmear process is applied to etch the inside of via holes to ensure adhesion of wiring layers, then the wiring layers can be formed with good adhesion by the anchor effect, but the surface of the insulating resin layer is also etched and roughened, causing residue upon etching the seed layer and leading to electric short-circuits between wiring layers
Solution Approach 1:
The patent segments the insulating resin layer into two distinct layers: a first insulating resin layer that undergoes the desmear process to provide adhesion, and a second insulating resin layer that remains smooth to prevent residue formation. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the insulating resin structure are given different surface qualities. The first insulating resin layer has a roughened surface for adhesion, while the second insulating resin layer maintains a smooth surface to prevent residue. This local differentiation resolves the contradiction between adhesion requirements and manufacturing precision.
2Reliability
If the surface of the insulating resin layer is roughened to ensure adhesion of wiring layers, then the wiring layers can be formed with good adhesion, but it becomes difficult to form fine wiring layers with line width of 10 μm or less with good reliability
Solution Approach 1:
The patent divides the insulating resin structure into two layers with different surface characteristics. The first layer provides roughness for adhesion, while the second layer provides smoothness for precise fine wiring formation, enabling both adhesion and fine wiring reliability.
Solution Approach 2:
The solution applies different surface qualities to different regions: the first insulating resin layer has rough surface for adhesion, while the second insulating resin layer has smooth surface for precise pattern formation, resolving the contradiction between adhesion and fine wiring precision.
3Reliability
If the surface of the insulating resin layer is roughened to ensure adhesion of wiring layers, then the wiring layers can be formed with good adhesion, but transmission loss of high-frequency signals occurs in the wiring layers formed on the unevenness
Solution Approach 1:
The patent segments the insulating resin into two layers: the first layer with rough surface for adhesion, and the second layer with smooth surface that prevents signal loss. The smooth second layer acts as a protective barrier over the rough first layer, eliminating transmission loss while maintaining adhesion.
Solution Approach 2:
Different surface qualities are assigned to different layers: the first insulating resin layer provides roughness for adhesion, while the second insulating resin layer provides smoothness to prevent high-frequency signal loss, resolving the contradiction between adhesion and energy 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
This approach enables the reliable formation of fine wiring layers with good adhesion on smooth insulating resin layers, reducing the risk of electric short-circuits and transmission loss, and improving the yield of narrow pitch wiring layers.
Implementation Method 1
forming a metal plating layer in the opening portion of the plating resist by applying an electroplating that utilizes the seed layer as a plating power feeding path
Implementation Method 2
forming a first wiring layer on the first coupling agent layer, by etching the seed layer, the copper layer, and the first copper tin alloy layer while using the metal plating layer as a mask
Data Source
AI summary
A method of manufacturing a wiring substrate, includes obtaining a laminated body in which a first copper tin alloy layer and a copper layer are arranged in sequence on a first coupling agent layer, on a first insulating resin layer, forming a seed layer on the copper layer, forming a plating resist in which an opening portion is provided on the seed layer, forming a metal plating layer in the opening portion of the plating resist by applying an electroplating that utilizes the seed layer as a plating power feeding path, removing the plating resist, and forming a first wiring layer on the first coupling agent layer by etching the seed layer, the copper layer, and the first copper tin alloy layer while using the metal plating layer as a mask.