Wired Circuit Board Dual Barrier Layer Etching Protection
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Solution Overview
Problem
The existing method for producing a wired circuit board allows etching liquid to enter between the peripheral end edge of the Au layer and the inner surface of the insulating layer, potentially damaging the copper layer during etching, as the nickel layer is not an effective etching stopper.
Innovation Solution
A method involving the deposition of a first barrier layer and a continuous second barrier layer on the insulating layer, with the second barrier layer made of chromium, to prevent etching liquid from entering the conductor layer, and the use of a tapered insulating layer surface to enhance contact area and prevent liquid ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If only a single Au layer is used as the etching stopper layer, then the manufacturing process is simple, but the etching liquid can enter between the Au layer and the insulating layer, causing damage to the copper layer
Solution Approach 1:
The single Au layer is divided into two separate barrier layers: a first barrier layer (Au) and a second barrier layer (Cr). This segmentation allows each layer to perform its protective function independently, with the first barrier layer preventing etching liquid from reaching the copper layer and the second barrier layer providing additional protection at the interface with the insulating layer.
Solution Approach 2:
The patent uses a composite barrier structure combining two different materials (Au and Cr) with complementary properties. The Au layer provides excellent etching resistance, while the Cr layer adheres well to the insulating layer and prevents liquid infiltration, creating a more reliable composite protection system than either material alone.
2Reliability
If the Au layer is made thicker to prevent etching liquid entry, then protection is improved, but the conductor layer may be damaged due to excessive pressure or stress
Solution Approach 1:
The barrier function is segmented between two thinner layers rather than one thick layer. The first barrier layer (Au) is kept thin to avoid excessive pressure on the copper layer, while the second barrier layer (Cr) provides the additional protection needed, distributing the protective function across multiple layers.
Solution Approach 2:
The second barrier layer (Cr) acts as an intermediary between the first barrier layer (Au) and the insulating layer. It provides a transition zone that prevents etching liquid from penetrating to the Au layer while maintaining mechanical balance and preventing excessive stress on the conductor layer.
3Reliability
If a second barrier layer is added continuously over the first barrier layer and insulating layer surface, then etching liquid protection is significantly improved, but the device complexity increases
Solution Approach 1:
The barrier system is segmented into two functional layers with distinct roles. The first barrier layer (Au) provides primary etching resistance, while the second barrier layer (Cr) provides secondary protection and adhesion to the insulating layer. This segmentation achieves superior protection while keeping each individual layer relatively simple.
Solution Approach 2:
The second barrier layer serves multiple functions: it prevents etching liquid infiltration, provides adhesion between the first barrier layer and the insulating layer, and creates a continuous protective surface. This multi-functionality justifies the additional layer by consolidating multiple protective roles in a single component.
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 method effectively suppresses the entry of etching liquid into the conductor layer, reducing damage and improving the strength and reliability of the wired circuit board, particularly when the conductor layer is thin, thereby enhancing the reliability of the imaging device.
Implementation Method 1
the two barrier layers can sufficiently suppress entrance of the etching liquid into the conductor layer
Implementation Method 2
a first barrier layer is provided at one side surface in the thickness direction of the metal plate exposed from the opening by plating
Data Source
AI summary
A method for producing a wired circuit board, the method including the steps of: a first step of providing an insulating layer having an opening penetrating in the thickness direction at one side surface in the thickness direction of the metal plate, a second step of providing a first barrier layer at one side surface in the thickness direction of the metal plate exposed from the opening by plating, a third step of providing a second barrier layer continuously at one side in the thickness direction of the first barrier layer and an inner surface of the insulating layer facing the opening, a fourth step of providing a conductor layer so as to contact the second barrier layer, and a fifth step of removing the metal plate by etching.