Matte Cured Coating Film for Scratch-Hiding Solder Resist
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Solution Overview
Problem
Existing matte solder resist layers on printed wiring boards are prone to visible scratches during manufacturing, deteriorating product quality and yield due to the visibility of claw marks when the layer is scraped.
Innovation Solution
A cured coating film with specific gloss measurements (Gs(20°)≤5, Gs(85°)≥35, and a ratio R of 0.35 to 4.0) is developed to ensure a matte-like appearance while making scratches unnoticeable, achieved by controlling surface gloss at different angles and incorporating a surface morphology with both uneven and flat portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface roughening is applied to improve solder adhesion and wiring concealment, then solder adhesion resistance and wiring concealment improve, but scratches become visually recognizable as defects
Solution Approach 1:
The invention applies different surface properties to different regions of the coating film. The bulk of the film maintains a rough surface for solder adhesion, while the top surface layer provides scratch concealment through controlled light scattering. This local differentiation allows simultaneous achievement of adhesion performance and defect masking.
Solution Approach 2:
The invention utilizes optical property changes through controlled surface morphology. By creating a specific surface structure with controlled roughness parameters, the coating film changes how it interacts with light - scattering incident light to create a matte appearance that conceals scratches while maintaining the underlying rough structure for solder adhesion.
2Reliability
If a roughened surface is created to improve solder adhesion, then solder adhesion resistance improves, but the surface exhibits low gloss that makes scratches more noticeable
Solution Approach 1:
The invention applies different surface properties to different regions of the coating film. The bulk of the film maintains a rough surface for solder adhesion, while the top surface layer provides scratch concealment through controlled light scattering. This local differentiation allows simultaneous achievement of adhesion performance and defect masking.
Solution Approach 2:
The invention creates a composite surface structure combining rough and smooth characteristics. The coating film comprises a base layer with rough surface topology for adhesion and a surface layer with controlled optical scattering properties. This composite structure integrates both roughness for solder bonding and optical properties for scratch concealment.
3Reliability
If matte finish is achieved through surface roughening, then solder adhesion and wiring concealment improve, but scratches remain visible as quality defects
Solution Approach 1:
The invention applies different surface properties to different regions of the coating film. The bulk of the film maintains a rough surface for solder adhesion, while the top surface layer provides scratch concealment through controlled light scattering. This local differentiation allows simultaneous achievement of adhesion performance and defect masking.
Solution Approach 2:
The invention utilizes optical property changes through controlled surface morphology. By creating a specific surface structure with controlled roughness parameters, the coating film changes how it interacts with light - scattering incident light to create a matte appearance that conceals scratches while maintaining the underlying rough structure for solder 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
The solution provides a matte-like cured coating film that effectively hides scratches, enhancing product quality and yield by ensuring scratches are not visually recognized, even when inevitable during manufacturing.
Implementation Method 1
when the light incident on a cured coating film is reflected on the surface of the cured coating film
Data Source
AI summary
A matte-like cured coating film of a curable resin composition is provided on a substrate such as a wiring board, in which scratches are unnoticeable. The cured coating film satisfies Gs (20°)≤5 and Gs (85°)≥35 and has a ratio R represented by the formula R={Gs (85°)/Gs (60°}/{Gs (60°)/Gs (20°)} ranging from 0.35 to 4.0, where Gs (20°), Gs (60°), and Gs (85°) are 20° gloss, 60° gloss, and 85° gloss on a surface of the cured coating film measured according to JIS Z 8741-1997, respectively.