PCB Substrate Surface Roughness Control for Adhesion and Circuit Formability
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Solution Overview
Problem
Existing substrates for printed wiring boards achieve high adhesion strength between conductive layers and base films but compromise circuit formability due to increased surface profile, limiting their ability to form fine conductive patterns effectively.
Innovation Solution
A substrate with a base film surface having a maximum height Sz of 0.05 μm to 0.9 μm, treated with methods like alkali or plasma treatment, and a conductive layer formed using a conductive ink with metal particles, allowing for improved adhesion and circuit formability through controlled surface roughness and electroless plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the base film surface profile is increased to improve adhesion strength, then adhesion strength between conductive layer and base film is improved, but circuit formability for forming fine conductive pattern decreases
Solution Approach 1:
The invention changes the parameter of surface profile from a qualitative description to a quantitative measurement using maximum height Sz according to ISO25178. By establishing a specific numerical range (0.05 μm or more and less than 0.9 μm), the invention transforms the surface roughness control into a precise parameter optimization problem, enabling both improved adhesion strength through adequate roughness and good circuit formability through controlled maximum height.
Solution Approach 2:
The invention replaces the conventional contact profilometer measurement method with a non-contact laser profilometer measurement method. This substitution eliminates mechanical contact that could damage the delicate surface structure, provides more accurate three-dimensional surface characterization, and enables precise measurement of the maximum height Sz parameter without altering the surface being measured.
2Measurement precision
If conventional contact profilometer measurement is used, then surface roughness can be measured, but measurement accuracy for three-dimensional surface characterization is insufficient
Solution Approach 1:
The invention replaces the mechanical contact profilometer system with an optical laser profilometer system. This substitution enables non-contact measurement, providing accurate three-dimensional surface topography data including the maximum height Sz parameter, without the limitations of mechanical contact measurement and without physically altering the surface being measured.
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 enables the formation of fine conductive patterns with maintained adhesion strength, enhancing both circuit formability and adhesion between the conductive layer and base film, while reducing the need for expensive vacuum equipment.
Implementation Method 1
treated with methods like alkali or plasma treatment
Implementation Method 2
treated with methods like alkali or plasma treatment
Implementation Method 3
allowing for improved adhesion and circuit formability through controlled surface roughness and electroless plating
Data Source
AI summary
An object is to provide a substrate for a printed wiring board that has good circuit formability while maintaining adhesion strength between a conductive layer (2) and a base film (1). The substrate includes a base film having an insulating property (1) and a conductive layer (2) formed on at least one surface of the base film (1). The maximum height Sz, which is defined in ISO25178, of the surface of the base film (1) is 0.05 μm or more and less than 0.9 μm.