Printed Wiring Board Laminate Crystal Orientation
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Solution Overview
Problem
Printed wiring boards face challenges in achieving sufficient bending endurance, particularly when subjected to harsh demands like 180° bending, as existing methods struggle to maintain structural integrity and fine-pitch wiring requirements.
Innovation Solution
A laminate for printed wiring boards is developed, comprising an insulating resin substrate and two metal layers with controlled crystal orientation, where the metal layers have a specific area ratio of crystal grains with a difference in angle from the perpendicular of less than 15°, enhancing bending endurance and circuit formability through the use of ion milling and EBSD observation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a subtractive method is used to form wiring patterns, then the manufacturing process is simple, but the wiring pattern has a trapezoidal shape that spreads toward the bottom, limiting fine-pitch wiring capability
Solution Approach 1:
The patent inverts the conventional subtractive approach by using an additive method where copper plating is formed first to create the wiring pattern, and then unnecessary copper is removed. This reversal allows precise control of wiring shape and dimensions while achieving fine-pitch patterns, resolving the contradiction between manufacturing simplicity and wiring precision.
2Manufacturing precision
If a semi-additive method is used to achieve fine-pitch wiring, then wiring precision is improved, but bending endurance deteriorates due to micro-cracking and through-cracking
Solution Approach 1:
The patent applies local quality by creating a multi-layer copper structure where different layers have different functions. The first copper layer provides adhesion and seed function, while the second copper layer provides structural strength and bending endurance. This local differentiation resolves the contradiction between achieving fine-pitch precision and maintaining bending reliability.
Solution Approach 2:
The patent uses composite material structure by combining multiple copper layers with different crystal orientations and properties. The first copper layer has specific crystal orientation for adhesion, while the second layer has different orientation for mechanical strength. This composite approach maintains wiring precision while significantly improving bending endurance by preventing micro-cracking.
3Manufacturing precision
If copper plating is performed to achieve desired thickness, then circuit formability is improved, but the metal layer develops poor bending endurance against harsh demands like 180° bending
Solution Approach 1:
The patent segments the copper metal layer into multiple distinct layers (first copper layer and second copper layer) with different thicknesses, crystal orientations, and functions. This segmentation allows each layer to be optimized independently - the first layer for adhesion and circuit formation, the second layer for bending resistance - thereby resolving the contradiction between circuit formability and bending endurance.
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 laminate exhibits improved bending endurance and circuit formability, allowing for more reliable and dense wiring patterns while maintaining structural integrity under bending stress.
Implementation Method 1
when a cross section parallel to a thickness direction of the laminate is processed by means of ion milling
Implementation Method 2
the cross section of the metal layer 1 and the metal layer 2 is observed with EBSD
Data Source
AI summary
A laminate for printed wiring board is used in a method of manufacturing printed wiring boards that includes a process of forming a circuit by any one of a semi-additive method, a partly additive method, a modified semi-additive method, and an embedding method. The laminate includes an insulating resin substrate, a metal layer 1 and a metal layer 2 in this order. When a cross section that is parallel to the thickness direction of the laminate is processed by means of ion milling and the cross sections of the metal layer 1 and the metal layer 2 were observed with EBSD, each of the metal layer 1 and the metal layer 2 has one or plural crystal grain(s) at the processed cross section, and an area ratio of the total area of crystal grains of which a difference in angle of the <100> crystal direction from a perpendicular of the processed cross section is 15° or less from among the one or plural crystal grains to the total area of the plural crystal grains was 15% or higher but less than 97% in the metal layer 1 and the metal layer 2.