Wiring Board Outer Conductive Layer Thickness Optimization
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Solution Overview
Problem
Existing wiring boards face challenges in ensuring reliable and improved mountability of electronic components due to variations in conductive layer thickness and unevenness, which can lead to decreased connection reliability and component mountability.
Innovation Solution
A wiring board design featuring alternately laminated conductive and insulating resin layers on both surfaces of a core substrate, where the metal foil layer thickness of outermost conductive layers is greater than that of non-outermost conductive layers, ensuring a thicker copper foil layer for improved reliability and mountability, achieved through a combination of subtractive and modified semi-additive manufacturing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal foil layer thickness is increased to improve reliability and mountability, then the connection reliability and component mountability are improved, but the board thickness increases and wiring density decreases
Solution Approach 1:
The patent applies different metal foil layer thicknesses to different locations: the outermost conductive layers have a first thickness (greater than 5 μm) while intermediate conductive layers have a second thickness (3 μm or less). This local differentiation ensures reliable component mounting on outer surfaces while maintaining wiring density in internal layers, thus resolving the contradiction between reliability and board thickness.
2Reliability
If the metal foil layer thickness is increased to improve anchor effect and flatness, then the mountability is improved, but the wiring density and board complexity increase
Solution Approach 1:
The patent specifies that only outermost conductive layers require thick metal foil (greater than 5 μm) for proper component mounting and anchor effect, while intermediate layers use thin metal foil (3 μm or less) to maintain high wiring density. This localized approach to thickness optimization resolves the contradiction between mountability and wiring density.
3Ease of manufacture
If uniform metal foil layer thickness is used across all conductive layers, then the manufacturing process is simplified, but the connection reliability and mountability decrease
Solution Approach 1:
The patent implements different metal foil thickness specifications for different conductive layer positions: outermost layers use thick foil (greater than 5 μm) for reliable connections, while intermediate layers use thin foil (3 μm or less). This can be achieved through selective lamination or differential plating processes, balancing manufacturing feasibility with connection reliability requirements.
4Strength
If thick metal foil layer is used in all conductive layers, then the anchor effect and flatness are improved, but the board thickness increases and manufacturing cost increases
Solution Approach 1:
The patent applies thick metal foil (greater than 5 μm) only to outermost conductive layers where components are mounted and anchor effect is critical, while using thin metal foil (3 μm or less) in intermediate layers. This localized thick-foil application provides sufficient anchor effect and flatness for component mounting without unnecessarily increasing overall board thickness, thus resolving the contradiction between strength and dimensions.
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 design enhances the reliability and mountability of electronic components by ensuring a sufficient thickness of outermost conductive layers, improving flatness and anchor effect, while allowing for dense wiring patterns and reduced board thickness.
Implementation Method 1
each of the conductive layers includes a metal foil layer and a plating layer formed on the metal foil layer
Data Source
AI summary
A wiring board includes core substrate, a first build-up layer on first surface of the substrate and including conductive and insulating resin layers, and a second build-up layer on second surface of the substrate and including conductive and insulating resin layers. The first build-up is formed such that each conductive layer includes a metal foil layer and a plating layer on the foil layer and the foil layer of a conductive layer on an outermost resin layer has thickness greater than thickness of the foil layer of a conductive layer on a non-outermost resin layer, and the second build-up is formed such that each conductive layer includes a metal foil layer and a plating layer on the foil layer and the foil layer of a conductive layer on an outermost resin layer has thickness greater than thickness of the foil layer of a conductive layer on a non-outermost resin layer.