Wiring Substrate Manufacturing with Thermal Expansion Matching
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Solution Overview
Problem
Existing methods for manufacturing wiring substrates often result in wrinkles in the build-up wiring layer due to thermal expansion coefficient differences between the temporary substrate and the wiring layer, leading to reliability and cost issues.
Innovation Solution
A method using a nonwoven glass fabric epoxy resin substrate with a thermal expansion coefficient matching the build-up wiring layer, allowing for equal thermal expansion and preventing wrinkles, involves tentatively fixing a metal foil to the substrate with an adhesive layer and cutting out the inside portion to separate the foil and wiring layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a temporary substrate is used to form a build-up wiring layer in a detachable state, then the wiring substrate can be manufactured with flexibility and ease of separation, but wrinkles occur in the build-up wiring layer due to thermal expansion coefficient differences between the temporary substrate and the wiring layer
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the temporary substrate by selecting a material (nonwoven glass fabric epoxy resin substrate) whose thermal expansion coefficient matches that of the build-up wiring layer. This parameter matching prevents differential thermal expansion during heating steps, thereby eliminating wrinkle formation while maintaining the detachable manufacturing process.
Solution Approach 2:
The patent employs a composite temporary substrate made of nonwoven glass fabric impregnated with epoxy resin. This composite material provides both the necessary mechanical properties for handling and the matched thermal expansion coefficient to prevent wrinkles, while still allowing easy separation of the build-up wiring layer after manufacturing.
2Adaptability or versatility
If the thermal expansion coefficients of the temporary substrate and build-up wiring layer are different, then manufacturing flexibility is maintained, but heat stress causes wrinkles during heating steps
Solution Approach 1:
The patent modifies the thermal expansion coefficient parameter of the temporary substrate to match that of the build-up wiring layer. By selecting a nonwoven glass fabric epoxy resin substrate with appropriate thermal expansion properties, the patent eliminates heat stress-induced wrinkles during heating steps while preserving manufacturing flexibility.
Solution Approach 2:
The patent creates homogeneity in thermal expansion behavior between the temporary substrate and the build-up wiring layer by material selection. This homogeneous thermal response prevents differential expansion and contraction during temperature changes, ensuring reliable wrinkle-free production.
3Ease of operation
If selective attachment of metal foil peripheral side is used, then easy separation is achieved, but the structure requires precise cutting out of the inside portion inward from the adhesive layer
Solution Approach 1:
The patent segments the attachment function by applying adhesive only to the peripheral side of the metal foil rather than the entire surface. This segmentation allows the central portion to be easily separated by cutting, simplifying the separation process while maintaining secure attachment at the boundaries.
Solution Approach 2:
The patent applies adhesive locally only to the peripheral region of the metal foil, creating different functional zones: the peripheral region provides strong attachment for structural support, while the central region allows easy separation. This local quality differentiation simplifies the cutting and separation operations.
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 approach ensures reliable and cost-effective manufacturing of wiring substrates without wrinkles, improving production yields and enabling high-reliability electronic component mounting by matching thermal expansion coefficients and using the metal foil as a reinforcing member.
Implementation Method 1
tentatively fixing a metal foil onto at least one surface of the temporary substrate by selectively attaching a peripheral side of the metal foil to a peripheral portion of a wiring formation region on the temporary substrate with an adhesive layer
Implementation Method 2
A method using a nonwoven glass fabric epoxy resin substrate with a thermal expansion coefficient matching the build-up wiring layer, allowing for equal thermal expansion and preventing wrinkles
Data Source
AI summary
In a method of manufacturing a wiring substrate according to the present invention, a metal foil is tentatively fixed onto a temporary substrate, which is made of a nonwoven fabric impregnated with resin, by selectively attaching a peripheral side of the metal foil to an outer peripheral portion of a wiring formation region of the temporary substrate, thereafter, a build-up wiring layer is formed on the metal foil, and the metal foil is separated from the temporary substrate by cutting out an inside portion of a structure, the portion being inward from the adhesive layer, in this way, a wiring member including the build-up wiring layer formed on the metal foil is obtained.