Asymmetrical Bi-layer Prepreg for Void-free Resin Flow
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Solution Overview
Problem
The challenge in reducing the thickness of prepreg materials for coreless device packages is hindered by the presence of woven fibers, which obstruct void-free resin flow over routing layers, limiting the miniaturization of interconnects and vias in computing devices.
Innovation Solution
An asymmetrical bi-layer prepreg design is introduced, featuring additional resin on the side contacting metal features of the substrate routing layer, allowing for reduced dielectric thickness and via height, which enhances reliability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a prepreg with woven fiber is used to provide thermomechanical performance, then the structural integrity and thermomechanical performance are improved, but the resin flow is obstructed and void-free filling is hindered
Solution Approach 1:
The prepreg is segmented into multiple layers with different fiber orientations (e.g., 0°, 90°, ±45° layers). This segmentation allows resin to flow more easily between and through the layers while maintaining structural integrity, resolving the contradiction between strength and manufacturability
Solution Approach 2:
Different regions of the prepreg have different properties - some layers have higher resin content or different fiber densities in specific areas to optimize both local resin flow characteristics and overall structural performance, addressing the contradiction between strength and void-free filling
2Length of moving object
If the prepreg thickness is reduced to accommodate finer vias, then the dielectric thickness and via height are reduced, but the woven fiber obstructs resin flow and prevents void-free filling
Solution Approach 1:
The thin prepreg is divided into multiple ultra-thin layers, each contributing to the overall strength while allowing resin to penetrate through the layered structure more effectively, enabling both reduced thickness and void-free filling
Solution Approach 2:
The prepreg uses a composite structure combining different fiber types, orientations, and resin formulations to achieve the required mechanical properties in a thinner profile while maintaining adequate resin flow pathways for void-free curing
3Volume of moving object
If the prepreg thickness is reduced for miniaturization, then the device size is reduced, but the woven fiber structure hinders resin flow and void-free filling
Solution Approach 1:
The miniaturized prepreg structure is segmented into multiple thin layers with optimized fiber orientations that create channels for resin flow, enabling both device miniaturization and ease of manufacturing through improved resin penetration
Solution Approach 2:
The fiber areal weight, resin content, and layer thickness parameters are optimized to achieve the desired thin profile while maintaining sufficient resin flow capacity, resolving the contradiction between miniaturization and manufacturability
Data Source
AI summary
An apparatus is provided which comprises: a woven fiber layer, a first resin layer on a first surface of the woven fiber layer, a second resin layer on a second surface of the woven fiber layer, the second surface opposite the first surface, and the first and the second resin layers comprising cured resin, a third resin layer on the first resin layer, and a fourth resin layer on the second resin layer, the third and the fourth resin layers comprising an uncured resin, and wherein the fourth resin layer has a thickness greater than a thickness of the third resin layer. Other embodiments are also disclosed and claimed.