Package Substrate Layer Stack Using ABF for Fine-Line Wiring
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Solution Overview
Problem
Conventional package substrates face challenges in forming fine lines and spaces due to the use of prepreg with glass fiber, limiting their ability to meet the increasing functional requirements of electronic products and resulting in warpage issues during manufacturing.
Innovation Solution
The package substrate employs a core board with different insulating layers, using prepreg for rigidity and Ajinomoto build-up film (ABF) for fine line formation, allowing for multi-layer fine lines and thinning designs without warpage, with conductive vias connecting the layers and blind vias for electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If prepreg with glass fiber is used for insulating layers, then rigidity and dimensional stability are improved, but the ability to form fine lines and spaces deteriorates
Solution Approach 1:
The insulating layers are segmented into two types: lower insulating layers made of prepreg with glass fiber for rigidity, and upper insulating layers made of ABF material for fine line formation. This segmentation allows each layer type to fulfill its specific function without compromise.
Solution Approach 2:
Different regions of the package substrate are assigned different insulating layer materials based on local requirements. The lower insulating layers use prepreg for structural support, while the upper insulating layers use ABF for high-precision wiring, creating local quality optimization throughout the substrate structure.
2Ease of manufacture
If conventional build-up process with PP material is used, then manufacturing simplicity is maintained, but multi-layer fine lines capability deteriorates
Solution Approach 1:
The manufacturing process is segmented into two stages: first forming lower insulating layers with PP material using conventional build-up process, then forming upper insulating layers with ABF material for fine line wiring. This segmentation enables both manufacturing simplicity and fine line capability.
Solution Approach 2:
The package substrate uses a composite structure combining PP material and ABF material in different insulating layers. This composite approach leverages the manufacturing simplicity of PP and the fine line formation capability of ABF, achieving both goals simultaneously.
3Device complexity
If uniform insulating layer material is used throughout, then manufacturing process simplicity is improved, but wiring density and functional capability deteriorate
Solution Approach 1:
The insulating layers exhibit local quality variation where lower layers use PP material for structural support and upper layers use ABF material for high-density wiring. This local differentiation enables high wiring density while maintaining manufacturing process simplicity through standardized procedures for each layer type.
Data Source
AI summary
A package substrate is provided, in which a first circuit structure is formed on a core board body, and a second circuit structure is formed on the first circuit structure. A second insulating layer of the second circuit structure is made of an ABF material that is different from a material forming a first insulating layer of the first circuit structure, so that a second circuit layer with fine lines/spaces can be formed by the ABF material of the second insulating layer to achieve a purpose of multi-layer fine lines.