Alternating Thick-Thin RDL Stack for Low-Loss Package Routing
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Solution Overview
Problem
As semiconductor packages grow larger to accommodate more functions, particularly in AI applications, long redistribution lines (RDLs) experience high resistance values, leading to significant insertion loss, especially for high-speed signals.
Innovation Solution
The method involves forming packages with alternating thick and thin dielectric layers and RDLs, where thick dielectric layers are used with thicker RDLs for lateral routing and thin dielectric layers with thinner RDLs for electromagnetic shielding, reducing insertion loss while maintaining impedance balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If packages are made larger to accommodate more functions, then the routing ability is improved, but the redistribution lines become longer and experience higher resistance values causing significant insertion loss
Solution Approach 1:
The patent divides the redistribution lines into multiple segments by stacking multiple RDL layers vertically. Instead of having a single long horizontal routing path, the routing is segmented across multiple layers, allowing signals to travel shorter distances horizontally on each layer while achieving the same overall routing capability. This segmentation reduces the total length of redistribution lines and consequently reduces insertion loss.
Solution Approach 2:
The patent transitions from two-dimensional planar routing to three-dimensional stacked routing by adding vertical dimension through multiple RDL layers. This dimensional change allows signals to route vertically between layers via vias, creating shorter horizontal path lengths on each individual layer while maintaining the ability to reach distant destinations through the stacked architecture.
2Loss of energy
If thicker RDLs are used to reduce resistance, then insertion loss is reduced, but package warpage increases
Solution Approach 1:
The patent applies different RDL thicknesses to different functional layers based on their specific requirements. Thick RDLs are used in layers where current carrying capacity is critical, while thinner RDLs are used in layers where electromagnetic shielding is the primary function. This localized differentiation allows optimization of each layer's performance characteristics while controlling overall package warpage through balanced结构设计.
Solution Approach 2:
The patent creates a composite structure with alternating thick and thin dielectric layers and corresponding thick and thin RDL layers. This composite architecture combines the advantages of both thick RDLs (lower resistance) and thin RDLs (better planarity and warpage control) in a unified structure, allowing the system to achieve low insertion loss while maintaining package stability.
3Adaptability or versatility
If more dielectric layers are added to support more RDL layers, then routing ability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the dielectric layers into thick and thin alternating layers, each serving specific routing or shielding functions. This segmentation allows for optimized manufacturing processes where each layer type can be processed with appropriate parameters, and enables pre-bonding testing of routing layers before final assembly, thereby managing manufacturing complexity through structured differentiation.
Data Source
AI summary
A method includes forming a plurality of dielectric layers, which processes include forming a first plurality of dielectric layers having first thicknesses, and forming a second plurality of dielectric layers having second thicknesses smaller than the first thicknesses. The first plurality of dielectric layers and the second plurality of dielectric layers are laid out alternatingly. The method further includes forming a plurality of redistribution lines connected to form a conductive path, which processes include forming a first plurality of redistribution lines, each being in one of the first plurality of dielectric layers, and forming a second plurality of redistribution lines, each being in one of the second plurality of dielectric layers.