Packaging Substrate RDL Structure for Finer Interconnect Pitch
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Solution Overview
Problem
The challenge of connecting high-density integrated circuits (ICs) to packaging substrates is exacerbated by the miniaturization of components, leading to unreliable and ineffective connections due to thermal expansion mismatches and limited solder bump/contact pad pitch, which compromises signal integrity and reliability.
Innovation Solution
A packaging substrate with a dual-layer redistribution layer (RDL) comprising organic and inorganic buildup layers, enabling reduced solder bump/contact pad pitch and enhanced adhesion, along with copper pillar extensions for flexible interconnects, addresses these challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional organic dielectric layers are used for packaging substrate interconnects, then manufacturing is simpler, but solder bump/contact pad pitch cannot be reduced sufficiently and adhesion is poor
Solution Approach 1:
The redistribution layer is segmented into multiple layers including organic dielectric layers and inorganic dielectric layers. The inorganic dielectric layer is further divided into first and second inorganic dielectric layers with different materials (e.g., silicon oxide and silicon nitride). This segmentation enables reduced solder bump/contact pad pitch while maintaining manufacturability through specialized adhesion layers at each interface.
Solution Approach 2:
The substrate employs a composite structure combining organic dielectric materials (e.g., epoxy resin, polyimide) and inorganic dielectric materials (e.g., silicon oxide, silicon nitride) in alternating layers. This composite approach leverages the advantages of both material types: organic materials provide flexibility and ease of manufacturing, while inorganic materials enable higher precision and better adhesion for reduced pitch interconnects.
2Productivity
If component miniaturization is pursued to increase density, then functionality and efficiency improve, but connection reliability deteriorates due to thermal expansion mismatches
Solution Approach 1:
The substrate structure incorporates multiple dielectric layers with different thermal expansion coefficients. The inorganic dielectric layers (silicon oxide, silicon nitride) have different thermal properties than the organic dielectric layers, creating a gradient structure that accommodates thermal expansion mismatches during miniaturization while maintaining connection reliability.
Solution Approach 2:
Specialized adhesion layers are introduced as intermediary elements between the organic and inorganic dielectric layers. These adhesion layers serve as buffers that mediate the thermal expansion differences between dissimilar materials, preventing delamination and maintaining reliable connections despite component miniaturization and associated thermal stresses.
3Reliability
If single-layer RDL structure is used, then device complexity is lower, but signal integrity and interconnect reliability are compromised
Solution Approach 1:
The single RDL is segmented into multiple sub-layers (first organic dielectric layer, first inorganic dielectric layer, second inorganic dielectric layer, second organic dielectric layer) with distinct functional zones. Each layer is optimized for specific requirements: inorganic layers provide precise patterning for signal integrity, while organic layers provide mechanical flexibility and stress relief, collectively enhancing overall interconnect reliability.
Solution Approach 2:
The multi-layer RDL structure uses composite materials strategically arranged to enhance signal integrity. The inorganic dielectric layers (silicon oxide, silicon nitride) provide low-k properties for reduced signal loss and crosstalk, while the organic dielectric layers provide mechanical support and stress management. This composite approach improves signal integrity without excessive complexity increase.
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 solution allows for smaller solder bump/contact pad pitch, improving signal integrity, reducing power consumption, and enhancing chip-to-substrate and substrate-to-PCB interconnect reliability while maintaining economic viability and manufacturability.
Implementation Method 1
depositing a first exterior layer including a first inorganic dielectric material onto a first side of a packaging substrate including a core and one or more interior layers on the first side
Implementation Method 2
depositing conductive material within the structures of the first exterior layer to form a plurality of vias electrically connected to the plurality of conductive traces
Data Source
AI summary
A packaging substrate is provided. The packaging substrate includes a core and first organic buildup layers on a first side of the core. The first organic buildup layers include an organic dielectric material and at least one of first metallic traces, first metallic vias, or first metallic pads. The packaging substrate includes second organic buildup layers on a second side of the core that is opposite the first side. The second organic buildup layers include the organic dielectric material and at least one of second metallic traces, second metallic vias, or second metallic pads. The packaging substrate includes first inorganic buildup layers disposed on the first organic buildup layers. The first inorganic buildup layers include an inorganic dielectric material and at least one of third metallic traces, third metallic vias, or third metallic pads.