Package Substrate Flow Features for Uniform Underfill Epoxy
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Solution Overview
Problem
The capillary underfill process in semiconductor devices often results in uncontrolled epoxy flow, leading to void formation due to uneven flow rates between die spaces and interconnects, with existing solutions increasing costs and lacking control over flow rate modulation.
Innovation Solution
Incorporating lithographically defined flow control features, such as pads and lines, on the package substrate to modulate the epoxy flow rate, which are fabricated using existing interconnect processes, allowing for precise control and flexibility in increasing or decreasing the flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trenches, epoxy barriers, or ink barriers are used to control epoxy flow, then flow control is improved, but manufacturing cost increases due to additional deposition and etching processes
Solution Approach 1:
The patent combines the flow control function with existing interconnect structures (pads and bumps) that are already present on the substrate. By integrating flow control features into the existing interconnect fabrication process, the patent eliminates the need for separate deposition and etching processes, thereby maintaining manufacturing cost efficiency while achieving precise epoxy flow control.
Solution Approach 2:
The patent makes the interconnect structures serve dual functions: electrical connection and epoxy flow control. The pads and bumps that are already required for electrical interconnection are designed to also act as flow control features, allowing the same structures to perform multiple functions and eliminating the need for additional dedicated flow control features.
2Manufacturing precision
If epoxy barriers are used to control epoxy flow, then flow rate reduction is achieved, but control over flow rate modulation is limited and positioning precision is poor
Solution Approach 1:
The patent applies different geometric configurations and material properties to different interconnect structures based on their specific location and function. By varying the pad size, bump height, and spacing locally across the substrate, the patent achieves precise control over epoxy flow rates in different regions, enabling both flow rate reduction and enhancement where needed.
Solution Approach 2:
The patent controls epoxy flow rate by modifying physical parameters of the interconnect structures, including pad dimensions, bump height, spacing between features, and material composition. By adjusting these parameters, the patent can modulate the capillary pressure and contact angle, thereby precisely controlling the epoxy flow rate to achieve both reduction and enhancement as needed.
3Speed
If spaces between neighboring die are used as low resistance pathways, then epoxy flow speed increases along die edges, but void formation occurs beneath the die
Solution Approach 1:
The patent introduces flow control features (pads and bumps) as intermediary structures between the epoxy source and the die. These intermediary features act as mediators that regulate the epoxy flow, directing it uniformly toward the die and preventing the formation of low-resistance pathways along the die edges that would otherwise cause void formation.
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 flow control features effectively manage epoxy flow, reducing void formation by adjusting flow rates, ensuring uniform underfill and maintaining assembly cost efficiency by utilizing existing processes.
Implementation Method 1
Capillary underfill process is driven by the epoxy wetting substrate side and die side components
Implementation Method 2
Capillary underfill process is driven by the epoxy wetting substrate side and die side components
Data Source
AI summary
Embodiments disclosed herein include electronic packages with underfill flow control features. In an embodiment, an electronic package comprises a package substrate and a plurality of interconnects on the package substrate. In an embodiment, a die is coupled to the package substrate by the plurality of interconnects and a flow control feature is adjacent on the package substrate. In an embodiment, the flow control feature is electrically isolated from circuitry of the electronic package. In an embodiment, the electronic package further comprises an underfill surrounding the plurality of interconnects and in contact with the flow control feature.