Grounded Conformal Shielding for WLCSP EMI Protection
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Solution Overview
Problem
Conformal shielding is not compatible with wafer-level chip-scale packages (WLCSP) due to the lack of a connection point to grounded metal layers in the redistribution layer, leading to ineffective electromagnetic interference (EMI) shielding.
Innovation Solution
A conductive layer extending to the edge of the package is exposed during the deposition of the conformal shield, allowing it to be grounded, thus providing effective EMI shielding without the area and volume penalties associated with traditional PCB metal cages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional PCB metal cage shields are used for EMI shielding, then EMI protection is effective, but PCB area and volume increase due to thickness and soldering space requirements
Solution Approach 1:
The invention extracts the shielding function from the PCB plane and implements it through vertical conformal shields deposited on the package sidewalls. This removes the need for large PCB area metal cages while maintaining EMI protection, directly resolving the contradiction between shielding effectiveness and PCB area occupation
Solution Approach 2:
The invention transitions from 2D PCB plane shielding to 3D conformal sidewall shielding. By depositing conductive material on the vertical sidewalls of the package, the shielding function is moved to a different spatial dimension, achieving effective EMI protection with minimal PCB area occupation
2Object-affected harmful factors
If thick metal cage shields are installed for EMI protection, then EMI shielding is effective, but manufacturing complexity and costs increase due to additional steps
Solution Approach 1:
The invention merges the EMI shielding function with the existing package structure by depositing conformal shields on the sidewalls during the packaging process. This integration eliminates the need for separate metal cage components and their associated assembly steps, reducing manufacturing complexity while maintaining shielding effectiveness
Solution Approach 2:
The conformal shield structure serves multiple functions: it provides EMI shielding, maintains package structural integrity, and integrates with the existing WLCSP packaging process. This multi-functionality eliminates the need for separate shielding components, thereby reducing manufacturing complexity
3Area of stationary object
If conformal shields are applied to WLCSP structures, then PCB area is saved, but the shields cannot be grounded because redistribution layer metals do not extend to the package edge
Solution Approach 1:
The invention performs preliminary action by extending the ground metal pattern to the package edge during the redistribution layer fabrication process, before the conformal shield deposition. This pre-prepared ground connection point ensures that when the conformal shield is deposited on the sidewall, it can be properly grounded, resolving the grounding issue while maintaining PCB area savings
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 achieves excellent EMI shielding for WLCSP architectures with minimal increase in Z-height and no need for direct soldering to the PCB, saving space and reducing manufacturing complexity.
Implementation Method 1
A conductive layer extending to the edge of the package is exposed during the deposition of the conformal shield
Data Source
AI summary
Embodiments disclosed herein include electronic packages with conformal shields and methods of forming such packages. In an embodiment, the electronic package comprises a die having a first surface, a second surface opposite the first surface, and sidewall surfaces. A redistribution layer is over the first surface of the die, and the redistribution layer comprises a first conductive layer. In an embodiment, an under ball metallization (UBM) layer is over the redistribution layer, and a conductive shield is over the sidewall surfaces of the die and the second surface of the die. In an embodiment, the conductive shield is electrically coupled to the UBM layer.