EMI Shield for RF Multi-Chip Packages
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Solution Overview
Problem
Package on package (PoP) RF integrated circuit devices face challenges with poor thermal conductive paths and limited electrical performance due to the location and number of soldering balls, which lead to heat buildup and parasitic inductance, affecting the performance of RF components.
Innovation Solution
A multi-chip package design featuring an EMI shield with a metal casing, a dielectric layer, and signal lines electrically isolated from the metal casing, providing improved thermal dissipation and reducing parasitic inductance by creating a strong electrical ground contact surface and thermally conductive path for heat absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional EMI shield with metal casing is used to shield RF components, then electromagnetic interference protection is improved, but thermal dissipation performance deteriorates due to poor thermal conductive paths
Solution Approach 1:
The EMI shield is segmented into multiple functional layers: a metal casing layer for EMI shielding, a dielectric layer for electrical isolation, and a ground contact layer for thermal and electrical conduction. This segmentation allows each layer to optimize its specific function without compromising others, resolving the contradiction between EMI protection and thermal dissipation.
Solution Approach 2:
The shield employs a composite structure combining metal (for EMI shielding and thermal conduction), dielectric material (for electrical isolation), and conductive elements (for ground contact and thermal paths). This composite approach enables simultaneous achievement of EMI protection, thermal dissipation, and electrical performance.
2Device complexity
If soldering balls are limited in number and located at edges to simplify packaging, then manufacturing complexity is reduced, but parasitic inductance increases and electrical performance deteriorates
Solution Approach 1:
The ground contact mechanism transitions from point contacts (soldering balls at edges) to a distributed planar ground contact surface. This dimensional expansion from 0D/1D to 2D contact provides numerous parallel conduction paths, reducing parasitic inductance while maintaining manufacturing simplicity.
Solution Approach 2:
The dielectric layer with integrated ground contact patterns acts as an intermediary between the metal casing and the RF components. This intermediary provides optimized electrical and thermal conduction paths without requiring complex packaging structures, resolving the contradiction between simplicity and performance.
3Volume of moving object
If ICs are stacked vertically in PoP configuration to increase component density, then device miniaturization is achieved, but thermal conductive paths become poor and heat buildup occurs
Solution Approach 1:
The ground contact layer replicates the thermal conduction function of traditional heat sinks and thermal vias by providing multiple parallel conduction paths through the dielectric layer. This copying of thermal management functionality within the vertical stack enables effective heat dissipation without increasing device volume.
Solution Approach 2:
The metal casing and ground contact structure serve multiple functions simultaneously: EMI shielding, thermal conduction, and electrical grounding. This multi-functionality eliminates the need for separate thermal management components, maintaining compact size while improving heat dissipation.
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 enhances thermal and electrical performance by effectively dissipating heat and reducing parasitic inductance, thereby improving the overall performance of RF components within the PoP devices.
Implementation Method 1
The EMI shield 400 includes a metal casing 702 adapted to shield the multi-chip package 900 from radio frequency radiation
Implementation Method 2
A dielectric layer is deposited over at least a portion of an inner surface of the metal casing. A plurality of signal lines are formed at the dielectric layer such that the plurality of signal lines are electrically isolated from the metal casing by the dielectric layer
Implementation Method 3
providing improved thermal dissipation and reducing parasitic inductance by creating a strong electrical ground contact surface and thermally conductive path for heat absorption
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
One feature pertains to a multi-chip package that includes a substrate and an electromagnetic interference (EMI) shield coupled to the substrate. At least one integrated circuit is coupled to a first surface of the substrate. The EMI shield includes a metal casing configured to shield the package from radio frequency radiation, a dielectric layer coupled to at least a portion of an inner surface of the metal casing, and a plurality of signal lines. The signal lines are coupled to the dielectric layer and electrically isolated from the metal casing by the dielectric layer. At least one other integrated circuit is coupled to an inner surface of the EMI shield, and at least a portion of the inner surface of the EMI shield faces the first surface of the substrate. The signal lines are configured to provide electrical signals to the second circuit component.