Conformal RF Shielding for Semiconductor Packages
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Solution Overview
Problem
Existing methods for compartmental shielding in semiconductor devices, such as wire fences and laser ablation, face inefficiencies due to increased gaps between ground structures as mold caps thicken, leading to reduced RF shielding effectiveness, particularly in Through Mold Via Package on Package (TMV PoP) configurations.
Innovation Solution
A method involving a semiconductor package with a substrate and electronic components, where a mold compound is applied and partially removed to create gaps for a conductive coating, which is then applied to the exposed areas to form a compartmentalized EMI shield, reducing the gap between components and enhancing shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire fence or laser ablation methods are used for compartmental shielding, then shielding structure can be formed, but the gap between ground structures increases as mold cap thickness increases, reducing shield effectiveness
Solution Approach 1:
The patent transitions from planar/2D shielding approaches (wire fences, laser ablated vias) to a 3D conformal coating approach that wraps around components in multiple dimensions. The conductive coating is applied to the mold compound surfaces and sides, creating a three-dimensional shield structure that maintains consistent shielding coverage regardless of mold cap thickness, thereby resolving the gap increase problem in the vertical dimension.
Solution Approach 2:
The patent changes the physical state and application method of the shielding material. Instead of discrete wire elements or ablated holes, a continuous conductive coating is applied in a liquid or aerosol state that conforms to complex geometries, then cures to form a solid shield. This parameter change allows the shield to adapt to varying mold cap thicknesses while maintaining optimal gap distances between shielding regions.
2Area of stationary object
If conformal shielding is applied to thick mold caps, then full coverage is achieved, but the gap between ground structures increases, reducing RF shielding performance
Solution Approach 1:
The patent applies different shielding configurations to different local regions. The conductive coating is selectively applied to specific surfaces and sides of the mold compound, with varying thicknesses and continuity based on local shielding requirements. This local quality approach ensures optimal shielding in critical areas while maintaining overall coverage, preventing the uniform gap increase that occurs with traditional thick-cap conformal shielding.
3Reliability
If laser ablation is used to create shields, then compartmental shielding is achieved, but it becomes difficult to perform after singulating units in TMV PoP configurations
Solution Approach 1:
The patent performs the shielding action before the final singulation step. The conductive coating is applied to the mold compound while units are still connected in arrays, allowing uniform application across multiple units simultaneously. This preliminary action eliminates the need for post-singulation laser ablation, making the process feasible for TMV PoP configurations where through-mold vias are present and laser access would be blocked.
Solution Approach 2:
The patent replaces the laser ablation process (optical/thermal system) with a conformal coating deposition process. Instead of removing material through laser energy, the shield is built up by depositing conductive material that conforms to the mold compound geometry. This substitution eliminates the fundamental limitation of laser inaccessibility in thick mold caps and TMV PoP structures.
4Reliability
If wire fence is used for perimeter shielding in two-tier structures, then perimeter protection is achieved, but consistent wire loop height is difficult to maintain
Solution Approach 1:
The patent uses a flexible conformal coating that can wrap around and adapt to the varying heights of two-tier component structures. Unlike rigid wire fences that require precise height matching, the liquid or aerosol conductive coating flows to conform to the underlying topology, creating a continuous shield that maintains consistent electrical properties regardless of local height variations in the two-tier configuration.
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
This approach significantly enhances RF shielding by minimizing the gap between electronic components, thereby improving the effectiveness of the EMI shield and facilitating easier implementation on two-tier structures by maintaining a consistent wire loop height.
Implementation Method 1
A conductive coating is applied to the mold compound and an area where the portion of the mold compound is removed... significantly enhances RF shielding by minimizing the gap between electronic components, thereby improving the effectiveness of the EMI shield
Data Source
AI summary
A semiconductor device has a substrate having a plurality of metal traces. At least one electronic component is electrically coupled to a first surface of the substrate. A mold compound is used for encapsulating portions of the electronic component and the first surface of the substrate, wherein a portion of the mold compound is removed around at least one side of the electronic component. A conductive coating is applied to the mold compound and an area where the portion of the mold compound is removed.