Embedded Ferromagnetic Shielding for Low-Frequency EMI Packages
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Solution Overview
Problem
Semiconductor devices are susceptible to electromagnetic interference (EMI), particularly low-frequency magnetic interference, which conventional conductive shielding layers fail to address effectively due to issues with delamination and crystalline defects in ferromagnetic films.
Innovation Solution
The integration of ferromagnetic film within the semiconductor package, sandwiched between two encapsulant layers, and the use of conductive pillars to enhance magnetic shielding, providing improved absorption of low-frequency magnetic fields and reducing delamination risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferromagnetic film is applied using lamination process, then magnetic shielding effectiveness is improved, but delamination occurs at the interface between magnetic film and adjacent layers
Solution Approach 1:
A separate adhesive layer is introduced as an intermediary between the ferromagnetic film and the encapsulant or metal shielding layer. This adhesive layer serves as a mediator that bonds the magnetic film to the substrate, preventing direct contact between incompatible surfaces and eliminating delamination issues while preserving magnetic shielding effectiveness.
Solution Approach 2:
The shielding structure is transformed into a composite multi-layer system consisting of the ferromagnetic film, adhesive layer, and substrate (encapsulant or metal shielding layer). This composite structure combines materials with different properties - the ferromagnetic film provides magnetic shielding, the adhesive layer provides bonding, and the substrate provides structural support, resolving the adhesion problem while maintaining shielding performance.
2Reliability
If ferromagnetic film is deposited using physical vapor deposition, then magnetic shielding is achieved, but crystalline defects occur due to high permeability requirements
Solution Approach 1:
The patent changes the deposition parameters and material properties by using sputtering instead of physical vapor deposition, and by specifying particular ferromagnetic alloy compositions (such as nickel-iron-molybdenum or nickel-iron-molybdenum-copper). These parameter changes enable achievement of high magnetic permeability while reducing crystalline defects through controlled deposition conditions and material selection.
Solution Approach 2:
Complex ferromagnetic alloy compositions are used as composite materials with multiple elements (nickel, iron, molybdenum, copper) to achieve the desired magnetic properties. These composite materials provide high permeability with reduced crystalline defects compared to simpler ferromagnetic films deposited by conventional methods.
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
Enhances the effectiveness of magnetic shielding by locating ferromagnetic film closer to the semiconductor die, reducing delamination, and improving the absorption of magnetic emissions, thereby protecting the semiconductor devices from interference.
Implementation Method 1
materials with a high magnetic permeability or ferrites are used to protect sensitive components
Implementation Method 2
Conductive shielding layers can be formed over semiconductor packages to reduce some interference
Data Source
AI summary
A semiconductor device has a substrate. A semiconductor die is disposed over the substrate. A first encapsulant is deposited over the semiconductor die. A ferromagnetic film is disposed over the first encapsulant. A second encapsulant is deposited over the ferromagnetic film. A shielding layer is optionally formed over the substrate, first encapsulant, and second encapsulant.