Package Lid Composite Coatings for Adhesion and RF Shielding
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Solution Overview
Problem
There is a need for improved packaging of integrated devices that enhances both the adhesion strength of the package lid to the substrate and provides effective radio frequency (RF) shielding to protect against external factors and electromagnetic interference.
Innovation Solution
A package lid is designed with a core material sandwiched between two conductive layers of different materials, where the first conductive layer improves adhesion using an adhesive and the second conductive layer enhances RF shielding by being electrically connected to the substrate, thereby increasing the mechanical robustness and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single conductive layer is used in the package lid, then the structure is simple, but the adhesion strength and RF shielding performance cannot be simultaneously optimized
Solution Approach 1:
The package lid employs a composite structure with multiple conductive layers (e.g., copper layer for adhesion, aluminum layer for RF shielding) with different materials and properties. Each layer serves a specific function: the first conductive layer optimizes adhesion to the substrate, while the second conductive layer enhances RF shielding performance. This composite approach allows simultaneous optimization of adhesion strength and RF shielding without requiring a single material to perform both functions.
Solution Approach 2:
The lid structure is segmented into multiple functional layers rather than using a single monolithic layer. The conductive layers are separated and positioned at different locations within the lid, with each layer dedicated to a specific function (adhesion, shielding, structural support). This segmentation allows independent optimization of each layer's properties and thickness to meet specific performance requirements for both adhesion and RF shielding.
2Object-affected harmful factors
If a thick conductive layer is used for RF shielding, then shielding performance improves, but adhesion strength decreases
Solution Approach 1:
Instead of using a single thick conductive layer for RF shielding, the invention employs multiple thinner conductive layers with different materials. The first conductive layer (e.g., copper) is optimized for adhesion with thickness suitable for bonding, while the second conductive layer (e.g., aluminum) provides RF shielding functionality. This composite layered approach achieves effective RF shielding without compromising adhesion strength, as each layer is optimized for its specific function rather than requiring one layer to perform both.
Solution Approach 2:
Different regions and layers of the lid have different material compositions and thicknesses tailored to local functional requirements. The first conductive layer has properties and thickness optimized for adhesion to the substrate, while the second conductive layer has properties optimized for RF shielding. This local differentiation of material quality allows each layer to perform its specific function at optimal levels without the trade-offs inherent in using a uniform thick layer for both purposes.
3Reliability
If multiple conductive layers with different materials are used, then both adhesion and RF shielding are improved, but manufacturing complexity increases
Solution Approach 1:
The multiple conductive layers are deposited and configured on the lid substrate before the lid is attached to the package body. This preliminary preparation of the layered structure allows for controlled deposition and alignment of different materials while the lid is still accessible for processing. By completing the complex multi-layer fabrication beforehand, the actual assembly process becomes simpler, as the pre-fabricated lid with integrated layers is then merely attached to the package body in a single subsequent step.
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 the adhesion strength of the package lid to the substrate, improving drop test performance and providing effective RF shielding, reducing noise and interference in integrated devices like MEMS microphones.
Implementation Method 1
The package lid is attached to the package substrate using an adhesive, and the package lid and the package substrate can define a package interior. A portion of the first conductive layer contacts the adhesive.
Implementation Method 2
The second conductive layer enhances RF shielding by being electrically connected to the substrate, thereby increasing the mechanical robustness and reducing electromagnetic interference.
Data Source
AI summary
Packaged integrated devices and methods of forming the same are provided. In one embodiment, a packaged integrated device includes a package substrate, a package lid, and an integrated circuit or microelectromechanical systems (MEMS) device. The package lid is mounted to a first surface of the package substrate using an epoxy, and the package lid and the package substrate define a package interior. The package lid includes an interior coating suited to good adhesion with the epoxy, and an exterior coating suited to RF shielding, where the materials of the interior and exterior coatings are different. In one example, the interior lid coating is nickel whereas the exterior lid coating is tin.