Semiconductor RF Shielding Sidewall Contact
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Solution Overview
Problem
Existing semiconductor devices face challenges with RF shielding methods that require additional space on the substrate, are costly, and suffer from issues like flux creep and delamination, particularly when using embedded or conformal shields.
Innovation Solution
A semiconductor device with a substrate featuring a dielectric and metal layer, where a mold compound is used to encapsulate the die and partially encapsulate the substrate, with a conductive material applied to cover the mold compound and contact the metal layer, utilizing a multi-step process including sawing and laser ablation to expose metal traces for RF shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an embedded RF shield is attached to the substrate, then RF shielding is achieved, but additional space on the substrate is required and molding becomes difficult
Solution Approach 1:
The RF shield is moved from the traditional planar substrate surface to the vertical sidewalls of the package. By forming conductive shields on the side surfaces of the mold compound rather than embedding them in the substrate plane, the solution utilizes the third dimension (vertical space) to achieve RF shielding without consuming additional substrate area.
2Reliability
If a conformal shield with exposed pads is used, then RF shielding is achieved, but large contact pads are required on the substrate surface
Solution Approach 1:
The contact mechanism is changed from large planar pads on the substrate surface to narrow vertical contact traces on the sidewalls. The conductive shield extends vertically along the side surfaces and makes contact with ground planes through vertical traces, eliminating the need for large horizontal contact pads.
3Reliability
If external shields are soldered to the motherboard, then RF shielding is achieved, but additional board space is required and the process is costly
Solution Approach 1:
The RF shielding function is merged with the package structure itself. Instead of adding a separate external shield component, the mold compound is formed with integrated sidewall protrusions that directly support the conductive shield material, combining the packaging and EMI shielding functions into a single integrated structure.
4Reliability
If metal shield is fully embedded in mold compound, then RF shielding is achieved, but transfer molding becomes difficult
Solution Approach 1:
The mold compound is segmented into distinct regions: a main body and vertical sidewall protrusions. This segmentation allows the mold to form the protrusions as integral parts of the molding process, creating cavities that accommodate the conductive shield material while maintaining easy mold release and manufacturing feasibility.
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 provides effective RF shielding without the need for large contact pads, reducing substrate size and minimizing encapsulation issues, while ensuring reliable electrical contact and efficient RF interference reduction.
Implementation Method 1
utilizing a multi-step process including sawing and laser ablation to expose metal traces for RF shielding
Data Source
AI summary
A semiconductor device has a substrate comprising at least one dielectric layer and at least one metal layer on a first surface of the substrate. A die is attached to the first surface of the substrate. A mold compound is used to encapsulate the die and partially encapsulate the first surface of the substrate. The mold compound has a protrusion proximate to the at least one metal layer. A conductive material covers the mold compound, including the protrusion, and contacts the at least one metal layer.