Leadless Package Shielding With Ground-Lead Bumps for Full EM Enclosure
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Solution Overview
Problem
Existing leadless semiconductor packages face challenges in achieving complete electromagnetic (EM) shielding, particularly for high-sensitivity applications, with current solutions providing only partial shielding and high costs.
Innovation Solution
A full-enclosure EM shielding is achieved by combining a plated shield with a modified leadframe and grounding arrangement, where ground leads are stamped to form bumps, overmolded, and connected to an EM shielding enclosure, ensuring complete coverage without contacting signal leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal plates and casings are used for EM shielding, then shielding effectiveness is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the EM shielding function with the package encapsulation structure by integrating the shielding enclosure as part of the molding compound assembly, eliminating the need for separate shielding plates and casings. The shielding is achieved through the grounded conductive enclosure formed by the molding compound, which merges multiple functions into a single integrated structure.
Solution Approach 2:
The molding compound serves multiple functions: it provides mechanical protection, environmental sealing, and electromagnetic shielding. By making the molding compound conductive and grounding it, the same material that protects physically also protects electromagnetically, eliminating the need for dedicated shielding materials and simplifying the overall structure.
2Object-affected harmful factors
If custom shielding solutions are designed for specific PCB layouts, then shielding effectiveness is improved, but reproducibility decreases and cost increases
Solution Approach 1:
The shielding solution is made universal and layout-independent by integrating the shielding function into the package itself rather than designing custom shields for specific PCB positions. The conductive molding compound enclosure provides omnidirectional shielding that works regardless of PCB placement or orientation, enabling high-volume standardized manufacturing.
Solution Approach 2:
The EM shielding is built into the package structure during the molding process itself, before the package is mounted on the PCB. This preliminary integration of shielding functionality eliminates the need for subsequent customization or adjustment based on specific PCB layouts, ensuring consistent reproducibility across all manufactured units.
3Object-affected harmful factors
If existing shielding methods are used, then partial shielding is achieved, but complete shielding of all internal components is not realized
Solution Approach 1:
The patent segments the shielding approach by creating multiple grounded conductive elements within the package structure, including conductive leads extending from different sides and a conductive enclosure, ensuring that all internal components are surrounded by shielding material rather than relying on a single shielding point.
Solution Approach 2:
The shielding structure is nested within the package itself, with the conductive molding compound enclosure containing the semiconductor die and leads, which are themselves surrounded by the conductive material. This nested arrangement ensures complete coverage of all internal components with multiple layers of shielding protection.
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 significantly improved EM shielding performance, especially for high-frequency and high-speed applications, ensuring internal components are fully protected from electromagnetic interference.
Implementation Method 1
Properly positioned, these materials absorb or reflect unwanted EM energy, preventing the energy from reaching the sensitive parts of the device
Implementation Method 2
Properly positioned, these materials absorb or reflect unwanted EM energy, preventing the energy from reaching the sensitive parts of the device
Implementation Method 3
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation)
Implementation Method 4
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation)
Implementation Method 5
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation)
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A
AI summary
Structures and methods for electromagnetic shielding of leadless semiconductor packages provide complete module-level electromagnetic shielding by combining plated shielding with proposed modified ground lead arrangement and ground pad grounding. A package including a leadframe, ground leads, and signal leads is stamped to form a "bump" in the ground leads around the perimeter of the package. After overmolding, the package is cut to expose the bumps; then, a full shielding enclosure is formed over the top of the package into contact with the exposed ground leads. Components of the leadframe that extend to the perimeter of the device, such as corner bars connecting to the center flag, can also be stamped and brought into contact with the shield. The ground leads may further be connected to a center flag of the leadframe for full-enclosure shielding. The signal leads remain electrically isolated from the leadframe and the shielding enclosure.