Leadless Semiconductor Package Shielding With Ground Lead Bumps
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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 existing shielding solutions (plates, casings, wires) are used to protect selected components, then partial EM shielding is achieved, but the cost is very high and reproducibility is very low
Solution Approach 1:
The shielding structure is segmented into multiple functional components: a leadframe with integrated ground leads, a molding compound encapsulation, and a conductive shielding layer. Each component serves a specific shielding function, allowing mass production through modular assembly while achieving complete enclosure shielding.
Solution Approach 2:
The leadframe serves multiple functions: structural support, electrical grounding, and EM shielding. The ground leads are stamped to create raised bumps that simultaneously provide mechanical positioning and electrical contact with the shielding layer, eliminating the need for separate shielding components and reducing manufacturing complexity.
2Object-affected harmful factors
If current shielding solutions are implemented, then about 30 decibels of EM noise shielding is achieved, but complete shielding is not realized
Solution Approach 1:
The invention merges the ground lead function with the shielding function by integrating the conductive shielding layer directly onto the raised bumps of the ground leads. This combination creates a continuous shielding enclosure that completely surrounds the sensitive components, achieving full 360-degree protection rather than partial shielding.
Solution Approach 2:
The shielding structure uses a nested configuration where the conductive shielding layer is deposited inside the cavity formed by the molding compound, which itself encloses the leadframe and sensitive components. This nested arrangement ensures complete electromagnetic containment with multiple shielding layers working together.
3Ease of manufacture
If the first cut extends through the molding compound layer, then ground leads are exposed for shielding connection, but signal leads may be damaged
Solution Approach 1:
The stamping process creates local quality differences by raising only the ground leads to a higher elevation while leaving signal leads at the original level. This localized elevation allows the cutting process to expose ground leads for shielding connection without cutting into signal leads, as the ground leads protrude above the molding compound surface at specific locations.
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
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation), or other shielding methods dispose a layer of EM shielding
Implementation Method 3
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation), or other shielding methods dispose a layer of EM shielding
Implementation Method 4
metal plating, metal (or other EM shielding material) deposition (e.g., sputtering, evaporation), or other shielding methods dispose a layer of EM shielding
Data Source
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.