MOSFET Package Structure with Stacked Input Capacitor for EMI Suppression
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Solution Overview
Problem
Conventional MOSFET modules in switching power supplies face challenges with electromagnetic interference (EMI) due to parasitic inductance and limited heat dissipation, particularly when using copper plates and mounting input capacitors on Printed Circuit Boards (PCBs).
Innovation Solution
A package structure featuring a pair of MOSFETs and an input capacitor stacked on an up lead frame, with conductive elements connected between the top and bottom lead frames to form a short EMI loop and enhance heat dissipation, utilizing a wire-free bonding process to reduce parasitic inductance and improve thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional copper plate and PCB mounting techniques are used for input capacitor, then EMI suppression is achieved, but parasitic inductance increases and heat dissipation capability is limited
Solution Approach 1:
The patent merges the input capacitor with the lead frame structure by directly mounting the capacitor onto the lead frame itself, eliminating the need for separate PCB mounting. This integration reduces the number of connection points and minimizes parasitic inductance while maintaining EMI suppression capability through the low-inductance lead frame path.
Solution Approach 2:
The patent transitions from planar PCB mounting to a three-dimensional stacked configuration where the input capacitor is mounted vertically on the lead frame. This dimensional change reduces the current loop area and parasitic inductance by creating a more compact, vertically-integrated EMI filter structure.
2Ease of manufacture
If conventional single-sided heat dissipation through bottom lead frame is used, then manufacturing is simplified, but heat dissipation capability is limited
Solution Approach 1:
The patent segments the heat dissipation function into two independent paths: the bottom lead frame and the top lead frame. Each lead frame can be independently attached to heat sinks or cooling structures, allowing heat to be dissipated from both the top and bottom surfaces of the package, effectively doubling the heat dissipation capability.
Solution Approach 2:
The patent adds a vertical dimension to heat dissipation by utilizing the top lead frame surface for heat sinking, in addition to the traditional bottom lead frame attachment. This transforms single-sided heat dissipation into dual-sided heat dissipation, significantly improving thermal management capability.
3Object-generated harmful factors
If wire-free bonding process is used, then parasitic inductance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent merges the electrical connection and mechanical support functions into the lead frame structure itself. The lead frame serves as both the structural substrate and the electrical conductor, eliminating the need for separate wire bonds. This integration reduces parasitic inductance while the standardized lead frame geometry maintains manufacturing precision.
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 configuration achieves reduced parasitic inductance, improved heat dissipation through dual-sided cooling, and increased flexibility for forming more powerful System-in-Package (SiP) modules with optimized EMI suppression.
Implementation Method 1
a first conductive element (210a) mounted between the inner surface (2522) of the up lead frame (250) and the up surface (242) of the bottom lead frame (240), wherein the first conductive element (210a) comprises a first terminal (212a) electrically connected with the up lead frame (250) and a second terminal (214a) electrically connected with the bottom lead frame (240)
Implementation Method 2
improved heat dissipation through dual-sided cooling
Data Source
AI summary
The invention discloses a package structure for better heat-dissipation or EMI performance. A first conductive element and a second conductive element are both disposed between the top lead frame and the bottom lead frame. The first terminal of the first conductive element is electrically connected to the bottom lead frame, and the second terminal of the first conductive element is electrically connected to the top lead frame. The third terminal of the second conductive element is electrically connected to the bottom lead frame, and the fourth terminal of the second conductive element is electrically connected to the top lead frame. In one embodiment, a heat dissipation device is disposed on the top lead frame. In one embodiment, the molding compound is provided such that the outer leads of the top lead frame are exposed outside the molding compound.