Power Device Packaging with Bottom Source Electrode

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Solution Overview

Problem

Existing semiconductor power devices face high power consumption, expensive cup-shaped metal can production, and challenges in adjusting the gate electrode to match PCB pads, along with high substrate resistance, which limits the application and efficiency of DC-DC power converter devices.

Innovation Solution

The development of a power device with a bottom source electrode and a lead frame unit comprising multiple bases, where a semiconductor chip is flipped and attached, with a bridge-shaped metal clip and conductive epoxy used for electrical connections, and a plastic packaging structure that exposes the necessary bases for contact, allowing for improved heat dissipation and reduced substrate resistance through wafer level chip scale packaging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a cup-shaped metal can is used to package the power device, then heat dissipation performance is improved, but manufacturing cost increases

Engineering Contradiction:

Improveheat dissipation performanceVSAvoidmanufacturing cost

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent replaces the expensive cup-shaped metal can with a plastic packaging structure that is more cost-effective to manufacture. The plastic package includes a cavity designed to hold the semiconductor chip and lead frame, providing adequate heat dissipation through the molded plastic material and exposed lead frame surfaces without requiring expensive metal forming processes.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Stability of the object's composition

If the gate electrode is fixed in the packaging structure, then structural stability is improved, but adaptability to different PCB pad configurations decreases

Engineering Contradiction:

Improvestructural stabilityVSAvoidadaptability to PCB pad configurations

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent makes the gate electrode position adjustable relative to the packaging structure. The lead frame is designed with a gate electrode that can be positioned at different locations on the lead frame, allowing the contact surface of the gate electrode to be adjusted to match different PCB pad configurations. This dynamic positioning capability is achieved through the flexible lead frame design that allows repositioning during the packaging process.

Inventive Principle:

Principle #15Dynamics

3Length of moving object

If conventional WLCSP packaging is used, then chip thickness is reduced, but substrate resistance remains high

Engineering Contradiction:

Improvechip thicknessVSAvoidsubstrate resistance

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The patent performs power device processing and electrical connection formation on the semiconductor wafer before the wafer is thinned and packaged. This preliminary action includes forming the drain electrode, source electrode, and gate electrode connections while the wafer is still at its original thickness, ensuring low resistance connections are established before the thinning process. The wafer is then thinned to ultra-thin specifications and packaged, achieving both reduced thickness and maintained low substrate resistance.

Inventive Principle:

Principle #10Preliminary action

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 solution enables the production of ultra-thin chips with reduced substrate resistance, improved heat dissipation, and cost-effective manufacturing, facilitating better electrical connections and expanded application in power devices.

Implementation Method 1

a first metal base (111) and a second metal base (112) separated from each other, a semiconductor chip (31) flipped and attached onto the first metal base (111) and the second metal base (112) by a conductive epoxy

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 2

a plastic packaging structure (160) encapsulating the lead frame unit, the primary packaging structure (130) and the bridge-shaped metal clip (150), wherein a bottom surface of the first metal base (111), a bottom surface of the second metal base (112), bottom surfaces of the third metal base (113) and the fourth metal base (114) are exposed from a bottom surface of the plastic packaging body (160)

Methodology Applied

Scientific EffectThermal Conduction: Conduction (thermal)

Data Source

PatentUS9391005B2Method for packaging a power device with bottom source electrode

Publication Date: 2016.07.12 ALPHA & OMEGA SEMICONDUCTOR INC

AI summary

A power semiconductor package has an ultra thin chip with front side molding to reduce substrate resistance; a lead frame unit with grooves located on both side leads provides precise positioning for connecting numerous bridge-shaped metal clips to the front side of the side leads. The bridge-shaped metal clips are provided with bridge structure and half or fully etched through holes for relieving superfluous solder during manufacturing process.