DBC Substrate Power Package Electrical Isolation

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Solution Overview

Problem

Conventional power semiconductor devices lack sufficient electrical isolation, posing safety hazards and potential damage to circuit components due to high voltages at the backside of the package, which can couple to other components or operators, and require improved thermal coupling and mounting solutions.

Innovation Solution

A packaged power semiconductor device with a direct-bonded copper (DBC) substrate, where the semiconductor die is mounted on a DBC substrate with exposed copper layers for soldering and encapsulation, providing electrical isolation and enhanced thermal conductivity through a hole in the encapsulant for screw mounting and heat dissipation, while maintaining industry-standard package layouts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the backside of the package is electrically coupled to the semiconductor die, then electrical connectivity is achieved, but electrical isolation and safety are compromised

Engineering Contradiction:

Improveelectrical isolationVSAvoidpackage structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The package structure is segmented into electrically isolated zones: the metal back plane is separated from the semiconductor die electrical connection path, creating distinct electrical domains. This segmentation allows the backside to be mechanically supported while maintaining electrical isolation from high-voltage nodes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediate insulating structure is introduced between the metal back plane and the semiconductor die mounting area. This intermediary element provides mechanical support and thermal conduction pathways while blocking electrical coupling, resolving the contradiction between structural integrity and electrical isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If insulating pads or washers are used to electrically isolate the backside, then electrical safety is improved, but thermal coupling is degraded

Engineering Contradiction:

Improveelectrical isolationVSAvoidthermal coupling

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The package employs composite material structures combining electrically conductive metals (for thermal conduction) with electrically insulating ceramics or polymers (for electrical isolation). This composite approach enables simultaneous achievement of electrical safety and thermal management by selecting materials with appropriate property combinations.

Inventive Principle:

Principle #40Composite materials

3Reliability

If the package layout is optimized for electrical isolation, then safety is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveelectrical isolationVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The metal back plane is designed to serve multiple functions simultaneously: providing mechanical support, enabling thermal conduction through direct contact with the semiconductor package, and maintaining electrical isolation through its geometric configuration and material properties. This multi-functionality reduces the need for additional specialized components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Power

If high voltages are present at the backside of the package, then power semiconductor operation is enabled, but safety hazards and component damage risks increase

Engineering Contradiction:

Improvepower handling capabilityVSAvoidsafety hazard

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The high-voltage electrical connection is extracted from the backside of the package and relocated to the front or side terminals. This extraction removes the hazardous high-voltage node from the accessible backside surface, eliminating the safety hazard while preserving the power handling capability through alternative terminal configurations.

Inventive Principle:

Principle #2Taking out (Extraction)

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

The solution provides superior electrical isolation, thermal coupling, and safety features, reducing manufacturing costs and facilitating standardized mounting, thereby enhancing the performance and reliability of power semiconductor devices.

Implementation Method 1

enhanced thermal conductivity through a hole in the encapsulant for screw mounting and heat dissipation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

superior electrical isolation

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS9177888B2Electrically isolated power semiconductor package with optimized layout

Publication Date: 2015.11.03 LITTELFUSE INC

AI summary

A packaged power semiconductor device is provided with voltage isolation between a metal backside and terminals of the device. The packaged power semiconductor device is arranged in an encapsulant defining a hole for receiving a structure for physically coupling the device to an object. A direct-bonded copper (“DBC”) substrate is used to provide electrical isolation and improved thermal transfer from the device to a heatsink. At least one power semiconductor die is mounted to a first metal layer of the DBC substrate. The first metal layer spreads heat generated by the semiconductor die. In one embodiment, the packaged power semiconductor device conforms to a TO-247 outline and is capable of receiving a screw for physically coupling the device to a heatsink.