Power Module Internal Electrode Reduces Wire Heat Stress
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Solution Overview
Problem
Conventional power modules face challenges in achieving a long lifespan and design flexibility while maintaining low costs, due to heat stress on aluminum wires from repeated on-off cycles and high initial investments for transfer mold technology, as well as limitations in terminal shape and size with direct lead bonding.
Innovation Solution
A power module design featuring a heat spreader with solder-bonded power device chips and an insulating dam, where internal main electrodes are solder-bonded to the chip and externally connected via wire bonding, reducing heat stress on wires and allowing for efficient heat dissipation and flexible terminal designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum wire bonding is used to connect power device chip electrodes to external electrodes, then electrical connection is achieved, but heat stress from repeated on-off cycles reduces wire lifespan
Solution Approach 1:
The patent introduces an internal main electrode as an intermediary component between the power device chip and external electrode. This internal electrode acts as a heat sink, absorbing heat stress and preventing it from being directly transmitted to the aluminum wire. The wire connects to the internal electrode at a location with lower temperature, significantly reducing thermal fatigue and extending wire lifespan.
2Reliability
If direct lead bonding (DLB) is used to connect power device chip to external electrode, then bonding reliability is improved, but design freedom for terminal shape and electrode size is restricted
Solution Approach 1:
The patent segments the connection structure into multiple independent components: the power device chip, internal main electrode, and external electrode. This segmentation allows each component to be optimized independently - the internal electrode can be designed with various shapes and sizes to accommodate different terminal requirements, while maintaining reliable solder bonding to the chip.
3Reliability
If transfer mold technology is used to seal power device chip, then reliability and mass production capability are improved, but initial investment cost increases due to mold preparation
Solution Approach 1:
The patent replaces the expensive, reusable mold used in transfer mold technology with a simpler, cost-effective sealing structure made of inexpensive materials. The sealing is achieved through a combination of the insulating substrate, solder material, and encapsulant, eliminating the need for costly mold preparation while maintaining adequate sealing reliability for the application.
4Duration of action of moving object
If maximum rated bonding portion temperature is set low to increase life span, then wire fatigue life is improved, but power module size and cost increase
Solution Approach 1:
The patent introduces a vertical dimension to the thermal management strategy by positioning the internal main electrode directly beneath the power device chip. This three-dimensional arrangement creates a thermal gradient where heat is conducted downward into the internal electrode and dissipated, allowing the wire bonding region to operate at a lower temperature without increasing the horizontal footprint of the module.
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 design extends the lifespan of the power module by reducing heat stress on wires and enabling efficient heat dissipation, while also reducing manufacturing costs and increasing design freedom for various product sizes.
Implementation Method 1
a heat spreader fixed inside the outer casing, and the power device chip solder-bonded on the heat spreader
Implementation Method 2
the power device chip solder-bonded on the heat spreader... the bonding between the internal main electrode and the electrode of the power device chip is implemented by solder-bonding
Implementation Method 3
The external electrode and the other end of the internal main electrode are electrically connected to each other by wire bonding
Data Source
AI summary
A power module according to the present invention is a power module configured such that a power device chip is arranged within an outer casing and an electrode of the power device chip is connected to an external electrode that is integrated with the outer casing. The power module includes: a heat spreader fixed inside the outer casing; the power device chip solder-bonded on the heat spreader; an insulating dam formed on the heat spreader so as to surround the power device chip; and an internal main electrode having one end thereof solder-bonded to the electrode of the power device chip and the other end thereof fixed to an upper surface of the dam. The external electrode and the other end of the internal main electrode are electrically connected to each other by wire bonding.