Power Module Substrate Silver Electroplating Thermal Stress
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Solution Overview
Problem
Existing power module substrates face challenges in maintaining bonding reliability under severe temperature conditions, particularly in vehicle applications, where thermal stress is repetitive, and there is a need to improve the bonding strength between the resin layer and the circuit board, as well as the reliability of the silver layer on the metal plate.
Innovation Solution
A power module substrate is designed with an insulating substrate, a metal plate, and a first electroplating layer that includes a silver layer with a nickel layer and optionally a palladium layer, which enhances bonding reliability by suppressing oxidation and diffusion, and a second electroplating layer on a heat dissipation plate for improved thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silver layer is disposed on the upper surface of a metal plate to suppress oxide film formation, then the reliability of electrical connection is improved, but the silver layer peels off under repetitive thermal stress
Solution Approach 1:
The patent applies a multi-layer composite structure consisting of a metal plate, silver layer, and resin layer. This composite material approach allows each layer to contribute its specific properties: the metal plate provides structural support and electrical conductivity, the silver layer ensures reliable electrical connection, and the resin layer bonds them together while accommodating thermal expansion differences, thereby preventing silver layer peeling under thermal stress.
Solution Approach 2:
The resin layer acts as an intermediary between the metal plate and the silver layer. It mediates the thermal stress and mechanical bonding between these two layers, distributing the stress uniformly and preventing direct contact between the silver layer and the metal plate surface that would otherwise cause peeling under repetitive thermal conditions.
2Reliability
If a resin layer is used to cover the electronic component for sealing, then the protection and insulation are improved, but the bonding strength between the resin layer and the circuit board deteriorates under thermal stress
Solution Approach 1:
The patent modifies the chemical composition parameters of the resin layer by incorporating specific functional groups and adjusting the molecular structure. These parameter changes enhance the chemical bonding capability and thermal stability of the resin layer, allowing it to maintain strong bonding with the circuit board under repetitive thermal stress while preserving its sealing and insulation functions.
3Ease of manufacture
If a simple metal plate structure is used for the circuit board, then the manufacturing simplicity is maintained, but the ability to withstand repetitive thermal stress deteriorates
Solution Approach 1:
The patent transforms the simple metal plate structure into a composite structure consisting of a metal plate, silver layer, and resin layer. This composite structure maintains relative manufacturing simplicity while significantly improving thermal stress resistance through the synergistic properties of each layer and their interfaces, which distribute and accommodate thermal expansion forces.
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 effectively improves the bonding strength between the resin layer and the circuit board, reduces peeling of the silver layer from the metal plate, and enhances the reliability of electronic component sealing, while also providing enhanced thermal dissipation and reduced stress due to thermal expansion differences.
Implementation Method 1
a first electroplating layer that includes a silver layer with a nickel layer and optionally a palladium layer
Implementation Method 2
a first electroplating layer that includes a silver layer with a nickel layer and optionally a palladium layer, which enhances bonding reliability by suppressing oxidation and diffusion
Implementation Method 3
enhances the reliability of electronic component sealing, while also providing enhanced thermal dissipation and reduced stress due to thermal expansion differences
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A power module substrate 10 or the like including an insulating substrate 1 with an upper surface and a lower surface, a metal plate 2 with an upper surface and a lower surface, the lower surface facing and being bonded to the upper surface of the insulating substrate 1, and a first electroplating layer 3 that partly covers the central portion of the upper surface of the metal plate 2. The first electroplating layer 3 includes at least a silver layer, and the grain size of silver in the silver layer is more than or equal to the grain size of a metal in an upper surface portion of the metal plate 2.