Insulating Substrate Ni Barrier for Heat-Cycle Crack Resistance
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Solution Overview
Problem
Ceramic insulating substrates used in semiconductor power modules suffer from inadequate furnace passing resistance and heat cycle characteristics, leading to potential cracking when exposed to high-temperature thermal stress, particularly due to the formation of brittle compounds between solder components and brazing material layers.
Innovation Solution
A Ni plating layer is applied to cover the brazing material layer exposed between the ceramic substrate and the heat-dissipation-side metal plate, preventing direct contact with solder components and inhibiting their diffusion into the brazing material layer, thereby reducing stress concentration and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire copper plate is coated with Ni plating to improve corrosion resistance and soldering, then corrosion resistance and soldering are improved, but the brazing material layer becomes exposed and vulnerable to solder-induced dissolution and brittle compound formation
Solution Approach 1:
The patent applies Ni plating selectively to specific regions of the copper plate rather than the entire surface. The Ni plating is applied to the circuit pattern area to provide corrosion resistance and improve soldering, while deliberately leaving the brazing material layer exposure area unplated to prevent solder from causing brazing material layer dissolution and brittle compound formation.
2Temperature
If a thick heat sink plate is soldered to the heat-dissipation-side metal plate to improve heat dissipation, then thermal conductivity is improved, but the ceramic substrate becomes susceptible to cracking under heat cycle conditions
Solution Approach 1:
The patent introduces an intermediate protective structure consisting of the heat-dissipation-side metal plate bonded to the ceramic substrate via a brazing material layer. This intermediate layer acts as a stress buffer that absorbs thermal expansion differences between the ceramic substrate and the thick heat sink plate, preventing direct stress transmission that would cause ceramic cracking during heat cycles.
3Temperature
If the insulating substrate is designed with exposed brazing material layer to ensure thermal conductivity, then heat dissipation is improved, but the brazing material layer becomes vulnerable to solder component diffusion
Solution Approach 1:
The patent applies different surface treatments to different regions of the metal plate. The brazing material layer exposure area is deliberately left without Ni plating to maintain thermal conductivity and ensure proper brazing, while the circuit pattern area receives Ni plating to prevent solder component diffusion into the brazing material layer.
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 enhances the furnace passing resistance and heat cycle characteristics of the insulating substrate, preventing cracks and maintaining the heat release ability, even under high-temperature conditions, by preventing the formation of brittle compounds within the brazing material layer.
Implementation Method 1
a Ni plating layer that covers the brazing material layer exposed between the ceramic substrate and the heat-dissipation-side metal plate
Implementation Method 2
one principal surface of a heat-dissipation-side metal plate is brazed to one principal surface of a ceramic substrate via a brazing material layer provided therebetween
Data Source
AI summary
An insulating substrate in which one principal surface of a heat-dissipation-side metal plate is brazed to one principal surface of a ceramic substrate via a brazing material layer provided therebetween, in which a Ni plating layer that covers the brazing material layer exposed between the ceramic substrate and the heat-dissipation-side metal plate is provided, and at least a portion of the other principal surface of the heat-dissipation-side metal plate is not covered with a Ni plating layer, leaving the surface of the heat-dissipation-side metal plate exposed. According to the present invention, it becomes possible to obtain the insulating substrate having excellent furnace passing resistance of the insulating substrate (alone) and further having excellent heat cycle characteristics in a state of a heat sink plate being soldered to the insulating substrate.