Insulating Substrate Solder Resist for Heat Cycle Crack Prevention
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Solution Overview
Problem
Conventional insulating substrates for semiconductor power modules suffer from inadequate high-temperature heat cycle characteristics, leading to cracks in the ceramic substrate when a heat sink plate is soldered, due to the formation of brittle compounds from solder components entering the brazing material layer during heat cycles.
Innovation Solution
The insulating substrate incorporates a solder resist portion on the periphery and side surfaces of the heat-dissipation-side metal plate to prevent solder components from contacting the brazing material layer, thereby inhibiting the formation of brittle compounds and stress concentration, using methods like screen printing to form the solder resist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat sink plate is soldered to the heat-dissipation-side metal plate of the insulating substrate, then the thermal dissipation performance is improved, but cracks occur in the ceramic substrate due to solder components entering the brazing material layer during heat cycles
Solution Approach 1:
A solder resist layer is introduced as an intermediary substance between the solder and the brazing material layer. This solder resist prevents direct contact and interaction between solder components and the brazing material layer, thereby preventing the formation of brittle compounds while allowing thermal dissipation to proceed through the heat sink plate bonding
Solution Approach 2:
The bonding interface is segmented into distinct functional zones: a soldering region where the heat sink plate is bonded, and a protected region where the brazing material layer is shielded by solder resist. This segmentation prevents harmful interactions while maintaining necessary thermal pathways
2Strength
If solder is applied to bond the heat sink plate to the heat-dissipation-side metal plate, then the bonding strength is improved, but solder components penetrate into the brazing material layer forming brittle compounds
Solution Approach 1:
The solder resist acts as a protective intermediary that allows the solder to perform its bonding function on the heat sink plate while simultaneously preventing the solder components from penetrating into the brazing material layer, thus eliminating the harmful effect of brittle compound formation
Solution Approach 2:
The solder resist is applied in advance to the heat-dissipation-side metal plate before soldering, creating a protective barrier that prevents solder components from entering the brazing material layer during the subsequent soldering and heat cycle processes
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 prevents cracks in the ceramic substrate and maintains excellent heat cycle characteristics even with a heat sink plate soldered, ensuring reliable operation under high temperatures.
Implementation Method 1
solder components entering the brazing material layer during heat cycles
Implementation Method 2
one principal surface of a heat-dissipation-side metal plate is bonded to one principal surface of a ceramic substrate via a brazing material layer provided therebetween
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An insulating substrate 1 in which one principal surface of a heat-dissipation-side metal plate 12 is bonded to one principal surface of a ceramic substrate 10 via a brazing material layer 14 provided therebetween, and a solder resist portion 20 is formed on at least one selected from a periphery of the other principal surface of the heat-dissipation-side metal plate 12, a side surface of the heat-dissipation-side metal plate 12, and a surface of the brazing material layer 14. A solder resist prevents solder 31 from wrapping around the brazing material layer 14, and thereby, what is called "the brazing material layer 14 leaching into solder" no longer occurs and the occurrence of cracks inside the brazing material layer 14 is avoided. This prevents stress concentration from occurring in the ceramic substrate 10 at an inner portion relative to an end portion of the heat-dissipation-side metal plate 12.