Let's talk about the Infineon DSC (double-sided water cooling) vehicle scale module

01

On the Past

New energy vehicles are developing towards high power density and high reliability. In order to meet this demand, power modules are moving towards higher "extremes" in terms of electrical performance (Si-based and WBG material chips) and packaging (low stray inductance, advanced interconnection technology, excellent performance packaging materials and high heat dissipation performance).

NREL's Power Electronics Cooling Technology Research

The research and application of double-sided water cooling modules have already begun to develop. The figure below is the development history of automotive modules in the past few decades, which was summarized in "Comprehensive Review and State of Development of Double-Sided Cooled Package Technology for Automotive Power Modules" published by General Motors boss Liu Ming last year.

Among them, in addition to the several common vehicle-scale modules we have talked about before, there are many other forms of packaging appearances. This is different from the relatively consistent module packaging of industrial modules. The differentiation of vehicle-scale modules comes from the needs of automobile manufacturers for their own applications and is more inclined to differentiation.

The article also shows the development trend of power density of electric vehicle inverters.

It can be seen that Tesla's power density is at a very high level. At the same time, it shows that all companies are moving towards higher power density. The US Department of Energy's power density target for 2025 is 100kW/L.

Today we will learn about some characteristics of the double-sided water cooling module through Infineon's DSC module.

02

IFX DSC Module

First, the figure below is the topology diagram of Infineon DSC module.

Among them, considering the high sensitivity of SiC to module parasitic parameters, Infineon optimized the terminal layout of DSC, changing the situation where DC and AC are on the same side to DC and AC on different sides, in order to reduce the stray inductance of the loop.

By adopting double-sided water cooling, the thermal resistance Rth(jf) between the junction and the coolant is reduced by about 40% compared with the single-sided water cooling module with the same package. Through simulation, about 30% of the additional heat flows out from the top.

Schematic diagram of the structure of DSC

We can see the outline of a DSC module and its internal materials and structures. The back of the chip is connected to the bottom insulating substrate by, for example, soldering, sintering or adhesive bonding, while the front of the chip is connected to the upper insulating substrate by an electrically and thermally conductive spacer. The remaining space between the bottom and top substrates is filled with a polymer-based compound (the encapsulation of the integral molded structure) to safely separate the potentials within the module. The module is cooled indirectly, i.e. the coolant does not come into direct contact with the module. The module is pressed onto a cooler, usually made of aluminum, on both sides. The metal-to-metal defects are filled by thermally conductive silicone grease. Finally, cooling is achieved by forcing a water-glycol coolant in the cooler (not shown in the figure).

An important parameter for optimizing thermal performance is the use of a ceramic substrate with high thermal conductivity, which we briefly discussed in the previous article. The standard substrate used by Infineon is AlN.

03

Epoxy Molding Compound EMC

Double-sided water cooling modules generally use the same plastic packaging form as discrete devices. The main reason is that the traditional silicone filling method is not suitable for the stacking structure of dual-pulse water cooling. At the same time, plastic packaging achieves relatively low production costs and a higher degree of automation.

The following is a simple manufacturing diagram based on EMC (Epoxy Molding Compound) transfer mold.

The DSC module is placed in a mold cavity, and the EMC material is melted and pushed into the mold cavity by a plunger. The EMC fills the cavity, encapsulates the DSC, solidifies, and is ejected from the cavity. During the molding process, static pressure and mechanical compression may occur. Therefore, during this molding process, the module can be exposed to liquid-solid phase changes, high pressure and high temperature.

04

summary

Today we have briefly learned about some characteristics of the double-sided water cooling module and the simple process of plastic packaging. Sometimes I wonder, if all the unique technologies currently used in the automotive sector are integrated into one module, what will its performance or cost performance be? However, the mutual constraints of some parameters usually lead to compromises in the end, and not all solutions are optimal.