Increasing Power Density In Three-Phase Inverters With Direct-Cooled SiC Power Modules

Current trends in electrification are placing increasing demands on the power electronics for improved efficiency, higher power capability, and higher power density. Since these demands apply to systems, the requirements extend down to the component level. Silicon carbide (SiC) is poised to rapidly replace silicon (Si) in many applications due to the higher performance characteristics SiC enables. SiC devices offer faster switching speeds, lower dynamic loss, and lower conduction loss in a smaller die area compared to Si devices. To translate these semiconductor advantages into usable solutions, new power module designs are necessary to take full advantage of SiC.

Wolfspeed has developed a next-generation module that has been highly optimized to achieve the maximum performance out of Wolfspeed Generation 3 SiC MOSFETs. The XM3 half-bridge power modules offer the capability to carry high currents (300 to >600 A) in a small footprint (53 mm x 80 mm) with a terminal arrangement that allows for straight-forward bussing and interconnection.

Size comparison of flat baseplate XM3 power module with existing packages.

Friction Stir Welding Advantage

What is Friction Stir Welding?

Friction stir welding (FSW) is a solid-state joining process that uses frictional heat generated by a rotating tool to join materials.

The non-consumable tool with a central probe is rotated and inserted into the interface between two workpieces before traversing along the weld line. Most of the heat generation occurs under the tool shoulder as it moves along the interface, causing the material to heat and soften. The shoulder also acts to contain the softened material, which is mechanically mixed to create a solid phase weld.

What are the Advantages of Friction Stir Welding?

The process is primarily used in industry to join aluminum alloys of all grades, whether cast, rolled or extruded. FSW has been shown to weld aluminum alloy butt joints with a thickness of between 0.3mm and 75mm in a single pass, depending on the parent material used, the machine power and the structural stiffness of the workpiece.

  • As a solid-state welding process, FSW is a largely defect-free joining method with no hot cracking, porosity or solidification cracks
  • Due to the lower temperatures, there is a reduction in shrinkage and distortion in the material being joined
  • No filler materials, flux or shielding gas requirement for aluminum alloys
  • FSW is environmentally friendly as it produces no fume, spatter, or UV radiation
  • Uses machine tool technology, making the process easy to automate, highly repeatable and reducing need for skilled welders
  • Good mechanical properties, which for aluminum alloys typically equals or exceeds those obtainable by competing processes
  • Able to join many ‘non-weldable’ aluminum alloys, such as those from the 1xxx, 2xxx and 7xxx series

What are the Disadvantages of Friction Stir Welding?

While friction stir welding provides many advantages, there are a few limitations associated with the process.

  • Exit hole left after withdrawing tool from the materials to be joined
    Generally 4mm in diameter and 4mm deep
  • The need for significant down force and traversing forces means that clamping is more substantial than for tig or arc welds
  • Lacks the flexibility of manual and arc processes, for example, FSW cannot be used where metal deposition is required
  • Holes and Machined features need a setback from the weld line unlike in brazing.
  • Setback generally needs to be 3 – 5mm from the weld center line.

Wieland Microcool Friction Stir Welding

We have become the expert in friction stir welding high conductivity 1100 series aluminum MDT™ pin plates into all types of machined, extruded and cast aluminum alloys. Learn more

Introducing our new cold plate series, CP 4000

The 4000 Series aluminum friction stir welded cold plates, use a new optimized extruded tub. The MDT (micro deformation technology) inside allows for the very low thermal resistance, low pressure drop and balanced parallel flow.

  • The flat bottom makes mounting easy as well as adds the option for double sided cooling (with or with out MDT pin fin on the backside).
  • The included hose barbs significantly reduce pressure drop associated with screw in fittings and are available in multiple sizes.

Same 10+ sizes available as our best in class 3000 series cold plates. Optimized to work with the most common module foot prints.

New versions optimized specifically for Wolfspeed 62mm, CAS325 & XM3 packages.

Double-sided versions are available.


Quick turn custom versions available.

Try our free online cold plate simulator

Wieland Microcool Tool is an online simulation tool for cold plates and cooling elements developed for a diverse range of electronic cooling applications including CPU configurations, racks, servers, GPU graphics chips, high-output LEDs, power modules, IGBTs, and power semiconductors.

This online software can help you quickly determine which type of MDT fin or pin geometry will best suit your performance needs. With just a few inputs, the correlation-based software:

  • Provides thermal resistance, cold plate and fluid temperatures, as well as pressure drop performance
    Evaluates straight fins, in-line pin fins, and staggered pin fin geometries
  • Handles single-phase coolants (best methods including entrance effects)
  • Determines once-through and split flow (for pressure drop designs)
  • Generates complete graphical simulations (including 3D PDF output with graphs and incremental calculation output of the thermal views) and set of input/output results

Contact us and we can help you run a simulation or you can test one of our off the shelf standard cold plates with fast shipping
from the US.

Wieland Microcool friction stir welded cold plate with MDT pin fin inside

How it’s made – Wieland Microcool friction stir welded cold plate with MDT pin fin inside

Check out the video 

We start with an aluminum extrusion or plate, from there we machine the pockets for the MDT pin fin plates, and fluid manifolds.

Then we friction stir weld the fin plates into the tub or manifold. After welding we fly cut the top to remove the FSW flash and create the flat and smooth cooling surface. As a last step we add all holes, any finish machining and then leak test the finished cold plate.

Contact us to test one of our off the shelf standard cold plates or we can help you create a custom cold plate in days.


about us

Wieland Microcool is an industry leader in base plate, cold plate and total cooling loop system designs. We offer a myriad of fin and custom pin fin geometries designed to improve reliability and thermal efficiency in cooling electronic systems.


2100 Market Street NE
PO Box 2202
Decatur, AL 35601



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