Increased demand for radar capabilities has required increasingly more efficient thermal management techniques. Simple cold plates using tubes or channels are frequently used to cool high power components but restrictions on size, weight, and power have restricted their effectiveness. This project analyzed several thermal management approaches and used additive manufacturing to dramatically increase performance with materials and structures that could not be fabricated using traditional methods.

Conventional cooling methods flow coolant parallel to the heat source surface in a serpentine path under components. In parallel flow, a thermal gradient develops across the channel which diminishes the heat transfer effectiveness across the channel width. In addition, the coolant temperature increases as it removes heat from each component, becoming less effective as it progresses.

Using multiphysics simulation software, a cold plate design using manifolds and microchannels was designed to maximize cooling efficiency by dividing the coolant into several parallel paths and directing the flow into microchannels at a direction perpendicular to the heated surface. After a short length through the microchannels, the coolant returns to an adjacent manifold and exits the plate. By increasing the surface area and minimizing the microchannel path length, very large heat transfer coefficients were obtained with a corresponding low cold plate thermal resistance (<0.05 [in2-°C/W], normalized for area).

Typically, microchannel cold plates have been expensive to manufacture requiring precision machining, solder, and brazing. Using additive manufacturing, cold plates have been made with direct metal laser sintering using copper, aluminum, and titanium. By designing to the tolerances of the additive process and using guidelines to eliminate internal support structures, low thermal resistance cold plates have been produced and tested.

Using simulation, the optimum microchannel spacing, coolant flow rate, and manifold sizing have been determined to maximize heat removal and minimize pressure drop. Thin cold plates (<4 mm thick) can be designed to achieve two-sided cooling in high power radar applications. This advanced manufacturing process can place the highest cooling power at the hottest components to mitigate thermal issues in current and future platforms.

With an increase in reliability and performance, reduced weight and cost, adaptive sizing, and the ability to respond to increased power demands, thermal upgrades can be designed, manufactured, and validated in months instead of years.

Embedded components technology has launched its implementation in volume products demanding high levels of miniaturization. Small modules with embedded dies and passive components on the top side are mounted in hand held devices. Smartphones have been the enablers for this new technology using the capabilities of embedded components. With this technological background another business field became interesting for embedded components – the embedded power electronics. The roadmap of the automotive industry shows a clear demand for miniaturized power electronic applications. Drivers are the regulations for the international fleet emissions which are focusing on three major trends.

The first trend will be higher efficiency of “classic” internal combustion engines, the second will be the efficiency of body application and the last trend will be the electrification of the drive train. For all targets a huge potential for embedded power electronics is visible. A European project was launched in 2013 as a development project for new power packages and power modules using die embedding technology. For the realization of this technology, copper termination on MOSFETs, IGBTs and power diodes is necessary. Equipment and processes have been developed in the supply chain to support the development of power modules ranging from 500 W to 50 kW. For enhanced thermal performance of power modules, a concept for double sided cooling has been developed. Beside full area contacting the MOSFET on the drain side with copper and contacting the embedded components in a power core with an isolated metal substrate with silver sinter paste, a very effective concept for reducing thermal resistances and stray inductance was shown. With the realization of the 500W demonstrator the proof of concept was realized. This paper will focus on the behavior of the power module for operational conditions of a PedEleC (Pedal Electric Cycle) application. The full reliability evaluation (thermal shock test, reflow test and power cycling) and switching behavior was shown. Furthermore, the thermal properties of the PedEleC power module were verified with the results from thermal simulation. In addition, more detailed investigation of the electrical properties before and after reliability treatment of a single chip  test vehicle was shown.

Keywords: power embedding, PCB technology, miniaturization, automotive requirement, electro mobility

This presentation covers Stretchable hybrid electronics.  Stretchable electronics have the most industry uses in wearable technology and for mobile sensing and response devices.  Thermosetting resins are used in the layers of the flexible electronics.  A new thermosetting resin is tested for stretchability, temperature, and washability.  The slides also discuss flexible encapsulants added for extra support over components.  

This presentation covers additive manufacturing and the direct deposit of multiple metals.  This additive capability is best utilized for the production of complicated circuits such as Radar and antennas.  There are a lot of potential uses for additive manufacturing including prototyping and low volume high complexity PCBs.

The defense industry has realized the importance of Additive Manufacturing (AM) and how this technology can be utilized where parts can be fabricated inexpensively with reduction in lead times.

The company investigated how AM could further reduce the cost and lead time of critical components such as cold plates. Traditionally, these parts were fabricated using a subtractive machining and brazing process incurring a twenty-six-week lead time after receipt of order to an external supplier.

With newly developed in-house AM capability, the lead time was reduced to four weeks and concurrently provided an overall material/manufacturing cost savings.

Cold plate thermal and structural performance was not compromised.

Thermally conductive adhesives are widely implemented in a variety of electronic assemblies. These adhesives combine the function of mechanical fasteners and thermal interface materials into one product. This combination of roles allows for the preparation of assemblies that are smaller, lighter, and easier to manufacture than traditional combinations of pads and greases or gels with mechanical fasteners. The use of thermally conductive adhesives requires an increased understanding of their mechanical properties, especially their fracture behavior so that the reliability of an assembly can be accurately determined. Since most thermally conductive adhesives are composed of a filler in conjunction with a polymeric resin this study examined the effects of the filler particle size distribution and morphology on the fracture behavior and mechanical properties of a silicone adhesive. It was seen that a greater proportion of small filler and an increased filler surface area for spherical fillers improved the fracture toughness of the adhesive.

The trend of incorporating more and more electronic devices into our daily life is bringing challenges for the industry. The need for smaller and more powerful devices is also facing one problem: heat dissipation. Processor chips, large capacitors, inverters, transformers and some ICs are usually the components in an electronic assembly generatingheat. Heat can reduce performance and usable life of the electronics and thus require thermal management to improve reliability and prevent premature failure.  More than 50% of power module failures are temperature related due to inadequate or improper thermal management.

Thermal Interface Materials (TIMs) play a key role in the thermal management of electronic systems by providing a path of low thermal resistance between the heat generating devices and the heat spreader/sink. Typical TIM solutions include adhesives, greases, gels, phase change materials, pads, and solder alloys. Among these different solutions, greases typically offer better thermal performance, reduce manufacturing cycle times and frequently are considered the lowest cost solution. In the area of thermal management, silicone thermally conductive greases are extensively used due to their proven thermal and environmental stability coupled with excellent wet-out performance. This paper presents reliability data to explore the thermal performance of a silicone thermally conductive grease formulation when exposed to different conditions such as: high temperature ageing, thermal cycling, damp heat, and power cycling.