Power density in a 3D power package

This article is part of the Power Management Series: Diving into Power Density

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What you will learn:

  • Various 3D packaging integration techniques to increase power density.
  • Different methods of chip cooling using 3D packaging.

New and emerging technologies for 3D packaging are being deployed at the printed circuit board (PCB) level. Power density goals can be simplified by integrating components into chip-scale packages that use stacking techniques, integration, transposers, and more. Advanced cooling methods will help make 3D packaging a viable option.

The latest technological innovations and cooling methods will improve power density in new designs and bring it up to standard in older designs. These innovations and methods, in this article, will significantly improve power density in 3D power conditioning.

Integration and integration

Face up/face down

Current technology allows elements such as active and/or passive components, magnetic elements and integrated filters to be integrated into the printed circuit board.

Texas Instruments’ MicroSIP was the first commercial DC-DC converter produced with the HERMES “face-down approach”. The HERMES project aims to integrate active matrices, facing up or down (flip chip), and passive (thin) components inside the dielectric layers of a PCB.

Snap integration

Plated through-hole (PTH) and blind via (BV) are two technologies that allow embed (fig. 1).

Reliability of 3D Integrated Power Packaging

Increasing power density in power electronics designs will require better cooling techniques in the future, such as integrated cooling. Temperature control of power components is crucial for device reliability and performance. However, innovative thermal management of power electronic systems is a major bottleneck for power densification.

Wirebond/Solder Die Attach vs Sintered Interconnects

For optimal power density reliability, traditional wire bonding techniques must evolve to sintered interconnects, which would eliminate wire bond failures.

Sintered silver feeders are an alternative interconnect technology to standard solders. The technology is different from other interconnect technologies due to its improved thermal and mechanical properties. High fatigue life is achieved when tested against standard solder die attachment and aluminum wire top contacts.

Embedded components

Capacitors

There are two methods for integrating capacitors into 3D structures:

  • Integrated capacitor films
  • Built-in capacitor devices

Inductors

There are two ways to integrate inductors into 3D structures:

  • Planar magnetic
  • Inductors removed

Cooling Methods in 3D Power Packaging

Integrated manifold and microchannel coolers

These types of coolers can be integrated directly into the substrate or chip and will provide localized heat removal at high volumetric rates from the back of active integrated circuits and power electronic devices. (Fig.2). They can be used in many forms; for example, single-phase or two-phase, silicon or ceramic and different alloy substrates, filter size, working fluid, fluid velocity and temperature.

Force-fed two-phase manifold cooler

A series of parallel microchannels can have a collector oriented perpendicularly to distribute the flow (Fig.3). A micro-grooved surface is made of monocrystalline silicon carbide (SiC).

Adequate thermal insulation of power supplies from each other

The 3D integrated power electronics will use new packaging technologies. The reliability of these cooling methods is still being understood and modelled.

Fluid immersion cooling

Immersion cooling has become a solution to overcome obstacles, such as single-phase cooling, by a method of boiling a coolant directly from the electronic components. This will help eliminate the need for most thermal interface materials and packaging constraints found in many other approaches.

State-of-the-art immersion cooling systems use heat transfer dielectric liquids due to electrical considerations. This has fundamental drawbacks related to the relatively low boiling point, low critical heat flux (2), and relatively poor thermophysical properties (e.g., thermal conductivity, latent heat, surface tension) compared to better performing fluids such as water. However, trade-offs must be considered as water can damage electronic systems. Check out “Best Heat Transfer Fluids for Liquid Cooling (boydcorp.com)” for viable heat transfer fluid options.

High heat transfer from microjet impact

Improving the power density of advanced electronics, and in particular gallium nitride (GaN) high electron mobility transistors (HEMTs) in RF power amplifiers, presents a major challenge in thermal management . The high heat transfer capability of microjet impact can be used to bring cooling directly to the back of the power electronic device (Fig.4).

Cooling loop of high power density electronic devices using liquid metal coolant

This method uses liquid gallium alloys, which have a thermal conductivity (about 28 W/m/K) 40 times greater than the thermal conductivity of water.

Summary

This article has suggested some very powerful methods that designers can use to increase power density in 3D packaging. For example, embedding and integration has been mentioned as a good way to improve power density. Various cooling methods have also been discussed as ways to increase power density. Which method best suits your 3D packaging design?

Read more articles in the Power Management Series: Diving into Power Density

The references

1. Reliability of 3D Integrated Power Packaging (psma.com)

2. “Integrated Microjets for Thermal Management of High Power Density Electronic Devices”, IEEE Journals and Magazines

3. Study and realization of a cooling loop for high power density electronic devices using a liquid metal coolant, Grenoble Electrical Engineering Laboratory (G2Elab)

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