Low-Cost Energy-Efficient On-Chip Hotspot Targeted Microjet Cooling for High- Power Electronics

status: publishe

Conjugate Heat Transfer and Fluid Flow Modeling for Liquid Microjet Impingement Cooling with Alternating Feeding and Draining Channels

status: publishe

Nozzle array scaling analysis of the thermal performance of liquid jet impingement coolers for high performance electronic applications

status: accepte

High-Efficiency Polymer-Based Direct Multi-Jet Impingement Cooling Solution for High-Power Devices

© 1986-2012 IEEE. A high-efficiency three-dimensionally (3-D) shaped polymer multi-jet impingement cooler based on cost-efficient fabrication techniques is introduced for the cooling of high-power applications. State-of-the-art highly efficient multi-jet cooling solutions rely on expensive Si or ceramic fabrication techniques, while low-cost cooling solutions have been proposed for less performant single-jet impingement. In this paper, we present the concept, modeling, design, fabrication, experimental characterization, and benchmarking with literature data of a multi-jet impingement based liquid cooling solution, fabricated using low-cost polymer fabrication techniques, targeted to directly cool the backside of high-power devices. For the modeling study, unit cell model and full system level models are used to study the nozzle array scaling trends and thermal and fluidic jet-to-jet interactions. Furthermore, design guidelines for high-power electronics cooling are provided, including geometry selections, material selection, and fabrication techniques. Based on the design guidelines and cooling concept, this paper demonstrates a 3-D-shaped polymer impingement cooler with a 4 × 4 nozzle array, showing a very good thermal performance with low required pumping power. The multi-jet cooler can achieve heat transfer coefficients up to 6.25 × 10 4 W/m 2 ·K with a pump power as low as 0.3 W. The benchmarking study confirms furthermore that multi-jet cooling is more efficient than single-jet cooling and that direct cooling on the backside of the semiconductor device is more efficient than cooling the substrate or base plate.status: publishe

Performance and Perspectives of Zero-Level MEMS Chip Packages with Vertical Interconnects

This paper presents the performance of a MEMS zero-level chip cap package implemented with through-the-cap vertical interconnects. The interconnect as well as the hermetic bond and sealing are established using flip-chip thermo-compression bonding by creating a copper-tin to gold metallic (solder) joint. The hermeticity of the packages is assessed via electrical measurements of encapsulated MEMS resonators and the RF performance of 3D interconnects is evaluated via microwave measurements of integrated coplanar waveguides. Design guidelines imposed by concurrent requirements of the flip-chip assembly process and the RF performance are discussed. The developed technology for the MEMS cap uses CMOS-compatible materials and the CMOS fabrication process

Experimental characterization of a chip-level 3-D printed microjet liquid impingement cooler for high-performance systems

The chip-level bare die direct liquid impingement jet cooling is regarded as a highly efficient cooling solution for high-performance applications. Furthermore, it shows potential to be integrated inside the chip package. In previous studies, we demonstrated this cooling concept using a prototype fabricated with mechanical micromachining using polymers. With the improvement of fabrication resolution, additive manufacturing or 3-D printing technology enables the fabrication of low-cost polymer microjet coolers with complex internal 3-D geometries and allows easy customization of the cooler design. In this paper, a chip-level impingement jet cooler with a 4 × 4 jet array and 575-μm nozzle diameter is fabricated with highresolution stereolithography, and assembled directly on the top of the bare die. The modeling study shows that the pressure drop in the 3-D printed cooler is reduced by 24% compared to the micromachined (MM) cooler with the same nozzle dimensions thanks to an improved more complex internal geometry. The fabrication quality and tolerances of the printed cooler are evaluated using optical measurements, scanning acoustic microscope (SAM) inspection, and cross-sectional analysis, showing a measured average nozzle diameter of 575 μm compared to the designed nozzle diameter of 600 μm. Moreover, the 3-D computational fluid dynamics (CFD) simulations used in this paper are experimentally validated by chip temperature measurements. The achieved minimal thermal resistance of 3-D printed 4×4 cooler is 0.16 cm 2 ·K/W for a flow rate of 1000 mL/min. The benchmarking study shows the cooler size can be reduced by a factor of 6.5 by using the 3-D printing technology compared to the MM cooler

3D Printed Liquid Jet Impingement Cooler: Demonstration, Opportunities and Challenges

© 2018 IEEE. Liquid jet impingement cooling is a very efficient cooling technology for high performance devices. Previous studies demonstrated that polymers can be used as a cost effective alternative for Si for the fabrication of impingement coolers. The recent developments in additive manufacturing or 3D printing technology enable the potential to fabricate low cost polymer coolers with complex internal channels. In this paper, the use of 3D printing is discussed for the fabrication of a chip level polymer impingement cooler. The paper presents the cooler design, the manufacturability aspects and the characterization of several 3D printed coolers with different nozzles arrays. The challenges and opportunities for the use of 3D printing for this applications are discussed. A methodology to provide design guidelines for 3D printed liquid impingement jet coolers is elaborated.status: Published onlin

Advanced experimental back-end-of-line (BEOL) stability test: Measurements and simulations

Chip–package interaction (CPI) is becoming a critical issue for the reliability of back-end-of-line (BEOL) during or after package assembly. Complex BEOL layer stacks must have sufficient mechanical strength to survive the thermally induced stresses during processing or working lifetime. Therefore, it is necessary to assess possible failure mechanisms already at early phases of development so that the integrity of the chips can be guaranteed. This paper presents an advanced experimental stability test that combines a BABSI test (Bump Assisted BEOL Stability Indentation test) with in-situ monitoring of the induced stress during this test. A good agreement was found between the applied loads to the BEOL stack, the response of stress sensors below the bump (a Cu pillar) and finite element simulations.status: publishe