Reliability of Bonded Interfaces for Automotive Power Electronics

2013 ◽  
Author(s):  
Douglas DeVoto ◽  
Paul Paret ◽  
Sreekant Narumanchi ◽  
Mark Mihalic
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Carbon Fibers ◽  
Thermal Performance ◽  
Coefficient Of Thermal Expansion ◽  
Base Plate ◽  
Acoustic Microscopy ◽  
Thermal Cycles ◽  
Interface Materials ◽  
Sintered Silver

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase change materials pose bottlenecks to heat removal and are also associated with reliability concerns. There is an industry trend towards high thermal performance bonded interfaces. However, due to coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a problem from a reliability standpoint. These defects manifest themselves in increased thermal resistance in the package. The objective of this research is to investigate and improve the thermal performance and reliability of emerging bonded interface materials for power electronics packaging applications. We present results for thermal performance and reliability of bonded interfaces based on thermoplastic (polyamide) adhesive, with embedded near-vertical aligned carbon fibers, as well as sintered silver material. The results for these two materials are compared to conventional lead-based (Sn63Pb37) bonded interfaces. These materials were bonded between 50.8-mm × 50.8-mm cross-sectional footprint silicon nitride substrates and copper base plate samples. Samples of the substrate/base plate bonded assembly underwent thermal cycling from −40°C to 150°C according to Joint Electron Devices Engineering Council standard Number 22-A104D for up to 2,000 cycles. The dwell time of the cycle was 10 minutes and the ramp rate was 5°C/minute. Damage was monitored every 100 cycles by acoustic microscopy as an indicator of an increase in thermal resistance of the interface layer. The acoustic microscopic images of the bonded interfaces after 2,000 thermal cycles showed that thermoplastics with embedded carbon fibers performed quite well with no defects, whereas interface delamination occurred in the case of sintered silver material. Both these materials showed a superior bond quality as compared to the lead-based solder interface even after 1,000 thermal cycles.

Thermal Performance and Reliability of Large-Area Bonded Interfaces in Power Electronics Packages

2011 ◽  
Author(s):  
Sreekant Narumanchi ◽  
Douglas DeVoto ◽  
Mark Mihalic ◽  
Tim Popp ◽  
Patrick McCluskey
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Coefficient Of Thermal Expansion ◽  
Heat Removal ◽  
Acoustic Microscopy ◽  
Large Area ◽  
Electronics Packages ◽  
Interface Materials

In automotive power electronics packages (e.g., insulated gate bipolar transistor [IGBT] packages), conventional polymeric thermal interface materials (TIMs) such as greases, gels, and phase-change materials pose a bottleneck to heat removal and are also associated with reliability concerns. High thermal performance bonded interfaces have become an industry trend. However, due to mismatches in the coefficient of thermal expansion between materials/layers and the resultant thermomechanical stresses, there could be voids and crack formations in these bonded interfaces as well as delaminations, which pose a problem from a reliability standpoint. These defects manifest themselves in increased thermal resistance in the package, which acts as a bottleneck to heat removal from the package. Hence, the objective of this research is to investigate and improve the thermal performance and reliability of novel bonded interface materials for power electronics packaging applications. Thermal performance and reliability of bonds/joints is presented for bonds based on a thermoplastic (polyamide) adhesive with embedded micron-sized carbon fibers, sintered silver (Ag), and conventional lead (Pb)-based solder materials. These materials form a bond between 50.8 mm × 50.8 mm footprint direct-bond-copper (DBC) substrate and copper (Cu) base plate samples. Samples undergo thermal cycling (−40°C to 150°C) for up to 2,000 cycles as an upper limit. Damage occurrence is monitored every 100 temperature cycles by several non-destructive techniques, including steady-state thermal resistance measurement, acoustic microscopy, and high-voltage potential testing. This yields a consistent story on the thermal performance and reliability of large-area joints under accelerated stress conditions.

scholarly journals Stress Intensity of Delamination in a Sintered-Silver Interconnection

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000190-000197 ◽  
Author(s):  
D. J. DeVoto ◽  
P. P. Paret ◽  
A. A. Wereszczak
Keyword(s):  
Stress Intensity ◽  
Power Electronics ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Coefficient Of Thermal Expansion ◽  
Heat Removal ◽  
Element Model ◽  
Large Area ◽  
Degradation Rates ◽  
Sintered Silver

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase-change materials pose bottlenecks to heat removal and are also associated with reliability concerns. The industry trend is toward high thermal performance bonded interfaces for large-area attachments. However, because of coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a reliability problem. These defects manifest themselves in increased thermal resistance. This research aims to investigate and improve the thermal performance and reliability of sintered-silver for power electronics packaging applications. This has been experimentally accomplished by the synthesis of large-area bonded interfaces between metalized substrates and copper base plates that have subsequently been subjected to thermal cycles. A finite element model of crack initiation and propagation in these bonded interfaces will allow for the interpretation of degradation rates by a crack-velocity (V)-stress intensity factor (K) analysis. A description of the experiment and the modeling approach are discussed.

Characterizing Bulk Thermal Conductivity and Interface Contact Resistance Effects of Thermal Interface Materials in Electronic Cooling Applications

2003 ◽  
Author(s):  
Vadim Gektin ◽  
Sai Ankireddi ◽  
Jim Jones ◽  
Stan Pecavar ◽  
Paul Hundt
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Performance ◽  
Electronic Cooling ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Contact ◽  
Interface Materials ◽  
Bulk Thermal Conductivity

Thermal Interface Materials (TIMs) are used as thermally conducting media to carry away the heat dissipated by an energy source (e.g. active circuitry on a silicon die). Thermal properties of these interface materials, specified on vendor datasheets, are obtained under conditions that rarely, if at all, represent real life environment. As such, they do not accurately portray the material thermal performance during a field operation. Furthermore, a thermal engineer has no a priori knowledge of how large, in addition to the bulk thermal resistance, the interface contact resistances are, and, hence, how much each influences the cooling strategy. In view of these issues, there exists a need for these materials/interfaces to be characterized experimentally through a series of controlled tests before starting on a thermal design. In this study we present one such characterization for a candidate thermal interface material used in an electronic cooling application. In a controlled test environment, package junction-to-case, Rjc, resistance measurements were obtained for various bondline thicknesses (BLTs) of an interface material over a range of die sizes. These measurements were then curve-fitted to obtain numerical models for the measured thermal resistance for a given die size. Based on the BLT and the associated thermal resistance, the bulk thermal conductivity of the TIM and the interface contact resistance were determined, using the approach described in the paper. The results of this study permit sensitivity analyses of BLT and its effect on thermal performance for future applications, and provide the ability to extrapolate the results obtained for the given die size to a different die size. The suggested methodology presents a readily adaptable approach for the characterization of TIMs and interface/contact resistances in the industry.

Integrated Vapor Chamber Heat Spreader for Power Module Applications

2017 ◽  
Author(s):  
Clayton L. Hose ◽  
Dimeji Ibitayo ◽  
Lauren M. Boteler ◽  
Jens Weyant ◽  
Bradley Richard
Keyword(s):  
Heat Flux ◽  
Thermal Resistance ◽  
Power Electronics ◽  
Coefficient Of Thermal Expansion ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Power Module ◽  
Heat Spreader

This work presents a demonstration of a coefficient of thermal expansion (CTE) matched, high heat flux vapor chamber directly integrated onto the backside of a direct bond copper (DBC) substrate to improve heat spreading and reduce thermal resistance of power electronics modules. Typical vapor chambers are designed to operate at heat fluxes > 25 W/cm2 with overall thermal resistances < 0.20 °C/W. Due to the rising demands for increased thermal performance in high power electronics modules, this vapor chamber has been designed as a passive, drop-in replacement for a standard heat spreader. In order to operate with device heat fluxes >500 W/cm2 while maintaining low thermal resistance, a planar vapor chamber is positioned onto the backside of the power substrate, which incorporates a specially designed wick directly beneath the active heat dissipating components to balance liquid return and vapor mass flow. In addition to the high heat flux capability, the vapor chamber is designed to be CTE matched to reduce thermally induced stresses. Modeling results showed effective thermal conductivities of up to 950 W/m-K, which is 5 times better than standard copper-molybdenum (CuMo) heat spreaders. Experimental results show a 43°C reduction in device temperature compared to a standard solid CuMo heat spreader at a heat flux of 520 W/cm2.

Thermal Resistance Analysis of Sn-Bi Solder Paste Used as Thermal Interface Material for Power Electronics Applications

2014 ◽  
Vol 136 (1) ◽  
Author(s):  
Rui Zhang ◽  
Jian Cai ◽  
Qian Wang ◽  
Jingwei Li ◽  
Yang Hu ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Heat Dissipation ◽  
Laser Flash ◽  
Acoustic Microscopy ◽  
Thermal Interface Material ◽  
Solder Paste ◽  
Good Reliability ◽  
Thermal Interface ◽  
Power Modules

To promote heat dissipation in power electronics, we investigated the thermal conduction performance of Sn-Bi solder paste between two Cu plates. We measured the thermal resistance of Sn-Bi solder paste used as thermal interface material (TIM) by laser flash technique, and a thermal resistance less than 5 mm2 K/W was achieved for the Sn-Bi TIM. The Sn-Bi solder also showed a good reliability in terms of thermal resistance after thermal cycling, indicating that it can be a promising candidate for the TIM used for power electronics applications. In addition, we estimated the contact thermal resistance at the interface between the Sn-Bi solder and the Cu plate with the assistance of scanning acoustic microscopy. The experimental data showed that Sn-Bi solder paste could be a promising adhesive material used to attach power modules especially with a large size on the heat sink.

scholarly journals Electric-Drive Vehicle Power Electronics Thermal Management: Current Status, Challenges, and Future Directions

2021 ◽  
Author(s):  
Gilberto Moreno ◽  
Sreekant Narumanchi ◽  
Xuhui Feng ◽  
Paul Anschel ◽  
Steve Myers ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Thermal Management ◽  
Power Density ◽  
Thermal Performance ◽  
Electric Drive ◽  
Thermal Analyses ◽  
Heat Fluxes ◽  
Current Status ◽  
Dielectric Fluid

Abstract Effective thermal management of traction-drive power electronics is critical to the advancement of electric-drive vehicles and is necessary for increasing power density and improving reliability. Replacing traditional silicon devices with more efficient, higher temperature, higher voltage, and higher frequency wide-bandgap (WBG) devices will enable increased power density but will result in higher device heat fluxes. Compact packaging of high-temperature WBG devices near low-temperature-rated components creates thermal management challenges that need to be addressed for future power-dense systems. This paper summarizes the thermal performance of on-road automotive power electronics thermal management systems and provides thermal performance and pumping-power metrics for select vehicles. Thermal analyses reveal that the package/conduction resistance dominates the total thermal resistance (for existing automotive systems). We model advanced packaging concepts and compare the results with existing packaging designs to quantify their thermal performance enhancements. Double-side-cooled configurations that do not use thermal interface materials are package concepts predicted to provide a low junction-to-fluid thermal resistance (compared to current packages). Dielectric-fluid-cooled concepts enable a redesign of the package to reduce the package resistance, can be implemented in single- and two-phase cooling approaches, and allow for cooling of passive components (e.g., capacitors) and bus bars.

Thermal Performance Measurements of Thermal Interface Materials Using the Laser Flash Method

2007 ◽  
Author(s):  
Vinh Khuu ◽  
Michael Osterman ◽  
Avram Bar-Cohen ◽  
Michael Pecht
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Composite Structures ◽  
Laser Flash ◽  
Flash Method ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Layer Composite ◽  
Interface Materials

Thermal interface materials are used to reduce the interfacial thermal resistance between contacting surfaces inside electronic packages, such as at the die-heat sink or heat spreader-heat sink interfaces. In this study, the change in thermal performance was measured for elastomeric gap pads, gap fillers, and an adhesive throughout reliability tests. Three-layer composite structures were used to simulate loading conditions encountered by thermal interface materials in actual applications. The thermal resistance of the thermal interface material, including contact and bulk resistance, was calculated using the Lee algorithm, an iterative method that uses properties of the single layers and the 3-layer composite structures, measured using the laser flash method. Test samples were subjected to thermal cycling tests, which induced thermomechanical stresses due to the mismatch in the coefficients of thermal expansion of the dissimilar coupon materials. The thermal resistance measurements from the laser flash showed little change or slight improvement in the thermal performance over the course of temperature cycling. Scanning acoustic microscope images revealed delamination in one group of gap pad samples and cracking in the putty samples.

Reliability Assessment of a New Power Electronics Packaging Material: Silver Diamond Composite

2013 ◽  
Vol 10 (2) ◽  
pp. 54-58 ◽  
Author(s):  
M. Faqir ◽  
J. W. Pomeroy ◽  
T. Batten ◽  
T. Mrotzek ◽  
S. Knippscheer ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Power Electronics ◽  
Structural Changes ◽  
Coefficient Of Thermal Expansion ◽  
Base Plate ◽  
Electronics Packaging ◽  
Case Scenario ◽  
Worst Case ◽  
New Material ◽  
Work Samples

A reliability analysis of silver diamond composites in terms of both thermal and mechanical properties is presented. This new material is an attractive solution for power electronics packaging, because an improvement of 50% in terms of thermal management and channel temperature can be obtained when using silver diamond composites as a base plate in packages compared with the more traditionally used materials such as CuW. However, to date, little is known about the reliability of this new material, such as changes induced in its properties by thermal cycling. Assessment of the reliability of silver diamond composites is the aim of this work. Samples were submitted to 10 thermal cycles from room temperature to 350°C, and subsequently, a further 500 cycles of thermal shock as well as thermal cycling from −55°C to 125°C following typical standards used in space and military applications. In the worst-case scenario, thermal conductivity only decreased from 830 W/m·K to ∼700 W/m·K. An increase in the coefficient of thermal expansion and a change in diamond stress, were also observed after thermal cycling. Some structural modifications at the silver-diamond interface were found to be the underlying reason for the observed material properties change. These structural changes take place after the initial thermal cycling, and are constant thereafter. Changes found in thermal properties are satisfactory for enabling a significant improvement to standard CuW packaging materials.

Experimental Characterization of Heat Transfer and Thermal Energy Storage Capability Using Swirling Two-Phase Flow in the Package Integrated Cyclone COoler (PICCO)

2020 ◽  
Author(s):  
Peter deBock ◽  
Rinaldo Miorini ◽  
Cathleen Hoel ◽  
Darin Sharar ◽  
Bryan Whalen
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Resistance ◽  
Power Electronics ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Two Phase ◽  
Thermal Capacitance

Abstract The increasing demand for high power density wide-bandgap power electronics has propelled heat transfer research leading to a constant increase in the thermal performance of cold plates and heat sinks. Most of this research has focused on reducing thermal resistance of the package which can have a detrimental effect on transient thermal performance if thermal capacitance is reduced. In order to provide both a low thermal resistance and a higher thermal capacitance integrated into the package and near the thermal junction, a new cold plate called the Package Integrated Cyclone COoler (PICCO) was developed. GE Research and the US Army Research Lab collaborated to explore and validate the potential of this concept. The PICCO coldplate, which is enabled by 3D printing, establishes a swirling coolant flow field to remove heat. The swirling flow is anticipated to significantly aid in vapor removal from the surface and hence allow for the fluid to provide thermal capacitance through two-phase heat transfer efficiently. This paper describes the experiment design and development for thermal storage and cooling performance characterization of PICCO. The test rig includes a high-pressure capability gear pump moving fluid first through a Coriolis flowmeter and then through PICCO, where the fluid is accelerated in the cyclone and heated by miniaturized ceramic heaters, simulating SiC power electronics. The coolant releases the accumulated enthalpy to a plate-fin heat exchanger that is connected to a chiller. Several absolute and differential pressure transducers and thermocouples monitor the state of FC-72. The experiments will provide empirical transfer functions characterizing the PICCO pressure drop, heat transfer coefficient, critical heat flux and thermal energy storage capability.

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