Integrated Heat Sink Research Articles

Development and numerical optimization of a cylindrical wire-fin-type integrated ionic wind heat sink for cooling high-power LEDs

Light-emitting diodes (LEDs) are becoming increasingly high-power and compact, which makes rotary fans incompetent in some cooling situations. The ionic wind technique can compensate for the shortcomings of rotating fans, owing to its benefits of no moving parts and compact structure. Integrating the ionic wind generator with heat dissipation fins can effectively reduce the size of LED devices, but research in this area is still insufficient. In this study, an integrated ionic wind heat sink is designed for cooling LEDs. The multi-physical characteristics of discharge, flow, and heat transfer are numerically studied. The geometric parameters’ impact degree and mechanism on the multi-physical characteristics are analyzed. The performance optimization of the integrated heat sink is realized and verified. The fin length, flow channel center angle, and relative position of the fin have a large influence on the average velocity of ionic wind. The relative position of the wire electrode determines the electric field strength distribution, and it has the greatest influence on the ionic wind performance. The emitting electrode being placed at the inlet edge of the collecting electrode produces a high ionic wind flow rate. The integrated ionic wind heat sink designed in this study exhibits an outstanding cooling performance and temperature uniformity. This device can cool down the surface of a heat source with a power of 200 W to below 91 °C and make the average heat transfer coefficient reach 18.6 W/(m2·K). This study proposes a valuable method to optimize the integrated ionic wind heat sink for cooling high-power electronic devices.

Novel approach to cooling microelectronics with complex fins configuration

This paper presents a numerical simulation and optimisation of a complex microchannel featuring innovative fin designs. The primary objective of the study is to minimise resistance in the heat sink by utilizing intricate fin structures. Three different approaches are explored: firstly, cylindrical solid fins are designed and placed on the heat sink; secondly, the solid fins are drilled halfway (50 %); and in the third scenario, the solid fins are drilled 87.5 % and mounted on the heat sink. In the simulation set-up, the heat sink has a heat load of 250 W imposed on the bottom wall and single-phase water of Reynolds number between 400 and 500 flows in a forced convection laminar condition to remove the heat at the bottom and internally within the fins walls surface area, while an air stream of Reynolds number between 3 and 6 flows convectively across the cylindrical fins to dissipate excess heat externally. The finite volume method and computational fluid dynamic code, are employed to discretise the geometry with heat and fluid fields solved. The optimisation is performed for parallel and counter flows and the outcomes compete favorably. Similarly, the influence of the Reynolds number on minimised temperature and resistance results is discussed. The results show that in parallel flow the integrated heat sink with half hollow fins is best with a minimised resistance of 27.2 %, while in the counter flow the hollow fins are superior with a declined resistance of 19 %. The study is validated with experimental results in open literature.

Kirigami-inspired organic and inorganic film-based flexible thermoelectric devices with built-in heat sink

Thermoelectric (TE) devices can convert heat to electricity directly, which offers a unique opportunity to realize waste heat recovery. However, conventional TE devices inevitably use heat sinks, which are bulky, rigid and heavy, limiting practical applications. Herein, we propose a fully integrated film-based TE device with intrinsically built-in fins as heat sink in a hexagonal honeycomb device structure, that simultaneously achieves high TE performance and conformability, as confirmed by experiments and modelling. A flexible Kapton substrate with copper electrodes, integrating either carbon nanotube (CNT) veils or bismuth telluride (Bi2Te3) TE ‘legs’, both of n- and p-type, achieved a remarkable specific power of 185.4 nW K−2 for a Bi2Te3-based device and 53.1 nW K−2 for a CNT-based device, thanks to the heat dissipation effect granted by the built-in fins. Besides, the addition of oriented polymer films interconnects, contracting when above their glass transition temperature, allowed a single substrate two-dimensional (2D) TE device to self-fold into a three-dimensional (3D) hexagonal honeycomb structure, with built-in fins, contactlessly and autonomously. The demonstrated shape-programmed kirigami-inspired scalable TE device paves the way for realising self-powered applications comprising hundreds of TE legs with both inorganic (e.g., Bi2Te3) and organic (e.g. CNT veils) TE materials and integrated heat sinks.

Numerical Simulation for Cooling of Integrated Toroidal Octagonal Inductor Using Nanofluid in a Microchannel Heat Sink

This paper presents a comprehensive numerical simulation study focused on the cooling of integrated toroidal octagonal inductor using nanofluids within a microchannel heat sink. The investigation utilizes COMSOL Multiphysics 6.0 integrated with the Fluid Flow and Conjugate Heat Transfer Module. The primary objective is to explore and understand fluid flow and heat transfer characteristics within the integrated inductor. The study involves testing three distinct fluids, water, CuO-water nanofluid, and Al2O3-water nanofluid, under laminar flow conditions within microchannels. The choice of fluid plays a significant role in heat transfer, interacting with the microchannel geometry to optimize performance. Three-dimensional computational fluid dynamics (CFD) models are meticulously developed; focusing on toroidal inductors equipped with micro pin fins heat sinks. The study commences by detailing the geometry of the micro coil and the integrated heat sink. The simulation encompasses a mathematical model that captures the intricate interplay between the governing Navier-Stokes equations for fluid dynamics and the heat transfer equations within the integrated inductor. As φ increases, temperature, viscosity, and pressure decrease. CuO-water and Al2O3-water nanofluids play a significant role in influencing laminar flow and key thermal parameters in the toroidal inductor. These nanofluids, which consist of base fluids (water) with dispersed nanoparticles (CuO or Al2O3), are employed as cooling agents to enhance heat transfer. The presence of nanoparticles in the fluid alters its thermal properties, leading to changes in the flow dynamics and overall heat dissipation within the toroidal inductor.The laminar flow characteristics are affected by the nanofluid's viscosity, density, and thermal conductivity. Additionally, the Nusselt number, Reynolds number, and thermal resistance are key thermal parameters that reflect the performance of the cooling system. The nanofluid's influence on these parameters is crucial for understanding and optimizing the thermal management of the integrated toroidal inductor. The enhancement of heat dissipation in the toroidal inductor is achieved through improved thermal properties of the nanofluid. Higher nanoparticle concentrations result in better heat transfer rates, leading to lower temperatures in the toroidal inductor. This, in turn, improves the overall efficiency and performance of the cooling system. The viscosity of the nanofluid is influenced by the presence of nanoparticles. The pressure within the microchannels is also affected by the nanoparticle concentration. An increase in φ can lead to changes in pressure drop along the microchannels. Understanding these variations is crucial for designing an effective cooling system.

Thermal Performance and Parametrical Analysis of Topologically-optimized Cross-flow Heat Sinks Integrated with Impact Jet

In this work, two novel cross-flow heat sink structures are firstly designed by means of topological optimization with the objective function which aims to achieve the minimum temperature difference and pressure drop or with the other objective function which aims to get the minimum mean temperature and pressure drop, namely, TOS1 and TOS2. By analyzing the effect of six channel heights Hch of TOS1 and TOS2 with the evaluation criterion j/f, we obtain that TOS2 with the Hch of 5 mm has the best ability of heat dissipation. A impact jet part is then implemented into the TOS2 to form a new integrated heat sink, that is, ITOS. Numerical results show that the ITOS exhibits much better thermal performance than TOS2 and TOS1. The in-depth parametric study on the flow and thermal behaviors of the ITOS shows that the average temperature of the bottom surface of the ITOS increases with the height of the channel of the bottom plate, while the temperature difference peaks at the Hch of 2 mm. The increase of the ratio of cross-flow fluid to total fluid leads to a reduction of the heat dissipation ability, implying that the high thermal performance of the impinging jet plays an important role in the heat transfer process of such ITOS. Finally, the convective heat transfer experiment of the ITOS with the Hch of 5 mm is conducted to testify the optimization and simulation results.

Experimental optimization of various heat sinks using passive thermal management system

Organic phase change materials are extensively researched for passive cooling of electronic components due to the high heat of fusion, however, owing to the issue of thermal conductivity, it is difficult to improve the thermal performance of electronic components. However, the effective thermal performance of modern electronic devices is becoming popular due to thermal constraints of the circuit's non-uniform temperature distribution and high heating power generation. Thus, nanomaterials incorporated into phase change materials (PCMs) to improve thermal conductivity, which aids in heat removal and sustains significant heat sink operational performance for extended periods of time. In current research work, at heating powers of (10–30 W), the thermal performance outcome of three heat sink -configurations such as unfinned heat sink, circular pin-finned heat sink and metallic foam integrated heat sink were investigated with several alumina nanomaterials mass concentrations (0.15, 0.20 and 0.25 wt%) incorporated in phase change materials (for example RT-70HC). All three heat sinks revealed lower base temperature with the addition of alumina NePCM (αRT-70HC) phase change materials in their internal cavity compared to the empty unfinned heat sink. The findings showed good performance of metallic foam integrated heat sink in lowering the temperature & increasing safe functional time at two distinct temperatures. The largest decrease in temperature was found to be 35.76% and the largest growth in maximum functional time was 400% for metallic foam integrated heat sink. Therefore, using alumina nanomaterials in phase change material is recommended to optimize the thermal performance of the passive cooling techniques.

Enhanced Electric Motors Using Multi-Functional 3D Printed Winding With Integrated Heat Sinks

Electrical machines are the central components of many energy conversion systems. Developing the performance of these devices is critical for improved energy management in our society. A new generation of electrical equipment has been enabled by the recent development of additive manufacturing (AM) technologies. This research takes advantage of the greater design freedom given by such approaches to enhance the heat dissipation qualities of the machines in two aspects. Firstly, varying-thickness windings fill up the available space leading to a reduced winding resistance so that the Joule losses can be decreased. Secondly, a novel design of a multi-functional 3D-printed winding is presented. This innovative design accomplishes self-cooling capabilities by including heat sinks into the end-winding. It is achieved by extending the heads of the coils from each turn extremity, creating heat sinks as part of the winding itself. The heat can be extracted directly from the coils to the ambient environment without intermediate pieces. The suggested approaches reduce heat generation and improve heat transmission, allowing for a higher input current. This results in machines with larger power densities for the same volume of permanent magnets while keeping passive cooling. We study a linear coreless permanent magnet machine to explore the concept. Nevertheless, this approach can be applied to different types of electrical machines possibly accommodating other cooling methods.

Research on performance of heat sink with no dielectric copper-aluminum connection

Air-cooled copper-aluminum composite heat sink is generally used for heat dissipation of electronic components. If the traditional copper-aluminum connection mode is used, such as welding, copper plugging and locking, bad phenomena such as pores, impurities and interface thermal resistance easily occur on the bonding surface, resulting in decreased heat conduction efficiency, heat dissipation efficiency and lower strength of the bonding surface. Therefore, we introduce a mortise-tenon connected heat sink, and optimize the honeycomb structure of the heat dissipation fin to design a new type of air cooled heat sink with no dielectric copper-aluminum connection. CFD simulation software is used to study the heat dissipation performance of the traditional and new heat sink, and the obtained data are comparatively analyzed to verify feasibility of the process. The result shows that the mass of the honeycomb heat sink is reduced by 37.1%, the surface area is increased by 47.8%, and the heat dissipation performance of the new copper-aluminum heat sink is 60% higher than that of pure copper integrated heat sink. It is concluded that heat sink with mortise-tenon connection has superior performance than traditional integrated air cooled heat sink, and honeycomb heat sink has superior performance than solid plate heat sink.

Investigation of flow and heat transfer behavior of integrated pin fin-aluminum foam heat sink

• A novel aluminium foam heat sink (AFHS) consisting of pin fin inserts is proposed. • The developed mathematical model is validated with experimental data. • Thermo-hydraulic characteristics of proposed heat sinks are numerically studied. • Pin fin inserts lead to an enhancement on the heat removal capability of AFHS. • Pressure drop along the flow direction increases with pin fin insertion into AFHS. With the rapid development in the electronics industry, the thermal management of high power density electronic products (HPDEPs) has become very important and requires innovative heat removal technologies. In this study, an integrated heat sink (IHS) fabricated by combining aluminum foam and pin-finned heat sink configurations that are frequently used in the cooling of electronic products has been proposed as an effective solution for the thermal management of HPDEPs. The heat removal and pressure drop characteristics of the IHS were numerically investigated for its various design conditions such as the length/height ratio ( L/H ), fin profile, fin/foam height ratio ( H fin /H foam ), and heat sink/fin volume ratio ( V hs /V f ) over the range of Reynolds ( Re Dh ) number from 500 to 3500 by using the COMSOL Multiphysics v5.4. Before the numerical study was performed, to verify the outcomes of the developed simulation models, some of the IHS subjected to the numerical study were fabricated and their pressure drop and heat removal performances were experimentally examined in the range of Re Dh from 596 to 3551. As a result of the study, it was found that the thermal contact resistance ( TCR ) between the IHS and the heated surface has a greater effect on the Nusselt ( Nu ) number compared to the TCR between the solid fins and aluminum foam. The in-line or staggered arrangement of pin fins inside the aluminum foam did not lead to any significant difference in the overall performance of investigated IHS. For all the IHS examined, an increase in Re Dh results in a similar increase in the Nu and ΔP along the flow direction. In general, the most efficient IHS among the investigated ones in terms of the H fin /H foam ratio is the IHS with half-length fins, H fin /H foam =15/30. Average values of thermal performance factor ( ƞ) of the IHS with H fin /H foam ratio of 15/30 in in-line and staggered arrangement over the Re Dh number studied are 1.3 and 1.25 times higher relative to IHS with H fin /H foam ratio of 30/15. For a fixed number of fins, η of the IHS with fins of 4mm diameter is superior up to Re Dh =2000, after which, the situation varies in favor of the 8mm solid finned aluminum foam heat sink. Increasing the fin diameter from 4mm to 12mm in both fin configurations worsens the average value of ƞ by 10%. For a constant fin diameter, IHSs with 9 fins in in-line and 8 fins in staggered configuration have the highest ƞ when the Re Dh is greater than 2500 and 2000, respectively. Among the fin profiles examined, the IHS with elliptical fins is found to have the highest η , with a value of 1.24, at Re Dh =3500.

Thermal performance and flow pattern of an immersion spray array cooling vapor chamber

An immersion spray array cooling vapor chamber (ISVC) is proposed for high-power electronic devices. Experimental and numerical studies on thermal performance and flow pattern have been conducted. It is shown that increasing the inlet temperature of the coolant facilitates the heat transfer performance and temperature uniformity of the ISVC within the safe working temperature range of electronic devices. The immersed spray impingement process includes a stage of velocity reduction from the nozzle exit to the target surface, a process of velocity boundary layer formation on the target surface, and a flow collision region formation process of adjacent sprays. As the inlet flow rate increases, the effect of the spray on the target surface is enhanced and the interaction between adjacent sprays is stronger. The perturbation effect of the spray on the fluid in the impingement cavity is positively influenced by the inlet flow rate. The spray array has a strong stirring effect on the water in the spray chamber in the XY, XZ and YZ planes. The heat transfer capacity of the ISVC is enhanced with a larger inlet flow rate due to the enhanced spray effect and larger spray coverage area. The temperature uniformity of the ISVC is improved with an increase of flow rate. The ISVC operating limit heating powers of 2.0 L/min, 4.0 L/min and 7.0 L/min flow rates are 531 W, 575 W and 600 W. Compared to the existing integrated heat sink combined vapor chamber and array jet impingement, the operating limit heating power of ISVC is increased by at least 68%.

Thermal Performance Analysis of Various Heat Sinks Based on Alumina NePCM for Passive Cooling of Electronic Components: An Experimental Study

In the modern digital world, electronic devices are being widely employed for various applications where thermal performance represents a significant technical challenge due to continued miniaturization, high heat generated in the system, and non-uniform high-temperature causing failure. Phase change materials (PCMs) owing to the immense heat of fusion are primarily considered for thermal management, but their insulating properties hedge their applications in electronics cooling. Nano-enhanced phase change materials (NePCMs) have the ability to improve the thermal conductivity of PCM, decrease system temperature and escalate the operating time of devices. Accordingly, the current study focused on the experimental investigations for the thermal performance of three heat sinks (HS) with different configurations such as a simple heat sink (SHS), a square pin-fins heat sink (SpfHS), and Cu foam integrated heat sink (CufmHS) with various alumina nanoparticles mass concentrations (0.15, 0.20 and 0.25 wt%) incorporated in PCM (RT-54HC) and at heat flux (0.98–2.94 kW/m2). All HSs reduced the base temperature with the insertion of NePCM compared to the empty SHS. The experimental results identified that the thermal performance of CufmHS was found to be superior in reducing base temperature and enhancing working time at two different setpoint temperatures (SPTs). The maximum drop in base temperature was 36.95%, and a 288% maximum working time enhancement was observed for CufmHS. Therefore, NePCMs are highly recommended for the thermal management of the electronic cooling system.

Comparative analysis of integrated heat sink vapor chamber with conventional heat sink for LED cooling

A light-emitting diode (LED) is an electronic component to transfer electrical energy into light. The conventional heat sink (CHS) removes the heat generated in LEDs; it still faces severe heat removal issues that affect the light quality and lighting efficiency and lower the life of LEDs. The thermal performance of the vapor chamber (VC) depends upon working fluid selection, fill ratio, thermal resistance (Rt), and VC material. The integrated heat sink vapor chamber (IHSVC) has a less thermal resistance and temperature drop than the CHS. Thereby, IHSVC can provide effective cooling over a CHS. In the presented research, we studied the thermal performance of microgroove IHSVC occupied with acetone for LED cooling application and compared CFD simulation results in terms of temperature distribution in CHS and IHSVC. A more uniform temperature distribution with a drop of 5 K inside IHSVC prove to be a good option compared to CHS with a temperature drop of 16 K. Due to incorporating a vapor sink at the base of a heat sink, better heat transfer takes place, and a 68.5 % less temperature drop for the case of a 60 W heat source applied to the 50 mm × 50 mm base area of the heat sink. It shows that the heat source area is inversely proportional to thermal resistance. The thermal resistance of the IHSVC decreases by 49.6 % with a 1.25-time increase in the source area at the base. Due to uniform temperature distribution with less temperature drop, an integrated vapor sink at the base of a conventional heat is the better option for effectively cooling LED.

Effects of central cut on performance intensification of counter-flow integral heat sinks

To enhance the thermal management of different miniature systems, a counter-current integral minichannel heat sink with a central cut is proposed and investigated through a numerical approach. Six different lengths of the central cut are adopted, and their performances are estimated at various Reynolds numbers ranging from 100 to 900. Obtained results depict that, not only does the central cut provides fluid exchange between adjacent minichannels, but it also leads to generating several vortices. These consequences lead to breaking down and redeveloping the boundary layers. Drawn conclusions imply that short length of the central cut (a = 5 mm) does not bring any noticeable improvement, but by adopting medium values for this factor (a = 10 and 15, and 20 mm), the performance index is remarkably improved up to 69.2%. Outcomes reveal that there is an optimal central cut length, i.e., a = 15 mm, at which the heat transfer enhancement factor adopts the highest value (Nu ratio = 1.92), and also the junction surface achieves the best temperature uniformity (∆Tmax.b = 2.08 K). However, with the further increase of the central cut length, the thermal performance declines, and the junction surface temperature gets an increasing trend.

Investigating the performance of a NMPCM integrated heat sink for chipset cooling

The demand for effective cooling solutions is critical for electronic chip sets, since it improves the operation and longevity of electronic equipment. The heat removal from a finned heat sink (HS) integrated computer processor with the aid of a nano-mixed PCM (NMPCM) is investigated in this work. The heat generation of the chipset is replicated with the aid of a plate heater and the plate-finned heat sink is studied under three conditions, the first configuration is the plate-finned heat sink containing no PCM (FHS), the second configuration is the HS containing the plain PCM (P-FHS), and the last configuration is the HS containing a nanoparticle mixed PCM (NP-FHS). The NMPCM was prepared through the careful mixing of 0.5% nano-titania within the paraffin. The results showed that the assimilation of PCM and NMPCM with the finned-HS (NP-FHS) was verified to be effective in reducing the heating rate of the chip sets, comparing to the FHS and P-FHS configurations. Explicitly, the NMPCM had assisted to postpone the baseline temperature of the HS by 32 min and 14 min, respectively at the heating rate of 3.5 kW/m2 and 4.5 kW/m2, respectively.[copyright information to be updated in production process]

Experimental investigation on enhanced flow and heat transfer performance of micro-jet impingement vapor chamber for high power electronics

In this study, two novel micro-jet impingement vapor chamber configurations, including separated micro-jet impingement vapor chamber (SJVC) and integrated micro-jet impingement vapor chamber (IJVC), were designed and tested. The flow character and thermal performance of SJVC were investigated and compared with the traditional liquid cooling vapor chamber (separated microchannel vapor chamber, SCVC). The experimental and simulation results show that although the heat transfer performance of SJVC is slightly worse than SCVC, its flow performance and temperature uniformity have obvious advantages over SCVC (SCVC pressure drop is 1.49–1.77 times that of SJVC). Therefore, the comprehensive performance of SJVC is better than SCVC. To verify the heat transfer advantages of integrated heat sink, the heat transfer performance of SJVC and IJVC was also compared. The experimental results show that the thermal resistance of IJVC is even smaller, and the IJVC heater temperature is lower, indicating that the heat transfer performance of heat sink module could be further improved when designed as an integrated structure. In sum, SJVC and IJVC have promising application potentials in thermal management of high power electronic devices, and the research results have certain guiding significance to the development of efficient heat transfer technology for high heat flux applications.

Thermal Performance Investigation of Slotted Fin Minichannel Heat Sink for Microprocessor Cooling

Due to high heat flux generation inside microprocessors, water-cooled heat sinks have gained special attention. For the durability of the microprocessor, this generated flux should be effectively removed. The effective thermal management of high-processing devices is now becoming popular due to high heat flux generation. Heat removal plays a significant role in the longer operation and better performance of heat sinks. In this work, to tackle the heat generation issues, a slotted fin minichannel heat sink (SFMCHS) was investigated by modifying a conventional straight integral fin minichannel heat sink (SIFMCHS). SFMCHSs with fin spacings of 0.5 mm, 1 mm, and 1.5 mm were numerically studied. The numerical results were then compared with SIFMCHSs present in the literature. The base temperatures recorded for two slots per fin minichannel heat sink (SPFMCHS), with 0.5 mm, 1 mm, and 1.5 mm fin spacings, were 42.81 °C, 46.36 °C, and 48.86 °C, respectively, at 1 LPM. The reductions in base temperature achieved with two SPFMCHSs were 9.20%, 8.74%, and 7.39% for 0.5 mm, 1 mm, and 1.5 mm fin spacings, respectively, as compared to SIFMCHSs reported in the literature. The reductions in base temperature noted for three SPFMCHSs were 8.53%, 9.05%, and 5.95% for 0.5 mm, 1 mm, and 1.5 mm fin spacings, respectively, at 1 LPM, as compared to SIFMCHSs reported in the literature. In terms of heat transfer performance, the base temperature and thermal resistance of the 0.5 mm-spaced SPFMCHS is better compared to 1 mm and 1.5 mm fin spacings. The uniform temperature distribution at the base of the heat sink was observed in all cases solved in current work.

Ultrafast Silicon MZI Optical Switch With Periodic Electrodes and Integrated Heat Sink

The compact, high-speed, low-power consumption Mach-Zehnder interferometer (MZI)-type optical switch using thermo-optical effect is a key device in future optical integrated circuits. In this study, we achieved ultra-high-speed switching operation of 0.4 μs and low electrical power operation of 23 mW with a small device footprint by loading an asymmetric doped MZI structure and an integrated heat sink. This optical switch can be fabricated in the standard manufacturing process of silicon photonic devices, has high practicality and will be a useful tool in various optical integrated circuits.

Study of the performance of an integrated liquid cooling heat sink for high-power IGBTs

• An integrated heat sink was manufactured. • The performance of three common heat sinks were compared. • The cooling water temperatures have effect on the performance of the integrated heat sink. • The installation angles have effect on the performance of the integrated heat sink. To address the challenge of heat management for high-power IGBTs, a type of microchannel liquid cooling heat sinks integrated vapor chamber (VC integrated heat sink) was developed. Firstly, it compared with the VC separate heat sink and the simple microchannel heat sink under the same conditions. The experimental results showed that the VC integrated heat sink had less thermal resistance than the VC separated heat sink, and the relatively simple microchannel heat sink could significantly improve the temperature uniformity. The influence of the cooling water flow rate, temperature and inclination angle on the VC integrated heat sink was further studied. Reductions in the cooling water temperature led to decreases in the heat source temperature but did not improve temperature uniformity. The inclination angle had a significant influence on the performance of the VC integrated heat sink. The performance of the VC integrated heat sink was optimal when the inclination angle was 60°.

A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform.

This paper reports on a bidirectional Knudsen pump (KP) with a 3D-printed thermal management platform; the pump is intended principally for microscale gas chromatography applications. Knudsen pumps utilize thermal transpiration, where non-viscous flow is created against a temperature gradient; no moving parts are necessary. Here, a specialized design leverages 3D direct metal laser sintering and provides thermal management that minimizes loss from a joule heater located on the outlet side of KP, while maintaining convective cooling on the inlet side. The 3D-KP design is integrative and compact, and is specifically intended to simplify assembly. The 3D-KP pumping area is ≈1.1 cm2; with the integrated heat sink, the structure has a footprint of 64.2 × 64.2 mm2. Using mixed cellulose ester (MCE) membranes with a 25 nm average pore diameter and 525 μm total membrane thickness as the pumping media, the 3D-KP achieves a maximum flow rate of 0.39 sccm and blocking pressure of 818.2 Pa at 2 W input power. The operating temperature is 72.2 °C at ambient room temperature. In addition to MCE membranes, anodic aluminum oxide (AAO) membranes are evaluated as the pumping media; these AAO membranes can accommodate higher operating temperatures than MCE membranes. The 3D-KP with AAO membranes with 0.2 μm average pore diameter and 531 μm total membrane thickness achieves a maximum flow rate of 0.75 sccm and blocking pressure of 496.1 Pa at 9.8 W at an operating temperature of 191.2 °C.

Detection of Sealant Delamination in Integrated Circuit Package Using Nondestructive Evaluation

Abstract This paper presents the development of a nondestructive evaluation method for delamination detection in integrated circuit (IC) packages. The developed method allows for quantitative detection of sealant delamination between integrated heat sink (IHS) and substrate, which is considered a potential failure mechanism in IC packages. The proposed method is expected to overcome the destructive nature of most existing techniques, while maintaining low cost of development. The reported development consists of the following processes: First, flash thermographic analysis is investigated and shown to be incapable of detecting a realistic sealant delamination. Then, ultrasonic guided waves (UGWs) are used as the chosen interrogation method due to their sensitivity to small-size damage and structural thickness variations. The complexity of the received ultrasonic signals caused by the geometric heterogeneity is resolved using a time–frequency signal processing technique. The extracted ultrasonic information, including time-of-arrival (TOA) and amplitude of wave modes received from different sensing paths under multiple excitation frequencies, is then used to construct a feature space. A multivariate Gaussian model is implemented as an information fusion and delamination detection tool, which investigates the distribution of feature space including correlations between features. Results from the developed model are compared with two existing evaluation methods, including pullout force measurement and a delamination metric. The developed method is seen to possess a similar level of accuracy with a nondestructive nature.