High Thermal Conductivity Of Copper Research Articles

High speed laser cladded Ti-Cu-NiCoCrAlTaY burn resistant coating and its oxidation behavior

To improve the high temperature oxidation resistance and burn resistance performance of titanium alloy, Ti-Cu-NiCoCrAlTaY composite coating was designed and deposited on TC4 alloy using a novel high speed laser cladding technology. The chemical composition, constituent phases, microstructure and morphology of the coating were characterized by EDS, XRD, SEM and 3D laser microscope respectively. The oxidation behavior of laser-cladded Ti-Cu-NiCoCrAlTaY coating and TC4 titanium alloy was analyzed at 800 °C. It was found that the functional coating has good oxidation performance attributed to the formation of dense double layered composite oxide scales. The flame-retardant functions of TC4 substrate and Ti-Cu-NiCoCrAlTaY coating were evaluated through laser spot melting test. The high thermal conductivity of copper and high anti-oxidation of NiCoCrAlTaY promote the flame retardant performance. The formation of TiCu eutectic transition zone in front of the substrate also helps to delay the combustion process.

Measurement of Thermophysical Properties of Loose Coal Based on Multi-dimensional Constant Temperature Boundary Unsteady Heat Transfer Model

Based on the unsteady state heat transfer model, production solution method is proposed to calculate the thermal diffusivity and thermal conductivity of loose coal. By constructing the heat transfer model of the infinite large plate and the infinitely long cylinder, the temperature rise formula of the production solution method is established. The measured temperature rise is then used by the MATLAB programming software to inversely calculate the thermophysical parameters of the loose coal. During the experiment, a constant temperature boundary was constructed using an incubator and a high thermal conductivity copper cylindrical case. The experiment selected anthracite, bituminous coal in Panyi Mine, and bituminous coal in Lizuo Mine for thermophysical property measurement. The results show that the relative deviation between each measurement result and related literature is within 5 %, and each sample is tested three times. The deviations are less than 5 %, which verify the stability of the test method. Finally, the experimental model was established in the ANSYS FLUENT simulation software, and the thermophysical parameters of the measured coal samples were substituted into the model for simulation calculation. It was found that the simulation temperature rise was consistent with the measured temperature rise.

Fabrication of Mesh Patterns Using a Selective Laser-Melting Process

The selective laser-melting (SLM) process can be applied to the additive building of complex metal parts using melting metal powder with laser scanning. A metal mesh is a common type of metal screen consisting of parallel rows and intersecting columns. It is widely used in the agricultural, industrial, transportation, and machine protection sectors. This study investigated the fabrication of parts containing a mesh pattern from the SLM of AISI 304 stainless steel powder. The formation of a mesh pattern has a strong potential to increase the functionality and cost-effectiveness of the SLM process. To fabricate a single-layered thin mesh pattern, laser layering has been conducted on a copper base plate. The high thermal conductivity of copper allows heat to pass through it quickly, and prevents the adhesion of a thin laser-melted layer. The effects of the process conditions such as the laser scan speed and scanning path on the size and dimensional accuracy of the fabricated mesh patterns were characterized. As the analysis results indicate, a part with a mesh pattern was successfully obtained, and the application of the proposed method was shown to be feasible with a high degree of reliability.

Thermal hydraulic performance of micro-channel heat sink with composite metal foam-solid fin design

<p indent="0mm">Three-dimensional (3D) interconnect technology promises significant performance advantages for the next generation of high speed and multi-functional electronic devices, however, the large-scale integration of electronic circuit and vertical stacking of multi-functional dice have been demonstrated to result in substantially increased waste-heat generation rates and localized hotspots. Efficient thermal management solutions are imperative to ensure the operating temperature of components below a reasonable level. Among various cooling techniques, metal foam heat sink has been identified as a promising alternative for electronic cooling, because of the large specific surface area, high effective thermal conductivity and intensive fluid mixing capability that foam material provided. In this study, a novel micro-channel heat sink with combined metal foam-solid fin, namely combined fin heat sink (CFHS), was established for electronics cooling. Numerical simulations based on Brinkman-Darcy extended momentum equation and local thermal non-equilibrium energy equations were carried out to investigate the fluid flow and heat transfer characteristics. To simplify the computations, a single channel was used as the computational domain with a dimension of 20 mm×2.4 mm× <sc>6 mm.</sc> The constant heat flux of <sc>100 W/cm²</sc> was supplied at the bottom wall to simulate the high-powered electronic device. Metal foam and fin were made of high thermal conductivity copper, and pure water was used as the working coolant. It was assumed that the metal foam was fully saturated with fluid in laminar flow state and the thermal resistance between the metal foam and fin was neglected. Effects of combined fin configuration on the flow and heat transfer performances were studied to determine the optimal porosity and dimensionless metal foam layer thickness for designing the CFHS. The thermal performance of the novel heat sink was compared to that of the conventional heat sink, and the total thermal resistance was analyzed based on the simplified thermal resistance network. The results indicate that the CFHS is more favorable in promoting thermal performance that the average Nusselt number of CFHS is 2.53 times higher than that of the conventional heat sink, while accompanied by the high pressure drop as a penalty. The flow resistance and specific area are two conflicting parameters that affect the thermal and hydraulic performances of the CFHS, our results show that there exists a critical dimensionless metal foam thickness and optimal porosity, which are 0.9 and 0.3, respectively. Compared with the conventional heat sink, the total thermal resistance of CFHS is significantly reduced by 56%, and the thermal performance factor of CFHS performs 1.32 times higher. The presented CFHS thus provides a feasible solution for thermal management of electronic devices with high-powered density.

A review on laser beam welding of copper alloys

With exponentially increasing copper alloys consumption globally, the automatization, high efficiency, and quality improvement of the copper joining process become inevitable in modern industrial production. In this context, laser welding presents a particular suitability for joining of copper alloys because of its high precision, high-energy concentration, and rapid processing potentials. Studies have shown that laser welding of copper has two principal challenges. Namely, the high laser power required due to the low laser beam absorptivity and high thermal conductivity of copper, and the low process stability. Interestingly, with the recent laser technology improvements, the tremendous laser power required will eventually be solved. Although some achievements were obtained in previous studies, the problem of spattering and high porosity associated with low process stability still exist. In this review, the effect of the most significant laser welding processing parameters on the joint’s performances were systematically examined; the microstructure, mechanical, and electrical properties and metallurgical defects of copper laser welds were discussed. Furthermore, laser welding of copper to other metals particularly copper to steel and copper to aluminum dissimilar alloys in terms of structure and properties relationships were also discussed.

Selective laser melting of copper using ultrashort laser pulses

Within the field of laser-assisted additive manufacturing, the application of ultrashort pulse lasers for selective laser melting came into focus recently. In contrast to conventional lasers, these systems provide extremely high peak power at ultrashort interaction times and offer the potential to control the thermal impact at the vicinity of the processed region by tailoring the pulse repetition rate. Consequently, materials with extremely high melting points such as tungsten or special composites such as AlSi40 can be processed. In this paper, we present the selective laser melting of copper using 500 fs laser pulses at MHz repetition rates emitted at a center wavelength of about 1030 nm. To identify an appropriate processing window, a detailed parameter study was performed. We demonstrate the fabrication of bulk copper parts as well as the realization of thin-wall structures featuring thicknesses below 100 $${\upmu }$$ m. With respect to the extraordinary high thermal conductivity of copper which in general prevents the additive manufacturing of elements with micrometer resolution, this work demonstrates the potential for sophisticated copper products that can be applied in a wide field of applications extending from microelectronics functionality to complex cooling structures.

Modeling, simulation, and analysis of the impact(s) of single angular-type particles on ductile surfaces using smoothed particle hydrodynamics

Modeling the impact of single angular particles contributes to an understanding of the fundamental mechanisms of erosive wear. However, most previous studies focus on well-defined symmetrical particles, which are not representative of abrasive particles. Hence, this study develops a mesh-free model based on smoothed particle hydrodynamics to simulate the impact(s) of arbitrarily shaped particles on ductile material. These particles are modeled as polygonal rigid bodies by measuring the corner vertices. Oxygen-free high thermal conductivity copper is selected as the target material. The ductile material properties are modeled using the Mie–Grüneisen equation of state and the Johnson–Cook model. In order to investigate the erosion dependency of angular-type particles on the initial orientation, simulations are performed by varying the initial input conditions and using different types of angular particles. Common deformation mechanisms such as cutting, machining, ploughing, and prying-off are successfully reproduced by the model. The initial orientation is found to influence the erosion mechanism through three shape-related parameters, namely the rake angle, centroid offset angle, and angularity of the impacting vertex. In particular, the rake angle significantly influences the erosion mechanism through particle rotation, although this effect decreases as the angularity increases. The centroid offset angle additionally changes the position of the critical rake angle, producing an opposite effect on the backward and forward impact. For irregularly shaped particles, the complexity is reflected in the irregular relationship between kinetic energy loss and the initial orientation of the particle; the variation in the rebound angle exhibits a similar trend to the kinetic energy loss.

Enhanced Injection Molding Simulation of Advanced Injection Molds.

The most time-consuming phase of the injection molding cycle is cooling. Cooling efficiency can be enhanced with the application of conformal cooling systems or high thermal conductivity copper molds. The conformal cooling channels are placed along the geometry of the injection-molded product, and thus they can extract more heat and heat removal is more uniform than in the case of conventional cooling systems. In the case of copper mold inserts, cooling channels are made by drilling and heat removal is facilitated by the high thermal conductivity coefficient of copper, which is several times that of steel. Designing optimal cooling systems is a complex process; a proper design requires injection molding simulations, but the accuracy of calculations depends on how precise the input parameters and boundary conditions are. In this study, three cooling circuit designs and three mold materials (Ampcoloy 940, 1.2311 (P20) steel, and MS1 steel) were used and compared using numerical methods. The effect of different mold designs and materials on cooling efficiency were examined using calculated and measured results. The simulation model was adjusted to the measurement results by considering the joint gap between the mold inserts.

싱글모드 파이버 레이저를 이용한 SUS304와 Cu의 고속 겹치기 용접에서 접합부 및 인장시험 파단부의 특성에 관한 연구

To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single- mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.

Copper Coated Carbon Nanotube Wick Wetted with Ultrahigh Temperature Ceramic Nanofluid and Silver Nanofluid in Heat Pipes with Enhanced Stability

. High thermal conductivity of copper and carbon nano tubes are used in variety of thermal management applications to improve cooling performance. Deposition of copper over these nanotubes increases the hydrophilic wicking surface and increased conductivity and stiffness. The CNT coating and micro patterning are able to provide significant performance enhancements by reducing the surface superheat up to 72% . Conductivity can be increased further by wetting the wicks with conductive fluids. The nanofluids are of great use in this area. Ceramic nanofluid has a very good stability and silver nanofluid has a very good thermal conductivity and hence their mixture is of great use in high temperature applications. Adding of ceramics also ensure the stability of nanofluid suspensions and prevent coagulation. This paper suggests wetting the wicks with ceramic and silver nano fluid mixture in the ratio of 1:5 to increase conductivity and stability for high temperature applications further.

Fabricating Copper Components with Electron Beam Melting

Abstract The ability to make components from copper and copper alloys via additive manufacturing is spurring a range of novel applications. Although the high thermal conductivity of copper presents challenges for direct AM processes, fully dense copper components with complex geometries have been demonstrated. Of particular interest is the ability to use AM methods to fabricate internal cooling channels and mesh structures to optimize thermal management. This article describes feasibility studies to evaluate AM processing of copper parts.

Thermal Expansion Behavior of the Electroless Copper Coated Cu-SiC&lt;sub&gt;p&lt;/sub&gt; Composites Fabricated via the Conventional Powder Metallurgical Technique

The introduction of the metal matrix composites as the advanced electronic packaging materials is highly anticipated because their thermal properties can be engineered to match those of semiconductors, ceramics substrates and optical fibers. Among these advanced packaging materials, silicon carbide particles reinforced copper matrix (Cu-SiCp) composites are highly rated due to the high thermal conductivity of copper and low coefficient of thermal expansion (CTE) of silicon carbide. However, the Cu-SiCp composites fabricated via the conventional powder metallurgy (PM) technique usually have immature thermophysical properties due to the weak bonding between the copper matrix and the SiCp reinforcement. In order to improve the bonding between the two constituents, the SiCp were coated with copper via electroless coating process prior to PM fabrication processes. Based on the experimental results, The CTE and porosity of the Cu-SiCp composites were significantly affected by the volume fraction of SiCp. Furthermore, the CTE and porosity of the Cu-Coated Cu-SiCp composites were significantly lower than the non-Coated Cu-SiCp composites. These differences were mainly contributed by the nature of the bonding between the copper matrix and SiCp reinforcement.

Effects of processing parameters on the convective heat transfer rate during ultrasound assisted low temperature immersion treatment of a stationary sphere

The effect of ultrasound irradiation, as a novel method, on the enhancement of convective heat transfer between a stationary copper sphere and cooling medium was experimentally studied at different Re and Pr numbers. The high thermal conductivity of copper allowed the application of lumped system analysis which led to more accurate results on convective heat transfer. The ultrasonic cooling system included a refrigerated circulator, a flow meter, an ultrasound generator (25kHz) and an ultrasonic bath. The studied parameters were sphere diameter (0.01 or 0.02m), flow rate (1.67×10−5, 2.5×10−5m3s−1), fluid temperature (0, −5, −10, −15 and −20°C) and ultrasound intensity (0, 190, 890 and 2800Wm−2), leading to Re range of 0.98–3.4 and Pr range of 68.3–188.9. The Nu number varied from 6.8 to 19 for non-irradiated samples. When ultrasound was irradiated (890Wm−2) the range of Nu number increased to 11–31. Enhancement factors from 30% to 119% were observed for the irradiated samples. The largest values of the enhancement factor were observed for low values of Re and Pr which demonstrated a better efficiency of ultrasound irradiation at higher viscosities and lower flow rates as a result of its mixing and cavitation effects. The results obtained in this study confirmed that ultrasound irradiation is able to enhance the convective heat transfer rate between the cooling medium and the submerged object. Irradiation effect was independent of sphere diameter and a linear relationship was detected between the ultrasound intensity and the Nu number. A correlation was suggested to predict the values of Nu at the presence or absence of ultrasound for different Re and Pr values with good agreement with the experimental data (R2=0.90). The obtained data for copper can be generalized for food products with similar geometries and can be used for process design, as the convective heat transfer is mostly controlled by the cooling medium.

Focus on bioinstrumentation and biotechnologies

Focus on bioinstrumentation and biotechnologies

An investigation into the tribological performance of Physical Vapour Deposition (PVD) coatings on high thermal conductivity Cu-alloy substrates and the effect of an intermediate electroless Ni–P layer prior to PVD treatment

The use of high thermal conductivity copper alloys in plastic injection moulds provides the benefit of rapid moulding cycles through effective heat transfer. However, copper alloys are relatively soft and wear rapidly so manufacturers are now developing copper alloys with increased hardness and wear resistance. Their wear resistance can be further improved by the deposition of hard coatings such as electroplated chromium, electroless nickel and Physical Vapour Deposition (PVD) coatings. In this paper, the tribological performance of three proprietary high-strength Cu alloys (Ampcoloy® 940, Ampcoloy® 944 and Ampcoloy® 83) coated with PVD CrN and CrAlN coatings has been evaluated. A medium phosphorous content electroless Ni–P (ENi–P) plated layer was also deposited as a pre-treatment to PVD CrN and CrAlN coatings to increase the load support. The effect of this intermediate ENi–P layer was also evaluated. Surface roughness and instrumented hardness measurements were used to characterise all coated systems in both plated (i.e. with the intermediate ENi–P coating) and standard (i.e. unplated) conditions. Scratch tests were also performed to evaluate the effect of the ENi–P on PVD coating adhesion to Cu alloy substrates. The tribological behaviour of PVD-coated Cu alloy systems was evaluated by pin-on-disc wear tests and ball-on-plate impact tests. Results demonstrate that the ENi–P layer improves the load support for PVD coatings on Cu alloys, thereby improving their tribological performance. However, for PVD-coated Cu alloys in the standard condition, the Cu alloy substrate type plays an important role in the tribological performance of PVD coatings. For instance, PVD CrN coatings were more suited to a certain Cu alloy type whilst CrAlN to the other two types.

Effects of Hardeners and Catalysts on the Reliability of Copper to Copper Adhesive Joint

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

Direct metal deposition (DMD) of H13 tool steel on copper alloy substrate: Evaluation of mechanical properties

H13 tool steel powder was clad on copper alloy substrate both directly and using 41C stainless steel (high Ni steel) powder as a buffer layer by direct metal deposition (DMD). Cu–steel bimetallic die casting and injection molding tools are of high interest for reduction of cycle time by efficient heat extraction due to high thermal conductivity of copper. The mechanical properties of these bimetallic structures were investigated in terms of bond strength, impact energy and fracture toughness. The bond interfaces of these claddings showed porous and crack free transition regions. The bond strength was higher in the directly clad H13 tool steel compared to the H13 tool steel clad with 41C stainless steel as buffer layer. The fracture morphology in tensile test specimens showed ductile dimple fracture. Presence of necking just below the interface depicted the softening of substrate in heat affected zone (HAZ) during cladding. The Charpy impact energy is little higher in the 41C stainless steel buffered specimens compared to the directly clad H13 tool steel specimens but the fracture toughness results showed reduction of fracture toughness in the 41C stainless steel buffered specimens due to the low strength in the tensile test. However the fracture toughness value was in the ductile region for both deposits.

CNT単分散高熱伝導性銅基複合材料によるThermal Managementの試み

CNT単分散高熱伝導性銅基複合材料によるThermal Managementの試み

Thermal Design Methodology for an Embedded Power Electronic Module Using Double-Sided Microchannel Cooling

This paper presents a thermal design methodology for an integrated power electronic module (IPEM) using embedded, single-phase, and laminar-flow rectangular microchannels. Three-dimensional packaging of electronic components in a small and compact volume makes thermal management more challenging, but IPEMs also offer the opportunity to extract heat from both the top and the bottom side of the module, enabling double-sided cooling. Although double-sided cooling of IPEMs can be implemented using traditional aluminum heat sinks, microchannels offer much higher heat transfer coefficients and a compact cooling approach that is compatible with the shrinking footprint of electronic packages. The overall goal of this work was to find the optimal microchannel configuration for the IPEM using double-sided cooling by evaluating the effect of channel placement, channel dimensions, and coolant flow rate. It was found that the high thermal conductivity copper of the direct bonded copper (DBC) layer is the most feasible location for the channels. Based on a new analytical heat transfer model developed for microchannels in IPEM structures, several design configurations were proposed in this study that employ the microchannels in the copper layers of the top and bottom DBCs. The designs included multiple parallel channels in copper as well as a single wide microchannel. The analytical model was verified using a finite element model, and the competing design configurations were compared against a commercial cooler. For a typical IPEM structure dissipating on the order of 100W of heat, it was concluded that a single microchannel DBC heat sink is preferable to multiple parallel channels under a double-sided cooling configuration, considering thermal performance, pressure drop and fabrication trade-offs.

Cross flow heat exchange of textile cellular metal core sandwich panels

This paper presents a combined experimental and theoretical study on the thermal–hydraulic performance of a novel type of periodic textile cellular structure, subjected to forced convection using both air and water as a coolant. The samples were fabricated as sandwich panels, with the textile cores bonded to two solid face-sheets using a brazing alloy. These efficient load supporting sandwich structures can also be used for active cooling. The effects of cell topology, pore fraction and material properties (high thermal conductivity copper or low thermal conductivity stainless steel) on both coolants flow resistance and heat transfer rate were measured. The flow friction factor is found to depend mainly on the open area ratio in the flow direction (which is dependent upon cell topology and pore fraction), whilst the amount of heat transferred is dependent upon solid conductivity, pore fraction and surface area density. Analytical models were used to develop predictive relations between both the pressure loss and heat transfer performance for different textile geometries. Good agreement between the predictions and measurements were obtained. Due to high thermal capacity of water, it was found that the model for water cooling must account for the additional contribution due to thermal dispersion. The dispersion conductivity was found to be related to coolant property, local flow velocity, wire diameter and pore fraction. Finally, the thermal performance of brazed woven textiles is compared with other heat exchanger media, such as open-celled metallic foams and louvered fins.