铜颗粒低温烧结技术的研究进展

金属纳米材料因具有良好的导电导热性以及能够在较低温度下进行烧结,是功率器件在高温高压高频等工作环境下服役所需的关键电子封装材料之一.文中对应用于功率器件封装领域的铜颗粒实现烧结的研究进行了综述,阐明了目前通过铜颗粒烧结技术实现低温键合的研发背景.从铜颗粒烧结材料的制备、工艺参数和还原方法等关键影响因素出发,讨论、归纳了基于不同烧结机理的低温烧结铜颗粒材料接头的力学性能和电学性能.此外,介绍了铜颗粒烧结技术在贴片封装和全铜互连领域中应用的优良特性.通过对该领域研究成果的分析,结果表明,目前铜烧结材料仍然受到氧化问题的挑战,需要进一步在接头性能的精准调控方面深入研究.

Exploration of the enhanced performances for silk fibroin/sodium alginate composite coatings on biodegradable Mg-Zn-Ca alloy

To expand the future clinic applications of biodegradable magnesium alloy,polymer coatings with excellent biocompatibility are the keys to solve the local alkalinity and rapid hydrogen release.Natural-organic silk fibroin provides an approach to fabricate a protective coating on biomedical Mg-Zn-Ca alloy,however,the adhesion force and mechanical properties of the coating on substrates are ought to be further improved without any chemical conversion/intermediate layer.Hereby,based on VUV/O;surface activation,a hybrid of silk fibroin and sodium alginate is proposed to enhance the adhesion force and mechanical properties of the composite coatings on hydrophilic Mg-Zn-Ca alloy surfaces.Various mass ratios of sodium alginate addition were investigated to achieve the optimum coating strategy.The nanoscratch test and nanoindentation test confirmed that the adhesion force was tripled and mechanical properties index was significantly improved when the mass ratio of silk fibroin/sodium alginate was 70/30 compared to pure silk fibroin or sodium alginate coatings.Meanwhile,the corrosion rate of the coated Mg-Zn-Ca alloy was significantly delayed with the addition of sodium alginate,resulting in a reaction layer during corrosion process.Furthermore,the mechanisms for both adhesion and corrosion processes were discussed in detail.Our findings offer more possibilities for the controllable surface performance of degradable metals.

β-Ga2O3 MOSFETs on the Si substrate fabricated by the ion-cutting process

β-Ga2O3 MOSFETs are demonstrated on heterogeneous Ga2O3-Al2O3-Si(GaOISi)substrate fabricated by ion-cutting process.Enhancement(E)-and depletion(D)-modeβ-Ga2O3 transistors are realized on by varying the channel thickness(Tch).E-mode GaOISi transistor with a Tchof 15 nm achieves a high threshold voltage VTHof^8 V.With the same T increase,GaOISi transistors demonstrate more stable ON-current IONand OFF-current IOFFperformance compared to the reported devices on bulk Ga2O3 wafer.Transistors on GaOISi achieve the breakdown voltage of 522 and 391 V at 25°C and 200°C,respectively.

Fabrication of Ag@Ag_(2)O-MnO_(x) composite nanowires for high-efficient room-temperature removal of formaldehyde

Efficient removal of pollutant formaldehyde(HCHO) at room temperature using transition-metal oxides remains a huge challenge to date. Manganese oxide can oxidize formaldehyde, however, how to control the valence states of manganese is the key to further improve the removal efficiency. We have successfully prepared porous manganese oxide nanowires(Mn OxNWs) with large surface area and multiple valence states of manganese using simple electrospinning followed by thermal calcination and potassium permanganate solution post-treatment(C/S process). The contents of trivalent and tetravalent manganese increased significantly after C/S process. Moreover, the composition of silver oxide coated silver nanowires(Ag@Ag_(2) O NWs) is realized by assistance with oxygen plasma, which further enhanced high valence manganese. The formaldehyde removal efficiency by Ag@Ag_(2) O–Mn Oxcomposite nanowires can reach 93.7%. The high-efficient catalytic activity is confirmed to attribute to the higher surface area of composite nanowires, the high-valence manganese and the silver oxide for oxidation of formaldehyde.

Recycled low-temperature direct bonding of Si/glass and glass/glass chips for detachable micro/nanofluidic devices

Silicon and glass are two of the most ideal materials for micro/nanofluidic devices,which have been widely used for research in multidisciplinary fields.However,many micro/nanofluidic devices enable only single use due to the irreversible bonding between Si/glass or glass/glass chips.If the silicon-and glass-based devices are fabricated to be detachable,the substrates can be reused and bonded again without repeating expensive micro/nanofabrication processes.Herein,we present a recycled direct bonding method for Si/glass and glass/glass chips based on oxygen plasma activation and low-temperature annealing processes.Strong bonding strength and void-free bonding interface are obtained after annealing at 150℃.The surfaces and the bonding interfaces are characterized to elucidate the bonding mechanisms.Moreover,immersion tests are carried out to investigate the interfacial corrosion resistance in various chemical and biological solutions as well as explore a detachable method.The bonding strengths are controlled to meet the demand for micro/nanofluidic devices and the bonding interfaces can be separated in ethanol.As a result,we succeed in the experiment of bonding and detaching of glass substrates without fracturing,which is repeated for three times.

Efficient thermal dissipation in wafer-scale heterogeneous integration of single-crystalline𝛽β-Ga_(2)O_(3)thin film on SiC

The semiconductor,β-Ga_(2)O_(3)is attractive for applications in high power electronic devices with low conduction loss due to its ultra-wide bandgap(∼4.9 eV)and large Baliga’s figure of merit.However,the thermal conductivity of𝛽β-Ga_(2)O_(3)is much lower than that of other wide/ultra-wide bandgap semiconductors,such as SiC and GaN,which results in the deterioration of𝛽β-Ga_(2)O_(3)-based device performance and reliability due to self-heating.To overcome this problem,a scalable thermal management strategy was proposed by heterogeneously integrating wafer-scale single-crystalline𝛽β-Ga_(2)O_(3)thin films on a highly thermally conductive SiC substrate.Characterization of the transferred𝛽β-Ga_(2)O_(3)thin film indicated a uniform thickness to within±2.01%,a smooth surface with a roughness of 0.2 nm,and good crystalline quality with an X-ray rocking curves(XRC)full width at half maximum of 80 arcsec.Transient thermoreflectance measurements were employed to investigate the thermal properties.The thermal performance of the fabricated𝛽β-Ga_(2)O_(3)/SiC heterostructure was effectively improved in comparison with that of the𝛽β-Ga_(2)O_(3)bulk wafer,and the effective thermal boundary resistance could be further reduced to 7.5 m 2 K/GW by a post-annealing process.Schottky barrier diodes(SBDs)were fabricated on both a𝛽β-Ga_(2)O_(3)/SiC heterostructured material and a𝛽β-Ga_(2)O_(3)bulk wafer.Infrared thermal imaging revealed the temperature increase of the SBDs on𝛽β-Ga_(2)O_(3)/SiC to be one quarter that on the𝛽β-Ga_(2)O_(3)bulk wafer with the same applied power,which suggests that the combination of the𝛽-Ga_(2)O_(3)thin film and SiC substrate with high thermal conductivity promotes heat dissipation in𝛽β-Ga_(2)O_(3)-based devices.