银粉的形状对低温固化导电银浆导电性能的影响

研究了银粉含量、形状、表面处理工艺对低温固化导电银浆导电性能的影响。结果显示,最理想的银粉质量含量在65%~70%之间。同时,鳞片状银粉和球形粉的混合体制成的浆料导电性能最佳。另外,最好的固化条件是150℃、2 h。     

Effects of silver oxalate additions on the physical characteristics of low-temperature-curing MOD silver paste for thick-film applications

In this paper, the effect of silver oxalate addition on physical characteristics of metallo-organic-decomposition (MOD) silver screen-printable paste for thick film technology was investigated. The addition of silver oxalate in the paste not only produces fresh fine silver particles after curing, but also reduces the decomposition temperature of the lubricant coated on the silver flakes. This is an effective route to provide fine silver particles to the paste without significantly changing the rheological behavior. At the curing temperature of 225 °C, the resistivity decreases from 180.1 to 31.9 μΩ-cm, as the silver oxalate content increases from 0 to 10 wt%. This is due to the fact that active silver catalysts produced increase the packing density of silver flakes, and also the removal of lubricant from the surface of silver flakes enhances the electrical conductivity, thereby decreasing the resistance of film.     

Review of silver nanoparticle based die attach materials for high power/temperature applications

There has been a significant rise in the number of research papers on silver nanoparticle based solutions for harsh environment die attach. However, sintering nanoparticles is a complex process, affected by many different factors, such as the sintering temperature profile, particle size, sintering pressure, sintering environment, and organic compounds inside the nanoparticle paste used for stabilisation of the particles and easier processing. Therefore, numerous routes exist for establishment of sintered structures, and each lab has selected their own techniques and criteria for sintering silver nanoparticles. This has resulted in formation of a significant amount of knowledge and data in this field, but without appropriate correlation between utilised parameters. In this review data has been collected from a wide range of researchers in the field and an attempt made to correlate the results. By finding connections between the datasets, we present a broad and general understanding of the sintering processes to help researchers produce desired sintered structures. The collected data and investigated parameters include sintering pressure, metallisation, effect of thermal aging and cycling, highest sintering temperature, and particle size distributions. Some particularly interesting innovations in the field to address the shortcomings of sintering silver joints are investigated and some insights on sintering process are also provided, such as the understanding that higher sintering pressure causing improved strength might potentially reduce the long term thermal resistance of the die attach.     

高温铜电子浆料的制备及性能研究

以铜粉、玻璃粉和有机载体为原料,采用丝网印刷将铜浆料印刷到氧化铝陶瓷基片上,制备高温烧结型铜电子浆料。通过X射线衍射仪、扫描电子显微镜、能谱仪和四探针导电性测试仪对烧结后的试样行了表征。结果表明:在氮气保护性气氛下、烧结温度为450℃、玻璃粉质量分数为8%时,铜电子浆料烧结后的铜导电膜层导电性最佳,方阻值为23.62 mΩ/□,133 d内电阻的变化率仅为28.7%,铜导电膜层光滑平整。     

导电银浆的制备和性能研究

采用商用微米银片为导电相,玻璃粉为粘结剂,乙基纤维素、松油醇和曲拉通为有机载体制备了烧渗型银浆。利用扫描电子显微镜、方阻仪和百格测试法对烧结银浆的显微结构、导电性和附着力进行表征和研究。实验结果表明:烧结温度、玻璃粉含量和导电相的性质对银浆烧结后的显微结构、导电性和附着力均有较大影响。其中,烧结温度不仅对玻璃粉的熔化情况有影响,而且对烧结后的银浆中银片间的接触程度和与基材的润湿性等也有影响;玻璃粉的含量是影响烧结银浆的导电性和附着力的主要因素;微米银片中掺杂纳米银会导致烧结体中导电颗粒间的致密性下降,进而导致烧结后的银浆的导电性和附着力均下降。     

电子浆料用纳米Ag粉的制备及表面处理

以有机酸为分散剂,三乙醇胺为还原剂,采用高温化学还原法制备纳米Ag粉,并对粉体进行表面处理。研究了Ag2O粉比表面积、还原剂添加量、反应温度、表面处理及干燥温度等对Ag粉性能的影响。在醇类溶剂中于(88±2)℃还原比表面积大于3.000m2/g的Ag2O粉,制备了黑色纳米Ag粉,其粒径为50～150nm,比表面积大于8.000m2/g,振实密度高于2.5g/cm3。用液体树脂对Ag粉进行表面处理拓宽了粉体干燥温度,能有效阻止团聚和自烧结的发生,提高粉体分散性。     

纳米银及其导电浆料的制备与研究

以聚丙烯酸铵为保护剂,水合肼或葡萄糖为还原剂,采用液相化学还原法成功制备了单分散的纳米银颗粒.利用透射电子显微镜,X射线衍射对样品的形貌和结构进行了分析.利用紫外-可见分光光度计对纳米银溶胶的粒径大小分布及其稳定性进行了分析.把制得的纳米银分散在一定量丙三醇中,涂在载玻片上并烧结,对其表面性能进行分析.研究结果表明,所制备的纳米银溶胶的稳定性较好,氨水及还原剂的种类对纳米银的粒径和形貌有重要的影响.以水合肼为还原剂制得的纳米银的平均粒径为10 nm,粒径分布在6 nm到15 nm.烧结后的纳米银的表面形状较好,具有良好的导电性,其体积电阻率约为3.5×10-5Ω·cm.     

低温共烧陶瓷内电极用导电银浆烧结匹配性能

采用优化后的玻璃粉配制成导电银浆,与MgSiO3-CaSiO3生瓷片共烧后形成导电厚膜,探讨了不同玻璃粉配方对所制厚膜的微观结构、热学性能、附着力、线膨胀系数和导电性能的影响,研究了导电银浆与基片低温共烧的匹配性能。结果表明,SiO2-Al2O3-B2O3-CaO-Li2O系玻璃粉配制的导电银浆低温共烧后获得的导电厚膜平滑、均匀、致密;随着该系玻璃粉中Li2O含量的增加,导电银浆的线胀系数逐渐降低;Li2O的质量分数为6%时,该浆料线胀系数最低,为18.482×10–6℃–1;Li2O的质量分数为2%时,导电厚膜与基片的线膨胀匹配性良好,导电性能最好,方阻为3.02 m?/□。     

无铅玻璃粉及硅基银导电浆料的制备

为了解无铅玻璃粉中各组分含量对玻璃粉性能的影响,采用正交实验法对各组分含量进行筛选,得到流动性为32.80mm、转变温度为446℃的性能较好的无铅低熔玻璃粉,其组成为:w(Bj<,2>O<,3>)62.7%、w(B<,2>O<,3>)18.8%、w(ZnO)1.5%、w(碳族氧化物A)6.O%、w(碳族氧化物D)8.0...     

Fabrication and advanced electrical and stability characterization of laser-shaped thick-film and LTCC microresistors for high temperature applications

Thick-film and LTCC (Low Temperature Co-fired Ceramics) technologies are well-established and relatively low-cost fabrication method of passives. This paper presents systematic studies of fabrication and a wide spectrum of geometrical and electrical properties of thick-film and LTCC microresistors with dimensions down to 30 × 200 μm². The geometrical parameters (average length, width and thickness, relations between designed and real dimensions, distribution of planar dimensions) are correlated with basic electrical properties of resistors (sheet resistance, temperature dependence of resistance), long-term stability as well as durability of microresistors to short electrical pulses in the temperature range from 25 °C to 400 °C.     

Formulation and characterization of anisotropic conductive adhesive paste for microelectronics packaging applications

There has been a steadily increasing interest in using electrically conductive adhesives as interconnecting materials in electronics manufacturing. In this paper, several anisotropic conductive adhesive (ACA) pastes were formulated, which consist of diglycidyl ether of bisphenol F or diglycidyl ether of bisphenol A as polymer matrix, imidazoles as curing agents, and different sizes of silver (Ag) powders or gold (Au)-coated polymer spheres as conductive particles. The effects of ACA resin and different curing agents, as well as different conductive particles, on flexible substrate of the flip-chip joint were studied. The results show that the size and type of different conductive particles have very limited influence on an ACA flip-chip joint. The ACA resin as well as the curing agent can affect the reliability of the joint. The same results can be applied for the failure analysis of ACA flip-chip technology.     

Thermomechanical reliability of a silver nano-colloid die attach for high temperature applications

The last several years have seen the advent of silicon carbide (SiC) power devices operating at temperatures well above 125 °C. These devices have the potential to provide higher switching speed and lower on-state losses with higher thermal conductivity. Developing reliable technologies for packaging is now the main hurdle to successful operation of SiC based power electronics at high temperature. This paper evaluates a novel silver nano-particle colloid material that has been suggested for use as a die attachment for high temperature environments. The material synthesis together with fundamental mechanical and electrical properties is presented relative to the low temperature sintering process. Using thermal fatigue data measured for this material, a low cycle fatigue curve for the silver nano-particle colloid was developed. A Coffin–Manson relationship was derived for the solder; which together with calculated strains in the joint, allows the low cycle fatigue life of the die attachment to be predicted.     

用纳米银棒和颗粒制备高导电性油墨

研制了一种高导电性油墨。首先,分别以乙二醇和N,N-二甲基甲酰胺为还原剂,还原硝酸银溶液得到纳米银棒和纳米银球形颗粒。用纳米银棒和纳米银球形颗粒混合银粉、双酚A环氧树脂/酚醛树脂、丁酮等其他助剂配制导电油墨。研究了不同固化温度、固化时间对所制油墨导电性能的影响。结果表明,在150℃固化20 min该油墨印刷的导电图形具有很致密的表面结构和丰富的三维导电网络,其体积电阻率达3.6 10–6.cm。     

LT-GaAs with high breakdown strength at low temperature for power MISFET applications

Low temperature grown GaAs has been fabricated containing a limited amount of excess arsenic. The material has a low conductivity in the order of 100KΩ cm, due to hopping in a deep donor band. This σ-LT-GaAs was grown reproducibly by using the lattice mismatch as the primary parameter for substrate temperature calibration. Breakdown fields, in the order of 100kV/cm, are observed for planar structures and increased at low measurement emperatures. Low hopping conductivity and high breakdown field are also observed in the lossy dielectric metal-insulator-semiconductor field-effect transistor device using σ-LT-GaAs as a surface layer. The record radio frequency power density of 4.0W/mm at 77K is extracted from the dc output characteristics.     

Accelerated active ageing test on SiC JFETs power module with silver joining technology for high temperature application

This paper presents the accelerated active power cycling test (APCT) results on SiC JFETs power module dedicated to operate at high temperature. This study partly focuses on the new chip joining technology (LTJT), which permit to use SiC JFETs transistors at higher temperatures. We present the different die attachments tested with high temperature lead solder and silver sintering joining technologies. Active power cycling results for high junction temperature T_jmax = 175 °C with ΔT_j = 80 K to perform an evaluation of main damages during active test are carried out and a comparison between lead and silver chip joining technologies is presented.     

LTCC package for high temperature applications

There is a growing demand for sensors and electronics that can work in harsh environments and at high temperature. Applications include sensors and actuators for control in petroleum and geothermal industry, process monitoring and distributed control systems in the automotive and aerospace fields. Process development and packaging materials for electronic devices are closely connected to such packaging issues. In many cases the package is as important as the device itself in meeting the applications needs.Low temperature co-fired ceramics (LTCC) and thick-film technologies have the potential to incorporate multilayer structures, enabling fabrication of specialized packaging systems. LTCC technology enables easy electrical or optical connections within and between layers in addition to enabling use of integrated passive components, heaters, sensors, converters etc.This paper presents attempts to develop a reliable packaging technology for silicon carbide (SiC) based hydrogen sensors operating at temperatures up to 300 °C. Some simulations of thermal properties were carried out and package structures were made and investigated. The package protects the sensor against mechanical damage and makes possible easy electrical connections. Moreover, the heater and temperature sensors allow for proper temperature regulation of the element. The manufacturing process, basic electrical parameters of the integrated heater as well as real temperature distribution are presented.     

高温银浆中超细银粉的形态对压电陶瓷振子电性能的影响

通过对高温银浆中超细银粉的形态分布对压电陶瓷振子电性能影响的研究,得到了超细球形银粉和片状银粉的相对比例与振子的一些电性能参数的变化曲线,实验结果表明在制备银浆时,可采用在球形银粉中加入适量片状银粉的方法来提高振子的电性能。     

Multiple-gap back-lighted thyratrons for high power applications

Switching of high voltage and high current simultaneously with a fast current rate of rise by an optically triggered back-lighted thyratron is reported at very high pulsed power levels, including 100-kV stand-off voltage and >70-kA switched peak current. This switch is triggered by an unfocused ultraviolet light incident on the back of the cathode and is referred to as a back-of-the-cathode, light-activated thyratron (BLT). It has a simple structure that can be electrically isolated from the trigger circuit. The switch closure is a glow discharge rather than an arc; this dramatically reduces electrode degradation. The holdoff capability of one gap is limited by surface flashover and field emission. Experiments for improved holdoff voltage were conducted by scaling the BLT into multiple-gap switch configurations. The voltage of a multiple-gap chamber is divided among gaps, reducing the voltage across one gap. Hence the holdoff voltage is enhanced by additional stacks of intermediate electrode and insulator. Simultaneous optical triggering of each gap for precision timing, and plasma triggering, are also discussed. The results suggest that fairly simple multiple-gap configurations of the device are useful for applications such as multiple high-power modulator systems for accelerators     

Flexible transparent conductive film based on silver nanowires and reduced graphene oxide

Silver nanowires (AgNWs) with diameter of 90—150 nm and length of 20—50 μm were successfully synthesized by a polyol process. Graphene oxide (GO) was prepared by Hummers method, and was reduced with strong hydrazine hy-drate at room temperature. The flexible transparent conductive films (TCFs) were fabricated using the mixed cellulose eater (MCE) as matrix and AgNWs and reduced graphene oxide (rGO) as conductive fillers by the improved vacuum fil-tration process. Then, the optical, electrical and mechanical properties of the AgNWs-rGO films were investigated. The results show that for the AgNWs-rGO film produced with the deposition densities of AgNWs and rGO as 110 mg·m-2 and 55 mg·m-2, the optical transmission at 550 nm is 88.4% with Rs around 891 Ω·sq-1, whereas the optical transmission for the AgNWs-rGO film with deposition densities of AgNWs and rGO of 385 mg·m-2 and 55 mg·m-2 is 79.0% at 550 nm with Rs around 9.6 Ω·sq-1. There is little overt increase in Rs of the AgNWS-rGO film after tape tests for 200 times. The bending test results indicate that the change in Rs of AgNWs-MCE film is less than 2% even after 200 cycles of compressive or tensile bending. The excellent mechanical properties of the AgNWs-rGO film can be attributed to the burying of AgNWs and rGO at the surface of MCE