Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Sintered silver nanoparticles(AgNPs)arewidely used in high-power electronics due to their exceptional properties.However,the material reliability is significantly affected by various microscopic defects.In this work,the three primary micro-defect types at potential stress concentrations in sintered AgNPs are identified,categorized,and quantified.Molecular dynamics(MD)simulations are employed to observe the failure evolution of different microscopic defects.The dominant mechanisms responsible for this evolution are dislocation nucleation and dislocation motion.At the same time,this paper clarifies the quantitative relationship between the tensile strain amount and the failure mechanism transitions of the three defect types by defining key strain points.The impact of defect types on the failure process is also discussed.Furthermore,traction-separation curves extracted from microscopic defect evolutions serve as a bridge to connect the macro-scale model.The validity of the crack propagation model is confirmed through tensile tests.Finally,we thoroughly analyze how micro-defect types influence macro-crack propagation and attempt to find supporting evidence from the MD model.Our findings provide a multi-perspective reference for the reliability analysis of sintered AgNPs.

Study on the performance of silver paste sintered sealing joints for hermetic packaging

The traditional hermetic packaging methods,which require high temperatures and high voltages,would have adverse effects on electronics devices.Based on current-assisted sintering technology,we proposed a new hermetic packaging method using silver paste.Comparing the microstructure of the joints sintered with different currents,we found that with the increasing sintering current from 4.7 kA to 5.3 kA,the density of the joint increases,which improves the hermeticity and bonding strength of the joints.The results of thermal cycling tests showed that the sealing joints sintered at 4.7 kA with larger porosity are more prone to fail because pores tend to be sources of defects under thermal cycling.After 250 ℃ high thermal storage,there is the coarsening of the pores and the delamination near the Ag/Au interface,degrading the sealing performance of the sintered joint.Besides,the sealing joints sintered at 5.3 kA exhibit superior reliability when exposed to high temperatures.

Preparation and properties of porous ceramics from spodumene flotation tailings by low-temperature sintering

Porous ceramics were prepared with spodumene flotation talings(SFT),kaolin and low-melting point glass(LPG)powder,whose pores were formed by the chemical reaction of hydrogen peroxide(H_(2)O_(2)).LPG was used to reduce the sintering temperature of porous ceramics and kaolin was used to realize the adsorption to methylene blue(MB)of porous ceramics.The average flexural strength,compressive strength,apparent porosity,water absorption and maximum MB adsorption capacity were 5.60 MPa,4.66 MPa,52.27%,44.32%and 0.7 mg/g,respectively.Moreover,the results of orthogonal experiments present that the sintering temperature and the dosage of H_(2)O_(2)had great influence on the mechanical properties and apparent porosity of porous ceramics,respectively.The main reason for the improvement of mechanical properties of porous ceramics was that LPG gradually became soft with increasing the sintering temperature,which made the mineral particles adhere to each other closely.Kaolinite was not completely converted into metakaolin at 550℃,which might be the main reason why porous ceramics had adsorption properties.

Low-Temperature Sintering and Microwave DielectricProperties of Ba_2Ti_3Nb_4O_(18) Ceramics

The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.

Sintering behavior and mechanical properties of sintered ceramics based on spodumene tailings

In this study,ceramics was prepared by slip casting(no pressure was used during shaping step)and atmospheric pressure sintering with low-melting point glass(LPG)powder as the binding material to facilitate the transformation of spodumene flotation tailings(SFTs)into ceramics at lower temperatures.The influence of sintering temperature and mass ratio of LPG on the mechanical properties(flexural strength and compressive strength)of ceramic materials was studied by orthogonal test.The results showed that when the mass ratio of LPG powder was higher than or equal to 20 wt%and the sintering temperature was higher than or equal to 550℃,mutual adhesion between the sample particles was realised and consequently the ceramic materials could be prepared with good mechanical properties(the maximum flexural strength=19.55 MPa,the maximum compressive strength=42.25 MPa,average porosity=24.52%,average apparent density=1.66 g/cm^(3),and average water absorption=14.79%).The sintered ceramics were characterized by XRF,XRD,optical microscopy analysis,SEM,TGA-DSC and FT-IR.The formation of liquid phase at high temperature may lead to the mutual bonding between particles,which might be the main reason for the improvement of mechanical properties of ceramic materials.Overall,SFTs were successfully sintered at low temperature to prepare ceramic materials with good mechanical properties,which are crucial for energy conservation and environmental preservation.

STUDY ON STRENGTH AND PETROGRAPHIC STRUCTURE OF CLINKER BY LOW-TEMPERATURE BURNING

In this paper,the strength and petrographic structure of clinker by low-temperature burning are studied. The results show that both the calcining temperature of Ca-CO3 and sintering temperature clinker decreases by 150 degrees C compared with those in traditional rotary kiln,the rate of f-CaO in the clinker sintered at 1300 degrees C is 0.29% similar to 2.81%, the strength of the clinker is 62. 5MPa with maximum 69. 4MPa at a specific area of 2900 similar to 3400cm(2)/g. The results also show that the types of petrographic structure of the clinker can be classified as: homogeneous structure, inlaid or edged structure,stain-melting structure and porous structure. The clinker sintered at 1300 +/- 15 degrees C temperature and with enough retention period is mainly in homogeneous structure.

低温烧结无颗粒型银导电墨水的制备及其性能研究

导电墨水是柔性印制电子发展的关键,然而,目前导电墨水的烧结温度仍较高,限制了其在某些柔性基材上的使用。本文以乙酸银作为前驱体、氨水为络合剂、乙醇为助剂、甲酸为还原剂,制备了一种可低温烧结的无颗粒型银导电墨水。将该导电墨水滴涂到PET基材后于烘箱中进行烧结成银膜,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱仪(FTIR)等测试设备对制备的导电墨水和薄膜进行表征。系统研究了还原剂甲酸以及助剂乙醇对导电墨水及薄膜的性能影响。结果表明,该导电墨水具备良好的稳定性,经过90℃低温烧结60 min,其电阻率为11.83μΩ·cm。通过调控墨水配方,银薄膜的粗糙度和均匀性得到显著改善,且薄膜具有良好的弯折性能。

石英玻璃纤维织物基底柔性电极制备与性能研究

目的研制用于石英玻璃纤维织物基底的银/苯氧树脂基丝网印刷导电银浆,印制具有良好导电性能和力学性能的柔性电极,并探索烧结方式对电极性能的影响。方法以苯氧树脂为有机载体,不同粒径银粉为导电填料,二元酸酯混合物(DBE)为溶剂制备导电银浆。在石英玻璃纤维织物表面丝网印刷柔性电极,对比不同电极体积电阻率优化银浆组分配比。通过弯折实验表征电极力学性能,通过加热实验研究电极温度稳定性,对比高温烧结与电磁感应烧结对电极的影响。结果银浆含质量分数50%的片状银粉和质量分数10%的超细银粉时,印刷后电极体积电阻率最低且为1.75×10^(-5)Ω·cm,触变性满足丝网印刷要求。电极与基底附着力达到5B级别,弯折后电阻变化率<3%。电极在220℃高温烧结后导电性提升了51.54%,但烧结时间长达1h;经电磁感应烧结在14s内导电性提升了46.7%。结论使用大、小粒径银粉组合可提高石英玻璃纤维织物表面印刷电极中银颗粒的堆积密度,有利于实现电极的良好导电性和稳定性,电磁感应烧结方法可进一步快速提升电极导电性。本文提出的柔性电极制备方法有望对航空航天材料的多功能化、智能化发展提供重要技术支撑。

压阻式压力传感器芯片悬空型无引线封装结构的设计与实验

传感器的无引线封装技术取消了传统的引线键合连接,因而在极端环境下,具有耐高温、抗冲击能力强等特点,有广阔的发展前景。但在常规无引线封装结构中,芯片与玻璃基座烧结固连,会受到高温热固耦合下的热应力影响,进而降低测量精度。针对这一问题,以压阻式压力传感器芯片作为封装对象,提出了一种芯片悬空型无引线封装结构,对其封装材料的选择进行了研究并对整体热应力分布及大小进行了仿真分析;通过实验探究了封装结构中金属电极-导电银浆-金属插针电学互连通道在高温环境下的电学稳定性和力学强度;对采用该封装结构的压力传感器样品进行了输出和温度性能测试。结果表明,该封装结构整体所受热应力显著低于常规结构;电学互连通道的接触电阻远小于芯片压敏电阻,高低温循环条件下其阻值变化小于14Ω;高低温冲击后其拉伸破坏拉力在1.2 N以上;传感器样品输出电压线性度良好,在25~225℃内最大热零点漂移小于0.01%FS/℃,最大热满量程输出漂移小于0.20%FS/℃,相比于常规无引线封装结构显著减小了传感器热零点漂移,验证了该封装结构的可行性,为解决常规无引线封装结构中芯片热应力自释放问题提供了一个新的研究思路。

Structure,far-infrared spectroscopy,microwave dielectric properties,and improved low-temperature sintering characteristics of tri-rutile Mg_(0.5)Ti_(0.5)TaO_(4) ceramics

In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,and the low-firing characteristics were studied.It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis,the selected area electron diffraction(SAED),and the high-resolution transmission electron microscopy(HRTEM)along the[110]zone axis.With the increase in sintering temperature,the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics.Intrinsically,theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values,indicating the importance of structural features to dielectric properties.Furthermore,a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,where 2–4 wt%Li_(2)O–MgO–ZnO–B_(2)O_(3)–SiO_(2)(LMZBS)glass frit was adopted to reduce the suitable temperature from 1275 to 1050℃ without significantly deteriorating the microwave dielectric characteristics.Specifically,Mg_(0.5)Ti_(0.5)TaO_(4) ceramics containing 2 wt% glass addition sintered at 1050℃for 4 h possess excellent microwave dielectric properties:dielectric constant(ε_(r))=44.3,quality factor multiplied by resonant frequency(Q×f)=23,820 GHz(f=6.2 GHz),and the temperature coefficient of resonant frequency(τ_(f))=123.2 ppm/℃.

Design of advanced porous silver powder with high-sintering activity to improve silicon solar cells

Silver(Ag)paste is widely used in semiconductor metallization,especially in silicon solar cells.Ag powder is the material with the highest proportion in Ag paste.The morphology and structure of Ag powder are crucial which determine its characteristics,especially for the sintering activity.In this work,a simple method was developed to synthesize a type of microcrystalline spherical Ag particles(SP-A)with internal pores and the structural changes and sintering behavior were thoroughly studied by combining ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),in-situ heating X-ray diffraction(XRD),focused ion beam(FIB),and thermal analysis measurement.Due to the unique internal pores,the grain size of SP-A is smaller,and the coefficient of thermal expansion(CTE)is higher than that of traditional solid Ag particles.As a result,the sintering activity of SP-A is excellent,which can form a denser sintered body and form silver nanoparticles at the Ag–Si interface to improve silver silicon contact.Polycrystalline silicon solar cell built with SP-A obtained a low series resistance(Rs)and a high photoelectric conversion efficiency(PCE)of 19.26%.These fill a gap in Ag particle structure research,which is significant for the development of high-performance electronic Ag particles and efficient semiconductor devices.

纳米银无压封装互连技术

纳米银无压烧结技术作为一种新型封装互连技术,凭借烧结银层的优异性能,逐步在第三代半导体器件的封装互连领域应用和推广。目前,无压烧结银技术只适用于芯片级别小面积互连领域,在基板级别大面积互连领域存在若干瓶颈,有待深入研究。文章详细介绍了现有的小面积无压烧结纳米银互连工艺以及可靠性,在此基础上,针对大面积无压烧结银工艺所面临的瓶颈,引入一种双层印刷焊膏(双印法)的低温无压烧结工艺。采用超声扫描成像技术对烧结质量进行表征,获得双印法中使用的两层银焊膏的成分优化配比并对其烧结机理进行分析,为纳米银基板级大面积无压烧结互连提供一种可行方案。最后,展望了基板级别大面积无压烧结银工艺的发展趋势和应用前景。

基于ENEPIG镀层的无压纳米银膏烧结失效分析

总结了在化学镍钯浸金(ENEPIG)镀层上采用纳米银膏进行无压烧结时出现的失效模式。通过分析烧结镀层的微观形貌及力学性能,确认界面污染、烧结不充分及镀层缺陷是导致烧结失效的主要原因。应特别关注镍原子向镀层表面扩散导致的烧结失效风险。为保证烧结质量的稳定性和可靠性,需要充分重视界面的洁净度,对芯片、基板的存储条件和存储寿命实施严格管控,还需要优化烧结曲线,充分考虑溶剂释出所需时间、烧结峰值温度及其停留时间、降温速率等因素。研究结果为纳米银膏的无压烧结研究提供了新的理论参考。

镀银板表面粗糙度对纳米银焊膏快速烧结互连质量的影响

通过施加15 MPa的压力,在265℃空气气氛下使用预制完成的镀银板表面印刷纳米银焊膏组装的三明治结构制备烧结银连接层。研究了3种铜镀银板表面粗糙度对烧结银连接界面结合强度的影响。研究结果表明,烧结时间为8 min、镀银板算术平均表面粗糙度为1.630μm、最大粗糙度深度为12.030μm时,可以有效促使烧结银连接层与基板表面形成高强度的冶金连接和机械联锁,最终获得了61.09 MPa的高剪切强度,表明烧结银层与烧结界面的结合强度得到了较大提升。研究结果可为选择合适的基板粗糙度提供实验依据,从而获得高强度、高可靠性的低温快速烧结银互连接头。

Microwave dielectric properties and compatibility with silver of low-fired Li_2MgTi_3O_8 ceramics with Li_2O-MgO-B_2O_3 frit

The effects of Li2O-MgO-B2O3 （LMB） glass additive on the sintering characteristics, phase purity, microstructure, and microwave dielectric properties of Li2MgTi3O8 ceramics were investigated. The experimental results demonstrate that the addition of LMB glass effectively lowers the sintering temperature of Li2MgTi3O8 ceramic from 1025 ℃ to 875 ℃ and induces no obvious degradation of the microwave dielectric properties. Typically, the 1.5%LMB glass-added Li2MgTi3O8 ceramic sintered at 875 ℃ for 4 h shows excellent microwave dielectric properties of Q×f=45403 GHz, εr=25.9 and τf≈0 ℃-1. The dielectric ceramic exhibits stability against the reaction with the Ag electrode, which indicates that the ceramics could be applied in multilayer microwave devices requiring low firing temperatures.

Sintering of monoclinic SrAl_(2)Si_(2)O_(8) ceramics and their Sr immobilization

Monoclinic SrAl_(2)Si_(2)O_(8) ceramics for Sr immobilization were prepared by a liquid-phase sintering method.The sintering temperature,mineral phase composition,microstructure,flexural strength,bulk density,and Sr ion leaching characteristics of the SrAl_(2)Si_(2)O_(8) ceramics were investigated.A crystalline monoclinic SrAl_(2)Si_(2)O_(8) phase formed through liquid-phase sintering at 1223 K.The introduction of four flux agents(B_(2)O_(3),CaO·2B_(2)O_(3),SrO·2B_(2)O_(3),and BaO·2B_(2)O_(3))to the SrAl_(2)Si_(2)O_(8) ceramics not only reduced the densification temperature and decreased the volatilization of Sr during high-temperature sintering but also impacted the mechanical properties of the ceramics.Product consistency tests showed that the leaching concentration of Sr ions in the sample with flux agent B_(2)O_(3) was the lowest,whereas that of Sr ions in the sample with flux agent BaO·2B_(2)O_(3) was the highest.These results show that the leaching concentration of Sr ions depends largely on the amorphous phase in the ceramics.Meanwhile,the formation of mineral analog ceramics containing Sr is an important factor to improve Sr immobilization.

Low-temperature sintered(Na_(1/2)Bi_(1/2))TiO_(3)-based incipient piezoceramics for co-fired multilayer actuator application

Low-temperature sintered(Na_(1/2)Bi_(1/2))_(0.935)Ba_(0.065)Ti_(0.975)(Fe_(1/2)Nb_(1/2))_(0.025)O_(3)(NBT-BT-0.025FN)lead-free incipient piezoceramics were investigated using high-purity Li_(2)CO_(3) as sintering aids.With the ≤0.5 wt%Li_(2)CO_(3) addition,the introduced Li^(+) cations precede to enter the A-sites of the perovskite lattice to compensate for the A-site deficiencies.Once the addition exceeds 0.5 wt%,the excess Lit cations will occupy B-sites and give rise to the generation of oxygen vacancies,which accelerate the mass transport and thus lower the sintering temperature effectively from 1100℃ down to 925℃.It was also found that a small amount of Lit addition has little effect on the phase structure and electromechanical properties of the system,but overweight seriously disturbs these characteristics because of the large lattice distortion.The sintered NBT-BT-0.025FN incipient piezoceramics with 1.25 wt%Li_(2)CO_(3) addition at 925℃ provides a large strain of 0.33% and a corresponding large signal piezoelectric coefficient d_(33)^(*) of 550 pm/V at 60 kV/cm,indicating this system is a very promising candidate for lead-free co-fired multilayer actuator application.

纳米银印刷电路低温烧结研究进展

纳米银导电油墨是目前应用较多的金属系导电油墨。由于织物、纸张、塑料等柔性电路基底耐热性差,印刷电路的低温烧结(<200℃)乃至室温烧结,已经成为研究热点。结合文献报道及课题组工作,本文讨论了纳米银及其制备技术;分析对比了几种低温烧结技术,重点考察了化学烧结。相对其他烧结技术,化学烧结适用范围广、操作简单、高效节能,通过配体交换法可得到电阻率为1.21×10^(-7)Ω·m的纳米银印刷电路;光子烧结时间短,效率高,但价格昂贵;电烧结选择性强,受制于电热转换;微波烧结具有较高的选择性,但耗时长,且烧结效果与纳米颗粒的大小密切相关;等离子体烧结要求真空条件,设备复杂,烧结时间长。总体上,选择具体印刷电路的低温烧结方式,要综合考虑导电油墨、印刷电路和基材等因素。

纳米银双面烧结SiC半桥模块封装技术

为满足雷达阵面高功率密度的需求,SiC宽禁带半导体器件在电源模块应用中逐步取代传统硅功率器件。传统焊接及导电胶粘工艺存在导电性能差、热阻大、高温蠕变等缺点,无法发挥SiC功率器件高结温和高功率的优势。纳米银烧结是大功率器件最合适的界面互连技术之一,具有低温烧结高温使用的优点和良好的高温工作特性。文中针对高功率电源模块大电流传输对低压降及高效散热的需求,基于高功率半桥电源模块开展了SiC芯片的纳米银双面烧结工艺技术研究,突破了成型银焊片制备、纳米银焊膏高平整度点涂、无压烧结等关键技术,并通过烧结界面微观分析以及芯片剪切强度和焊片剥离强度测试对烧结工艺参数进行了优化。最后对半桥模块进行了静态测试和双脉冲测试。该模块的栅极泄漏电流<1.5 n A,开关切换时间<125 ns,漏极电压过冲<12.5%,满足产品应用需求。

功率模块纳米银烧结技术研究进展

大功率器件工作时产热量大,如果不能及时导出将严重降低互连层的性能,从而影响功率模块性能和可靠性。纳米银烧结技术可以实现低温连接、高温服役的要求,且具有优秀的导热导电性能和高温可靠性,已成为近几年功率模块封装互连材料的研究热点。归纳总结并对比分析了近年来关于纳米银烧结的研究,探讨了影响纳米银烧结接头初始剪切强度的工艺参数以及高温长期可靠性问题,评述了纳米银烧结的新技术和发展趋势。