Enhancing mechanical properties via adding Ni and Zn in Cu/Sn3.5Ag/Cu transient liquid phase bonding for advanced electronic packaging

Journal of Materials Science: Materials in Electronics - Recently, the transient liquid phase (TLP) bonding process has become a promising method in advanced electronic packaging. Full...     

电子封装用Diamond/Cu复合材料的化学镀镍

通过采用在Diamond/Cu复合材料表面化学镀镍的方法来改善其焊接性.化学镀镍前,采用SnCl2溶液和PdCl2溶液对复合材料表面进行敏化、活化等预处理.研究了pH值和温度对化学镀镍沉积速度的影响.利用SEM、EDX、XRD和划痕实验等措施对镀层进行了研究,结果表明,在Diamond/Cu复合材料表面获得了均匀、致密...     

Properties of SnAgCu/SnAgCuCe soldered joints for electronic packaging

For quad flat packages (QFP256), lead-free soldered joints reliability in service is a critical issue. In this paper, soldering experiments of quad flat package (QFP256) devices were carried out by means of infrared reflow soldering system with Sn–3.8Ag–0.7Cu and Sn–3.8Ag–0.7Cu–0.03Ce lead-free solders, respectively, and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR micro-joints tester. The results indicate that the tensile strength of Sn–Ag–Cu–Ce soldered joints is better than that of Sn–Ag–Cu soldered joints. In particular, the addition of trace Ce to the Sn–Ag–Cu solder can refine the microstructures and decrease the thickness of the intermetallic compound layer of Sn–Ag–Cu solder alloys. In addition, the stress–strain response of Sn–Ag–Cu/Sn–Ag–Cu–Ce soldered joints in quad flat packaging was investigated using finite element method based on Garofalo–Arrhenius model. The simulated results indicate creep distribution of soldered joints is not uniform, the heel and toe of soldered joints, the area between soldered joints and leads are the creep concentrated sites. The creep strain of Sn–Ag–Cu–Ce soldered joints is lower than that of Sn–Ag–Cu soldered joints.     

Ceramic joining III bonding of alumina via Cu/Nb/Cu interlayers

A method of ceramic-ceramic joining that exploits a multilayer interlayer designed to form a thin, potentially transient layer of liquid phase has been used to join alumina to alumina. Microdesigned multilayer Cu/Nb interlayers were used to achieve bonding at 1150 °C. Flexure strengths of as-bonded samples ranged from 119 to 255 MPa, with an average of 181 MPa. The ability to form strong ceramic/metal interfaces is also indicated by instances of ceramic failure. Microstructural and chemical characteristics of fracture surfaces were evaluated using SEM, EDS and microprobe. The impact of post-bonding anneals of 10 h duration at 1000 °C in gettered argon on room-temperature joint strength was assessed. High strengths (198 to 238 MPa) were obtained. The retention of strength following annealing in low oxygen partial pressure argon differs from the behaviour previously observed in Cu/Pt bonded alumina. Effects of the anneal on interfacial microstructure were determined, and an explanation for this difference in behaviour is proposed.     

MEMS器件自动引线键合系统

引线键合是MEMS传感器最常用的封装形式之一,传统IC引线键合设备的批量制造特点限制了MEMS制造的灵活性.本文将连续变倍显微镜作为视觉传感器建立柔性显微视觉系统,并与改造后的手动引线键合机相结合,建立了面向MEMS的自动引线键合系统.通过分析变倍显微镜的成像模型提出了一种适用于变倍显微镜的自动调焦方法,以获取不同倍数下的清晰图像.利用变倍显微镜可以连续变倍的特点,在低放大倍数下进行大范围粗定位,高放大倍数下进行精定位,从而实现大范围高精度定位.最后通过实验验证了该系统的实用性.     

Cu/Sn等温凝固芯片键合工艺研究

研究了Cu/Sn等温凝固芯片键合工艺,对等离子体处理、键合气氛、压力以及Sn层厚度等因素对焊层的键合强度的影响进行了分析和优化。实验表明,等离子体处理过程的引入是保证键合质量的重要因素,在功率500W、时间200s的处理条件下,得到了最大的键合强度;而键合气氛对键合质量有显著的影响,在真空环境下,能得到最佳的键合质量;压力对键合质量的影响较小,施加较小的压力(0.05MPa)即能得到较大的剪切强度;而Sn层厚度对键合质量的影响极小,而较薄的厚度能够缩短键合时间。在最优化条件下,得到的键合强度值全部达到了美军标规定的6.25MPa的强度要求(对于2mm×2mm芯片)。     

Intermetallic compound layer growth between SnAgCu solder and Cu substrate in electronic packaging

Growth kinetics of intermetallic compound (IMC) layers formed between SnAgCu solder for reflow soldering and Cu substrate by solid state isothermal aging were investigated at temperatures between 100 and 140 °C. For the aged samples, two distinct layers of IMCs of the type Cu₆Sn₅ and Cu₃Sn were identified with the later adjacent to the copper substrate. In the as-soldered samples, only a single layer of interfacial Cu₆Sn₅ type IMC was formed. Moreover, the apparent activation energies were 96.75 kJ/mol (total IMC), 85.98 kJ/mol (Cu₆Sn₅ IMC) and 105.92 kJ/mol (Cu₃Sn IMC), respectively.     

Cu/LDPE防银变色包装膜的制备及其性能研究

以铜粉作为有效成分,采用挤出流延法成功制备了Cu/LDPE防银变色包装膜.利用热重分析仪(TGA)、差示扫描量热仪(DSC)、傅里叶红外光谱(FT-IR)、X射线衍射仪(XRD)、紫外可见光分光光度计(UV-Vis)以及阻隔性能、光学性能、力学性能、银片色差等测试,研究了平均粒径D50为10.11μm的铜粉在不同含量时...     

Study of anodized Al substrate for electronic packaging

Al metal substrate with an anodic film separating the circuitry from the metal plate was developed by the means of anodization in this study. It was shown that an anodic film around 20–30 m thickness possessed the better properties, the resistivity was greater than 10¹⁴ cm, the dielectric constant was about 7 and the breakdown voltage exceeded 1000 V, which could satisfy the needs of the packaging. Electroless copper plating was attempted to complete the metallization of the anodized Al substrate, on which a fine Cu deposit could be obtained when the anodic film was sealed in a bath containing Ni, F ions.     

电子封装用SiCp/Al复合材料的组织与性能

本文选用粒径为20μm和60μm的SiC混合颗粒,采用挤压铸造方法制备了体积分数为70%的SiCp/LD11(Al-12%Si)复合材料.材料组织致密,颗粒分布均匀.复合材料具有低膨胀、高导热的特性和十分优异的力学性能,并且可以通过退火处理进一步降低其热膨胀系数.采用化学镀方法,在复合材料表面涂覆镍层,以其做为底座的二极管满足器件的可靠性测试要求.     

Microstructure and thermo-physical properties of a SiC/pure-Al composite for electronic packaging

A preform comprised of 70 vol% SiC particles was infiltrated with commercially pure aluminium to produce the electronic packaging composite. A dense and uniform microstructure was found in the composite. The incorporation of high volume fraction of SiC particles led to a reduction of coefficient of thermal expansion while maintaining a relatively high thermal conductivity. The correlation between the microstructure features and thermo-physical properties was discussed. The performance of the electronic assemblies using the composite baseplate was evaluated. After 80 thermal shocks (–55 to 150 °C), the thermal resistance kept almost constant, demonstrating the potential application of this composite in the electronic packaging.     

Reliability of SnAgCu/SnAgCuCe solder joints with different heights for electronic packaging

Finite element simulation and experiments were used to analyze the reliability of SnAgCu/SnAgCuCe solder joints with different heights. With the increase of height of solder joints, the tensile strength of SnAgCu and SnAgCuCe solder joints drops significantly. With the same height, the tensile strength of SnAgCuCe solder joints show enhanced reliability comparing with that of SnAgCu solder joints. The heights of lead-free solder joints can markedly influence the failure modes of SnAgCu/SnAgCuCe solder joints, three models [intermetallic compound (IMC), solder/IMC, solder] can be demonstrated with the variation of height. Based on finite element methods, it is found the maximum stress concentrated location show a relationship with heights of solder joints, smaller height can keep the high reliability of solder joints.     

Magnetic nanoparticle-based solder composites for electronic packaging applications

Sn–Ag–Cu (SAC) alloys are regarded as the most promising alternative for traditional Pb–Sn solders used in electronic packaging applications. However, the higher reflow temperature requirement, possible intermetallic formation, and reliability issues of SAC alloys generate several key challenges for successful adoption of Pb-free solder for next generation electronic packaging needs. Localized heating in interconnects can alleviate thermal stresses by preventing subjection of entire package to the higher reflow temperatures associated with the SAC solders. It had been demonstrated that SAC solder–FeCo magnetic nanoparticles (MNPs) composite paste can be reflowed locally with AC magnetic fields, enabling interconnect formation in area array packages while minimizing eddy current heating in the printed circuit board.Solder/magnetic nanocomposite pastes with varying MNP concentration were reflowed using AC magnetic fields. Differential scanning calorimetry results show a reduced undercooling of the composite pastes with the addition of MNPs. TEM results show that the FeCo MNPs are distributed in Sn matrix of the reflowed solder composites. Optical and SEM micrographs show a decrease in Sn dendrite regions as well as smaller and more homogeneous dispersed Ag₃Sn with the addition of MNPs. The MNPs promote Sn solidification by providing more heterogeneous nucleation sites at relatively low undercoolings. The mechanical properties were measured by nanoindentation. The modulus, hardness, and creep resistance, increase with the MNP concentration. The enhanced mechanical properties are attributed to grain boundary and dispersion strengthening.The reflow of solder composites have been modeled based on eddy current power loss in the substrate and magnetic power losses in the solder bumps. Induction reflow of pure solder bumps (<300 μm) in an area array package using 500 Oe magnetic field at 300 kHz requires excessive eddy current power loss in the substrate, resulting in extreme temperatures that lead to blistering and delamination of the substrate. Solder–MNP composites with modest MNP loading showed temperature increases sufficient to achieve solder reflow when subjected to the same AC magnetic fields. Thermomechanical behavior of a solder joint was also modeled under cyclic temperature variations. The stress and strain are highly localized at the interface between solder and substrate. Plastic work accumulated per cycle can be used for lifetime prediction.In this article we review lead-containing and lead-free solder systems, and the electronic packaging technologies pertinent to soldering process. Recent research on the effects of MNPs on localized heating, microstructure evolution, mechanical properties, and thermomechanical reliability are summarized.     

环保型电子封装用Sip/Al复合材料性能研究

为研究电子封装用Sip/Al复合材料热物理及力学性能,利用挤压铸造方法制备了体积分数为65%的Sip/LD11(Al-12%Si)可回收环保型复合材料.采用TEM观察、膨胀仪、激光导热综合测试仪以及万能电子拉伸试验机等设备及技术对复合材料进行研究.结果表明:Sip/LD11复合材料组织致密,材料中未观察到孔洞和缺陷;20～50℃时复合材料的热膨胀系数为8.1×10-6/℃,并随着温度的升高而增加,退火处理能够降低复合材料的热膨胀系数;Sip/LD11复合材料铸造状态和热处理状态的热导率分别为132.9、160.1 W/m·℃,复合材料的弯曲强度和比模量较高;可以采用化学镀方法在复合材料表面涂覆Ni层,镀层结合强度良好,是一种优异的电子封装用复合材料.     

Ceramic joining II partial transient liquid-phase bonding of alumina via Cu/Ni/Cu multilayer interlayers

Multilayer Cu/Ni/Cu interlayers that form a thin layer of a Cu-rich transient liquid phase have been used to join alumina to alumina at 1150 °C. The method and bonding conditions yield an assembly bonded by a Ni-rich (>94 at% Ni) interlayer at a temperature substantially lower than those normally required for solid-state diffusion bonding with pure Ni interlayers. Flexure strengths of as-bonded beams ranged from 61 to 267 MPa with an average of 160 MPa and a standard deviation of ±63 MPa. The highest flexure strengths were observed in samples where failure occurred in the ceramic. Post-bonding anneals of 10 h duration in air and gettered-argon at 1000 °C decreased the average room temperature strength to 138 and 74 MPa, respectively. In as-processed and annealed samples, varying degrees of interfacial spinel formation are indicated. Spinel formation may contribute to the scatter in as-processed samples, and the decrease in strength values resulting from annealing.     

LCP微球对LCP/尼龙6共混体系力学性能的影响

制备了分散相呈球状微粒形貌的液晶聚合物/尼龙6 (LCP/PA6)共混体系,选用离聚物磺化聚苯乙烯锌盐(Zn-SPS)和反应性嵌段共聚物苯乙烯-马来酸酐共聚物(SMA)作为体系的增容剂,探讨了在相间相互作用得以改善时,利用LCP微球改善 LCP/尼龙6 共混体系韧性的可能性。试样受拉后的形貌观察表明,在增容体系中,LCP微球很好地镶嵌在尼龙6基体中,粒子脱落的空洞发生了较大的形变。力学性能测试结果表明,LCP的加入使材料的拉伸强度低于纯尼龙6,加入增容剂后共混材料拉伸强度有所提高,其中LCP/PA6 (质量比10/90)共混体系增容后的拉伸强度与纯尼龙6 相当。所研究的增容体系的拉伸断裂吸收能均比未增容体系有所增加。其中,当 LCP的质量分数为4%时,Zn-SPS增容体系的拉伸断裂吸收能比未增容体系和纯尼龙6分别增加了12%和62%;当LCP的质量分数为10 %时,SMA增容体系的拉伸断裂吸收能比未增容体系和纯尼龙6分别增加了46%和55%。表明在适当条件下,利用LCP微球可以在保持共混体系的拉伸强度的同时提高材料的韧性。     

Preparation and properties of Si3N4/PS composites used for electronic packaging

A kind of polymer composite was fabricated using polystyrene as the matrix and Si₃N₄ powder as filler employing the method of heat press molding. Microstructure, thermal conductivity and dielectric constant of the Si₃N₄ filled composite were evaluated. The effect of the volume fraction of Si₃N₄, the particle size of the polystyrene matrix and the silane treatment of Si₃N₄ filler on the thermal conductivity of the composite was investigated; dielectric constant of the composite was evaluated. The main factors that affect the thermal conductivity of the composite were confirmed through theoretical analyzing of the experimental data and the thermal conductivity model. Experimental results show that with the filler content increasing, a thermally conductive network is formed in the composites, thus the thermal conductivity of the composite increases rapidly. The composites experience a highest thermal conductivity of 3.0 W/m K when the volume fraction of the filler reaches 40%. The increasing of thermal conductivity is dominated by the ease of forming a thermal conductive network. A larger polystyrene particle size, a higher Si₃N₄ filler content and the silane treatment of the filler have a beneficial effect on improving the thermal conductivity. The dielectric constant increases with the content of Si₃N₄ filler, however, it remains at a relatively low lever (<4, at 1 MHz).