用田口方法优化SMT无铅焊膏印刷质量

焊膏印刷是PCB贴片安装的重要环节,采用无铅焊膏后,由于焊膏物理性能的变化,需要重新摸索调整无铅焊膏的印刷参数,以获得最好的焊膏印刷质量。影响质量的多个因子多水平的完备试验是不现实的,文中采用田口方法试验,得到了在工程实际中适合无铅焊膏印刷的多个参数的近似最佳数值。该方法还可以广泛应用于电子产品质量控制优化。     

Ni含量对Sn-0.7Cu无铅钎料钎焊性能的影响

本文以Sn-0.7Cu无铅钎料为基础,以改善二元Sn-Cu钎料合金的性能为目标,研究了Ni含量对Sn-0.7Cu钎料合金组织和性能的影响。通过组织观察、力学性能测试、熔化特性测试、润湿性能测试、电阻率测试、耐腐蚀性测试、时效处理等,研究了Ni含量对Sn-0.7Cu-xNi(x=0.5, 1.0, 1.5, 2.0)钎料合金凝固行为和钎焊性能的影响规律。结果表明：随着Ni含量添加,金属间化合物相(Ni3Sn4)体积分数逐渐增大,Ni含量为2%时,硬度最大值为14.2 HV;Ni含量为0.5%时,熔程最小为4.4 ℃;Ni含量为1%时,铺展面积最大值为92.4 mm2;在Ni含量为2%时,电阻率最大为1.1x10-7 Ω·m;IML厚度随着时效时间的延长先增加后趋于均匀;在Ni含量为2%时,钎料在酸性腐蚀条件下最稳定。     

高性能铌酸钾钠无铅压电陶瓷研制

用常规氧化物固溶方法制备了无铅压电铌酸盐((Na0.5K0.5)1-xLixSbyNb1-yO3)陶瓷。实验结果表明,Li+和Sb5+的引入提高了陶瓷的压电性能。在一定配比范围内(Li和Sb在10%摩尔分数以内),材料为斜方、四方相共存的钙钛矿结构,材料的压电常数d33在270 pC/N以上,机电耦合系数kp、kt、k33分别达到49×10–2、43×10–2、64×10–2。介质损耗tgδ小于2.0×10_2,居里温度tC高达375℃。     

Thermosonic bonding of lead-free solder with metal bump for flip-chip bonding

While extensive research on the lead-free solder has been conducted, the high melting temperature of the lead-free solder has detrimental effects on the packages. Thermosonic bonding between metal bumps and lead-free solder using the longitudinal ultrasonic is investigated through numerical analysis and experiments for low-temperature soldering. The results of numerical calculation and measured viscoelastic properties show that a substantial amount of heat is generated in the solder bump due to viscoelastic heating. When the Au bump is thermosonically bonded to the lead-free solder bump (Sn-3%Ag-0.5%Cu), the entire Au bump is dissolved rapidly into the solder within 1 sec, which is caused by the scrubbing action of the ultrasonic. More reliable solder joints are obtained using the Cu/Ni/Au bump, which can be applied to flip-chip bonding.     

从专利角度探讨Sn-Zn无铅焊料研究现状

无铅焊料的研发及专利权的保护是我国电子行业亟待解决的问题。文中结合中国专利权的特点,描述了世界各国在无铅焊料专利上的竞争以及Sn-Zn无铅焊料的专利申请状况,并据此分析了Sn- Zn无铅焊料的研发及应用状况、专利Sn-Zn无铅焊料的特点以及应用障碍,以期对我国自主知识产权的Sn-Zn无铅焊料的研发及无铅专利保护有所帮助。     

感应自加热重熔无铅焊料凸台的剪切失效模式

通过两次高频感应重熔制备了Cu焊盘上S n3．5Ag焊料和Sn3．0Ag0．5Cu焊料凸台,并进行了120℃下的老化试验以及老化试件的剪切强度试验,分析了不同老化时间下两种无铅焊料凸台的剪切断裂模式。焊料凸台的剪切载荷-位移曲线的特征以及对焊料凸台剪切断口的扫描电镜形貌分析结果表明,不同老化时间下无铅焊料凸台的剪切断裂表现为塑性、韧性和脆性三种断裂模式。对凸台焊料合金的组织以及界面观察结果表明,随老化时间不断生长的脆性金属间化合物层以及焊料组织粗大是致使断裂失效模式转变的根本原因。     

介电常数可调的无铅高压陶瓷电容器材料的研究

在BaTiO3瓷的基础上加入SrTiO3,CaCO3,Bi2O3.3TiO2等,以合理工艺制度,烧制成具有(1-z)(Ba1-x-ySrxCay)TiO3.z(Bi2O3.3TiO2)化学形式的瓷料。通过正交实验法研究了不同添加剂对该系统高压陶瓷电容器材料性能的影响,同时在此基础上进一步优化配方,得到了介电常数可调、综合性能较佳的瓷料配方,其中介电常数较高、性能较好的配方为:0.97(Ba0.6Sr0.3Ca0.1)TiO3.0.03(Bi2O3.3TiO2),其性能为:εr=3802,tanδ=4.2×10-3,Eb=9.2 kV.mm-1;介电损耗最低、耐压强度最大的配方为:0.96(Ba0.45Sr0.4Ca0.15)TiO3.0.04(Bi2O3.3TiO2)其性能为:rε=2089,tanδ=6×10-4,Eb=16.9 kV.mm-1。     

在无铅环境中的热风整平

当电子工业走向无铅焊接的时候,热风焊料整平仍然是继续可焊性保护的优选方法。     

Effect of silver content on thermal fatigue life of Sn-xAg-0.5Cu flip-chip interconnects

The thermal fatigue properties of Sn-xAg-0.5Cu (x=1, 2, 3, and 4 in mass%) flip-chip interconnects were investigated to study the effect of silver content on thermal fatigue endurance. The solder joints with lower silver context (x=1 and 2) had a greater failure rate compared to those with higher silver content (x=3 and 4) in thermal fatigue testing. Cracks developed in the solders near the solder/chip interface for all joints tested. This crack propagation may be mainly governed by the nature of the solders themselves because the strain-concentrated area was similar for tested alloys independent of the silver content. From the microstructural observation, the fracture was a mixed mode, transgranular and intergranular, independent of the silver content. Higher silver content alloys (x=3 and 4) had finer Sn grains before thermal cycling according to the dispersion of the Ag₃Sn intermetallic compound, and even after the cycling, they suppressed microstructural coarsening, which degrades the fatigue resistance. The fatigue endurance of the solder joints was strongly correlated to the silver content, and solder joints with higher silver content had better fatigue resistance.     

Low-cycle fatigue prediction model for pb-free solder 96.5Sn-3.5Ag

Low-cycle fatigue (LCF) data of Sn-Ag eutectic solder (96.5Sn-3.5Ag) under various temperatures and frequencies has been described using three different prediction models, i.e., Coffin-Manson model, Smith-Watson-Topper (SWT) model, and Morrow energy model. The LCF behavior represented by the present prediction models showed temperature and frequency dependences, i.e., the fatigue ductility coefficient increased with increasing frequency and decreasing temperature. In order to better correlate the LCF data, a flow stress and/or frequency-dependent modifications were introduced to the Coffin-Manson and Morrow energy models. The frequency-modified Coffin-Manson model could not describe the influence of temperature on LCF behavior, while the flow stress-modified frequency-modified Morrow energy model, into which the metallurgical response (flow stress and frequency) was introduced to account for the effect of temperature and frequency on LCF behavior, gave reasonable predictions of LCF data under various temperatures and frequencies.