Increasing global concern about the environment is bringing regulatory (European directives) and consumer ("green products") pressure on the electronics industry in Europe and Japan to reduce or completely elimi...Increasing global concern about the environment is bringing regulatory (European directives) and consumer ("green products") pressure on the electronics industry in Europe and Japan to reduce or completely eliminate the use of lead (Pb) in products. Among all lead-free solder alloys, SnAgCu solder system, which has better thermo-mechanical properties compared with those of SnPb solder, is proven to be one of the promising candidates for electronic assembly. Previous work also revealed that adding a small amount of rare earth Ce into SnAgCu solder can visibly improve the properties and inhibit the excessive growth of the intermetallic compound layer. Thermal fatigue properties of SnAgCuCe soldered joints in QFP devices under thermal conditions have been investigated by finite element method and experiments. Based on creep model of low stress and high stress, corresponding creep subroutine was established for simulating the stress and strain response of SnAgCuCe soldered joint from -55 ℃ to 125 ℃, and fatigue life was calculated using creep fatigue life prediction equation. Moreover, thermal cycling experiments were conducted, the experimental results were found to be close to the simulated results. In addition, the tensile force of SnAgCuCe soldered joints decreased with increasing number of thermal cycles, and the fracture mechanism transformed from toughness fracture to brittle intergranular fracture. Moreover the tensile force changes and fracture microstructure evolution could benefit the quantitative evaluations of the mechanical performances of lead-free soldered joints under thermal cycling loadings.展开更多
The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with...The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with Sn-Ag-Cu lead-free solder and Sn-Pb solder respectively,and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR-1000 micro-joints tester.The results indicate that sound QFP micro-joints without bridging or solder ball are gained by means of diode laser soldering method with appropriate laser processing parameters,and the pitch of the QFP devices is as fine as to 0.4mm.Tensile strength of QFP micro-joints increases gradually with the increase of laser output power,the maximum tensile strength presents when the laser output power increase to a certain value.The results also indicate that the mechanical properties of QFP micro-joints soldered by diode laser soldering system are better than those of QFP micro-joints soldered by IR reflow soldering method.The experimental results may provide a theory guide for investigation of diode laser soldering.展开更多
SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover...SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover, the SnAgCuCe solder alloys can provide good quality joints with Cu substrates. However, there is few report of the constitutive model for SnAgCu solder bearing micro-amounts rare earth Ce. In this paper, the unified viscoplastic constitutive model, Anand equations, is used to represent the inelastic deformation behavior for SnAgCu and SnAgCuCe solders. In order to obtain the acquired data for the fitting of the material parameters of this unified model, a series of experiments of constant strain rate test were conducted under isothermal conditions at different temperatures. The Anand parameters of the constitutive equations for SnAgCu and SnAgCuCe solder were determined from separated constitutive relations and experimental results. Nonlinear least-square fitting was selected to determine the model constants. And the simulated results were then compared with experimental measurements of the stress-inelastic strain curves: excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from 25℃ to 150 ℃, and the strain rate ranges from 0.01 s^-1 to 0.001 s ^-1. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress-strain response of lead free soldered joints. Based on the Anand model, the investigations of thermo-mechanical of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by finite element code were done under thermal cyclic loading, it is found that the reliability of SnAgCu soldered joints can be improved remarkably with addition of rare earth Ce. The results may provide a theory guide for developing constitutive model for lead-free solders.展开更多
介绍了X波段功率放大器封装外壳应用的特点及应用,选用了AlSi为外壳材料,镀金层以其良好的可焊接性和防腐性得到了广泛的应用,但镀层必须均匀、不变色、不起皮、不起泡,因此,必须对AlSi外壳材料的镀金质量严格控制。研究实验表明AlSi外...介绍了X波段功率放大器封装外壳应用的特点及应用,选用了AlSi为外壳材料,镀金层以其良好的可焊接性和防腐性得到了广泛的应用,但镀层必须均匀、不变色、不起皮、不起泡,因此,必须对AlSi外壳材料的镀金质量严格控制。研究实验表明AlSi外壳材料镀层的质量受材料制备粉末粒度的影响较大,试验中比较了粉末粒度为13. 19μm和4. 64μm的镀层形貌影响,当制备粉末粒度为13. 19μm时明显不均匀,出现断层,厚度较小,无法实现实用的镀层,而4. 64μm制备粉末的材料镀层则均匀镀层,厚度适中。其次在相同制备粉末粒度条件下,电镀电流密度对材料镀层质量也有一定的影响,当电镀电流密度为20 m A/cm^2时,可以实现相对比较均匀的镀层,并且镀层的缺陷较少,当把电流密度增加到25 m A/cm^2时,镀层明显不均匀,缺陷较多。研究结果表明采用4. 64μm制备粉末的材料、电镀电流密度为20 m A/cm^2时,AlSi外壳材料的镀层连续、完整,其焊接性测试结果满足MIL-STD-883的标准要求。研究结果为AlSi外壳材料的广泛应用提供了技术保障,对微波器件、组件的发展具有十分重要的意义。展开更多
基金supported by Nanjing University of Aeronautics and Astronautics Doctoral Dissertation Innovation and Excellence Producing Foundation of China (Grant No. BCXJ09-07)Jiangsu Provincial General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China (Grant No. CX09B_074Z)Jiangsu Provincial Six Kind Skilled Personnel Project of China (Grant No. 06-E-020)
文摘Increasing global concern about the environment is bringing regulatory (European directives) and consumer ("green products") pressure on the electronics industry in Europe and Japan to reduce or completely eliminate the use of lead (Pb) in products. Among all lead-free solder alloys, SnAgCu solder system, which has better thermo-mechanical properties compared with those of SnPb solder, is proven to be one of the promising candidates for electronic assembly. Previous work also revealed that adding a small amount of rare earth Ce into SnAgCu solder can visibly improve the properties and inhibit the excessive growth of the intermetallic compound layer. Thermal fatigue properties of SnAgCuCe soldered joints in QFP devices under thermal conditions have been investigated by finite element method and experiments. Based on creep model of low stress and high stress, corresponding creep subroutine was established for simulating the stress and strain response of SnAgCuCe soldered joint from -55 ℃ to 125 ℃, and fatigue life was calculated using creep fatigue life prediction equation. Moreover, thermal cycling experiments were conducted, the experimental results were found to be close to the simulated results. In addition, the tensile force of SnAgCuCe soldered joints decreased with increasing number of thermal cycles, and the fracture mechanism transformed from toughness fracture to brittle intergranular fracture. Moreover the tensile force changes and fracture microstructure evolution could benefit the quantitative evaluations of the mechanical performances of lead-free soldered joints under thermal cycling loadings.
基金supported by Nanjing University of Aeronautics and Astronautics Doctoral Dissertation Innovation and Excellence Producing Foundation of China (Grant No. BCXJ09-07)Jiangsu Provincial General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China (Grant No. CX09B_074Z)the Six Kind Skilled Personnel Project of Jiangsu Province of China(Grant No. 06-E-020)
文摘The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with Sn-Ag-Cu lead-free solder and Sn-Pb solder respectively,and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR-1000 micro-joints tester.The results indicate that sound QFP micro-joints without bridging or solder ball are gained by means of diode laser soldering method with appropriate laser processing parameters,and the pitch of the QFP devices is as fine as to 0.4mm.Tensile strength of QFP micro-joints increases gradually with the increase of laser output power,the maximum tensile strength presents when the laser output power increase to a certain value.The results also indicate that the mechanical properties of QFP micro-joints soldered by diode laser soldering system are better than those of QFP micro-joints soldered by IR reflow soldering method.The experimental results may provide a theory guide for investigation of diode laser soldering.
基金supported by Doctoral Dissertation Innovation and Excellence Producing Foundation of Nanjing University of Aeronautics and Astronautics,China(Grant No.BCXJ09-07)Jiangsu Provincial Six Kind Skilled Personnel Project of China(Grant No.06-E-020)Jiangsu General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China(Grant No.CX09B_074Z)
文摘SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover, the SnAgCuCe solder alloys can provide good quality joints with Cu substrates. However, there is few report of the constitutive model for SnAgCu solder bearing micro-amounts rare earth Ce. In this paper, the unified viscoplastic constitutive model, Anand equations, is used to represent the inelastic deformation behavior for SnAgCu and SnAgCuCe solders. In order to obtain the acquired data for the fitting of the material parameters of this unified model, a series of experiments of constant strain rate test were conducted under isothermal conditions at different temperatures. The Anand parameters of the constitutive equations for SnAgCu and SnAgCuCe solder were determined from separated constitutive relations and experimental results. Nonlinear least-square fitting was selected to determine the model constants. And the simulated results were then compared with experimental measurements of the stress-inelastic strain curves: excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from 25℃ to 150 ℃, and the strain rate ranges from 0.01 s^-1 to 0.001 s ^-1. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress-strain response of lead free soldered joints. Based on the Anand model, the investigations of thermo-mechanical of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by finite element code were done under thermal cyclic loading, it is found that the reliability of SnAgCu soldered joints can be improved remarkably with addition of rare earth Ce. The results may provide a theory guide for developing constitutive model for lead-free solders.
文摘介绍了X波段功率放大器封装外壳应用的特点及应用,选用了AlSi为外壳材料,镀金层以其良好的可焊接性和防腐性得到了广泛的应用,但镀层必须均匀、不变色、不起皮、不起泡,因此,必须对AlSi外壳材料的镀金质量严格控制。研究实验表明AlSi外壳材料镀层的质量受材料制备粉末粒度的影响较大,试验中比较了粉末粒度为13. 19μm和4. 64μm的镀层形貌影响,当制备粉末粒度为13. 19μm时明显不均匀,出现断层,厚度较小,无法实现实用的镀层,而4. 64μm制备粉末的材料镀层则均匀镀层,厚度适中。其次在相同制备粉末粒度条件下,电镀电流密度对材料镀层质量也有一定的影响,当电镀电流密度为20 m A/cm^2时,可以实现相对比较均匀的镀层,并且镀层的缺陷较少,当把电流密度增加到25 m A/cm^2时,镀层明显不均匀,缺陷较多。研究结果表明采用4. 64μm制备粉末的材料、电镀电流密度为20 m A/cm^2时,AlSi外壳材料的镀层连续、完整,其焊接性测试结果满足MIL-STD-883的标准要求。研究结果为AlSi外壳材料的广泛应用提供了技术保障,对微波器件、组件的发展具有十分重要的意义。