Subjects -> METALLURGY (Total: 59 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 2)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 12)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Advanced Joining Processes     Open Access  
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 7)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 42)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research & Technology     Full-text available via subscription  
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 3)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 35)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 7)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 8)
Soldering & Surface Mount Technology     Hybrid Journal   (Followers: 2)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 8)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Soldering & Surface Mount Technology
Journal Prestige (SJR): 0.399
Citation Impact (citeScore): 1
Number of Followers: 2  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0954-0911 - ISSN (Online) 1758-6836
Published by Emerald Homepage  [362 journals]
  • Impact of thermal interface material on luminous flux curve of InGaAlP
           low-power light-emitting diodes
    • Authors: Muna E. Raypah, Mutharasu Devarajan, Shahrom Mahmud
      Abstract: One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-03-08
      DOI: 10.1108/SSMT-10-2020-0040
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Role of aging temperature on thermomechanical fatigue lifetime of solder
           joints in electronic systems
    • Authors: Waluyo Adi Siswanto, Kirill Borodin, Zaid Hamid Mahmoud, A. Surendar, Sami Sajjadifar, Galiya Abdilova, Jun Chang
      Abstract: The purpose of this study is to investigate the effect of aging temperature on the barrel-type solder joint lifetime of electronic devices and to include these effects in the modified prediction model. Several accelerated shear stress tests under different stress amplitudes and aging temperatures were performed. It was found that by aging temperature increasing, the lifetime decreases. Morrow energy model was also found as the best prediction model when the aging temperature is taken into consideration. It is confirmed.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-03-01
      DOI: 10.1108/SSMT-07-2020-0029
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Interfacial reaction between Ni particle reinforcements and liquid
           Sn-based eutectic solders
    • Authors: Chung-Yung Lin
      Abstract: This paper aims to derive a model of growth kinetics of the intermetallic compound (IMC) layer formed in the reaction between liquid Sn-based solders and Ni particle reinforcements and to compare with the experimental data to verify the effects of Sn concentration and alloying element. A composite solder was manufactured by mechanically introducing Ni particle reinforcements into a solder matrix. The effect of the non-reactive alloying elements, Ag, Pb and Bi, on the growth kinetics of the IMC formed between liquid Sn-based eutectic solders and Ni particles, reacting this composite solder at 250°C–280°C was studied. Experimental results showed that only the IMC Ni3Sn4 was present as a reaction product. Using the diffusion-controlled reaction mechanism, a kinetic equation quantifying both Sn concentration and alloying element effects was derived and verified by comparing the kinetic data obtained using four different solders with different concentrations of Sn and the alloying elements. The similarity between the activation energies of these four solders confirms that the diffusion of Sn atoms through the IMC is the rate-controlling step. Besides, the kinetic values are independent of the geometry of Ni, whether spherical particle or flat substrate.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-02-15
      DOI: 10.1108/SSMT-10-2020-0046
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Reliability analysis of SnAgCu lead-free solder thermal interface
           materials in microelectronics
    • Authors: Mathias Ekpu
      Abstract: In microelectronics industry, the reliability of its components is a major area of concern for engineers. Therefore, it is imperative that such concerns are addressed by using the most reliable materials available. Thermal interface materials (TIMs) are used in electronic devices to bridge the topologies that exists between a heat sink and the flip chip assembly. Therefore, this study aims to investigate the reliability of SAC405 and SAC396 in a microelectronics assembly. In this paper, SnAgCu solder alloys (SAC405 and SAC396) were used as the TIMs. The model, which comprises the chip, TIM and heat sink base, was developed with ANSYS finite element analysis software and simulated under a thermal cycling load of between −40°C and 85°C. The results obtained from this paper were based on the total deformation, stress, strain and fatigue life of the lead-free solder materials. The analyses of the results showed that SAC405 is more reliable than SAC396. This was evident in the fatigue life analysis where it was predicted that it took about 85 days for SAC405 to fail, whereas it took about 13 days for SAC396 to fail. Therefore, SAC405 is recommended as the TIM of choice compared to SAC396 based upon the findings of this investigation. This paper is centred on SnAgCu solders used as TIMs. This paper demonstrated that SAC405 is a reliable solder TIM. This can guide manufacturers of electronic products in deciding which SAC solder to apply as TIM during the assembly process.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-02-08
      DOI: 10.1108/SSMT-07-2020-0033
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Influence of ultrasounds on interfacial microstructures of Cu-Sn solder
    • Authors: Xu Han, Xiaoyan Li, Peng Yao, Dalong Chen
      Abstract: This study aims to investigate the interfacial microstructures of ultrasonic-assisted solder joints at different soldering times. Solder joints with different microstructures are obtained by ultrasonic-assisted soldering. To analyze the effect of ultrasounds on Cu6Sn5 growth during the solid–liquid reaction stage, the interconnection heights of solder joints are increased from 30 to 50 μm. Scallop-like Cu6Sn5 nucleate and grow along the Cu6Sn5/Cu3Sn interface under the traditional soldering process. By comparison, some Cu6Sn5 are formed at Cu6Sn5/Cu3Sn interface and some Cu6Sn5 are randomly distributed in Sn when ultrasonic-assisted soldering process is used. The reason for the formation of non-interfacial Cu6Sn5 has to do with the shock waves and micro-jets produced by ultrasonic treatment, which leads to separation of some Cu6Sn5 from the interfacial Cu6Sn5 to form non-interfacial Cu6Sn5. The local high pressure generated by the ultrasounds promotes the heterogeneous nucleation and growth of Cu6Sn5. Also, some branch-like Cu3Sn formed at Cu6Sn5/Cu3Sn interface render the interfacial Cu3Sn in ultrasonic-assisted solder joints present a different morphology from the wave-like or planar-like Cu3Sn in conventional soldering joints. Meanwhile, some non-interfacial Cu3Sn are present in non-interfacial Cu6Sn5 due to reaction of Cu atoms in liquid Sn with non-interfacial Cu6Sn5 to form non-interfacial Cu3Sn. Overall, full Cu3Sn solder joints are obtained at ultrasonic times of 60 s. The obtained microstructure evolutions of ultrasonic-assisted solder joints in this paper are different from those reported in previous studies. Based on these differences, the effects of ultrasounds on the formation of non-interfacial IMCs and growth of interfacial IMCs are systematically analyzed by comparing with the traditional soldering process.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-01-25
      DOI: 10.1108/SSMT-06-2020-0026
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Effect of Zn-powder content on the property of Cu/SAC0307 powder/Cu joint
           under ultrasonic assisted at low temperature
    • Authors: Gui-sheng Gan, Liujie Jiang, Shiqi Chen, Yongqiang Deng, Donghua Yang, Zhaoqi Jiang, Huadong Cao, Mizhe Tian, Qianzhu Xu, Xin Liu
      Abstract: Low-Ag SAC solder will lead to a series of problems, such as increased the melting range and declined the solderability and so on. These research studies do not have too much impact on the improvement of solders’ performance but were difficult to achieve satisfactory results. It is urgent to develop new soldering technology to avoid the bottleneck of lead-free solder. low-temperature-stirring soldering and ultrasonic-assisted soldering was developed in the authors’ early work, but slag inclusion and pore would gather and grow up to lead decreasing of the shear strength. In this paper, Cu/SAC0307 +Zn power/Cu joints with ultrasonic-assisted at low-temperature was successfully achieved. 45um Zn-powder and SAC0307 No.4 solder powder were mixed to fill the Cu-Cu joint, and the content of Zn-powder were 0 and 5%, 7.5% and 10%, 12.5% and 15% respectively. During the soldering process under ambient atmosphere %252C the heating platform provided a constant 220%253 F and the ultrasonic vibrator applied a constant pressure of 4 MPa to the copper substrate. The soldering process was completed after holding 70 s at 300 W. The Zn particles made the IMC at the joint interface and in the soldering seam from scallop-type Cu6Sn5 to flat-type Cu5Zn8. The shear strength of joints without Zn was only 12.43 MPa, the shear strength of joints with 10% Zn reached a peak of 34.25 MPa, and the shear strength of joints containing 10% Zn was 63.71% higher than that of joints without zinc particles, and then the shear strength decreased. In addition, with the increase of zinc content, the fracture mode of the joint changed from the brittle fracture of the original layered tears to the mixed tough and brittle fracture. A new method that Zn micron-size powders and SAC0307 micron-size powders was mixed to fill the joint, and successfully achieved micro-joining of Cu/Cu under ultrasonic-assisted without flux at low-temperature.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-01-13
      DOI: 10.1108/SSMT-08-2020-0035
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Life prediction in c-Si solar cell interconnections under in-situ thermal
           cycling in Kumasi in Ghana
    • Authors: Frank Kwabena Afriyie Nyarko, G. Takyi
      Abstract: A numerical study on the reliability of soldered interconnects of c-Si solar photovoltaic cells has been conducted. A three-year data (2012–2014) from outdoor weathering of PV modules was used to generate temperature cycle profiles to serve as thermal loads and boundary conditions for the investigation of the thermo-mechanical response of the soldered interconnects when subjected to real outdoor conditions using finite element analysis (FEA) Software (Ansys. 18.2). Two types of soldered interconnections, namely, Sn60Pb40 and Sn3.8Ag0.7Cu (Pb-free), were modelled in this study. Life prediction results from accumulated creep energy density damage show that the solder interconnects will achieve maximum life under the 2014 thermal cycle loading. In particular, the Sn60Pb40 solder interconnection is expected to achieve 14,153 cycles (25.85 years) whilst the Pb-free solder interconnection is expected to achieve 9,249 cycles (16.89 years). Additionally, under the test region average (TRA) thermal cycle, the Pb-free and Pb-Sn solder interconnections are expected to achieve 7,944 cycles (13.69 years) and 12,814 cycles (23.4 years), respectively. The study shows that Sn60Pb40 solder interconnections are likely to exhibit superior reliability over the Pb-free solder interconnections at the test site. This study would be useful to electronics manufacturing industry in the search for a suitable alternative to SnPb solders and also the thermo-mechanical reliability research community and manufacturers in the design of robust PV modules. The study has provided TRA data/results which could be used to represent the test region instead of a particular year. The study also indicates that more than six thermal cycles are required before any meaningful conclusions can be drawn. Finally, the life of the two types of solders (SnPb and Pb-free) as interconnecting materials for c-Si PV have been predicted for the test region (Kumasi in sub-Saharan Africa).
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-01-11
      DOI: 10.1108/SSMT-10-2020-0045
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2021)
  • Property of Sn-37Pb solder bumps with different diameter during thermal
    • Authors: Guisheng Gan, Donghua Yang, Yi-ping Wu, Xin Liu, Pengfei Sun, Daquan Xia, Huadong Cao, Liujie Jiang, Mizhe Tian
      Abstract: The impact strength of solder joint under high strain rate was evaluated by board level test method. However, the impact shear test of single solder bump was more convenient and economical than the board level test method. With the miniaturization of solder joints, solder joints were more prone to failure under thermal shock and more attention has been paid to the impact reliability of solder joint. But Pb-free solder joints may be paid too much attention and Sn-Pb solder joints may be ignored. In this study, thermal shock test between −55°C and 125°C was conducted on Sn-37Pb solder bumps in the BGA package to investigate microstructural evolution and growth mechanism of interfacial intermetallic compounds (IMCs) layer. The effects of thermal shock and ball diameter on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed. With the increase of ball size, the same change tendency of shear strength with thermal shock cycles. The shear strength of the solder bumps was the highest after reflow; with the increase of the number of thermal shocks, the shear strength of the solder bumps was decreased. But at the time of 2,000 cycles, the shear strength was increased to the initial strength. Minimum shear strength almost took place at 1,500 cycles in all solder bumps. The differences between maximum shear strength and minimum shear strength were 9.11 MPa and 16.83 MPa, 17.07 MPa and 15.59 MPa in φ0.3 mm and φ0.4 mm, φ0.5 mm and φ0.6 mm, respectively, differences were increased with increasing of ball size. With similar reflow profile, the thickness of IMC decreased as the diameter of the ball increased. The thickness of IMC was 2.42 µm and 2.17 µm, 1.63 µm and 1.77 µm with increasing of the ball size, respectively. Pb-free solder was gradually used to replace traditional Sn-Pb solder and has been widely used in industry. Nevertheless, some products inevitably used a mixture of Sn-Pb and Pb-free solder to make the transition from Sn-Pb to Pb-free solder. Therefore, it was very important to understand the reliability of Sn-Pb solder joint and more further research works were also needed.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2021-01-14
      DOI: 10.1108/SSMT-12-2019-0046
      Issue No: Vol. 33, No. 2 (2021)
  • Useful lifetime estimation of solder joints in power semiconductors
           employed in current source and voltage source inverters
    • Authors: Hao Zou, Fang Xie, Bo Du, G. Kavithaa
      Abstract: The purpose of this paper is to find the optimum inverter type as the solder joint reliability point of view. In this paper, finite element model(ing) simulations supported with power cycling aging experiments were used to demonstrate the best inverter type as the solder joint reliability point of view. It was found that inverter types highly affect the solder joint health during its nominal operating. The authors confirm the originality of this paper.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-12-28
      DOI: 10.1108/SSMT-05-2020-0018
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Optimized cerium addition for microstructure and mechanical properties of
    • Authors: Riaz Muhammad, Umair Ali
      Abstract: This paper aims to analyze the effect of cerium addition on the microstructure and the mechanical properties of Tin-Silver-Copper (SAC) alloy. The mechanical properties and refined microstructure of a solder joint are vital for the reliability and performance of electronics. SAC305 alloys are potential choices to use as lead-free solders because of their good properties as compared to the conventional Tin-Lead solder alloys. However, the presence of bulk intermetallic compounds (IMCs) in the microstructure of SAC305 alloys affects their overall performance. Therefore, addition of cerium restrains the growth of IMCs and refines the microstructure, hence improving the mechanical performance. SAC305 alloy is doped with various composition of xCerium (x = 0.15, 0.35, 0.55, 0.75, 0.95) % by weight. Pure elements in powdered form were melted in the presence of argon with periodic stirring to ensure a uniform melted alloy. The molten alloy is then poured into a pre-heated die to obtain a tensile specimen. The yield strength and universal tensile strength were determined using a fixed strain rate of 10 mm per minute or 0.1667 mm s^(−1). The IMCs are identified using X-ray diffraction, whereas the elemental phase composition and microstructure evolution are, respectively, examined by using electron dispersive spectroscopy and scanning electron microscopy. Improvement in the microstructure and mechanical properties is observed with 0.15% of cerium additions. The tensile test also showed that SAC305-0.15% cerium exhibits more stress-bearing capacity than other compositions. The 0.75% cerium doped alloy indicated some improvement because of a decrease in fracture dislocation regions, but microstructure refinement and the arrangement of IMCs are not those of 0.15% Ce. Different phases of Cu_6 Sn_5, Ag_3 Sn and CeSn_3 and ß-Sn are identified. Therefore, the addition of cerium in lower concentrations and presence of Ce-Sn IMCs improved the grain boundary structure and resulted refinement in the microstructure of the alloy, as well as an enhancement in the mechanical properties. Characterization of microstructure and evaluation of mechanical properties are carried out to investigate the different composition of SAC305-xCerium alloys. Finally, an optimized cerium composition is selected for solder joint in electronics.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-11-16
      DOI: 10.1108/SSMT-03-2020-0010
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Thermomechanical fatigue lifetime evaluation of solder joints in power
           semiconductors using a novel energy based modeling
    • Authors: Buen Zhang, Noor H. Jabarullah, Ayad F. Alkaim, Svetlana Danshina, Irina V. Krasnopevtseva, Yuan Zheng, Nisith Geetha
      Abstract: This paper aims to establish a more accurate model for lifetime estimation. Finite element model simulation and experimental tests are used to enhance the lifetime prediction model of the solder joint. A more precise model was found. It is confirmed that the paper is original.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-11-16
      DOI: 10.1108/SSMT-06-2020-0028
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • An investigation on mechanical random vibration fatigue damage of solder
           joints in electronic systems
    • Authors: Feng Wang, Fangfang Zhang, Qixiang Huang, Mohammad Salmani
      Abstract: The purpose of this paper is to propose a method with capability of short-time implementation. This paper was directed using both experimental tests and simulations to propose a comprehensive method for lifetime estimation of the solder joints. A new method with good agreement with experimental tests has been proposed. It is confirmed that paper is original.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-11-11
      DOI: 10.1108/SSMT-07-2020-0031
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Thermal-mechanical reliability analysis of WLP with fine-pitch copper post
    • Authors: Haiyan Sun, Bo Gao, Jicong Zhao
      Abstract: This study aims to investigate the several parameters in wafer-level packaging (WLP) to find the most critical factor impacting the thermal fatigue life, such as the height of copper post, the height of solder bump, the thickness of chip. The FEA results indicate the height of solder bumps is the most important factor in the whole structure. The copper post bumps with 65 µm pitch are proposed to investigate the thermal-mechanical performance of WLP. The thermal cycle simulation is used to evaluate the reliability of WLP by using finite element analysis (FEA). Taguchi method is adopted to obtain the sensitivity of parameters of three-dimension finite element model, for an optimized configuration. It can be found that the optimal design has increased thermal fatigue life by 147% compared with the original one. It is concluded that the finite element simulation results show outstanding thermal-mechanical performances of the proposed 65 µm pitch copper post bumps of WLP, including low plastic strain, high thermal fatigue life, which are desired for mobile device.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-11-02
      DOI: 10.1108/SSMT-06-2020-0027
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Effect of Sb additions on the creep behaviour of low temperature lead-free
           Sn–8Zn–3Bi solder alloy
    • Authors: Guang Ren, Maurice Collins
      Abstract: This paper aims to investigate the creep behaviour of the recently developed Sn–8Zn–3Bi–xSb (x = 0, 0.5, 1.0 and 1.5) low temperature lead-free solder alloys. An in-house compressive test rig was developed to perform creep tests under stresses of 20–40 MPa and temperature range 25°C–75 °C. Dorn power law and Garofalo hyperbolic sine law were used to model the secondary creep rate. High coefficient of determination R2 of 0.99 is achieved for both the models. It was found that the activation energy of Sn–8Zn–3Bi solder alloy can be significantly increased with addition of Sb, by 60% to 90 kJ/mol approximately, whereas the secondary creep exponent falls in the range 3–7. Improved creep resistance is attributed to solid solution strengthening introduced by micro-alloying. Creep mechanisms that govern the deformation of these newly developed lead-free solder alloys have also been proposed. The findings are expected to fill the gap of knowledge on creep behaviour of these newly developed solder alloys, which are possible alternatives as lead-free interconnecting material in low temperature electronic assembly.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-10-26
      DOI: 10.1108/SSMT-05-2020-0023
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Cleaning control of stencil printing subject to performance deterioration
    • Authors: Rui Xi, Jiangyou Yu, Le Cao, Xiaojiang Zheng, Jun Guo
      Abstract: Most solder paste printers are configured to periodically clean the stencil to maintain printing quality. However, a periodical cleaning control may result in excessive cleaning operations. The purpose of this paper is to develop a control method to schedule stencil cleaning operations appropriately. A hybrid failure rate model of the stencil printing process with age reduction factor and failure rate increase factor is presented. A stencil cleaning policy based on system reliability is introduced. An optimization model used to derive the optimal stencil cleaning schedule is provided. An aperiodic stencil cleaning control with good adaptability is achieved. A comparative analysis indicates that aperiodic control has better printing system reliability than traditional periodical control under the same cleaning resource consumption. Periodical cleaning control commonly used in industrial printing process often results in excessive cleaning operations. By incorporating the printing system reliability, this paper develops an aperiodic stencil cleaning control method based on hybrid failure rate model of the stencil printing process. It helps to reduce unnecessary cleaning operations while keeping printing quality stable.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-09-21
      DOI: 10.1108/SSMT-12-2019-0043
      Issue No: Vol. ahead-of-print, No. ahead-of-print (2020)
  • Application of multi-quality parameter design in the optimization of
           underfilling process – a case study of a vehicle electronic module
    • Authors: Chien-Yi Huang, Li-Cheng Shen, Ting-Hsuan Wu, Christopher Greene
      Abstract: This paper aims to discuss the key factors affecting the quality characteristics, such as the number of solder balls, the spread distance of residual underfill and the completion time of the underfilling. The Taguchi method is applied to configure the orthogonal table and schedule and execute the experiment. In addition, principal components analysis is used to obtain the points. Then, based on gray relational analysis and the technique for order preference by similarity to ideal solution, the closeness between each quality characteristic and the ideal solution is adopted as the basis for evaluating the quality characteristics. The optimal parameter combination is proposed, which includes 4 dispensing (11 mg/dispensing), a “half flow” interval state, 80°C preheating module PCB board and an L-shaped dispensing path and verification testing is performed. For vehicles and handheld electronic products, solder joints that connect electronic components to printed circuit boards may be cracked due to collision, vibration or falling. Consequently, solder balls are closely surrounded and protected by the underfill to improve joint strength and resist external force factors, such as collision and vibration. This paper addresses the defects caused during the second reflow process of a vehicle electronic communication module after the underfilling process.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-10-08
      DOI: 10.1108/SSMT-05-2020-0016
      Issue No: Vol. 33, No. 2 (2020)
  • An investigation on function of current type on solder joint degradation
           in electronic packages
    • Authors: Wenhui Cai, Fei Huang, Kai Liu, Mohammed Alaazim
      Abstract: As in real applications several alternating current (AC) currents may be injected to the electronic devices, this study aims to analyze their effects on the lifetime of the solder joints and, consequently, shed the light on these effects at the design phase for other researchers to consider. In this paper, the authors investigated on current waveform shapes on the performance and reliability of the solder joints in electronic package. Three common and extensively used current shapes in several simulations and experiments were selected to study their effects on the solder joint performance. The results demonstrate a sever thermal swing and stress fluctuation in the solder joint induced in the case of triangle current type because the critical states lack any relaxation time. In fact, the stress intensification in the solder under application of the triangle current type has been shown to contribute to increasing brittle intermetallic compounds. An accelerated increase of on-state voltage of power semiconductor was also observed in under application of the triangle current type. The originality of this paper is confirmed.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-09-23
      DOI: 10.1108/SSMT-06-2020-0025
      Issue No: Vol. 33, No. 2 (2020)
  • Spatial analysis of underfill flow in flip-chip encapsulation
    • Authors: Fei Chong Ng, Mohd Hafiz Zawawi, Mohamad Aizat Abas
      Abstract: The purpose of the study is to investigate the spatial aspects of underfill flow during the flip-chip encapsulation process, for instance, meniscus evolution and contact line jump (CLJ). Furthermore, a spatial-based void formation mechanism during the underfill flow was formulated. The meniscus evolution of underfill fluid subtended between the bump array and the CLJ phenomenon were visualized numerically using the micro-mesh unit cell approach. Additionally, the meniscus evolution and CLJ phenomenon were modelled analytically based on the formulation of capillary physics. Meanwhile, the mechanism of void formation was explained numerically and analytically. Both the proposed analytical and current numerical findings achieved great consensus and were well-validated experimentally. The variation effects of bump pitch on the spatial aspects were analyzed and found that the meniscus arc radius and filling distance increase with the pitch, while the subtended angle of meniscus arc is invariant with the pitch size. For larger pitch, the jump occurs further away from the bump entrance and takes longer time to attain the equilibrium meniscus. This inferred that the concavity of meniscus arc was influenced by the bump pitch. On the voiding mechanism, air void was formed from the air entrapment because of the fluid-bump interaction. Smaller voids tend to merge into a bigger void through necking and, subsequently, propagate along the underfill flow. The microscopic spatial analysis of underfill flow would explain fundamentally how the bump design will affect the macroscopic filling time. This not only provides alternative visualization tool to analyze flow pattern in the industry but also enables the development of accurate analytical filling time model. Moreover, the void formation mechanism gave substantial insights to understand the root causes of void defects and allow possible solutions to be formulated to tackle this issue. Additionally, the microfluidics sector could also benefit from these spatial analysis insights. Spatial analysis on underfill flow is scarcely conducted, as the past research studies mainly emphasized on the temporal aspects. Additionally, this work presented a new mechanism on the void formation based on the fluid-bump interaction, in which the formation and propagation of micro-voids were numerically visualized for the first time. The findings from current work provided fundamental information on the flow interaction between underfill fluid and solder bump to the package designers for optimization work and process enhancement.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-09-05
      DOI: 10.1108/SSMT-05-2020-0017
      Issue No: Vol. 33, No. 2 (2020)
  • The formation of intermetallic layer structure of SAC405/Cu and
           SAC405/ENImAg solder joint interfaces
    • Authors: Rabiatul Adawiyah Mohamed Anuar, Saliza Azlina Osman
      Abstract: The surface finish is an essential step in printed circuit boards design because it provides a solderable surface for electronic components. The purpose of this study to investigate the effects of different surface finishes during the soldering and ageing process. The solder joints of Sn-4.0Ag-0.5Cu/Cu and Sn-4.0Ag-0.5Cu/electroless nickel/immersion silver (ENImAg) were investigated in terms of intermetallic (IMC) thickness, morphology and shear strength. The microstructure and compositions of solder joints are observed, and analyzed by using scanning electron microscopy (SEM-EDX) and optical microscope (OM). Compounds of Cu6Sn5 and (Cu, Ni)6Sn5 IMC were formed in SAC405/Cu and SAC405/ENImAg, respectively, as-reflowed. When the sample was exposed to ageing, new layers of Cu3Sn and (Ni, Cu)3Sn5 were observed at the interface. Analogous growth in the thickness of the IMC layer and increased grains size commensurate with ageing time. The results equally revealed an increase in shear strength of SAC405/ENImAg because of the thin layer of IMC and surface finish used compared to SAC405/Cu. Hence, a ductile fracture was observed at the bulk solder. Overall, the ENImAg surface finish showed excellent performance of solder joints than that of bare Cu. The novel surface finish (ENImAg) has been developed and optimized. This alternative lead-free surface finish solved the challenges in electroless nickel/immersion gold and reduced cost without affecting the performance.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-07-14
      DOI: 10.1108/SSMT-03-2019-0009
      Issue No: Vol. 33, No. 2 (2020)
  • An experimental study of carbonyl powder power inductor cracking during
           reflow process
    • Authors: Faisal Rehman, Rafiq Asghar, Kashif Iqbal, Ali Aman, Agha Ali Nawaz
      Abstract: In surface mount assembly (SMA) process, small components are subjected to high temperature variations, which result in components’ deformation and cracking. Because of this phenomenon, cracks are formed in the body of carbonyl powder ceramic inductor (CPCI) in the preheat and cooling stages of the reflow oven. These cracks become the main cause of board failure in the ageing process. The purpose of this paper is to ascertain the thermal stress, thermal expansion of carbonyl iron ceramics and its effects on crack commencement and proliferation in the preheat stage of reflow oven. Moreover, this paper also categorized and suggested important parameters of reflow profile that could be used to eliminate these thermal shock failures. In this paper, two different reflow profiles were studied that evaluate the thermal shock of CPCI during varying ΔT at the preheat zone of the reflow oven. In the first profile, the change in temperature ΔT at preheat zone was set to 3.26°C/s, which has resulted in a number of device failures because of migration of micro cracks through the CPCI. In the second profile, this ΔT at preheat stage is minimized to 2.06°C/s that eliminated the thermal stresses; hence, the failure rates were significantly reduced. TMPC0618H series lead (Pb)-free CPCI is selected for this study and its thermal expansion and thermal shock are observed in the reflow process. It is inferred from the results that high ΔT at preheat zone generates cracks in the carbonyl powder-type ceramics that cause device failure in the board ageing process. Comparing materials, carbonyl powder ceramic components are less resistant to thermal shock and a lower rate of temperature change is desirable. The proposed study presents an experimental analysis for mitigating the thermal shock defects. The realization of the proposed approach is validated with experimental data from the printed circuit boards manufacturing process.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-07-14
      DOI: 10.1108/SSMT-10-2019-0033
      Issue No: Vol. 33, No. 2 (2020)
  • Automatic optical inspection system for IC solder joint based on
           local-to-global ensemble learning
    • Authors: Wenjie Chen, Nian Cai, Huiheng Wang, Jianfa Lin, Han Wang
      Abstract: Automatic optical inspection (AOI) systems have been widely used in many fields to evaluate the qualities of products at the end of the production line. The purpose of this paper is to propose a local-to-global ensemble learning method for the AOI system based on to inspect integrated circuit (IC) solder joints defects. In the proposed method, the locally statistically modeling stage and the globally ensemble learning stage are involved to tackle the inspection problem. At the former stage, the improved visual background extraction–based algorithm is used for locally statistically modeling to grasp tiny appearance differences between the IC solder joints to achieve potential defect images for the subsequent stage. At the latter stage, mean unqualified probability is introduced based on a novel ensemble learning, in which an adaptive weighted strategy is proposed for revealing different contributions of the base classifier to the inspection performance. Experimental results demonstrate that the proposed method achieves better inspection performance with an acceptable inspection time compared with some state-of-the-art methods. The approach is a promising method for IC solder joint inspection, which can simultaneously grasp the local characteristics of IC solder joints and reveal inherently global relationships between IC solder joints.
      Citation: Soldering & Surface Mount Technology
      PubDate: 2020-07-09
      DOI: 10.1108/SSMT-03-2020-0011
      Issue No: Vol. 33, No. 2 (2020)
  • Soldering & Surface Mount Technology
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Heriot-Watt University
Edinburgh, EH14 4AS, UK
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