Papers by Keyword: Solder Joint

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Authors: Yong Cheng Lin, Xu Chen, Xing Shen Liu, Guo Quan Lu
Abstract: The reliability of solder joints in flip chip assemblies with both compliant (flex) and rigid (PCB) substrates was studied by accelerated temperature cycling tests and finite element modeling (FEM). In-process electrical resistance measurements and nondestructive evaluations were conducted to monitor solder joint failure behavior, hence the fatigue failure life. Meanwhile, the predicted fatigue failure life of solder joints was obtained by Darveaux’s crack initiation and growth models. It can be concluded that the solder joints in flip chip on flex assembly (FCOF) have longer fatigue life than those in flip chip on rigid board assembly (FCOB); the maximum von Mises stress/strain and the maximum shear stress/strain of FCOB solder joints are much higher than those of FCOF solder joints; the thermal strain and stress in solder joints is reduced by flex buckling or bending and flex substrate could dissipate energy that otherwise would be absorbed by solder joint. Therefore, the substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during temperature cycling.
Authors: H.E. Fang, Chi Loong Chow, Fan Yang
Authors: Ling Feng Shi, Chen Meng, Yuan Ming Xiao, Li Ye Cheng, Cheng Shan Cai, Xin Quan Lai
Abstract: With the miniaturization of portable products, integrate circuit becomes thinner, the effect of warpage on Package-on-Package (POP) stacking assemble on integrate circuit have become more distinct. It will lead to the deformation of the chip substrate and the more serious effectiveness of the solder joint. Consequently, in this paper, a novel method by adding fixed metal pillars in the middle of POP stacking substrates can well suppress warpage problems caused by the uneven heating reflow materials. Finally, this new method is feasible by analyzing the stress of warp model.
Authors: Tung Han Chuang, Shiu Fang Yen
Abstract: In this study, 0.1~1.0 wt.% of pure Ce was added into a Sn3Ag0.5Cu solder alloy, resulting in the formation of precipitated CeSn3 clusters of a size greater than 20 1m in the reflowed solder matrix. After natural aging at room temperature for more than 3 days, oxidation on the surface of the CeSn3 clusters was much heavier than in the undoped Sn3Ag0.5Cu solder matrix. In addition, many tin whiskers with a diameter of about 0.1 to 0.3 μm had been squeezed out of the oxide layer of the CeSn3 precipitates. The increase in aging time at room temperature causes the tin whiskers to grow rapidly. The whiskers can grow even to a length of over 300 μm after 21 days of storage. The whisker growth rate in one particular case reached 8.6Å/s after room temperature storage for only one day. The whiskers formed during storage at a higher temperature (1500C have a coarse diameter of 1 to 3 μm. In some cases, high temperature storage results in the formation of short whiskers in a hillock shape with a diameter of about 5 to 10 μm.
Authors: Yong Cheng Lin, Yu Chi Xia
Abstract: More and more solder joints in circuit boards and electronic products are changing to lead free solder, placing an emphasis on lead free solder joint reliability. Solder joint fatigue failure is a serious reliability concern in area array technologies. In this study, the effects of substrate materials on the solder joint thermal fatigue life were investigated by finite element model. Accelerated temperature cycling loading was imposed to evaluate the reliability of solder joints. The thermal strain/stress in solder joints of flip chip assemblies with different substrates was compared, and the fatigue life of solder joints were evaluated by Darveaux’s crack initiation and growth model. The results show the mechanisms of substrate flexibility on improving solder joint thermal fatigue.
Authors: Yusuke Tomizawa, Takehito Suzuki, Katsuhiko Sasaki, Ken-Ichi Ohguchi, Daisuke Echizenya
Abstract: Recently, Halt (Highly accelerated limit test) is widely employed for evaluation of reliability of electronic products. Halt condition is quite severe. The tested products are subjected to mechanical impacts, thermal shock, and vibration at same time. However, there has not been a reasonable and accurate evaluation method for Halt yet. To construct an accurate evaluation method of Halt, basic deformation mechanism of parts of the electronic products should be clarified from both experimental and theoretical points of view. In this paper, focusing on solder joints of circuit boards of electronic products, ratchetting deformation, especially, biaxial ratchetting deformation of solder joints is revealed from both experimentally and theoretically. The authors have already conducted biaxial ratchetting test combining axial and torsional cyclic loading using a tubular specimen of Type 304 stainless steel. However, as for solders, it is difficult to make tubular specimen. Since size of the solder joints is micron, a small size joint specimen of copper tube and solder is employed in this paper. First, to confirm the quality of the joint specimen such as boundary between copper and solder, both the tensile and cyclic loading tests are conducted at several temperatures using Sn-3Ag-0.5Cu. The basic characteristic of tensile and fatigue failure is obtained from these tests. After the confirmation of the accuracy of the joint specimen, biaxial ratchetting tests are conducted superposing the tensile load on cyclic torsion. The biaxial ratchetting tests are conducted using a biaxial loading testing machine developed for the joint specimens of solder and copper.
Authors: Ouk Sub Lee, Man Jae Hur, Yeon Chang Park, Dong Hyeok Kim
Abstract: The difference in the Coefficient of Thermal Expansion (CTE) between the chip and the substrate generate thermal displacement in the solder joint. It seems to be a main cause of failure in the solder joint when the chip and the substrate are heated repeatedly. The failure of the solder joints by thermal fatigue is known to be influenced by varying boundary conditions such as the difference in CTE, the height of solder, the Distance of the solder joint from the Neutral Point (DNP) and the temperature variation. In this paper, the effects of varying boundary conditions on the failure probability of the solder joint are studied by using the probabilistic approach methods such as the First Order Reliability Method (FORM) and the Second Order Reliability Method (SORM).
Authors: Ning Zhang, Li Tian, Yao Wu Shi, Jian Lin, Yong Ping Lei, Hai Yan Zhao
Abstract: Using the interactive software, this study was mainly focused on developing a 3-D joint shape after the as-reflowed soldering which is the one of chief factors affecting the reliability. From the results, the soldering process can be simulated and observed directly. By changing the various conditions and constraints, such as surface tension, wetting angle and specific gravity, it makes a comparison between the simulated result and the experimental one. The simulated parameters are based on those of the traditional eutectic Sn-Pb solder. After slicing and comparing the different profiles of the simulated shape, the 3-D simulated geometry fits well with the experimental one.
Authors: T. Kumazawa, K. Kaminishi
Abstract: Deformation measurements with a thermocouple were applied in a deformation test of solder joints. The thermocouple is effectively combined with a conventional testing machine. The lead–solder and non–lead solder joints were pulled and sheared. The load-displacement and electromotive force (Emf)–displacement curves can be continuously derived from the signals of a load cell and the thermocouple. The Emfs in tension were compared with that in shear. The maximum Emf value in tension was larger than the emf value in shear, which meant in weakness of the solder joint in shear. Fracture occurred at the interface between the copper layer pad and solder, and the obtained Emf is closely related to fracture at the interface. The maximum Emf value in the non-lead solder was smaller than the Emf value in the lead–solder.
Authors: Hardinna Wirda Kahar, A.M. Zetty Akhtar, Siti Rabiatull Aisha Idris, Mahadzir Ishak
Abstract: This paper presents a study on relationship of cooling rates towards the intermetallic compound (IMC) morphology. Cooling rate is an important parameter as it has significant effect towards the IMC microstructure formation that indirectly affects solders joint reliability. However, there is still insufficient study regarding the effect of cooling rate on the IMC thickness and microstructure behavior by using Nickel Boron as surface finish material in the electronic packaging industry. In this study, Sn-3Ag-0.5Cu solder was used on Nickel Boron as coating layer. Cooling rates were obtained by cooling specimens in different media which is water and air. The elemental composition was confirmed using Energy-dispersive X-ray spectroscopy and the microstructure of each IMC then analyzed using optical microscope, image analyzer and ImageJ. In this study, faster cooling rate (water) found to provide thicker IMC (6μm) compared to the other medium used. The morphology shape of each IMC also differs between different medium of cooling. IMC that undergoes faster cooling showed continues like layer while the one using air cooling formed scallop like IMC.
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