Creep of thermally aged SnAgCu-solder joints

Technische Universität Dresden, Dresden, Saxony, Germany
Microelectronics Reliability (Impact Factor: 1.43). 02/2007; 47(2):223-232. DOI: 10.1016/j.microrel.2006.09.006
Source: DBLP


The creep behaviour of Sn96.5Ag3.5- and Sn95.5Ag3.8Cu0.7-solder was studied specifically for its dependence on technological and environmental factors. The technological factors considered were typical cooling rates and pad metallizations for solder joints in electronic packaging. The environmental factors included microstructural changes as a result of thermal aging of solder joints. Creep experiments were conducted on three types of specimens—flip–chip joints, PCB solder joints and bulk specimens. flip–chip specimens were altered through the selection of various under bump metallizations (Cu vs. NiAu), cooling rates (40 K/min vs. 120 K/min), and thermal storage (24 h, 168 h, and 1176 h at 125 °C). PCB solder joints were studied by using a copper pin soldered into a thru-hole connection on a printed circuit board having a NiAu metallization. Bulk specimens contained the pure alloys. The creep behaviour of the SnAg and SnAgCu solders varied in dependence of specimen type, pad metallization and aging condition. Constitutive models for SnAg and SnAgCu solders as they depend on the reviewed factors are provided.

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    • "The Ag– Cu–Sn tertiary system has been vastly employed in brazing and soldering processes due to high wettability, acceptable mechanical properties and environmentally friendly characteristics [19]. The 60Ag–30Cu– 10Sn interlayer that is employed in the current study has better baseline reliability under mechanical loads in real applications, has a relatively higher melting point than other Ag–Cu–Sn variants, minimizes the creeping effect [20]. It is also shown that the strength of joints with an interlayer can be further enhanced when subjected to a suitable post-joining heat treatment at an adequate temperature and duration. "
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    ABSTRACT: Joining cylindrical and bar-shaped components manufactured from dissimilar materials is frequently required in various industrial applications. The current study focuses on developing equal channel angular pressing (ECAP) as a severe plastic deformation process for solid state joining of tubular aluminium alloy 6061 components and SAE 1018 steel rods. The influence of using a 0.1 mm thick 60Ag-30Cu-10Sn interlayer in addition to annealing at 220, 320, 420 and 520 °C for 60 minutes is investigated as well. Finite element analysis (FEA) is performed in order to evaluate the deformation behaviour of the workpieces during the ECAP joining process. XRD and EDX analyses as well as nanoindentation and shear tests are carried out to evaluate the joints' characteristics. The FEA outcomes show remarkable accumulation of equivalent plastic strain with relatively low strain inhomogeneity. Moreover, the experimental results indicate that with increasing annealing temperature, joint strength exhibits improvement as well. It is also revealed that the application of an interlayer at any specific annealing temperature leads to achieving higher shear strength values. According to the results, shear strength of up to 32 MPa is feasible by having an interlayer and with subsequent annealing at 520 °C.
    Materials and Design 12/2015; 87. DOI:10.1016/j.matdes.2015.08.062 · 3.50 Impact Factor
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    • "For example the effect of pad geometry on tombstone effect [Huang, 2005], influences of the moisture absorption on PBGA package's warpage during reflow process [Chien, 2003], [Lee, 1998] and the creep behaviour of joints soldered with Vapour Phase reflow were studied [Wiese, 2007]. Besides, the effect of SnAgCu alloy composition on tombstoning during VP soldering was investigated by Huang et al. [Huang, 2005]. "
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    ABSTRACT: Purpose: The purpose of this paper is to compare the reliability and intermetallic layer (IML) of solder joints prepared with infrared (IR) and vapour phase (VP) soldering. The reliability of 0603-sized resistors' solder joints formed with IR and VP soldering was investigated. The IML of the joints was analysed based on image processing algorithm automatically. Design/methodology/approach: For the reliability analyses, the ageing method was a highly accelerated stress test (HAST) with +105°C maximum temperature, fully saturated (100 per cent) relative humidity at +0.5 atm overpressure. The joints were characterised based on the thickness of their IML and on their shear strength in as-reflowed stage, and after 400, 800, 1,200, 1,600 and 2,000 hours of HAST. An image processing algorithm was developed to measure the thickness of the IMLs on cross-sectional scanning electron microscopy (SEM) images automatically. Findings: The increase of the IML thickness is lower in the case of HAST ageing compared to other methods. The thickness increment of the Cu6Sn5 layer was higher for IR and lower for VP soldering; the Cu3Sn layer cannot be inspected even after 2,000 hours of HAST ageing. The results of shear strength measurements show better reliability for VP soldered joints. Practical implications: The developed image processing method is applicable to obtain quantitative results about the IMLs in an effective fast way. Originality/value: There is a lack of information in the literature regarding the reliability comparison of solder joints formed with VP and conventional reflow processes. Thus, we performed research about the lifetime of solder joints formed with VP and IR reflow method.
    Soldering and Surface Mount Technology 08/2014; 26(4-4):214-222. DOI:10.1108/SSMT-09-2013-0023 · 0.87 Impact Factor
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    ABSTRACT: This study points out the influence of cooling rate and solders composition on the microstructure of bulk SnAgCu. Therefore the alloys SnAg3.8Cu0.7, SnAg3.0Cu0.5 and SnAg3.5Cu0.4 were solidified with different cooling rates from 0.35 K/min to 37.4 K/min. During these experiments the temperature of the solder was measured. Changes in microstructure were investigated after thermal storage at 125degC, for 0.05 h, 0.5 h, 5 h, 50 h and 500 h. In an additional experiment a temperature gradient was generated inside different solder samples during solidification. The cross sections of these bulk samples indicate influence and dependence on phase growth, caused by this directed solidification. The chosen alloys, SnAg3.0Cu0.5, SnAg3.0Cu1.5 and SnAg3.0Cu0.5Au0.14 show effects on microstructure, caused by impurities like Au and Cu, which can solute from the PCB metallization during reflow. Another experiment shows the potential and the advantages of a new developed method for temperature measurements during the reflow process
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