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... work [1] on mechanical studies of solder joints has demonstrated that mechanical failure of the joint does not happen in a sudden, catastrophic manner, but occurs as a gradual change, usually in the form of cracking. Typical cracking of a solder joint of a 2512-type chip resistor is illustrated in Figure 1. The work reported here has investigated the suitability of a number of these techniques to study cracking in lead-free solder joints, and hence their used in assessing joint lifetime. ...
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... the pull test (see Figures 11-13) a constant force of 100N was applied over 20 sec at a rate of 3.3 N/sec and held for 60 sec (Figure 14). The deformation was measured using a strain gauge (Figure 12) mounted on the top of a resistor. ...
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... the pull test (see Figures 11-13) a constant force of 100N was applied over 20 sec at a rate of 3.3 N/sec and held for 60 sec (Figure 14). The deformation was measured using a strain gauge (Figure 12) mounted on the top of a resistor. ...
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... the pull test (see Figures 11-13) a constant force of 100N was applied over 20 sec at a rate of 3.3 N/sec and held for 60 sec (Figure 14). The deformation was measured using a strain gauge (Figure 12) mounted on the top of a resistor. Figure 13 illustrates the primary deformation mode of the resistor-substrate system, as calculated using the FEA software tool PHYSICA [5]. ...
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... deformation was measured using a strain gauge (Figure 12) mounted on the top of a resistor. Figure 13 illustrates the primary deformation mode of the resistor-substrate system, as calculated using the FEA software tool PHYSICA [5]. The measurements indicate that the solder joint integrity goes through a deterioration phase, and that the top of the resistor is subjected to smaller compression stresses after a high number of cycles. ...
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... measurements indicate that the solder joint integrity goes through a deterioration phase, and that the top of the resistor is subjected to smaller compression stresses after a high number of cycles. As shown in Figure 14 the dependence of compression with time does not show the expected steady progression from unloaded (0 cycles) to fully loaded (1200 cycles). This is confirmed in Figure 15 with the non-linearity of the compression as a function of the number of cycles i.e. the compression increases after 1000 cycles for both SbAgCu and SnAg soldered joints. ...
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... shown in Figure 14 the dependence of compression with time does not show the expected steady progression from unloaded (0 cycles) to fully loaded (1200 cycles). This is confirmed in Figure 15 with the non-linearity of the compression as a function of the number of cycles i.e. the compression increases after 1000 cycles for both SbAgCu and SnAg soldered joints. This effect may be associated with the alignment of the specimen, the bonding of the strain gauge, and/or the small resistor joint area. ...
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... the 3-point bend test the force was applied to the substrate on the side opposite to that of the resistor (see Figures 16 and 17), and the substrate deformation was monitored and measured at the top of the resistor body. The extent of the deformation depends on the force exerted on the resistor through the solder joint. ...
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... extent of the deformation depends on the force exerted on the resistor through the solder joint. In Figure 18 the strain gauge measurements of deformation are plotted as a function of the assembly displacement at the mid point between the resistor's soldered joints. The test specimens had been soldered using SnAgCu alloy and had not been subjected to any thermal cycling. ...
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... issue, together with those associated with strain gauge attachment, means this test approach cannot be recommended for assessing cracking or solder joint lifetimes until further development has been undertaken. Figure 19 shows a comparison between the strain gauge measurement of deformation and a surface strain calculated using an FEA model based purely on elastic deformation. The two curves coincide for displacements less than ~125 µm. ...
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... 20 illustrates the layout and the direction of the forces on the assembly. The FEA model calculations were promising (see Figure 21), with a clear relationship showing the influence on the crack length of a theoretical compressive strain on the top-side of the resistor. However, this testing method was rejected as the simulation also highlighted that the practical test would cause further propagation of the cracks and a consequential peeling of the remaining solder joint, as illustrated schematically in Figure 22. ...
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... However, considering the other components, once again it can be said that the components will maintain their mechanical integrity for the expected life of 25 years. The measured shear values are comparable with similar research results reported in literature [7]. ...
Reliability is of increasing importance for electronics systems operating at harsh environments, such as the electronic telecommunication systems used at subsea level. The aim of this research was to investigate the reliability of such electronic systems through a simulated accelerated thermal cycle test. The paper presents a step-by-step process of designing accelerated thermal cycle test using field operating conditions. The Coffin-Mansion equation was used to calculate the accelerated factor for the thermal cycle test. In order to simulate the expected life time of 25 years, the solder assembly samples were subjected to 400 temperature cycles, with every cycle lasting for 40 minutes. Reliability was determined by measuring shear strengths of solder joints of different electronic components at set intervals. Although some of the components showed an initial decrease in shear strength, it was generally concluded that the electronic assemblies are able to maintain their shear strength for up to 25 years. The fracture surfaces of the solder joints, after shear testing, were also analyzed for brittle and ductile fractures, with the use of scanning electron microscopy (SEM).
... However, they used lead solder alloys and cylindrical test specimens, which are different from actual solder materials and shapes. In other previous studies, only oneshaped joint, either ball grid array or legged chip joint, was evaluated [5][6][7][8][9]. The fatigue life evaluation only for one shape of joint is not realistic because different stress states caused by various joint shapes affect the fatigue life of solder joints. ...
... Each of five different chips was mounted on a PCB, and a pair of grooves was made at the center of the specimen to cause stress concentration as shown in Fig. 1(b) [8]. In addition, a daisy chain was imbedded on the PCB to measure the resistance change at real time by using a data logger as shown in Fig. 1(c) [9,11]. The daisy chain was designed to be long enough from the chip not to cause any thermal damage to the chip when the daisy chain was being soldered. ...
Reliability is of increasing importance for electronics systems operating at harsh environments, such as the electronic telecommunication systems used at subsea level. The aim of this research was to investigate the reliability of such electronic systems through a simulated accelerated thermal cycle test. The paper presents a step-by-step process of designing accelerated thermal cycle test using field operating conditions. The Coffin-Mansion equation was used to calculate the accelerated factor for the thermal cycle test. In order to simulate the expected life time of 25 years, the solder assembly samples were subjected to 400 temperature cycles, with every cycle lasting for 40 min. Reliability was determined by measuring shear strengths of solder joints of different electronic components at set intervals. Although some of the components showed an initial decrease in shear strength, it was generally concluded that the electronic assemblies are able to maintain their shear strength for up to 25 years. The fracture surfaces of the solder joints, after shear testing, were also analyzed for brittle and ductile fractures, with the use of scanning electron microscopy (SEM).
