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A method for non-destructively tracking the integrity of flip chip solder joints through life is investigated in this paper. An industry standard double-sided PCB was designed and manufactured with 14 flip chips to assess the failure patterns of each flip chip and each solder joint in lifetime vibration tests. Two configurations of PCB finish were...
Contexts in source publication
Context 1
... the Pb HASL surface finish boards, the flip chips were found to reach complete failure after 380 vibration cycles where each cycle is 4 minutes, equivalent to 25.33 hours or 91,200 [19]. The ultrasound C-scan images used in the solder joint through-life monitoring were obtained using the Sonoscan Gen6™ C-Mode Scanning Acoustic Microscope machine in the LJMU laboratory as shown in Figure 4. For through-life assessment the Gen6 was used for 2D Acoustic Micro Imaging (AMI) often called C-SAM. ...
Context 2
... extracting the region of interest as illustrated in section 5.3, the mean intensity of all the solder joints in all the flip chips under consideration were calculated. Figure 14 shows a scatter plot for the mean intensity variation of all the solder joints of U19 at cycle 0, before the test, and at cycle 65, the last test cycle before complete failure. From the mean intensity calculation of the solder joints, it can be seen that as the vibration cycling progresses and flip chips start to fail, three types of solder joints can be identified. ...
Citations
... Utilizing advanced manufacturing techniques, such as controlled atmosphere soldering, contributes to enhanced joint quality [153]. Extensive thermal cycling testing during the product development phase is crucial to identifying potential weak points in solder joints [154,155]. The use of accelerated testing methods can simulate and help understand the effects of temperature extremes on solder joint reliability [156]. ...
... Several models have been developed to predict interconnection reliability during thermal cycling. Solder joints may also be subjected to long-term isothermal cycling states, such as vibrations [13,14]. ...
SAC305(Sn-3.0Ag-0.5Cu) has gained the highest acceptance as a solder alloy. The fatigue performance of solder joints has become an essential reliability assessment criterion due to the transition to more reliable lead-free alloys from highly predictable lead-based alloys. This study examines the shear fatigue characteristics of sandwich test vehicles for SnPb and SAC305 at different temperatures using both Organic Sol-derability Preservative (OSP) and Electroless Nickel-Immersion Silver (ENIG) surface finishes. The fatigue experiments were performed using an Instron micromechanical tester at a constant strain rate, and micro-structural analysis was carried out using Scanning Electron Microscopy (SEM) to identify the Intermetallic Compound (IMC) morphology and failure mode. The stress-strain (hysteresis) loops of SnPb and SAC305 were measured, and the fatigue life of the specimens was estimated using the strain-life equation at various temperatures. SAC305 was observed to have a better fatigue life than SnPb, particularly at higher strain levels or testing temperatures. The OSP surface finish demonstrated superior fatigue properties compared to the ENIG surface finish. Additionally, elevated testing temperatures were found to accelerate fatigue failure in solder joints. The Arrhenius model was utilized to develop a general empirical model that predicts the fatigue life of SAC305 and SnPb solder alloys with OSP and ENIG surface finishes as a function of the strain level and testing temperature.
... Baishya et al. studied the effects of vibration on the reliability of area array solder joints in an industry-grade printed circuit board (PCB). Two trigger points within the lifetime of a solder joint could be found, and the first one could be detected in crack initiation at around 35-40% of its lifetime, while the second trigger point indicated just before complete mechanical failure, tracked at around 80-85% of the lifetime [17]. Xia et al. studied the vibration reliability of lead-free solder joints of Package-on-Package and found that the cracks usually originated in the bottleneck position of the solder balls, extended within bulk solder, and then propagated along the interface between the IMC layer and the bulk solder under the vibration loading [18]. ...
The electronic devices suffer great vibration and temperature fluctuation in an airborne environment, which has been always a big challenge for reliability design. In this paper, the reliability of the complex electronic components for airborne applications under a thermal cycling test, random vibration and combined loading has been investigated by experiment tests and finite element simulation. The fatigue life and failure location under different loadings have been compared and discussed, respectively. The results indicated that the combined fatigue life was much shorter than a single-factor experiment. The failed solder joints mostly appeared at the interface between the solder and the copper pad on the component side and the location was at the corner for all three harsh environment tests. Nevertheless, several differences could be observed. For temperature cycling, all the specimens failed due to the increase in daisy chain resistance rather than the open circuit for the combined loading test. That is because the degeneration of the solder caused by temperature variation led to lower stress levels and fatigue life. Moreover, the pins fractured at the welding regions have been observed. The modified Coffin—Manson model, Miner’s linear fatigue damage criterion and Steinberg’s model and rapid life-prediction approach were used to predict the fatigue life under temperature cycling, random vibration and combined loading, respectively. With these methods, the accurate numerical models could be developed and validated by experiment results. Thanks to the simulation, the design time could be effectively shortened and the weak point could be determined.
The video-based frequency measurement method for bridge cable vibration offers advantages such as speed, efficiency, and non-contact compared to traditional sensor-based methods. However, the presence of complex backgrounds in video images can affect the accuracy of cable frequency measurement. To address the problem, a novel phase-based frequency measurement method is proposed, which focuses on extracting cable edge vibration from background noise in the spatial and temporal domains. Firstly, in the spatial domain, to process the vibration signals more precisely, each video sequence is divided into multiple subregions. To enhance the edge vibration within the subregions while initially suppressing background noise, the Otsu threshold segmentation method is employed for subregion categorization. Subsequently, the phase-based vibration estimation method is utilized to build the spatial domain vibration representation of the subregions based on the phase differences between adjacent frames, while maintaining optical flow consistency. Then, the temporal vibrational waveforms are extracted, which may still include noise from the background edges. To restore the cable vibration, a combination of singular spectrum analysis and nonnegative matrix factorization is further designed for characterizing cable vibrations and attenuating the noise in the temporal domain. Finally, the cable vibration restored from all subregions are synthesized, forming the ultimate cable signal. The proposed method has been evaluated through extensive testing in outdoor environments, and it has exhibited remarkable enhancements in measuring cable vibration frequencies when dealing with complex background interference compared to the existing methods.
This article presents a pioneering use of thin-film solder joint in the electrical interconnection of high-temperature thin-film sensors (TFSs), which aims to improve the low tolerance of traditional soldered balls in extreme environments. The structure of the thin-film solder joint, composed of silver foil, solder joint paste, and metal wire, has a negligible mass compared to traditional soldered balls. As a result, the inertia force on the solder joint/substrate interface during vibration and force impact is greatly reduced, improving the reliability of the solder joint under thermal–mechanical coupling impacts. The thin-film solder joint has been verified using both metal (AgPd paste) and ceramic (TiB2/SiCNO paste) solders, and can withstand extreme environments such as thermal shock and high “
${g}$
” loading. The designed thin-film solder joint can withstand impact energy of up to 3 J at 1000 °C without failure, which is six times higher than that of traditional soldered balls (with a statistical failure rate of up to 67% under 0.5 J impact). The thin-film solder joint was successfully used for electrical interconnection of high-temperature thin-film strain gauges (TFSGs), demonstrating excellent reliability under thermal–mechanical coupling impacts at 1000 °C. Our high-tolerance thin-film solder joints show promising potential for use in electrical interconnection in harsh environments.
Purpose
Surface mount technology (SMT) is widely used and plays an important role in electronic equipment. The purpose of this paper is to reveal the effects of interface cracks on the fatigue life of SMT solder joint under service load and to provide some valuable reference information for improving service reliability of SMT packages.
Design/methodology/approach
A 3D geometric model of SMT package is established. The mechanical properties of SMT solder joint under thermal cycling load and random vibration load were solved by 3D finite element analysis. The fatigue life of SMT solder joint under different loads can be calculated by using the modified Coffin–Manson model and high-cycle fatigue model.
Findings
The results revealed that cracks at different locations and propagation directions have different effect on the fatigue life of the SMT solder joint. From the location of the cracks, Crack 1 has the most significant impact on the thermal fatigue life of the solder joint. Under the same thermal cycling conditions, its life has decreased by 46.98%, followed by Crack 2, Crack 4 and Crack 3. On the other hand, under the same random vibration load, Crack 4 has the most significant impact on the solder joint fatigue life, reducing its life by 81.39%, followed by Crack 1, Crack 3 and Crack 2. From the crack propagation direction, with the increase of crack depth, the thermal fatigue life of the SMT solder joint decreases sharply at first and then continues to decline almost linearly. The random vibration fatigue life of the solder joint decreases continuously with the increase of crack depth. From the crack depth of 0.01 mm to 0.05 mm, the random vibration fatigue life decreases by 86.75%. When the crack width increases, the thermal and random vibration fatigue life of the solder joint decreases almost linearly.
Originality/value
This paper investigates the effects of interface cracks on the fatigue life and provides useful information on the reliability of SMT packages.
