Plastic Strain Distribution as a Precursor for Transition From Ductile to Brittle Failure in Lead-Free Solder Joints

2009 ◽  
Author(s):  
Feng Gao ◽  
Jianping Jing ◽  
Frank Z. Liang ◽  
Richard L. Williams ◽  
Jianmin Qu
Keyword(s):  
Brittle Fracture ◽  
Plastic Strain ◽  
Solder Joint ◽  
Failure Mode ◽  
Strain Distribution ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Loading Rates ◽  
Free Solder

One of the major failure modes in lead-free solder joints is the brittle fracture at the solder/Cu pad interface under dynamic loading conditions. Such brittle fracture often leads to catastrophic premature failure of portable electronic devices. Therefore, it is desirable to design the package and the solder joints in such a way that brittle interfacial fracture can be avoided during drop test. To develop such design guidelines, we studied in this paper the dynamic failure of a single solder joint (SSJ). The SSJs with different geometry and substrate surface finish were prepared by laser-cutting from a BGA package assembled on a printed circuit board (PCB). The SSJs were tested under various shear loading rates, ranging from 5 mm/s to 500 mm/s. In conjunction with the experimental tests, finite element analyses (FEA) of these SSJ samples subjected to various loading rates were also conducted. Results from both experimental testing and numerical simulations show that the distribution of plastic strain near the solder/IMC interface is a key indictor of the failure mode. For a given sample geometry and loading rate, if the maximum solder plastic strain lies near the solder/IMC interface, the failure will be more likely to be ductile failure within the solder alloy. On the other hand, if the maximum plastic strain is mainly located at the edge of the interface between solder and the IMC layer with very little plasticity within the solder near the interface, brittle fracture of the IMC/Cu interface will be more likely to occur. Since numerically computing the plastic strain distribution in a solder joint is much easier than predicting joint failure, results of this study provide us with an effective means to predict the type of failure mode of a solder joint under dynamic loading.

Loading Mixity on the Interfacial Failure Mode in Lead-Free Solder Joint

2011 ◽  
pp. 121-121-18
Author(s):  
Feng Gao ◽  
Jianping Jing ◽  
Frank Z. Liang ◽  
Richard L. Williams ◽  
Jianmin Qu
Keyword(s):  
Solder Joint ◽  
Failure Mode ◽  
Lead Free ◽  
Lead Free Solder ◽  
Interfacial Failure ◽  
Free Solder

The Effects of Electromigration to the Solder Joint Formation: A Comparison Between 99.3Sn-0.7Cu and 96.5Sn-3.0Ag-0.5Cu Lead Free Solder

2012 ◽  
Vol 622-623 ◽  
pp. 195-199 ◽  
Author(s):  
M.A.A. Mohd Salleh ◽  
A.R. Nik Nurhidayatul Suhada ◽  
Flora Somidin ◽  
Rafezi Ahmad Khairel ◽  
C.S. Lee ◽  
...  
Keyword(s):  
Solder Joint ◽  
Room Temperature ◽  
Solder Joints ◽  
Research Work ◽  
Cathode Region ◽  
Lead Free ◽  
Lead Free Solder ◽  
Joint Formation ◽  
Current Stress ◽  
Free Solder

Electromigration effects on the solder joint formation of 99.3Sn-0.7Cu and 96.5Sn-3.0Ag-0.5Cu lead-free solder with Cu electroplated Ni layer wire were investigated. The electromigration effects on the solder joints were studied after current density stressing at 1 x 103 A/cm2 in room temperature for 0 h, 120 h, and 240 h. The research work found that intermetallic compound (IMC) formation on the joint is increases for both solders with longer period of current stress applied. Higher IMC thickness growth in 99.3Sn-0.7Cu solder joint compared to 99.3Sn-0.7Cu is detected and both anode regions of the solder joints show higher IMC thickness growth compared to cathode region. Experimental results show 99.3Sn-0.7Cu solder joint is more prone to failure under current stress compared to 96.5Sn-3.0Ag-0.5Cu solder joint with thicker IMC which translates to higher brittleness.

SAC–xTiO2 nano-reinforced lead-free solder joint characterizations in ultra-fine package assembly

2018 ◽  
Vol 30 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Fakhrozi Che Ani ◽  
Azman Jalar ◽  
Abdullah Aziz Saad ◽  
Chu Yee Khor ◽  
Roslina Ismail ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Solder Joint ◽  
Solder Joints ◽  
Ion Beam ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Content Type ◽  
X Ray ◽  
Free Solder

Purpose This paper aims to investigate the characteristics of ultra-fine lead-free solder joints reinforced with TiO2 nanoparticles in an electronic assembly. Design/methodology/approach This study focused on the microstructure and quality of solder joints. Various percentages of TiO2 nanoparticles were mixed with a lead-free Sn-3.5Ag-0.7Cu solder paste. This new form of nano-reinforced lead-free solder paste was used to assemble a miniature package consisting of an ultra-fine capacitor on a printed circuit board by means of a reflow soldering process. The microstructure and the fillet height were investigated using a focused ion beam, a high-resolution transmission electron microscope system equipped with an energy dispersive X-ray spectrometer (EDS), and a field emission scanning electron microscope coupled with an EDS and X-ray diffraction machine. Findings The experimental results revealed that the intermetallic compound with the lowest thickness was produced by the nano-reinforced solder with a TiO2 content of 0.05 Wt.%. Increasing the TiO2 content to 0.15 Wt.% led to an improvement in the fillet height. The characteristics of the solder joint fulfilled the reliability requirements of the IPC standards. Practical implications This study provides engineers with a profound understanding of the characteristics of ultra-fine nano-reinforced solder joint packages in the microelectronics industry. Originality/value The findings are expected to provide proper guidelines and references with regard to the manufacture of miniaturized electronic packages. This study also explored the effects of TiO2 on the microstructure and the fillet height of ultra-fine capacitors.

Thermal Cycling Reliability of Chip Resistor Lead Free Solder Joints

2003 ◽  
Author(s):  
N. Islam ◽  
J. C. Suhling ◽  
P. Lall ◽  
T. Shete ◽  
H. S. Gale ◽  
...  
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Fatigue Resistance ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Snagcu Alloy ◽  
Temperature Ranges ◽  
Free Solder

In this study, we have examined the thermal cycling reliability of several lead free chip resistor solder joint configurations. Five sizes of resistors (2512, 1206, 0805, 0603, 0402), 2 temperature ranges (−40 to 125°C and −40 to 150°C), and five different solder types have been examined. The solders include the normal SnAgCu alloy recommended by earlier studies (95.5Sn-3.8Ag-0.7Cu), and several variations that include small percentages of Bismuth and Indium to enhance fatigue resistance. Results have been compared to data for standard 63Sn-37Pb joints.

Deformation Behavior of SAC305 Solder Joints With Multiple Grains

2020 ◽  
Author(s):  
Debabrata Mondal ◽  
Abdullah Fahim ◽  
KM Rafidh Hassan ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Grain Size ◽  
Solder Joint ◽  
Deformation Behavior ◽  
Thermal Loading ◽  
Solder Joints ◽  
Lead Free ◽  
External Loading ◽  
Lead Free Solder ◽  
Material Anisotropy ◽  
Free Solder

Abstract Lead-free solder joints are the most widely used interconnects in electronic packaging industries. Usually solder joints in most of the electronic devices are exposed to an environment where variation of temperature exists, which indicates cyclic thermal loading to be a very common type of external loading. Moreover, due to difference in the coefficient of thermal expansion (CTE) among dissimilar contact materials, shear stress develops in junctions under thermal loading, which significantly deteriorates the overall reliability. Hence, characterization of lead-free solder materials under thermal loading is essential to predict the performance and deformation behavior of joints in practical applications. A significant portion of the studies in this field are concerned with thermal loading of lead-free solder interconnects, each of which has a very small diameter, in sub-millimeter range. Although the solder balls have very small dimensions, most of the analyses considered them as a bulk material with homogeneous and isotropic properties. However, with the decrease of specimen dimensions, size effects and material directionality play a significant role in deformation mechanisms. Since a very few grains exist in a small specimen, individual grain properties play a vital role on overall material response. Therefore, modeling from the grain structure and orientation point of view could be an effective and more accurate way to predict solder joint deformation behavior under thermal loading. In this study, the effect of grain size and orientation of SAC305 is investigated for predicting anisotropic behavior of solder joints under thermal load. A simplified three-dimensional model of beach-ball configuration solder joint was generated and simulated using ABAQUS finite element (FE) software. Experimentally obtained directional properties such as elastic modulus and CTE were assigned to the computational geometry to create material anisotropy. The effects of material anisotropy were studied for varying grain size specimens, as well as for specimens with varying grain orientation.

Effect of Micro Structure on Fatigue Characteristics of Lead Free Solder Joints

2011 ◽  
Author(s):  
Takahiro Akutsu ◽  
Qiang Yu
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Solder Joint ◽  
Crack Propagation ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Micro Structure ◽  
Free Solder

This paper presents the influence of the micro structure on the crack propagation in lead free solder joint. The author’s group have studied the Manson-Coffin’s law for lead free solder joint by using the isothermal fatigue test and FEM analytical approaches to establish the practicable evaluation of thermal fatigue life of solder joints, for example, for the Sn-Cu-Ni solder, because this solder is attracted from the aspect of the decrease of solder leach in the flow process and material cost. However, even if the same loading is given to the solder joints of BGA test piece, there was a large dispersion in the fatigue life. Even though the effect of the shape difference has been considered, the range of the dispersion could not been explained sufficiently. In the study, the fatigue crack propagation modes in the solder joints were investigated, and an internal fatigue crack mode and an interfacial fatigue crack mode were confirmed. And the tendency of a shorter on fatigue life in the interfacial fatigue mode was confirmed. To clarify the mechanism of these fatigue crack modes, the crystal grain size in the solder joints was investigated before the fatigue test and also after the test. Furthermore, the verification of the mechanism using FEM models considering the crystal grain size was carried out. First of all, each element in FEM models matching to the average crystal grain size was made. Second, the inelastic strain ranges in each FEM models were studied. As a result, it was shown that the influence of the crude density of the crystal grain to the fatigue crack progress can be evaluated. In addition, the micro structure of the solder joint of large-scale electronic devices is observed, and FEM model was made based on the observation result. As a result, it was shown that the influence of the directionality with the crystal grain to the fatigue crack progress can be evaluated.

RELIABILITY EVALUATION OF BGA SOLDER JOINTS DURING ACCELERATED LIFE TEST

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4553-4558
Author(s):  
OUK SUB LEE ◽  
NO HOON MYOUNG ◽  
DONG HYEOK KIM ◽  
MAN JAE HUR ◽  
SI WOON HWANG
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Solder Joints ◽  
Coefficient Of Thermal Expansion ◽  
Accelerated Life Test ◽  
Lead Free ◽  
Lead Free Solder ◽  
Metal Fatigue ◽  
Mechanical Loads ◽  
Free Solder

The use of BGA (Ball Grid Array) interconnects utilizing the lead-free solder joint has grown rapidly because of its small volume and diversity of application. Thus, it requires the continuous quantification and refinement of lead-free solder joint reliability. The lead-free solder creep and cyclically applied mechanical loads cause metal fatigue on the lead-free solder joint which inevitably leads to an electrical discontinuity. In the field application, BGA solder joints experience mechanical loads during temperature changes caused by power up/down events as the result of the CTE (Coefficient of Thermal Expansion) mismatch between the substrate and the Si die. In this paper, extremely small resistance changes at joint area corresponding to through-cracks generated by thermal fatigue were measured. In this way, the failure was defined in terms of anomalous changes in electrical resistance of the joint. Furthermore the reliability of BGA solder joints in thermal cycling is evaluated by using the modified coffin-Manson criterion which may define and distinguish failure. Any change in circuit resistance according to the accumulated damage induced by the thermal cycling in the joint was recorded and evaluated in order to quantitate reliability of solder joint.

A Basic Study on Creep-Fatigue Damages Interaction for Sn-3.0Ag-0.5Cu as Lead Free Solder Material

2015 ◽  
Author(s):  
Hirokazu Oriyama ◽  
Takashi Kawakami ◽  
Takahiro Kinoshita
Keyword(s):  
Solder Joint ◽  
Fatigue Damage ◽  
Solder Joints ◽  
Mechanical Design ◽  
Low Cycle Fatigue ◽  
Creep Damage ◽  
Lead Free ◽  
Lead Free Solder ◽  
Creep Fatigue ◽  
Free Solder

Sn-Ag-Cu solder materials have been widely used for the mount process of electronics devices or semiconductor packages on print circuit board (PCB). The solder joints are sometimes opened under thermal cyclic loads as low cycle fatigue phenomenon. The fatigue life of solder joint has been investigated by many researchers with experimental and numerical methods. Generally, the induced thermal stress in solder joints should be relaxed as soon and creep damage is considered to be ignored in order to estimate lives of joints. However, it is probable that long term stress is applied to solder joints by the elastic follow-up phenomenon which are depending on the stiffness ratio between solder joints and the electronics device, because the elastic strain in PCB or the electronics device shifts to creep strain in solder joints gradually during a long time. Then the creep damage of solder joint should be counted for the mechanical design of mounted PCBs. And it is known that the interaction between creep damage and fatigue damage significantly shorten the life. In this study, it was discussed whether the interaction between fatigue damage and creep damage has to be considered or not for the mechanical design of the lead free solder joint with basic creep-fatigue tests at an elevated temperature.

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