Fracture Life Evaluation of Cu-Cored Solder Joint in BGA Package

2009 ◽  
Author(s):  
Hisashi Tanie ◽  
Nobuhiko Chiwata ◽  
Motoki Wakano ◽  
Masaru Fujiyoshi ◽  
Takeyuki Itabashi
Keyword(s):  
Solder Joint ◽  
Crack Propagation ◽  
Shape Analysis ◽  
Fracture Mechanism ◽  
Solder Joints ◽  
Joint Stiffness ◽  
Molten Solder ◽  
Initiation Point ◽  
Mps Method ◽  
Propagation Analysis

A Cu-cored solder joint has an accurate height, a low thermal resistance, and a low electric resistance. However, the fracture mechanism of Cu-cored solder joints has yet to be clarified, and thus the fracture life cannot be predicted. We evaluated the fracture life of Cu-cored solder joints by using our molten-solder-shape analysis and crack-propagation analysis methods. Our molten-solder-shape analysis is based on the moving-particle semi-implicit (MPS) method. In the MPS method, a continuum is expressed as an assembly of particles. In contrast to finite element analysis (FEA), the MPS method can easily express a large deformation and any geometric topology changes, because the continuum does not need to be divided into elements. Using our molten-solder-shape analysis, we could calculate the shapes of Cu-cored solder after the reflow process. Our crack-propagation analysis has a feature where a crack initiation point and the crack propagation paths are automatically calculated and where the fracture life is quantitatively evaluated using FEA. Using our crack-propagation analysis, we could analyze the fracture mechanism of Cu-cored solder joints. By combining our molten-solder-shape and crack-propagation analyses, we could evaluate the fracture life of Cu-cored solder joints in a ball grid array package. As a result, we found that the fracture life of Cu-cored solder joints is longer than that of conventional joints. The height of a joint is one of the reasons for the improved fracture life. Since the height of a Cu-cored solder joint is controlled by the size of the core ball, the height is larger and more highly accurate than that in conventional joints. Accordingly, the solder strain and strain variation are decreased. Joint stiffness is the second reason for the improved fracture life. Cu is harder than solder, so the joint stiffness of a Cu-cored joint is greater than that of conventional joints. Accordingly, the displacement of a joint is decreased. The crack-propagation behavior is the third reason for the improved fracture life. In a conventional solder joint, a solder crack only propagates near the interface of the solder and the land. In a Cu-cored solder joint, a solder crack not only propagates near the interface of the solder and the land, but also at the interface of the solder and core ball. The crack-propagation life is longer than that in a conventional joint due to crack-path scattering. We found that the fracture life of Cu-cored solder joints is improved by using these mechanisms.

Shape Prediction of Molten Micro-Solder Joints Using Particle Method and Application to Evaluation of Fracture Life

2007 ◽  
Author(s):  
Hisashi Tanie
Keyword(s):  
Solder Joint ◽  
Crack Propagation ◽  
Prediction Method ◽  
Molten Solder ◽  
Lead Free ◽  
Analysis Method ◽  
Shape Prediction ◽  
And Topology ◽  
Propagation Analysis ◽  
Topology Changes

The reliability of a micro-solder joint in a semiconductor structure greatly depends on the solder shape. Therefore, many methods to predict the shape of the molten solder have been proposed [1–3]. However, some problems arise when conventional methods are applied to predict the solder shape of miniaturized and lead-free joints. The first problem is the difficulty in expressing the large deformation and topology change of the solder. In a miniaturized joint, the shape of molten solder changes significantly during the reflow process, and even topology changes (e.g., merging with other solder in a neighboring joint or splitting into several pieces) can occur. These phenomena need to be expressed if we are to predict the solder shape of the miniaturized joint. The second problem is the difficulty in expressing the effect of solder wettability. The solder shape is known to depend on the solder wettability, and the wettability of lead-free solders is different from conventional solders. To predict the lead-free solder shape, we need to express the effect of the wettability. Therefore, I developed a new shape prediction method that solves these problems using the moving-particle semi-implicit (MPS) method [4, 5]. MPS is suitable for calculating incompressible flow and can be used to easily express large deformation and topology changes. However, the original MPS method cannot sufficiently express the effect of solder wettability. Therefore, I enhanced the surface tension formulation of MPS, making it possible to express this effect. I applied this method to predict the solder shapes of various packages (e.g., a thin small outline package (TSOP) and a flip-chip package) and found that the method is effective in predicting the solder shapes of miniaturized joints. Moreover, I was able to evaluate the fracture life of a solder joint with the predicted solder shape by coupling the shape prediction method with our crack propagation analysis method, which was demonstrated at a previous InterPACK [6]. In this crack propagation analysis method, crack initiation points and propagation paths are automatically calculated, and the fracture life is evaluated quantitatively by finite element analysis. I applied these combined methods to evaluate the fracture life of solder joints that had different solder shapes due to different wettability conditions. As a result, I was able to find the differences in crack initiation points and to evaluate crack propagation paths and fracture lives in different wettability conditions.

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.

718 Crack Propagation Analysis of Cu-cored Solder Joint

2008 ◽  
Vol 2008.21 (0) ◽  
pp. 311-312
Author(s):  
Hisashi TANIE ◽  
Takeyuki ITABASHI ◽  
Nobuhiko CHIWATA ◽  
Motoki WAKANO
Keyword(s):  
Solder Joint ◽  
Crack Propagation ◽  
Propagation Analysis

scholarly journals Study on Establishing Degradation Model of Chip Solder Joint Material under Coupled Stress

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1813
Author(s):  
Longteng Li ◽  
Bo Jing ◽  
Jiaxing Hu
Keyword(s):  
Solder Joint ◽  
Crack Propagation ◽  
Integrated Circuit ◽  
Solder Joints ◽  
Propagation Time ◽  
Strain Accumulation ◽  
Degradation Model ◽  
Accumulation Time ◽  
Degradation Data ◽  
Coupled Stress

The chip is the core component of the integrated circuit. Degradation and failure of chip solder joints can directly lead to function loss of the integrated circuit. In order to establish the degradation model of chip solder joints under coupled stress, this paper takes quad flat package (QFP) chip solder joints as the study object. First, solder joint degradation data and failure samples were obtained through fatigue tests under coupled stress. Three types of micro failure modes of solder joints were obtained by scanning electron microscope (SEM) analysis and finite element model (FEM) simulation results. Second, the characterization of degradation data was obtained by the principal component of Mahalanobis distance (PCMD) algorithm. It is found that solder joint degradation is divided into three stages: strain accumulation stage, crack propagation stage, and failure stage. Later, Coffin–Manson model and Paris model were modified based on the PCMD health index and strain simulation. The function relationship between strain accumulation time, crack propagation time, and strain was determined, respectively. Solder joint degradation models at different degradation stage were established. Finally, through strain simulation, the models can predict the strain accumulation time and failure time effectively under each failure mode, and their prediction accuracy is above 85%.

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