Ju Guo‐kui, Wei Xi‐cheng, Sun Peng and Liu Johan
The purpose of this paper is to compare the growth kinetics of interfacial intermetallic compound (IMC) layer and its effect on the tensile strength of two solder (Sn3.0Ag0.5Cu…
Abstract
Purpose
The purpose of this paper is to compare the growth kinetics of interfacial intermetallic compound (IMC) layer and its effect on the tensile strength of two solder (Sn3.0Ag0.5Cu and Sn0.4Co0.7Cu) joints.
Design/methodology/approach
The samples annealed, respectively, at 85, 120 and 150°C up to 1,000 h were tensile tested and their cross‐sections were observed by scanning electron micrography.
Findings
The results showed that, for both solder joints, an approximately linear reduction in tensile joint strength with an increase in the IMC layers' thickness occurred. The tensile strength of Cu/Sn3.0Ag0.5Cu solder joints is slightly better than that of Cu/Sn‐0.7Co‐0.4Cu solder joints under analogous aging conditions. In addition, the growth kinetics of the overall interfacial IMC layer in Sn0.4Co0.7Cu solder joints can be simply described by the classical growth kinetic theory for solid‐state diffusion with an activation energy of 2,996.85 J/mol and interdiffusion constant of 4.15×0−17 m2/s which are relatively lower, compared with Sn3.0Ag0.5Cu solder on copper with 14,167.8 J/mol and 65.33×10−17 m2/s, respectively.
Originality/value
The paper is of value in evaluating the growth kinetics of Sn3.0Ag0.5Cu and Sn0.4Co0.7Cu solder joints, and in discussing and contrasting the influence of IMC growth on their tensile strength.
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Keywords
Xingchen Yan, Kexin Xu, Junjie Wang, Xicheng Wei and Wurong Wang
The purpose of this paper is to comparatively investigate the microstructure and interfacial intermetallic compound (IMC) layer of Cu/SACPG/Ni and Cu/SAC0307/Ni solder joints…
Abstract
Purpose
The purpose of this paper is to comparatively investigate the microstructure and interfacial intermetallic compound (IMC) layer of Cu/SACPG/Ni and Cu/SAC0307/Ni solder joints after thermal aging.
Design/methodology/approach
The specimens were thermally aged at 150°C for 0, 24, 168 and 500 h. The microstructure and morphology of the interface IMC layer were observed by means of scanning electron microscope. The IMCs and the solder bump surface were analyzed by EDS. Moreover, the thickness of IMC layer was measured by using the image analysis software.
Findings
The morphology of IMC of Cu/SAC0307/Ni solder joint was consistent with that of the Cu/SACPG/Ni joint, which indicates that the addition of P and Ge had little effect on the IMC formation. The needle-like (Cu,Ni)6Sn5 was formed at the interface of solder/Ni solder joints. Meanwhile, the tiny particles inferred as Ag3Sn phase attached to the surface of (Cu,Ni)6Sn5. The growth rate of IMC layer of the Cu/SACPG/Ni joint was smaller than that of Cu/SAC0307/Ni joint with aging time increasing, which means the addition of trace P and Ge can slightly suppress the diffusion rate of the interfacial IMC.
Originality/value
There are no previous studies on the formation mechanism of the IMC layer of SAC0307 solder alloys with P and Ge addition.
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Peng Liu, Xiao Fei Chen, Ya Xi Cheng and Shan Shan Xiao
Teacher well-being has been a concern, but there has been a lack of research on how teacher leadership can contribute to teacher well-being in a high-accountability context and a…
Abstract
Purpose
Teacher well-being has been a concern, but there has been a lack of research on how teacher leadership can contribute to teacher well-being in a high-accountability context and a hierarchical education system such as that of China, particularly through the meditating roles of trust in the leader and teacher efficacy. Therefore, the purpose of this study was to understand the relationship between teacher leadership and teacher well-being while exploring the mediating roles of trust in leaders and teacher efficacy in this relationship.
Design/methodology/approach
Using structural equation modeling (SEM) and bootstrap methods with valid answers from 1,144 teachers in 25 primary schools in 1 Chinese city, this study mainly answered three questions: Is there a significant relationship between teacher leadership and teacher well-being? Is there a significant mediating effect of trust in leaders on the relationship between teacher leadership and teacher well-being? Is there a significant mediating effect of teacher efficacy on the relationship between teacher leadership and teacher well-being?
Findings
This study reported a positive relationship between teacher leadership and teacher well-being. This study also found positive mediating roles for trust in leaders and teacher efficacy in the relationship between teacher leadership and teacher well-being in a high-accountability and hierarchical system like that of China.
Originality/value
This study provides an understanding of the transferability of teacher leadership theories across cultures and has practical significance for educational practice in high-accountability and hierarchical education contexts similar to that of China.