IMC Evolution Research Articles

Effect of AlN on the microstructure evolution of Cu/Sn58Bi/Cu solder joints for 3D packaging at different bonding times

Cu/Sn58Bi/Cu and Cu/Sn58Bi-0.05AlN/Cu were prepared by transient liquid-phase bonding (TLP) bonding process for low temperature bonding and high temperature service. The evolution of interfacial IMC and the influence mechanism of AlN on TLP solder joints were studied. During the bonding process, the top and bottom IMC show asymmetric growth. With the increase of bonding time, Cu6Sn5 and Cu3Sn in the two solder joints continue to grow, and finally complete IMC morphology can be formed, of which Cu6Sn5 IMC is more and Cu3Sn IMC is less. In addition, by calculating the growth rate of Cu3Sn IMC, it was found that the growth rate of Cu3Sn IMC at both ends of the three-dimensional solder joint containing AlN is suppressed.

Study on the interfacial evolution and mechanical properties of Cu/SAC105/Cu solder joint modified by Si3N4 nanowires

In the present study, Si3N4 nanowires (NWs) with a mass fraction of 0.6 wt% were incorporated into Sn1.0Ag0.5Cu (SAC105) solder. Cu/SAC105/Cu and Cu/SAC105-Si3N4/Cu 3D structure joints were constructed by transient liquid-phase (TLP) bonding. To investigate the influence mechanism of Si3N4 NWs, the interfacial IMC evolution and mechanical properties of two solder joints were analyzed. It was found that the interfacial Cu3Sn IMC layer thickness of the joints containing Si3N4 NWs was thinner than that of the undoped ones at any given time. The growth of interfacial Cu6Sn5 IMC was inhibited, resulting in the retarded formation of interfacial IMC bridging and full-IMC joints. In addition, combined with the fracture morphology analysis, the brittle fracture behavior of the solder joints was suppressed, and the shear strength of the joints showed a significant improvement following the introduction of Si3N4 NWs. Moreover, Si3N4 NWs were found exposed on the fracture surface of Cu3Sn IMC layer, demonstrating that the doping of Si3N4 NWs shaped a joint similar to that of reinforced concrete structure, which facilitates the limitation of dislocations and crack expansion.

Molecular dynamics simulation and experimental study of tin growth in SAC lead-free microsolder joints under thermo-mechanical-electrical coupling

Sn-Ag-Cu system lead-free solders are considered to be promising solder series. The growth of Sn whiskers on the solder surface is an important factor that threatens the reliability of electronic products. In this study, the IMC evolution and whiskers growth of Sn-0.3Ag-0.7Cu (SAC0307) microsolder joints under thermal-mechanical-electrical coupling were investigated by the combination of molecular dynamics simulation and experimental methods. The simulation and experimental results revealed that the electric field intensity had the greatest influence on the atomic diffusion. When the electric field intensity was 0.004 V/Å, the diffusion speed of copper atom to solder reached the maximum, and the intermetallic compounds Cu6Sn5 and Cu3Sn were formed at the interface, which provided the long-term driving force for the growth of tin whiskers at the weak oxide film on the surface. Tin whiskers were inclined to grow at the anode, while holes and cracks were tend to produce at the cathode. When the external pressure stress was 0.03 nN, most of tin atoms were precipitated. When the temperature was 393 K, the whiskers slowly grew to 3.3 µm in length at the growth rate of 0.0182 Å/s. The results can provide the basis for the growth mechanism of tin whisker in real service situations.

Interface mechanical behavior of gold alloy wire bonding

The connection between the internal chip and external pins of the semiconductor package and the connection between the chip play an important role in establishing the electrical connection between the chip and the outside and ensuring the input/output between the chip and the outside. It is the key to the entire subsequent packaging process. Wire bonding has a dominant position in connection methods due to its simple process, low cost, and application of a variety of packaging forms. In high-reliability fields such as military and aerospace applications, bonding wires are usually used as chip interconnect materials. The bonding wires have good electrical conductivity, thermal conductivity, and oxidation resistance, but there are some reliability problems in bonding due to the production of Au-Al compounds. In this paper, Al element is used to modify the bonding alloy wire innovatively, the mechanical properties of Au-Al and Au-Pd system bonding points and the growth and evolution of IMC are studied, and the influence of Al and Pd elements on the reliability of bonding points is evaluated.

Effect of Zinc Addition on the Evolution of Interfacial Intermetallic Phases at Near-Eutectic 50In-50Sn/Cu Interfaces

The effect of Zn addition on the evolution of IMC at near-eutectic 50In-50Sn/Cu interfaces was investigated at 210°C. In 50In-(50-x)Sn-xZn/Cu(x = 0, 6) diffusion couples, two types of intermetallic compound layers were observed: e-Cu3(In,Sn) adjacent to the Cu substrate and η-Cu2(In,Sn) adjacent to the solder, which were formed though a solid–solid diffusion reaction and solid–liquid reaction, respectively. The growth of e-Cu3(In,Sn) was at the expense of η-Cu2(In,Sn). In 50In-44Sn-6Zn/Cu diffusion couple, the growth of e-Cu3(In,Sn) was grain-boundary diffusion controlled and n (the time constant) was 0.31. But in the 50In-50Sn/Cu diffusion couple, due to the slow growth of η-Cu2(In,Sn), the time constant of e-Cu3(In,Sn) was down to 0.19. With the addition of Zn in the 50In-50Sn/Cu couple, the diffusion of Cu was alleviated. Zn exhibited high activity and moderated the dissipation of the main atoms (In/Sn) in the solder. So the growth of Cu3(In,Sn) was suppressed significantly.

Study of the effect of Sn grain boundaries on IMC morphology in solid state inter-diffusion soldering

This paper reports on 3D phase field simulations of IMC growth in Co/Sn and Cu/Sn solder systems. In agreement with experimental micrographs, we obtain uniform growth of the CoSn3 phase in Co/Sn solder joints and a non-uniform wavy morphology for the Cu6Sn5 phase in Cu/Sn solder joints. Furthermore, simulations were performed to obtain an insight in the impact of Sn grain size, grain boundary versus bulk diffusion, IMC/Sn interface mobility and Sn grain boundary mobility on IMC morphology and growth kinetics. It is found that grain boundary diffusion in the IMC or Sn phase have a limited impact on the IMC evolution. A wavy IMC morphology is obtained in the simulations when the grain boundary mobility in the Sn phase is relatively large compared to the interface mobility for the IMC/Sn interface, while a uniform IMC morphology is obtained when the Sn grain boundary and IMC/Sn interface mobilities are comparable. For the wavy IMC morphology, a clear effect of the Sn grain size is observed, while for uniform IMC growth, the effect of the Sn grain size is negligible.

Development cooperation of local communities (inter-municipal cooperation – IMC) under the implementation of local government reform

The hereby article has analyzed the issue of the territorial communities’ cooperation (intermunicipal cooperation – IMC), in particular in the framework of the on-going local self-government reform in Ukraine.It is proved justification of the researches of the notion «territorial community» as an object of the public administration science. It is also defined the main characteristics of the territorial communities’ cooperation (intermunicipal cooperation – IMC), in particular taking into account the concepts of «new public management» and «good governance». It is pointed out the particularities of the current status and further IMC evolution in Ukraine. The experience of other countries in the field of local self-government reform implementation and IMC development have been studied and systematized. It has been also analyzed the possibilities of the implementation in Ukraine of the best national and international practices in this field.The main directions of further IMC development are examined in order to ensure the implementation of the provisions of the European Charter of Local Self-Government. It is also noted that IMC represents an innovative tool for local sustainable development and municipal consolidation in Ukraine and other European countries.The benefit of the article is to highlight the main stages of IMC projects realization. The article also provides a deep analysis of key advantages and possible difficulties in IMC projects realization. It shows that IMC gives the opportunity for local authorities to unite their resources (financial, economic, perssonel etc.) for increasing the efficiency of their work and improving the quality of the municipal services to be provided for the citizens. Consequently, provision of the high quality services to the citizens became a main mission of all local public authorities in the framework of the implementation of the new public management and good governance standards on all levels. It reflects also the main European tendencies in the field of public administration reform which are fixed in the different documents of the international organizations and European institutions. By analysis of the current status of local self-government reform, the best national and international practices, the proposals on further IMC development in Ukraine are presented. Thus, the author proposed to set up more valuable and effective cooperation between the respective local public authorities, organization of the special training programmes in order to ensure further IMC development.

Phase segregation, interfacial intermetallic growth and electromigration-induced failure in Cu/In–48Sn/Cu solder interconnects under current stressing

The evolution of microstructure in Cu/In–48Sn/Cu solder bump interconnects at a current density of 0.7 × 104 A/cm2 and ambient temperature of 55 °C has been investigated. During electromigration, tin (Sn) atoms migrated from cathode to anode, while indium (In) atoms migrated from anode to cathode. As a result, the segregation of the Sn-rich phase and the In-rich phase occurred. A Sn-rich layer and an In-rich layer were formed at the anode and the cathode, respectively. The accumulation rate of the Sn-rich layer was 1.98 × 10−9 cm/s. The atomic flux of Sn was calculated to be approximately 1.83 × 1013 atoms/cm2s. The product of the diffusivity and the effective charge number of Sn was determined to be approximately 3.13 × 10−10 cm2/s. The In–48Sn/Cu IMC showed a two layer structure of Cu6(Sn,In)5, adjacent to the Cu, and Cu(In,Sn)2, adjacent to the solder. Both the cathode IMC and the anode IMC thickened with increasing electromigration time. The IMC evolution during electromigration was strongly influenced by the migration of Cu atoms from cathode to anode and the accumulation of Sn-rich and In-rich layers. During electromigration, the Cu(In,Sn)2 at the cathode interface thickened significantly, with a spalling characteristic, due to the accumulation of In-rich layer and the migration of Cu atoms - while the Cu(In,Sn)2 at the anode interface reduced obviously, due to the accumulation of Sn-rich layer. The mechanism of electromigration-induced failure in Cu/In–48Sn/Cu interconnects was the cathode Cu dissolution-induced solder melt, which led to the rapid consumption of Cu in the cathode pad during liquid-state electromigration and this finally led to the failure.