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Formation of AuSnx IMCs in laser reflowed solder joints protected by N2 atmosphere at room temperature, 60°C, 100°C and 130°C was investigated respectively. The solder balls were Sn-2.0Ag-0.75Cu-3.0Bi, and 120μm in diameter. The surface finish of one pad in the solder joints was 4.0μmAu/0.1μmNiFe/0.01μmTa, the other pad was made of Cu plated with 3.0μm thickness of Au. The laser reflow time was within...
Pure Sn, Sn-0.7Cu, Sn-1.5Cu and Sn-3.0Cu solder joints were fabricated by a laser reflow soldering method, and then they were aged at 125degC for various periods. After 600 hours treatment, we found that thickness of Intermetallic Compounds (IMCs) in the pure Sn solder joints was 54mum. However, in the solder joints with Cu addition, formation of AuSn4 IMCs was inhibited, and other two kinds of Sn-Cu-Au...
As the solder joints become increasingly small and contain only a few grains, their mechanical properties cannot be determined from conventional mechanical tests as with bulk samples, and there may be a considerable variation in mechanical behavior from joint to joint because of the anisotropy of mechanical properties. In this paper, elastic constants of single-crystal AuSn4 and AuSn2 were preliminarily...
Properties of body-centered tetragonal beta-Sn are highly anisotropic. The crystal orientation of the beta-Sn has a marked effect on the stress state in the SnAgCu solder joints. A finite element analysis has been performed of the thermal cycling of the SnAgCu solder and solder joints. Significant amounts of stresses at the solder/Cu interface and in the plane of the grain boundary was found. The...
As-reflowed Sn-Ag-Cu solder joints in various diameters were found to contain only several beta-Sn crystal grains. With the solder joints increasingly miniaturized, there is no obvious change in the grain number in a solder joint. The aged Sn-Ag-Cu solder joints are composed of very limited number of beta-Sn crystal grains as well. It appears that the solder joint size and thermal aging have less...
To meet the urgent demands of future electronic packages, the solder joints have to become increasingly miniaturized. Compared to the large solder joints, mechanics behavior for the samll solder joints is very different, resulting in a series of reliability issues. Therefore, it is very important to understand the mechanics behavior of the small solder joints. In this paper, the shear test of the...
Independent elastic constants of single-crystal Au5Sn and AuSn were determined through first-principles calculations to characterize their elastic anisotropy. The ideal elastic moduli and Poissonpsilas ratio of Au5Sn were determined using the Voigt-Reuss-Hill method and were very close to the range of experimental results; but the ideal Youngpsilas modulus of AuSn was much smaller than the experimentally...
Au surface finish is very common used as a protection layer on pad. In the traditional reflow process, Au is dissolved into solder, and AuSn4 intermetallic components (IMCs) forms. However, for the solder joints fabricated by laser soldering, the morphology and distribution of the AuSnx IMC are quite different from that in solder joints fabricated by traditional reflow methods. This paper reports...
The growth of Au-Sn intermetallic compounds (IMCs) is a major concern to the reliability of solder joints in microelectronic, optoelectronic and micro-electronic-mechanical system (MEMS) which has a layer of Au metallization on the surface of components or leads. This paper presents the growth behavior of Au-Sn IMCs at interfaces of Au metallization and Sn-based solder joints with the addition Cu...
The growth of Au-Sn intermetallic compounds (IMCs) is a major concern to the reliability of solder joints in microelectronic, optoelectronic and micro-electro-mechanical system (MEMS) which has a layer of Au metallization on the surface of components or leads. This paper presents the growth behavior of Au-Sn IMCs at interfaces of Au metallization and Sn-based solder joints with the addition Cu alloying...
The interfacial reaction between Sn-Ag-Cu and Sn-Ag lead-free solder balls and Au/Ni/Cu pads in laser reflow process are presented in this paper. A continuous intermetallic compound layer and some needle-like AuSn4 were observed at the interface of solder and pad, their morphology and distribution were strongly dependent on the laser input energy. Some voids were observed at the interface of solder...
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