Authors: Ikuo Shohji, Satoshi Shimoyama, Hisao Ishikawa, Masao Kojima
Abstract: Impact properties of solder ball joints with Sn-9mass%Zn and Sn-3mass%Ag-
0.5mass%Cu lead-free solders were investigated under aging at 423 K. In the case of the joints with
Cu electrodes, both Sn-9Zn and Sn-3Ag-0.5Cu joints have similar impact forces before aging. For the
Sn-3Ag-0.5Cu joint, fracture occurred in an intermetallic compound (IMC) layer formed in a joint
interface regardless of aging, and thus the impact force was stable upon aging at 423 K for 500 h. For
the Sn-9Zn joint, fracture mode changed from solder fracture to other fracture upon aging and thus
this change led a decrease in the impact force.
In the Sn-9Zn joint with an electroless Ni/Au plated electrode, fracture occurred in the solder
regardless of aging, and thus impact properties improved compared with the joint using the Cu
electrode. The impact properties are superior to those of the Sn-3Ag-0.5Cu joints with the Cu and the
electroless Ni/Au electrodes.
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Authors: Wan Chang Sun, Ming Feng Tan, Jian Hua Lu, Lei Zhang, Quan Zhou
Abstract: Electroless Ni-P and Ni-P-Al2O3 composite coatings on low carbon steel (Q235) sheets were prepared by adopting optimum plating process. The cross-section morphology and structure as well as the phase transformation of the composite coatings were studied by scanning electron microscopy(SEM), X-ray diffraction(XRD). It was shown that the Al2O3 particles homogeneously dispersed in the entire Ni-P film matrix, and the structure of Ni-P-Al2O3 composite coatings as deposited was amorphous. The corrosion behaviors were evaluated by electrochemical tests. The experimental results indicated that the corrosion resistance of Ni-P-Al2O3 coatings was superior to Ni-P coatings due to the effect of Al2O3 particles. In addition, the oxidation resistance test, which was carried out by using oxidation weight method, showed that ternary Ni-P-Al2O3 composite coating had a better oxidation resistance than Ni-P coating.
831
Abstract: Now the protection method for PCB welding board, widely used coating technology is ENIG , but in use course found that the coating will appear “black mat” that is fatal flaw in the welding process, in order to solve this problem, the engineers and technicians have taken various methods of strict control parameter, despite the improvement, but has not eradicated “black mat” this hidden trouble .Electroless palladium layer is introduced in ENEPIG surface coating new technology, from the reaction mechanism stopped nickel-plate oxidation, in the process of immersion gold blocked off nickel-plate contacted with Immersion gold solution, and effectively prevent pervasion and migration of nickel , thus effectively inhibit oxidation of nickel surface, prevent the “black mat” flaw . Not only have given the technology production process and parameter control, but also have microcosmic appearance and diffusibility analysis for the products by using SEM and EDS , the results showed that palladium layer is non-crystalline film with good uniformity of coating thickness, and did not find pervasion of nickel on gold surface, successfully achieve ENEPIG PCB mass production, replace ENIG technology .
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