Nickel diffusion

In electronic applications, where it is common to deposit copper and/or copper alloy and tin in sequence, with a nickel diffusion barrier layer, 0.5 fim thick, between the layers present, no failure occurs. Without the nickel layers between bronze/-copper/tin layers themselves, for instance, intermetaUic brittle layer(s) and Kirkendall voids are formed, leading eventually to separation of the coated system and substrate. 

Iron meteorite cooling rates a study of nickel diffusion... 

SY Irrit eyes, skin, resp sys possible skin sens to cobalt, nickel diffuse pulm fib loss of appetite, nau, cough blood changes TO Eyes, skin, resp sys, blood ... 

Nickel diffusion in CulnSe2 thin films was studied at 430 to 520C. Thin films of CulnSe2 were prepared by selenization of CulnSe2-Cu-ln multilayered... 

Procedure. A drop of the test solution, acidified with acetic acid, is placed on filter paper impregnated with rubeanic acid (spot test paper is best). Two zones are formed of difiering acetic acid content. In the central zone the acid concentration is the greatest, and here only the copper is precipitated in the form of an olive-green or black circle. The nickel diffuses farther and forms a blue to violet ring around the central zone. This ring develops more towards the middle as the acetic acid evaporates. 

Low-force, low-voltage separable cormectors and contacts also have wide use in electronic systems [11,12], A variety of different configurations exist, but the substrate of most is made from copper, brass, bronze, or copper-beryllium. The use of copper alloys ensures some susceptibility to environmental degradation. To reduce interfacial resistance and corrosion, the substrate is plated with a nickel diffusion barrier and then with a precious metal (e.g., gold, palladium) [11,13], However, a trade-off exists between plating cost (thickness) and reliability [14]. Hence, physical defects (pores and cracks) are usually present. In the past, connectors and contacts could not be coated because of interference with their function, although some new coating inhibition formulations have been developed for this purpose [11,12]. 

Figure 5.1 (a) A copper-nickel diffusion couple before a high-temperature heat treatment, (b) Schematic repre-... 

Table 16.3 gathers values of corrosion constant and nickel diffusion coefficient in alloy at two temperatures 850°C and 1,100°C. 

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