Cu6Sn5 layer in the copper-tin reaction couple

Linear growth of the Cu6Sn5 layer in the copper-tin reaction couple 

The Cu-Sn specimens for experiments were prepared by sequential deposition of copper (560 nm) and tin (200 or 560 nm) films on quartz discs under vacuum. To prevent any reaction during the specimen preparation, a tin film was deposited after cooling the substrate with a copper film down to the liquid nitrogen temperature (for more detail, see Ref. 64). 

At room temperature a tin film of 200 nm thick was completely consumed in the formation of the CueSn5 intermetallic compound within 35 days. The dependence of the thickness of the Cu6Sn5 layer on the duration of interaction of copper with tin at 20°C for a 560 nm Cu-500 nm Sn specimen, obtained by K.N. Tu and R.D. Thompson, is shown in Fig. 1.11. It is seen that the experimental points produce a straight line in the coordinates x-t, indicative of linear growth kinetics. 

The formation of the Cu6Sn5 intermetallic layer is due to partial chemical reaction between the diffusing tin atoms and the surface copper 

From the data in Fig. 1.11 (see also Ref. 64), it follows that k0sni+ ocU2 = 4x10 14 ms-1. 

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