| 摘要 |
<p>The tin in the bath coats a metal substrate by a replacement reaction; and the bath contains stannous ions, thiourea as at least one complex-former for the stannous ions, and an inhibitor preventing the etching of the metal substrate. The pref. bath contains min. 0.05, esp. 0.05-0.2 mole/l stannous ions; a mole ratio thiourea:stannous ion of min. 10:1, pref. 18-30:1; and mineral acid to keep the pH below 1.0. The pref. bath also contains a hypophosphite; and an inhibitor preventing a loose discoloured Sn deposit, esp. 0.1-3 g/l of a phenol-sulphonic acid or its salt. The yield of tin is min. 40% of the initial tin content in the bath. This bath is similar to those described in US 3303029 and 3917486, used for depositing Sn on Cu, esp. during the mfr. of printed circuit boards. The addn. of an inhibitor prevents the formation of loose, black Sn deposits, and provides a high Sn yield.</p> |
