| 摘要 |
<p>Mfr. of printed circuit boards in which Sn or Sn/Pb is deposited electrolytically over the whole of the copper surface including the interior of metallised holes. The circuit is then photoengraved using either a single step process with iron perchloride etch or a two step process with HF/H2O2 and ammonium persulphate. Finally, the Sn/Pb is made to flow over the exposed Cu edges by fluxing and immersing in oil at 250 degrees C. The Sn/Pb layers are uniform in thickness and compn. due to uniform field and current densities during deposition.</p> |
