| 摘要 |
A method of preparing printed circuit boards is described in which the solder mask on the circuit pattern and, optionally, the solder on the through-holes surrounding pads, and like areas to receive solder, is applied over a layer of lead covering the copper layer at said loci. This method eliminates the need to strip tin-lead alloy etch resist which step is commonly employed in prior processes. The method overcomes the problems associated with migration of tin into the copper layer which can occur when tin-lead alloys are applied directly over copper. |
