Penetrating Low Temperature Immersion Tin
Original Publication Date: 1981-Nov-01
Included in the Prior Art Database: 2005-Feb-12
The solderability of copper surfaces on printed circuit boards and in plated through holes can be enhanced by a coating of tin. The tin coating can be applied by an immersion tin process where part of the copper is replaced by tin from a hot (70 Degrees C) aqueous solution containing stannous chloride and other chemicals. In addition to the disadvantages of high temperature preparation and operation, the concentrated aqueous solution has a relatively high surface tension. A primary and essential requirement for subsequent solder assembly of connectors in circuit boards is penetration of the immersion tin solution into small holes which are relatively long. Unless the immersion tin solution penetrates these high aspect ratio holes, tin plating cannot occur and connectors will be only partially soldered in place.