Improved Lead Structure for Surface Mount Components
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
The reliability of Surface Mount Components (SMCs) is strongly dependent upon the strength of the solder bonds which hold the components Plastic Leaded Chip Carriers (PLCCs), Small Outline Packages (SOPs), etc. to circuit boards. It has been found that larger area components, high I/O count PLCCs for example, may fail because the surface solder bonds fail when the components are subjected to physical stress. The strongest bonds are those for which the solder fillet completely surrounds the I/O lead. The structure described below facilitates the flow of the solder over the entire I/O lead during the solder reflow operation. Elimination of trapped gas is important. Before vapor phase reflow, the circuits are baked with the components in place to drive volatile liquids from the solder paste.