SMT HANDBOOK - LEAD DESIGN

Beyond the factors under the control of the connector manufacturer, one of the most critical variables affecting the quality of the solder joint is the design of the solder pad on the board. Pad layout for specific connector applications depends on a number of variables:

lead configuration
connector pitch
accuracy and consistency of placement equipment
tolerance build-up among components
number, spacing and proximity of traces
solder paste thickness and alloy
type of reflow process and number cycles

Because there is such a variety of factors that affect solder joint quality, it is important to specify and obtain connectors of the highest quality, designed to meet the stringent needs of surface mount applications, to avoid needless complications in the board manufacturing process.