>From jamesp Tue Nov 5 11:47:33 1996 To: [log in to unmask] Subject: re: Surface Mount Land Patterns Content-Length: 1003 Gary, Thanks for the "X" info. This "X" column of information is probably the only information in the spec that we habitually ignore, being that we have found it characteristically excessive in the width dimension. We have found that the wider pads tend to allow skewing during reflow. We have been assuming the strength in the Sn pedestal and toe/heel fillet as the primary region of concern for solder formation. I'm not sure if this is wise, but we have made our assumptions for "X" dims : nom. +.005 and not being concerned as much about a side fillet. What is your opinion about this? Is there possibly another mechanism for skewing that we didn't think of? For long term reliability reasons we are trying to minimize temp exposures from rework as much as possible The numbers have improved, but haven't neccessarily determined the direct causes for the skewing. Thanks in advance, James Patten TRW Space Electronics **************************************************************************** * The mail list is provided as a service by IPC using SmartList v3.05 * **************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ****************************************************************************