By no means should you press fit a connector or pin of any sort into a platted thru hole that has intermal layer thermal layers, or internal pads for that matter. By pressing the pin into the hole you run the risk of breaking the continuity of the PTH and not make a connection to the internal layers, or possibly making only intermittent connections internally. >>> Eddie Brunker <[log in to unmask]> 09/23/97 09:50am >>> I posted a question a few days ago about Press Fit Connectors. I've started to understand the answer myself. Press Fit connectors are a mechanical means of making contact with no soldering. PTH connectors which go through a soldering process that requires CAD layout to have thermal relief to copper planes. This means a connection to the via which doesn't go all the way around the circumference but only makes contact in two or four points. This is to reduce the heat sinking effect of the copper plane on the via which would cool it during a thermal cycle (soldering operation) and thereby create potential defects. Press Fit connectors can be mechanically inserted without soldering therefore the via can be connected to the plane along its full circumference with no thermal relief (a solid contact). This solid contact in turn gives lower inductance for power pins on a backplane.(Which is what the designers want). I get the impression that Press Fit is used not just by Compact PCI protocall (in our case 6U card computers) but anyone heading at high bus speeds in a backplane. Obviously the speeds are going up and this is to be commended. But the trend of the assembly industry to use Press Fit connectors to address this is seriously worrying. Why should the Design fraternity dictate the assembly technique and not the end result required. In other words if they want reduced inductance why don't they just specify no thermal relief and let the assembly heads worry about the means of connection and whether soldering will be a problem. APPLYING A FEW TONS OF PRESSURE TO AN ASSEMBLY to attach a connector seems to me to be primitive method. Yet this is the trend for manufacture in the future for high speed applications. Why is this basic method being promoted for the future? Do people out there have any means of automating this process within a line? How can rework ever be possible considering the assemblies are expensive board level computers worth thousands of pounds (dollars). What is the typical yield for such a process? How easy is it to destroy assemblies in a Press? Does anyone out there use solid connection to vias on copper planes for the wave soldering process? Has anybody done any trials on this? Pressumably the thermal aspect can be sorted by sufficient pre-heat. Do wave solder machines need to use convection pre heat zones. Are such machines available? It would be nice to see the design people told that there should be a STOP TO THIS BARBARIAN ASSEMBLY TECHNIQUE. It would be nice to see the connector manufacturers make connectors which provide shielding and conform to Compact PCI format and IEC1076 (or high speed bus formats) in Plated Through Hole OR Surface Mount packages. Pressumably SURFACE MOUNT WOULD HAVE NO THERMAL RELIEF DEMANDS as modern Convection ovens have no problems dealing with solid contacts to vias. So why not develop the Surface Mount version of the connector? Please, please, please there must be someone out there with an opinion on this. Thanks ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################