Investigation of rework for straddle mount connectors

Abstract

With the advancement of the motherboard multiple functions, more and more connectors are mounted on the Printed Circuit Board (PCB) to interconnect electronic components or sub-functional daughtercards. Among different types of connectors, Straddle Mount Connector (SMC), a typical surface mount connector with leads to be soldered on both top and bottom sides of the PCB and with high mechanical strength, is widely used on server motherboards and other systems to serve as power or signal interconnection. As the straddle mount connectors have leads on both top and bottom sides of the printed circuit board, it brings some challenges for the hot gas rework process without compromising the quality and reliability. The traditional hot gas rework nozzle of blowing hot air on localized one side of PCB is not suitable for the rework of straddle mount connectors, the heat can not be evenly distributed on the leads soldered on both sides of PCB, , especially for the board with thickness more than 4mm, when the solder on bottom side get melted, the top side temperature will be too high and causing damage to PCB. It is also very difficult to remove the straddle mount connectors from PCB by using the traditional rework method, nozzle and fixture. This paper presents a rework processes for straddle mount connector with a newly designed nozzle that can evenly distributing the hot air on both sides. The fixtures for removing and replacing the connectors during rework process will be discussed as well.. The rework process will be optimized and compared with the traditional singleside method in this work. The test configuration and the experimental data will be reported in details. The results indicate that the straddle mount connectors can be removed and placed successfully and conveniently by using the newly designed nozzle and fixtures. In addition, the reliability performance of this new method on the solder joint after rework will be also discussed, including thermal shock and accelerated temperature cycling, etc.