Most electronic systems include a printed circuit board with several surface mount devices connected to the printed circuit board. As used herein, the term surface mount device includes connectors and semiconductor packages. Frequently, the surface mount devices are connected to the printed circuit board through the use of solder. Sometimes it is necessary to remove and replace a surface mount device. When removing a surface mount device, it is necessary to melt the solder and then lift the device from the printed circuit board. When replacing a surface mount device, it is, necessary to uniformly melt the solder that is used to attach the device.
Problems arise in the prior art when melting the solder associated with a surface mount device. The problem arises because existing flow control nozzles do not uniformly distribute a hot gas stream. This is a particular problem in the case of long (e.g., 4 inches) surface mount devices. As a result, the solder melts unevenly. Consequently, solder that is not completely melted will produce greater resistance when lifting the surface mount device from the printed circuit board. This can result in damage to the surface mount device and printed circuit board. Another problem is that the surface mount device may become damaged if it is exposed to excessive heat while waiting for the solder at another part of the surface mount device to melt.
In view of the foregoing, there is a need for an improved technique of melting solder associated with surface mount devices positioned on a printed circuit board. The improved technique should provide relatively uniform gas distribution to facilitate substantially uniform melting of the solder. This will allow a surface mount device to be lifted from a printed circuit board or re-soldered to a printed circuit board with minimal damage.