Metal fusion bonding – With means to remove – compact – or shape applied flux or filler – By fluid blast or suction
Reexamination Certificate
1997-12-17
2001-06-19
Ryan, Patrick (Department: 1725)
Metal fusion bonding
With means to remove, compact, or shape applied flux or filler
By fluid blast or suction
C228S042000, C228S119000, C228S191000, C228S234100, C228S264000
Reexamination Certificate
active
06247630
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to the mounting and removal of electronic components from a printed circuit board. More particularly, this invention relates to a technique for uniformly melting the solder attaching a surface mount device to a printed circuit board.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
A flow control nozzle for hot gases includes an input end to receive a hot gas. An output end of the flow control nozzle delivers the hot gas to a surface mount device connected with solder to a printed circuit board. A gas distribution mechanism is positioned between the input end and the output end. A gas flow control mechanism is positioned in the gas distribution mechanism to selectively alter the flow of the hot gas through the gas distribution mechanism such that the gas distribution mechanism and the gas flow control mechanism operate to deliver the hot gas to the output end in a substantially uniform manner that facilitates substantially uniform melting of the solder.
The gas flow control mechanism of the invention is relatively easy to fabricate. Despite its relatively simple structure, the gas flow control mechanism provides refined flow control. As a result, solder is melted relatively uniformly, thereby allowing removal and replacement of surface mount devices.
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Product manual, “Freedom 2000 Rework Station”, Conceptronic, Inc., Nov. 1994.
Cilia Michael
Terry Lance
Tran Camnhung
Pennie & Edmonds LLP
Ryan Patrick
Stoner Kiley
Sun Microsystems Inc.
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