Metal fusion bonding – Including means to apply flux or filler to work or applicator – By partial or total immersion of work or applicator into liquid
Reexamination Certificate
1999-04-23
2001-02-13
Heinrich, Samuel M. (Department: 1725)
Metal fusion bonding
Including means to apply flux or filler to work or applicator
By partial or total immersion of work or applicator into liquid
C228S049500, C228S261000, C239S413000
Reexamination Certificate
active
06186388
ABSTRACT:
BACKGROUND
This invention relates to soldering.
In one method of soldering, printed circuit boards (PCBs) which are populated with components pass, one at a time, through a three step process: flux is applied to electrical connection points on both the PCB and the components; the PCB and the components are preheated; and the electrical connection points are brought in contact with molten solder.
SUMMARY
In general, in one aspect, the invention features soldering parts (e.g., printed circuit boards) by indexing the parts sequentially and continuously through a series of processing stations. Each of the series of processing stations includes at least one processing position, and the indexer indexes the parts from processing position to processing position. At different processing stations, the parts indexed into those processing stations are simultaneously processed.
Implementations of the invention may include one or more of the following features. The indexer may have a chain and flights connected to the chain and separated along the chain by an indexing distance. Solder may be applied to the parts at a soldering station. The soldering station may include a solder fountain. The solder fountain may have a solder manifold with a first aperture, a solder well plate with second apertures, where the solder well plate is mounted above the solder manifold with the second apertures above the first aperture, modular solder well plates mounted above the second apertures, and a solder chimney mounted to each of the modular solder well plates. The solder chimneys may provide passageways from the solder manifold to a top of the solder chimneys where the parts are soldered, the parts may be of different part types, and each of the modular solder well plates may correspond to one of the different part types. The solder fountain may also include another solder chimney mounted to each of the modular solder well plates. The soldering station may further include a rough part locator that roughly locates a part indexed into the soldering station and a precise part locator that precisely locates the part. The soldering station may also include a guide rail for supporting the part, and a mechanism for raising and lowering the guide rail. Additionally, flux may be applied to precise areas of the parts at a flux station, and the flux station may include a rough part locator that roughly locates a part indexed into the flux station and a precise part locator that precisely locates the part. The flux station may further include a guide rail for supporting the part and a mechanism for raising and lowering the guide rail. The flux station may include a flux sprayer for applying flux to the part, where the flux sprayer includes an air valve, a flux valve, and a controller coupled to activate and deactivate separately the air valve and the flux valve. The controller may activate the air valve before activating the flux valve and deactivate the flux valve before deactivating the air valve. Furthermore, the parts may be preheated and glue used to mount components to the parts may be cured in an oven. The oven may include sparging tubes for blowing heated gas on the parts as the parts are indexed to an exit end of the oven. The oven may also have a guide rail for supporting the parts as they are indexed through the oven and a support rail for supporting the guide rail, where the support rail includes thermal expansion slots for allowing the support and guide rails to thermally expand longitudinally and where the support rail is held in a fixed position at one end and is free to expand away from the fixed position. Moreover, the processing stations may include an identification station having a sensor for determining a type of a part indexed into the station, and the soldering system may include a controller for controlling subsequent processing stations in response to the sensor. The controller may control the amount of time flux is sprayed at each of the parts according to the identified part type, and the controller may control the pump speed of a solder pump according to the identified part type. The parts may be printed circuit boards, and the parts may include pallets having an aperture for holding one of the printed circuit boards. The pallets may include additional apertures for holding additional printed circuit boards.
In another aspect, the invention features a solder fountain. The solder fountain includes a solder manifold for containing solder, and the solder manifold has a first aperture. The solder fountain also includes a solder well plate having second apertures, where the solder well plate is mounted above the solder manifold with the second apertures above the first aperture. Further, the solder fountain includes modular solder well plates mounted above the second apertures, and a solder chimney mounted to each of the modular solder well plates. The solder chimneys provide passageways from the solder manifold to a top of the solder chimneys where solder is applied to the parts. The parts are of different part types, and each of the modular solder well plates corresponds to one of the different part types.
Implementations of the invention may include one or more of the following features. The chimney passageway may be an unrestricted passageway. The solder fountain may include a rough part locator having a stopper arm with an end that provides a datum point and a pusher arm for pushing the part against the stopper arm and a precise part locator having a datum bushing and a slotted bushing on the part and a datum pin and an expansion pin for respectively engaging the datum bushing and the slotted bushing.
In another aspect, the invention features a flux unit for applying flux to precise areas of printed circuit boards. The flux unit includes a rough part locator that roughly locates a printed circuit board within the flux unit and a precise part locator that precisely locates the printed circuit board.
Implementations of the invention may include one or more of the following features. The rough part locator may include a stopper arm having an end that provides a datum point and a pusher arm for pushing the part against the stopper arm. The precise part locator may include a datum bushing and a slotted bushing on the printed circuit board and a datum pin and an expansion pin for respectively engaging the datum bushing and the slotted bushing.
In another aspect, the invention features a flux unit for applying flux to precise areas of printed circuit boards. The flux unit includes a flux sprayer for applying flux to the printed circuit boards, where the flux sprayer includes an air valve, a flux valve, and a controller coupled to activate and deactivate separately the air valve and the flux valve.
In another aspect, the invention features a convection oven for preheating printed circuit boards. The oven includes multiple sequential indexed positions, a nitrogen input mechanism for providing a nitrogen environment, and a pair of parallel guide rails for supporting the printed circuit boards within the oven. The oven also includes sparging tubes for blowing heated nitrogen on a printed circuit board at an oven exit and a pair of parallel support rails for supporting the pair of guide rails. The support rails include thermal expansion slots for allowing the support and guide rails to thermally expand longitudinally and a fastening mechanism extending through the slots for maintaining a set width between the guide rails.
In another aspect, the invention features a method for use in connection with soldering printed circuit boards of different types moving along an automated production line. The method includes identifying a type of each of the printed circuit boards that approaches a flux station on the production line and applying flux to a specific area of the printed circuit board for an amount of time corresponding to the type of the board.
In another aspect, the invention features a method for use in connection with soldering printed circuit boards of different types moving along an automated p
Sadler Steven P.
Vinciarelli Patrizio
Fish & Richardson P.C.
Heinrich Samuel M.
VLT Corporation
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