Electric resistance heating devices – Heating devices – Concentrated heated air stream
Reexamination Certificate
1999-02-22
2001-03-13
Jeffery, John A. (Department: 3742)
Electric resistance heating devices
Heating devices
Concentrated heated air stream
C239S391000, C239S397000, C228S191000, C228S264000
Reexamination Certificate
active
06201930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus for separating and removing integrated circuit chips from circuit boards and for replacing the integrated circuit chips, and more particularly, the invention relates to a system including a heating device for generating a flow of heated air, a circuit board holder for positioning a circuit board during chip removal, and a auxiliary preheater for heating the circuit board.
2. Brief Description of the Related Art
Hot gas desoldering tools are known for removing integrated circuit chips from circuit boards. Generally these tools direct a jet of hot gas at a component to melt the solder which connects the component leads to the circuit board. However, these known tools have a tendency to melt or otherwise damage the component being removed, the surrounding components, or the circuit board by overheating. These known desoldering tools have the additional disadvantage that they are difficult to adjust to a proper location and temperature and are generally difficult to use.
Integrated circuit chips that are to be removed may be traditional dual inline packages (DIP) with metal leads protruding from two sides, may have leads extending from all sides, or may be surface mount devices. Surface mount devices have leads at the perimeter of the device which are flush with the bottom surface of the device. Surface mount devices may also have connection points in the form of conductive pads on a bottom surface of the device allowing connection to the circuit board directly under the component. These surface mount devices allow the components to be more compact but are more difficult to remove without damage. It is desirable to be able to remove a variety of different component sizes and types with a single desoldering tool. Therefore, tools are provided with interchangeable nozzles for accommodating different chips. However, known tools with different nozzles do not provide systems for easily interchanging the nozzles even when hot. Accordingly, it would be desirable to provide a system of interchangeable nozzles which are easy to change.
Desoldering tools also may include a suction removal system for lifting a component off of the circuit board after the solder has been melted. However, these suction systems must be manually advanced into contact with the component risking component damage and adding an additional step for the user. Accordingly, it would be desirable to provide a fully automatic suction removal system for lifting a desoldered component off of a circuit board.
It would also be desirable to provide a system for desoldering which is easy to use, prevents damage to the circuit board or components, and easily accommodates components and circuit boards of different sizes and types.
SUMMARY OF THE INVENTION
The present invention relates to a safe and easily used system for removing and/or reattaching components, such as surface mount technology (SMT) components, from a printed circuit board.
In accordance with one aspect of the invention an automatic vacuum pickup system is provided for removing a component from a circuit board after desoldering. The system includes a desoldering device for directing a heated gas through a nozzle and focusing the gas to solder connection areas of a component on a circuit board to melt solder connections, a suction source connected to the desoldering device, a suction tip provided in the nozzle of the desoldering device for automatically applying suction to the component without manual lower of the suction tip, a suction path extending from the suction source to the suction tip, and a lifting device for applying a predetermined upward force to the suction tip after the application of the suction to the component, wherein the predetermined force is sufficient to lift the component after the solder connections have all been melted but insufficient to lift the component before all the solder connections have been melted.
In accordance with another aspect of the present invention, a desoldering tool includes a tool head, a heating element within the tool head, a fan for passing a gas over the heating element to provide a heated gas stream for desoldering of components from a circuit board, a nozzle removably connected to the tool head for directing the heated gas stream to the component to be removed, a nozzle connection on the tool head for receiving the nozzle, the nozzle connection including at least one spring element for forming a snap-in connection with the nozzle, and a nozzle release mechanism including a rotatable member which rotates about the axis of the nozzle to disengage the at least one spring element and release the nozzle.
In accordance with an additional aspect of the present invention, a desoldering tool includes a tool head, a heating element within the tool head, an adjustable speed fan for passing a gas over the heating element to provide a heated gas stream for desoldering of components from a circuit board, a nozzle for directing the heated gas stream to the component to be removed, a temperature sensor positioned to sense a temperature of the gas stream exiting the nozzle, and a controller for adjusting the speed of the fan based on an output of the temperature sensor to achieve a predetermined temperature for desoldering.
In accordance with a further aspect of the invention, a circuit board holder for positioning circuit boards during attachment or removal of components includes a frame for supporting the circuit board above a work surface, two parallel movable side rails supported on the frame and movable toward and away from one another to accommodate circuit boards of varying sizes, and at least two movable clips positioned on each of the movable side rails for grasping the circuit board, wherein the clips are movable along the rails to a position at which the clips can grasp the circuit board without contacting components on the circuit board.
According to another aspect of the invention, an auxiliary preheater is provided for warming a circuit board in preparation for removal of components from the circuit board. The auxiliary preheater includes a ceramic positive temperature coefficient heating element, and a variable speed fan for directing gas over the heating element toward a circuit board which is positioned above the auxiliary preheater.
In accordance with a further aspect of the invention, a method of controlling a desoldering tool includes the steps of:
providing a desoldering tool with a variable speed fan and a heating element;
providing a plurality of interchangeable nozzles for connection to the desoldering tool to direct heated gas over a component, each of the nozzles configured to provide an airflow profile for a particular size and type of component, the nozzles each having a coded portion which is recognized by the desoldering tool;
inserting one of the nozzles into the desoldering tool; and automatically setting an airflow profile of the fan based on the recognition of the coded portion of the nozzle by the desoldering tool.
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Carlomagno Mike
Close Seth
Lui Raymond
Wallingford Jeff
Burns Doane Swecker & Mathis L.L.P.
Jeffery John A.
Metcal Inc.
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