Metal fusion bonding – Process – Plural joints
Reexamination Certificate
2000-04-26
2001-06-26
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Plural joints
C228S212000, C228S006200, C228S049100, C228S049500
Reexamination Certificate
active
06250538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for mounting components onto substrates of an electrical assembly. In particular, the present invention relates to the mounting of electrical components onto printed circuit boards wherein the method and apparatus for mounting such components includes a compensating element that facilitates an optimal component mounting operation.
2. Description of the Prior Art
U.S. Pat. No. 5,285,946 discloses an apparatus for placing electrical components onto the surface of printed circuit boards. The apparatus includes a suction pipette tip that is spring mounted onto a retaining device. This spring-mounted feature results in a cushioning effect that provides the required contact pressure which is necessary for placing the components onto the substrate, while not damaging the electrical component.
However, the spring-mounted feature may not work as effectively when the electrical component is supplied or delivered to the mounting apparatus by a known component delivery or supply mechanism. During the delivery or supply of the components to the mounting apparatus, a substantial amount of force may be exerted onto the electrical component due to the spring-mounted feature of the retaining device which operates to retrieve the component from the delivery mechanism. This force may be so great that the electrical component is dropped from the retaining device, such as, a suction pipette. If an electrical component is dropped during the delivery of the electrical component to the mounting apparatus, the mounting operation of this specific electrical component must be repeated. In addition, the dropped electrical component would necessarily remain in the mounting apparatus and thus may fatally effect the operation of the mounting apparatus due to errors that may result in the movement of the mounting heads or substrates.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a method and apparatus for mounting electrical components onto substrates of electrical assemblies that provides an effective and optimal delivery of the electrical components from a delivery mechanism. In addition, the present invention supplies an effective and optimal contact pressure that is exerted onto the electrical components as it is delivered from the delivery mechanism or mounted onto the substrate during the component mounting operation.
The present invention includes a retaining device that employs a compensating element to meet these objectives. The compensating element essentially has two members—a spring-type member and a damping member. The spring-type member compensates for the thicknesses of a variety of different substrates and components by generating a contact pressure that is effectively applied during the component mounting operation without resulting in damage to the substrate or component. In addition, the damping member acts to effectively damp or compensate for the force that is exerted by the spring-type member during the component delivery stage. In this way, the retaining device is less likely to drop the component during the delivery stage because the this force is effectively reduced to an amount of force that is less than that generated by a freely oscillating spring.
In an embodiment, the damping member is a shock absorber-type.
In an embodiment, the force due to the delivery of the component acts directly upon a first end of the retaining device that faces towards the delivery mechanism.
In an embodiment, the damping member includes a coupling member that acts to acts to couple the retaining device to the mounting head depending on the position of the retaining device relative to the mounting head. The coupling member is engaged or disengaged by a control unit that allows for the precise and controlled coupling of the restraining device to the mounting head. The coupling member acts to securely couple the retaining device to the mounting head as the mounting unit apparatus acts to receive the electrical component from the delivery mechanism. In turn, the coupling elements acts to decouple or disengage the retaining device from the mounting head so that the spring member can apply an optimal spring contract pressure to the component for mounting the component onto the substrate.
In an embodiment, the coupling member include vacuum coupling, magnetic coupling, friction coupling or mechanical coupling member.
REFERENCES:
patent: 4019668 (1977-04-01), Diepeveen
patent: 4066200 (1978-01-01), Diepeveen
patent: 4140263 (1979-02-01), Diepeveen
patent: 5285946 (1994-02-01), Tomigashi et al.
patent: 5351872 (1994-10-01), Kobayashi
patent: 5368217 (1994-11-01), Simmons et al.
patent: 5422554 (1995-06-01), Rohde
patent: 5447266 (1995-09-01), Misono
patent: 5535873 (1996-07-01), Sakamoto et al.
patent: 5537204 (1996-07-01), Woodhouse
patent: 5661239 (1997-08-01), Takeuchi
patent: 5667129 (1997-09-01), Morita et al.
patent: WO 92/22827 (1992-12-01), None
patent: WO 97/37522 (1997-10-01), None
patent: WO 98/37744 (1998-08-01), None
Bachthaler Thomas
Barnowski Frank
Grasmueller Hans-Horst
Numberger Richard
Cooke Colleen
Dunn Tom
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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