In the electronics industry, components having at least one planar surface are often handled by a vacuum pickup tool. The typical vacuum pickup tool comprises a shaft whose tip is provided with an orifice surrounded by a sealing surface. The sealing surface about the orifice, when brought into contact with the planar surface on the component, forms a substantially airtight seal therewith. When a partial vacuum is drawn through the orifice, a vacuum will be drawn over a portion of the area on the surface of the component. In this way, a force, referred to as a "vacuum" force, caused by a difference between the air pressure and partial vacuum, is exerted against the component which allows the component to be engaged by the vacuum pickup tool at a storage site. Once engaged, the component can then be transported for placement on a circuit board. By interrupting the vacuum drawn through the orifice, the component can be released from the vacuum pickup tool and the component can be thereafter bonded to the circuit board.
The magnitude of the vacuum force on the component varies with the size of the area (referred to as the vacuum area) on the planar surface of the component over which the vacuum is drawn. The size of the vacuum area varies directly with the size of the orifice, so that the larger the orifice, the heavier the component that can be engaged by the vacuum pickup tool. However, making the orifice larger than the area of the planar surface on the component prevents the formation of an airtight seal between the tool tip and the component which reduces magnitude of the force exerted on the component.
Presently, the range in the size and weight of the components to be handled is so wide as to preclude the use of a vacuum pickup tool having a single diameter orifice in its tip. In the past, this problem has been overcome by making the tip at the end of the vacuum pickup tool detachable. In this way, the tip can be interchanged with one having a different size orifice so as to permit components of a different size and weight to be engaged by the vacuum pickup tool. However, the interchange of tips requires either manual intervention or the addition of complex mechanical equipment to automatically change the tips, both alternatives being undesirable.
Thus, there is a need for a vacuum pickup tool which may be automatically adjusted in a convenient, simple manner to handle components of different size and weight.