Adaptive clamp width adjusting device

The present invention describes an adaptive clamp width adjusting device (200) for use in an integrated circuit package process machine. The device (200) includes a travel component (210) and a fixed component (310). The travel component (210) carries a clamp (220a,220b) with an adjustable width and a rotary screw (230a) operable for such adjustment by a driven wheel (232). The fixed component (310), mounted on a base plate (312), includes a motor (320) and a drive wheel (324) attached to the motor shaft. When the device (200) is in a clamp width conversion station (40a), the travel component (210) is aligned above the fixed component (310) so that when the base plate (312) is raised and the drive wheel (324) engages the driven wheel (232), the clamp width is operable to be adjusted by the motor (320) according to a width of a workpiece (W).

FIELD OF INVENTION

The present invention relates to an adaptive clamp width adjusting device. In particular, the invention relates to a clamp adaptive for holding a range of leadframe strips during processing of semiconductor integrated circuits.

BACKGROUND

Manufacture of semiconductor integrated circuits is gearing towards surface mount technology, in which, integrated circuits are formed in packages that are then singulated into individual devices. Examples of these packages are ball grid arrays (BGA) and chip scale packages (CSP). These integrated circuits are often formed on a leadframe or substrate. For example, the leadframes/substrate comes in strips and may vary in widths from about 25-80 mm and lengths from about 140-270 mm.

These packages are often tested and laser marked before being delivered; these machines are generally automated and they process thousands of packages or strips an hour. For a machine to handle a range of semiconductor packages, the handler and associated clamps must accommodate a range of widths of leadframes on which the packages are removeably mounted. Currently, some machine suppliers provide a change kit for each package type and/or leadframe/substrate; when a machine is configured to handle a particular package and/or leadframe, the machine's handler is equipped with a change kit that has a clamping unit associated with the particular package and/or leadframe. A disadvantage of changing the handler with a change kit is that it takes manual effect and time to carrying out the change. Human intervention may introduce errors following the change.

In one approach, U.S. Pat. No. 6,958,917, assigned to Fuji Machine Mfg., Ltd., describes a fragile substrate holding device. The holding device has a contact portion of a receiving member and moveable member being made of an elastically deformable material such as rubber. The holding device may also have a velocity reducing device.

It can thus be seen that there exists a need for a simple and robust device to adaptively hold or clamp the leadframe/substrate of integrated circuit packages during manufacture. Preferably, the clamp device is automated and dispenses with human intervention.

FIG. 1shows a conventional laser marking machine5. As shown inFIG. 1, the laser marking machine5, similar to that illustrated in U.S. Pat. No. 7,155,299, issued to the present assignee, includes an input pick-and-place handler10operable in a Y-direction to pick a strip of integrated circuit (IC) package W one at a time from an input magazine20. Each IC package W is then moved to an input station40of a conveyor30. At the input station40is a clamping device42for holding the IC package for it to be moved along the conveyor30. As shown inFIG. 1, the conveyor30consists of three sections, namely, an input track32, a marking track34and an output track36.

Along the marking track34is a pre-marking inspection station50, a laser marking station52and a post-marking inspection station54. The processed IC packages W are then transferred to an output station60on the output track36. At the output station70is an output pick-and-place handler80operable to move the processed IC packages W to an output magazine70.

SUMMARY

The following presents a simplified summary to provide a basic understanding of the present invention. This summary is not an extensive overview of the invention, and is not intended to identify key features of the invention. Rather, it is to present some of the inventive concepts of this invention in a generalised form as a prelude to the detailed description that is to follow.

The present invention seeks to provide a new pallet for an integrated circuit process machine. The pallet comprises a substrate clamp, which has an adaptive clamp width adjusting or setting device to hold a substrate having a range of widths.

In one embodiment, the present invention provides an adaptive clamp width setting device. The device comprises a travel component and a fixed component. The travel component comprises a fixed clamp portion, an adjustable clamp portion and a rotary screw for adjusting a distance between the fixed and adjustable clamp portions, with the rotary screw being operable by a driven wheel attached thereto. The fixed component comprises a base plate and a motor mounted on the base plate, with the motor shaft having a drive wheel attached thereto. When the clamp width is to be adjusted or set to accommodate a workpiece, the travel component is moved into alignment over the fixed component and the base plate is raised so that the drive wheel engages with the driven wheel and the distance between the fixed and moveable clamp portions is operatively adjusted by controlling the motor according to a width of the workpiece.

In another embodiment, the present invention provides an integrated circuit process machine comprising an adaptive clamp width setting device. The process machine comprises a laser marking machine and/or a testing machine.

DETAILED DESCRIPTION

One or more specific and alternative embodiments of the present invention will now be described with reference to the attached drawings. It shall be apparent to one skilled in the art, however, that this invention may be practised without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals or series of numerals will be used throughout the figures when referring to the same or similar features common to the figures.

FIG. 2shows a laser marking machine100in functional blocks incorporating an adaptive clamp width adjusting or setting device200for use in an integrated circuit package process machine according to an embodiment of the present invention. As shown inFIG. 2, the machine100is similar in functions to the previous machine5except that there are now two conveyors30ain parallel. Each conveyor30acarries a moveable or travel component210of the adaptive clamp width adjusting device200. There are six stations or positions along the conveyors30a. As seen inFIG. 2, on the left hand side of each conveyor30ais an input station40. To the left of the input station is a clamp-width-conversion station40a, while at the extreme right is an output station60. Intermediate to the input- and output-stations are the pre-marking-inspection station50, laser-marking station52and post-marking-inspection station54. To move the adaptive clamp width adjusting device200from station to station, each conveyor30ahas a motor90and linear drive. In other embodiments, other types of motor90and associated position feedback devices are used. For example, the motor90may be a servo motor; it may be coupled with a linear encoder for error detection and correction. The motor90may be a stepper motor coupled with linear and/or rotary encoders. In another embodiment, the motor90is a dc or ac motor coupled with linear and/or rotary encoders. In yet another embodiment, the motor90is a linear motor.

FIG. 3shows a perspective view of the travel component210according to an embodiment of the present invention. As shown inFIG. 3, the travel component210includes a clamp portion that is fixed220awith respect to a longitudinal axis of the conveyor110and an adjustable clamp portion220b. The adjustable clamp portion220bis mounted on a pair of linear guides222so that the adjustable clamp and fixed clamp portions220a,220bare parallel to each other and the distance between them is adaptive to a width of the IC package or strip W to be secured therebetween. As shown inFIG. 3, each of the two ends of the clamps220a,220bhas an L-shaped arm224. One end of the L-shaped arm224is connected to operatively open a jaw221of each clamp220a,220bwhilst its free end has a roller228. The lower sides of the rollers228on each end of the travel component210are arranged to fall within a horizontal plane that corresponds to an actuator plate P disposed in the input station40such that by raising the actuator plate P, the rollers228are mutually rotated upwards, thereby opening the associated clamping jaws221. In the same way, a similar actuator plate P in the output station60is operable to open the clamping jaws221. Each jaw221is biased to close against an associated support bar221athat is fixed with respect to the travel component210by a resilient member (not shown inFIG. 3). In an embodiment, the resilient member is a tension spring. In another embodiment, the resilient member is a compression spring. In yet another embodiment, the resilient member is a torsion spring.

Referring toFIGS. 3,5A and5B, the adjustable clamp portion220bis moveable by a rotary screw-nut assembly230. Both ends of the lead screw230aare separately supported by a bearing231whilst the nut230bis fixedly linked to the linear guides222. As seen inFIG. 5B, the end of the rotary screw230a, on the same side as the fixed clamp220a, has a driven gear232. Mounted on the end of the rotary screw230aand on a near side of the gear232is a brake lever240. The brake lever240is arranged such that a friction disk242is biasedly disposed between the brake lever240and the near side of the driven gear232. One end of the brake lever240has a cam follower244whilst the opposite end is pivoted about a pin246. At an intermediate position between the cam follower244and the pivot pin246, the brake lever240is biased against the friction disk242by a compression spring248. In one embodiment, the rotary screw230ais a leadscrew. In another embodiment, the rotary screw230ais a ballscrew.

The fixed or drive component310of the adaptive clamp width adjusting device200is disposed in the clamp-width-conversion station40aof the conveyor110. As shown inFIG. 4, the fixed or drive component310is mounted on a base plate312. The base plate312is operable to move from a home or retracted position to a conversion or extended position by means of linear actuators314and linear guides315. Mounted on the base plate312are two bearing units322through which two separate drive gears324and associated shafts326are rotatable. A motor320with two in-line output shafts326are coupled to the respective drive gears324so that the motor320, output shafts326and drive gears324form a common longitudinal axis that is parallel to the longitudinal axis of the rotary screw230aon the travel component210. Each drive gear324is substantially below the matching driven gear232on the travel component210when the clamp adjusting device200is moved into the clamp-width-conversion station40a; the teeth of drive gears324and driven gears232are engaged when the base plate312is raised to its extended position by the actuators314. At the same time, the cam follower244on the brake lever240has moved on a cam surface330S of a release cam330located on the drive component310of the adaptive clamp width adjusting device200, such that pressure exerted on the friction pad242is released and the motor320is then operable to turn the gears232,324, thereby operative to adjust the distance between the adjustable clamp portion220band the fixed clamp portion220ato accommodate another type of IC package W having a different width.

An advantage of the present invention is that the travel component210of the adaptive clamp width adjusting device200is operable to travel on the respective conveyor110without a motor mounted thereon. This means that the mass and inertia of the travel component210are smaller and this entails the use of a smaller drive motor90for the conveyor110. In addition, an actuator plate P for opening jaws of the adaptive clamp width adjusting device200need only be provided at the input- and output-stations40,60associated with the respective conveyor110. With the present invention, the mass and inertia of the moveable component210are lighter by at least the masses and inertias of the motor and actuator plates when compared to known devices. In addition, there is no need to provide a flexible cable carrier and cable for a motor on the travel component210.

Another advantage of the present invention is that the drive component310uses one motor320to drive two gears324. With this invention, two conveyors110are operable in parallel, and any idle time of the IC package processing machine is reduced; as a result, the machine throughput (in terms of units handled per hour) and productivity are increased.

In another embodiment of the adaptive clamp width adjusting device200, the drive gears324and driven gear232are made of matching friction wheels. In one embodiment, the friction wheel is made of a material that is non-slip, such as, an elastomer. In another, the friction wheel is made up of a solid material but the contact surface is coated with or covered by a non-slip material. In another embodiment, the friction wheel has a non-slip band on the contact surface. In yet another embodiment, only one friction wheel has such a non-slip coating, surface or band.

Other embodiments of the friction brake are also possible. For example, in an embodiment, a tension spring is used instead of a compressing spring. In another embodiment, a torsion spring operable at the pivot pin246may be used.

While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the invention. For example, whilst a laser marking machine is described, the principle of the present invention may be used in an IC strip testing machine. In addition, the IC strip testing machine may be integrated with a laser marking machine. In another example, a leadscrew may be used in place of a ballscrew, or vice versa. In yet another example, a linear drive may be configured with a belt and pulley drive or a linear motor.