WO2001004573A1

WO2001004573A1 - Flatness tester for shipping trays

Info

Publication number: WO2001004573A1
Application number: PCT/US2000/018737
Authority: WO
Inventors: Paul W. Shaw; Curt A. Hurd; Richard M. Stein
Original assignee: Re Source America IP
Current assignee: Re Source America IP
Priority date: 1999-07-12
Filing date: 2000-07-10
Publication date: 2001-01-18
Anticipated expiration: 2002-01-12

Abstract

A method for testing the flatness of shipping trays. The method consists of generating an optical field, placing an optical detector in communication with the optical field, actuating the optical field to a platen, having a shipping tray on the platen and monitoring an interaction of the shipping tray with the optical field, and using a detector to detect the magnitude of the interaction of the shipping tray with the optical field to measure the shipping tray's flatness and determining if the tray's flatness is within a specified tolerance.

Description

FLATNESS TESTER FOR SHIPPING TRAYS

Technical Field

The invention relates generally to reusable, refurbished planar packaging and shipping trays which can be used to protect devices during their manufacture, transport and storage. More particularly this invention relates to an apparatus for testing the planarity of a packaging tray.

Background Information Planar shipping or packaging trays are commonly used to transport and store products or articles of manufacture. The planarity of the trays allows stacking for ease of shipping and/or storing articles contained in the trays. The shipping trays can be used for storing a variety of products such as semiconductor chips, porcelain, and other fragile products.

Typically, shipping trays have an interlocking profile on their perimeter to allow stacking. When shipping trays are stacked on top of each other the cavities in the trays form volumes used for storing products. When trays are stacked, these features protect the products by restricting device movement, regardless of stack orientation. By maintaining tray flatness, a better fit between trays is achieved which results in improved product protection.

During manufacture, some products need to be exposed to high temperatures as part of a baking or curing process. In an effort to reduce manufacturing time, some product manufacturers have employed shipping trays made of plastic materials that can withstand high temperatures. This allows the manufacturer to cure the products while the products are in the tray. This eliminates the transfer of products from a vessel for "baking" the products to a tray for shipment and/or storage. However, trays may warp due to repeated exposure to high temperatures. Warped trays have reduced ability to protect the product.

Products are often placed in trays for storage and eventual shipment to facilities that incorporate the products as components into other products. Many trays of this type are discarded after a single use. If the tray remains flat after use it may be reused. Many manufacturers require that the planarity tolerance of trays be less than 0.030 inches to prevent damage to products due to excessive movement within the tray during shipment and transport. There are three typical methods for checking planarity. In the first method the tray is placed on a known flat surface such as a granite surface plate. Then, using a height gauge, the upper surfaces of the tray are measured and compared to those specified by design. Any tray having a point with a measured height that exceeds the sum of the design height and the specified planarity tolerance is considered defective. The second method, an alternative to the first method, consists of placing a feeler gauge less than or equal to the specified planarity tolerance under the perimeter of the tray. If the feeler gauge freely passes under the perimeter, the tray is considered defective.

The third method of checking tray planarity employs a coordinate measuring machine. Using this method, the tray is placed on the platen of the machine, which has a mechanized arm that is able to travel in the X, Y, and Z axis relative to the platen. Following a pre-programmed route, the arm of the coordinating measuring machine is brought down on various points of the tray's upper surface, measuring the height of the tray at that point. As with the first method, if the sensed height of the tray exceeds the sum of the design height and the planarity tolerance, the tray is considered defective. These methods have several disadvantages. In all cases, the rate of inspection is slow, sometimes precluding the testing of all trays. Since all trays may not be inspected, sampling methods are employed in a statistically-controlled manufacturing environment. The two manual methods are labor intensive and prone to inaccuracy due to human error. The use of a coordinate measuring machine is more accurate, but is exceedingly slow and the equipment is expensive. That method also entails contact with the tray, which can lead to inaccurate measurement due to displacement or distortion of the tray.

Accordingly, there is a need in the art for an accurate and expedient means of measuring the planarity of shipping or storage trays.

Summary of the Invention The present invention provides an apparatus for testing the flatness of an object. In a preferred embodiment, the object is a reusable shipping tray. In a highly-preferred embodiment, the object is a shipping tray adapted for transporting semiconductor chips. In one embodiment an apparatus of the invention comprises an optical field generator, an actuator for moving the optical field into communication with the packaging tray, a detector for detecting the optical filed, and a processor in communication with the detector for determining the flatness of a tray. In another embodiment of the invention, the optical field generated by a laser. In another embodiment of the invention, the optical field is generated by an array of lasers. In addition there is a corresponding array of detectors that move in tandem with the array of lasers.

In a preferred embodiment, an apparatus of the invention comprises an actuator that is a ground shuttle for moving the optical field into communication with the object to be tested.

In another preferred embodiment, an apparatus of the invention comprises a detector that detects any interaction of the optical field with the object to be tested. The interaction corresponds to a measured response. The measured response is compared to a predetermined tolerance level. In another embodiment of the invention, a graphical interface processor allows a user to view the measured response. The graphical interface also allows the user to change the predetermined tolerance level depending on the object to be measured. The object to be measured is rejected if the detector measures a response greater than a predetermined tolerance level.

The invention also comprises a lift mechanism adjacent to the actuator for positioning and loading each object and a feed conveyor proximal to the lift mechanism for stacking the objects to be measured.

Another embodiment of the invention provides a method for measuring the flatness of an object. In one embodiment, the method comprises generating an optical field, actuating the optical field into communication with an object, using a detector to detect a response of the object interacting with the optical field, and processing a signal from the detector which corresponds to the optical field interacting with the object to determine the object's planarity.

In another embodiment, a method of the invention comprises generating an optical field, placing an optical detector in communication with the optical field, actuating the optical field to a platen, providing an object on the platen, and monitoring an interaction of the object with the optical field, using a detector to detect the magnitude of the interaction of the object with the optical field, and determining whether the objects planarity corresponds to a predetermined tolerance level.

Another embodiment of the invention relates to a system for measuring the planarity of packaging trays. In one embodiment, the system comprises an optical field, a load plane for loading packaging trays, a precision ground shuttle that actuates an optical field into communication with the packaging trays, a detector for detecting a response to an interaction of the optical field with the packaging trays, and a processor in communication with the detector for monitoring the interactions of the packaging trays with the optical field.

In another embodiment of the invention, a system further comprising a feed conveyor in the load plane for moving the packaging trays onto a lift mechanism wherein the precision ground shuttle is orthogonally positioned near the load plane and adjacent to the lift mechanism onto which the packaging trays are placed.

In another embodiment of the invention, the system detects a response that falls within a predetermined tolerance level, and sends the trays that are within the predetermined tolerance level for stacking. When the system detects a response falling outside a predetermined level, the trays that are outside the predetermined tolerance level are sent to a repository.

The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.

Brief Description of the Drawings In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. FIG. 1 is a perspective view of a shipping tray. FIG 2 is a top view of the flatness tester system. FIG 3 is a side view of the flatness tester system. FIG 4 is a schematic diagram illustrating tray flatness being measured.

Detailed Description of the Invention Referring to FIG. 1, shown is a shipping tray 10, which is used for shipping products. The tray may be used for multiple shipments provided the tray remains flat, as defined by a planarity within a certain tolerance level. Typically this tolerance level is set to be less than or equal to 0.030 inches.

Referring to FIG 2, shown is a top view of a system 12 for measuring the flatness of an object and FIG. 3 is a side view of the system 12. Many different objects can be measured by this invention, however, for exemplification of this invention, the object that is measured is a shipping tray used for transporting semiconductor chips. Stacks of shipping trays 14, 16 and 18 to be measured are loaded onto the system 12. Referring to FIG. 3, stacks of trays to be measured 14, 16, and 18 are placed on an input conveyor 50. The input conveyor or load plane 50 is driven by belt drive 60 which may be driven by any conventional source known to those skilled in the art. The conveyor 50 loads the lift mechanism or elevator 52 with a stack of trays 14 to be measured. The elevator 52 lifts the stack of trays 14 so that individual trays from tray stack 14 may be picked up by a feed conveyor or gripper 54. The gripper 54 picks up an individual tray 20A from tray stack 14 at gripper position 54A and places the tray 20B on a platen 58 at gripper position 54B.

Once the tray 20B is on the platen 58 a shuttle 22 (FIG 2) passes over tray 20B. The shuttle 22 has a laser 24 and a detector 26. The laser 24 may be an array of lasers and the detector 26 may be an array of detectors. The shuttle 22 is driven by an actuator (not shown) which moves the shuttle 22, with the attached laser 24 and detector 26 over shipping tray 20B. The actuator can be a servo motor and can be connected to the shuttle by a belt.

Figure 4 is a schematic showing how a shipping tray 20B is measured using a laser 24 and detector 26. The laser 24 is a measuring laser and is known in the art as a laser micrometer. The laser 24 generates an optical field 64 which interacts with shipping tray 20B, and casts a shadow 66 which is detected by detector 26. The detector 26 can read either the shadow 66 or a portion of the optical field above the shadow 67. The height of the reading, which is either the shadow 66 or the optical field above the shadow 67 is a measured response, corresponds to the height of the shipping tray 20B. The detector 26 is comprised of a Closed Coupled Device (CCD) image sensor 27, which converts the shadow 66 or the optical field above the shadow 67 to a voltage, and the voltage is sent to processor 72 by way of connector 68. The processor 72 has an analog to digital converter 80 which converts the voltage to a digital signal which can be read by processor 72.

The processor 72 has the design height and planarity tolerance information for a plurality of shipping tray designs stored in the processor 72. The processor 72 takes the digital signal which represents the height of shipping tray 20B and compares the height as determined from digital signal to the design height of the tray plus a planarity tolerance. The planarity tolerance is typically 0.030 inches. If the measured tray height is within the design height plus the planarity tolerance, the processor 72 determines that the shipping tray 20B may be reused. If the measured tray height is greater than the design height plus the planarity tolerance, the processor 72 rejects that shipping tray 20B. The processor 72 has a graphical user interface 78 which allows a user to view a histogram of measured responses. In addition, the graphical user interface 78 also allows a user to select the configuration of the shipping tray being measured from multiple shipping tray configurations that are stored in processor 72. Once the processor 72 determines that a shipping tray 20B may be reused, the gripper at 54B takes shipping tray 20B and moves to gripper position 54C and tray position 20C. Shipping tray 20C is then picked up by rotary conveyor 28 and is placed on a stack of acceptable shipping trays 32. As the stack of acceptable shipping trays 32 is filled a drop elevator 74 moves the stack of trays 32 down so additional acceptable trays can be added to stack 32. As the stack of acceptable trays 32 reaches full height, output conveyor 76 moves the full stack of acceptable trays over so a new stack of acceptable trays may be started. FIGS 2 and 3 show stacks of acceptable trays 32, 34 and 36. The cycle time for taking, measuring, and stacking a shipping tray takes six seconds or less. If processor 72 determines that shipping tray 20C may not be reused, rotary gripper 28 takes tray 20C and places tray 20C in scrap bin/repository 40.

Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.

Claims

Claims What is claimed is: 1. A system for testing planarity of an object comprising: an optical field generator; an actuator for moving an optical field into communication with an object; a detector for detecting a response to an interaction of the optical field with the object; and a processor in communication with the detector for monitoring the interaction of the optical field with the object.

2. The system of claim 1 wherein the object comprises a packaging tray.

3. The system of claim 2 wherein the packaging trays are used for transporting semiconductor chips.

4. The system of claim 2 wherein the packaging trays are recyclable and reusable.

5. The system of claim 1 wherein said optical field generator comprises a laser.

6. The system of claim 5 wherein said laser comprises a laser micrometer.

7. The system of claim 5 wherein said optical field generator comprises an array of lasers and a corresponding array of detectors.

8. The system of claim 1 wherein the optical field and the detector move in tandem.

9. The system of claim 1 wherein the detector detects any interaction of the optical field with the object.

10. The system of claim 1 wherein the object casts a shadow onto the detector when the object interacts with the optical field.

11. The system of claim 10 wherein the shadow on the detector corresponds to a measured response.

12. The system of claim 11 wherein the magnitude of the measured response is compared to a predetermined tolerance level.

13. The system of claim 11 wherein the measured response comprises a voltage.

14. The system of claim 1 wherein said actuator comprises a ground shuttle for moving the optical field into communication with the object.

15. The system of claim 1 wherein the processor comprises a graphical interface.

16. The system of claim 15 wherein the graphical interface allows a user to view a histogram of the measured response.

17. The system of claim 15 wherein the graphical interface allows a user to change the style of packaging trays.

18. The system of claim 1 wherein the object is rejected when the detector measures a response greater than a predetermined tolerance level.

19. The system of claim 1 further comprising: a lift mechanism adjacent to the actuator for positioning and loading each object; and a feed conveyor proximal to the lift mechanism for stacking the objects.

20. A method for testing planarity of an object comprising the steps of: generating an optical field; actuating the optical field into communication with an object; using a detector to detect a response to the object interacting with the optical field; and processing a signal from the detector which corresponds to the optical field interacting with the object.

21. A method for testing planarity of an obj ect comprising the steps of: generating an optical field; placing an optical detector in communication with the optical field; actuating the optical field to a platen; having an object on the platen and monitoring an interaction of the object with the optical field; using a detector to detect the magnitude of the interaction of the object with the optical field; and determining whether the magnitude of the interaction corresponds to a predetermined tolerance level.

22. The method of claim 21 wherein having an object on the platen casts a shadow onto the detector.

23. The method of claim 22 wherein a shadow on the detector corresponds to the magnitude of the interaction of the object with the optical field.

24. The method of claim 21 wherein the interaction comprises an optical response to the object interacting with the optical field.

25. The method of claim 21 wherein said testing has a cycle time less than or equal to approximately 6 seconds per object.

26. The method of claim 21 wherein the predetermined tolerance level is less than or equal to approximately 30 mils.

27. A system for testing planarity of packaging trays comprising: an optical field; a load plane for loading packaging trays; a precision ground shuttle that actuates an optical field into communication with the packaging trays; a detector for detecting a response to an interaction of the optical field with the packaging trays; and a processor in communication with the detector for monitoring the interactions of the packaging trays with the optical field.

28. The system of claim 27 further comprising: a feed conveyor in the load plane for moving the packaging trays onto a lift mechanism wherein the precision ground shuttle is orthogonally positioned near the load plane and adjacent to the lift mechanism onto which the packaging trays are placed.

29. The system of claim 27 wherein packaging trays that produce a response that falls within a predetermined tolerance level are sent to a stacker for stacking.

30. The system of claim 27 wherein the packaging trays that produce a response that falls above a predetermined tolerance level are sent to a repository.