A method and apparatus for ultrasonic inspection of one or more objects in an object holder. In a first embodiment of the method, the objects are immersed in a tank containing coupling fluid and a flow of fluid is generated in the tank beneath the object holder, thereby producing a suction pressure that tends to hold the objects in the holder. Each object is insonified with ultrasound from an ultrasonic transducer and the ultrasound reflected from or transmitted through the object is sensed. In a further embodiment, the object to be inspected is moved between the upper and lower chambers of a scanning station, over a surface in the lower chamber. A coupling fluid is supplied to the upper chamber so that coupling fluid flows through one or more holes in the bottom of the upper chamber and fills the space between the ultrasound emitting surface of the ultrasonic transducer and the object to be scanned, thereby providing coupling for the ultrasound and tending the hold the objects in the object holder.
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23. An ultrasonic test chamber for use in inspecting an object in an object holder, the ultrasonic test chamber comprising at least one of a de-bubbling station and a scanning station,
station chamber;
wherein the upper scanning station chamber is operable to receive and dispense coupling fluid at a rate sufficient to provide fluid coupling between the ultrasonic transducer and the object and to provide a static fluid pressure acting on the object and tending to retain the object in the object holder.
17. A method for removing bubbles from the surface of an object in an object holder prior to ultrasonic scanning of the object, the method comprising
moving the object between the upper surface of a lower de-bubbling chamber and a cover containing at least one aperture large enough to allow fluid and bubbles to pass but small enough to prevent passage of the object; and
supplying a flow of fluid to a lower de-bubbling chamber so that fluid flows upwards past the object through the at least one aperture in the cover.
16. A method for removing bubbles from the surface of an object in an object holder prior to ultrasonic scanning, the method comprising:
supplying a flow of fluid to an upper de-bubbling chamber so that fluid flows through one or more holes in the bottom of the upper de-bubbling chamber; and
moving the object beneath the upper de-bubbling chamber through the flow of fluid from the one or more holes in the bottom of the upper de-bubbling chamber,
wherein the static pressure of the fluid exerts a downward force on the object tending to hold the object in the object holder.
1. A method for ultrasonic scanning of an object supported by an object holder in a scanning station, the scanning station comprising an upper chamber and housing an ultrasonic transducer with an ultrasound emitting surface, the method comprising:
moving the object beneath the upper chamber;
insonifying the object with ultrasound from the ultrasonic transducer;
supplying a coupling fluid to the upper chamber so that coupling fluid flows through one or more holes in the bottom of the upper chamber onto the object, thereby filling the space between the ultrasound emitting surface of the ultrasonic transducer and the object; and
sensing ultrasound reflected from or transmitted through the object,
wherein the static pressure of the coupling fluid exerts a downward force on the object tending to hold the object in the object holder.
18. A method for ultrasonic inspection of an object in an object holder holding one or more objects, the method comprising:
immersing the object and the object holder in a tank containing coupling fluid;
generating a flow of fluid in the tank beneath the object holder, whereby a suction pressure is produced tending to hold the one or more objects in the object holder;
the de-bubbling station comprising:
an upper de-bubbling chamber having at least one opening in its bottom surface, the at least one opening being sized so that the object cannot pass through; and
a lower de-bubbling chamber located below the upper de-bubbling chamber and spaced therefrom to allow the object to pass between the upper de-bubbling chamber and the lower de-bubbling chamber;
wherein the lower de-bubbling chamber is operable to supply a flow of fluid directed towards the object and the upper chamber is operable to receive at least some of the flow of fluid through the at least one opening; and
the scanning station comprising:
a holder support structure for supporting the object holder;
an upper scanning station chamber positioned above the holder support structure; and
a first ultrasonic transducer located within the upper scanning
insonifying the object with ultrasound from an ultrasonic transducer; and
sensing ultrasound reflected from or transmitted through the object.
2. A method in accordance with
3. A method in accordance with
4. A method in accordance with
collecting the coupling fluid in the lower chamber; and
recirculating the coupling fluid to the upper chamber.
5. A method in accordance with
6. A method in accordance with
7. A method in accordance with
8. A method in accordance with
9. A method in accordance with
10. A method in accordance with
11. A method in accordance with
flowing the coupling fluid from a de-bubbling chamber between the
raised surface of the lower chamber and the object holder.
12. A method in accordance with
13. A method in accordance with
14. A method in accordance with
reducing the air pressure below the object holder so as to prevent the object from being dislodged from the object holder.
15. A method in accordance with
reducing the air pressure below the object holder so as to prevent the object from being dislodged from the object holder; and
removing fluid from the object in the object holder using a brush.
19. A method in accordance with
20. A method in accordance with
21. A method in accordance with
22. A method in accordance with
24. An ultrasonic test chamber in accordance with
25. An ultrasonic test chamber in accordance with
26. An ultrasonic test chamber in accordance with
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28. An ultrasonic test chamber in accordance with
29. An ultrasonic test chamber in accordance with
30. An ultrasonic test chamber in accordance with
31. An ultrasonic test chamber in accordance with
a lower scanning station chamber located below the upper scanning station chamber and spaced from it to allow the object to pass between the upper scanning station chamber and the lower scanning station chamber.
32. An ultrasonic test chamber in accordance with
33. An ultrasonic test chamber in accordance with
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This application claims priority to and benefit of earlier filing date of U.S. Provisional Application No. 60/396,347, filed Jul. 16, 2002, the content of which is incorporated herein by reference.
This invention relates generally to the field of ultrasonic testing. More particularly, this invention relates to a system and method for ultrasonic inspection of objects supported by an object holder.
Non-destructive inspection of parts has been used for many years. More recently, ultrasonic inspection has been extended to small parts such as integrated circuits or other electronic components. During the manufacture of Integrated circuits, the parts are often loosely arranged in trays or holders to facilitate transfer of the parts through the production process. In order to prevent delays in the production process, an ultrasonic tester that can accommodate trays of parts is required.
An ultrasonic tester may include three sections. The first section is a de-bubbling area where the parts in the carriers are wetted and air bubbles are removed. The normal convention is to submerge the parts and ‘wiggle’ them to remove the air bubbles. The second section is a scanning station where wetted and bubble free parts are ultrasonically scanned. In order to complete the scan in a short time, the ultrasonic transducer must be moved across the parts at high speed in close proximity to the parts. The result is a motion in the fluid that tends to move the parts in the carriers or dislodge them from the carrier. The third section is a drying area, where a gas stream is used to dry any residual coupling fluid from the parts. Typically compressed and/or heated air is directed across the parts. Each of these processes tends to dislodge the parts when they are loosely arranged in a tray or carrier.
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however, both as to organization and method of operation, together with objects and advantages thereof, may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:
While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one or more specific embodiments, with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawings.
One aspect of the present invention is a method and a system for ultrasonic scanning of parts in which coupling fluid is used to hold parts in a parts holder or tray. A further aspect of the invention is method and system for holding parts in a parts holder while bubbles are removed from parts before they are scanned. Still further aspects of the invention will be apparent from the following detailed description of illustrative embodiments.
In one embodiment, the ultrasonic test chamber of the present invention includes three functional sections: a de-bubbling station, a scanning station and a dryer.
An assembled ultrasonic test chamber 100 is shown in FIG. 2. The upper chamber 102 is supported by a frame (not shown) so that the moveable plate or scan bar (104 in
Fluid flow through the tray of parts is restricted, so fluid may be added to the tray from the upper chamber at a rate sufficient to maintain sufficient fluid in the tray to permit acoustic coupling of the ultrasonic beam to the top of the parts in the tray. If measurement of transmission through the part is not required, the lower chamber may be omitted or replaced with a fluid-capture tray. A more detailed view of the upper chamber 102 is shown in FIG. 3. The chamber is viewed from above. In use, the tray of parts first passes below a region of perforations or holes 302. In a further embodiment, the region 302 may contain a single slot. Region 302 is the de-bubbling region. Fluid is passed from below the parts and directed toward the underside of the parts so as to remove air bubbles. Excess fluid passes through the perforations or one or more slots 302 and enters the upper chamber. Additional fluid may be added to the upper chamber as required. The perforations or slots are sized so as prevent the parts from being dislodged by the fluid flow. Excess fluid may escape through one or more channels 304, 306, 308, 310, or through drain pipes (not shown). A track 312 is provided to guide the scanning bar 104. The scanning bar slides from left to right and right to left with the first transducer as it traverses the parts in the tray. The ultrasonic beam or transducer passes through opening 314. The parts in the tray are held in place by the scanning bar. In a further embodiment, the de-bubbling area and the scanning area may be separated.
A more detailed view of the lower chamber 110 is shown in FIG. 4. The chamber is viewed from above. In use, the tray of parts enters on the right of the figure, moving in the direction of arrow 410. The lower chamber is positioned below the tray of parts 106 (not shown). The tray of parts moves along a track. One rail of the track lies in the slot between openings 402 and 406, the other lies in the slot between opening 404 and 408. In the embodiment shown in
In a further embodiment, the upper and lower chambers may be integrated, and height of the flat plate varied to accommodate trays of varying thickness.
A more detailed view of the spring fingers 506 is shown in FIG. 6. In this embodiment, a sheet of metal 602 is bent to form an angle. Slots 604 are formed in the metal on one side of the fold. The material between the slots forms the spring fingers. Projection 606 may be included to facilitate attachment of the set of the spring fingers to the upper chamber.
A more detailed description of the operation is given below, together with some alternative embodiments.
De-Bubbling Area
The de-bubbling area is where the parts in the carriers are wetted and air bubbles are removed. Several aspects of the de-bubbling area are now described.
Side Fluid Penetration
The test chamber of the present invention is partially filled with a coupling fluid, such as water, to facilitate coupling of the ultrasonic beam to the part under test. The test chamber has one or more openings in the sides, below the level of the fluid, to allow a parts carrier to passing into the chamber. In one embodiment, this opening is the gap between the upper and lower chambers. Since fluid will leak from the opening, additional fluid is passed into the chamber to maintain the fluid level. Preferably, the fluid leaking from the one or more openings is collected and returned to the chamber. The carrier does not have to be raised or lowered, so the system is compatible with production line configurations and handling equipment
Water Jet
To remove any air bubbles adhering to the parts, a stream of water or other fluid is forced across the parts. Preferably, the flow of water is from bottom to top because that is the directions the air bubbles will float when separated from the part or carrier.
Perforated or Slotted Cover
In the case where the water jet is flowing upward, the water will tend to dislodge the parts from the carrier. A perforated or slotted cover is used to hold the parts in the carrier. The holes are large enough to let water and air bubbles pass but small enough so that parts can not pass or be dislodged.
Scanning Station
The scanning station is where wetted and bubble free parts are ultrasonically scanned. The ultrasonic transducer is moved across the parts at high speed in close proximity to the parts. The result is a motion in the fluid that tends to move the parts in the carriers or dislodge them from the carrier. For though-transmission (TT) tests, separate transducers or arrays of transducers are used above and below the carrier. The scanning station of the present invention uses one or more of the following approaches to hold the parts in the holder:
Carriers with Retaining Clips
In a first embodiment of the present invention, a carrier with retaining clips is used to prevent the parts in the carriers from being dislodged. In some areas of the semiconductor part manufacturing process, it is advantageous to hold the parts in a carrier with a retaining clip. For example, the Auer Company manufactures metal carriers commonly referred to as boats that have retaining clips (For example, Auer part number A27150-001 manufactured in 9/00 per drawings 110892 Rev. B). Boats can be used in curing ovens and other stages of semiconductor manufacturing. Current practice is to remove the parts from these “boats” and place them in JEDEC trays before scanning ultrasonically. By scanning the parts in the “boats” the parts do not have to be moved to another carrier and the parts are held in place during the ultrasonic scan.
High Pressure Above Carrier
In one embodiment of the invention, fluid is added to the parts carrier from above. The fluid is added at one or more positions away from the scanning area, so that fluid flow does not tend to dislodge the parts. Furthermore, since flow through the parts carrier is restricted, the static fluid pressure above the parts is higher than the pressure below the parts. This results in a net downward force acting to hold parts in the part carrier. Thus, the coupling fluid tends to hold the parts in place rather than to dislodge them.
Low Pressure Under Carrier
Because any motion in the fluid (caused for example by transducer movement) around the parts may tend to move the part in the holder during the scan (which results in a blurred ultrasonic image) or dislodge the part entirely from the holder, it is desirable to have some type of force holding the parts in to holder. Since materials other than the coupling fluid (typically deionized water) will have a different acoustic impedance and degrade the ultrasonic image, it is desirable for this force to be applied via the coupling fluid. In one embodiment of the invention a fluid flow is maintained below the carrier. This results in a net downward force on the parts that will tend to hold the parts in the carrier. The flow is maintained across the raised region of the lower chamber.
Retaining Strip
In a further embodiment, where additional force is required to hold the parts in the holder at the scanning station, a retaining strip is used. The retaining strip is comprised of a continuous strip or a series of fingers made out of a spring-like material that applies a slight downward pressure to the top of the parts. The fingers are positioned so that they do not cover the parts at the scan line. Two rows of retaining strips, one prior to and one after the scanning line are used.
Scanning Bar (Moving Cover)
In a further embodiment, a flat plate or bar mounted flush with the bottom of the transducer is used to prevent the parts in the holders from being dislodged. The flat plate, referred to as a scanning bar, acts as a barrier between the fluid around the transducer that is disturbed during motion and the fluid surrounding the parts in the holder. This prevents the disturbed fluid from tending to affect the position of the parts. If the scanning bar is kept in close proximity to the top of the holder it will also insure that parts can not leave the holder in the scanning station. To keep the size and mass of the scanning bar small, the scanning bar can be integrated with a stationary cover to insure that the parts cannot leave the holder while in the scanning station.
The above techniques, namely scanning bar, retaining strip, high-pressure and low pressure, can be used in any and all possible combinations.
Fixed Through-Transmission Transducer
Through-transmission tests typically require a transmitter on one side of the part and a receiver on the other side. Typically, both of these transducers will move together at the same rate and directions. By using a single element or array transducer for either the UT transmitter or receiver, only one of the two transducers will be in motion thereby reducing the disturbance to the fluid around the parts and simplifying the mechanics required to implement a system. In the preferred embodiment, the fixed transducer is located below the holder so that the moving transducer can be in closer proximity to the parts which is currently a requirement for the high frequency scans.
Fixed Array (Linear and Area)
If any/all of the ultrasonic transducers required are linear or area arrays the speed required can be reduced thereby reducing the tendency for the parts to move or be dislodged from the holder. In the preferred embodiment, the transducers will completely cover the width of a tray and will not be required to move at all. The array could be integrated with a top or bottom cover plate. The array could also be used in conjunction with a fixed through-transmission transducer.
Dryer
After the ultrasonic scanning of the parts in the holder is completed, it is desirable to remove the coupling fluid from the parts to prevent the fluid from affecting the quality or appearance (i.e. water spots) of the parts. The dryer of the present invention includes one or more of the following:
Gas Stream
A gas stream can be used to dry any residual coupling fluid from the parts. Typically compressed and/or heated air is directed across the parts. By using a vacuum or suction from beneath the holder, drying gas will still flow across the parts but it will tend to hold the parts in the holder rather than dislodge them. Additionally, an air-knife can be used to blow residual fluid from the upper surface of the parts.
Wicking Material
If any liquid residue is left on parts, a wicking material may be placed in contact with the part to remove the moisture.
Brush
If any liquid residue is left on parts, the parts may be passed under a brush, so that bristles of the brush contact with the part and remove the moisture. Preferably, the brush contacts the lower surface of the part.
While the invention has been particularly shown and described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. In addition, it is evident that many alternatives, modifications, permutations and variations will become apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.
Busch, Ralph E., Fallon, Brandon D., McKeon, James C.
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