|Application:||Picking die from dicing tape|
|Equipment:||Model 4750 Die Ejector System; Model 4800 Die Ejector Grid System; Model 830 Pick and Place System|
|Process:||Wafers are diced on adhesive tape so the die are contained, yet are easily removed for storage in waffle packs or bonding into a package. Die removal from dicing tape should not cause damage to the die. The space between die is generally very small, which prohibits gripping the die and pulling it from the tape, but this is a viable technique, especially if the diced wafer has been expanded. A more common method is to push the die from the tape with a pin. The tape can also be drawn away from the die by vacuum. The released die is generally picked by a vacuum tool and placed. One other method pulls the tape around a sharp edge, but the die can’t bend as the tape does, so it slides off.|
|Machine Discussion:||The first and most widely used mechanism to remove die form tape is the poker pin. The pin pierces the tape to push the die from the tape to release it while holding the tape down. Three or more pins may be needed for large die that would potentially be broken by a single pin. The pin holding tool should be interchangeable to allow for various pin configurations. A platform to support the wafer and film frame is needed.
Another method is the grid ejector. This device has an array of points that support the wafer on the tape. The points are designed to have several under each die. Application of vacuum causes the tape to be pulled away from the die into the spaces between the points. With the area of tape in contact with the die so reduced the die can generally be lifted from the tape by vacuum tool. Various sizes of grids with various pitches of points are needed to cover the variety of wafer and die sizes. This technique doesn’t work well with small die (>3mm sq.), however it works well with large die (>1 cm sq.) that can be a problem for poker pins. This method causes the least stress on the die.
Die can be gripped and pulled from tape with tweezers or a mechanized gripper. The tip of the gripper needs to be thin enough to fit in the saw kerf or the matrix needs to be expanded to increase the gap between die. Tweezers have the advantage of being very versatile in the hands of a skilled user, but they have the disadvantage of causing die damage for most users.
Die picking from tape is frequently integrated with other functions such as die bonding or sorting. These other functions are beyond the scope of this paper, but the picking method will be influenced. The poker pin design is most readily integrated into automatic equipment because of its ability to positively push the die from the tape. The ejector grid design works well into manual equipment because targeting a die is easier. Drawing tape over a sharp edge does not incorporate well into equipment because a control of the die is lost as soon as it clears the tape. Grippers have been sparsely applied because they tend to be complex and they aren’t easily changes for the die size.
|Machine Features:||The Model 4750 Die Ejector System and the Model 4800 Die Ejector Grid System have the features required to perform this application.
The Model 4750 is a poker plate system that comes with a vacuum plate (sized to order) that holds the film frame and a supply of ten interchangeable poker pins. The poker pins are activated by a footswitch control. A zoom microscope and a projected image crosshair alignment assembly with an illuminator are available for providing a precise, magnified view of pin to die alignment.
The Model 4800 is a die ejector grid system . The grid surface comes in a variety of sizes to match a range of die sizes. A vacuum plate located below the grid applies even pressure to pull the tape away from the wafer. The system’s control console maintains the temperature of the heater plate and pressure to the vacuum port.
These systems can be integrated with a die bonder, such as the Model 830 Pick and Place system.
|Required Equipment:||The following equipment from Semiconductor Equipment Corporation is required to perform this application:|
|The following equipment from Semiconductor Equipment Corporation is optional to perform this application:|
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