News Column

Patent Issued for Pick and Place Tape Release for Thin Semiconductor Dies

August 27, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventor Webb, Bucknell C. (Ossining, NY), filed on August 11, 2011, was published online on August 12, 2014.

The assignee for this patent, patent number 8801352, is International Business Machines Corporation (Armonk, NY).

Reporters obtained the following quote from the background information supplied by the inventors: "In the fabrication of semiconductor chips, semiconductor wafers are divided into individual dies, which are then packaged into chips or otherwise mounted onto some intermediate carrier or printed circuit board. This process generally involves two steps, wafer dicing and wafer sorting. In general, wafer dicing involves sawing a wafer into individual dies. In preparation of the wafer dicing process, a wafer is mounted on a cutting ring, placed in a chuck face down, and wafer tape is stretched over the back of the wafer. The tape is evenly distributed onto the wafer using a roller device, and then excess tape is cut away from the ring. Thereafter, the wafer is mounted on chuck for dicing, wherein a diamond blade is used to cut the wafer into individual dies. With the dicing process, the wafer is cut into individual dies without cutting through the wafer tape so that the individual dies remain attached to the wafer tape after the dicing process. The diced wafer is then ready for a wafer sorting process where the individual dies are removed from the wafer tape.

"Typically, a semi-automated or fully automated pick and place tool is used to separate the individual dies from the wafer tape. In general, pick and place tools operate by lifting an individual die from the wafer tape and placing the die onto a package, substrate, wafer or other dies (3-D package). With both types (semi-automated and fully automated) of pick and place tools, the wafer tape with the diced wafer is mounted to the tool such that the wafer tape is stretched over a frame. A soft vacuum collet is then placed against an individual die to be removed. Then, one or more eject pins push up through the wafer tape to elevate the die and loosen and dislodge the die from the tape. The vacuum collet then lifts the die from the tape and places the released die into a final package or in an intermediate carrier, for example. With a semi-automatic pick and place tool, a human operator manually turns a series of positioning (XY) knobs to center a target die in the crosshairs displayed on a monitor. The monitor allows the operator to position the pick-up collet over the center of the die. With an automated pick and place tool, the positioning (XY) and centering process is performed automatically using a pattern recognition system.

"When using pick and pace tools as described above, significant bending forces can be exerted on a die as the eject pin presses up and the tape pulls down on the edges of the die. These bending forces can cause the die to crack or otherwise break. With semiconductor technologies that use SiGe substrates, or thinning of silicon wafers, the resulting semiconductor dies tend to be fragile. These thin, fragile dies are highly susceptible to cracking and damage due to bending forces exerted on the dies when being separated from wafer tape using conventional pick and place tape release techniques and tools."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventor's summary information for this patent: "Exemplary embodiments of the invention generally include pick and place tape release techniques and tools that allow thin, fragile semiconductor dies to be removed from wafer tape with reduced tape release forces applied to the semiconductor dies.

"In one exemplary embodiment of the invention, a method for removing semiconductor die from wafer tape includes mounting a wafer ring having wafer tape and one or more dies attached to the wafer tape, and aligning an ejector pin assembly under a target die to be removed from the wafer tape. The ejector pin assembly includes a vacuum housing, an ejector pin, a suction plate, and an aperture formed in the suction plate in alignment with the ejector pin. The method further includes generating a vacuum in the vacuum housing to draw the tape against a surface of the suction plate, extending the ejector pin through the vacuum housing out from the aperture of the suction plate to push against a backside of the target die and release the tape from the backside of the target die, and drawing the tape down against the suction plate by suction force of the vacuum as the tape releases from the backside of the target die.

"In another exemplary embodiment of the invention, a pick and place tape release tool includes a mounting frame to securely mount a wafer ring having wafer tape and one or more dies attached to the wafer tape, and an ejector pin assembly. The ejector pin assembly includes a vacuum housing, an ejector pin, a suction plate disposed on a top side of the vacuum housing, an aperture formed in the suction plate in alignment with the ejector pin, and a vacuum mechanism to apply a vacuum within the vacuum housing and generate a suction force through the aperture of the suction plate to draw the wafer tape down to the surface of the suction plate.

"These and other exemplary embodiments, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in conjunction with the accompanying figures."

For more information, see this patent: Webb, Bucknell C.. Pick and Place Tape Release for Thin Semiconductor Dies. U.S. Patent Number 8801352, filed August 11, 2011, and published online on August 12, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8801352.PN.&OS=PN/8801352RS=PN/8801352

Keywords for this news article include: Electronics, Semiconductor, International Business Machines Corporation.

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Source: Electronics Newsweekly


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