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IMEC presents 'bendy' packaging for ICs

Posted: 10 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Peter Clarke? IMEC? Intec? package?

Leading European research institute IMEC and the Intec laboratory at the University of Ghent have developed a process to produce ultra-thin flexible packaging for ICs.

The two organizations have been working within a European Union supported project called Shift (Smart high-integration of flex technologies). Shift began on Jan. 1, 2004 and is due to end on Dec. 31, 2008. It is expected to have a total budget of about $14 million, with around $7.2 million coming from the European Union and Swiss authorities.

The final package is 50?n thick and is bendable, and could allow new applications of highly-integrated electronic systems where multiple packaged die could be included in an intelligent flexible board or sheet material, IMEC said. Packaged chips could be used in flexible boards, smart textiles and flexible displays.

The process has been demonstrated with silicon die thinned down to between 20?n and 30?n thickness. The packaging includes polyimide layers and metal, taking the overall thickness out to 50-micron. The chip package can provide an "interposer" with a contact fan out with more relaxed pitches to enable testing of the chip before embedding, IMEC said.

The base substrate is a 20?n thick polyimide layer spin-coated on a rigid glass carrier. For the fixation and the placement of the chips on the polyimide layer a bicyclobutane of less than 5?n thickness is used as adhesive. Bicyclobutane is resistant to the high curing temperature of the top polyimide since its solvents evaporate during a pre-curing phase. By placing the chips properly, either in vacuum or with a dispensed bicyclobutane, void-free bonds can be obtained. Current research focuses on the optimization of the chip placement on dispensed and pre-cured bicyclobutane and on avoiding voids by controlling the dispensed quantity. In this way, no vacuum environment will be required.

After the chip is fixed on the polyimide layer a covering polyimide layer is spin-coated on the fixed die with a thickness of 20?n. To make contacts to the chip openings are laser drilled using a shaped laser beam. Via diameters with a top diameter down to 20?n can be realized in this way, IMEC said.

Then a top metal layer of an alloy of titanium tungsten and copper is sputtered on and lithographically patterned, metalizing the contacts to the chip and providing a fan out to the contacts of the chips. Finally, the package is released from the rigid carrier.

- Peter Clarke
EE Times




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