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  7. Fujitsu Achieves Breakthrough in Ultrafine-Pitch Solder Bumping and Flip-Chip Bonding

Fujitsu Achieves Breakthrough in Ultrafine-Pitch Solder Bumping

Storage Leaders Begin Testing Serial Attached SCSI Hard Disk Drives for Enterprise Solutions

Fujitsu Limited

Tokyo, December 15, 2003

Fujitsu Computer Products of America, Inc. (FCPA), one of the world's leading suppliers of hard disk drives and computer peripherals, today announced that its small form factor (SFF), full-speed 3Gb/second serial attached SCSI (SAS) hard disk drive interface is being tested for next generation enterprise storage solutions by HP. The Fujitsu SAS interface leverages the recognized benefits of SCSI with the latest serial technology and Fujitsu expects SAS to become the enterprise I/O interface of choice for the new 2.5" small form factor enterprise hard disk drives. HP's testing of Fujitsu's 3Gb/second SAS interface in enterprise solutions is intended to take advantage of reduced form factor hard disk drives and the increased performance associated with serial attached SCSI.

With the continuing strive toward downsizing and higher functionality of a variety of devices such as mobile phones and digital cameras, demand is increasing for both finer bump pitch and high-precision interconnection technologies, which enable downscaling of LSIs and LSI packaging.

Flip-chip bonding, which is widely utilized as ideal for reducing the mounting area of LSIs and LSI packaging, entails interconnection of molten solder bumps(1). In order to avoid short-circuiting between solder bumps, currently bump pitches are in general between about 200 micron to 250 micron.

To enable further downsizing of LSIs and LSI packaging, both finer pitch solder bumping and high-precision flip-chip bonding(2) capable of avoiding short-circuiting between solder bumps are indispensable.

Fujitsu's New Technologies
Fujitsu has succeeded in developing the world's first-ever ultrafine-pitch solder bumping technology with 35 micron pitch, and high-precision flip-chip bonding technology that ensures interconnections. Features of the new technologies are as follows:

1. Ultrafine-pitch solder bumping technology
This new technology adopts solder bump formation using a plating method(6). To narrow down the bump pitch, it is necessary to refine the photo-resist resolution used for bump formation, raise the bump height, and have even formation. However in the past, the smaller the bump pitch became, the more increasingly difficult it was to have even formation of bumps, due to the fact that the plating solution did not sufficiently reach photo-resist openings. This resulted in uneven bump formation.

With Fujitsu's new technology, by improving the photo-resist material, optimizing the parameters for exposure and developing of photo-resist patterns, and precisely controlling the electric current used during plating, the even formation of ultrafine-pitch bumps with height is now possible. Furthermore, as part of Fujitsu's eco-friendly mission, lead-free solder bumps have been used.

2. High-precision flip-chip bonding technology
With conventional flip-chip bonding, by heating the bumps while a calibrated force is applied to them, the bumps are melted and then pressure-welded. However, with ultrafine-pitch bumps, short-circuiting frequently occurred when this method was employed due to neighboring bumps coming into contact with each other. Furthermore, in order to ensure connection to the connection surface, a unique process to mechanically planarize bumps was necessary to eliminate any bump height deviations.

With Fujitsu's new technology, by employing precision-control of temperature and force during flip-chip bonding, high-precision flip-chip bonding is now possible without the need to employ a bump planarization process. Through these new techniques, short-circuiting can be avoided and connections can be ensured even during flip-chip bonding of LSIs with ultrafine-pitch solder bumps in area-array configuration.

Utilizing this technology, Fujitsu has begun to supply to Value Added Technologies (4)(VATECH) of South Korea a chip-on-chip Multi-Chip Module(7) (MCM) , consisting of 4 units of detection signal-processing CMOS devices for which the entire connection surface is covered with 160,000 ultrafine-pitch solder bumps in full area-array configuration, that have been flip-chip bonded to an X-ray detection device. VATECH has succeeded in installing this chip-on-chip MCM and verifying operation of a dental X-ray image sensor.

The chip-on-chip MCM for the dental X-ray imaging sensor has been manufactured by Fujitsu Integrated Microtechnology Ltd. with assistance from Fujitsu Laboratories Ltd.

Future Developments
In order to meet demands for further miniaturization and higher functionality of mobile devices and others, Fujitsu is committed to the continued development of downscaled LSIs and LSI packaging utilizing this new technology. Fujitsu is also exploring the applicability of this technology for stud bumps (5)and gold bumps,(6) which were not alternatives with conventional solder bump pitches.

Solder bump formation using the plating method

Solder bump formation using the plating method (141 KB)

  • [1] solder bumps

    A protruding electrode on the surface of a semiconductor chip, formed through an evaporation method, plating method, or printing method.

  • [2] chip bonding

    An interconnection technique whereby a chip with bumps is flipped over and attached onto a board (or in the case of a chip-on-chip MCM, onto another chip).

  • [3] Fujitsu Achieves Breakthrough in Ultrafine-Pitch Solder Bumping

    A common method for forming solder bumps. A seed layer is applied employing a sputtering method, photo-resist is coated on, and then openings are created only in the bump area through a photolithographic process. The wafer is then dipped in plating solution, and the solder is deposited (see figure).

  • [4] Value Added Technologies

    Headquarters: 7511 Seokwoori Dongtanmyun Hwaseongsi Kyunggido 445-811 South Korea President & CEO: Chang Joon Ro. Specialized developer and producer of X-ray imaging systems for medical and dental application, and TFT-LCD test systems, founded in 1992.

  • [5] stud bumps

    Chiefly used in System-in-Package (SiP) applications. Gold balls are made of gold wire and formed into bumps using cutting techniques. Only applied on the peripheral configuration of a chip pad.

  • [6] plating methodgold bumps,

    Chiefly used in chips for LCDs, or in TAB (tape-automated bonding) - BGA. Bumps are formed by gold plating. Only applied on the peripheral configuration of a chip pad.

  • [7] chip-on-chip Multi-Chip Module

    Of the various multi-chip modules in which several chips are combined within one package, a module in which the upper "daughter" chip is flip-chip mounted on the lower "mother" chip.

About Fujitsu Computer Products of America, Inc.

Fujitsu Computer Products of America, Inc. (FCPA) conducts engineering and marketing activities in San Jose, CA and sales operations throughout the United States. FCPA's current product and service offerings include hard disk drives, tape drives, magneto-optical drives, scanners and scanner maintenance. FCPA is located at 2904 Orchard Parkway, San Jose, CA, 95134. For more information about Fujitsu products and services, call us at 800-626-4686 or 408-432-6333.
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About Fujitsu

Fujitsu is a leading provider of customer-focused IT and communications solutions for the global marketplace. Pace-setting technologies, highly reliable computing and telecommunications platforms, and a worldwide corps of systems and services experts uniquely position Fujitsu to deliver comprehensive solutions that open up infinite possibilities for its customers' success. Headquartered in Tokyo, Fujitsu Limited (TSE:6702) reported consolidated revenues of 4.6 trillion yen (US$38 billion) for the fiscal year ended March 31, 2003.  
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Please understand that product prices, specifications and other details are current on the day of issue of the press release, however, may change thereafter without notice.

Date: 15 December, 2003
City: Tokyo
Company: Fujitsu Limited, , , , ,

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