Hitachi puts TAB on RDRAM chip-scale
Oct. 02, 1998 (Electronic Engineering Times - CMP via COMTEX) -- Tokyo
- Hitachi Cable Ltd. has developed a tape automated bonding (TAB) tape
carrier optimized for Direct Rambus-memory chip-scale packages (CSP).
The Hitachi Chip Mounting Tape uses a package called the Hitachi
Compliant Chip Package, which is based on a micro-BGA developed by
Tessera Inc. and licensed to Hitachi Cable (Tokyo).
"We are going to supply the TAB tape to our customers so that they
can assemble RDRAMs in micro-BGAs by themselves," said Yoshihiro
Matsuyama, senior executive managing director of Hitachi Cable.
The TAB tape bonds an RDRAM to the tape with elastomers. The tape
functions as a polyimid flexible interposer for the inner leads, and
absorbs the different expansion rates of the die and the
printed-circuit board.
The approach enables use of the reel-to-reel method, cutting costs.
"It will be five times faster than the conventional method and the cost
will be about the same as the thin small-outline package eventually,"
said Gen Murakami, director of semiconductor packaging technology at
Hitachi Cable.
Murakami said the compliant-chip package supports a micro-BGA device
with a bare silicon surface. The package has a pin pitch of 0.5 mm to
1.27 mm, with up to 300 pins.
The package exceeds the Joint Electron Engineering Device Council
(Jedec) level 1 requirements for humidity and temperature. Hitachi
Cable developed an elastomer with a fluorine-type core for the TAB
tape, which withstands 1,000 hours in 85 percent humidity at
85degreesC, Murakami said.
TAB has been used since last year for flash memories and SRAM
packaged in CSPs and is being extended to micro-BGAs intended for
64-Mbit RDRAMs. Hitachi Cable plans to apply this technology to devices
like microprocessors and logic ICs as well and to license it in an
early stage so that multiple vendors can supply the TAB tapes.
Assembly plans afoot
Hitachi Cable plans a production capacity of 50 million units by the
end of next year. In parallel, the company will start an assembly
business using the technology with 10 million units of RDRAM assembly
capacity per year.
Rambus and Intel have worked to strengthen the in-frastructure, and
lower the expected costs, of CSP required for the RDRAMs.
Norihiko Naono, a director of Rambus Japan, said that "within three
years, a 2 billion-unit RDRAM market will emerge."
Naono said Rambus defined the electrical specifications and did not
specify the specific form of CSP. "It is the RDRAM vendors who actually
select the form of the package [for DRDRAM]. But thus far, only Hitachi
Cable has been able to supply a package. All of the RDRAM devices under
testing employ Hitachi Cable's package."
Akira Minamikawa, senior analyst at ICD Japan Ltd., said an adequate
supply of CSP is now a concern in the electronics industry. "Currently,
CSPs are mainly used for devices for compact portable equipment, but
from now on, RDRAMs will be the demand driver."
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