Hitachi, Renesas Develop Stacked-chip Interconnection Technology
By Lee Mather
TOKYO, JAPAN – Hitachi Ltd. and Renesas Technology Corp.’s new stacked chip technology uses a through-hole interconnection method, enabling chips to bond at room temperature. This eliminates the need for wire bonding, and also reduces package thickness by more than 60% for advanced system-in-package (SiP) products. The method offers a new packaging option for 3-D stacked SiP product development.
LSI chips between 30- and 50-µm thick are formed with through-hole electrodes between the top and bottom sides and gold stud bumps, allowing the bumps and electrodes to connect via a compressive force at room temperature. With this technology, a 2-layer SiP’s thickness is reduced by 60% or more, or from 1.25 mm to 0.5 mm or less. It also enables a 1 mm or less package thickness when stacking 10 LSI chip layers. Chip-to-chip interconnection also is performed at room temperature, simplifying manufacturing.
 Cross section of test sample stacked multi-chip. |
Most SiPs currently achieve electrical interconnection between chips using wire bonding, putting limits on package thickness. Also, since chip-to-chip connections are made via package substrate wiring, the number of substrate layers increases, leading to increased substrate costs. Since connecting stacked chips requires longer wiring, it also causes lower performance. This new technology eliminates these issues, and will allow future SiP products to be made smaller and thinner, and with higher speed and larger capacity.
For interconnecting chips, a mechanical caulking operation makes use of gold stud-bump plasticity, enabling gold stud bumps and through-holes to interconnect electrically at room temperature by applying force. This can also be used for room-temperature connection between a chip and substrate, while “conventional” through-hole electrode techniques using solder or other metallic bumps require high-temperature bonding.
Thin, 30- to 50-µm through-hole electrodes form on a wafer’s backside, and as these electrodes are fixed to the glass wafer with a removable adhesive, they must form at a temperature lower than the maximum temperature that the adhesive can withstand. However, with this new process, the etching and film-forming occurs at a temperature less than 150°C, and the breakdown voltage between through-holes achieves the same level as inside LSIs.
Carsem to Double Malaysian Test Operations by 2005’s End
SCOTTS VALLEY, CALIF. – Carsem plans to expand its test services operation manufacturing space at its S-site facility from 40,000 sq. ft. to 96,000 sq. ft. by the end of 2005. Together with its current 14,000-sq.-ft. test operation at its M-site facility, this expansion will bring the total area for wafer-probe and final test services to 110,000 sq. ft.
“As a result of escalating pressure to reduce cycle time and costs, we are seeing a tremendous increase in our customer’s desire to outsource their wafer-probe and final test requirements,” states Allan Calamoneri, Carsem’s VP of test business development. “For example, due to several key customers’ increasing demands, we recently added 50 wafer-probe systems, along with the associated testers, and expect to add another 45 final test systems by the end of this year.”
Cookson Opens Technical Service Center in Shanghai
JERSEY CITY, N.J. – Cookson Electronics has unveiled its advanced Technical Service Center and warehouse facility in Shanghai, China to provide hands-on, local-language technical support to PCB and semiconductor packaging fabricators and assemblers in Northern and Eastern China. It is located in the Zhong Dian Lu Ke Industrial Park in Pudong, Shanghai.
“This new facility, which includes technical support, applications engineering, sales, and warehousing, is a key investment in the future of our company, and it demonstrates our commitment to serve the China market,” says Rick Reagan, executive VP of Cookson Electronics Assembly Materials in the Asia-Pacific region.
This new facility will also put the existing processes into practice at Cookson’s other facilities worldwide, and professionals from the Assembly Materials Group, Enthone, and Polyclad will share the facility. For the last 3 years, as part of Cookson’s ongoing strategic plan for Asia, they have earmarked more than $10 million to augment its manufacturing, technical support, marketing, and sales organization in China.