Toshiba Corp exhibited a prototype of a 16-Gbyte microSDHC memory card, which features the industry's largest capacity, at CEATEC JAPAN 2008.
"This is a prototype and has not been mass-produced yet," Toshiba's demonstrator said.
The maximum capacity of microSDHC memory cards currently released in the market is 8 Gbytes. To realize the capacity of 16 Gbyte, a total of 17 chips, sixteen 8-Gbit NAND flash memory chips and one controller chip, were stacked inside the card.
The chips are installed directly on the microSDHC memory card without using a package. With microSDHC, the thinnest part of the external dimensions needs to be 0.7mm thick. In order to stack 17 chips inside the thin card, Toshiba downsized the NAND flash memory chips to 18μm in thickness. The thickness of the chips it previously used was 60 to 70μm, according to Toshiba.
To use 18μm-thick chips, it is required to develop a new wafer feeding method, film for lamination on the downsized wafers and a wafer pick-up method after cutting, according to the company.