Advanced Packaging - Tessera Introduces its MVP

(March 19, 2008) SAN JOSE, CA — Whether the acronym stands for micro via package or most valuable package, it looks like Shellcase MVP, introduced yesterday by Tessera Technologies, will answer to both. This recent addition to the SHELLCASE family is reportedly one of the industry's first applications of through silicon via (TSV) technologies and supports 3D die-stacking of the image sensor with other ICs. It is said to provide manufacturers with the ability to develop thinner, more sophisticated consumer devices faster at a lower overall cost.

"This is our unique way to offer a TSV solution," explained Shlomo Oren, general manager of Tessera Israel. He says the company has developed a low-cost via-through-pad technology that can be done quickly on the entire wafer. Vias are created through the backside of the wafer to the bond pad without drilling directly through the silicon, Oren explained. The process avoids micro-cracks and is a stable, high-yield process. After the vias are formed, they are filled and electrical routing is formed. Using TSVs eliminates the need for metallization of the scribe lines, allowing for an additional 5% die per wafer due to increased usable wafer area.

Oren explained that the rest of the processes are the same as those used for SHELLCASE OC and RT, both wafer level chip scale packages (WLCSP) that encapsulate the active area of the image sensor die with a glass prior to dicing, and feature ball grid array (BGA) assembly. First, the wafer is encapsulated with a cover glass at the initial stage of processing, as in all the SHELLCASE processes. The next two steps are what differentiate MVP from OC and RT; namely through via creation, followed by via fill and routing of electrical contacts. Solder bumps are then formed on the wafer backside, and then the wafer is singulated into individually packaged die.

In 2007, more than 400,000 8-inch wafers were packaged using Tessera's SHELLCASE technology, according to the company. Current licensees can use their existing infrastructure to adopt the SHELLCASE MVP technology rapidly, in addition to leveraging legacy processes and toolsets for reduced initial investment, faster time-to-market, and improved return on investment (ROI).

"We've managed to develop a package technology capable of using existing infrastructure in our licensee's factories," said Oren, "We didn't want to develop a technology and then have to wait two years to use it while the infrastructure catches up and lose the market window."

Other companies making progress with WLCSP image sensor technology include Toshiba and STMicroelectronics, but these are captive companies — its all for internal use, said Oren. Because Tessera's business model is IP development & management of electronics and optics miniaturization and interconnect technologies, with the intent of licensing and commercialization, their technologies are readily available.

SHELLCASE MVP targets original equipment manufacturers (OEMs) and camera module manufacturers building lower profile, thinner, and more sophisticated consumer devices for camera phones, digital cameras, PDAs and laptops, as well as digital scanners and fingerprint identification devices. Compliance with JEDEC Level 1 moisture sensitivity requirements also reportedly makes the new technology suitable for automotive and other market segments which require higher reliability.

"The proliferation of camera modules in a growing range of applications is driving the need for thinner, lower cost and more reliable image sensor packaging, and with our latest SHELLCASE technology, manufacturers will be able to easily meet these demands," said Michael Bereziuk, COO, Tessera, adding that OEMs and camera module manufacturers will reap these benefits without needing to modify or redesign the image sensor wafer used.

According to Oren, Tessera expects a quick transfer of the SHELLCASE MVP technology to high volume manufacturing in less than six months. They hope to have completed the transfer to the first licensee by May, with a product launch announced in the summer.

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