Packaging article: Back end gets its own TIS

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Back end gets its own Technology Innovation Showcase

The back end gets its own section of the Technology Innovation Showcase this year to introduce new ideas in packaging and test from small companies to the wider industry. “We were looking for people who were thinking outside the box,” says Ron Leckie, president of Infrastructure Advisors; who was one of the judges on the volunteer committee selecting innovators likely to intrigue show visitors. “We tend to be linear thinkers in this industry, and we go very aggressively charging down the path, but don’t look off to the side.” Companies had to have the data to show their products worked to solve a real industry problem, though many are still looking for partners to help complete commercial development. Check out their innovations ranging from 3-D x-ray images inside assembled packages and long lasting high-power DUV solid state lasers, to insulated bonding wire and plastic protective rounds for ultra thin wafers at SEMICON West, Assembly/Packaging and Test TechXPOT, West Hall Level 2.

Xradia, Concord, California, will be showing off 3-D images and virtual de-layering of structures inside a fully assembled semiconductor package live on the show floor in its MicroXCT 3-D transmission x-ray microscope. Image slices are taken through the rotating sample and reconstructed into full 3-D volumetric tomographic reconstruction, with micron resolution sufficient for failure analysis. No sample preparation is needed, so the package is not damaged and any defects remain intact, and the unit can still be electrically tested afterwards. “With conventional 2-D x-ray imaging, the solder balls can block the view of key structure behind them,” points out Vice President of Marketing, Bill Turnquist, “so you can’t see many critical defects in other levels. The MicroXCT gives you high resolution vision inside your package without destroying it.”

While conventional x-ray microscopes get high resolution only by putting the sample very close to a very small point source, Xradia instead uses unique proprietary optics to achieve micron resolution, while allowing the sample to be further away from the source, so there’s room for something as big as four inches to be rotated completely and imaged in 3-D. The company has just shipped the first units to commercial users.

Deep Photonics says its high power, deep ultra-violet (DUV) solid state lasers for micromachining enable drilling of finer, cleaner vias, and wafer dicing with less waste. The Deep Photonics’ lasers produce both CW and pulsed 266 nm output, at multiple watts of power, with lifetimes exceeding 10,000 hours. The Corvallis, Oregon, company says it gets around the usual via drilling problem of ablating the resin faster than the reinforcing fibers, and leaving behind fibers that cause problems with plating by using its 266 nm laser, evaporating both fiber and resin at the same rate. “We have very motivated customers in via drilling, pressing to solve this problem,” says Vice President Jim Field.

Key to the process is the company’s new non-linear optical frequency conversion material, which has a damage threshold more than 100 times that of conventional best-of-breed materials, so it holds up better under extreme use at high power. “The failure mechanism is typically water in the crystal,” explains CEO Joe LaChapelle. “Our crystal is chemically inert and absolutely does not absorb water from the atmosphere.” Conveniently, dependable fiber lasers developed for telecommunications networks also help boost reliability of the DUV system. The high power fiber laser pumps 1064 nm light through two cavities of frequency-conversion crystal, reducing the wavelength to 266 nm.

Advanced Material Sciences’ new idea is to replace the tape used for wafer support with a disk of thermoplastic polymer. Applied with heat and pressure to the wafer, the thin, flexible circle of plastic flows to conform to its topography, stiffens and protects the wafer through grinding below 75 μm, and then dissolves off in a bath of commonly used industry solvent without inducing stress. “Though it’s not a fully mature technology, companies have been willing to work with us to develop the process, since it fills a gap between tape and full complex wafer support systems,” says sales and marketing Vice President Jason Krogh, noting that the product is being tested at both wafer and device companies. “We’re now looking for automation companies to work with to take this to the next level.”

Company founders from the passives industry started with a thin material familiar from making multilayer ceramic capacitors, then adjusted the chemistry of the paint-like liquid until they could cast, cure and die-cut it into rounds with extremely smooth, flat surfaces that could be easily adhered to and removed from wafers. Throughput for putting the coating on 200 mm wafers is about 60 wafers per hour, and the company is about to launch manufacturing on 300 mm substrates at its plant in Hillsboro, Oregon.

Primary applications driving demand are aggressive wafer thinning to pack more flash chips into stacked packages, and thinning power semiconductors with back side metal, since the plastic withstands the heat of the backside refractory process better than conventional tape. AMS is also working on thinning glass-ceramic for products such as lithium ion batteries.

Insulated bonding wire that can cross and touch without shorting may at last be ready for use in real products. Microbonds, Markham, Ontario, Canada, says its coated bonding wire is now in the final stages of qualification for manufacturing at several customers, and Microbonds expects commercial production to begin within six months. Major bonding wire supplier Tanaka Denshi Kogyo will apply the coating when it makes the gold wire in its own plant under license, and Microbonds is discussing licensing agreements with other gold bonding wire suppliers, as it intends to be an open-source supplier and concentrate on its core coating chemistry.

First application, says CEO John Scott, is as a drop-in solution for yield problems, such as those caused by mold compounds causing the wires to bend and short. “People want to see it proven in manufacturing first,” he notes. “Once they see the reliability, then they can think about how else they can use it.” The company is now working with bonder makers to enhance bonder software to allow wiring that’s not parallel, opening the way to designs that can pack more wires in less space.

The company has been working on the challenging chemistry of getting dielectric to stick to gold, and applying it uniformly at manufacturing speeds, since back in 1999. Scott says the coating is less than 1 micron thick, so the increase in wire size is minimal, the core properties of the wire remain unchanged, and no changes are needed to the standard tool set.

Aguila Technologies, San Marcos, California, is introducing to commercial markets a conductive adhesive it developed to remove heat from the military’s very high power, high heat radar chips. The material can be processed like a polymer by screen printing or syringe dispensing, but specially formulated metals within the polymer binder form a solid when heated, says President Albert Capote. The sintered particles from a continuous metallurgical bond at the interface, instead of the point-to-point contacts formed by the metal particles in the usual polymer adhesive, increasing thermal conductivity to 16 W/m-K, or 10 times that of conventional silver-epoxy adhesive.

First target application is to replace high-temperature gold-tin solder with the lower temperature, easier-to-use alternative. “We’re coming out of a very limited environment,” says Capote. “But we’re looking to get into power devices like motor controllers and LEDs.” With a couple of high volume products, he figures the price could be comparable to high performance die attach materials.

Less likely is adoption into mainstream IC markets, where most hot-running products use flip-chip packaging, but Capote argues that even here it could be time for the packaging industry to consider some new approaches, noting that the sector hasn’t been the fastest to consider new materials. “We’ve plotted the adoption of solder paste, conductive resin, surface mount technology, and the typical adoption cycle for packaging is 10–15 years,” notes Capote. “We find the electronics industry to really be very old and stodgy about adoption.”

With its high-speed virtual simulator of the Agilent 93000 tester now apparently successfully beta tested at a major chip maker in Texas, and readying for commercial launch in the fall, Segin Semiconductor Solutions, Dundee, Scotland, next plans to tackle a mixed-signal SoC version of its pre-silicon validation software. “We are ready to partner with a major ATE company to do the first SoC mixed signal test simulation software with another chip company,” says Business Director Roddy Beat, noting the need to first muscle out some standards for mixed signal. Also in the pipeline from the company are versions of its core generic ATE validation software to specifically simulate Teradyne Catalyst and LTX Fusion testers. The virtual test platform enables efficient debugging of ATE test code before silicon delivery, reducing time to tested parts.

Synova says its water-jet guided laser tool has cut breakage by some 30 percent at a major European chip maker who manufacture edge-grinding low-k wafers. The tool supplier is also working with other chip makers on dicing GaAs and low-k wafers and wafer-level packages with its system that uses water around the laser to avoid thermal damage and wash away particulates, while limiting mechanical stress and improving chip fracture strength.

Sales and marketing Vice President Phil Durrant notes the less stressful system cuts wafers down to 50 μm thin up to five times faster than a saw, or up to 300 mm/s.

Based in Ecubens, Switzerland, outside Lausanne, Synova started by selling to dentists, but now gets 60 percent of its revenues from semiconductors and related industries like solar cells. It’s added a new layer of executive management and more engineers to expand to 50 employees in recent months.

Full 3-D inspection of bumped wafers could become fast enough to be practical in production with ICOS Vision Systems’ approach. In its WI-3000 product, the Heverlee, Belgium based company uses an improved confocal system to inspect 8-inch wafers at 60 wafers per hour. A high-speed camera, along with very fast processing algorithms, are the key enablers.

The product performs full 2-D and 3-D inspection in parallel and with high accuracy and repeatability (1µm accuracy for 3-D measurement items), measuring bump height, co-planarity and position of bumps and detects surface defects down to 3 µm.

“As bump sizes and bump pitches are continuously decreasing, we estimate that the industry will have an increasing need for full 3-D inspection,” says Pieter Vandewalle, marketing director.

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