Handling quality

UNTERPREMSTÄTTEN, AUSTRIA—Pursuit of excellence is a key motivator for Austriamicrosystems, a provider of mixed-signal ICs for power-management, sensor, and mobile-entertainment applications. The company employs innovative test and test-handling techniques to ensure the quality of the devices that it sells into communications, industrial, medical, and automotive markets.

Moritz Gmeiner, Austriamicrosystems’ director of corporate communications, said the company focuses on highly integrated low-power and high-accuracy analog devices. The company, he said, has in its 25 years in business developed a significant amount of IP that it employs in the design and production of both standard ICs and custom ASICs. Available IP building blocks include ones dedicated to power-management, mobile-entertainment, wireline-communication, bus-system, car-access, metering, sensor, sensor-interface, medical, and high-voltage applications as well as general-purpose analog and digital functions.

ASICs, Gmeiner said, have historically made up the bulk of Austriamicrosystems’ business, outpacing standard products by 80% to 20% five years ago. That’s changing, though, as the company identifies high-volume opportunities for new standard ICs, which now make up close to a 40% share of the company’s business.

In addition to providing standard and custom devices, the company also offers foundry services. In December 2007, Fingerprint Cards (www.fingerprints.com) became one of the most recent companies to take advantage of that service, announcing that Austriamicrosystems would manufacture its FPC1011C 30x18x2-mm fingerprint sensor chip that it uses in products ranging from fingerprint sensors and biometric processor ASICs to complete biometric submodules.

Alfred Binder, test-handling manager, poses at Austriamicrosystems’ headquarters in front of a photomask display that illustrates the diversity of products the company has produced over the past 25 years.

As part of its foundry offerings, Austriamicrosystems offers fast prototyping through its Multi-Project-Wafer (MPW) service, as well as offering full production, assembly, and test services. In 2008, Austriamicrosystems will offer more than 150 MPW start dates, made possible through cooperative operations with research organizations such as CMP-TIMA (tima.imag.fr) and Fraunhofer IIS (www.iis.fraunhofer.de) and with prototyping services such as Europractice (www.europractice-ic.com) and MOSIS (www.mosis.com).

To take advantage of the MPW service, customers deliver their completed GDSII data at specific dates, and Austriamicrosystems then supplies untested packaged samples or dies within a short lead time—typically eight weeks for CMOS and 10 weeks for 0.35-µm high-voltage CMOS, SiGe-BiCMOS, and embedded flash processes.

The company’s own designs find use in power-management and lighting-management applications in mobile devices such as cell phones. For mobile entertainment, the company makes a single-chip media player system as well as audio front ends that provide power management to support long play times—while also implementing digital rights management.

Moritz Gmeiner: The company focuses on highly integrated low-power and high-accuracy analog standard and custom solutions.

The company also makes magnetic rotary encoder ICs that provide up to 12-bit resolution for industrial and automotive applications. Gmeiner noted that these products can serve in electronic stability control applications and can monitor gearbox and gas-pedal positions.

Supporting the production of this plethora of products are six design centers in Austria, Italy, Switzerland, and India as well as a 200-mm wafer fab here. The company has a 0.35-µm CMOS base process as well as modular specialty processes for high-voltage CMOS, SiGe, and embedded-flash/EEPROM fabrication. Production capacity is 8000 wafer starts per month. A cooperative effort with Taiwan Semiconductor Manufacturing Co. (www.tsmc.com) ensures access to state-of-the-art processes for both partners. In addition, Austriamicrosystems in 2007 began cooperating with IBM in the development of a 0.18-µm high-voltage CMOS process that is expected to yield products in 2009.

Austriamicrosystems offers more than 80 package types—ranging from small outline ICs to ceramic pin grid arrays with up to 447 leads. The diversity of products that Austriamicrosystems makes poses significant test challenges with respect to functionality as well as packaging. A look at devices introduced in the fourth quarter of 2007 illustrates the diversity of the Austriamicrosystems product line’s functionality and package styles:

• the AS1341 20-V step-down DC/DC converter in a 3x3-mm TDFN eight-pin package,
• the AS3693 and AS3694 LED drivers for LCD backlighting applications in TQFP64 packages,
• the AS1542 1-Msample/s, 16-input, 12-bit ADC in a 28-pin TSSOP package,
• the AS5305 high-speed, high-resolution magnetic linear motion encoder IC in a lead-free TSSOP20 package,
• the AS1358/59 and AS1361/62 LDO regulators in a five-pin TSOT23 package and a six-pin TSOT23 package, respectively,
• the AS1528/29 micro-power, 10-bit, 150-ksample/s ADCs in eight-pin 3x3-mm TDFN packages, and
• the AS1538 12-bit, eight-channel, low-power ADC in a 16-pin TSSOP package.

To ensure the quality of the products it produces, the company has test centers in Austria and in Calamba, the Philippines, that use high-end testers from LTX, with 45 testers deployed in Austria and 10 deployed in the Philippines, according to Wolfgang Peisser, director of backend operations. Peisser said Austriamicrosystems chooses to rely on one test vendor, for which it can serve as a technology driver. A single test vendor, he said, helps the company leverage its test IP across the many types of devices. Further, he noted, a single vendor provides the consistency demanded by automotive customers.

Wolfgang Peisser: Austriamicrosystems chooses to rely on one tester and one handler vendor, for which it can serve as a technology driver.

In addition to the LTX testers, the company has chosen Multitest as its handler supplier; Austriamicrosystems deploys 13 pick-and-place handlers and 13 gravity handlers in Austria plus five pick-and-place and 11 gravity handlers in the Philippines. Peisser said the company’s mix of packages—ranging from tiny small outline transistor (SOT) devices to large ball-grid arrays (BGAs), complicates the test and handling process, requiring close cooperation among Austriamicrosystems, LTX, and Multitest. He expressed support for the mechanical-interface standardization efforts of the Semiconductor Test Consortium’s STIX committee (Ref. 2), but he added that interfacing a tester and handler is a complex problem that won’t soon yield to standardization efforts.

Figure 1.  High-speed vision-alignment technology enables a pick-and-place handler to accurately position a device for insertion into a test contactor. Courtesy of Multitest.

The vision-alignment technology employs multiple cameras to scan and align up to four devices simultaneously (for quad-site test) before the stroke-to-test-contactor operation occurs. Each device is scanned and positioned separately, and all devices being contacted in parallel in multisite applications are aligned individually—without alignment information being transferred from one device to another. Without that alignment process, Binder said, yield can fall off two to three percent or more because of package tolerances.

The Austria test area, Binder explained, is 25 years old, and as it has grown, different generations of testers and handlers have appeared. “We have one of the first Synchromasters in Europe,” which was acquired 20 years ago, he explained. The LTX Synchromaster testers have subsequently been augmented with new LTX Fusion systems.

Austriamicrosystems has been working with Multitest for 16 years and has some vintage MT850 gravity handlers installed, Binder said. The company has recently added MT9510 pick-and-place handlers. Binder explained that for some applications, he finds pick-and-place systems to be more reliable than gravity-feed machines because they avoid problems associated with tiny singulated devices sticking together. He said Austriamicrosystems is one of the first Multi-test customers to employ a pick-and-place handler for use with 3x3-mm QFN packages.

Binder added that many gravity machines are dedicated to specific package styles—so, if a company purchases a dedicated gravity handler for a package that doesn’t generate projected sales, it could be stuck with a €250,000 handler it has no use for. With the Multitest pick-and-place handler, he explained, a simple €20,000 change kit is all that’s needed to adapt the handler for a new package. Then, should volumes be sufficient, a gravity handler can augment the pick-and-place machine.

Temperature is another critical issue, Binder said, with respect to both temperature range and accuracy. Automotive parts, such as the automotive version of the company’s new AS5140H contactless magnetic rotary encoder for accurate angular measurement over 360°, must be fully qualified to AEC-Q100 standards and specified for an extended ambient temperature range of –40°C to +150°C.

But apart from temperature range, maintaining proper device temperature during test also presents challenges. “For devices such as automotive devices, it is very, very critical to test them at the right temperatures,” said Binder. He explained that a key problem is the low thermal inertia of very small parts, and that such devices’ temperature can shift several degrees because of heat conduction through leads and test sockets. A simple heat chuck and nozzle arrangement won’t suffice to accurately control temperatures, he said, adding that Multitest’s temperature-chamber approach provides adequate soak time for multiple parts to ensure temperature stability and accuracy without compromising throughput.

Binder, who has followed many changes over his 17-year career at Austriamicrosystems, expects to see more challenges in the future—with part sizes and lead pitches shrinking further and temperature ranges increasing. But he expressed confidence that ongoing cooperative efforts among Austriamicrosystems and its customers and equipment suppliers will be able to meet those challenges head on.