Designing the Future of 5G Production Test Today

The promise of 5G is significantly greater mobile speeds for real-time connectivity for mission-critical applications. 5G has the potential to connect billions of IoT devices with a wide variety of speed and data volume requirements.

Engineers developing 5G are looking at phased arrays and may have >60 radio frequencies to handle in the same device, which places an enormous technical and economic load on manufacturers' automated test equipment and processes.

In both engineering characterization and production, the challenge of testing 5G devices is how to test a broad spectrum including higher frequencies while maintaining high throughput. With the significant increase in test content that 5G brings, we are developing ways to provide fast, accurate measurements on 5G devices and accelerate time to market.

Moving from promise to practical solutions

In telecomm, the leap from 4G to 5G telecommunications promises to radically transform the world we live in. It represents the next generation of LTE (Long Term Evolution) mobile networking, and will push download speeds from the current 100 Mbps up to >100 gigabits per second. In addition, latency times will plummet to less than 1 millisecond.

The long-term consequences of this inflection point will be profound. Global interconnectivity will soar, with literally billions of devices participating in the Internet of Things. Remote control of intricate processes such as medical procedures and driverless cars will become commonplace. Immersive real-time experiences, such as remote virtual reality, will find their way into routine use. A full-length feature film in 4K will download in less than a minute.

But like all technology advancements, bringing 5G to market requires an array of supporting tools to ensure the end products meet expectations. It will require significant performance advances in chip technology and manufacturing processes—all the while keeping price/performance at an economically viable level.

We’re already underway with RF test technology

From engineering to production, FormFactor has embraced this challenge, and is participating in the first wave of 5G devices. One major objective of this new standard is to reduce the cost per bit (data cost) compared to 4G LTE by operating in a wider spectrum of bands in the mmWave region of RF signals for mobile networks. The main challenges associated with 5G device testing in the mmW region are:

Frequent calibration required to ensure accurate measurement with minimum cross talk
Handling the large number of RF channels due to phased-array antennas for beam forming
Significantly longer test time due to the increased number of frequencies and test conditions, where test automation is essential to ensure fast time to market.

To meet these demands in the engineering lab, FormFactor has expanded its Contact Intelligence™ technology and introduced the Autonomous RF Assistant, a combination of hardware and software components added to FormFactor's newest probe systems, enabling true hands-free operation over multiple temperatures. With the Autonomous RF Assistant, an operator can start a test and leave the system measuring during a whole shift, overnight, or even over the weekend. The system automatically recalibrates if performance drifts and probes are dynamically corrected for the most accurate pad placement. This allows users to test more devices in less time and leads to more accurate design models and faster time to market.

For production testing, we’ve responded with Katana-RF, Pyrana and Pyramid products to enable sub-6 GHz to 80+ GHz testing in multi-site configurations to achieve lowest cost of test. Our unique probe cards bring together two industry-leading technologies; our robust MEMS probes and our Pyramid membrane technology. Our Katana-RF and Pyrana products utilize vertical MEMS probe technology which provides the advantage of high compliance and particle tolerance, enabling test capability up to 30+GHz. Our Pyramid probe cards utilize membrane probe technology which offers ultra low-inductance and superior signal integrity, enabling test capability of 80+ GHz.

Our long experience manufacturing and employing MEMS probes and developing state-of-the-art RF wafer probe cards is unparalleled in the industry. That experience has allowed us to bring to market new RF wafer probe solutions with the highest parallelism available, lowering production test costs and providing superior RF test capability.

Empowering 5G Device Calibration with WinCal software, Infinity probes and calibration standards

FormFactor's WinCal software when used with Infinity Probes provides a complete RF calibration and characterization capability in a single software package. Integrated into WinCal are various calibration methods, including SOLT, SOLR, LRRM, mTRL, as well as the ability to do de-embedding. Using the math scripting capability, device parameters can easily be extracted post-calibration, including trace capacitance and inductance, Ft of a transistor, Mason’s Gain, and the ability to write custom algorithms for more complex analysis in the lab.

FormFactor RF experts also improve 5G test cell calibration with our proprietary Impedance Standards Substrates (ISS). Using our proven standards ensures greater accuracy and better repeatability in on-wafer calibration of vector network analyzers.

Navigating multiple high frequency channels

Techniques developed to enhance signal fidelity in 5G devices such as Orthogonal Frequency Division Multiplexing (OFDM) and Multi-Input Multi-Output (MIMO) mean that new generations of chips will have upwards of 100 RF channels operating at frequencies above 30 GHz at the wafer level. This rapidly expanding RF channel count, which is expected to reach more than 32 lines per die, poses some substantial problems during test. In engineering, more device tests will be needed to support the expanded speed bands, increasing the workload to complete testing.

With years of experience with high-frequency testing, FormFactor is the perfect partner to help you navigate the transition to multi-channel high frequency device testing. With the help of our autonomous RF probe systems, FormFactor can help you reach beyond the capabilities of today's engineering probe systems, to address the challenges of ever-increasing channels and higher RF frequencies.

Supporting 5G and Its Enormous Test Requirements

In the 5G future, wafer-level production testers will be expected to routinely measure up to 240 RF channels at a time. Currently, no production testers can handle these high channel counts. The expense of calibrating, generating, and routing so many signals between measurement instrumentation and the device under test promises to be considerable using conventional test system architectures.

At FormFactor, we are actively researching a cost- effective alternative: to intelligently optimize the test resources between testers and probe cards to support the parallel test of significant higher RF channels. This would include upconverters/downconverters that translate between RF signals and IF signals, COTS switching for cost-effective signal routing, and power splitters capable of feeding many channels in parallel.

As 5G moves forward, FormFactor is fully committed to collaborating with leading manufacturers to develop innovative test and measurement approaches that will support the enormous infrastructure required to fulfill its exciting promise.