Development Trends of Automotive Electronics and Advanced Packaging

Wirebond once dominated this market, when most chips were relatively uncomplicated and had long product cycles—sometimes as long as 5 to 7 years. But as automakers begin planning for a faster-paced future of driver assistance or fully autonomous driving, they are also beginning to consider using advanced packaging to maintain their technological advantage and bring products to market more quickly. Automotive OEMs are accelerating the electrification of vehicles at their own pace, and to this end, they are embracing new packaging methods to differentiate themselves in this increasingly competitive market.

“We are seeing an increasing number of new and different packaging options and considerations for automotive applications,” said Edward Fontanilla, vice president of product technical marketing at STATS ChipPAC. “One example is high-frequency radar devices used in 77GHz advanced driver assistance systems (ADAS). These high-frequency radar devices require much tighter RF signal isolation and aggressive performance targets. Fan-out wafer-level packaging (FOWLP), and especially embedded wafer-level ball grid array (eWLB), is becoming the packaging technology of choice.”

Fontanilla points out some advantages of using the fan-out approach in automotive electronics, including:

The laminate substrate is no longer required, but is replaced by a copper redistribution layer (RDL). This RDL has shorter connection distances, which significantly reduces impedance. Like many advanced packaging methods, it allows for smaller form factors and lower parasitics in the interconnects, which is critical for high-frequency applications. Wafer-level processing has lower tolerances, which allows better yields and is cost-effective for high-frequency applications. Like all fan-out technologies, it provides greater design flexibility because there is less routing interference and the RF channels have adequate isolation. Others have also talked about a similar increase in interest in advanced packaging among automakers.

“The carmakers themselves are directly interested in this, especially the Tier 1s,” said Jean-Marc Yannou, senior technical director at ASE Europe. “OEMs like Audi realize that differentiation in cars is increasingly coming from electronics, because carmakers have solved most of the problems with the internal combustion engine. So they are moving towards electric or hybrid. That is one differentiator. Another differentiator is the cars that have been going premium. Consumers want a lot of gadgets in their cars, like being able to electrically adjust the seats, heat the seats, open the trunk or the sunroof at the push of a button.”

He noted that automotive OEMs are well aware that they can differentiate their vehicles through electronic components. They also understand that they cannot differentiate by using a different CMOS technology, so there is no big difference between them at the older nodes and migrating to 10/7nm nodes. For automotive applications, the scale is not yet large enough to significantly reduce prices when device geometries shrink. "The level of investment/capex is so high that the automakers need very, very high volumes to justify the move," Yannou said. "They will follow, but they are following the wireless industry very well. They are still five years behind in the adoption of new generation CMOS technology nodes."

But when it comes to packaging, it's a completely different picture. "In the past, silicon nodes were the same and we were just followers in the wireless industry," he said. "Now, we're doing more and more things that are actually specific to the automotive industry. Audi has said that all the differentiation in semiconductors (which is itself the differentiation of electronics and cars in general) will be packaging. Packaging can be used to push performance to a higher level by reducing the overall size, with better heat dissipation and lower electrical losses."

While the size of the electronics package can be a design factor, given the large interior space of a car, the real focus is on the ability to hide the circuitry. “The electronics must not be visible to the user’s eye, and miniaturization is an important factor,” Yannou said. However, it is not a simple matter of replacing one technology with another, but also factors need to be considered, such as how these devices are used, in what environment, and which packaging technology is best. Currently, manufacturers are basically betting on fan-out, but they may also shift to include other packaging technologies.

“The context of use is critical,” said Tom Salmon, vice president of collaborative technology platforms at SEMI. “You need to think about whether it’s under the hood or in an infotainment system, and what that will look like in 2025. Then, what materials do you need for your package? Because it’s not like the past where you had Tier 1 and Tier 2 players defining the next 20 years, it could be very different.” Packaging also offers some flexibility, because not all components need to change for each new application. As a successor to the now-defunct International Technology Roadmap For Semiconductors, the development team of the Heterogeneous Integration Road Map is currently working on a series of reference platforms for different markets, such as automotive. For these markets, different working groups are developing guidelines for 2.5D, 3D and fan-out technologies.

“The goal is to create the optimal platform for developing the right device and still have the flexibility to use wafer-level packaging or chip-level packaging or whatever is optimized for a particular environment,” Salmon said. Fan-out has been getting a lot of attention lately. Jan Vardaman, president of TechSearch International, called fan-out wafer-level packaging a disruptive technology because it doesn’t require a substrate or traditional underfill, and all packaging is done at the foundry or OSAT. But she noted it does require chip-package co-design.

“For performance reasons, radar modules use fan-out wafer-level packaging,” Vardaman said. “This is RF, so very low parasitics are very important. There is also a lot of wirebond and QFN (Quad Flat No-lead Package) today. Microcontrollers with higher pin counts are migrating from wirebond to flip chip, and there are some system-in-package modules in various components.”

Underlying this shift in how chips are put together are concerns about reliability, which has long been a focus in safety-critical markets such as automotive. The discussion used to be relatively straightforward, but as more electronics are added to cars, new levels of complexity are being added. Packaging is just another aspect of this discussion.

“Functional safety requires a systematic approach, but it’s hard to determine how to achieve it,” said Robert Bates, chief safety officer for the embedded systems division at Mentor, a Siemens business. “You need to plan for the possibility of random failures. They do happen. You need to do this with the understanding that both hardware and software are becoming increasingly complex. For machine learning and neural networks, the software is not directly implemented for the end purpose. And for safety-critical hardware, it’s often several generations old, and you’re introducing unproven and different scenarios into the autonomous system.”

While advanced packages have the ability to insert and remove devices, the process would have to be much more predictable if those devices were developed to work in those packages. The problem is that in the mad scramble to stay ahead of the technology, automakers are increasingly using a variety of commercially available components that were not developed for advanced packaging and have not been tested for extended periods of time in extreme environments. “That puts the tier-one and tier-two suppliers in a difficult position, and they need to provide more data,” Bates said. While data can be simulated, there is much less available data from real-world testing, which puts the onus on companies to do more validation and testing on these devices.

The push for self-driving cars and advanced electronics can be traced at least in part to Tesla Inc., a company that until a few years ago was largely ignored by most of the big, profitable automakers. Tesla’s introduction of self-driving technology changed all that, upending supply chains and calling into question relationships that had been in place for decades. Suddenly, automakers had to compete with one another to keep up, and they were working harder and harder to develop driver-assistance and fully autonomous driving technologies.

But instead of developing everything based on existing devices, they began searching for the best technology, no matter where it came from. But it wasn't just a matter of one or two devices. It required a mix and match of electronic content, including RF subsystems, power management units, engine controllers, sensor suites, and advanced logic using CPUs, GPUs, and various hardware accelerators.

Furthermore, many of these devices were developed by companies that previously had little or no communication with each other. ASE’s Yannou recalls a recent meeting organized by an OEM between ASE and Tier 1 Valeo: “The Valeo guys were a little irritated at first because they asked me what one of my sub-tier subcontractors and I were doing here. The OEM told Valeo: ‘You need to work with ASE, you need to do this integrated module together. If you can do everything on one side of the PCB, then you can free up space on the second side of the PCB so you can build the WiFi module on the other side.’” That project is still going on today.

This has a direct impact on the packaging technologies being developed for cars. Most automotive infotainment applications still use wirebond, such as GPS, audio controllers and USB devices, as well as MCUs, instrumentation, power management systems and body systems (including Ethernet, transceivers and interior lighting components) used in electric and hybrid vehicles. But according to STATS' Fontanilla, fan-out is becoming more popular for new systems such as ADAS and more modern infotainment, instrumentation and body systems.