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Chip Scale Review November • December • 2018


Advanced eWLB solutions for 77GHz ADAS

mmWave applications

By Dian Wang, Fazhi An

[Calterah Semiconductor Technology (Shanghai) Co., Ltd.]


Seung Wook Yoon

[STATS ChipPAC Pte Ltd. JCET Group]

emiconductor packaging can

have a significant impact on

the overall device cost and

performance. In terms of the performance,

size and scalability, traditional packaging

technologies are reaching their limits with

respect to the severe challenges related to

emerging applications. Over the next 10

years, the automotive integrated circuit

(IC) market is forecasted to outgrow the

rest of the IC market by a factor of two [1].

Currently, 8,000 electronic components

are used in the Audi A8 and over 2,000

electronic parts are used per automobile

on average with 80% of innovations in

automotive technology coming from

semiconductors [2].

I n t e rms of pe r formance, powe r

consumption, integration and reliability

at a required cost, current and future

demands of automotive semiconductors

are met by developing advanced silicon

process technology, innovative packaging

solutions based on chip and package

co-design, low-cost materials, reliable

interconnect technologies, and advanced

assembly and test manufacturing systems.

Emerging WLCSP market of

mmWave applications

Market trends as experienced by end

applications drive the emergence and

evolution of any package technology.

Cu r rently, t he pr ima r y automot ive

packaging solution is leaded or laminate

wire bonding, which account for more

than 80% of the total assembly market.

The smallest possible package size

is the wafer-level chip-scale package

(WLCSP) because the final package is no

larger than the required circuit area. Since

its introduction, WLCSP has experienced

signif icant growth on account of its

small form factor, lower cost, and high-

performance requirements of mobile and

portable applications.

WLCSP and 77GHz radar sensors with

fan-out wafer-level packaging (FOWLP)

are already well adopted in the automotive

market for cabin or infotainment and

automot ive d r iver assist ant system

(ADAS) safet y [3,4]. The r ange of

applications continues to expand with the

ultimately larger wave in the development

of next-generation automotive capabilities,

i.e., electric vehicles (EV) and automated

vehicles (AV). The car radar market is

expected to grow 28% annually (2015-

2022) and reach more than $200M in

packaging and assembly.

eWLB/FOWLP for 77GHz mmWave

& automotive radar applications

In today’s vehicle safety systems,

r a d a r i s u s ed i n conju nc t ion wit h

cameras, ultrasound and other sensors

to obtain information about a vehicle’s

surroundings. As shown in

Table 1

, a

radar sensor has more advantages over

other ADAS sensors. It can easily operate

in cloudy, rainy weather conditions, and

at night. It supports a longer operating

distance too.

With Si-based front-end technologies

showing improved performance, wireless

systems at millimeter wave (mmWave)

frequencies are becoming more and more

important [4-6]. Adaptive cruise control

(ACC) radar systems at 77GHz [7, 8],

point-to-point radio links at 60GHz, or

high-resolution radio imaging at 94 and

140GHz [9] are just a few examples of

the applications observed for upcoming

markets. The impact of packaging on

the overall electrical performance of the

IC becomes increasingly important with

frequencies increasing beyond 10GHz.

Therefore, for the crucial development

of commercial mmWave applications,

the availability of high-performance

packages for monolithic microwave

integrated circuits (MMIC) is crucial.

Traditionally, many of these systems

used frequencies in the 24GHz band. For

automotive, both a narrow band (NB) and

an ultra-wide band (UWB) are currently

available. Due to spectrum regulations

and standards developed by the European

Telecommunications Standards Institute

(ETSI) and Federal Communications

Commission (FCC), the use of the UWB

band will be phased out by the year 2022

(the “sunset date”) in both Europe and

the U.S. In phasing out the 24GHz UWB,

the regulating authorities have opened

up frequencies for automotive radar in

the 77GHz band. Radar

sensors serve short-, mid-

a n d l o n g - r a n g e r a d a r

(SRR, MRR, LRR) with

the bandwidth available

from 77-81GHz providing

up t o 4GHz of swe e p

bandwidth [10,11].

A v e r y p r o m i s i n g

s o l u t i o n f o r mmWave

packaging is the embedded

wafer-level ball-grid array

(eWLB) platform [12,13].

It is based on an embedded

device technology with

fan-out redistribution. The

thin-film redistribution layer (RDL) of the

eWLB enables very flexible and highly

customizable package designs. The

length of the redistribution lines is within

the range of the die size. eWLB has the

ability to attain minimum interconnection

l e n g t h a n d e x c e l l e n t e l e c t r i c a l


Table 1:

Comparison of various ADAS solutions.