［ Basic Technologies ］

Establishment of Analytical
Technologies for Multi-Board
Signal Integrity (SI)Toru Ogoda,
Yuto Ihara,
Wataru Mochizuki

Signal integrity, Speed-up, Voltage lowering, Multiple boards

Keywords

In recent years, signiﬁcant progress in the technology of integrating electronic circuits has led to the signiﬁcant performance improvement of electronicequipment.
There has also been an increase in the speed, frequency, low voltage, andminiaturization of electronic equipment where various noises (noise) need not
be considered. The use of a multi-circuit board, however, may affect the stable
operation of electronic equipment.
Still more, in signal transmission path among multiple boards (multi-boards)
through connectors and cables, signal degradation is deepened by increasing
the speed and frequency. As a result, it is essential to identify and take measures at the upstream stage of development.
In addition to conventional analytical approaches for Signal Integrity (SI) in
printed circuit boards, we are making every effort to establish a new SI analyticaltechnology with multi-boards. We expect that this will result in the improvementof working efﬁciency and reduction of developing time frame in order to market
high-quality products at a much faster rate.

Abstract

1 Preface
Along with the high-speed performance ofDouble Data Rate (DDR) memories and interfaces,
waveform integrity is deteriorated by increased
losses in data transmission path. This makes it difﬁcult to maintain correct transmission of signals fromthe driver Integrated Circuit (IC) to the receiver IC. In
addition, in order to respond to requirements for fur-ther miniaturization, the need to transmit fast signals to the multiple boards (multi-boards) joined
through connectors is increasing. Fig. 1 shows theevolution and issues of memory devices and Fig. 2
shows the requirements and measures. In order toresolve such issues, Signal Integrity (SI) analysis is
fully implemented in upstream of development so

Data transfer rate/operating frequency

Requirements from
customers andthe market

geing
lowaolt
dvSp

2000

Fig. 1～ 3200 Mbps/pin
1600 MHz
DDR3 (1.5 V)

ased
as gine～ 2133 Mbps/pin
cr arde m1066 MHz
ity cedlib
DDR2 (1.8 V)
ra dudu of re High speed,et～ 800 Mbps/pin
si ullarge capacity
No res400 MHzagdineean

DDR5 (1.1 V)～ 6400 Mbps/pin
3200 MHz
DDR4 (1.2 V)

up

2005

2010

2015

2020

Evolution and Issues of Memory Devices

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Cost
reduction

Measureagainstspeedingup

Noise
reduction

Requirements

Stablesignaltransmission
with multiboards

Measures

Miniaturization

StableIC operation

Radioactive
noise
suppression(Year)

Simultaneously with speeding up, SI-related issues are recently
noted such as signal retardation, reﬂection, and crosstalk.

06

Reductionof developmentperiodConditions required forprinted circuit boards

Fig. 2Requirements and Measures

According to requirements from customers and the market,measured items in printed circuit board development are shown.

that we can deliver highly quality products to ourcustomers in the shortest possible time frame. This
paper introduces a multi-board SI analytical technology at the stage of upstream development for
printed circuit boards.

2 Analytical Approach for Multi-Board
SIFig. 3 shows the condition of connector jointsand Fig. 4 shows multi-board SI analysis. A transmission path through a connector is modeled inorder to secure signal integrity while signal waveforms are transmitted from the sending side to theConnector

Fig. 3

Condition of Connector Joints

receiving side without causing turbulence.
The network parameter in each transmission
path (S parameter hereafter) is acquired as described below.
( a ) Device model of semiconductor parts
An Input-output Buffer Information Speciﬁcation(IBIS) model distributed by the respective semiconductor parts makers is procured.
( b ) Printed circuit board model
An S parameter in the high-speed signal transmission path is acquired from board design datausing an electromagnetic ﬁeld analyzing tool (ANSYSSIwave) (1).
( c ) Connector model
It is an ideal method if S parameters are procured from the respective manufacturers.
Fig. 5 shows an observation of a connector
cross-section and a measurement of dimensions.
Fig. 6 shows a 3D model. After an S parameter isacquired with the use of an electromagnetic ﬁeld
analyzing tool.
Combining the characteristics obtained from( a ) to ( c ), a network topology of transmission pathis established and SI analysis is then carried out. By
doing so, multi-board analysis can be realized inconsideration of connector characteristics.

A conﬁguration of a multi-board used for analysis is shown.

IBIS(Provided from parts maker)

Cross-section observation/
Size measurement(a) Device model ofsemiconductor parts

Modeling

Devicemodel

Printed circuitboard model

io

SATA_TXPSATA_TXP

inv_io

SATA_TXN

SATA_TXN－2－4－60.1 1
100 10,000
Frequency (MHz)(b) Printed circuit board model

Port9Port2

Port10Port3

Port11Port4Port12Port5Port13Port6Port14

Port7Port15

Port8Port16Device
model

SATA_TXPSATA_TXP

io

SATA_TXN

SATA_TXN

inv_ioNetwork topology of transmission path0－10－15Connector
characteristic－20
100 10,0000.1 1
Frequency (MHz)

500(c) Connector model2500－250－500

Fig. 4

Port1

Printed circuitboard model－5

Voltage (mV)0Characteristic (dB)Characteristic (dB)Electromagnetic
field analysis

Connector
model

0100

200Time (ps)300

Multi-Board SI Analysis

For the quality assurance of signal transmission paths between multi-boards, SI analysis is indispensable. For the resolution of issues
like signal retardation, reﬂection, and crosstalk, this supporting tool is actively used.

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07

5.02

5.37

7.63

8.38

4.54

3 Postscript

0.2
Unit: mmFig. 5

Observation of Connector Cross-Section andMeasurement of Dimensions

Observation of connector cross-section in the mating state andmeasurement of dimensions by means of a microscope areshown.

This paper introduced multi-board SI analyzing
technologies we are working on. If we adapt SI analytical technologies to printed circuit board designs
and single out potential issues existing in theupstream of development, it is possible to avoid
reworking attributable to SI and offer our quality
products to our customers within the shortest possible time. There is concern in terms of signal degradation if a multi-stage conﬁguration through connectors is established for the purpose of miniaturization.
By virtue of SI analyzing approaches, however, thepresence of any issues can be examined before
going into trial manufacturing.
Based on our expertise established from application of analytical technology and modelingapproach, we will be able to realize overall systemmodeling, not just limited to parts. Going forward,
we will develop technologies of radioactive disturbance noise suppression and misoperation avoiding
systems against the intrusion of electromagnetic
waves generated from external equipment.
・ANSYS SIwave is the trademark and/or service mark of ANSYS,
Inc. or its afﬁliated companies in U.S.A. or other countries.
・All product and company names mentioned in this paper are
the trademarks and/or service marks of their respective owners.
《Reference》( 1 ) Nishigaya, et al.: “SI/PI Simulation Technologies for High-SpeedDesign”, Meiden Review, Vol.168, No.3/2016, pp.29-32

Fig. 63D Model

A 3D model (including interior structure) established based on
the measured data is shown.

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