Measurement of quartz crystal unit parameters - Part 6: Measurement of drive level dependence (DLD)

IEC 60444-6:2021 is available as IEC 60444-6:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60444-6:2021 applies to the measurements of drive level dependence (DLD) of quartz crystal units. Two test methods (A and C) and one referential method (B) are described. “Method A”, based on the p-network according to IEC 60444-5, can be used in the complete frequency range covered by this part of IEC 60444. “Reference Method B”, based on the p-network or reflection method according to IEC 60444-5 or IEC 60444-8 can be used in the complete frequency range covered by this part of IEC 60444. “Method C”, an oscillator method, is suitable for measurements of fundamental mode crystal units in larger quantities with fixed conditions.
NOTE The measurement methods specified in this document are not only applicable to AT-cut, but also to other crystal cuts and vibration modes, such as doubly rotated cuts (IT,SC) and to tuning fork crystal units (by using a high impedance test fixture). This edition includes the following significant technical changes with respect to the previous edition:
- some equations have been removed and corrected;
- it has been specified in the note of the Scope that the measurement methods specified in this document are not only applicable to AT-cut but also to other crystal cuts and vibration modes.

Mesure des paramètres des résonateurs à quartz - Partie 6: Mesure de la dépendance du niveau d’excitation (DNE)

IEC 60444-6:2021 est disponible sous forme de IEC 60444-6:2021 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
L’IEC 60444-6:2021 s’applique aux mesures de la dépendance du niveau d’excitation (DNE) des résonateurs à quartz. Deux méthodes d’essai (A et C) et une méthode de référence (B) sont décrites. La méthode A, basée sur le réseau en p conformément à l’IEC 60444-5, peut être utilisée dans la plage de fréquences complète couverte par la présente partie de l’IEC 60444. La méthode de référence B, basée sur le réseau en p ou sur la méthode de réflexion conformément à l’IEC 60444-5 ou à l’IEC 60444-8, peut être utilisée dans la plage de fréquences complète couverte par la présente partie de l’IEC 60444. La méthode C, une méthode avec un oscillateur, est adaptée pour les mesures de résonateurs sur le mode fondamental en plus grandes quantités avec des conditions fixes. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
- certaines équations ont été supprimées ou corrigées;
- il est spécifié dans la note du Domaine d’application que les méthodes de mesure spécifiées dans le présent document ne s’appliquent pas uniquement à la coupe AT, mais aussi à d’autres coupes de cristaux et à d’autres modes de vibration.

General Information

Status
Published
Publication Date
31-Aug-2021
Current Stage
PPUB - Publication issued
Completion Date
01-Sep-2021
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IEC 60444-6
Edition 3.0 2021-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement of quartz crystal unit parameters –
Part 6: Measurement of drive level dependence (DLD)
Mesure des paramètres des résonateurs à quartz –
Partie 6: Mesure de la dépendance du niveau d’excitation (DNE)
IEC 60444-6:2021-09(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60444-6
Edition 3.0 2021-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement of quartz crystal unit parameters –
Part 6: Measurement of drive level dependence (DLD)
Mesure des paramètres des résonateurs à quartz –
Partie 6: Mesure de la dépendance du niveau d’excitation (DNE)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.140 ISBN 978-2-8322-1014-4

Warning! Make sure that you obtained this publication from an authorized distributor.

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60444-6:2021 © IEC 2021
CONTENTS

FOREWORD ......................................................................................................................... 3

INTRODUCTION ................................................................................................................... 5

1 Scope ............................................................................................................................ 6

2 Normative references..................................................................................................... 6

3 Terms and definitions .................................................................................................... 6

4 DLD effects ................................................................................................................... 6

4.1 Reversible changes in frequency and resistance .................................................... 6

4.2 Irreversible changes in frequency and resistance ................................................... 7

4.3 Causes of DLD effects ........................................................................................... 7

5 Drive levels for DLD measurement ................................................................................. 7

6 Test methods ................................................................................................................. 8

6.1 Method A (fast standard measurement method) ..................................................... 8

6.1.1 Testing at two drive levels .............................................................................. 8

6.1.2 Testing according to specification ................................................................... 9

6.2 Method B (Multi-level reference measurement method) ........................................ 10

Annex A (normative) Relationship between electrical drive level and mechanical

displacement of quartz crystal units ..................................................................................... 12

Annex B (normative) Method C: DLD measurement with oscillation circuit ........................... 15

Bibliography ....................................................................................................................... 20

Figure 1 – Maximum tolerable resistance ratio for the drive level dependence as a

function of the resistances R or R .................................................................................... 9

12 13

Figure B.1 – Insertion of a quartz crystal unit in an oscillator ............................................... 15

Figure B.2 – Crystal unit loss resistance as a function of dissipated power ........................... 16

Figure B.3 – Behaviour of the R of a quartz crystal unit ..................................................... 17

Figure B.4 – Block diagram of circuit system ....................................................................... 17

Figure B.5 – Installed −R in scanned drive level range ..................................................... 18

osc

Figure B.6 – Drive level behaviour of a quartz crystal unit if −R = 70 Ω is used as

osc

test limit in the Annex B test ................................................................................................ 18

Figure B.7 – Principal schematic diagram of the go/no-go test circuit ................................... 19

---------------------- Page: 4 ----------------------
IEC 60444-6:2021 © IEC 2021 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT OF QUARTZ CRYSTAL UNIT PARAMETERS –
Part 6: Measurement of drive level dependence (DLD)
FOREWORD

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

rights. IEC shall not be held responsible for identifying any or all such patent rights.

IEC 60444-6 has been prepared by IEC technical committee 49: Piezoelectric, dielectric and

electrostatic devices and associated materials for frequency control, selection and detection. It

is an International Standard.

This third edition cancels and replaces the second edition published in 2013. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) some equations have been removed and corrected;

b) it has been specified in the note of the Scope that the measurement methods specified in

this document are not only applicable to AT-cut but also to other crystal cuts and vibration

modes.
---------------------- Page: 5 ----------------------
– 4 – IEC 60444-6:2021 © IEC 2021
The text of this International Standard is based on the following documents:
FDIS Report on voting
49/1374/FDIS 49/1377/RVD

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.

A list of all parts in the IEC 60444 series, published under the general title Measurement of

quartz crystal unit parameters, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 60444-6:2021 © IEC 2021 – 5 –
INTRODUCTION

The drive level (expressed as power/voltage across or current through the crystal unit) forces

the resonator to produce mechanical oscillations by way of piezoelectric effect. In this process,

the acceleration work is converted to kinetic and elastic energy and the power loss to heat. The

latter conversion is due to the inner and outer friction of the quartz resonator.

The frictional losses depend on the velocity of the vibrating masses and increase when the

oscillation is no longer linear or when critical velocities, elongations or strains, excursions or

accelerations are attained in the quartz resonator or at its surfaces and mounting points (see

Annex A). This causes changes in resistance and frequency, as well as further changes due to

the temperature dependence of these parameters.

At “high” drive levels (e.g. above 1 mW or 1 mA for AT-cut crystal units) changes are observed

by all crystal units and these also can result in irreversible amplitude and frequency changes.

Any further increase of the drive level may could destroy the resonator.

Apart from this effect, changes in frequency and resistance are observed at “low” drive levels

in some crystal units (e.g. below 1 μW or 50 μA for AT-cut crystal units). In this case, if the loop

gain is not sufficient, the start-up of the oscillation is difficult. In crystal filters, the transducer

attenuation and ripple will change.

Furthermore, the coupling between a specified mode of vibration and other modes (e.g. of the

resonator itself, the mounting and the back-fill gas) also depends on the level of drive.

Due to the differing temperature response of these modes, these couplings give rise to changes

of frequency and resistance of the specified mode within narrow temperature ranges. These

changes increase with increasing drive level. However, this effect will not be considered further

in this part of IEC 60444.

In this new edition, the concept of DLD in IEC 60444-6:2013 is maintained. However, the more

suitable contents for the user’s severe requirements have been introduced.
---------------------- Page: 7 ----------------------
– 6 – IEC 60444-6:2021 © IEC 2021
MEASUREMENT OF QUARTZ CRYSTAL UNIT PARAMETERS –
Part 6: Measurement of drive level dependence (DLD)
1 Scope

This part of IEC 60444 applies to the measurements of drive level dependence (DLD) of quartz

crystal units. Two test methods (A and C) and one referential method (B) are described. “Method

A”, based on the π-network according to IEC 60444-5, can be used in the complete frequency

range covered by this part of IEC 60444. “Reference Method B”, based on the π-network or

reflection method according to IEC 60444-5 or IEC 60444-8 can be used in the complete

frequency range covered by this part of IEC 60444. “Method C”, an oscillator method, is suitable

for measurements of fundamental mode crystal units in larger quantities with fixed conditions.

NOTE The measurement methods specified in this document are not only applicable to AT-cut, but also to other

crystal cuts and vibration modes, such as doubly rotated cuts (IT,SC) and to tuning fork crystal units (by using a high

impedance test fixture).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.

IEC 60444-5, Measurement of quartz crystal unit parameters – Part 5: Methods for the

determination of equivalent electrical parameters using automatic network analyzer techniques

and error correction

IEC 60444-8, Measurement of quartz crystal unit parameters – Part 8: Test fixture for surface

mounted quartz crystal units
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 DLD effects
4.1 Reversible changes in frequency and resistance

Reversible changes are changes in frequency and resistance occurring under the same drive

levels after repeated measurements made alternatively at low and high levels, or after

continuous or quasi-continuous measurements from the lowest to the highest level and back, if

these changes remain within the limits of the measurement accuracy.
---------------------- Page: 8 ----------------------
IEC 60444-6:2021 © IEC 2021 – 7 –
4.2 Irreversible changes in frequency and resistance

Irreversible changes are significant changes in frequency and/or resistance occurring at low

level after an intermediate measurement at high level e.g. when a previously high resistance at

low level has changed in the repeated measurement to a low resistance. Especially, when the

crystal unit has not been operated for several days, its resistance may have changed back to a

high value when operated again at a lower level. Greater attention should be paid to the

irreversible effect since it can significantly impair the performance of devices, which are

operated only sporadically.
4.3 Causes of DLD effects

Whereas the mostly reversible effects are due to excessive crystal drive level, the irreversible

effects are due to production, especially to imperfect production techniques. Examples of

causes are:

– particles on the resonator surface (partly bound by oils, cleaning agents, solvents or bound

electro-statically);

– mechanical damage of the resonator (e.g. fissures due to excessively coarse lapping

abrasive which may increase in size);

– gas and oil inclusions in the electrodes (e.g. due to a poor vacuum or an inadequate coating

rate during evaporation);

– poor contacting of the electrodes at the mounting (e.g. the conductive adhesive has an

inadequate metal component, was insufficiently baked out or was overheated; also

excessive contact resistance between the conductive adhesive and the electrodes or

mounting);
– mechanical stresses between mounting, electrodes and quartz element.
5 Drive levels for DLD measurement

For the DLD measurement, a low and a high level of drive (and possibly further levels) are

applied. The high level is the nominal drive level, which should be equal to the level in the

application at its steady state.

It should be noted that this level should be below the maximum applicable level that is derived

in Annex A. If not specified, a standard value for the crystal current of 1 mA, corresponding to

the velocity v = 0,2 m/s for AT-cut crystal units, shall be used. The drive level in watt is

max

then calculated with the mean value of the specified maximum and minimum resistances.

The minimum drive level occurring at the start-up of an oscillator can be determined only in a

few cases by active or passive measuring methods due to the noise limits of the measuring

instruments for measurements according to IEC 60444-5, at approximately 1 nW or 10 μA

(depending on the equipment, the lowest power value can be reduced to 0,1 nW or 1 μA).

A velocity v = 0,01 m/s, corresponding to 50 μA for AT-cut crystals, has proved to be

max
practical value for π-network measurements (see “Method A”).
Two methods and one referential method of DLD measurement are described below.

“Method A” is based on the π-network method according to IEC 60444-5, which can be used in

the complete frequency range covered by this document. It allows the fast selection of drive

level sensitive quartz crystal units by a sequence of three measurements. The allowed variation

of the series resonance resistances given in Figure 1 is based on long-term examinations of

crystal units of different manufacturers and proved to be a reliable indicator for crystal units

showing start-up problems. If necessary, this method should also be extended by measuring a

large number of different drive levels. However, in practice, this is not necessary in most cases

(see 6.1).
---------------------- Page: 9 ----------------------
– 8 – IEC 60444-6:2021 © IEC 2021

In the industrial area, there are some commercially available crystal test systems like Saunders

250B or Kolinker KH1820 . Their software offers several variants for measuring DLD.

“Method B” is used for devices where strict oscillation start-up requirements have to be fulfilled

and for high reliability devices.

“Method C” as shown in Annex B is an oscillator method, which is especially suitable for

measuring fundamental mode crystal units in larger quantities with fixed measurement

conditions (maximum drive level, R , ) in an economical way.
1 max

If the proposed measurement techniques are not sufficient in special cases, the user should

have an original oscillator with slightly reduced feedback or an original filter.

“Method B” is stricter than “Method A”.

“Method B” is based on the π-network method or reflection method according to IEC 60444-5

or IEC 60444-8, which can be used in the complete frequency range covered by this document.

Recommendation: These methods can be used for all types of crystals, however:
– “Method A” is recommended for filter and oscillator crystals;

– “Method B” is recommended for applications with strict start-up conditions, for high reliability

and for high stability applications. It is the reference method for failure analysis etc.;

– “Method C” in Annex B is a go/no-go measurement technique for oscillator crystals.

6 Test methods
6.1 Method A (fast standard measurement method)
6.1.1 Testing at two drive levels

Testing is performed at low and high drive levels as described in Clause 5 with measurements

of series resonance frequency and resistance according to IEC 60444-5. The tolerances are

± 10 % for the levels of current and ± 20 % for those of power.

a) Storage for at least one day at 105 °C and after that at least 2 hours at room temperature

or, storage for one week at room temperature.

b) The temperature should be kept constant during the measurement (in accordance with

IEC 60444-5).
f = f RR=
, .
c) Measurement at low drive level (10 μA): s s1 11
f = f RR=
d) Measurement at high drive level (1 mA): , .
ss2 1 12
f = f RR=
e) Measurement at low drive level (10 μA): , .
ss3 1 13

f) Calculation of γ = RR . The value of γ shall be smaller than the maximum value of γ

12 11 12 12
given by the line drawn in Figure 1 (abscissa = R ).

g) The tolerable frequency change ff− shall be 5 × 10 × f unless otherwise specified

ss21 s1
in the detail specification.

h) Calculation of γ = RR . The value of γ shall be smaller than (γ +12) , where the value

13 11 13 13
of is taken from Figure 1 (abscissa = R ).
___________

Saunders 250B and Kolinker KH1820 are examples of suitable products available commercially. This information

is given for the convenience of users of this document and does not constitute an endorsement by IEC of these

products.
---------------------- Page: 10 ----------------------
IEC 60444-6:2021 © IEC 2021 – 9 –
i) The tolerable frequency change ff− shall be 2,5 × 10 × f , unless otherwise
ss31 s1
specified in the detail specification.

j) The resistance value shall not exceed the maximum value given by the detail specification

at any drive levels.
6.1.2 Testing according to specification

Testing is performed at low to high drive levels and back again to low level as described in 6.1.1.

These and, if necessary, further levels with their tolerances, the permissible deviations of the

frequency and resistance as well as storage conditions shall be specified in the detail

specification.

NOTE The given γ -curve was verified by results obtained over many years of experience with crystal units for

many oscillator types. In most cases, there will be no trouble in start-up, but in critical oscillator configurations,

problems could occur. As it is not possible to manufacture crystal units, which have a constant resistance at any

drive level, the proposed ϒ-curve gives tolerable relations.

Definition of drive level values can be agreed between manufacturer and customer.

Use the nominal drive level of the detail specification as value for the high drive level. For

measurement at very high drive levels, an additional amplifier may be required.
Figure 1 – Maximum tolerable resistance ratio γ for the drive
level dependence as a function of the resistances R or R
12 13

The maximum drive level recommended to be selected so that with a further increase of the

drive level by 50 %, the resistance does not increase reversibly by more than 10 % or the

frequency changes by more than 0,5 × 10 .
I = K ⋅
---------------------- Page: 11 ----------------------
– 10 – IEC 60444-6:2021 © IEC 2021
where
I is the recommended current for oscillating state;
is the overtone order;
A is the electrode size in mm ;
f is the frequency in MHz;
-2 -1/2
K is 0,35 mA ⋅ mm ⋅ s .
6.2 Method B (Multi-level reference measurement method)

Testing is performed at low and high drive levels as described in Clause 5 with measurements

of resonance frequency and resistance according to IEC 60444-5. The tolerances are ±10 %

for the levels of current and ±20 % for those of power.

a) Storage for at least one day at 105 °C and after that at least 2 hours at room temperature

or storage for one week at room temperature.

NOTE If considered as necessary, the customer and the maker agree on a higher temperature and a longer

duration for the storage before DLD measurement.

b) The temperature should be kept constant during the measurement IAW (in accordance with

IEC 60444-5).

c) The drive level is applied by two types of measurement units. It should also be applied

sequentially starting from the lowest to the highest value and then back to the lowest value.

A definition for the unit of drive levels shall be specified between the crystal manufacturer

and the user.
1) When the unit of a drive level is mA;

Measurement drives level: from 2 μA to nominal drive level in at least 7 levels which are

logarithmically scaled. (Refer to the equation given under item f)).
2) When the unit of a drive level is μW;

Measurement drives level: From 2 nW to nominal drive level in at least 7 levels which

are logarithmically scaled. (Refer to the equation given under item f)).

d) The maximum frequency excursion over all drive levels shall be less than the following

specifications.
fi ,,− fi
( ) ( )
ssmax min −6
1) <×5 10
NOM
or,
fi ,,− fi
( ) ( )
ssmax min
<×0.5 f
ADJ
NOM
where
is the maximum value for frequency measurement values with i = 1 to 2⋅N-1
fi( ),
s max
drive levels;
fi , is the minimum value for frequency measurement values with i = 1 to 2⋅N-1
...

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