IEC 60758:2004

INTERNATIONAL IEC
STANDARD
Third edition
2004-12
Synthetic quartz crystal –
Specifications and guide to the use

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INTERNATIONAL IEC
STANDARD
Third edition
2004-12
Synthetic quartz crystal –
Specifications and guide to the use

� IEC 2004 � Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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International Electrotechnical Commission

For price, see current catalogue

– 2 – 60758 � IEC:2004(E)
CONTENTS
FOREWORD.4

1 Scope.6

2 Normative references .6

3 Terms and definitions .6

4 Specification for as-grown synthetic quartz crystal.10

4.1 Standard values .10

4.2 Requirements and measuring methods .11
4.3 Marking .17
5 Specification for lumbered synthetic quartz crystal .18
5.1 Standard values .18
5.2 Requirements and measuring methods .18
5.3 Delivery conditions .19
6 Inspection rule for synthetic quartz crystal and lumbered synthetic quartz crystal .19
6.1 Inspection rule for as-grown synthetic quartz crystal.19
6.2 Inspection rule for lumbered synthetic quartz crystal .20
7 Guide to the use of synthetic quartz crystal .21
7.1 General .21
7.2 Shape and size of synthetic quartz crystal .22
7.3 Standard method for evaluating the quality of synthetic quartz crystal .23
7.4 Other methods for checking the quality of synthetic quartz crystal .23
7.5 Alpha-grade.24
7.6 Optional grading (only as ordered), in inclusions, etch channels, Al content .24
7.7 Ordering .26

Annex A (informative) Frequently used sampling procedures .36
Annex B (informative) Numerical example.38
Annex C (informative) Example of reference sample selection .39
Annex D (informative) Explanations of point callipers.40
Annex E (informative) Infrared absorbance alpha value compensation .41

Bibliography.45

Figure 1 – Idealized sections of a synthetic quartz crystal grown on a Z-cut seed .27
Figure 2 – Quartz crystal axis and face designation .28
Figure 3 – Typical example of cutting wafers of AT-cut plate, minor rhombohedral-cut
plate, X-cut plate, Y-cut plate and Z-cut plate .29
Figure 4 – Frequency-temperature characteristics of the test specimen for slope.30
Figure 5 – Quartz crystal axis and face designation .31
Figure 6 – A synthetic quartz crystal grown on a Z-cut seed of small X-dimensions
(Crystals of other shapes are produced when Z-cut seeds of other proportions, or seeds
of other cuts, are used.) .32
Figure 7 – An example of an early 1970s relation between the extinction coefficient of
infra-red radiation and the Q-value of synthetic quartz .32

60758 � IEC:2004(E) – 3 –
Figure 8 – Lumbered synthetic quartz crystal outline and dimensions along X-, Y- and

Z-axes .33

Figure 9 – Angular deviation for reference surface.34

Figure 10 – Centrality of the seed with respect to the dimension along the Z- or Z�-axis.35

Figure D.1a � Point callipers .40

Figure D.1b � Digital point callipers.40

Figure E.1 – Schematic of measurement set-up .42

Figure E.2 � Graph relationship between averaged alpha and measured alpha at three

wave numbers of � , � and � .44
3500 3585 3410
Table 1 – Inclusion densities for the grades .10
Table 2 – Infra-red quality indications for the grades.10
Table 3 – Etch channel densities for the grades .11
Table 4 � Test conditions and requirements for the lot-by-lot test for group A .20
Table 5 � Test conditions and requirements for the lot-by-lot test for group B .20
Table 6 � Test conditions and requirements for the lot-by-lot test.21
Table B.1 � Commodity bar sampling method 1 .38
Table B.2 � Commodity bar sampling .38
Table E.1 � Example of calibration data at � .43
Table E.2 � Example of calibration data at � .43
Table E.3 � Example of calibration data at � .43
– 4 – 60758 � IEC:2004(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
SYNTHETIC QUARTZ CRYSTAL –
SPECIFICATIONS AND GUIDE TO THE USE

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment
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6) All users should ensure that they have the latest edition of this publication.
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arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
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.
International Standard IEC 60758 has been prepared by IEC technical committee 49:
Piezoelectric and dielectric devices for frequency control and selection.
This third edition cancels and replaces the second edition, published in 1993, and its
amendments 1 (1997) and 2 (2001).

This edition includes the following significant technical changes with respect to the previous
edition:
a) it combines the information given in the second edition and in the amendments into one
single document;
b) it adds the infrared absorbance alpha value compensation method as Annex E.
The text of this standard is based on the following documents:
FDIS RVD
49/696/FDIS 49/701/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

60758 � IEC:2004(E) – 5 –
The committee has decided that the contents of this publication will remain unchanged until the

maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be

 reconfirmed,
 withdrawn,
 replaced by a revised edition, or

 amended.
A bilingual version of this publication may be issued at a later date.

– 6 – 60758 � IEC:2004(E)
SYNTHETIC QUARTZ CRYSTAL �
SPECIFICATIONS AND GUIDE TO THE USE

1 Scope
This International Standard applies to synthetic quartz single crystals intended for manu-
facturing piezoelectric elements for frequency control and selection.

2 Normative references
The following referenced documents are indispensable for the application 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 60068-1:1988, Environmental testing � Part 1: General and guidance
IEC 60122-1:2002, Quartz crystal units of assessed quality � Part 1: Generic specification.
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 61994 (all parts), Piezoelectric and dielectric devices for frequency control and selection �
Glossary
3 Terms and definitions
For the purposes of this document, the following terms and definitions, as well as those given in
IEC 61994, apply.
3.1
hydrothermal crystal growth
literally, crystal growth in the presence of water, elevated temperatures and pressures by a
crystal growth process believed to proceed geologically within the earth's crust. The industrial
synthetic quartz growth processes utilize alkaline water solutions confined within autoclaves at
supercritical temperatures (330 °C to 400 °C) and pressures (700 to 2 000 atmospheres). The
autoclave is divided into two chambers: the dissolving chamber, containing raw quartz chips at
the higher temperature; the growing chamber, containing cut seeds at the lower temperature

(see 7.1.2)
3.2
synthetic quartz crystal (also known as cultured quartz crystal)
������������������ ������������������������������������������������������������������������������
and in the as-grown condition
3.2.1
as-grown synthetic quartz crystal
single crystal quartz grown hydrothermally. As-grown refers to the state of processing and
indicates a state prior to whatever treatment�might occur after growth, excluding quality control
operations
3.2.2
as-grown Y-bar
crystals which are produced using seed with the largest dimension in the Y-direction

60758 � IEC:2004(E) – 7 –
3.2.3
as-grown Z-bar
crystals in which the Z-grown sector is much larger that the X-grown sector. The relative size of

the growth sector is controlled by the X-dimension of the seed

3.3
synthetic quartz crystal batch

synthetic quartz crystals grown at the same time in one autoclave

3.4
seed
rectangular parallelepiped quartz plate or bar to be used as a nucleus for crystal growth
3.5
growth zones
regions of a synthetic quartz crystal resulting from growth along different crystallographic
directions (see Figure 1)
3.6
orientation of a synthetic quartz crystal
orientation of its seed with respect to the orthogonal axes specified in 3.7
3.7
orthogonal axial system of a quartz crystal
3.7.1
axial system for quartz illustrated in Figure 2
NOTE The Z-cut seed may be oriented at an angle of less than 20° to the Y-axis, in this case the axial system
becomes X, Yc, Zc.
3.7.2
AT-cut plate
rotated Y-cut crystal plate oriented at an angle of about +35° around the X-axis or about -3° from
the z (minor rhombohedral)-face as shown in Figure 3
3.7.3
z (minor rhombohedral)-cut plate
crystal plate parallel to the z (minor rhombohedral)-face as shown in Figure 3a
3.7.4
X-cut plate
crystal plate perpendicular to the X-axis as shown in Figure 3b

3.7.5
Y-cut plate
crystal plate perpendicular to the Y-axis as shown in Figure 3b
3.7.6
Z-cut plate
crystal plate perpendicular to the Z-axis as shown in Figure 3b
3.8
dimensions
dimensions pertaining to growth on Z-cut seed rotated less than 20° from the Y-axis

– 8 – 60758 � IEC:2004(E)
3.8.1
gross dimensions
maximum dimensions along the X-, Y-, or Y�-, and Z- or Z�-axes measured along the X-, Y�- and

Z�-axes
3.8.1.1
effective Z-dimension
°
as-grown effective Z dimension defined as the minimum measure in the Z (� = 0 ) or Z� direction

in usable Y or Y� area of an as-grown crystal and described by Z ,as shown in Figure 1
eff
3.8.1.2
minimum Z-dimension
minimum distance from seed surface to Z-surface described by Z as shown in Figure 1d
min
3.8.2
dimensions pertaining to growth on a Z-cut seed rotated more than 20° from the X-axis
(under consideration)
3.9
inclusions
any foreign material within a synthetic quartz crystal, visible by examination of scattered light
from a bright source with the crystal immersed in a refractive index-matching liquid.
A particularly common inclusion is the mineral acmite (sodium iron silicate)
3.9.1
seed veil
array of inclusions or voids at the surface of the seed upon which a crystal has been grown
3.9.2
etch channel
roughly cylindrical void that is present along dislocation line after etching a quartz crystal
3.10
dopant
any additive used in the growth process which may change the crystal habit, chemical
composition, physical or electrical properties of the synthetic quartz batch
3.11
pre-dimensioned bar
any bar whose as-grown dimensions have been altered by sawing, grinding, lapping, etc.,
to meet a particular dimensional requirement

3.12
impurity concentration
concentration of impurities relative to silicon atoms
3.13
dislocations
linear defects in the crystal due to misplaced planes of atoms
3.14
etch channel
roughly cylindrical void present along a dislocation line after etching a test wafer prepared from
a quartz crystal
60758 � IEC:2004(E) – 9 –
3.15
autoclave
vessel for the high-pressure high-temperature condition required for growth of synthetic quartz

crystal
3.16
right-handed quartz or left-handed quartz

handedness of quartz crystal as determined by observing the sense of handedness of the optical

rotation in the polarized light. Right-handed quartz is the crystal of dextrorotatory and

left-handed quartz is the crystal of levorotary

3.17
twins
twins follow laws of crystallography relating symmetrically to specific faces or axes.
The following types have been identified in synthetic quartz crystals:
a) Electrical twins
Quartz crystal in which regions with the common Z-axis exist showing a polarity reversal of
the electrical X-axis.
b) Optical twins
Quartz crystal in which regions with the common Z-axis exhibit handedness reversal of the
optical Z-axis
3.18
infrared absorption coefficient �-value
coefficient (referred to as the �-value) established by determining the relationship between
absorption of two wavelengths: one with minimal absorption due to OH impurity, the other with
high absorption due to presence of OH impurities in the crystal lattice. The OH impurity creates
mechanical loss in resonators and its presence is correlated to the presence of other
loss-inducting impurities. The �-value is a measure of OH concentration and is correlated with
expected mechanical losses due to material impurities. The infrared absorption coefficient
�-value is determined using the following equation:
1 T
� = log
t T
where
� is the infrared absorption coefficient;
t is the thickness of Y-cut sample, in centimetres;
–1 –1
T is the per cent transmission at a wave number of 3 800 cm or 3 979 cm ;

–1 –1 –1
T is the per cent transmission at a wave number of 3 410 cm , 3 500 cm or 3 585 cm .
3.19
lumbered synthetic quartz crystal
synthetic quartz crystal whose X- and Z- or Z�- surfaces in the as-grown condition have been
processed flat and parallel by sawing, grinding, lapping, etc., to meet specified dimensions and
orientation
3.19.1
lumbered Y-bar
quartz bars which are lumbered from an as-grown Y-bar
3.19.2
lumbered Z-bar
quartz bars which are lumbered from an as-grown Z-bar

– 10 – 60758 � IEC:2004(E)
3.20
reference surface
surface of the lumbered bar prepared to specific flatness and orientation with respect to a

crystallographic direction (typically the X-direction)

4 Specification for as-grown synthetic quartz crystal

4.1 Standard values
4.1.1 Orientation of the seed
Standard orientation for the seeds are Z-cuts and rotated X-cuts, minor rhombohedral

(z-minor) cut, 1°30� rotated Z-cut, 2° rotated Z-cut, 5° rotated Z-cut, and 8°30� rotated Z-cut, the
Z�-axis of the latter three seeds being rotated as shown in Figure 2.
4.1.2 Inclusion density
The inclusion density (measured as in 4.2.5.3) for each grade shall not exceed the figures in any
required size range for that grade listed in Table 1.
Table 1 – Inclusion densities for the grades
Grade/size Densities per cm
range
10-30 30-70 70-100 >100
Pm
Ia 2 1 0 0
Ib 3 2 1 1
I 6 4 2 2
II 9 5 4 3
III 12 8 6 4
Users requiring a grade in only one or more of the size ranges may designate their requirement
as the grade followed by the appropriate size range.
4.1.3 Infra-red quality indications, � , � , �
3500 3585 3410
An infra-red extinction coefficient value (�-value) of synthetic quartz (measured as in 4.2.6)
shall be as listed under the appropriate heading for � , � , or � in Table 2 for the
3500 3585 3410
various grades:
Table 2 – Infra-red quality indications for the grades
a
Grades Maxima Pre-1987
D D D Q � 10 units
3500 3585 3410
Aa 0,026 0,015 0,075 3,8
A 0,033 0,024 0,082 3,0
B
0,045 0,050 0,100 2,4
C 0,060 0,069 0,114 1,8
D 0,080 0,100 0,145 1,4
E 0,120 0,160 0,190 1,0
a
These Q-values were obtained from D-measurements and empirical
correlation, and were in common usage prior to 1987. These are included
here as the previous labels to maintain continuity through the change in
emphasizing D-labels. D is the physical meaurement now used to control and
specify quality in sythetic quartz.

60758 � IEC:2004(E) – 11 –
The test limits above either correspond to or are unchanged (except in the cases of grades B and

D) from the � limits that correspond to the Q-value grades listed in the first edition of
IEC 60758. This earlier publication designated some of the same grades in terms of minimum

indicated Q's in 10 units, as follows:

A = 3,0;
B = 2,2 (basis used herein), changed from 2,4 in the earlier edition;

C = 1,8;
D = 1,4 (revised);
E = 1,0 (the same as the earlier D-grade).

4.1.4 Frequency-versus-temperature characteristics (Figure 4 and 4.2.7)
The frequency-versus-temperature characteristics of synthetic quartz crystal units shall be
assessed by determination of the fractional frequency deviation measured at 15 �C and 35 �C
with respect to the series resonance frequency at 25 �C. The fractional deviation shall satisfy the
following:
–6
– fractional frequency deviation at 15 °C: +0,5 to +1,5 � 10 ;
–6
– fractional frequency deviation at 35 °C: –0,5 to –1,5 � 10 .
Measurement shall be made in accordance with 4.7.3 of IEC 60122-1.
4.1.5 Etch channel density
When required, �������������������������� ����� cm (measured as in 4.2.8) for each grade, shall
comply with the listings in Table 3.
Table 3 – Etch channel densities for the grades
Grade Maximum number U per cm
1 10
2 30
3 100
4 300
5 600
4.2 Requirements and measuring methods

4.2.1 Orientation
The orientation of the seed shall be along specified directions, with a deviation of less than
30 min from nominal.
4.2.2 Handedness
The handedness of the seed shall be specified, either right-hand or left-hand (see Figure 2).
4.2.3 Synthetic quartz crystal dimensions
The dimension shall be measured by calipers or point calipers which enable the hollow point of
a synthetic quartz crystal to be measured (see Annex D).

– 12 – 60758 � IEC:2004(E)
4.2.3.1 Dimension along Y or Y�-axis

The dimension shall be as specified (see Figure 1d).

4.2.3.2 Dimension along Z or Z�-axis dimension shall be measured by a neck ipers

The dimension along the Z or Z�-axis shall be specified as the maximum dimension along the

Z or Z�-axis in the greater X zone (see Figure 1c).

4.2.3.3 Dimension Z or Z�
eff eff
The Z or Z� dimension shall be specified as the minimum dimension along the Z or Z�-axis
eff eff
(see Figure 1c).
4.2.3.4 Dimension Z or Z�
min min
The dimension shall be as specified (see Figures 1c and 1d).
4.2.3.5 Dimension along X-axis
The gross dimension along the X-axis shall be as specified (see Figure 1c).
4.2.4 Seed dimensions
4.2.4.1 Z or Z�-dimension
The Z or Z�-dimension (i.e. thickness) of the Z-cut or rotated Z-cut seed shall be less than 3 mm,
unless otherwise specified.
4.2.4.2 X-dimension
The dimension X of the seed shall be as specified.
4.2.5 Imperfections
4.2.5.1 Twinning
There shall be no electrical or optical twinning in the usable region. The existence of twinning
shall be checked by visual inspection.
4.2.5.2 Cracks and fractures
There shall be no cracks or fractures in the usable region. The existence of cracks and fractures
shall be checked by visual inspection.
4.2.5.3 Inclusion density
The following two measuring methods are used and either one may be chosen.
Method 1
Inclusions within stated ranges are counted visually per cm in sample volumes within a crystal
using a stereo binocular microscope operating at 30� to 40� magnification equipped for counting
within either a circular or a square field and with a calibrated reticule scale for determining
particle sizes, intense side illumination (such as halogen lamps) over a recessed black matt
background, an index matching liquid (n = 1,55, approximately) for transparency, and means of
measuring the dimensions of the sample volumes counted.

60758 � IEC:2004(E) – 13 –
Method 2
In case it is difficult to apply method 1, crystals are compared with reference samples

appropriately representing each grade range, immersing within an index matching liquid

(n = 1,55 approximately) for transparency, or applying such liquid to the surface. The reference

samples shall be agreed upon between the supplier and the user. An example for the reference
sample selection procedure is given in Annex C.

4.2.5.3.1 Sampling
Because of the considerable costs in time, labour and money, some plan for sampling both bars

and regions within the bars is normally used by agreement between the supplier and the buyer

when quality control of either inclusion density or etch channel density is required.
Clearly, the preferrable low-cost inspection situation is the one in which the densities of
inclusions or etch channels are well below the test limits, and infrequent samples can be justified.
Since such situations are not always attainable, more rigorous inspection strategies will
sometimes be required for appropriate density control, and shall be found, worked out, and
agreed upon between the supplier and the user.
Sound statistical methods are required in order to meet appropriate agreed-upon assured
quality level tests and ensure that the crystals and the volumes counted within them are
sufficiently representative. Since sampling procedures and statistical confidence tests are
described in the literature, their principles will not be repeated here.
4.2.5.3.2 Batch sampling
In most batch sampling, a suitable sample bar or group of bars is chosen to represent the batch
population. The number of bars shall depend on the number in the batch, the type of crystal, the
intended application, the separation between the mean and the target inclusion densities and
the AQL confidence level requirement needed to provide sufficient assurance that the batch
inclusion density in each size range shall be below their applicable grade test limits. The sample
bar group shall reasonably represent the batch with respect to inclusion densities. Deviations, if
any, are allowed and shall be towards higher, not lower, inclusion densities for safe assurance.
4.2.5.3.3 Volumes within a bar
A group of volumes within each sample bar is next chosen for inclusion counting. The
boundaries of the volumes are defined by the area of the focal field of the microscope (or the
outline of a square reticule) and either the height of the bar or the length range of the depth
adjustment of the microscope chosen for use. It is necessary to determine and total the volumes
throughout which counts are accumulated. The volumes selected for counting should include
mainly regions (usually Z-growth zones as in Figure 3) whose material will be present and active

in the finished devices and should not avoid dense inclusion volumes within these regions. The
number of volumes per bar shall be at least six or more for reasonable statistical confidence.
The sample volume locations within a bar shall be appropriately distributed in its X-, Y-, Z-axes
to include the variations of the inclusion density with these independent variables. Typical
synthetic quartz bars (Figure 3a) are long in the Y- and small in the X- and Z-axes dimensions.
Normally, the greatest variation of inclusion density appears over a zone's grown direction, for
example, the Z-dimension in the Z-zone (Figures 1a and 3). Thus, for large Z-crystals, the
sampled regions shall be located at varied Z-distances from the seed to ensure that the bar's
range of Z is well represented by the group of sample volumes. Similarly, any noted variations
over Y or X shall be sampled, if such variations are present.
To aid in distributing sample volumes within a typical bar, its lesser X-surface is marked with
transverse Z�-lines, perpendicular to the seed at regular 10 mm intervals over the Y-length of
the surface. Sample volumes for inclusion counting are chosen as needed from within each
rectangle formed by the marks and the crystal surfaces. To locate the sample volumes at
varied distances from the seed, in small crystals (where a Z-zone measures less than double

– 14 – 60758 � IEC:2004(E)
the field diameter of the microscope), they should be alternated near and far from the seed.

For larger crystals, the volumes should be sequenced in Z over its range to ensure that each

inclusion band is represented in the sample volumes.

Several frequently used sampling plans are illustrated in Annex A.

4.2.5.3.4 Inclusion counting
The circular or square field of view chosen for counting within its marked rectangle is scanned

vertically over its chosen X-height within the microscope's range of depth adjustment, as

follows.
If the sample is a Y-bar with a relatively small X-height, the scans will be at a series of sites
varied in Z along its length (under side illumination, with its lesser X-surface up). Beginning in a
rectangle positioned at one end of the usable zone, an inclusion count is taken in an X-cylinder
(or parallelipiped) volume. Starting slightly below the lesser X-surface (and not counting surface
material), all visible inclusions in focus are categorized and counted in each of the size
categories required by the customer's order: 10 � to 30 �, 30 ��to 70 �, 70 � to 100 �,
and greater than 100 �. The microscope is then lowered and the newly focused inclusions
counted and added into their size categories. This process is continued through the chosen
X-height; the procedure is repeated at the next sample position, and so on.
The counts from the bar's sample sites in each of the four size categories are summed by
category and divided by the calculated total of the sampled volumes, to obtain an average count
per cm for each category in one bar. The count averages in each category from all the sample
bars from a run are averaged and recorded as required to represent the size distribution for the
run. Maximum and minimum bar averages may also be recorded, if desired or required.
A numerical example is given in Annex B.
4.2.6 Evaluation of infra-red quality by alpha-measurement
The infra-red absorption per centimetre at one or more of 3 410, 3 500 or 3 585 wave numbers
is measured in a Y-cut slice scan as the difference between the absorption at the chosen wave
–1 –1
number and absorption in the background outside the band, at 3 800 cm or at 3 979 cm
when using a single beam instrument. Since alpha are known to vary directly with the total
Z-growth size distribution of the crystals in one batch, a user may designate his preference in the
batch distribution for sample testing. Such choices are often either an average Z-crystal or a
maximum Z-crystal (for worst-case maximum alpha-measurement).
The following two measuring methods are used and either one shall be chosen.
Method 1
The wave number is fixed and the positional transmission data are measured by scanning the
sample.
Method 2
The sample is fixed and the transmission data are measured at chosen wave numbers on
several points in the sample.
4.2.6.1 Preparation of the Y-cut slice
The synthetic quartz crystal to be sampled is mounted on a substrate then sliced with a quartz
saw to yield at least one Y-cut slice whose thickness after lapping and polishing will fall in the
range of 5 mm to 10 mm. The 5 mm thickness is appropriate f�������� -material, to resolve its
-variations; the mid-����������������� ������������ mm thickness is appropriate for the lowest
-material to measure its small absorption.

60758 � IEC:2004(E) – 15 –
After sawing, the slice is lapped on both major surfaces: first, with a homogenized mixture of

25 ��������������������������������������������������3 ������������ �������������������������

is optional�������������������������� �

4.2.6.2 Calibration of a standard Y-cut slice in an infra-red spectrophotometer

The infra-red spectrophotometer is turned on, allowed to warm and fully stabilize, then

calibrated. The normal daily calibration includes its transmission (0 % – 100 %) or absorbance

(log T = 1,0 – 0) limit settings, chart speed and synchronized sample scanning arrangement. For
evaluation and normal use, a 1,5 mm width aperture is located in the sample beam. For the

������� -value measurements, a 5 mm width aperture may be required. The aperture's height

shall not exceed the X-dimension of the seed or 5,0 mm. A polished Y-cut standard reference

slice is placed first in the sample holder, which is then mounted in the scanning device.
The wave number control is set at a background setting (outside, but near the OH absorption
–1
band), usually 3800 ± 3 cm , and the sample is translated through the beam with synchronized
chart advance at the fixed wave number. Such scanning is done only in the Z-growth zones of
the Y-cut slice (illustrated in Figures 1 and 3). In certain cases where background noise may be
–1
a problem, such as single beam operation, a higher background wave number 3 979 ± 3 cm ,
may be used for lowered background noise. If the background scan trace is not reasonably
flat outside the original seed’s boundaries, a thin film of fluorolube grease shall be applied to
both major surfaces of the semi-polished Y-cut slice. Baseline changes shall not exceed 0,02
absorption units during a background scan. After the sample has completed a successful scan at
–1
background, the wave number is adjusted to the chosen 3 410, 3 500 or 3 585 ± 3 cm . The
sample is returned to its original position and the chart paper rerolled to the position where its
wave number scan began. The sample is then scanned to plot its infra-red absorption at this
wave number in the absorption band.
���������������� -values (maximum and minimum) are calculated from this reference scan,
using the equation:
** *
A � A
� �
Y - cut slice thickness in centimeters
where
A* is the chosen value of 3 800 and 3 979;
A** is the chosen value of 3 410, 3 500 and 3 585.
NOTE� A is the logarithm (base 10) of the fraction of the incident beam absorbed by the sample at the subscript wave
number.
����������������������������������������������������������������� ���� readings are
max min
repeatable within ±0,004 units of the standard's values for them. A standardization correction
may be calculated as needed to bring the instrument's reading on a standard slice to an
accepted value and used while current.
4.2.6.3 Test measurement of a Y-cut slice
After successful calibration, each prepared (preferably polished) unknown slice is scanned at
the background and chosen OH absorption band wave numbers, using a thin film of oil as
needed in cases where there is only a semi-polish. Their pertinent -values are calculated using
the equation above. Regions excluded from this determination are ±2,0 mm from the seed
centre and the excess growth beyond the appropriate pre-dimensioned bar dimensions.
4.2.6.4 Compensation of alpha value by standard sample
Correlation between the test equipment of each manufacturer cannot be assured by strict
adherence to uniform measuring conditions and procedures. Therefore, it is necessary to
����������������������������������� � The recommended compensation value is determined by
each manufacturer referencing the procedure described in Annex E.

– 16 – 60758 � IEC:2004(E)
4.2.7 Frequency versus temperature characteristics

The specifications for the quartz crystal unit for evaluating the frequency-versus-temperature

characteristics shall be as follows, and measurements shall be made as specified in

IEC 60122-1:
� frequency 10 MHz ± 10 kHz (fundamental);

� location of specimen Z-zone;

� orientation of plate AT-cut; 35° 13� ± 30�;

� shape of plate square flat and parallel plate with one edge along the
X-axis;
� lateral dimensions of plate 8 mm � 8 mm;
� diameter of electrodes 4 ± 0,1 mm;
� plate back of frequency deviation 70 � kHz;
� electrode material silver or gold;
� supporting points at two points on opposite corners;
� finish of surface lapped (average particle size of abrasive shall be less
than 3 �!�����������������"�� kHz;
� flatness of surface when illuminated with monochromatic light through an
optical flat glass and examined within a circular zone
of 6 mm diameter, the product of the fringe curvature
and the frequency expressed in MHz shall not exceed
5 if measured with yellow light or 6 if measured with
green light;
� parallelism both surfaces of the plate shall be parallel within 10�;
� seal hermetically enclosed in a dry nitrogen atmosphere at
standard atmospheric conditions for temperature and
pressure (see 5.1 of IEC 60068-1).
The specification shall state minimum and maximum slope of frequency-versus-temperature
characteristics (Figure 4).
4.2.8 Etch channel density
The etch channel density is measured by counting channels in an etched AT-cut sample slice of
the sampled quartz crystal as seen under a binocular microscope at up to 35� magnification.

4.2.8.1 Sampling the crystals from a batch
Sampling a batch to achieve a specified statistical confidence level requires the use of AQL
confidence statistics appropriate in this, the etch channel case, because the etch channel
population depends on both the channels in the seeds and the process that grows the material
on the seeds. It is preferable to presort and group seeds for their etch channel densities and
record their group locations in autoclaves or ensure that there is an adequate sample of the
seeds as well as the growth on them, because of the possibility that some of the seeds may differ
greatly from the others, unless intentionally controlled during planting.
4.2.8.2 Preparation of AT-cut slice for etching
A sample synthetic quartz crystal is cut to yield an AT-cut slice (at 35,25° ± 1° to the Y-plane) of
a thickness to finish at 6,4 mm ± 0,5 mm. The slice should preferably contain full seed height,
although thinner slices and lesser seed heights may be used in special cases, provided the
specified amount of material is removed in each lapping. The slice's identity should be marked
with a diamond scribe, preferably on its lesser X-surface, to an adequate depth to ensure that
the identity will not be lost in lapping and etching.

60758 � IEC:2004(E) – 17 –
After sawing and marking, the slice is lapped on both major surfaces; first, with a homogenized

�����������"#� ������������������������������������������������������������������� 3 ��

abrasive. A minimum of 0,25 mm total thickness of quartz shall be removed in the first abrasive

lapping, and of 0,10 mm total thickness in the second abrasive lapping. The slice is then

cleaned to ensure a uniform etching rate over its surfaces, as evidenced by its uniform matt

appearance after etching.
4.2.8.3 Etching procedure for lapped AT-cut slice

Within a fume hood, using appropriate safety equipment (including apron, gloves, eyeglasses,

and splatter shields), an excess of ammonium bifluoride is added to deionized water in a suitable

container to make a saturated solution at 75 °C ± 2 °C. The ammonium bifluoride is maintained

at the 75 °C ± 2 °C temperature, with the use of a constant temperature liquid bath.
A polytetrafluoroethylene (PTFE)-coated thermometer in the solution is used for monitoring the
temperature. If different etch temperatures are preferred, the etch time will be adjusted
appropriately to comply with the stock removal requirement below.
The lapped and
...