ISO 6901:1984

International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATlON.MEXJlYHAPOAHAR OPrAHM3AUMfI i-lo CTAH~APTt43AL&IM~ORGANlSATlON INTERNATIONALE DE NORMALISATION
Magnetic disk for data storage
Information processing -
- 160 000 flux transitions per track, 356 mm
devices
(14 in) outer diameter
- Disque magnktique pour unit& de stockage des don&es -
Traitemen t de l’in forma tion 760 Ooo transitions de flux par piste,
diamktre extbieur 356 mm (14 in)
First edition - 1984-12-15
iz U DC 681327.63 Ref. No. IS0 6901-1984 (E)
-
3 Descriptors : data processing,
information interchange, data storage devices, magnetic disks, specifications, dimensions, tests, physical
properties, magnetic properties, surface properties, surface defects.
0
ul
-
Price based on 16 pages

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Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of
national standards bodies (IS0 member bodies). The work of preparing International
Standards is normally carried out through IS0 technical committees. Each member
body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the IS0 Council. They are approved in accordance with IS0 procedures requiring at
least 75 % approval by the member bodies voting.
International Standard IS0 6901 was prepared by Technical Committee lSO/TC 97,
lnforma tion processing systems.
0 International Organization for Standardization, 1984 0
Printed in Switzerland
ii

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Contents
Page
1
1 Scope and field of application .
1
Reference .
2
................................................. 1
3 General requirements
2
4 Dimensions .
2
5 Physical characteristics .
4
Testing of magnetic characteristics .
6
Surfacetests. . 7
7
.................................................... 7
8 Trackqualitytests
.................................... 8
9 Requirements for magnetic surfaces
....................................... 8
10 Defects of the magnetic surfaces
Annexes
13
..............................................
A Air cleanliness class 100
..................... 14
B Method for measuring friction between head and disk
............................... 16
C Measurement of the effective track width
. . .
III

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INTERNATIONAL STANDARD IS0 6901-1984 (E)
Magnetic disk for data storage
Information processing -
- 160 000 flux transitions per track, 356 mm
devices
(14 in) outer diameter
1 Scope and field of application 3.1 .l Operation
This International Standard specifies the mechanical, physical The operating temperature of the air surrounding the disk shall
and magnetic characteristics of a lubricated magnetic disk of
be within the range of 15 to 57 OC (59 to 135 OF) at a relative
356 mm (14 in) outer diameter intended for mounting in data humidity of 8 to 80 %. The wet bulb temperature shall not
storage devices. exceed 26 OC (79 OF). The air surrounding the disk shall be of
cleanliness class 100, as defined in annex A.
NOTE - The original design of the subject of this international Stan-
dard was made using the Imperial measurement system. Some later
3.1.2 Storage
developments, however, have been made using Sl units. In the pro-
cess of conversion into the alternative system, values may have been
The storage temperature shall be within the range - 40 to
rounded. Therefore, the two sets of figures are consistent with, but not
exactly equal to, each other. Either set may be used, but the two shall + 65 OC (- 40 to + 150 OF) at a relative humidity of 8 to
be neither mixed nor reconverted.
80 %. The wet bulb temperature shall not exceed 30 OC
(86 OF). Under no circumstances shall condensation on the disk
be allowed to occur.
2 Reference
Storage under the extreme conditions of the above range is not
recommended. A temperature gradient of more than IO OC
Method of indicating surface
I S 0 1302, Technical drawings
(18 OF) per hour should be avoided.
texture on drawings.
3.2 Test conditions
3 General requirements
Unless otherwise stated, measurements shall be carried out at
23 - + 3 OC (73 + 5 OF), 40 to 60 % relative humidity after a
3.1 Operation and storage environment
period of acclimatization during which condensation on the
disk shall not be allowed to occur. Tests requiring the use of
To prevent corruption of data, the ambient stray magnetic field
heads shall be performed in air of cleanliness class 100.
intensity at the surface of the disk shall not exceed 4 000 A/m.
When heads are present, the general ambient field shall be
reduced to take account of the concentrating effect of the core 3.3 Material
of the head.
The disk may be constructed from any suitable material so long
as the dimensional, inertial and other functional requirements
NOTE - This will usually require the limitation of the allowed ambient
field to the range of 300 to 2 000 A/m. of this International Standard are maintained.
1

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IS0 69014984 (E)
3.4 Coefficient of thermal expansion
4.3 Concentricity
The coefficient of thermal expansion of the disk material shall The centre of the circumference of the outer edge of the disk
be shall be contained in a circle of diameter 50 pm (0.002 0 in)
concentric with the centre of the circumference of the inner
edge.
AL 1
L57 - b5
-1
-X K-1 = (24 - + 1) x lo-s K-’
Lht L 42
4.4 Thickness
peroF = (13,3 + 0,5) x lo-6perOF
The thickness of the disk shall be
I
e = 1,905 + 0,025 mm (0.075 + 0.001 in)
The sample length L is equal to
4.5 Edge chamfer (see figure 3)
L57 + L15(f13.; L59)
2
For a distance
I < 1,3 mm (0.05 in)
where L,, (L,,,) and L,, (L59) are the lengths at 57 OC (135 OF)
and 15 OC (59 OF), respectively.
from the edges of the disk, the disk contour shall be relieved
within the extended boundaries of the disk surfaces. In order to
3.5 Surface identification
avoid unbalance, the chamfer shall be uniform at all points on
the circumference.
The direction of relative motion between head and disk shall be
consistent. The disk surface that is to rotate counter-clockwise
4.6 Clamping area
shall be identified.
On both sides of the disk, the clamping area shall be an area
4 Dimensions (see figures 1 to 3)
free of magnetic coating, limited by the inner edge and a radius
9 :
For measurement of the radii indicated hereafter, the disk shall
r2 > 91,0 mm (3.53 in)
be mounted on a reference hub (see figure 1) having a
diameter, measured at 23 + 0,5 OC (73 + 1 OF), of
Between r2 and the start of the chamfer, the variation of the
disk thickness shall not exceed 7,5 pm (300 pin).
163,255 _ i o,. mm (6.624 2 _ : ooo4 in)
d, =
I
4.7 Location of magnetic surfaces
and an outer radius
On both sides of the disk, the area of magnetic surface over
= 90,5 If: 0,l mm (3.563 + 0.004 in)
r1
which heads may fly shall extend from an inside radius r3 to an
outside radius r4 :
All radii are referred to the axis of symmetry of this reference
hub. The cylindrical surface of the reference hub defined by d, r3 G 94,0 mm (3.70 in)
shall be contained between two coaxial cylindrical surfaces
r4 > 176,0 mm (6.93 in)
10 pm (0.000 4 in) apart.
4.1 Inner diameter
5 Physical characteristics
The inner diameter of the disk, measured at 23 + 0,5 OC
5.1 Moment of inertia
(73 + 1 OF), shall be
The moment of inertia of the disk shall not exceed :
168,280 + :fo5’ mm (6.625 2 ’ iSM)20 in)
d2 =
8,O g-m2 (27.3 lb+91
shall be contained
The circumference of the inner edge
circles 25 000 pin) apart. 52 . Maximum rotational frequency
tween two concentric pm (1
The disk shall be capable of withstanding the effect of stress at
4.2 Outer diameter
a rotational frequency of 4 000 r/min.
The outer diameter of the disk shall be
5.3 Runout
356,24 + 0,13 mm (14.025 + 0.005 in)
d3 =
For measuring the axial runout and the velocity and the ac-
The circumference of the outer edge shall be contained be- celeration of axial runout, the disk shall be clamped and driven
according to 5.3.1.
tween two concentric circles 25 pm (1 000 pin) apart.
2

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IS0 6901-1984 (El
edges, as well as on the clamping conditions in the device in
The requirements of 5.3.2, 5.3.3 and 5.3.4 shall be met at all
which it is mounted. It is therefore not specified in this Inter-
radii between r3 and r4.
national Standard.
mping
5.3.1 Test spindle requ irements and cla
conditions (see figure 1) 54 . Surface roughness
The disk shall be clamped on the reference hub by a force
5.4.1 Magnetic surfaces
F= 1 500 + 200 N (340 + 45 Ibf)
The finished magnetic surfaces shall have a surface roughness
less than 0,025 pm (1 .O l-tin), arithmetic average, with a maxi-
evenly applied over an annular surface on the disk defined by
mum deviation in height of 0,25 pm (10 pin) from the average,
when measured with a stylus of radius 2,5 pm (100 pin) with a
r5 = 86,5 mm (3.41 in)
0,5 mN load, and a 750 vrn (0.03 in) upper cut-off range.
= 90,4 mm (3.56 in)
r6
The finished magnetic surfaces shall have an undulation profile
with a peak-to-peak amplitude of less than 0,15 pm (6.0 pin)
The finish of the surface of the reference hub on which the disk
when measured over a radial length of 4,8 mm (0.19 in) with a
rests shall be of class N 5 [maximum arithmetical deviation
stylus of radius 2,5 pm (100 pin) with a 0,5 mN load, and a
0,4 pm (16 pin)] as defined in IS0 1302.
lower cut-off range of 250 pm (0.01 in).
At any rotational frequency up to the maximum frequency (see
5.2), the axial runout of the reference hub shall not exceed
5.4.2 Clamping area
1,O pm (40 pin).
The finished surface of the clamping area shall have a surface
roughness less than 0,8 pm (30 pin), arithmetic average, with a
5.3.2 Axial runout
maximum deviation in height of 2,0 pm (80 pin) from the
when measured with a stylus of radius 2,5 pm
average,
The axial runout at any rotational frequency up to the maximum
(100 pin) with a 0,5 mN load, and a 750 pm (0.03 in) upper cut-
frequency (see 5.2) shall not exceed 0,lO mm (0.004 in), total
off range.
indicator reading. Moreover, every point of each surface of the
disk shall be located between two planes perpendicular to the
axis of the reference hub and distant from each other by
5.5
Cleaning of the magnetic surfaces
0,20 mm (0.008 in). These two planes shall be equidistant from
the clamping plane of the respective disk surface.
The cleaning method shall be agreed between supplier and pur-
chaser.
5.3.3 Velocity of axial runout
5.6 Durability of the magnetic surfaces
With the disk revolving at 3 600 L- 36 r/min, the velocity of
axial runout of the recording disk surfaces shall not exceed
51 mm/s (2.0 in/s). It shall be measured within the band width
defined by a low-pass filter with a cut-off frequency of 3 kHz
and a high frequency roll-off of 18 dB/octave. The probe
diameter shall be 1,7 mm (0.067 in).
Measurements shall be taken as follows :
5.3.4 Acceleration of axial runout
5.6.1 Head conditioning
With the disk revolving at 3 600 + 36 r/min, the acceleration
Condition the head (of type specified in 6.4) by 50 take-off and
of axial runout shall not exceed 76,2 m/s2 (3 000 in/s2) within
landing operations outside the test area defined in 5.6.2. All
the measurement band-width defined by a low-pass filter with a
write operations on a track shall be preceded by DC-erasure
cut-off frequency of 7 kHz and a high frequency roll-off of
(see 6.5.2) of that track.
18 dB/octave.
Further, within the pass band defined by a low frequency cut-
5.6.2 Read amplitude
off of 2,5 kHz and a high frequency cut-off of 5 kHz, the ac-
celeration shall not exceed 38,l m/s2 (1 500 in/s% The high
Select two reference tracks, A and B, 12,7 mm (0.50 in) apart.
and low frequency roll-off shall be 24 dB/octave using a non-
Write at 2f(see 6.9) on these two tracks and on at least 20 test
contact capacity probe. The probe diameter shall be 1,7 mm
tracks evenly spaced between A and B. Measure the read
(0.067 in).
amplitude on each track before moving the head to the next
track. The average read signal from the two reference tracks
before the wear test shall be :
5.3.5 Radial runout
EA + EB
tricity (see
The radial runout of the disk depends on the concen
E
AV =
(see 4.1 and 4.2) of the inner and outer 2
4.3) and circularity
3

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IS0 6901-1984 (E)
5.6.3 Wear test The method of measurement is described in annex B.
Locate the head between tracks A and B so that no part of the
5.10 Discharge path
head touches an area which would be flown over when the pole
tip of the head is on either track A or track B.
The disk shall allow flow of electrical charges from the
magnetic surface to the clamping area.
Without moving the head, perform 10 000 take-off and landing
operations, during which the disk shall be accelerated and
decelerated between 0 and 3 000 r/min. Acceleration and
6 Testing of magnetic characteristics
deceleration time between 0 and 1 000 r/min shall be within
3 + 0,5 s.
6.1 General conditions
5.6.4 Head wear factor
6.1 .I Rotational frequency
Repeat the procedure given in 5.6.2 using the same tracks. The
average read signal from the two reference tracks after the
The rotational frequency shall be 3 600 & 36 r/min in any test
wear test shall be
period.
E’A + E’B
E’AV =
6.1.2 Ambient stray magnetic field
2
The intensity of the ambient stray magnetic field shall not
The head wear factor is defined as
exceed 300 A/m.
EAV
6.2 Track and recording conditions
E’AV
Multiply the second set of readings for the test tracks by this
6.2.1 Width of tracks
head wear factor.
For testing purposes, the effective track width shall be
5.6.5 Durability criteria
40 + - 4 pm (1 600 + 160 pin)
The following requirements shall be met :
A suggested method of measuring the effective track width is
a) the head wear factor shall be G 1 ,l 1;
described in annex C.
b) for each of the test tracks the corrected reading derived
in 5.6.4 shall not differ by more than 10 % from the reading 6.2.2 Track spacing
taken in 5.6.2.
For testing purposes, the track centreline spacing shall be such
that the whole area defined in 6.2.3 will be tested.
5.7 Head/disk gliding requirements
The magnetic surface shall be free of surface defects which
6.2.3 Tested area
would cause head to disk contact when the head is flying at
0,35 pm (14 pin) minimum at radius r3, and proportionally
All functional tests and all track quality tests shall be performed
increasing in flying height to 043 pm (17 pin) minimum at
between an innermost track having its centreline at a radius r7
radius r4.
and an outermost t ack having its centreline at a radius r8 :
5.8 Dynamic head/disk friction
r7 = 101,2 mm 3.98 in)
In the area between radii r3 and r4, the average dynamic coef-
= 166,4 mm 6.55 in)
%
ficient of friction ,u~ shall not be greater than 0,200. Its peak-to-
peak variation Ap, shall not exceed 0,035.
6.2.4 Location of the line of access
The method of measuring is described in annex B.
The line of access shall be radial within 0,25 mm (0.010 in).
5.9 Static head/disk friction
6.2.5 Recording offset angle
In the area between radii r3 and r4, the static coefficient of fric-
At the instant of writing or reading a magnetic transition, the
tion ,u~, when measured after the head has been in stationary
contact with the disk under the conditions of 3.1.1 for at least transition may have an angle of 60’ maximum with the line of
48 h, shall not be greater than 1,O. access.

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NOTE - A suitable test head is a 3350- type head without amplifier,
6.3 Standard reference surface
selected to conform to the req uir ‘ements listed hereunder.
6.3.1 Characteristics
6.4.1 Gap width
The standard reference surface shall be characterized at the in-
The width of the recording gap (measured optically) shall be
nermost and outermost tracks (radii r7 and rg) using a test head
specified in 6.4 having its calibration factors (see 6.4.9) equal
37 + 4 pm (I 450 + 150 pin)
-
to 1.
When recorded at If (see 6.9) using this test head, the track
6.4.
...