ASTM F144-80(2000)
(Practice)Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
SCOPE
1.1 This practice covers the preparation and testing of a reference glass-metal sandwich seal for determining stress in the glass or for determining the degree of thermal expansion (or contraction) mismatch between the glass and metal. Tests are in accordance with Method F218 (Section 2).
1.2 This practice applies to all glass and metal (or alloy) combinations normally sealed together in the production of electronic components.
1.3 The practical limit of the test in deriving mismatch is approximately 300 ppm, above which the glass is likely to fracture.
1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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An American National Standard
Designation: F 144 – 80 (Reapproved 2000)
Standard Practice for
Making Reference Glass-Metal Sandwich Seal and Testing
for Expansion Characteristics by Polarimetric Methods
This standard is issued under the fixed designation F 144; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope The glass and metal are cleaned, treated, and sized to specified
proportions. Plane-interfaced seals are formed, annealed, and
1.1 This practice covers the preparation and testing of a
measured for residual optical retardation. The stress parallel to
reference glass-metal sandwich seal for determining stress in
the interface in each seal is calculated from the optical
the glass or for determining the degree of thermal expansion
retardation, and the average stress and thermal expansion
(or contraction) mismatch between the glass and metal. Tests
mismatch are computed for the sample.
are in accordance with Method F 218 (Section 2).
1.2 This practice applies to all glass and metal (or alloy)
4. Significance and Use
combinations normally sealed together in the production of
4.1 The term “reference” as employed in this practice
electronic components.
implies that either the glass or the metal of the reference
1.3 The practical limit of the test in deriving mismatch is
glass-metal seal will be a “standard reference material” such as
approximately 300 ppm, above which the glass is likely to
those supplied for other physical tests by the National Institute
fracture.
ofStandardsandTechnology,orasecondaryreferencematerial
1.4 This standard does not purport to address all of the
whose sealing characteristics have been determined by seals to
safety problems, if any, associated with its use. It is the
a standard reference material (see NBS Special Publication
responsibility of the user of this standard to establish appro-
260). Until standard reference materials for seals are estab-
priate safety and health practices and determine the applica-
lished by the NIST, secondary reference materials may be
bility of regulatory limitations prior to use.
agreed upon between manufacturer and purchaser.
2. Referenced Documents
5. Apparatus
2.1 ASTM Standards:
5.1 Polarimeter, as specified in Method F 218 for measur-
F15 Specification for Iron-Nickel-Cobalt Sealing Alloy
2 ing optical retardation and analyzing stress in glass.
F30 Specification for Iron-Nickel Sealing Alloys
5.2 Cut-Off Saw, with diamond-impregnated wheel and No.
F31 Specification for 42 Percent Nickel-6 Percent
2 180 grit abrasive blade under flowing coolant for cutting and
Chromium-Iron Sealing Alloy
fine-grinding glass rod.
F47 Test Method for Crystallographic Perfection of Silicon
3 5.3 Glass Polisher, buffing wheel with cerium oxide polish-
by Preferential Etch Techniques
ing powder or laboratory-type equipment with fine-grinding
F79 Specification for Type 101 Sealing Glass
4 and polishing laps.
F 105 Specification for Type 58 Borosilicate Sealing Glass
5.4 Heat-Treating and Oxidizing Furnaces, with suitable
F 218 Test Method for Analyzing Stress in Glass
controls and with provisions for appropriate atmospheres
F 256 Specification for Chromium-Iron SealingAlloys with
2 (Annex A1) for preconditioning metal, if required.
18 or 28 % Chromium
5.5 Sealing Furnace, radiant tube, muffle or r-f induction
3. Summary of Practice with suitable controls and provision for use with inert atmo-
sphere.
3.1 Seals of a standard configuration are prepared from
5.6 Annealing Furnace, with capability of controlled cool-
representative specimens of the glass and metal to be tested.
ing.
5.7 Ultrasonic Cleaner, optional.
This specification is under the jurisdiction of ASTM Committee C14 on Glass
5.8 Fixture for Furnace Sealing, design as suggested in
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
Annex A2.
Physical and Mechanical Properties.
5.9 Micrometer Caliper, with index permitting direct read-
Current edition approved July 3, 1980. Published September 1980. Originally
ing of 0.02 cm.
published as F 144 – 71 T. Last previous edition F 144 – 73.
Annual Book of ASTM Standards, Vol 10.04.
5.10 Immersion Mercury Thermometer.
Annual Book of ASTM Standards, Vol 10.05.
Annual Book of ASTM Standards, Vol 15.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 144 – 80 (2000)
6. Materials
6.1 Metal—Five representative specimen pairs of the metal
from either rod or plate stock with dimensions satisfying the FIG. 2 General Seal Configuration.
requirements of 7.1. The surfaces to be sealed should be
relatively free of scratches, machine marks, pits, or inclusions
polished surfaces should satisfy the dimensional criteria of 6.2
that would induce localized stresses. The sealing surfaces
and 7.2, and be without chips, nicks, or scratches. Remove any
should terminate in sharp edges at the peripheral corners to act
surface contaminants which could produce bubbly seals. An
as a glass stop. Edges that are rounded, such as appear on
ultrasonic wash may be used. See Annex A1.
tumbled parts, will have the tendency to permit glass overflow.
The opposite faces of each plate should be parallel within 0.5°.
9. Procedure for Making the Sandwich Seal
6.2 Glass—Five representative specimens of rod or plate
9.1 Record dimensions of metal plates and glass parts.
glass, cut with either diamond-impregnated or other abrasive
9.2 Make the seal in a furnace or by induction heating of the
cutting wheels under flowing water. Dimensions (volume)
metal utilizing suitable specimen holders or supports under
must satisfy the requirements of 7.2, and the faces should be
controlled conditions of temperature and time. See Annex A2.
flat and parallel within 0.5° for uniform flow during sealing.
10. Annealing
7. Test Specimens
10.1 Once a symmetrical, bubble-free seal has been made,
7.1 The metal specimens may take the form of circular,
proper annealing of the seal becomes the most critical part of
square,orrectangularplates.Ineachcasethedimensiond,Fig.
the procedure. It is by this operation that all stresses are
1, designates the path along which the optical retardation in the
relieved except those due to the difference in thermal contrac-
finished seal is measured. Two identical metal plates of any of
tion of the two materials from annealing temperature levels.
the indicated shapes are required for a seal. The thickness, t ,
m
This process involves heating the seal to a temperature
of each plate should be at least 0.7 mm and d/t should be at
m
somewhat higher than the annealing point of the glass and
least 6.
maintaining this temperature for a time sufficient to relieve the
7.2 Glass with suitable optical transmission of any shape
existing strain. The test specimen is then cooled slowly at a
maybeused,provideditflowsessentiallybubble-freetofillthe
constant rate.As an alternative, annealing can proceed directly
entire volume between the metal plates as in Fig. 2. Experience
on cooling during the making of a seal.
indicates, however, that best results are obtained with flat glass
10.2 Seal stress and associated expansion mismatch can be
conforming closely to the outline of the metal plates. The
varied markedly by annealing schedule modification. For this
thickness of the glass before sealing shall be such that it equals
reason, when the test is used as an acceptance specification, it
t after sealing within 15 %. Thus, the volume of glass
m
is strongly recommended that producer and user mutually
necessary to fill the void between the metal plates to a
definetheannealingscheduleandestablishrigidcontrolsforits
thickness equal to that of a single plate becomes the determin-
maintenance.
ing dimensional criterion for the glass.
7.3 When used as an acceptance test by producer and user,
11. Procedure for Measuring Optical Retardation
thenumberoftestsealsrepresentingonedeterminationshallbe
11.1 For each specimen measure the retardation in the
established by mutual agreement. However two seals are a
annealed seal due to the stress parallel to the interface
minimum requirement for one determination.
according to Method F 218.
11.1.1 Positiontheplaneoftheseal(inanimmersionliquid,
8. Preparation of Specimens
if needed) in a direction 45° from the direction of vibration of
8.1 Metal—Chemically clean the specimens to remove
the polarizer and analyzer, so that the line of sight, or light
surface contaminants, especially lubricants and fingerprints
path, is through the maximum glass dimension in the direction
from fabrication and handling. Usually it is advisable to
d shown in Fig. 1. In a circular seal, for example, this would be
preoxidize parts as described in Annex A1. Preoxidation
the diameter.
promotes a better glass-to-metal bond and relieves cold work-
11.1.2 Determine the retardation along the light path
ing stresses.
through the glass in terms of degrees of rotation of analyzer.
8.2 Glass—Using optical glass techniques grind and polish
Rotate in a direction that causes the curved black fringes seen
the sealing surfaces of the glass specimens with either wet
within the glass to appear to merge in the center of cross
abrasive wheels or water slurries of abrasive on a lap. The
section of the glass and away from the glass–metal interfaces.
Rotate the analyzer so that any light or “gray” area which may
exist between the fringes disappears and a dark spot, or area, is
formed. This condition is termed the point of extinction.
NOTE 1—Sealing combinations may exist in which the thermal expan-
sion coefficients of glass and metal at room temperature may differ
significantly. In these cases it may be important to record the temperature
of the refraction liquid (or t
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