Thermal measuring and testing – Thermal testing of a nonthermal quantity – Expansion or contraction characteristics
Reexamination Certificate
1998-07-09
2004-01-06
Fulton, Christopher W. (Department: 2859)
Thermal measuring and testing
Thermal testing of a nonthermal quantity
Expansion or contraction characteristics
C374S049000
Reexamination Certificate
active
06672759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention is directed to increasing the accuracy of the measurement of thermal expansion coefficients (CTE) performed on thin film samples. More specifically, in accordance with the present invention, the CTE increased measurement accuracy is obtained using any of the following procedures: (a) by measuring the baseline using the same set-up used in the measurement; (b) by identifying a correction factor; (c) by using specific, low expansion clamps; or (d) by extracting the CTE from measurements of samples with various lengths.
2. Description of the Related Art
The testing of plastics is generally carried out for the same reasons as apply to the testing of other materials, namely to determine their suitability for a particular application, for quality control purposes or to obtain a better understanding of their behavior under various conditions. It is necessary for a manufacturer to be able to measure its performance with relation to other materials and thus be in a position to assess the market likely to be available to it.
The physical testing of plastics must be standardized if the comparison of physical data from two or more different sources is to have any meaning. The physical testing of plastics can be classified generally as (a) dimensional; (b) thermal; (c) mechanical; (d) electrical; and (e) optical. The results of physical tests carried out on a material often depend upon the ambient conditions of temperature, humidity, the size, shape and method of preparation of the test pieces and the techniques of measurement employed.
Testing of the thermal properties of plastics is important to give the plastic user some idea of the range of safe temperatures at which the plastic can be used. Some of the important thermal properties are thermal conductivity, coefficient of thermal or linear expansion, specific heat, softening point, heat distortion temperature and mold shrinkage.
The present invention relates to accurately measuring the CTE as this test is now advantageously used to test thin samples of polymers such as polyimide, and to a lesser extent, epoxy resins used in computer applications.
CTE's of materials are typically measured using a thermal mechanical analyzer (TMA). A TMA is an instrument used which is capable of measuring the displacement of a measuring probe with great accuracy in the compression mode, typical for CTE testing of rigid samples. The probe is in contact with a sample to be measured and detects changes in sample dimensions in probe direction and transmits results to a displacement detection unit. Test sample dimensions can change by the application of temperature or weight to the sample.
These dimensional changes may be time dependent. In the case of CTE measurements, the contact with the sample must be chosen so that the sample dimension does not change as a consequence of the probe; or if the sample dimension does change, such change is minimal and reproducible.
FIGS. 1A and 1B
are generally equivalent with the exception that
1
A operates in a compression mode, while
1
B works in a tension mode such that the probe becomes the second sample holder. The sample in
1
B is connected to the two holders by clamps shown in FIG.
3
.
A typical TMA is depicted in
FIG. 1A
(prior art) comprising a probe (
1
), sample holder (
2
), heater (
3
), micrometer (
4
) (shown for illustrative purposes and not an essential part of a TMA), thermocouple (
5
), differential transformer (
6
), core (
7
), force generator (
8
). In a typical use, the plastic sample to be tested is held between sample holder (
2
) and probe (
1
). A force is applied to the sample, and the resulting changes in sample length are detected by the independently connected differential transformer (
6
) and core (
7
).
The TMA can be used in tensile mode for flexible samples pursuant to the present invention and is depicted in
FIG. 1B
(prior art). (Many identical elements are present in the structures depicted in FIG.
1
A and FIG.
1
B. To assist in an understanding of the structures of
FIGS. 1A and 1B
and to avoid confusion, the elements depicted in
FIG. 1B
which are also contained in
FIG. 1A
are indicated immediately after the numerical designation of the elements in
FIG. 1B
in brackets.) The unit comprises a load generator (
10
)(
8
), a core(
11
)(
7
), differential detector (
12
)(
6
), micrometer (
13
)(
4
), sample holder (
14
)(
2
), outer tube (
15
) not included in
FIG. 1A
, probe (
16
)(
1
), sample (
17
), and furnace (
18
)(
3
). The TMA module (
19
) receives a TMA/SS signal (
20
), a temperature signal from thermocouple (
21
) (
5
) and provides heater power (
22
). Also included in this apparatus is a means for processing software (
23
) used to provide certain instructions to the apparatus during operation as hereinafter described.
In this embodiment, with respect to the apparatus depicted in
FIG. 1B
, sample cylinder holder
14
is adjustably attached to differential transformer
12
via micrometer
13
. When micrometer
13
is adjusted to an initial position, sample cylinder
14
is stationary with respect to detector
12
. Probe
16
is connected to core
11
and sample
17
. The top of probe (
16
) is also connected to a first end of balance arm (
24
). The other end of balance arm (
24
) is connected to electric load generator (
10
) which controls the load according to CPU guidance. The manner in which the force on the probe is generated is not relevant to the invention. There are a plurality of different ways that this may be accomplished. Differential detector (
12
) detects the movement of probe (
16
) as the sample (
17
) length changes, and outputs this as a TMA signal (
20
). Recorded signals are time, temperature, dimensional change and load.
There are a variety of probes that are used in the TMA depending upon what test is being conducted. The probes are configured for expansion, volume expansion, compression and penetration. In addition, accessories for tension and three point bending, and cubical are available. When combined with a dynamic loading program, a variety of applications not pertinent to this discussion are possible.
Presently, several ways of accomplishing contact of the probe to a sample exist. However, if the sample is a thin film, there is essentially only one way to guarantee continuous contact between the probe and the film while at the same time not bending the film.
In the method of the present invention, sample (
30
) is held by two clamps (
31
) and (
32
) as shown in
FIGS. 2A and 2B
(prior art front and side views respectively).
FIGS. 2A and 2B
show that top clamp (
31
) is held by or connected to probe (
33
) while bottom clamp (
32
) is stationary or fixed to stationary sample holder (
34
). Probe (
33
) and stationary sample holder support (
34
) are made from a material (such as quartz) which possesses a very small expansion coefficient so as not to interfere with the expansion of the sample.
Using the set up described above and depicted in
FIGS. 2A and 2B
, sufficient tensile force is applied to the probe so that the sample film (
30
) is under light tension. The length of the sample between the clamps (
31
) and (
32
) is recorded. For CTE measurements the sample is heated (cooled) and the probe displacement with temperature is measured.
FIG. 3
depicts a different side view of the elements depicted in FIG.
2
B and includes a depiction of displacement sensor comprising calibrated measuring means (
4
) indicating one way in which measured displacement is determined. Elements (
43
) and (
44
) are made of a material with limited thermal expansion, such as quartz, and element (
43
) is subjected to a pulling force in direction (
45
). Distance L is the sample length. It is generally assumed that clamps (
41
) and (
42
), used to hold sample (
40
) do not contribute to the measured displacement. This is specifically stated in the user manual of one such instrument; (See:
Seiko TMA Users Manual
, Appendix-A, A-3).
FIG. 3
is identical
Beck Thomas A.
International Business Machines - Corporation
Morris Daniel
Pruchnic Jr. Stanley J.
LandOfFree
Method for accounting for clamp expansion in a coefficient... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for accounting for clamp expansion in a coefficient..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for accounting for clamp expansion in a coefficient... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3187125