JPS6110751A - Measurement for diffusivity of heat by intermittent heating - Google Patents

Abstract

PURPOSE:To enable the determination for diffusivity of heat at the right angle (surface way) to the thickness way from AC temperatures at two distance points, by covering a part of a sample plate to be measured to irradiating heat energy intermittently. CONSTITUTION:A sample plate 1 to be measured with a fixed thickness of about 0.1-0.5mm., for instance, is covered partially with a cover plate 2. The exposed section of the plate is irradiated with heat energy converted to AC with a chopper 3. Here, a thermocouple 6 welded at a distance Lf from the end of the cover plate 2 measures AC temperature through a sensor 7 and a lockin amplifier 8. In an equipment thus arranged, amplitudes of AC temperatures are determined varying the frequency with the sample plate 1 set at two points of distances Lf1 and Lf2 to the thermocouple 6 from the end of the cover plate 2. Then, when a characteristic curve of AC temperature is plotted as determined from the logarithm of the amplitude ratio with the root of the frequency as variable, straight line is obtained. Heat diffusion rate can be calculated from the gradient of the straight line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal diffusivity measurement method using intermittent heating for determining the thermal diffusivity in a direction perpendicular to the thickness direction (plane direction) of a thin sample plate.

Conventionally, various methods have been devised to measure thermal diffusivity, but it has not been possible to determine the thermal diffusivity in the direction perpendicular to the thickness direction of a thin sample.

However, in recent years, with advances in electronics technology, semiconductors are often deposited on thin electrical insulators, such as ceramic plates, to a film thickness of e'0.5w or less, and thin plate-like materials such as It has become necessary to know the thermal properties of

The object of the present invention is to provide a method for measuring the thermal diffusivity of a thin sample plate in the c-plane direction (direction perpendicular to the thickness direction) of a thin sample plate, which satisfies such requirements. A part of one side of a certain sample plate to be measured is covered with a covering member, and thermal energy of a certain amplitude is intermittently irradiated to the one side, and two The AC temperature Tic at the distance point is measured at various AC frequencies, and the slope m is calculated from the characteristic line of the logarithm of the amplitude ratio of the AC temperature at the two distance points with the square root of the frequency as a variable. lf is the distance between two points.

The method is characterized in that the thermal diffusivity Df in the surface direction of the sample plate to be measured is obtained.

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an example of a measuring device used to determine the thermal diffusivity D (ff) in a direction perpendicular to the thickness direction (plane direction) of a sample plate to be measured.

In the same figure, (1) has a thickness of, for example, 0.1 to 0.5
The sample plate to be measured is about 100 m thick, and a cover plate (2)' is placed on top of the sample plate (1) and covers a part of one side of the sample plate (1), and is moved along the surface of the sample plate (1). You can arrange it freely and also cover the plate (
A heat source (4), such as a tungsten lamp, equipped with a chopper (3) was placed on top of the heat source (2). The chopper (3) consists of a semi-circular plate which is rotatably supported at its diametrical center as shown in the figure N2, and which is rotated at a predetermined number of revolutions by a motor (not shown).

(5) is a micrometer connected to the cover plate (2), and (6) is a sample plate (1) to be measured which is shielded from the thermal energy irradiation of the heat source (4) by the cover plate (2). A thermocouple spot-welded at a distance Lf from the end of the cover plate (2) on the surface of the cover plate (2). the lock-in amplifier (8);
Next, the AC output of the thermocouple (6) is amplified.

Note that the sample plate (1) to be measured was placed in a heat bath (not shown) to increase the thermal resistance when heat escapes from the sample plate (1) to the outside.

Next, using the measuring device, the sample plate to be measured (1) of the present invention is prepared.
A method for measuring the thermal diffusivity Df in the plane direction will be explained.

On the exposed part of one side of the sample plate to be measured (υ),
It irradiates thermal energy of amplitude Q per unit area, which is converted into alternating current.

At this time, the AC temperature 'I'ae detected by the thermocouple (6)
is given by the following equation as the distance Lf (D function).

However, ρ is the density of the sample plate (1), 0 is the specific heat of the sample plate (1), and the reciprocal of kf is the thermal diffusion length, kf = y儒bia - However, f is the alternating current frequency Df of the thermal energy by the chopper, As is clear from equation (1), the thermal diffusivity in the plane direction of 1) is the amplitude value ITao+ of the AC temperature 'rac of the sample plate to be measured (1) at the distance Lf, and this value is The output signal is amplified by a lock-in amplifier (8).

Taking the ratio of the amplitude lTa011 + l'rao2+ of the AC temperature at two points at distances Lf, , Lf from the end of the cover plate (2) in the shielded part of the sample to be measured (1), (3) When formula (4) is transformed from the equation, it becomes the linear equation of Equation 4, and is the gradient mf of the -order equation.

Thus, by moving the cover plate (2) using the micrometer (5), the distance from the end of the cover plate (2) on the sample plate (1) to the thermocouple (6) is 2 of Lf, , Lf2. Amplitude value of AC temperature at various frequencies at point I T B 0
, l + I Ta cml lock-in amplifier (8)
Obtained from the output of Then, the AC temperature Ta(
4+ Ta (obtain the rate Df of the amplitude ratio of 4.

In the above embodiments of the present invention, the thermal diffusivity was obtained by drawing the characteristic line and determining the slope of the characteristic line. You can ask for it.

As described above, according to the present invention, it is possible to obtain the thermal diffusivity in the direction perpendicular to the thickness direction of a thin sample plate having a thickness of, for example, 0.5 mm or less.

[Brief explanation of the drawing]

Figure 1 is a diagram of the measuring device used to carry out the present invention;
The figure shows a plan view of the fc first figure, excluding the heat source and lock-in amplifier.

Claims (1)

[Claims] 1. A portion of one side of a sample plate to be measured having a constant thickness is covered with a covering member, and thermal energy of a constant amplitude is intermittently irradiated to the one side to shield the sample plate to be measured. The AC temperature Tac at two distance points from the end of the covering member in the section is measured at various AC frequencies, and the logarithmic characteristic of the amplitude ratio of the AC temperature at the two distance points with the square root of the frequency as a variable. Find the slope m from the line and use the following formula: m=√(π/D_f)l_f, where l_f is the distance between two points. A method for measuring thermal diffusivity by intermittent heating, characterized in that the thermal diffusivity D_f in the surface direction of the sample plate to be measured is obtained.