RU2068559C1 - Method of nondestructive testing of articles - Google Patents

Abstract

FIELD: radio electronics, microelectronics. SUBSTANCE: in compliance with proposed method of nondestructive testing thermophysical characteristics (thermal conductivity, heat capacity and temperature coefficient of resistance) are found. For determination of two components (temperature and current) of temperature coefficient of resistance of sample is measured at two temperatures, temperature component of temperature coefficient of resistance is determined by results of measurement of resistance and temperature and current component is calculated as difference of temperature coefficient of resistance and its temperature component. EFFECT: increased reliability of proposed method.

Description

 The invention relates to methods for conductometric monitoring of products and can be used to determine the thermophysical characteristics of products of electronic and microelectronic equipment, as well as for sorting products by thermophysical parameters.

 A known method for determining the thermophysical characteristics used to control products without their destruction. The method consists in heating the sample with a current pulse and determining the dynamic value of the resistance during cooling, followed by the calculation of thermophysical characteristics (1).

 The disadvantage of this method is its limited nature and the inability to determine some characteristics, for example, the temperature coefficient of resistance.

 The aim of the invention is to expand the functionality of the method and the determination of both the temperature and current component of the TCS.

 The method is implemented in the following sequence of operations.

 The test sample is heated by the current flowing through it. Work is carried out in a pulsed mode (since heating is carried out by current pulses) with frequency modulation of pulses. The amplitude of the heating current pulses is stabilized. The dynamic value of the voltage across the sample is recorded. From the obtained implementation, the low-frequency component is isolated and the phase difference between the modulating signal and the low-frequency component of the voltage is measured, as well as the voltage along the front and the fall of each pulse in the implementation. The measurement results determine the thermal conductivity, heat capacity and temperature coefficient of resistance of the test sample.

частота следования импульсов тока как функция времени в соответствии с законом модуляции;
τ_o длительность импульса.For a specific sample are normalized:
I _{o the} amplitude of the current pulses;
R _{o the} resistance of the sample in an unheated state;
U _o I _o • R _o voltage on the sample in an unheated state;
S is the surface area of the sample;
ω circular frequency of the modulating signal;

repetition rate of current pulses as a function of time in accordance with the law of modulation;
τ _o pulse duration.

The following informative features are measured:
Φ _o the phase difference between the low-frequency component of the voltage and the modulating signal;
U _fr voltage measured on the sample along the front of the pulse;
U _cn voltage measured on the sample by the decay of the pulse.

где α температурный коэффициент сопротивления,
C теплоемкость образца,
l теплопроводность образца.Thermophysical characteristics are determined by the following formulas:

where α is the temperature coefficient of resistance,
C is the heat capacity of the sample,
l thermal conductivity of the sample.

Частота определяется в момент времени Φ_o/ω
h коэффициент теплоотдачи,
ρ плотность вещества.The coefficient K _{o is} determined by calibration, a _o and b _{o are} calculated according to the measurement results:

The frequency is determined at time Φ _o / ω
h heat transfer coefficient,
ρ is the density of the substance.

When determining TCS (a), the initial temperature T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ at which the derivative of the measurement, and R _{o the} initial value of the resistance of the sample at temperature T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ .

где R_o начальное сопротивление образца при начальной температуре T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ ,
T=T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ -T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ разность между вторым значением и начальным значением температуры,
ΔR разность значений сопротивлений образца при температуре T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ и T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ .
Далее определяют токовую составляющую ТКС (α_I)
α_I=α-α_т (3)
где α температурный коэффициент сопротивления.When determining the temperature component of the TCS (α _t ), the sample resistance is additionally measured at temperature T $\genfrac{}{}{0ex}{}{\text{o}}{\text{I}}$ other than T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ and calculate α _t according to the formula

where R _{o the} initial resistance of the sample at the initial temperature T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ ,
T = T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ -T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ the difference between the second value and the initial temperature value,
ΔR the difference in the values of the resistance of the sample at temperature T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ and T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ .
Next, determine the current component of the TCS (α _I )
α _I = α-α _t (3)
where α is the temperature coefficient of resistance.

Claims (1)

The method of non-destructive testing of products, namely, that the object is heated by amplitude-stabilized current pulses with frequency modulation, the low-frequency component of the change in the amplitude of the voltage pulses is isolated, the phase difference between the modulating signal and the low-frequency component of the voltage is measured, the voltage is measured along the edge and decay of each pulse, and according to the measurement results determine the heat capacity, thermal conductivity and temperature coefficient of resistance, characterized in that, in order to asshireniya functionality of the method and the determination of both the temperature and the current temperature coefficient of resistance component further measured resistance of the sample at a temperature different from the temperature at which it is determined initial resistance, determined from measurements of the temperature component of the temperature coefficient of resistance

where R _{0 is the} initial resistance of the sample at the initial temperature T ₀ ;
T = T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ -T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$ the difference between the second value and the initial temperature value;
ΔR = R ₁ -R _{2 the} difference in values of the resistances of the sample at temperatures T = T $\genfrac{}{}{0ex}{}{\text{o}}{\text{1}}$ -T $\genfrac{}{}{0ex}{}{\text{o}}{\text{o}}$
and calculate the current component of the temperature coefficient of resistance
α _I = α-α _t
where α is the temperature coefficient of resistance.