Comprehensive knowledge explanation of semiconductor electronic component analysis and temperature test

Date：2022-08-08 16:43:00Views：857

Temperature is an external representation of the motion energy (internal energy) of the internal molecules (atoms, electrons) of a substance. The higher the temperature, the more the irregular motion of the internal molecules of the substance is. The larger the temperature difference between the two objects, and the more the heat exchange between the two objects. Temperature test is an environmental test frequently carried out by quality and reliability engineers. If you want to do a good job in temperature test, you need to master a lot of knowledge. In order to help you understand deeply, this paper will summarize the relevant knowledge of temperature test. If you are interested in what this article is about to cover, read on.

Influence of temperature on semiconductor electronic components

Temperature related test is an introduction to environmental test, including high temperature test, low temperature test and temperature change test. The high and low temperature test mainly verifies whether the product is deformed or affected by function under extreme temperature conditions and whether it can operate normally. The temperature change test is mainly used to test the tolerance of the product to withstand the extreme temperature repeatedly.

Failure mode of specimen under high temperature

The parts and materials used in the product may soften, reduce efficiency, change characteristics, potential damage and oxidation at high temperature.

The main effects of high temperature environment on the equipment are:

a. Softening or melting of fillers and sealing strips;

b. The viscosity of the lubricant decreases, the volatilization is accelerated, and the lubrication effect is reduced;

c. The stability of electronic circuit decreases and the insulation is damaged;

d. Accelerate the aging of polymer materials and insulating materials, including oxidation, cracking, chemical reaction, etc;

e. The expansion of the material causes an increase in mechanical stress or wear.

Failure mode of specimen under low temperature

The parts and materials used in the products may be cracked, embrittled, the movable parts may be stuck, and the characteristics may be changed at low temperature.

The main effects of low temperature environment on the equipment are:

a. Make the material hard and brittle;

b. The viscosity of lubricant increases, the flow ability decreases and the lubrication effect decreases;

c. The performance of electronic components changes;

d. Water condenses and freezes;

e. Seal failure;

f. Material shrinkage causes mechanical structure changes.

Failure mode of specimen under temperature change

Mechanical failure, cracking, seal damage, leakage and other phenomena may occur to the parts and materials used in the product when the temperature changes dramatically.

The main effects of the drastic temperature changes on the equipment are:

a. Make the assembly point or welding point of components loose or fall off;

b. Cracking the material itself;

c. The performance of electronic components changes;

d. Leakage caused by seal failure;

Non heat dissipation test piece and heat dissipation test piece

The test piece that does not generate heat is a non heat dissipation test piece. In the laboratory, the following stricter definitions can be adopted: under the free air condition without forced air circulation and the air pressure (86-106kpa) specified by the standard atmosphere for the test, the test sample with the difference between the hottest spot temperature on the surface of the test sample and the ambient temperature less than 5 ℃ after the temperature of the test sample reaches a stable level.

If the ambient temperature is constant, the heat flow direction of the non heat dissipation test piece is as follows: when the ambient temperature is high, the heat is transferred from the ambient atmosphere to the test piece; On the contrary, heat is transferred from the test piece to the surrounding atmosphere. The heat transfer process will continue until the temperature of each part of the test piece reaches the ambient air temperature. After which the heat transfer process is stopped. The final stable temperature of the non heat dissipation test piece is the average temperature of the test chamber where the test sample is placed.

The heat generated in the test piece is the heat dissipation test piece. It is strictly defined as the test sample in which the difference between the hottest spot temperature on the surface of the test sample and the ambient temperature is greater than 5 ℃ after the temperature of the test sample is stable under the free air condition without forced air circulation and the air pressure (86-106kpa) specified by the standard atmosphere for the test.

The heat generated by the heat dissipating test piece is continuously radiated to the surrounding atmosphere until the heat generated by the test piece is balanced with the heat dissipated in the surrounding atmosphere, and the temperature of the test piece is stable. When the ambient temperature rises or falls, the temperature inside the test piece will rise or fall along with it until a new equilibrium is reached. The final stable temperature of the heat dissipation test piece needs to be measured repeatedly. When the temperature of the test piece changes by 3 ℃, measure the time interval between them. When the ratio of the two adjacent time intervals is greater than 1.7, it is considered that the temperature stable state has been reached.

product

For the current products, the product itself does not generate heat in the non working state, so the temperature test conducted in the non working state of the test piece can be treated as a non heat dissipation test piece. At present, the products for temperature test under working conditions mainly include fuel pump, ignition coil, idle speed regulator, etc. These products shall be used as heat dissipation test pieces if temperature test is conducted under working conditions. In particular, the ignition coil has a large heating capacity during operation, and the temperature on it should be monitored.

Influence of air velocity in test area

The heat exchange efficiency between the air and the test sample in the test area depends on the speed of the air flow.

For the non heat dissipating test piece, the higher air flow speed can make the temperature of each part of the test piece reach the temperature of the surrounding air quickly. Generally, when no test piece is placed in the test area, the air flow speed shall not be less than 2m / s.

For the heat dissipation test piece, when the temperature of the hottest spot of the test piece is higher than the ambient temperature, the test shall be conducted in the environment without forced air flow (free air condition), otherwise the temperature of the test piece will be reduced, thus reducing the severity of the test.

Placement of test pieces in the test area

When multiple samples are subjected to high temperature test in the same test chamber, it shall be ensured that all samples are at the same ambient temperature and have the same installation conditions. For heat dissipation samples, other test pieces shall not be affected by radiation heat dissipation, i.e. the interval between test pieces shall be large enough, so that for a single test piece, the temperature change caused by the heat radiated by other heat dissipation test pieces is small and negligible. For high-temperature or low-temperature test with constant temperature for non heat dissipation test pieces, the spacing between test pieces may not be required, because the temperature of the test pieces is consistent with the temperature in the temperature test chamber after the temperature is constant, no heat exchange occurs, and the spacing between test pieces will not affect the test. For the temperature change test pieces of non heat dissipation test pieces, the interval shall be kept so that there is enough air flow between the test pieces to accelerate the heat exchange between the test pieces and the temperature test chamber, so that the test pieces can reach the specified temperature as soon as possible.

Determination of test duration

A common rule in chemistry is that the reaction speed is faster at high temperature. This rule is applied to the technology for accelerated testing, which is also called the Arrhenius equation.

The Arrhenius relationship is mathematically expressed as:

AF (T) = e ^ (EA / k) * (1 / T actual – 1 / T laboratory)

Where, value:

AF = acceleration coefficient

EA = activation energy

K = Boltzmann constant (8.65 × 10-5ev/K)

T actual = temperature under actual load (absolute temperature)

Tlaboratory = temperature under laboratory load (absolute temperature)

In order to determine the acceleration coefficient, the activation energy must be known. For general electronic components, the commonly used value is ea = 0.44ev

(for low-temperature or high-temperature test conducted when the product is not working, the duration of the test is determined according to the characteristics of the test sample and the test purpose after the temperature of the test sample is stable. It can also be selected from the following grades: 2, 16, 72, 96h. T = tstability + to (to is generated by calculation or = 2, 16, 72, 96h).

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