In maintenance occasions, the thermal imager often can quickly locate the short circuit / open circuit point in the board without circuit diagram for further processing. In electrothermal engineering, there is no need to touch or power off. Thermal images are captured by infrared thermal imager, and detailed thermal analysis is carried out by infrared analysis software.

Characteristics of infrared thermal imager in electronic industry：

■ It can be monitored at any time without contact, power failure, sampling and disassembly.

■ It can realize rapid scanning and imaging, with fast, sensitive, visual and intuitive image display, high monitoring efficiency and low labor intensity.

■ Passive detection is adopted, which does not affect the working state of the target circuit board, and is simple and convenient.

■ It is convenient for computer analysis and intelligent management.

■ Infrared diagnosis is widely used, with high benefit and investment ratio.

■ Infrared detection is conducive to the state management of electronic circuit integration.

■ Infrared on-line monitoring does not require detailed information drawings of components. The inspectors do not need to have strong professional skills, nor do they need to conduct in-depth analysis of the circuit. They can quickly and accurately judge the faulty components or circuit circuits, and can timely diagnose hidden troubles according to the formulated infrared fault standards, so they can effectively avoid sudden failures of electronic equipment.

■ The operation is simple, convenient and safe. In the case of live detection, infrared detection is not only safe and convenient, but also has low requirements for detection conditions and environment.

Electronic equipment usually focuses on the detection parts

Resistors, capacitors, diodes, triodes, etc. are thermal defect prone electronic devices.

Module circuit, such as power drive circuit, data acquisition circuit and other modules.

Heat distribution of thermal devices such as heat dissipation modules.

Examples of infrared thermal imaging technology in LED products

Research and development

1、 LED module drive circuit

In the research and development of LED products, engineers are required to design some driving circuits, such as rectifier circuit modules. Using the thermal imager, engineers can quickly and easily find the temperature difference on the circuit, which is convenient to improve the circuit design.

2、 LED light source semiconductor chip heating

利用热像仪，工程师可以根据得到的光源半导体芯片发热红外热图，分析出其芯片在工作时的温度，以及温度的分布情况，在此基础，达到提高LED产品寿命的目的。

Quality management

1、 Semiconductor lighting: uniformity of packaged LED

By capturing the LED packaging process of the production line with the thermal imager, modifying the parameters and improving the necking process, the product yield can be effectively improved and the cost can be reduced.

2、 Temperature management of LED detection chip before packaging

The detection of temperature before LED chip packaging can avoid the abnormal temperature of the chip after packaging and reduce the scrap rate.

Functions and characteristics of electronic detection software

The thermal imager transmits the thermal imaging video of the target circuit board to the computer through USB cable or network cable. The computer software compares the thermal image video with the standard thermal image video in the database through the specific analysis tool set by the user, so as to obtain the fault difference points. The software provides point, line and surface (rectangle, circle, etc.) analysis tools.

The software will divide the area or graphic area according to the user's settings, and compare the temperature difference value of the same area in the thermal image video of the circuit board to be tested with the standard thermal image video in the database. The user can select the maximum temperature or average temperature value of the area to calculate the temperature difference or temperature appreciation.

Features of software

1、 Custom report template

The report template is used to generate the alarm report. Users can design the layout and style of the report according to the actual requirements, and finally generate the PDF report.

2、 Optional detection mode

When testing electronic components, different methods can be selected according to different situations: real-time detection mode and video detection mode. After entering the real-time detection mode, the current screen is displayed as real-time video. When the user selects video detection and enters the video detection mode, the left side is the standard video and the right side is the video to be detected.

3、 Image fusion technology

By adjusting the fusion and comparison of visible light image and infrared image, the fault point can be identified and located quickly, and the work efficiency can be greatly improved (the fusion setting of the real-time window can be carried out only in real-time monitoring).

4、 Alarm setting function

The default alarm setting of the system is the alarm setting value of standard video recording, and the user can also manually change the corresponding temperature difference value.

Maximum temperature difference: the difference between the maximum temperatures of two identical areas / analysis tools

Average temperature difference: the difference between the average temperatures of two identical areas / analysis tools

Temperature rise difference value: the difference between the temperature rise of two same areas / analysis tools

5、 Automatically generate alarm reports

After an alarm occurs, when the detection stops in the difference screen, the system automatically generates a PDF alarm report in the folder directory specified by the user.

Applicable Machine

1、 Infrared nondestructive testing

Infrared nondestructive testing is to identify the quality of metal or non-metallic materials and detect internal defects by measuring heat flow or heat. For some local defects that cannot be detected by X-ray and ultrasonic, infrared nondestructive testing can achieve better results.

Infrared nondestructive testing mainly has the following typical applications:

(1) Nondestructive testing of welding defects.The welded junction surface is uneven, so it is difficult to find defects by X-ray, ultrasonic, eddy current and other methods. If an AC voltage is applied to both ends of the welding area, AC current will flow through the crater. Due to the skin effect of current, the current density near the surface will be greater than that of the lower layer. Due to the action of current, the crater will generate a certain amount of heat. The amount of heat is proportional to the resistivity of the material and the square of the current density. In the welding area without defects, the current distribution is uniform, the heat generated everywhere is roughly equal, and the surface temperature distribution of the welding area is uniform. The welding area with defects has high resistance, which increases the loss and temperature in this area. Thermoelectricity can be clearly measured by using infrared temperature measuring equipment, so it can be concluded that there are welding defects under the hot spot.

(2) Internal defect detection of castings.The internal structure of some precision castings is very complex, and the traditional nondestructive detection method can not accurately find the internal defects. When infrared nondestructive detection is used, only liquid Freon cooling is needed inside the casting to achieve the best cooling effect, and then the infrared thermal imager is used to quickly scan the whole surface of the casting. If there is residual core or uneven wall thickness in the channel, it can be clearly seen in the heat map. If the cooling channel is unblocked and the cooling effect is good, a series of uniform white stripes are displayed on the heat map; If the passage is blocked and the cooling liquid is blocked, black stripes are displayed at the blockage

(3) Fatigue crack detection.A point radiation source is used to inject energy into a small area of the skin surface. Then, the surface temperature is measured with infrared radiation thermometer. If there are fatigue cracks on or near the skin surface, the heat conduction will be affected, and the heat near the crack will not be transmitted quickly, causing the surface temperature near the crack to rise quickly. When the radiation source is on both sides of a crack, the temperature on both sides is very high because the crack does not allow heat flow. When the heat source moves to the crack, the surface temperature drops to the normal temperature. In the actual measurement, due to the limitation of the size of the radiation source, the influence of the position of the radiation source and infrared detector, and the influence of the high-speed scanning speed, there will be some errors.

2、Application of infrared detection in PCB Fault Diagnosis

The existing conventional circuit fault detectors need to measure the voltage, current, impedance of key points and lines in the circuit and the necessary parameters of components. According to the relevant results obtained from the measurement, combined with the fault phenomenon and the in-depth understanding of the schematic diagram, they can diagnose the fault position of the circuit board or the fault components. It is difficult to meet the requirements of modern national defense through this conventional circuit board fault detection method, because this method has several defects: (1) it must have detailed maintenance information such as circuit schematic diagram, board diagram, component layout diagram, etc. (2) Its measurement method is contact measurement, which will inevitably affect the distribution parameters of the circuit, and it is impossible to be used for real-time fault detection of high-frequency circuits. (3) It is slow, time-consuming and laborious, and it is difficult to meet the high requirements for time and speed in the war environment. (4) It is difficult to diagnose potential faults, so it is difficult to avoid sudden failures of equipment at critical moments.

Using the infrared detection technology, the working state of hundreds of devices in a wide range can be detected quickly without touching at the same time without the need for staff to conduct in-depth analysis of the circuit, and the fault circuit or component in the circuit can be identified within dozens of seconds or even a few seconds after power on, without affecting the frequency characteristics of the circuit during detection; Moreover, it can quantitatively subdivide the state of components in the circuit from intact to fault into several levels, which enables the maintenance personnel to discover the hidden dangers of circuit faults in time and avoid the sudden occurrence of faults at critical moments.

3、Fault detection principle and equipment

When the circuit board is working, the components on it will emit heat, and the thermal image of the circuit board can be taken by the infrared instrument. During fault detection, firstly, it is necessary to take the thermal image of the normal circuit board when it is working, and save it to the database as a standard board; Secondly, take the thermal image of the faulty circuit board when it is working as the board to be tested; Thirdly, through the method of image processing, the plates to be tested are preprocessed, registered, compared and information extracted; Finally, according to the preset threshold, the number and location of faults are obtained.

Due to the late start of our country, there are still relatively few infrared fault detection equipment. At present, the existing equipment includes printed circuit board infrared fault diagnosis instrument, which is the molding equipment engaged in the research of infrared detection earlier in China; TIP-I circuit fault detector has a high fault diagnosis rate; The portable infrared circuit fault detection system makes the infrared detector more miniaturized.

4、 Summary

The application of infrared detection technology is very extensive and of great significance, which leads to more and more branch studies. Infrared thermal imaging is a key technology in infrared inspection. Some countries with developed technology are competing to study thermal imaging technology and develop it with huge human and material resources, which is developing very rapidly. Improving the accuracy of infrared image processing and developing intelligent fault detection equipment are key research directions, and more in-depth research should be done in these areas in the future.

Applicable Machine