CN112858401B - Thermal resistance testing device and method for detecting brazing defects of heterogeneous workpieces - Google Patents
Thermal resistance testing device and method for detecting brazing defects of heterogeneous workpieces Download PDFInfo
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Abstract
A thermal resistance testing device and a method for detecting brazing defects of heterogeneous workpieces belong to the field of electronic engineering, the method mainly realizes nondestructive detection of the brazing defects of the heterogeneous workpieces through an electrical parameter method, and the brazing quality of brazing layers of different workpieces is distinguished according to the thermal resistance tested by a four-channel brazing thermal resistance tester and a proposed brazing evaluation algorithm. The power is applied to the temperature measuring probe, heat flows through the inside of the test workpiece to the heat dissipation platform, and the whole transient temperature rise curve is converted into the thermal resistance of different materials through a structural function method in data analysis software. The position of the temperature measuring probe is moved to complete the scanning type thermal resistance test on the whole workpiece to be tested, and the coupling thermal resistance calculation is carried out on all sampling points of the same workpiece to obtain the effective area ratio Q values of different workpieces so as to distinguish the quality of brazing of the brazing layer. The method can realize complete program control calculation through a computer and can realize effective characterization on the quality of the brazing layer of the heterogeneous workpiece.
Description
Technical Field
The invention belongs to the field of electronic engineering, and relates to a device and a method for detecting brazing defects of heterogeneous workpieces through thermal resistance measurement.
Background
With the rapid promotion and development of industrial technology, brazing plays an important role in the fields of aerospace instruments, airborne equipment, aircraft structures, engine structures and the like; brazing is applicable to a wide variety of materials and structures, and for some complex components brazing is the only feasible joining method. In the brazing process, defects are often generated on a brazing layer due to the influence of a brazing process flow and a brazing operation process, common brazing defects mainly comprise cavities, cracks and impurities, the quality of the brazing layer has a critical influence on the overall heat dissipation performance of a product, the reliability and the service life of the product are important, the quality of the brazing layer of the product is effectively detected, the service capacity of materials and the service capacity of equipment can be improved, and the brazing technology can be widely applied. The traditional brazing defect detection method is mostly used for workpieces with simple structures, and when the structures of the workpieces are complex, the resolution of detection results is low; meanwhile, when the workpiece has multi-layer brazing, it is difficult to check the quality of each brazing layer.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a thermal resistance testing device and a thermal resistance testing method for detecting the brazing defects of heterogeneous workpieces.
The technical method of the invention is as follows:
in order TO accurately and quickly measure the brazing quality of a brazing layer of a heterogeneous workpiece, the invention designs a set of brazing thermal resistance testing device system, a TO247 packaged SiC diode is selected as a temperature measuring probe, the temperature measuring probe is fixed on the surface of the heterogeneous workpiece by adopting a trapezoidal workpiece testing clamp, power is applied TO the temperature measuring probe through an external power supply, heat flows through the inside of the tested workpiece TO a heat dissipation platform, the thermal resistance composition of each layer of material in the whole testing process is extracted according TO a transient temperature rise response curve by a structural function method, the probe is moved TO sequentially complete a scanning thermal resistance test on the surface of the workpiece, and the brazing quality of brazing layers of different workpieces can be evaluated by performing coupling calculation on the thermal resistance values of all sampling points of the same workpiece, so that the invention provides a thermal resistance testing device and a method for detecting the brazing defects of the heterogeneous workpiece, which comprise the following steps:
obtaining temperature-sensitive parameter values of the temperature measuring probe at different environmental temperatures, namely a temperature calibration curve, and calculating a temperature coefficient K;
calculating the temperature rise change of the whole test process according to the transient temperature rise response curve based on an electrical parameter method, and calculating the thermal resistance value R of each sampling test point according to the temperature rise delta T and the temperature coefficient K th ；
Performing scanning type thermal resistance test on the workpiece based on a brazing thermal resistance tester to obtain thermal resistance values of different sampling positions of the workpiece, and performing coupling thermal resistance calculation on all sampling points of the same workpiece to obtain an effective area ratio Q of the workpiece;
the testing and calculating method is adopted to carry out the same calculation on a plurality of samples of the heterogeneous workpieces, the effective area ratio Q of different workpieces is obtained, and the Q value is screened so as to realize the detection of the brazing defect.
On the other hand, the invention also provides a four-channel brazing thermal resistance tester, which comprises:
the tester host computer: the temperature measuring probe is used for providing a measuring excitation signal, controlling a time sequence and collecting and processing a temperature measuring voltage signal;
power supply: the temperature measuring probe is used for providing a working power supply for the temperature measuring probe;
program control module: the system is used for calculating and switching parameters set by a software interface;
data analysis software: for data processing, thermal resistance R th And calculating the effective area ratio Q, and issuing an integral test on-off command.
The experimental device for realizing the method comprises the following steps: a temperature measuring probe and a test fixture; the soldering thermal resistance tester comprises a data acquisition card, a MOSFET tube, a capacitor and a plurality of resistors; 1, a computer; 4 power supplies with the maximum single-channel output of 40W are provided; the constant temperature platform can be adjusted at 0-100 ℃.
The specific test method comprises the following steps:
the method comprises the following steps: placing a temperature measuring probe (a TO247 packaged SiC diode) in an incubator, adjusting the initial temperature of the incubator TO be stable, and collecting the conduction voltage drop of the temperature measuring probe by adopting a keithley 2400 high-precision source meter; changing the temperature of the incubator to carry out repeated tests to obtain a temperature coefficient graph of the temperature T and the conduction pressure drop V, wherein the slope of the temperature correction curve is the temperature coefficient K of the temperature measuring probe;
step two: placing a test fixture right above a tested workpiece, ensuring that a central shaft of the test fixture corresponds to the central position of the tested workpiece, adjusting a test probe of the fixture to be in perfect contact with the side wall of the tested workpiece, and ensuring that the heights of a left probe and a right probe are consistent with the height of the side wall of the tested workpiece;
step three: heating connecting wires of different external power supplies are respectively connected to temperature measuring probes fixed in a test fixture, the current value of the external power supply is adjusted to provide heating power for the temperature measuring probes, and the on-off of the heating power is controlled by a switch control circuit of a tester host;
step four: the acquisition test lines are also respectively connected to the corresponding temperature measurement probes, the acquisition current in the range of 0-20 mA is provided by a high-precision test current source circuit of the tester host, and data are acquired by a high-precision amplifying circuit and an MP424 high-precision acquisition card;
step five: the data analysis software processes the acquired transient temperature rise response curve by a structure function method of a key technology to obtain the spectrum value forms of temperature rise and thermal resistance of different materials, and analyzes the thermal resistance composition of each layer of material on a heat flow path of the workpiece to be detected so as to obtain the thermal resistance value of the brazing layer part of the workpiece to be detected;
step six: according to the length of the temperature measuring probe and the length of the workpiece to be measured, 10 sampling points are selected, and the whole workpiece to be measured can be subjected to scanning type sampling thermal resistance test by moving a sliding block of the test fixture; an algorithm of thermal resistance coupling values of all sampling points of the same workpiece is embedded into data analysis software, and the algorithm can calculate the coupling thermal resistance of 10 sampling points of the same workpiece to obtain the effective area ratio Q of the workpiece;
step seven: and (3) sequentially placing different workpieces under the test fixture for testing, repeating the same test operation, obtaining the Q values of the different test workpieces by data analysis software, and screening out qualified workpieces by comparing the Q' values of the standard workpieces.
Drawings
FIG. 1: a temperature calibration curve chart of the temperature measuring probe;
FIG. 2: test fixture test schematic (front view);
FIG. 3: the appearance schematic diagram of the brazing thermal resistance tester;
FIG. 4 is a schematic view of: schematic diagram of a testing system of a brazing thermal resistance tester;
FIG. 5 is a schematic view of: obtaining a schematic diagram of the thermal resistance by a structural function method;
FIG. 6: obtaining a flow chart of the effective area ratio Q;
Detailed Description
The invention is described in more detail below with reference to the figures and the detailed description.
The specific test method of the invention comprises the following steps:
the method comprises the following steps: placing the temperature measuring probe in an incubator, adjusting the initial temperature of the incubator to a stable state, and collecting the conduction voltage drop of the temperature measuring probe by adopting a keithley 2400 high-precision source meter when the temperature of the incubator is raised to a set temperature and kept for 10 minutes and the junction temperature of the temperature measuring probe is considered to be the same as the internal temperature of the incubator; changing the temperature of the incubator to carry out repeated tests to obtain a temperature coefficient graph of the temperature T and the conduction voltage drop V, wherein the slope of the curve is the temperature coefficient K of the temperature measuring probe as shown in figure 1;
step two: placing a test fixture right above a tested workpiece, ensuring that a central shaft of the test fixture corresponds to the central position of the tested workpiece, adjusting a test probe of the fixture to be in perfect contact with the side wall of the tested workpiece, and ensuring that the heights of a left probe and a right probe are consistent with the height of the side wall of the tested workpiece, wherein a schematic diagram is shown in fig. 2;
step three: four external power supplies are used for respectively providing heating current sources for four channels of the soldering thermal resistance tester, and the appearance of the soldering thermal resistance tester is shown in figure 3. The heating connecting wires of the external power supply are respectively connected to the four temperature measuring probes of the test fixture, power can be applied to the test probes by adjusting the working currents of the four power supplies, so that a heat source is generated, the whole test system of the brazing thermal resistance tester is shown in figure 4, and the on-off state of the heating current source can be switched by a switch control circuit in the tester. The maximum output current of the power supply is 40A;
step four: connecting an acquisition test wire of a soldering thermal resistance tester to a temperature measuring probe, providing a test current in a range of 0-20 mA through a high-precision test current source circuit of a tester host, performing voltage acquisition with the precision of 1 mu s through an MP424 high-precision acquisition card, and caching the acquired data in a PC memory;
step five: the industrial control computer processes the whole transient temperature rise response curve by a structure function method of a key technology to obtain the spectrum value forms of temperature rise and thermal resistance of different materials, analyzes the thermal resistance composition of each layer of material on a heat flow path of the workpiece to be detected and further obtains the thermal resistance value of the brazing layer part of the workpiece to be detected, and the whole thermal resistance obtaining schematic diagram is shown in figure 5;
step six: selecting 10 sampling points according to the length of a temperature measuring probe (the length is 15 mm) and the length of a workpiece to be measured (150 mm), and carrying out scanning type sampling thermal resistance test on the whole workpiece to be measured by moving a sliding block of a test fixture; meanwhile, an algorithm is provided for calculating the coupling thermal resistance of all sampling points of the same workpiece, and the algorithm is embedded into data analysis software, the specific algorithm is shown in fig. 6, the algorithm can calculate the coupling thermal resistance of all sampling points of the same workpiece, and further the effective area ratio Q of the workpiece is obtained, and the Q value is used for calibrating the quality of a brazing layer of the brazing workpiece.
Step seven: sequentially placing different workpieces under a test fixture for same test, repeating the second step, the third step, the fourth step and the fifth step, obtaining effective area ratios Q of the different test workpieces through data analysis software, and screening out qualified workpieces by comparing the Q' values of the standard workpieces selected by the traditional complex detection method;
the beneficial effects of the invention are: the method is simple and easy to implement, low in experiment cost and short in detection period, can perform nondestructive detection on the brazing defects of the heterogeneous workpieces, and makes up for the defects of the traditional brazing detection method. The computer can realize complete program control measurement and calculation, four-path simultaneous test can realize data sampling with the minimum sampling interval of 1 mu s, and the sampling precision is high. Meanwhile, the temperature rise measuring precision of the four-channel brazing thermal resistance tester is superior to 0.1 ℃, and the thickness resolution precision of a brazing layer can reach 30 mu m.
Claims (2)
1. A thermal resistance testing method for detecting brazing defects of heterogeneous workpieces is characterized by comprising the following steps:
obtaining temperature-sensitive parameter values of the temperature measuring probes at different environmental temperatures, namely temperature calibration curves, and calculating temperature coefficients of the four temperature measuring probes;
a four-channel brazing thermal resistance tester is independently designed, the temperature rise change in the whole testing process is calculated according to a transient temperature rise response curve based on an electrical parameter method, and the thermal resistance value R of each sampling testing point is calculated by a structural function method in data analysis software through temperature rise delta T and a temperature coefficient K th ；
Selecting a plurality of sampling points for testing, carrying out scanning type thermal resistance testing on the workpiece through a brazing thermal resistance tester to obtain thermal resistance values of different sampling positions of the workpiece, providing an algorithm for carrying out coupling thermal resistance calculation on all the sampling points of the same workpiece, and embedding the algorithm into data analysis software to directly obtain an effective area ratio Q of the workpiece to be tested;
testing and evaluating a plurality of samples of the heterogeneous workpieces by adopting the testing and calculating method to obtain effective area ratios Q of different workpieces; meanwhile, selecting a normally used workpiece as a standard workpiece, and screening out a qualified brazing workpiece by comparing the effective area ratio Q' of the selected standard workpiece;
the experimental device for realizing the method comprises the following steps: the device comprises a four-channel soldering thermal resistance tester host, four power supplies and a program control module; the tester host controls to realize simultaneous heating and collection of four channels, the heating and collection time is controlled by the program control module, and the test fixture can simultaneously clamp four temperature measurement probes to realize simultaneous collection of four channels;
the step of calculating and obtaining the effective area ratio Q based on the transient temperature rise response curve and the coupling thermal resistance comprises the following steps:
placing the temperature measuring probe in an incubator, acquiring the pressure drop of the temperature measuring probe by adjusting the temperature of the incubator, and acquiring the temperature coefficient K of the temperature measuring probe according to the temperature T and the pressure drop V; measuring the thermal resistance of different sampling points of the workpiece, fixing a temperature measuring probe by using a test fixture, respectively setting the same test current for four channels in a data analysis software interface of the brazing thermal resistance tester, and calculating and switching the parameters set by the software interface through a program control module; heating currents of the four temperature measuring probes are respectively provided by four external power supplies, and the on-off of the power supplies is controlled by a switch control circuit of a main machine of the brazing thermal resistance tester; the data is acquired at the minimum sampling interval of 1 mu s by adopting an MP424 acquisition card, and the temperature rise curve is processed by a structural function method in data analysis software to acquire the thermal resistance values of different materials; the test fixture is moved to fix the sliding block of the temperature measuring probe, the sampling position of the probe can be changed, the scanning type thermal resistance sampling test can be completed on the workpiece to be tested, the thermal resistance values of 10 sampling points of the same workpiece are coupled and calculated through an algorithm in data analysis software, the effective area ratio Q of the workpiece can be obtained, and the workpiece with qualified brazing quality can be screened out compared with the Q' value of a standard workpiece selected by a traditional complex method.
2. The thermal resistance test method for detecting the brazing defects of the heterogeneous workpieces as set forth in claim 1, wherein the specific test method comprises the following steps:
the method comprises the following steps: placing the temperature measuring probe in an incubator, adjusting the initial temperature of the incubator to be stable, and collecting the conduction voltage drop of the temperature measuring probe by adopting a keithley 2400 high-precision source meter; changing the temperature of the incubator to carry out repeated tests to obtain a temperature coefficient graph of the temperature T and the conduction pressure drop V, wherein the slope of the temperature correction curve is the temperature coefficient K of the temperature measuring probe;
step two: placing a test fixture right above a tested workpiece, ensuring that a central shaft of the test fixture corresponds to the central position of the tested workpiece, adjusting a test probe of the fixture to be in perfect contact with the side wall of the tested workpiece, and ensuring that the heights of a left probe and a right probe are consistent with the height of the side wall of the tested workpiece;
step three: heating connecting wires of different external power supplies are respectively connected to temperature measuring probes fixed in a test fixture, the magnitude of the current value of the external power supply is adjusted to provide heating power for the temperature measuring probes, and the on-off of the heating power is controlled by a switch control circuit of a tester host;
step four: the acquisition test lines are also respectively connected to the corresponding temperature measurement probes, the acquisition current in the range of 0-20 mA is provided by a high-precision test current source circuit of the tester host, and data are acquired by a high-precision amplifying circuit and an MP424 high-precision acquisition card;
step five: the data analysis software processes the acquired transient temperature rise response curve through a structure function method of a key technology to obtain the temperature rises of different materials and the spectrum value forms of thermal resistance, and analyzes the thermal resistance composition of each layer of material on a heat flow path of the workpiece to be detected so as to obtain the thermal resistance value of the brazing layer part of the workpiece to be detected;
step six: according to the length of the temperature measuring probe and the length of the workpiece to be measured, 10 sampling points are selected, and the whole workpiece to be measured can be subjected to scanning type sampling thermal resistance test by moving a sliding block of the test fixture; an algorithm of thermal resistance coupling values of all sampling points of the same workpiece is embedded into data analysis software, and the algorithm can be used for calculating the coupling thermal resistance of a plurality of sampling points of the same workpiece to obtain the effective area ratio Q of the workpiece;
step seven: and (3) sequentially placing different workpieces under the test fixture for testing, repeating the same test operation, obtaining the Q values of the different test workpieces by data analysis software, and screening out qualified workpieces by comparing the Q' values of the standard workpieces.
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