A solder joint electro-thermal migration test method

Abstract

The present invention belongs to the field of solder joint migration technology, and specifically relates to a solder joint electro-thermal migration test method. The method conducts three tests on three specimens, namely an electro-thermal migration coupling test, an electromigration test, and a thermal migration test. The electro-thermal migration coupling test and the electromigration test differ only in that the former is conducted in an air bath, while the latter is conducted in an oil bath. During the electro-thermal migration coupling test, the temperature field change data at the positive and negative ends of the specimen are applied to the hot and cold ends of the specimen in the thermal migration test. This allows the design of an isolated electromigration specimen consistent with the electro-thermal migration coupling test conditions and an isolated thermal migration test consistent with the test conditions. This achieves the purpose of decoupling electro-thermal migration from electromigration and thermal migration, enables the study of large solder joint electromigration and thermal migration, their effects and mechanisms in electro-thermal migration, and seeks ways and methods for regulating electromigration and thermal migration in solder joint electro-thermal migration.

Description

Technical Field

[0001] The invention belongs to the technical field of solder joint migration, and in particular relates to a solder joint electro-thermal migration test method. Background Art

[0002] In microelectronic connections, lead-free solder joints are key structures for achieving electrical connections, mechanical support, and heat conduction between various units of electronic products. High-density device packaging provides higher integration and more I / Os while further reducing the size of solder joints in microelectronic packaging structures. Especially under harsh working conditions, the current density can easily reach 10 4 A / cm 2 Simultaneously, the ambient heat generates a significant amount of Joule heat. This heat creates large temperature gradients in the solder joints, reaching 1000K / cm-3000K / cm. Lead-free solder joints not only face challenges such as mechanical and long-term creep, but also experience electron windage and temperature gradients generated by the flowing current, leading to electromigration and thermal migration. This can cause defects such as hillocks, cracks, and segregation within the solder joints, significantly reducing the service reliability of lead-free solder joints in microelectronic packaging. Solder failure caused by this electro-thermal migration and their coupled effects has become one of the most common failure modes in lead-free solder joints for microelectronic interconnects. High current density coupled with high heat generation creates large temperature gradients, which undoubtedly have a significant impact on the service life of lead-free solder joints and has become a prominent issue affecting the reliability of lead-free solder joints used in interconnects of high-density devices and advanced packaging. However, to date, there is insufficient understanding of the electro-thermal migration phenomenon in microelectronic solder joints, and there are few reports on the electro-thermal migration and their coupled effects in microelectronic solder joints.

[0003] Electromigration and thermal migration in microelectronics solder joints are a complex phenomenon, a significant issue affecting the reliability of lead-free solder joints used in advanced packaging interconnects for high-density devices, particularly those in high-density electronic packaging under harsh operating conditions. However, due to insufficient understanding of electromigration, thermal migration, and their coupling effects, as well as limitations in research methods and approaches, our understanding of electromigration and thermal migration in microelectronic interconnects remains to be further refined. Research on electromigration and thermal migration in lead-free solder joints, their coupling effects, mechanisms, and their characteristic phenomena is still in its infancy. Therefore, the key to understanding the mechanisms of electromigration and thermal migration is to design new equipment, research methods, and approaches based on the understanding of electromigration to study its effects under ideal conditions.

[0004] Moreover, electricity and heat exist together, especially when the current density of tiny solder joints is greater than 10 4 A / cm 2Under harsh operating conditions with temperature gradients exceeding 1000K / cm, significant current crowding and Joule heating damage solder joints. Currently, existing technologies are still unable to experimentally study the mechanisms and regulation of electro-thermal migration and their coupling, severely hindering the progress of electro-thermal migration research. Summary of the Invention

[0005] The purpose of the present invention is to provide a solder joint electro-thermal migration test method to solve the problem in the prior art that it is impossible to decouple electro-thermal migration and coupling effects through a test approach.

[0006] In order to solve the above technical problems, the technical solutions provided by the present invention and the corresponding beneficial effects of the technical solutions are as follows:

[0007] A solder joint electro-thermal migration test method of the present invention comprises the following steps:

[0008] 1) selecting at least three identical specimens, each of which comprises at least two pieces of parent metal and a weld for welding the parent metals together;

[0009] 2) Conduct an electro-thermal migration coupling test on the first test: Set the sample's environmental conditions to an air bath, apply power to both ends of the sample, and measure the temperature changes at both ends of the sample during the power-on process. After a set time has elapsed, measure solder joint migration data under the electro-thermal migration coupling test; the temperature changes include the temperature changes at each set time interval;

[0010] 3) Perform an electromigration test on the second sample: Set the sample's environmental condition to an oil bath, apply power to the second sample using the same power-on conditions as in step 2), and after the set time has elapsed, detect solder joint migration data under the electromigration test;

[0011] 4) Performing a thermal migration test on the third sample: Set the sample's environmental condition to an air bath, apply a temperature field to both ends of the third sample based on the temperature change at both ends of the sample detected in step 2), and after a set time, measure the solder joint migration data under the thermal migration test;

[0012] 5) Determine the extent to which the solder joint is affected by at least one of electromigration, thermomigration, and electro-thermomigration interaction on solder joint migration based on the solder joint migration data under the electro-thermomigration coupling test, the solder joint migration data under the electromigration test, and the solder joint migration data under the thermomigration test.

[0013] The beneficial effects of the above technical solution are as follows: Based on the connotations of electromigration and thermomigration, the present invention designs an isolated electromigration specimen and an isolated thermomigration test consistent with the test conditions for electro-thermomigration coupling, thereby achieving decoupling of electro-thermomigration from electromigration and thermomigration. The only difference between the isolated electromigration specimen and the electro-thermomigration coupling test is that the environmental conditions of the isolated electromigration specimen are oil bath conditions, while the environmental conditions of the electro-thermomigration coupling test are air bath conditions. The temperature field applied to the hot and cold ends of the isolated thermomigration test is the temperature field actually detected at the positive and negative ends in the electro-thermomigration coupling test. Therefore, based on the solder joint migration data detected by the three specimens, the degree of influence of at least one of electromigration, thermomigration, and electro-thermomigration interaction on solder joint migration is explored. This enables the study of solder joint electromigration and thermomigration under harsh working conditions of high current and large temperature gradient, as well as their effects and mechanisms in electro-thermomigration, and seeks ways and methods for regulating electromigration and thermomigration in lead-free solder joint electro-thermomigration.

[0014] Furthermore, in order to analyze the migration of solder joints, the solder joint migration data in steps 2), 3), 4), and 5) include at least one of the following data: joint interface structure thickness and shear strength.

[0015] Furthermore, in order to digitize the influence of the solder joint on the migration of the solder joint under the action of thermal migration, electromigration, and electro-thermal migration, the solder joint migration data is the thickness of the joint interface tissue. The influence of the solder joint on the migration of the solder joint under the action of electromigration, the influence of the solder joint on the migration of the solder joint under the action of thermal migration, and the influence of the solder joint on the migration of the solder joint under the interaction of electro-thermal migration are respectively: A 电-热 *A 电 / (A 电 +A 热 ), A 电-热 *A 热 / (A 电 +A 热 ), A 电-热 *(A 电 +A 热 -A 电-热 ) / (A 电 +A 热 ), A 电-热 A represents the thickness of the joint interface structure under the electro-thermal migration coupling test, 电 A represents the thickness of the joint interface tissue under the electromigration test. 热 Indicates the thickness of the joint interface tissue under the thermal transfer test.

[0016] Furthermore, during the electromigration test in step 1), the end of the sample connected to the positive pole of the power supply is called the anode of the sample, and the end connected to the negative pole of the power supply is called the cathode of the sample. During the thermal migration test in step 4), the end of the sample with a higher temperature is called the hot end, and the end of the sample with a lower temperature is called the cold end. When applying the temperature field in step 4), the temperature is applied to the cold end of the sample according to the temperature change of the anode of the sample, and the temperature is applied to the cold end of the sample according to the temperature change of the cathode of the sample.

[0017] Furthermore, the power supply in step 2) and step 3) is performed by constant current power supply.

[0018] Furthermore, the solder joint size is 0.1 to 1 mm 2 .

[0019] Furthermore, in order to accurately determine the actual temperature change at both ends of the solder joint so that the third solder joint can simulate the temperature rise of a real sample when performing the thermal migration test, the set interval time period is 1 minute.

[0020] Furthermore, in order to study the electromigration, thermomigration and their coupling effects, mechanisms, dominant factors and their intrinsic correlations of solder joints under large temperature gradients, the constant current was 50A and the setting time was 30 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the coupling test device of the present invention;

[0022] Figure 2 It is a schematic structural diagram of a sample fixture in a coupling test device of the present invention;

[0023] Figure 3 It is a schematic structural diagram of a sample of the present invention;

[0024] Figure 4 It is a schematic structural diagram of the thermal migration test device of the present invention;

[0025] Figure 5 It is a flow chart of the solder joint electro-thermal migration test method of the present invention.

[0026] Among them, 11-coupling test device body, 12-insulation cover, 121-through hole, 13-temperature field measurement and control board, 14-coupling test device switch, 15-environmental chamber, 16-specimen slot, 161-gypsum gasket, 162-specimen conductive clip, 163-wire connection hole, 164-conductive bolt, 165-heat dissipation hole, 166-parent material, 167-solder point, 21-thermal migration test device body, 22-thermal migration test device switch, 231-cold end control display panel, 232-hot end control display panel, 241-cold end power terminal, 242-hot end power terminal, 251-cold end support frame, 252-hot end support frame, 261-cold end asbestos insulation layer, 262-hot end asbestos insulation layer, 27-fixing bolt, 28-specimen, 291-cold end heating plate, 292-hot end heating plate. DETAILED DESCRIPTION

[0027] Based on the connotations of electromigration and thermomigration, the present invention designs isolated electromigration and thermomigration tests that are consistent with the electro-thermomigration test conditions. The isolated electromigration test conditions are consistent with the electro-thermomigration test conditions except for the environmental conditions. The environmental conditions for the electro-thermomigration coupling test are an air bath, while the environmental conditions for the electromigration test are an oil bath. The isolated thermomigration test conditions are based on the temperature field applied to both ends of the sample, which corresponds to the temperature changes at both ends of the sample during the electro-thermomigration coupling test. These three tests are intended to study thermomigration, electromigration, and their coupling effects, and to explore the inherent connections between electromigration, thermomigration, and electro-thermomigration.

[0028] A solder joint electro-thermal migration test method implemented based on this concept is described in detail below with reference to the accompanying drawings and embodiments.

[0029] Method Example:

[0030] Before introducing an embodiment of the present invention's solder joint electro-thermomigration testing method, the following describes the present invention's solder joint electro-thermomigration testing platform. In this embodiment, the solder joint electro-thermomigration testing platform includes two test devices: one set of devices for the electro-thermomigration coupling test and electromigration test, referred to as the coupling test device, and another set of devices for the thermal migration test, referred to as the thermal migration test device.

[0031] The structure of the coupling test device is as follows: Figure 1As shown, the coupling test device includes a coupling test device body 11, which is provided with an access port for taking and placing samples. An environmental chamber 15 is provided within the coupling test device body 11, and the environmental chamber 15 is connected to the access port. The maximum operating temperature of the environmental chamber is less than 300°C. The coupling migration device also includes a thermal insulation cover 12 for covering the access port. The thermal insulation cover 12 includes a multi-layer cover body, and the adjacent two layers of the cover body are nested with each other to form a seal to improve the sealing of the device, isolate the outside air, and avoid the influence of the ambient temperature. The environmental chamber 15 can simultaneously meet the requirements of the electro-thermal migration coupling test in an air bath environment and the thermal migration test in an oil bath environment. When the thermal insulation cover 12 is in the open state, the environmental chamber 15 can achieve the environmental conditions of an air bath. When the thermal insulation cover 12 is in the closed state, silicone oil can be placed in the environmental chamber 15 to achieve constant temperature conditions for solder joint electromigration. Due to the good heat dissipation of silicone oil, it avoids the generation of large temperature gradients, thus achieving the conditions of electromigration test and the environmental conditions of an oil bath.

[0032] A through hole 121 is provided on the heat-insulating cover 12 for inserting a high-temperature resistant wire during the electromigration test, thereby supplying power to the sample and detecting the temperature change at both ends of the sample. The power supply current meets the requirements of 0-100A. The coupling test device body 11 is also equipped with a sample slot 16 for placing the sample and the sample fixture. The sample fixture is used to place and fix the sample and make contact with the conductive material and is fixed in the sample slot 16. The structure of the sample is as follows: Figure 3 As shown, it includes a base material 66 and a welding spot 167 for welding the base materials 166 together, and the welding spot size is 0.1-1mm 2 , the center lines of the base material 166 and the welding point 167 are on the same horizontal line, which can improve the welding point overlap stability; the structure of the sample fixture is as follows Figure 2 As shown, it includes a gypsum gasket 161 and a sample conductive clip 162. A wire connection hole 163 is located above the gypsum gasket 161 to facilitate sample removal. A conductive bolt 164 is located above the wire connection hole 163 to connect the sample to the conductor. A heat dissipation hole 165 is installed below the conductive bolt 164 to prevent the fixture from overheating and burning, and to provide fixed support. The heat dissipation hole 165 is located above the sample conductive clip 162 to prevent the sample conductive clip from rusting due to heat. Furthermore, the gypsum gasket 161 and the wire connection hole 163 are connected by a hexagonal bolt to improve shock absorption. The sample conductive clip 162 is connected to the sample via a contact gasket to improve conductivity and avoid current concentration effects. The sample fixture is heat-resistant to 300°C.

[0033] Moreover, the temperature change at both ends of the sample is detected by setting thermocouples at both ends of the sample, thereby realizing effective observation of the temperature change at both ends of the sample. The temperature field measurement and control board 13 is set on the coupling test device body 11. The temperature field measurement and control board 13 can be used to set the set temperature of the environmental box 15 under oil bath conditions on the one hand, and can display the temperature change at both ends of the sample detected by the two thermocouples on the other hand. The temperature field measurement and control board 13 can record the temperature field change, and the temperature field change range is 0-2500K / cm. The coupling test device switch 14 is used to control whether the entire coupling test device is working or not. In addition, a drainage hole ( Figure 1 (not shown) the silicone oil can be discharged outside the entire device.

[0034] The structure of the thermal migration test device is as follows Figure 4 As shown, the thermal migration test device includes a thermal migration device body 21. The thermal migration device body 21 is provided with a cold end control display panel 231 and a hot end control display panel 232. These two control panels are used to set the temperature field change parameters to adjust the temperature of the cold end and hot end of the sample. When setting the cold end and hot end heating temperatures, the frequency of the cold end and hot end heating and the degree of heating at this frequency can be set according to the test conditions. The heating temperatures of the cold end and hot end can be the same or different, and for one end (cold end or hot end), the early and late heating rates can be the same or different, which can be set according to the needs. The two control panels can also display the actual temperature changes at both ends of the sample. The thermal migration device body 21 is provided with a thermal migration test device switch 22 for controlling whether the entire thermal migration test device is in operation. The distinction between the two ends of the cold end here is that the end with a relatively higher temperature is called the hot end, and the end with a relatively lower temperature is called the cold end.

[0035] Two asbestos insulation layers are installed above the thermal migration device body 21: a cold-end asbestos insulation layer 261 and a hot-end asbestos insulation layer 262. These layers prevent excessive heat dissipation that could affect accuracy, improve thermal conductivity and insulation performance, and minimize temperature fluctuations during the test. A cold-end heater 291 is installed above the cold-end asbestos insulation layer 261, while a hot-end heater 292 is installed above the hot-end asbestos insulation layer 262. The cold-end heater 291 is connected to the cold-end power supply terminal 241 via a wire, while the hot-end heater 292 is connected to the hot-end power supply terminal 242 via a wire. These two power supply terminals are used to convert the electrical energy of the input current into thermal energy. A cold-end support frame 251 is installed outside the cold-end asbestos insulation layer 261, while a hot-end support frame 252 is installed outside the hot-end asbestos insulation layer 262. These two support frames are in the shape of a "J" and are used to secure the asbestos insulation layers.

[0036] A sample 28 is provided on the upper portion of the cold end asbestos insulation layer 261 and the hot end asbestos insulation layer 262. The structure of the sample 28 is the same as that of the Figure 3 The sample 28 is identical and also includes a base material and a solder joint for welding the base materials together. One end of the sample 28 contacts the cold end heating plate 291, and the other end contacts the hot end heating plate 292 to achieve heating of both the cold and hot ends of the sample. The fixing bolt 27 is used to fix the sample 28 and the two thermocouples (not shown) that detect the temperature at both ends of the sample to ensure that the sample is in a compressed state and improve the efficiency of heat conduction. The two thermocouples are used to provide timely feedback on the temperature of the hot and cold ends of the solder joint.

[0037] The entire device also includes a microelectronic control module. This module acquires thermocouple data and the temperature field parameters set via the cold-end control display panel 231 and the hot-end control display panel 232. It also controls the cold-end and hot-end temperatures based on the set temperature field parameters via the cold-end heating terminals and the hot-end heating terminals. The temperature fields at the cold and hot ends vary between 0 and 2500 K / cm, with an accuracy of 1 K / cm and a measurement frequency of once per minute.

[0038] It should be noted that, in addition to the above-mentioned devices, in order to implement the solder joint electro-thermal migration test method of the invention, other devices in the prior art can also be used to implement the electro-migration test, thermal migration test, and electro-thermal migration coupling test. The following is a detailed description of an embodiment of the solder joint electro-thermal migration test method of the invention. The overall process is as follows: Figure 5 As shown:

[0039] Step 1: Prepare test materials.

[0040] This example uses lead-free composite solder as the research object. SAC305 lead-free composite solder is prepared by powder metallurgy and welded to base material 167 by overlapping. The soldering point after welding is 166. In this experiment, the soldering temperature is 270℃, the soldering time is 210s, and the cooling method is air cooling. A stable sample is obtained, and the soldering point size is 0.5mm. 2 It should be noted that three samples were made, and all factors and conditions of the three samples were the same, including solder joint size, brazing temperature, brazing time, cooling time, etc.

[0041] Step 2: Conduct a solder joint electro-thermal migration coupling test on the first sample.

[0042] The electro-thermal migration coupling test parameters of the lead-free composite solder joints were set to a current density of 10000A / cm by the coupling test device. 2 , that is, the circuit is 50A and powered for 30 hours, the environmental box 5 is filled with air, and the electromigration test of the solder joint in the air environment is determined by the test to be an electro-thermal migration coupling test. Figure 2The sample is clamped in a sample fixture and a constant current is applied to the cathode and anode of the sample. The end of the sample connected to the positive pole of the power supply is called the anode, and the end of the sample connected to the negative pole of the power supply is called the cathode. During this process, the thermocouple will measure and record the temperature field changes of the anode and cathode areas of the sample every minute. After 30 hours, the sample is removed and air-cooled for 10 minutes. Through electron microscopy analysis and performance testing, the electrical and thermal migration coupling behavior and effects of the solder joint (also known as solder joint migration data) are recorded, including the thickness of the joint interface structure, shear strength, resistance value changes, etc. The median failure time theorem is used to calculate the service life prediction of the solder joint under this condition, as well as the evolution law of the temperature field on the cathode and anode sides of the solder joint, for reference and comparative analysis with subsequent tests.

[0043] It should be noted that in this step, the temperature field data collected for the positive and negative levels is not hourly temperature change data, but minute-by-minute temperature field change data. This is to obtain the actual temperature change of the sample, so that the actual temperature change data can be applied to the two ends of the third sample in the subsequent step four. This will make the third sample simulate the actual temperature change, gradually rising to a certain temperature over time, rather than jumping to a certain temperature all at once. Of course, as another embodiment, it is also feasible to collect temperature field data every 2 minutes at this time. The key point is that the interval time should not be too long.

[0044] The thickness of the joint interface structure was determined by measuring the thickness and roughness of the interface IMC. Since the interface IMC is uneven and mostly wavy, its thickness could not be directly measured. Instead, SEM images were imported into AutoCAD software. Three different regions of the joint interface were randomly selected from the SEM images, and the area and length of these regions were measured. Finally, the thickness of the joint interface structure was calculated using the equal-area method. The shear strength was determined using a test force accuracy of ±0.5% and a tensile rate of 0.5 mm / min. The joint was clamped and fixed at the beginning of the test. To ensure the validity of the test results, three joint specimens were tested under the same test conditions. The arithmetic mean of the three joint specimens was taken as the final shear strength under these test conditions. The shear specimens were then placed in a JSM-IT100 tungsten filament scanning electron microscope for observation. The fracture morphology of the shear fracture was used to investigate the fracture location and mechanism of the brazed joint.

[0045] Step three: perform an electromigration test on the second sample.

[0046] Using a coupling test device, the environmental chamber is filled with silicone oil. The strong heat dissipation performance of the silicone oil bath condition can prevent large temperature gradients from occurring in the anode and cathode areas of the sample. The test materials, parameters, and test methods are consistent with those in step 2. The only difference is that the air bath environmental conditions in the electro-thermal migration coupling test are replaced with oil bath conditions. In the test below the critical temperature gradient of thermal migration, the electromigration behavior and effects under the same conditions in step 2 are isolated. The electromigration test is carried out for 30 hours. After the test, the sample is removed and air-cooled for 10 minutes. Through microstructure and performance analysis, the current density is recorded as 10,000 A / cm 2 The numerical values ​​of polarity phenomenon, shear strength and resistance of the solder joint interface are changed, and the service life of the solder joint under isolated electromigration conditions is predicted by the median aging time theorem.

[0047] Step 4: Conduct a thermal migration test on the third sample.

[0048] First, using a thermal migration test device, according to the temperature field change data of the cold end and hot end corresponding to the anode and cathode areas of the solder joint measured and recorded in step 2, the data signal is transmitted to the temperature field heating device in the thermal migration test device, and the temperature field is applied to the cold end and hot end of the sample respectively. That is, the temperature change data measured in the anode area will be applied to the cold end of the third sample, and the temperature change data measured in the cathode area will be applied to the hot end of the third sample. In this process, the temperature of the hot end and the cold end will gradually increase in a step-by-step manner. Then, a dynamic thermal migration test is carried out for the same time as step 2 (30 hours). The materials used in this thermal migration test and the temperature field conditions measured are the same as those in step 2. Under the condition of no power, the thermal migration phenomenon of the solder joint under the evolution of the temperature field at the cold and hot ends of the solder joint under the electro-thermal migration coupling effect is isolated, and the thermal migration behavior and effect of the solder joint are recorded through microstructure and performance analysis, including the numerical value of the polarity phenomenon at the solder joint interface, the shear strength value, and the evolution law of the temperature field at the cathode and anode sides of the solder joint.

[0049] Step 5: Electro-thermal migration coupling mechanism and regulation method.

[0050] Based on the three test results in steps 2, 3, and 4 above, by comparing and analyzing the surrounding tissue with thermal and mechanical properties, the thickness ratios of the three groups of solder joints at the cathode and anode levels and the cold and hot interfaces at the corresponding time were obtained, and the proportion of electro-thermal migration under their coupling was compared and analyzed to study the influence of electro-migration, thermal migration, and electro-thermal migration interaction on solder joint migration. For example, the three groups of tests all tested the thickness of the joint interface tissue. The thickness of the joint interface tissue under the electro-thermal migration coupling test in step 2 was A. 电-热 The thickness of the joint interface tissue under the electromigration test in step 3 is A电 , the thickness of the joint interface structure under the heat transfer test in step 4 is A 热 , then the influence of solder joint on solder joint migration under the action of electromigration is: A 电-热 *A 电 / (A 电 +A 热 ), the influence of solder joint on solder joint migration under the action of thermal migration is: A 电-热 *A 热 / (A 电 +A 热 ), the influence of solder joint on solder joint migration under the interaction of electro-thermal migration is: A 电-热 *(A 电 +A 热 -A 电-热 ) / (A 电 +A 热 If all three test groups are testing shear strength, the calculation method is similar, except that the joint interface tissue thickness data is replaced with the corresponding shear strength data.

[0051] Through the above method, the effects, mechanisms, dominant factors and internal relationships of electromigration, thermal migration and their coupling in lead-free solder joints can be explored. According to the results of a solder joint electro-thermal migration test method of the present invention, the proportion of electro-thermal migration under their coupling can be reasonably controlled to obtain high-quality and high-reliability lead-free solder joints under the electro-thermal migration coupling.

[0052] In summary, based on the connotations of electromigration, thermomigration and electro-thermal coupling effects, the present invention designs electro-thermal migration test devices and related specimens that meet the requirements of high current density and large temperature gradient, thereby maximally eliminating the current crowding effect and Joule heat solder joint damage caused by excessive contact resistance. Moreover, based on the principle of consistency between the temperature and materials of the electro-thermal migration coupling test, the electro-thermal migration coupling test, the electro-migration test in an isolated state, and the thermo-migration test in an isolated state are rationally designed to explore the electro-migration and thermo-migration of lead-free solder joints and their coupling mechanisms and control approaches and means. Based on this, the present invention intends to focus on studying the proportion and internal correlation of electro-migration and thermo-migration under harsh working conditions with large currents and large temperature gradients, the influence of their electro-thermal coupling, the mechanism of action, and electro-thermal control, and is expected to draw some important conclusions or corresponding physical models. Based on the research results obtained, it is convenient to propose reasonable anti-electro-thermal migration means and methods to obtain high-quality and high-reliability solder joints.

[0053] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A solder joint electro-thermal migration test method, characterized in that: The steps include: 1) selecting a plurality of identical specimens, each of which comprises at least two pieces of parent metal and a weld for welding the parent metals together; 2) Conducting an electro-thermal migration coupling test on the first test: Setting the sample's environmental conditions to an air bath, applying power to both ends of the sample, and detecting temperature changes at both ends of the sample during the power-on process. After a set time has elapsed, detecting solder joint migration data under the electro-thermal migration coupling test; wherein the temperature change includes the temperature change at each set time interval; 3) Perform an electromigration test on the second sample: Set the sample's environmental condition to an oil bath, apply power to the second sample using the same power-on conditions as in step 2), and after the set time has elapsed, detect solder joint migration data under the electromigration test; 4) Performing a thermal migration test on the third sample: Set the sample's environmental condition to an air bath, apply a temperature field to both ends of the third sample based on the temperature change at both ends of the sample detected in step 2), and after a set time, measure the solder joint migration data under the thermal migration test; 5) Determine the extent to which the solder joint is affected by at least one of electromigration, thermomigration, and electro-thermomigration interaction on solder joint migration based on the solder joint migration data under the electro-thermomigration coupling test, the solder joint migration data under the electromigration test, and the solder joint migration data under the thermomigration test.

2. The solder joint electro-thermal migration test method according to claim 1, characterized in that: The solder joint migration data in steps 2), 3), 4) and 5) include at least one of the following data: joint interface structure thickness and shear strength.

3. The solder joint electro-thermal migration test method according to claim 2, characterized in that: The solder joint migration data is the thickness of the joint interface structure. The influence degree of the solder joint on the solder joint migration under the action of electromigration, the influence degree of the solder joint on the solder joint migration under the action of thermal migration, and the influence degree of the solder joint on the solder joint migration under the interaction of electro-thermal migration are respectively: A 电-热 *A 电 / (A 电 +A 热 ), A 电-热 *A 热 / (A 电 +A 热 ), A 电-热 *(A 电 +A 热 -A 电-热 ) / (A 电 +A 热 ), A 电-热 A represents the thickness of the joint interface structure under the electro-thermal migration coupling test, 电 A represents the thickness of the joint interface tissue under the electromigration test. 热 Indicates the thickness of the joint interface tissue under the thermal transfer test.

4. The solder joint electro-thermal migration test method according to claim 1, characterized in that: During the electromigration test in step 1), the end of the sample connected to the positive pole of the power supply is called the anode of the sample, and the end connected to the negative pole of the power supply is called the cathode of the sample. During the thermal migration test in step 4), the end of the sample with a higher temperature is called the hot end, and the end of the sample with a lower temperature is called the cold end. When applying the temperature field in step 4), the temperature is applied to the cold end of the sample according to the temperature change of the anode of the sample, and the temperature is applied to the cold end of the sample according to the temperature change of the cathode of the sample.

5. The solder joint electro-thermal migration test method according to claim 1, characterized in that: The power supply in step 2) and step 3) is constant current power supply.

6. The solder joint electro-thermal migration test method according to claim 1, characterized in that: Solder spot size is 0.1~1mm 2 .

7. The solder joint electro-thermal migration test method according to claim 1, characterized in that: The set interval time period is 1 minute.

8. The solder joint electro-thermal migration test method according to claim 5, characterized in that: The current of the constant current is 50A and the set time is 30 hours.

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