Method for measuring range of heat affected zone after ball burning of bonding wire

Abstract

The invention provides a method for measuring the range of a heat affected zone after ball burning of a bonding wire, and the method comprises the steps: carrying out the ball burning of a to-be-measured bonding wire based on a selected target ball burning process parameter, and cutting off the to-be-measured bonding wire after ball burning, thereby obtaining the to-be-measured bonding wire after ball burning; clamping and fixing an unburned ball end of the to-be-tested bonding wire after ball burning, and carrying out microhardness test by using a microhardness tester to obtain hardness measurement results of a plurality of measurement points of the to-be-tested bonding wire; wherein the hardness of a heat affected zone is different from that of the base metal after the bonding wire to be measured is subjected to ball burning, and part of the measuring points are located in the heat affected zone; the range of the heat affected zone after the bonding wire is subjected to ball firing is determined based on the positions of the measuring points with different hardness from the base metal in the multiple measuring points, the radial grain size of the bonding wire does not need to be observed, the range of the heat affected zone is measured by utilizing the hardness value difference between the heat affected zone and the base metal, the microstructure sample preparation process is omitted, and the cost is reduced. And the measurement process is simplified.

Description

Technical Field

[0001] The present application relates to the technical field of bonding wires, and in particular to a method for determining the range of a heat-affected zone of a bonding wire after sintering. Background Art

[0002] The bonding process of bonding wire includes processes such as ball burning, first welding, wire arching, second welding and tail retention. Ball burning is a process of melting the end of the bonding wire into a spherical shape by means of arc ignition, using the heat generated instantly by the high-voltage arc, so as to carry out the subsequent first bonding process. In the process of the high-voltage arc melting the end of the bonding wire into a spherical shape, a large amount of heat energy is conducted through heat conduction to increase the temperature near the ball end and coarsen the grains, thus forming a relatively low strength area, which is the heat affected zone (HAZ).

[0003] The length of the heat-affected zone directly determines the bonding arc height and bonding strength, and is an extremely important indicator of bonding wires. The shorter the heat-affected zone, the lower the arc that can be formed during bonding, the smaller the space occupied, and the higher the bonding strength.

[0004] At present, the method for measuring the length of HAZ after the bonding wire melt ball is microscopic observation. The bonding wire is mounted, polished, and corroded to prepare a metallographic sample or an electron microscope observation sample. The length of HAZ is determined by observing the grain size in the axial microstructure of the bonding wire.

[0005] The method of measuring the HAZ length by directly observing the radial grain size of the bonding wire requires a high level of sample preparation, and as the diameter of the bonding wire decreases, the success rate of sample preparation also decreases, which increases the difficulty of intuitively measuring the HAZ range. Summary of the invention

[0006] In view of this, the purpose of the present application is to provide a method for determining the range of the heat affected zone after sintering of a bonding wire. There is no need to observe the radial grain size of the bonding wire. The difference in hardness value between the HAZ and the base material is used to achieve the determination of the HAZ range, thereby eliminating the microstructure sample preparation process and simplifying the measurement process.

[0007] The present application provides a method for determining the range of a heat-affected zone after a bonding wire is sintered. The method comprises:

[0008] Based on the selected target ball firing process parameters, the bonding wire to be tested is subjected to ball firing treatment. After the ball firing is completed, the bonding wire to be tested is cut off to obtain the bonding wire to be tested after ball firing;

[0009] The unburned ball end of the bonding wire to be tested after ball sintering is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measuring points of the bonding wire to be tested from the initial measuring point to the ball end; wherein the hardness of the heat-affected zone of the bonding wire to be tested after ball sintering is different from the hardness of the base material; some of the multiple measuring points are located in the heat-affected zone; and the initial measuring point is located outside the heat-affected zone;

[0010] Based on the positions of the measurement points with different hardness from the base material in the hardness measurement results of the multiple measurement points of the bonding wire to be tested, the range of the heat affected zone of the bonding wire after ball sintering is determined.

[0011] In some embodiments, in the method for determining the range of the heat affected zone of the bonding wire after balling, the unburned ball end of the bonding wire to be tested after balling is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested from the initial measurement point to the ball end, including:

[0012] An initial measurement point is determined at a position of a first preset length from the ball-shaped end of the bonding wire to be measured, and then the measurement points of the bonding wire to be measured are determined in sequence in the direction of the ball-shaped end of the bonding wire to be measured according to the first measurement interval and hardness values ​​are measured to determine the hardness measurement result of each measurement point; the hardness measurement result of the initial measurement point is the hardness measurement result of the base material;

[0013] When it is determined that the first comparison result between the hardness measurement results of adjacent measurement points meets the preset change condition, the measurement points of the bonding wire to be measured are determined in sequence according to the second measurement interval toward the unburned ball end of the bonding wire to be measured, and the hardness value is measured;

[0014] When it is determined that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material, the measurement is stopped to obtain the final measurement point.

[0015] In some embodiments, in the method for determining the range of the heat affected zone after the bonding wire is balled, the determination of the range of the heat affected zone after the bonding wire is balled based on the position of the measurement point with different hardness from the base material in the hardness measurement results of multiple measurement points of the bonding wire to be measured comprises:

[0016] The distance between the final measuring point and the spherical end is determined as the length of the heat affected zone of the bonding wire after sintering.

[0017] In some embodiments, in the method for determining the range of the heat affected zone after the bonding wire is sintered, the first measurement interval is 5-10 times the second measurement interval.

[0018] In some embodiments, in the method for determining the range of the heat-affected zone after the bonding wire is sintered, the smaller the first measurement interval and the second measurement interval are, the higher the determination accuracy of the range of the heat-affected zone is.

[0019] In some embodiments, in the method for determining the range of the heat affected zone after the bonding wire is sintered, the first comparison result between the hardness measurement results of adjacent measurement points is judged to meet the preset change condition, including:

[0020] Determine whether the difference between the hardness values ​​of adjacent measuring points is greater than a first preset threshold;

[0021] If it is greater than, it is determined that the first comparison result between the hardness measurement results of adjacent measuring points meets the preset change condition.

[0022] In some embodiments, in the method for determining the range of the heat affected zone after the bonding wire is sintered, the hardness measurement result of the latest measurement point is judged to be restored to the hardness measurement result of the base material; comprising:

[0023] Obtain and determine the hardness value of the latest measurement point and the hardness value of the initial measurement point;

[0024] Determine whether the difference between the hardness values ​​of the latest measurement point and the initial measurement point is less than a second preset threshold;

[0025] If so, it is determined that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material.

[0026] In some embodiments, in the method for determining the range of the heat affected zone after the bonding wire is sintered, the range determination method further includes:

[0027] Based on the hardness value of the base material measured by the microhardness tester, a preset hardness correction coefficient and a hardness correction rule, the hardness value of the base material is corrected to obtain a corrected hardness value of the base material;

[0028] Based on the hardness measurement results, hardness values, preset hardness correction coefficients and hardness correction rules of the measurement points in the heat affected zone measured by the microhardness tester, the hardness value of the heat affected zone is corrected to obtain the corrected hardness value of the heat affected zone.

[0029] In some embodiments, the method for determining the range of the heat affected zone after the bonding wire is sintered further includes:

[0030] Based on different selected ball firing process parameters, the range of the heat affected zone of the bonding wire to be tested is measured to obtain the range of the heat affected zone of the bonding wire to be tested under different ball firing process parameters;

[0031] Based on the range of the heat-affected zone under the different ball-sintering process parameters, the ball-sintering process parameters for the bonding wire to be tested are optimized to obtain optimized ball-sintering process parameters.

[0032] In some embodiments, in the method for determining the range of the heat-affected zone after the balling of the bonding wire, after the balling is completed, the bonding wire to be tested is cut off, including:

[0033] After the ball burning is completed, the bonding wire to be tested is cut off from the splitter, and the length of the cut-off point from the ball burning point is determined according to the fixture size of the microhardness tester.

[0034] In an embodiment of the present application, a method for determining the range of a heat-affected zone of a bonding wire after balling is provided. The bonding wire to be tested is balled based on selected target balling process parameters. After balling is completed, the bonding wire to be tested is cut to obtain the bonding wire to be tested after balling. The unballed end of the bonding wire to be tested after balling is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points between the initial measurement point and the ball end of the bonding wire to be tested. The hardness of the heat-affected zone of the bonding wire to be tested after balling is different from the hardness of the base material. Some of the multiple measurement points are located in the heat-affected zone. The initial measurement point is located outside the heat-affected zone. Based on the hardness measurement results of the multiple measurement points of the bonding wire to be tested, the measurement results of the hardness of the bonding wire to be tested that are different from the hardness of the base material are determined. The position of the point is used to determine the range of the heat affected zone of the bonding wire after the ball is sintered; in this way, the method for determining the range of the heat affected zone of the bonding wire after the ball is sintered described in the embodiment of the present application directly performs microhardness measurement on the surface of the bonding wire, and makes use of the qualitative relationship between the range of the heat affected zone of the bonding wire after the ball is sintered and the measured hardness value (due to the influence of heat during ball sintering, the structure of the material in the heat affected zone changes, thereby causing changes in its hardness, strength and other properties). By observing the change in the indentation size during the microhardness measurement, the range of the heat affected zone of the bonding wire after the ball is sintered is obtained. There is no need to observe the radial grain size of the bonding wire. The difference in hardness values ​​between the HAZ and the base material is used to achieve the determination of the HAZ range, which eliminates the microstructure sample preparation process, simplifies the measurement process, and improves the measurement success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A flow chart showing a method for determining the range of a heat-affected zone after a bonding wire is sintered is shown in an embodiment of the present application;

[0037] Figure 2 A schematic diagram of the process of performing a microhardness test using a microhardness tester according to an embodiment of the present application is shown;

[0038] Figure 3 A flow chart of a method for performing microhardness testing using a microhardness tester according to an embodiment of the present application is shown;

[0039] Figure 4 A flow chart of a method for determining whether a first comparison result between hardness measurement results of adjacent measurement points meets a preset change condition according to an embodiment of the present application is shown;

[0040] Figure 5 A flow chart of a method for determining how to restore the hardness measurement result of the latest measurement point to the hardness measurement result of the base material according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0041] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art can add one or more other operations to the flowchart under the guidance of the content of the present application, or remove one or more operations from the flowchart.

[0042] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0043] It should be noted that the term "comprising" will be used in the embodiments of the present application to indicate the existence of the features declared thereafter, but does not exclude the addition of other features.

[0044] The bonding process of bonding wire includes processes such as ball burning, first welding, wire arching, second welding and tail retention. Ball burning is a process of melting the end of the bonding wire into a spherical shape by means of arc ignition, using the heat generated instantly by the high-voltage arc, so as to carry out the subsequent first bonding process. In the process of the high-voltage arc melting the end of the bonding wire into a spherical shape, a large amount of heat energy is conducted through heat conduction to increase the temperature near the ball end and coarsen the grains, thus forming a relatively low strength area, which is the heat affected zone (HAZ).

[0045] Specifically, bonding wires are an important structural material in semiconductor packaging, used to achieve electrical connection between the connection points (bonding points) of the circuit inside the chip and the internal contact points of the lead frame when assembling semiconductor devices and integrated circuits. It is usually a fine metal wire with excellent thermal conductivity, electrical and mechanical properties, as well as excellent chemical stability.

[0046] Depending on the raw materials, bonding wires can be divided into aluminum wire, copper wire, gold wire, silver wire and various alloy wires. Different types of bonding wires differ in performance, cost and application scenarios.

[0047] Bonding wire is widely used in the microelectronics industry, especially in traditional packaging processes such as semiconductor integrated circuits, sensors, and optoelectronics, where it plays a key role as a core material.

[0048] Bonding is a technology that directly combines two homogeneous or heterogeneous semiconductor materials with clean and atomically flat surfaces under certain conditions after surface cleaning and activation. This technology bonds the wafers together through van der Waals forces, molecular forces, and even atomic forces.

[0049] The bonding process usually includes multiple steps, such as ball burning, primary welding, wire arching, secondary welding and tail retention. Among them, ball burning is a form of arc ignition, which uses the heat generated instantly by the high-voltage arc to melt the end of the bonding wire into a spherical shape for the subsequent first bonding process. In this process, the high-voltage arc not only melts the end of the bonding wire into a spherical shape, but also increases the temperature near the ball end and coarsens the grains through heat conduction, forming a relatively low-strength area, namely the heat-affected zone (HAZ).

[0050] The length of the heat-affected zone directly determines the bonding arc height and bonding strength, and is an extremely important indicator of bonding wires. The shorter the heat-affected zone, the lower the arc that can be formed during bonding, the smaller the space occupied, and the higher the bonding strength.

[0051] At present, the method for measuring the length of HAZ after the bonding wire melt ball is microscopic observation. The bonding wire is mounted, polished, and corroded to prepare a metallographic sample or an electron microscope observation sample. The length of HAZ is determined by observing the grain size in the axial microstructure of the bonding wire.

[0052] The method of measuring the HAZ length by directly observing the radial grain size of the bonding wire requires a high level of sample preparation, and as the diameter of the bonding wire decreases, the success rate of sample preparation also decreases, which increases the difficulty of intuitively measuring the HAZ range.

[0053] Based on this, a method for determining the range of a heat-affected zone of a bonding wire after balling is provided in an embodiment of the present application. The bonding wire to be tested is balled based on the selected target balling process parameters. After the balling is completed, the bonding wire to be tested is cut to obtain the bonding wire to be tested after balling. The unballed end of the bonding wire to be tested after balling is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested from the initial measurement point to the spherical end. The hardness of the heat-affected zone of the bonding wire to be tested after balling is different from the hardness of the base material. Some of the multiple measurement points are located in the heat-affected zone. The initial measurement point is located outside the heat-affected zone. The hardness measurement results of the multiple measurement points of the bonding wire to be tested are different from the hardness of the base material. The position of the measuring point is used to determine the range of the heat affected zone of the bonding wire after balling. In this way, the method for determining the range of the heat affected zone of the bonding wire after balling described in the embodiment of the present application directly performs microhardness measurement on the surface of the bonding wire, and makes use of the qualitative relationship between the range of the heat affected zone of the bonding wire after balling and the measured hardness value (due to the influence of heat during balling, the structure of the material in the heat affected zone changes, thereby causing changes in its hardness, strength and other properties). By observing the change in the indentation size during the microhardness measurement, the range of the heat affected zone of the bonding wire after balling is obtained. There is no need to observe the radial grain size of the bonding wire. The difference in hardness values ​​between the HAZ and the base material is used to achieve the determination of the HAZ range, which eliminates the microstructure sample preparation process, simplifies the measurement process, and improves the measurement success rate.

[0054] Please refer to Figure 1 , Figure 1 A flow chart of a method for determining the range of a heat-affected zone after sintering of a bonding wire according to an embodiment of the present application is shown.

[0055] like Figure 1 As shown, the method for determining the range of the heat-affected zone after the bonding wire is sintered comprises the following steps S101-S103:

[0056] S101, performing ball burning treatment on the bonding wire to be tested based on the selected target ball burning process parameters, and after the ball burning is completed, cutting the bonding wire to be tested to obtain the bonding wire to be tested after ball burning;

[0057] S102, clamping and fixing the unburned ball end of the bonding wire to be tested after the ball sintering, and performing a microhardness test using a microhardness tester to obtain hardness measurement results of multiple measuring points of the bonding wire to be tested from the initial measuring point to the ball end; wherein the hardness of the heat-affected zone of the bonding wire to be tested after the ball sintering is different from the hardness of the base material; some of the multiple measuring points are located in the heat-affected zone; and the initial measuring point is located outside the heat-affected zone;

[0058] S103, determining the range of the heat affected zone of the bonding wire after ball sintering based on the positions of the measurement points with different hardness from the base material in the hardness measurement results of the multiple measurement points of the bonding wire to be tested.

[0059] In the step S101, the bonding wire to be tested is subjected to a ball-sintering process based on the selected target ball-sintering process parameters. After the ball-sintering process is completed, the bonding wire to be tested is cut to obtain the ball-sintered bonding wire to be tested.

[0060] In the embodiment of the present application, the diameter of the bonding wire to be tested is ≥20 μm.

[0061] In other words, the diameter of the bonding wire to be tested must be ≥20μm, so that the microhardness tester can be used to test the hardness of the bonding wire to be tested, and the change trend of the radial hardness value of the bonding wire can be analyzed to determine the length of the heat affected zone after the molten ball.

[0062] Microhardness testing calculates the hardness value by applying a certain load to the surface of the material and then measuring the diagonal length of the indentation. When the diameter of the bonding wire is too thin, the indentation may not be accurately formed or measured because the size of the indentation may be close to or smaller than the diameter of the bonding wire itself, resulting in increased test errors. In addition, too thin bonding wires are more likely to deform when subjected to load, which will also affect the accuracy of hardness testing.

[0063] Moreover, for bonding wires with too thin a diameter, it becomes more difficult to clamp and stabilize the test piece, which may lead to more unstable factors during the test and further affect the accuracy of the test results.

[0064] Therefore, the method for determining the range of the heat-affected zone after the bonding wire is sintered as described in the embodiment of the present application is applicable to bonding wires with a diameter greater than or equal to 20 μm. If the diameter of the bonding wire is too thin, other measurement methods should be considered to determine the range of the heat-affected zone.

[0065] The heat affected zone is also called the HAZ area.

[0066] Specifically, appropriate ball burning process parameters are selected to perform ball burning treatment on the bonding wire to be measured.

[0067] Different types of bonding wires, due to differences in their materials (such as gold, silver, copper, alloys, etc.) and diameters or thicknesses, will significantly affect key process parameters such as the temperature and time required for sintering.

[0068] For example, for bonding wires with softer materials, such as certain alloy materials, lower heating temperatures and shorter heating times may be required to avoid deformation or damage to the material due to overheating; while for bonding wires with harder materials, such as pure gold or silver, higher temperatures and longer heating times may be required to ensure uniform formation of the sphere. In addition, the thickness of the bonding wire is also an important consideration. Thinner bonding wires may be more susceptible to heat, so more finely controlled heating parameters are required to prevent breakage caused by thermal stress concentration.

[0069] Therefore, in actual operation, technicians need to select appropriate sintering process parameters according to the specific material and thickness of the bonding wire, combined with previous experience and experimental data, including the selection of heating equipment, setting of heating temperature, control of heating time, etc.

[0070] In the method for determining the range of the heat-affected zone of the bonding wire after the ball burning described in the embodiment of the present application, after the ball burning is completed, the bonding wire to be tested is cut off, including:

[0071] After the ball burning is completed, the bonding wire to be tested is cut off from the splitter, and the length of the cut-off point from the ball burning point is determined according to the fixture size of the microhardness tester.

[0072] After the ball burning is completed, the technician needs to carefully remove the bonding wire to be tested from the splitter and select a suitable position for cutting. The length from the cutting point to the ball burning is not determined arbitrarily, but needs to be accurately calculated based on the fixture size of the microhardness tester.

[0073] The fixture design of the microhardness tester has its specific size limitations, which determine the size of the sample that can be placed in the fixture for testing. In order to ensure that the heat affected zone (HAZ) of the bonding wire to be tested can be fully exposed in the test area of ​​the hardness tester, this distance should be long enough to ensure that after truncation, the burnt ball and the surrounding heat affected zone can be completely retained on the test section. At the same time, the size limitations of the fixture should also be taken into account to avoid the test section being too long to fit into the fixture.

[0074] Therefore, in actual operation, the length of the cutoff point from the sintered ball is determined according to the fixture size of the microhardness tester to ensure that the HAZ area of ​​the bonding wire to be tested can be fully exposed in the test area of ​​the hardness tester, providing accurate and reliable samples for subsequent HAZ area range determination.

[0075] In the step S102, the unburned ball end of the bonding wire to be tested after the ball is sintered is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested from the initial measurement point to the ball end; wherein the hardness of the heat affected zone of the bonding wire to be tested after the ball is sintered is different from the hardness of the base material; some of the multiple measurement points are located in the heat affected zone; and the initial measurement point is located outside the heat affected zone.

[0076] The hardness of the heat-affected zone of the tested bonding wire after sintering is different from the hardness of the base material. Specifically, the hardness of the heat-affected zone is lower than the hardness of the base material.

[0077] In this way, the multiple measuring points include measuring points on the base material and measuring points in the heat affected zone. The hardness of the measuring points on the base material and the measuring points in the heat affected zone are different. Therefore, based on the qualitative relationship between the range of the heat affected zone of the bonding wire after ball burning and the hardness value, the range of the heat affected zone of the bonding wire after ball burning is determined.

[0078] For details, please refer to Figure 2 , Figure 2 A schematic diagram of the process of performing a microhardness test using a microhardness tester according to an embodiment of the present application is shown.

[0079] Please refer to Figure 3 , Figure 3 A flow chart of a method for performing microhardness testing using a microhardness tester according to an embodiment of the present application is shown.

[0080] like Figure 3 As shown, the unburned ball end of the bonding wire to be tested after the ball is burned is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested from the initial measurement point to the ball end, including the following steps S301-S303:

[0081] S301, determining an initial measurement point at a position of a first preset length from the ball-shaped end of the bonding wire to be measured, and then determining the measurement points of the bonding wire to be measured in sequence in the direction of the ball-shaped end of the bonding wire to be measured according to the first measurement interval and measuring the hardness value to determine the hardness measurement result of each measurement point; the hardness measurement result of the initial measurement point is the hardness measurement result of the base material;

[0082] S302, when it is determined that the first comparison result between the hardness measurement results of adjacent measurement points meets the preset change condition, sequentially determine the measurement points of the bonding wire to be measured according to the second measurement interval toward the unburned ball end of the bonding wire to be measured, and measure the hardness value;

[0083] S303. When it is determined that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material, the measurement is stopped to obtain the final measurement point.

[0084] The first preset length may be B mm.

[0085] Reference Figure 2 The unsintered ball end of the bonding wire 200 to be tested is clamped and fixed for microhardness test. The initial measuring point 202 is B mm away from the ball end, and then the ball end 201 is radially ( Figure 2 The hardness values ​​are measured in sequence (from right to left in the middle), and the measurement is performed once every aμm. When the hardness value of the measuring point 202 is found to have changed significantly (as shown by a significant change in the indentation size), the measurement interval is reduced to bμm, and the measurement is performed in the opposite direction ( Figure 2 When the hardness value is found to be restored to the same level as the base material hardness (as shown by the final indentation size being similar to the initial indentation size), stop the measurement.

[0086] In the embodiment of the present application, in the method for determining the range of the heat affected zone after the bonding wire is sintered, the first measurement interval is 5-10 times the second measurement interval.

[0087] The distance B from the ball-shaped end of the bonding wire to be measured is generally in the range of 0.2 to 0.5 mm, while the first measurement interval a and the second measurement interval b are in the micrometer level (a is about 50 micrometers).

[0088] In the method for measuring the range of the heat-affected zone after the bonding wire is sintered as described in the embodiment of the present application, the smaller the first measurement interval and the second measurement interval are, the higher the measurement accuracy of the range of the heat-affected zone is.

[0089] The first comparison result between the hardness measurement results of adjacent measurement points in step S302 is judged to meet the preset change condition, that is, after the hardness value is found to have changed significantly, it can also be found through observation that the indentation size has changed significantly.

[0090] Specifically, the hardness value changes significantly, which is manifested as a decrease of 10 to 20 HV.

[0091] Based on this, please refer to Figure 4 , Figure 4 A flow chart of a method for determining whether a first comparison result between hardness measurement results of adjacent measurement points meets a preset change condition in an embodiment of the present application is shown.

[0092] like Figure 4 As shown, in the method for determining the range of the heat affected zone of the bonding wire after sintering balling described in the embodiment of the present application, the first comparison result between the hardness measurement results of adjacent measurement points is judged to meet the preset change condition, including the following steps S401-S402:

[0093] S401, determining whether the difference between the hardness values ​​of adjacent measuring points is greater than a first preset threshold;

[0094] S402: If greater than, determine that the first comparison result between the hardness measurement results of adjacent measurement points meets a preset change condition.

[0095] Here, exemplarily, the first preset threshold is 10HV.

[0096] Please refer to Figure 5 , Figure 5 A flow chart of a method for determining whether the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material according to an embodiment of the present application is shown;

[0097] In some embodiments, Figure 5 As shown, in the method for determining the range of the heat affected zone of the bonding wire after sintering of the bonding wire according to the embodiment of the present application, the step of determining whether the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material includes the following steps S501-S503:

[0098] S501, obtaining and determining the hardness value of the latest measurement point and the hardness value of the initial measurement point;

[0099] S502, determining whether the difference between the hardness values ​​of the latest measurement point and the initial measurement point is less than a second preset threshold;

[0100] S503: If yes, determine that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material.

[0101] In the embodiment of the present application, a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested. The left-first-right-then measurement method is adopted, that is, first measuring with a large interval distance and then approximating with a small interval distance. This method can reduce the number of hardness points measured while ensuring measurement accuracy, thereby improving efficiency.

[0102] In some embodiments, of course, if the first measurement a is set small enough, a unidirectional measurement method can be used, that is, direct measurement with a small interval distance. In this case, there is no need to set the b parameter, but the workload during testing will be greatly increased.

[0103] Whether the difference between the hardness values ​​of the latest measurement point and the initial measurement point is less than a second preset threshold value, the second preset threshold value is very small, and is 0.5 HV as an example only.

[0104] When the difference between the hardness values ​​of the latest measurement point and the initial measurement point is less than the second preset threshold, it indicates that the hardness values ​​of the latest measurement point and the initial measurement point are substantially consistent.

[0105] In the step S103, based on the positions of the measurement points with different hardness from the base material in the hardness measurement results of the multiple measurement points of the bonding wire to be tested, the range of the heat affected zone of the bonding wire after ball sintering is determined.

[0106] Specifically, in the method for determining the range of the heat affected zone of the bonding wire after balling described in the embodiment of the present application, the determination of the range of the heat affected zone of the bonding wire after balling based on the position of the measurement point with different hardness from the base material in the hardness measurement results of multiple measurement points of the bonding wire to be measured includes:

[0107] The distance between the final measuring point and the spherical end is determined as the length of the heat affected zone of the bonding wire after sintering.

[0108] Specifically, after the test is completed, based on the target measurement distance and the second measurement distance, the range of the heat affected zone after the bonding wire is sintered is determined to be greater than the difference between the target measurement distance and the second measurement distance, and less than the target measurement distance.

[0109] In other words, when the distance A between the final measuring point and the spherical end is measured by a microhardness tester, the length of the HAZ is approximately between Ab and A.

[0110] Since the value of b is very small, the length of the heat affected zone after the bonding wire is sintered is determined to be A, and its error meets the error requirements.

[0111] In other words, the second measuring distance b can be set based on the error requirement of the range of the heat-affected zone.

[0112] It should be noted that since the surface of the bonding wire is a cylindrical surface, the reading directly measured by the hardness tester is not the actual hardness value of the bonding wire, but it does not affect the change trend of the hardness value, so it will not affect the accuracy of the HAZ range measurement method proposed in this scheme. If the actual hardness value of the bonding wire is required, refer to the curved surface hardness measurement method in "GB / T4340.1-2009 Vickers Hardness Test Method" and obtain the actual hardness value of the material by adding a correction factor.

[0113] Based on this, the method for determining the range of the heat affected zone after the bonding wire is sintered described in the embodiment of the present application further includes:

[0114] Based on the hardness value of the base material measured by the microhardness tester, a preset hardness correction coefficient and a hardness correction rule, the hardness value of the base material is corrected to obtain a corrected hardness value of the base material;

[0115] Based on the hardness measurement results, hardness values, preset hardness correction coefficients and hardness correction rules of the measurement points in the heat affected zone measured by the microhardness tester, the hardness value of the heat affected zone is corrected to obtain the corrected hardness value of the heat affected zone.

[0116] Here, the number of measurement points in the heat affected zone may be one or more.

[0117] Correspondingly, the corrected hardness value of the heat affected zone may be one or more.

[0118] When there are multiple corrected hardness values ​​of the heat affected zone, the corresponding measurement points are evenly distributed along different positions of the heat affected zone. Therefore, the multiple hardness values ​​comprehensively reflect the hardness changes of the heat affected zone, thereby providing a deeper understanding of the hardness characteristics of the heat affected zone and its differences from the base material.

[0119] A specific measurement example is described below.

[0120] Taking silver bonding wire as an example, the initial measurement point is 0.3mm away from the spherical end, and then the hardness value is measured in sequence along the radial direction of the spherical end, with a measurement every 50μm. The hardness value of the original base material of the bonding wire is about 80HV (the hardness value converted after querying the national standard correction coefficient, and the subsequent hardness values ​​are all corrected hardness values). When the hardness value is found to be reduced to about 65HV, the measurement interval is reduced to 10μm, and the measurement is carried out in the opposite direction. When the hardness value is found to be restored to the same level as the base material hardness, the measurement is stopped, and the distance A between the final hardness measurement point and the spherical end is measured using a microhardness tester, which is the length of the HAZ.

[0121] In some embodiments, the method for determining the range of the heat affected zone after the bonding wire is sintered further includes:

[0122] Based on different selected ball firing process parameters, the range of the heat affected zone of the bonding wire to be tested is measured to obtain the range of the heat affected zone of the bonding wire to be tested under different ball firing process parameters;

[0123] Based on the range of the heat-affected zone under the different ball-sintering process parameters, the ball-sintering process parameters for the bonding wire to be tested are optimized to obtain optimized ball-sintering process parameters.

[0124] According to product requirements and actual application scenarios, determine the optimization target of the heat-affected zone range, such as minimizing the length of the heat-affected zone to improve bonding strength and reliability.

[0125] Specifically, according to the measurement and analysis results, the ball firing process parameters are adjusted, such as reducing the ball firing current, shortening the ball firing time or adjusting the protective gas flow rate, so as to obtain different ball firing process parameters to achieve the optimization goal.

[0126] By optimizing the sintering process parameters, the length of the heat-affected zone can be significantly reduced, thereby improving the mechanical properties and reliability of the bonding wire and increasing the bonding strength; reducing the scrap rate and rework rate caused by improper process parameters and reducing production costs.

[0127] The method for determining the range of the heat affected zone of the bonding wire after balling described in the embodiment of the present application directly performs microhardness measurement on the surface of the bonding wire, and uses the qualitative relationship between the range of the heat affected zone of the bonding wire after balling and the measured hardness value (due to the influence of heat during balling, the structure of the material in the heat affected zone changes, thereby causing changes in its hardness, strength and other properties). By observing the change in the indentation size during the microhardness measurement, the range of the heat affected zone of the bonding wire after balling is obtained. There is no need to observe the radial grain size of the bonding wire. The difference in hardness values ​​between the HAZ and the base material is used to achieve the determination of the HAZ range, which eliminates the process of preparing microstructure samples, simplifies the measurement process, and improves the measurement success rate.

[0128] Furthermore, the method for determining the range of the heat affected zone of the bonding wire after ball sintering described in the embodiment of the present application uses a microhardness tester to perform a microhardness test. When obtaining the hardness measurement results of multiple measurement points of the bonding wire to be tested, a left-first-right-then measurement method is adopted, that is, first measuring with a large interval distance and then approximating with a small interval distance. This method can reduce the number of hardness points measured while ensuring the measurement accuracy, thereby improving efficiency.

[0129] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for determining the range of the heat-affected zone after the bonding wire is sintered, characterized in that: The range determination method comprises: Based on the selected target ball firing process parameters, the bonding wire to be tested is subjected to ball firing treatment. After the ball firing is completed, the bonding wire to be tested is cut off to obtain the bonding wire to be tested after ball firing; The unburned ball end of the bonding wire to be tested after ball sintering is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measuring points of the bonding wire to be tested from the initial measuring point to the ball end; wherein the hardness of the heat-affected zone of the bonding wire to be tested after ball sintering is different from the hardness of the base material; some of the multiple measuring points are located in the heat-affected zone; and the initial measuring point is located outside the heat-affected zone; Based on the positions of the measurement points with different hardness from the base material in the hardness measurement results of the multiple measurement points of the bonding wire to be tested, the range of the heat affected zone of the bonding wire after ball sintering is determined.

2. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 1, characterized in that: The unburned ball end of the bonding wire to be tested after the ball is burned is clamped and fixed, and a microhardness test is performed using a microhardness tester to obtain hardness measurement results of multiple measurement points of the bonding wire to be tested from the initial measurement point to the ball end, including: An initial measurement point is determined at a position of a first preset length from the ball-shaped end of the bonding wire to be measured, and then the measurement points of the bonding wire to be measured are determined in sequence in the direction of the ball-shaped end of the bonding wire to be measured according to the first measurement interval and hardness values ​​are measured to determine the hardness measurement result of each measurement point; the hardness measurement result of the initial measurement point is the hardness measurement result of the base material; When it is determined that the first comparison result between the hardness measurement results of adjacent measurement points meets the preset change condition, the measurement points of the bonding wire to be measured are determined in sequence according to the second measurement interval toward the unburned ball end of the bonding wire to be measured, and the hardness value is measured; When it is determined that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material, the measurement is stopped to obtain the final measurement point.

3. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 2, characterized in that: The step of determining the range of the heat affected zone of the bonding wire after ball sintering based on the position of the measurement point with different hardness from the base material in the hardness measurement results of the multiple measurement points of the bonding wire to be tested comprises: The distance between the final measuring point and the spherical end is determined as the length of the heat affected zone of the bonding wire after sintering.

4. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 2, characterized in that: The first measurement interval is 5-10 times the second measurement interval.

5. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 4, characterized in that: The smaller the first measurement interval and the second measurement interval are, the higher the measurement accuracy of the range of the heat affected zone is.

6. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 2, characterized in that: The step of determining that the first comparison result between the hardness measurement results of adjacent measurement points meets the preset change condition includes: Determine whether the difference between the hardness values ​​of adjacent measuring points is greater than a first preset threshold; If it is greater than, it is determined that the first comparison result between the hardness measurement results of adjacent measuring points meets the preset change condition.

7. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 2, characterized in that: The method of determining that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material comprises: Obtain and determine the hardness value of the latest measurement point and the hardness value of the initial measurement point; Determine whether the difference between the hardness values ​​of the latest measurement point and the initial measurement point is less than a second preset threshold; If so, it is determined that the hardness measurement result of the latest measurement point is restored to the hardness measurement result of the base material.

8. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 2, characterized in that: The range determination method further comprises: Based on the hardness value of the base material measured by the microhardness tester, a preset hardness correction coefficient and a hardness correction rule, the hardness value of the base material is corrected to obtain a corrected hardness value of the base material; Based on the hardness measurement results, hardness values, preset hardness correction coefficients and hardness correction rules of the measurement points in the heat affected zone measured by the microhardness tester, the hardness value of the heat affected zone is corrected to obtain the corrected hardness value of the heat affected zone.

9. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 1, characterized in that: The range determination method further comprises: Based on different selected ball firing process parameters, the range of the heat affected zone of the bonding wire to be tested is measured to obtain the range of the heat affected zone of the bonding wire to be tested under different ball firing process parameters; Based on the range of the heat-affected zone under the different ball-sintering process parameters, the ball-sintering process parameters for the bonding wire to be tested are optimized to obtain optimized ball-sintering process parameters.

10. The method for determining the range of the heat affected zone after the bonding wire is sintered according to claim 1, characterized in that: After the ball burning is completed, the bonding wire to be tested is cut off, including: After the ball burning is completed, the bonding wire to be tested is cut off from the splitter, and the length of the cut-off point from the ball burning point is determined according to the fixture size of the microhardness tester.

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