Board-level SMD packaging high-temperature point bending equivalent life test method

Abstract

The invention discloses a board-level SMD packaging high-temperature point bending equivalent life test method, and relates to the technical field of electronic packaging, and the method comprises the steps: designing a board-level SMD packaging high-temperature point bending test board; carrying out board-level SMD packaging strain analysis under conventional temperature circulation to obtain a conventional temperature circulation strain difference characteristic value; carrying out board-level SMD packaging strain analysis under a high-temperature point bending condition to obtain a high-temperature point bending strain difference characteristic value; based on the conventional temperature cyclic strain difference characteristic value, the high-temperature point bending strain difference characteristic value and the life model, obtaining a high-temperature point bending acceleration factor; and obtaining a board-level SMD packaging high-temperature point bending equivalent life test scheme based on the high-temperature point bending acceleration factor. The problems that in the prior art, the testing period is long, the efficiency is low, and the comprehensive stress borne by the packaging body in actual use cannot be comprehensively simulated are solved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging, and in particular to a high-temperature point bending equivalent life test method for a board-level SMD package. Background Art

[0002] As electronic products develop towards high performance and miniaturization, SMD (surface mount device) packaging has become one of the most commonly used packaging methods for electronic components. SMD packaging has the advantages of high density, low weight and high reliability, and is widely used in various electronic products such as integrated circuits, sensors, and communication equipment. However, as the functions of electronic products become increasingly complex, especially the reliability requirements under environmental conditions such as high temperature and mechanical stress continue to increase, higher requirements are placed on the reliability testing of SMD packages.

[0003] At present, the reliability verification of SMD packages is mainly carried out through temperature cycle tests, which simulate the thermal stress and thermal expansion effects that SMD packages may encounter in actual working environments by cycling between different temperatures. Temperature cycle tests are widely used to evaluate the heat resistance of solder joints and packages, and to verify whether they can maintain normal functions and structural stability during long-term use.

[0004] However, existing temperature cycling tests have many limitations: (1) Long test cycle and low efficiency. The temperature cycle test cycle is long and requires multiple high and low temperature cycles, which not only wastes a lot of time, but also has low efficiency when verifying multiple processes or design solutions.

[0005] (2) It is difficult to simulate the comprehensive stress that the package is subjected to in actual use. Conventional temperature cycle tests mainly focus on the impact of thermal stress on the SMD package, and cannot fully simulate the impact of mechanical stress (such as bending stress and vibration stress) on solder joints and the package, resulting in inaccurate actual reliability assessment of the package in some cases.

[0006] (3) Unable to quickly screen and verify process parameters. Since the temperature cycle test cycle is long and mainly focuses on the impact of thermal cycles, the optimization and screening process of process parameters requires a long period of testing and analysis. The time consumption of conventional test methods leads to bottlenecks in the R&D process, reducing overall productivity and market response speed.

[0007] (4) It is impossible to accurately evaluate the durability of solder joints at high temperatures. In temperature cycle tests, thermal stress is mainly applied to solder joints through temperature changes, but no in-depth evaluation is conducted on stress concentration and fatigue issues at solder joints at high temperatures. Summary of the invention

[0008] In view of the above-mentioned deficiencies in the prior art, the present invention provides a board-level SMD package high-temperature point bending equivalent life test method that solves the limitations of the existing temperature cycle test.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a board-level SMD package high temperature point bending equivalent life test method, comprising the following steps: S1: Design board-level SMD package high temperature point bending test board; S2: Based on the board-level SMD package high temperature point bending test board, the board-level SMD package strain analysis under conventional temperature cycle is carried out to obtain the conventional temperature cycle strain difference characteristic value; S3: Based on the board-level SMD package high-temperature point bending test board, the board-level SMD package strain analysis under high-temperature point bending conditions is carried out to obtain the high-temperature point bending strain difference characteristic value; S4: Based on the conventional temperature cycle strain difference characteristic value, the high temperature point bending strain difference characteristic value and the life model, the high temperature point bending acceleration factor is obtained; S5: Based on the high temperature point bending acceleration factor, the board-level SMD package high temperature point bending equivalent life test plan is obtained.

[0010] Furthermore, the board-level SMD package high-temperature spot bending test board in S1 includes fixing holes, an SMD array and a stress application area.

[0011] Furthermore, S2 includes the following sub-steps: S21: Establish the finite element model of the board-level SMD package high temperature point bending test board; S22: Setting the temperature profile under conventional temperature cycle; S23: Place the finite element model of the board-level SMD package high-temperature spot bending test board in the temperature field of the temperature profile under conventional temperature cycling, and calculate the characteristic value of the conventional temperature cycle strain difference , the formula is:

[0012]

[0013] in, For the The highest and lowest temperature strain difference characteristic values ​​of the package, For the The highest and lowest temperature strain difference characteristic values ​​of the package solder joints in the package, is the total number of packages in the SMD array.

[0014] Furthermore, S3 includes the following sub-steps: S31: Establish the finite element model of the board-level SMD package high temperature spot bending test board and the indenter; S32: Setting the temperature profile under high temperature point bending conditions; S33: Place the finite element model of the board-level SMD package high-temperature spot bending test board and the pressure head in the temperature field of the temperature profile under the high-temperature spot bending condition, move the pressure head downward according to the set value, and calculate the high-temperature spot bending strain difference characteristic value , the formula is:

[0015]

[0016] in, For the The characteristic value of the strain difference between the highest and lowest points of the package in the package is: For the The strain difference characteristic value of the package solder joint in a package at the highest point and the lowest point of the pressure head.

[0017] Furthermore, the S4 includes the following sub-steps: S41: Calculate the ratio matrix of the conventional temperature cycle strain difference eigenvalue and the high temperature point bending strain difference eigenvalue for:

[0018] S42: Calculate the high temperature point bending acceleration factor based on the ratio matrix and the life model, wherein the life model is:

[0019] in, is the number of life cycles, is the fatigue ductility coefficient, is the fatigue ductility index; The high temperature point bending acceleration factor is:

[0020] in, is the high temperature point bending acceleration factor matrix; High temperature point bending acceleration factor matrix The average value is taken as the high temperature point bending acceleration factor .

[0021] Furthermore, according to the high temperature point bending acceleration factor Equivalent temperature cycle times of board-level SMD package , get the number of stress cycles for:

[0022] Based on the number of stress cycles , obtain the board-level SMD package high temperature point bending equivalent life test plan.

[0023] Compared with the prior art, the present invention proposes a board-level SMD package high temperature point bending equivalent life test method, which significantly improves the reliability evaluation efficiency and accuracy of SMD packages in high temperature environments. The beneficial effects of the present invention are reflected in the following aspects: (1) Significantly shorten the test cycle and improve test efficiency. The present invention uses a high-temperature spot bending test to replace the traditional temperature cycle test. It only takes about 20 seconds to complete a high-temperature spot bending cycle, while the temperature cycle test usually takes more than 20 minutes. It can effectively shorten the test cycle, meet the needs of rapid screening and verification of multiple process parameters, and significantly reduce test time and R&D costs.

[0024] (2) Comprehensively simulate comprehensive stress to improve the accuracy of reliability assessment. The present invention combines finite element analysis with high-temperature spot bending test to comprehensively consider the joint effects of mechanical stress (bending stress) and thermal stress on solder joints and packages under high temperature conditions. It can more realistically reflect the stress response of solder joints and packages in actual working environments, and avoid the reliability assessment deviation caused by traditional temperature cycle tests that ignore mechanical stress.

[0025] (3) Rapid screening and verification of process parameters, supporting parallel verification of multiple schemes. The present invention utilizes the acceleration characteristics of the point bending test, combined with the life model to calculate the equivalent cycle life, to rapidly screen and verify different process parameters, significantly improving the efficiency of process optimization and design scheme verification, and meeting the needs of rapid product iteration.

[0026] (4) Accurately evaluate the durability of solder joints and reduce the risk of failure. The present invention addresses the stress concentration and fatigue problems of solder joints under high temperature conditions. It uses the pressure head displacement control technology to accurately apply mechanical stress and calculate the strain characteristic value. It can discover the potential failure mode of solder joints under the combined action of high temperature mechanical stress and thermal stress, and reduce the reliability risk of products in practical applications.

[0027] (5) Reduced testing costs and wide application range. Since the test method of the present invention can complete high-temperature reliability testing in a relatively short time and does not require complex temperature cycling equipment, the testing cost is significantly reduced. While meeting the requirements for precise testing, it is applicable to various types of SMD packages and test environments and has a wide range of engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention provides a flow chart of a method for testing the equivalent life of a board-level SMD package at a high temperature.

[0029] Figure 2 This is a schematic diagram of the distribution of a typical SMD package test board.

[0030] Figure 3 Schematic diagram of the high temperature spot bending test device for board-level SMD packaging.

[0031] Figure 4 This is a schematic diagram of the SMD package size parameters.

[0032] Figure 5 This is a schematic diagram of the size parameters of the high temperature point bending pressure head.

[0033] Figure 6 This is a single cycle profile of a conventional temperature cycling test.

[0034] Figure 7 It is the environmental temperature profile of high temperature spot bending test.

[0035] Figure 8 This is the displacement profile of the pressure head in the high-temperature point bending test.

[0036] Fig. 9 This is the mesh division diagram of the finite element model of a typical case.

[0037] Among them: 1. Typical SMD package test board; 2. Fixing holes; 3. SMD array; 4. Stress application area. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, a board-level SMD package high temperature point bending equivalent life test method includes the following steps: S1: Design board-level SMD package high temperature point bending test board; S2: Based on the board-level SMD package high temperature point bending test board, the board-level SMD package strain analysis under conventional temperature cycle is carried out to obtain the conventional temperature cycle strain difference characteristic value; S3: Based on the board-level SMD package high-temperature point bending test board, the board-level SMD package strain analysis under high-temperature point bending conditions is carried out to obtain the high-temperature point bending strain difference characteristic value; S4: Based on the conventional temperature cycle strain difference characteristic value, the high temperature point bending strain difference characteristic value and the life model, the high temperature point bending acceleration factor is obtained; S5: Based on the high temperature point bending acceleration factor, the board-level SMD package high temperature point bending equivalent life test plan is obtained.

[0040] The board-level SMD package high-temperature spot bending test board in S1 includes fixing holes 2, an SMD array 3 and a stress application area 4.

[0041] In this embodiment, the SMD devices to be tested are arranged on the board-level SMD package high temperature spot bending test board. The distribution of the typical SMD package test board 1 is as follows: Figure 2As shown, it mainly includes three parts: fixing holes 2, SMD array 3 and stress application area 4. The circuit board is mainly placed as follows Figure 3 The high temperature spot bending test is carried out in the device shown, and the fixing hole 2 is fixed with a standard stud. The circuit board design parameters include the circuit board length l pcbx ,Width l pcby ,thick h pcbz , fixed hole diameter r 1 and the coordinates ( x f1 , y f1 )、( x f2 , y f2 )、( x f3 , y f3 )、( x f4 , y f4 ), etc. The SMD array size parameters include the x-direction spacing d x , y-direction spacing d y , x Number of directions n x , y direction quantity n y The SMD package parameters mainly include package length lx, width ly, thickness lz, solder joint height hsold, standoff height hstand, pad spacing dsold, pad length lxpad, pad width lypad, such as Figure 4 The pressing is performed with a circular pressing head, and the size parameters are the pressing head radius Rind and the pressing head height Hind, as shown in Figure 5 shown.

[0042] The S2 includes the following sub-steps: S21: Establish the finite element model of the board-level SMD package high temperature point bending test board; S22: Setting the temperature profile under conventional temperature cycle; S23: Place the finite element model of the board-level SMD package high-temperature spot bending test board in the temperature field of the temperature profile under conventional temperature cycling, and calculate the characteristic value of the conventional temperature cycle strain difference , the formula is:

[0043]

[0044] in, For the The highest and lowest temperature strain difference characteristic values ​​of the package, For the The highest and lowest temperature strain difference characteristic values ​​of the package solder joints in the package, is the total number of packages in the SMD array.

[0045] In this embodiment, the board-level SMD package strain is analyzed for conventional temperature cycle conditions. First, a finite element model of the board-level SMD package test board is established, including settings such as geometric model, material assignment, mesh division, and boundary conditions; then, the temperature conditions of the conventional temperature cycle are determined, mainly including room temperature as T0, maximum temperature T1, high temperature immersion time t1, minimum temperature T2, low temperature immersion time t2, and temperature change rate v. The temperature profile of the conventional temperature cycle is as follows: Figure 6 As shown, where t11=(T1-T0) / v, t12=t11+t1, t13=t12+(T1-T2) / v, t14=t13+t2, t15=t14+(T0-T2) / v; further, all models are placed in the temperature field of the above temperature profile, and all strain difference eigenvalue matrices of the package body and solder joints in the SMD package at the highest and lowest temperature time points are calculated. , the mean, maximum or minimum value can be selected as the characteristic value. Finally, the highest value U of the vertical displacement of the high-temperature and low-temperature circuit boards in the pressure head area is extracted Ind-1 , minimum value U Ind-2 .

[0046] The S3 includes the following sub-steps: S31: Establish the finite element model of the board-level SMD package high temperature spot bending test board and the indenter; S32: Setting the temperature profile under high temperature point bending conditions; S33: Place the finite element model of the board-level SMD package high-temperature spot bending test board and the pressure head in the temperature field of the temperature profile under the high-temperature spot bending condition, move the pressure head downward according to the set value, and calculate the high-temperature spot bending strain difference characteristic value , the formula is:

[0047]

[0048] in, For the The characteristic value of the strain difference between the highest and lowest points of the package in the package is: For the The strain difference characteristic value of the package solder joint in a package at the highest point and the lowest point of the pressure head.

[0049] In this embodiment, the board-level SMD package strain is analyzed for the high-temperature point bending condition. First, a finite element model of the board-level SMD package test board and the indenter is established, including a geometric model, material assignment, mesh division, boundary conditions, and contact settings; then, the temperature profile of the high-temperature point bending condition is set, mainly using the highest temperature T1, high-temperature immersion time t1, and temperature change rate v that are consistent with step S2. The temperature profile of the high-temperature point bending condition is as follows: Figure 7 As shown, t11=(T1-T0) / v, t12=t11+t1; then, the displacement value of the pressure head is set vertically to the circuit board, and the initial value is selected as 1.5~2 times U Ind-1 , select U for downward displacement Ind-2 , the downward movement time is t3, the displacement holding time is t4, and the displacement curve is as follows Figure 8 As shown, t11=(T1-T0) / v, t12=t11+t1, t21=t12+t3, t22=t21+t4, t23=t22+t3, the temperature is maintained unchanged, and the pressure head bending cycle is repeated; then, all models are placed in the temperature field of the above temperature profile, and the pressure head is moved downward by a displacement U Ind-2 , calculate the eigenvalue matrix of all strain differences between the package body and solder joints at the highest and lowest points of the indenter in the SMD package , you can select the mean, maximum or minimum value as the eigenvalue.

[0050] The S4 comprises the following sub-steps: S41: Calculate the ratio matrix of the conventional temperature cycle strain difference eigenvalue and the high temperature point bending strain difference eigenvalue for:

[0051] S42: Calculate the high temperature point bending acceleration factor based on the ratio matrix and the life model, wherein the life model is:

[0052] in, is the number of life cycles, is the fatigue ductility coefficient (material-dependent), is the fatigue ductility index (material related); The high temperature point bending acceleration factor is:

[0053] in, is the high temperature point bending acceleration factor matrix; High temperature point bending acceleration factor matrix The average value is taken as the high temperature point bending acceleration factor .

[0054] According to the high temperature point bending acceleration factor Equivalent temperature cycle times of board-level SMD package , get the number of stress cycles for:

[0055] Based on the number of stress cycles , obtain the board-level SMD package high temperature point bending equivalent life test plan.

[0056] The board-level SMD package high temperature point bending equivalent life test plan is shown in Table 1: Table 1 Board-level SMD package high temperature point bending equivalent life test plan

[0057] Through this technical solution, the present invention can provide an efficient and accurate high-temperature reliability testing method for SMD packages. Since the high-temperature point bending cycle can be completed in 20 seconds at the shortest, while the temperature cycle usually takes more than 20 minutes, by quickly applying stress and with a clear equivalent relationship, the problems of high cost, long cycle and limitations in the prior art can be solved, and it has broad application prospects.

[0058] In one embodiment of the present invention, the specific operation process of the board-level SMD package high temperature point bending equivalent life test method is as follows: S1: Design a board-level SMD package high temperature point bending test board.

[0059] 1) Test board structure design Design a test plate suitable for high temperature spot bending test (such as Figure 2 The SMD device array to be tested is arranged on the test board, and the key parameters are as follows: Circuit board: Circuit board length l pcbx = 40mm, width l pcby = 40mm, thick h pcbz = 2mm; Fixing hole: hole diameter r 1 = 2.0 mm and coordinates (4 mm, 4 mm), (36 mm, 4 mm), (36 mm, 36mm), (4 mm, 36 mm); SMD array: x-direction spacing d x = 6.0 mm, y-direction spacing d y= 6.0 mm, x Number of directions n x = 5, number in y direction n y =5; SMD package: package length lx = 2.0 mm, width ly = 1.27 mm, thickness lz = 0.5 mm, solder joint height hsold = 0.5 mm, standoff height hstand = 0.2 mm, pad spacing dsold = 1.2 mm, pad length lxpad = 0.8 mm, pad width lypad = 1.4 mm; Circular indenter: indenter radius Rind = 1.0 mm, indenter height Hind = 2.0 mm.

[0060] 2) Test equipment The test device includes a bracket for fixing the test plate, a loading mechanism for an adjustable pressure head, and a heating device. The bracket fixes the four fixed points of the test plate, and the pressure head is vertically aligned with the center area of ​​the test plate. The heating device uses a constant temperature heating box, which can stably control the test environment temperature at T1=150°C.

[0061] S2: Based on the board-level SMD package high temperature spot bending test board, the board-level SMD package strain analysis under conventional temperature cycle is carried out to obtain the conventional temperature cycle strain difference characteristic value.

[0062] 1) Finite element model establishment A three-dimensional geometric model of the test board is established, and material properties are assigned to the test board and SMD package. The PCB board is made of FR4 material, the SMD solder joint is SAC305, and the package is made of barium titanate ceramic. Using commercial finite element analysis software, the mesh is divided as follows Fig. 9 The boundary conditions are set to be fixed at the four corners of the test board, and the remaining SMD package and SMD solder joints, SMD solder joints and PCB boards are all bound.

[0063] 2) Temperature cycle conditions The temperature profile of the temperature cycle is defined as follows: room temperature T0 = 25 °C, maximum temperature T1 = 150 °C, minimum temperature T2 = −40 °C, heating rate v = 20 °C / min, high temperature immersion time t1 = 15 min, low temperature immersion time t2 = 15 min, and a single cycle time of 48 min.

[0064] Calculate the eigenvalue matrix of all strain differences of the package body and solder joints at the highest and lowest temperature time points in the SMD package , here we select the maximum value as the eigenvalue, and the calculation results of the eigenvalue matrix are shown in Table 2: Table 2 Eigenvalue matrix Calculation results

[0065] Extract the maximum vertical displacement value U of the high-temperature and low-temperature circuit boards in the pressure head area Ind-1 = 0.1105mm, minimum value U Ind-2 = -0.0451 mm.

[0066] S3: Based on the board-level SMD package high-temperature spot bending test board, the board-level SMD package strain analysis under high-temperature spot bending conditions is carried out to obtain the high-temperature spot bending strain difference characteristic value.

[0067] 1) Finite element model establishment On the basis of the finite element model of the board-level SMD package test board established above, a finite element model of the indenter is added, which is located just above the board-level SMD package test board, and the contact is set to a general contact type.

[0068] 2) High temperature bending cycle conditions The high temperature spot bending cycle conditions are defined as follows: room temperature T0 = 25°C, maximum temperature T1 = 150°C, heating rate v = 20°C / min, high temperature immersion time t1 = 15 min, and the overall time is t12 = t11 + t1 = (T1-T0) / v + t1 = 21.25 min. After that, the high temperature spot bending test is carried out while maintaining the highest temperature T1 level. The initial position of the indenter is at 2 times the U Ind-1 , that is, at 0.221mm, the downward displacement is selected as U Ind-2 = -0.0451 mm, downward movement time t3 = 5s, displacement holding time t4 = 10s, upward movement t3 = 5s and then lift to the initial position of the pressure head, the high temperature level remains unchanged and the point bending is applied reciprocally periodically.

[0069] Calculate the eigenvalue matrix of all strain differences between the package body and solder joints at the highest and lowest points of the indenter in the SMD package , here we select the maximum value as the eigenvalue, and the eigenvalue matrix is ​​shown in Table 3 below: Table 3 Eigenvalue matrix Calculation results

[0070] S4: Based on the conventional temperature cycle strain difference characteristic value, the high temperature point bending strain difference characteristic value and the life model, the high temperature point bending acceleration factor is obtained.

[0071] Calculate the ratio matrix of the conventional temperature cycle strain difference eigenvalue and the high temperature point bending strain difference eigenvalue As shown in Table 4 below: Table 4 Ratio matrix Calculation results

[0072] Then, based on the life model, the acceleration factor matrix of the conventional temperature cycle test and the high temperature spot bending test can be calculated: As shown in Table 5 below: Table 5 Acceleration factor matrix Calculation results

[0073] Finally, calculate Average value as acceleration factor =7.9355.

[0074] S5: Based on the high temperature point bending acceleration factor, the board-level SMD package high temperature point bending equivalent life test plan is obtained.

[0075] Combined acceleration factor Value, it is known that the SMD life device undergoes the above equivalent temperature cycle = 10000 times, the total time of conventional temperature cycle is 480000 min, and through the board-level SMD package high temperature point bending equivalent life test, the stress cycle is times, the calculation formula is:

[0076] The board-level SMD package high temperature point bending equivalent life test plan is shown in Table 6: Table 6 Results of the board-level SMD package high temperature point bending equivalent life test program

[0077] It can be calculated that the total test duration is 1588375 s, which is approximately 26472.92 min, greatly shortening the test duration.

[0078] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the invention.

Claims

1. A board-level SMD package high temperature point bending equivalent life test method, characterized in that: The following steps are involved: S1: Design board-level SMD package high temperature point bending test board; S2: Based on the board-level SMD package high temperature point bending test board, the board-level SMD package strain analysis under conventional temperature cycle is carried out to obtain the conventional temperature cycle strain difference characteristic value; S3: Based on the board-level SMD package high-temperature point bending test board, the board-level SMD package strain analysis under high-temperature point bending conditions is carried out to obtain the high-temperature point bending strain difference characteristic value; S4: Based on the conventional temperature cycle strain difference characteristic value, the high temperature point bending strain difference characteristic value and the life model, the high temperature point bending acceleration factor is obtained; S5: Based on the high temperature point bending acceleration factor, the board-level SMD package high temperature point bending equivalent life test plan is obtained.

2. A board-level SMD package high temperature point bending equivalent life test method according to claim 1, characterized in that: The S1 medium-level SMD package high-temperature spot bending test board comprises a fixing hole (2), an SMD array (3) and a stress application area (4).

3. A board-level SMD package high temperature point bending equivalent life test method according to claim 1, characterized in that: The S2 includes the following sub-steps: S21: Establish the finite element model of the board-level SMD package high temperature point bending test board; S22: Setting the temperature profile under conventional temperature cycle; S23: Place the finite element model of the board-level SMD package high-temperature spot bending test board in the temperature field of the temperature profile under conventional temperature cycling, and calculate the characteristic value of the conventional temperature cycle strain difference , the formula is: in, For the The highest and lowest temperature strain difference characteristic values ​​of the package in the package, For the The highest and lowest temperature strain difference characteristic values ​​of the package solder joints in the package, is the total number of packages in the SMD array.

4. A board-level SMD package high temperature point bending equivalent life test method according to claim 3, characterized in that: The S3 includes the following sub-steps: S31: Establish the finite element model of the board-level SMD package high temperature spot bending test board and the indenter; S32: Setting the temperature profile under high temperature point bending conditions; S33: Place the finite element model of the board-level SMD package high-temperature spot bending test board and the pressure head in the temperature field of the temperature profile under the high-temperature spot bending condition, move the pressure head downward according to the set value, and calculate the high-temperature spot bending strain difference characteristic value , the formula is: in, For the The characteristic value of the strain difference between the highest and lowest points of the package in the package is: For the The strain difference characteristic value of the package solder joint in a package at the highest point and the lowest point of the pressure head.

5. A board-level SMD package high temperature point bending equivalent life test method according to claim 4, characterized in that: The S4 includes the following sub-steps: S41: Calculate the ratio matrix of the conventional temperature cycle strain difference eigenvalue and the high temperature point bending strain difference eigenvalue for: S42: Calculate the high temperature point bending acceleration factor based on the ratio matrix and the life model, wherein the life model is: in, is the number of life cycles, is the fatigue ductility coefficient, is the fatigue ductility index; The high temperature point bending acceleration factor is: in, is the high temperature point bending acceleration factor matrix; High temperature point bending acceleration factor matrix The average value is taken as the high temperature point bending acceleration factor .

6. A board-level SMD package high temperature point bending equivalent life test method according to claim 5, characterized in that: According to the high temperature point bending acceleration factor Equivalent temperature cycle times of board-level SMD package , get the number of stress cycles for: Based on the number of stress cycles , obtain the high temperature point bending equivalent life test plan of the board-level SMD package.

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