Computer combinatorial design method for high dynamic load

Abstract

The invention relates to a computer combinatorial design method for a high dynamic load, and belongs to the technical field of computers. The method comprises the following steps: determining a computer combination three-dimensional model according to a space envelope; computer combination structure design parameters are determined according to the dynamic load conditions; determining a computer circuit installation and reinforcement mode; determining a BGA chip reinforcing mode; constructing a computer combination finite element model, performing grid division and endowing corresponding structural material parameters; performing modal analysis on the computer combination; carrying out random vibration load dynamics analysis on the computer combination; calculating the fatigue life of the most dangerous welding spot of the BGA chip; if the fatigue life does not meet the requirement, the design is optimized; and if the requirements are met, carrying out impact load dynamics analysis, calculating the impact frequency of the most dangerous welding spot of the BGA chip, and if the requirements are not met, carrying out optimization design until the design requirements are met. The design efficiency can be improved, and the development cost can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of computer technology, and specifically relates to a computer-integrated design method for high dynamic loads. Background Technology

[0002] With the improvement of computer module performance, computer modules are developing towards miniaturization, integration, and high performance. Ball Grid Array (BGA) chips have become the main processing chips in most computer modules. As the most important core component of a computer module, the reliability of the BGA chip under high dynamic loads directly determines the reliability of the entire electronic device. During operation, computer modules must withstand extremely high dynamic loads such as random vibration and impact, with random vibration exceeding 20g and impact exceeding 10,000g. Among the failure phenomena under high dynamic loads, BGA chip solder joint failure accounts for more than 50% of the total failures. Under high dynamic loads, especially perpendicular to the printed circuit board, BGA chips may experience solder ball fatigue fracture, intermetallic compound (IMC) fracture, printed circuit board pad peeling, and pitting. These failure modes cause the computer module to malfunction. The conventional design method is to use full potting of the circuit board. However, due to the mismatch between the thermal expansion coefficients of the potting compound and the chip, chip failure can occur at high and low temperatures. At the same time, full potting is not conducive to the testing and repair of the circuit board and increases the weight of the entire device.

[0003] In the case of no potting, BGA chips are often reinforced with epoxy resin at the four corners. However, simply using epoxy resin cannot guarantee that BGA chips will work reliably under high dynamic loads. Therefore, a multi-dimensional composite design approach must be adopted for computer assembly.

[0004] Conventional computer-aided design simulations treat BGA chips as a single mass block without simulating the solder joints, resulting in unrealistic simulation results and an inability to identify chip failures in the early design stages. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by the present invention is how to provide a computer assembly design method for high dynamic loads, so as to solve the problem of BGA chip failure in computer assemblies under high dynamic loads.

[0007] (II) Technical Solution

[0008] To address the aforementioned technical problems, this invention proposes a computer-aided design method for high dynamic loads, comprising the following steps:

[0009] S1. Determine the computer-assembled 3D model based on the spatial envelope;

[0010] S2. Determine the computer structure design parameters;

[0011] S3. Determine the method for reinforcing and mounting the computer circuitry;

[0012] S4. Determine the BGA chip reinforcement method;

[0013] S5. Based on the computer-aided structural model, a finite element model is constructed. The computer-aided structural model is simplified and meshed, and corresponding structural material parameters are assigned to the structural elements. Each structural element corresponds to a structure in the computer-aided structural model.

[0014] S6. Perform modal analysis on the computer assembly to obtain the first n resonant frequencies of the computer assembly; the cumulative effective mass ratio of the first n frequencies in the direction perpendicular to the computer circuit printed circuit board is required to be greater than 0.95.

[0015] S7. Perform random vibration load dynamic analysis on the computer assembly to obtain the maximum strain of the most dangerous solder joint of the BGA chip;

[0016] S8. Based on the maximum strain of the most dangerous solder joint, the fatigue life of the most dangerous solder joint of the BGA chip is calculated using the Steinberg damage model and the Coffin-Manson fatigue failure model.

[0017] S9. Determine whether the design requirements are met; if the requirements are met, proceed to S10; if the requirements are not met, repeat S1~S8.

[0018] S10. Perform impact load dynamic analysis on the computer assembly to obtain the normal stress of the most dangerous solder joint of the BGA chip;

[0019] S11. Calculate the number of failure impacts of the most dangerous solder joint of the BGA chip based on the Power principle life prediction model.

[0020] S12. Determine whether the failure impact count meets the design requirements;

[0021] S13. If the design requirements are not met, repeat S1~S12 by optimizing the design until the requirements are met.

[0022] (III) Beneficial Effects

[0023] This invention proposes a computer assembly design method for high dynamic loads. By employing a multi-dimensional composite design approach, it enables rapid and accurate failure prediction of the computer assembly structure and BGA chip solder joints during the design phase, meeting the requirements for computer assembly design under high dynamic loads. The design process of this invention is scientific and effective, avoiding extensive experimental verification, improving design and production efficiency, saving product development costs, and ensuring the success of product design on the first attempt. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a structural design method for computer assemblies under high dynamic load environments, as described in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of a computer combination model according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of BGA chip hardening;

[0027] Figure 4 This is a schematic diagram of a BGA chip.

[0028] Figure 5 A schematic diagram of a computer-aided finite element model provided in this embodiment of the invention;

[0029] Figure 6 The computer-combined random vibration spectrum provided in this embodiment of the invention;

[0030] Figure 7 The computer-combined shock spectrum provided in this embodiment of the invention;

[0031] Figure 8 This invention provides a random vibration 1σ strain contour map of the solder joints of a computer assembly BGA chip, as shown in an embodiment of the invention.

[0032] Figure 9 This is a schematic diagram of the computer combination model after adopting optimization scheme one in an embodiment of the present invention;

[0033] Figure 10 This is a 1σ strain cloud diagram of the random vibration of the BGA chip solder joint in the computer assembly structure after adopting the optimized scheme one in this embodiment of the invention;

[0034] Figure 11 This is a schematic diagram of the computer combination model after adopting optimization scheme two in an embodiment of the present invention;

[0035] Figure 12 This is a 1σ strain cloud diagram of the random vibration of the BGA chip solder joint in the computer assembly structure after adopting optimization scheme two in an embodiment of the present invention.

[0036] Figure 13 This is a schematic diagram of the computer combination model after adopting optimization scheme three in an embodiment of the present invention;

[0037] Figure 14 This is a 1σ strain cloud diagram of the random vibration of the BGA chip solder joint in the computer assembly structure after adopting optimization scheme three in an embodiment of the present invention.

[0038] Figure 15 The 1σ normal stress cloud diagram is provided for the impact dynamic analysis of the BGA chip solder joints after adopting the third optimization scheme in the embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0040] This invention belongs to the technical field of computer-aided design for robust vibration damping and buffering technology and simulation analysis and calculation methods for solder joints of ball grid array (BGA) chip, and specifically relates to a computer-aided design for high dynamic loads.

[0041] To overcome the shortcomings of the prior art, this invention provides a computer assembly design method for high dynamic loads, in order to solve the problem of BGA chip failure in computer assemblies under high dynamic loads.

[0042] This invention provides a computer-aided assembly design method for high dynamic loads, belonging to the technical fields of computer-aided assembly reinforcement, vibration damping, and ball grid array (BGA) chip solder joint calculation and simulation analysis. The method includes: determining a three-dimensional model of the computer assembly based on its spatial envelope; determining the structural design parameters of the computer assembly based on dynamic load conditions; determining the computer circuit mounting reinforcement method; determining the BGA chip reinforcement method; constructing a finite element model of the computer assembly, meshing, and assigning corresponding structural material parameters; performing modal analysis on the computer assembly; performing random vibration load dynamic analysis on the computer assembly; calculating the fatigue life of the most critical solder joint of the BGA chip; determining whether the requirements are met; if not, re-performing the random vibration load dynamic analysis through optimized design; if the requirements are met, performing impact load dynamic analysis, calculating the number of impacts on the most critical solder joint of the BGA chip; if not, continuing optimized design and dynamic analysis until the design requirements are met; if the requirements are met, the design is complete. This invention employs computer-aided design methods, finite element simulation methods, random vibration fatigue calculation methods, and impact load impact number calculation methods for high dynamic loads. It can accurately analyze and calculate the stress and lifespan of computer-aided BGA chip solder joints under high dynamic load environments, identify design defects during the design phase, optimize design methods, improve design efficiency, and reduce development costs.

[0043] To address the aforementioned technical problems, this invention proposes a computer-aided design method for high dynamic loads, comprising the following steps:

[0044] S1. Determine the computer-assembled 3D model based on the spatial envelope;

[0045] S2. Determine the computer structure design parameters;

[0046] S3. Determine the method for reinforcing and mounting the computer circuitry;

[0047] S4. Determine the BGA chip reinforcement method;

[0048] S5. Based on the computer-aided structural model, a finite element model is constructed. The computer-aided structural model is simplified and meshed, and corresponding structural material parameters are assigned to the structural elements. Each structural element corresponds to a structure in the computer-aided structural model.

[0049] S6. Perform modal analysis on the computer assembly to obtain the first n resonant frequencies of the computer assembly; the cumulative effective mass ratio of the first n frequencies in the direction perpendicular to the computer circuit printed circuit board (Z direction) is required to be greater than 0.95;

[0050] S7. Perform random vibration load dynamic analysis on the computer assembly to obtain the maximum strain of the most dangerous solder joint of the BGA chip;

[0051] S8. Based on the maximum strain of the most dangerous solder joint, the fatigue life of the most dangerous solder joint of the BGA chip is calculated using the Steinberg damage model and the Coffin-Manson fatigue failure model.

[0052] S9. Determine whether the design requirements are met; if the requirements are met, proceed to S10; if the requirements are not met, repeat S1~S8.

[0053] S10. Perform impact load dynamic analysis on the computer assembly to obtain the normal stress of the most dangerous solder joint of the BGA chip;

[0054] S11. Calculate the number of failure impacts of the most dangerous solder joint of the BGA chip based on the Power principle life prediction model.

[0055] S12. Determine whether the failure impact count meets the design requirements;

[0056] S13. If the design requirements are not met, repeat S1~S12 by optimizing the design until the requirements are met.

[0057] Example 1:

[0058] To achieve the above objectives, the present invention provides a computer-aided design method for high dynamic loads, which specifically includes the following steps:

[0059] S1. Determine the three-dimensional model of the computer assembly structure based on the spatial envelope;

[0060] S2. Determine the computer structure design parameters;

[0061] S3. Determine the method for reinforcing and mounting the computer circuitry;

[0062] S4. Determine the BGA chip reinforcement method;

[0063] S5. Based on the computer-aided structural model, a finite element model is constructed. The computer-aided structural model is simplified and meshed, and corresponding structural material parameters are assigned to the structural elements. Each structure corresponds to one type of structure in the computer-aided structural model.

[0064] S6. Perform modal analysis on the computer assembly to obtain the first n resonant frequencies of the computer circuit; the cumulative effective mass ratio of the first n frequencies in the direction perpendicular to the printed circuit board (Z direction) is required to be greater than 0.95.

[0065] S7. Perform random vibration load dynamic analysis on the computer assembly to obtain the maximum strain of the most dangerous solder joint of the BGA chip;

[0066] S8. Based on the maximum strain of the most dangerous weld joint, the fatigue life of the weld joint is calculated using the Steinberg damage model and the Coffin-Manson fatigue failure model.

[0067] S9. Determine whether the design requirements are met; if the requirements are met, proceed to S10; if the requirements are not met, repeat S1~S8.

[0068] S10. Perform impact load dynamic analysis on the computer assembly to obtain the maximum normal stress of the most dangerous solder joint of the BGA chip;

[0069] S11. Calculate the number of failure impacts of the most dangerous solder joint of the BGA chip based on the Power principle life prediction model.

[0070] S12. Determine whether the design requirements are met;

[0071] S13. If the design requirements are not met, optimize the design and perform dynamic analysis of random vibration and impact loads until the requirements are met.

[0072] Preferably, in step S1, the computer assembly includes: a computer circuit (1), a computer board frame (2), an upper cover (3), a lower cover (4), a heat-conducting pad (5), and a vibration damper (6).

[0073] Preferably, in step S1, the computer circuit (1) includes a printed circuit board (1-1), components (1-2), a BGA chip (1-3), and BGA chip solder joints (1-3-1).

[0074] Preferably, step S1 includes: determining the initial three-dimensional model of the computer circuit (1), computer board frame (2), upper cover (3), and lower cover (4) based on the external envelope and internal communication relationship.

[0075] Preferably, step S1 includes: determining the initial three-dimensional model of the vibration damper (6) based on random vibration and impact conditions.

[0076] Preferably, in step S2, the structural design parameters are the material parameters of the computer circuit (1), computer board frame (2), upper cover (3), lower cover (4), printed circuit board (1-1), components (1-2), BGA chip (1-3), BGA chip solder joint (1-3-1), thermal pad (5), vibration damper (6) and the thickness of printed circuit board (1-1).

[0077] Preferably, in step S2, the material parameters include material density, elastic modulus, Poisson's ratio, and tensile strength.

[0078] Preferably, in step S3, the computer circuit installation and reinforcement method includes the printed circuit board screw fixing method.

[0079] Preferably, in step S4, the BGA chip reinforcement method includes four-corner L-shaped epoxy adhesive (1-4) reinforcement, underfill adhesive (1-5) reinforcement, etc.

[0080] Preferably, in step S5, the computer assembly structure model is simplified by including simplified mounting holes, small chamfers, and small rounded corners.

[0081] Preferably, in step S5, the mesh division is performed using a hexahedral mesh to refine the mesh division of the printed circuit board (1-1), BGA chip (1-3), BGA chip solder joint (1-3-1), and vibration damper (6).

[0082] Preferably, in step S6, the first-order frequency of the computer printed circuit board is calculated using the Rayleigh method, as shown in the following expression:

[0083] (1)

[0084] In the formula, ω is the first natural angular frequency of the computer circuit, k is a coefficient, a is the length of the computer circuit printed circuit board, b is the width of the computer circuit printed circuit board, and D is the bending stiffness of the printed circuit board. The mass per unit area of ​​a computer circuit printed circuit board (including the mass of the printed circuit board and the mass of the components on it).

[0085] The expression for calculating D is as follows:

[0086] (2)

[0087] In the formula, E y Let δ be the elastic modulus of the computer circuit printed circuit board, δ be the thickness of the computer circuit printed circuit board, and μ be the Poisson's ratio of the computer circuit printed circuit board.

[0088] Preferably, in step S6, the modal analysis is based on a finite element model of the computer assembly, and modal analysis is performed on the computer assembly to obtain the natural frequencies and corresponding mode shapes of the computer assembly.

[0089] Preferably, in step S7, the strain is the maximum strain of the most dangerous solder joint of the BGA chip.

[0090] Preferably, in step S8, the fatigue life calculation process for the BGA chip solder joints is as follows:

[0091] The fatigue life of the most critical solder joint on the BGA chip was calculated using the Steinberg three-zone fatigue life prediction model, and obtained according to the following formula:

[0092] (3)

[0093] In the formula, S is the damage ratio, and N is the damage ratio. 1σ N 2σ N 3σ These represent the material failure cycles corresponding to strain levels of 1σ, 2σ, and 3σ, respectively, where n is the number of cycles. 1σ n 2σ n 3σ These represent the cumulative number of cycles under strains of 1σ, 2σ, and 3σ, respectively.

[0094] n 1σ n 2σ n 3σ Calculated by the following formula:

[0095] (4)

[0096] In the formula, f0 is the average natural frequency of the computer circuit, and T is the total time of random vibration.

[0097] Based on the Coffin-Manson high-cycle fatigue empirical formula, the material failure cycle number N of the BGA solder joint at strain levels of 1σ, 2σ, and 3σ is obtained by calculating the maximum strain of the most critical solder joint. 1σ N 2σ N3σ :

[0098]

[0099] (5)

[0100]

[0101] In the formula, These represent the maximum 1σ, 2σ, and 3σ strains of the most dangerous solder joints on the BGA chip, respectively, where E is the elastic modulus of the BGA chip solder joint material, and σ is the maximum strain of the most dangerous solder joint on the BGA chip. b The tensile strength of the BGA chip solder joint material.

[0102] Preferably, in step S9, the design requirement is met as follows: the damage ratio of the most dangerous solder joint of the BGA chip is less than 0.3.

[0103] Preferably, in step S10, the normal stress is the maximum normal stress of the most dangerous solder joint of the BGA chip under impact load.

[0104] Preferably, in step S11, the failure impact count of the most dangerous solder joint of the BGA chip is calculated according to the Power principle lifetime prediction model, and is obtained according to the following formula:

[0105] (6)

[0106] In the formula, N 50 σ represents the average number of impact cycles. z C1 and C2 are constants, representing the maximum normal stress (in MPa) at the most dangerous solder joint of the BGA chip.

[0107] Preferably, in step S12, the design requirement is met as follows: the average impact life number is greater than 50.

[0108] Preferably, in step S13, the optimized design includes: mounting thermal pads for device mounting on both sides of the printed circuit board to reduce vibration and buffer, filling the solder joints at the bottom of the BGA chip with adhesive, increasing the density of the printed circuit board mounting screws (to increase the resonant frequency of the computer circuit), reducing the distance between the printed circuit board mounting screws and the BGA chip, adjusting the thickness of the printed circuit board, and adding a vibration damper.

[0109] Preferably, in step S13, the optimization design can take a combination of one or more measures.

[0110] Example 2:

[0111] This example provides a computer-aided design method for computer-generated integrated structures under high dynamic loads, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0112] S1: Determine the computer-assembled 3D model based on the spatial envelope;

[0113] like Figure 2 The computer assembly structure includes: computer circuit 1, computer board frame 2, upper cover 3, lower cover 4, and thermal pad 5.

[0114] The software used for the 3D model in this example is Creo.

[0115] S2: Determine the computer architecture design parameters;

[0116] The computer board frame, top cover, and bottom cover are made of aluminum alloy; the printed circuit board is made of FR-4 material; the chip is made of silicon; and the BGA chip solder joints are made of tin-lead solder. This example uses a BGA chip as an example, and the material parameters of each structure and component are shown in Table 1.

[0117] Table 1. Computer structural material parameters

[0118] Serial Number Structure name Material <![CDATA[Material density ( / kg / m 3 )]]> Elastic modulus ( / GPa) Poisson's ratio Tensile strength ( / MPa) 1 Computer board frame, top cover, bottom cover aluminum alloy 2780 70 0.3 420 2 Computer circuit printed circuit board FR-4 1850 22 0.2 300 3 BGA chip silicon 2500 170 0.22 150 4 BGA chip solder joints Tin-lead solder 8500 30 0.35 40 5 BGA chip solder joint filler glue Filler glue 1130 3.08 0.48 /

[0119] The thickness of the printed circuit board in this example is 2mm.

[0120] S3: Determine the method for reinforcing and mounting the computer circuitry;

[0121] Printed circuit board reinforcement such as Figure 3 As shown, the printed circuit board is reinforced with 17 screws.

[0122] S4: Determine the BGA chip hardening method;

[0123] BGA chip reinforcement, such as Figure 3 As shown, the BGA chip is reinforced with L-shaped epoxy resin at its four corners.

[0124] BGA chips such as Figure 4 As shown.

[0125] S5. Based on the computer-aided structural model, a finite element model is constructed. The computer-aided structural model is simplified and meshed, and corresponding structural material parameters are assigned to the structural elements. Each structure corresponds to one type of structure in the computer-aided structural model.

[0126] The mounting holes, chamfers, and fillets of the computer assembly structure model are simplified.

[0127] All structural models of the computer assembly are meshed using hexahedral meshes. The printed circuit board 1-1, BGA chip 1-3, and BGA chip solder joint 1-3-1 are then meshed using more refined hexahedral meshes. Figure 5 As shown.

[0128] The material parameters assigned to the structure are shown in Table 1.

[0129] S6: Perform modal analysis on the four mounting holes of the computer assembly to obtain the first six frequencies of the computer circuit. As shown in Table 2, the cumulative effective mass ratio of the first six frequencies in the direction perpendicular to the printed circuit board (Z direction) is 0.9558, which is greater than 0.95 and meets the design requirements.

[0130] Table 2. Cumulative effective mass ratio of the first six modes in the Z direction

[0131] order Natural frequency ( / Hz) Cumulative effective mass ratio 1 896.16 0.9372 2 1292.8 0.94254 3 1425.3 0.9428 4 1617. 0.95144 5 1663.6 0.95567 6 1691.4 0.9558

[0132] S7: Perform random vibration load dynamic analysis on the computer assembly. The random vibration spectrum is as follows: Figure 6 As shown, the strain of the BGA chip solder joint is obtained as follows: Figure 8 As shown, the maximum strain of the most dangerous solder joint of the BGA chip is:

[0133]

[0134] S8: Based on the average natural frequency of the computer circuit and the vibration time of random vibration, the cumulative number of cycles under 1σ, 2σ, and 3σ strains is calculated as follows:

[0135]

[0136] The material failure cycle number of the BGA solder joint at strain levels of 1σ, 2σ, and 3σ was calculated based on the maximum strain of the most critical solder joint.

[0137]

[0138] The final calculated damage ratio S of the most dangerous weld point is 11330957.

[0139] S9: The damage ratio is much greater than 0.3, which does not meet the design requirements. Repeat S1~S8.

[0140] Optimization Solution 1: Add thermal pads between the computer circuit components and the top and bottom covers, such as... Figure 9 Repeat S1 to S8 to perform random vibration dynamics analysis.

[0141] Strain contour plot of BGA chip solder joint under random vibration, as shown Figure 10 As shown, the strain of the most dangerous solder joint of the BGA chip is 2.88e-4.

[0142] The damage ratio of the most dangerous solder joints of the BGA chip under random vibration is 42.7, which does not meet the requirements.

[0143] Optimization Option 2: Based on Optimization Option 1, fill the bottom of the BGA chip solder joints with adhesive (1-5), such as... Figure 11 As shown. Repeat S1~S8 to perform random vibration dynamics analysis.

[0144] Strain contour plot of BGA chip solder joint under random vibration, as shown Figure 12 As shown, the strain of the most dangerous solder joint of the BGA chip is 1.81e-4.

[0145] The damage ratio of the most dangerous solder joint of the BGA chip under random vibration is 0.91, which does not meet the requirements.

[0146] Optimization Scheme 3: Based on Optimization Scheme 1, add a shock absorber (6) to the external computer assembly, such as... Figure 13 As shown. Repeat S1~S8 to perform random vibration dynamics analysis.

[0147] Strain contour plot of BGA chip solder joint under random vibration, as shown Figure 14 As shown, the strain of the most dangerous solder joint of the BGA chip is 3.86e-5.

[0148] The damage ratio of the most dangerous solder joint of the BGA chip under random vibration is 2.3e-6, which is less than 0.3 and meets the requirements.

[0149] S10: Perform impact load dynamic analysis on the computer assembly, and the impact spectrum is as follows. Figure 7 As shown, the 1σ normal stress cloud diagram of the BGA chip solder joint is obtained, as follows. Figure 15 As shown.

[0150] The maximum normal stress at the most dangerous weld joint is 28.66 MPa;

[0151] S11: The failure impact count of the BGA chip solder joint calculated according to the Power principle lifetime prediction model is 23343, which is greater than 50, and meets the design requirements.

[0152] Therefore, the final computer assembly design included L-shaped adhesive reinforcement on all four sides of the chip, adding thermal pads to the top and bottom of the computer printed circuit board components, and adding vibration dampers to the outside of the computer assembly.

[0153] This invention has been successfully applied to the structural design of a computer assembly, passed the test of high dynamic loads, and met the design requirements.

[0154] Beneficial effects

[0155] This invention proposes a computer assembly structure design method for high dynamic loads. By employing a multi-dimensional composite design approach, it can quickly and accurately predict failures of the computer assembly structure and BGA chip solder joints during the design phase, meeting the requirements of computer assembly design under high dynamic loads. The design process of this invention is scientific and effective, avoiding extensive experimental verification, improving design and production efficiency, saving product development costs, and ensuring the need for successful product design on the first attempt.

[0156] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A computer-aided design method for high dynamic loads, characterized in that, The method includes the following steps: S1. Determine the computer-assembled 3D model based on the spatial envelope; S2. Determine the design parameters of the computer assembly structure; S3. Determine the method for reinforcing and mounting the computer circuitry; S4. Determine the BGA chip reinforcement method; S5. Based on the computer-aided structural model, a finite element model is constructed. The computer-aided structural model is simplified and meshed, and corresponding structural material parameters are assigned to the structural elements. Each structural element corresponds to a structure in the computer-aided structural model. S6. Perform modal analysis on the computer assembly to obtain the first n resonant frequencies of the computer assembly; the cumulative effective mass ratio of the first n frequencies in the direction perpendicular to the computer circuit printed circuit board is required to be greater than 0.

95. S7. Perform random vibration load dynamic analysis on the computer assembly to obtain the maximum strain of the most dangerous solder joint of the BGA chip; S8. Based on the maximum strain of the most dangerous solder joint, the fatigue life of the most dangerous solder joint of the BGA chip is calculated using the Steinberg damage model and the Coffin-Manson fatigue failure model. S9. Determine whether the design requirements are met; if the requirements are met, proceed to S10; if the requirements are not met, repeat S1~S8. S10. Perform impact load dynamic analysis on the computer assembly to obtain the normal stress of the most dangerous solder joint of the BGA chip; S11. Calculate the number of failure impacts of the most dangerous solder joint of the BGA chip based on the Power principle life prediction model. S12. Determine whether the failure impact count meets the design requirements; S13. If the design requirements are not met, repeat S1~S12 by optimizing the design until the requirements are met.

2. The computer-aided design method for high dynamic loads as described in claim 1, characterized in that, In step S1, the computer assembly includes: computer circuit (1), computer board frame (2), upper cover (3), lower cover (4), thermal pad (5), and vibration damper (6); the computer circuit (1) includes printed circuit board (1-1), components (1-2), BGA chip (1-3), and BGA chip solder joint (1-3-1).

3. The computer-aided design method for high dynamic loads as described in claim 2, characterized in that, In step S1, the initial three-dimensional models of the computer circuit (1), computer board frame (2), upper cover (3), and lower cover (4) are determined according to the external envelope and internal communication relationship; the initial three-dimensional model of the vibration damper (6) is determined according to the random vibration and impact conditions.

4. The computer-aided design method for high dynamic loads as described in claim 3, characterized in that, In step S2, the structural design parameters are the material parameters of the computer circuit (1), computer board frame (2), upper cover (3), lower cover (4), printed circuit board (1-1), BGA chip (1-3), BGA chip solder joint (1-3-1), thermal pad (5), and vibration damper (6), as well as the thickness of the printed circuit board (1-1); the material parameters include material density, elastic modulus, Poisson's ratio, and tensile strength.

5. The computer-aided design method for high dynamic loads as described in claim 4, characterized in that, In step S3, the computer circuit installation and reinforcement method includes the printed circuit board screw fixing method; in step S4, the BGA chip reinforcement method includes four-corner L-shaped epoxy glue (1-4) reinforcement and bottom filler glue (1-5) reinforcement.

6. The computer-aided design method for high dynamic loads as described in claim 4, characterized in that, In step S5, the computer assembly structure model is simplified, including the installation holes, small chamfers, and small rounded corners of the simplified structure; the mesh is divided into hexahedral meshes, and the printed circuit board (1-1), BGA chip (1-3), BGA chip solder joints (1-3-1), and vibration damper (6) are meshed with higher density.

7. The computer-aided design method for high dynamic loads as described in claim 4, characterized in that, In step S6, the modal analysis is based on the finite element model of the computer assembly, and modal analysis is performed on the computer assembly to obtain the natural frequencies and corresponding mode shapes of the computer assembly. The first-order frequency of the computer printed circuit board is calculated using the Rayleigh method, and the expression is as follows: (1) In the formula, ω is the first natural angular frequency of the computer circuit, k is a coefficient, a is the length of the computer circuit printed circuit board, b is the width of the computer circuit printed circuit board, and D is the bending stiffness of the printed circuit board. The mass per unit area of ​​a computer circuit printed circuit board; The expression for calculating D is as follows: (2) In the formula, E y Let δ be the elastic modulus of the computer circuit printed circuit board, δ be the thickness of the computer circuit printed circuit board, and μ be the Poisson's ratio of the computer circuit printed circuit board.

8. The computer-aided design method for high dynamic loads as described in claim 7, characterized in that, In step S8, the fatigue life calculation process for the BGA chip solder joints is as follows: The fatigue life of the most critical solder joint on the BGA chip was calculated using the Steinberg three-zone fatigue life prediction model, and obtained according to the following formula: (3) In the formula, S is the damage ratio, and N is the damage ratio. 1σ N 2σ N 3σ These represent the material failure cycles corresponding to strain levels of 1σ, 2σ, and 3σ, respectively, where n is the number of cycles. 1σ n 2σ n 3σ These represent the cumulative number of cycles under strains of 1σ, 2σ, and 3σ, respectively. n 1σ n 2σ n 3σ Calculated by the following formula: (4) In the formula, f0 is the average natural frequency of the computer circuit, and T is the total time of random vibration; Based on the Coffin-Manson high-cycle fatigue empirical formula, the material failure cycle number N of the BGA solder joint at strain levels of 1σ, 2σ, and 3σ is obtained by calculating the maximum strain of the most critical solder joint. 1σ N 2σ N 3σ : (5) In the formula, These represent the maximum 1σ, 2σ, and 3σ strains of the most critical solder joints in a BGA chip, respectively, where E is the elastic modulus of the BGA chip solder joint material, and σ is the maximum strain of the most dangerous solder joint in a BGA chip. b The tensile strength of the BGA chip solder joint material.

9. The computer-aided design method for high dynamic loads as described in claim 8, characterized in that, In step S11, the failure impact count of the most dangerous solder joint of the BGA chip is calculated based on the Power principle lifetime prediction model, using the following formula: (6) In the formula, N 50 σ represents the average number of impact cycles. z C1 and C2 are constants, representing the maximum normal stress at the most dangerous solder joint of the BGA chip.

10. The computer-aided design method for high dynamic loads as described in claim 9, characterized in that, In step S13, the optimized design includes: mounting thermal pads for device mounting on both sides of the printed circuit board to reduce vibration and buffer, filling the solder joints at the bottom of the BGA chip with adhesive, increasing the density of the printed circuit board mounting screws, reducing the distance between the printed circuit board mounting screws and the BGA chip, adjusting the thickness of the printed circuit board, and adding a vibration damper.

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