PCBA bump structure electromagnetic shielding method

Abstract

The invention belongs to the technical field of controller electromagnetic shielding and circuit boards, and particularly provides a PCBA salient point structure electromagnetic shielding method, which comprises the following steps of: determining the width size of ground bar exposed copper used for surrounding a whole board of electronic devices according to layout parameters of a target controller, and calculating the maximum size of solder ball salient points arranged on the ground bar exposed copper according to the width size of the ground bar exposed copper; according to a shielding effectiveness formula, calculating the maximum distance between two adjacent solder ball bumps to obtain the maximum linear size of a pore; calculating the minimum number of the solder ball bumps according to the width size, the maximum size and the maximum linear size of the pores; cAE simulation is carried out based on a first solder ball parameter composed of the maximum size, the maximum linear size of pores and the minimum number to obtain a second solder ball parameter, ground bar exposed copper is arranged on the target controller according to the second solder ball parameter, a tin planting process is carried out on the ground bar exposed copper through a punching steel mesh, and an optimization controller provided with solder ball bumps is obtained. Therefore, an electromagnetic shielding technical scheme with good electromagnetic protection reliability and low cost is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of controller electromagnetic shielding and circuit board technology, and in particular to an electromagnetic shielding method for a PCBA bump structure. Background Art

[0002] With the rapid development of intelligent vehicles, the integration of chips is getting higher and higher. The high-speed digital signals (such as PWM, CLK, ADC sampling) and analog signals (sensor input) inside the vehicle controller are susceptible to coupling interference from external electromagnetic fields (such as inverters and radio equipment), resulting in signal distortion. This will have a great impact on the decision-making of intelligent driving of the entire vehicle, especially the signal end’s judgment of information will be adversely affected. However, if electromagnetic shielding is done well, the noise floor can be effectively reduced. For example, the shielding body can absorb / reflect interference, reduce the noise level of the ADC sampling circuit, improve the signal-to-noise ratio (SNR), and reduce the error rate of signal acquisition. Therefore, the electromagnetic shielding of the controller is of great significance.

[0003] At present, most controllers use shielding materials for EMC structural shielding, such as conductive foam, SMT patch foam, conductive glue, etc. to fill gaps to reduce leakage. Although it can play an electromagnetic protection role to a certain extent, its reliability is poor for automotive products. For example, it is difficult for conductive foam to achieve all-round shielding for special-shaped grooves, and the conformability and shell structure processing requirements are high. In addition, additional workstations are required for assembly; SMT patch foam is prone to aging and falling off under high-temperature operating conditions of vehicle-mounted equipment for a long time, which can easily cause short circuits to electronic components; conductive glue is a mixture of a large amount of metal particles and base liquid silicone, so the texture is hard and the surface roughness is difficult to control. In addition, the structure is line contact, and it is inevitable that large gaps will be generated due to the uneven and warped surface of the structure during installation, resulting in a low yield rate. In addition, this solution requires the purchase of a set of expensive dispensing equipment, which requires constant debugging, and the equipment and control costs are high.

[0004] Therefore, it is necessary to provide a controller electromagnetic shielding technology solution with good electromagnetic protection reliability and low cost. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an electromagnetic shielding method for a PCBA bump structure.

[0006] The present invention provides a method for electromagnetic shielding of a PCBA bump structure, comprising the following specific steps:

[0007] Determining, based on the layout parameters of the target controller, the width of the exposed copper of the ground strip that will be used to surround the entire electronic components on the circuit board of the target controller;

[0008] Calculating the maximum size of the solder ball bumps disposed on the exposed copper of the ground strip according to the width dimension;

[0009] According to the shielding effectiveness formula, the shielding effectiveness threshold and electromagnetic wave parameters are used to calculate the maximum distance between two adjacent solder bumps to obtain the maximum linear size of the pore.

[0010] Calculate the minimum number of solder ball bumps based on the width of the exposed copper strip, the maximum size of the solder ball bumps, and the maximum linear size of the aperture;

[0011] Perform CAE simulation based on the first solder ball parameters consisting of the maximum size of the solder ball bump, the maximum linear size of the pores, and the minimum number, and obtain the second solder ball parameters according to the simulation results;

[0012] According to the layout parameters and the width size, setting the ground strip exposed copper on the target controller;

[0013] According to the second solder ball parameters, a tin planting process is performed on the exposed copper of the ground strip through a perforated steel mesh to obtain an optimized controller provided with solder ball bumps;

[0014] Wherein, the shell of the optimization controller contacts the solder ball bumps to form an electromagnetic shielding structure.

[0015] In a possible implementation, before determining the width of the exposed copper of the ground strip used to surround the entire electronic components on the circuit board of the target controller according to the layout parameters of the target controller, the following specific steps are also included:

[0016] The shielding effectiveness of the initial whole machine controller is tested. If the shielding effectiveness is lower than a preset value, the initial whole machine controller is used as the target controller.

[0017] In a possible implementation, the layout parameters include outermost contour space parameters of the target controller and layout parameters of electronic components on a circuit board.

[0018] In a possible implementation, the electromagnetic wave parameter is frequency or wavelength.

[0019] In one possible implementation, during CAE simulation, statics simulation is used to simulate the contact between the solder ball bumps and the structural end surface under different tightening torques of the screws on the controller.

[0020] In one possible implementation, strain gauges are placed near the solder ball bumps during CAE simulation, and the strain results of the strain gauge channels are observed by applying torque to determine the correctness of the mechanical simulation results.

[0021] In a possible implementation, the second solder ball parameters include solder ball specifications, dimensional tolerance, material, quantity, gaps between solder ball bumps, and arrangement.

[0022] In a possible implementation, the following specific steps are also included:

[0023] Matching actual solder ball parameters of the solder ball bump set on the optimization controller with the second solder ball parameters to obtain a parameter matching result;

[0024] When the parameter matching result does not meet the requirements, the optimization controller is re-tinned until the final parameter matching result meets the requirements.

[0025] In a possible implementation, the following specific steps are also included:

[0026] Measuring the DC impedance of the solder ball bumps on the optimization controller to obtain an impedance test value;

[0027] Matching the impedance test value with an impedance threshold to obtain an impedance matching result;

[0028] When the impedance matching result does not meet the requirements, the material of the solder ball bumps is adjusted, and the optimization controller is re-tinned until the final impedance matching result meets the requirements.

[0029] In a possible implementation, the following specific steps are also included:

[0030] Performing a full-band electromagnetic wave interference test on the optimized controller to obtain an interference test result;

[0031] Matching the interference test result with a standard value to obtain a test matching result;

[0032] When the matching result does not meet the requirements, the second solder ball parameters are adjusted until the final test matching result meets the requirements.

[0033] The technical solution provided by the present invention has at least the following beneficial effects:

[0034] By setting ground strips with exposed copper around the entire electronic components on the controller circuit board, and setting tin ball bumps on the ground strips, the tin ball bumps contact the shell to form an electromagnetic shielding structure, thereby realizing a controller electromagnetic shielding technology solution with good electromagnetic protection reliability and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A flow chart of the electromagnetic shielding method for a PCBA bump structure provided by an embodiment of the present invention;

[0036] Figure 2An exploded diagram of the optimized controller obtained by the electromagnetic shielding method based on the PCBA bump structure provided by an embodiment of the present invention;

[0037] Figure 3 A partial structural diagram of an optimized controller obtained based on the electromagnetic shielding method of a PCBA bump structure provided by an embodiment of the present invention;

[0038] In the accompanying drawings, 100 is the upper shell; 200 is the PCBA assembly; 210 is the electronic chip; 220 is the exposed copper of the ground strip; 230 is the solder ball bump; 240 is the circuit board; 300 is the lower shell; 400 is the screw; and 401 is the screw hole. DETAILED DESCRIPTION

[0039] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0040] Please refer to Figures 2 to 3 An optimized controller structure, based on the PCBA bump structure electromagnetic shielding method of the present invention, comprises a housing and a PCBA assembly 200. The housing comprises an upper housing 100 and a lower housing 300. The PCBA assembly 200 comprises an electronic chip 210, exposed ground copper strips 220, solder bumps 230, and a circuit board 240. The electronic chip 210 is disposed in the circuit area of ​​the circuit board 240. The exposed ground copper strips 220 are arranged on the circuit board 240 around the circuit area. A plurality of solder bumps 230 are arranged on the exposed ground copper strips 220 at predetermined intervals. The upper housing 100 and the PCBA assembly 200 are connected, and the upper housing 100 and the solder bumps 230 contact each other to form an electromagnetic shielding structure. The upper housing 100 and the lower housing 300 are fastened together to form a shielding cavity. The PCBA assembly 200 is located within the shielding cavity. Screw holes 401 are provided in the upper housing 100, the PCBA assembly 200, and the lower housing 300 for receiving screws 400 for fixing. The shell material of the upper shell 100 and the lower shell 300 is metal or a good conductor, and can also be replaced with a combination of plastic parts and metal spraying. For example, the interior of the upper shell 100 and the lower shell 300 is a plastic part, and a metal layer is sprayed on the surface of the plastic part.

[0041] like Figure 1 The present invention provides a method for electromagnetic shielding of a PCBA bump structure, comprising the following specific steps:

[0042] S100: Determine the width of the exposed copper ground strip 220 for surrounding the entire electronic components on the circuit board 240 in the target controller according to the layout parameters of the target controller.

[0043] In a possible implementation, the layout parameters include outermost contour space parameters of the target controller and layout parameters of electronic components on the circuit board 240 .

[0044] In this embodiment, the electronic device includes an electronic chip 210 .

[0045] In a possible implementation, before step S100, the following specific steps are further included:

[0046] The shielding effectiveness of the initial whole machine controller is tested. If the shielding effectiveness is lower than a preset value, the initial whole machine controller is used as the target controller.

[0047] In this embodiment, the PCBA without solder ball bumps 230 is tested and assembled to the whole machine (such as Figure 2 ), obtain the initial test unit, measure its unshielded and shielded (with the upper shell 100 and the lower shell 300 installed) field strength, and then calculate its shielding effectiveness according to the electromagnetic shielding effectiveness calculation formula SE = 20lg (E1 / E2). Among them, E1 represents the electric field strength without a shielding body, E2 represents the electric field strength with a shielding body, and the unit of SE is decibel (dB). At this time, two situations can be discussed: if the shielding effectiveness measurement result is greater than the preset value (such as: 40dB), it is preliminarily determined that the structural shell can shield the radiation value of the product as required; if the shielding effectiveness measurement result is less than the preset value (such as: 40dB), it is preliminarily determined that the structural shell alone cannot shield the radiation value of the product as required, and the shielding effectiveness of the initial whole machine controller needs to be improved.

[0048] S200: Calculating the maximum size of the solder ball bump 230 disposed on the ground strip copper 220 according to the width size.

[0049] In this embodiment, the maximum size of the solder ball bump 230 includes a maximum diameter, and the contact surface between the solder ball bump 230 and the ground strip copper 220 is approximately circular.

[0050] S300: According to the shielding effectiveness formula, the shielding effectiveness threshold and the electromagnetic wave parameters, the maximum distance between two adjacent solder ball bumps 230 is calculated to obtain the maximum linear size of the aperture.

[0051] In this embodiment, the shielding effectiveness formula can be understood as a calculation formula for electromagnetic shielding effectiveness.

[0052] In a possible implementation, the electromagnetic wave parameter is frequency or wavelength.

[0053] S400: Calculating the minimum number of the solder ball bumps 230 according to the width of the exposed copper ground strip 220 , the maximum size of the solder ball bumps 230 , and the maximum linear size of the aperture.

[0054] In this embodiment, the relationship between shielding effectiveness SE, frequency f / wavelength λ, and aperture size d can be used to determine the maximum linear dimension of the aperture, thereby determining the minimum number of solder ball bumps 230 required. It should be noted that, in theory, when aperture size d is greater than λ / 2, electromagnetic waves can pass through the aperture without attenuation. As aperture size d decreases, the attenuation effect of the aperture on electromagnetic waves gradually becomes apparent. When aperture size d is less than 1 / 2 of the wavelength, the attenuation of the electromagnetic wave can be expressed as A = 201g(λ / 2d).

[0055] S500: Perform CAE simulation based on the first solder ball parameters consisting of the maximum size of the solder ball bump 230, the maximum linear size of the pores, and the minimum number, and obtain second solder ball parameters according to the simulation results.

[0056] In a possible implementation, during CAE simulation, statics simulation is used to simulate the contact between the solder ball bump 230 and the structural end surface under different tightening torques of the screw 400 on the controller.

[0057] In this embodiment, the structural end surface is the surface of the upper housing 100 that contacts the solder ball bumps 230 .

[0058] In one possible implementation, during CAE simulation, a strain gauge is arranged near the solder ball bump 230 , and the strain results of the strain gauge channel are observed by applying torque to determine the correctness of the mechanical simulation results.

[0059] In a possible implementation, the second solder ball parameters include solder ball specifications, dimensional tolerance, material, quantity, gaps between solder ball bumps 230 , and arrangement.

[0060] In this embodiment, combined with the aforementioned preconditions such as the width of the exposed copper strip 220 and the distance between the PCBA and the end face of the structure, the first solder ball parameters of the solder ball bump 230 can be determined. The first solder ball parameters include parameters such as the maximum size, the maximum linear size of the pores, and the minimum number, which can be used as input conditions for subsequent selection and verification.

[0061] In a specific embodiment, during CAE simulation, the solder ball design value and spacing (i.e., the first parameter) are first imported into the structural 3D model. Static simulation is then performed using CAE to simulate the contact between the solder ball bump 230 and the structural end face under different tightening torques of the entire machine screw 400. This ensures that the solder ball bump 230 and the structural end face are in complete contact and fit, while ensuring that the maximum stress of the material is less than the allowable stress. For example, if a force of 4 N.m is used to tighten the screw 400 during installation, the torque load acting on the screw 400 during the mechanical simulation is also 4 N.m. After defining the relevant materials, dividing the grid, and ensuring proper constraint matching, a mechanical simulation is performed, and the equivalent strain and allowable stress of the solder ball bump 230 material are observed during the simulation. If the equivalent strain of the material is greater than 0, it is determined that the solder ball bump 230 is in complete contact with the housing; if the allowable stress is less than 26 MPa, it is determined that there is no risk of material fracture failure.

[0062] If the solder ball bump 230 cannot make perfect contact with the structural end face, there are two cases: if the equivalent strain of the entire area becomes 0, it is determined that the solder ball bump 230 cannot make perfect contact with the housing under the input torque condition, and the torque of the screws 400 or their number or position can be adjusted until good contact is achieved; if the equivalent strain of most areas is greater than 0, but the equivalent strain of some solder ball bumps 230 is 0, then only the number and position of the screws 400 or the solder ball bumps 230 can be adjusted until the equivalent strain of all solder ball bumps 230 is greater than 0.

[0063] To ensure a closed loop of the simulation, a strain gauge may be arranged near the solder ball bump 230 , and the strain results of the strain gauge channel may be observed by applying torque to determine the correctness of the mechanical simulation results.

[0064] S600: Setting the ground strip exposed copper 220 on the target controller according to the layout parameters and the width size.

[0065] S700: performing a tin implantation process on the exposed copper strip 220 through a perforated steel mesh according to the second solder ball parameters to obtain an optimized controller provided with solder ball bumps 230;

[0066] The shell of the optimization controller contacts the solder ball bumps 230 to form an electromagnetic shielding structure.

[0067] In this embodiment, after CAE simulation, the corresponding solder ball solution, i.e., the second solder ball parameters (such as the specifications, dimensional tolerances, materials, quantity, gaps between the solder ball bumps 230, arrangement, etc.) can be obtained. The solder ball solution is frozen and released into the proof drawing, and then the tin planting process is performed on the ground strip copper 220 through a perforated steel mesh, so that the solder ball bumps 230 can be set on the PCBA component 200, thereby obtaining the final optimized controller.

[0068] It should be noted that the present invention is applicable to the design of PCBA bump shielding structures for controller products. Through theoretical calculations, CAE simulation verification, and practical automated process control, it can rapidly design the complete electromagnetic shielding structure of controller products, and the design has wide applicability. Comparative verification in actual electromagnetic shielding tests has confirmed that the electromagnetic shielding structure designed according to the electromagnetic shielding method for PCBA bump structures provided by the present invention has excellent shielding effectiveness, high reliability for mass production, and significantly reduces electromagnetic shielding design time, especially reducing the time and testing costs associated with repeated testing and structural changes after design freeze.

[0069] In a possible implementation, after step S700, the following specific steps are further included:

[0070] Matching actual solder ball parameters of the solder ball bump 230 set on the optimization controller with the second solder ball parameters to obtain a parameter matching result;

[0071] When the parameter matching result does not meet the requirements, the optimization controller is re-tinned until the final parameter matching result meets the requirements.

[0072] In this embodiment, the actual solder ball parameters (such as the solder ball size value) of the solder ball bump 230 set on the optimization controller can be scanned using an AOI optical scanning device. By comparing the solder ball size value with the original design data (i.e., the second solder ball parameter), it can be determined whether the actual solder ball parameters are within the tolerance range of the drawing, thereby ensuring consistency between the design and actual measurement. If it is not within the tolerance range of the drawing, it is necessary to return to the previous step and re-solder until the requirements are met.

[0073] In a possible implementation, the following specific steps are also included:

[0074] Measuring the DC impedance of the solder ball bumps 230 on the optimization controller to obtain an impedance test value;

[0075] Matching the impedance test value with an impedance threshold to obtain an impedance matching result;

[0076] When the impedance matching result does not meet the requirements, the material of the solder ball bumps 230 is adjusted, and the optimization controller is re-tinned until the final impedance matching result meets the requirements.

[0077] In this embodiment, the impedance threshold can be set to 0.1 ohm. In specific implementations, the DC impedance of the solder ball bump 230 at low frequency can be measured using an impedance meter. The judgment process is as follows: If the measured DC impedance is within 0.1 ohm, the material conductivity of the solder ball bump 230 is determined to be good and meets the requirements; if the measured DC impedance exceeds 0.1 ohm, the material conductivity of the solder ball bump 230 is determined to be poor and does not meet the requirements, and the material of the solder ball bump 230 needs to be adjusted.

[0078] In a possible implementation, the following specific steps are also included:

[0079] Performing a full-band electromagnetic wave interference test on the optimized controller to obtain an interference test result;

[0080] Matching the interference test result with a standard value to obtain a test matching result;

[0081] When the matching result does not meet the requirements, the second solder ball parameters are adjusted until the final test matching result meets the requirements.

[0082] In this embodiment, after the optimized controller is subjected to electromagnetic wave interference testing across the entire frequency band, the measurement values ​​corresponding to each frequency band, i.e., the interference test results, can be obtained. By comparing the interference test results across the entire frequency band with the standard values ​​provided by the customer, two situations can be considered: if the measurement values ​​across all frequency bands are lower than the standard values ​​provided by the customer, the design is deemed reasonable; if the measurement value of a certain frequency band in the entire frequency band is higher than the standard value, the second solder ball parameters need to be adjusted until the final test matching result meets the requirements. For example, the measurement value at the 1.6GHz frequency band is 13dB, which is higher than the 10dB provided by the customer. Excluding leakage from board-side wiring, the remaining 3dB can be reduced by adjusting the gap between the solder ball bumps 230 or changing their arrangement, etc., to reduce the impact of radiation until it meets the customer's standards, thus completing the closed loop from design, simulation, to testing.

[0083] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion fall within the protection scope of the present invention.

Claims

1. A method for electromagnetic shielding of a PCBA bump structure, characterized in that: The specific steps include: Determining, based on the layout parameters of the target controller, the width of the exposed copper of the ground strip that will be used to surround the entire electronic components on the circuit board of the target controller; Calculating the maximum size of the solder ball bumps disposed on the exposed copper of the ground strip according to the width dimension; According to the shielding effectiveness formula, the shielding effectiveness threshold and electromagnetic wave parameters are used to calculate the maximum distance between two adjacent solder bumps to obtain the maximum linear size of the pore. Calculate the minimum number of solder ball bumps based on the width of the exposed copper strip, the maximum size of the solder ball bumps, and the maximum linear size of the aperture; Perform CAE simulation based on the first solder ball parameters consisting of the maximum size of the solder ball bump, the maximum linear size of the pores, and the minimum number, and obtain the second solder ball parameters according to the simulation results; According to the layout parameters and the width size, setting the ground strip exposed copper on the target controller; According to the second solder ball parameters, a tin planting process is performed on the exposed copper of the ground strip through a perforated steel mesh to obtain an optimized controller provided with solder ball bumps; Wherein, the shell of the optimization controller contacts the solder ball bumps to form an electromagnetic shielding structure.

2. The electromagnetic shielding method for a PCBA bump structure according to claim 1, wherein: Before determining the width of the exposed copper of the ground strip used to surround the entire electronic components on the circuit board of the target controller according to the layout parameters of the target controller, the following specific steps are also included: The shielding effectiveness of the initial whole machine controller is tested. If the shielding effectiveness is lower than a preset value, the initial whole machine controller is used as the target controller.

3. The electromagnetic shielding method of PCBA bump structure according to claim 1, characterized in that: The layout parameters include outermost contour space parameters of the target controller and layout parameters of electronic components on the circuit board.

4. The electromagnetic shielding method for a PCBA bump structure according to claim 1, wherein: The electromagnetic wave parameter is frequency or wavelength.

5. The electromagnetic shielding method for PCBA bump structure according to claim 1, characterized in that: During CAE simulation, statics simulation was used to simulate the contact between the solder ball bumps and the structural end faces of the controller screws under different tightening torques.

6. The electromagnetic shielding method for a PCBA bump structure according to claim 5, characterized in that: During CAE simulation, strain gauges are placed near the solder ball bumps, and the strain results of the strain gauge channels are observed by applying torque to determine the correctness of the mechanical simulation results.

7. The electromagnetic shielding method of a PCBA bump structure according to claim 1, wherein: The second solder ball parameters include solder ball specifications, dimensional tolerances, materials, quantity, gaps between solder ball bumps, and arrangement.

8. The electromagnetic shielding method for a PCBA bump structure according to claim 1, wherein: The following specific steps are also included: Matching actual solder ball parameters of the solder ball bump set on the optimization controller with the second solder ball parameters to obtain a parameter matching result; When the parameter matching result does not meet the requirements, the optimization controller is re-tinned until the final parameter matching result meets the requirements.

9. The electromagnetic shielding method of a PCBA bump structure according to claim 8, characterized in that: The following specific steps are also included: Measuring the DC impedance of the solder ball bumps on the optimization controller to obtain an impedance test value; Matching the impedance test value with an impedance threshold to obtain an impedance matching result; When the impedance matching result does not meet the requirements, the material of the solder ball bumps is adjusted, and the optimization controller is re-tinned until the final impedance matching result meets the requirements.

10. The electromagnetic shielding method of PCBA bump structure according to claim 9, characterized in that: The following specific steps are also included: Performing a full-band electromagnetic wave interference test on the optimized controller to obtain an interference test result; Matching the interference test result with a standard value to obtain a test matching result; When the matching result does not meet the requirements, the second solder ball parameters are adjusted until the final test matching result meets the requirements.

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