Hole opening method of template for PCB solder paste printing

Abstract

The invention provides a trepanning method of a template for PCB solder paste printing, and relates to the technical field of printed circuit boards. The method comprises the following steps: acquiring a template which is provided with M groups of opening areas and N opening sizes and is used for PCB solder paste printing; calculating the volume of the solder paste corresponding to each welding spot on a PCB (Printed Circuit Board) welded with the BGA wafer, and obtaining a liquid solder ball model; determining the initial height of each welding spot corresponding to the different trepanning areas of the template on the PCB; determining the final height of each welding spot according to the liquid solder ball model and the initial height; according to the final height, obtaining the safety distance of each trepanning area under each permutation and combination; and determining a target permutation and combination according to the safety distance of each trepanning area under different permutation and combination. According to the invention, the target permutation and combination is determined according to the safety distance of each trepanning area under different permutation and combination, and the problems of high complexity and low production efficiency caused by the need of a large number of trial and error experiments to optimize the BGA wafer process design are solved.

Description

Technical Field

[0001] This disclosure relates to the field of printed circuit board technology, and more particularly to a method for opening holes in a stencil used for solder paste printing on a PCB board. Background Technology

[0002] In the field of microelectronics manufacturing, with continuous technological advancements, the demand for integrated circuits, especially high-performance BGA (Ball Grid Array) chips, is increasing daily. BGA chips, with their high density, high pin count, and superior electrical performance, occupy a central position in data center construction and high-performance computing applications. However, while highly integrated BGA chips enhance system performance, they also significantly increase design complexity. This complexity is not only reflected in circuit design but also directly impacts subsequent manufacturing processes. Particularly in high-temperature processes, high-density layouts often lead to warping and deformation of the chip substrate, causing a series of manufacturing problems, such as short circuits in pressure areas and open circuits in tension areas during solder melting, posing a serious threat to chip yield and reliability.

[0003] In existing technologies, BGA chip manufacturing process design often relies on extensive trial-and-error experiments to optimize process parameters and ensure product performance. This approach is not only time-consuming and labor-intensive, but also increases the uncertainty and risk in the development process. At the same time, the high R&D costs further drive up the market price of the product, limiting its popularization and application.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This disclosure provides a method for opening holes in a template used for solder paste printing on a PCB board, which at least to some extent overcomes the problems of high complexity, low production efficiency, and high production cost caused by the need for a large number of trial and error experiments to optimize the BGA chip process design in related technologies.

[0006] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0007] According to one aspect of this disclosure, a method for opening holes in a stencil used for solder paste printing on a PCB board is provided, comprising: obtaining a stencil for solder paste printing on a PCB board having M sets of opening areas and N opening sizes; arranging and combining the M sets of opening areas and the N opening sizes, wherein each opening area includes multiple openings, and M and N are positive integers greater than 1 and M≥N; calculating the volume of solder paste corresponding to each solder joint on the PCB board to be soldered to a BGA chip, and obtaining a liquid solder ball model reflecting the deformation of both the solder paste and the BGA ball under stress; determining the initial height of each solder joint corresponding to different opening areas on the PCB board and the stencil, wherein each opening area corresponds to an initial height of a solder joint within a certain range; obtaining a safety distance for each opening area under each arrangement and combination based on the final height of each solder joint; and determining a target arrangement and combination based on the maximum value among the minimum values ​​of the safety distances for each opening area under different arrangements and combinations.

[0008] In some embodiments, obtaining a template for solder paste printing on a PCB board with M groups of opening areas and N opening sizes includes determining the opening size according to preset BGA design parameters, PCB design parameters and solder paste printing process parameters, wherein the opening size includes the opening diameter and opening thickness of the template.

[0009] In some embodiments, calculating the volume of solder paste corresponding to each solder joint on the PCB board soldered to the BGA chip, and obtaining a liquid solder ball model reflecting the stress deformation of both the solder paste and the BGA ball includes: calculating the volume of solder paste used based on the aperture diameter and aperture thickness of the opening of the template corresponding to each solder joint; and substituting the sum of the volume of solder paste corresponding to each solder joint and the volume of the BGA ball into the Young-Laplace differential equation to obtain the liquid solder ball model.

[0010] In some embodiments, the above-mentioned method for opening holes in the template used for solder paste printing on the PCB board further includes: when the total volume of solder paste and BGA ball corresponding to each solder joint is constant, the liquid solder ball model reflects the negative correlation between the load-bearing capacity and height of the solder paste and BGA ball.

[0011] In some embodiments, determining the initial height of each solder joint corresponding to different opening areas of the template on the PCB board includes: determining the initial height of each solder joint on the PCB board based on a first warpage value of the PCB board and a second warpage value of the BGA chip.

[0012] In some embodiments, determining the final height of each solder joint based on the liquid solder ball model and the initial height of each solder joint includes: determining the final height of each solder joint using a force balance model of each solder joint.

[0013] In some embodiments, determining the final height of each solder joint using a force balance model includes: the final height of the solder joint has a preset upper limit value; if the final height of the solder joint is greater than the preset upper limit value, the solder joint is considered to have an open circuit.

[0014] In some embodiments, the force balance model reflects the relationship between the total load on multiple solder joints and the final height of each solder joint.

[0015] In some embodiments, determining the final height of each solder joint using a force balance model of each solder joint further includes: the final height of the solder joint has a preset lower limit value; if the final height of the solder joint is less than the preset lower limit value, the solder joint is considered to have a short circuit.

[0016] In some embodiments, obtaining the safe distance of each opening region under each permutation and combination based on the final height of each solder joint includes: substituting the final height of each solder joint into the liquid solder ball model and obtaining the safe distance of each solder joint; and determining the safe distance of each opening region based on the minimum safe distance of each solder joint in each opening region.

[0017] The PCB solder paste printing template opening method provided in the embodiments of this disclosure involves obtaining a PCB solder paste printing template with M sets of opening areas and N opening sizes, arranging and combining the M sets of opening areas and N opening sizes; calculating the volume of solder paste corresponding to each solder joint on the PCB board to be soldered to the BGA chip, and obtaining a liquid solder ball model reflecting the stress deformation of both the solder paste and the BGA ball; determining the initial height of each solder joint corresponding to different opening areas on the PCB board and the template, wherein each opening area corresponds to an initial height of the solder joint within a certain range; determining the final height of each solder joint based on the liquid solder ball model and the initial height of each solder joint; obtaining the safety distance of each opening area under each arrangement based on the final height of each solder joint; and determining the target arrangement combination based on the maximum value among the minimum values ​​of the safety distances of each opening area under different arrangements. This disclosure determines the target arrangement combination by simulating a large amount of process data in a virtual environment, solving the problem of high production costs caused by the need for extensive trial-and-error experiments to optimize the BGA chip process design.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 A flowchart illustrating a method for opening holes in a stencil used for solder paste printing on a PCB board, according to an embodiment of this disclosure, is shown.

[0021] Figure 2 This diagram illustrates a BGA placed on a PCB using solder paste, according to an embodiment of the present disclosure.

[0022] Figure 3 A flowchart illustrating a specific example of a method for opening a stencil used in solder paste printing on a PCB board according to an embodiment of this disclosure;

[0023] Figure 4 This diagram illustrates the relationship between solder paste height and load-bearing capacity in an embodiment of this disclosure.

[0024] Figure 5 This illustration shows a 3D view of BGA and PCB warpage data in an embodiment of this disclosure;

[0025] Figure 6 A schematic diagram of an opening area is shown in an embodiment of this disclosure. Detailed Implementation

[0026] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0027] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0028] To facilitate understanding, before introducing the embodiments of this disclosure, the following explanations are provided for several terms involved in the embodiments of this disclosure:

[0029] PCB: Printed Circuit Board, provides interconnection between electronic components, serves as the support for electronic components, and is also the carrier for the electrical connections between electronic components;

[0030] BGA: Ball Grid Array, is a type of integrated circuit packaging.

[0031] The specific implementation methods of the embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0032] Figure 1 This diagram illustrates a method for creating openings in a stencil used for solder paste printing on a PCB board, as shown in an embodiment of this disclosure. Figure 1 As shown, the method for opening holes in the stencil used for solder paste printing on a PCB board provided in this embodiment includes the following steps:

[0033] S102, obtain a template for solder paste printing on a PCB board with M groups of opening areas and N opening sizes, and arrange the M groups of opening areas and N opening sizes in a combination, wherein each opening area includes multiple openings, and M and N are positive integers greater than 1 and M≥N.

[0034] It should be noted that the templates described above can be made of easily processed and manufactured materials, such as stainless steel, nickel alloys, and aluminum alloys. The opening dimensions mentioned above include both the opening thickness and the opening diameter.

[0035] It should be noted that multiple openings in the same opening area have the same opening size; openings in different opening areas may have the same or different opening sizes.

[0036] S104 calculates the volume of solder paste corresponding to each solder joint on the PCB board that is soldered to the BGA chip, and obtains a liquid solder ball model that reflects the deformation of both the solder paste and the BGA ball under stress.

[0037] It should be noted that when printing solder paste on a PCB board, a template must be placed on top of the PCB board. The template will make holes at the positions corresponding to the solder joints on the PCB board to print the solder paste. After the solder paste printing is completed, the template used for printing the solder paste will be removed.

[0038] It should be noted that the solder paste mentioned above refers only to the solder paste applied from the stencil to the PCB board. The BGA balling mentioned above can be solder balls on the BGA chip, wherein the volume of the solder balls on the BGA chip is a known parameter.

[0039] In a specific example, the liquid solder ball model reflects the relationship between the volume, load-bearing capacity, and shape (including diameter and height) of solder paste or solder balls. For instance, taking solder paste as an example, when the volume of solder paste is constant, the greater the load-bearing capacity, the smaller the height of the solder paste, and the larger the corresponding diameter of the solder paste.

[0040] In a specific example, the BGA chip is covered on the PCB board by its own solder balls and the solder paste on the PCB board. At this time, the BGA chip and the PCB board have not yet been soldered, that is, the solder balls on the BGA and the solder paste on the PCB board have not melted into solder.

[0041] S106, determine the initial height of each solder joint corresponding to different opening areas on the PCB board and the template, wherein each opening area corresponds to an initial height of solder joint within a certain range.

[0042] It should be noted that the different opening areas mentioned above correspond to the initial height of solder joints within a certain (preset) range. The initial height of the solder joints is a relative height, determined by the input PCB warpage and BGA warpage values. That is, the initial height of each solder joint is the height difference between the PCB board and the BGA chip at the location of that solder joint. The initial height of solder joints within the same opening area falls within a certain range, as detailed below. Figure 2 (A schematic diagram of BGA chip placed on PCB board with solder paste) shows that the upper and lower curves represent BGA chip and PCB board respectively, and the middle part represents solder paste (or solder paste and solder balls on BGA).

[0043] S108, based on the liquid solder ball model and the initial height of each solder joint, determine the final height of each solder joint.

[0044] It should be noted that the above final height is the actual height of the solder.

[0045] In a specific example, at this point, the solder paste melts together with the BGA ball to form solder, and the PCB board and BGA chip are completely soldered together. The height of the solder at each solder joint is the final height of the solder joint.

[0046] Because the PCB warpage and BGA warpage differ at different solder joint locations, and the total weight of the BGA chip is borne by all the solder balls it carries and the solder paste in contact with these solder balls, the load-bearing capacity varies at different solder joints. Furthermore, during the process of soldering the BGA chip to the PCB board by melting the solder balls and solder paste to form solder, the different load-bearing capacities at different solder joints result in different actual solder heights at different solder joints, meaning the final heights of the solder joints are different.

[0047] S110, based on the final height of each weld point, obtain the safe distance of each opening area under each permutation and combination.

[0048] As shown in the aforementioned liquid solder ball model, when the total volume of solder paste and solder balls is constant, the lower the height of the final solder, the larger the diameter of the solder, and the easier it is for it to contact the solder at adjacent solder joints, thus forming a short circuit. Therefore, for each solder joint, the minimum distance between it and its adjacent solder joints is the safe distance of the solder joint. For each opening area, the minimum safe distance of all solder joints in that opening area is the safe distance of that opening area.

[0049] S112, determine the target permutation combination based on the maximum value among the minimum safe distances of each opening area under different permutation combinations.

[0050] It should be noted that a short circuit is formed when the solder of adjacent solder joints comes into contact with each other. In other words, the larger the minimum safe distance between each opening area, the less likely a short circuit will occur, and this arrangement is safer.

[0051] In a specific example, since there are multiple regions, there are corresponding multiple template opening sizes. The following example illustrates this with different opening diameters in different regions: Assume there are three regions A, B, and C, and three opening diameters of 1mm, 2mm, and 3mm. There are several combinations. For example, in the first combination, the opening diameter in region A is 1mm, in region B it is 2mm, and in region C it is 3mm. In the second combination, the opening diameter in region A is 2mm, in region B it is 3mm, and in region C it is 1mm. For the first combination, assuming the safety distances between regions A, B, and C are 0.1mm, 0.2mm, and 0.3mm respectively, the minimum safety distance between these three regions is 0.1mm. For the second combination, assuming the safety distances between regions A, B, and C are 0.2mm, 0.3mm, and 0.4mm respectively, the minimum safety distance between these three regions is 0.2mm. Obviously, the minimum safe distance under the first permutation is less than the minimum safe distance under the second permutation. Therefore, the second permutation is the target (optimal) permutation because the larger the minimum safe distance, the less likely a short circuit will occur.

[0052] This disclosure determines the minimum safety distance under different permutations and combinations of different aperture regions and aperture sizes. Then, a maximum value is selected from these minimum values, and the permutation and combination corresponding to this maximum value is the target permutation and combination. By determining the target permutation and combination in this way, a large amount of process data can be simulated in a virtual environment, solving the problem of high production costs and design complexity caused by the need for a large number of trial and error experiments to optimize BGA wafer process design.

[0053] In one example of this disclosure, the stencil used to obtain solder paste for a PCB board with M groups of opening areas and N opening sizes includes determining the opening sizes based on preset BGA design parameters, PCB design parameters, and solder paste printing process parameters. The opening sizes include the opening diameter and thickness of the stencil. The BGA design parameters include the weight G1 of the BGA chip (excluding the weight of the BGA balls) and the volume of the solder balls on the BGA chip; the PCB design parameters include the diameter and position of the pads on the PCB board; and the solder paste printing process parameters include parameters related to the solder paste printing process specifications.

[0054] In one embodiment of this disclosure, such as Figure 3 As shown in the embodiments of this disclosure, the method for opening holes in the PCB board solder paste printing template includes the following steps: calculating the volume of solder paste corresponding to each solder joint on the PCB board soldered to the BGA chip, and obtaining a liquid solder ball model reflecting the deformation of both the solder paste and the BGA ball under stress.

[0055] S302, calculate the volume of solder paste to be used based on the aperture and thickness of the opening in the template corresponding to each solder joint.

[0056] S304. Substitute the sum of the volume of solder paste corresponding to each solder joint and the volume of the BGA ball into the Young-Laplace differential equation to obtain the liquid solder ball model.

[0057] In one example of this disclosure, the opening method of the stencil used for solder paste printing on the PCB board further includes: when the total volume of solder paste and BGA ball corresponding to each solder joint is constant, the liquid solder ball model reflects the negative correlation between the load-bearing capacity and height of the solder paste and BGA ball.

[0058] For example, when the volume of solder paste is constant, the greater the load-bearing force, the smaller the height of the solder paste, and the larger the corresponding diameter of the solder paste. Figure 4 (A schematic diagram of solder paste height and load capacity is shown, with the horizontal axis representing solder paste height and the vertical axis representing load capacity.)

[0059] It should be noted that the Young-Laplace differential equation refers to the relationship between additional pressure and radius of curvature in physics:

[0060] General formula: Ps=γ(1 / R1+1 / R2), where Ps is the pressure and R1 and R2 are the radii.

[0061] In one example of this disclosure, determining the initial height of each solder joint corresponding to different opening areas on the PCB board and the template includes: determining the initial height of each solder joint on the PCB board based on a first warpage value of the PCB board and a second warpage value of the BGA chip.

[0062] In one example of this disclosure, determining the final height of each solder joint based on the liquid solder ball model and the initial height of each solder joint includes: determining the final height of each solder joint using a force balance model of each solder joint.

[0063] The following formula (1) is the calculation formula for the weld joint to achieve force balance:

[0064]

[0065] Where n is the number of solder joints, W i Z represents the load-bearing capacity of the i-th weld joint. i G1 represents the final height of the i-th solder joint at the equilibrium position, and G1 represents the weight of the BGA chip (excluding the weight of the BGA ball).

[0066] It should be noted that the above force balance model is based on the mechanical principle in physics, namely that the net force on an object is zero when it is at rest or in uniform linear motion. During the welding process, when the weld joint is subjected to multiple forces, it seeks a stable equilibrium state, and this state determines the final height and shape of the weld joint.

[0067] For example, suppose a BGA chip is soldered to a PCB via three solder joints. Due to warping of both the BGA chip and the PCB, the three solder joints have three different initial heights. The weight G1 of the BGA chip is then borne by these three solder joints. Using the liquid solder ball model, we can determine the final height of each solder joint at this point (the height of the solder paste and the solder formed by the molten BGA ball).

[0068] In one example of this disclosure, determining the final height of each solder joint using a force balance model includes: the final height of the solder joint has a preset upper limit value; if the final height of the solder joint is greater than the preset upper limit value, the solder joint is considered to have an open circuit. The preset upper limit value can be set according to actual needs.

[0069] In one example of this disclosure, the force balance model reflects the relationship between the total load on multiple weld joints and the final height of each weld joint.

[0070] In one example of this disclosure, determining the final height of each solder joint using a force balance model further includes: the final height of the solder joint has a preset lower limit value; if the final height of the solder joint is less than the preset lower limit value, the solder joint is considered to have a short circuit. The preset lower limit value can be set according to actual needs.

[0071] In one example of this disclosure, obtaining the safety distance of each opening region under each permutation and combination based on the final height of each solder joint includes: substituting the final height of each solder joint into the liquid solder ball model and obtaining the safety distance of each solder joint; and determining the safety distance of each opening region based on the minimum value of the safety distance of each solder joint in each opening region.

[0072] For example, in the same opening area, different solder pastes are subjected to different forces and heats, which leads to different actual heights (final heights) of different solder joints in the same area, and different safety distances between different solder joints. Suppose they are 0.1mm, 0.2mm, and 0.3mm. In this case, the safety distance of the opening area is 0.1mm.

[0073] Figure 5 The figures are 3D views of the BGA and PCB warpage data in a specific embodiment of this invention. Using the X and Y coordinates of the solder joints, warpage values ​​h1 and h2 for each solder joint on the BGA and PCB solder surfaces are calculated through interpolation. Then, the initial height (relative height) of the solder joint is obtained as h = h1 - h2. This process is repeated for each solder joint to obtain the initial height of all solder joints. In this example, the number of solder joints n = 9352, and the initial height range is 0.0154mm to 0.1629mm. The solder joints are divided into three regions according to their height range, as shown in Table 1 below. Each region corresponds to an opening diameter (assuming the opening thickness is the same). Figure 6 (Diagram of the opening area) As shown. By assigning three different opening diameters to the three opening areas respectively, different arrangements and combinations can be obtained.

[0074] Table 1: Template Opening Area

[0075]

[0076]

[0077] By incorporating the initial height of the solder joint into the liquid solder ball model, the force on the solder joint at this height can be calculated using the following formula (2):

[0078]

[0079] Where: n is the number of solder joints, W i Let z be the load-bearing capacity of the i-th weld joint. iLet F be the height of the i-th solder joint. Check if F equals G1. If F > G1, increase the height of each solder joint and recalculate. If F < G1, decrease the height of each solder joint and recalculate. Continue until F - G1 < 1. e-3 N can be considered as the BGA chip being in force balance. At this point, the final height of each solder joint can be obtained.

[0080] In particular, according to embodiments of this disclosure, the process described above with reference to the flowchart can be implemented as a computer program product, which includes a computer program that, when executed by a processor, implements the above-described method for opening holes in the template used for solder paste printing on a PCB board.

[0081] Furthermore, although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0082] From the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of this disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) or on a network, including several instructions to cause a computing device (such as a personal computer, server, mobile terminal, or network device, etc.) to execute the methods according to the embodiments of this disclosure.

[0083] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A method for creating openings in a stencil used for solder paste printing on a PCB board, characterized in that, include: Obtain a template for solder paste printing on a PCB board with M groups of opening areas and N opening sizes. Arrange and combine the M groups of opening areas and the N opening sizes, wherein each opening area includes multiple openings, and M and N are positive integers greater than 1 and M≥N. Calculate the volume of solder paste corresponding to each solder joint on the PCB board that is soldered to the BGA chip, and obtain a liquid solder ball model that reflects the deformation of both the solder paste and the BGA ball under stress. Determine the initial height of each solder joint corresponding to different opening areas on the PCB board and the template, wherein each opening area corresponds to the initial height of the solder joint within a certain range. Based on the liquid solder ball model and the initial height of each solder joint, the final height of each solder joint is determined; Based on the final height of each weld point, obtain the safe distance of each opening area under each permutation and combination; The target permutation combination is determined based on the maximum value among the minimum values ​​of the safety distances of the opening regions under different permutation combinations.

2. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 1, characterized in that, The method for obtaining a PCB board solder paste printing template with M groups of opening areas and N opening sizes includes determining the opening size according to preset BGA design parameters, PCB design parameters and solder paste printing process parameters, wherein the opening size includes the opening diameter and opening thickness of the template.

3. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 2, characterized in that, The calculation of the volume of solder paste corresponding to each solder joint on the PCB board soldered to the BGA chip, and the acquisition of a liquid solder ball model reflecting the stress deformation of both the solder paste and the BGA ball, includes: The volume of solder paste used is calculated based on the aperture diameter and aperture thickness of the opening in the template corresponding to each solder joint; Substituting the sum of the volume of the solder paste corresponding to each solder joint and the volume of the BGA ball into the Young-Laplace differential equation, the liquid solder ball model is obtained.

4. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 3, characterized in that, The method further includes: When the total volume of the solder paste and the BGA ball corresponding to each solder joint is constant, the liquid solder ball model reflects the negative correlation between the load-bearing capacity and height of the solder paste and the BGA ball.

5. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 1, characterized in that, The determination of the initial height of each solder joint corresponding to the different opening areas on the PCB board and the template includes: The initial height of each solder joint on the PCB is determined based on the first warp value of the PCB and the second warp value of the BGA chip.

6. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 1, characterized in that, The step of determining the final height of each solder joint based on the liquid solder ball model and the initial height of each solder joint includes: The final height of each solder joint is determined by a force balance model for each solder joint.

7. The method for opening holes in a stencil used for solder paste printing on a PCB board according to claim 6, characterized in that, The determination of the final height of each weld joint using a force balance model for each weld joint includes: The final height of the solder joint has a preset upper limit value. If the final height of the solder joint is greater than the preset upper limit value, the solder joint is considered to be open circuit.

8. The method for opening holes in the stencil used for solder paste printing on a PCB board according to claim 6 or 7, characterized in that, The force balance model reflects the relationship between the total load-bearing capacity of the multiple solder joints and the final height of each solder joint.

9. The method for opening holes in a stencil used for solder paste printing on a PCB board according to claim 6, characterized in that, The step of determining the final height of each weld joint using a force balance model of each weld joint also includes: The final height of the solder joint has a preset lower limit value. If the final height of the solder joint is less than the preset lower limit value, the solder joint is considered to have a short circuit.

10. The method for opening holes in a stencil used for solder paste printing on a PCB board according to claim 1, characterized in that, The step of obtaining the safety distance of each opening area under each permutation and combination based on the final height of each weld point includes: Substitute the final height of each solder joint into the liquid solder ball model, and obtain the safety distance of each solder joint; The safety distance of each of the opening regions is determined based on the minimum safety distance of each of the weld points in each of the opening regions.

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