Method and apparatus for automatically designing steel mesh opening of QFN device

Abstract

A method and apparatus for automatically designing a steel mesh opening of a QFN device, and an electronic device and a storage medium. The method comprises: for a target device that has been subjected to QFN device verification, acquiring, as device parameters of the target device, a device pin height and a device appearance size in a device specification, a pin pad length, a pin pad width and a pad outer edge size of the target device on a PCB in ECAD data, and a preset pin pad steel mesh thickness and a preset pin bottom soldering tin thickness (S1); on the basis of the pin pad length and the pin pad width, determining a pin pad steel mesh opening parameter calculation model of the target device (S2); and on the basis of the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, determining a pin pad steel mesh opening design result of the target device (S3). The method can accurately design a steel mesh opening for a QFN device, and can improve the quality of steel meshes and the welding quality, ensure product reliability, and reduce repair costs.

Description

A method and device for automatically designing QFN device steel mesh openings Technical Field

[0001] The invention belongs to the technical field of printed circuit boards, and in particular relates to a method and a device for automatically designing a QFN device steel mesh opening. Background Art

[0002] With the increasing integration of electronic products, the requirements for product specifications and sizes are constantly increasing. Small, exquisite, and fully functional products are more popular in the market, resulting in more stringent requirements for the size of internal components. QFN devices better meet this requirement. They are not only lightweight, but also have pins located at the bottom of the device, which can save space. However, in the actual production soldering process, QFN devices are particularly prone to cold soldering and bridging. The best solution to this problem is to accurately control the amount of solder, and the control of the amount of solder is mainly reflected in the stencil opening. A good stencil opening size plays a decisive role in soldering quality. Therefore, automatic and accurate design of the stencil opening for QFN devices is particularly important.

[0003] Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention provides a method, device, electronic device, and storage medium for automatically designing the stencil openings for QFN devices. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides a method for automatically designing a QFN device stencil opening, comprising:

[0006] For the target device that has completed QFN device verification, obtain the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge size of the target device on the PCB in the ECAD data, and the pre-set pin pad steel mesh thickness and pin bottom solder thickness as the device parameters of the target device;

[0007] Determining a pin pad stencil opening parameter calculation model for the target device based on the pin pad length and the pin pad width; wherein the pin pad stencil opening parameter calculation model is pre-constructed based on device parameters of a QFN device, and includes a first model for calculating the pin pad stencil opening length of the QFN device, and a second model for calculating the pin pad stencil opening width of the QFN device;

[0008] According to the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, the pin pad steel mesh opening design results of the target device are determined, including the pin pad steel mesh opening length and the pin pad steel mesh opening width, as well as the pin pad steel mesh opening center coordinates.

[0009] In a second aspect, an embodiment of the present invention provides a device for automatically designing a QFN device steel mesh opening, the device comprising:

[0010] A device parameter acquisition module is used to obtain, for a target device that has completed QFN device verification, the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge dimensions of the target device on the PCB in the ECAD data, as well as the preset pin pad steel mesh thickness and pin bottom solder thickness as device parameters of the target device;

[0011] a pin pad stencil opening parameter calculation model determination module, configured to determine a pin pad stencil opening parameter calculation model for the target device based on the pin pad length and the pin pad width; wherein the pin pad stencil opening parameter calculation model is pre-constructed based on device parameters of a QFN device, and includes a first model for calculating the pin pad stencil opening length of the QFN device, and a second model for calculating the pin pad stencil opening width of the QFN device;

[0012] The pin pad steel mesh opening design module is used to determine the pin pad steel mesh opening design results of the target device according to the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, including the pin pad steel mesh opening length and pin pad steel mesh opening width, as well as the pin pad steel mesh opening center coordinates.

[0013] In a third aspect, an embodiment of the present invention provides an electronic device, comprising a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus;

[0014] The memory is used to store computer programs;

[0015] The processor is configured to implement the steps of the method for automatically designing the openings of the QFN device steel mesh provided by the embodiment of the present invention when executing the program stored in the memory.

[0016] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the method for automatically designing the steel mesh opening of a QFN device provided in an embodiment of the present invention are implemented.

[0017] Beneficial effects of the present invention:

[0018] An embodiment of the present invention pre-constructs a pin pad stencil opening parameter calculation model for QFN devices; for a target device that has completed QFN device verification, the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge dimensions of the target device on the PCB in the ECAD data, as well as the pre-set pin pad stencil thickness and pin bottom solder thickness are obtained as device parameters, and substituted into the determined pin pad stencil opening parameter calculation model to determine the pin pad stencil opening design results, including the pin pad stencil opening length and pin pad stencil opening width, as well as the pin pad stencil opening center coordinates.

[0019] Furthermore, the present invention can also use modeling calculation to determine the design results of the heat dissipation pad steel mesh opening, including the heat dissipation pad steel mesh opening method, the length, width and center coordinates of the unit opening on the heat dissipation pad steel mesh.

[0020] Therefore, the embodiment of the present invention can accurately design the steel mesh opening for the QFN device through QFN device steel mesh opening modeling, which can improve the steel mesh quality and welding quality, avoid the problems of cold solder joints, false solder joints and bridging of QFN devices, thereby ensuring product reliability, effectively reducing rework costs, and saving enterprise costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic flow chart of a method for automatically designing a QFN device stencil opening according to an embodiment of the present invention;

[0022] FIG2( a ) is a schematic diagram of determining a device pin pad according to an embodiment of the present invention;

[0023] FIG2( b ) is another schematic diagram of determining the device pin pad according to an embodiment of the present invention;

[0024] FIG3 is a schematic diagram illustrating a heat dissipation pad of a QFN device according to an embodiment of the present invention;

[0025] FIG4 is a schematic diagram of the pin height of a QFN device according to an embodiment of the present invention;

[0026] 5( a ) and 5 ( b ) are respectively a bottom view and a side view of a QFN device according to an embodiment of the present invention;

[0027] FIG6 is a schematic diagram illustrating the front end length of a pin of a QFN device after mounting according to an embodiment of the present invention;

[0028] FIG7 is a schematic diagram illustrating the opening length of the stencil for the pin pads of a QFN device according to an embodiment of the present invention;

[0029] FIG8 is a schematic diagram illustrating the opening width of the QFN device pin pad steel mesh according to an embodiment of the present invention;

[0030] FIG9 is a schematic diagram of a cross-shaped opening pattern used in a steel mesh for a heat dissipation pad of a QFN device according to an embodiment of the present invention;

[0031] FIG10 is a schematic diagram of a crisscross pattern used for the openings of the heat dissipation pad steel mesh of a QFN device according to an embodiment of the present invention;

[0032] 11( a ) and 11 ( b ) are schematic diagrams of two types of pin pads during the QFN device verification process in Example 1 of the present invention;

[0033] FIG11( c ) is a schematic diagram of a heat dissipation pad during the verification process of a QFN device in Example 1 of the present invention;

[0034] 12( a ) to 12 ( d ) are schematic diagrams showing device parameters of the QFN device in Example 1 of the present invention;

[0035] FIG13 is a schematic diagram of the design results of the QFN device foot pad steel mesh opening in Example 1 of the present invention;

[0036] 14( a ) and 14 ( b ) are schematic diagrams of two types of pin pads during the QFN device verification process in Example 2 of the present invention;

[0037] FIG14( c ) is a schematic diagram of a heat dissipation pad during the verification process of a QFN device in Example 2 of the present invention;

[0038] 15( a ) to 15 ( d ) are schematic diagrams showing device parameters of the QFN device in Example 2 of the present invention;

[0039] FIG16 is a schematic diagram of the steel mesh opening design results of the QFN device foot pad in Example 2 of the present invention;

[0040] FIG17 is a schematic diagram of the design results of the steel mesh opening for the heat dissipation pad of the QFN device in Example 2 of the present invention;

[0041] FIG18 is a schematic structural diagram of an apparatus for automatically designing stencil openings for a QFN device provided by an embodiment of the present invention;

[0042] FIG19 is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0044] In a first aspect, an embodiment of the present invention provides a method for automatically designing a QFN device stencil opening, as shown in FIG1 , which may include the following steps:

[0045] S1, for the target device that has completed QFN device verification, obtain the device pin height and device external dimensions in the device data sheet, the pin pad length, pin pad width and pad outer edge size of the target device on the PCB in the ECAD data, as well as the pre-set pin pad steel mesh thickness and pin bottom solder thickness as device parameters of the target device;

[0046] In order to accurately determine the QFN device on the PCB for steel mesh opening design, the embodiment of the present invention first performs QFN device verification.

[0047] In an optional implementation manner, the process of verifying the QFN device includes:

[0048] 1) Obtain the part properties of the device to be verified from the ECAD data;

[0049] ECAD data is a type of circuit design file data. It contains all components on a circuit board and their part attributes. Part attributes include part number, part shape, device center coordinates, pin pad size, center pad size, center pad center coordinates, and the center coordinates of each pin pad.

[0050] The part number and part shape are respectively represented by a string of characters; the device center coordinates, the central large pad center coordinates and the center coordinates of each pin pad respectively include the x-coordinate and y-coordinate of the device center, the central large pad center and the center of each pin pad; the pin pad size and the central large pad size include their respective lengths and widths.

[0051] 2) Determine whether the keyword QFN is contained in the part number and / or part shape; if so, determine that the device to be inspected is a QFN device;

[0052] If at least one of the part number and part shape contains the keyword QFN, it is determined that the device to be verified is a QFN device and the subsequent steps are continued; if neither the part number nor the part shape contains the keyword QFN, it is determined that the device to be verified is not a QFN device and the subsequent steps are stopped.

[0053] 3) After determining that the device to be tested is a QFN device, determine the side symmetry of the QFN device based on the device center coordinates and the center coordinates of each pin pad, and count the number of pin pads on each side;

[0054] This step determines the side symmetry of the QFN device and the number of pin pads on each side for subsequent steel mesh opening design and positioning.

[0055] Among them, side symmetry includes bilateral symmetry or quadrilateral symmetry; bilateral symmetry means that the pin pads on a group of opposite sides of the QFN device are symmetrical along the x-axis or symmetrical along the y-axis; quadrilateral symmetry means that the pin pads on a group of opposite sides of the QFN device are symmetrical along the x-axis and symmetrical along the y-axis.

[0056] In an optional embodiment, judging the side symmetry of the QFN device based on the device center coordinates and the center coordinates of each pin pad, and counting the number of pin pads on each side, includes:

[0057] ① Determine whether the horizontal distances between the center coordinates of the two pin pads in each group of matching pin pads and the center coordinate of the device are the same on a set of opposite sides of the QFN device whose side extends in the y direction. If so, determine that the group of matching pin pads is a y-axis symmetrical figure. When all groups of matching pin pads on the group of opposite sides are determined to be y-axis symmetrical figures, determine that the pin pads on the group of opposite sides of the QFN device whose side extends in the y direction are all symmetrical along the y axis, which is referred to as the pin pads of the QFN device being symmetrical along the y axis. For each side of the group of opposite sides, count the number of pin pads on the side with the same x coordinate in the center coordinates to obtain the number of pin pads on the side. The matching pin pads on the group of opposite sides of the QFN device whose side extends in the y direction are distributed along opposite sides of the y direction, and their center coordinates have the same y coordinates.

[0058] Please refer to FIG. 2( a ) for understanding. FIG. 2( a ) is a schematic diagram of determining a device pin pad according to an embodiment of the present invention.

[0059] This step is for a group of opposite sides of the QFN device whose edge extension direction is the y direction, that is, a group of opposite sides distributed left and right, and a plurality of pads are respectively provided on the left side and the right side. The two pin pads with the same y coordinates of the center coordinates on the left side and the right side can be regarded as a group of matching pin pads. For example, in Figure 2(a), the coordinates of pin pad 3 are (X1, Y1), and the coordinates of pin pad 16 are (X2, Y2). If Y1=Y2, pin pads 3 and 16 are determined to be a group of matching pin pads. For example, after judgment, pin pads 1 and 18, 2 and 17, 4 and 15, 5 and 14, and 6 and 13 are also a group of matching pin pads.

[0060] For each set of matching pin pads, calculate the horizontal distance a between the center coordinates of the left pin pad and the center coordinates of the device, as well as the horizontal distance b between the center coordinates of the right pin pad and the center coordinates of the device. A determination is made as to whether a and b are the same. If so, the set of matching pin pads is determined to be y-axis symmetric. For example, if a = b is calculated for pin pads 3 and 16, the set of matching pin pads is determined to be y-axis symmetric. Pin pads 1 and 18, 2 and 17, 4 and 15, 5 and 14, and 6 and 13 are then sequentially determined to be y-axis symmetric. If all sets of matching pin pads are determined to be y-axis symmetric, the pin pads on opposite sides of the QFN device extending in the y-direction are determined to be symmetric along the y-axis, meaning that the pin pads of the QFN device are symmetric along the y-axis.

[0061] Then, for the left edge, count the number of pin pads with the same x-coordinate in their center coordinates, that is, count the number of points F with the same coordinates on the x-axis, to get the number of pin pads on that edge. For the right edge, count the number of pin pads with the same x-coordinate in their center coordinates, that is, count the number of points E with the same coordinates on the x-axis, to get the number of pin pads on that edge.

[0062] ② Determine whether the vertical distances between the center coordinates of the two pin pads in each group of matching pin pads and the center coordinate of the device are the same on a set of opposite sides of the QFN device whose side extends in the x-direction. If so, determine that the group of matching pin pads is an x-axis symmetrical figure; and when all groups of matching pin pads on the group of opposite sides are determined to be x-axis symmetrical figures, determine that the pin pads on the group of opposite sides of the QFN device whose side extends in the x-direction are all symmetrical along the x-axis, which is referred to as the pin pads of the QFN device being symmetrical along the x-axis; and for each side in the group of opposite sides, count the number of pin pads on the side with the same y coordinate in the center coordinates to obtain the number of pin pads on the side; wherein, a group of matching pin pads on the group of opposite sides of the QFN device whose side extends in the x-direction are distributed along opposite sides of the x-direction, and their center coordinates have the same x coordinate;

[0063] Please refer to Figure 2(b) for understanding. Figure 2(b) is another schematic diagram for determining the pin pads of a device according to an embodiment of the present invention. For simplicity, the pin pad numbers are not shown in this figure. Please refer to the pin pad numbers on the upper and lower sides in Figure 2(a).

[0064] This step is for a group of opposite sides of the QFN device whose edge extension direction is the x-direction, that is, a group of opposite sides distributed up and down, and the upper side and the lower side are respectively provided with multiple pads. The two pin pads with the same x-coordinates of the center coordinates on the upper side and the lower side can be regarded as a group of matching pin pads. For example, the coordinates of the pin pad 22 are (X1, Y1), and the coordinates of the pin pad 9 are (X2, Y2). If X1=X2, the pin pads 22 and 9 are determined to be a group of matching pin pads. For example, it is determined that the pin pads 24 and 7, 23 and 8, 21 and 10, 20 and 11, and 19 and 12 are also a group of matching pin pads.

[0065] For each set of matching pin pads, the vertical distance a between the center coordinates of the upper pin pad and the center coordinates of the device, as well as the vertical distance b between the center coordinates of the lower pin pad and the center coordinates of the device, are calculated. A determination is made as to whether a and b are the same. If so, the set of matching pin pads is determined to be x-axis symmetric. For example, for pin pads 22 and 9, if a = b is calculated, the set of matching pin pads is determined to be x-axis symmetric. Pin pads 24 and 7, 23 and 8, 21 and 10, 20 and 11, and 19 and 12 are then sequentially determined. If all sets of matching pin pads are determined to be x-axis symmetric, the pin pads on a set of opposite sides of the QFN device extending in the x-direction are determined to be symmetric along the x-axis, i.e., the pin pads of the QFN device are symmetric along the x-axis.

[0066] Then, for the upper edge, count the number of pin pads with the same y coordinates in the center coordinates, that is, count the number of points G with the same coordinates on the y-axis, to obtain the number of pin pads on the edge. For the lower edge, count the number of pin pads with the same y coordinates in the center coordinates, that is, count the number of points H with the same coordinates on the y-axis, to obtain the number of pin pads on the edge.

[0067] It should be noted that the same symbols in ① and ②, such as a, b, X1, Y1, etc., are only used as examples and do not mean that they have the same meaning in these two steps. Please refer to each step and the corresponding drawings for the specific meaning of the symbols. Moreover, the numbering order of the pin pads in ① and ② is not limited to the above examples.

[0068] ③ If the pin pad of the QFN device is symmetrical along the x-axis or symmetrical along the y-axis, the side symmetry of the QFN device is determined to be bilateral symmetry; if the pin pad of the QFN device is symmetrical along the x-axis and symmetrical along the y-axis, the side symmetry of the QFN device is determined to be quadrilateral symmetry.

[0069] That is to say, if the pin pads on one set of opposite sides of the QFN device are symmetrical along the x-axis or symmetrical along the y-axis, it is bilaterally symmetrical; if the pin pads on one set of opposite sides of the QFN device are symmetrical along the x-axis and the pin pads on the other set of opposite sides are symmetrical along the y-axis, it is quadrilaterally symmetrical.

[0070] 4) The larger of the pin pad size and the central large pad size is determined as the maximum pad; determine whether the center coordinates of the maximum pad coincide with the center coordinates of the device. If so, determine that the target device has a heat dissipation pad, and the heat dissipation pad is the largest pad.

[0071] Those skilled in the art will appreciate that not all QFN devices have heat dissipation pads. Therefore, after step 3), it is necessary to further determine the condition of the heat dissipation pad.

[0072] Please refer to Figure 3 for further details. Figure 3 is a schematic diagram illustrating the thermal pad design of a QFN device according to an embodiment of the present invention. This step first compares the pin pad size with the central pad size. If the larger pad exists, the larger pad is determined as the maximum pad. If the maximum pad does not exist, the target device does not have a thermal pad. After determining that the maximum pad exists, the center coordinates of the maximum pad coincide with the device center coordinates. If so, the thermal pad is determined to be the maximum pad, indicating that the target device has a thermal pad. In Figure 3, D2 represents the outer edge size of the pad; L and W represent the pin pad length and width.

[0073] S2, determining a pin pad steel mesh opening parameter calculation model of the target device based on the pin pad length and pin pad width;

[0074] Among them, the pin pad steel mesh opening parameter calculation model is pre-built based on the device parameters of the QFN device, including a first model for calculating the pin pad steel mesh opening length of the QFN device, and a second model for calculating the pin pad steel mesh opening width of the QFN device.

[0075] To facilitate understanding of the solution, the construction process of the pin pad steel mesh opening parameter calculation model is explained here.

[0076] For QFN devices, the process of building a calculation model for the pin pad stencil opening parameters includes:

[0077] Step a1: For QFN devices, obtain the device pin height and device dimensions from the device datasheet; obtain the pin pad length, pin pad width, and pad outer edge dimensions from the ECAD data; set the corresponding pin pad stencil thickness and pin bottom solder thickness; and obtain the corresponding preset ratio parameters;

[0078] For the device pin height, please refer to the QFN device pin height schematic diagram shown in FIG4 , and FIG5( a ) and FIG5( b ) respectively show the bottom view and side view of the QFN device.

[0079] The device pin height is represented by h; the device outer dimension is represented by D1; the pin pad length is represented by L; the pin pad width is represented by W; and the pad outer edge dimension is represented by D2. The pin pad stencil thickness is represented by t, and can be set accordingly for different QFN devices. The pin bottom solder thickness is represented by y, and can also be set accordingly for different QFN devices. For example, in one optional embodiment, y can be 0.03mm. The preset ratio parameter is represented by d, and can be selected according to different soldering conditions, such as different soldering equipment, such as hot air furnaces and gas phase furnaces, with different settings for d.

[0080] Step a2, calculate the front end length of the pin after mounting based on the device's overall dimensions and the outer edge dimensions of the pad;

[0081] Please refer to Figure 6 for a schematic diagram of the front end length of the QFN device after mounting.

[0082] Calculate the difference between the outer edge dimension D2 of the pad and the device outer dimension D1, and use the ratio of the difference to 2 as the front end length of the QFN device after mounting, expressed as A, that is:

[0083] Step a3, calculating the ratio of the pin pad length to the pin pad width to obtain the pad aspect ratio;

[0084] Specifically, the pad aspect ratio L / W is calculated.

[0085] Step a4: If the pad aspect ratio is greater than the corresponding preset ratio parameter, set the known parameter of the pin pad stencil opening to the pin pad stencil opening width and the pin pad width of the QFN device, and set the pin pad stencil opening to align with the inner edge of the pin pad. According to the pin pad length, pin pad width, the front end length of the pin after placement, the pin height, the pin pad stencil thickness, and the solder thickness at the bottom of the pin, a first model is constructed to calculate the pin pad stencil opening length of the QFN device;

[0086] For a pad aspect ratio L / W>d, step a4 may include:

[0087] Step b1, constructing a unit model based on the pin pad length, pin pad width, pin front end length after mounting, pin height, and pin bottom solder thickness of the QFN device;

[0088] Specifically, step b1 may include:

[0089] Step c1, taking the product of the front end length of the pin after mounting and the pin height as the first unit sub-model;

[0090] Specifically, the first unit sub-model is A*h;

[0091] Step c2, taking the quotient of the first unit sub-model and 2 as the second unit sub-model;

[0092] Specifically, the second unit sub-model is (A*h) / 2;

[0093] Step c3, taking the product of the second unit sub-model and the width of the pin pad of the QFN device as the third unit sub-model;

[0094] Specifically, the third unit sub-model is (A*h) / 2*W;

[0095] Step c4, using the difference between the pin pad length of the QFN device and the front end length of the pin after mounting as the fourth unit sub-model;

[0096] Specifically, the fourth unit submodel is LA;

[0097] Step c5, multiplying the fourth unit sub-model by the width of the pin pad of the QFN device and the solder thickness at the bottom of the pin as the fifth unit sub-model;

[0098] Specifically, the fifth unit submodel is (LA)*W*y;

[0099] Step c6: Determine the sum of the third unit sub-model and the fifth unit sub-model as the unit model.

[0100] Specifically, the unit model is (A*h) / 2*W+(LA)*W*y;

[0101] Step b2, determining the product of the unit model and 2 as the molecular model;

[0102] Specifically, the molecular model is [(A*h) / 2*W+(LA)*W*y]*2;

[0103] Step b3, using the product of the known parameters of the pin pad stencil opening of the QFN device and the pin pad stencil thickness as the denominator model;

[0104] Specifically, the denominator model is the known parameter of the pin pad steel mesh opening*t;

[0105] Step b4, constructing a corresponding model based on the ratio of the numerator model and the denominator model;

[0106] Specifically, the corresponding model is the numerator model / denominator model;

[0107] When the known parameter of the pin pad stencil opening of the QFN device is the pin pad stencil opening width, the corresponding model is the first model. That is, for the first model, the known parameter of the pin pad stencil opening = W, and the pin pad stencil opening width W1 of the QFN device = W. In this case, step b4 yields the first model.

[0108] Specifically, the first model can be expressed as:

[0109] Wherein, L1 represents the opening length of the pin pad steel mesh of the QFN device.

[0110] Please refer to Figure 7 for an understanding of the pin pad steel mesh opening length L1.

[0111] In the case of the pad aspect ratio L / W>d, since the known pin pad width W is used as the pin pad steel mesh opening width, and the steel mesh opening is aligned with the inner pin pad edge, it can be understood that the center coordinates of the pin pad steel mesh opening will be offset relative to the center coordinates of the pin pad. Therefore, it is necessary to calculate the offset and specifically calculate the center coordinates of the pin pad steel mesh opening based on the offset and the center coordinates of the pin pad. This part will be explained later.

[0112] Step a5: If the pad aspect ratio is less than or equal to the corresponding preset ratio parameter, set the known parameter of the pin pad stencil opening to the pin pad stencil opening length and the pin pad length of the QFN device, and set the pin pad stencil opening width to expand equidistantly from the center of the pin pad to both sides. According to the pin pad length, pin pad width, the front end length of the pin after placement, the pin height, the pin pad stencil thickness, and the solder thickness at the bottom of the pin, a second model is constructed to calculate the pin pad stencil opening width of the QFN device;

[0113] For a pad aspect ratio of L / W ≤ d, step a5 may also include steps b1 to b4. When the known parameter of the QFN device's lead pad stencil opening is the lead pad stencil opening length, the corresponding model is the second model. That is, for the second model, the known parameter of the lead pad stencil opening = L, and the QFN device's lead pad stencil opening length L1 = L. In this case, step b4 yields the second model.

[0114] Specifically, the second model can be expressed as:

[0115] Wherein, W1 represents the opening width of the pin pad steel mesh of the QFN device.

[0116] Please refer to Figure 8 for an understanding of the pin pad steel mesh opening width W1.

[0117] It should be noted that, when the pad aspect ratio L / W ≤ d, if the gap value between the steel mesh opening widths is less than the process capability value q, the steel mesh thickness t is adjusted.

[0118] It can be understood that when the pad aspect ratio L / W ≤ d, since the pin pad steel mesh opening width expands outward from the pin pad center to both sides, the pin pad steel mesh opening center coordinates will not offset relative to the pin pad center coordinates, and the pin pad steel mesh opening center coordinates are equal to the pin pad center coordinates, and no recalculation is required.

[0119] Then, based on the above modeling, in S2, the pin pad steel mesh opening parameter calculation model of the target device is determined based on the pin pad length and pin pad width, including:

[0120] Calculate the ratio of the pin pad length to the pin pad width of the target device to obtain the pad aspect ratio of the target device;

[0121] Determine whether the pad aspect ratio of the target device is greater than the corresponding preset ratio parameter;

[0122] If so, determining that the pin pad stencil opening parameter calculation model of the target device is the first model;

[0123] If not, determine that the pin pad stencil opening parameter calculation model of the target device is the second model.

[0124] Specifically, when L / W>d, the pin pad stencil opening parameter calculation model of the target device is the first model; when L / W≤d, the pin pad stencil opening parameter calculation model of the target device is the second model.

[0125] S3, according to the device parameters of the target device and the pin pad stencil opening parameter calculation model, determine the pin pad stencil opening design result of the target device, including the pin pad stencil opening length and the pin pad stencil opening width, as well as the pin pad stencil opening center coordinates.

[0126] Specifically, S3 may include:

[0127] S31, if the pin pad stencil opening parameter calculation model is the first model, the device parameters of the target device are correspondingly substituted into the first model to obtain the pin pad stencil opening length of the target device; according to the size relationship between the pin pad length of the target device and the pin pad stencil opening length of the target device, the deviation amount obtained by the absolute value of the difference between the pin pad length of the target device and the pin pad stencil opening length of the target device, and the center coordinates of each pin pad of the target device, the center coordinates of each pin pad of the target device are determined; the pin pad stencil opening design result of the target device is obtained from the pin pad stencil opening length of the target device, the pin pad stencil opening width and the calculated center coordinates of each pin pad stencil opening;

[0128] In S31, the device parameters of the target device are correspondingly substituted into the first model to obtain the pin pad steel mesh opening length of the target device. For details, please refer to the calculation formula of L1, which will not be described here.

[0129] In this case, the center coordinates of the pin pad stencil openings will be offset relative to the center coordinates of the pin pads, and the center coordinates of the pin pad stencil openings of the target device need to be recalculated.

[0130] Specifically, according to the size relationship between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, the deviation amount obtained by the absolute value of the difference between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, and the center coordinates of each pin pad of the target device, the center coordinates of the steel mesh opening of each pin pad of the target device are determined, including:

[0131] Case 1: If the pin pad stencil opening length of the target device is greater than or equal to the pin pad length of the target device, if there is a pair of opposite sides of the pin pad that are symmetrical along the x-axis, the center coordinates of the pin pad stencil opening on the upper side of the pair of opposite sides are calculated as (x 中 , y 中 +M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 -M); if there is a pair of opposite sides of the pin pad that are symmetrical along the y-axis, calculate the center coordinates of the pin pad steel mesh opening on the left side of the pair of opposite sides as (x 中 -M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 +M,y 中 );

[0132] For case 1, L1≥L,x 中 and y 中 They represent the x-coordinate and y-coordinate of the center coordinates of the corresponding pin pad respectively; M = |L-L1|, which represents the deviation; L represents the pin pad length of the target device; and L1 represents the pin pad steel mesh opening length of the target device.

[0133] Refer to Figure 2(a) or Figure 2(b) to understand that no matter whether the QFN device is bilaterally symmetrical or quadrilaterally symmetrical, as long as a pair of symmetrical sides are symmetrical along the x-axis, the center coordinates of the pin pad steel mesh opening on the upper side of the pair of sides are (x 中 ,y 中 +M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 -M);

[0134] Similarly, regardless of whether the QFN device is bilaterally symmetrical or quadrilaterally symmetrical, as long as a set of symmetrical sides is symmetrical along the y-axis, the center coordinates of the pin pad steel mesh opening on the left side of the set of sides are (x 中 -M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 +M,y 中 ).

[0135] Case 2: If the pin pad stencil opening length of the target device is smaller than the pin pad length of the target device, if there is a pair of opposite sides of the pin pad that are symmetrical along the x-axis, the center coordinates of the pin pad stencil opening on the upper side of the pair of opposite sides are calculated as (x 中 ,y 中 -M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 +M); if there is a pair of opposite sides of the pin pad that are symmetrical along the y-axis, calculate the center coordinates of the pin pad steel mesh opening on the left side of the pair of opposite sides as (x 中 +M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 -M,y 中 );

[0136] For case 2, L1<L,x 中 and y 中 They represent the x-coordinate and y-coordinate of the center coordinates of the corresponding pin pad respectively; M = |L-L1|, which represents the deviation; L represents the pin pad length of the target device; and L1 represents the pin pad steel mesh opening length of the target device.

[0137] Refer to Figure 2(a) or Figure 2(b) to understand that no matter whether the QFN device is bilaterally symmetrical or quadrilaterally symmetrical, as long as a pair of symmetrical sides are symmetrical along the x-axis, the center coordinates of the pin pad steel mesh opening on the upper side of the pair of sides are (x 中 ,y 中 -M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 +M);

[0138] Similarly, regardless of whether the QFN device is bilaterally symmetrical or quadrilaterally symmetrical, as long as a set of symmetrical sides is symmetrical along the y-axis, the center coordinates of the pin pad steel mesh opening on the left side of the set of sides are (x 中 +M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 -M,y 中).

[0139] Please refer to the relevant drawings to understand the calculation principle of the center coordinates of the steel mesh openings of each pin pad in the above cases 1 and 2.

[0140] Then, for the first model, the pin pad steel mesh opening design results of the target device include the calculated pin pad steel mesh opening length of the target device, the known pin pad steel mesh opening width of the target device, that is, the pin pad width of the target device, and the calculated center coordinates of each pin pad steel mesh opening.

[0141] S32. If the pin pad steel mesh opening parameter calculation model is the second model, the device parameters of the target device are correspondingly substituted into the second model to obtain the pin pad steel mesh opening width of the target device; the pin pad steel mesh opening width, the pin pad steel mesh opening length and the center coordinates of each pin pad of the target device are used to obtain the pin pad steel mesh opening design result of the target device.

[0142] In S32, the device parameters of the target device are correspondingly substituted into the second model to obtain the pin pad steel mesh opening width of the target device. The calculation formula of W1 can be referred to for understanding, which will not be repeated here.

[0143] It can be understood that for the second model, the pin pad steel mesh opening design results of the target device obtained include the calculated pin pad steel mesh opening width of the target device, the known pin pad steel mesh opening length of the target device, that is, the pin pad length of the target device, and the known center coordinates of each pin pad steel mesh opening, that is, the center coordinates of the pin pad.

[0144] At this point, the pin pad stencil opening design result of the target device can be obtained. However, as mentioned above, during the QFN device verification process, it is also determined whether the QFN device has a heat dissipation pad. Therefore, when it is determined that the target device has a heat dissipation pad, the method for automatically designing the QFN device stencil opening also includes:

[0145] S4, based on the heat dissipation pad size of the target device, the preset heat dissipation pad size shrinkage ratio and the bridge width, determine the heat dissipation pad steel mesh opening design result of the target device, including the heat dissipation pad steel mesh opening method, the length, width and center coordinates of the unit opening on the heat dissipation pad steel mesh.

[0146] That is to say, when the target device, which is a QFN device, also has a heat dissipation pad, it is also necessary to design the heat dissipation pad steel mesh opening.

[0147] In an optional implementation, S4 may include:

[0148] S41, shrinking the heat dissipation pad size of the target device according to a preset heat dissipation pad size shrinkage ratio to obtain a shrinking length and a shrinking width;

[0149] The target device's thermal pad dimensions include length and width. Shrinking the target device's thermal pad dimensions according to a preset thermal pad shrinkage ratio involves multiplying the thermal pad length and width by the preset thermal pad shrinkage ratio to obtain the shrinked length and width.

[0150] In the embodiment of the present invention, the preset shrinkage ratio of the heat dissipation pad size can be set as needed, for example, the value range can be 10% to 40%.

[0151] For ease of description, the length of the heat dissipation pad is denoted by L2, the width of the heat dissipation pad is denoted by W2, and the retracted length and retracted width are denoted by L3 and W3, respectively.

[0152] S42, determining whether the heat dissipation pad size of the target device is less than or equal to a preset size;

[0153] The preset size can be set as needed, for example, it can be 25mm 2 wait.

[0154] S43, if yes, determine that the heat dissipation pad steel mesh opening method of the target device adopts a cross-shaped method; and calculate the length and width of the unit opening on the heat dissipation pad steel mesh in the cross-shaped method according to the heat dissipation pad size, the retracted width and the bridge width of the target device; and calculate the center coordinates of the four unit openings in the cross-shaped method according to the center coordinates of the heat dissipation pad of the target device, the calculated unit opening length, the unit opening width and the bridge width;

[0155] It's understandable that a cross-shaped pattern results in four unit openings. For details on the cross-shaped pattern used for heatsink stencil openings, see Figure 9. The bridge width in Figure 9 represents the bridge width, and the cross-shaped bridge represents the cross-shaped pattern. Each unit opening represents a stencil opening on the heatsink pad.

[0156] Among them, S43 specifically includes:

[0157] S431, calculating the difference between the heat sink pad length and the retracted width and the bridge width in turn from the heat sink pad length of the target device, and determining the ratio of the obtained difference to 2 as the length of the unit opening on the heat sink pad steel mesh in the cross-type configuration;

[0158] The length of the unit opening on the heat dissipation pad steel mesh in the cross-type rack is expressed as L 长 . L 长 =(L2-W3-W 架桥 ) / 2

[0159] In the above formula of this step, W 架桥 Indicates the bridge width; L 长 Indicates the calculated length of the unit opening; W 宽 Indicates the calculated width of the unit opening. The bridge width can be set as needed, for example, in the range of 0.12 to 0.5 mm.

[0160] S432, calculating the difference between the heat sink width and the bridge width in the heat sink pad size of the target device, and determining the ratio of the obtained difference to 2 as the width of the unit opening on the heat sink pad steel mesh in the cross-type configuration;

[0161] The width of the unit opening on the heat dissipation pad steel mesh in the cross-type rack is expressed as W 宽 .W 宽 =(W2-W3-W 架桥 ) / 2

[0162] S433, calculate the center coordinates of the four unit openings in the cross-frame mode and obtain:

[0163] The center coordinate of the upper left unit opening is (x coordinate of the center coordinate of the heat dissipation pad - W 架桥 / 2-W 宽 / 2, y coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+L 长 / 2);

[0164] The center coordinate of the lower left unit opening is (x coordinate of the center coordinate of the heat dissipation pad - W 架桥 / 2-W 宽 / 2, y coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-L 长 / 2);

[0165] The center coordinate of the upper right unit opening is (x coordinate of the center coordinate of the heat dissipation pad + W 架桥 / 2+W 宽 / 2, y coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+L 长 / 2);

[0166] The center coordinate of the lower right unit opening is (x coordinate of the center coordinate of the heat dissipation pad + W 架桥 / 2+W 宽 / 2, y coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-L 长 / 2);

[0167] Among them, W 架桥Indicates the bridge width; L 长 Indicates the calculated length of the unit opening; W 宽 Indicates the calculated width of the cell opening.

[0168] S44, if not, determine that the target device's heat sink pad steel mesh opening method adopts a crisscross method; and calculate the length and width of the unit opening on the heat sink pad steel mesh in the crisscross method according to the target device's heat sink pad size, the retracted width and the bridge width; and calculate the center coordinates of the 9 unit openings in the crisscross method according to the center coordinates of the target device's heat sink pad, the calculated length of the unit opening, the width of the unit opening and the bridge width.

[0169] It is understandable that the crisscross pattern will result in nine unit openings. For details on the crisscross pattern used for the heatsink stencil openings, please refer to Figure 10.

[0170] Among them, S44 specifically includes:

[0171] S441, calculating the product of the bridge width and 2 to obtain a bridge width product result;

[0172] Specifically, the product of the bridge width = W 架桥 *2;

[0173] S442, calculating the difference between the heat sink pad length in the heat sink pad size of the target device and the product of the indented width and the bridge width, and determining the ratio of the obtained difference to 3 as the length of the unit opening on the heat sink pad steel mesh in the cross-shaped pattern;

[0174] The length of the unit opening on the heat dissipation pad steel mesh in the cross-shaped structure can also be expressed as L 长 , at this time: L 长 =(L2-W3-W 架桥 *2) / 3

[0175] S443, calculating the difference between the heat sink width and the product of the indented width and the bridge width in the heat sink pad size of the target device, and determining the ratio of the obtained difference to 3 as the width of the unit opening on the heat sink pad steel mesh in the cross-shaped pattern;

[0176] The width of the unit opening on the heat dissipation pad steel mesh in the cross-shaped structure can also be expressed as W 宽 , at this time: W 宽 =(W2-W3-W 架桥 *2) / 3

[0177] S444, calculate the center coordinates of the 9 unit openings in the crisscross pattern to obtain:

[0178] The center coordinate of the upper left unit opening is (x coordinate of the center coordinate of the heat dissipation pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink + W 架桥 +L 长 );

[0179] The center coordinate of the left middle unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink pad);

[0180] The center coordinate of the lower left unit opening is (x coordinate of the center coordinate of the heat dissipation pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink pad - W 架桥 -L 长 );

[0181] The center coordinates of the upper and middle unit openings are (x coordinates of the center coordinates of the heat dissipation pad, y coordinates of the center coordinates of the heat dissipation pad + W 架桥 +L 长 );

[0182] The center coordinates of the center unit opening are (x coordinate of the center coordinate of the heat dissipation pad, y coordinate of the center coordinate of the heat dissipation pad);

[0183] The center coordinates of the opening of the middle and lower units are (x coordinate of the center coordinate of the heat dissipation pad, y coordinate of the center coordinate of the heat dissipation pad - W 架桥 -L 长 );

[0184] The center coordinate of the upper right unit opening is (x coordinate of the center coordinate of the heat dissipation pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink + W 架桥 +L 长 );

[0185] The center coordinate of the right middle unit opening is (x coordinate of the center coordinate of the heat dissipation pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink pad);

[0186] The center coordinate of the lower right unit opening is (x coordinate of the center coordinate of the heat dissipation pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink pad - W 架桥 -L 长 );

[0187] Among them, W 架桥 Indicates the bridge width; L长 Indicates the calculated length of the unit opening; W 宽 Indicates the calculated width of the cell opening.

[0188] But it should be noted that the L in the cross and well-shaped methods 长 、W 宽 Although the same symbols are used, the calculation methods are different. Please understand them in conjunction with the corresponding parts.

[0189] Through the above step S4, the heat dissipation pad steel mesh opening design result of the target device can be determined, including the heat dissipation pad steel mesh opening method, the length, width and center coordinates of the unit opening on the heat dissipation pad steel mesh, together with the pin pad steel mesh opening design result of the target device as its steel mesh opening design result.

[0190] An embodiment of the present invention pre-constructs a pin pad stencil opening parameter calculation model for QFN devices; for a target device that has completed QFN device verification, the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge dimensions of the target device on the PCB in the ECAD data, as well as the pre-set pin pad stencil thickness and pin bottom solder thickness are obtained as its device parameters, and substituted into the determined pin pad stencil opening parameter calculation model to determine the pin pad stencil opening design results, including the pin pad stencil opening length and pin pad stencil opening width, as well as the pin pad stencil opening center coordinates.

[0191] Furthermore, the present invention can also use modeling calculation to determine the design results of the heat dissipation pad steel mesh opening, including the heat dissipation pad steel mesh opening method, the length, width and center coordinates of the unit opening on the heat dissipation pad steel mesh.

[0192] Therefore, the embodiment of the present invention can accurately design the steel mesh opening for the QFN device through QFN device steel mesh opening modeling, which can improve the steel mesh quality and welding quality, avoid the problems of cold solder joints, false solder joints and bridging of QFN devices, thereby ensuring product reliability, effectively reducing rework costs, and saving enterprise costs.

[0193] To facilitate understanding of the embodiments of the present invention, two specific embodiments are given below for illustrative purposes.

[0194] 1) Example 1

[0195] For the verification of QFN devices, please refer to FIG. 11 (a) and FIG. 11 (b) for understanding. FIG. 11 (a) and FIG. 11 (b) are two schematic diagrams of the pin pads of the QFN device according to Example 1 of the present invention.

[0196] Get the device's part properties from the ECAD data, including:

[0197] Part number: QFN50P400X400_24_HS280N;

[0198] Part shape: QFN50P400X400_24_HS280N;

[0199] Device center coordinates: X: 22.720mm, Y: 137.274mm;

[0200] Pad outer edge size: size(4.3mm,4.3mm);

[0201] Pin pad size: size(0.25mm,0.55mm); where size is calculated as 0.25mm*0.55mm;

[0202] Central large pad size: size (2.45mm, 2.45mm);

[0203] Center coordinates of the central large pad: X: 22.720mm, Y: 137.274mm;

[0204] The center coordinates of each pin pad are shown in Table 1.

[0205] Table 1

[0206] It is determined that the above-mentioned part number and / or part shape contain the keyword QFN, so the device is determined to be a QFN device.

[0207] Referring to FIG11(a), the center coordinates of the No. 3 pin pad (20.72, 137.52), the center coordinates of the device (22.72, 137.27), and the center coordinates of the No. 16 pin pad (24.72, 137.52) are used to calculate: the horizontal distance between the center coordinates of the No. 3 pin pad and the center coordinates of the device is a = 22.72-20.72 = 2.0; the horizontal distance between the center coordinates of the No. 16 pin pad and the center coordinates of the device is b = 24.72-22.72 = 2.0. Since a = b = 2.0, the No. 3 pin pad and the No. 16 pin pad are symmetrical figures along the y-axis. Similarly, the left and right pin pads are all symmetrical along the y-axis.

[0208] Then, the number of points with the same coordinates as points E and F on the X-axis is counted respectively. The number of pads at point F is 6, that is, the number of pads for pins 1-6 is 6; the number of pads at point E is 6, that is, the number of pads for pins 13-18 is 6.

[0209] Similarly, referring to FIG11(b), the center coordinates of the No. 22 pin pad (22.47, 139.27), the center coordinates of the device (22.72, 137.27), and the center coordinates of the No. 9 pin pad (22.47, 135.27) are used to calculate: the vertical distance between the center coordinates of the No. 22 pin pad and the center coordinates of the device is a = 139.27 - 137.27 = 2, and the vertical distance between the center coordinates of the No. 9 pin pad and the center coordinates of the device is b = 137.27 - 135.27 = 2. Since a = b = 2.0 at this time, the No. 22 pin pad and the No. 9 pin pad are symmetrical figures along the x-axis. By analogy, the upper and lower pin pads are all symmetrical along the x-axis.

[0210] Then, by counting the number of points with the same coordinates as points G and H on the Y-axis, it can be found that the number of pads for pins 7-12 and 19-24 is 6.

[0211] Furthermore, since the pin pads of the device are symmetrical along the x-axis and the y-axis, the device has pin pads on all four sides, and the side symmetry is four-sided symmetry.

[0212] Further determine whether the device has a heat dissipation pad. Please refer to Figure 11(c) for understanding. Figure 11(c) is a schematic diagram of the heat dissipation pad of the QFN device of Example 1 of the present invention. Since the pin pad size of the device is size (0.25mm, 0.55mm) and the central large pad size is size (2.45mm, 2.45mm), the central large pad is the largest pad in the package, and the center coordinates of the largest pad are (22.720, 137.274), which coincide with the device center coordinates (22.720, 137.274). Therefore, this central large pad is a heat dissipation pad.

[0213] The following is a detailed description of the steel mesh opening design process for this device.

[0214] Please refer to Figures 12(a) to 12(d) for an understanding. Figures 12(a) to 12(d) are schematic diagrams of the device parameters of the device. Specifically, obtain the device pin height h = 0.2mm and device outer dimension D1 = 4.0mm from the device specification; obtain the pin pad length L = 0.55mm, pin pad width W = 0.25mm, and pad outer edge dimension D2 = 4.3mm from the ECAD data on the PCB; and obtain the pre-set pin pad stencil thickness t = 0.12mm and pin bottom solder thickness y = 0.03mm. These are used as the device parameters of the device.

[0215] Among them, the front end length of the pin after mounting is calculated as: A = (D2-D1) / 2 = (4.3-4.0) / 2 = 0.15mm.

[0216] The device's pad aspect ratio is calculated to be L / W = 0.55 / 0.25 = 0.22. Since the preset ratio parameter d = 3 (indicating hot air furnace heating), L / W < d, the second model is used to calculate the pin pad stencil opening parameter. Given the pin pad length L, the pin pad stencil opening width W1 is calculated. Specifically, the pin pad length L is used as the pin pad stencil opening length L1. The pin pad stencil opening width extends outward from the center of the pin pad. Substituting the corresponding parameters into the calculation formula for W1, the pin pad stencil opening width W1 is calculated.

[0217] Therefore, the second model shows that the pin pad stencil opening length L1 = 0.55mm, the pin pad stencil opening width W1 = 0.2mm, and the pin pad stencil opening center coordinate = the pin pad center coordinate. The foot pad stencil opening design results for this device include L1, W1, and the center coordinate of the pin pad stencil opening. See Figure 13 for an understanding of the foot pad stencil opening design results.

[0218] Since the device has a heat dissipation pad, the heat dissipation pad steel mesh opening design is also required.

[0219] The heat sink pad size of the device is size(2.45mm,2.45mm), and the calculated area is 2.45*2.45=6mm 2 , the area is smaller than the preset size 25mm 2 , the heat sink pad steel mesh opening method adopts the cross-shaped method. The center coordinates of the four unit openings need to be calculated.

[0220] Bridge width W 架桥 Set to 0.2mm; the shrinkage ratio of the heat dissipation pad size is set to 10%.

[0221] The unit opening length in the cross-type rack is:

[0222] The unit opening width in the cross-type rack is:

[0223] According to the calculation formula of the center coordinates of the four unit openings in the cross mode of S433, the coordinates of the four unit openings are obtained as follows:

[0224] The coordinates of the upper left unit opening are (22.72-0.1-0.5=22.12, 137.274+0.1+0.5=137.874);

[0225] The coordinates of the lower left unit opening are (22.72-0.1-0.5=22.12, 137.274-0.1-0.5=136.674);

[0226] The coordinates of the upper right unit opening are (22.72+0.1+0.5=23.32, 137.274+0.1+0.5=137.874);

[0227] The coordinates of the lower right unit opening are (22.72+0.1+0.5=23.32, 137.274-0.1-0.5=136.674);

[0228] The heat dissipation pad steel mesh opening design results of the device are obtained, including the heat dissipation pad steel mesh opening method is a cross frame method, and the length L of the unit opening on the heat dissipation pad steel mesh 长 , width W 宽 and the center coordinates of each unit opening.

[0229] 2) Example 2

[0230] For the verification of QFN devices, please refer to FIG. 14( a ) and FIG. 14( b ) for understanding. FIG. 14( a ) and FIG. 14( b ) are two schematic diagrams of the pin pads of the QFN device according to Example 2 of the present invention.

[0231] Get the device's part properties from the ECAD data, including:

[0232] Part number: QFN50P800X800X100-24N;

[0233] Part shape: QFN50P800X800X100-24N;

[0234] Device center coordinates: X: 22.720mm, Y: 137.274mm;

[0235] Pad outer edge size: size(8.5mm,8.5mm);

[0236] Pin pad size: size (0.25mm, 0.99mm);

[0237] Central large pad size: size (5.2mm, 5.2mm);

[0238] Center coordinates of the central large pad: X: 22.720mm, Y: 137.274mm;

[0239] The center coordinates of each pin pad are shown in Table 2.

[0240] Table 2

[0241] It is determined that the above-mentioned part number and / or part shape contain the keyword QFN, so the device is determined to be a QFN device.

[0242] Referring to FIG14(a), the center coordinates of the No. 3 pin pad (18.72, 137.52), the center coordinates of the device (22.72, 137.27), and the center coordinates of the No. 16 pin pad (26.72, 137.52) are used to calculate: the horizontal distance between the center coordinates of the No. 3 pin pad and the center coordinates of the device is a = 22.72-18.72 = 4.0; the horizontal distance between the center coordinates of the No. 16 pin pad and the center coordinates of the device is b = 26.72-22.72 = 4.0. Since a = b = 4.0, the No. 3 pin pad and the No. 16 pin pad are symmetrical figures along the y-axis. Similarly, the left and right pin pads are all symmetrical along the y-axis.

[0243] Then count the number of points with the same coordinates as points E and F on the X-axis. The number of pads at point F is 6, that is, the number of pads for pins 1-6 is 6; the number of pads at point E is 6, that is, the number of pads for pins 13-18 is 6.

[0244] Similarly, referring to FIG14(b), the center coordinates of the No. 22 pin pad (22.47, 141.27), the center coordinates of the device (22.72, 137.27), and the center coordinates of the No. 9 pin pad (22.47, 133.27) are used to calculate: the vertical distance between the center coordinates of the No. 22 pin pad and the center coordinates of the device is a = 141.27 - 137.27 = 4.0, and the vertical distance between the center coordinates of the No. 9 pin pad and the center coordinates of the device is b = 137.27 - 133.27 = 4.0. Since a = b = 4.0 at this time, the No. 22 pin pad and the No. 9 pin pad are symmetrical figures along the x-axis. By analogy, the upper and lower pin pads are all symmetrical along the x-axis.

[0245] Then, by counting the number of points with the same coordinates as points G and H on the Y-axis, it can be found that the number of pads for pins 7-12 and 19-24 is 6.

[0246] Furthermore, since the pin pads of the device are symmetrical along the x-axis and the y-axis, the device has pin pads on all four sides, and the side symmetry is four-sided symmetry.

[0247] Further determine whether the device has a heat dissipation pad. Please refer to Figure 14(c) for understanding. Figure 14(c) is a schematic diagram of the heat dissipation pad of the QFN device of Example 2 of the present invention. Since the pin pad size of the device is size (0.25mm, 0.99mm) and the central large pad size is size (5.2mm, 5.2mm), the central large pad is the largest pad in the package, and the center coordinates of the largest pad are (22.720, 137.274), which coincide with the device center coordinates (22.720, 137.274); therefore, this central large pad is a heat dissipation pad.

[0248] Please refer to Figures 15(a) to 15(d) for understanding. Figures 15(a) to 15(d) are schematic diagrams of device parameters for the QFN device in Example 2 of the present invention. Specifically, the device pin height h = 0.2mm and device outer dimension D1 = 8mm of the device in the device specification are obtained; the pin pad length L = 0.99mm, pin pad width W = 0.25mm, and pad outer edge dimension D2 = 8.5mm of the device on the PCB in the ECAD data are obtained; and the pre-set pin pad stencil thickness t = 0.1mm and pin bottom solder thickness y = 0.03mm are obtained. The above are used as the device parameters of the device.

[0249] Among them, the front end length of the pin after mounting is calculated as: A = (D2-D1) / 2 = (8.5-8) / 2 = 0.25mm.

[0250] The device's pad aspect ratio is calculated to be L / W = 0.99 / 0.25 = 3.96. Since the preset ratio parameter d = 3 (indicating hot air furnace heating), L / W > d, the pin pad stencil opening parameter calculation model is determined to be the first model. Given the pin pad width W, the pin pad stencil opening length L1 is calculated. Specifically, the pin pad width W is used as the pin pad stencil opening width W1. The pin pad stencil opening is aligned with the inner edge of the pin pad. Substituting the corresponding parameters into the calculation formula for L1, the pin pad stencil opening length L1 is calculated.

[0251] Therefore, the first model yields a pin pad stencil opening length of L1 = 0.944mm and a pin pad stencil opening width of W1 = 0.25mm. Because the center coordinates of the pin pad stencil opening are offset relative to the center coordinates of the pin pad, calculations must be made based on the center coordinates of the pin pad and the offset. For more information, see Figures 14(a) and 14(b).

[0252] Since the device's pin pad stencil opening length L1 = 0.944 mm is smaller than the device's pin pad length L = 0.99 mm, this corresponds to Case 2 in S31 : M = |L-L1| = |0.99-0.944| = 0.046 mm.

[0253] Since the device is four-sided symmetrical, for the two sides symmetrical along the y-axis:

[0254] The center coordinates of the pin pad steel mesh opening on the left side, that is, the center coordinates of the pin pad steel mesh openings from 1 to 16 are (x 中 +M,y 中 )=(x 中 +0.046=18.72+0.046=18.766,y 中 );

[0255] The center coordinates of the pin pad steel mesh opening on the right side, that is, the center coordinates of the pin pad steel mesh openings from 13 to 18, are (x 中 -M,y 中 )=(x 中 -M=x 中 -0.046=26.72-0.046=26.674, y 中 );

[0256] For two sides symmetric along the x-axis:

[0257] The center coordinates of the pin pad steel mesh opening on the upper side, that is, the center coordinates of the pin pad steel mesh openings from 19 to 24 are (x 中 ,y 中 -M)=(x 中 ,y 中 -M=y 中 -0.046=141.27-0.046=141.224);

[0258] The center coordinates of the pin pad steel mesh opening on the lower side are, that is, the center coordinates of the pin pad steel mesh openings from 7 to 12 are (x 中 ,y 中 + M) = (x 中 ,y 中 +M=y 中 +0.046=133.7+0.046=133.316).

[0259] Among them, x 中 and y 中 Respectively represent the x-coordinate and y-coordinate of the center coordinate of the corresponding pin pad.

[0260] The calculation results of the center coordinates of each pin pad are shown in Table 3.

[0261] Table 3

[0262] The design results for the device's foot pad stencil opening include L1 = 0.944mm, W1 = 0.25mm, and the center coordinates of the pin pad stencil opening. See Figure 16 for the design results.

[0263] Since the device has a heat dissipation pad, the heat dissipation pad steel mesh opening design is also required.

[0264] The heat sink pad size of the device is size(5.2mm,5.2mm), and the calculated area is 5.2*5.2=27.04mm 2 , the area is larger than the preset size by 25mm2 , the heat sink pad steel mesh opening method adopts the well-shaped pattern. The center coordinates of the 9 unit openings need to be calculated.

[0265] Bridge width W 架桥 Set to 0.2mm; the shrinkage ratio of the heat dissipation pad size is set to 10%.

[0266] The unit opening length in the well-shaped pattern is:

[0267] The unit opening width in the well-shaped pattern is:

[0268] According to the calculation formula of the center coordinates of the 9 unit openings in the cross-shaped pattern in S444, the coordinates of the 9 unit openings are obtained as follows:

[0269] The coordinates of the upper left unit opening are (22.72-0.2-1.25=21.27, 137.27+0.2+1.25=138.72);

[0270] The coordinates of the opening of the left middle unit are (22.72-0.2-1.25=21.27, 137.27);

[0271] The coordinates of the lower left unit opening are (22.72-0.2-1.25=21.27, 137.27-0.2-1.25=135.82);

[0272] The coordinates of the opening of the upper and middle units are (22.72, 137.27+0.2+1.25=138.72);

[0273] Central unit opening coordinates (22.72, 137.27);

[0274] The coordinates of the middle and lower unit opening are (22.72, 137.27-0.2-1.25=135.82);

[0275] The coordinates of the upper right unit opening are (22.72+0.2+1.25=24.17, 137.27+0.2+1.25=138.72);

[0276] Coordinates of the right middle unit opening (22.72+0.2+1.25=24.17, 137.27);

[0277] The coordinates of the lower right unit opening are (22.72+0.2+1.25=24.17, 137.27-0.2-1.25=135.82);

[0278] The heat dissipation pad steel mesh opening design results of the device are obtained, including the heat dissipation pad steel mesh opening method is a well-shaped method, and the length L of the unit opening on the heat dissipation pad steel mesh 长 , width W 宽 The center coordinates of each unit opening are shown in Figure 17 for the design results of the heatsink stencil opening.

[0279] In a second aspect, corresponding to the above method embodiment, an embodiment of the present invention further provides a device for automatically designing a QFN device stencil opening, as shown in FIG18 , the device comprising:

[0280] The device parameter acquisition module 1801 is used to obtain, for a target device that has completed QFN device verification, the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge dimensions of the target device on the PCB in the ECAD data, and the preset pin pad stencil thickness and pin bottom solder thickness as device parameters of the target device;

[0281] A pin pad stencil opening parameter calculation model determination module 1802 is configured to determine a pin pad stencil opening parameter calculation model for a target device based on the pin pad length and the pin pad width. The pin pad stencil opening parameter calculation model is pre-built based on device parameters of a QFN device and includes a first model for calculating the pin pad stencil opening length of the QFN device and a second model for calculating the pin pad stencil opening width of the QFN device.

[0282] The pin pad steel mesh opening design module 1803 is used to determine the pin pad steel mesh opening design results of the target device based on the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, including the pin pad steel mesh opening length and pin pad steel mesh opening width, as well as the pin pad steel mesh opening center coordinates.

[0283] For specific details, please refer to the relevant content of the method for automatically designing the steel mesh opening of the QFN device described in the first aspect, which will not be repeated here.

[0284] In a third aspect, an embodiment of the present invention further provides an electronic device, as shown in FIG19 , including a processor 1901, a communication interface 1902, a memory 1903, and a communication bus 1904, wherein the processor 1901, the communication interface 1902, and the memory 1903 communicate with each other via the communication bus 1904.

[0285] Memory for storing computer programs;

[0286] The processor is configured to implement, when executing the program stored in the memory, any of the steps of the method for automatically designing the opening of the QFN device stencil provided in the first aspect of the embodiment of the present invention.

[0287] The communication bus mentioned in the above electronic device may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The communication bus may be divided into an address bus, a data bus, a control bus, etc.

[0288] The communication interface is used for communication between the above electronic device and other devices.

[0289] The memory may include a random access memory (RAM) or a non-volatile memory (NVM), such as at least one disk memory.

[0290] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc.

[0291] The method provided in the embodiment of the present invention can be applied to electronic devices. Specifically, the electronic devices can be: desktop computers, portable computers, smart mobile terminals, servers, etc., which are not limited here.

[0292] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of any method for automatically designing the steel mesh opening of a QFN device provided in the first aspect of the embodiment of the present invention are implemented.

[0293] For the device / electronic device / storage medium embodiments, the specific implementation principles, processes and technical effects are similar to those of the method embodiments and will not be repeated here.

[0294] The above description is a further detailed description of the present invention in conjunction with specific preferred embodiments. The specific implementation of the present invention is not limited to these descriptions. Those skilled in the art may combine and combine the different embodiments or examples described in this specification. Those skilled in the art may also make several simple deductions or substitutions without departing from the scope of the present invention, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for automatically designing a QFN device steel mesh opening, characterized in that: include: For the target device that has completed the QFN device verification, the device pin height and device size in the device specification, the pin pad length, pin pad width and pad outer edge size of the target device on the PCB in the ECAD data, and the pre-set pin pad steel mesh thickness and pin bottom solder thickness are obtained as device parameters of the target device; Based on the pin pad length and the pin pad width, determining a pin pad steel mesh opening parameter calculation model of the target device; wherein the pin pad steel mesh opening parameter calculation model is pre-constructed based on the device parameters of the QFN device, including a first model for calculating the pin pad steel mesh opening length of the QFN device, and a second model for calculating the pin pad steel mesh opening width of the QFN device; According to the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, the pin pad steel mesh opening design result of the target device is determined, including the pin pad steel mesh opening length and the pin pad steel mesh opening width, as well as the pin pad steel mesh opening center coordinates.

2. The method for automatically designing the opening of a QFN device steel mesh according to claim 1, characterized in that: The QFN device verification process includes: Obtaining part properties of the device to be verified from the ECAD data; wherein the part properties include part number, part shape, device center coordinates, pin pad size, central large pad size, central large pad center coordinates, and center coordinates of each pin pad; Determine whether the part number and / or the part shape contains the keyword QFN; if so, determine that the device to be tested is a QFN device; After determining that the device to be checked is a QFN device, judging the side symmetry of the QFN device according to the center coordinates of the device and the center coordinates of each pin pad, and counting the number of pin pads on each side; wherein the side symmetry includes two-side symmetry or four-side symmetry; the two-side symmetry means that the pin pads on a group of opposite sides of the QFN device are symmetrical along the x-axis or symmetrical along the y-axis; the four-side symmetry means that the pin pads on a group of opposite sides of the QFN device are symmetrical along the x-axis and symmetrical along the y-axis; The larger of the pin pad size and the central large pad size is determined as the maximum pad; whether the center coordinate of the maximum pad coincides with the center coordinate of the device is determined, and if so, it is determined that the target device has a heat dissipation pad, and the heat dissipation pad is the maximum pad.

3. The method for automatically designing the opening of a QFN device steel mesh according to claim 2, characterized in that: When it is determined that the target device has a heat dissipation pad, the method further includes: Based on the heat dissipation pad size of the target device, the preset heat dissipation pad size shrinkage ratio and the bridge width, the heat dissipation pad steel mesh opening design result of the target device is determined, including the heat dissipation pad steel mesh opening method, the length, width and center coordinates of the unit opening on the heat dissipation pad steel mesh.

4. The method for automatically designing the opening of a QFN device steel mesh according to claim 1, characterized in that: For QFN devices, the construction process of the pin pad steel mesh opening parameter calculation model includes: For QFN devices, obtain the device pin height and device dimensions from the device specification; obtain the pin pad length, pin pad width and pad outer edge dimensions from the ECAD data; set the corresponding pin pad steel mesh thickness and pin bottom solder thickness; and obtain the corresponding preset ratio parameters; Calculate the front end length of the pin after mounting based on the device dimensions and the outer edge dimensions of the pad; Calculate the ratio of the pin pad length to the pin pad width to obtain the pad aspect ratio; If the pad aspect ratio is greater than the corresponding preset ratio parameter, set the known parameter of the pin pad steel mesh opening to the pin pad steel mesh opening width and the pin pad width of the QFN device, and set the pin pad steel mesh opening to align with the inner edge of the pin pad, and construct a first model based on the pin pad length, pin pad width, front end length of the pin after mounting, pin height, pin pad steel mesh thickness and pin bottom solder thickness to calculate the pin pad steel mesh opening length of the QFN device; If the pad aspect ratio is less than or equal to the corresponding preset ratio parameter, set the known parameter of the pin pad steel mesh opening to the pin pad steel mesh opening length and the pin pad length of the QFN device, and set the pin pad steel mesh opening width to expand equidistantly from the center of the pin pad to both sides, and construct a second model based on the pin pad length, pin pad width, front end length of the pin after mounting, pin height, pin pad steel mesh thickness and pin bottom solder thickness to calculate the pin pad steel mesh opening width of the QFN device; Correspondingly, based on the pin pad length and the pin pad width, a pin pad steel mesh opening parameter calculation model of the target device is determined, including: Calculating the ratio of the pin pad length to the pin pad width of the target device to obtain the pad length-to-width ratio of the target device; Determine whether the pad aspect ratio of the target device is greater than a corresponding preset ratio parameter; If yes, determine that the pin pad steel mesh opening parameter calculation model of the target device is the first model; If not, determine that the pin pad steel mesh opening parameter calculation model of the target device is the second model.

5. The method for automatically designing the opening of a QFN device steel mesh according to claim 4, characterized in that: A first model is constructed based on the pin pad length, the pin pad width, the pin front end length after mounting, the pin height, the pin pad steel mesh thickness, and the pin bottom solder thickness, or a second model is constructed based on the pin pad length, the pin pad width, the pin front end length after mounting, the pin height, the pin pad steel mesh thickness, and the pin bottom solder thickness, including: The unit model is constructed based on the pin pad length, pin pad width, pin front end length after mounting, pin height and pin bottom solder thickness of the QFN device; Determine the product of the unit model and 2 as a molecular model; The product of the known parameters of the pin pad stencil opening of the QFN device and the pin pad stencil thickness is used as the denominator model; A corresponding model is constructed according to the ratio of the numerator model and the denominator model; wherein, when the known parameter of the pin pad steel mesh opening of the QFN device is the pin pad steel mesh opening width, the corresponding model is the first model; when the known parameter of the pin pad steel mesh opening of the QFN device is the pin pad steel mesh opening length, the corresponding model is the second model.

6. The method for automatically designing the opening of a QFN device steel mesh according to claim 5, characterized in that: The unit model is constructed based on the pin pad length, pin pad width, pin front end length after mounting, pin height and pin bottom solder thickness of the QFN device, including: The product of the front end length of the pin after mounting and the pin height is used as the first unit sub-model; Taking the quotient of the first unit sub-model and 2 as the second unit sub-model; The product of the second unit sub-model and the width of the pin pad of the QFN device is used as the third unit sub-model; The difference between the pin pad length of the QFN device and the front end length of the pin after mounting is used as the fourth unit sub-model; The product of the fourth unit sub-model, the width of the pin pad of the QFN device, and the solder thickness at the bottom of the pin is used as the fifth unit sub-model; A sum of the third unit sub-model and the fifth unit sub-model is determined as the unit model.

7. The method for automatically designing the opening of a QFN device steel mesh according to claim 6, characterized in that: Determining a pin pad stencil opening design result of the target device according to the device parameters of the target device and the pin pad stencil opening parameter calculation model, including: If the pin pad steel mesh opening parameter calculation model is the first model, the device parameters of the target device are correspondingly substituted into the first model to obtain the pin pad steel mesh opening length of the target device; according to the size relationship between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, the deviation amount obtained by the absolute value of the difference between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, and the center coordinates of each pin pad of the target device, determine the center coordinates of each pin pad steel mesh opening of the target device; the pin pad steel mesh opening length of the target device, the pin pad steel mesh opening width and the calculated center coordinates of each pin pad steel mesh opening are used to obtain the pin pad steel mesh opening design result of the target device; If the pin pad steel mesh opening parameter calculation model is the second model, the device parameters of the target device are substituted into the second model to obtain the pin pad steel mesh opening width of the target device; the pin pad steel mesh opening width of the target device, the pin pad steel mesh opening length and the center coordinates of each pin pad are used to obtain the pin pad steel mesh opening design result of the target device.

8. The method for automatically designing the opening of a QFN device steel mesh according to claim 7, characterized in that: According to the size relationship between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, the deviation amount obtained by the absolute value of the difference between the pin pad length of the target device and the pin pad steel mesh opening length of the target device, and the center coordinates of each pin pad of the target device, the center coordinates of the steel mesh openings of each pin pad of the target device are determined, including: If the pin pad steel mesh opening length of the target device is greater than or equal to the pin pad length of the target device, if there is a pair of side edges of the pin pad symmetric along the x-axis, the center coordinates of the pin pad steel mesh opening on the upper side of the pair of side edges are calculated as (x 中 ,y 中 +M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 -M); if there is a pair of opposite sides of the pin pad that are symmetrical along the y-axis, calculate the center coordinates of the pin pad steel mesh opening on the left side of the pair of opposite sides as (x 中 -M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 +M,y 中 ); If the pin pad steel mesh opening length of the target device is less than the pin pad length of the target device, if there is a pair of side edges of the pin pad symmetric along the x-axis, the center coordinates of the pin pad steel mesh opening on the upper side of the pair of side edges are calculated as (x 中 ,y 中 -M), the center coordinate of the pin pad steel mesh opening on the lower side is (x 中 ,y 中 +M); if there is a pair of opposite sides of the pin pad that are symmetrical along the y-axis, calculate the center coordinates of the pin pad steel mesh opening on the left side of the pair of opposite sides as (x 中 +M,y 中 ), the center coordinate of the pin pad steel mesh opening on the right side is (x 中 -M,y 中 ); Among them, x 中 and 中 Respectively represent the x-coordinate and y-coordinate in the center coordinates of the corresponding pin pad; M=|L-L1|, represents the deviation; L represents the pin pad length of the target device; L1 represents the pin pad steel mesh opening length of the target device.

9. The method for automatically designing the opening of a QFN device steel mesh according to claim 3, characterized in that: Based on the heat dissipation pad size of the target device, the preset heat dissipation pad size shrinkage ratio and the bridge width, the heat dissipation pad steel mesh opening design result of the target device is determined, including: The heat dissipation pad size of the target device is shrunk according to the preset heat dissipation pad size shrinkage ratio to obtain the shrunk length Degree and indented width; Determining whether the heat dissipation pad size of the target device is less than or equal to a preset size; If yes, determine that the heat sink pad steel mesh opening method of the target device adopts a cross-shaped method; and calculate the length and width of the unit opening on the heat sink pad steel mesh in the cross-shaped method according to the heat sink pad size of the target device, the retracted width and the bridge width; and calculate the center coordinates of the four unit openings in the cross-shaped method according to the center coordinates of the heat sink pad of the target device, the calculated length of the unit opening, the width of the unit opening and the bridge width; If not, determine that the target device's heat sink pad steel mesh opening method adopts a tic-tac-toe method; and calculate the length and width of the unit opening on the heat sink pad steel mesh in the tic-tac-toe method based on the heat sink pad size of the target device, the retracted width and the bridging width; and calculate the center coordinates of the 9 unit openings in the tic-tac-toe method based on the center coordinates of the target device's heat sink pad, the calculated length of the unit opening, the width of the unit opening and the bridging width.

10. The method for automatically designing the opening of a QFN device steel mesh according to claim 9, characterized in that: According to the heat dissipation pad size of the target device, the retracted width and the bridge width, the length and width of the unit opening on the heat dissipation pad steel mesh in the cross-type frame mode are calculated; and according to the center coordinates of the heat dissipation pad of the target device, the calculated length of the unit opening, the width of the unit opening and the bridge width, the center coordinates of the four unit openings in the cross-type frame mode are calculated, including: Calculate the difference between the heat dissipation pad length of the target device and the shrinkage width and the bridge width in turn, and determine the ratio of the obtained difference to 2 as the length of the unit opening on the heat dissipation pad steel mesh in the cross-type manner; Calculate the difference between the heat sink width and the bridge width in the heat sink size of the target device, and determine the ratio of the difference to 2 as the width of the unit opening on the heat sink steel mesh in the cross-type manner; The center coordinates of the four unit openings in the cross-shaped calculation frame are obtained as follows: The center coordinate of the upper left unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-W 宽 / 2, y coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+L 长 / 2); The center coordinate of the lower left unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-W 宽 / 2, y coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-L 长 / 2); The center coordinate of the upper right unit opening is (x coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+W 宽 / 2, y coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+L 长 / 2); The center coordinate of the lower right unit opening is (x coordinate of the center coordinate of the heat sink pad + W 架桥 / 2+W 宽 / 2, y coordinate of the center coordinate of the heat sink pad - W 架桥 / 2-L 长 / 2); Among them, W 架桥 Indicates the bridge width; L 长 represents the calculated length of the unit opening; W 宽 Represents the calculated width of the cell opening.

11. The method for automatically designing the opening of a QFN device steel mesh according to claim 9, characterized in that: According to the heat dissipation pad size of the target device, the retracted width and the bridge width, the length and width of the unit opening on the heat dissipation pad steel mesh in the crisscross pattern are calculated; and according to the center coordinates of the heat dissipation pad of the target device, the calculated length of the unit opening, the width of the unit opening and the bridge width, the center coordinates of 9 unit openings in the crisscross pattern are calculated, including: Calculate the product of the bridge width and 2 to obtain a bridge width product result; Calculate the difference between the heat dissipation pad length in the heat dissipation pad size of the target device and the product of the inward-retracted width and the bridge width, and determine the ratio of the obtained difference to 3 as the length of the unit opening on the heat dissipation pad steel mesh in the cross-shaped manner; Calculate the difference between the heat sink width and the product of the inward-shrinking width and the bridge width in the heat sink width of the target device, and determine the ratio of the difference to 3 as the width of the unit opening on the heat sink steel mesh in the cross-shaped pattern; Calculate the center coordinates of the 9 unit openings in the tic-tac-toe pattern and get: The center coordinate of the upper left unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink pad + W 架桥 +L 长 ); The center coordinate of the left middle unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink pad); The center coordinate of the lower left unit opening is (x coordinate of the center coordinate of the heat sink pad - W 架桥 -W 宽 , the y coordinate of the center coordinate of the heat sink pad - W 架桥 -L 长 ); The center coordinates of the opening of the upper and middle units are (x coordinates of the center coordinates of the heat sink pad, y coordinates of the center coordinates of the heat sink pad + W 架桥 +L 长 ); The center coordinate of the center unit opening is (x coordinate of the center coordinate of the heat dissipation pad, y coordinate of the center coordinate of the heat dissipation pad); The center coordinates of the opening of the middle and lower units are (x coordinates of the center coordinates of the heat sink pad, y coordinates of the center coordinates of the heat sink pad - W 架桥 -L 长 ); The center coordinate of the upper right unit opening is (x coordinate of the center coordinate of the heat sink pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink pad + W 架桥 +L 长 ); The center coordinate of the right middle unit opening is (x coordinate of the center coordinate of the heat sink pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink pad); The center coordinate of the lower right unit opening is (x coordinate of the center coordinate of the heat sink pad + W 架桥 +W 宽 , the y coordinate of the center coordinate of the heat sink pad - W 架桥 -L 长 ); Among them, W 架桥 Indicates the bridge width; L 长 represents the calculated length of the unit opening; W 宽 Represents the calculated width of the cell opening.

12. A device for automatically designing the opening of a QFN device steel mesh, characterized in that: include: A device parameter acquisition module is used to obtain, for a target device that has completed QFN device verification, the device pin height and device external dimensions in the device specification, the pin pad length, pin pad width and pad outer edge dimensions of the target device on the PCB in the ECAD data, and the pre-set pin pad steel mesh thickness and pin bottom solder thickness as device parameters of the target device; A pin pad steel mesh opening parameter calculation model determination module, used to determine the pin pad steel mesh opening parameter calculation model of the target device based on the pin pad length and the pin pad width; wherein the pin pad steel mesh opening parameter calculation model is pre-constructed based on the device parameters of the QFN device, including a first model for calculating the pin pad steel mesh opening length of the QFN device, and a second model for calculating the pin pad steel mesh opening width of the QFN device; The pin pad steel mesh opening design module is used to determine the pin pad steel mesh opening design result of the target device according to the device parameters of the target device and the pin pad steel mesh opening parameter calculation model, including the pin pad steel mesh opening length and the pin pad steel mesh opening width, as well as the pin pad steel mesh opening center coordinates.

13. An electronic device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; The memory is used to store computer programs; The processor is used to implement the method steps described in any one of claims 1-11 when executing the program stored in the memory.

14. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method steps described in any one of claims 1 to 11 are implemented.

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