Novel resistance welding blocking point structure for improving ink hole blocking, blocking point net and design method

Abstract

The invention discloses a novel resistance welding blocking point structure for improving printing ink hole blocking, a blocking point net and a design method.The novel resistance welding blocking point structure comprises a main body part and a star-shaped part, the star-shaped part comprises eight prismatic tables connected with the circumferential face of the main body part, and the included angles between the extension lines of the central axes of every two adjacent prismatic tables are equal and are 45 degrees; the extension lines of the central axes of the two opposite prismatic tables coincide and pass through the central axis of the main body part; the top surface area of each prismatic table is smaller than the bottom surface area, and the top surface area of the star-shaped part is also smaller than the bottom surface area; when the main body part does not completely cover the conductive hole, the top surface or the bottom surface of the part shaped like the Chinese character'mi 'is selected to cover the area, not covered by the main body part, of the conductive hole according to the expansion and contraction condition of the PCB, so that the ink hole entering risk and the welding resistance quality are both considered. According to the method, the hole blocking reject ratio and the blocking point deviation reject ratio can be remarkably reduced, the processing capability is improved, and the risks of copper leakage and thin ink can be effectively avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board manufacturing, and particularly relates to a novel solder resist stop point structure for improving ink hole blocking, a stop point screen and a design method. BACKGROUND

[0002] In PCB manufacturing, the stop point screen is used in the solder resist process to control the solder resist ink to completely cover the via opening. When the via aperture is relatively small, for example, a small via with a finished aperture of ≤0.35 mm, in consideration of the stop point offset, the traditional circular stop point usually adopts a size that is equal to the drill bit or is enlarged by 0.05 mm-0.1 mm (2 mil-4 mil) in total, for example, if the drill hole aperture is 0.3 mm, the circular stop point diameter is designed to be 0.3 mm-0.4 mm to compensate for the influence of printing offset. However, due to the hole distance requirement, the circular stop point diameter generally should not exceed 0.4 mm, otherwise it may lead to insufficient ink bridge, for example, if the hole distance is 0.5 mm and the circular stop point diameter is 0.4 mm, only 0.1 mm of ink bridge is left (the IPC standard requires ≥0.075 mm).

[0003] In the current industry, the alignment accuracy of a standard printing machine is about ±0.15 mm (6 mil), that is, due to the influence of equipment accuracy, the alignment deviation of the ink coverage area from the designed position is 0.15 mm. This alignment accuracy limitation makes the small hole stop point design face challenges: on the one hand, a large enough stop point size is needed to cover the alignment deviation, and on the other hand, it is necessary to avoid affecting the insulation between holes due to the too large stop point size. In actual production, the double effects of printing offset and ink bleeding will cause the ink to enter the hole, resulting in the problem of small hole blocking. It is worth noting that due to the capillary effect, the smaller the hole diameter, the easier the ink is absorbed into the hole due to surface tension, and the more serious the blocking phenomenon, and the worse the stop point ability.

[0004] As shown in FIG. 1, for vias with hole diameters of 0.2 mm, 0.35 mm and 0.4 mm (corresponding to the hollow circles in FIG. 2), according to the stop point design, the diameter of the small hole stop point (corresponding to the solid circles in FIG. 2) should be 0.05 mm (2 mil) larger than the hole diameter, and the diameters of the small hole stop points are 0.25 mm, 0.4 mm and 0.45 mm respectively. The small hole stop point below 0.4 mm is within the control range, however, if the small hole stop point is obviously offset, for example, as shown in FIG. 3, the small hole stop point is offset by 0.15 mm, the area of the small hole stop point below 0.4 mm covering the hole is <2 / 3, thereby increasing the risk of ink entering the hole. Figure 1 Figure 1 Figure 1 Figure 1

[0005] ​​​​In the premise of ensuring the quality stability, the industry usually requires that the finished product aperture corresponding to the minimum blocking point capacity is greater than 0.4 mm (corresponding to the drill bit diameter greater than 0.45 mm). However, in the PCB manufacturing process, with the development trend of PCB towards high density, miniaturization and reliability, the aperture is required to be smaller and smaller, and at the present stage, the solder mask process is faced with the problems of ink entering the hole, deviation and side etching when the aperture is small. SUMMARY

[0006] In order to solve the above technical problems, the application provides a new solder mask blocking point structure, a blocking point net and a design method for improving ink hole blocking.

[0007] In a first aspect, the application provides a new solder mask blocking point structure for improving ink hole blocking, which is suitable for the application scene of the ink solder mask process of small conductive holes on the finished product aperture of the PCB board less than or equal to 0.4 mm, comprising: The top surface and the bottom surface of the main body part are both circular, and the centers of the top surface and the bottom surface are on the same central axis, and the diameters of the top surface and the bottom surface are equal; when the main body part is used to cover the conductive hole, due to the alignment deviation between the central axis of the main body part and the central axis of the conductive hole limited by the alignment accuracy of the printing machine, the main body part does not completely cover the conductive hole; The me-shaped part includes eight prisms connected with the circumferential surface of the main body part, the included angle between the extension lines of the central axes of the two adjacent prisms is equal and the included angle is 45°, and the extension lines of the central axes of the two opposite prisms coincide and pass through the central axis of the main body part; the top surface area of each prism is smaller than the bottom surface area, and the top surface area of the me-shaped part is also smaller than the bottom surface area; according to the expansion and contraction of the PCB board, the top surface or the bottom surface of the me-shaped part is selected to cover the area of the conductive hole not covered by the main body part, so as to take into account the risk of ink entering the hole and the quality of solder mask.

[0008] Optionally, when the length of the top surface of each prism is equal to the length of the bottom surface, the width of the top surface of each prism is denoted as W1, the width of the bottom surface of each prism is denoted as W2, and the following relationship is satisfied: 1.2≤W2 / W1≤1.5, 80um≤W1≤100um, 80um≤W2≤100um.

[0009] Optionally, the cross-sectional shape of each prism is isosceles trapezoidal.

[0010] Optionally, the length of the new solder mask blocking point structure, that is, the distance between the two end faces of the two opposite prisms away from the main body part, is denoted as L, the offset distance between the central axis of the main body part and the central axis of the conductive hole due to the alignment deviation is denoted as a, and the diameter of the top surface or the bottom surface of the main body part is denoted as Φ, and the following relationship is satisfied: L=a×2+Φ.

[0011] Optionally, the diameter of the top or bottom surface of the main body is equal to the finished diameter of the conductive hole; or the diameter of the top or bottom surface of the main body is 0.05 mm larger than the finished diameter of the conductive hole.

[0012] Optionally, depending on the expansion and contraction of the PCB board, the top or bottom surface of the star-shaped portion is selected to cover the area of ​​the conductive hole not covered by the main body, specifically including: When the expansion and contraction distance of the PCB board exceeds the preset value, the position of the conductive hole differs greatly from the original design position. The bottom surface of the star-shaped part is used to contact the PCB board surface to cover the area of ​​the conductive hole that is not covered by the main body, so as to increase the effective area of ​​the star-shaped part to block ink from entering the hole. When the expansion and contraction distance of the PCB board is less than the preset value, the position of the conductive hole is less different from the original design position. The top surface of the star-shaped part is used to contact the PCB board surface to cover the area of ​​the conductive hole that is not covered by the main body, so as to reduce the obstruction of the solder mask surface.

[0013] Secondly, the present invention also provides a novel solder resist baffle mesh for improving ink clogging, comprising: Mesh body; The aforementioned novel solder resist blocking structure is set on the mesh body in the area corresponding to the conductive holes with a finished aperture of ≤0.4mm; When there are two adjacent novel solder resist blocking point structures, the star-shaped parts of the two adjacent novel solder resist blocking point structures can be directly connected together through the end face of their prisms away from the main body, or the star-shaped parts of the two adjacent novel solder resist blocking point structures can be connected together with a gap through a mesh wire.

[0014] Optionally, the weld resist mesh further includes: A circular blocking structure is disposed on the mesh body in the area corresponding to the conductive holes with a finished aperture > 0.4 mm. When the circular blocking structure and the novel solder resist blocking structure are adjacent, the circumferential surface of the circular blocking structure and the end face away from the main body of the ridge in the star-shaped part of the novel solder resist blocking structure are directly connected together, or the circumferential surface of the circular blocking structure and the end face away from the main body of the ridge in the star-shaped part of the novel solder resist blocking structure are connected together with a gap through the mesh wire.

[0015] Optionally, the weld resist mesh further includes: A window structure is provided on the mesh body in the area corresponding to at least two conductive holes with an adjacent hole edge spacing of ≤0.25mm. When the window structure and the novel solder resist blocking structure are adjacent, the side of the window structure and the end face away from the main body of the cross-shaped part of the novel solder resist blocking structure are directly connected together, or the side of the window structure and the end face away from the main body of the cross-shaped part of the novel solder resist blocking structure are connected together with a gap by a mesh wire.

[0016] Thirdly, the present invention also provides a design method for a novel solder resist dot mesh to improve ink clogging, comprising: Functional areas are defined based on the spacing between adjacent conductive holes on the PCB board. Areas with a spacing of ≤0.25mm are designated as open-window areas, and areas with a spacing of >0.25mm are designated as non-open-window areas. An open window design is adopted in the area corresponding to the window opening area on the solder resist blocking mesh; In the area corresponding to the non-windowed area on the solder mask blocking mesh, a new type of solder mask blocking structure or a circular blocking structure is adopted according to the finished hole diameter of the conductive hole. The aforementioned new type of solder mask blocking structure is adopted for the position of the conductive hole with a finished hole diameter ≤ 0.4 mm, and a circular blocking structure is adopted for the position of the conductive hole with a finished hole diameter > 0.4 mm.

[0017] One or more technical solutions provided in this invention have at least the following technical effects or advantages: The novel solder resist blocking structure of this invention includes a main body and a star-shaped section. This improvement stems from the discovery in reliability testing that the influence of the drill hole diameter on the hole size varies in different directions, especially at 45°. The same issue exists in actual ink printing. Considering the limitations of the printing press's alignment accuracy during actual printing, the blocking point may shift in any direction across the entire plane relative to its designed position corresponding to the conductive hole. The improved novel solder resist blocking structure's star-shaped section has eight truncated pyramids that connect to the circumferential surface of the main body. The included angle between the extensions of the central axes of two adjacent pyramids is equal and 45°. The extensions of the central axes of two opposing pyramids coincide and pass through the central axis of the main body; that is, the star-shaped section of the novel solder resist structure is radial. The multi-directional branching, star-shaped section effectively covers areas where conductive holes are not covered by the main body due to alignment deviations in any direction. It is particularly reinforced in the sensitive 45° direction identified during testing, more effectively blocking offsets at various angles. Even when printing is off-center, the prisms on the star-shaped section still block the conductive holes, preventing excessive ink entry and clogging, thus reducing the defect rate caused by misalignment of the blocking points. Actual verification shows that the clogging defect rate using the new solder resist blocking point structure decreased from 4.92% with traditional circular blocking points to 0.14%, and the blocking point misalignment defect rate decreased from 3.43% with traditional circular blocking points to 0.21%, significantly improving stability and reliability.

[0018] Furthermore, practical verification has shown that the novel solder resist blocking structure of this invention not only facilitates mass production but also improves process capability. Compared to the minimum blocking capability of traditional circular blocking points, which corresponds to a finished hole diameter > 0.4 mm (corresponding to a drill bit diameter > 0.45 mm), the minimum blocking capability of the novel solder resist blocking structure corresponds to a finished hole diameter > 0.1 mm (corresponding to a drill bit diameter > 0.15 mm), thus enhancing the blocking capability. In other words, the novel solder resist blocking structure of this invention is well-suited for small conductive holes, exhibiting excellent blocking capability for them and effectively solving the problem of small hole clogging that occurs when using traditional circular blocking points.

[0019] Furthermore, considering the impact of different PCB board expansion and contraction on the risk of ink entering the via and the quality of solder mask, the top surface area of ​​each frustum in the star-shaped section is made smaller than the bottom surface area. This makes it easier to choose whether to use the top or bottom surface of the star-shaped section to contact the PCB board based on the actual expansion and contraction of the PCB board. This better covers the areas of conductive vias not covered by the main body, thus balancing the risk of ink entering the via and the quality of solder mask, and meeting customer design requirements.

[0020] Specifically, when the PCB board experiences significant expansion and contraction, i.e., the expansion and contraction distance exceeds the preset value, the position of the conductive hole differs greatly from the original design position, and the offset distance between the baffle mesh and the conductive hole is large. In this case, the bot side of the baffle mesh is used to contact the PCB board surface, that is, the bottom surface of the star-shaped part is used to contact the PCB board surface to cover the area of ​​the conductive hole not covered by the main body. The star-shaped part actually blocks a larger area of ​​ink entering the hole, which can more effectively avoid the risk of ink entering the hole and better reduce the ink clogging defect rate.

[0021] When the expansion and contraction of the PCB board is relatively minor, that is, when the expansion and contraction distance of the PCB board is less than the preset value, the position of the conductive hole is less different from the original design position, the dot mesh is neatly aligned with the conductive hole, and the offset distance is small. At this time, the top surface of the dot mesh is used to contact the PCB board surface to reduce the obstruction of the solder mask surface. That is, the top surface of the star-shaped part is used to contact the PCB board surface to cover the area of ​​the conductive hole that is not covered by the main body. Since the smaller the obstruction of the solder mask surface, the larger the amount of ink can be applied, which can more effectively avoid the risk of copper leakage and thin ink.

[0022] Furthermore, the top and bottom lengths of each frustum are equal, and the top width W1 of each frustum is shorter than the bottom width W2. This means the top and bottom of the frustums are asymmetrically designed. This satisfies the basic design requirement that the top area of ​​each frustum is smaller than the bottom area, while also ensuring that the end face of each frustum furthest from the main body is a vertical surface. This facilitates direct connection between two adjacent novel solder mask blocking structures, improving connection stability. Additionally, the ratio of the bottom width W2 to the top width W1 of each frustum is within the range of 1.2-1.5, allowing for flexible adjustment of the specific ratio to adapt to the actual solder mask requirements of different PCBs and improve process efficiency. Furthermore, the bottom width W2 and top width W1 of each frustum are set between 80um and 100um. The specific values ​​are determined by the specifications of the printing dot screen currently used. For example, when using 43T mesh, the wire diameter is 80um, so the top width W1 can be set to 0.08mm and the bottom width W2 to 0.09mm. This makes the line width of the star-shaped part small enough so that the ink penetration can cover the dot print. Compared with the traditional circular dot print, which is often caused by the dot print being too large compared to the conductive hole, resulting in unacceptable dot prints, excessively large conductive hole openings, and side exposure, this method can meet customer requirements and improve the product qualification rate.

[0023] Furthermore, the cross-section of each frustum is an isosceles trapezoid. The hypotenuse design of the isosceles trapezoid can distribute the vertical load into axial and lateral forces, reducing stress concentration. It is suitable for bearing pressure or lateral loads and has the characteristic of uniform force distribution. Moreover, the wide base and narrow top structure of the isosceles trapezoid can effectively resist lateral forces, prevent overturning, and improve the resistance to lateral deformation. In general, it can improve the geometric stability and reliability of the new type of weld resistance point structure.

[0024] Furthermore, the length L of the new solder resist blocking structure directly affects the hole spacing process capability and blocking capability. Based on the results of actual tests, the length L is designed as L = a × 2 + Φ. The value of the length L is positively correlated with the offset distance a and the diameter Φ of the main body. This can avoid the new solder resist blocking structure being too long and affecting the process capability, and also avoid the new solder resist blocking structure being too short and resulting in poor blocking capability.

[0025] Furthermore, the diameter Φ of the top or bottom surface of the main body is designed based on the actual finished hole diameter Z. The diameter of the top or bottom surface of the main body can be equal to the finished hole diameter of the conductive hole, i.e., Φ=Z; the diameter of the top or bottom surface of the main body can also be 0.05mm larger than the finished hole diameter of the conductive hole, i.e., Φ=Z+0.05. The specific value of the diameter Φ of the top or bottom surface of the main body can be designed according to actual production needs to meet the customer's design requirements for different circuit boards. Attached Figure Description

[0026] Figure 1 The diagram shows the coverage of through holes with diameters of 0.25mm, 0.4mm, and 0.45mm by traditional circular stop points with diameters of 0.15mm, 0.25mm, 0.35mm, and 0.4mm, respectively. Figure 2 This is a schematic diagram illustrating the inspiration for the novel solder resist blocking structure of this invention; Figure 3 This is a schematic diagram of the bottom surface of the novel resist welding point structure of the present invention; Figure 4 This is a top view of the novel weld resistance blocking point structure of the present invention; Figure 5 This is a schematic diagram of the bottom surface of the star-shaped portion of the novel solder resist blocking structure of the present invention; Figure 6 This is a schematic diagram of the top surface of the star-shaped portion of the novel solder resist blocking structure of the present invention; Figure 7 This is a schematic diagram showing the included angle between the extended lines of the central axes of two adjacent frustums in the star-shaped portion of the novel resist solder block structure of the present invention; Figure 8 This is a schematic diagram showing that the extended lines of the central axes of two opposing frustums in the cross-shaped portion of the novel solder resist blocking structure of the present invention are collinear. Figure 9 This is a diagram showing the dimensional parameters of the novel solder resist blocking structure of the present invention on the bottom surface; Figure 10 This is a diagram showing the dimensional parameters of the novel solder resist blocking structure of the present invention on the top surface; Figure 11 This is a cross-sectional schematic diagram of the frustum of the cross-shaped portion of the novel solder resist blocking structure of the present invention; Figure 12 The top and bottom images are schematic diagrams showing the coverage of a 0.2mm diameter conductive hole by a traditional circular stop with a diameter of 0.25mm and a new solder resist stop structure with a main body diameter of 0.25mm, respectively, under the same offset. Figure 13 The top and bottom images are schematic diagrams showing the coverage of a 0.2mm diameter conductive hole by a traditional circular stop with a diameter of 0.25mm and a new solder resist stop structure with a main body diameter of 0.2mm, respectively, under the same offset. Figure 14 This is a schematic diagram showing the arrangement of traditional circular stop points; Figure 15 This is a schematic diagram showing an arrangement of novel solder resist blocking points. Figure 16 A schematic diagram illustrating an open window design for neatly arranged, unblocked holes; Figure 17 A comparison chart showing the impact of using traditional circular stop points (old stop points) and new solder resist stop point structures (new stop points) on the hole plugging defect rate; Figure 18 A comparison chart showing the impact of using traditional circular stop points (old stop points) and new solder resist stop point structures (new stop points) on the stop point misalignment defect rate; In the diagram: 10 - main body, 20 - cross-shaped part, 21 - first frustum, 22 - second frustum, 23 - third frustum, 24 - fourth frustum, 25 - fifth frustum, 26 - sixth frustum, 27 - seventh frustum, 28 - eighth frustum. Detailed Implementation

[0027] This invention provides a novel solder resist blocking structure, blocking mesh, and design method to improve ink clogging, solving the problems of ink entering the hole, offsetting, and side etching that often occur in traditional solder resist processes when the hole diameter becomes smaller.

[0028] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0029] For better understanding, the following will be described in detail in conjunction with the drawings of the specification and specific embodiments. Obviously, the embodiments described in the present invention are some embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0030] It should be noted that the present invention makes improvements to the traditional stop point structure. The inspiration comes from the discovery that the influence of the drilling diameter on the hole roughness varies in different directions during the reliability test, especially most significantly in the 45° direction. For example, the glass fibers in FR-4 are vertically interwoven (0° and 90°) by warp and weft to form a grid-like structure. Since the glass fibers will be cut obliquely during the mechanical processing of the PCB board (drilling, routing grooves, etc.), resulting in the separation of the glass fibers and the resin, the problem of hole roughness is more obvious. The same problem also exists during the actual ink printing process. As Figure 2 shown, the white dots are small conductive holes, and the black dots are large conductive holes. All small conductive holes are regularly arranged together. The small conductive holes in the middle enclose a circle, and the remaining small conductive holes are linearly distributed, and the multiple lines form a "rice" character shape. Based on this, the shape of the new solder mask stop point structure of the present invention corresponds to the shape formed by the overall arrangement of the conductive holes.

[0031] The small conductive holes referred to in the present invention refer to conductive holes with a finished product aperture ≤ 0.4 mm, such as small holes with a finished product aperture of 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm. Conductive holes are also called VIA holes (Via Hole), which are holes on the PCB board used to connect circuits between different layers, including through holes, blind holes, and buried holes. Large conductive holes refer to conductive holes with a finished product aperture > 0.4 mm.

[0032] Please refer to the following Figures 3-13 for a detailed description of the new solder mask stop point structure for improving ink plugging holes in the embodiments of the present invention. This new solder mask stop point structure is applicable to the application scenario of the ink solder mask process for small conductive holes with a finished product aperture ≤ 0.4 mm on a PCB board (printed circuit board) to meet the requirements of non-plugging hole design.

[0033] The new type of resist welding point structure mainly includes a main body 10 and a star-shaped part 20.

[0034] The top and bottom surfaces of the main body 10 are both circular, with their centers on the same central axis. The diameters of the top and bottom surfaces are equal, meaning the bottom surface of the main body 10 consists of two equal circles. It should be noted that the main body 10 is cylindrical, and the height between its top and bottom surfaces is much smaller than the diameter of either surface, making the main body 10 generally resemble a circular plate. The height of the main body 10 depends on the height of the frustum of the cross-shaped portion 20. Specifically, the height of the main body 10 can be equal to, slightly greater than, or slightly less than the height of the frustum. Adjustments can be made based on actual conditions, and this invention does not impose any limitations.

[0035] During the solder mask process, when the main body 10 is used to cover the conductive hole, due to the limited alignment accuracy of the printing machine, there is an alignment deviation between the central axis of the main body 10 and the central axis of the conductive hole. The alignment accuracy of the current industry standard printing machine is about ±0.15mm (6mil), and the deviation direction is any direction on the plane. The actual offset distance is 0.05mm, 0.10mm, 0.15mm, etc.

[0036] The cross-shaped portion 20 includes eight frustums that are connected to the circumferential surface of the main portion 10, namely the first frustum 21, the second frustum 22, the third frustum 23, the fourth frustum 24, the fifth frustum 25, the sixth frustum 26, the seventh frustum 27, and the eighth frustum 28.

[0037] The included angle between the extensions of the central axes of two adjacent frustums is equal and equal to 45°. Figure 7 The angle between the extensions of the central axes of the first frustum 21 and the second frustum 22 shown is 45°.

[0038] The extensions of the central axes of the two opposing frustums coincide and pass through the central axis of the main body 10, as shown below. Figure 8 The extensions of the central axes of the first frustum 21 and the fifth frustum 25 shown are collinear and pass through the central axis of the main body 10.

[0039] The top surface area of ​​each frustum is smaller than the bottom surface area, and the top surface area of ​​the star-shaped section is also smaller than the bottom surface area. Depending on the expansion and contraction of the PCB board, the top or bottom surface of the star-shaped section is selected to cover the area of ​​the conductive hole not covered by the main body 10, in order to balance the risk of ink entering the hole and the quality of solder mask.

[0040] Specifically, when the expansion and contraction distance of the PCB board exceeds the preset value, the position of the conductive hole differs significantly from the original design position. The bottom surface of the star-shaped part 20 is used to contact the PCB board surface to cover the area of ​​the conductive hole not covered by the main body, thereby increasing the effective area of ​​the star-shaped part 20 to block ink from entering the hole.

[0041] When the expansion and contraction distance of the PCB board is less than the preset value, the position of the conductive hole is less different from the original design position. The top surface of the star-shaped part 20 is used to contact the PCB board surface to cover the area of ​​the conductive hole not covered by the main body part 10, so as to reduce the obstruction of the solder mask surface.

[0042] Where the length of the top face of each frustum is equal to the length of the bottom face, the width of the top face of each frustum is denoted as W1 (corresponding to...). Figure 10 The top width W1 of each frustum is denoted as W2 (corresponding to the top width W1 of each frustum). Figure 9 The bottom width W2 and the top width W1 are less than the bottom width W2, satisfying the relationship 1.2 ≤ W2 / W1 ≤ 1.5. Figures 9-11 As shown, the width of the top surface of the frustum, W1, is smaller than the width of the bottom surface, W2.

[0043] like Figure 11 As shown, the cross-sectional shape of each frustum is an isosceles trapezoid.

[0044] Please continue to refer to this. Figures 9-11 Since the values ​​of the length L of the new resist welding point structure, the bottom width W2 of the frustum, and the top width W1 of the frustum will affect the actual resist welding situation, it is necessary to design their specific values ​​according to actual needs.

[0045] The length L of the new solder resist blocking structure, that is, the distance between the two end faces of the two opposite frustums away from the main body 10, directly affects the hole spacing process capability and blocking capability. It needs to satisfy the relationship L=a×2+Φ, where a represents the offset distance between the central axis of the main body 10 and the central axis of the conductive hole, and Φ represents the diameter of the top or bottom surface of the main body 10.

[0046] The diameter of the top or bottom surface of the main body 10 will affect the blocking capability. The diameter of the top or bottom surface of the main body 10 can be equal to the finished diameter of the conductive hole, or the diameter of the top or bottom surface of the main body can be 0.05mm larger than the finished diameter of the conductive hole. The specific selection should be made according to the actual situation.

[0047] Figure 12 The novel solder resist blocking structure shown in the image below has a top or bottom surface diameter of 0.25 mm, a finished diameter of 0.2 mm for the conductive hole, and a top or bottom surface diameter of 0.05 mm larger than the finished diameter of the conductive hole. Figure 12Compared to the traditional circular stop with a diameter of 0.25mm used in the above figure, the new solder mask stop structure can block most of the conductive holes when the offset distance is the same, while the area of ​​the conductive holes not covered by the traditional circular stop exceeds half.

[0048] Figure 13 The novel solder resist blocking structure shown in the image below has a top or bottom surface diameter equal to the finished diameter of the conductive hole, both being 0.2 mm. Figure 13 Compared to the traditional circular stop with a diameter of 0.25mm used in the above figure, the new solder mask stop structure can also block most of the conductive holes when the offset distance is the same. Therefore, in PCBs with small hole-to-hole spacing, it is preferable to design the top or bottom surface diameter of the main body to be equal to the finished hole diameter of the conductive hole.

[0049] Each as Figure 17 and Figure 18 As shown, actual verification shows that the hole plugging failure rate of the new solder resist blocking point structure (corresponding to the new blocking point) is reduced from 4.92% when using the traditional circular blocking point (corresponding to the old blocking point) to 0.14%, and the blocking point misalignment failure rate of the new solder resist blocking point structure (corresponding to the new blocking point) is reduced from 3.43% when using the traditional circular blocking point (corresponding to the old blocking point) to 0.21%, which significantly improves stability and reliability.

[0050] The specific values ​​for the base width W2 and top width W1 of each frustum need to consider the specifications of the printing dot screen currently used. As shown in Table 1, the most commonly used specifications in the industry are DPP32, DPP36, and DPP43. These three specifications have mesh counts of 32, 36, and 43, respectively, and line diameters of 100µm, 90µm, and 80µm. Therefore, the values ​​for the base width W2 and top width W1 of each frustum can be set between 80µm and 100µm. Taking the top width W1 as an example, when using a DPP43 printing dot screen, its line diameter is 80µm. Following the design principle of "line diameter 80µm = 0.08mm = top width W1," the top width W1 can be set to 0.08mm.

[0051] Table 1 Specifications of Printing Dot Screens

[0052] Secondly, the present invention provides a novel solder resist blocking mesh for improving ink clogging, comprising: a mesh body and the aforementioned novel solder resist blocking structure.

[0053] It is understandable that the new type of solder resist blocking structure is set on the mesh body in the area corresponding to the conductive holes with a finished hole diameter of ≤0.4mm.

[0054] When there are two adjacent novel solder resist blocking point structures, the connection relationship between the two adjacent novel solder resist blocking point structures corresponds to two cases.

[0055] Scenario 1, such as Figure 15 As shown, the star-shaped sections of two adjacent novel resist-welding point structures can be directly connected together via the end faces of their frustums that are away from the main body. Figure 14 Compared to the traditional method of connecting circular blocking points with gaps, the direct connection of two adjacent new solder mask blocking point structures results in a larger shielding area, making it suitable for PCBs with smaller hole-edge distances.

[0056] In scenario two, the star-shaped sections of two adjacent new solder mask blocking structures are connected together with a gap by mesh. Compared to scenario one, there is a gap between the two adjacent new solder mask blocking structures in scenario two, which is suitable for PCBs with larger hole-to-edge distances.

[0057] To meet the solder mask requirements of PCBs with both small and large conductive vias, a novel solder mask blocking structure and a traditional circular blocking structure can be combined and arranged to design a hybrid design of a novel solder mask blocking mesh that improves ink clogging. The mesh includes a mesh body, the aforementioned novel solder mask blocking structure, and a circular blocking structure.

[0058] The connection relationship between the mesh body and the solder resist blocking structure is as described in the previous embodiment and will not be repeated here.

[0059] The circular blocking structure is set on the mesh body in the area corresponding to the conductive holes with a finished aperture > 0.4 mm. When the circular blocking structure and the new solder resist blocking structure are adjacent, the circumferential surface of the circular blocking structure and the end face away from the main body of the ridge in the star-shaped part of the new solder resist blocking structure are directly connected together, or the circumferential surface of the circular blocking structure and the end face away from the main body of the ridge in the star-shaped part of the new solder resist blocking structure are connected together with a gap through the mesh wire.

[0060] To meet the solder mask requirements of PCBs with densely distributed small conductive holes, a novel solder mask blocking structure and a window structure can be combined and arranged to design a novel solder mask blocking mesh with diversified design to improve ink blockage. The mesh includes: a mesh body, the aforementioned novel solder mask blocking structure and window structure.

[0061] The connection relationship between the mesh body and the weld resist blocking structure is as described above and will not be repeated here.

[0062] The window structure is set on the mesh body in the area corresponding to at least two conductive holes with an adjacent hole edge spacing of ≤0.25mm; when the window structure and the new type of solder resist blocking structure are adjacent, the side of the window structure and the end face away from the main body of the cross-shaped part of the new type of solder resist blocking structure are directly connected together, or the side of the window structure and the end face away from the main body of the cross-shaped part of the new type of solder resist blocking structure are connected together with a gap through the mesh wire.

[0063] like Figure 16 As shown, the SMD PAD (surface mount pad) is designed with 4×4 PTH holes (PlatedThrough Holes). These neatly arranged, unfilled holes adopt an open window design for exposure. Similarly, during the printing process, since the distance between adjacent holes is less than 0.25mm, it is generally recommended that customers adopt an open window design for these neatly arranged, unfilled holes.

[0064] Thirdly, the present invention provides a design method for a novel solder resist baffle mesh that improves ink clogging, comprising the following steps.

[0065] Step 1: Delineate functional areas based on the spacing between adjacent conductive holes on the PCB board. Areas with a spacing of ≤0.25mm between adjacent holes are designated as open-window areas, while areas with a spacing of >0.25mm between adjacent holes are designated as non-open-window areas.

[0066] Step 2: In the area corresponding to the opening area on the solder resist blocking mesh, an open window design is adopted.

[0067] Step 3: In the area corresponding to the non-windowed area on the solder mask blocking mesh, adopt a new solder mask blocking structure or a circular blocking structure according to the finished hole diameter of the conductive hole. The aforementioned new solder mask blocking structure is used for the position of conductive hole with a finished hole diameter ≤ 0.4mm, and the circular blocking structure, i.e., the traditional circular blocking structure, is used for the position of conductive hole with a finished hole diameter > 0.4mm.

[0068] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A novel solder resist blocking structure for improving ink clogging, characterized in that, This is suitable for applications involving ink solder masking of small conductive holes with a finished hole diameter ≤0.4mm on PCBs, including: The main body (10) has a circular top and bottom surface, and the centers of the top and bottom surfaces are on the same central axis, and the diameters of the top and bottom surfaces are equal. When the main body (10) is used to cover the conductive hole, due to the limited alignment accuracy of the printing machine, there is an alignment deviation between the central axis of the main body and the central axis of the conductive hole, and the main body (10) does not completely cover the conductive hole. The star-shaped portion (20) includes eight frustums that are connected to the circumferential surface of the main body portion (10). The included angle between the extensions of the central axes of two adjacent frustums is equal and is 45°. The extensions of the central axes of two opposite frustums coincide and pass through the central axis of the main body portion (10). The top surface area of ​​each frustum is smaller than the bottom surface area. The top surface area of ​​the star-shaped portion (20) is also smaller than the bottom surface area. Depending on the expansion and contraction of the PCB board, the top or bottom surface of the star-shaped portion (20) is selected to cover the area of ​​the conductive hole not covered by the main body portion (10) in order to balance the risk of ink entering the hole and the quality of solder resist.

2. The novel solder resist blocking structure as described in claim 1, characterized in that, When the length of the top surface of each frustum is equal to the length of the bottom surface, the width of the top surface of each frustum is denoted as W1, and the width of the bottom surface of each frustum is denoted as W2, satisfying the following relationship: 1.2≤W2 / W1≤1.5, 80um≤W1≤100um, 80um≤W2≤100um.

3. The novel solder resist blocking structure as described in claim 1, characterized in that, The cross-sectional shape of each frustum is an isosceles trapezoid.

4. The novel solder resist blocking structure as described in claim 1, characterized in that, The length of the novel resist welding point structure, that is, the distance between the two end faces of the two opposite frustums away from the main body (10), is denoted as L. The offset distance between the central axis of the main body (10) and the central axis of the conductive hole due to the alignment deviation is denoted as a. The diameter of the top or bottom surface of the main body (10) is denoted as Φ. The relationship L=a×2+Φ is satisfied.

5. The novel solder resist blocking structure as described in claim 4, characterized in that, The diameter of the top or bottom surface of the main body (10) is equal to the finished diameter of the conductive hole; or the diameter of the top or bottom surface of the main body (10) is 0.05 mm larger than the finished diameter of the conductive hole.

6. The novel solder resist blocking structure as described in claim 1, characterized in that, The method of selecting the top or bottom surface of the star-shaped portion (20) to cover the area of ​​the conductive hole not covered by the main body portion (10) based on the expansion and contraction of the PCB board specifically includes: When the expansion and contraction distance of the PCB board exceeds the preset value, the position of the conductive hole differs greatly from the original design position. The bottom surface of the cross-shaped part (20) is used to contact the PCB board surface to cover the area of ​​the conductive hole not covered by the main body part (10), so as to increase the effective area of ​​the cross-shaped part (20) to block ink from entering the hole. When the expansion and contraction distance of the PCB board is less than the preset value, the position of the conductive hole is less different from the original design position. The top surface of the star-shaped part (20) is used to contact the PCB board surface to cover the area of ​​the conductive hole not covered by the main body part (10) in order to reduce the obstruction of the solder resist surface.

7. A novel solder resist baffle mesh for improving ink clogging, characterized in that, include: Mesh body; The novel solder resist blocking structure as described in any one of claims 1-6 is provided on the mesh body in the area corresponding to the conductive holes with a finished aperture ≤ 0.4 mm; When there are two adjacent novel weld resist blocking point structures, the star-shaped parts (20) of the two adjacent novel weld resist blocking point structures can be directly connected together by the end face of their prisms away from the main body part (10), or the star-shaped parts (20) of the two adjacent novel weld resist blocking point structures can be connected together by mesh wire with a gap.

8. The weld resist mesh as described in claim 7, characterized in that, Also includes: A circular blocking structure is set on the mesh body in the area corresponding to the conductive holes with a finished aperture > 0.4 mm; When the circular blocking structure and the novel solder resist blocking structure are adjacent, the circumferential surface of the circular blocking structure and the end face away from the main body (10) on the ridge of the cross-shaped part (20) of the novel solder resist blocking structure are directly connected together, or the circumferential surface of the circular blocking structure and the end face away from the main body (10) on the ridge of the cross-shaped part (20) of the novel solder resist blocking structure are connected together with a gap by a wire mesh.

9. The weld resist mesh as described in claim 7, characterized in that, Also includes: A window structure is provided on the mesh body in the area corresponding to at least two conductive holes with a spacing of ≤0.25mm between adjacent holes; When the window structure and the novel weld resist block structure are adjacent, the side of the window structure and the end face away from the main body (10) on the ridge of the cross-shaped part (20) of the novel weld resist block structure are directly connected together, or the side of the window structure and the end face away from the main body (10) on the ridge of the cross-shaped part (20) of the novel weld resist block structure are connected together with a gap by a wire mesh.

10. A design method for a novel solder resist baffle mesh to improve ink clogging, characterized in that, include: Functional areas are defined based on the spacing between adjacent conductive holes on the PCB board. Areas with a spacing of ≤0.25mm are designated as open-window areas, and areas with a spacing of >0.25mm are designated as non-open-window areas. An open window design is adopted in the area corresponding to the window opening area on the solder resist blocking mesh; In the area corresponding to the non-windowed area on the solder mask blocking mesh, a novel solder mask blocking structure or a circular blocking structure is adopted according to the finished hole diameter of the conductive hole. The novel solder mask blocking structure as described in any one of claims 1-6 is adopted for the position of the conductive hole with a finished hole diameter ≤ 0.4 mm, and the circular blocking structure is adopted for the position of the conductive hole with a finished hole diameter > 0.4 mm.

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