A method for printing and curing a thermal paste on both sides of a circuit board

Abstract

The application discloses a kind of printed and cured methods of circuit board double-sided heat paste, including top pad, and top pad is provided with several avoiding holes and grooves;The printed and cured method includes cleaning step, top first printing step, bottom first printing step and first curing step;Top first printing step, circuit board is assembled on the first machine table, and heat paste is printed on the top of circuit board by first printing machine in several first specified areas, and several first specified areas can be matched and corresponded with several avoiding holes and grooves;Bottom first printing step, top pad is assembled on the second machine table, and the top of circuit board is connected on top pad, and several first specified areas are moved to the top of several avoiding holes and grooves;Heat paste is printed on the bottom of circuit board by second printing machine in several second specified areas;First curing step, through oven, circuit board is placed and baked.The application helps to avoid scratch and scratch away heat paste, and saves a curing step.

Description

Technical Field

[0001] This invention relates to the field of thermal paste printing and curing technology for circuit boards, and particularly to a method for printing and curing thermal paste on both sides of circuit boards. Background Technology

[0002] With technological advancements, heat dissipation management for printed circuit boards (PCBs) has become increasingly crucial. Besides thermal conductivity, PCB heat dissipation materials must also possess excellent chemical resistance, high-temperature resistance, high-pressure resistance, and electrical insulation properties to meet demanding application environments. While traditional thermally conductive metal materials have high thermal conductivity, they lack corrosion and oxidation resistance and electrical insulation, limiting their application in modern electronic products. Current technologies typically use thermal paste as the heat dissipation material for PCBs, and PCB heat dissipation has evolved from single-sided to double-sided cooling. However, in the current production process of printing and curing double-sided thermal paste, the top and bottom surfaces of the PCB require separate printing and curing processes, necessitating at least two high-temperature baking steps. For applications requiring thicker thermal paste, four high-temperature baking steps are required to achieve the double-layer thermal paste printing and curing process. This results in a long production cycle, significant heat consumption, and the repeated baking can degrade the solder resist film performance and cause scratches on the thermal paste surface, affecting the heat dissipation effect and operational reliability of the final electrical product. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for printing and curing thermal paste on both sides of circuit boards, which helps to avoid scratching or even scraping off the thermal paste, and saves one curing step.

[0004] According to an embodiment of the present invention, a method for printing and curing double-sided thermal paste on a circuit board includes a top pad, the top pad having a plurality of clearance holes and grooves. Printing curing methods include: Cleaning steps; In the first printing step on the top surface, the circuit board is assembled on the first machine platform, and thermal paste is printed on several first designated areas on the top surface of the circuit board by the first printing machine. The several first designated areas can be matched and correspond to several clearance slots. In the first printing step on the bottom surface, the top surface pad is assembled on the second machine, the top surface of the circuit board is attached to the top surface pad, and several first designated areas are moved to the top of several clearance slots; thermal paste is printed on several second designated areas on the bottom surface of the circuit board by the second printing machine. The initial curing step involves leaving the circuit board in an oven to stand and bake.

[0005] A method for printing and curing thermal paste on double sides of a circuit board according to an embodiment of the present invention has at least the following beneficial effects: This invention utilizes a cleaning step to clean the top and bottom surfaces of the circuit board, which helps reduce the poor adhesion of foreign objects to the circuit board surface, increases the bonding force between the thermal paste and the circuit board, and improves the printing effect of the thermal paste on the circuit board.

[0006] This invention utilizes a top surface pad with several clearance slots that correspond to several designated areas on the top surface of a circuit board. During the initial top surface printing step, thermal paste is pressed and penetrated into these designated areas. Then, these designated areas are aligned with the clearance slots on the top surface pad, and the top surface of the circuit board is attached to the top surface pad. At this point, the thermal paste in these designated areas is positioned within the clearance slots on the top surface pad. The clearance slots on the top surface pad provide clearance and containment space for the thermal paste in these areas, helping to prevent scratching or even removing the thermal paste and improving the heat dissipation effect of the circuit board.

[0007] Compared to existing technologies, this invention utilizes a top pad in the initial bottom printing step, which helps prevent the thermal paste printed on the top surface of the circuit board from being scratched during the bottom thermal paste printing step, thus reducing the likelihood of scratches or even damage to the thermal paste on the top surface of the circuit board. Furthermore, by using a top pad in the initial bottom printing step, this invention helps reduce the direct contact between the thermal paste on the top surface of the circuit board and the second printing plate, which could cause the circuit board to tilt, thereby improving the quality of the thermal paste printing process on the bottom surface of the circuit board.

[0008] Compared to existing technologies that require the circuit board to be placed in an oven for resting and baking after the initial printing step, and then removed from the oven for the bottom surface initial printing step, followed by another resting and baking process, this invention saves one resting and baking curing step by performing the top and bottom surface initial printing steps separately before the initial curing step. This helps shorten the circuit board production cycle, reduces heat consumption, and minimizes the degradation of the solder resist film performance caused by multiple baking processes.

[0009] According to an embodiment of the present invention, a method for printing and curing thermal paste on a circuit board includes a top surface pad having a plurality of first positioning holes and a plurality of first positioning pins, with the plurality of first positioning pins and the plurality of first positioning holes being connected one-to-one; the circuit board having a plurality of second positioning holes, with the plurality of second positioning holes and the plurality of first positioning pins being detachably connected one-to-one; in the initial printing step on the bottom surface, before the top surface of the circuit board is attached to the top surface pad, the plurality of second positioning holes are fitted onto the plurality of first positioning pins one-to-one.

[0010] According to an embodiment of the present invention, a method for printing and curing thermal paste on a circuit board is provided, wherein a top surface pad is provided with a first anti-fool hole and a second positioning pin connected to each other, the circuit board is provided with a second anti-fool hole, and the second anti-fool hole and the second positioning pin are detachably assembled; in the first printing step on the bottom surface, before attaching the top surface of the circuit board to the top surface pad, the second anti-fool hole is fitted onto the second positioning pin.

[0011] According to an embodiment of the present invention, a method for printing and curing double-sided thermal paste for circuit boards further includes, after the initial curing step: The top surface is printed again. The circuit board is assembled on the first machine table, and thermal paste is printed on several first designated areas on the top surface of the circuit board by the first printing machine. In the bottom reprinting step, the top surface of the circuit board is attached to the top surface pad, and several first designated areas are moved to the top of several clearance slots; thermal paste is printed on several second designated areas on the bottom surface of the circuit board by a second printing machine. The circuit board undergoes a second curing step, involving resting and baking in an oven.

[0012] According to an embodiment of the present invention, a method for printing and curing thermal paste on both sides of a circuit board includes a second curing step in which the circuit board is placed in an oven and kept at a third preset temperature for a third preset time; the circuit board is then placed in the oven and baked at a fourth preset temperature for a fourth preset time; the fourth preset temperature is higher than the third preset temperature.

[0013] According to an embodiment of the present invention, a method for printing and curing thermal paste on a circuit board includes, in the first curing step, placing the circuit board in an oven and maintaining it at a first preset temperature for a first preset time; then placing the circuit board in the oven and baking it at a second preset temperature for a second preset time; the second preset temperature is higher than the first preset temperature.

[0014] According to an embodiment of the present invention, a method for printing and curing thermal paste on both sides of a circuit board is provided, wherein the fourth preset time is greater than the second preset time.

[0015] According to an embodiment of the present invention, a method for printing and curing double-sided thermal paste on a circuit board further includes, between the initial curing step and the top surface re-printing step: The cooling step involves placing the circuit board on a temporary storage rack for heat dissipation.

[0016] According to an embodiment of the present invention, a method for printing and curing double-sided thermal paste on a circuit board includes a cleaning step in which the circuit board is sprayed with an acidic cleaning solution using a cleaning device, and then sprayed with clean water using the same cleaning device.

[0017] According to an embodiment of the present invention, a method for printing and curing thermal paste on both sides of a circuit board involves washing the circuit board with clean water using a cleaning device, and then drying the circuit board with hot air blown out by the cleaning device.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a top view of the top pad of an embodiment of the present invention; Figure 2 This is a side view of the top pad and circuit board according to an embodiment of the present invention; Figure 3 This is a flowchart of a method for printing and curing thermal paste on both sides of a circuit board according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: Top surface pad 100; clearance slot 110; first positioning hole 120; first anti-fool hole 130; first positioning pin 140; second positioning pin 150; measuring slot 160; Circuit board 200; second positioning hole 210; second anti-fool hole 220. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0023] In the description of the invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. If the terms "first" and "second" are used, they are only for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0024] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0025] With technological advancements, heat dissipation management for PCBs has become increasingly important. Besides thermal conductivity, heat dissipation materials for PCBs must also possess excellent chemical resistance, high-temperature resistance, high-voltage resistance, and electrical insulation properties to meet demanding application environments. While traditional thermally conductive metal materials have high thermal conductivity, they are insufficient in corrosion resistance and oxidation resistance, and lack electrical insulation, limiting their application in modern electronic products.

[0026] In existing technologies, thermal paste is commonly used as the heat dissipation material for circuit boards 200, and the heat dissipation of existing circuit boards 200 has evolved from single-sided heat dissipation to double-sided heat dissipation. However, in the current production process of printing and curing double-sided thermal paste on circuit boards 200, the top and bottom surfaces of the circuit board 200 need to undergo a separate printing and curing process, thus requiring at least two high-temperature baking processes. For cases where the thermal paste thickness requirement is high, four high-temperature baking processes are required to achieve the double-layer thermal paste printing and curing process. For example, currently, for cases requiring a thermal paste thickness of 150±30μm, four screen printing and four high-temperature baking processes are typically required to achieve the double-layer thermal paste printing and curing process on the circuit board 200, with a production cycle of 10-12 hours.

[0027] Existing methods for printing and curing double-sided thermal paste for circuit boards have long production cycles, significant heat consumption, and repeated baking can easily cause a decline in the performance of the 200mm solder resist film on the circuit board. At the same time, scratches are easily found on the surface of the thermal paste, affecting the heat dissipation effect and operational reliability of the final electrical product.

[0028] The following description, in conjunction with the accompanying drawings, further elaborates on various embodiments of a method for printing and curing thermal paste on double-sided circuit boards according to this application.

[0029] Reference Figures 1 to 3The present invention provides a method for printing and curing double-sided thermal paste for circuit boards, including a top pad 100, wherein the top pad 100 is provided with a plurality of clearance holes 110. The printing curing method may include, but is not limited to, steps S100, S200, S300, and S400.

[0030] Step S100, cleaning step, cleaning the double-sided sided surface of the circuit board 200; In some specific embodiments, the top and bottom panels of the circuit board 200 are cleaned through a cleaning step to reduce the adhesion of foreign matter on the surface of the circuit board 200, and at the same time help to increase the bonding force between the thermal paste and the circuit board 200 during printing.

[0031] Step S200, the first printing step on the top surface, involves assembling the circuit board 200 onto the first machine platform and printing thermal paste on several first designated areas on the top surface of the circuit board 200 using the first printing machine. The several first designated areas correspond to several clearance slots 110.

[0032] Specifically, similar to existing technologies, a first machine base (not shown) is positioned below a first printing press (not shown). The upper surface of the first machine base has several suction holes, and a negative pressure generator (not shown) is installed inside the first machine base. After the circuit board 200 is placed on the first machine base, the negative pressure generator uses the suction holes to adhere the circuit board 200 to the first machine base, thus fixing the circuit board 200 relatively to the first machine base. Specifically, after the first machine base adheres the circuit board 200, adhesive tape (not shown) can be used to attach the circuit board 200 to the first machine base to improve the relative fixation between the circuit board 200 and the first machine base.

[0033] Specifically, a top graphic screen (not shown) is mounted on the first printing press. The top graphic screen has several graphic areas (not shown), with mesh openings exposed in the graphic areas (not shown), while other areas of the top graphic screen do not expose mesh openings. Thermal paste is extruded onto the top graphic screen using the first printing press. The first printing press then uses a doctor blade to force the thermal paste through the mesh openings of the graphic areas of the top graphic screen into a first designated area of ​​the circuit board 200 below.

[0034] Specifically, the first printing press is equipped with a charge-coupled device mechanism to achieve alignment and positioning between the top graphic screen and the circuit board 200.

[0035] Specifically, the process for manufacturing the top-side graphic screen is as follows: 32T taut mesh is glued onto an aluminum frame with strong adhesive. The mesh is then degreased and cleaned. Next, 50-micron capillary film is cut according to the mesh size and attached to the mesh. Then, photoresist is applied to the capillary film and dried. After exposure using a photolithography machine, the capillary film in several graphic areas is washed away with water to expose the mesh holes. After drying, the top-side graphic screen is obtained.

[0036] Specifically, the several first designated areas (not shown in the figure) on the top surface of the circuit board 200 refer to several areas on the top surface of the circuit board 200 where thermal paste needs to be printed. Different shapes of pads, vias, conductive lines, etc. are arranged at different locations on the circuit board 200. Thermal paste needs to be printed near the areas on the circuit board 200 where high-heat-generating components are planned to be soldered, while thermal paste does not need to be printed in the areas on the circuit board 200 where low-heat-generating components are planned to be soldered.

[0037] Step S300, the first printing step on the bottom surface, may include, but is not limited to, steps S310, S340 and S350.

[0038] Step S310: Assemble the top pad 100 onto the second machine base; Step S340: The top surface of the circuit board 200 is attached to the top surface pad 100, and several first designated areas are moved to the top of several clearance slots 110. Step S350: Print thermal paste on several second designated areas on the bottom surface of the circuit board 200 using a second printing press; Specifically, the second printing press (not shown) is positioned below the second printing press (not shown). The upper surface of the second printing press has several suction holes, and a negative pressure generator (not shown) is installed inside the second printing press. After the top pad 100 is placed on the second printing press, the negative pressure generator uses the suction holes to adhere the top pad 100 to the second printing press, thus fixing the top pad 100 to the second printing press. Specifically, after the second printing press adheres to the top pad 100, adhesive tape (not shown) can be used to attach the top pad 100 to the second printing press to improve the relative fixation between the top pad 100 and the second printing press.

[0039] Specifically, a bottom graphic screen (not shown) is mounted on the second printing press. The bottom graphic screen also has several graphic areas (not shown). These graphic areas can be identical to or different from those on the top graphic screen. Mesh openings are exposed in the graphic areas of the bottom graphic screen (not shown), while other areas of the bottom graphic screen do not. The second printing press extrudes thermal paste onto the top of the bottom graphic screen. Using a doctor blade, the second printing press forces the thermal paste through the mesh openings of the graphic areas of the bottom graphic screen into a second designated area of ​​the circuit board 200 below.

[0040] Specifically, the second printing press is also equipped with a charge-coupled device mechanism to achieve alignment and positioning between the bottom graphic screen and the circuit board 200.

[0041] Specifically, the manufacturing process of the bottom graphic screen is the same as that of the top graphic screen.

[0042] Specifically, the several second designated areas on the bottom surface of the circuit board 200 refer to several areas on the bottom surface of the circuit board 200 where thermal paste needs to be printed. The several first designated areas and the several second designated areas may be completely identical or different.

[0043] Step S400, the first curing step, involves leaving the circuit board in an oven and baking it.

[0044] Specifically, an oven (not shown) is used to heat the circuit board 200 placed therein, so that the thermal paste on the circuit board 200 can be fully allowed to stand and level before baking and curing. In some specific embodiments, after S100, S200, and S300 are applied to one circuit board 200, it is placed in a cage rack (not shown). Then, S100, S200, and S300 are applied to several other circuit boards 200. After a certain number of other circuit boards 200 are placed in the cage rack, the cage rack and the circuit boards 200 are placed together in the oven for standing and baking.

[0045] Cleaning the top and bottom surfaces of the circuit board 200 through a cleaning step helps reduce the poor adhesion of foreign objects to the circuit board 200 surface, increases the bonding force between the thermal paste and the circuit board 200, and improves the printing effect of the thermal paste on the circuit board 200.

[0046] By setting a top surface pad 100, which has several clearance slots 110, the clearance slots 110 can be matched and correspond to several first designated areas on the top surface of the circuit board 200. Through the initial printing step on the top surface, thermal paste is pressed and penetrated into several first designated areas on the top surface of the circuit board 200; then, the several first designated areas of the circuit board 200 are aligned with the clearance slots 110 of the top surface pad 100, and the top surface of the circuit board 200 is then attached to the top surface pad 100. At this time, the thermal paste located in the several first designated areas on the top surface of the circuit board 200 is correspondingly placed in the clearance slots 110 of the top surface pad 100. The clearance slots 110 of the top surface pad 100 provide clearance and accommodation space for the thermal paste located in the several first designated areas on the top surface of the circuit board 200, which helps to avoid scratching or even scraping away the thermal paste and helps to improve the heat dissipation effect of the circuit board 200.

[0047] Compared to existing technologies, by using the top pad 100 in the first bottom printing step, the thermal paste printed on the top surface of the circuit board 200 is prevented from being scratched during the bottom thermal paste printing step, which helps reduce the occurrence of scratches or even damage to the thermal paste on the top surface of the circuit board 200. On the other hand, by using the top pad 100 in the first bottom printing step, the present invention helps reduce the direct contact between the thermal paste on the top surface of the circuit board 200 and the second machine, which could cause the circuit board 200 to tilt, thus improving the quality of the thermal paste printing operation on the bottom surface of the circuit board 200.

[0048] Compared to existing technologies, which require placing the circuit board 200 in an oven for a resting and baking process after the initial printing step, and then removing the circuit board 200 from the oven for the bottom surface initial printing step, followed by another resting and baking process, this invention saves one resting and baking curing step by performing the top and bottom surface initial printing steps separately before the initial curing step. This helps improve the production efficiency of the circuit board 200, saves energy costs, and reduces the degradation of the solder resist film performance caused by multiple baking processes.

[0049] According to some embodiments of this application, refer to Figure 3 In step S100, the cleaning step may include, but is not limited to, steps S110 and S120.

[0050] Step S110: Use an acidic cleaning solution to spray and clean the circuit board 200 using a cleaning device; Specifically, the cleaning equipment is a horizontal roller conveyor pretreatment equipment for solder resist (not shown in the figure). The horizontal roller conveyor pretreatment equipment for solder resist sprays a dilute sulfuric acid cleaning solution with a concentration range of 3% to 5% onto the upper and lower surfaces of the circuit board 200. The spraying time lasts from 18 to 22 seconds, preferably 20 seconds.

[0051] Step S120: Use a cleaning device to spray clean water to clean the circuit board 200.

[0052] Specifically, a horizontal roller conveyor is used to pre-treat the solder resist with water, and the upper and lower surfaces of the circuit board 200 are sprayed with clean water for 45 to 60 seconds, preferably 50 seconds.

[0053] Furthermore, after step S120, where the circuit board 200 is washed with clean water using a cleaning device, step S130 is also included, where the circuit board 200 is dried by blowing hot air through the cleaning device.

[0054] Specifically, a horizontal roller conveyor is used to transport the solder resist pretreatment equipment to blow hot air onto the upper and lower surfaces of the circuit board 200. The hot air temperature range is 70°C to 90°C, preferably 80°C. The hot air drying time for each circuit board 200 lasts from 18 to 22 seconds, preferably 20 seconds.

[0055] According to some embodiments of this application, refer to Figure 1 and Figure 2 The top surface pad 100 is provided with a plurality of first positioning holes 120 and a plurality of first positioning pins 140, and the plurality of first positioning pins 140 are connected to the plurality of first positioning holes 120 one by one; the circuit board 200 is provided with a plurality of second positioning holes 210, and the plurality of second positioning holes 210 are detachably connected to the plurality of first positioning pins 140 one by one; specifically, each first positioning pin 140 is set perpendicular to the top surface pad 100, each first positioning pin 140 can be set perpendicular to the circuit board 200, and each first positioning pin 140 can be perpendicular to the circuit board 200 and then inserted into the corresponding second positioning hole 210.

[0056] In step S300, the first printing step on the bottom surface, refer to Figure 3 Before step S340, when the top surface of the circuit board 200 is attached to the top surface pad 100, step S320 is also included, in which a plurality of second positioning holes 210 are fitted one-to-one onto a plurality of first positioning pins 140.

[0057] It is easy to understand that by fitting a number of second positioning holes 210 one by one onto a number of first positioning pins 140, it helps to position the circuit board 200 and the top pad 100 in a direction parallel to the top pad 100, and helps to improve the accuracy of aligning a number of first designated areas of the circuit board 200 with a number of clearance slots 110 of the top pad 100.

[0058] Furthermore, referring to Figure 1 and Figure 2The top pad 100 is provided with a first anti-fool hole 130 and a second positioning pin 150 connected to each other. The circuit board 200 is provided with a second anti-fool hole 220. The second anti-fool hole 220 and the second positioning pin 150 are detachably assembled. Specifically, the second positioning pins 150 are all set perpendicular to the top pad 100, and the second positioning pins 150 are all perpendicular to the circuit board 200 and then inserted into the second anti-fool hole 220.

[0059] In step S300, the first printing step on the bottom surface, refer to Figure 3 Before step S340, when the top surface of the circuit board 200 is attached to the top surface pad 100, step S330 is also included, when the second anti-fool hole 220 is fitted onto the second positioning pin 150.

[0060] It is easy to understand that by fitting the second anti-fool holes 220 one by one onto the second positioning pins 150, it helps to avoid assembling the circuit board 200 onto the top pad 100 in the wrong direction, and helps to improve the positional accuracy of moving the first designated areas above the clearance slots 110 in step S340; it also helps to improve the positional accuracy of printing thermal paste on the bottom surface of the circuit board 200 in step S350 by the second printing machine in the second designated areas.

[0061] According to some embodiments of this application, refer to Figure 3 After step S400 and the first curing step, steps S600, S700 and S800 may be included, but are not limited to.

[0062] Step S600, Top Surface Reprinting Step: The circuit board 200 is assembled on the first machine base, and thermal paste is printed on several first designated areas on the top surface of the circuit board 200 by the first printing machine. Specifically, the implementation of step S600, the top surface re-printing step, is similar to that of step S200, the top surface initial printing step. First, the circuit board 200 is assembled on the first printing platform. Then, a charge-coupled device (CCD) mechanism is used to align and position the top surface graphic screen mounted on the first printing machine with the circuit board 200. Then, the thermal paste is extruded again from the first printing machine onto the top surface graphic screen. The first printing machine uses a squeegee to force the thermal paste through the mesh holes corresponding to several graphic areas of the top surface graphic screen, permeating it into the first designated area of ​​the circuit board 200 below. This prints the thermal paste onto the surface of the thermal paste formed in step S200, the top surface initial printing step, thereby increasing the thickness of the thermal paste in several first designated areas on the top surface of the circuit board 200.

[0063] Step S700, the bottom surface reprinting step, may include, but is not limited to, steps S730 and S740.

[0064] S730, The top surface of the circuit board 200 is attached to the top surface pad 100, and several first designated areas are moved to the top of several clearance slots 110. Step S740: Print thermal paste on several second designated areas on the bottom surface of the circuit board 200 using a second printing press.

[0065] Specifically, in step S300, the first printing step on the bottom surface, after the top surface pad 100 is assembled on the second machine base, the top surface pad 100 is maintained on the second machine base. Specifically, the implementation of step S700, the bottom surface re-printing step, is similar to that of step S300, the bottom surface initial printing step. First, the top surface of the circuit board 200 is attached to the top surface pad 100, and several first designated areas are moved above several clearance slots 110. At this time, the thermal paste located in several first designated areas on the top surface of the circuit board 200 is correspondingly placed in several clearance slots 110 of the top surface pad 100. The clearance slots 110 of the top surface pad 100 provide clearance and accommodating space for the thermal paste located in several first designated areas on the top surface of the circuit board 200. Then, the charge-coupled device mechanism is used to align and position the bottom graphic screen mounted on the second printing press with the circuit board 200. Then, the thermal paste is extruded again by the second printing press above the bottom graphic screen. The second printing press uses a scraper to force the thermal paste through the mesh holes of several graphic areas of the bottom graphic screen, permeating it into the second designated area of ​​the circuit board 200 below. Thermal paste is printed onto the surface of the thermal paste formed in step S300, the first printing step on the bottom surface, to increase the thickness of the thermal paste in several second designated areas on the bottom surface of the circuit board 200.

[0066] Specifically, in step S700, the bottom surface re-printing step, refer to Figure 3 Before step S730, when the top surface of the circuit board 200 is attached to the top surface pad 100, step S710 is also included, in which a plurality of second positioning holes 210 are fitted one-to-one onto a plurality of first positioning pins 140.

[0067] Furthermore, before step S730, when the top surface of the circuit board 200 is attached to the top surface pad 100, step S720 is also included, when the second anti-fool hole 220 is fitted onto the second positioning pin 150.

[0068] Step 800, the second curing step, involves leaving the circuit board in the oven to stand and bake for 200 minutes.

[0069] Specifically, the oven is used to heat the circuit board 200 placed inside, so that the thermal paste on the circuit board 200 can be fully allowed to stand and level before being baked and cured. In some specific embodiments, after steps S600 and S700 are performed on one circuit board 200, it is placed in a rack. Then, steps S600 and S700 are performed on several other circuit boards 200. After several other circuit boards 200 are placed in the rack and a certain number are reached, the rack and several circuit boards 200 are placed together in the oven for standing and baking.

[0070] It's easy to understand that for cases where the thermal paste thickness requirement is relatively small, specifically less than 120 μm, steps S200, S300, and S400 are sufficient to meet the thermal paste thickness requirements for the top and bottom surfaces of the circuit board 200. However, for cases where the thermal paste thickness requirement is relatively large, specifically in the range of 120 μm to 180 μm, after steps S200, S300, and S400, due to the combined effects of thermal paste leveling, air bubble overflow, and curing shrinkage, the thermal paste thickness on the top and bottom surfaces of the circuit board 200 may not meet the requirements. Therefore, steps S600, S700, and S800 are also required to increase the thermal paste thickness on the top and bottom surfaces of the circuit board 200 to meet the thermal paste thickness requirements.

[0071] It is easy to understand that for thermal paste with a thickness requirement of 120 um to 180 um, two curing steps can be saved in the entire printing and curing process, reducing the curing steps from four in the existing technology to two. This helps to shorten the production cycle of the circuit board 200, reduce heat consumption, and reduce the degradation of the solder resist film performance of the circuit board 200 caused by multiple baking.

[0072] According to some embodiments of this application, refer to Figure 3 Between step S400, the first curing step and step S600, the top surface reprinting step, there may be steps including but not limited to step S500.

[0073] Step S500, cooling step: place the circuit board 200 on a temporary storage rack for heat dissipation.

[0074] Specifically, in step S500, the cooling step, the circuit board 200 together with the pig cage rack is taken out of the oven, and then the circuit board 200 is taken out of the pig cage rack and placed on a temporary storage rack (not shown in the figure) to dissipate heat from the circuit board 200 under normal temperature conditions so that the temperature of the circuit board 200 drops to below 40°C.

[0075] Furthermore, referring to Figure 3 Step 800 and the second curing step may include, but are not limited to, steps 810 and 820.

[0076] Step 810: Place the circuit board 200 in the oven and maintain it at the third preset temperature for the third preset time; Step 820: Keep the circuit board 200 in the oven and bake it at the fourth preset temperature for the fourth preset time; the fourth preset temperature is higher than the third preset temperature.

[0077] Specifically, after placing the circuit board 200 in the oven, it is kept at a third preset temperature for a third preset time to allow the circuit board 200 to stand still, allowing air bubbles in the thermal paste to automatically escape to the outside, while also allowing the surface of the thermal paste to level. Specifically, the circuit board 200 is kept in the oven and baked at a fourth preset temperature for a fourth preset time to bake the circuit board 200, causing the molecular chains of the thermal paste to cross-link, thereby achieving the curing of the thermal paste.

[0078] It is easy to understand that allowing the thermal paste on the circuit board 200 to stand and then cure helps to reduce air bubbles in the thermal paste and also helps to improve the smoothness of the thermal paste surface.

[0079] Furthermore, in step S400, the initial curing step may include, but is not limited to, steps 410 and 420.

[0080] Step 410: Place the circuit board 200 in an oven and maintain it at a first preset temperature for a first preset time; Step 420: Keep the circuit board 200 in the oven and bake it at the second preset temperature for the second preset time; the second preset temperature is higher than the first preset temperature.

[0081] Specifically, after placing the circuit board 200 in the oven, it is kept at a first preset temperature for a first preset time to allow the circuit board 200 to stand still, allowing air bubbles in the thermal paste to automatically overflow and the surface of the thermal paste to level. Specifically, the circuit board 200 is kept in the oven and baked at a second preset temperature for a second preset time to allow the molecular chains of the thermal paste to cross-link, thereby achieving curing of the thermal paste.

[0082] It is easy to understand that allowing the thermal paste on the circuit board 200 to stand and then cure helps to further reduce air bubbles in the thermal paste and also helps to further improve the smoothness of the thermal paste surface.

[0083] Furthermore, the fourth preset time is greater than the second preset time.

[0084] It's easy to understand that the shorter second preset time compared to the fourth preset time helps the thermal paste achieve pre-curing after step S400, the first curing step, meaning the surface of the thermal paste is cured while the interior remains uncured. Conversely, the longer fourth preset time compared to the second preset time allows the thermal paste to achieve complete curing after step 800, the second curing step, meaning both the surface and interior of the thermal paste are fully cured. The fourth preset time being longer than the second preset time helps shorten the entire printing and curing cycle, and also reduces the total time the thermal paste is exposed to high temperatures, thus reducing performance degradation caused by prolonged exposure to high temperatures.

[0085] In some specific embodiments, the first preset temperature range is 45°C to 55°C, preferably 50°C; the second preset temperature range is 145°C to 155°C, preferably 150°C; the third preset temperature range is 45°C to 55°C, preferably 50°C; and the fourth preset temperature range is 145°C to 155°C, preferably 150°C.

[0086] In some specific embodiments, the first preset time range is 28 to 32 minutes, preferably 30 minutes; the second preset time range is 28 to 32 minutes, preferably 30 minutes; the third preset time range is 28 to 32 minutes, preferably 30 minutes; and the fourth preset time range is 58 to 62 minutes, preferably 60 minutes.

[0087] It is understood that in some other embodiments, a bottom pad is also included. The bottom pad has a similar structure to the top pad 100. The bottom pad also has several clearance slots, several positioning holes, several anti-fooling holes, and several positioning pins. The positioning pins can be matched and connected to the positioning holes and anti-fooling holes. The circuit board 200 is provided with several positioning holes and several anti-fooling holes corresponding to the positioning pins of the bottom pad. See reference. Figure 1 and Figure 2 The clearance slots, positioning holes, anti-fooling holes, and positioning pins of the bottom pad have the same structure and connection method as those of the top pad 100, and will not be described again here. The positioning holes and anti-fooling holes of the circuit board 200 corresponding to the bottom pad have the same structure and connection method as those of the circuit board 200 corresponding to the top pad 100, and will not be described again here.

[0088] Specifically, in step S600, the top surface reprinting step, the bottom pad is first assembled onto the first machine base, and then the circuit board 200 is assembled onto the bottom pad to assemble the circuit board 200 onto the first machine base. The bottom pad helps to reduce scratches and damage to the thermal paste on the bottom surface of the circuit board 200.

[0089] It is understood that, in some other embodiments, reference is made to... Figure 1 and Figure 2 The top surface pad 100 is also provided with several measuring holes and slots 160, and the printing and curing method may include, but is not limited to, step S900.

[0090] Step S900, Test Step: Perform thickness measurement and high voltage test on the top and bottom surface thermal paste of the circuit board 200.

[0091] In some embodiments, reference is made to Figure 3 In some embodiments, steps S900 and the test step are set after step S500; in other embodiments, steps S900 and the test step are set after step S800; and in still other embodiments, steps S900 and the test step are set between steps S500 and S500, and also after step S800, in order to meet the testing requirements of thermal paste of different thicknesses.

[0092] Specifically, a certain graphic area or several graphic areas of the top graphic screen do not correspond to several first designated areas. In steps S200 and S600, the first printing machine uses a squeegee to press the thermal paste through the mesh holes of the graphic area of ​​the top graphic screen into one or several areas outside the first designated areas on the top surface of the circuit board 200, forming a top surface test thermal paste.

[0093] Specifically, the top surface test thermal paste and the measurement slots 160 can be matched. In steps S340 and S730, when the top surface of the circuit board 200 is attached to the top surface pad 100, the top surface test thermal paste can be moved into the corresponding measurement slots 160. The measurement slots 160 of the top surface pad 100 provide clearance and accommodation space for the top surface test thermal paste on the circuit board 200. This helps to reduce scratches on the top surface test thermal paste.

[0094] Specifically, a structured light thickness gauge (not shown in the figure) is used to measure the thickness of the thermal paste on the top surface, and the thickness of the thermal paste in several first designated areas on the top surface of the circuit board 200 is inferred from this measurement. Specifically, a breakdown strength tester (not shown in the figure) is used to perform a dielectric withstand voltage test on the thermal paste on the top surface, applying progressively increasing high voltage to detect the withstand voltage value of the thermal paste under high voltage, and the withstand voltage value of the thermal paste in several first designated areas on the top surface of the circuit board 200 is inferred from this test. This helps to avoid scratching or damaging the thermal paste in several first designated areas on the top surface of the circuit board 200.

[0095] In some embodiments, the bottom pad also has a plurality of measuring holes and slots 160, and the plurality of measuring holes and slots 160 in the bottom pad have the same structure as the plurality of measuring holes and slots 160 in the top pad 100.

[0096] Specifically, a certain graphic area or several graphic areas of the bottom graphic screen do not correspond to several second designated areas. In steps S350 and S740, the second printing machine uses a squeegee to press the thermal paste through the mesh holes of the aforementioned graphic area of ​​the bottom graphic screen and penetrate it into one or several areas outside the second designated areas on the bottom surface of the lower circuit board 200, forming bottom test thermal paste.

[0097] Specifically, the bottom surface test thermal paste and the measurement slots 160 of the bottom surface pad can be matched. In step S600, the top surface re-printing step, when the bottom surface of the circuit board 200 is attached to the bottom surface pad, the bottom surface test thermal paste can be moved accordingly into the measurement slots 160 of the bottom surface pad. The measurement slots 160 of the bottom surface pad provide clearance and accommodating space for the bottom surface test thermal paste located on the circuit board 200. This helps reduce scratches on the bottom surface test thermal paste.

[0098] Specifically, a structured light thickness gauge is used to measure the thickness of the thermal paste on the bottom surface, and the thickness of the thermal paste in several second designated areas on the bottom surface of the circuit board 200 is inferred from this measurement. Conversely, a dielectric breakdown strength tester is used to perform a dielectric withstand voltage test on the thermal paste on the bottom surface, and the withstand voltage value of the thermal paste in several second designated areas on the bottom surface of the circuit board 200 is inferred from this test. This helps to avoid scratching or damaging the thermal paste in the several second designated areas on the bottom surface of the circuit board 200.

[0099] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0100] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for printing and curing thermal paste on both sides of a circuit board, characterized in that, Includes a top surface pad (100), wherein the top surface pad (100) is provided with a plurality of clearance slots (110); The printing curing method includes: Cleaning steps; In the first printing step on the top surface, the circuit board (200) is assembled on the first machine platform, and thermal paste is printed on several first designated areas on the top surface of the circuit board (200) by the first printing machine. The several first designated areas can be matched and correspond to several of the clearance slots (110). In the first printing step on the bottom surface, the top surface pad (100) is assembled on the second machine platform, the top surface of the circuit board (200) is attached to the top surface pad (100), and several first designated areas are moved to above several clearance slots (110); thermal paste is printed on several second designated areas on the bottom surface of the circuit board (200) by the second printing machine. The initial curing step involves leaving the circuit board in an oven and baking it (200).

2. The method for printing and curing double-sided thermal paste on a circuit board according to claim 1, characterized in that, The top surface pad (100) is provided with a plurality of first positioning holes (120) and a plurality of first positioning pins (140), and the plurality of first positioning pins (140) are connected to the plurality of first positioning holes (120) one by one; the circuit board (200) is provided with a plurality of second positioning holes (210), and the plurality of second positioning holes (210) are detachably connected to the plurality of first positioning pins (140) one by one; in the first printing step on the bottom surface, before the top surface of the circuit board (200) is attached to the top surface pad (100), the plurality of second positioning holes (210) are fitted onto the plurality of first positioning pins (140) one by one.

3. The method for printing and curing double-sided thermal paste on a circuit board according to claim 2, characterized in that, The top pad (100) is provided with a first anti-fool hole (130) and a second positioning pin (150) connected to each other. The circuit board (200) is provided with a second anti-fool hole (220). The second anti-fool hole (220) and the second positioning pin (150) are detachably assembled. In the first printing step on the bottom surface, before attaching the top surface of the circuit board (200) to the top pad (100), the second anti-fool hole (220) is fitted onto the second positioning pin (150).

4. The method for printing and curing double-sided thermal paste on a circuit board according to claim 1, characterized in that, Following the initial curing step, the process also includes: The top surface is reprinted in the following steps: the circuit board (200) is assembled on the first machine base, and thermal paste is printed on several first designated areas on the top surface of the circuit board (200) by the first printing machine. In the bottom reprinting step, the top surface of the circuit board (200) is attached to the top surface pad (100), and several first designated areas are moved to above several clearance slots (110); thermal paste is printed on several second designated areas on the bottom surface of the circuit board (200) by a second printing machine. The circuit board (200) is then left to stand and bake in the oven.

5. The method for printing and curing double-sided thermal paste on a circuit board according to claim 4, characterized in that, In the re-curing step, the circuit board (200) is placed in the oven and kept at a third preset temperature for a third preset time; the circuit board (200) is then placed in the oven and baked at a fourth preset temperature for a fourth preset time; the fourth preset temperature is higher than the third preset temperature.

6. The method for printing and curing double-sided thermal paste on a circuit board according to claim 5, characterized in that, In the first curing step, the circuit board (200) is placed in the oven and kept at a first preset temperature for a first preset time; the circuit board (200) is then kept in the oven and baked at a second preset temperature for a second preset time; the second preset temperature is higher than the first preset temperature.

7. The method for printing and curing double-sided thermal paste on a circuit board according to claim 6, characterized in that, The fourth preset time is greater than the second preset time.

8. The method for printing and curing double-sided thermal paste on a circuit board according to claim 4, characterized in that, Between the initial curing step and the top surface re-printing step, the following is also included: In the cooling step, the circuit board (200) is placed on a temporary storage rack for heat dissipation.

9. The method for printing and curing double-sided thermal paste on a circuit board according to claim 1, characterized in that, In the cleaning step, the circuit board (200) is sprayed with acidic cleaning solution using a cleaning device, and then the circuit board (200) is sprayed with clean water using the same cleaning device.

10. A method for printing and curing double-sided thermal paste on a circuit board according to claim 9, characterized in that, After the circuit board (200) is washed with clean water by the cleaning equipment, the circuit board (200) is dried by blowing hot air through the cleaning equipment.

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