Circuit board and its manufacturing method

Abstract

The present application provides a circuit board and a method for manufacturing the same. The method for manufacturing the circuit board includes performing surface treatment on a board; performing a solder paste screen printing operation on the board after surface treatment; performing a reflow soldering operation on the board after solder paste screen printing; performing a wiping operation on the board after the reflow soldering operation; and performing text processing on the board after the wiping operation. In the above method for manufacturing a circuit board, no peelable glue or high-temperature resistant red glue is used. On the one hand, the cost of circuit board production can be reduced. On the other hand, the phenomenon of high rejection rate of the board caused by incomplete removal of glue from small vias of the board is reduced, thereby improving the product qualification rate of the circuit board and increasing the production efficiency of the circuit board.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board production, and particularly to a printed circuit board and a preparation method thereof. Background Art

[0002] During the production of printed circuit boards, selective tin spraying surface treatment needs to be performed on the surface of the printed circuit board so that operators can perform better installation or soldering.

[0003] In the traditional selective tin spraying surface treatment operation on the surface of printed circuit boards, usually, a peelable glue or a high-temperature resistant red glue is pasted on the area of the printed circuit board surface where tin spraying is not required to achieve the shielding effect. Then, tin spraying operation is performed on the surface of the printed circuit board, and then the board and the peelable glue or the high-temperature resistant red glue are separated. Finally, the colloid adhered to the surface of the board is removed, thus completing the selective tin spraying operation on the surface of the printed circuit board. However, the traditional selective tin spraying surface treatment operation has the phenomena of more complex processes and longer flow, thus affecting the production efficiency of the printed circuit board, and the cost of the peelable glue or the high-temperature resistant red glue is relatively high, that is, the production cost is relatively high. Summary of the Invention

[0004] An object of the present invention is to overcome the deficiencies in the prior art and provide a printed circuit board and a preparation method thereof with simple operation, high production efficiency and low production cost.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A method for preparing a printed circuit board, comprising:

[0007] Performing surface treatment on a board;

[0008] Performing solder paste screen printing operation on the board after surface treatment;

[0009] Performing reflow soldering operation on the board after solder paste screen printing;

[0010] Performing wiping operation on the board after reflow soldering operation;

[0011] Performing text processing on the board after wiping operation.

[0012] In one embodiment, in the step of performing solder paste screen printing operation on the board after surface treatment, the following specific steps are included:

[0013] Performing solder paste screen printing operation on the board after surface treatment by using a solder paste screen printing stencil.

[0014] In one embodiment, the mesh number of the solder paste screen printing stencil is 100T - 120T.

[0015] In one embodiment, the silk screen printing stencil is provided with optical positioning points.

[0016] In one embodiment, the conditions for the reflow soldering operation are as follows: the reflow soldering speed is 800 mm / min to 1000 mm / min, and the temperature is 150 °C to 270 °C.

[0017] In one embodiment, in the step of wiping the board that has undergone the reflow soldering operation, the following specific steps are included:

[0018] Use a wiping pen to wipe the board that has undergone the reflow soldering operation.

[0019] In one embodiment, the wiping pen is a fiber rod.

[0020] In one embodiment, in the step of surface-treating the board, the following specific steps are included:

[0021] Perform an immersion gold operation or an immersion silver operation or a gold plating operation on the surface of the board.

[0022] In one embodiment, after the step of wiping the board that has undergone the reflow soldering operation and before the step of performing text processing on the wiped board, the following steps are further included:

[0023] Inspect the wiped board.

[0024] A circuit board is obtained by using the circuit board preparation method described in any one of the above embodiments.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] In the above circuit board preparation method, by performing a silk screen printing of solder paste on the surface-treated board to print the solder paste on the preset surface of the board, then subjecting the board with the silk screen-printed solder paste to a reflow soldering operation to cure the solder paste on the preset surface of the board, and then wiping the board after the reflow soldering operation to remove the crystals of the flux remaining on the tin layer, thereby completing the selective tin spraying treatment operation on the surface of the board, and finally performing text processing on the wiped board to leave corresponding mark numbers on the board, so as to facilitate better identification and installation by the operator. By using the above silk screen printing of solder paste operation, reflow soldering operation and wiping operation, the operation is simple and convenient, thereby improving the production efficiency of the circuit board. In addition, since the above circuit board preparation method does not use peelable glue or heat-resistant red glue stickers, on the one hand, the production cost of the circuit board can be reduced, and on the other hand, the phenomenon of high rejection rate of the board caused by incomplete removal of the glue in the small through-holes of the board is reduced, thereby improving the product qualification rate of the circuit board. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a flow chart of a method for preparing a circuit board according to one embodiment of the present invention;

[0029] Figure 2 This is a reflow curve diagram of the solder paste in the reflow soldering furnace of Example 1. DETAILED DESCRIPTION

[0030] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0031] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] The present application provides a method for preparing a circuit board, comprising performing surface treatment on a board; performing a screen printing solder paste operation on the board after the surface treatment; performing a reflow soldering operation on the board after the screen printing solder paste; performing a wiping operation on the board after the reflow soldering operation; and performing text processing on the board after the wiping operation.

[0034] The above-mentioned method for preparing a circuit board involves performing a solder paste screen printing operation on the surface-treated board to print the solder paste on the preset surface of the board. Then, the board with the solder paste screen printed is subjected to a reflow soldering operation to cure the solder paste on the preset surface of the board. Next, the board after the reflow soldering operation is wiped to remove the crystals of the flux remaining on the tin layer, thereby completing the selective tin spraying treatment operation on the surface of the board. Finally, the board after the wiping operation is subjected to text processing to leave corresponding marking numbers on the board for better identification and installation by the operator. By using the above solder paste screen printing operation, reflow soldering operation, and wiping operation, the operations are simple and convenient, thus improving the production efficiency of the circuit board. In addition, since the above method for preparing a circuit board does not use peelable glue or high-temperature resistant red glue, on the one hand, it can reduce the production cost of the circuit board, and on the other hand, it can reduce the phenomenon of high scrap rate of the board caused by incomplete removal of the glue in the small through holes of the board, thereby improving the product qualification rate of the circuit board.

[0035] Please refer to Figure 1 , for a better understanding of the technical solutions and beneficial effects of the present application, the following further describes the present application in detail with specific embodiments. The method for preparing a circuit board in one embodiment includes some or all of the following steps:

[0036] S100. Perform surface treatment on the board. It can be understood that by performing surface treatment on the board, a gold layer or a silver layer is formed on the surface of the board to facilitate the installation and soldering by the operator.

[0037] S200. Perform a solder paste screen printing operation on the surface-treated board. It can be understood that after performing the solder paste screen printing operation on the board

[0038] , a tin layer can be formed on the surface of the board, enabling two different metal welding areas to be formed on the surface of the board, namely the gold plating area + the printed tin area or the silver plating area + the printed tin area, thereby improving the diversification of circuit board soldering, enhancing the market competitiveness of the circuit board, and also facilitating better installation and soldering by the operator.

[0039] S300. Perform a reflow soldering operation on the board with the solder paste screen printed. It can be understood that since the solder paste printed on the surface of the board is a wet paste layer, a reflow soldering operation is required to enable the solder paste to better cure on the surface of the board to form a tin layer on the surface of the board.

[0040] S400. Wipe the board after the reflow soldering operation. It can be understood that by wiping the board after the reflow soldering operation, the crystals of the flux remaining on the tin layer are removed to obtain a tin layer with a higher flatness for better soldering and installation by the operator.

[0041] S500. Perform text processing on the board after the wiping operation. It can be understood that by performing text processing on the board after the wiping operation, corresponding marking numbers are left on the board to facilitate better identification of the installation by the operator. It is worth mentioning that text processing is carried out after the board has completed the reflow soldering operation, and clear and non-yellowing fonts can be obtained to ensure a circuit board with better text effects.

[0042] For the above-mentioned circuit board preparation method, by performing a solder paste screen printing operation on the surface-treated board to print the solder paste on the preset surface of the board, then performing a reflow soldering operation on the board after solder paste screen printing to cure the solder paste on the preset surface of the board, and then performing a wiping operation on the board after the reflow soldering operation to remove the crystals of the flux remaining on the tin layer, thus completing the selective tin spraying treatment operation on the board surface. Finally, perform text processing on the board after the wiping operation to leave corresponding marking numbers on the board to facilitate better identification of the installation by the operator. By using the above solder paste screen printing operation, reflow soldering operation and wiping operation, the operations are simple and convenient, thus improving the production efficiency of the circuit board. In addition, since the above-mentioned circuit board preparation method does not use peelable glue or high-temperature resistant red glue, on the one hand, the production cost of the circuit board can be reduced, and on the other hand, the phenomenon of high scrap rate of the board caused by incomplete removal of the glue in the small through holes of the board can be reduced, thus improving the product qualification rate of the circuit board.

[0043] In one embodiment, in the step of performing a solder paste screen printing operation on the surface-treated board, the following specific steps are included: Use a screen printing stencil to perform a solder paste screen printing operation on the surface-treated board.

[0044] It can be understood that by using a screen printing stencil to perform a solder paste screen printing operation on the surface-treated board, since the screen printing stencil is adapted to the board, the solder paste can be attached to the corresponding position of the board through the mesh holes of the screen printing stencil in the screen printing machine, thereby realizing the operation of selectively printing solder paste on the board surface, and thus the operation of selectively printing solder paste on the board surface can be quickly completed. In this embodiment, the screen printing stencil is provided with corresponding windows, and the windows are adapted to the positions where the solder paste is preset to be printed on the board, so that the solder paste can flow to the preset positions of the board, thus meeting the requirements of production standards.

[0045] It should be noted that, compared with the traditional selective solder spraying operation of applying glue, since the traditional solder spraying uses hot air leveling operation, the board needs to be fully immersed in a high-temperature tin furnace for tin dipping operation. Then, the dipped board is quickly lifted vertically upward away from the liquid surface of the tin solution, and then a high-temperature air blowing and leveling operation is performed on the board to adhere the tin solution to the solder pads and vias. This not only has a long dipping time and a cumbersome process, but also requires removing the removable glue or applying high-temperature resistant red glue subsequently. Especially for the glue layer attached to small vias, there is a problem of high removal difficulty, which is likely to cause the board to be scrapped. In contrast, the present application uses a silk screen stencil to selectively print solder paste on the board, which can play a good role in blocking small vias that do not require solder paste printing. Thus, the solder paste can be printed at the preset positions on the board to achieve the operation of quickly selectively printing solder paste on the board. This is not only simple and convenient in operation, but also improves the production efficiency of printed circuit boards and can also save energy and reduce emissions.

[0046] In one embodiment, the solder paste includes 25% - 30% of flux and 70% - 75% of solder powder. It can be understood that by compounding and using 25% - 30% of flux and 70% - 75% of solder powder, a solder paste with better fluidity can be obtained, so that when performing the silk screen printing of solder paste, the solder paste can better flow from the apertures of the silk screen stencil to the preset positions on the board, that is, the solder paste can better flow into the preset positions on the board.

[0047] It should be further noted that, compared with traditional solder paste, solder paste usually containing more than 80% of solder powder is used to make the tin layer on the board reach a full state. However, in actual use, the solder paste with more than 80% of solder powder has poor fluidity, which not only affects the speed of the solder paste flowing into the preset positions on the board but also easily causes the apertures of the silk screen stencil to be blocked. On the one hand, this will cause waste of solder paste, and on the other hand, the blocked apertures of the silk screen stencil will affect the speed of the solder paste flowing into the preset positions on the board, thus affecting the production efficiency of the printed circuit board. On the other hand, when the apertures of the silk screen stencil are severely blocked, it is easy to cause the phenomenon that the solder paste does not flow into the preset positions on the board during the process of silk screen printing solder paste, resulting in a low fullness of the tin layer on the board surface, and further affecting the welding performance of the board. In contrast, the present application uses 70% - 75% of solder powder, which not only has better fluidity, is more conducive to the solder paste flowing into the preset positions on the board, improves the speed of silk screen printing solder paste on the board, and thus improves the production efficiency of the printed circuit board, but also is not easy to block the apertures of the silk screen stencil, thereby ensuring that the silk screen printing solder paste operation proceeds more smoothly. If solder paste with less than 70% of solder powder is used, due to the low content of solder powder less than 70%, the fullness of the tin layer on the board obtained after the reflow soldering operation is low, not delicate and prone to the phenomenon of false soldering, thus affecting the product quality of the printed circuit board.

[0048] In one embodiment, the solder paste is a water-soluble solder paste. It can be understood that since the water-soluble solder paste is an environmentally friendly solder paste and is easily soluble in water, it enables the operator to clean the solder paste remaining on the screen printer and the screen printing stencil more quickly, thereby reducing the production cost of cleaning the solder paste. Moreover, the cleaning solution is relatively friendly to the environment, thus providing good protection to the environment.

[0049] In one embodiment, the viscosity of the solder paste is 60 Pa·s to 120 Pa·s. It can be understood that by using a solder paste with a viscosity of 60 Pa·s - 120 Pa·s, since the solder paste with a viscosity of 60 Pa·s to 120 Pa·s is a low-viscosity solder paste, it endows the solder paste with high fluidity, so as to increase the speed at which the solder paste flows into the preset position of the board, thereby improving the production efficiency of printing the solder paste on the board. Also, because the solder paste with a viscosity of 60 Pa·s to 120 Pa·s has a relatively low viscosity, it effectively avoids the phenomenon that the solder paste is likely to adhere to the screen printing stencil during the process of flowing into the preset position of the board, causing the aperture to become smaller or blocked, so as to ensure the amount of solder paste used on the board, and further ensure that after the reflow soldering operation, a solder layer with high fullness, no roughness and no copper exposure can be obtained, that is, the product quality of the circuit board is improved.

[0050] It should be further noted that conventionally, solder paste with a viscosity of 200 Pa·s to 600 Pa·s is usually used, that is, the relative viscosity of the solder paste is relatively high. Since the solder paste with a relatively high viscosity is likely to adhere to the screen printing stencil during the process of flowing into the preset position of the board, it not only affects the speed at which the solder paste flows into the preset position of the board, but also easily causes a large amount of waste of the solder paste and the phenomenon of blocking the aperture of the screen printing stencil. However, in this application, a solder paste with a viscosity of 60 Pa·s to 120 Pa·s is used, and its viscosity is relatively lower than that of the solder paste with a viscosity of 200 Pa·s to 600 Pa·s, which can effectively reduce the phenomenon that the solder paste adheres to the screen printing stencil during the process of flowing into the preset position of the board. In this way, not only can the solder paste be printed quickly and accurately on the preset position of the board, thereby increasing the speed of screen printing the solder paste on the board, and further improving the production efficiency of the circuit board, but also a standard-compliant solder layer can be obtained on the surface of the board in cooperation with the subsequent reflow soldering operation, thus ensuring the product quality of the circuit board. In addition, since the solder paste with a lower viscosity is not likely to adhere to the screen printing stencil during the process of flowing into the preset position of the board, the cleaning cycle of the screen printing stencil can be extended, that is, the screen printing stencil needs to be cleaned only when the number of screen printing times of a single screen printing stencil reaches 25 to 35 times, thereby increasing the printing cycle of screen printing the solder paste on the board, and further improving the production efficiency of the circuit board. Further, since during the process of printing the solder paste, a small amount of solder paste will remain on the working surface of the screen printer, and since the solder paste is a water-soluble solder paste, it is convenient for the operator to clean the solder paste remaining on the working surface of the screen printer, thereby shortening the cleaning time of the screen printer, and further enabling the screen printer to enter the operation of screen printing the solder paste more quickly, and further making the production link and the cleaning link of the circuit board more compact, and further improving the production efficiency of the circuit board.

[0051] Further, if solder paste with a viscosity lower than 60 Pa·s is used, due to the too low viscosity, the fluidity of the solder paste is very good, so that the speed of the solder paste flowing into the preset position of the board is too fast, and it is easy to have the phenomenon of too thick solder paste printing, which may cause the phenomenon of solder paste overflow when the subsequent components are pressed down to the solder layer. In this way, not only the rejection rate of the circuit board products is increased, but also a large amount of solder paste is wasted, and the production cost of the circuit board is increased. However, the solder paste with a viscosity of 60 Pa·s to 120 Pa·s in this application can improve the speed of screen printing solder paste on the board under the condition of ensuring that a qualified circuit board can be obtained. It can also extend the cleaning cycle of the screen printing stencil, improve the production efficiency of the circuit board, and shorten the cleaning time of the screen printing machine, so that the production process and cleaning process of the circuit board are more compact, and the production efficiency of the circuit board can be further improved.

[0052] In one embodiment, the printing speed of the screen printing machine is controlled to be 60 mm / s to 100 mm / s. It can be understood that since the solder paste with a viscosity of 60 Pa·s to 120 Pa·s has a certain fluidity, and the printing speed of the screen printing machine is controlled to be 60 mm / s to 100 mm / s. In this way, not only does the screen printing machine have a high screen printing speed to ensure that the solder paste printed by the screen printing machine has a high output rate, thus ensuring a high production efficiency of the circuit board, but also it can ensure that the solder paste with a viscosity of 60 Pa·s to 120 Pa·s can be better printed on the preset position of the board to form a qualified solder layer, effectively avoiding the phenomenon of solder paste overflow when the subsequent components are pressed down to the solder layer, not only ensuring the product quality of the circuit board, but also reducing the waste of solder paste and saving the production cost of the circuit board.

[0053] In one embodiment, the viscosity of the solder paste is 70 Pa·s to 110 Pa·s, and a circuit board with more stable quality can be obtained.

[0054] In one embodiment, the mesh number of the screen printing stencil is 100T to 120T, so that the solder paste can well pass through the mesh holes of the 100T to 120T screen printing stencil under the action of the screen printing machine and flow into the preset position of the board to form a qualified solder layer. In a preferred embodiment, the mesh number of the screen printing stencil is 120T. When the mesh number of the screen printing stencil is 120T, under the condition of ensuring a relatively fast speed for the solder paste to flow into the preset position of the board during screen printing of the solder paste, it can also ensure that a solder layer with a thickness of 100 μin to 1000 μin can be obtained after the reflow soldering operation, thus effectively avoiding the increase in production cost or the appearance of defective products caused by too thick solder layer. That is, by using a screen printing stencil with a mesh number of 120T, a qualified circuit board can be quickly obtained. In this way, under the condition of improving the production efficiency of the circuit board, the cost of screen printing solder paste on the board is reduced and the product rejection rate of the circuit board is decreased.

[0055] In one embodiment, the screen printing stencil is provided with optical positioning points. It can be understood that by providing optical positioning points on the screen printing stencil and corresponding optical alignment points on the board, the board can be accurately aligned with the optical positioning points of the screen printing stencil through the optical alignment points, so that the window of the screen printing stencil is aligned with the preset position of the board. Then, the screen printing machine is started, so that the solder paste can pass through the window of the screen printing stencil under the action of the screen printing machine and flow into the preset position of the board, so as to realize that the solder paste can be accurately printed on the preset position of the board, thus completing the selective printing of the solder paste on the surface of the board. Compared with the traditional selective spraying of solder operation, it is not only simple in operation but also high in printing efficiency of the solder paste.

[0056] In one embodiment, an offset is set on the screen printing stencil to ensure that the solder paste can be fully printed on the preset position of the board, so that when the board is subjected to reflow soldering operation subsequently, a circuit board with a high degree of fullness, fineness and good welding performance of the tin layer can be obtained.

[0057] In one embodiment, the offset of the window of the screen printing stencil is greater than 1 mil - 2 mil of the size of the preset position of the board to ensure that the solder paste can be printed more comprehensively on the preset position of the board, thereby ensuring that a circuit board with a high degree of fullness, fineness and good welding performance of the tin layer is obtained.

[0058] In one embodiment, the screen printing stencil is provided with a plurality of windows, and the size of each window is adapted to the preset position of the board, so that a single screen printing stencil can perform screen printing of solder paste on multiple boards. In this way, the screen printing machine can realize screen printing of solder paste on multiple boards at one time, thereby improving the efficiency of producing circuit boards.

[0059] In one embodiment, the conditions for the reflow soldering operation are: the reflow soldering speed is 800 mm / min - 1000 mm / min, and the temperature is 150°C - 270°C.

[0060] It can be understood that by putting the board after screen printing the solder paste into the reflow soldering furnace and controlling the reflow soldering speed to be 800 mm / min - 1000 mm / min and the temperature to be 150°C - 270°C, the solder paste can be solidified and formed on the board, and then a tin layer with a thickness of 100 uin - 1000 uin can be obtained on the surface of the board.

[0061] In one embodiment, the specific steps of controlling the temperature to 150℃~270℃ include: heating the reflow oven in sections, with the temperature of the first section being 150℃~160℃, the temperature of the second section being 170℃~180℃, the temperature of the third section being 190℃~200℃, the temperature of the fourth section being 210℃~220℃, the temperature of the fifth section being 220℃~230℃, the temperature of the sixth section being 240℃~250℃, the temperature of the seventh section being 260℃~270℃, and the temperature of the eighth section being 250℃~260℃.

[0062] It can be understood that since the solder paste contains rosin, diluent and stabilizer, when the board enters the first preset temperature, that is, maintained at 150℃~160℃ for 50S~90S, the diluent in the solder paste will slowly begin to evaporate through heating. Since the solder paste of the present application includes 25%~30% flux and 70%~75% solder powder, that is, the flux content is higher than that of traditional solder paste, when the board is heated to 150℃~160℃ and maintained for 50S~90S, the board can maintain a slower and more uniform temperature rise, so that the diluent in the solder paste slowly begins to evaporate, effectively avoiding Because the temperature rises too quickly, the rosin, diluent and stabilizer in the solder paste soften rapidly and collapse, resulting in the formation of solder balls. It is worth mentioning that when the board is heated to 150℃~160℃ and maintained for 50S~90S, the flux inside the solder paste can begin to volatilize, so that when the board enters the second and third preset temperature sections, 25%~30% of the diluent in the flux can be quickly volatilized and the activation of the flux can be improved, so that when the board enters the fourth section at a temperature of 210℃~220℃, the solder powder can melt more quickly to obtain liquid tin.

[0063] Furthermore, when the board enters the fourth stage of the preset temperature of 210°C to 220°C, the fifth stage of the preset temperature of 220°C to 230°C, the sixth stage of the preset temperature of 240°C to 250°C, and the seventh stage of the preset temperature of 260°C to 270°C, and is maintained for 65S to 85S. It can be understood that when the board enters the fourth stage of the preset temperature, the fifth stage of the preset temperature, and the sixth stage of the preset temperature, the solder powder in the solder paste slowly begins to turn into liquid tin. When the board is maintained at above 220°C for 65S to 85S, the peak temperature of the temperature curve is 250°C to 260°C, so that the solder powder in the solder paste can be completely melted into liquid tin, so that the liquid tin can cover the surface of the preset position of the board and form a full and delicate tin layer. Finally, the eighth stage of the temperature is 250°C to 260°C, so that the board enters the cooling stage, thereby ensuring that the board can obtain a tin layer with a thickness of 100uin to 1000uin after the reflow soldering operation.

[0064] It should be further noted that when the heating rate of the reflow soldering furnace is greater than 2 °C / s, the rapid heating of the board causes a large thermal shock force on the board, resulting in the phenomenon that the board is prone to deformation, thereby increasing the rejection rate of the circuit board products. When the heating rate is less than 1 °C / s, the diluent in the solder paste volatilizes slowly, which affects the melting time of the solder powder, thereby prolonging the cycle time of the reflow soldering operation, and reducing the fullness and fineness of the tin layer. In this application, the board is heated in eight stages at a heating rate of (1 °C to 2 °C) / s and combined with a reflow soldering speed of 800 mm / min to 1000 mm / min, so that the heating distribution of the board is uniform, ensuring that the diluent in the solder paste can be completely volatilized, improving the activation performance of the flux, and ensuring that the board can obtain a full and fine tin layer after reflow soldering.

[0065] In one embodiment, the reflow soldering operation is a vacuum reflow soldering operation. It can be understood that when using the vacuum reflow soldering operation, since the solder paste contains 25% to 30% of the flux and has good fluidity, when the board is placed in the reflow soldering furnace and the vacuum component of the reflow soldering furnace is started, it can not only accelerate the volatilization of the diluent in the flux, so that the diluent in the flux can volatilize more quickly and comprehensively, but also the vacuum reflow soldering operation is beneficial to the overflow of bubbles in the molten solder powder, thereby reducing the void ratio of the solder joints formed at the preset positions of the board when the liquid tin solidifies, reducing the voids in the solder joints in the tin layer, and improving the product quality of the circuit board.

[0066] In one embodiment, the conditions of the vacuum reflow soldering operation are a vacuum degree of 50 mbar to 100 mbar and a holding time of 2 s to 3 s. By controlling the conditions of the vacuum reflow soldering operation to be a vacuum degree of 50 mbar to 100 mbar and a holding time of 2 s to 3 s, the volatilization speed of the diluent in 25% to 30% of the flux can be kept evenly distributed, and combined with the eight-stage segmented temperature of the reflow soldering furnace, a tin layer with high fullness, fineness and low solder joint voids can be obtained more quickly.

[0067] In one embodiment, in the step of wiping the board after the reflow soldering operation, the following specific steps are included: using a wiping pen to wipe the board after the reflow soldering operation to remove the crystals of the flux remaining on the tin layer. It can be understood that by using a wiping pen to wipe the crystals of the flux remaining on the tin layer of the board, a tin layer with a higher flatness can be obtained on the board surface. In one embodiment, the wiping pen is a fiber rod to better wipe the crystals of the flux remaining on the tin layer of the board to obtain a tin layer with a higher flatness.

[0068] In one embodiment, in the step of wiping the board that has undergone the reflow soldering operation with a wiping pen, the following specific steps are included: Wipe back and forth along the short direction of the pads in the tin layer with a fiber rod to remove the crystals of the soldering flux remaining in the tin layer, so as to obtain a tin layer with a relatively high flatness.

[0069] In order to more quickly erase the crystals of the soldering flux remaining on the tin layer of the board, in one embodiment, the board after the reflow soldering operation is cooled to cool the board to 50°C to 60°C. It can be understood that when the board drops to 50°C to 60°C, the operator immediately takes out the board from the reflow soldering furnace for wiping operation, so that the operator can more quickly and labor-savingly remove the crystals of the remaining soldering flux on the tin layer.

[0070] In one embodiment, the fiber rod is an electric fiber rod, so that the operator can quickly remove the crystals of the remaining soldering flux on the board.

[0071] In one embodiment, the vibration frequency of the electric fiber rod is 30 times per minute to 80 times per minute. Under the condition of ensuring the quick removal of the crystals of the remaining soldering flux on the board, it also effectively avoids loosening of the tin layer by the electric fiber rod, so as to ensure obtaining a circuit board that meets the product standards.

[0072] In one embodiment, the electric fiber rod includes an electric fiber rod body and a fiber rod, and the fiber rod is detachably connected to the electric fiber rod body, so that the operator can replace the damaged fiber rod.

[0073] In one embodiment, the electric fiber rod body is provided with an installation matching part, and the fiber rod is inserted into the installation matching part to realize the detachable connection between the electric fiber rod body and the fiber rod.

[0074] In one embodiment, the diameter of the fiber rod is 1 mm to 10 mm, so that the operator can quickly remove the crystals of the remaining soldering flux on the board.

[0075] In this embodiment, the diameter of the fiber rod is 5 mm. Since the diameter of the fiber rod used is 5 mm, the diameter of the fiber rod is relatively moderate. In this way, using a fiber rod with a diameter of 5 mm can effectively and quickly remove the crystals of the remaining soldering flux on the board, thereby improving the production efficiency of the circuit board and not scratching the solder mask in other areas of the board, so as to ensure obtaining a circuit board that meets the quality standards.

[0076] In one embodiment, the step of surface treating the board includes the following specific step: performing a gold treatment, a silver treatment, or a gold plating operation on the board surface. It is understood that by performing the gold treatment, the silver treatment, or the gold plating operation on the board surface, two different metal welding areas are formed on the board surface, thereby increasing the diversity of surface welding of the circuit board, thereby improving the market competitiveness of the circuit board and better meeting the needs of a diversified market.

[0077] In one embodiment, after the step of wiping the board that has undergone the reflow operation and before the step of performing text processing on the board after the wiping operation, the following step is also included: inspecting the board after the wiping operation.

[0078] It can be understood that by inspecting the boards after the wiping operation, unqualified boards are effectively prevented from flowing into the next process, thereby ensuring the factory quality of the circuit boards.

[0079] In one embodiment, the step of inspecting the plate after the wiping operation includes the following specific steps: using a magnifying glass to inspect the plate after the wiping operation to prevent unqualified plates from flowing into the next process.

[0080] A circuit board is obtained using the circuit board preparation method described in any of the above embodiments. It is understood that the circuit board prepared using the circuit board preparation method of the present application not only has two different metal welding areas on the surface of the circuit board, for example, the surface of the circuit board is formed with a gold-plated area + a tin-printed area, or the surface of the circuit board is formed with a gold-plated area + a tin-printed area, etc., but in particular, the tin-printed area has a high degree of fullness and fineness, and good welding performance, thereby increasing the diversity of metal welding areas on the surface of the circuit board, thereby improving the market competitiveness of the circuit board to better meet the needs of market diversification. In addition, the circuit board obtained by the circuit board preparation method of the present application not only has high production efficiency of the circuit board but also meets product standards in quality.

[0081] Compared with the prior art, the present invention has at least the following advantages:

[0082] The above-mentioned circuit board preparation method performs a screen printing solder paste operation on the surface-treated board to print the solder paste on the preset surface of the board, then performs a reflow soldering operation on the board after the screen printing solder paste to solidify the solder paste on the preset surface of the board, and then wipes the board after the reflow soldering operation to remove the crystals of the flux remaining in the tin layer, thereby completing the selective tin spraying treatment operation on the board surface, and finally performs text processing on the board after the wiping operation to leave corresponding marking numbers on the board so that the operator can better identify the installation. The above-mentioned screen printing solder paste operation, reflow soldering operation and wiping operation are simple and convenient to operate, thereby improving the production efficiency of the circuit board. In addition, since the above-mentioned circuit board preparation method does not use peelable glue or high-temperature resistant red glue, on the one hand, it can reduce the cost of circuit board production, and on the other hand, it reduces the phenomenon of high board scrap rate caused by incomplete removal of glue from small through holes of the board, thereby improving the product qualification rate of the circuit board.

[0083] The following are some specific examples, where "%" refers to percentages by weight. It should be noted that the following examples are not exhaustive and that the materials used in the following examples are all commercially available unless otherwise specified.

[0084] Example 1

[0085] Perform metallization operation on the surface of the plate;

[0086] A 120T screen printing screen is used to screen-print solder paste on the surface-treated panels. The solder paste consists of 25% flux and 75% solder powder. The viscosity of the solder paste is 60 Pa.s and the printing speed is 80 mm / s.

[0087] The board after screen printing of solder paste is placed in a reflow oven for staged temperature increase; the temperature of the first section of the reflow oven is 150°C, the temperature of the second section is 170°C, the temperature of the third section is 190°C, the temperature of the fourth section is 210°C, the temperature of the fifth section is 230°C, the temperature of the sixth section is 240°C, the temperature of the seventh section is 270°C, the temperature of the eighth section is 260°C, and then cooled to 55°C, and the reflow speed is controlled to 800 mm / min and the heating rate is 1.5 degrees / second.

[0088] Using a fiber rod to wipe the board after the reflow operation to remove the crystals of the soldering flux remaining in the tin layer;

[0089] After the wiping operation, the board is inspected and then text processing is performed.

[0090] Example 2

[0091] Perform silvering operation on the surface of the plate;

[0092] A 110T screen printing screen was used to screen-print solder paste on the surface-treated panels. The solder paste consisted of 28% flux and 72% solder powder. The viscosity of the solder paste was 90 Pa.s and the printing speed was 60 mm / s.

[0093] The board after screen printing of solder paste is placed in a reflow oven for staged temperature increase; the temperature of the first section of the reflow oven is 155°C, the temperature of the second section is 175°C, the temperature of the third section is 195°C, the temperature of the fourth section is 215°C, the temperature of the fifth section is 225°C, the temperature of the sixth section is 245°C, the temperature of the seventh section is 265°C, and the temperature of the eighth section is 255°C, and then cooled to 50°C, and the reflow speed is controlled to 900 mm / min and the heating rate is 1 degree / second.

[0094] Using a fiber rod to wipe the board after the reflow operation to remove the crystals of the soldering flux remaining in the tin layer;

[0095] After the wiping operation, the board is inspected and then text processing is performed.

[0096] Example 3

[0097] Perform gold plating on the surface of the board;

[0098] A 100T screen printing screen is used to screen-print solder paste on the surface-treated board. The solder paste contains 30% flux and 70% solder powder. The viscosity of the solder paste is 120 Pa.s and the printing speed is 100 mm / s.

[0099] The board after screen printing of solder paste is placed in a reflow oven for staged temperature increase; the temperature of the first section of the reflow oven is 160°C, the temperature of the second section is 180°C, the temperature of the third section is 200°C, the temperature of the fourth section is 220°C, the temperature of the fifth section is 210°C, the temperature of the sixth section is 250°C, the temperature of the seventh section is 260°C, the temperature of the eighth section is 250°C, and then cooled to 60°C, and the reflow speed is controlled to 1000 mm / min and the heating rate is 2 degrees / second.

[0100] Using a fiber rod to wipe the board after the reflow operation to remove the crystals of the soldering flux remaining in the tin layer;

[0101] After the wiping operation, the board is inspected and then text processing is performed.

[0102] Example 4

[0103] Perform metallization operation on the surface of the plate;

[0104] Use a silk screen printing stencil with 120T mesh count to perform the operation of screen printing solder paste on the surface-treated board. The solder paste includes 25% flux and 75% solder powder. The viscosity of the solder paste is 70 Pa.s, and the printing speed is 80 mm / s;

[0105] Put the board after screen printing the solder paste into a reflow oven for segmented temperature rise; the first section temperature of the reflow oven is 152 °C, the second section temperature is 172 °C, the third section temperature is 192 °C, the fourth section temperature is 212 °C, the fifth section temperature is 232 °C, the sixth section temperature is 242 °C, the seventh section temperature is 270 °C, the eighth section temperature is 261 °C, then cool to 55 °C, and control the reflow speed to be 800 mm / min, the vacuum condition to be 60 mbar, the vacuum time to be 2S, and the heating rate to be 1.5 degrees per second.

[0106] Use a fiber rod to wipe the board after the reflow soldering operation to remove the crystals of the flux remaining on the tin layer;

[0107] After inspecting the board after the wiping operation, perform text processing.

[0108] Test the circuit boards obtained by the circuit board preparation methods in Examples 1 to 4 respectively, and obtain the data in Table 1:

[0109] Table 1

[0110]

[0111] It can be seen from Table 1 that the thermal stress test, solderability test, thermal shock test, reflow soldering, ion contamination, and wet film solder resistance of the circuit boards obtained by the circuit board preparation methods in Examples 1 to 4 all meet the standard requirements. In particular, the solder layer of the circuit board obtained in Example 4 has a higher fullness and is more delicate.

[0112] In addition, the present application also analyzed the reflow of the solder paste in the reflow oven of Example 1. For details, please refer to Figure 2 , and it can be concluded that the rising temperature of the solder paste reflow in the reflow oven of Example 1 is relatively slow, that is, the heating rate is (1 degree - 2 degrees) per second, and the rising slope in the solder paste reflow curve is between 1.5 and 1.9. As a result, the entire peak shape of the solder paste reflow is relatively slow, and further, it can ensure that the board can obtain a solder layer with high fullness and delicacy after the reflow soldering operation, and all mechanical properties meet the standards.

[0113] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing a circuit board, characterized in that, Including: Performing surface treatment on the board; Performing solder paste screen printing on the surface-treated board using a screen printing stencil with a mesh count of 100T - 120T; wherein, corresponding windows are provided on the screen printing stencil, and the windows are adapted to the positions on the board where solder paste is preset to be printed; the offset of the windows of the screen printing stencil is greater than 1 mil - 2 mil of the size of the positions on the board where solder paste is preset to be printed; the solder paste includes 25% - 30% of flux and 70% - 75% of solder powder, and the viscosity of the solder paste is 60 pa.s - 120 pa.s; Performing reflow soldering operation on the board after solder paste screen printing; wherein, during the reflow soldering operation, the reflow soldering speed is 800 mm / min - 1000 mm / min, and the reflow soldering furnace is heated in stages. The temperature of the first stage is 150°C - 160°C, the temperature of the second stage is 170°C - 180°C, the temperature of the third stage is 190°C - 200°C, the temperature of the fourth stage is 210°C - 220°C, the temperature of the fifth stage is 220°C - 230°C, the temperature of the sixth stage is 240°C - 250°C, the temperature of the seventh stage is 260°C - 270°C, and the temperature of the eighth stage is 250°C - 260°C; Performing a wiping operation on the board after reflow soldering; Performing text processing on the board after the wiping operation.

2. The method for preparing a circuit board according to claim 1, wherein The screen printing stencil is provided with optical positioning points.

3. The method for preparing a circuit board according to claim 1, characterized in that In the step of performing a wiping operation on the board after reflow soldering, the following specific steps are included: Performing a wiping operation on the board after reflow soldering using a wiping pen.

4. The method for manufacturing a circuit board according to claim 3, characterized in that, The wiping pen is a fiber rod.

5. The method for preparing a circuit board according to claim 1, wherein, In the step of performing surface treatment on the board, the following specific steps are included: Performing electroless gold plating operation or electroless silver plating operation or gold plating operation on the surface of the board.

6. The method for preparing a circuit board according to claim 1, characterized in that, After the step of performing a wiping operation on the board after reflow soldering and before the step of performing text processing on the board after the wiping operation, the following steps are further included: Performing an inspection operation on the board after the wiping operation.

7. A circuit board, characterized in that, Obtained by using the method for preparing a circuit board according to any one of claims 1 - 6.

Images