Circuit board double-sided screen printing method and circuit board thereof

Abstract

The invention provides a circuit board double-sided silk-screen method and a circuit board thereof. The circuit board double-sided silk-screen method comprises the following steps: carrying out first positioning on a circuit substrate after a resistance welding process; performing primary screen printing on the circuit substrate; carrying out primary low-temperature baking and primary pre-curing on the circuit substrate subjected to primary screen printing; turning over the circuit substrate which is pre-cured for the first time and positioning again; carrying out secondary silk-screen printing on the back surface of the circuit substrate, and carrying out secondary low-temperature baking and secondary curing on the circuit substrate after the secondary silk-screen printing; and carrying out baking and thermocuring on the circuit substrate subjected to secondary curing to obtain the circuit board. The circuit substrate is obtained through low-temperature baking, and the low-temperature curing silk-screen printing ink is pre-cured, so that the low-temperature curing silk-screen printing ink is prevented from being touched and deformed, and the quality of a printing ink curing layer formed by the circuit board is relatively high; the baking and curing temperature of the low-temperature curing silk-screen printing ink is relatively low, so that the pre-curing speed of the low-temperature curing silk-screen printing ink is relatively high, and the production efficiency of double-sided printing of the circuit board is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of circuit board manufacturing, and in particular to a double-sided silk screen printing method for a circuit board and a circuit board thereof. Background Art

[0002] During the production process of PCB circuit boards, various characters need to be silk-screened on the circuit boards that have been solder-resistant. The circuit boards are printed with ink on their surface by a silk-screen printer, and then the ink is cured and adhered to the surface of the circuit boards by baking.

[0003] When the existing screen printer screens the circuit board, it can only screen print on one side of the circuit board. After the screen printing, it needs to be completely cured before the other side of the PCB can be screen printed. The complete curing time is long, which reduces its work efficiency. When performing double-sided screen printing, it is necessary to reinstall and adjust the contact between the circuit board and the screen printing ink equipment, so that the screen printing force of the circuit board is different, making the ink thickness on both sides of the circuit board uneven. After the double-sided screen printing, the surface ink of the circuit board is baked, and it is not cured, which is easy to be touched during the production process, resulting in the destruction of the ink layer.

[0004] For example, a PCB character screen printing production system and method disclosed in the comparative document CN201910514562.0 provides a PCB to be screen-printed to a first screen printer through a first plate placing machine; then the PCB to be screen-printed is screen-printed through the first screen printer; the screen-printed PCB is baked through a first baking machine so that the characters on the PCB are more stable. When the first screen printer needs maintenance, the second plate placing machine is started, and the surface-treated PCB is continued to be provided to the first baking machine through the second plate placing machine. In this way, the first baking machine is always in working state, avoiding the first baking machine from being in an idle state due to the maintenance of the first screen printer, thereby maximizing the use of energy by the PCB character screen printing production system and greatly reducing the energy consumption in the PCB character screen printing production process. At the same time, this embodiment uses the second plate placing machine to enable the PCB character screen printing production system to always be in a continuous production state, thereby increasing the processing capacity of the PCB character screen printing production system, which is conducive to increasing the output of the PCB character screen printing production system.

[0005] For example, the comparative document CN200910192814.9 discloses a method for printing text on both sides of a printed circuit board. The printed circuit board with text printed on one side is turned over to the other side and placed in another screen printing machine. The screen is positioned and aligned with the printed circuit board by positioning pins, and ink is poured onto the screen for printing. The text on the other side is printed, and the printed circuit board is taken out, placed in an oven after standing, and a printed circuit board with text on both sides is obtained. This solution saves the time required for the first side of the printed circuit board to stand, bake, and cool to room temperature. However, after printing the first side, the text on the first side is easily touched when turning over to the other side, thereby destroying the printing quality. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a double-sided silk screen printing method for a circuit board with low-temperature preliminary curing, fast double-sided silk screen printing speed and uniform silk screen ink thickness, and a circuit board thereof.

[0007] The purpose of this disclosure is achieved through the following technical solutions:

[0008] A double-sided silk screen printing method for a circuit board comprises the following steps:

[0009] Positioning the circuit substrate after the solder resist process for the first time;

[0010] Performing screen printing on the circuit substrate once by using a low temperature curing screen printing ink device;

[0011] The circuit substrate is moved to an oven, and the circuit substrate after the screen printing is subjected to a low-temperature baking, wherein the temperature of the low-temperature baking is 65° C.-75° C., so that the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time;

[0012] The circuit substrate is moved to a low-temperature curing screen printing ink device, and the circuit substrate pre-cured for the first time is turned over 180 degrees and positioned again;

[0013] Performing secondary screen printing on the back side of the circuit substrate by low temperature curing screen printing ink equipment to obtain a circuit substrate;

[0014] Performing secondary low-temperature baking on the circuit substrate after secondary screen printing, wherein the temperature of the secondary low-temperature baking is 65° C.-75° C., so as to secondary solidify the low-temperature ink on the surface of the circuit substrate;

[0015] The circuit substrate that has been cured for the second time is baked and thermally cured to obtain a circuit board.

[0016] In one embodiment, the step of first positioning the circuit substrate after the solder resist process includes:

[0017] A flip clamping mechanism for clamping the circuit substrate after the solder resist process above the silk screen nail bed;

[0018] The supporting nail columns of the supporting platform of the silk-screen nail bed are controlled to move relative to the circuit substrate so as to support and abut against the bottom of the circuit substrate.

[0019] In one embodiment, the circuit substrate is moved to a low-temperature curing screen printing ink device, and the steps of flipping the circuit substrate pre-cured for the first time by 180 degrees and re-positioning the substrate include:

[0020] The circuit substrate moves along the slide rail to the low-temperature curing screen printing ink device;

[0021] The flip clamping mechanism flips the circuit substrate 180 degrees;

[0022] The supporting nail columns of the supporting platform of the silk-screen nail bed are controlled to move relative to the circuit substrate so as to support and abut against the bottom of the circuit substrate again.

[0023] In one embodiment, the circuit substrate is moved to a low-temperature curing screen printing ink device, and the circuit substrate after screen printing is low-temperature baked once to pre-cure the low-temperature curing ink on the surface of the circuit substrate for the first time, and before the circuit substrate pre-cured for the first time is turned over 180 degrees and positioned again, the following steps are also included:

[0024] The surface of the circuit substrate that has been pre-cured for the first time is cleaned of ink residues.

[0025] In one embodiment, after the circuit substrate after the secondary screen printing is subjected to secondary low-temperature baking to secondary solidify the low-temperature ink on the surface of the circuit substrate, the secondary solidified circuit substrate is baked and thermally cured to obtain the circuit board, the following steps are also included:

[0026] The surface of the circuit substrate that has been post-cured is cleaned of ink residues.

[0027] In one embodiment, the low-temperature baking time is 15s-30s.

[0028] In one embodiment, the secondary low-temperature baking time is 15s-30s.

[0029] In one embodiment, the temperature of the baking and thermal curing is 70° C.-80° C., and the time of the baking and thermal curing is 40 min-50 min.

[0030] In one embodiment, after the secondary cured circuit substrate is baked and thermally cured, the following steps are further included:

[0031] The circuit substrate is developed and exposed.

[0032] A circuit board is prepared by the circuit board double-sided silk screen printing method described in any of the above embodiments.

[0033] Compared with the prior art, the present invention has at least the following advantages:

[0034] The above-mentioned double-sided silk-screen printing method for circuit boards and the circuit boards thereof are characterized in that the circuit substrate is silk-screened once by a low-temperature curing silk-screen printing ink device and then low-temperature baked. The circuit substrate is flipped over and then silk-screened for a second time and then low-temperature baked for a second time. The low-temperature curing silk-screen printing ink is pre-cured to avoid the low-temperature curing silk-screen printing ink from being touched and deformed, so that the ink curing layer formed on the circuit board has a higher quality; the low-temperature curing silk-screen printing ink has a lower baking and curing temperature, so that the low-temperature curing silk-screen printing ink has a faster pre-curing speed, thereby improving the production efficiency of double-sided printing of the circuit board; the low-temperature curing silk-screen printing ink has a lower pre-curing and curing cross-linking, which makes it convenient to remove stains of the low-temperature curing silk-screen printing ink, thereby improving the quality of double-sided silk-screen printing of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is an operation flow chart of a double-sided screen printing method for a circuit board according to an embodiment;

[0037] Figure 2 It is a structural schematic diagram of a low temperature curing screen printing ink device according to an embodiment;

[0038] Figure 3 for Figure 2 Another structural schematic diagram of the low-temperature curing screen printing ink equipment is shown. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0040] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0042] In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments:

[0043] The present invention relates to a double-sided silk-screen printing method for a circuit board. In one embodiment, the double-sided silk-screen printing method for a circuit board comprises the following steps:

[0044] The circuit substrate after the solder resist process is positioned for the first time; the circuit substrate is moved to an oven, and the circuit substrate is screen-printed once by a low-temperature curing screen printing ink device; the circuit substrate after the first screen printing is low-temperature baked, and the temperature of the low-temperature baking is 65°C-75°C, so that the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time; the circuit substrate is moved to the low-temperature curing screen printing ink device, and the circuit substrate pre-cured for the first time is turned 180 degrees and positioned again; the back of the circuit substrate is screen-printed for the second time by a low-temperature curing screen printing ink device to obtain a circuit substrate; the circuit substrate after the second screen printing is low-temperature baked for the second time, and the temperature of the second low-temperature baking is 65°C-75°C, so that the low-temperature ink on the surface of the circuit substrate is secondarily cured; the circuit substrate that is secondarily cured is baked and thermally cured to obtain a circuit board.

[0045] like Figure 1 As shown, it is a double-sided silk screen printing method for a circuit board according to an embodiment of the present invention, comprising the following steps:

[0046] S101 performs the first positioning of the circuit substrate after the solder resist process. In this embodiment, the circuit substrate is first horizontally mounted on the screen printing nail bed 100 of the low temperature curing screen printing ink equipment 10, so that the circuit substrate is fixed above the screen printing nail bed 100.

[0047] S103 performs screen printing on the circuit substrate once by using the low temperature curing screen printing ink device 10. In this embodiment, during the screen printing process, the screen frame is placed on the circuit substrate and clamped and fixed, and after adding the low temperature curing screen printing ink, the screen frame on the circuit substrate is uniformly moved by the scraper at a set ink scraping speed, so that the low temperature curing screen printing ink is printed on the circuit substrate, thereby obtaining a circuit substrate with a uniform screen printing ink layer.

[0048] S105 The circuit substrate is moved to the oven 20, and the circuit substrate after the screen printing is subjected to a low-temperature baking. The temperature of the low-temperature baking is 65°C-75°C, so that the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time. In this embodiment, the low-temperature curing ink can be a low-temperature heat-curing epoxy resin glue. The low-temperature curing ink has the characteristics of low curing temperature and fast curing speed. By performing a low-temperature baking on the circuit substrate, the low-temperature curing silk-screen ink on the surface of the circuit substrate is initially cured to prevent the low-temperature curing silk-screen ink from flowing and destroying the silk-screen pattern. The low-temperature baking makes the temperature of the oven 20 lower, and the thermal curing deformation of the low-temperature curing ink is less, so that the low-temperature curing ink is pre-cured more evenly.

[0049] S107 The circuit substrate is moved to the low-temperature curing screen printing ink device 10, and the circuit substrate pre-cured for the first time is turned over 180 degrees and re-positioned. In this embodiment, the circuit substrate is first turned over 180 degrees and then clamped horizontally on the screen printing nail bed 100, so that the position of the circuit substrate on the screen printing nail bed 100 is fixed, so that the circuit substrate is installed on the screen printing nail bed 100 at the same position for two screen printings, saving the tedious operation of adjusting the circuit substrate, thereby improving the production speed.

[0050] S109: Perform secondary screen printing on the back of the circuit substrate by low temperature curing screen printing ink equipment 10 to obtain a circuit substrate. The circuit substrate is installed in the same position on the screen printing nail bed 100, and the same screen printing conditions are controlled so that the ink coating thickness of the first screen printing and the second screen printing of the circuit substrate is the same.

[0051] S111 performs a secondary low-temperature baking on the circuit substrate after the secondary screen printing, and the temperature of the secondary low-temperature baking is 65°C-75°C, so as to secondary cure the low-temperature ink on the surface of the circuit substrate. In this embodiment, by baking the low-temperature curing screen printing ink of the circuit substrate, the low-temperature curing screen printing ink on the second surface of the circuit substrate is quickly cured, and the thermal curing deformation of the low-temperature curing ink is less, so that the low-temperature curing ink on the second surface of the circuit substrate is pre-cured more evenly.

[0052] S113 bakes and thermally cures the secondary cured circuit substrate to obtain a circuit board. In this embodiment, the pre-curing speed of the double-sided silk screen printing method of the circuit board is fast, which speeds up the silk screen printing speed, reduces energy consumption and production costs, and bakes and thermally cures the pre-cured low-temperature curing ink to further cure, thereby improving the connection strength between the low-temperature curing ink layer and the circuit board.

[0053] The above-mentioned double-sided silk-screen printing method for circuit boards and the circuit boards thereof are characterized in that the circuit substrate is silk-screened once by a low-temperature curing silk-screen printing ink device and then low-temperature baked. The circuit substrate is flipped over and then silk-screened for a second time and then low-temperature baked for a second time. The low-temperature curing silk-screen printing ink is pre-cured to avoid the low-temperature curing silk-screen printing ink from being touched and deformed, so that the ink curing layer formed on the circuit board has a higher quality; the low-temperature curing silk-screen printing ink has a lower baking and curing temperature, so that the low-temperature curing silk-screen printing ink has a faster pre-curing speed, thereby improving the production efficiency of double-sided printing of the circuit board; the low-temperature curing silk-screen printing ink has a lower pre-curing and curing cross-linking, which makes it convenient to remove stains of the low-temperature curing silk-screen printing ink, thereby improving the quality of double-sided silk-screen printing of the circuit board.

[0054] like Figure 2 and Figure 3 As shown, in one embodiment, the low-temperature curing screen printing ink equipment 10 includes a screen printing nail bed 100, a flip clamping mechanism 200, a conveying mechanism 300 and a screen printing mechanism 400, the screen printing mechanism 400 is provided with a screen printing nail bed 100, the screen printing nail bed 100 is provided with a liftable support platform 110 and a control component 120, the control component 110 is used to control the lifting and lowering of the support platform 110, a plurality of spaced support nail columns 111 are provided on the surface of the support platform 110, a flip clamping mechanism 200 is provided above the support nail columns 111, the flip clamping mechanism 200 includes a movable splint 210 and a flip component 220, the movable splint 210 is connected to the flip component 220, the flip component 220 is slidably arranged on the conveying mechanism 300, and the conveying mechanism 300 is connected to the conveying end of the oven 10. In this embodiment, the movable clamp 210 can clamp both sides of the circuit substrate, and the circuit substrate clamped by the movable clamp 210 is moved above the support platform 110 through the flip component 220 and the conveying mechanism 300. The control component 110 controls the support nail column 111 of the support platform 110 to rise and fall to contact the circuit substrate. When the silk screen printing is completed, the conveying mechanism 300 moves the circuit substrate clamped by the flip clamping mechanism 200 to the oven 20 for baking for the first pre-curing. The conveying mechanism 300 moves the circuit substrate pre-cured for the first time to the support platform 110, and the flip component 220 of the flip clamping mechanism 200 flips the circuit substrate pre-cured for the first time and then performs the next silk screen printing, so that the silk screen printing position of the circuit substrate is the same, the ink layer cured on the surface of the circuit substrate is uniform, and there is no need to adjust the circuit substrate, thereby speeding up the production efficiency.

[0055] In one embodiment, the step of first positioning the circuit substrate after the solder resist process includes:

[0056] A flip clamping mechanism 200 clamps the circuit substrate after the solder resist process on the top of the silk screen nail bed 100;

[0057] The support nail column 111 of the support platform 110 of the screen printing nail bed 100 is controlled to move relative to the circuit substrate so as to support and abut against the bottom of the circuit substrate. In this embodiment, the circuit substrate can be moved to a fixed position above the screen printing nail bed 100 by flipping the cylinder clamp of the clamping mechanism 200, so that the installation position of the circuit substrate is fixed, and the support nail column 111 of the lifting platform is abutted against the bottom of the circuit substrate by controlling the lifting platform to rise. When the support nail column 111 contacts the bottom of the circuit substrate, the support nail column 111 is used to support the circuit substrate.

[0058] In one embodiment, the circuit substrate is moved to the low temperature curing screen printing ink device 10, and the steps of flipping the circuit substrate pre-cured for the first time by 180 degrees and re-positioning the substrate include:

[0059] The circuit substrate moves along the conveying mechanism 300 to the low temperature curing screen printing ink device 10;

[0060] The flipping clamping mechanism 200 flips the circuit substrate 180 degrees;

[0061] The support nail column 111 of the support platform 110 of the screen printing nail bed 100 is controlled to move relative to the circuit substrate to support and abut against the bottom of the circuit substrate again. In this embodiment, the support nail column 111 of the support platform 110 is away from the bottom of the circuit substrate, so that there is enough space between the circuit substrate and the support nail column 111 to ensure that the flip clamping mechanism 200 can flip the circuit substrate; the low-temperature curing screen printing ink on the surface of the circuit substrate has been solidified, and the low-temperature curing screen printing ink will not flow during the flipping of the circuit substrate. After the circuit substrate is flipped, the support nail column 111 supports the circuit substrate again, so that the force on the circuit substrate is the same as the force on the circuit substrate for the first positioning, and the circuit substrate remains horizontal, so that the low-temperature curing screen printing ink of the second screen printing of the circuit substrate is evenly distributed.

[0062] Furthermore, in one of the embodiments, the support pin 111 of the lifting platform is provided with a pressure sensor, and the contact pressure between the circuit substrate and the support pin 111 is 100Pa-1000Pa. In this embodiment, the lifting platform is provided with a pressure sensor, and when the support pin 111 contacts the circuit substrate or the bottom of the circuit substrate, the pressure sensor of the lifting platform displays the pressure change to feedback whether the support pin 111 and the circuit substrate are in contact. When the pressure between the support pin 111 and the circuit substrate is greater than 1000Pa, the support pin 111 abuts against the circuit substrate so that the circuit substrate bends and deforms upwards, and when the pressure between the support pin 111 and the circuit substrate is less than 100Pa, the support pin 111 is not in contact with the circuit substrate, and the support pin 111 cannot effectively support the circuit substrate for silk-screen printing. In order to ensure the flatness of the screen printing ink of the circuit substrate by the squeegee of the screen printing mechanism 400, when the support nail column of the support platform of the screen printing nail bed is controlled to move relative to the circuit substrate to support and abut against the bottom of the circuit substrate, when the pressure between the support nail column 111 and the circuit substrate is greater than 1000Pa, the following steps are also included:

[0063] Increase the downward stroke of the squeegee, reduce the speed of the squeegee simultaneously, and increase the downward stroke of the support nail column of the support platform by 1mm-2mm.

[0064] In this embodiment, the amount of the downward stroke of the squeegee is increased by 1mm-2mm, so that the position of the squeegee is lowered, so that the pressure of the squeegee on the circuit substrate is increased, thereby reducing the upward deformation of the circuit substrate, and the support pin is lowered, so that the upward bending of the circuit substrate is reduced, so that the quality of the ink layer after the circuit substrate is better. The squeegee speed of the squeegee is between 60mm / s and 200mm / s, and the speed of the squeegee is reduced so that the speed increment of the squeegee speed is reduced by 30mm / s to 200mm / s, so that the filling of the squeegee when the circuit substrate is screen-printed is more uniform, so that the ink layer after the circuit substrate is screen-printed is more uniform.

[0065] When the pressure between the supporting nail column 111 and the circuit substrate is less than 100 Pa, the following steps are also included:

[0066] The support platform increases the upward travel of the support nail column. In this embodiment, the increase in the upward travel of the support nail column is 1mm-2mm, so that the support nail column rises, and by controlling the rise of the support platform, multiple support nail columns of the support platform evenly support the bottom of the circuit substrate, so that the circuit substrate can be smoothly screen-printed, and the ink layer formed after the circuit substrate is screen-printed is uniform.

[0067] In one embodiment, the contact pressure between the circuit substrate after the solder resist process and the support pin 111 is the same as the contact pressure between the circuit substrate after the repositioning and the support pin 111. In this embodiment, the control component 110 controls the contact pressure between the support pin 111 and the circuit substrate after the first positioning and the support pin 111 and the repositioned circuit substrate to be the same, so that the force of the first screen printing and the second screen printing of the circuit substrate is the same, and the uniformity of the ink pattern formed by the screen printing under the same screen printing conditions is the same, so that the screen printing ink solidified layer finally formed on both sides of the circuit substrate is more uniform.

[0068] In one embodiment, the circuit substrate is moved to the low-temperature curing screen printing ink device 10, and the circuit substrate after the screen printing is low-temperature baked once to pre-cure the low-temperature curing ink on the surface of the circuit substrate for the first time, and the circuit substrate pre-cured for the first time is turned over 180 degrees and positioned again, and the following steps are also included:

[0069] Clean the ink residue on the surface of the circuit substrate that is pre-cured for the first time. In this embodiment, during the screen printing process of the circuit substrate, the low-temperature curing screen printing ink is easy to stain the edge of the circuit substrate. Since the initially cured low-temperature curing screen printing ink is not completely cured, its internal cross-linking polymerization degree is low, so that the ink residue on the surface of the circuit substrate can be wiped off by a cleaning agent, so that the ink residue on the surface of the circuit substrate is reduced. Specifically, the cotton cloth is soaked with ink opening water or ink cleaning agent, and then scrubbed with the cotton cloth.

[0070] Furthermore, in one of the embodiments, the PP glue in the production line is easy to adhere to the surface of the circuit substrate. Therefore, in order to reduce the adhesion of the PP glue, before the circuit substrate is screen printed once with a low-temperature curing screen printing ink, the circuit substrate after the solder mask process is first positioned, and the following steps are also included:

[0071] The circuit substrate is surface treated before the first screen printing. In this embodiment, the circuit substrate is surface treated by a dust sticking machine, which uses a dust sticking rubber roller to absorb the residual PP glue on the surface of the circuit substrate to keep the surface of the circuit substrate clean.

[0072] When PP glue still remains on the circuit substrate, the circuit substrate is subjected to a low-temperature baking after a screen printing, and the following steps are also included:

[0073] Increase the preset baking temperature of low-temperature baking by 2℃-3℃, and extend the preset baking time of low-temperature baking by 3s-5s;

[0074] After the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time, the melted PP glue is removed.

[0075] In this embodiment, the preset baking temperature of a low-temperature baking is 65°C-75°C, and the preset baking time of a low-temperature baking is 15s-30s. By increasing the temperature and time of the low-temperature baking, the residual PP glue is further melted, thereby removing the residual PP glue on the surface of the circuit substrate, so that the surface of the obtained circuit substrate remains clean.

[0076] Furthermore, static electricity is generated during the movement of the circuit substrate, and dust in the air will continue to adsorb on the surface of the circuit substrate. Therefore, after the surface of the circuit substrate is cleaned, the circuit substrate is also subjected to a static electricity removal operation. In this embodiment, static electricity is easily generated when the circuit substrate is rubbed during movement, and the surface of the circuit substrate with static electricity is easy to adsorb dust in the air. First, the ion blower is aimed at the circuit substrate to blow, so that the ion airflow is evenly blown on the surface of the circuit board to eliminate the static electricity of the circuit substrate or ground the circuit substrate, and then the circuit substrate is screen printed.

[0077] In one embodiment, after the circuit substrate after the secondary screen printing is subjected to secondary low-temperature baking to secondary solidify the low-temperature ink on the surface of the circuit substrate, the secondary solidified circuit substrate is baked and thermally cured to obtain the circuit board, the following steps are also included:

[0078] Clean the ink residue on the secondary cured surface of the circuit substrate. In this embodiment, similarly, during the screen printing process of the circuit substrate, the low-temperature curing screen printing ink is easy to stain the edge of the circuit substrate. Since the initially cured low-temperature curing screen printing ink is not completely cured, its internal cross-linking polymerization degree is low, so that the ink residue on the surface of the circuit substrate can be wiped off by a cleaning agent, so that the ink residue on the surface of the circuit substrate is reduced.

[0079] Furthermore, in one of the embodiments, similarly, the PP glue in the production line is easy to adhere to the surface of the circuit substrate. Therefore, in order to reduce the adhesion of the PP glue, the back of the circuit substrate is screen-printed twice by low-temperature curing screen printing ink to obtain the circuit substrate, and the circuit substrate that has been pre-cured for the first time is turned over 180 degrees and re-positioned, and the following steps are also included:

[0080] The circuit substrate is surface treated before the secondary screen printing. In this embodiment, the circuit substrate is surface treated by a dust sticking machine, which uses a dust sticking rubber roller to absorb the residual PP glue on the surface of the circuit substrate to keep the surface of the circuit substrate clean.

[0081] Similarly, when PP glue still remains on the circuit substrate, the circuit substrate after the secondary screen printing is subjected to secondary low-temperature baking, and the following steps are also included:

[0082] Increase the preset baking temperature of the second low-temperature baking by 1°C-2°C, and extend the preset baking time of the second low-temperature baking by 1s-2s;

[0083] After the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time, the melted PP glue is removed.

[0084] In this embodiment, after the PP glue is removed from the circuit substrate after the first screen printing, after the circuit substrate is turned over, less PP glue remains on the circuit substrate. Therefore, the preset baking temperature of the secondary low-temperature baking is increased to a lower value, and the preset baking time of the secondary low-temperature baking is extended to a shorter value, so that less melted PP glue on the surface of the circuit substrate can also be removed. The preset baking temperature of the secondary low-temperature baking is 65°C-75°C, and the preset baking time of the secondary low-temperature baking is 15s-30s. By increasing the temperature and time of the secondary low-temperature baking, the residual PP glue is further melted, thereby removing the residual PP glue on the surface of the circuit substrate, so that the surface of the obtained circuit substrate remains clean.

[0085] In one embodiment, the low-temperature baking time is 15s-30s. In this embodiment, when the low-temperature baking time is less than 15s, the low-temperature curing silk screen ink is not completely cured, and it is easy to flow during the movement of the circuit substrate, thereby causing defects in the silk screen pattern. When the low-temperature baking time is greater than 30s, the baking time is too long, which easily makes the low-temperature curing silk screen ink completely cured, and the low-temperature curing silk screen ink is difficult to remove. When the low-temperature curing silk screen ink remains on the circuit substrate, it is inconvenient to clean the circuit substrate. When the low-temperature baking time is 15s-30s, the low-temperature curing silk screen ink is initially cured, and the adhesion between the low-temperature curing silk screen ink and the circuit substrate is poor, which can be easily wiped off with a cleaning agent.

[0086] In one embodiment, the time of the second low-temperature baking is 15s-30s. In this embodiment, the time of the second low-temperature baking is the same as the time of the first low-temperature baking, so that the low-temperature curing silk screen ink of the circuit substrate is pre-cured, the low-temperature curing silk screen ink of the circuit substrate is prevented from flowing, and the low-temperature curing silk screen ink of the circuit substrate is easy to remove.

[0087] Furthermore, in one embodiment, when the first low-temperature rapid baking and the second low-temperature baking are 15s-30s, the baking time of the circuit substrate may be too long due to the different amounts of low-temperature curing silk screen ink applied to circuit boards of different specifications, making it difficult to remove the low-temperature curing silk screen ink on the surface of the circuit substrate. Therefore, before the circuit substrate is clamped on the silk screen nail bed 100 and the silk screen nail bed 100 adjusts the support nail column 111 to contact the bottom of the circuit substrate, the following steps are also included:

[0088] Screen printing low temperature curing screen printing ink on the test board;

[0089] The test board is baked at a low temperature for a preset baking time so that a screen printing ink solidification layer is formed on the surface of the test board;

[0090] The test plate is scrubbed by soaking a cotton cloth soaked in a cleaning agent for 10 to 20 times;

[0091] If the cured layer of the silk-screen ink can be completely wiped off, the ink can be easily removed and the preset baking time remains unchanged;

[0092] If the cured layer of the silk-screen ink cannot be completely erased, the preset baking time is reduced by 1s-2s and the above steps are repeated.

[0093] In this embodiment, the preset baking time is 15s-30s, and the preset baking time of 15s ensures that the low-temperature curing screen printing ink does not flow. Since the low-temperature curing screen printing ink dries quickly and is initially cured due to low-temperature baking, the degree of curing affects the adhesion between the formed screen printing ink solidified layer and the plate. When the adhesion is large, it is difficult to remove the screen printing ink solidified layer from the plate, making it difficult and time-consuming to clean the ink residue. Therefore, by reducing the baking time to obtain an optimal preset baking time, the ink can be easily removed, thereby speeding up production efficiency.

[0094] In one of the embodiments, the temperature of the baking heat curing is 70℃-80℃, and the time of the baking heat curing is 40min-50min. In this embodiment, when the baking curing temperature is less than 70℃, the low-temperature curing screen printing ink is not completely cured, and the ink is unevenly distributed on the surface of the printed matter, resulting in color difference, spots or blurring. When the baking curing temperature is greater than 80℃, the curing speed of the circuit substrate is too fast, which easily makes the curing speed of each part of the circuit substrate different, thereby increasing the stress in the curing layer on the surface of the circuit substrate, resulting in slight deformation of the curing layer and unevenness. When the baking curing temperature is 70℃-80℃, the warm curing screen printing ink is cured evenly, so that the ink curing layer of the circuit board is uniform and flat.

[0095] Furthermore, in order to ensure that the circuit substrate is completely cured and the internal stress of the glue curing board is reduced, the circuit substrate that has been cured for the second time is baked and thermally cured to obtain the circuit board, and the following steps are also included:

[0096] Cooling the circuit board;

[0097] The circuit board is subjected to secondary baking and curing.

[0098] In this embodiment, after the baking and thermal curing, the moisture and solvent in the low-temperature curing silk screen ink evaporate quickly, and after the circuit board is cooled, the thermal stress of the circuit board is reduced. The circuit board is baked and cured for the second time, so that the curing reaction of the low-temperature curing silk screen ink of the circuit board is more complete.

[0099] In one embodiment, the circuit substrate that has been cured for the second time is baked and thermally cured to obtain a circuit board, further comprising the following steps:

[0100] The circuit substrate is developed and exposed. In this embodiment, after the circuit substrate is baked and cured, the solder resist layer of the circuit substrate is not exposed, and is exposed after being shielded by a film, so that the shielded portion of the solder resist layer is not completely cured. Then a developer is added to react, and the developer reacts to the unexposed portion, so that the solder resist layer on the surface of the circuit board has a window to expose the pad.

[0101] Furthermore, after developing and exposing the circuit substrate, the method further comprises the following steps:

[0102] The circuit board is baked after segmentation.

[0103] In this embodiment, complete curing has a high requirement for baking temperature. The solder mask layer and the circuit substrate in the solder mask stage are not completely cured. By baking in sections, the cured layer of the circuit substrate is not easily deformed, thereby keeping the surface of the circuit board flat after baking in sections.

[0104] The present application also provides a circuit board, which is prepared by the circuit board double-sided silk screen printing method. In this embodiment, the circuit board double-sided silk screen printing method has a uniform ink layer after silk screen printing and curing on the circuit board, and the ink layer pattern is clear.

[0105] Compared with the prior art, the present invention has at least the following advantages:

[0106] The above-mentioned double-sided silk-screen printing method for circuit boards and the circuit boards thereof are characterized in that the circuit substrate is silk-screened once by a low-temperature curing silk-screen printing ink device and then low-temperature baked. The circuit substrate is flipped over and then silk-screened for a second time and then low-temperature baked for a second time. The low-temperature curing silk-screen printing ink is pre-cured to avoid the low-temperature curing silk-screen printing ink from being touched and deformed, so that the ink curing layer formed on the circuit board has a higher quality; the low-temperature curing silk-screen printing ink has a lower baking and curing temperature, so that the low-temperature curing silk-screen printing ink has a faster pre-curing speed, thereby improving the production efficiency of double-sided printing of the circuit board; the low-temperature curing silk-screen printing ink has a lower pre-curing and curing cross-linking, which makes it convenient to remove stains of the low-temperature curing silk-screen printing ink, thereby improving the quality of double-sided silk-screen printing of the circuit board.

[0107] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the disclosed patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent shall be subject to the attached claims.

Claims

1. A double-sided screen printing method for a circuit board, characterized in that: The following steps are involved: Positioning the circuit substrate after the solder resist process for the first time; Performing screen printing on the circuit substrate once by using a low temperature curing screen printing ink device; The circuit substrate is moved to an oven, and the circuit substrate after the screen printing is subjected to a low-temperature baking, wherein the temperature of the low-temperature baking is 65° C.-75° C., so that the low-temperature curing ink on the surface of the circuit substrate is pre-cured for the first time; The circuit substrate is moved to a low-temperature curing screen printing ink device, and the circuit substrate pre-cured for the first time is turned over 180 degrees and positioned again; Performing secondary screen printing on the back side of the circuit substrate by low temperature curing screen printing ink equipment to obtain a circuit substrate; Performing secondary low-temperature baking on the circuit substrate after secondary screen printing, wherein the temperature of the secondary low-temperature baking is 65° C.-75° C., so as to secondary solidify the low-temperature ink on the surface of the circuit substrate; The circuit substrate that has been cured for the second time is baked and thermally cured to obtain a circuit board.

2. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: The step of first positioning the circuit substrate after the solder resist process comprises: A flip clamping mechanism for clamping the circuit substrate after the solder resist process above the silk screen nail bed; The supporting nail columns of the supporting platform of the silk-screen nail bed are controlled to move relative to the circuit substrate so as to support and abut against the bottom of the circuit substrate.

3. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: The circuit substrate is moved to a low-temperature curing screen printing ink device, and the steps of flipping the circuit substrate pre-cured for the first time by 180 degrees and re-positioning the substrate include: The circuit substrate moves along the slide rail to the low-temperature curing screen printing ink device; The flip clamping mechanism flips the circuit substrate 180 degrees; The supporting nail columns of the supporting platform of the silk-screen nail bed are controlled to move relative to the circuit substrate so as to support and abut against the bottom of the circuit substrate again.

4. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: The circuit substrate is moved to the low-temperature curing screen printing ink device, and the circuit substrate after the screen printing is low-temperature baked once to pre-cure the low-temperature curing ink on the surface of the circuit substrate for the first time, and the circuit substrate pre-cured for the first time is turned over 180 degrees and positioned again, and the following steps are also included: The surface of the circuit substrate that has been pre-cured for the first time is cleaned of ink residues.

5. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: After the circuit substrate after the secondary screen printing is subjected to secondary low-temperature baking to secondary solidify the low-temperature ink on the surface of the circuit substrate, the secondary solidified circuit substrate is baked and thermally cured to obtain the circuit board, and the following steps are also included: The surface of the circuit substrate that has been post-cured is cleaned of ink residues.

6. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: The low-temperature baking time is 15s-30s.

7. The double-sided screen printing method for a circuit board according to claim 6, characterized in that: The time of the secondary low-temperature baking is 15s-30s.

8. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: The temperature of the baking and thermal curing is 70° C.-80° C., and the time of the baking and thermal curing is 40 min-50 min.

9. The double-sided screen printing method for a circuit board according to claim 1, characterized in that: After the secondary cured circuit substrate is baked and thermally cured, the following steps are also included: The circuit substrate is developed and exposed.

10. A circuit board, characterized in that: The circuit board is prepared by the circuit board double-sided silk screen printing method according to any one of claims 1 to 9.

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