A method for manufacturing PCB characters

Abstract

This invention discloses a method for manufacturing PCB characters, comprising the following steps: manufacturing a screen printing stencil and setting a light-transmitting window on the stencil, the window corresponding to the character area to be printed on the production board; screen printing photosensitive ink onto the production board with a solder resist layer already formed using the stencil, so that a layer of photosensitive ink is screen printed at the position corresponding to the window on the production board, and pre-curing the photosensitive ink through pre-baking; preparing an exposure film according to the character graphic to be printed, and exposing the photosensitive ink on the production board through the exposure film, so that the photosensitive ink at the corresponding character graphic is exposed and cured; removing the uncured photosensitive ink outside the character graphic by developing, to form the character; and finally, baking to completely cure the character. This invention solves the problem that screen printing cannot produce dense and small characters due to process limitations, and also solves the problem of character printers losing characters during printing and being unable to produce diverse character colors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board manufacturing, and particularly relates to a PCB character manufacturing method. BACKGROUND

[0002] The character process in the PCB manufacturing process is to print the characters needed by the customer on the PCB board surface through screen printing with a certain mesh or through inkjet printing by a character printer, so as to provide indication information for the customer's component installation and maintenance.

[0003] Among them, the minimum process capability of screen printing is the line width / line spacing / character height of the character: 0.1 / 0.1 / 0.8mm, and the conventional screen printing character is made by using thermosetting ink. The process is that a corresponding character pattern is first made on the screen, and then the character is directly printed by using the graphic screen hole, and then solidified. If the character is too small, it cannot be printed clearly due to the limitation of the photosensitive paste used to make the graphic screen hole, and the screen printing will cause fat oil and unclear characters.

[0004] The process capability of the character printer is the line width / line spacing / character height of the character: 0.075 / 0.075 / 0.5mm, but the printed character also has defects. The UV-curable ink is used, the ink particles are small, the tension is small, the diffusion ability is weak, and the combination of the formed character and the board surface is weak after light curing, which is easy to cause the character to fall off. In addition, due to the limitation of the color of the printed character ink, it is not possible to make characters of colors other than white. SUMMARY

[0005] The present application provides a PCB character manufacturing method to solve the problem that the screen printed character cannot be made due to the process capability, and also solves the problem that the printed character of the character printer falls off and cannot be made with various character colors.

[0006] In a first aspect, in order to solve the above technical problems, the present application provides a PCB character manufacturing method, comprising the following steps:

[0007] S1, a screen for screen printing is made, and a light-transmitting window is arranged on the screen, the window corresponding to the character area of the production board to be printed;

[0008] S2, the photosensitive ink is screen printed on the production board with the solder mask layer by using the screen, so as to screen print a layer of photosensitive ink at the position corresponding to the window on the production board;

[0009] S3, then the photosensitive ink is pre-baked to make the photosensitive ink pre-cured;

[0010] S4. Create an exposure film based on the character graphic to be printed, and expose the photosensitive ink on the production board through the exposure film so that the photosensitive ink at the corresponding character graphic is exposed and cured.

[0011] S5. Remove the unexposed and uncured photosensitive ink outside the character graphic by developing to form the character, and finally bake to completely cure the character.

[0012] Furthermore, the following steps are included between steps S1 and S2:

[0013] S11. Sandblast the production board that has been coated with solder resist.

[0014] Furthermore, in step S1, the single side of the window opening is 0.5mm-1mm larger than the character area.

[0015] Furthermore, in step S3, the pre-baking temperature is 75℃ and the time is 30 minutes.

[0016] Furthermore, in step S5, the baking temperature is 150℃ and the time is 30 minutes.

[0017] Secondly, for boards with characters printed on both sides, the present invention also provides another method for manufacturing PCB characters, including the following steps:

[0018] S10. Make a first screen and a second screen for screen printing, and set a light-transmitting first window and a second window on the first screen and the second screen respectively. The first window corresponds to the first character area of ​​the character to be printed on the first surface of the production board, and the second window corresponds to the second character area of ​​the character to be printed on the second surface of the production board.

[0019] S20. Photosensitive ink is screen-printed onto the production board with the solder resist layer made by the first screen printing plate, so as to screen-print a layer of photosensitive ink at the position corresponding to the first window on the first surface of the production board, and the photosensitive ink is pre-cured by pre-baking.

[0020] S30. Then, photosensitive ink is screen-printed onto the production board with the solder resist layer made by the second screen printing plate, so as to screen-print a layer of photosensitive ink at the position corresponding to the second window on the second surface of the production board, and the photosensitive ink is pre-cured by pre-baking.

[0021] S40. Create exposure films according to the characters to be printed on the two surfaces of the production board, and expose the photosensitive ink on the two surfaces of the production board with the two exposure films respectively, so that the photosensitive ink at the corresponding character graphics on the two surfaces of the production board is exposed and cured.

[0022] S50. The unexposed and uncured photosensitive ink outside the character graphic is removed by development to form the character, and finally the character is completely cured by baking.

[0023] Furthermore, the following steps are included between steps S10 and S20:

[0024] S12. Sandblast the production board that has been coated with solder resist.

[0025] Furthermore, in step S10, the first window is 0.5mm-1mm larger on one side than the first character area, and the second window is 0.5mm-1mm larger on one side than the second character area.

[0026] Furthermore, in steps S20 and S30, the pre-baking temperature is 75°C and the time is 30 minutes.

[0027] Furthermore, in step S50, the baking temperature is 150°C and the baking time is 30 minutes.

[0028] Furthermore, the thick copper plate is a multilayer board in which the inner core board and the outer copper foil are pressed together by a prepreg, and the multilayer board has successively undergone drilling, copper plating, full-board electroplating and outer circuit fabrication processes.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention uses photosensitive ink for screen printing to create characters, replacing the existing method of using thermosetting ink. By using photosensitive ink, the character graphics are created through pre-baking, exposure, and development, resulting in clearer and more compact fonts. More characters can be printed in a more concentrated area, and the adhesion is better. This solves the problem that screen printing cannot produce dense and small characters due to process limitations. It does not require strict precision on the screen printing stencil, eliminating the need for high-precision graphic mesh holes, thus reducing process difficulty. After screen printing, there is no need to specifically check the clarity of the characters; a partial ink printing method can be used to cover the character area. Specifically, this invention uses a relatively large window on the stencil that completely covers the entire character area. This partial ink printing method avoids the ink affecting the solder resist window and the inside of the holes, thus reducing the need for subsequent surface treatment quality and the removal of ink from the holes. Furthermore, compared to full-surface photosensitive ink printing, it greatly reduces the amount of photosensitive ink used, achieving precise ink alignment and effectively reducing production costs.

[0031] In addition, the characters produced by this method have higher precision than those of outer layer graphics and solder mask openings, and can be produced at high density. The character spacing can be as small as 0.05mm, and a large number of characters can be completed in a very small area. The character color can also meet any customer requirements. Generally speaking, as many colors of solder mask ink are available, as many colors of characters can be produced. Even some special graphics and markings can achieve the mixed production of multiple color characters, which solves the problem of character printers dropping characters and being unable to produce diverse character colors. Detailed Implementation

[0032] To better understand the technical content of this invention, the technical solution of this invention will be further introduced and explained below in conjunction with specific embodiments.

[0033] Example 1

[0034] The method for manufacturing a circuit board shown in this embodiment includes the following processing steps in sequence:

[0035] (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the copper layer thickness on both surfaces of the core board is 0.5oz.

[0036] (2) Inner layer circuit fabrication (negative film process): Inner layer pattern transfer, photosensitive film is coated using a vertical coating machine, and the film thickness is controlled at 8μm. The inner layer circuit is exposed using a fully automatic exposure machine with 5-6 exposure rulers (21 exposure rulers). After development, the inner layer circuit pattern is formed; Inner layer etching, the inner layer circuit is etched out on the core board after exposure and development. The inner layer line width is measured to be 3mil; Inner layer AOI, and then the inner layer circuit is inspected for defects such as open circuits, short circuits, line gaps, and line pinholes. Defective products are scrapped, and defect-free products are sent to the next process.

[0037] (3) Lamination: The browning speed is based on the thickness of the bottom copper. The core board, prepreg, and outer copper foil are stacked in sequence as required. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the laminated board to form a multilayer board.

[0038] (4) Drilling: Drilling is performed on the multilayer board according to the design requirements based on the existing drilling technology.

[0039] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole walls using chemical copper plating. The backlight test is level 10, and the copper plating thickness in the hole is 0.5μm.

[0040] (6) Full-board electroplating: Electroplating the entire board for 120 minutes at a current density of 18ASF to thicken the copper layer in the holes and on the board surface.

[0041] (7) Fabrication of outer layer circuitry (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuitry. The outer layer circuitry is exposed using an exposure ruler of 5 to 7 divisions (or 21 divisions). After development, the outer layer circuitry pattern is formed on the multilayer board. The outer layer pattern is electroplated, and then copper and tin are plated on the multilayer board respectively. The electroplating parameters are set according to the required copper thickness. Copper plating is performed at a current density of 1.8 ASD for 60 minutes, and tin plating is performed at a current density of 1.2 ASD for 10 minutes, with a tin thickness of 3 to 5 μm. Then, the film is removed, etched, and tin is removed in sequence to etch the outer layer circuitry on the multilayer board. The copper thickness of the outer layer circuitry is greater than or equal to 70 μm. The outer layer AOI is performed using an automatic optical inspection system. By comparing with the CAM data, the outer layer circuitry is inspected for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0042] (8) Solder resist: After screen printing solder resist ink on the surface of the multilayer board, it is then subjected to pre-curing, exposure, development and heat curing treatment in sequence to cure the solder resist ink into a solder resist layer; specifically, solder resist ink is applied to the TOP side, thereby coating a layer on the lines and substrate that do not need to be soldered to prevent bridging between lines during soldering, provide a permanent electrical environment and chemical corrosion resistance, and at the same time play a role in beautifying the appearance.

[0043] (9) Silkscreening characters: This includes the following steps:

[0044] a. Make a screen for screen printing and set a light-transmitting window on the screen. The window corresponds to the character area of ​​the characters to be printed in the production plate. That is, the area of ​​the window can cover the area of ​​all the printed characters. Generally, the window is made into a square window. That is, the window that can cover all the characters is determined by the horizontal length and width of all the characters, which facilitates production and simplifies the process.

[0045] In the above, the window is 0.5mm-1mm larger on one side than the character area. This allows the range of photosensitive ink for subsequent screen printing to be larger than the horizontal length and width of all characters. This avoids incompleteness caused by character misalignment due to manufacturing errors, ensuring that the edges of the characters produced later are clear and complete. In addition, it can reduce the precision requirements of the window on the screen, making production easier and improving production efficiency.

[0046] b. Sandblasting the production board removes grease residues that adhere to the surface after the solder resist ink has cured, and increases surface tension, thereby improving the adhesion between the solder resist surface and the character ink.

[0047] c. Screen printing photosensitive ink onto the production board using a screen printing plate, so as to screen print a layer of photosensitive ink at the corresponding windowed character area position on the production board.

[0048] d. Then, the photosensitive ink is pre-baked to pre-cur it and prevent it from flowing out randomly. The pre-baking temperature is 75℃ and the time is 30 minutes. By reasonably controlling the pre-baking temperature and time, it can be removed by development while maintaining a certain curing performance, ensuring that the ink outside the character graphics can be removed by development later.

[0049] e. Create an exposure film based on the characters and graphics to be printed on the production board, so that the corresponding positions of the characters and graphics in the exposure film are light-transmitting areas. Then, expose the photosensitive ink on the production board through the exposure film so that the photosensitive ink at the corresponding character and graphics is exposed and cured. During exposure, a 21-level exposure scale is used and the exposure is performed at levels 9-11.

[0050] f. Remove the unexposed and uncured photosensitive ink outside the character graphic by developing to form the character, and finally bake to completely cure the character; the baking temperature is 150℃ and the time is 30min.

[0051] (10) Surface treatment (immersion nickel and gold): The copper surface of the solder pads at the solder mask opening position is uniformly deposited with a nickel layer and a gold layer of a certain required thickness through chemical principle. The thickness of the nickel layer is 3-5μm; the thickness of the gold layer is 0.05-0.1μm.

[0052] (11) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0053] (12) Molding: Based on existing technology and design requirements, the circuit board is made with a shape tolerance of + / -0.05mm.

[0054] (13) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our company's inspection standards. If there are any defects, repair them in time to ensure excellent quality control for customers.

[0055] (14) FQA: Re-test the appearance of the circuit board, the thickness of the copper in the holes, the thickness of the dielectric layer, the thickness of the solder mask, the thickness of the inner copper layer, etc. to see if they meet the customer's requirements.

[0056] (15) Packaging: The circuit boards are sealed according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0057] Example 2

[0058] This embodiment shows a method for manufacturing a circuit board. Characters need to be made on both surfaces of the circuit board. The processing steps are basically the same as those in Embodiment 1, except for step (9), which is as follows:

[0059] (9) Silkscreening characters: This includes the following steps:

[0060] a. Make a first screen and a second screen for screen printing, and set a first window and a second window that are transparent to light on the first screen and the second screen respectively. The first window corresponds to the first character area of ​​the character to be printed on the first surface of the production board, and the second window corresponds to the second character area of ​​the character to be printed on the second surface of the production board. That is, the range of the window can cover the area of ​​all printed characters on the corresponding surface of the production board. Generally, the window is made into a square window, that is, the window that can cover all characters is determined by the horizontal length and width of all characters on each surface, which is convenient for production and simplifies the process.

[0061] In the above, the first window is 0.5mm-1mm larger on one side than the first character area, and the second window is 0.5mm-1mm larger on one side than the second character area. This allows the range of photosensitive ink for subsequent screen printing to be larger than the horizontal length and width of all characters on the corresponding surface, avoiding incompleteness caused by character misalignment beyond the ink range due to manufacturing errors. This ensures that the edges of the characters produced later are clear and complete. In addition, it can reduce the precision requirements of the window on the screen, making manufacturing easier and improving production efficiency.

[0062] b. Sandblasting the production board removes grease residues that adhere to the surface after the solder resist ink has cured, and increases surface tension, thereby improving the adhesion between the solder resist surface and the character ink.

[0063] c. Screen printing photosensitive ink onto the production board using the first screen printing plate, so as to screen print a layer of photosensitive ink at the position corresponding to the first window on the first surface of the production board, and pre-curing the photosensitive ink by pre-baking; the temperature of pre-baking is 75℃ and the time is 30min.

[0064] d. Then, photosensitive ink is screen-printed onto the production board using a second screen to screen-print a layer of photosensitive ink at the position corresponding to the second window on the second surface of the production board, and the photosensitive ink is pre-cured by pre-baking; the pre-baking temperature is 75℃ and the time is 30min.

[0065] e. Create an exposure film for each of the characters and graphics to be printed on the two surfaces of the production board, so that the corresponding positions of the characters and graphics in the exposure film are light-transmitting areas. Then, expose the photosensitive ink on the two surfaces of the production board using the two exposure films, so that the photosensitive ink at the corresponding positions of the characters and graphics on the two surfaces of the production board is exposed and cured.

[0066] f. Remove the unexposed and uncured photosensitive ink outside the character graphic by developing to form the character, and finally bake to completely cure the character; the baking temperature is 150℃ and the time is 30min.

[0067] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for making a PCB character, characterized in that, The method comprises the following steps: S1, making a screen printing plate, and setting a light-transmitting window on the screen printing plate, the window corresponding to a character area of characters to be printed in the production board, the window covering all the areas of the printed characters, and a single side of the window being 0.5-1 mm larger than the character area; S2, screen printing photosensitive ink on the production board with the solder resist layer through the screen printing plate to screen print a layer of photosensitive ink at a position corresponding to the window in the production board; S3, then pre-baking the photosensitive ink to make the photosensitive ink pre-cured; S4, making an exposure film according to the character pattern to be printed, and exposing the photosensitive ink on the production board through the exposure film to make the photosensitive ink corresponding to the character pattern exposed and cured; S5, removing the photosensitive ink not exposed and cured outside the character pattern through developing to form dense and small characters, and finally baking the characters to make them completely cured.

2. The method of claim 1, wherein, The steps S1 and S2 further comprise the following step: S11, sandblasting the production board with the solder resist layer.

3. The method of claim 1, wherein the PCB character is made of a material selected from the group consisting of copper, silver, gold, and aluminum. In the step S3, the pre-baking temperature is 75℃, and the time is 30 min.

4. The method of claim 1, wherein, In the step S5, the baking temperature is 150℃, and the time is 30 min.

5. A method of making a PCB character, characterized by, The method comprises the following steps: S10, making a first screen printing plate and a second screen printing plate, and setting a first light-transmitting window and a second light-transmitting window on the first screen printing plate and the second screen printing plate respectively, the first window corresponding to a first character area of characters to be printed in a first surface of the production board, the second window corresponding to a second character area of characters to be printed in a second surface of the production board, the window covering all the areas of the printed characters, a single side of the first window being 0.5-1 mm larger than the first character area, and a single side of the second window being 0.5-1 mm larger than the second character area; S20, screen printing photosensitive ink on the production board with the solder resist layer through the first screen printing plate to screen print a layer of photosensitive ink at a position corresponding to the first window in the first surface of the production board, and pre-baking the photosensitive ink to make it pre-cured; S30, then screen printing photosensitive ink on the production board with the solder resist layer through the second screen printing plate to screen print a layer of photosensitive ink at a position corresponding to the second window in the second surface of the production board, and pre-baking the photosensitive ink to make it pre-cured; S40, making an exposure film according to the character pattern to be printed in the two surfaces of the production board respectively, and exposing the photosensitive ink on the two surfaces of the production board through the two exposure films to make the photosensitive ink corresponding to the character pattern in the two surfaces of the production board exposed and cured; S50, removing the photosensitive ink not exposed and cured outside the character pattern through developing to form dense and small characters, and finally baking the characters to make them completely cured.

6. The method of claim 5, wherein the PCB characters are made by, The steps S10 and S20 further comprise the following step: S12, sandblasting the production board with the solder resist layer.

7. The method of claim 6, wherein the PCB characters are made by, In the steps S20 and S30, the pre-baking temperature is 75℃, and the time is 30 min.

8. The method of claim 6, wherein the PCB characters are made by, In the step S50, the baking temperature is 150℃, and the time is 30 min.