Printed circuit board (PCB) ink surface leveling processing method and light-emitting diode (LED) circuit board

Abstract

The invention discloses a PCB ink surface leveling processing method and an LED circuit board, and relates to the field of LED circuit board processing, and the method sequentially comprises the following steps: PCB processing, ink printing, ink pre-baking, film pasting, hot-pressing leveling, vacuum film pressing, film tearing, exposure and development, and the ink surface is subjected to leveling processing in a manner of pre-baking and then film pressing. And the ink layer on the copper surface and the ink layer on the PP surface are consistent in height. Therefore, the influence of the ink height on the SMT steel mesh is reduced, the melting stress of SMT solder paste is reduced, and the welding requirements of smaller LED components are met.

Description

Technical Field

[0001] The invention relates to the field of LED circuit board processing, and in particular to a PCB ink surface leveling processing method and an LED circuit board. Background Art

[0002] As the size of LED components is getting smaller and smaller, the thermal stress difference required by the corresponding pad SMT patch is getting higher and higher, which leads to higher and higher requirements for the ink flatness of the PCB. The ink layer of the printed circuit board made by traditional printing method, due to the difference in the thickness of the circuit copper layer, forms a natural height difference between the ink layer on the copper surface and the ink layer on the PP surface after printing. Affected by the height difference of the ink layer at different positions, when the SMT steel mesh is covered on the cured ink layer, the steel mesh will be tilted with one side high and the other side low, resulting in different thicknesses of solder paste at different positions when brushing solder paste. The melting time of tin of different thicknesses is inconsistent, which leads to uneven force at different positions of the circuit board, resulting in higher melting stress of the SMT solder paste in the local area of ​​the circuit board. Since the surface-mount electronic components themselves are relatively light in weight, they will be warped on one side under the action of stress.

[0003] Therefore, the object of the present invention is to provide a method for solving the problem that the SMT steel mesh is tilted when applying solder paste due to the uneven ink layer. Summary of the invention

[0004] To achieve the above object, the present invention adopts the following technical solution: a PCB ink surface leveling processing method, comprising the following steps in sequence: Processing PCB: pre-processing the circuit board according to the normal process, and making circuits on the surface of the circuit board; Ink printing: full-page printing of ink on both sides of the circuit board; Ink pre-baking: baking the circuit board to bake the ink to a semi-cured state; Film pasting: Paste the front and back sides of the circuit board with film, stretch the PE film on both sides of the circuit board, align the stretched PE film and cover it on the front and back sides of the circuit board, and stick the PE film on the front and back sides of the circuit board; Hot pressing and leveling: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is hot pressed, the PE film is heated to below its melting point, and the ink is squeezed and leveled with the PE film in a tensioned state; Vacuum lamination: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is vacuumed, and the ink and the PE film are squeezed and flattened; Film tearing: tear off the PE film on both sides of the circuit board at the same time; Exposure and development: While tearing off the PE film on the front and back of the circuit board, use UV light to expose the ink on the front and back of the circuit board.

[0005] Preferably, in the ink pre-baking step, the circuit board is baked at 75° C. for 40-50 minutes to bake the ink to a semi-cured state.

[0006] Preferably, in the hot pressing and flattening step, hot pressing is performed at 80°C for 2 minutes with a hot pressing pressure of 5 Kg / cm 2 .

[0007] Preferably, the vacuum lamination step is carried out in a negative pressure chamber, and the vacuum is evacuated to 500 mm Hg, and the vacuum is evacuated to a pressure less than or equal to one atmosphere.

[0008] Preferably, in the film pasting step, the front and back sides of the circuit board are film pasted throughout, the circuit board is located at the center of the PE film, the length of the circuit board is less than or equal to the length of the PE film, and the width of the circuit board is less than or equal to the width of the PE film.

[0009] Preferably, in the film pasting step, the PE film torn off in the film tearing step is cleaned, and the cleaned PE film is used to paste the front and back surfaces of the circuit board.

[0010] Preferably, in the hot pressing and leveling step, hot pressing the PE films on the front and back sides of the circuit board specifically includes: rolling, extruding and heating the PE films on the front and back sides of the circuit board by means of heated rollers.

[0011] Preferably, in the vacuum lamination step, the vacuuming operation of the PE films on the front and back sides of the circuit board specifically includes: rolling and squeezing the PE films on the front and back sides of the circuit board with a vacuum roller to squeeze out the air between the ink and the PE film.

[0012] Preferably, in the film tearing step, tearing off the PE films on the front and back sides of the circuit board at the same time specifically includes: moving the PE film on the front side of the circuit board through a vacuum roller along a first direction, and moving the PE film on the back side of the circuit board through another vacuum roller along a second direction, the first direction and the conveying direction of the circuit board form an obtuse angle, the second direction and the conveying direction of the circuit board form an obtuse angle, and the first direction and the second direction are mirror-imaged with respect to the conveying direction of the circuit board.

[0013] The present invention also provides an LED circuit board, which is processed by the above-mentioned PCB ink surface flattening processing method, and the pads on the LED circuit board are SMT mounted with LED components. The working principle of the present invention is: by pre-baking and then laminating, the ink layer is repeatedly flattened to flatten the ink surface, so that the ink layer on the copper surface and the ink layer on the PP surface are in the same height.

[0014] The beneficial effect of the present invention is that the ink surface is flattened by pre-baking and then laminating, so that the ink layer on the copper surface and the ink layer on the PP surface are of the same height, thereby reducing the influence of the ink height on the SMT steel mesh, thereby reducing the melting stress of the SMT solder paste, and meeting the welding requirements of smaller LED components. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings further illustrate the present invention, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention.

[0016] Figure 1 A flowchart is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0017] It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0018] An embodiment of the present invention provides a PCB ink surface flattening processing method and an LED circuit board, such as Figure 1 As shown, the following steps are included in sequence: Processing PCB: pre-processing the circuit board according to the normal process, and making circuits on the surface of the circuit board; Ink printing: full-page printing of ink on both sides of the circuit board; Ink pre-baking: bake the circuit board at 75℃ for 40-50min to bake the ink to a semi-cured state; Film pasting: Paste the front and back sides of the circuit board with film, stretch the PE film on both sides of the circuit board, align the stretched PE film and cover it on the front and back sides of the circuit board, and stick the PE film on the front and back sides of the circuit board; Hot pressing and leveling: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is hot pressed at 80℃ for 2 minutes and the hot pressing pressure is 5Kg / cm 2 , heat the PE film to below its melting point, and squeeze and flatten the ink and the PE film in a tensioned state; Vacuum lamination: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is vacuumed to 500 mm Hg, and the air pressure is less than or equal to one atmosphere, and the ink and the PE film are squeezed and flattened; Film tearing: tear off the PE film on both sides of the circuit board at the same time; Exposure and development: While tearing off the PE film on the front and back of the circuit board, use UV light to expose the ink on the front and back of the circuit board.

[0019] An embodiment of the present invention provides a PCB ink surface flattening processing method and an LED circuit board, such as Figure 1As shown, the following steps are included in sequence: Processing PCB: pre-processing the circuit board according to the normal process, and making circuits on the surface of the circuit board; Ink printing: full-page printing of ink on both sides of the circuit board; Ink pre-baking: bake the circuit board at 75℃ for 40-50min to bake the ink to a semi-cured state; Film pasting: clean the PE film torn off in the film-tearing step, and use the cleaned PE film to paste the entire front and back of the circuit board. Tighten the PE film on both sides of the circuit board, the circuit board is located at the center of the PE film, the length of the circuit board is less than or equal to the length of the PE film, and the width of the circuit board is less than or equal to the width of the PE film. Align the stretched PE films and cover them on the front and back of the circuit board, and paste the PE film on the front and back of the circuit board; Hot pressing and leveling: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is rolled and squeezed by a heated roller to heat it. The PE film is hot pressed for 2 minutes at 80°C and the hot pressing pressure is 5Kg / cm 2 , heat the PE film to below its melting point, heat the ink to a semi-solidified state, and squeeze and flatten the ink and the PE film in a tensioned state; Vacuum lamination: It is carried out in a negative pressure chamber, and the vacuum is pumped to 500 mm Hg, and the air pressure is less than or equal to one atmosphere. When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is rolled and squeezed by a vacuum roller to squeeze the air between the ink and the PE film, and the ink and the PE film are squeezed and flattened; Film tearing: The PE film on the front side of the circuit board is moved along the first direction by a vacuum roller, and the PE film on the back side of the circuit board is moved along the second direction by another vacuum roller, and the PE films on the front and back sides of the circuit board are torn off at the same time. The angle formed by the first direction and the conveying direction of the circuit board is an obtuse angle, and the angle formed by the second direction and the conveying direction of the circuit board is an obtuse angle. The first direction and the second direction are mirror images with respect to the conveying direction of the circuit board; Exposure and development: While tearing off the PE film on the front and back of the circuit board, use UV light to expose the ink on the front and back of the circuit board.

[0020] An embodiment of the present invention provides an LED circuit board, which is processed by the PCB ink surface leveling processing method as described in the above embodiment, and LED components are mounted on pads on the LED circuit board by SMT.

[0021] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which should be considered as the scope of this specification.

Claims

1. A PCB ink surface leveling method, characterized in that: The following steps are included in sequence: Processing PCB: pre-processing the circuit board according to the normal process, and making circuits on the surface of the circuit board; Ink printing: full-page printing of ink on both sides of the circuit board; Ink pre-baking: baking the circuit board to bake the ink to a semi-cured state; Film pasting: Paste the front and back sides of the circuit board with film, stretch the PE film on both sides of the circuit board, align the stretched PE film and cover it on the front and back sides of the circuit board, and stick the PE film on the front and back sides of the circuit board; Hot pressing and leveling: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is hot pressed, the PE film is heated to below its melting point, and the ink is squeezed and leveled with the PE film in a tensioned state; Vacuum lamination: When the PE film and the circuit board are kept in contact, the PE film on the front and back of the circuit board is vacuumed, and the ink and the PE film are squeezed and flattened; Film tearing: tear off the PE film on both sides of the circuit board at the same time; Exposure and development: While tearing off the PE film on the front and back of the circuit board, use UV light to expose the ink on the front and back of the circuit board.

2. The PCB ink surface leveling method according to claim 1, characterized in that: In the ink pre-baking step, the circuit board is baked at 75°C for 40-50 minutes to bake the ink to a semi-cured state.

3. The PCB ink surface leveling method according to claim 1, characterized in that: In the hot pressing and leveling step, hot pressing was performed at 80°C for 2 minutes with a hot pressing pressure of 5 Kg / cm 2 .

4. The PCB ink surface leveling method according to claim 1, characterized in that: The vacuum lamination step is carried out in a negative pressure chamber, and the vacuum is evacuated to 500 mm Hg, and the vacuum is evacuated to a pressure less than or equal to one atmosphere.

5. The PCB ink surface leveling method according to claim 1, characterized in that: In the film pasting step, the front and back sides of the circuit board are film pasted throughout, the circuit board is located at the center of the PE film, the length of the circuit board is less than or equal to the length of the PE film, and the width of the circuit board is less than or equal to the width of the PE film.

6. The PCB ink surface leveling method according to claim 1, characterized in that: In the film pasting step, the PE film torn off in the film peeling step is cleaned, and the cleaned PE film is used to paste the front and back sides of the circuit board.

7. The PCB ink surface leveling method according to claim 3, characterized in that: In the hot pressing and leveling step, hot pressing the PE films on the front and back sides of the circuit board specifically includes: rolling and extruding and heating the PE films on the front and back sides of the circuit board by means of a heated roller.

8. The PCB ink surface leveling method according to claim 4, characterized in that: In the vacuum lamination step, the vacuuming operation of the PE films on the front and back sides of the circuit board specifically includes: rolling and squeezing the PE films on the front and back sides of the circuit board by a vacuum roller to squeeze out the air between the ink and the PE film.

9. The PCB ink surface leveling method according to claim 1, characterized in that: In the film tearing step, tearing off the PE films on the front and back sides of the circuit board at the same time specifically includes: moving the PE film on the front side of the circuit board through a vacuum roller along a first direction, and moving the PE film on the back side of the circuit board through another vacuum roller along a second direction, the first direction and the conveying direction of the circuit board form an obtuse angle, the second direction and the conveying direction of the circuit board form an obtuse angle, and the first direction and the second direction are mirror-imaged with respect to the conveying direction of the circuit board.

10. An LED circuit board, characterized in that: The LED circuit board is processed by the PCB ink surface leveling processing method according to any one of claims 1 to 9, and LED components are mounted on the pads of the LED circuit board by SMT.

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