Carrier plate processing method for fine circuit

Abstract

The invention discloses a carrier plate processing method for a fine circuit. The method comprises the following steps: step 1, laser drilling; step 2, copper deposition; step 3, film pasting; step 4, exposing; step 5, developing; step 6, pattern hole filling; 7, stripping the film; and step 8, flash etching. According to the invention, by designing the process of firstly drilling the X-shaped through hole, ablating the line gap and then carrying out flash etching processing, the thickness of the bottom copper can be effectively reduced, and the problem of unqualified line width caused by too large copper thickness and too large lateral erosion in the flash etching process can be avoided; green-light picosecond laser drilling equipment is adopted during laser drilling, and compared with conventional infrared laser drilling, the precision and quality are higher; a circle of reinforcing rib frame is additionally electroplated during pattern hole filling, so that the ultrathin copper foil core can be better kept stable and flat in the subsequent process, and the problems of plate body deformation and the like are effectively prevented; the method is high in practicability and has high popularization significance.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing processes, and more particularly to a method for processing a carrier board for fine circuits. Background Technology

[0002] Due to the demand for miniaturization and high integration in electronic products, the need for fine-line circuitry on substrates is becoming increasingly urgent. For fine-line circuitry of 12-14µm, conventional MSAP processes are difficult to achieve. This is because the material uses an ultra-thin 3µm copper foil core, which, after a horizontal copper plating process, can reach 4µm. Finally, the flash etching step requires etching 4µm of the base copper along with approximately 3-4µm of side etching on one side, resulting in the original 12µm linewidth being unacceptable, leaving only 4-6µm.

[0003] Currently, some processes have proposed new solutions to reduce the thickness of the base copper and minimize linewidth defects caused by side etching. For example, patent number CN201710762186—a method for fabricating ultra-fine lines—proposes that during the lamination process, PP is laminated to a substrate, and after drilling, a 0.5-1 μm copper sputtering process is used to form a 0.5-1 μm plating layer on the PP surface. Then, a 1-2 μm copper plating layer is deposited on the board surface, resulting in a base copper thickness of only 3 μm. The lines are then implemented using the MSAP process. While this process effectively reduces the base copper thickness and the risk of side etching, for 12-14 μm lines, a 3 μm base copper thickness still has a significant impact on side etching.

[0004] In addition, sputtering copper has a low deposition rate and high cost, relying on expensive sputtering targets, which poses challenges to production efficiency and cost control. On the other hand, equipment parameters (such as sputtering voltage and gas composition) need to be precisely controlled, and the discharge process is easily disturbed, affecting the uniformity and repeatability of the film. Summary of the Invention

[0005] Therefore, it is necessary to provide a carrier board processing method for fine circuits to address the shortcomings of existing technologies.

[0006] A method for fabricating a carrier board for fine circuits includes the following steps:

[0007] Step 1: Laser drilling. Using laser drilling equipment, X-shaped through holes are drilled on the 3 μm ultrathin copper foil core and the line gaps are ablated.

[0008] Step 2: Plating copper, depositing 1µm of copper into the lines, gaps, and holes of the ultra-thin copper foil core;

[0009] Step 3: Apply film, and apply dry film to both sides of the ultra-thin copper foil core;

[0010] Step 4: Exposure. Using exposure equipment, the double-sided circuitry of the ultra-thin copper foil core is exposed.

[0011] Step 5: Development. The exposed ultra-thin copper foil core double-sided circuit is developed using a developing solution.

[0012] Step 6: Pattern filling. Pattern filling is performed on the X-shaped through holes on the ultra-thin copper foil core. The copper thickness is increased simultaneously during the filling process.

[0013] Step 7: Remove the remaining dry film from the ultrathin copper foil core;

[0014] Step 8: Flash etching, flash etching the 1µm bottom copper on both sides of the ultrathin copper foil core to form the final circuit;

[0015] Step 9: Roller coating ink. Roller coat solder resist ink on both sides of the ultra-thin copper foil core.

[0016] Furthermore, in step 1, the laser drilling equipment used is a green picosecond laser drilling equipment.

[0017] Furthermore, in step 6, while filling the holes with the pattern, a copper reinforcing rib frame is electroplated around the edge of the ultra-thin copper foil core.

[0018] Furthermore, in step 9, when applying the ink by roller coating, the gaps on the ultra-thin copper foil core are first filled with solder resist ink by screen printing or roller coating, and then the entire board is coated with solder resist ink by roller coating.

[0019] In summary, the beneficial effects of the fine circuit substrate processing method of this invention are as follows: by designing a process of first drilling X-shaped through holes and ablating the circuit gaps, followed by flash etching, the thickness of the base copper can be effectively reduced, thereby avoiding the problem of unqualified line width caused by excessive copper thickness and excessive side etching during the flash etching process; the use of green picosecond laser drilling equipment during laser drilling provides higher precision and quality compared to conventional infrared laser drilling; the additional electroplating of a reinforcing rib frame during pattern filling allows the ultra-thin copper foil core to maintain better stability and flatness in subsequent processes, effectively preventing problems such as board deformation; the design of a two-stage coating method for solder resist ink makes the solder resist ink roll coating effect smoother; this invention is highly practical and has strong promotional value. Attached Figure Description

[0020] Figure 1 This is a cross-sectional structural diagram of steps 1 to 3 in this invention;

[0021] Figure 2 This is a cross-sectional structural diagram of steps 4 to 6 in this invention;

[0022] Figure 3 This is a cross-sectional structural diagram of steps 7 to 9 in this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0024] like Figures 1 to 3 As shown, the present invention provides a method for fabricating a carrier board for fine circuits, comprising the following steps:

[0025] Step 1: Laser drilling. Using a green picosecond laser drilling device, X-shaped through holes are drilled on a 3 μm ultrathin copper foil core, and the gaps between the lines are ablated. Traditional CO2 infrared light mainly burns the copper foil with thermal effects. The absorption rate of the copper foil by laser is low, and it is easy to produce residual adhesive, sputtered copper and suspended copper. Green picosecond direct laser is a cold laser processing, which mainly uses light ablation. The laser utilization rate is high, and the green laser can reduce problems such as residual adhesive, suspended copper and copper peeling.

[0026] Step 2: Plating copper, depositing 1µm of copper into the lines, gaps, and holes of the ultra-thin copper foil core;

[0027] Step 3: Apply film, and apply dry film to both sides of the ultra-thin copper foil core;

[0028] Step 4: Exposure. Using exposure equipment, the double-sided circuitry of the ultra-thin copper foil core is exposed.

[0029] Step 5: Development. The exposed ultra-thin copper foil core double-sided circuit is developed using a developing solution.

[0030] Step 6: Pattern filling. The X-shaped through holes on the ultra-thin copper foil core are pattern filled. The copper thickness is increased simultaneously during the filling process. At the same time, a copper reinforcing frame is electroplated around the edge of the ultra-thin copper foil core. The additional electroplated copper reinforcing frame can provide a certain degree of support and stability to the overall board surface of the ultra-thin copper foil core, making it less prone to bending and deformation. After the final processing of the carrier board is completed, the reinforcing frame can be removed by milling in the scrap area.

[0031] Step 7: Remove the remaining dry film from the ultrathin copper foil core;

[0032] Step 8: Flash etching, flash etching the 1µm bottom copper on both sides of the ultrathin copper foil core to form the final circuit;

[0033] Step 9: Roller coating ink. Roller coating solder resist ink onto both sides of the ultra-thin copper foil core. When roller coating ink, first fill the gaps on the ultra-thin copper foil core with solder resist ink by screen printing or roller coating, and then roll the solder resist ink onto the entire board by roller coating.

[0034] The method of first filling the gaps with ink and then applying ink to the entire plate in two stages results in a smoother finish compared to the conventional one-time coating.

[0035] In summary, the beneficial effects of the fine circuit substrate processing method of this invention are as follows: by designing a process of first drilling X-shaped through holes and ablating the circuit gaps, followed by flash etching, the thickness of the base copper can be effectively reduced, thereby avoiding the problem of unqualified line width caused by excessive copper thickness and excessive side etching during the flash etching process; the use of green picosecond laser drilling equipment during laser drilling provides higher precision and quality compared to conventional infrared laser drilling; the additional electroplating of a reinforcing rib frame during pattern filling allows the ultra-thin copper foil core to maintain better stability and flatness in subsequent processes, effectively preventing problems such as board deformation; the design of a two-stage coating method for solder resist ink makes the solder resist ink roll coating effect smoother; this invention is highly practical and has strong promotional value.

[0036] The embodiments described above illustrate only one implementation of the invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the invention. Therefore, the scope of protection of the invention patent should be determined by the appended claims.

Claims

1. A method for fabricating a carrier board for fine circuits, characterized in that, Includes the following steps: Step 1: Laser drilling. Using laser drilling equipment, X-shaped through holes are drilled on the 3 μm ultrathin copper foil core and the line gaps are ablated. Step 2: Plating copper, depositing 1µm of copper into the lines, gaps, and holes of the ultra-thin copper foil core; Step 3: Apply film, and apply dry film to both sides of the ultra-thin copper foil core; Step 4: Exposure. Using exposure equipment, the double-sided circuitry of the ultra-thin copper foil core is exposed. Step 5: Development. The exposed ultra-thin copper foil core double-sided circuit is developed using a developing solution. Step 6: Pattern filling. Pattern filling is performed on the X-shaped through holes on the ultra-thin copper foil core. The copper thickness is increased simultaneously during the filling process. Step 7: Remove the remaining dry film from the ultrathin copper foil core; Step 8: Flash etching, flash etching the 1µm bottom copper on both sides of the ultrathin copper foil core to form the final circuit; Step 9: Roller coating ink. Roller coat solder resist ink on both sides of the ultra-thin copper foil core.

2. The method for fabricating a fine circuit board as described in claim 1, characterized in that: In step 1, the laser drilling equipment used is a green picosecond laser drilling equipment.

3. The method for fabricating a fine circuit board as described in claim 1, characterized in that: In step 6, while filling the holes in the pattern, a copper reinforcing rib frame is electroplated around the edge of the ultra-thin copper foil core.

4. The method for fabricating a fine circuit board as described in claim 1, characterized in that: In step 9, when applying the ink, the gaps on the ultra-thin copper foil core are first filled with solder resist ink by screen printing or roller coating, and then the entire board is coated with solder resist ink by roller coating.

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