Manufacturing method of ultrathin high-density carrier plate

Abstract

The invention discloses a method for manufacturing an ultrathin high-density carrier plate. The method comprises the following steps of: cutting a copper-clad plate according to the size of a jointed plate; carrying out LDD brownification treatment on the copper-clad plate; performing laser drilling on the copper-clad plate; after the brownification film is removed, plasma degumming treatment and copper deposition treatment are sequentially carried out on the copper-clad plate; forming an inner-layer circuit pattern on the copper-clad plate, then carrying out hole-filling electroplating treatment, and removing a plate surface copper layer at a non-circuit pattern position through etching after film stripping; laminating copper foils with the thickness of 9 microns on the two surfaces of the copper-clad plate through PP (Polypropylene), and then laminating to form a production plate; lDD browning processing is carried out on the production board; laser drilling is conducted on the production board; after the brownification film is removed, plasma degumming treatment and copper deposition treatment are sequentially carried out on the production board; an outer layer circuit pattern is formed on a production board, then hole filling electroplating processing is carried out, a board surface copper layer at a non-circuit pattern position is removed through etching after film stripping, and the ultra-thin high-density carrier board is manufactured. By the adoption of the method, the problem that BT-like plates cannot be machined through a conventional manufacturing process is solved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, specifically to a method for manufacturing an ultra-thin, high-density substrate. Background Technology

[0002] "Substrate-like PCB," or SLP for short, is a type of PCB based on existing HDI technology. Similar to an IC substrate, but not quite at the same level. While it offers higher precision than traditional HDI, it is still primarily used to support various active components, not as a semiconductor packaging IC substrate.

[0003] With the widespread adoption of 5G networks, the deepening research into 6G technology, and the rapid development of emerging technologies such as artificial intelligence and autonomous driving, the market demand for high-performance communication and electronic equipment continues to rise. Against this backdrop, substrate-like circuit boards (PCBs), with their superior performance in high-frequency communication equipment, can meet the requirements of 5G and future communication technologies for high-speed signal transmission and highly integrated circuit boards, thus experiencing significant growth in demand in the communications field. Simultaneously, to cope with the ever-increasing data processing demands, the scale of data center construction continues to expand, and the application of PCBs in key components such as server motherboards has further driven market demand.

[0004] The challenges in fabricating substrate-like structures: 1. Fine circuit fabrication: Substrate-like boards typically require line width / spacing to be less than or equal to 30μm. This requires high-precision photolithography and etching techniques to ensure the accuracy and consistency of the circuits and avoid problems such as short circuits and open circuits.

[0005] 2. Micro-hole fabrication: Substrates require the fabrication of micro-holes to achieve electrical connections between multiple layers. Currently, mainstream laser drilling technology needs to control the accuracy within ±25μm and ensure that the hole shape is regular, the upper and lower hole diameter ratios are consistent, and there are no issues such as side etching, glass fiber protrusion, and residual adhesive at the bottom of the hole.

[0006] 3. Processing of ultra-thin core boards: The core boards of carrier-like boards are usually thin. When the board thickness is ≤0.2mm, deformation problems are prone to occur. Breakthroughs are needed in board structure, board expansion and contraction control, lamination parameter optimization and interlayer positioning system to achieve effective control of warpage and lamination thickness of ultra-thin core boards.

[0007] 4. Material Selection and Matching: The substrate requires materials with low dielectric constant and low loss factor, such as ABF and BT resin, to meet the requirements of high-frequency and high-speed signal transmission. Simultaneously, it is necessary to ensure that the material's coefficient of thermal expansion is similar to that of the silicon chip; otherwise, warping problems may easily occur during high-temperature soldering.

[0008] 5. Reliability Assurance: Substrate-like boards are used in high-end electronic equipment and must meet the electrical and connection reliability requirements under long-term high temperature, high humidity and vibration conditions, which places extremely high demands on manufacturing processes and quality control.

[0009] The conventional manufacturing process for high-density interconnect printed circuit boards (PCBs) is as follows: material preparation → inner layer patterning → inner layer etching → inner layer AOI → browning → lamination → laser drilling → debrowning → mechanical drilling → copper plating → full board electroplating → hole patterning → hole filling electroplating → selective resin plugging (if applicable) → ceramic grinding → outer layer patterning → pattern electroplating → outer layer etching → outer layer AOI → screen printing solder mask / characters → surface treatment → molding → electrical testing → FOC → FQA → packaging. However, using this conventional technology to manufacture carrier-like PCBs is too difficult and cannot be implemented. Specifically: 1. The above manufacturing process is mainly for laser-drilled boards with an inner copper layer thickness of 0.5oz and an outer copper layer thickness of 0.33oz. However, the carrier-like board manufacturing process uses a special copper-clad laminate with a copper thickness of 9μm. This special copper-clad laminate is a BT-like board, which is an unconventional board. Its processing method is completely different from the existing processing methods for 1 / 3oz and H / Hoz copper thicknesses. The existing processing method cannot cover the processing flow of this special board. The browning and debrowning processes in the conventional process will result in a thinner bottom copper layer, affecting product reliability. The process processing method needs to be adjusted. 2. With a line width and spacing of 0.02 / 0.02mm and extremely fine circuit patterns, conventional electroplating and etching methods would result in excessively thick copper on the surface, leading to severe side etching and flying lines, making it impossible to produce the required line width and spacing.

[0010] 3. The laser hole diameter is 0.05mm. The existing conventional laser hole diameter is 75um-125um. The existing laser hole processing parameters and electroplating efficiency cannot meet the production requirements of 0.05mm laser holes.

[0011] 4. The ultra-thin core board and the thickness of each layer need to be processed by a thin-plate production line, and conventional control methods cannot meet the production requirements. Summary of the Invention

[0012] In view of the above-mentioned technical defects, the present invention provides a method for manufacturing an ultra-thin, high-density substrate-like board, which solves the problem that conventional manufacturing processes cannot process BT-like boards.

[0013] To address the aforementioned technical problems, this invention provides a method for manufacturing an ultrathin, high-density carrier-like substrate, comprising the following steps: S1. Cut copper-clad laminates with BT material as the substrate according to the panel size. The overall thickness of the copper-clad laminate is ≤0.051mm, and the copper thickness on both surfaces is 9μm. S2. Perform LDD browning treatment on the copper clad laminate to form a browning film on the surface of the copper clad laminate; S3. Perform laser drilling on the copper-clad laminate to drill through holes with a diameter of 0.05mm; the thickness-to-diameter ratio during laser drilling should be controlled below 0.7; S4. After removing the brown coating, the copper-clad laminate is first subjected to plasma desmearing, and then copper plating is performed to metallize the vias; during the removal of the brown coating, the underlying copper must not be etched. S5. After the film is applied to the copper-clad laminate, the inner layer circuit pattern is formed by exposure and development, so that the inner layer circuit and vias are exposed. S6. Perform hole-filling electroplating on the copper-clad laminate, and after removing the film, remove the copper layer on the board surface from the non-circuit pattern area by etching. S7. After laminating 9μm thick copper foil on both surfaces of the copper-clad laminate using PP, the laminate is formed into a production board. S8. Perform LDD browning treatment on the production board to form a browning film on the surface of the production board; S9. Perform laser drilling on the production board to drill blind holes with a diameter of 0.05mm; the thickness-to-diameter ratio during laser drilling should be controlled below 0.7; S10. After removing the brown coating, the production board is first subjected to plasma desmearing, and then copper plating is performed to metallize the blind vias; during the removal of the brown coating, the underlying copper must not be etched. S11. After the film is applied to the production board, the outer layer circuit pattern is formed by exposure and development, so that the outer layer circuit and blind vias are exposed. S12. The production board is subjected to hole-filling electroplating treatment, and after the film is removed, the copper layer on the board surface in the non-circuit pattern area is removed by etching. S13. Finally, the production board is subjected to solder mask layer fabrication, surface treatment and molding in sequence to obtain an ultra-thin high-density carrier board.

[0014] Furthermore, in step S2, when the overall thickness of the copper-clad laminate is 0.051 mm, the laser drilling adopts a double-sided drilling method to drill through holes, so that the thickness-to-diameter ratio during laser drilling is controlled below 0.7.

[0015] Furthermore, in step S7, the PP is of type 1017 and the thickness of the PP is ≤25μm, so that the thickness-to-diameter ratio is controlled below 0.7 when drilling blind holes with laser later.

[0016] Furthermore, in step S2, after the LDD browning treatment, the copper thickness on both surfaces of the copper-clad laminate is controlled at 7±1um; in step S8, after the LDD browning treatment, the copper thickness on both surfaces of the production board is controlled at 7±1um.

[0017] Furthermore, in step S6, after the via-filling electroplating, the copper thickness on both surfaces of the copper-clad laminate is controlled at 12±2um; in step S12, after the via-filling electroplating, the copper thickness on both surfaces of the production board is controlled at 12±2um, and the via-filling depression is controlled at ≤5um.

[0018] Furthermore, in steps S4 and S10, the time control after copper plating is ≤4 hours, that is, the board should be processed in the next step within 4 hours after copper plating.

[0019] Furthermore, in steps S4 and S10, a de-browning agent without micro-etching ability is used when removing the brown film.

[0020] Furthermore, in steps S5 and S11, the board is pre-treated before applying the film. Micro-etching is not allowed in the pre-treatment. Only the board surface is cleaned with water. The entire piece of film is pressed together when applying the film.

[0021] Furthermore, in steps S6 and S12, the linewidth of the circuit is increased by 5μm on top of the etching compensation during etching. Furthermore, in step S8, when the required number of circuit layers on the production board is six or more, steps S7 to S12 are repeated in a layer-stacking manner between steps S12 and S13 until the required number of circuit layers is reached.

[0022] Compared with the prior art, the present invention has the following beneficial effects: In this invention, a special copper-clad laminate with a copper thickness of 9 μm is first used to replace the existing ordinary copper-clad core board with a copper thickness of 0.5 oz. The thickness of the outer copper foil is also replaced from the existing 0.33 oz to a special copper foil with a thickness of 9 μm. Because the thickness of the base copper is only 9 μm, ultra-fine circuits can be fabricated without reducing the copper content, ensuring that the line width and line spacing after etching are within 20 ± 5 μm. Furthermore, the method of this invention strictly controls the processes of browning, debrowning, copper immersion, and hole-filling electroplating to avoid the problem of the base copper being too thin or too thick. Secondly, taking advantage of the small thickness of the base copper, laser drilling can be performed directly. By strictly controlling the overall thickness of the inner copper-clad laminate and the thickness-to-diameter ratio of the laser-drilled holes after the outer lamination, through holes and blind holes with a diameter of 0.05 mm can be fabricated.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Detailed Implementation

[0024] To better understand the technical content of the present invention, the present invention will be further introduced and described below in conjunction with specific embodiments. It should be noted that if there are descriptions such as "first" and "second" in the text, they are used to distinguish different components, plates, etc., and do not represent the order of priority, nor do they limit "first" and "second" to different types.

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Example This embodiment provides a method for manufacturing an ultrathin, high-density carrier-like substrate, which includes the following processing steps in sequence: (1) Cutting: Cut copper-clad laminate, copper foil and PP according to the panel size of 520mm×620mm. The overall thickness of the copper-clad laminate is 0.051mm. The inner substrate of the copper-clad laminate is BT material (i.e. BT resin board). The copper layer thickness on both surfaces of the copper-clad laminate is 9μm. The thickness of the copper foil is 9μm. The PP is of type 1017 and the thickness of the PP is ≤25μm.

[0027] (2) Browning: The copper-clad laminate is subjected to LDD browning treatment to form a browning film on the surface of the copper-clad laminate; the outer copper surface is treated by LDD browning process to increase the roughness of the copper surface and improve the absorption capacity of the copper foil to laser. The thickness of the bottom copper after LDD browning is controlled at 7±1um to meet the requirements of subsequent laser drilling production.

[0028] (3) Laser drilling: According to the drilling data, laser drilling is performed on the copper-clad board to drill through holes with a diameter of 0.05mm. Here, since the thickness of the copper-clad board is 0.051mm, in order to control the thickness-to-diameter ratio during laser drilling to be below 0.7, double-sided drilling is used to drill through holes. That is, drilling is performed on the same drilling position on both sides of the copper-clad board, and the thickness-to-diameter ratio during each laser drilling is controlled to be below 0.7.

[0029] In the above, the smallest aperture of 0.9 is used for laser drilling.

[0030] Adhesive removal: After removing the brown coating, the copper-clad laminate is subjected to plasma adhesive removal treatment to remove drilling contaminants generated during drilling.

[0031] In the above, a decal removal solution without micro-etching ability is used when removing the brown film. That is, the decal removal solution does not etch the underlying copper during the decal removal process, thus avoiding the problem of the underlying copper being too thin.

[0032] Specifically, debrowning agents mainly include organic solvents, chelating agents, and mild stripping agents.

[0033] Plating copper: The copper-clad laminate is treated with etched copper lines to metallize the through holes.

[0034] In the above, when performing copper plating, pay attention to using the thin board mode for processing, and control the time after copper plating to ≤4 hours, that is, the board should be processed in the next process within 4 hours after copper plating; backlight control ≥9 levels.

[0035] Inner layer patterning: After the film is applied to the copper clad laminate, the inner layer circuit pattern is formed by exposure and development, so that the inner layer circuit and vias are exposed, while the rest is covered by the film.

[0036] In the above process, the board must be pre-treated before applying the film. No micro-etching is allowed during the pre-treatment. Only water washing is required to clean the board surface. Care must be taken not to etch away the copper plating layer. The film should be applied as a whole piece to ensure the adhesion between the dry film and the copper surface.

[0037] Through-hole plating: A through-hole plating process is performed on the copper-clad laminate to thicken the copper layer on the board surface and fill the through holes.

[0038] In the above, after the through-hole electroplating, the copper thickness on both surfaces of the copper-clad laminate is controlled at 12±2um, and the through-hole filling depression is controlled at ≤5um.

[0039] Etching: After stripping, the copper layer on the board surface is removed by rapid etching to remove the non-circuit pattern area, leaving the electroplated circuit pattern. During rapid etching, the etching uniformity is controlled to be above 97%. During etching, the line width is increased by 5μm on the basis of etching compensation to ensure that the line width and line spacing after etching are within 20±5um.

[0040] (9) Lamination: After the copper clad laminate and copper foil are pre-stacked together with PP (the specific board arrangement order from top to bottom is copper foil, PP, copper clad laminate, PP, copper foil), the production board is formed by lamination.

[0041] (10) Browning: The production board is subjected to LDD browning treatment to form a browning film on the surface of the production board; the outer copper surface is treated by LDD browning process to increase the roughness of the copper surface and improve the absorption capacity of the copper foil to laser. The thickness of the bottom copper after LDD browning is controlled at 7±1um to meet the requirements of subsequent laser drilling production.

[0042] (11) Laser drilling: According to the drilling data, laser drilling is performed on the production board to drill blind holes with a diameter of 0.05mm that connect the outer layer circuit and the second outer layer circuit. Here, since the PP thickness between the outer copper foil and the second outer layer circuit is only ≤25μm, the requirement that the thickness-to-diameter ratio of laser drilling is controlled below 0.7 is met.

[0043] In the above, the smallest aperture of 0.9 is used for laser drilling.

[0044] (12) Removal of adhesive: After removing the brown film, the production board is subjected to plasma adhesive removal treatment to remove the drilling contaminants generated during drilling.

[0045] In the above, a decal removal solution without micro-etching ability is used when removing the brown film. That is, the decal removal solution does not etch the underlying copper during the decal removal process, thus avoiding the problem of the underlying copper being too thin.

[0046] Specifically, debrowning agents mainly include organic solvents, chelating agents, and mild stripping agents.

[0047] (13) Plating copper: The production board is plating copper using the eclipse plating copper line to make the blind holes metallized.

[0048] In the above, when performing copper plating, pay attention to using the thin board mode for processing, and control the time after copper plating to ≤4 hours, that is, the board should be processed in the next process within 4 hours after copper plating; backlight control ≥9 levels.

[0049] Inner layer pattern: After the film is applied to the production board, the outer layer circuit pattern is formed by exposure and development, so that the outer layer circuit and blind vias are exposed, while the rest is covered by the film.

[0050] In the above process, the board must be pre-treated before applying the film. No micro-etching is allowed during the pre-treatment. Only water washing is required to clean the board surface. Care must be taken not to etch away the copper plating layer. The film should be applied as a whole piece to ensure the adhesion between the dry film and the copper surface.

[0051] (15) Hole-filling electroplating: The production board is subjected to hole-filling electroplating treatment to thicken the copper layer on the board surface and fill the blind holes.

[0052] In the above, after the hole-filling electroplating, the copper thickness on both surfaces of the production board is controlled at 12±2um, and the hole-filling depression of the blind holes is controlled at ≤5um.

[0053] (16) Etching: After stripping, use rapid etching to remove the copper layer on the board surface where there are no circuit patterns, leaving the electroplated circuit patterns. During rapid etching, the etching uniformity is controlled to be above 97%. During etching, the line width of the circuit is increased by 5μm on the basis of etching compensation to ensure that the line width and line spacing after etching are within 20±5um.

[0054] (17) Solder resist and screen printing: After screen printing solder resist ink on the surface of the production 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, the solder resist ink on the TOP side and the characters on the TOP side are added with "UL mark", thereby coating a layer on the lines and substrates 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 beautify the appearance.

[0055] (18) Surface treatment (immersion nickel and gold): The copper surface of the solder pads of 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.

[0056] (19) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0057] (20) Molding: Based on existing technology and design requirements, the outer shape is shaped with a tolerance of + / -0.05mm; a four-layer, two-stage ultra-thin high-density carrier plate is produced.

[0058] (21) FQC: In accordance with the customer's acceptance standards and our company's inspection standards, inspect the appearance of ultra-thin high-density substrates. If there are any defects, repair them in time to ensure excellent quality control for customers.

[0059] (22) FQA: Re-test the appearance, hole copper thickness, dielectric layer thickness, green solder mask thickness, inner layer copper thickness, etc. of the ultra-thin high-density substrate to see if they meet the customer's requirements.

[0060] (23) Packaging: The ultra-thin high-density substrate is sealed and packaged according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in it before shipment.

[0061] In other embodiments, when the number of ultra-thin high-density substrate circuit layers to be manufactured is six or more, between steps (16) and (17), steps S9 to S16 are repeated in a lamination manner to continue laminating the outer copper foil until the required number of circuit layers is reached.

[0062] 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 manufacturing an ultrathin, high-density carrier-like substrate, characterized in that, Includes the following steps: S1. Cut copper-clad laminates with BT material as the substrate according to the panel dimensions, wherein the overall thickness of the copper-clad laminate is ≤ 0.051mm, with a copper thickness of 9μm on both surfaces; S2. Perform LDD browning treatment on the copper clad laminate to form a browning film on the surface of the copper clad laminate; S3. Perform laser drilling on the copper-clad laminate to drill through holes with a diameter of 0.05mm; the thickness-to-diameter ratio during laser drilling should be controlled below 0.7; S4. After removing the brown coating, the copper-clad laminate is first subjected to plasma desmearing, and then copper plating is performed to metallize the vias; during the removal of the brown coating, the underlying copper must not be etched. S5. After the film is applied to the copper-clad laminate, the inner layer circuit pattern is formed by exposure and development, so that the inner layer circuit and vias are exposed. S6. Perform hole-filling electroplating on the copper-clad laminate, and after removing the film, remove the copper layer on the board surface from the non-circuit pattern area by etching. S7. After laminating 9μm thick copper foil on both surfaces of the copper-clad laminate using PP, the laminate is formed into a production board. S8. Perform LDD browning treatment on the production board to form a browning film on the surface of the production board; S9. Perform laser drilling on the production board to drill blind holes with a diameter of 0.05mm; the thickness-to-diameter ratio during laser drilling should be controlled below 0.7; S10. After removing the brown coating, the production board is first subjected to plasma desmearing, and then copper plating is performed to metallize the blind vias; during the removal of the brown coating, the underlying copper must not be etched. S11. After the film is applied to the production board, the outer layer circuit pattern is formed by exposure and development, so that the outer layer circuit and blind vias are exposed. S12. The production board is subjected to hole-filling electroplating treatment, and after the film is removed, the copper layer on the board surface in the non-circuit pattern area is removed by etching. S13. Finally, the production board is subjected to solder mask layer fabrication, surface treatment and molding in sequence to obtain an ultra-thin high-density carrier board.

2. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In step S2, when the overall thickness of the copper-clad laminate is 0.051 mm, the laser drilling is carried out by drilling through holes on both sides, so that the thickness-to-diameter ratio during laser drilling is controlled below 0.

7.

3. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In step S7, the PP is of type 1017 and the thickness of the PP is ≤25μm, so that the thickness-to-diameter ratio is controlled below 0.7 when drilling blind holes with laser later.

4. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In step S2, after LDD browning treatment, the copper thickness on both surfaces of the copper-clad laminate is controlled at 7±1um; in step S8, after LDD browning treatment, the copper thickness on both surfaces of the production board is controlled at 7±1um.

5. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 4, characterized in that, In step S6, after the via-filling electroplating, the copper thickness on both surfaces of the copper-clad laminate is controlled at 12±2um; in step S12, after the via-filling electroplating, the copper thickness on both surfaces of the production board is controlled at 12±2um, and the via-filling depression is controlled at ≤5um.

6. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In steps S4 and S10, the time control after copper plating is ≤4 hours, that is, the board should be processed in the next process within 4 hours after copper plating.

7. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In steps S4 and S10, a de-browning agent without micro-etching ability is used to remove the brown film.

8. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In steps S5 and S11, the board is pre-treated before applying the film. Micro-etching is not allowed in the pre-treatment. Only the board surface is cleaned with water. The whole piece of film is pressed into place when applying the film.

9. The method for manufacturing an ultrathin, high-density carrier-like substrate according to claim 1, characterized in that, In steps S6 and S12, the linewidth of the circuit is increased by 5μm on top of the etching compensation during etching.

10. The method for manufacturing an ultrathin, high-density substrate according to any one of claims 1-9, characterized in that, When the required number of circuit layers on the production board is six or more, steps S7 to S12 are repeated in a stacking manner between steps S12 and S13 until the required number of circuit layers is reached.