A method for laser drilling and positioning of a package substrate

Abstract

The application discloses a packaging substrate same-layer laser drilling and positioning method, adopts a combined process of same-layer step-by-step processing, and selects CO2 laser drilling when the aperture of a blind hole is greater than or equal to 60 microns, and selects Pico laser drilling when the aperture of the blind hole is 30 microns and less than 60 microns; the combined process of the two kinds of laser drilling can fully exert the advantages of different types of lasers; meanwhile, high-precision positioning marks and auxiliary positioning technology are introduced, target point design is shared by the combined process, and the drilling alignment degree is further optimized, so that the alignment degree Ring ring is less than 15 microns, and the production level is obtained.

Description

Technical Field

[0001] This invention relates to the field of packaging substrate technology, and more specifically to a method for laser drilling and positioning of the same layer of a packaging substrate. Background Technology

[0002] With the rapid development of electronic devices towards miniaturization and multifunctionality, the design requirements for packaging substrates are becoming increasingly stringent. In-layer via design, as an emerging solution, can effectively meet the needs of high-density wiring while enabling interconnection between different functional modules. However, this design faces numerous challenges in laser drilling processes, especially in alignment control. Due to the significant difference in aperture between large and small holes, traditional single-laser processing methods struggle to balance the efficiency of large holes with the precision of small holes, resulting in substantial relative positional deviations between large and small holes in the same layer. Furthermore, with the increasing demand for thinner, lighter, and higher-frequency devices in consumer electronics, the number and density of micro-blind vias on packaging substrates are constantly increasing, further exacerbating the difficulty of alignment control.

[0003] Laser drilling technology for packaging substrates, a key process in the manufacturing of high-density interconnect printed circuit boards (PCBs), has undergone technological innovation from traditional mechanical drilling to laser drilling. CO2 lasers, due to their high energy density and low cost, were initially widely used in the processing of through-holes and blind vias in packaging substrates, particularly demonstrating significant advantages in creating through-holes with large apertures. However, with the miniaturization and multifunctionality of electronic devices, the demand for processing micro-blind vias and micro-through-holes in packaging substrates has increased, making ultraviolet lasers and femtosecond lasers increasingly popular research areas. Ultraviolet lasers, with their high-precision cold-working characteristics, can effectively reduce the heat-affected zone and are suitable for processing micro-holes with apertures smaller than 50 μm. Femtosecond lasers further improve processing accuracy through ultrashort pulse technology, avoiding problems such as "drilling contamination" and "thermal damage," becoming an important tool for manufacturing high-quality packaging substrates. Nevertheless, existing laser drilling technologies still have certain limitations. For example, CO2 lasers are prone to thermally induced internal stress problems when processing micro-holes, while the high equipment costs of ultraviolet lasers and femtosecond lasers limit their application in large-scale production.

[0004] How to select the appropriate drilling method based on the hole size while ensuring processing efficiency and achieving high alignment has become a key issue to be solved in the design of holes of the same size in the same layer. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a method for same-layer laser drilling and positioning of a packaging substrate. It employs a combined process of step-by-step processing within the same layer. For blind vias with a diameter ≥60μm, CO2 laser drilling is selected; for blind vias with a diameter ≤30μm and <60μm, Pico laser drilling is selected. This combination of two laser drilling processes not only fully leverages the advantages of different laser types but also further optimizes drilling alignment by introducing high-precision positioning marks and auxiliary positioning technology.

[0006] To address the aforementioned technical problems, this invention provides a method for laser drilling and positioning of a packaging substrate on the same layer, comprising the following steps: S1. A first alignment through hole is formed by mechanical drilling in the core layer; wherein, the core layer includes a core board layer, and a first copper foil and a first carrier copper are sequentially stacked on both sides of the core board layer; S2. Remove the first carrier copper, attach a dry film to the surface of the first copper foil, align and position based on the first alignment through hole, expose and etch the second alignment target point and the third alignment target point, and then expose the first copper foil after development. S3. Grasp the second alignment target point and create the first blind hole by CO2 laser drilling; S4. Grasp the second alignment target point and create the second blind hole by drilling with a Pico laser. S5. A conductive layer is formed by depositing copper in the first and second blind holes. After cleaning and lamination, the first copper foil of the first pattern to be electroplated is exposed by exposure and development based on the third alignment target point. S6. Conductive circuits are formed by electroplating copper on the first copper foil exposed in step S5 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain an inner layer board including the conductive circuit. S7. A prepreg, a second copper foil, and a second carrier copper are stacked on both sides of the inner layer plate and then pressed together. S8. Create the fourth alignment hole by X-ray drilling, and complete the edge trimming and deburring based on the fourth alignment hole; then create the fifth alignment hole by X-ray drilling, and remove the second carrier copper. S9. Grab the fifth alignment hole, create the sixth alignment target point through Pico laser drilling, and group the sixth alignment target point into several units. Sequentially grab the sixth alignment target point of a single unit and create the third blind hole in the corresponding area through Pico laser drilling; at the same time, create the plum blossom target point through Pico laser drilling. S10. Sequentially grasp the sixth alignment target point of a single unit and create the fourth blind hole in the corresponding area by CO2 laser drilling; S11. A conductive layer is formed by depositing copper in the third and fourth blind holes. After cleaning and lamination, the second copper foil with the second pattern to be electroplated is exposed by exposure and development based on the plum blossom target point. S12. Conductive lines are formed by electroplating copper on the second copper foil exposed in step S11 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain the packaging substrate.

[0007] This invention addresses the different sizes of blind holes to be processed by employing a combined CO2 laser and Pico laser drilling method. A layer-by-layer, step-by-step processing technique is used: CO2 laser drilling is selected for blind holes with a diameter ≥60μm, while Pico laser drilling is selected for blind holes with a diameter ≤30μm and <60μm. This combined laser drilling process fully leverages the advantages of different laser types. Furthermore, high-precision positioning marks and auxiliary positioning technology are introduced, and the combined process shares a common target point design, further optimizing drilling alignment and ultimately achieving a manufacturing level with an alignment ring of <15μm.

[0008] Furthermore, in S1, the number of the first alignment through holes is 3-5, and the hole diameter is 0.9-1.1mm.

[0009] Furthermore, in S2, the number of the second alignment target points is 3-5, and the aperture is 0.9-1.1 mm; The number of the third target sites is 25-30.

[0010] Furthermore, in S3, the diameter of the first blind hole is ≥60μm.

[0011] Furthermore, in S4, the aperture R1 of the second blind hole is: 30μm≤R1<60μm.

[0012] Furthermore, in S6 and S12, the thickness of the conductive lines is 13-21 μm; the flash etch amount is 3-4 μm.

[0013] Furthermore, in S7, the material of the prepreg is PP.

[0014] Furthermore, in S8, the number of the fourth alignment holes is 2-4, and the hole diameter is 1.5-2.5mm; The number of fifth alignment holes is 3-5, and the hole diameter is 0.9-1.1 mm.

[0015] Furthermore, in S9, the number of the sixth pair of target points is 48-80 and is a multiple of 4, and the number of the sixth pair of target points in each unit is 4; The aperture R2 of the third blind hole is: 30μm≤R2<60μm; The number of plum blossom targets is 10-14.

[0016] Furthermore, in S10, the diameter of the fourth blind hole is ≥60μm.

[0017] The beneficial effects of this invention are: This invention addresses the different sizes of blind holes to be processed by combining CO2 laser and Pico laser drilling methods. It employs a layered, step-by-step processing technique. For blind holes with a diameter ≥60μm, CO2 laser drilling is used; for blind holes with a diameter ≤30μm and <60μm, Pico laser drilling is used. This combined laser drilling process fully leverages the advantages of different laser types, effectively solving the customer's design requirement for coexisting holes of varying sizes within the same layer, and overcoming the limitations of existing laser equipment in meeting the processing needs of small-diameter holes.

[0018] This invention introduces high-precision positioning marks and auxiliary positioning technology, combines processes with a shared target design, further optimizes drilling alignment, and ultimately achieves a manufacturing level with an alignment Ring <15μm. Attached Figure Description

[0019] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram showing the location of the first aligned through-hole in the Core layer of Embodiment 1; Figure 2 This is a schematic diagram of the second alignment target point shared by CO2 laser drilling and Pico laser drilling on the inner layer plate in Example 1; Figure 3 This is a schematic diagram of the fifth alignment hole, the sixth alignment target point, and the plum blossom target on the primary packaging board in Example 1; Figure 4 This is the AOI detection result diagram of step (12) in Example 1; Figure 5 This is the AOI detection result diagram of step (21) in Example 1; The labels in the diagram are as follows: 1. Core layer; 2. Inner layer board; 3. Primary packaging board. 001, First alignment through hole; 002, Second alignment target point; 003, Fifth alignment hole; 004, Sixth alignment target point; 005, Plum blossom target. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This embodiment relates to a method for laser drilling and positioning of a packaging substrate on the same layer, including the following steps: S1. A first alignment through hole is formed by mechanical drilling in the core layer; wherein, the core layer includes a core board layer, and a first copper foil and a first carrier copper are sequentially stacked on both sides of the core board layer; S2. Remove the first carrier copper, attach a dry film to the surface of the first copper foil, align and position based on the first alignment through hole, expose and etch the second alignment target point and the third alignment target point, and then expose the first copper foil after development. S3. Grasp the second alignment target point and create the first blind hole by CO2 laser drilling; S4. Grasp the second alignment target point and create the second blind hole by drilling with a Pico laser. S5. A conductive layer is formed by depositing copper in the first and second blind holes. After cleaning and lamination, the first copper foil of the first pattern to be electroplated is exposed by exposure and development based on the third alignment target point. S6. Conductive circuits are formed by electroplating copper on the first copper foil exposed in step S5 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain an inner layer board including the conductive circuit. S7. A prepreg, a second copper foil, and a second carrier copper are stacked on both sides of the inner layer plate and then pressed together. S8. Create the fourth alignment hole by X-ray drilling, and complete the edge trimming and deburring based on the fourth alignment hole; then create the fifth alignment hole by X-ray drilling, and remove the second carrier copper. S9. Grab the fifth alignment hole, and create the sixth alignment target point (exposing the core board layer) by drilling with a Pico laser. Group the sixth alignment target point into several units, and sequentially grab the sixth alignment target point of each unit to create the third blind hole in the corresponding area by drilling with a Pico laser. At the same time, create the plum blossom target point by drilling with a Pico laser. S10. Sequentially grasp the sixth alignment target point of a single unit and create the fourth blind hole in the corresponding area by CO2 laser drilling; S11. A conductive layer is formed by depositing copper in the third and fourth blind holes. After cleaning and lamination, the second copper foil with the second pattern to be electroplated is exposed by exposure and development based on the plum blossom target point. S12. Conductive lines are formed by electroplating copper on the second copper foil exposed in step S11 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain the packaging substrate.

[0023] This embodiment selects a combined CO2 laser and Pico laser drilling method based on the diameter of the blind holes to be processed. It employs a layer-by-layer, step-by-step processing technique. For blind holes with a diameter ≥60μm, CO2 laser drilling is used; for blind holes with a diameter ≤30μm and <60μm, Pico laser drilling is used. This combined laser drilling process fully leverages the advantages of different laser types. Furthermore, high-precision positioning marks and auxiliary positioning technology are introduced, and the combined process shares a common target point design, further optimizing drilling alignment. The final result is an alignment ring of <15μm.

[0024] In some embodiments, in S1, the number of the first alignment vias is 3-5, and the aperture is 0.9-1.1 mm. In S2, the number of the second alignment targets is 3-5, and the aperture is 0.9-1.1 mm; the number of the third alignment targets is 25-30. In S3, the aperture of the first blind via is ≥60 μm. In S4, the aperture R1 of the second blind via is: 30 μm ≤ R1 < 60 μm. In S6 and S12, the thickness of the conductive line is 13-21 μm; the flash etch amount is 3-4 μm. In S7, the material of the prepreg is PP. In S8, the number of the fourth alignment vias is 2-4, and the aperture is 1.5-2.5 mm; the number of the fifth alignment vias is 3-5, and the aperture is 0.9-1.1 mm. In S9, the number of the sixth alignment target points is 48-80 and a multiple of 4, and the number of the sixth alignment target points in each unit is 4; the aperture R2 of the third blind hole is: 30μm≤R2<60μm; the number of plum blossom targets is 10-14. In S10, the aperture of the fourth blind hole is ≥60μm.

[0025] Example 1 This embodiment relates to a method for laser drilling and positioning of a packaging substrate on the same layer, including the following steps: (1) Cutting materials, providing Core layer materials, including core board layer, thin copper (first copper foil) with a thickness of 3μm disposed on both sides of core board layer + carrier copper (first carrier copper) with a thickness of 18μm.

[0026] (2) Mechanical drilling: Drill four 1.0mm pairs of through holes (first alignment through holes) in the Core layer, such as... Figure 1 As shown, the first alignment via 001 is located at the four corners of Core layer 1.

[0027] (3) Tear off the first carrier copper to expose the first copper foil and obtain the inner layer plate.

[0028] (4) CFM: The dry film is attached to the surface of the 3μm first copper foil; the pattern of the circular hole to be etched (4 1.0mm second alignment target points and 28 third alignment target points used for pattern LDI) is exposed on the dry film and the first copper foil exposed at the circular hole pattern after development is etched through the DES line (DES etching conditions: line speed 5.0m / min, vacuum two fluid only, pressure: 0.25Mpa).

[0029] (5) AOI blind hole inspection: After DES, the blind hole opening quality is inspected by AOI to confirm whether there are defects such as large holes, small holes, or no opening.

[0030] (6) CO2 laser drilling: by grasping four 1.0mm second alignment target points of CFM windowing, the finished hole diameter of 60μm X-type hole (first blind hole) is completed.

[0031] (7) Pico laser drilling: By grasping four 1.0mm second alignment target points for CFM windowing, a single-sided blind hole (second blind hole) with a finished diameter of 40μm is fabricated. Steps (6) and (7) share four second alignment target points, such as... Figure 2 As shown, the second alignment target 002 is located at the four corners of the inner plate 2.

[0032] (8) Horizontal P line, remove the glue residue in the first and second blind holes by passing through the horizontal P line at a speed of 2.0m / min.

[0033] (9) mSAP copper plating, mSAP film application, exposure, and development: Conductive layers are deposited in the first and second blind vias at a copper plating line speed of 1.5 m / min; the board surface is cleaned by the dry film pretreatment line and then the film is laminated, and the film is left to stand for 60 min; 28 third alignment target points are irradiated with ultraviolet light from the exposure machine to attach the dry film to the surface of the first copper foil and expose the pattern to be electroplated; the board is left to stand for 60 min after exposure; the uncured dry film is removed by the development line to expose the pattern to be VCP (the first pattern to be electroplated).

[0034] (10) mSAP vertical electroplating: electroplating is performed on the first exposed pattern to be electroplated after development at a current density of 14ASF for 60 minutes through the VCP vertical electroplating line. The copper thickness is 17μm. After electroplating, the layer is added to form a conductive line.

[0035] (11) mSAP stripping and mSAP flash etching: Remove the dry film on the first copper foil after copper plating; use flash etching with a value of 3.5um to form a circuit that meets the requirements.

[0036] (12) AOI inspection of circuit quality and alignment quality, meeting the requirements of via ring <12.5μm fabrication, and AOI inspection showing no off-center via defects, such as... Figure 4 As shown.

[0037] (13) The inner layer board is laminated with prepreg (PP), second copper foil and second carrier copper on both sides and then pressed together to obtain the primary encapsulation board.

[0038] (14) After lamination, three 2.0 mm diameter positioning holes (fourth alignment holes) are drilled through X-ray drilling. Based on the fourth alignment holes, the edge burrs of the board are removed. Then, four 1.0 mm alignment holes (fifth alignment holes) are drilled through X-ray drilling. After the second carrier copper is removed, the second copper foil is exposed. The LDD browning is completed according to the micro-etching amount of 0.6±0.05μm, and the copper surface is brownish-brown.

[0039] (15) Pico laser drilling: Four fifth alignment holes are selected, and 56 alignment concave target points (sixth alignment target points) exposed to the core board layer are burned out using the Pico laser target. The 56 sixth alignment target points are selected and divided into 14 groups of four to form 14 units. The 40μm diameter blind holes (third blind holes) of the 14 units are fabricated in sequence. At the same time, 12 plum blossom targets (plum blossom target points) used for pattern LDI alignment are laser-cut. The schematic diagram of the fifth alignment hole 003, the sixth alignment target point 004, and the plum blossom target 005 on the primary packaging board 3 is shown below. Figure 3 As shown, the number of the sixth pair of target points and the number of plum blossom targets are different from the actual numbers and are only for illustration.

[0040] (16) CO2 laser drilling, grabbing 56 sixth alignment target points, dividing them into 14 groups of four to form 14 units, and sequentially completing the fabrication of the fourth blind hole with a diameter of 60μm in the 14 units; among them, the CO2 laser and Pico laser share the sixth alignment target point.

[0041] (17) Remove the brown coating on the copper surface according to the micro-etching amount of 1.3μm, remove the adhesive residue in the blind hole with a horizontal P-line speed of 1.4m / min, and inspect the contents of the blind hole with AOI.

[0042] (18) Copper plating, film application, exposure, and development: Conductive layers are plated in the third and fourth blind holes at a copper plating line speed of 1.5 m / min; the board surface is cleaned by the dry film pretreatment line and then the film is pressed, and the film is left to stand for 30-60 min after application; based on the plum blossom target, the dry film is applied to the surface of the second copper foil by irradiation with ultraviolet light from the exposure machine and the pattern to be electroplated is exposed; the pattern is left to stand for 60 min after exposure; the uncured dry film is removed by the development line to expose the pattern to be VCP (the second pattern to be electroplated).

[0043] (19) mSAP vertical electroplating: Electroplating is performed on the exposed pattern after development at a current density of 14ASF for 60 minutes through the VCP vertical electroplating line. The copper thickness is 17um. After electroplating, the layer is added to form a conductive line.

[0044] (20) Film removal: Remove the dry film on the copper foil after copper plating.

[0045] (21) Flash etching and AOI: A flash etching amount of 3.5µm is used to form a circuit that meets the requirements. AOI is used to inspect the circuit quality and alignment quality, ensuring that the via ring is <15µm. AOI shows no defects such as off-center vias. Figure 5 As shown.

[0046] This invention addresses the varying diameters of blind holes to be processed by employing a combined CO2 laser and Pico laser drilling method. A layer-by-layer, step-by-step processing technique is used: CO2 laser drilling is selected for blind holes with a diameter ≥60μm, while Pico laser drilling is selected for blind holes with a diameter between 30μm and 60μm. This combined laser drilling process fully leverages the advantages of different laser types, effectively addressing the customer's design requirement for coexisting holes of different sizes within the same layer and overcoming the limitations of existing laser equipment in processing small-diameter holes. High-precision positioning marks and auxiliary positioning technology are introduced, and the combined process uses a shared target point design to further optimize drilling alignment, ultimately achieving a manufacturing level with an alignment ring of <15μm.

[0047] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for laser drilling and positioning on the same layer of a packaging substrate, characterized in that, Includes the following steps: S1. A first alignment through hole is formed by mechanical drilling in the core layer; wherein, the core layer includes a core board layer, and a first copper foil and a first carrier copper are sequentially stacked on both sides of the core board layer; S2. Remove the first carrier copper, attach a dry film to the surface of the first copper foil, align and position based on the first alignment through hole, expose and etch the second alignment target point and the third alignment target point, and expose the first copper foil after development. S3. Grasp the second alignment target point and create the first blind hole by CO2 laser drilling; S4. Grasp the second alignment target point and create the second blind hole by drilling with a Pico laser. S5. A conductive layer is formed by depositing copper in the first and second blind holes. After cleaning and lamination, the first copper foil of the first pattern to be electroplated is exposed by exposure and development based on the third alignment target point. S6. Conductive circuits are formed by electroplating copper on the first copper foil exposed in step S5 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain an inner layer board including the conductive circuit. S7. A prepreg, a second copper foil, and a second carrier copper are stacked on both sides of the inner layer plate and then pressed together. S8. Create the fourth alignment hole by X-ray drilling, and complete the edge trimming and deburring based on the fourth alignment hole; then create the fifth alignment hole by X-ray drilling, and remove the second carrier copper. S9. Grab the fifth alignment hole, create the sixth alignment target point through Pico laser drilling, and group the sixth alignment target point into several units. Sequentially grab the sixth alignment target point of a single unit and create the third blind hole in the corresponding area through Pico laser drilling; at the same time, create the plum blossom target point through Pico laser drilling. S10. Sequentially grasp the sixth alignment target point of a single unit and create the fourth blind hole in the corresponding area by CO2 laser drilling; S11. A conductive layer is formed by depositing copper in the third and fourth blind holes. After cleaning and lamination, the second copper foil with the second pattern to be electroplated is exposed by exposure and development based on the plum blossom target point. S12. Conductive lines are formed by electroplating copper on the second copper foil exposed in step S11 through vertical electroplating. After removing the pressure film, flash etching is performed to obtain the packaging substrate.

2. The method for laser drilling and positioning on the same layer of the packaging substrate as described in claim 1, characterized in that, In S1, the number of the first alignment through holes is 3-5, and the hole diameter is 0.9-1.1mm.

3. The method for laser drilling and positioning on the same layer of the packaging substrate as described in claim 1, characterized in that, In S2, the number of the second alignment target points is 3-5, and the aperture is 0.9-1.1 mm; The number of the third target sites is 25-30.

4. The method for laser drilling and positioning on the same layer of the packaging substrate as described in claim 1, characterized in that, In S3, the diameter of the first blind hole is ≥60μm.

5. The method for laser drilling and positioning on the same layer of the packaging substrate as described in claim 1, characterized in that, In S4, the aperture R1 of the second blind hole is: 30μm≤R1<60μm.

6. The method for laser drilling and positioning on the same layer of the packaging substrate as described in claim 1, characterized in that, In S6 and S12, the thickness of the conductive lines is 13-21 μm; the flash etch amount is 3-4 μm.

7. The method for laser drilling and positioning of the same layer of the packaging substrate as described in claim 1, characterized in that, In S7, the material of the prepreg is PP.

8. The method for laser drilling and positioning of the same layer of the packaging substrate as described in claim 1, characterized in that, In S8, the number of fourth alignment holes is 2-4, and the hole diameter is 1.5-2.5mm; The number of fifth alignment holes is 3-5, and the hole diameter is 0.9-1.1 mm.

9. The method for laser drilling and positioning of the same layer of the packaging substrate as described in claim 1, characterized in that, In S9, the number of the sixth pair of target points is 48-80 and is a multiple of 4, and the number of the sixth pair of target points in each unit is 4; The aperture R2 of the third blind hole is: 30μm≤R2<60μm; The number of plum blossom targets is 10-14.

10. The method for laser drilling and positioning of the same layer of the packaging substrate as described in claim 1, characterized in that, In S10, the diameter of the fourth blind hole is ≥60μm.

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