Method for processing interconnect structure, controller, laser processing apparatus, and circuit board

Abstract

The application provides a processing method of an interconnection structure, a controller, a laser processing device and a circuit board. First, a sub-circuit board with a first interconnection structure is provided, the first interconnection structure comprising a hole structure and a pad structure; then manufacturing information of the first interconnection structure is acquired; based on the manufacturing information, drilling processing is performed at an end position using an ultrashort pulse laser beam, and part of the conductive material at the position where the pad structure and the conductive plating layer are interconnected and the plug hole material within the drilling depth range are removed together to form an opening structure at the end position, the opening size and the bottom size of the opening structure decreasing along the longitudinal direction; finally, a second interconnection structure is formed on the outer side of the sub-circuit board, the end of the second interconnection structure filling the opening structure and communicating with the first interconnection structure. The application can effectively inhibit the interconnection interface position of the interconnection structure from being separated due to thermal stress, and improve the service life and performance reliability of the interconnection structure in the circuit board.

Description

Technical Field

[0001] This application belongs to the field of laser processing technology, and particularly relates to a processing method, controller, laser processing equipment and circuit board for an interconnect structure. Background Technology

[0002] As electronic products evolve towards miniaturization and high performance, the number of stacked layers and interconnect density of printed circuit boards (PCBs) are continuously increasing. High-layer-count PCBs and high-density interconnects (HDIs) are widely used in fields such as artificial intelligence (AI) servers and communication base stations. To achieve higher-density wiring within a limited space, PCBs require interconnect structures that span multiple circuit layers to enable electrical connections between different circuit layers.

[0003] In related technologies, Figure 1 A schematic cross-sectional view of a printed circuit board is shown. (As shown) Figure 1 As shown in (a), an interconnect structure for achieving high-density interconnection of multiple circuit layers in a printed circuit board is typically fabricated in the following manner: First, a plating through hole (PTH) 10 is processed through the sub-circuit board, and an insulating material 11, mainly composed of resin, is filled inside the plating through hole 10 by a plugging process. Then, a multi-layer circuit layer 12 is fabricated on the sub-circuit board that is vertically interconnected with the end of the plating through hole 10, forming a cross-layer interconnect structure (first interconnect structure 13 and second interconnect structure 14) that extends along at least one side of the plating through hole 10 and connects the multi-layer circuit layer 12. The pad structure at the end of the plating through hole 10 and the interconnect end of the adjacent circuit layer together constitute an interconnect interface 15. This cross-layer interconnect structure is the key to achieving high-density wiring and extremely fast signal transmission rate in printed circuit boards.

[0004] However, as the number of circuit layers on printed circuit boards continues to increase and the interconnection density on the circuit boards continues to improve, the number of vertically connected layers in the above interconnection structure is also increasing, and the corresponding composition structure is becoming more and more complex. Reliability problems are prone to occur during use, especially in long-term working conditions and environments with high-speed signal transmission. The interconnection interface 15 of the interconnection structure is prone to cracking, resulting in signal transmission interruption or poor contact, which seriously affects the service life and performance reliability of multilayer boards. Summary of the Invention

[0005] This application provides a method for processing interconnect structures, a controller, a laser processing equipment, and a circuit board, which can suppress cracking at the interconnect interface of the interconnect structure caused by thermal stress, and improve the service life and performance reliability of the interconnect structure in the circuit board.

[0006] A first aspect of this application provides a method for processing an interconnect structure, comprising: providing a sub-circuit board having a first interconnect structure, the first interconnect structure including a hole structure and a pad structure, the inner wall of the hole structure being covered with a conductive plating layer, the pad structure being located outside the hole opening of the hole structure and communicating with the conductive plating layer, and the interior of the first interconnect structure being filled with a plugging material; acquiring manufacturing information of the first interconnect structure, the manufacturing information including the end position of the first interconnect structure, the thickness of the pad structure, and the inner diameter of the hole structure; performing drilling processing at the end position using an ultrashort pulse laser beam, removing part of the conductive material at the connection position between the pad structure and the conductive plating layer and the plugging material within the drilling depth range to form an opening structure at the end position, the opening size and bottom size of the opening structure decreasing longitudinally, and the bottom size being the same as the inner diameter of the hole structure; forming a second interconnect structure on the outside of the sub-circuit board, wherein the end of the second interconnect structure is filled with the opening structure and communicates with the first interconnect structure.

[0007] In the technical solution of this application, drilling is mainly performed at the end position using an ultra-short pulse laser beam to form an opening structure with a longitudinally decreasing opening size and a bottom size that is the same as the inner diameter of the hole structure. This allows the end of the second interconnect structure to fill the opening structure on the first interconnect structure, increasing the thickness of the second interconnect structure at the end position of the first interconnect structure and enhancing the bonding strength between the first and second interconnect structures at the interconnect interface. This effectively suppresses the cracking at the interconnect interface position of the interconnect structure caused by thermal stress, thereby improving the service life and performance reliability of the interconnect structure in the circuit board.

[0008] Optionally, in one possible implementation of the first aspect, the drilling process includes: determining a first borehole diameter and a first borehole depth based on manufacturing information, wherein the first borehole diameter is a predetermined width larger than the inner diameter of the hole structure. The first drilling depth is greater than the thickness of the pad structure by a predetermined depth. The ultrashort pulse laser beam is modulated into a flat-top beam with a flat-top energy distribution, and the flat-top beam is controlled to perform the first laser processing with a first drilling diameter and a first drilling depth. Therefore, by determining the first drilling diameter and depth based on manufacturing information and using a flat-top beam to perform the first laser processing, the size and morphology of the opening structure can be precisely controlled, ensuring processing accuracy and consistency.

[0009] Optionally, in another possible implementation of the first aspect, the aforementioned predetermined width and the predetermined depth Satisfying at least one of the following characteristics: Predetermined width The inner diameter of the hole structure is 10% to 30%; the predetermined depth is... The width ranges from 5μm to 30μm. Therefore, by limiting the predetermined width or depth, the coverage and bonding strength of the opening structure are ensured while avoiding filling difficulties and reliability risks caused by excessive removal of conductive material or excessively deep processing.

[0010] Optionally, in another possible implementation of the first aspect, the aforementioned manufacturing information also includes the thickness of the conductive coating. Before determining the first borehole diameter and first borehole depth based on manufacturing information, the process also includes obtaining the taper angle θ for drilling the first interconnect structure using an ultrashort pulse laser; based on the thickness of the conductive coating... Thickness of the pad structure The predetermined width is determined by the taper angle θ. , to make the predetermined width satisfy: Therefore, by determining the constraint relationship of the predetermined width based on the conductive plating thickness, the pad structure thickness, and the taper angle, the sidewall of the opening structure does not penetrate the connection position between the pad structure and the conductive plating, thereby protecting the integrity of the interconnect structure.

[0011] Optionally, in another possible implementation of the first aspect, the method further includes adjusting the thickness of the conductive coating. Thickness of the pad structure The predetermined depth is determined by the taper angle θ. , to the predetermined depth satisfy: Therefore, by determining the predetermined depth constraint relationship based on the conductive plating thickness, pad structure thickness, and taper angle, the depth of the opening structure is ensured not to exceed the safety threshold, thereby avoiding damage to the conductive plating during processing and guaranteeing interconnect reliability.

[0012] Optionally, in another possible implementation of the first aspect, the drilling process further includes at least one of the following features: controlling a flat-top beam to perform a second laser processing on the first interconnect structure with a second drilling diameter and a second drilling depth, wherein the second drilling diameter is smaller than the projected size of the interconnect pad, and the second drilling depth is smaller than the thickness of the pad structure; controlling the flat-top beam to perform a third laser processing on the first interconnect structure with a third drilling diameter and a third drilling depth, wherein the third drilling diameter is equal to the inner diameter of the hole structure, and the cumulative depth of the third drilling depth and a predetermined depth L is less than or equal to 30 μm. Thus, by using the second or third laser processing to pre-process or compensate for the pad structure, the sidewall and bottom morphology of the opening structure are optimized, further improving processing accuracy and interconnect quality.

[0013] Optionally, in another possible implementation of the first aspect, before controlling the flat-top beam to perform the first laser processing with a first drilling diameter and a first drilling depth, the processing mode of the flat-top beam is determined based on the first drilling diameter and the focused spot size of the flat-top beam. This includes: if the first drilling diameter is less than or equal to the maximum value of the focused spot size, the processing mode is laser punching, and the processing spot size of the focused spot is equal to the first drilling diameter; if the first drilling diameter is greater than the maximum value of the focused spot size, the processing mode is laser winding processing or a combination of laser winding processing and laser punching, and the projected cross-section size of the laser winding processing or the combined laser winding processing and laser punching is equal to the first drilling diameter. Thus, by selecting the laser punching or winding processing mode based on the comparison between the first drilling diameter and the focused spot size of the flat-top beam, the processing accuracy can be guaranteed while adapting to the requirements of opening structures of different sizes, thereby improving process compatibility and processing efficiency.

[0014] Optionally, in another possible implementation of the first aspect, forming the second interconnect structure on the outer side of the sub-circuit board includes: metallizing the opening structure, the metallization process including copper plating and electroplating, to form an end interconnect structure that fills the opening structure on the sub-circuit board. Thus, electrical and mechanical connection between the second interconnect structure and the first interconnect structure is achieved through the interconnect interface formed by the end interconnect structure of the second interconnect structure and the interconnect pads of the first interconnect structure.

[0015] Optionally, in another possible implementation of the first aspect, the aforementioned hole structure is an electroplated through-hole penetrating the sub-circuit board, and the second interconnect structure includes multiple conductive blind via structures continuously stacked along the longitudinal direction. This configuration expands the application of the processing method in high-density multilayer interconnect scenarios, supporting more complex interconnect structure stacking.

[0016] Optionally, in another possible implementation of the first aspect, the pad structure described above is an interconnect pad or a pre-processed interconnect pad line. Thus, by setting the pad structure as an interconnect pad or a pre-processed interconnect pad line, it is compatible with both formed and unformed pad states, providing flexible process selection.

[0017] Optionally, in another possible implementation of the first aspect, the aforementioned ultrashort pulse laser beam is an ultrafast laser with a pulse width less than or equal to the picosecond level. The wavelength of the ultrafast laser includes ultraviolet light in the 340nm to 360nm band, green light in the 500nm to 540nm band, and infrared light in the 1000nm to 1100nm band. Therefore, by using an ultrashort pulse laser beam with a pulse width less than or equal to the picosecond level for processing, a cold processing mechanism is utilized to reduce heat accumulation, avoid resin shrinkage and interfacial cracking caused by heat effects, and ensure the processing quality of the open structure.

[0018] Optionally, in another possible implementation of the first aspect, the aforementioned ultrafast laser is a green picosecond laser with a wavelength in the range of 500nm to 540nm. This achieves a balance between good absorption rates on both metallic and resin materials and high processing efficiency.

[0019] A second aspect of this application provides a controller, a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the computer program to implement the processing method of the interconnect structure described in the first aspect.

[0020] A third aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the processing method for the interconnect structure described in the first aspect.

[0021] A fourth aspect of this application provides a computer program product that, when the computer program is run, causes the processing method of the interconnect structure described in the first aspect to be executed.

[0022] The fifth aspect of this application provides a laser processing apparatus, comprising: a laser for emitting an ultrashort pulse laser beam; a beam control device for transmitting, controlling, and deflecting the ultrashort pulse laser beam, wherein the beam control device includes a beam shaping mechanism and a beam deflection mechanism, the beam shaping mechanism controlling the ultrashort pulse laser beam into a flat-top beam with a flat-top energy distribution, and the beam deflection mechanism controlling the flat-top beam to perform laser processing according to a laser processing path; a processing platform for carrying a sub-circuit board; and a controller for controlling the laser, beam control device, and processing platform to work together to realize the steps of the processing method for the interconnect structure of the first aspect.

[0023] The sixth aspect of this application provides a circuit board including a first interconnect structure and a second interconnect structure, which are obtained by processing the interconnect structure according to the processing method of the first aspect or by processing the laser processing equipment of the fifth aspect.

[0024] It is understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a cross-section of a sub-circuit board; Figure 2 This is a schematic flowchart of a method for processing an interconnect structure according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a sub-circuit board provided in an embodiment of this application; Figure 4 This is a schematic diagram of the manufacturing process of a first interconnect structure provided in an embodiment of this application; Figure 5 This is a schematic diagram of a sub-circuit board structure after drilling, provided in an embodiment of this application; Figure 6 This is a schematic diagram of a second interconnection structure provided in an embodiment of this application; Figure 7 This is a cross-sectional schematic diagram of a sub-circuit board provided in an embodiment of this application; Figure 8 This is a schematic diagram of the structure of a controller provided in an embodiment of this application; Figure 9 This is a schematic diagram of the structure of a laser processing device provided in an embodiment of this application. Detailed Implementation

[0027] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0028] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0029] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0030] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0031] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0033] It should be understood that the sequence number of each step in this embodiment does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this application embodiment.

[0034] In related technologies, such as Figure 1As shown in (a), an interconnect structure for achieving high-density interconnection of multiple circuit layers in a printed circuit board is typically fabricated in the following manner: first, an electroplated hole 10 penetrating the sub-circuit board is processed, and an insulating material 11 whose main component is resin is filled inside the electroplated hole 10 through a plugging process. Then, a multi-layer circuit layer 12 is fabricated on the sub-circuit board that is vertically interconnected with the end of the electroplated hole 10, forming a cross-layer interconnect structure (first interconnect structure 13 and second interconnect structure 14) that extends along at least one side of the electroplated hole 10 and connects the multi-layer circuit layer 12. The pad structure at the end of the electroplated hole 10 and the interconnect end of the adjacent circuit layer together constitute an interconnect interface 15. This cross-layer interconnect structure is the key to achieving high-density wiring and extremely fast signal transmission rate in printed circuit boards. However, as the number of circuit layers on printed circuit boards continues to increase and the interconnection density on the circuit boards continues to improve, the number of vertically connected layers in the above interconnection structure is also increasing, and the corresponding composition structure is becoming more and more complex. Reliability problems are prone to occur during use, especially in long-term working conditions and environments with high-speed signal transmission. The interconnection interface 15 of the interconnection structure is prone to cracking, resulting in signal transmission interruption or poor contact, which seriously affects the service life and performance reliability of multilayer boards.

[0035] You can refer to, for example Figure 1 The enlarged schematic diagram of the interconnect interface 15 shown in Figure (b) illustrates the problem. Through analysis of the circuit board's structure and manufacturing method, the inventors determined that the aforementioned problem primarily arises because the thickness 151 of the interconnect interface 15 at the location corresponding to the via-filling material is less than the thickness 152 at the location corresponding to the interconnect pad of the first interconnect structure 13. Both the via-filling material in the electroplated holes and the insulating substrate that isolates the conductive lines in the circuit board contain a large amount of resin. When the circuit board temperature changes, the deformation of the via-filling material and the insulating substrate is far greater than the deformation of the conductive material constituting the circuit structure. This difference in deformation compresses the interconnect covering the via-filling material, causing the end of the second interconnect structure 14 that contacts the pad structure of the first interconnect structure 13 to be lifted, resulting in the first interconnect structure 13 and the second interconnect structure 14 detaching at the interconnect interface 15. Furthermore, as the number of stacked circuit layers on the circuit board increases, the thickness of the interconnect interfaces between each circuit layer decreases to increase the interconnect density, making this detachment even more likely.

[0036] In view of this, embodiments of this application provide a method for processing an interconnect structure, a controller, a laser processing device, and a circuit board. The method first provides a sub-circuit board with a first interconnect structure, which includes a hole structure and a pad structure. The inner wall of the hole structure is covered with a conductive plating layer, and the pad structure is located outside the hole opening and communicates with the conductive plating layer. The interior of the first interconnect structure is filled with a plugging material. Then, manufacturing information of the first interconnect structure is obtained, including the end position of the first interconnect structure, the thickness of the pad structure, and the inner diameter of the hole structure. Next, an ultrashort pulse laser beam is used to drill at the end position, removing a portion of the conductive material at the connection point between the pad structure and the conductive plating layer, along with the plugging material within the drilling depth range, to form an opening structure at the end position. The opening size and bottom size of the opening structure decrease longitudinally, and the bottom size is the same as the inner diameter of the hole structure. Finally, a second interconnect structure is formed on the outside of the sub-circuit board, wherein the end of the second interconnect structure is filled with the opening structure and communicates with the first interconnect structure. Therefore, by using an ultra-short pulse laser beam to drill holes at the end positions, an opening structure is formed with the opening size decreasing longitudinally and the bottom size being the same as the inner diameter of the hole structure. This allows the end of the second interconnect structure to fill the opening structure on the first interconnect structure, increasing the thickness of the second interconnect structure at the end position of the first interconnect structure and enhancing the bonding strength between the first and second interconnect structures at the interconnect interface. This effectively suppresses the cracking of the interconnect interface between the first and second interconnect structures caused by thermal stress, thereby improving the service life and performance reliability of the interconnect structure in the circuit board.

[0037] To illustrate the technical solution of this application, specific embodiments are described below.

[0038] Reference Figure 2 The diagram illustrates a flowchart of a processing method for an interconnect structure provided in an embodiment of this application. Figure 2 As shown, the fabrication method of this interconnect structure may include the following steps: Step 201: Provide a sub-circuit board with a first interconnect structure. The first interconnect structure includes a hole structure and a pad structure. The inner wall of the hole structure is covered with a conductive plating layer. The pad structure is located outside the hole of the hole structure and communicates with the conductive plating layer. The interior of the first interconnect structure is filled with a plugging material.

[0039] The hole structure can be a through hole that penetrates the upper and lower surfaces of the sub-circuit board, or a blind hole that only penetrates a portion of the depth on one side of the sub-circuit board. Its specific form depends on the design requirements, and this application does not impose any restrictions on it.

[0040] In this embodiment, a sub-circuit board refers to a basic unit used to construct a circuit board with multiple stacked circuit layers, such as a multilayer board or a high-density interconnect board. See, for example... Figure 3The diagram shows a structural schematic of a sub-circuit board. Figure 3 An exemplary diagram illustrates a sub-circuit board 30 comprising a core board 31 and add-on circuit structures 32 located on both sides of the core board 31. The add-on circuit structures 32 are composed of multiple longitudinally stacked circuit layers 321. Each circuit layer 321 includes a signal transmission circuit layer 3211 and an insulating material layer 3212, with the insulating material layer 3212 filling the spaces between adjacent signal transmission circuit layers 3211. It should be understood that the sub-circuit board may consist solely of the core board 31, or it may consist of the core board 31 and at least one circuit layer 321 stacked on at least one side of the core board. Figure 3 The number of line layers 321 shown is only an example. In actual applications, the required number of layers can be set according to the wiring requirements. This application does not limit this.

[0041] The core board 31 includes an intermediate insulating dielectric layer 311 and a signal connection layer 312 covering the upper and / or lower surfaces of the intermediate insulating dielectric layer 311. The core board 31 serves as the supporting substrate for the circuit board. The intermediate insulating dielectric layer 311 can be an organic substrate layer (composed of fiberglass cloth or quartz cloth impregnated with epoxy resin, etc.), a ceramic substrate layer (formed by sintering a mixture of alumina, aluminum nitride, silicon nitride, and various additives), or a glass substrate layer (whose main component can be silicon dioxide), etc. The signal connection layer 312 is typically a copper foil layer covering the surface of the intermediate insulating dielectric layer 311. Subsequent etching processes can form the required signal transmission lines on the surface of the intermediate insulating dielectric layer 311.

[0042] The insulating material layer 3212 provides support and insulation for the signal transmission line layer 3211 of the adjacent two line layers. It can be a single insulating substrate layer or obtained by laminating multiple insulating substrate layers. The insulating substrate includes BT resin layer, Ajinomoto Build-up Film (ABF) thin film layer, ceramic substrate layer, polytetrafluoroethylene (PTFE), polyimide (PI), etc. The signal transmission line layer 3211 can be used to transmit electrical or optical signals. It can be formed on the insulating material layer 3212 by lamination or electrochemical deposition, and the required circuit pattern can be formed by etching. It is usually a metal substrate such as copper or silver, but this application does not limit it.

[0043] For ease of explanation, the embodiments described below in this application use a sub-circuit board where the hole structure of the first interconnection structure only penetrates the upper surface of the sub-circuit board as an example. However, those skilled in the art will understand that the method of this application is also applicable to sub-circuit boards where the hole structure of the first interconnection structure extends from the upper surface to the lower surface of the sub-circuit board.

[0044] Figure 4 Image (c) shows a schematic diagram of a first interconnect structure provided in an embodiment of this application. Figure 4 As shown in (c), the sub-circuit board 30 includes a first interconnect structure 40. The first interconnect structure 40 includes a hole structure 401 and a pad structure 402. The hole structure 401 is an opening structure formed on the sub-circuit board 30 by drilling, penetrating part or all of the depth of the sub-circuit board 30, and its aperture can be set according to design requirements. The inner wall of the hole structure 401 is covered with a conductive plating layer 4011, which is formed on the hole wall of the hole structure 401 by metallization treatment (e.g., chemical copper plating process and electroplating process), making the hole structure 401 conductive and able to connect multiple signal transmission line layers in the sub-circuit board 30 as needed. The thickness of the conductive plating layer 4011 can be controlled according to the electroplating process parameters.

[0045] Continue to refer to Figure 4 In (c), the pad structure 402 is located outside the orifice of the hole structure and is connected to the conductive plating layer 4011. The pad structure 402 is typically located on the signal transmission line layer at the end of the hole structure 401, and the thickness of the pad structure 402 can be determined according to the circuit board design requirements. In one embodiment, the pad structure 402 can be an interconnect pad, which can be used as a contact area for the first interconnect structure 40 to electrically connect with other line layers. It can be formed by patterning the pre-processed interconnect pad lines located at the end of the hole structure 401, and the size of the interconnect pad can be determined according to the circuit board design requirements. In another embodiment, the pad structure 402 can also be a pre-processed interconnect pad line that has not yet been patterned. The opening structure of the first interconnect structure 40 can be processed first, and then the pre-processed interconnect pad line can be patterned into an interconnect pad. It is understood that regardless of the state of the pad structure 402, it remains outside the orifice of the hole structure 401 and maintains electrical connection with the conductive plating layer 4011 of the hole structure 401.

[0046] In this embodiment, the first interconnect structure 40 is filled with a via-filling material 4012. The via-filling material 4012 is an insulating material filling the cavity structure 401. Its main component is a resin material with good flowability and dimensional stability after curing, such as epoxy resin, BT resin, polyimide (PI), etc. Other insulating materials suitable for via-filling processes can also be used. The via-filling material 4012 is injected into the cavity structure 401 through a via-filling process (such as screen printing, vacuum pressing, injection molding, etc.) and forms a dense filler after curing. The via-filling material 4012 is used to seal the cavity structure and simultaneously enhance the mechanical strength of the cavity structure 401.

[0047] It should be understood that Figure 4The first interconnect structure shown in (c) is merely an illustration of a specific embodiment. In practical applications, multiple first interconnect structures can be distributed on the sub-circuit board. The aperture, depth, conductive plating thickness, and pad size and thickness of each first interconnect structure can be independently set according to design requirements. Furthermore, the pad structure of the first interconnect structure can be located on either side of the sub-circuit board or on both sides simultaneously; this application does not impose any limitations on this. The processing method provided in this application is applicable to these different configurations.

[0048] In one possible implementation, the first interconnect structure 40 can be fabricated as follows: First, drilling (using mechanical drilling or laser drilling) can be performed on the sub-circuit board 30 to form the hole structure 401, as shown below. Figure 4 As shown in (a). Then, the surfaces of the hole structure 401 and the sub-circuit board 30 are metallized. For example, a thin layer of copper can be deposited on the hole wall of the hole structure 401 and the surface of the sub-circuit board 30 using a chemical copper plating process to provide a conductive base for subsequent electroplating. Then, the copper layer is thickened using an electroplating process, forming a conductive plating layer 4011 of predetermined thickness on the inner wall of the hole structure 401 and a circuit plating layer on the surface of the sub-circuit board 30. The pad structure 402 refers to the circuit plating layer located in the area outside the hole opening of the hole structure, such as... Figure 4 As shown in (b). Next, the pore structure is filled with pore-filling material 4012 and cured to obtain the result shown in [image]. Figure 4 The first interconnect structure 40 is shown in (c). Additionally, the circuit plating layer on the surface of the sub-circuit board can be patterned using photolithography and etching processes to form interconnect pad pre-processed circuits or interconnect pads. It is understood that the conductive material of the pad structure 402 and the conductive plating layer 4011 of the hole structure 401 can be formed in the same metallization step, or they can be formed in different metallization steps. For example, after forming the conductive plating layer 4011 and the circuit plating layer through the first metallization process, the circuit plating layer generated in the first metallization process is removed, and then a second metallization process is used to form the pad structure on the outside of the hole opening of the hole structure 401. The above embodiments focus on providing a first interconnect structure 40 with the above structural features; its specific fabrication method does not affect the implementation of subsequent processing methods in this application.

[0049] The following steps will describe in detail how to fabricate the opening structure based on the first interconnect structure and form the second interconnect structure.

[0050] Step 102: Obtain the manufacturing information of the first interconnect structure, including the end position of the first interconnect structure, the thickness of the pad structure, and the inner diameter of the hole structure.

[0051] Manufacturing information refers to data parameters related to the geometric features and spatial position of the first interconnect structure. These parameters are used to subsequently determine process parameters such as the laser beam spot size, pulse beam, and processing path for drilling. Manufacturing information can be obtained by directly reading preset processing parameters from the circuit board design drawings, by real-time measurement of the sub-circuit board using online measurement equipment, or by pre-measuring and inputting the data into the processing system using offline detection methods. This application does not limit the specific method of obtaining manufacturing information, as long as accurate parameters of the first interconnect structure can be obtained before laser processing.

[0052] In this embodiment, the end position of the first interconnect structure refers to the spatial coordinates of the end of the first interconnect structure exposed on the surface of the sub-circuit board along the thickness direction of the sub-circuit board, which also corresponds to the positioning coordinates of the pad structure on the sub-circuit board. Since multiple first interconnect structures may be distributed on the sub-circuit board, each of which may be located in different areas of the sub-circuit board and may be distributed on one or both sides of the sub-circuit board surface, it is necessary to accurately determine the end position of each first interconnect structure to be processed as a positioning reference for laser processing. The end position can be calibrated using reference points on the sub-circuit board (such as positioning holes, board edges, etc.) as a reference, and can be achieved by identifying the contour features of the pad structure or the center position of the hole structure through a visual positioning system. Accurate end position information is crucial to ensuring that the laser beam accurately acts on the target area and avoids processing deviations.

[0053] In the embodiments of this application, such as Figure 5 As shown in (a), the thickness 51 of the pad structure refers to the dimension of the pad structure in the direction perpendicular to the surface of the sub-circuit board, i.e., the thickness of the signal transmission line layer where the pad structure is located. The thickness 51 of the pad structure determines the total amount of conductive material that needs to be removed during laser processing, and is also an important basis for determining the drilling depth. This thickness information can be obtained directly from the circuit board design parameters, or it can be measured by a contact or non-contact thickness gauge.

[0054] In the embodiments of this application, such as Figure 5 As shown in (a), the inner diameter 52 of the hole structure refers to the diameter of the hole structure in the direction perpendicular to its axial direction, that is, the inner diameter of the circular hole enclosed by the conductive plating layer. This inner diameter 52 determines the cross-sectional dimensions of the plugging material and is also an important benchmark for determining the process parameters of the laser beam required for drilling and for processing control. The inner diameter of the hole structure can be directly read from the design drawings or obtained through actual measurement using a vision system, microscope, or laser measuring instrument.

[0055] It should be noted that the parameters in the above manufacturing information may have manufacturing tolerances, which can be compensated for in actual processing based on measurement results and processing requirements. For example, if the measured pad structure thickness deviates from the design value, it can be adjusted accordingly when determining the drilling depth to ensure processing quality. Furthermore, for multiple first interconnect structures on the same sub-circuit board, if their structural parameters differ (e.g., different pad structure thicknesses in different areas), the corresponding laser processing parameters can be determined separately based on their respective manufacturing information to achieve differentiated processing.

[0056] In this embodiment, the manufacturing information obtained in step 102 will serve as the basis for determining the laser processing procedure to be performed in step 103, ensuring that the ultrashort pulse laser beam can accurately process the required opening structure at the end position of the first interconnect structure. The following will describe in detail how laser processing is performed based on this manufacturing information in conjunction with subsequent steps.

[0057] Step 103: Drill holes at the end position using an ultrashort pulse laser beam, separating the conductive material at the connection point between the pad structure and the conductive plating layer, and drilling to a depth (e.g., ...). Figure 5 The plugging material within the range of 53 shown in (a) is removed together to form an opening structure at the end position. The opening size and bottom size of the opening structure decrease longitudinally, and the bottom size is the same as the inner diameter of the hole structure.

[0058] Ultrashort pulse laser beams refer to pulsed lasers with pulse widths less than or equal to nanoseconds, including nanosecond lasers, picosecond lasers, and femtosecond lasers. The extremely short duration of a single pulse in an ultrashort pulse laser beam enables it to possess high peak power and a wide spectral bandwidth, concentrating laser energy within a very small temporal and spatial range. This induces multiphoton absorption and / or avalanche ionization along the beam's penetration path, breaking the molecular chains of the material, causing it to vaporize, and forming smaller particles, thus achieving rapid material removal. For the first interconnect structure, on the one hand, ultrashort pulse laser beams have excellent processing capabilities for both conductive materials and via materials constituting the conductive plating layer and pad structure. They can utilize the aforementioned mechanism to simultaneously remove the substrate along the beam's penetration path without requiring separate processing of the conductive and via materials. On the other hand, the interaction mechanism between the ultrashort pulse laser beam and the material is primarily cold processing, which can significantly reduce the thermal impact on the structure surrounding the beam's penetration path during processing, and reduce the thermal stress between the remaining insulating material (mainly resin) and the conductive circuit structure around the beam's penetration path during drilling. Furthermore, the smooth sidewalls of the opening structure formed along the beam penetration path of the ultrashort pulse laser help reduce the difficulty of subsequent electroplating of the opening structure.

[0059] In this embodiment of the application, drilling refers to the process of removing the substrate along the laser beam penetration path by using a laser beam to strike or scan the surface of the sub-circuit board at a fixed point, thereby forming an opening structure of a predetermined shape and size. Figure 5 This illustration shows a schematic diagram of a sub-circuit board structure after drilling, according to an embodiment of this application. Figure 5 As shown in (a), drilling requires removing a portion of the conductive material at the connection point between the pad structure and the conductive plating layer. This means the drilling area covers the region where the edge of the pad structure connects to the conductive plating layer. Simultaneously, drilling also requires removing a certain depth of plugging material, ensuring the bottom of the opening structure is located inside the plugging material, with the bottom dimension matching the inner diameter of the hole structure. In this embodiment, the sidewalls of the opening structure are made of the same conductive material as the conductive plating layer and the pad structure, while the bottom wall is the plugging material. This allows for a larger opening size, reducing the difficulty of filling and aligning the second interconnect structure on the outside of the opening structure. Furthermore, the processed opening structure simultaneously exposes both the plugging material and the surrounding conductive material, providing a larger bonding area for the subsequent second interconnect structure.

[0060] Reference Figure 4 In section (c), after filling the pore-filling material 4012, due to the fluidity of the material before curing, a slight protrusion structure 404 will form at the end of the pore-filling material 4012, in conjunction with the background art. Figure 1 It is understood that retaining the protrusion structure 404 would further increase the difference between the thickness 151 of the interconnect interface at the via material location and the thickness 152 of the interconnect pad location, reducing the reliability of the interconnect interface. In one embodiment, preprocessing is used to make the surface of the via material of the first interconnect structure on the sub-circuit board flush with the surface of the pad structure. Specifically, after the sub-circuit board is filled, the protrusion structure at the end of the via material can be removed by brush leveling until the surface of the via material is flush with the surface of the pad structure. In another embodiment, the end of the via material of the first interconnect structure includes a protrusion structure. During the processing of the opening structure, the protrusion structure can be removed simultaneously using an ultrashort pulse laser beam, which can omit the step of preprocessing the protrusion structure on the sub-circuit board.

[0061] Further references can be made. Figure 5 A schematic diagram of the opening structure shown in (b) is provided. Figure 5 As shown in (b), the opening structure is a recessed area formed after drilling. Its geometric characteristics are as follows: the opening size (i.e., the lateral width of the opening structure on the surface of the sub-circuit board) and the bottom size (i.e., the lateral width of the bottom wall of the opening structure) decrease along the longitudinal direction (i.e., the depth direction).

[0062] To achieve high-precision, high-quality machining of open structures, the specific process of drilling is described below.

[0063] In one embodiment, drilling may specifically include the following steps: determining a first drilling diameter and a first drilling depth based on manufacturing information, wherein the first drilling diameter is a predetermined width larger than the inner diameter of the hole structure. The first drilling depth is greater than the thickness of the pad structure by a predetermined depth. The ultrashort pulse laser beam is modulated into a flat-top beam with a flat-top energy distribution, and the flat-top beam is controlled to perform the first laser processing with a first drilling diameter and a first drilling depth. Therefore, by determining the first drilling diameter and depth based on manufacturing information and using a flat-top beam to perform the first laser processing, the size and morphology of the opening structure can be precisely controlled, ensuring processing accuracy and consistency.

[0064] It should be noted that you can refer to, for example Figure 5 The manufacturing information comparison diagram shown in (b) indicates that the first drilling diameter refers to the diameter of the projected cross-section of the laser beam on the processing area of ​​the sub-circuit board during laser processing. The first drilling diameter is set to be a predetermined width larger than the inner diameter of the hole structure. Set the preset width. The purpose is to ensure that the opening size of the opening structure is larger than the inner diameter of the hole structure, thereby removing not only the plugging material but also some of the conductive material in the edge area of ​​the pad structure during processing. The first drilling depth refers to the depth to which the laser beam removes material during laser processing. The first drilling depth is set to a predetermined depth L that is larger than the thickness of the pad structure. The purpose of setting L is to ensure that the depth of the opening structure is greater than the thickness of the pad structure, increase the sidewall size of the opening structure, provide a larger bonding area for the subsequent second interconnect structure, increase the thickness of the second interconnect structure at the end position of the first interconnect structure, reduce the difference between the thickness 151 of the interconnect interface 15 between the first and second interconnect structures above the plugging material and the thickness 152 at the interconnect pad position, and also reduce the volume of the plugging material in the first interconnect structure and reduce the thermal stress effect of the plugging material on the interconnect interface.

[0065] After determining the first borehole diameter and depth, the ultrashort pulse laser beam needs to be modulated into a flat-top beam with a flat-top energy distribution. Typically, the original laser pulse emitted by the laser is a Gaussian beam, with an energy distribution across its cross-section that is high in the middle and low at the edges. If a Gaussian beam is directly used to process the opening structure, firstly, the Gaussian beam has a higher beam energy density and peak energy compared to a flat-top beam, which can easily break down the connection between the conductive plating and the pad structure during the processing of the opening structure, damaging the electrical performance of the first interconnect structure; secondly, due to the uneven energy distribution of the Gaussian beam, the energy applied by the laser beam to the bottom of the opening structure will be uneven, causing the bottom wall of the opening structure to be uneven or causing the plugging material on the outer side of the bottom wall of the opening structure to shrink inward and detach from the conductive plating, resulting in an uneven bottom wall of the opening structure. Figure 5 As shown in 54 and 55 of (c). This uneven bottom morphology brings at least two problems: first, during subsequent electroplating, the uneven area at the bottom of the opening structure is prone to electroplating defects, increasing the difficulty of electroplating; second, during use, the interface between the end of the interconnect structure and the filler material is prone to cracking due to thermal stress, reducing the reliability of the interconnect. Therefore, in this embodiment, an optical shaping component can be used to shape the Gaussian beam, converting it into a flat-top beam with uniform energy distribution. The flat-top beam has a more uniform energy density distribution on the cross-section. When it irradiates the material surface, the removal process of the conductive material by the laser beam is more controllable, and the energy accumulation at each point in the coverage area of ​​the laser beam is basically consistent, thereby enabling the processing of an opening structure with a flat bottom. After the shaped flat-top beam is focused, the ultrashort pulse laser beam is controlled to perform the first laser processing with the first drilling diameter and the first drilling depth as the processing target, thus forming an opening structure with a predetermined size at the end position.

[0066] In one embodiment, the predetermined width M and predetermined depth L satisfy at least one of the following characteristics: the predetermined width is 10% to 30% of the inner diameter of the hole structure; the predetermined depth is 5 μm to 30 μm. Thus, by limiting the predetermined width or predetermined depth, the coverage and bonding strength of the opening structure are ensured while avoiding filling difficulties and reliability risks caused by excessive removal of conductive material or excessively deep processing.

[0067] It should be noted that setting the predetermined width M to 10% to 30% of the inner diameter of the hole structure has the following technical considerations: First, if the predetermined width M is too small (e.g., less than 10%), the opening size of the aperture structure will be close to the inner diameter of the hole structure, resulting in a small alignment tolerance during laser processing. This can easily lead to residual plugging material at the edge or damage to the conductive plating due to alignment deviation, affecting the reliability of subsequent interconnects, while the increase in lateral contact area is limited. Second, if the predetermined width M is too large (e.g., greater than 30%), it will excessively remove the conductive material from the pad structure, and may even cause the laser beam to penetrate to the insulating material layer below the pad structure, resulting in a break in the connection between the pad structure and the conductive plating, thus compromising the integrity of the interconnect structure. Therefore, controlling the predetermined width within the range of 10% to 30% of the inner diameter of the hole structure can maximize the lateral contact area while ensuring complete coverage of the plugged hole, providing sufficient tolerance for processing alignment, and avoiding the risks associated with excessive removal of conductive material.

[0068] Furthermore, setting the predetermined depth L to 5μm to 30μm has the following technical considerations: If the predetermined depth is less than 5μm, the thickness of the conductive material layer subsequently filled within the opening structure will be too thin, failing to effectively buffer the thermal stress caused by resin expansion in the plugging material, thus having limited effect on preventing interconnect interface cracking; if the predetermined depth is greater than 30μm, new problems will arise: on the one hand, an excessively deep opening structure will increase the difficulty of subsequent electroplating, and may even lead to the bottom of the opening structure not being completely filled, forming voids; on the other hand, an excessively deep opening structure will cause new pits to form on the surface of the added-layer circuit located outside the interconnect interface during the electroplating process, requiring additional processing steps for these pits in the fabrication process of the second interconnect structure, or introducing new reliability issues to the interconnect structure. Therefore, setting the predetermined depth to 5μm to 30μm ensures sufficient conductive material thickness to suppress the effect of resin expansion, while avoiding the process difficulties and reliability risks caused by excessive depth.

[0069] In one embodiment, reference can continue. Figure 5 In section (b), the manufacturing information also includes the thickness of the conductive coating. Before determining the first borehole diameter and first borehole depth based on manufacturing information, the process also includes obtaining the taper angle θ for drilling the first interconnect structure using an ultrashort pulse laser; based on the thickness of the conductive coating... Thickness of the pad structure The predetermined width is determined by the taper angle θ. , to make the predetermined width satisfy: Therefore, by determining the constraint relationship of the predetermined width based on the conductive plating thickness, the pad structure thickness, and the taper angle, the sidewall of the opening structure does not penetrate the connection position between the pad structure and the conductive plating, thereby protecting the integrity of the interconnect structure.

[0070] It should be noted that, in order to ensure that the connection between the pad structure and the conductive plating layer is not damaged during laser processing, the predetermined width needs to be... Constraints are applied. In laser drilling, due to the divergence characteristics of the laser beam and the physical mechanism of material removal, the sidewalls of the drilled opening structure typically form a certain taper. This taper angle θ is an inherent parameter when drilling the first interconnect structure with an ultrashort pulse laser. It refers to the angle of inclination of the hole wall relative to the vertical direction, which can be obtained through experimental calibration or theoretical calculation. When the laser beam processes with the first drilling diameter, the sidewalls of the opening structure contract inward along the depth direction, and the amount of contraction is determined by the taper angle and the processing depth.

[0071] Specifically, the thickness of the known pad structure is The thickness of the conductive coating is The taper angle is θ, and the predetermined width is... Characterizes the difference between the diameter of the first borehole and the inner diameter of the borehole structure. Predetermined width. for and Twice the sum. Considering the extreme case, when the sidewall of the open structure just passes through the inflection point O where the pad structure connects to the conductive plating, Corresponding to the predetermined width The limit value is If the predetermined width Exceeding this limit, the sidewall of the opening structure may penetrate the connection point between the pad structure and the conductive plating layer (i.e., the inner corner area where the conductive plating layer and the pad structure meet), causing damage to this connection point and affecting the integrity of the first interconnect structure. Therefore, to ensure that the contraction of the sidewall of the opening structure in the depth direction does not reach the connection point between the pad structure and the conductive plating layer, it is necessary to set... This ensures that the sidewalls of the opening structure are within a safe area and do not damage the critical connection parts of the first interconnection structure.

[0072] In one embodiment, reference can continue. Figure 5 In (b), the above method further includes adjusting the thickness of the conductive coating. Thickness of the pad structure The predetermined depth is determined by the taper angle θ. , to the predetermined depth satisfy: Therefore, by determining the predetermined depth constraint relationship based on the conductive plating thickness, pad structure thickness, and taper angle, the depth of the opening structure is ensured not to exceed the safety threshold, thereby avoiding damage to the conductive plating during processing and guaranteeing interconnect reliability.

[0073] It should be noted that, in addition to the predetermined width In addition to imposing constraints, it is also necessary to define the predetermined depth. Constraints are applied to ensure that the conductive coating is not damaged during laser processing.

[0074] Specifically, when the laser processes at the first drilling depth, the sidewalls of the opening structure contract inward along the depth direction. The thickness of the conductive plating is known to be... The taper angle is θ, and the predetermined depth is... This characterizes the depth to which laser processing penetrates the plugging material. When the sidewall of the opening structure extends downwards at a taper angle θ, its horizontal shrinkage increases with depth. Considering the extreme case where the sidewall of the opening structure just passes through the connection point O between the pad structure and the conductive plating, the horizontal shrinkage of the sidewall is exactly equal to the thickness of the conductive plating. At this point, the processing depth satisfy If the predetermined depth Exceeding this limit, the sidewalls of the opening structure may cut into the inner side of the conductive coating, causing penetration or damage to the conductive coating and affecting the conductivity of the hole structure. Therefore, to ensure that the contraction of the sidewalls of the opening structure in the depth direction does not reach the inner sidewall of the conductive coating, a predetermined depth needs to be ensured. This ensures that the bottom of the opening structure is within a safe depth range, preventing damage to the conductive plating and thus protecting the electrical connectivity of the first interconnect structure.

[0075] In one embodiment, the drilling process further includes at least one of the following features: controlling a flat-top beam to perform a second laser processing on the first interconnect structure with a second drilling diameter and a second drilling depth, wherein the second drilling diameter is smaller than the projected size of the interconnect pad, and the second drilling depth is smaller than the thickness of the pad structure; controlling the flat-top beam to perform a third laser processing on the first interconnect structure with a third drilling diameter and a third drilling depth, wherein the third drilling diameter is equal to the inner diameter of the hole structure, and the cumulative depth of the third drilling depth and a predetermined depth L is less than or equal to 30 μm. Thus, by using the second or third laser processing to pre-process or compensate for the pad structure, the sidewall and bottom morphology of the opening structure are optimized, further improving processing accuracy and interconnect quality.

[0076] It should be noted that, in addition to the first laser processing, a second and / or third laser processing can be added according to actual processing needs to further optimize the morphology and processing accuracy of the opening structure. The second laser processing uses a second drilling diameter and a second drilling depth to pre-process or compensate for the first interconnect pad structure. The second drilling diameter is smaller than the projected size of the interconnect pad, meaning the processing area is smaller than the overall range of the interconnect pad; the second drilling depth is smaller than the thickness of the pad structure, meaning the processing only affects a portion of the pad structure's thickness and does not penetrate the pad structure. The second laser processing, based on penetration of the pad structure, can work in conjunction with the first laser to increase the total opening size of the opening structure, further improving the interconnect reliability of the first and second interconnect structures.

[0077] In addition, the third laser processing uses a third drilling diameter and a third drilling depth to compensate for the pad structure. The third drilling diameter is equal to the inner diameter of the hole structure, meaning the processing area matches the cross-sectional area of ​​the plugging material. The cumulative depth of the third drilling depth and the predetermined depth L is less than or equal to 30 μm. The third laser processing can be performed after the first laser processing to trim the edges or bottom of the opening structure, removing any residual burrs or protrusions, and further improving the sidewall and bottom morphology of the opening structure. Through the third laser processing, the sidewalls of the opening structure can be made smoother and the bottom flatter, thereby improving the quality of subsequent electroplating and interconnect reliability.

[0078] In practical applications, a second laser processing, a third laser processing, or both can be performed simultaneously, depending on the processing requirements. This application does not impose any restrictions on this.

[0079] In one embodiment, before controlling the flat-top beam to perform the first laser processing with a first drilling diameter and a first drilling depth, the processing mode of the flat-top beam is determined based on the first drilling diameter and the focused spot size of the flat-top beam. This includes: if the first drilling diameter is less than or equal to the maximum value of the focused spot size, the processing mode is laser punching, and the processing spot size of the focused spot is equal to the first drilling diameter; if the first drilling diameter is greater than the maximum value of the focused spot size, the processing mode is laser winding processing or a combination of laser winding processing and laser punching, and the projected cross-section size of the laser winding processing or the combined laser winding processing and laser punching is equal to the first drilling diameter. Therefore, by selecting the laser punching or winding processing mode based on the comparison between the first drilling diameter and the focused spot size of the flat-top beam, the processing accuracy can be guaranteed while adapting to the requirements of opening structures of different sizes, thereby improving process compatibility and processing efficiency.

[0080] It should be noted that the choice of laser processing method depends on the relative relationship between the first borehole diameter and the maximum value of the focused spot size of the flat-top beam. After shaping and focusing, the focused spot size emitted towards the sub-circuit board can be adjusted according to the design of the optical system. In practical applications, the first borehole diameter can be calculated based on the inner diameter of the hole structure and the predetermined width M, while the focused spot size is an inherent parameter of the laser processing equipment or an adjustable parameter within a fixed range. To adapt to the processing requirements of opening structures of different sizes, this embodiment provides differentiated laser processing strategies.

[0081] When the diameter of the first drilled hole is less than or equal to the maximum value of the focused spot size of the flat-top beam, laser punching can be used to process the opening structure. Laser punching refers to aiming the laser beam at the center of the target location and removing material at a single spot location by emitting a certain number of laser pulses, thus forming the opening structure. Since the focused spot size is large enough to cover the entire diameter range of the first drilled hole, a single punching operation can remove both the conductive material of the pad structure and the plugging material within the target area, forming the desired opening structure. Punching is a highly efficient method with relatively simple alignment requirements, making it suitable for batch processing of small-sized opening structures.

[0082] When the diameter of the first borehole exceeds the maximum focusing spot size of the flat-top beam, a single spot cannot cover the entire target area, necessitating a scanning process. Specifically, a laser-guided cutting method can be used, where the laser beam is controlled to move along a concentric circle or spiral trajectory to gradually remove material within the target area, forming an opening structure of the required size and shape. Alternatively, a combination of cutting and punching can be employed. For example, punching can be used to remove most of the material in the central area, followed by cutting to refine the edges, improving processing efficiency and ensuring the accuracy of the opening structure's morphology. In the cutting process, the scanning range of the laser beam determines the projected cross-section of the processing area, which is equal to the diameter of the first borehole. By appropriately setting the scanning trajectory and overlap rate, the opening size and bottom morphology of the opening structure can be precisely controlled, meeting the processing requirements of large-sized opening structures.

[0083] In one feasible embodiment, the ultrashort pulse laser beam is an ultrafast laser beam, and the focused spot size of the corresponding flat-top beam is in the range of 10 micrometers to 85 micrometers. When the inner diameter of the hole structure is less than or equal to 85 micrometers, the size of the focused spot can be adjusted to match the inner diameter of the hole structure, and the opening structure can be processed by laser punching. When the inner diameter of the hole structure is greater than 85 micrometers, a suitable size of focused spot can be selected, and the opening structure can be processed by laser winding or by a combination of laser winding and laser punching.

[0084] In one embodiment, the ultrafast laser beam used in laser processing is an ultrafast laser with a pulse width less than or equal to the picosecond level. The wavelength of the ultrafast laser can be ultraviolet light in the 340nm to 360nm band, green light in the 500nm to 540nm band, or infrared light in the 1000nm to 1100nm band. Ultrafast lasers include picosecond lasers (pulse width at the picosecond level) and femtosecond lasers (pulse width at the femtosecond level). The selection of ultrafast laser processing for opening structures is based on the following considerations: compared to nanosecond lasers, ultrafast lasers have a higher proportion of "cold processing" in the substrate removal process, which helps to further reduce the impact of heat accumulation during the processing of opening structures.

[0085] Furthermore, the ultrafast laser used in laser processing is a green picosecond laser with a wavelength in the 500nm to 540nm range. On one hand, the maximum focused spot size achievable by laser beams of different wavelengths is inversely proportional to the wavelength. Green ultrafast lasers can provide a larger focused spot size compared to ultraviolet ultrafast lasers, improving the processing efficiency of the opening structure. On the other hand, although infrared ultrafast lasers can provide a larger focused spot size than green ultrafast lasers, their beam energy density and peak energy are much higher. This can easily lead to over-processing of the connection points between the pad structure and the conductive plating during the processing of the opening structure, damaging the interconnect integrity of the first interconnect structure. Selecting a green picosecond laser with a wavelength in the 500nm to 540nm range for processing the opening structure balances processing efficiency and quality.

[0086] In this embodiment, the process of fabricating an opening structure at the end of the first interconnect structure is completed through the above-described embodiments. The morphology, size, and fabrication method of this opening structure are carefully designed to create an optimized interconnect interface between the first and second interconnect structures. The following will describe in detail how the second interconnect structure is formed based on this opening structure in conjunction with subsequent steps.

[0087] Step 104: A second interconnect structure is formed on the outside of the sub-circuit board, wherein the end of the second interconnect structure is filled with an opening structure and communicates with the first interconnect structure.

[0088] Among them, one can refer to, for example Figure 6 The diagram shows a structural schematic of a second interconnection structure, as follows: Figure 6As shown, the second interconnect structure 60 refers to a conductive structure formed on the surface of the sub-circuit board through a layer-addition process, used to connect the newly added circuit layer with the existing first interconnect structure 40. The end of the second interconnect structure 60 facing the sub-circuit board is filled into the opening structure formed in step 103, creating an interconnect interface with reliable electrical and mechanical connections between the second interconnect structure 60 and the first interconnect structure 40. Through this step, the previously prepared opening structure is integrated with the newly added circuit layer, enabling signals to be transmitted from the signal transmission circuit layer inside the sub-circuit board to the newly added circuit layer, achieving interlayer interconnection of the multilayer circuit board. The final cross-section of the processed sub-circuit board is shown in the figure. Figure 7 As shown, the second interconnect structure 60 includes a plurality of conductive blind via structures 601 continuously stacked along the longitudinal direction.

[0089] In one embodiment, forming a second interconnect structure on the outer side of a sub-circuit board may include the following steps: metallizing the opening structure, the metallization process including copper plating and electroplating, to form an end interconnect structure filling the opening structure on the sub-circuit board, such as... Figure 7 As shown in 602. Thus, by performing copper plating and electroplating metallization on the opening structure, an end interconnect structure that fills the opening structure is formed. Through the interconnect interface formed by the end interconnect structure of the second interconnect structure and the interconnect pads of the first interconnect structure, the electrical and mechanical connection between the second interconnect structure and the first interconnect structure is realized.

[0090] It should be noted that the metallization process can include two steps: chemical copper plating and electroplating. First, a thin layer of copper is deposited on the inner wall of the opening structure (including the bottom and side walls of the opening structure) and the surface of the pad structure using a chemical copper plating process. Then, this copper layer is thickened using an electroplating process to form a conductive layer that completely fills the opening structure and extends to a predetermined thickness along the outer surface of the pad structure. The end interconnect structure of the second interconnect structure can be formed by patterning this conductive layer. The thickness of the end interconnect structure at the corresponding via material location is greater than the thickness at the corresponding pad structure location. Due to the special design of the opening structure, the end interconnect structure of the second interconnect structure forms an anchoring effect within the opening structure, enhancing the bonding force with the first interconnect structure. At the same time, the thickness of the end interconnect structure at the via material location is greater than the thickness at the corresponding pad structure location. This reduces the thermal stress of the via material on the end interconnect structure by reducing the volume of the via material, and also reduces the deformation of the end interconnect structure after being affected by thermal stress.

[0091] In one embodiment, such as Figure 7As shown, the hole structure is an electroplated through-hole penetrating the sub-circuit board, and the second interconnect structure includes multiple conductive blind via structures 601 continuously stacked longitudinally. The conductive blind via structure is obtained by processing blind vias in the newly added circuit layer and then metallizing them. Specifically, through-hole structures penetrating the upper and lower surfaces of the sub-circuit board can be processed using a drilling process. These through-hole structures are then metallized and plugged to form electroplated through-holes, thus forming a sub-circuit board with an electroplated through-hole structure. Both the upper and lower surfaces of the sub-circuit board have pad structures 402 connecting the electroplated through-holes. Opening structures can be processed on the pad structures located on the upper and lower surfaces of the sub-circuit board using an ultrashort pulse laser beam. Through repeated layer-adding processes, multiple conductive blind via structures 601 can be sequentially stacked on the opening structures at both ends of the first interconnect structure. Each conductive blind via structure 601 is electrically connected to its adjacent sub-interconnect structure, forming a longitudinally stacked interconnect channel. This stacking structure can significantly improve the wiring density of the circuit board, meeting the requirements of high-density interconnection. Because the sub-interconnect structure formed within the opening structure in this application has excellent bonding strength and electrical reliability, it can support the stacking of more layers of blind vias.

[0092] In this embodiment, the fabrication of the second interconnect structure was completed through the above-described embodiments. This second interconnect structure includes an end interconnect structure with a filled opening and a conductive blind via structure formed on top of it (one or more conductive blind via structures can be provided depending on actual needs). The end interconnect structure forms a reliable electrical and mechanical connection with the conductive plating layer and plugging material of the first interconnect structure, thereby achieving interconnection between the newly added circuit layer and the internal circuit layers of the sub-circuit board. It should be noted that in actual production, steps 103 and 104 can be repeated on one or both sides of the sub-circuit board according to design requirements, adding layers sequentially to form a multilayer board with more layers. Each time a layer is added, the method provided in this application can be used to process an opening structure at the corresponding location to enhance the reliability of interlayer interconnection.

[0093] The interconnect structure processing method disclosed in the above embodiments of this application uses an ultrashort pulse laser beam to drill holes at the end positions, forming an opening structure with a longitudinally decreasing opening size and a bottom size the same as the inner diameter of the hole structure. This allows the end interconnect structure of the second interconnect structure to fill the opening structure on the first interconnect structure. The thickness of the end interconnect structure of the second interconnect structure at the plugging material position is greater than the thickness at the pad structure position. This reduces the thermal stress on the end interconnect structure by reducing the volume of the plugging material, reduces the deformation of the end interconnect structure after being affected by thermal stress, and enhances the bonding strength between the first and second interconnect structures at the interconnect interface. This effectively suppresses the cracking at the interconnect interface position of the interconnect structure caused by thermal stress, and improves the service life and performance reliability of the interconnect structure in the circuit board.

[0094] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because based on this application, some steps can be performed in other orders.

[0095] Figure 8 This is a schematic diagram of the controller provided in an embodiment of this application. Figure 8 As shown, the controller 800 of this embodiment includes: at least one processor 810 ( Figure 8 The diagram shows only one processor, a memory 820, and a computer program 821 stored in the memory 820 and executable on the at least one processor 810. When the processor 810 executes the computer program 821, it implements the steps in the processing method embodiment of the above interconnect structure.

[0096] The controller 800 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller may include, but is not limited to, a processor 810 and a memory 820. Those skilled in the art will understand that... Figure 8 This is merely an example of controller 800 and does not constitute a limitation on controller 800. It may include more or fewer components than shown, or combine certain components, or different components, such as input / output devices, network access devices, etc.

[0097] The processor 810 may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0098] In some embodiments, the memory 820 may be an internal storage unit of the controller 800, such as a hard disk or memory of the controller 800. In other embodiments, the memory 820 may be an external storage device of the controller 800, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the controller 800. Furthermore, the memory 820 may include both internal storage units and external storage devices of the controller 800. The memory 820 is used to store operating systems, applications, boot loaders, data, and other programs, such as the program code of computer programs. The memory 820 can also be used to temporarily store data that has been output or will be output.

[0099] It should be noted that, for the sake of convenience and brevity, the structure of the controller described above can also be referred to the specific description of the structure in the method embodiment, which will not be repeated here.

[0100] Specifically, Figure 9 This application illustrates a laser processing apparatus, comprising: A laser used to emit ultrashort pulse laser beams; A beam control device is used to transmit, control, and deflect an ultrashort pulse laser beam. The beam control device includes a beam shaping mechanism and a beam deflection mechanism. The beam shaping mechanism is used to control the ultrashort pulse laser beam into a flat-top beam with a flat-top energy distribution. The beam deflection mechanism is used to control the flat-top beam to perform laser processing according to the laser processing path. The processing platform is used to support the sub-circuit boards; The controller is used to control the coordinated operation of the aforementioned laser, beam control device, and processing platform to achieve, for example... Figures 2 to 7 The fabrication method of the interconnect structure.

[0101] In some embodiments of this application, the laser can be an ultrashort pulse laser, such as a nanosecond laser, picosecond laser, femtosecond laser, or other types of lasers, and this application does not limit this. A laser capable of providing suitable laser pulse wavelength, pulse width, and pulse frequency can be selected according to processing requirements. The power, spot size, and number of pulses of the laser beam emitted by the laser can all be set according to processing requirements.

[0102] In some embodiments of this application, the beam control device, in addition to the beam deflection mechanism, may also include, but is not limited to, beam adjustment components (e.g., apertures, beam expanders, or beam shrinkers) and focusing lenses. The beam adjustment components can be used to adjust the size and shape of the vertical cross-section of the laser beam along the beam transmission direction. The focusing lens can be used to adjust the focal length, thereby affecting the energy density distribution of the laser spot formed by the laser beam at the processing position of the workpiece. The various components within the beam control device cooperate to transmit, control, and deflect the laser beam, forming a laser spot with specific parameters to process the signal transmission substrate.

[0103] A beam deflection mechanism may include one or any combination of a galvanometer, a rotating mirror, an acousto-optic modulator (AOM), an acousto-optic deflector (AOD), an electro-optic modulator (EOM), an electro-optic deflector (EOD), a liquid crystal variable attenuator (LCVA), a micro-electro-mechanical systems (MEMS) based variable optical attenuator (VOA), and an optical attenuator wheel. Among these, the galvanometer and rotating mirror are beam deflection components controlled by mechanical motion, and their beam deflection control inevitably involves acceleration and deceleration during the start and end times of beam deflection. The AOM and AOD, on the other hand, are beam deflection components controlled by electrical signals, allowing for rapid, abrupt adjustments to the beam deflection process through parameter adjustments of the control information.

[0104] This application embodiment also provides a circuit board, which includes a first interconnect structure and a second interconnect structure, wherein the first interconnect structure and the second interconnect structure are based on... Figures 2 to 7 The described interconnect structure fabrication method or such Figure 9 It is produced by laser processing equipment.

[0105] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0106] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0107] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0108] In the embodiments provided in this application, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0111] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0112] The implementation of all or part of the processes in the methods of the above embodiments can also be accomplished by a computer program product. When the computer program product is run on a controller, the controller can implement the steps in the various method embodiments described above.

[0113] The embodiments described above are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for fabricating an interconnect structure, characterized in that, include: A sub-circuit board is provided with a first interconnect structure, the first interconnect structure including a hole structure and a pad structure, the inner wall of the hole structure is covered with a conductive plating layer, the pad structure is located outside the hole opening of the hole structure and communicates with the conductive plating layer, and the interior of the first interconnect structure is filled with a plugging material. Obtain manufacturing information of the first interconnect structure, including the end position of the first interconnect structure, the thickness of the pad structure, and the inner diameter of the hole structure; A short pulse laser beam is used to drill holes at the end position, removing part of the conductive material at the connection between the pad structure and the conductive plating layer, as well as the plugging material within the drilling depth range, to form an opening structure at the end position. The opening size and bottom size of the opening structure decrease longitudinally, and the bottom size is the same as the inner diameter of the hole structure. A second interconnect structure is formed on the outside of the sub-circuit board, wherein the end of the second interconnect structure fills the opening structure and communicates with the first interconnect structure.

2. The method according to claim 1, characterized in that, The drilling process includes: The first borehole diameter and the first borehole depth are determined based on the manufacturing information, wherein the first borehole diameter is a predetermined width larger than the inner diameter of the hole structure. The first drilling depth is a predetermined depth greater than the thickness of the pad structure. ; The ultrashort pulse laser beam is modulated into a flat-top beam with a flat-top energy distribution, and the flat-top beam is controlled to perform the first laser processing with the first borehole diameter and the first borehole depth.

3. The method according to claim 2, characterized in that, The predetermined width M and the predetermined depth L satisfy at least one of the following characteristics: The predetermined width M is 10% to 30% of the inner diameter of the hole structure; The predetermined depth L is 5 μm to 30 μm.

4. The method according to claim 3, characterized in that, The manufacturing information also includes the thickness of the conductive plating layer. ; Before determining the first borehole diameter and the first borehole depth based on the manufacturing information, the method further includes obtaining the taper angle θ of the ultrashort pulse laser for drilling the first interconnect structure. According to the thickness of the conductive coating The thickness of the pad structure The predetermined width is determined by the taper angle θ. , so that the predetermined width satisfy: .

5. The method according to claim 4, characterized in that, It also includes, based on the thickness of the conductive coating The thickness of the pad structure The predetermined depth is determined by the taper angle θ. , so that the predetermined depth satisfy: .

6. The method according to any one of claims 2-4, characterized in that, The drilling process also includes at least one of the following features: The flat-top beam is controlled to perform a second laser processing on the first interconnect structure with a second drilling diameter and a second drilling depth, wherein the second drilling diameter is smaller than the projected size of the interconnect pad and the second drilling depth is smaller than the thickness of the pad structure. The flat-top beam is controlled to perform a third laser processing on the first interconnect structure with a third drilling diameter and a third drilling depth. The third drilling diameter is equal to the inner diameter of the hole structure, and the cumulative depth of the third drilling depth and the predetermined depth L is less than or equal to 30 μm.

7. The method according to any one of claims 2-4, characterized in that, Before controlling the flat-top beam to perform the first laser processing with the first borehole diameter and the first borehole depth, the processing mode of the flat-top beam is determined based on the first borehole diameter and the focused spot size of the flat-top beam, including: When the diameter of the first drill hole is less than or equal to the maximum value of the focused spot size, the processing mode is laser punching, and the processing spot size of the focused spot is equal to the diameter of the first drill hole; When the diameter of the first borehole is greater than the maximum value of the focused spot size, the processing mode is laser winding processing or a combination of laser winding processing and laser punching processing, and the projected cross-section of the laser winding processing or the combined laser winding processing and laser punching processing is equal to the diameter of the first borehole.

8. The method according to any one of claims 1-4, characterized in that, The formation of the second interconnect structure on the outer side of the sub-circuit board includes: The opening structure is metallized, including copper plating and electroplating, to form an end interconnect structure that fills the opening structure on the sub-circuit board.

9. The method according to any one of claims 1-4, characterized in that, The hole structure is an electroplated through-hole that penetrates the sub-circuit board, and the second interconnect structure includes a plurality of conductive blind via structures continuously stacked in the longitudinal direction.

10. The method according to any one of claims 1-4, characterized in that, The pad structure is an interconnect pad or a pre-fabricated interconnect pad circuit.

11. The method according to any one of claims 1-4, characterized in that, The ultrashort pulse laser beam is an ultrafast laser with a pulse width less than or equal to the picosecond level, and the wavelength of the ultrafast laser includes ultraviolet light in the 340nm to 360nm band, green light in the 500nm to 540nm band, and infrared light in the 1000nm to 1100nm band.

12. The method according to claim 11, characterized in that, The ultrafast laser is a green picosecond laser with a wavelength in the range of 500nm to 540nm.

13. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the processing method for the interconnect structure as described in any one of claims 1 to 12.

14. A laser processing device, characterized in that, include: A laser used to emit ultrashort pulse laser beams; A beam control device is used to transmit, control, and deflect the ultrashort pulse laser beam. The beam control device includes a beam shaping mechanism and a beam deflection mechanism. The beam shaping mechanism is used to control the ultrashort pulse laser beam into a flat-top beam with a flat-top energy distribution. The beam deflection mechanism is used to control the flat-top beam to perform laser processing according to the laser processing path. The processing platform is used to support the sub-circuit boards; A controller is used to control the laser, the beam control device, and the processing platform to work together to realize the processing method of the interconnected structure as described in any one of claims 1 to 12.

15. A circuit board, characterized in that, The circuit board includes a first interconnect structure and a second interconnect structure, which are obtained by the processing method of the interconnect structure according to any one of claims 1 to 12 or by processing based on the laser processing equipment according to claim 14.

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