HDI plate with cross-layer laser holes and preparation method thereof

Abstract

The embodiment of the invention discloses an HDI plate with cross-layer laser holes and a preparation method of the HDI plate. The preparation method of the HDI board comprises the following steps: laminating a plurality of circuit boards provided with first positioning marks with different sizes, preliminarily aligning and pressing, determining the alignment state of the first positioning marks through transmission detection equipment, determining the position of a target blind hole according to second positioning marks, windowing, and performing laser drilling to form a cross-layer laser hole. And forming a metal layer on the inner wall of the hole, and filling and leveling up the hole. According to the embodiment of the invention, the number of pressing times and the number of punching times in the HDI plate processing process are reduced, the problems of expansion and shrinkage changes and dislocation caused by multiple pressing times are effectively improved, the product yield is improved, and the production and processing period is remarkably shortened.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of circuit boards, and in particular to an HDI board with cross-layer laser holes and a preparation method thereof. Background Art

[0002] With the rapid development of various technologies in the fields of communications and electronics, the development and launch of high-intelligence products, PCB layout (PCB Layout, PCB L) is also developing towards high-density and high-interconnection. New products are constantly turning to high-density interconnect (High Density Interconnect, HDI) design. The requirements for aperture and stacking are constantly increasing, resulting in the need for a technology that can reduce the number of press-fits and thus reduce costs.

[0003] The current normal method of laser hole processing for multi-stage HDI boards is generally to press and overlap laser holes for multiple times to meet the purpose of connecting each layer. This solution is difficult to control the laser hole yield due to the influence of overlapping riveting techniques and laser hole alignment methods during multiple pressing processes, and it is difficult to meet the production and manufacturing of high-density PCB design solutions. Summary of the invention

[0004] The present invention provides an HDI board with cross-layer laser holes and a preparation method thereof, so as to solve the problem that the laser hole yield is difficult to control due to the influence of the overlapping riveting technique and the laser hole alignment method during multiple pressing processes.

[0005] In a first aspect, an embodiment of the present invention provides an HDI board with cross-layer laser holes, comprising:

[0006] A plurality of circuit boards are stacked, preliminarily aligned and pressed together; the circuit boards include a substrate and metal foils located on two sides of the substrate facing away from each other, and first positioning marks of different sizes are arranged at the same position of the metal foils of different circuit boards; a second positioning mark is also arranged on the outermost metal foil; the relative positions of the projections of the first positioning marks on each circuit board along the thickness direction are aligned; a cross-layer laser hole penetrates from the outermost metal foil to the metal foil of the target layer in sequence, and there is at least one layer of metal foil between the metal foil of the target layer and the metal foil of the outermost layer; the inner wall of the cross-layer laser hole is formed by a metal layer, and the metal layer is respectively connected to the metal foils of the outermost layer and the target layer; the cross-layer laser hole is filled with a filler.

[0007] Optionally, the circuit boards are stacked in sequence in the order that the size of the first positioning mark gradually increases or decreases.

[0008] Optionally, the projections of the first positioning marks on each circuit board along the thickness direction are in a sequentially annular state.

[0009] Optionally, the filling in the cross-layer laser hole is flush with the surface of the outermost metal foil.

[0010] Optionally, the metal layer is located outside the outermost metal foil and covers the cross-layer laser holes.

[0011] In a second aspect, an embodiment of the present invention further provides a method for preparing an HDI board having cross-layer laser holes, comprising:

[0012] Stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated; wherein the circuit board comprises a substrate and metal foils located on two sides of the substrate facing away from each other, and first positioning marks of different sizes are arranged at the same position of the metal foils of different circuit boards; and a second positioning mark is also arranged on the outermost metal foil;

[0013] Using a transmission detection device, checking the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state;

[0014] Determine the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil to obtain the target blind hole position;

[0015] Opening a window at a target blind hole position on the outermost metal foil to form a window opening area;

[0016] Laser drilling is performed in the window opening area until the metal foil of the target layer is reached to form a cross-layer laser hole; there is at least one layer of metal foil between the metal foil of the target layer and the outermost layer of metal foil;

[0017] forming a metal layer on the inner wall of the cross-layer laser hole to connect the metal foils of the outermost layer and the target layer respectively;

[0018] Fill the cross-layer laser holes.

[0019] Optionally, before stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated, the process includes: patterning the metal foil on each circuit board to form a corresponding target circuit.

[0020] Optionally, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated includes:

[0021] According to the order in which the size of the first positioning mark gradually increases or decreases, the plurality of circuit boards are stacked, preliminarily aligned and pressed together.

[0022] Optionally, using a transmission detection device to check the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state, includes:

[0023] By using a transmission detection device, when it is found that the projections of the first positioning marks on the circuit boards along the thickness direction are in a sequentially ring-shaped state, it is determined that the first positioning marks are in an aligned state.

[0024] Optionally, determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil to obtain the target blind hole position includes:

[0025] Detecting the expansion and contraction ratio of the metal foil before and after lamination;

[0026] Determining a theoretical position of a target blind hole on the outermost layer of the metal foil according to a second positioning mark on the outermost layer of the metal foil;

[0027] According to the theoretical position of the target blind hole on the outermost metal foil and the expansion / contraction ratio, the actual position of the target blind hole on the outermost metal foil is determined.

[0028] Optionally, before laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole, the method further includes:

[0029] Determining laser drilling target manufacturing conditions according to at least one of the size parameters of the target blind hole, the metal foil, and the substrate and the materials of the metal foil and the substrate;

[0030] Laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole, including:

[0031] According to the laser drilling target manufacturing conditions, laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0032] Optionally, before forming a metal layer on the inner wall of the cross-layer laser hole to respectively connect the metal foils of the outermost layer and the target layer, the method further includes:

[0033] Automatic optical detection equipment is used to detect and determine whether the cross-layer laser holes meet the target conditions.

[0034] Optionally, after the cross-layer laser holes are filled, the method further includes:

[0035] Detecting the filling flatness of the cross-layer laser holes;

[0036] When the filling in the cross-layer laser hole is concave or convex, the cross-layer laser hole is corrected to make the filling in the cross-layer laser hole flush with the surface of the outermost metal foil.

[0037] Optionally, after the cross-layer laser holes are filled, the method further includes:

[0038] A metal layer is formed on the outer side of the outermost metal foil to cover the cross-layer laser hole.

[0039] The present invention provides an HDI board with a cross-layer laser hole and a preparation method thereof. The preparation method comprises stacking, preliminarily aligning and pressing a plurality of circuit boards provided with first positioning marks of different sizes, using a transmission detection device to determine the alignment state of the first positioning mark, and then determining the position of the target blind hole according to the second positioning mark and opening a window, so as to achieve accurate alignment of the circuit board, improve the expansion and contraction changes and misalignment problems caused by multiple pressing, complete the cross-layer laser hole by one-time laser drilling, then form a metal layer on the inner wall of the hole, and finally fill the hole, so as to ensure the reliability of the cross-layer electrical connection, simplify the process flow, improve the product yield, and significantly shorten the production and processing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A flow chart of a method for preparing an HDI board with cross-layer laser holes provided in an embodiment of the present invention;

[0042] Figure 2 for Figure 1 The structural flow chart of the method for preparing the patterned composite substrate is shown;

[0043] Figure 3 A schematic diagram of the structure of an HDI board with cross-layer laser holes provided by an embodiment of the present invention;

[0044] Figure 4 for Figure 3 A schematic diagram of the structural longitudinal section of the HDI board shown;

[0045] Figure 5 A flow chart of another method for preparing an HDI board with cross-layer laser holes provided by an embodiment of the present invention;

[0046] Figure 6 A flow chart of a method for preparing another HDI board with cross-layer laser holes provided in an embodiment of the present invention;

[0047] Figure 7 A flow chart of a method for preparing another HDI board with cross-layer laser holes provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0049] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the directional words such as "upper", "lower", "left", "right" and the like described in the embodiments of the present invention are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present invention. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes and do not represent any order, quantity or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0050] The term “including” and its variations used in the present invention are open inclusions, that is, “including but not limited to.” The term “based on” means “based at least in part on.” The term “one embodiment” means “at least one embodiment.”

[0051] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or interdependence.

[0052] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0053] Figure 1 A flow chart of a method for preparing an HDI board with cross-layer laser holes provided in an embodiment of the present invention, Figure 2 for Figure 1 The structural flow chart of the method for preparing a graphical composite substrate is shown in FIG. Figure 3 A schematic diagram of the structure of an HDI board with cross-layer laser holes provided by an embodiment of the present invention, Figure 4 for Figure 3 The structural longitudinal section diagram of the HDI board shown in the figure is shown in the figure. Figure 1-Figure 4 The method for preparing the HDI board with cross-layer laser holes includes:

[0054] S110, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated; wherein the circuit board comprises a substrate and metal foils located on two sides of the substrate facing away from each other, and first positioning marks of different sizes are arranged at the same position of the metal foils of different circuit boards; and a second positioning mark is also arranged on the outermost metal foil;

[0055] Specifically, refer to Figure 2 a) Figure, Figure 6 and Figure 7 Each circuit board 10 is composed of a substrate and metal foils 11 covering both sides. In accordance with the stacking order, the circuit boards 10a, 10b, 10c, 10d, ... 10x are sequentially included. The same position of the metal foils 11 of different circuit boards 10 is provided with first positioning marks 12 of different sizes, such as Figure 6 As shown, the circuit boards 10a, 10b, 10c, 10d, ... 10x correspond to each other, namely 12a, 12b, 12c, 12d, ... 12x, respectively. The first positioning mark 12 can be of any size and shape. For example, the first positioning mark 12 can be a triangle, a rectangle, a cross, etc.; the metal foil 11 can be copper or other metals that can achieve the conductive function, which is not limited in the embodiment of the present invention; the second positioning mark 13 set on the outermost metal foil 11 can be consistent with the first positioning mark 12 in terms of position, size, shape, etc., or different, and the second positioning mark 13 can be one or more;

[0056] Exemplarily, multiple circuit boards to be laminated are stacked in a predetermined order, and after preliminary alignment to ensure the relative position of each layer is correct, hand rivet holes are punched out and manual stacking and riveting are performed to ensure the accuracy of the pattern and the pressing accuracy. In this step, the metal foil of each layer of the circuit board is provided with first positioning marks of different sizes, which help to achieve accurate alignment during the stacking process.

[0057] S120, using a transmission detection device to check the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state.

[0058] The transmission detection device here may be an X-ray detector, which can non-destructively check the inner layer structure to determine whether the first positioning mark 12 is in an aligned state.

[0059] Specifically, refer to Figure 3This step utilizes the penetrability of X-rays and the absorption characteristics of materials to detect the intensity of reflected or transmitted X-rays and generate a digital image of the circuit board. When using the transmission detection equipment to confirm the alignment status, it is by observing the projection of the first positioning mark 12 along the thickness direction, such as: 12b, 12c, and ensuring that these projections are located in the same area in the vertical direction, thereby ensuring that each layer of the circuit board is highly aligned.

[0060] S130, determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil, and obtaining the target blind hole position.

[0061] Among them, the position of the blind hole can be determined based on the second positioning mark 13 only, or it can be positioned together with the first positioning mark 12; the blind hole can be understood as a hole that penetrates part of the substrate but not completely through, which is used to achieve connectivity between the inner layer and the outer layer, and the target blind hole refers to a blind hole that connects the outer layer circuit with the target inner layer circuit.

[0062] Specifically, refer to Figure 3 When determining the position of the target blind hole, the second positioning mark 13 on the outermost metal foil 11 may be used in combination with the first positioning mark 12 to accurately locate the starting position of the blind hole. This is because the position of the target blind hole relative to the second positioning mark 13 is usually marked in the engineering file. When the second positioning mark 13 is determined, the position of the target blind hole can be determined based on the relative positions of the two in the engineering file.

[0063] For example, assuming that the engineering document specifies that the target blind hole is located 5 mm to the left of the second positioning mark, after finding the second positioning mark, the position of the target blind hole can be determined by measuring 5 mm to the left.

[0064] S140, opening a window at a target blind hole position on the outermost metal foil to form a window opening area.

[0065] Here, windowing can be understood as forming an opening on the metal foil leading to the substrate to facilitate subsequent laser drilling.

[0066] Specifically, refer to Figure 2 As shown in FIG. b), a window opening operation is performed at a predetermined position of the outermost metal foil 11 to form a window opening area 14, which provides a necessary opening for subsequent laser drilling. The window opening operation can be achieved by laser cutting, mechanical drilling or chemical etching.

[0067] For example, by combining Conform coating technology with precision laser cutting, laser hole production on high-density HDI is achieved, ensuring the consistency of the window area with design requirements.

[0068] S150, laser drilling is performed in the window opening area until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0069] Among them, laser drilling can be understood as drilling holes in the window area using high-energy laser pulses.

[0070] Specifically, refer to Figure 2 As shown in Figure c), by controlling the high-energy laser pulse, the material in the window area 14 is gradually removed until the cross-layer laser hole 15 is formed. The advantage of this technology is that it can achieve high-precision cross-layer laser hole production while maintaining the verticality and smoothness of the hole wall, which is crucial for subsequent electroplating and metallization processes.

[0071] For example, a CO2 laser drilling machine may be used to perform this process. CO2 lasers are often used in the production of HDI boards due to their stable performance and suitability for processing a variety of materials.

[0072] S160, forming a metal layer on the inner wall of the cross-layer laser hole to respectively connect the metal foils of the outermost layer and the target layer.

[0073] The metal layer 16 may be copper or other conductive metals; the metal layer 16 may be formed by copper deposition, electroplating or other methods; the metal layer may completely fill the inner wall or only cover a layer.

[0074] Specifically, refer to Figure 2 d), the inner wall metal layer 16 of the cross-layer laser hole 15 is used to achieve electrical connection between the metal foil of the outermost layer and the target layer. In addition, before constructing the metal layer 16, the hole wall may need to be pre-treated, such as cleaning, decontamination, activation, etc., to ensure good adhesion between the metal layer 16 and the hole wall. After constructing the metal layer 16, tools such as automatic optical inspection equipment can be used to detect the quality and consistency of the metal layer 16 to ensure the reliability of the electrical connection.

[0075] S170, filling and leveling the cross-layer laser holes.

[0076] The filler may be metal or other materials, such as resin, polymer, etc.

[0077] Specifically, refer to Figure 2 e) Figure and Figure 4 The cross-layer laser holes 15 are filled and leveled, and the filler 17 used can be metal 17a or non-metallic material 17b such as resin. For laser holes 15 with different numbers of layers, the selected filling material 17 may also be different.

[0078] For example, in the embodiment of the present invention, metal filling is generally used for laser holes that span one layer, and resin filling is generally used for laser holes that span two layers or more. When the filler is a resin material, an automatic glue filling machine is used for filling, and then the resin is cured by ultraviolet light to ensure that the filler is flush with the surface of the metal foil.

[0079] It should be noted that the metal foil in the circuit board to be laminated in the above S110 is not a whole plane metal layer, but a metal foil that has been prepared into a corresponding circuit pattern. In view of this, before the above S110, the preparation method of this embodiment also includes:

[0080] S100, patterning the metal foil on each circuit board to form a corresponding target circuit.

[0081] The patterning process may include photolithography, etching, decontamination and washing to form the desired target circuit. The target circuit includes not only the target circuit, positioning marks, etc., but also test points, conductive patterns, etc.

[0082] Specifically, in the circuit board patterning process, a negative film is first made according to the circuit design drawing, and then the negative film is placed on the metal foil of the circuit board coated with photosensitive resist. After being exposed by an exposure machine, it is developed with a developer to remove the unexposed resist. Finally, the exposed metal part is etched with an etching solution to remove the excess metal and form a precise circuit pattern.

[0083] Exemplarily, in the manufacturing process of a four-layer circuit board, first, a negative film is made according to a pre-designed circuit pattern. The negative film is placed on the first layer of the circuit board copper foil coated with photosensitive resist and exposed for 30 seconds by an LDI exposure machine of a specific wavelength. Next, the exposed circuit board is placed in a developer and developed for 2 minutes at 25°C to remove the unexposed resist area. Finally, an etching solution with a concentration of 30% is used to etch the exposed metal part for 15 minutes, thereby forming a precise circuit pattern on the metal foil of the first layer of the circuit board. The patterning process of the second, third and fourth layers of the circuit board is completed in sequence according to the same steps.

[0084] Optionally, before S160, an automatic optical inspection device is used to inspect and determine whether the cross-layer laser drilling holes meet the target conditions.

[0085] Among them, the target conditions can be: whether the hole wall has defects such as discontinuity, holes, residues or foreign matter; the verticality and surface finish of the hole, etc.

[0086] Specifically, before the metal layer 16 is formed on the inner wall of the cross-layer laser hole 15, an automatic optical inspection device is used to perform a comprehensive inspection to ensure that the quality and consistency of each hole meet the manufacturing standards.

[0087] For example, the diameter, position, and depth of the cross-layer laser holes can be measured by an automated optical inspection device to ensure that they meet the design specifications. If any holes that do not meet the target conditions are detected, the automated optical inspection device will automatically mark these holes for subsequent repair or removal.

[0088] Optionally, after S170, the filling flatness of the cross-layer laser holes is detected;

[0089] S171. When there is a depression or protrusion in the filling in the cross-layer laser hole, the cross-layer laser hole is corrected so that the filling in the cross-layer laser hole is flush with the surface of the outermost metal foil.

[0090] Specifically, an automatic optical inspection device can be used to inspect the surface flatness of the filler 17. The automatic optical inspection device can quickly identify whether there are depressions or protrusions on the surface of the filler 17. If the filler is concave, additional filling material can be used to supplement it; if the filler is convex, it can be processed by grinding or polishing.

[0091] Optionally, after S170, it also includes:

[0092] S172, forming a metal layer on the outer side of the outermost metal foil to cover the cross-layer laser holes.

[0093] The metal layer may be copper or other suitable conductive materials, and may be the same material as the metal foil, or a different material may be selected for specific electrical or chemical properties.

[0094] Specifically, refer to Figure 2 f), if the outermost metal foil 11 is made of copper, then the formed metal layer 18 can be copper to ensure the consistency and conductivity of the electrical connection; if it is necessary to enhance wear resistance or oxidation resistance, a nickel layer or a gold layer can be formed on the outside of the cross-layer laser hole 15; if it is necessary to provide specific surface properties for subsequent welding or packaging processes, a tin layer or other solder layer may be further formed on the metal layer 18.

[0095] The above technical scheme achieves precise alignment of the circuit boards by stacking, preliminarily aligning and pressing a plurality of circuit boards provided with first positioning marks of different sizes, using transmission detection equipment to determine the alignment state of the first positioning mark, and then determining the position of the target blind hole and opening a window according to the second positioning mark, thereby improving the expansion and contraction changes and misalignment problems caused by multiple pressings, completing the cross-layer laser hole through one-time laser drilling, forming a metal layer on the inner wall of the hole, and finally filling the hole, thereby ensuring the reliability of the cross-layer electrical connection, simplifying the process flow, improving the product yield, and significantly shortening the production and processing cycle.

[0096] Figure 5 A flow chart of another method for preparing an HDI board with cross-layer laser holes provided in an embodiment of the present invention. Based on the above embodiment, this embodiment further specifies S110, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated as follows:

[0097] According to the order in which the size of the first positioning mark gradually increases or decreases, a plurality of circuit boards to be laminated are stacked, preliminarily aligned and pressed together;

[0098] By using the transmission detection equipment, when it is found that the projections of the first positioning marks on each circuit board along the thickness direction are in a sequentially ring-shaped state, it is determined that each first positioning mark is in an aligned state.

[0099] For details not yet provided in this embodiment, please refer to the previous embodiment.

[0100] like Figure 5 As shown, a method for preparing an HDI board with cross-layer laser holes provided by an embodiment of the present invention includes the following steps:

[0101] S210, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated in the order of gradually increasing or decreasing sizes of the first positioning marks.

[0102] Specifically, after obtaining the order of the sizes of the first positioning mark, it is necessary to accurately measure and align each layer of the circuit board, and arrange the stacking order of the HDI board according to the order of the sizes. Finally, after the alignment is completed, the hand rivet holes are punched out and the manual stacking and riveting operations are carried out to ensure the accuracy of the graphics and the pressing accuracy.

[0103] Exemplarily, the size of the first positioning mark increases gradually from top to bottom in the order of the layers. Then, when stacking, the largest positioning mark will be located at the bottom layer, and the smallest positioning mark will be located at the top layer.

[0104] S220, using a transmission detection device, when it is found that the projections of the first positioning marks on each circuit board along the thickness direction are in a sequentially ring-shaped state, determining that each first positioning mark is in an aligned state.

[0105] The sequentially encircled state may be understood as the positioning marks of each layer being arranged and projected in a certain fixed order. It should be noted that the fixed order should not be limited to from large to small or from small to large.

[0106] Specifically, on the projection image, the projection of the inner layer mark should be located at the center of the projection of the outer layer mark, forming a nested pattern. If the projection of the first positioning mark presents a regular ring shape, it indicates that the circuit boards have been accurately aligned in the predetermined order and position. This ring-shaped arrangement not only indicates physical alignment, but also helps to assist in judging the expansion and contraction ratio of each layer during the lamination process.

[0107] Exemplarily, image processing software may be used to assist in analyzing the transmission image, automatically detect and confirm the alignment status of the first positioning mark, reduce interference from human factors, and improve production efficiency and product quality.

[0108] S230, determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil, and obtaining the target blind hole position.

[0109] S240, opening a window at a target blind hole position on the outermost metal foil to form a window opening area.

[0110] S250, laser drilling is performed in the window opening area until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0111] S260, forming a metal layer on the inner wall of the cross-layer laser hole to respectively connect the metal foils of the outermost layer and the target layer.

[0112] S270, filling the cross-layer laser holes.

[0113] In an embodiment of the present invention, multiple circuit boards to be laminated are stacked, preliminarily aligned, and pressed together in the order in which the size of the first positioning mark gradually increases or decreases. The above method provides a clear order for the stacking of the circuit boards, avoids confusion in the stacking order, and thus reduces the alignment deviation caused by the wrong order. Using a transmission detection device, when it is found that the projection of the first positioning mark on each circuit board along the thickness direction is in a sequential ring state, it is determined that each first positioning mark is in an aligned state. The above method can intuitively and accurately reflect whether the relative positions of each layer of circuit boards are accurately aligned, which helps to timely discover and correct minor alignment errors and improve alignment accuracy.

[0114] Figure 6 A flow chart of another method for preparing an HDI board with cross-layer laser holes provided in an embodiment of the present invention. Based on the above embodiments, this embodiment further specifies S130 or S230, determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil, and obtaining the target blind hole position as follows:

[0115] Detect the expansion and contraction ratio of metal foil before and after lamination;

[0116] Determine the theoretical position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil;

[0117] According to the theoretical position of the target blind hole on the outermost metal foil and the expansion / contraction ratio, the actual position of the target blind hole on the outermost metal foil is determined.

[0118] For details not yet provided in this embodiment, please refer to the above embodiments.

[0119] like Figure 6 As shown, a method for preparing an HDI board with cross-layer laser holes provided by an embodiment of the present invention includes the following steps:

[0120] S310, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated.

[0121] S320, using a transmission detection device to check the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state.

[0122] S330, detecting the expansion and contraction ratio of the metal foil before and after lamination.

[0123] The expansion / contraction ratio can be understood as the ratio of the change in the size of the metal foil due to the effects of heat and pressure during the lamination process.

[0124] Specifically, the following steps can be followed: ① Before lamination, record the original dimensions of the metal foil. ② After lamination, measure the dimensions of the metal foil again to determine the changes in its length and width. ③ By comparing the dimensions before and after lamination, calculate the expansion and contraction ratio, usually expressed as a percentage.

[0125] For example, suppose that before lamination, the length of a circuit board is 10 cm and the width is 8 cm. After lamination, the length becomes 10.1 cm and the width becomes 8.05 cm. Then the expansion and contraction ratio of the length is: (10.1-10) / 10×100%=1%; the expansion and contraction ratio of the width is: (8.05-8) / 8×100%=0.625%.

[0126] S340, determining a theoretical position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil.

[0127] Specifically, determining the theoretical position of the target blind hole on the outermost metal foil can be understood as determining the position of the blind hole according to the original size of the circuit board before lamination, which is usually based on design drawings or predetermined layout parameters.

[0128] S350, determining the actual position of the target blind hole on the outermost metal foil according to the theoretical position of the target blind hole on the outermost metal foil and the expansion / contraction ratio.

[0129] Specifically, according to the expansion and contraction ratio measured in S330, the actual size change of the metal foil of the circuit board after lamination is calculated, and the theoretical position obtained in S340 is adjusted accordingly to accurately determine the actual position of the blind hole on the outermost metal foil. Finally, the actual position of the blind hole is marked on the outermost metal foil to provide accurate positioning information for the subsequent laser drilling step.

[0130] S360, opening a window at a target blind hole position on the outermost metal foil to form a window opening area.

[0131] S370, laser drilling is performed in the window opening area until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0132] S380, forming a metal layer on the inner wall of the cross-layer laser hole to respectively connect the metal foils of the outermost layer and the target layer.

[0133] S390, fill the cross-layer laser holes.

[0134] In the embodiment of the present invention, the expansion and contraction ratio of the metal foil before and after lamination is detected; the theoretical position of the target blind hole on the outermost metal foil is determined according to the second positioning mark on the outermost metal foil; the actual position of the target blind hole on the outermost metal foil is determined according to the theoretical position of the target blind hole on the outermost metal foil and the expansion and contraction ratio. Through the above method, the actual position of the blind hole after lamination can be determined more accurately, avoiding positioning deviation caused by dimensional changes caused by hot pressing, thereby improving the processing accuracy and quality of the product.

[0135] Figure 7 A flow chart of another method for preparing an HDI board with cross-layer laser holes provided in an embodiment of the present invention. Based on the above embodiments, this embodiment performs laser drilling in the window area in S150 / S250 / S370 until the metal foil of the target layer is reached to form a cross-layer laser hole, which is further embodied as follows:

[0136] Determining laser drilling target manufacturing conditions according to at least one of the size parameters of the target blind hole, the metal foil, and the substrate and the material of the metal foil and the substrate;

[0137] According to the laser drilling target manufacturing conditions, laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0138] For details not yet provided in this embodiment, please refer to the above embodiments.

[0139] like Figure 7 As shown, a method for preparing an HDI board with cross-layer laser holes provided by an embodiment of the present invention includes the following steps:

[0140] S410, stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated.

[0141] S420, using a transmission detection device to check the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state.

[0142] S430, determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil, and obtaining the target blind hole position.

[0143] S440, opening a window at a target blind hole position on the outermost metal foil to form a window opening area.

[0144] S450, determining laser drilling target manufacturing conditions according to at least one of the size parameters of the target blind hole, the metal foil, and the substrate and the material of the metal foil and the substrate.

[0145] Specifically, according to the size of the target blind hole, the corresponding parameters of the laser drilling machine are set to ensure the accuracy and consistency of the drilling; according to the material properties of the metal foil and substrate, the power and pulse frequency of the laser are adjusted to achieve the best drilling effect.

[0146] For example, in a 6-layer board, a first-order HDI board refers to blind holes 1-2, 2-5, and 5-6, that is, 1-2 and 5-6 need to be laser drilled. A second-order HDI board refers to blind holes 1-2, 2-3, 3-4, 4-5, and 5-6, that is, 2 laser drillings are required. For a first-order circuit board, it usually has fewer layers and a simpler structure, and the laser drilling conditions may focus more on speed and cost-effectiveness; for a second-order or multi-order circuit board, it may have more complex interlayer connection requirements, and the laser drilling conditions may require more sophisticated adjustments to ensure the accuracy and reliability of the interlayer connection.

[0147] S460, laser drilling is performed in the window area according to the laser drilling target production conditions until the metal foil of the target layer is reached to form a cross-layer laser hole.

[0148] Specifically, the drilling area is determined based on the laser drilling target production conditions, combined with the positioning of the conformal window opening method and the positioning of the laser drilling operation. Before laser drilling, the target is burned and aligned, and the equipment is tested and calibrated through trial drilling to ensure the accuracy of laser drilling and reduce the offset. Finally, after laser drilling, the automatic optical inspection machine is used to quickly screen and preliminarily inspect the quality of the hole to ensure that the size, shape and position of the hole meet the specification requirements.

[0149] S470, forming a metal layer on the inner wall of the cross-layer laser hole to respectively connect the metal foils of the outermost layer and the target layer.

[0150] S480, fill the cross-layer laser holes.

[0151] In an embodiment of the present invention, the laser drilling target manufacturing conditions are determined according to the size parameters of the target blind hole, metal foil, and substrate, and at least one of the materials of the metal foil and substrate; laser drilling is performed in the window area according to the laser drilling target manufacturing conditions until the metal foil of the target layer is reached to form a cross-layer laser hole. Through the above method, the size parameters of the target blind hole are taken into account, and it can be ensured that the diameter and depth of the laser drilling meet the design requirements, and the drilling precision and accuracy are improved, thereby improving the electrical connection performance and reliability of the product.

[0152] The embodiment of the present invention further provides an HDI board with cross-layer laser holes, and further reference is made to Figure 3 and Figure 4 The HDI board with cross-layer laser holes includes: a plurality of stacked, preliminarily aligned and pressed circuit boards 10, such as Figure 3 As shown, in the stacking order, the circuit boards 10a, 10b, 10c, 10d, ... 10x are included in sequence; the circuit board includes a substrate and metal foils 11 located on two sides of the substrate away from each other, and the same position of the metal foils 11 of different circuit boards 10 is provided with first positioning marks of different sizes, such as Figure 3 The shown ones correspond to the circuit boards 10a, 10b, 10c, 10d...10x, which are 12a, 12b, 12c, 12d...12x respectively; a second positioning mark 13 is also provided on the outermost metal foil; the relative positions of the projections of the first positioning marks 12 on each circuit board along the thickness direction are aligned; the cross-layer laser holes 15 penetrate from the outermost metal foil to the metal foil of the target layer in sequence, and there is at least one layer of metal foil between the metal foil of the target layer and the metal foil of the outermost layer; the inner wall of the cross-layer laser hole is formed by the metal layer 15, and the metal layer is respectively connected to the metal foils of the outermost layer and the target layer; the cross-layer laser hole is filled with filler 17.

[0153] Optionally, the circuit boards are stacked in sequence in the order that the size of the first positioning mark 12 gradually increases or decreases.

[0154] Optionally, the projections of the first positioning marks 12 on each circuit board along the thickness direction are in a ring-shaped state.

[0155] Optionally, the filler 17 in the cross-layer laser hole is flush with the surface of the outermost metal foil 11 .

[0156] Optionally, the metal layer is located outside the outermost metal foil 11 and covers the cross-layer laser holes 15 .

[0157] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An HDI board with cross-layer laser holes, characterized in that: include: A plurality of stacked, preliminarily aligned and pressed circuit boards; the circuit boards include a substrate and metal foils located on two sides of the substrate facing away from each other, first positioning marks of different sizes are arranged at the same position of the metal foils of different circuit boards; a second positioning mark is also arranged on the outermost metal foil; the relative positions of the projections of the first positioning marks on each circuit board along the thickness direction are in an aligned state; The cross-layer laser hole penetrates from the outermost layer of metal foil to the metal foil of the target layer in sequence, and there is at least one layer of metal foil between the metal foil of the target layer and the metal foil of the outermost layer; the inner wall of the cross-layer laser hole is formed by a metal layer, and the metal layer is respectively connected to the metal foils of the outermost layer and the target layer; the cross-layer laser hole is filled with a filler.

2. The HDI board according to claim 1, characterized in that: The circuit boards are stacked in sequence in the order that the size of the first positioning mark gradually increases or decreases.

3. The HDI board according to claim 1, characterized in that: The projections of the first positioning marks on each of the circuit boards along the thickness direction are in a sequentially annular state.

4. The HDI board according to claim 1, characterized in that: It also includes a metal layer, which is located on the outer side of the outermost metal foil and covers the cross-layer laser hole.

5. A method for preparing an HDI board with cross-layer laser holes, characterized in that: Stacking, preliminarily aligning and pressing a plurality of circuit boards to be laminated; wherein the circuit board comprises a substrate and metal foils located on two sides of the substrate facing away from each other, and first positioning marks of different sizes are arranged at the same position of the metal foils of different circuit boards; and a second positioning mark is also arranged on the outermost metal foil; Using a transmission detection device, checking the relative position of the projection of the first positioning mark on each of the circuit boards along the thickness direction to determine that each of the first positioning marks is in an aligned state; Determine the position of the target blind hole on the outermost layer of the metal foil according to the second positioning mark on the outermost layer of the metal foil, and obtain the target blind hole position; Opening a window at the target blind hole position on the outermost metal foil to form a window opening area; Performing laser drilling in the window opening area until reaching the metal foil of the target layer to form a cross-layer laser hole; the metal foil of the target layer and the metal foil of the outermost layer are separated by at least one layer of the metal foil; forming a metal layer on the inner wall of the cross-layer laser hole to connect the metal foils of the outermost layer and the target layer respectively; The cross-layer laser holes are filled and leveled.

6. The preparation method according to claim 5, characterized in that: Stack, align and press multiple circuit boards to be laminated, including: According to the order in which the size of the first positioning mark gradually increases or decreases, the plurality of circuit boards are stacked, preliminarily aligned and pressed together.

7. The preparation method according to claim 5, characterized in that: Using a transmission detection device to check the relative position of the projection of the first positioning mark on each circuit board along the thickness direction to determine that each first positioning mark is in an aligned state, including: By using a transmission detection device, when it is found that the projections of the first positioning marks on the circuit boards along the thickness direction are in a sequentially ring-shaped state, it is determined that the first positioning marks are in an aligned state.

8. The preparation method according to claim 5, characterized in that: Determining the position of the target blind hole on the outermost metal foil according to the second positioning mark on the outermost metal foil to obtain the target blind hole position includes: Detecting the expansion and contraction ratio of the metal foil before and after lamination; Determining a theoretical position of a target blind hole on the outermost layer of the metal foil according to a second positioning mark on the outermost layer of the metal foil; According to the theoretical position of the target blind hole on the outermost metal foil and the expansion / contraction ratio, the actual position of the target blind hole on the outermost metal foil is determined.

9. The preparation method according to claim 5, characterized in that: Before laser drilling is performed in the window opening area until the metal foil of the target layer is reached to form a cross-layer laser hole, the method further includes: Determining laser drilling target manufacturing conditions according to at least one of the size parameters of the target blind hole, the metal foil, and the substrate and the materials of the metal foil and the substrate; Laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole, including: According to the laser drilling target manufacturing conditions, laser drilling is performed in the window area until the metal foil of the target layer is reached to form a cross-layer laser hole.

10. The preparation method according to claim 5, characterized in that: After the cross-layer laser holes are filled, the method further includes: Detecting the filling flatness of the cross-layer laser holes; When the filling in the cross-layer laser hole is concave or convex, the cross-layer laser hole is corrected to make the filling in the cross-layer laser hole flush with the surface of the outermost metal foil.

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