A method for manufacturing an asymmetric structure HDI board and an HDI board

Abstract

The present invention provides a method for manufacturing an asymmetric HDI board and an HDI board, wherein the method first manufactures a motherboard and then manufactures a daughterboard. The manufacturing process of the motherboard includes: obtaining core boards of each layer of the motherboard layer, performing copper reduction treatment on the obtained core boards of each layer, and completing the manufacturing of each layer of the core boards; pre-stacking and pressing the manufactured core boards of each layer according to a preset laminated stacking design. On the pressed motherboard, all through holes on the motherboard are drilled, the drilled through holes are electroplated, and copper cladding is made at the openings of the through holes. On the basis of the motherboard, each sub-board layer of the daughterboard is pressed layer by layer on the side of the motherboard away from the copper cladding; after each sub-board layer is pressed, a blind hole is drilled on the pressed sub-board layer, and the drilled blind hole is electroplated and plugged, and the through-hole connection with the motherboard layer is realized layer by layer. This method can ensure that the hole copper is closely connected with the copper layer on the surface of the substrate, enhance the bonding force between the hole copper and the copper layer on the surface of the substrate, and improve the quality of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB processing, and in particular to a manufacturing method of an asymmetric HDI board and the HDI board. Background Art

[0002] HDI board (High Density Interconnector) is a high-density interconnected printed circuit board. It uses advanced micro blind buried hole technology and laser drilling processes to achieve higher circuit density and more complex design and production in a limited space. It is particularly suitable for high-performance and high-efficiency electronic products. Traditional HDI generally adopts a 1+N+1 symmetrical structure, and its blind buried holes and wiring design are relatively symmetrically distributed. Traditional symmetrical structure HDI boards have certain disadvantages in space utilization, wiring complexity and cost, signal transmission performance, design flexibility, and the ability to cope with complex applications. With the continuous development of electronic products towards miniaturization and high performance, asymmetric structure HDI boards are gradually becoming the mainstream choice in the market. Compared with symmetrical structure HDI, asymmetric structure HDI products have an asymmetric structure, which is more flexible and complex in circuit wiring and connection design. The main features of asymmetric HDI include the following aspects: Asymmetric HDI adopts asymmetric circuit wiring between different layers. Parameters such as line width, line spacing, impedance and copper plating between circuit layers can be designed and optimized according to needs to meet specific circuit requirements; the circuit patterns and distribution of each layer in asymmetric HDI are usually irregular to achieve higher line density and more functions; the inner layer of asymmetric HDI usually contains multiple levels and complex circuit patterns to support a large amount of signal and power transmission. Asymmetric HDI is usually used in advanced electronic devices with high density, high speed, high frequency and multi-function requirements.

[0003] In the layer-by-layer manufacturing process of the existing asymmetric HDI structure, it is necessary to make holes on the substrate surface of the HDI board to the chip surface multiple times to achieve circuit connectivity. In the process of making multiple holes, it is necessary to perform multiple electroplating and multiple thinning of the copper layer on the substrate surface, and there is a certain difference in the thickness of the copper layer between each electroplating and copper layer thinning. Therefore, after multiple electroplating and copper layer thinning, the copper layer on the surface of some holes is too thin, resulting in the inability to achieve copper coating on the hole mouth surface of the hole. When the HDI board expands and contracts due to heat, the holes that cannot be coated with copper will cause the copper in the holes to tear and the copper layer on the surface of the substrate to form stratification, affecting the function of the product. Therefore, it is necessary to improve the production process of the existing asymmetric HDI structure to overcome the defects of the prior art. Summary of the invention

[0004] In order to overcome the problems existing in the related art, one of the purposes of the present invention is to provide a method for manufacturing an asymmetric HDI board. The method can solve the defect that the copper layer on the surface of the substrate is too thin after multiple copper reductions during the manufacturing process of the HDI board, and the copper coating cannot be achieved at the hole mouth. The method can ensure that the hole copper is tightly connected with the copper layer on the surface of the substrate, enhance the bonding force between the hole copper and the copper layer on the surface of the substrate, and improve the quality of the product.

[0005] A method for manufacturing an asymmetric HDI board, comprising:

[0006] In the manufacturing process, the motherboard of the HDI board is manufactured first, and then the daughterboard of the HDI board is manufactured based on the motherboard;

[0007] The manufacturing process of the motherboard includes: obtaining core boards of each layer of the motherboard, performing copper reduction treatment on the obtained core boards of each layer, and drilling, electroplating, plugging holes and making circuit patterns on the core boards of each layer;

[0008] Pre-stack the core boards of each layer after the circuit pattern is made according to the preset lamination structure design, and press the pre-stacked core boards as a whole;

[0009] On the pressed motherboard, all through holes on the motherboard are drilled, the drilled through holes are electroplated, and copper cladding is made at the opening of the drilled through holes on the side away from the daughter board;

[0010] The method of manufacturing a daughter board of the HDI board based on the mother board includes:

[0011] Laminating each sub-board layer of the sub-board layer by layer on the side of the motherboard away from the copper cladding, wherein the sub-board layer includes a prepreg and a copper foil;

[0012] After each sub-board layer is laminated, a blind hole is drilled on the laminated sub-board layer, and the drilled blind hole is electroplated and plugged to achieve through-hole connection with the motherboard layer layer by layer.

[0013] It should be noted that in the manufacturing method of the HDI board claimed for protection in the present application, the motherboard of the manufactured HDI board has a multi-layer structure, for example, the motherboard has L1-L6 layers, wherein the L6 layer is connected to the daughter board, and the copper cladding is made at the hole opening of the drilled through hole on the side away from the daughter board, that is, the copper cladding is made at the hole opening of the L1 layer of the motherboard.

[0014] The relationship between HDI signal transmission and the longitude and latitude of the board is mainly reflected in the glass fiber effect. The longitude and latitude structure of the board causes the signal to propagate at different speeds in the glass fiber and resin, which in turn affects the transmission line impedance fluctuation and differential skew. In the manufacturing process of conventional HDI boards, the signal lines of the PCB board are usually parallel in the X or Y direction when designing the data required by the production. Due to the consistency of the signal lines of the board and the longitude and latitude of the PP, the longitude and latitude will have a certain impact on the transmission of the signal, which is easy to cause distortion of high-frequency and high-speed signals.

[0015] In order to overcome this defect, in a preferred technical solution of the present invention, before manufacturing, it also includes engineering graphic design;

[0016] The engineering graphic design includes:

[0017] During the graphic design process of the core board of the motherboard, multiple PCB board graphics of the core board are spliced ​​on a substrate;

[0018] During the splicing process, the pattern of a single PCB board is rotated by a preset angle so that the pattern of the single PCB board and the longitude and latitude of the prepreg are staggered;

[0019] Among them, the preset angle is 10°-45°.

[0020] In a preferred technical solution of the present invention, in the manufacturing process of the motherboard, after the copper coating is made at the hole opening of the drilled hole away from the side of the daughterboard, the method further includes:

[0021] Plug all holes;

[0022] The circuit pattern is made on the side where the motherboard and the daughterboard are connected to complete the manufacture of the motherboard.

[0023] In a preferred technical solution of the present invention, in the manufacturing process of the motherboard, after the drilled through holes are electroplated, the method further includes:

[0024] The back drilling process is used to process the through holes that are not connected to the daughter board, thereby blocking the connection between the through holes and the daughter board.

[0025] In a preferred technical solution of the present invention, in the manufacturing process of the motherboard, before the pre-stacked core boards are pressed together as a whole, the process further includes:

[0026] Blind holes are made on adjacent core boards where the circuits of each layer are connected, and the blind holes are electroplated with copper, so that the adjacent core boards can be connected in circuit through the blind holes.

[0027] In a preferred technical solution of the present invention, during the manufacturing process of the daughter board, drilling holes on the laminated daughter board layer includes:

[0028] A laser drilling process is used to drill blind holes on the pressed daughter board, with a hole diameter of 0.075~0.2mm, and the drilled blind holes are electroplated and plugged.

[0029] In a preferred technical solution of the present invention, during the manufacturing process of the daughter board, drilling holes on the laminated daughter board layer includes:

[0030] A laser milling process is used to drill blind holes on the pressed daughter board. The diameter of the blind holes is the same as the diameter of the through holes on the mother board to which they are connected. The drilled holes are then electroplated and plugged.

[0031] In a preferred technical solution of the present invention, the plug holes manufactured in the motherboard or the plug holes manufactured in the daughterboard include resin plug holes and copper paste plug holes;

[0032] Wherein, the resin plugging hole comprises filling the hole wall of the blind hole with resin and then plating the flat pad;

[0033] The resin plugging method includes filling the hole wall of the blind hole with copper paste and then plating the pad.

[0034] In a preferred technical solution of the present invention, the copper cladding is made at the hole opening of the drilled hole away from the side of the daughter board, including:

[0035] The copper cladding extends outward from the opening of the blind hole, the copper cladding has a thickness greater than 5 μm, and a minimum distance from an edge of the copper cladding to an edge of the opening is greater than 25 μm.

[0036] The inner layer asymmetric structure of the asymmetric HDI board will deform after lamination due to the asymmetry of the board thickness, copper thickness, and pattern distribution, and will be affected by thermal expansion and contraction, resulting in board warping and even failure to use subsequent chips. In order to overcome this defect, in a preferred technical solution of the present invention, after the daughter board is pressed onto the mother board, it also includes:

[0037] Drilling an improvement hole at the edge of the pressed HDI board, wherein the improvement hole penetrates the motherboard and the daughterboard;

[0038] And along the direction from the center to the edge of the HDI board, the improved holes are arranged in M ​​rows, where M is a natural number greater than 1;

[0039] Among them, the positions of the improved holes in two adjacent rows are staggered;

[0040] The aperture of the improvement hole is 0.3mm-0.5mm, and in the same row of improvement holes, the diameter of the improvement hole is greater than the minimum distance between two adjacent improvement holes; and the aperture of the improvement hole is related to the material and thickness of the core board. Specifically, the aperture of the improvement hole is usually between 0.3mm and 0.5mm. However, the material hardness, flexibility and thermal conductivity of the PCB board will affect the effect of drilling; the thickness of the PCB board will also affect the depth and difficulty of drilling the improvement hole. Thicker boards require longer drilling time, and more heat and debris will be generated, so a larger aperture may be required to accommodate these debris and promote heat dissipation. Therefore, the greater the material hardness of the core board, the larger the aperture of the improvement hole, and the diameter of the improvement hole is positively correlated with the thickness of the core board.

[0041] In the existing HDI board manufacturing process, the efficiency of micro-blind hole filling electroplating is reduced due to the influence of the pool effect, and micro-blind hole filling electroplating depressions are likely to occur. In order to overcome this defect, in a preferred technical solution of the present invention, during the electroplating process of the core board of the motherboard, N rows of cyclic holes are drilled on the edge of a single core board, where N is a natural number greater than or equal to 1;

[0042] The diameter of the circulation hole is greater than 0.2 mm. The circulation hole can effectively improve the circulation path of the solution, reduce the influence of the pool effect, and improve the quality of blind hole electroplating.

[0043] A second object of the present invention is to provide an HDI board, which is manufactured based on the manufacturing method of the asymmetric structure HDI board as described above.

[0044] The beneficial effects of the present invention are:

[0045] The present invention provides a method for manufacturing an asymmetric HDI board, the method comprising: first manufacturing a motherboard of the HDI board, and manufacturing a daughterboard of the HDI board based on the motherboard; the manufacturing process of the motherboard comprises: obtaining core boards of each layer of the motherboard layer, performing copper reduction treatment on the obtained core boards of each layer, drilling holes, electroplating, plugging holes and making circuit patterns on the core boards of each layer; pre-stacking the core boards of each layer on which the circuit patterns are made according to a preset lamination stacking design, and pressing the pre-stacked core boards as a whole; on the pressed motherboard, drilling all the through holes on the motherboard, electroplating the drilled through holes, and making copper cladding at the hole opening on the side of the drilled through hole away from the daughterboard. On the basis of the motherboard, the daughterboard of the HDI board is manufactured, including: laminating each daughterboard layer of the daughterboard layer by layer on one side of the motherboard, wherein the daughterboard layer includes a prepreg and a copper foil; after laminating each daughterboard layer, a blind hole is drilled on the laminated daughterboard layer, and the drilled blind hole is electroplated and plugged, so as to realize the through-hole connection with the motherboard layer layer by layer. This method manufactures the motherboard and daughterboard of the HDI board separately, and after the motherboard is pressed, the through-hole connecting the motherboard and the daughterboard is manufactured on the motherboard at one time, and the electroplating is completed. Then, on the basis of the motherboard, each daughterboard layer is pressed and manufactured layer by layer to realize the connection between the motherboard and the daughterboard. The manufacturing method does not need to thin the copper layer on the surface of the substrate after each hole copper electroplating, thereby avoiding the extreme difference in copper layer thickness between electroplating and copper layer thinning, ensuring that there is sufficient copper thickness to achieve the connection between the cladding copper and the copper layer on the surface of the substrate, ensuring that the hole copper and the copper layer on the surface of the substrate are tightly connected, enhancing the bonding force between the hole copper and the copper layer on the surface of the substrate, and helping to improve product quality.

[0046] The present application also provides an HDI board manufactured based on the manufacturing method of the asymmetric structure HDI board. During the manufacturing process of the HDI board, reliable quality cladding copper can be formed at the hole mouth of the hole, so that the hole copper and the copper layer on the surface of the substrate are firmly connected and not easy to delaminate, and the product quality is reliable and the performance is outstanding. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic diagram of setting the improved holes on a single PCB board provided in an embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the arrangement of the circulation holes provided in the embodiment of the present invention on a single PCB board;

[0049] Figure 3 is a schematic structural diagram of an asymmetric HDI board provided in an embodiment of the present invention;

[0050] Figure 4 It is a schematic diagram of the structure of a substrate provided with copper cladding at the orifice provided by the present invention;

[0051] Figure 5It is a schematic diagram of the structure on the substrate provided by the present invention where no copper cladding is provided at the hole opening.

[0052] Reference numerals:

[0053] 1. Improved hole; 2. Circulation hole; 100, base copper foil; 200, cladding copper; 300, plugging material; 400, hole copper; 500, no cladding copper plating. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0055] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0056] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0057] In the existing layer-by-layer manufacturing process of asymmetric HDI, it is necessary to make holes on the substrate surface of the HDI board to the chip surface multiple times to achieve circuit connectivity. In the process of making multiple holes, it is necessary to perform multiple electroplating and multiple thinning of the copper layer on the substrate surface, and there is a certain difference in the thickness of the copper layer between each electroplating and copper layer thinning. Therefore, after multiple electroplating and copper layer thinning, the copper layer on the surface of some holes is too thin, resulting in the inability to achieve copper cladding on the hole mouth surface of the hole. When the HDI board expands and contracts due to heat, the holes that cannot be clad with copper will cause the copper layer on the surface of the substrate to tear and form stratification, affecting the function of the product.

[0058] Based on this, the present application provides a method for manufacturing an asymmetric HDI board to overcome the defects of the prior art.

[0059] Example 1

[0060] like Figure 1-Figure 5 As shown, the present invention provides a method for manufacturing an asymmetric HDI board, comprising:

[0061] In the manufacturing process, the motherboard of the HDI board is manufactured first, and then the daughterboard of the HDI board is manufactured based on the motherboard;

[0062] The manufacturing process of the motherboard includes: obtaining core boards of each layer of the motherboard, performing copper reduction treatment on the obtained core boards of each layer, and drilling, electroplating, plugging holes and making circuit patterns on the core boards of each layer;

[0063] Pre-stack the core boards of each layer after the circuit pattern is made according to the preset lamination structure design, and press the pre-stacked core boards as a whole;

[0064] Specifically, the motherboard has 6 layers, namely L1, L2, L3, L4, L5, and L6, wherein the L1 layer is the substrate layer of the motherboard. In the manufacturing method, the surface copper of the substrate is first reduced, and the specific copper reduction can be to reduce the copper on both sides of the copper layer on the surface of the substrate to 6-8um. Then all the holes of the substrate are drilled out and electroplating is completed. Simultaneously, the core boards of each layer of L2, L3, L4, and L5 can be made, and the circuit patterns of each layer of the core boards can be made, and then the L1-L6 layers are pressed together to form a motherboard. Among them, one side of the motherboard is connected to the daughter board.

[0065] On the pressed motherboard, all through holes on the motherboard are drilled, the drilled through holes are electroplated, and copper cladding is made at the opening of the drilled through holes on the side away from the daughter board;

[0066] Specifically, a copper clad portion is formed at the opening of the drilled hole on a side away from the daughter board, including:

[0067] The copper cladding can be formed at the hole opening by electroplating.

[0068] The copper cladding 200 extends outward from the opening of the blind hole, the copper cladding 200 has a thickness greater than 5 μm, and a minimum distance from the edge of the copper cladding to the edge of the opening is greater than 25 μm.

[0069] Copper cladding can strengthen the copper foil around the hole to ensure its adhesion and conductivity. Figure 4 The cladding copper 200 is covered on the base copper foil 100 of the substrate, thereby enhancing the bonding force between the hole copper 400 and the base copper foil 100. Figure 5If there is no clad copper 200, the hole copper 400 is connected to the non-clad copper plating layer 500. This combination method easily leads to delamination between the hole copper 400 and the base copper foil 100, affecting signal transmission.

[0070] The method of manufacturing a daughter board of the HDI board based on the mother board includes:

[0071] Laminating each sub-board layer of the sub-board layer by layer on the side of the motherboard away from the copper cladding, wherein the sub-board layer includes a prepreg and a copper foil;

[0072] After each sub-board layer is laminated, a blind hole is drilled on the laminated sub-board layer, and the drilled blind hole is electroplated and plugged to achieve through-hole connection with the motherboard layer layer by layer.

[0073] See also Figure 3 , based on the motherboard having L1-L6 layers, after the motherboard is manufactured, on the basis of the motherboard L6 layer, the first layer (i.e., L7 layer) of the daughterboard is laminated according to the structural diagram. During the manufacturing process of the daughterboard, blind holes are drilled on the daughterboard for each layer of daughterboard laminated. The blind holes on the daughterboard correspond to the through holes on the motherboard one by one, but the aperture of the blind holes on the daughterboard can be smaller than the through holes on the motherboard, so the processing technology of the blind holes on the daughterboard can be different from the processing technology of the through holes on the motherboard. For example, the processing technology of the blind holes of the daughterboard can be laser processing, and the through holes of the motherboard can be mechanical processing.

[0074] After blind holes are drilled in the L7 layer using a laser, the drilled blind holes are electroplated and filled to complete the circuit production of the L7 layer. Then, the laser stacking and filling processing of the L7-N layer is completed in sequence according to the production method of the L7 layer.

[0075] The above-mentioned manufacturing method of an asymmetric HDI board is to separately manufacture the motherboard and the daughterboard of the HDI board. After the motherboard is pressed, a through hole connecting the motherboard and the daughterboard is manufactured on the motherboard at one time, and the electroplating is completed. Then, on the basis of the motherboard, each daughterboard layer is pressed and manufactured layer by layer to achieve the connection between the motherboard and the daughterboard. This manufacturing method does not need to thin the copper layer on the surface of the substrate after each hole copper electroplating, thereby avoiding the extreme difference in copper layer thickness between electroplating and copper layer thinning, ensuring that there is enough copper thickness to achieve the connection between the cladding copper and the copper layer on the surface of the substrate, ensuring that the hole copper is tightly connected to the copper layer on the surface of the substrate, and enhancing the bonding force between the hole copper and the copper layer on the surface of the substrate, which helps to improve the quality of the product.

[0076] Furthermore, before manufacturing, it also includes engineering graphic design;

[0077] The engineering graphic design includes:

[0078] During the graphic design process of the core board of the motherboard, multiple PCB board graphics of the core board are spliced ​​on a substrate;

[0079] During the splicing process, the pattern of a single PCB board is rotated by a preset angle so that the pattern of the single PCB board and the longitude and latitude of the prepreg are staggered;

[0080] Among them, the preset angle is 10°-45°.

[0081] In the manufacturing process of conventional HDI boards, in order to facilitate design and optimization, the signal lines of the PCB board are usually parallel to the X or Y direction when designing the data according to production requirements. Due to the consistency between the signal lines of the sheet material and the longitude and latitude of the PP, the longitude and latitude will have a certain impact on the transmission of the signal, which can easily cause distortion of high-frequency and high-speed signals. This application rotates the normal PCB board graphics by 10°-45° when assembling asymmetric blind hole boards, and the specific angle can be adjusted according to the shape of the product. The routing direction of the signal graphics required by the design is staggered with the longitude and latitude of the PP, reducing the impact of the signal lines on signal transmission when they are parallel to the longitude or latitude, and improving the distortion of high-frequency and high-speed signals.

[0082] Furthermore, in the manufacturing process of the motherboard, after the copper coating is formed at the hole opening on the side of the drilled hole away from the daughterboard, the method further includes:

[0083] Plug all holes;

[0084] The circuit pattern is made on the side where the motherboard and the daughterboard are connected to complete the manufacture of the motherboard.

[0085] More specifically, in the plugging of motherboard manufacturing or the plugging of daughterboard manufacturing, resin plugging and copper paste plugging are included;

[0086] Wherein, the resin plugging hole comprises filling the hole wall of the blind hole with resin and then plating the flat pad;

[0087] The resin plugging method includes filling the hole wall of the blind hole with copper paste and then plating the pad.

[0088] The plugging of holes in the present application refers to the use of resin or copper paste to fill the through holes or blind holes, wherein the resin plugging can be to fill the blind holes and through hole walls with resin, and then plate the pads flat. The resin plugging has the following advantages: preventing PP glue from flowing into the hole during pressing, avoiding lamination due to lack of glue and explosion of the board; facilitating the reduction of vacuum in lamination, avoiding surface depression problems, and facilitating fine circuit production and characteristic impedance control; achieving arbitrary layer interconnection, using three-dimensional space through hole stacking technology; achieving higher density wiring, through patch design on the hole; eliminating impurities from entering the conductive hole, avoiding the involvement of corrosive impurities.

[0089] Copper paste plugging uses copper paste to fill blind holes and through holes. Compared with resin plugging, copper paste plugging has better heat dissipation effect and higher quality, but the production cost is also higher.

[0090] Furthermore, in the manufacturing process of the motherboard, after the drilled through holes are electroplated, the process further includes:

[0091] The back drilling process is used to process the through holes that are not connected to the daughter board, thereby blocking the connection between the through holes and the daughter board.

[0092] Specifically, see Figure 3 In an HDI board having L1-L6 motherboard layers and L7-L12 layers, L6 and L7 layers are connected, and back-drilled holes of L7-L12 layers in L1-L6 layers are drilled.

[0093] Furthermore, in the manufacturing process of the motherboard, before the pre-stacked core boards are pressed together as a whole, the process further includes:

[0094] Blind holes are made on adjacent core boards where the circuits of each layer are connected, and the blind holes are electroplated with copper, so that the adjacent core boards can be connected in circuit through the blind holes.

[0095] Furthermore, during the manufacturing process of the daughter board, drilling holes on the laminated daughter board layer includes:

[0096] A laser drilling process is used to drill blind holes on the pressed daughter board, with a hole diameter of 0.075~0.2mm, and the drilled blind holes are electroplated and plugged.

[0097] Furthermore, during the manufacturing process of the daughter board, drilling holes on the laminated daughter board layer includes:

[0098] A laser milling process is used to drill blind holes on the pressed daughter board. The diameter of the blind holes is the same as the diameter of the through holes on the mother board to which they are connected. The drilled holes are then electroplated and plugged.

[0099] In actual applications, different processing methods are used for blind hole processing of sub-boards with different design requirements.

[0100] Therefore, blind holes can be processed on the pressed sub-boards by laser drilling or laser milling as needed.

[0101] Furthermore, after the daughter board is pressed onto the mother board, the method further includes:

[0102] Drilling an improvement hole 1 at the edge of the pressed HDI board, wherein the improvement hole 1 penetrates the motherboard and the daughterboard;

[0103] And along the direction from the center to the edge of the HDI board, the improved holes 1 are arranged in M ​​rows, where M is a natural number greater than 1;

[0104] The positions of the improved holes 1 in two adjacent rows are staggered;

[0105] The diameter of the improved hole 1 is 0.3mm-0.5mm, and in the same row of improved holes 1, the diameter of the improved hole 1 is greater than the minimum distance between two adjacent improved holes 1; and the diameter of the improved hole 1 is related to the material and thickness of the core plate.

[0106] Wherein, the step of drilling the improvement hole 1 at the edge of each single PCB board comprises:

[0107] On a single PCB board, drill M rows of improvement holes 1 from the center to the edge of the PCB board, where M is a natural number greater than 1;

[0108] Wherein, the improved holes 1 between two adjacent rows of improved holes 1 are staggered with each other;

[0109] The diameter of the improved hole 1 is 0.3 mm-0.5 mm, and the diameter of the improved hole 1 is related to the material and thickness of a single PCB board.

[0110] The inner layer asymmetric structure of the HDI board will be deformed after lamination due to the asymmetry of the board thickness, copper thickness, and pattern distribution, and will be affected by thermal expansion and contraction, resulting in the inability to use the patch later. During the manufacturing process, this application designs a drill bit based on the material of the inner layer board, drills two rows of holes alternately on the edge of each single PCB, cuts off the longitude and latitude lines of the inner layer PCB, releases the stress generated in the Z-axis direction of the sheet material and the PP longitude and latitude lines, improves the deformation of the asymmetric structure HDI board after lamination, and improves product quality.

[0111] Further, during the electroplating process of the core board of the motherboard, N rows of cyclic holes 2 are drilled on the edge of a single core board, where N is a natural number greater than or equal to 1;

[0112] Wherein, the diameter of the circulation hole 2 is greater than 0.2 mm.

[0113] When HDI products are electroplated and blind holes are drilled by laser, there are no through holes in the middle of the PCB. During the spraying process, the solution will accumulate on the surface of the PCB to form a "pool". This will hinder the uniform distribution of the solution, making the blind holes in the center of the PCB more difficult to electroplate than the blind holes on the edge. This application drills a circulation hole 2 on the edge of the PCB. When drilling, a drill tip of 0.2-0.4mm can be selected for the inner layer board. When there is a large hole of more than 0.4mm in the middle of the outer layer board, the circulation path of the solution can be improved, and the quality of blind hole electroplating can be improved.

[0114] Example 2

[0115] This embodiment describes in detail the manufacturing process of the asymmetric HDI board of the present application, which is as follows:

[0116] See also Figure 3 The HDI board includes a motherboard and a daughterboard, wherein the motherboard has L1-L6 layers and the daughterboard has L7-L12 layers.

[0117] (1) Engineering design

[0118] The L1-L6 layers with only resin plug holes but no laser blind holes are set as the motherboard to be manufactured first. The blind holes of the L1-2, L1-L4, and L5-L6 layers are processed by back drilling. For those that cannot be processed by back drilling, conventional blind hole machining is used. The L7-L12 layers with both resin plug holes and laser blind holes are designed as daughter boards. After the motherboard is processed, the daughter boards are manufactured in sequence. The daughter boards with laser blind holes and resin plug holes are manufactured one by one. During the design stage, the resin blind hole design is changed to the laser stacking process, and the aperture of the blind hole is reduced to 4mil.

[0119] (2) Motherboard production

[0120] After the core board is cut, the copper surface of the core board that needs to be blind-hole-made separately in the L1-L2, L3-L4, and L5-L6 layers is reduced from 17um (0.5OZ) to 6um-8um on both sides. The copper reduction process is to use the micro-etching effect of the solution on the copper surface to evenly reduce the thickness of the copper surface. The specific steps include board entry, pickling, water washing, copper reduction, drying, and board removal. The thickness of the copper surface after thinning is 6-9um. Then drill the hole in the plate of this layer and complete the electroplating and etching of the L2, L3, L4, and L5 layers, and then complete the lamination of the L1-L6 layers to form a motherboard. The copper thickness of the formed motherboard is reduced to 10um-15um; the back-drilling holes of the L7-L12 layers in the L1-L6 layers are drilled, and after the through holes on the motherboard are resin plugged, the copper thickness of the entire motherboard is reduced to 20um-25um, and then copper is electroplated at the hole mouth of L1 to make a clad copper of more than 12um, and the L6 layer circuit is completed to complete the motherboard.

[0121] (3) Sub-board production

[0122] On the basis of the motherboard L6 layer, the L7 layer is pressed according to the design requirements, the hole diameter of the L7 hole is reduced to 4mil, and the processing technology is changed to the laser stacking process. The L7 layer is laser drilled using the new processing file. After the processing is completed, the laser hole residual glue is cleaned by plasma and then the blind hole is filled and electroplated. After all the laser blind holes of the L7 layer are filled, the circuit production of the L7 layer is completed. Finally, according to the production method of the L7 layer, the laser stacking and filling processing of the L7-L12 layers is completed in sequence.

[0123] Example 3

[0124] This embodiment describes in detail the manufacturing process of the asymmetric HDI board of the present application, which is as follows:

[0125] See also Figure 3The HDI board includes a motherboard and a daughterboard, wherein the motherboard has L1-L6 layers and the daughterboard has L7-L12 layers. The HDI board of this embodiment uses copper paste for plugging holes, and the entire manufacturing process is as follows:

[0126] (1) Engineering design

[0127] The L1-L6 layers that only have resin plugged holes and no laser blind hole processing are set as the motherboard to be produced first. The blind holes of the L1-2, L1-L4, and L5-L6 layers are processed by back drilling. The processes that cannot be processed by back drilling are processed by conventional blind hole machining methods. The L7-L12 layers that have both resin plugged holes and laser blind holes are designed as daughter boards. After the motherboard is processed, the daughter boards are made in sequence. The daughter boards with laser blind holes and resin plugged holes are made one by one, and the resin blind hole design is changed to laser milling technology. The diameter of the blind holes of the daughter boards is 1 to 2 mil smaller than the through holes of the motherboard; all blind holes and through holes are plugged with copper paste with a copper content of more than 70%.

[0128] (2) Motherboard production

[0129] After cutting, the copper surface of the L1-2, L3-L4, L5-L6 layers that need to make blind hole core boards separately is reduced from 17um (0.5OZ) to 6um-8um on both sides, and the holes in the plates of the core boards of each layer are drilled and the electroplating and etching of the L2, L3, L4, and L5 layers are completed. After the L1-L6 layers are pressed together to form the motherboard, the surface copper is reduced to 10um-15um. The back drilling holes of the L7-L12 layers in the L1-L6 layers are drilled out, and the copper is reduced to 20um-25um after the copper paste is plugged. Then, copper is electroplated to make a copper cladding of more than 12um and the L6 layer circuit is completed to complete the motherboard.

[0130] (3) Sub-board production

[0131] On the basis of the motherboard L6 layer, the L7 layer is pressed according to the designed structural diagram, the aperture of the resin plate hole is reduced by 1 to 2 mil, and the processing technology is changed to the laser milling process. The L7 layer is laser drilled using the new processing file. Then the residual glue of the laser hole is cleaned with plasma and the blind hole is filled with electroplating. All laser blind holes are filled according to the new processing file. The L7 plate hole is plugged with copper paste, and the circuit pattern of the L7 layer is made after polishing. According to the production method of the L7 layer, the laser stacking and filling processing of the L7-L12 layers is completed in sequence.

[0132] Example 4

[0133] This embodiment provides an HDI board, which is manufactured based on the manufacturing method of the asymmetric structure HDI board as described above.

[0134] During the manufacturing process of the HDI board, reliable quality cladding copper can be formed at the opening of the blind hole. The blind hole copper and the copper layer on the surface of the substrate are firmly connected and not easy to delaminate. The product has reliable quality and outstanding performance.

[0135] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings. In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0136] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0137] In addition, it should be noted that the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of this application. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing an asymmetric HDI board, characterized in that: In the manufacturing process, the motherboard of the HDI board is manufactured first, and then the daughterboard of the HDI board is manufactured based on the motherboard; The manufacturing process of the motherboard includes: obtaining core boards of each layer of the motherboard, performing copper reduction treatment on the obtained core boards of each layer, and drilling, electroplating, plugging holes and making circuit patterns on the core boards of each layer; Pre-stack the core boards of each layer after the circuit pattern is made according to the preset lamination structure design, and press the pre-stacked core boards as a whole; On the pressed motherboard, all through holes on the motherboard are drilled, the drilled through holes are electroplated, and copper cladding is made at the opening of the drilled through holes on the side away from the daughter board; The method of manufacturing a daughter board of the HDI board based on the mother board includes: Laminating each sub-board layer of the sub-board layer by layer on the side of the motherboard away from the copper cladding, wherein the sub-board layer includes a prepreg and a copper foil; After each sub-board layer is laminated, a blind hole is drilled on the laminated sub-board layer, and the drilled blind hole is electroplated and plugged to achieve through-hole connection with the motherboard layer layer by layer.

2. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: Before manufacturing, it also includes engineering graphic design; The engineering graphic design includes: During the graphic design process of the core board of the motherboard, multiple PCB board graphics of the core board are spliced ​​on a substrate; During the splicing process, the pattern of a single PCB board is rotated by a preset angle so that the pattern of the single PCB board and the longitude and latitude of the prepreg are staggered; Among them, the preset angle is 10°-45°.

3. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: In the manufacturing process of the motherboard, after making the copper cladding at the hole opening on the side of the drilled hole away from the daughterboard, it also includes: Plug all holes; The circuit pattern is made on the side where the motherboard and the daughterboard are connected to complete the manufacture of the motherboard.

4. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: In the motherboard manufacturing process, after the drilled through holes are electroplated, it also includes: The back drilling process is used to process the through holes that are not connected to the daughter board, thereby blocking the connection between the through holes and the daughter board.

5. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: In the manufacturing process of the motherboard, before the pre-stacked core board is pressed together as a whole, it also includes: Blind holes are made on adjacent core boards where the circuits of each layer are connected, and the blind holes are electroplated with copper, so that the adjacent core boards can be connected in circuit through the blind holes.

6. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: During the daughterboard manufacturing process, drilling holes in the laminated daughterboard layers includes: A laser drilling process is used to drill blind holes on the pressed daughter board, with a hole diameter of 0.075~0.2mm, and the drilled blind holes are electroplated and plugged.

7. The method for manufacturing an asymmetric HDI board according to claim 1, characterized in that: During the daughterboard manufacturing process, drilling holes in the laminated daughterboard layers includes: A laser milling process is used to drill blind holes on the pressed daughter board. The diameter of the blind holes is the same as the diameter of the through holes on the mother board to which they are connected. The drilled holes are then electroplated and plugged.

8. The method for manufacturing an asymmetric HDI board according to any one of claims 1 to 7, characterized in that: In the plugging holes made in the motherboard or the daughterboard, it includes resin plugging holes and copper paste plugging holes; Wherein, the resin plugging hole comprises filling the hole wall of the blind hole with resin and then plating the flat pad; The resin plugging method includes filling the hole wall of the blind hole with copper paste and then plating the pad.

9. The method for manufacturing an asymmetric HDI board according to any one of claims 1 to 7, characterized in that: The copper cladding is made at the hole opening on the side of the drilled hole away from the daughter board, including: The copper cladding extends outward from the opening of the blind hole, the copper cladding has a thickness greater than 5 μm, and a minimum distance from an edge of the copper cladding to an edge of the opening is greater than 25 μm.

10. The method for manufacturing an asymmetric HDI board according to any one of claims 1 to 7, characterized in that: After the daughter board is pressed onto the mother board, it also includes: Drilling an improvement hole at the edge of the pressed HDI board, wherein the improvement hole penetrates the motherboard and the daughterboard; And along the direction from the center to the edge of the HDI board, the improved holes are arranged in M ​​rows, where M is a natural number greater than 1; Among them, the positions of the improved holes in two adjacent rows are staggered; The diameter of the improved hole is 0.3mm-0.5mm, and in the same row of improved holes, the diameter of the improved hole is greater than the minimum distance between two adjacent improved holes; and the diameter of the improved hole is related to the material and thickness of the core plate.

11. The method for manufacturing an asymmetric HDI board according to any one of claims 1 to 7, characterized in that: During the electroplating process of the core board of the motherboard, N rows of cyclic holes are drilled on the edge of a single core board, where N is a natural number greater than or equal to 1; Wherein, the diameter of the circulation hole is greater than 0.2 mm.

12. An HDI board, characterized in that: The asymmetric structure HDI board is manufactured based on the manufacturing method according to any one of claims 1 to 11.

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