Continuous lamination manufacturing method for high-reliability multi-level HDI board

Abstract

The application provides a continuous pressing manufacturing method of a high-reliability multi-stage HDI board, which adjusts the shape of the metal layer between the through inner layer via hole, the blind hole and the blind hole connecting other layers in the multi-stage HDI board by improving the shaping and cleaning process of the electroplating process used in the continuous pressing manufacturing of the multi-stage HDI board, thereby improving the reliability of the connection of the holes in the multi-stage HDI board. Specifically, by adjusting the shape and thickness of the metal layer between the manufactured through inner layer via hole, the blind hole and the blind hole connecting other layers, a higher-strength and better-buffering inner layer via hole is constructed, meanwhile, the bonding performance of the metal layer connection between adjacent holes is improved, the separation between the metal plating layers when heated is avoided, and the overall connection reliability between all the metal plating layers in the multi-stage HDI board is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of printed circuit board manufacturing, and more particularly, to a continuous lamination manufacturing method of high-reliability multi-level HDI board. BACKGROUND

[0002] With the rapid development and wide application of integrated circuits, the types and applications of electronic devices are rapidly developing, and electronic products are also more intelligent and miniaturized. To match this, the types of printed circuit boards (PCBs) are also constantly updated. In modern electronic devices, with the continuous expansion and integration of functions, multi-layer PCBs, especially high-layer PCBs, have become the mainstream of complex circuit board design, and the design demand for high-density interconnection (HDI) PCBs is increasing. However, in multi-level HDI boards, as the number of layers of PCB design increases, designers often need to use more complex structures and technologies to achieve stable electrical connections and effective space utilization between different layers. Among them, buried holes, through holes, blind holes, etc. as common hole structures, in multi-level HDI boards, are often designed to have multi-level interconnected hole structures and make the hole structures body metallization to achieve their stable and reliable electrical connections. At the same time, resin plugs are often set in the inner layer to fill the gap between the hole walls or provide insulation protection for the signal path. However, the reliability of multi-level HDI board design is highly dependent on the reliability of multi-level hole connection, which often faces a series of challenges in the design and production of multi-level HDI boards.

[0003] In practical applications, one of the main challenges faced by multi-level hole structures in multi-level HDI boards is the problem of copper cracking between multi-level holes due to thermal expansion. In order to solve the problem of copper cracking caused by thermal expansion and effectively improve the reliability of electrical connections in multi-level HDI boards, existing technical solutions often adjust material selection matching, adjust process parameter matching, and improve hole manufacturing precision to ensure effective adhesion and prevent cracking of the connecting copper. Specifically, it includes, for example: 1. Adjusting the hole connection layout in the HDI board, in the design containing resin plugs, by selecting resin and filling materials with expansion coefficients close to the HDI board substrate material to reduce stress caused by thermal expansion mismatch; 2. Thick hole walls or irregular shapes may affect the adhesion of copper inside the hole, leading to poor soldering or reduced electrical performance. By improving the hole manufacturing process, the processing precision of the hole can be improved, thereby improving the reliability of electrical connections; 3. In the lamination manufacturing process of multi-level HDI boards, precise control of temperature and pressure can reduce uneven expansion caused by temperature differences, thereby reducing thermal stress; 4. By adding flexible layers or buffer layers such as soft copper foil layers in the design of multi-level HDI boards, the stress transmission caused by thermal expansion differences can be effectively alleviated, reducing the risk of copper cracking; 5. In designs containing long blind holes or long through holes, appropriately increasing the hole wall thickness or using reinforced structure design can help improve the mechanical strength of the hole wall and reduce cracks caused by thermal expansion.

[0004] But specifically, in the manufacturing process of multi-stage HDI board using continuous pressing, there is still a lack of improvement method for the overall process to ensure the tight connection between the copper layers of the formed multi-stage hole, the thickness of the copper layer between the hole connections of each layer is sufficient to resist the overall stress of thermal expansion effect, and then the connection reliability of each stage hole in the multi-stage HDI board is ensured, and the hole connection failure is avoided to the greatest extent. SUMMARY

[0005] The present application aims to overcome at least one of the above-mentioned defects of the prior art, and provides a continuous pressing manufacturing method of high-reliability multi-stage HDI board, which updates the continuous pressing manufacturing process of multi-stage HDI board, ensures the tight connection between the copper layers of the formed multi-stage hole, the thickness of the copper layer between the hole connections of each layer is sufficient to resist the overall stress of thermal expansion effect, and then the connection reliability of each stage hole in the multi-stage HDI board is ensured, and the hole connection failure is avoided to the greatest extent.

[0006] The technical scheme adopted by the present application is to provide a continuous pressing manufacturing method of high-reliability multi-stage HDI board, the multi-stage HDI board is provided with a plurality of stacked hole structures, the stacked hole structure includes an inner layer hole and a plurality of layers of blind holes stacked on both sides of the inner layer hole, and the manufacturing method includes the following steps:

[0007] S1. Inner layer sub-board manufacturing, a first through hole is manufactured on the inner layer sub-board, the first through hole is metalized after filling resin and solidifying to form an inner layer hole, the inner layer hole is shaped and then the surface is metalized, and a first pad is formed on both sides of the inner layer hole;

[0008] S2. Next outer layer sub-board manufacturing, a plurality of next outer layer sub-boards are manufactured on both sides of the inner layer sub-board by continuous pressing, and a first blind hole is manufactured on the next outer layer sub-board corresponding to the position of the inner layer hole, the first blind hole exposes the first pad; the first blind hole is shaped and then the whole body is metalized, and a second pad is formed on the side of the first blind hole away from the inner layer hole;

[0009] S3. Total pressing manufacturing, outer layer sub-boards are pressed on both sides of the next outer layer sub-board, and a second blind hole is manufactured on the outer layer sub-board corresponding to the position of the first blind hole, the second blind hole exposes the second pad;

[0010] Specifically, in the step S1, at least three times of electroplating process are included:

[0011] S11. Through hole electroplating, the first through hole manufactured on the inner layer sub-board is metalized;

[0012] S12. One-time full-board electroplating, thickening the metal plating layer on the inner wall of the first through-hole and forming a wrap metal layer protruding into the first through-hole at the aperture of the first through-hole;

[0013] S13. Inner layer via hole surface electroplating, metallizing the inner layer via hole surface and forming first pads on both sides of the inner layer via hole.

[0014] In the technical solution, a hole structure is provided in a multi-stage HDI board, which includes an inner layer via structure arranged in a multi-stage HDI center layer and a plurality of multi-stage blind holes arranged concentrically on both sides of the inner layer via structure, thereby saving wiring space in the multi-stage HDI board and realizing reliable electrical connection between layers of the multi-stage HDI board. Meanwhile, by improving the electroplating process used on the inner layer via, the shape of the metal layer between the inner layer via and the blind hole connected to other layers is adjusted, thereby improving the connection reliability between the inner layer via and the adjacent blind hole. Specifically, in the manufacturing process of the inner layer sub-board, three electroplating processes are included. A metal layer is plated on the inner wall of the first via by the first electroplating process. Then, the thickness of the metal plating layer on the inner wall of the first via is thickened and a wrap metal layer protruding into the first via is formed at the aperture of the first via by the second electroplating process while forming the inner layer circuit on the inner layer sub-board. After the resin is filled into the first via, the first pad is formed on the wrap metal layer and the top of the resin in the via by the third electroplating process. The self-bonding ability between the metal layers formed by multiple electroplating processes improves the overall reliability of the metal layer formed on the inner layer via by electroplating. Meanwhile, the thickness and shape of the metal plating layer at each position of the inner layer via are adjusted by multiple electroplating processes to ensure that the metal layer can provide sufficient buffering at each position of the inner layer via when heated. In the first electroplating process, the first via forming the inner layer via is electroplated throughout the body, thereby forming a uniform metal layer on the inner wall of the via and metallizing the first via. Preferably, the thickness of the metal layer plated in the first via by the first electroplating process is relatively thin, thereby ensuring the uniformity of electroplating in the first via, providing a good bonding surface for the newly electroplated copper layer when thickening the thickness of the metal layer on the sidewall by full-board electroplating in the subsequent process, improving the overall strength of the metal layer on the inner wall of the first via, and balancing the current distribution on the board surface at the first via during the subsequent full-board electroplating process, thereby enhancing the uniformity of the plating layer formed by the subsequent electroplating process. Further, the second electroplating process uses a full-board electroplating process. By arranging the wrap metal layer protruding into the first via, the area of the resin top in contact with the first pad is reduced after the resin is filled into the first via to form the inner layer via, thereby providing better buffering when the resin and the metal layer have different thermal expansions due to heating. Meanwhile, the wrap metal layer and the metal layer on the inner wall of the first via are connected to cover the metal plating layer formed by the first electroplating process, thereby further avoiding the possibility of connection failure of the inner layer via due to damage to the metal layer. Further, in the second full-board electroplating process, the first pad is manufactured by one-time electroplating, thereby simplifying the process and preventing the reliability risk of separation between the two metal layers after heating.

[0015] Preferably, in the multi-stage HDI board, the metal layer realizing the multi-stage hole connection adopts copper, and in the design of the inner layer via hole, a resin or filling material with an expansion coefficient close to that of the HDI board substrate material is selected, because the thermal expansion coefficient of copper is 17 PPM, a resin with a lower thermal expansion coefficient can be selected to reduce the difference in expansion and contraction of the resin and copper when heated, so as to improve the reliability of the electrical connection between the inner layer via hole and the metallized blind hole stacked thereon; preferably, a resin type with an expansion coefficient of not more than 60 PPM is used to reduce the stress caused by thermal expansion mismatch.

[0016] Further, in the step S1, at least two surface treatment processes are further included:

[0017] A11. Via hole surface treatment, before step S11, the inner wall and aperture of the first via hole are surface treated by deburring and a first plasma cleaning;

[0018] A12. Inner layer via hole surface treatment, after step S12 is completed and before step S13 is performed, the resin layer and wrap metal layer on both sides of the inner layer via hole are surface treated by a first grinding plate, chemical copper reduction, a second grinding plate, a second plasma cleaning, and chemical cleaning.

[0019] Specifically, in order to improve the manufacturing quality of the inner layer via hole and improve the bonding force of the first via hole and the metal layer electroplated thereon, before the via hole electroplating process, the burrs generated in the drilling of the first via hole are cleaned by the deburring process, and a slight etching is generated on the inner wall and aperture of the first via hole by the first plasma cleaning process, which provides a slightly rough surface for the subsequent via hole electroplating process and improves the adhesion strength of the metal layer plated on the inner wall and aperture of the first via hole. Further, after the first via hole is subjected to the first full-plate electroplating and resin via hole process, the thickness of the wrap metal layer and the protruding thickness and shape of the resin on the surface of the inner layer via hole are shaped by a first grinding plate, chemical copper reduction, a second grinding plate, a second plasma cleaning, and chemical cleaning process. Specifically, the thickness of the wrap metal layer and the protruding thickness of the resin are uniformly thinned by the first grinding plate, chemical copper reduction, and second grinding plate process to match the thickness of the circuit on the inner layer sub-board and improve the pressing manufacturing precision; then, the wrap metal layer surface and the resin surface are further adjusted to be clean and have a slight roughness by the second plasma cleaning and chemical cleaning process, thereby providing a good bonding surface for the formation of the first pad on the wrap metal layer and the resin surface by the second full-plate electroplating, further improving the connection strength of the metal layers in the inner layer via hole, improving the resistance to thermal expansion effect of the metal layers during thermal cycling, ensuring the overall connection reliability of the metal layers on the inner layer via hole, and further improving the overall electrical connection reliability of the multi-stage HDI board.

[0020] Preferably, the thickness of the wrap metal layer is 1.8±0.2 mil after the step S12; the thickness of the wrap metal layer is 1.6±0.2 mil after the once plate grinding process in the step A12; the thickness of the wrap metal layer is 1.25±0.2 mil after the chemical copper reduction process; the thickness of the wrap metal layer is 0.5-1 mil after the twice plate grinding process; and the relatively thick wrap metal layer provides sufficient buffer between the resin and the first pad.

[0021] After the step S13, the first pad with a thickness not less than 1.4 mil is formed by the once electroplating process, the thickness of the metal layer of the first pad is increased, and the resistance of the first pad to the metal layer cracking caused by the thermal expansion effect in the thermal cycle is improved.

[0022] Further, after the twice plasma cleaning process in the step A12, the etching trace with a depth not less than 0.2 mil is formed on the surface of the resin in the inner layer via hole, the connection area between the resin surface and the first pad is increased, the adhesion between the resin and the first pad in the inner layer via hole is improved, the connection reliability of the metal layer on the inner layer via hole is ensured, and the overall electrical connection reliability of the multi-level HDI board is improved.

[0023] Further, the step S11 further includes:

[0024] S111. once horizontal copper deposition, uniformly depositing a metal plating layer on the inner wall of the first via hole on the inner layer sub-board;

[0025] S112. plate surface electroplating, thickening the metal plating layer on the inner wall of the first via hole while forming the inner layer circuit on the inner layer board, and forming a wrap metal layer on the first via hole aperture; the deep plating capability in the first via hole is enhanced and the thickness uniformity of the metal plating layer in the first via hole is improved by adding the once horizontal copper deposition process before the plate surface electroplating, and the quality of the metal plating layer in the first via hole is optimized.

[0026] Similarly, the step S13 further includes:

[0027] S131. twice horizontal copper deposition, uniformly depositing a metal plating layer on the surface of the inner layer via hole;

[0028] S132. Second full surface plating, the inner layer via surface is metallized and the first pad is formed on both sides of the inner layer via; the wrap metal layer surface of the first via and the resin top surface are attached with uniform metal plating layer through the second horizontal copper plating process, the plating uniformity of the subsequent second full surface plating is improved, and meanwhile the adhesion of the metal plating layer formed on the resin via is enhanced, then the first pad with the required thickness is made through the second full surface plating process, and the resistance of the first pad to the metal layer cracking caused by the thermal expansion effect in the thermal cycle is improved.

[0029] Further, in the step S2, at least two plating processes and one surface treatment process are included:

[0030] S21. Blind hole plating, the shaped first blind hole is metallized throughout the body, and the plated metal layer protruding from the surface of the secondary outer layer sub-board is arranged;

[0031] S22. Blind hole surface treatment, the secondary outer layer sub-board subjected to the blind hole plating process is baked at 150-170°C for not less than 2h, then the surface of the secondary outer layer sub-board is ground and deoiled, the metal layer protruding from the surface of the secondary outer layer sub-board arranged at the blind hole is removed through the grinding process, the roughness of the resin surface of the secondary outer layer sub-board and the blind hole surface metal layer is increased, and then the surface of the secondary outer layer sub-board is cleaned through the deoiling treatment;

[0032] S23. Blind hole surface plating, the first blind hole surface away from the inner layer via is metallized, and the second pad covering the first blind hole surface is formed.

[0033] In the technical solution, in order to improve the manufacturing quality of the blind hole metallization on the secondary outer layer sub-board, ensure the good adhesion of the metal plating layer in the blind hole and the good adhesion with the adjacent metal layer, after the first blind hole exposing the first pad or the adjacent second pad is opened, the blind hole is electroplated by using a one-time plate surface electroplating process, so as to ensure the integrity of the metal plating layer in the first blind hole, and the metal plating layer is not easy to crack and separate during thermal cycling. Secondly, by baking the secondary outer layer sub-board subjected to the blind hole electroplating process at 150-170 DEG C for not less than 2h, the electroplated metal layer is effectively crystallized in the first blind hole, thereby improving the reliability of the metallization in the first blind hole. At the same time, the thickness of the secondary outer layer sub-board is reduced by the grinding process, and the surface of the metal plating layer in the blind hole is shaped after the blind hole electroplating, the roughness of the surface resin of the secondary outer layer sub-board and the metal layer of the blind hole surface is increased, and then the surface of the secondary outer layer sub-board is cleaned by the oil removal treatment, so as to improve the adhesion performance of the metal plating layer formed by the subsequent blind hole surface electroplating process and the metal plating layer filled in the blind hole, and reduce the reliability risk of separation of the two metal plating layers when heated. Finally, the blind hole surface is electroplated by using a two-time plate surface electroplating process, a second pad covering the metal plating layer in the blind hole is formed at the top of the blind hole, a better bonding surface is provided for the first blind hole formed on the second pad and the metal plating layer filled therein during the next pressing, the reliability of the metal layer connection between the multi-stage metallized blind holes is improved, and the overall electrical connection reliability of the multi-stage HDI board is further improved.

[0034] Further, after the step S23, the second pad with a thickness of not less than 0.5 mil is formed by a one-time electroplating process, the thickness of the metal layer of the second pad is improved, and the resistance of the second pad to the metal layer cracking caused by the thermal expansion effect during thermal cycling is improved.

[0035] The technical solution also provides a multi-stage HDI board, wherein a plurality of hole stacking structures are arranged on the multi-stage HDI board, the hole stacking structure comprises an inner layer via hole and a plurality of blind holes stacked on both sides of the inner layer via hole, and the multi-stage HDI board is manufactured according to the continuous pressing manufacturing method of the high-reliability multi-stage HDI board provided by the technical solution.

[0036] In the multi-stage HDI board, in the inner layer via hole, the metal layer includes an inner wall metal layer arranged on the inner wall of the first through hole, a wrap metal layer arranged on the surface aperture of the first through hole, and a first pad covering the wrap metal layer and the resin surface of the inner layer via hole; the wrap metal layer is arranged on the surface aperture of the first through hole and extends to the inside of the first through hole, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole is not more than the area of the first pad, and the blind holes arranged on both sides of the inner layer via hole are separated by a second pad. Further, the thickness of the inner wall metal layer is 1-4 mil, the thickness of the wrap metal layer is 0.5-1 mil, the thickness of the first pad is not less than 1.4 mil, and the thickness of the second pad is not less than 0.5 mil.

[0037] In the technical solution, by adjusting the shape and thickness of the metal layer between the conductive inner layer via hole and the blind hole connected to other layers, the connection reliability between the inner layer via hole and its adjacent blind hole is improved, by adjusting the thickness of the inner wall metal plating layer in the inner layer via hole, a inner layer via hole with higher strength and better buffering performance is constructed, at the same time, by forming a wrap metal layer connected with the inner wall metal layer of the inner layer via hole and protruding into the inner layer via hole at the top, the integrity between the metal plating layers in the inner layer via hole is improved, and separation between the metal plating layers when heated is avoided; at the same time, by arranging the first pad and the second pad covering the top of the inner layer via hole and the first blind hole, and making the first pad and the second pad completely cover the metal plating layer filled inside, the connection reliability of all metal plating layers in the multi-stage hole interlayer connection is improved, at the same time, by keeping the first pad and the second pad with a relatively thick thickness, the buffering capacity of the first pad and the second pad to thermal expansion effect is improved.

[0038] Further, the first blind hole is a laser hole, the first blind hole has a hole bottom close to the inner layer via hole and a hole aperture away from the inner layer via hole, and in the first blind hole formed on the multi-layer HDI board, the hole bottom area is not less than 85% of the hole aperture area; by adjusting the shape of the first blind hole in the laser-made multi-stage HDI board, specifically, the area of the first blind hole bottom is increased under the premise of ensuring the area of the first blind hole aperture, thereby improving the contact area and bonding performance of the first blind hole and the adjacent first pad and second pad, and thereby improving the connection reliability of the multi-stage HDI board connected by the metalized holes of each stage.

[0039] Compared with the prior art, the beneficial effects of the present application are:

[0040] 1. A hole structure is provided in a multi-level HDI board, which comprises an inner layer via structure arranged in a multi-level HDI center layer and a plurality of blind holes concentrically arranged on both sides of the inner layer via structure, so as to save the wiring space in the multi-level HDI board and realize reliable electrical connection between the layers of the multi-level HDI board. Meanwhile, by improving the electroplating process used on the inner layer via, the shape of the metal layer between the inner layer via and the blind hole connected to other layers is adjusted, so as to improve the connection reliability between the inner layer via and the adjacent blind hole.

[0041] 2. By shaping and cleaning the metal plating layer generated by multiple electroplating in the manufacturing process on demand, the adhesion between the metal plating layers in each electroplating is improved. Specifically, before the via electroplating process, the burrs and impurities generated by drilling on the inner wall and aperture of the first via are cleaned by the deburring process, and a slight etching is generated on the inner wall and aperture of the first via by the first plasma cleaning process, so as to provide a slightly rough surface for the subsequent via electroplating process and improve the adhesion strength of the metal layer plated on the inner wall and aperture of the first via. Further, after the first via is electroplated on the whole board surface and the resin via is processed, the thickness of the wrap metal layer on the surface of the inner layer via and the protruding thickness and shape of the resin are shaped by the first grinding plate, chemical copper reduction, second grinding plate, second plasma cleaning, and chemical cleaning processes. The thickness of the wrap metal layer and the protruding thickness of the resin are uniformly thinned by the first grinding plate, chemical copper reduction, and second grinding plate processes, so as to match the thickness of the circuit on the inner layer sub-board and improve the pressing manufacturing precision. Then, the surface of the wrap metal layer and the surface of the resin are kept clean and slightly rough by the second plasma cleaning and chemical cleaning processes, so as to provide a good bonding surface for the formation of the first pad on the wrap metal layer and the resin surface by the second electroplating on the whole board surface, further improve the connection strength of the metal layer in the inner layer via, improve the resistance to thermal expansion effect of the metal layer, ensure the overall connection reliability of the metal layer in the inner layer via, and further improve the overall electrical connection reliability of the multi-level HDI board. In the blind hole manufacturing process, the thickness of the secondary outer layer sub-board is reduced by the grinding plate process, and the surface of the metal plating layer in the blind hole is shaped after the blind hole is electroplated, so as to increase the roughness of the resin on the surface of the secondary outer layer sub-board and the metal layer on the surface of the blind hole. Then, the surface of the secondary outer layer sub-board is cleaned by the oil removal treatment, so as to improve the adhesion between the metal plating layer formed by the subsequent electroplating process on the surface of the blind hole and the metal plating layer filled in the blind hole, and reduce the risk of separation of the two metal plating layers when heated.

[0042] 3、By adjusting the shape and thickness of the metal layer between the inner layer via hole and the blind hole connected to other layers, the connection reliability between the inner layer via hole and its adjacent blind hole is improved, by adjusting the thickness of the inner wall metal plating layer in the inner layer via hole, a higher strength and better buffering performance inner layer via hole is constructed, at the same time, by forming a wrap metal layer connected with the inner wall metal layer of the inner layer via hole and protruding into the inner layer via hole at the top, the integrity between the metal plating layers in the inner layer via hole is improved, and the separation between the metal plating layers when heated is avoided; at the same time, by setting the first pad and the second pad covering the inner layer via hole and the top of the first blind hole, and making the first pad and the second pad completely cover the metal plating layer filled inside, the connection reliability of all metal plating layers in the interlayer connection of the multi-stage hole is improved, at the same time, by making the first pad and the second pad keep a relatively thick thickness, the buffering capacity of the first pad and the second pad to the thermal expansion effect is improved. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The flowchart of the continuous pressing manufacturing method of the high-reliability multi-stage HDI board provided by the present application.

[0044] Figure 2 The structure diagram of the metal layer on the inner layer via hole in the multi-stage HDI board provided by the present application.

[0045] Figure 3 The structure diagram of the metal layer on the blind hole in the multi-stage HDI board provided by the present application.

[0046] Figure 4 The structure diagram of the multi-stage HDI board provided by the embodiment 3 of the present application. DETAILED DESCRIPTION

[0047] The drawings of the present application are only used for illustrative description, and cannot be understood as the limitation of the present application. In order to better illustrate the following embodiments, some components of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some known structures and their descriptions in the drawings may be omitted.

[0048] Embodiment 1

[0049] As shown in Figure 1 , the present embodiment provides a continuous pressing manufacturing method of a high-reliability multi-stage HDI board, a plurality of stacked hole structures are arranged on the multi-stage HDI board, the stacked hole structure includes an inner layer via hole and a plurality of layers of blind holes stacked on both sides of the inner layer via hole, and the manufacturing method includes the following steps:

[0050] S1. Inner layer sub-board manufacturing, a first through-hole is made on the inner layer sub-board, the first through-hole is metalized, resin is filled and solidified after the first through-hole is metalized, and an inner layer via hole is formed; the inner layer via hole is shaped and then the surface of the inner layer via hole is metalized, and first pads are formed on both sides of the inner layer via hole;

[0051] S2. Sub-outer layer sub-board manufacturing, a plurality of sub-outer layer sub-boards are manufactured by continuous pressing on both sides of the inner layer sub-board, and a first blind hole is made on the sub-outer layer sub-board at a position corresponding to the inner layer via hole, the first blind hole exposing the first pad; the first blind hole is shaped and then the whole of the first blind hole is metalized, and second pads are formed on the side of the first blind hole away from the inner layer via hole;

[0052] S3. Total pressing manufacturing, outer layer sub-boards are pressed on the sub-outer layer sub-boards on both sides, and a second blind hole is made on the outer layer sub-board at a position corresponding to the first blind hole, the second blind hole exposing the second pad;

[0053] Specifically, in step S1, at least three electroplating processes are included:

[0054] S11. Through-hole electroplating, the first through-hole made on the inner layer sub-board is metalized;

[0055] S12. One-time full-plate electroplating, the metal plating layer thickness of the inner wall of the first through-hole is thickened, and a wrap metal layer protruding into the first through-hole is formed at the first through-hole opening;

[0056] S13. Inner layer via hole surface electroplating, the surface of the inner layer via hole is metalized and the first pads are formed on both sides of the inner layer via hole. By improving the electroplating process used on the inner layer via hole, the shape of the metal layer between the inner layer via hole and the blind holes of other layers is adjusted, thereby improving the connection reliability between the inner layer via hole and its adjacent blind holes

[0057] Further, in order to improve the manufacturing quality of the inner layer via hole, improve the bonding force of the first through-hole and the metal layer electroplated thereon, improve the resistance of the metal layer to thermal expansion effect during thermal cycling, ensure the overall connection reliability of the metal layer on the inner layer via hole, and further improve the overall electrical connection reliability of the multi-stage HDI board; in step S1, at least two surface treatment processes are also included:

[0058] A11. Through-hole surface treatment, before step S11, the inner wall and the opening of the first through-hole are surface treated by deburring and one-time plasma cleaning;

[0059] A12. Inner layer via hole surface treatment, after step S12 is completed and before step S13 is performed, the resin layer and the wrap metal layer on the surface of both sides of the inner layer via hole are surface treated by one-time plate grinding, chemical copper reduction, two-time plate grinding, two-time plasma cleaning, and chemical cleaning.

[0060] Preferably, the thickness of the wrap metal layer is 1.8±0.2 mil after step S12; the thickness of the wrap metal layer is 1.6±0.2 mil after the first plate grinding process in step A12; the thickness of the wrap metal layer is 1.25±0.2 mil after the chemical copper reduction process; the thickness of the wrap metal layer is 0.5-1 mil after the second plate grinding process; and the relatively thick wrap metal layer provides sufficient buffer between the resin and the first pad.

[0061] After step S13, the first pad with a thickness of no less than 1.4 mil is formed by the first plating process, the thickness of the metal layer of the first pad is increased, and the resistance of the first pad to the metal layer cracking caused by thermal expansion effect during thermal cycle is improved.

[0062] Further, after the second plasma cleaning process in step A12, the etching marks with a depth of no less than 0.2 mil are formed on the surface of the resin in the inner via, so as to increase the connection area between the resin surface and the first pad and improve the overall connection reliability of the metal layer on the inner via.

[0063] Further, step S11 further comprises:

[0064] S111. First horizontal copper deposition, uniformly depositing a metal plating layer on the inner wall of the first via formed on the inner sub-board;

[0065] S112. Plate surface plating, thickening the metal plating layer on the inner wall of the first via while forming the inner layer circuit on the inner board, and forming a wrap metal layer on the first via aperture; the deep plating capability in the first via is enhanced and the thickness uniformity of the metal plating layer in the first via is improved by adding the first horizontal copper deposition process before the plate surface plating, and the quality of the metal plating layer in the first via is optimized.

[0066] Similarly, step S13 further comprises:

[0067] S131. Second horizontal copper deposition, uniformly depositing a metal plating layer on the surface of the inner via;

[0068] S132. Second full plate surface plating, metallizing the surface of the inner via and forming the first pad on both sides of the inner via; the metal plating layer is uniformly attached to the surface of the wrap metal layer of the first via and the top surface of the resin by the second horizontal copper deposition process, the plating uniformity of the subsequent second full plate surface plating is improved, and the adhesion of the metal plating layer formed on the resin via is enhanced, and then the first pad with the required thickness is formed by the second full plate surface plating process at one time, and the resistance of the first pad to the metal layer cracking caused by thermal expansion effect during thermal cycle is improved.

[0069] Furthermore, in order to improve the manufacturing quality of the blind hole metallization on the sub-outer daughter board, ensure good adhesion of the metal plating layer in the blind hole and good adhesion with the adjacent metal layer, improve the reliability of the connection between the multi-level metallized blind holes through the metal layer, and thus improve the reliability of the electrical connection of the multi-level HDI board as a whole; in step S2, at least two electroplating processes and one surface treatment process are included:

[0070] S21 blind hole plating, the first blind hole after plastic body metallization, and the blind hole plated metal layer protruding from the outer surface of the sub-board set;

[0071] S22. Blind hole surface treatment: The sub-outer daughter board, having undergone the blind hole electroplating process, is baked at 150-170°C for not less than 2 hours to promote effective crystallization of the electroplated metal layer within the first blind hole, thereby improving the reliability of the metallization within the first blind hole. Subsequently, the surface of the sub-outer daughter board is ground and degreased. The grinding process removes the metal layer protruding from the surface of the sub-outer daughter board at the blind hole, thereby increasing the roughness of the resin layer on the surface of the sub-outer daughter board and the metal layer on the surface of the blind hole. The surface of the sub-outer daughter board is then cleaned by degreasing.

[0072] S23. Electroplating the surface of the blind hole metallizes the surface of the first blind hole facing away from the inner plug hole and forms a second pad covering the surface of the first blind hole.

[0073] Furthermore, after step S23, a second pad having a thickness of not less than 0.5 mil is formed through a single electroplating process, thereby increasing the thickness of the metal layer forming the second pad and improving the ability of the second pad to resist cracking of the metal layer caused by thermal expansion effects during thermal cycling.

[0074] Example 2

[0075] like Figures 2-3 As shown, this embodiment provides a multi-level HDI board. The multi-level HDI board is provided with a plurality of stacked hole structures. The stacked hole structures include inner plug holes and a plurality of layers of blind holes stacked on both sides of the inner plug holes. The multi-level HDI board is manufactured according to the continuous pressing method for manufacturing a high-reliability multi-level HDI board as provided in Example 1.

[0076] In the multi-stage HDI board, the metal layer in the inner layer via includes an inner wall metal layer arranged on the inner wall of the first via, a wrap metal layer arranged on the surface aperture of the first via, and a first pad covering the wrap metal layer and the resin surface of the inner layer via; the wrap metal layer is arranged on the surface aperture of the first via and extends to the inside of the first via, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole is not more than the area of the first pad, and the blind holes arranged on both sides of the inner layer via are separated by a second pad. Further, the thickness of the inner wall metal layer is 1-4 mil, the thickness of the wrap metal layer is 0.5-1 mil, the thickness of the first pad is not less than 1.4 mil, and the thickness of the second pad is not less than 0.5 mil.

[0077] Specifically, by adjusting the shape and thickness of the metal layer between the conductive inner layer via and the blind hole connected to other layers, the connection reliability between the inner layer via and its adjacent blind hole is improved, by adjusting the thickness of the inner wall metal layer in the inner layer via, a inner layer via with higher strength and better buffering performance is constructed, at the same time, by forming a wrap metal layer connected to the inner wall metal layer of the inner layer via and protruding into the inner layer via at the top, the integrity between the metal layers in the inner layer via is improved, and the separation between the metal layers when heated is avoided; at the same time, by arranging the first pad and the second pad covering the top of the inner layer via and the first blind hole, and making the first pad and the second pad completely cover the metal layer filled inside, the connection reliability of all metal layers in the multi-stage hole interlayer connection is improved, at the same time, by making the first pad and the second pad maintain a relatively thick thickness, the buffering capacity of the first pad and the second pad to thermal expansion effect is improved.

[0078] Further, the blind hole is a laser hole, the blind hole has an aperture on the side away from the inner layer via and a hole bottom on the side close to the inner layer via, and in the blind hole formed on the multi-layer HDI board, the hole bottom area is not less than 85% of the aperture area; by adjusting the shape of the laser to make the blind hole in the multi-stage HDI board, specifically, the area of the blind hole bottom is increased under the premise of ensuring the aperture area of the blind hole, thereby improving the contact area and bonding performance of the blind hole as a whole with the adjacent first pad and second pad, thereby improving the reliability of the connection through the metalized holes in the multi-stage HDI board.

[0079] Embodiment 3

[0080] As Figures 2-4As shown, the embodiment provides a 20-layer metal layer designed multi-stage HDI board, specifically, the multi-stage HDI board is made according to the continuous pressing manufacturing method of the high-reliability multi-stage HDI board as provided in the embodiment 1, and the metal layers of the multi-stage HDI board are all made of copper. In the inner plate pressing manufacturing, the L5-16 layers are pressed once to form the inner via hole with the resin plug, and the first pad is formed at the top of the inner via hole; subsequently, the L4-17, L3-18 and L2-19 layers are pressed three times to form the outer layer, and the first blind hole filled with copper by the electroplating process is added to the corresponding position of the inner via hole in the longitudinal direction each time, and the hole of the first blind hole forms the second pad; finally, the L1-20 layer is added to the outer sub-plate to form the total pressing, and the second blind hole filled with copper by the electroplating process is added to the corresponding position of the first blind hole, and the third pad covering the second blind hole is formed according to the required pattern on the second blind hole.

[0081] In the inner via hole, the metal layer includes the inner wall metal layer arranged on the inner wall of the first through hole, the wrap metal layer arranged on the surface hole of the first through hole, and the first pad covering the wrap metal layer and the resin surface of the inner via hole; the wrap metal layer is arranged on the surface hole of the first through hole and extends to the inside of the first through hole, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole is not more than the area of the first pad, and the blind holes arranged on both sides of the inner via hole are separated by the second pad.

[0082] Further, the thickness of the inner wall metal layer is 1-4 mil, the thickness of the wrap metal layer is 0.5-1 mil, the thickness of the first pad is not less than 1.4 mil, and the thickness of the second pad is not less than 0.5 mil.

[0083] Further, the first blind hole and the second blind hole are both laser holes, and in the first blind hole and the second blind hole, the bottom area is not less than 85% of the hole area.

[0084] Obviously, the above embodiments of the present application are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the specific embodiments of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the claims of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A continuous lamination method for manufacturing a high-reliability multi-level HDI board, the multi-level HDI board being provided with a plurality of via-in-via structures, each of the via-in-via structures comprising an inner via and a plurality of blind vias laminated on both sides of the inner via, the method comprising the following steps: S1. manufacturing an inner sub-board, a first via is formed on the inner sub-board, the first via is metallized, then filled with resin and cured to form an inner via, the inner via is shaped and then the surface thereof is metallized, and first pads are formed on both sides of the inner via; S2. manufacturing a secondary outer sub-board, a plurality of secondary outer sub-boards are laminated on both sides of the inner sub-board by continuous lamination, and a first blind via is formed on each of the secondary outer sub-boards at a position corresponding to the inner via, the first blind via exposes the first pad, the first blind via is shaped and then the entire surface thereof is metallized, and second pads are formed on the side of each of the first blind vias away from the inner via; S3. manufacturing a final lamination, outer sub-boards are laminated on both sides of the secondary outer sub-boards, and a second blind via is formed on each of the outer sub-boards at a position corresponding to the first blind via, the second blind via exposes the second pad; characterized in that, in the step S1, at least three electroplating processes are included: S11. via electroplating, the first via formed on the inner sub-board is metallized; S12. one-time full-plate electroplating, the thickness of the metal plating layer on the inner wall of the first via is thickened, and a wrap metal layer protruding into the first via is formed at the aperture of the first via; S13. inner via surface electroplating, the surface of the inner via is metallized, and the first pads are formed on both sides of the inner via; in the step S1, at least two surface treatment processes are also included: A11. via surface treatment, before the step S11, the inner wall and aperture of the first via are surface treated by deburring and one-time plasma cleaning; A12. inner via surface treatment, after the step S12 is completed and before the step S13 is performed, the resin layer and wrap metal layer on the surface of both sides of the inner via are surface treated by one-time plate grinding, chemical copper reduction, two-time plate grinding, two-time plasma cleaning, and chemical cleaning; after the step S12, the thickness of the wrap metal layer is 1.8±0.2 mil; after the one-time plate grinding process in the step A12, the thickness of the wrap metal layer is 1.6±0.2 mil; then, after the chemical copper reduction process, the thickness of the wrap metal layer is 1.25±0.2 mil; after the two-time plate grinding process, the thickness of the wrap metal layer is 0.5-1 mil; after the step S13, the first pad with a thickness not less than 1.4 mil is formed by one-time electroplating.

2. The method of claim 1, wherein the method further comprises: after the two-time plasma cleaning process in the step A12, an etching trace with a depth not less than 0.2 mil is formed on the surface of the resin in the inner via.

3. The continuous lamination method for manufacturing a high-reliability multi-level HDI board according to any one of claims 1-2, characterized in that, the step S11 further comprises: S111. First horizontal copper deposition, uniformly depositing a metal plating layer on the inner wall of the first via formed on the inner layer sub-board; S112. Board surface electroplating, thickening the metal plating layer on the inner wall of the first via while forming the inner layer circuit on the inner layer board, and forming a wrap metal layer on the first via aperture; The step S13 further comprises: S131. Second horizontal copper deposition, uniformly depositing a metal plating layer on the surface of the inner layer via; S132. Second full-board electroplating, metallizing the surface of the inner layer via and forming a first pad on both sides of the inner layer via.

4. The method of claim 3, wherein the method further comprises: The step S2 comprises at least two electroplating processes and one surface treatment process: S21. Blind hole electroplating, metallizing the first blind hole after shaping and protruding the metal layer formed by the blind hole electroplating process on the surface of the secondary outer layer sub-board; S22. Blind hole surface treatment, baking the secondary outer layer sub-board at a temperature of 150-170℃ for not less than 2h, then grinding and degreasing the surface of the secondary outer layer sub-board, removing the metal layer protruding on the surface of the secondary outer layer sub-board by grinding, increasing the roughness of the resin on the surface of the secondary outer layer sub-board and the metal layer on the surface of the blind hole, and then cleaning the surface of the secondary outer layer sub-board by degreasing; S23. Blind hole surface electroplating, metallizing the surface of the first blind hole away from the inner layer via and forming a second pad covering the surface of the first blind hole.

5. The method of claim 4, wherein the method further comprises: After the step S23, the second pad with a thickness of not less than 0.5mil is formed by one electroplating process.

6. A multi-level HDI board, wherein a plurality of via-in-via structures are arranged on the multi-level HDI board, each of the via-in-via structures comprising an inner via and a plurality of blind vias stacked on both sides of the inner via, and wherein the inner via comprises a first inner via and a second inner via, the first inner via is arranged on the second inner via, and the first inner via is connected to the second inner via through a first connecting hole and a second connecting hole. The multi-stage HDI board is made according to the continuous pressing method of the high-reliability multi-stage HDI board of any one of claims 1-5; In the multi-stage HDI board, the metal layer in the inner layer via includes an inner wall metal layer arranged on the inner wall of the first via, a wrap metal layer arranged on the surface aperture of the first via, and a first pad covering the wrap metal layer and the resin surface of the inner layer via; the wrap metal layer is arranged on the surface aperture of the first via and extends into the first via, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole is not more than the area of the first pad, and the blind holes arranged on both sides of the inner layer via are separated by a second pad.

7. The multi-tier HDI board of claim 6, wherein, The thickness of the inner wall metal layer is 1-4mil, the thickness of the wrap metal layer is 0.5-1mil, the thickness of the first pad is not less than 1.4mil, and the thickness of the second pad is not less than 0.5mil.

8. The multi-tier HDI board of claim 7, wherein, The blind hole is a laser hole, the blind hole has an aperture away from the inner layer via and a hole bottom close to the inner layer via, and in the blind hole formed on the multi-layer HDI board, the area of the hole bottom is not less than 85% of the area of the aperture.

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