Continuous pressing manufacturing method of high-reliability multi-order HDI (High Density Interconnect) board

Abstract

The invention provides a continuous pressing manufacturing method of a high-reliability multi-stage HDI plate, and the method comprises the steps: adjusting the shape of a metal layer for conducting inner-layer plug holes and blind holes and connecting the blind holes of other layers in the multi-stage HDI plate through improving the shaping and cleaning processes of an electroplating process adopted in the continuous pressing manufacturing of the multi-stage HDI plate; therefore, the connection reliability of each step of holes in the multi-step HDI board is improved. Specifically, by adjusting the shape and the thickness of the manufactured metal layers for conducting the inner-layer plug holes and the blind holes and connecting the blind holes of other layers, the inner-layer plug holes with higher strength and better buffer performance are constructed, meanwhile, the bonding performance of connection of the metal layers between the adjacent holes is improved, metal coatings are prevented from being separated when the metal coatings are heated, and the service life of the metal coatings is prolonged. And the overall connection reliability of all metal coatings in the multi-stage HDI plate is improved.

Description

Technical Field

[0001] The invention relates to the field of printed circuit board manufacturing, and more specifically to a continuous pressing and manufacturing method for a high-reliability multi-stage HDI board. Background Art

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

[0003] In practical applications, one of the main challenges faced by the multi-level hole structure in the multi-level HDI board is the cracking of the connecting copper between the 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 the multi-level HDI board, the existing technical solutions often adjust the material selection matching, adjust the process parameter matching and improve the hole manufacturing accuracy to ensure the effective adhesion of the connecting copper and prevent it from cracking. Specifically, it includes: 1. Adjusting the hole connection layout in the HDI board. In the design of resin plug holes, the stress caused by thermal expansion mismatch can be reduced by selecting resin and filling materials with expansion coefficients close to those of the HDI board substrate material; 2. Too thick hole walls or irregular shapes may affect the adhesion of copper in the holes, resulting in poor welding or reduced electrical performance. By improving the hole manufacturing process, the processing accuracy of the holes can be improved, thereby improving the reliability of electrical connections; 3. In the lamination manufacturing process of multi-stage HDI boards, the uneven expansion caused by temperature differences can be reduced by precisely controlling temperature and pressure, thereby reducing thermal stress; 4. By adding flexible layers or buffer layers, such as soft copper foil layers, in the stacking design of multi-stage HDI boards, the stress transfer caused by thermal expansion differences can be effectively alleviated, reducing the risk of copper cracking; 5. In the design of long blind holes or long through holes, appropriately increasing the hole wall thickness or using a reinforced structure design can help improve the mechanical strength of the hole wall and reduce cracks caused by thermal expansion.

[0004] However, specifically, in the manufacturing process of multi-level HDI boards using continuous pressing, there is still a lack of improvement methods for the overall process technology to ensure that the copper layers in the multi-level holes formed are tightly connected, and the thickness of the copper layers between the holes is sufficient to resist the overall stress of the thermal expansion effect, thereby ensuring the connection reliability of the holes in the multi-level HDI boards as a whole and avoiding hole connection failure to the greatest extent. Summary of the invention

[0005] The present invention aims to overcome at least one defect of the above-mentioned prior art, and provides a continuous pressing method for manufacturing a high-reliability multi-level HDI board, which updates the continuous pressing manufacturing process of the multi-level HDI board, ensures that the copper layers in the multi-level holes formed are tightly connected, and the thickness of the copper layers between the holes is sufficient to resist the overall stress of the thermal expansion effect, thereby ensuring the connection reliability of the holes of each level in the multi-level HDI board as a whole, and avoiding hole connection failure to the greatest extent.

[0006] The technical solution adopted by the present invention first provides a continuous pressing method for manufacturing a high-reliability multi-level HDI board, wherein the multi-level HDI board is provided with a plurality of stacked hole structures, wherein the stacked hole structures include an inner layer plug hole and a plurality of layers of blind holes stacked on both sides of the inner layer plug hole, and the manufacturing method comprises the following steps: S1. Making an inner layer daughter board, making a first through hole on the inner layer daughter board, metalizing the first through hole, filling it with resin and curing it to form an inner layer plug hole; shaping the inner layer plug hole and metalizing its surface, and forming first pads on both sides of the inner layer plug hole; S2. Manufacturing a sub-outer layer daughter board, manufacturing a plurality of sub-outer layer daughter boards on both sides of the inner layer daughter board by continuous lamination, and manufacturing a first blind hole at a position on the sub-outer layer daughter board corresponding to the inner layer plug hole, wherein the first blind hole exposes the first pad; shaping the first blind hole and then metalizing it throughout, and forming a second pad on the side of the first blind hole away from the inner layer plug hole; S3. Total pressing and production, pressing the outer sub-boards on both sides respectively, and making a second blind hole on the outer sub-board at the position corresponding to the first blind hole, wherein the second blind hole exposes the second pad; Specifically, in step S1, at least three electroplating processes are included: S11. Through-hole electroplating to metallize the first through-hole made on the inner daughter board; S12. A full-surface electroplating operation to thicken the metal coating on the inner wall of the first through hole and to form a wrap metal layer protruding toward the inside of the first through hole at the opening of the first through hole; S13. Electroplating the surface of the inner layer plug hole to metallize the surface of the inner layer plug hole and form first pads on both sides of the inner layer plug hole.

[0007] In the present technical scheme, a hole structure is provided in a multi-level HDI board, which includes an inner layer plug hole structure arranged in the center layer of the multi-level HDI and a multi-level blind hole structure concentrically arranged on both sides thereof, thereby saving wiring space in the multi-level HDI board and realizing reliable electrical connection between the layers of the multi-level HDI board. At the same time, by improving the electroplating process used on the inner layer plug hole, the shape of the metal layer between the inner layer plug hole and the blind holes connecting other layers is adjusted, thereby improving the connection reliability between the inner layer plug hole and its adjacent blind holes. Specifically, the manufacturing process of the inner layer sub-board includes three electroplating processes. The first electroplating is used to plate a metal layer on the inner wall of the first through-hole. The second electroplating is used to thicken the metal plating thickness of the inner wall of the first through-hole while forming the inner layer circuit on the inner layer sub-board. A wrap metal layer protruding toward the inside of the first through-hole is formed at the opening of the first through-hole. After the first through-hole is plugged with resin, the third electroplating process is used to form a first solder pad on the wrap metal layer and the top of the resin in the through-hole. The self-adhesion ability between the multiple electroplated metal layers is used to improve the overall reliability of the metal layer formed by electroplating on the inner layer plugging hole. At the same time, the thickness and shape of the metal plating at each location of the inner layer plugging hole are adjusted through multiple electroplating to ensure that the metal layer can play a sufficient buffering role at each location of the inner layer plugging hole when heated. Among them, the first electroplating process is to perform full-body electroplating on the first through hole forming the inner layer plug hole, so as to plate a uniform metal layer on the inner wall of the through hole, so that the first through hole is metallized throughout; preferably, the thickness of the metal layer plated in the first through hole by the first electroplating process is relatively thin, thereby ensuring the uniformity of electroplating in the first through hole, providing a good bonding surface for the newly electroplated copper layer when the thickness of the side wall metal layer is thickened by subsequent full-board electroplating, improving the overall strength of the metal layer on the inner wall of the first through hole, and ensuring that the current distribution on the board surface of the first through hole is balanced during the subsequent full-board electroplating process, thereby enhancing the uniformity of the plating formed by the subsequent electroplating process. Furthermore, the second electroplating process adopts a full-board electroplating process. By setting a wrap metal layer protruding into the first through hole, the area where the top of the resin contacts the first pad is reduced after the resin is poured into the first through hole to form an inner plug hole, thereby providing a better buffer when there is a difference in thermal expansion between the resin and the metal layer when heated; at the same time, by setting a connected wrap metal layer and the metal layer on the inner wall of the first through hole to cover the metal plating layer formed by the first through hole electroplating, the possibility of connection failure due to the destruction of the metal layer in the inner plug hole is further avoided. Furthermore, in the second full-board electroplating process, the production of the first pad is completed through a one-time electroplating, which simplifies the process and prevents the reliability risk of the subsequent separation of the two metal layers after heating due to the secondary electroplating.

[0008] Preferably, in a multi-level HDI board, copper is used for the metal layer for realizing multi-level hole connection. In the design of the inner plug hole, a resin or filling material having an expansion coefficient close to that of the HDI board substrate material is selected. Since the thermal expansion coefficient of copper is 17PPM, a resin with a lower thermal expansion coefficient can be selected to reduce the difference in expansion and contraction between the resin and copper when heated, thereby improving the reliability of the electrical connection between the inner plug hole and the metallized blind hole stacked thereon; preferably, a resin type with an expansion coefficient not greater than 60PPM is used to reduce the stress caused by thermal expansion mismatch.

[0009] Furthermore, in the step S1, at least two surface treatment processes are also included: A11. Surface treatment of the through hole: before step S11, the inner wall and the opening of the first through hole are surface treated by deburring and plasma cleaning; A12. Surface treatment of the inner plug hole. After step S12 is completed and before step S13 is performed, the resin layer and the wrap metal layer on both sides of the inner plug hole are surface treated by primary grinding, chemical copper reduction, secondary grinding, secondary plasma cleaning, and chemical cleaning.

[0010] Specifically, in order to improve the manufacturing quality of the inner layer plugging holes and improve the bonding strength between the first through hole and the electroplated metal layer thereon, before the through-hole electroplating process, a deburring process is used to clean the inner wall and the hole mouth of the first through hole from debris generated by drilling, and a plasma cleaning process is used to produce slight etching on the inner wall and the hole mouth of the first through hole, thereby providing a slightly rough surface for the subsequent through-hole electroplating process and improving the bonding strength of the metal layer plated on the inner wall and the hole mouth of the first through hole. Furthermore, after the first through hole has been subjected to the first full-board electroplating and resin plugging process, the thickness of the wrap metal layer on the surface of the inner plugging hole and the protruding thickness and shape of the resin are shaped through the processes of primary grinding, chemical copper reduction, secondary grinding, secondary plasma cleaning, and chemical cleaning. Specifically, the thickness of the wrap metal layer and the protruding thickness of the resin are uniformly thinned through the processes of primary grinding, chemical copper reduction, and secondary grinding to match the thickness of the circuit on the inner sub-board and improve the pressing accuracy; then, the surface of the wrap metal layer and the surface of the resin are further adjusted to be clean and slightly rough through the secondary plasma cleaning and chemical cleaning processes, thereby providing a good bonding surface for the subsequent formation of the first pad on the wrap metal layer and the surface of the resin through the second full-board electroplating, further improving the connection strength of each metal layer in the inner plugging hole, improving the metal layer's ability to resist thermal expansion effects during thermal cycles, ensuring the overall connection reliability of the metal layer on the inner plugging hole, and thereby improving the overall electrical connection reliability of the multi-stage HDI board.

[0011] Preferably, the method further includes selecting and controlling the thickness of each metal layer in the inner plug hole. After the step S12, the thickness of the wrap metal layer is 1.8±0.2mil; after the first grinding process in step A12, the thickness of the wrap metal layer is 1.6±0.2mil; then, after the chemical copper reduction process, the thickness of the wrap metal layer is 1.25±0.2mil; after the second grinding process, the thickness of the wrap metal layer is 0.5-1mil; by setting a relatively thick wrap metal layer, sufficient buffering is provided between the resin and the first pad; After step S13, the first pad having a thickness of not less than 1.4 mil is formed through a single electroplating process, thereby increasing the thickness of the metal layer forming the first pad and improving the ability of the first pad to resist cracking of the metal layer caused by thermal expansion effect during thermal cycling.

[0012] Furthermore, after the secondary plasma cleaning process in step A12, a bite mark with a depth of not less than 0.2 mil is formed on the resin surface in the inner layer plug hole, thereby increasing the connection area between the resin surface and the first solder pad, improving the bonding performance between the resin and the first solder pad in the inner layer plug hole, ensuring the overall connection reliability of the metal layer on the inner layer plug hole, and further improving the overall electrical connection reliability of the multi-level HDI board.

[0013] Furthermore, the step S11 also includes: S111. A horizontal copper deposition is performed once, and a metal coating is evenly plated on the inner wall of the first through hole produced on the inner sub-board; S112. Electroplating on the board surface, while forming the inner layer circuit on the inner layer board, thickens the metal plating thickness of the inner wall of the first through hole, and forms a wrap metal layer at the opening of the first through hole; by adding a horizontal copper plating process before electroplating on the board surface, the deep plating ability in the first through hole is enhanced and the thickness uniformity of the metal plating in the first through hole is improved, thereby optimizing the quality of the metal plating in the first through hole.

[0014] Similarly, the step S13 also includes: S131. A secondary horizontal copper deposition is performed to uniformly plate a metal coating on the surface of the inner plug hole; S132. A secondary full-surface electroplating is performed to metallize the surface of the inner-layer plug hole and form a first solder pad on both sides of the inner-layer plug hole; a uniform metal plating layer is attached to the surface of the wrap metal layer and the top surface of the resin on the first plug hole through a secondary horizontal copper plating process, thereby improving the plating uniformity of the subsequent secondary full-surface electroplating and at the same time enhancing the adhesion of the metal plating layer formed on the resin plug hole; then, a first solder pad of the required thickness is made at one time through a secondary full-surface electroplating process, thereby improving the first solder pad's ability to resist cracking of the metal layer due to thermal expansion effects during thermal cycles.

[0015] Furthermore, in the step S2, at least two electroplating processes and one surface treatment process are included: S21. Blind hole electroplating, so that the first blind hole after plastic surgery is metallized, and the metal layer of the blind hole electroplating protrudes from the surface of the sub-outer sub-board; S22. Surface treatment of the blind holes, baking the sub-outer sub-board after the blind hole electroplating process at 150-170°C for not less than 2h, then grinding and degreasing the surface of the sub-outer sub-board, grinding away the metal layer protruding from the surface of the sub-outer sub-board at the blind hole by the grinding process, increasing the roughness of the resin on the surface of the sub-outer sub-board and the metal layer on the surface of the blind hole, and then cleaning the surface of the sub-outer sub-board by degreasing; S23. Electroplating the surface of the blind hole to metallize the surface of the first blind hole facing away from the inner plug hole and to form a second pad covering the surface of the first blind hole.

[0016] In the present technical scheme, in order to improve the manufacturing quality of blind hole metallization on the sub-outer layer sub-board and ensure good adhesion of the metal plating layer in the blind hole and good adhesion with the adjacent metal layer, after opening the first blind hole to expose the first pad or the adjacent second pad, a single board surface electroplating process is used to perform blind hole electroplating, thereby ensuring 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 sub-outer layer sub-board that has undergone the blind hole electroplating process at 150-170°C for not less than 2h, the formed electroplated metal layer is effectively crystallized in the first blind hole, thereby improving the reliability of metallization in the first blind hole; at the same time, the thickness of the sub-outer layer sub-board is reduced by the grinding process, and the metal in the blind hole is polished after the blind hole electroplating. The surface of the coating is shaped to increase the roughness of the resin on the surface of the sub-outer layer sub-board and the metal layer on the surface of the blind hole, and then the surface of the sub-outer layer sub-board is cleaned by degreasing treatment, thereby improving the bonding performance of the metal coating formed by the subsequent blind hole surface electroplating process and the metal coating filled in the blind hole, and reducing the reliability risk of the two metal coatings separating when heated; finally, the blind hole surface is electroplated by a secondary board surface electroplating process, and a second pad covering the metal coating in the blind hole is formed on the top of the blind hole, which provides a better bonding surface for the first blind hole superimposed on the second pad formed during the next pressing and the metal coating filled therein, thereby improving the reliability of the connection between the multi-stage metallized blind holes through the metal layer, thereby improving the reliability of the overall electrical connection of the multi-stage HDI board.

[0017] Furthermore, after step S23, the 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 cycles.

[0018] The technical solution also provides a multi-level HDI board, on which a plurality of stacked hole structures are arranged, the stacked hole structures comprising inner layer plug holes and a plurality of layers of blind holes stacked on both sides of the inner layer plug holes, the multi-level HDI board is manufactured according to the continuous pressing manufacturing method of the high-reliability multi-level HDI board provided by the technical solution; In the multi-stage HDI board, in the inner plug 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 opening of the first through hole, and a first pad covering the wrap metal layer and the surface of the inner plug hole resin; the wrap metal layer is arranged on the surface opening 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 does not exceed the area of ​​the first pad, and the blind holes overlapped on both sides of the inner plug hole are separated by a second pad. Furthermore, 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.

[0019] In the technical solution, the shape and thickness of the metal layer between the conductive inner plug hole and the blind holes connecting other layers are adjusted, so as to improve the connection reliability between the inner plug hole and its adjacent blind holes. By adjusting the thickness of the metal plating on the inner wall of the inner plug hole, an inner plug hole with higher strength and better buffering performance is constructed. At the same time, by forming a wrap metal layer connected to the metal layers on the inner wall of the inner plug hole and protruding into the inner plug hole at the top, the integrity of the metal plating layers in the inner plug hole is improved, and the separation of the metal plating layers when heated is avoided. At the same time, by providing a first soldering pad and a second soldering pad covering the inner plug hole and the top of the first blind hole, and making the first soldering pad and the second soldering pad completely cover the metal plating filled therein, the connection reliability of all metal plating layers connected between layers in the multi-step hole is improved. At the same time, by keeping the first soldering pad and the second soldering pad thicker, the buffering capacity of the first soldering pad and the second soldering pad to cope with the thermal expansion effect is improved.

[0020] Furthermore, the first blind hole is a laser hole, the first blind hole has a hole opening on the side away from the inner layer plug hole and a hole bottom on the side close to the inner layer plug 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 opening area; by adjusting the shape of the first blind hole in the laser-made multi-level HDI board, specifically, the area of ​​the bottom of the first blind hole is increased while ensuring the hole opening area of ​​the first blind hole, thereby increasing the contact area and bonding performance of the first blind hole as a whole with the adjacent first pad and second pad, thereby improving the reliability of connection through each level of metallized holes in the multi-level HDI board.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. A hole structure provided in a multi-level HDI board, including an inner layer plug hole structure provided in the center layer of the multi-level HDI and a multi-level blind hole structure concentrically provided on both sides thereof, thereby saving wiring space in the multi-level HDI board and realizing reliable electrical connection between the layers of the multi-level HDI board. At the same time, by improving the electroplating process used on the inner layer plug hole, the shape of the metal layer between the inner layer plug hole and the blind holes connecting other layers is adjusted, thereby improving the connection reliability between the inner layer plug hole and its adjacent blind holes.

[0022] 2. By shaping and cleaning the metal coatings generated by multiple electroplating processes as needed in the manufacturing process, the bonding performance between the metal coatings during each electroplating is improved. Specifically, before the through-hole electroplating process, the inner wall and the hole mouth of the first through-hole are cleaned of debris generated by drilling through a deburring process, and a plasma cleaning process is used to produce a slight etching on the inner wall and the hole mouth of the first through-hole, providing a slightly rough surface for the subsequent through-hole electroplating process, thereby improving the bonding strength of the metal layer plated on the inner wall and the hole mouth of the first through-hole; further, after the first through-hole has undergone the first full-board electroplating and resin plugging process, the thickness of the wrap metal layer on the inner plugging surface and the protruding thickness and shape of the resin are shaped through a first grinding, chemical copper reduction, a second grinding, a second plasma cleaning, and a chemical cleaning process, and the first grinding, chemical copper reduction, and a second grinding process are used to remove the protruding thickness and shape of the wrap metal layer on the inner plugging surface. The thickness of the wrap metal layer and the protruding thickness of the resin are uniformly thinned to match the thickness of the circuit on the inner layer sub-board and improve the pressing accuracy; then, the surface of the wrap metal layer and the resin are further adjusted to be clean and slightly rough through secondary plasma cleaning and chemical cleaning processes, thereby providing a good bonding surface for the subsequent formation of the first pad through the second full-board electroplating on the wrap metal layer and the resin surface, further improving the connection strength of each metal layer in the inner layer plug hole, and improving the metal layer's ability to resist thermal expansion effects during thermal cycles, ensuring the overall connection reliability of the metal layer on the inner layer plug hole, thereby improving the overall electrical connection reliability of the multi-stage HDI board. In the blind hole manufacturing process, the thickness of the sub-outer layer sub-board is reduced through the plate grinding process. At the same time, the surface of the metal plating inside the blind hole is shaped after the blind hole electroplating, thereby increasing the roughness of the resin on the surface of the sub-outer layer sub-board and the metal layer on the surface of the blind hole. Then, the surface of the sub-outer layer sub-board is cleaned through degreasing treatment, thereby improving the bonding performance between the metal plating formed by the subsequent blind hole surface electroplating process and the metal plating filled in the blind hole, and reducing the reliability risk of the two metal plating layers separating when heated.

[0023] 3. By adjusting the shape and thickness of the metal layer between the conductive inner plug hole and the blind holes connecting other layers, the connection reliability between the inner plug hole and its adjacent blind holes is improved. By adjusting the thickness of the metal plating on the inner wall of the inner plug hole, an inner plug hole with higher strength and better buffering performance is constructed. At the same time, by forming a wrap metal layer that is connected to the metal layer of the inner wall of the inner plug hole and protruding into the inner plug hole at the top, the integrity of the metal plating layers in the inner plug hole is improved, and the separation of the metal plating layers when heated is avoided. At the same time, by providing a first soldering pad and a second soldering pad covering the inner plug hole and the top of the first blind hole, and making the first soldering pad and the second soldering pad completely cover the metal plating filled therein, the connection reliability of all metal plating layers connected between layers in the multi-step hole is improved. At the same time, by keeping the first soldering pad and the second soldering pad thicker, the buffering capacity of the first soldering pad and the second soldering pad to cope with the thermal expansion effect is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic flow chart of the continuous pressing method for manufacturing a high-reliability multi-stage HDI board provided by the present invention.

[0025] Figure 2 The schematic diagram is a structural diagram of the metal layer on the inner plug hole in the multi-level HDI board provided by the present invention.

[0026] Figure 3 It is a schematic diagram of the structure of the metal layer on the blind hole in the multi-level HDI board provided by the present invention.

[0027] Figure 4 This is a schematic diagram of the structure of a multi-level HDI board provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0028] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0029] Example 1 like Figure 1 As shown, this embodiment provides a continuous pressing method for manufacturing a high-reliability multi-level HDI board. The multi-level HDI board is provided with a plurality of stacked hole structures, the stacked hole structures including an inner layer plug hole and a plurality of layers of blind holes stacked on both sides of the inner layer plug hole. The manufacturing method includes the following steps: S1. The inner daughter board is made, a first through hole is made on the inner daughter board, the first through hole is metallized, and then filled with resin and cured to form an inner plug hole; the inner plug hole is shaped and then the surface is metallized, and a first pad is formed on both sides of the inner plug hole; S2. Making a sub-outer layer daughter board, making a plurality of sub-outer layer daughter boards on both sides of the inner layer daughter board by continuous lamination, and making a first blind hole at a position on the sub-outer layer daughter board corresponding to the inner layer plug hole, the first blind hole exposing the first pad; shaping the first blind hole and then metallizing it throughout, and forming a second pad on the side of the first blind hole away from the inner layer plug hole; S3. The total pressing is performed by pressing the outer sub-boards on both sides of the sub-outer sub-boards respectively, and making a second blind hole at the position corresponding to the first blind hole on the outer sub-board, and the second blind hole exposes the second pad; Specifically, in step S1, at least three electroplating processes are included: S11. Through-hole electroplating to metallize the first through-hole made on the inner daughter board; S12. A full-surface electroplating operation to thicken the metal coating on the inner wall of the first through hole and to form a wrap metal layer protruding toward the inside of the first through hole at the opening of the first through hole; S13. Electroplating the inner plug hole surface to metalize the inner plug hole surface and form the first pads on both sides of the inner plug hole. By improving the electroplating process used on the inner plug hole, the shape of the metal layer between the inner plug hole and the blind holes connecting other layers is adjusted, thereby improving the connection reliability between the inner plug hole and its adjacent blind holes. Furthermore, in order to improve the manufacturing quality of the inner plug hole, improve the bonding strength between the first through hole and the electroplated metal layer thereon, improve the resistance of the metal layer to the thermal expansion effect during thermal cycling, ensure the overall connection reliability of the metal layer on the inner plug hole, and thus improve the overall electrical connection reliability of the multi-level HDI board; in step S1, at least two surface treatment processes are also included: A11. Surface treatment of the through hole: before step S11, the inner wall and the opening of the first through hole are surface treated by deburring and plasma cleaning; A12. Surface treatment of the inner plug hole. After step S12 is completed and before step S13 is performed, the resin layer and the wrap metal layer on both sides of the inner plug hole are surface treated by primary grinding, chemical copper reduction, secondary grinding, secondary plasma cleaning, and chemical cleaning.

[0030] Preferably, the thickness of each metal layer in the inner plug hole is selected and controlled. After step S12, the thickness of the wrap metal layer is 1.8±0.2mil; after the first grinding process in step A12, the thickness of the wrap metal layer is 1.6±0.2mil; then, after the chemical copper reduction process, the thickness of the wrap metal layer is 1.25±0.2mil; after the second grinding process, the thickness of the wrap metal layer is 0.5-1mil; by setting a relatively thick wrap metal layer, sufficient buffering is provided between the resin and the first pad; After step S13, a first solder pad having a thickness of not less than 1.4 mil is formed through a single electroplating process, thereby increasing the thickness of the metal layer forming the first solder pad and improving the ability of the first solder pad to resist cracking of the metal layer caused by thermal expansion effects during thermal cycles.

[0031] Furthermore, after the secondary plasma cleaning process in step A12, a bite mark with a depth of not less than 0.2 mil is formed on the resin surface in the inner layer plug hole, thereby increasing the connection area between the resin surface and the first pad and improving the overall connection reliability of the metal layer on the inner layer plug hole.

[0032] Furthermore, step S11 also includes: S111. A horizontal copper deposition is performed once, and a metal coating is evenly plated on the inner wall of the first through hole produced on the inner sub-board; S112. Electroplating on the board surface, while forming the inner layer circuit on the inner layer board, thickens the metal plating thickness of the inner wall of the first through hole, and forms a wrap metal layer at the opening of the first through hole; by adding a horizontal copper plating process before electroplating on the board surface, the deep plating ability in the first through hole is enhanced and the thickness uniformity of the metal plating in the first through hole is improved, thereby optimizing the quality of the metal plating in the first through hole.

[0033] Similarly, step S13 also includes: S131. Secondary horizontal copper deposition to evenly plate the metal coating on the surface of the inner plug hole; S132. Secondary full-surface electroplating is performed to metalize the surface of the inner-layer plug hole and form the first solder pads on both sides of the inner-layer plug hole; a uniform metal plating layer is attached to the surface of the wrap metal layer and the top surface of the resin on the first plug hole through a secondary horizontal copper plating process, thereby improving the plating uniformity of the subsequent secondary full-surface electroplating and at the same time enhancing the adhesion of the metal plating layer formed on the resin plug hole. Subsequently, a first solder pad of the required thickness is made at one time through a secondary full-surface electroplating process, thereby improving the first solder pad's ability to resist cracking of the metal layer due to thermal expansion effects during thermal cycles.

[0034] Furthermore, in order to improve the manufacturing quality of blind hole metallization on the sub-outer layer 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: S21. Blind hole electroplating, so that the first blind hole after plastic surgery is metallized, and the metal layer of the blind hole electroplating protrudes from the surface of the sub-outer sub-board; S22. Surface treatment of blind holes, baking the sub-outer sub-board after the blind hole electroplating process at 150-170°C for not less than 2h, so as to promote the effective crystallization of the electroplated metal layer formed in the first blind hole, thereby improving the reliability of metallization in the first blind hole; then, grinding and degreasing the surface of the sub-outer sub-board, grinding away the metal layer protruding from the surface of the sub-outer sub-board at the blind hole by the grinding process, increasing the roughness of the resin on the surface of the sub-outer sub-board and the metal layer on the surface of the blind hole, and then cleaning the surface of the sub-outer sub-board by degreasing; S23. Electroplating the surface of the blind hole metalizes 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.

[0035] 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 cycles.

[0036] Example 2 like Figure 2-Figure 3 As shown, this embodiment provides a multi-level HDI board, on which a plurality of stacked hole structures are arranged, the stacked hole structures including inner layer plug holes and a plurality of layers of blind holes stacked on both sides of the inner layer plug holes, and the multi-level HDI board is manufactured according to the continuous pressing manufacturing method of the high-reliability multi-level HDI board provided in Example 1; In a multi-stage HDI board, in the inner plug 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 opening of the first through hole, and a first pad covering the wrap metal layer and the surface of the inner plug hole resin; the wrap metal layer is arranged on the surface opening of the first through hole and extends into the first through hole, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole does not exceed the area of ​​the first pad, and the blind holes overlapped on both sides of the inner plug hole are separated by a second pad. Furthermore, 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] Specifically, by adjusting the shape and thickness of the metal layer between the conductive inner-layer plug hole and the blind holes connecting other layers, the connection reliability between the inner-layer plug hole and its adjacent blind holes is improved. By adjusting the thickness of the inner wall metal plating in the inner-layer plug hole, an inner-layer plug hole with higher strength and better buffering performance is constructed. At the same time, by forming a wrap metal layer that is connected to the inner wall metal layer of the inner-layer plug hole and protrudes into the inner-layer plug hole at the top, the integrity of the metal plating layers in the inner-layer plug hole is improved, and the separation of the metal plating layers when heated is avoided. At the same time, by providing a first soldering pad and a second soldering pad covering the inner-layer plug hole and the top of the first blind hole, and making the first soldering pad and the second soldering pad completely cover the metal plating filled therein, the connection reliability of all metal plating layers connected between layers in the multi-step hole is improved. At the same time, by keeping the first soldering pad and the second soldering pad thicker, the buffering capacity of the first soldering pad and the second soldering pad to cope with the thermal expansion effect is improved.

[0038] Furthermore, the blind hole is a laser hole, the blind hole has a hole opening on the side away from the inner layer plug hole and a hole bottom on the side close to the inner layer plug hole, and in the blind hole formed on the multi-layer HDI board, the hole bottom area is not less than 85% of the hole opening area; by adjusting the shape of the blind hole in the laser-made multi-level HDI board, specifically, the area of ​​the blind hole bottom is increased while ensuring the blind hole opening area, thereby increasing the contact area and bonding performance of the overall blind hole with the adjacent first pad and second pad, thereby improving the reliability of connection through each level of metallized holes in the multi-level HDI board.

[0039] Example 3 like Figure 2-Figure 4 As shown, this embodiment provides a multi-level HDI board with a 20-layer metal layer design. Specifically, this multi-level HDI board is made according to the continuous pressing method for making a high-reliability multi-level HDI board as provided in Example 1, and the metal layers of this multi-level HDI board are all made of copper. When the inner layer board is pressed and made, a pressing is performed once based on the L5-16 layer to form an inner layer plug hole using resin plug hole, and a first pad is formed on the top of the inner layer plug hole; subsequently, three times of outer layer pressing are performed on L4-17, L3-18, and L2-19 respectively, and each time the pressing is performed, a first blind hole filled with copper by electroplating process is superimposed on the longitudinal corresponding position of the inner layer plug hole, and the hole mouth of the first blind hole forms a second pad; finally, the outer layer sub-board is superimposed on the L1-20 layer for total pressing, and a second blind hole filled with copper by electroplating process is superimposed on the corresponding position of the first blind hole, and a third pad covering the second blind hole is formed on the second blind hole according to the required pattern.

[0040] In the inner layer plug 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 opening of the first through hole, and a first solder pad covering the wrap metal layer and the surface of the inner layer plug hole resin; the wrap metal layer is arranged on the surface opening of the first through hole and extends into the first through hole, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole does not exceed the area of ​​the first solder pad, and the blind holes overlapped on both sides of the inner layer plug hole are separated by a second solder pad.

[0041] Furthermore, 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.

[0042] Furthermore, 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 hole bottom area is not less than 85% of the hole opening area.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A continuous pressing method for manufacturing a high-reliability multi-level HDI board, wherein the multi-level HDI board is provided with a plurality of stacked hole structures, wherein the stacked hole structures include an inner layer plug hole and a plurality of layers of blind holes stacked on both sides of the inner layer plug hole, and the manufacturing method comprises the following steps: S1. Making an inner layer daughter board, making a first through hole on the inner layer daughter board, metalizing the first through hole, filling it with resin and curing it to form an inner layer plug hole; shaping the inner layer plug hole and metalizing its surface, and forming first pads on both sides of the inner layer plug hole; S2. Manufacturing a sub-outer layer daughter board, manufacturing a plurality of sub-outer layer daughter boards on both sides of the inner layer daughter board by continuous lamination, and manufacturing a first blind hole at a position on the sub-outer layer daughter board corresponding to the inner layer plug hole, wherein the first blind hole exposes the first pad; shaping the first blind hole and then metalizing it throughout, and forming a second pad on the side of the first blind hole away from the inner layer plug hole; S3. Total pressing and production, pressing the outer sub-boards on both sides respectively, and making a second blind hole on the outer sub-board at the position corresponding to the first blind hole, wherein the second blind hole exposes the second pad; It is characterized in that, in the step S1, at least three electroplating processes are included: S11. Through-hole electroplating to metallize the first through-hole made on the inner daughter board; S12. A full-surface electroplating operation to thicken the metal coating on the inner wall of the first through hole and to form a wrap metal layer protruding toward the inside of the first through hole at the opening of the first through hole; S13. Electroplating the surface of the inner layer plug hole to metalize the surface of the inner layer plug hole and form a first solder pad on both sides of the inner layer plug hole.

2. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to claim 1, characterized in that: In the step S1, at least two surface treatment processes are also included: A11. Surface treatment of the through hole: before step S11, the inner wall and the opening of the first through hole are surface treated by deburring and plasma cleaning; A12. Surface treatment of the inner plug hole. After step S12 is completed and before step S13 is performed, the resin layer and the wrap metal layer on both sides of the inner plug hole are surface treated by primary grinding, chemical copper reduction, secondary grinding, secondary plasma cleaning, and chemical cleaning.

3. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to claim 2, characterized in that: After step S12, the thickness of the wrap metal layer is 1.8±0.2mil; after the first grinding process in step A12, the thickness of the wrap metal layer is 1.6±0.2mil; then, after the chemical copper reduction process, the thickness of the wrap metal layer is 1.25±0.2mil; after the second grinding process, the thickness of the wrap metal layer is 0.5-1mil; After step S13, the first pad having a thickness of not less than 1.4 mil is formed through a one-time electroplating process.

4. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to claim 2, characterized in that: After the secondary plasma cleaning process in step A12, a bite mark with a depth of not less than 0.2 mil is formed on the resin surface in the inner plug hole.

5. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to any one of claims 1 to 4, characterized in that: The step S11 also includes: S111. A horizontal copper deposition is performed once, and a metal coating is evenly plated on the inner wall of the first through hole produced on the inner sub-board; S112. Electroplating the board surface, forming the inner layer circuit on the inner layer board, thickening the metal plating thickness of the inner wall of the first through hole, and forming a wrap metal layer at the opening of the first through hole; The step S13 also includes: S131. A secondary horizontal copper deposition is performed to uniformly plate a metal coating on the surface of the inner plug hole; S132. Perform a second full-board electroplating to metalize the surface of the inner-layer plug hole and form a first solder pad on both sides of the inner-layer plug hole.

6. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to claim 5, characterized in that: In the step S2, at least two electroplating processes and one surface treatment process are included: S21. Blind hole electroplating, so that the first blind hole after plastic surgery is metallized, and the metal layer of the blind hole electroplating protrudes from the surface of the sub-outer sub-board; S22. Surface treatment of the blind holes, baking the sub-outer sub-board after the blind hole electroplating process at 150-170°C for not less than 2h, then grinding and degreasing the surface of the sub-outer sub-board, grinding away the metal layer protruding from the surface of the sub-outer sub-board at the blind hole by the grinding process, increasing the roughness of the resin on the surface of the sub-outer sub-board and the metal layer on the surface of the blind hole, and then cleaning the surface of the sub-outer sub-board by degreasing; S23. Electroplating the surface of the blind hole to metallize the surface of the first blind hole facing away from the inner plug hole and to form a second pad covering the surface of the first blind hole.

7. The continuous pressing method for manufacturing a high-reliability multi-level HDI board according to claim 6, characterized in that: After step S23, the second pad having a thickness of not less than 0.5 mil is formed through a one-time electroplating process.

8. A multi-level HDI board, wherein the multi-level HDI board is provided with a plurality of stacked hole structures, wherein the stacked hole structures include an inner layer plug hole and a plurality of layers of blind holes stacked on both sides of the inner layer plug hole, characterized in that: The multi-level HDI board is manufactured according to the continuous pressing method for manufacturing a high-reliability multi-level HDI board according to any one of claims 1 to 7; In the multi-stage HDI board, in the inner layer plug 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 opening of the first through hole, and a first solder pad covering the wrap metal layer and the surface of the inner layer plug hole resin; the wrap metal layer is arranged on the surface opening of the first through hole and extends into the first through hole, and the wrap metal layer protrudes from the inner wall metal layer; the cross-sectional size of the blind hole does not exceed the area of ​​the first solder pad, and the blind holes overlapped on both sides of the inner layer plug hole are separated by a second solder pad.

9. The multi-level HDI board according to claim 8, characterized in that: 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.

10. The multi-level HDI board according to claim 8, characterized in that: The blind hole is a laser hole, and the blind hole has a hole opening on the side away from the inner layer plug hole and a hole bottom on the side close to the inner layer plug hole. In the blind hole formed on the multi-layer HDI board, the hole bottom area is not less than 85% of the hole opening area.

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