Multilayer circuit board manufacturing method and multilayer circuit board

Abstract

The invention provides a multilayer circuit board manufacturing method and a multilayer circuit board. The multi-layer circuit board manufacturing method comprises the following steps: obtaining a transition core board, and carrying out etching treatment on the transition core board to form a bonding pad region; laminating the first core board on one side, deviating from the bonding pad area, of the transition core board to obtain a laminated substrate; drilling the first laminated substrate to form a to-be-metalized through hole; performing copper deposition treatment on the first laminated substrate to enable the to-be-metalized through hole to form a metalized through hole; wherein a copper-based layer is formed on the hole wall of the metalized through hole, and the copper-based layer is connected with the first bonding pad area; carrying out electroplating treatment on the first press-fit substrate after copper deposition; the side, provided with the first bonding pad area, of the first pressing substrate is pressed on the side, provided with the second bonding pad area, of the second pressing substrate, so that the first bonding pad area and the second bonding pad area are oppositely arranged, and the pressing assembly is obtained. According to the manufacturing method of the multilayer circuit board, the use reliability of the multilayer circuit board is relatively good.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of multilayer circuit boards, and in particular to a multilayer circuit board manufacturing method and a multilayer circuit board. BACKGROUND

[0002] A multilayer circuit board is a printed circuit board obtained by alternately stacking three or more conductive layers through insulating materials and realizing electrical connection between layers through through-hole plating. Multilayer circuit boards are widely used in automotive electronics, communication equipment, medical equipment, consumer electronics, industrial control, and aerospace fields. Multilayer circuit boards are manufactured using a multilayer circuit board manufacturing method.

[0003] The multilayer circuit board manufacturing method of the related art includes the following steps: S1, hole filling, exposing and developing a core board to obtain a core board containing a hole filling pattern, and then filling and electroplating to obtain a core board containing a hole filling; S2, preparing an inner layer circuit, performing inner layer pretreatment, inner layer coating, inner layer exposure, inner layer development, and inner layer etching on the inner layer of the core board containing the hole filling to obtain a core board containing an inner layer circuit; S3, pressing, pressing the core board containing the inner layer circuit with a prepreg and a copper foil to obtain a multilayer circuit board.

[0004] However, in the process of manufacturing the multilayer circuit board, the core board containing the hole filling pattern is filled and electroplated, i.e. the hole wall of the hole filling is plated with copper by electroplating solution, so that the hole wall of the hole filling is metallized to form a copper plating layer on the hole wall of the hole filling. Since the hole filling is completely located in the multilayer circuit board, the hole filling cannot penetrate the multilayer circuit board, and the electroplating solution can only flow into the hole filling through the interlayer gap, so that the convection speed of the electroplating solution is poor, making it difficult for the electroplating solution to flow uniformly in the hole filling during hole filling electroplating. Thus, the copper thickness uniformity of the copper plating layer on the hole wall of the hole filling is poor, which leads to the copper plating layer on the hole wall of the hole filling being prone to cracking, thereby reducing the use reliability of the multilayer circuit board. SUMMARY

[0005] The purpose of the present disclosure is to overcome the shortcomings in the prior art and provide a multilayer circuit board manufacturing method and a multilayer circuit board that can improve the use reliability of the multilayer circuit board.

[0006] The purpose of the present disclosure is achieved by the following technical solutions: A multilayer circuit board manufacturing method, comprising: obtaining a transition core board and performing etching treatment on the transition core board to form a pad area; wherein the pad area is located on one side of the transition core board; press the first core plate on the side of the transition core plate away from the pad area to obtain a press-fit substrate; wherein the number of the press-fit substrates is two, which are a first press-fit substrate and a second press-fit substrate, one side of the first press-fit substrate is provided with a first pad area, and one side of the second press-fit substrate is provided with a second pad area; drilling processing is performed on the first press-fit substrate to form a to-be-metallized via hole; wherein the to-be-metallized via hole is arranged in correspondence with the first pad area; copper deposition processing is performed on the first press-fit substrate, so that the to-be-metallized via hole forms a metallized via hole; wherein a base copper layer is formed on the hole wall of the metallized via hole, and the base copper layer is connected with the first pad area; electroplating processing is performed on the first press-fit substrate after copper deposition; the side of the first press-fit substrate provided with the first pad area is pressed on the side of the second press-fit substrate provided with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other to obtain a press-fit assembly.

[0007] In one of the embodiments, the step of obtaining a transition core plate and performing etching processing on the transition core plate to form a pad area comprises: obtaining the transition core plate and performing cleaning processing on the transition core plate; performing pattern transfer processing on the cleaned transition core plate; performing etching processing on the pattern-transferred transition core plate to form the pad area; and performing brown processing on the etched transition core plate.

[0008] In one of the embodiments, the step of performing pattern transfer processing on the cleaned transition core plate comprises: performing heating processing on the cleaned transition core plate; performing film pasting processing on the heated transition core plate; performing exposure processing on the film-pasted transition core plate; and performing developing processing on the exposed transition core plate.

[0009] In one of the embodiments, the step of pressing the first core plate on the side of the transition core plate away from the pad area to obtain a press-fit substrate comprises: stacking a prepreg on the side of the transition core plate away from the pad area; stacking the first core plate on the prepreg, so that the prepreg is located between the first core plate and the transition core plate; performing riveting positioning processing on the first core plate and the transition core plate; and pressing the first core plate on the side of the transition core plate away from the pad area to obtain the press-fit substrate.

[0010] In one of the embodiments, the step of pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area so that the first pad area and the second pad area are oppositely arranged to obtain the press assembly comprises: stacking prepreg on the side of the second press substrate provided with the second pad area; stacking the side of the first press substrate provided with the first pad area on the prepreg so that the prepreg is between the first pad area and the second pad area; clamping and positioning the first press substrate and the second press substrate; pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area so that the first pad area and the second pad area are oppositely arranged to obtain the press assembly.

[0011] In one of the embodiments, after the step of pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area so that the first pad area and the second pad area are oppositely arranged to obtain the press assembly, the multilayer circuit board manufacturing method further comprises: cutting the press assembly to obtain a multilayer circuit board semi-finished product; drilling the multilayer circuit board semi-finished product; copper plating the multilayer circuit board semi-finished product after drilling; electroplating the multilayer circuit board semi-finished product after copper plating; and manufacturing an outer layer pattern of the multilayer circuit board semi-finished product after electroplating.

[0012] In one of the embodiments, the step of manufacturing an outer layer pattern of the multilayer circuit board semi-finished product after electroplating comprises: grinding the multilayer circuit board semi-finished product after electroplating; laminating a film on the multilayer circuit board semi-finished product after grinding; exposing the multilayer circuit board semi-finished product after lamination; developing the multilayer circuit board semi-finished product after exposure; etching the multilayer circuit board semi-finished product after development; and tin plating the multilayer circuit board semi-finished product after etching.

[0013] In one of the embodiments, after the step of manufacturing an outer layer pattern of the multilayer circuit board semi-finished product after electroplating, the multilayer circuit board manufacturing method further comprises: solder mask processing the multilayer circuit board semi-finished product; and surface treatment of the multilayer circuit board semi-finished product after solder mask processing.

[0014] In one of the embodiments, the step of electroplating the first press substrate after copper plating specifically comprises: electroplating the first press substrate after copper plating by VCP line, and the current density of the electroplating is 3-5 A / dm 2The electroplating temperature of the electroplating treatment is 40-45 DEG C, and the electroplating time of the electroplating treatment is 30-40 min.

[0015] A multilayer circuit board is made by the method of any of the embodiments described above.

[0016] Compared with the prior art, the present disclosure has at least the following advantages: 1. The multilayer circuit board manufacturing method of the present disclosure first obtains a transition core plate and performs etching treatment on the transition core plate to remove part of the copper foil layer to form a pad area. The pad area is located on one side of the transition core plate, that is, only the pad area corresponding to the buried hole is reserved on one side of the transition core plate, which is used to ensure the electrical connection between the buried hole and the inner layer circuit. Then, the first core plate is pressed on the side of the transition core plate away from the pad area, that is, the first core plate and the transition core plate are pressed to form a symmetrical stacked structure through the prepreg to obtain a pressed substrate. The number of pressed substrates is two, which are the first pressed substrate and the second pressed substrate. One side of the first pressed substrate is provided with a first pad area, and one side of the second pressed substrate is provided with a second pad area. Then, the first pressed substrate is drilled to form a to-be-metallized via hole to facilitate subsequent copper deposition and electroplating treatment. The to-be-metallized via hole is arranged corresponding to the first pad area, and the first pad area is prepared for conduction between the inner layer circuit. Then, the first pressed substrate is subjected to copper deposition treatment, that is, a copper layer is deposited on the surface of the hole wall of the to-be-metallized via hole through chemical reaction, so that the to-be-metallized via hole forms a metallized via hole. The hole wall of the metallized via hole forms a base copper layer, which is connected with the first pad area, that is, the base copper layer is connected with the inner layer circuit and the first pad area, so that the first pad area is connected with the inner layer circuit through the base copper layer, and the metallized via hole serves as a connection bridge between the inner layer circuit and the first pad area, which ensures the electrical connection between the first pad area and the inner layer circuit. Then, the first pressed substrate after copper deposition is subjected to electroplating treatment, that is, the base copper layer is subjected to electroplating treatment, which is used to deposit a copper layer on the surface of the base copper layer, that is, a copper plating layer is formed on the surface of the base copper layer, which is used to thicken the conductive copper layer of the buried hole, so that the electrical connection between the first pad area and the inner layer circuit has high reliability. Then, the side of the first pressed substrate provided with the first pad area is pressed on the side of the second pressed substrate provided with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other, that is, the first pressed substrate and the second pressed substrate are pressed to form a symmetrical stacked structure through the prepreg to obtain a pressed assembly, so that the pressed assembly has a buried hole, and the pressed assembly can be used as an intermediate body of the multilayer circuit board for subsequent process treatment to manufacture the multilayer circuit board. 2. In the process of making a multilayer circuit board, the buried hole on the lamination assembly is subjected to copper plating treatment and electroplating treatment before lamination, and the buried hole is a metalized via hole, so that the buried hole on the first lamination substrate remains through during electroplating treatment, so that the buried hole penetrates the first lamination substrate, so that the electroplating solution can flow into the interior of the buried hole through the opening of the buried hole, thereby solving the problem that the electroplating solution can only flow into the buried hole through the interlayer gap in the prior art, so that the convection speed of the electroplating solution in the buried hole on the first lamination substrate is better, so that the electroplating solution flows uniformly in the buried hole on the first lamination substrate during electroplating treatment, thereby making the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the first lamination substrate better, that is, making the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the lamination assembly better, and further making the copper thickness uniformity of the copper plating layer on the wall of the buried hole of the multilayer circuit board better, so that the copper plating layer on the wall of the buried hole is less likely to break, and further making the use reliability of the multilayer circuit board better. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present disclosure, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0018] Figure 1 Flow chart of a multilayer circuit board manufacturing method of an embodiment. DETAILED DESCRIPTION

[0019] In order to facilitate understanding of the present disclosure, the present disclosure will be described more fully below with reference to the related drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thorough and comprehensive.

[0020] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] like Figure 1 As shown, one embodiment of the multilayer circuit board fabrication method is used to fabricate a multilayer circuit board. Further, the multilayer circuit board fabrication method includes some or all of the following steps: S101, Obtain a transition core board and perform an etching process on the transition core board to form a pad area; wherein the pad area is located on one side of the transition core board.

[0023] In this embodiment, a transition core board is obtained and etched to remove part of the copper foil layer to form a pad area. The pad area is located on one side of the transition core board, that is, only the pad area corresponding to the buried via is retained on one side of the transition core board to ensure the electrical connection between the buried via and the inner layer circuit.

[0024] S103, the first core board is pressed onto the side of the transition core board away from the pad area to obtain a pressed substrate; wherein, there are two pressed substrates, namely a first pressed substrate and a second pressed substrate, a first pad area is provided on one side of the first pressed substrate, and a second pad area is provided on one side of the second pressed substrate.

[0025] In this embodiment, the first core board is pressed onto the side of the transition core board away from the pad area, that is, the first core board and the transition core board are pressed together by a prepreg to form a symmetrical stacked structure to obtain a pressed substrate; there are two pressed substrates, namely the first pressed substrate and the second pressed substrate, the first pressed substrate has a first pad area on one side, and the second pressed substrate has a second pad area on one side.

[0026] S105, the first laminated substrate is drilled to form a through-hole to be metallized; wherein the through-hole to be metallized is correspondingly provided with the first pad area.

[0027] In this embodiment, the first lamination substrate is drilled to form through-holes to be metallized, so as to facilitate subsequent copper plating and electroplating processes; the through-holes to be metallized are set in correspondence with the first pad area to prepare for the conduction between the first pad area and the inner layer circuit.

[0028] S107, perform copper plating on the first laminated substrate to form a metallized via; wherein, a base copper layer is formed on the wall of the metallized via, and the base copper layer is connected to the first pad area.

[0029] In this embodiment, the first lamination substrate undergoes copper plating treatment, that is, a copper layer is deposited on the surface of the hole wall of the via to be metallized through a chemical reaction, so that the via to be metallized becomes a metallized via; a base copper layer is formed on the hole wall of the metallized via, and the base copper layer is connected to the first pad area, that is, the base copper layer is connected to the inner layer circuit and the first pad area respectively, so that the first pad area is electrically connected to the inner layer circuit through the base copper layer, so that the metallized via acts as a buried via, serving as a connection bridge between the inner layer circuit and the first pad area, and ensuring the electrical connection between the first pad area and the inner layer circuit.

[0030] S109, electroplating is performed on the first laminated substrate after copper plating.

[0031] In this embodiment, the first laminated substrate after copper plating is electroplated, that is, the base copper layer is electroplated to deposit a copper layer on the surface of the base copper layer, that is, a copper plating layer is formed on the surface of the base copper layer, which is used to thicken the conductive copper layer of the buried via, so as to make the electrical connection between the first pad area and the inner layer circuit more reliable.

[0032] S111, the side of the first bonding substrate with the first pad area is bonded to the side of the second bonding substrate with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other to obtain a bonding assembly.

[0033] In this embodiment, the side of the first bonding substrate with the first pad area is bonded to the side of the second bonding substrate with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other. That is, the first bonding substrate and the second bonding substrate are bonded together by prepreg to form a symmetrical stacked structure to obtain a bonding assembly. The bonding assembly has buried vias so that the bonding assembly can be used as an intermediate of the multilayer circuit board for subsequent processing to manufacture the multilayer circuit board.

[0034] Furthermore, the first and second pressing substrates are symmetrically distributed with prepregs on an axis, so that the pressing assembly is a symmetrical structure. The symmetrical structure makes the thermal stress distribution on the upper and lower surfaces uniform during pressing, avoiding the "saddle-shaped" deformation caused by uneven resin curing shrinkage on one side of the prepreg, effectively reducing the risk of warping of the multilayer circuit board, and making the multilayer circuit board more reliable.

[0035] The multilayer circuit board manufacturing method described above first obtains a transition core board and performs etching treatment on the transition core board to remove part of the copper foil layer to form a pad area. The pad area is located on one side of the transition core board, that is, only the pad area corresponding to the buried hole is reserved on one side of the transition core board, to ensure the electrical connection between the buried hole and the inner layer circuit. Then, the first core board is laminated on the side of the transition core board away from the pad area, that is, the first core board and the transition core board are laminated to form a symmetrical stacked structure through the prepreg, to obtain a laminated substrate. The number of laminated substrates is two, which are a first laminated substrate and a second laminated substrate. One side of the first laminated substrate is provided with a first pad area, and one side of the second laminated substrate is provided with a second pad area. Then, the first laminated substrate is drilled to form a to-be-metallized via hole, to facilitate subsequent copper deposition and electroplating treatment. The to-be-metallized via hole is arranged corresponding to the first pad area, and the first pad area is prepared for conduction between the inner layer circuit. Then, the first laminated substrate is subjected to copper deposition treatment, that is, a copper layer is deposited on the surface of the hole wall of the to-be-metallized via hole through chemical reaction, so that the to-be-metallized via hole forms a metallized via hole. The hole wall of the metallized via hole forms a base copper layer, and the base copper layer is connected with the first pad area, that is, the base copper layer is connected with the inner layer circuit and the first pad area, to make the first pad area connected with the inner layer circuit through the base copper layer, so that the metallized via hole acts as a connection bridge between the inner layer circuit and the first pad area, to ensure the electrical connection between the first pad area and the inner layer circuit. Then, the first laminated substrate after copper deposition is subjected to electroplating treatment, that is, the base copper layer is subjected to electroplating treatment, to deposit a copper layer on the surface of the base copper layer, that is, a copper plating layer is formed on the surface of the base copper layer, to thicken the conductive copper layer of the buried hole, to make the electrical connection between the first pad area and the inner layer circuit have high reliability. Then, the side of the first laminated substrate provided with the first pad area is laminated on the side of the second laminated substrate provided with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other, that is, the first laminated substrate and the second laminated substrate are laminated to form a symmetrical stacked structure through the prepreg, to obtain a laminated assembly, so that the laminated assembly has a buried hole, to make the laminated assembly be able to be used as an intermediate body of the multilayer circuit board for subsequent process treatment to manufacture the multilayer circuit board; In the process of manufacturing the multilayer circuit board, the buried hole on the lamination assembly is subjected to copper plating treatment and electroplating treatment before lamination. The buried hole is a metalized via hole, so that the buried hole on the first lamination substrate always remains through during electroplating treatment, so that the buried hole penetrates the first lamination substrate, and the electroplating solution can flow into the interior of the buried hole through the opening of the buried hole, thereby solving the problem that the electroplating solution can only flow into the buried hole through the interlayer gap in the prior art, so that the convection speed of the electroplating solution in the buried hole on the first lamination substrate is better, so that the electroplating solution flows uniformly in the buried hole on the first lamination substrate during electroplating treatment, thereby making the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the first lamination substrate better, that is, making the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the lamination assembly better, and further making the copper thickness uniformity of the copper plating layer on the wall of the buried hole of the multilayer circuit board better, so that the copper plating layer on the wall of the buried hole is less likely to break, and further making the use reliability of the multilayer circuit board better.

[0036] In one embodiment, the step of obtaining a transition core board and etching the transition core board to form a pad area includes: first, obtaining the transition core board and cleaning the transition core board to remove impurities and dirt on the surface of the transition core board, so that the surface of the transition core board is clean, and the surface cleanliness of the transition core board is high; then, performing a pattern transfer process on the cleaned transition core board to obtain an inner layer circuit; then, etching the pattern-transferred transition core board to remove part of the copper foil layer to form the pad area, the pad area being located on one side of the transition core board, that is, only the pad area corresponding to the buried hole is reserved on one side of the transition core board, to ensure electrical connection between the buried hole and the inner layer circuit; then, performing a brown oxidation process on the etched transition core board to oxidize the surface of the transition core board and enhance the bonding force between the transition core board and the first core board during lamination, so that the structural stability of the lamination substrate is high.

[0037] In one embodiment, the step of performing a pattern transfer process on the cleaned transition core board includes: first, heating the cleaned transition core board to ensure that there is no water residue on the surface of the transition core board, so that the dryness of the transition core board is high; then, performing a film lamination process on the heated transition core board, that is, laminating a photosensitive dry film on the copper surface of the transition core board by hot pressing; then, performing an exposure process on the film-laminated transition core board, that is, irradiating the photosensitive dry film with ultraviolet light to cause a photochemical reaction, so that the exposed area is cross-linked and solidified to form a "latent image" corresponding to the negative pattern; then, performing a development process on the exposed transition core board, that is, dissolving the photosensitive dry film in the unexposed area with a developing solution to retain the exposed part to form an etching protection layer, and expose the copper foil layer to be etched, so as to facilitate subsequent etching process, so that the manufacturing convenience of the multilayer circuit board is good.

[0038] Further, in one embodiment, the step of performing film pasting treatment on the heated transition core plate specifically includes: performing film pasting treatment on the heated transition core plate by a hot-press film pasting machine, the film pasting temperature of the film pasting treatment is 100-120℃, the film pasting pressure of the film pasting treatment is 0.4-0.6MPa, and the film pasting speed of the film pasting treatment is 1-3m / min. In this embodiment, the film pasting temperature of 100-120℃ can soften the photosensitive dry film, so that the photosensitive dry film can fully fill the micro concave pits on the surface of the copper foil, so that the bonding force between the photosensitive dry film and the transition core plate is higher, and at the same time, the film pasting pressure of 0.4-0.6MPa can ensure that the photosensitive dry film and the transition core plate are gapless and combined, which is used to eliminate the air bubbles between the photosensitive dry film and the transition core plate, and avoids the "leaching" defect during subsequent etching.

[0039] In one embodiment, the step of pressing the first core plate on the side of the transition core plate away from the pad area to obtain a pressed substrate includes: first, stacking prepreg on the side of the transition core plate away from the pad area, so that one side of the prepreg is connected with the transition core plate; then stacking the first core plate on the prepreg, so that the first core plate is connected to the other side of the prepreg, so that the prepreg is located between the first core plate and the transition core plate, i.e. the first core plate, the prepreg and the transition core plate are sequentially stacked; then performing riveting positioning treatment on the first core plate and the transition core plate, so that the positions of the first core plate, the prepreg and the transition core plate are fixed, avoiding the positions of the first core plate, the prepreg and the transition core plate from being deviated during subsequent pressing process, so as to facilitate subsequent pressing treatment; then pressing the first core plate on the side of the transition core plate away from the pad area, i.e. melting and bonding the first core plate and the transition core plate by high-temperature pressing, which is used to form a symmetrical stacking structure to obtain the pressed substrate, so that the structural stability of the pressed substrate is better.

[0040] In one of the embodiments, the step of pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area, so that the first pad area and the second pad area are arranged oppositely to obtain the press assembly includes: firstly, stacking a prepreg on the side of the second press substrate provided with the second pad area, so that one side of the prepreg is connected with the second press substrate; then, stacking the side of the first press substrate provided with the first pad area on the prepreg, so that the first press substrate is connected with the other side of the prepreg, so that the prepreg is located between the first pad area and the second pad area, that is, the first press substrate, the prepreg and the second press substrate are arranged in sequence; then, clamping and positioning the first press substrate and the second press substrate, so that the positions of the first press substrate, the prepreg and the second press substrate are fixed, avoiding the positions of the first press substrate, the prepreg and the second press substrate from deviating in the subsequent pressing process, so as to facilitate the subsequent pressing process; then, pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area, so that the first pad area and the second pad area are arranged oppositely, that is, the resin of the prepreg is melted and adhered to the first press substrate and the second press substrate by high-temperature pressing, so as to form a symmetrical stacked structure, so as to obtain the press assembly, so that the structural stability of the press assembly is good.

[0041] In one of the embodiments, after the step of pressing the side of the first press substrate provided with the first pad area against the side of the second press substrate provided with the second pad area, so that the first pad area and the second pad area are arranged oppositely to obtain the press assembly, the multilayer circuit board manufacturing method further includes: firstly, cutting the press assembly, so as to process the press assembly into a press assembly with a predetermined size, so as to obtain a multilayer circuit board semi-finished product; then, drilling the multilayer circuit board semi-finished product, so as to facilitate the subsequent copper plating process and electroplating process; then, carrying out copper plating on the multilayer circuit board semi-finished product after drilling, that is, depositing a copper layer on the surface of the hole wall of the hole obtained by drilling by chemical reaction, so that the hole wall is provided with a connecting copper layer, the connecting copper layer is used for connecting the inner layer circuit and the outer layer circuit, so that the connecting copper layer is used as a connecting bridge between the outer layer circuit and the inner layer circuit, so as to ensure the electrical connection between the outer layer circuit and the inner layer circuit; then, carrying out electroplating on the multilayer circuit board semi-finished product after copper plating, so that the surface of the connecting copper layer continues to deposit a copper layer, so as to thicken the connecting copper layer of the inner layer circuit and the outer layer circuit, so that the electrical connection between the outer layer circuit and the inner layer circuit has high reliability; then, carrying out outer layer pattern manufacturing on the multilayer circuit board semi-finished product after electroplating, so that the multilayer circuit board semi-finished product is provided with an outer layer circuit, so as to improve the use reliability of the multilayer circuit board.

[0042] In one embodiment, the step of performing outer layer pattern making processing on the multi-layer circuit board semi-finished product after electroplating includes: first, performing plate grinding processing on the multi-layer circuit board semi-finished product after electroplating, for removing the copper surface oxidation layer and oil stains of the multi-layer circuit board semi-finished product, increasing the surface roughness of the multi-layer circuit board semi-finished product, and improving the dry film adhesion; then, performing film pasting processing on the multi-layer circuit board semi-finished product after plate grinding, and pasting the photosensitive dry film on the copper surface of the multi-layer circuit board semi-finished product through hot pressing; then, performing exposure processing on the multi-layer circuit board semi-finished product after film pasting, that is, making the photosensitive dry film undergo photochemical reaction through ultraviolet light irradiation, cross-linking and solidifying the exposed area, and forming a "latent image" corresponding to the negative pattern; then, performing developing processing on the multi-layer circuit board semi-finished product after exposure, that is, dissolving the photosensitive dry film in the unexposed area through a developing solution, retaining the exposed part to form an etching protection layer, and exposing the copper foil layer to be etched, so as to facilitate subsequent etching processing; then, performing etching processing on the multi-layer circuit board semi-finished product after developing, for removing part of the copper foil layer to form an outer layer circuit; and then, performing tin plating processing on the multi-layer circuit board semi-finished product after etching, for forming a tin layer on the surface of the outer layer circuit, so as to isolate air and moisture, prevent the oxidation of the exposed outer layer circuit copper surface after etching, and make the multi-layer circuit board have high use reliability.

[0043] In one embodiment, after the step of performing outer layer pattern making processing on the multi-layer circuit board semi-finished product after electroplating, the multi-layer circuit board manufacturing method further includes: first, performing solder mask processing on the multi-layer circuit board semi-finished product to form a solder mask layer, the solder mask layer covers the non-pad area, isolates adjacent conductive circuits, avoids solder tin bridging during soldering, prevents soldering short circuit, and makes the multi-layer circuit board have high connection reliability; and then, performing surface treatment on the multi-layer circuit board semi-finished product after solder mask processing, for improving the solderability and oxidation resistance of the multi-layer circuit board.

[0044] In one embodiment, the step of performing electroplating processing on the first press-fit substrate after copper deposition is specifically: performing electroplating processing on the first press-fit substrate after copper deposition through VCP line, the current density of electroplating processing is 3-5 A / dm 2 , the electroplating temperature of electroplating processing is 40-45℃, and the electroplating time of electroplating processing is 30-40 min. In this embodiment, the current density of 3-5 A / dm 2 can make the copper plating layer thicken rapidly, for thickening the conductive copper layer of the buried hole, so as to make the electrical connection reliability between the first pad area and the inner layer circuit be high, and meanwhile, the electroplating temperature of 40-45℃ can accelerate the diffusion of copper ions, effectively reduce the risk of "dog bone" effect or local plating layer being too thin or too thick, and improve the electroplating uniformity.

[0045] Further, in one of the embodiments, after the step of surface treatment of the multi-layer circuit board semi-finished product after solder resist, the side edges of the multi-layer circuit board are provided with gold fingers, and the multi-layer circuit board manufacturing method further comprises: first, milling processing is performed along the edges of the multi-layer circuit board provided with the gold fingers to form a milling formed edge on the multi-layer circuit board, that is, the edges of the multi-layer circuit board away from the positions of the gold fingers are milled to form a milling formed edge on the multi-layer circuit board; then, stamping operation is performed along the edges of the multi-layer circuit board adjacent to the milling formed edge and the edges opposite to the milling formed edge to form a stamping formed edge on the multi-layer circuit board. In this embodiment, the number of gold fingers is multiple, and the multiple gold fingers are arranged side by side.

[0046] First, milling processing is performed along the edges of the multi-layer circuit board provided with the gold fingers to form a milling formed edge on the multi-layer circuit board, so that the milling formed edge is adjacent to the gold fingers; then, stamping operation is performed along the edges of the multi-layer circuit board adjacent to the milling formed edge and the edges opposite to the milling formed edge to form a stamping formed edge on the multi-layer circuit board, so that the stamping edges of the multi-layer circuit board are arranged away from the gold fingers, and at the same time, the edges adjacent to the gold fingers of the multi-layer circuit board are reduced, so that the debris generated during stamping does not damage the gold finger area, and the use reliability of the multi-layer circuit board is better.

[0047] Further, in one of the embodiments, the processing path of the milling processing along the edges of the multi-layer circuit board provided with the gold fingers extends linearly, and the extension direction of the processing path of the milling processing is perpendicular to the extension direction of the gold fingers. In this embodiment, the extension direction of the processing path of the milling processing is perpendicular to the extension direction of each gold finger. The distance between the processing path of the milling processing and the gold fingers is a first predetermined size.

[0048] Further, in one of the embodiments, the first predetermined size is 0.08mm-0.12mm. In this embodiment, the first predetermined size is 0.1mm, so that the processing path of the milling processing can better avoid the gold fingers, and the use reliability of the multi-layer circuit board is better.

[0049] Further, in one of the embodiments, the milled shaped edge is a milled cut surface, i.e. the edge of the multilayer circuit board is cut off along the edge of the multilayer circuit board provided with the gold fingers to form the milled cut surface. In one of the embodiments, when the milled shaped edge is the milled cut surface, the cutter used to form the milled shaped edge is a milling cutter. Further, the milling cutter is a V-cut cutter. In the embodiment, the milling cutter performs one-way V-cut milling shaping on the multilayer circuit board. Further, the angle of the cross section of the cutting edge of the milling cutter is 25°. Specifically, the milling cutter is a diamond cutter, so that the milling cutter has high strength and wear resistance. Further, the feed rate of the milling cutter is 6-10 m / min, which can reduce the collision between the milling cutter and the multilayer circuit board, so that the milling cutter can smoothly cut into the multilayer circuit board, thereby effectively reducing the impact vibration of the milling cutter on the multilayer circuit board, and the processing convenience of the multilayer circuit board is better.

[0050] In order to better form the milled cut surface by the milling cutter, further, the diameter of the milling cutter is 1.0-1.5 mm, and the rotating speed of the milling cutter is 30-45 krpm, so that the milling cutter can better form the milled cut surface.

[0051] Further, the down-cut speed of the milling cutter is 0.5-0.8 m / min. In the embodiment, the up-cut speed of the milling cutter is 10 m / min, so that the down-cut speed of 0.5-0.8 m / min and the up-cut speed of 10 m / min are combined to realize the mode of "slow down-cut + fast up-cut", and the "slow down-cut" can reduce the impact vibration of the milling cutter on the multilayer circuit board, and the "fast up-cut" can improve the processing efficiency.

[0052] Further, the advancing speed of the milling cutter is 0.9-1.2 m / min, so that the milling cutter can better form the milled cut surface.

[0053] In order to improve the forming precision of the milling cutter, further, the compensation value of the milling cutter in the depth direction is 1.35-1.40 mm, so as to improve the forming precision of the milling cutter.

[0054] Further, in one of the embodiments, the milling cutter comprises a cutter holder and a plurality of cutting parts, and the plurality of cutting parts are distributed at equal intervals along the circumference of the cutter holder. In the embodiment, the distance between the adjacent two cutting parts is equal, so that the plurality of cutting parts uniformly cut the multilayer circuit board during the rotation of the cutter holder, thereby the milling cutter has better processing effect on the multilayer circuit board. In one of the embodiments, each cutting part is detachably connected with the cutter holder, so that each cutting part can be regularly maintained or replaced, thereby reducing the use cost of the milling cutter, and improving the use convenience of the milling cutter.

[0055] Further, in one of the embodiments, the tool holder comprises a spindle, a mounting frame sleeved on the spindle, and a plurality of locking members, the mounting frame is provided with a plurality of mounting slots and a plurality of first fixing holes, the plurality of mounting slots and the plurality of first fixing holes are in one-to-one correspondence and in communication; each cutting part is clamped in a corresponding mounting slot, each cutting part is provided with a second fixing hole corresponding to the corresponding first fixing hole, and each locking member is respectively arranged in the corresponding first fixing hole and the second fixing hole, so that each cutting part is mounted and fixed on the mounting frame of the spindle, and the structural stability of each cutting part is better.

[0056] In order to firmly clamp the cutting part in the mounting slot, further, in one of the embodiments, the mounting slot extends in a tapered manner, and the slot width of the mounting slot is greater than the slot bottom width of the mounting slot, so that the cutting part is clamped in the mounting slot in an interference fit, and the cutting part is firmly clamped in the mounting slot, so that the positional stability of the cutting part is higher.

[0057] In order to avoid the shaking of the cutting part when clamped in the mounting slot, further, in one of the embodiments, at least two oppositely arranged auxiliary clamping ribs are protruded at the edge of the mounting frame provided with the mounting slot, and the at least two auxiliary clamping ribs are respectively abutted on the two side surfaces of the cutting part, when the cutting part is clamped in the mounting slot, the auxiliary clamping ribs are abutted on the cutting part, so that the cutting part is more reliably mounted on the mounting frame.

[0058] Further, in one of the embodiments, the auxiliary clamping rib is an elastic rib, and the auxiliary clamping rib is bent, and the two oppositely arranged auxiliary clamping ribs are bent towards each other, so that the two auxiliary clamping ribs are better elastically abutted on the two side surfaces of the cutting part.

[0059] The present disclosure also provides a multilayer circuit board made by the multilayer circuit board manufacturing method of any one of the above embodiments.

[0060] Compared with the prior art, the present disclosure has at least the following advantages: 1. The multilayer circuit board manufacturing method of the present disclosure, first, a transition core board is obtained, and the transition core board is etched to remove part of the copper foil layer to form a pad area. The pad area is located on one side of the transition core board, that is, only the pad area corresponding to the buried hole is reserved on one side of the transition core board, which is used to ensure the electrical connection between the buried hole and the inner layer circuit; then the first core board is pressed on the side of the transition core board away from the pad area, that is, the first core board and the transition core board are pressed to form a symmetrical stack structure through the prepreg to obtain a pressed substrate; the number of pressed substrates is two, which are the first pressed substrate and the second pressed substrate, one side of the first pressed substrate is provided with a first pad area, and one side of the second pressed substrate is provided with a second pad area; then the first pressed substrate is drilled to form a to-be-metallized via hole for subsequent copper deposition and electroplating treatment; the to-be-metallized via hole is arranged corresponding to the first pad area, and the first pad area is prepared for conduction between the inner layer circuit; then the first pressed substrate is subjected to copper deposition treatment, that is, a copper layer is deposited on the surface of the hole wall of the to-be-metallized via hole through chemical reaction, so that the to-be-metallized via hole forms a metallized via hole; the hole wall of the metallized via hole forms a base copper layer, and the base copper layer is connected with the first pad area, that is, the base copper layer is connected with the inner layer circuit and the first pad area respectively, so that the first pad area is connected with the inner layer circuit through the base copper layer, and the metallized via hole is used as a buried hole to serve as a connecting bridge between the inner layer circuit and the first pad area, and to ensure the electrical connection between the first pad area and the inner layer circuit; then the first pressed substrate after copper deposition is subjected to electroplating treatment, that is, the base copper layer is subjected to electroplating treatment, which is used to deposit a copper layer on the surface of the base copper layer, that is, a copper plating layer is formed on the surface of the base copper layer, which is used to thicken the conductive copper layer of the buried hole, so that the electrical connection between the first pad area and the inner layer circuit has high reliability; then the side of the first pressed substrate provided with the first pad area is pressed on the side of the second pressed substrate provided with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other, that is, the first pressed substrate and the second pressed substrate are pressed to form a symmetrical stack structure through the prepreg to obtain a pressed assembly, so that the pressed assembly has a buried hole, so that the pressed assembly can be used as an intermediate body of the multilayer circuit board for subsequent process treatment to manufacture the multilayer circuit board; 2. In the process of manufacturing a multilayer circuit board, the buried hole on the lamination assembly is subjected to copper plating treatment and electroplating treatment before lamination, and the buried hole is a metalized via hole, so that the buried hole on the first lamination substrate always remains through during electroplating treatment, so that the buried hole penetrates the first lamination substrate, so that the electroplating solution can flow into the interior of the buried hole through the opening of the buried hole, thereby solving the problem that the electroplating solution can only flow into the buried hole through the interlayer gap in the prior art, so that the convection speed of the electroplating solution in the buried hole on the first lamination substrate is better, so that the electroplating solution flows more evenly in the buried hole on the first lamination substrate during electroplating treatment, thereby making the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the first lamination substrate better, that is, the copper thickness uniformity of the copper plating layer on the wall of the buried hole on the lamination assembly is better, and further, the copper thickness uniformity of the copper plating layer on the wall of the buried hole of the multilayer circuit board is better, so that the copper plating layer on the wall of the buried hole is less likely to break, and further, the reliability of the multilayer circuit board is better.

[0061] The above-described embodiments only express several embodiments of the present disclosure, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the disclosed patent. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

Claims

1. A method for manufacturing a multilayer circuit board, characterized in that, include: A transition core board is obtained and etched to form a pad area; wherein the pad area is located on one side of the transition core board; The first core board is pressed onto the side of the transition core board away from the pad area to obtain a pressed substrate; wherein, there are two pressed substrates, namely a first pressed substrate and a second pressed substrate, a first pad area is provided on one side of the first pressed substrate, and a second pad area is provided on one side of the second pressed substrate. The first laminated substrate is drilled to form through-holes to be metallized; wherein the through-holes to be metallized are correspondingly provided to the first pad area; The first laminated substrate is subjected to copper plating treatment to form the through-hole to be metallized; wherein, the wall of the through-hole is formed with a base copper layer, and the base copper layer is connected to the first pad area; The first laminated substrate after copper plating is subjected to electroplating treatment. The first bonding substrate with the first pad area is bonded to the second bonding substrate with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other to obtain a bonding assembly.

2. The method for manufacturing a multilayer circuit board according to claim 1, characterized in that, The steps of obtaining a transition core board and etching the transition core board to form a pad area include: Obtain the transition core plate and clean it. The cleaned transition core board is then subjected to pattern transfer processing. The transition core board after pattern transfer is etched to form the pad area; The etched transition core board is then subjected to a browning treatment.

3. The method for manufacturing a multilayer circuit board according to claim 2, characterized in that, The steps for performing pattern transfer processing on the cleaned transition core board include: The cleaned transition core board is then subjected to heat treatment; The heated transition core board is then coated with a film. The transition core board after film application is exposed to light; The exposed transition core board is then subjected to a development process.

4. The method for manufacturing a multilayer circuit board according to claim 1, characterized in that, The step of pressing the first core board onto the side of the transition core board away from the pad area to obtain the laminated substrate includes: The prepreg is stacked on the side of the transition core board away from the pad area; The first core board is stacked on the prepreg, with the prepreg positioned between the first core board and the transition core board; The first core plate and the transition core plate are riveted and positioned. The first core board is pressed onto the side of the transition core board away from the pad area to obtain the pressed substrate.

5. The method for manufacturing a multilayer circuit board according to claim 1, characterized in that, The step of pressing the side of the first bonding substrate with the first pad area onto the side of the second bonding substrate with the second pad area, so that the first pad area and the second pad area are positioned opposite each other to obtain the bonding assembly, includes: The prepreg is stacked on the side of the second lamination substrate where the second pad area is provided; The side of the first laminated substrate with the first pad area is stacked on the prepreg, such that the prepreg is located between the first pad area and the second pad area. The first and second laminated substrates are clamped and positioned. The first bonding substrate with the first pad area is bonded to the second bonding substrate with the second pad area, so that the first pad area and the second pad area are arranged opposite to each other to obtain the bonding assembly.

6. The method for manufacturing a multilayer circuit board according to claim 1, characterized in that, After the step of pressing the side of the first bonding substrate with the first pad area onto the side of the second bonding substrate with the second pad area, so that the first pad area and the second pad area are opposite to each other to obtain a bonding assembly, the multilayer circuit board manufacturing method further includes: The pressing assembly is cut to obtain a multilayer circuit board semi-finished product; The multilayer circuit board semi-finished product is drilled; The multilayer circuit board semi-finished product after drilling is subjected to copper plating treatment. The multilayer circuit board semi-finished product after copper plating is subjected to electroplating treatment. The outer layer pattern is fabricated on the electroplated multilayer circuit board semi-finished product.

7. The method for manufacturing a multilayer circuit board according to claim 6, characterized in that, The steps for processing the outer layer pattern of the electroplated multilayer circuit board semi-finished product include: The electroplated multilayer circuit board semi-finished product is then subjected to a grinding process. The multilayer circuit board semi-finished product after grinding is then subjected to a film-coating process. The multilayer circuit board semi-finished product after film application is exposed to light; The exposed multilayer circuit board semi-finished product is then subjected to a development process; The developed multilayer circuit board semi-finished product is then etched. The etched multilayer circuit board semi-finished product is then subjected to tin plating.

8. The method for manufacturing a multilayer circuit board according to claim 6, characterized in that, After the step of processing the outer layer pattern of the electroplated multilayer circuit board semi-finished product, the multilayer circuit board manufacturing method further includes: The multilayer circuit board semi-finished product is subjected to solder resist treatment; The surface treatment of the multilayer circuit board semi-finished product after solder resist is performed.

9. The method for manufacturing a multilayer circuit board according to claim 1, characterized in that, The specific steps for electroplating the first laminated substrate after copper plating are as follows: The first laminated substrate after copper plating is electroplated using a VCP line, with a current density of 3-5 A / dm². 2 The electroplating temperature for the electroplating treatment is 40-45℃, and the electroplating time is 30-40 minutes.

10. A multilayer circuit board, characterized in that, The multilayer circuit board is manufactured using any one of claims 1 to 9.

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