KR100648235B1 - Method of fabricating multiple-layer printed circuit board - Google Patents

Abstract

A method for manufacturing a multilayered PCB(Printed Circuit Board) is provided to reduce manufacturing time by manufacturing the multilayered PCB by using a bulk lamination process. Metal films are formed on both surfaces of plural insulation layers(10), such that plural lamination plates are formed. Through-holes are formed to penetrate the respective lamination plates. A conductive paste is condensed inside the respective through-holes, such that a conductive bump(13) is formed. A circuit pattern(14) is formed by etching the respective lamination plates. Then, the lamination plates are pressed against one another. Coating films are formed at both surfaces of the respective lamination plates between the conductive bump forming process and the circuit pattern forming process.

Description

Manufacturing method of multilayer printed circuit board {Method Of Fabricating Multiple-layer Printed Circuit Board}

1A to 1C are cross-sectional views illustrating a method of manufacturing a multilayer printed circuit board according to the related art.

2a to 2e are cross-sectional views showing a first embodiment of a method for manufacturing a multilayer printed circuit board according to the present invention;

3A and 3B are cross-sectional views showing a second embodiment of a method for manufacturing a multilayer printed circuit board according to the present invention.

*** Explanation of the Major Symbols in the Drawings ***

10: insulating layer 11: metal thin film

12 through hole 13 conductive bump

14 circuit pattern 15 plating film

The present invention relates to a multilayer printed circuit board, and more particularly, in forming projections of a conductive bump, a metal thin film is formed on both sides of an insulating layer to form a laminated plate, and then a through hole is formed in the laminated plate, and a metal on one side is formed. By using a method of removing a thin film, the present invention relates to a multilayer printed circuit board manufacturing method capable of preventing a phenomenon in which conductive bumps of a portion in contact with a protective film are damaged when the protective film is peeled off according to the related art.

The printed circuit board includes a single-sided printed circuit board having wiring formed only on one surface of an insulated substrate, a double-sided printed circuit board having wiring formed on both sides, and a multilayer printed circuit board that is wired in multiple layers. In the past, single-sided printed circuit boards were used because of simple component parts and simple circuit patterns. Recently, double-sided printed circuit boards or multilayer printed circuit boards have been widely used due to the increased complexity of circuits and the demand for high density and miniaturized circuits. It is used.

In the trend of miniaturization, thinness, high density, packaging, and personal portability of electronic products, multilayered printed circuit boards are also undergoing fine patterning, miniaturization, and packaging simultaneously. Accordingly, in order to increase the fine pattern formation, reliability, and design density of multilayer printed circuit boards, the trend is changing to a structure in which the layer structure of the circuit is combined with the change of raw materials, and the component mounting density is also increasing. In addition, portable devices, along with high functionality, the Internet, moving pictures, and high-capacity data transmission and the like, complicate the design of printed circuit boards and require high difficulty technology.

The multilayer printed circuit board further includes a layer capable of wiring in order to enlarge a wiring area. Specifically, the multilayer printed circuit board is divided into an inner layer and an outer layer. An inner layer forms a power supply circuit, a ground circuit, a signal circuit, and the like, and an insulating layer is formed between the inner layer and the outer layer or between the outer layers. At this time, the wiring of each layer is connected using a via hole (through hole).

As a material of the inner layer, a thin core is used, and a four-layer structure in which an outer layer and an inner layer are bonded to each other as an insulating layer is basic. As the complexity of the circuit increases, six layers, eight layers, ten layers, or the like It may be composed of the above.

However, this method of manufacturing a build-up multilayer printed circuit board has a disadvantage in that it takes a long time to manufacture and it is difficult to inspect an intermediate product.

Therefore, at present, a manufacturing method of a batch lamination method for forming a circuit layer in which each circuit pattern is formed in parallel by an independent process, arranging them, and then completing a product in only one lamination has been studied.

At present, a method of electrically connecting circuit patterns formed above and below the insulating layer by forming a conductive bump penetrating the insulating layer among the methods for manufacturing a multilayer printed circuit board of the batch lamination method is known. In some embodiments, it is preferable that a part of the conductive bumps protrude from the circuit layer. This is to ensure good electrical contact between the conductive bumps in the lamination process.

1A to 1C illustrate a method of forming a protrusion of a conductive bump according to the related art, and includes preparing a laminate including a protective film 120, an insulating layer 100, and a metal thin film 110 (FIG. 1A), and applying the laminate to each laminate. After forming the through holes 130 (FIG. 1B), the conductive bumps 140 are formed in each through hole 130, the metal thin film 110 is etched to form the circuit pattern 150, and then the protective film. The method of peeling off 120 and forming a protrusion part (FIG. 1C) by the height of a protective film is used.

However, in the case of the method, there is a problem that the portion in contact with the protective film of the conductive bump is damaged in the process of peeling the protective film.

The present invention is to solve the above problems, in forming the projections of the conductive bump, by forming a metal thin film on both sides of the insulating layer to form a laminated plate, then forming a through hole in the laminated plate and removing the metal thin film on one surface The present invention provides a method for manufacturing a multilayer printed circuit board capable of preventing a phenomenon in which conductive bumps of a portion contacted with a protective film are damaged when the protective film is peeled off according to the related art.

The present invention comprises the steps of forming a plurality of laminates by forming a metal thin film on each side of the plurality of insulating layers; Forming through holes penetrating through the laminates; Filling each through hole with a conductive paste to form a conductive bump; Etching each of the metal thin films to form a circuit pattern; And pressing each of the laminates to form a multilayer printed circuit board.

In addition, between the step of forming the conductive bumps and the step of forming the circuit pattern, performing a plating to form a plated film on both sides of each laminated plate further comprises a multi-layer printed circuit board manufacturing method.

In addition, the pressing of the laminates is a method of manufacturing a multilayer printed circuit board, wherein the through-holes of the laminates are pressed to be connected on the same line.

In addition, the step of pressing each laminated plate is a multilayer printed circuit board manufacturing method, characterized in that the pressing by pressing at a pressure of 80 to 120kg / cm ^{2 in} a vacuum, 150 to 350 ℃ atmosphere.

In addition, the metal thin film is made of copper, the conductive bump is a multilayer printed circuit board manufacturing method characterized in that it comprises any one selected from copper, gold, silver, nickel or a mixture thereof.

In addition, the insulating layer is made of a thermoplastic synthetic resin or a thermosetting synthetic resin in a semi-cured state, the thermosetting synthetic resin in the semi-cured state is completely cured in the step of pressing the respective laminated plates, multi-layer printing Circuit board manufacturing method.

In addition, the step of forming a circuit pattern on each laminated plate, the step of forming a circuit pattern on both sides of any one of the laminated plate to form a core (Core) laminate; And removing the metal thin film on one surface of the remaining laminated board and forming a circuit pattern on the other surface.

In the compressing of the laminates, the laminates disposed on the core laminates may be disposed so that the circuit patterns face upwards, and the laminates disposed below the core laminates may be disposed so that the circuit patterns face downward. A multilayer printed circuit board manufacturing method characterized by the above-mentioned.

Hereinafter, with reference to the accompanying drawings will be described in detail the technical features of the present invention. The invention can be better understood by the examples, the following examples are for illustrative purposes of the invention and are not intended to limit the scope of protection defined by the appended claims.

2A to 2E are cross-sectional views showing a first embodiment of a method for manufacturing a multilayer printed circuit board according to the present invention, in which metal thin films 11 are formed on both surfaces of a plurality of insulating layers 10 to form a plurality of laminates. Step (FIG. 2A); Forming a through hole (12) penetrating each of the laminated plates (FIG. 2B); Filling each through hole with a conductive paste to form a conductive bump (13) (FIG. 2C); Etching each of the metal thin films 11 to form a circuit pattern 14 (FIG. 2D); And pressing each of the laminates (FIG. 2E).

First, a plurality of laminates are formed by forming metal thin films on both surfaces of the plurality of insulating layers (FIG. 2A). The insulating layer 10 is made of a synthetic resin, and preferably, a form in which glass fibers are impregnated with a synthetic resin. The synthetic resin is a thermoplastic resin or a thermosetting resin in a semi-cured state. The synthetic resin is adhesively connected to a plurality of laminates in the thermocompression step to be described later. In the thermosetting resin in the semi-cured state, the polymerization proceeds in the thermocompression step, thereby completely curing. The insulating layer may be formed of a multilayer structure as well as a single layer structure, the thickness is preferably 7 to 50㎛.

In this embodiment, a thermoplastic resin is used as the insulating layer. Specific examples may include, but are not limited to, polyamide, polyethylene, polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polypropylene, polybutylene terephthalate, and the like. Thermoplastic resins are easily flowable by heating and do not require polymerization to proceed in the process of curing, and thus, in the thermocompression bonding process described later, there is an advantage in that workability is better than that of a semi-cured thermosetting resin. .

The metal thin film 11 may be made of copper, aluminum, gold, or an alloy thereof. Preferably, in view of economics and electrical conductivity, a copper thin film is preferable. Preferably the thickness of the said metal thin film is 1-12 micrometers, More preferably, it is 2-9 micrometers. Metal thin films having a thickness of 12 μm or more are not suitable for fine patterning. The metal thin film preferably has a roughness Rz of 0.3 to 3 μm, more preferably 1.5 to 3 μm.

As a method of forming a metal thin film in the said insulating layer, the method of positioning an insulating layer film, heating, pressurizing, and laminating | stacking between metal thin films is widely used.

Next, through holes 12 penetrating the respective laminated plates are formed (FIG. 2B). In the formation of the through hole 12, a laser drill, a punch, a mechanical drill, or the like using a UV-YAG laser or a carbon dioxide laser is used. The through-holes are for electrically connecting the circuit patterns of the layers in the multilayer printed circuit board, and are later filled with a conductive material. The diameter of the through hole is preferably 20 to 50 µm.

Next, each of the through holes 12 is filled with a conductive paste to form a conductive bump 13 (FIG. 2C). The conductive paste is made of metal, powder, binder resin, solvent, or the like having high electrical conductivity such as gold, nickel, silver, and copper. Since the conductive paste has fluidity, it is preferable to fill the through hole in the through hole, and then dry and harden it.

Next, the metal thin films 11 are etched to form circuit patterns 14 (FIG. 2D). In more detail, an etching resist is formed along the circuit pattern on the other surface of the metal thin film, and then a portion where the resist is not formed is etched to form a circuit pattern.

In order to form the resist pattern, a circuit pattern printed on an artwork film must be transferred onto a substrate. There are various methods for transferring, but the most commonly used method is a method of transferring a circuit pattern printed on an artwork film by ultraviolet light to a dry film using a photosensitive dry film. Recently, liquid photo resists have been used instead of dry films.

The dry film or liquid photoresist to which the circuit pattern has been transferred serves as an etching resist, soaks the substrate in the etching solution, and then removes the etching resist to form a circuit pattern.

The multilayer printed circuit board manufacturing method according to the present invention is not a buildup method but a batch lamination method. In this case, as shown in the drawing, a core laminate having circuit patterns formed on both surfaces thereof and a laminate having a circuit pattern formed on one surface thereof may be divided and formed.

In the case of the remaining laminates other than the core laminate, the metal thin film 11 on one surface is removed, and the circuit pattern 14 is formed on the other surface. When the metal thin film 11 on one surface of the laminate is removed, the conductive bumps 13 protrude from the surface of the insulating layer by the thickness of the metal thin film, thereby forming protrusions. These protrusions provide good electrical connection of the bumps during compression of each laminate.

In the present invention, in forming the protrusion, unlike the prior art, it is not necessary to go through the process of peeling off the protective film. Therefore, it can prevent that the conductive bump of the part which contacted the protective film at the time of peeling of a protective film is damaged.

After the circuit pattern is formed, the external appearance of the circuit is inspected by a method such as automatic optical inspection to inspect whether the circuit is properly formed, and surface treatment such as black oxide treatment is performed.

Automatic optical inspection is a device for automatically inspecting the appearance of a printed circuit board. The device uses an image sensor and a computer's pattern recognition technology to automatically inspect the substrate's appearance. The pattern information of the target circuit is read by the image sensor and compared with the reference data to read out the defect. In the multilayer printed circuit board, when a failure occurs in one laminate, the entire printed circuit board cannot be used. Therefore, a faithful inspection of each circuit layer is required.

Next, each said laminated board is crimped | bonded (FIG. 2E). It is advantageous to arrange the through-holes of the laminates so that the through-holes are located on the same line.

In more detail, as shown in the drawing, the core laminate having circuit patterns formed on both surfaces thereof is positioned in the center, and the laminate disposed on the core laminate is disposed so that the circuit pattern faces upward, and the laminate disposed below the core laminate. Place the circuit pattern face down. The number of laminates disposed above and below the core laminate depends on how many layers the printed circuit board is manufactured.

In the case where the core laminate is not separately formed, the laminate placed on the upper side is arranged so that the circuit pattern faces upward, and the laminate placed below is placed and pressed so that the circuit pattern faces downward.

As a method of pressing each laminated plate to form a single printed circuit board, a thermocompression bonding method is used. This laminate | stacks by the method which puts each laminated board in a case, and presses / heats by inserting into a hotplate above and below a vacuum chamber. This method is called VHL (Vacuum Hydraulic Lamination) method.

In addition, there is a vacuum crimping method in which a heat transfer heater is provided as a heating source in a vacuum chamber and laminated in a pressurized state using gas. Since this method does not require a hot plate, there is an advantage in that it can be laminated at one time regardless of the number of laminates.

The insulating layer is made of a thermoplastic resin or a thermosetting synthetic resin in a semi-cured state. In the case of the thermoplastic resin, it is heated above the glass transition temperature in the thermocompression bonding step to increase the fluidity and the adhesiveness, thereby bonding the laminated sheets, and the semi-cured thermosetting synthetic resin bonds the laminated sheets while the polymerization proceeds. In addition, each bump is bonded to each other while the surface energy increases.

In the pressing step, the pressure applied to each laminate is preferably about 80 to 120 kg / cm ² , and the heating temperature varies depending on the material of the insulating layer, but about 150 to 350 ° C. is appropriate.

A second embodiment of the method for manufacturing a multilayer printed circuit board according to the present invention includes the steps of forming a plurality of laminates by forming metal thin films on both surfaces of the plurality of insulating layers; Forming through holes penetrating through the laminates; Filling each through hole with a conductive paste to form a conductive bump; Performing plating to form plating films on both sides of each laminate; Etching each of the metal thin film and the plating film to form a circuit pattern; And pressing each of the laminates.

The embodiment further includes the step of forming the plating film 15 on both sides of each laminated plate by plating, between the step of forming the conductive bumps and the step of forming the circuit pattern, as shown in FIG. 3A. Is characteristic.

Since the conductive bumps 13 are formed of a conductive paste, the surface exposed to the outside may be roughened while the organic solvent or the like is separated. In this case, the contactability is lowered and the resistance is increased. As described above, the present invention can solve the above problems by forming a plating film on the conductive bumps 13.

Copper is preferred as the plating material, preferably at a current density of 2 to 8 A / dm ² , copper sulfate 180 to 240 g / L, sulfuric acid 45 to 60 g / L and thiourea, dextrin, or thiourewa It is carried out in a bath containing additives such as compounds of Molasses.

In this embodiment, since the plating film is formed on the metal thin film and the conductive bump, the metal thin film 11 and the plating film 15 are etched to form a circuit pattern composed of the metal thin film and the plating film, as shown in FIG. 3B. do.

As described above, in the method of manufacturing a multilayer printed circuit board according to the present invention, by manufacturing a multilayer printed circuit board in a batch lamination method, an intermediate inspection of each laminated board can be easily performed, and a manufacturing time can be shortened. .

In the present invention, in forming the projections of the conductive bumps, a metal thin film is formed on both surfaces of the insulating layer to form a laminated plate, and then a through hole is formed in the laminated plate and a method of removing the metal thin film on one surface is used. When peeling a protective film in accordance with the technique of, it is possible to prevent the phenomenon that the conductive bumps of the part in contact with the protective film are damaged.

In addition, according to the present invention, after forming the conductive bumps and then forming a plating film on the conductive bumps and the metal thin film, the connection portions of the conductive bumps are roughened, whereby the resistance can be prevented from increasing.

Claims (8)

Forming a plurality of laminates by forming metal thin films on both surfaces of the plurality of insulating layers, respectively; Forming through holes penetrating through the laminates; Filling each through hole with a conductive paste to form a conductive bump; Etching each of the laminates to form a circuit pattern; And Comprising the step of pressing each of the laminated board manufacturing method of a multilayer printed circuit board. The method of claim 1, Between forming the conductive bumps and forming a circuit pattern, The method of manufacturing a multilayer printed circuit board, further comprising the step of forming a plating film on both sides of each laminated plate by plating. The method of claim 1, Pressing the laminates, And pressing through-holes of the laminated boards so as to be connected on the same line. The method of claim 1, Pressing the laminates, A method for manufacturing a multilayer printed circuit board, which is pressurized under a pressure of 80 to 120 kg / cm ^{2 in} a vacuum state at 150 to 350 ° C. The method of claim 1, The metal thin film is made of copper, The conductive bumps may include any one selected from copper, gold, silver, nickel or a mixture thereof. The method of claim 1, The insulating layer is made of a thermoplastic synthetic resin or a thermosetting synthetic resin in a semi-cured state, The semi-cured thermally curable synthetic resin is a method of manufacturing a multilayer printed circuit board, characterized in that the cured completely in the step of pressing each laminated plate. The method of claim 1, Forming a circuit pattern on each laminated plate, Forming a core laminate by forming circuit patterns on both surfaces of the laminate; And Removing the metal thin film on one surface of the remaining laminated board and forming a circuit pattern on the other surface. The method of claim 7, wherein Pressing the laminates, Placing a laminate plate disposed on the core laminate plate with the circuit pattern facing up, The method of manufacturing a multilayer printed circuit board, wherein the laminate is disposed under the core laminate so that the circuit patterns face downward.

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