KR100734244B1 - Multilayer printed circuit board and fabricating method thereof - Google Patents

Abstract

A multilayer printed circuit board and a method for manufacturing the same are provided to control a height of a conductive bump by adjusting a thickness of a copper foil when forming the copper foil. A method for manufacturing a multilayer printed circuit board includes the steps of: forming a first laminated plate(A) and a second laminated plate(B) having circuit patterns on upper and lower surfaces of a first insulating layer, a via hole which penetrates the first insulating layer and the circuit patterns to electrically connect the circuit patterns, and a conductive paste filled in the via hole; forming an interlayer connection layer(C) having a via hole in a second insulating layer, and a conductive paste filled in the via hole to be protruded from upper and lower surfaces of the second insulating layer; and thermally compressing the first laminated plate(A), the second laminated plate(B), and the interlayer connection plate(C) interposed between the first laminated plate(A) and the second laminated plate(B) whose via holes are located on the same line.

Description

Multilayer Printed Circuit Board and Fabrication Method Thereof}

1A to 1G are cross-sectional views illustrating a method of manufacturing a multilayer printed circuit board according to a conventional build-up method.

2A to 2D are cross-sectional views showing one embodiment of forming a first laminated plate and a second laminated plate on which a circuit pattern of the present invention is formed.

3A to 3C are cross-sectional views showing another embodiment of forming a first laminated plate and a second laminated plate on which a circuit pattern of the present invention is formed.

4A to 4D are cross-sectional views illustrating a process of forming an interlayer connection layer for electrically connecting a first laminate and a second laminate of the present invention.

5 is a cross-sectional view showing a state in which the first laminated plate and the second laminated plate and the interlayer connection layer of the present invention are collectively laminated;

6 is a cross-sectional view showing an embodiment of a multilayer printed circuit board of the present invention.

Explanation of symbols on the main parts of the drawings

110: insulating layer 113: copper foil

120: via hole 130: conductive paste

140: circuit pattern

The present invention relates to a multilayer printed circuit board and a method of manufacturing the same.

Recently, due to the rapid development of the electronics industry, as electronic products become smaller, thinner, higher density, and lighter, micropatterning, high precision, and miniaturization are simultaneously progressed on a printed circuit board (PCB), which is the basis thereof.

In order to improve the pattern formation, reliability, and design density of the printed circuit board, there is a tendency to change the structure of the circuit layer with the change of raw materials, and the parts are also SMT in the DIP (Dual-In-Line Package) type. As the surface mount technology is changed, the mounting density is also increasing.

In addition to the portableization of electronic devices, high functionalization, the Internet, moving pictures, and high-capacity data transmission and reception make the design of printed circuit boards complicated and require high-level technology.

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 multi-layered printed circuit board (MLB) 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 increased demand for high density and miniaturized circuits. have.

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 via holes.

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.

1A to 1G are cross-sectional views illustrating a method of manufacturing a multilayer printed circuit board according to a conventional build-up method. As shown in the drawing, first, the first via hole 102 is formed in a copper clad laminate (CCL) on which the copper foil 101 is coated on the insulating layer 100 (FIG. 1A).

Next, a plating layer 103 is formed on the surfaces of the copper foil 101 and the first via hole 102 (FIG. 1B). The plating layer 103 is formed by performing electroless plating first, followed by electroplating. The reason why electroless plating is performed before electrolytic plating is that electrolytic plating requiring electricity cannot be performed on the insulating layer. In other words, in order to form a conductive film necessary for electrolytic plating, electroless plating is thinly performed as a pretreatment.

Subsequently, the first via hole 102 is filled to form a connecting portion 104 (FIG. 1C). The connection part 104 may be made of an insulating ink, or may be made of a conductive paste according to the purpose of using a printed circuit board.

Thereafter, the copper foil 101 and the plating layer 103 are etched to form a circuit pattern (FIG. 1D). The circuit pattern formed on the insulating layer 100 and the circuit pattern formed under the insulating layer 100 are electrically connected through the plating layer 103 formed in the via hole 102.

Next, the film which consists of the insulating layer 105 and the copper foil 106 is laminated | stacked on both surfaces of the said copper foil laminated board (FIG. 1E). The insulating layer 105 serves to insulate circuits formed on and under the insulating layer 105.

Subsequently, a second via hole 108 serving as an electrical connection between the inner layer circuit and the outer layer circuit is formed, and then plated again to form a plating layer 107 (FIG. 1F). When the second via hole 108 is formed, more precise processing is required than when forming the first via hole 102 of the inner layer. Therefore, it is preferable to use a laser drill.

Thereafter, the copper foil 106 and the plating layer 107 of the outer layer are etched to form an outer layer circuit pattern (FIG. 1G).

In the manner described above, by forming additional outer layers and forming circuit patterns, multilayer printed circuit boards having more layers can be produced.

Such a conventional method for manufacturing a multilayer printed circuit board takes a long time since the formation of the insulating layer and the formation of the circuit layer are repeated. If a failure occurs in the circuit layer of one layer, the laminated structure itself until now is There is a problem that the product yield is very low because becomes a defective product.

In order to form the second via hole, a portion where the first via hole is formed must be avoided. Therefore, unnecessary space is required, and thus there is a limit to manufacturing a printed circuit board having a high density and high integration structure.

Therefore, the manufacturing method of the batch lamination system which forms the laminated board in which each circuit pattern was formed by an independent process, and completes a product by one lamination | stacking is currently researched.

There is a method of electrically connecting the circuit patterns of the laminates formed on the upper and lower portions of the insulating layer by forming the conductive bumps penetrating the insulating layer of the multilayer laminated printed circuit board manufacturing method currently being studied.

In this case, a protective film is formed on the upper and lower portions of the insulating layer, a via hole penetrating the insulating layer and the protective film is formed, and the via hole is filled with a conductive paste and the protective film is removed to protrude by the height of the protective film. The method of forming a conductive bump is used.

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

Accordingly, an object of the present invention is to form a copper foil on the upper and lower portions of the insulating layer, form a via hole penetrating the insulating layer and the copper foil, and then fill the via hole with a conductive paste and remove the copper foil to thereby form a conductive bump of the interlayer connection layer. The present invention provides a multilayer printed circuit board and a method of manufacturing the same.

Another object of the present invention is to provide a multilayer printed circuit board and a method of manufacturing the same, which shorten the manufacturing time and improve the product yield by thermally compressing the first laminated plate, the second laminated plate and the interlayer connection layer by laminating them together.

A preferred embodiment of the multilayer printed circuit board of the present invention includes a first insulating layer, a first circuit pattern formed on both surfaces of the first insulating layer, and a first via hole penetrating the first insulating layer and the first circuit pattern. And a first laminated plate made of a conductive paste filled in the first via hole and in contact with the first circuit pattern;

An interlayer connection layer comprising a second insulating layer, a second via hole formed at a position corresponding to the first via hole, and a conductive paste filled in the second via hole; And

A third insulating layer, a second circuit pattern formed at a position corresponding to the first circuit pattern on both surfaces of the third insulating layer, a third via hole penetrating through the third insulating layer and the second circuit pattern; A second laminated plate made of a conductive paste filled in the third via hole and in contact with the second circuit pattern;

And an interlayer connection layer is interposed between the first laminate and the second laminate, and the conductive paste is pressed and electrically connected to each other.

In a preferred embodiment of the method of manufacturing a multilayer printed circuit board of the present invention, a circuit pattern is formed on an upper surface and a lower surface of a first insulating layer, and the first insulating layer and the circuit for electrically connecting the circuit pattern. Forming a first laminated plate and a second laminated plate in which a via hole penetrates the pattern, the conductive hole is filled in the via hole, and a via hole is formed in the second insulating layer, and the conductive paste is formed in the via hole. Forming an interlayer connection layer protruding from and filling the upper and lower surfaces of the second insulating layer, and interposing the first and second laminates with the interlayer connection layer interposed between the first and second laminates. And positioning the via holes of the interlayer connection layer so as to be connected on the same line, and then thermally compressing the via holes.

Hereinafter, a multilayer printed circuit board of the present invention and a manufacturing method thereof will be described in detail with reference to FIGS. 2 to 6. The method of manufacturing a multilayer printed circuit board of the present invention comprises the steps of: forming a first laminated plate and a second laminated plate having a large circuit pattern, forming an interlayer connection layer for electrically connecting the first laminated plate and the second laminated plate, And laminating the first laminated plate, the second laminated plate, and the interlayer connection layer.

2A to 2D are cross-sectional views illustrating an embodiment of forming a first laminated plate and a second laminated plate on which a circuit pattern of the present invention is formed. As shown in the drawing, first, a copper clad laminate (CCL) (A) having copper foils 113 formed on both surfaces of the insulating layer 110 is prepared (FIG. 2A).

Copper foil laminate refers to a thin laminate that is generally coated with a thin layer of copper as an original plate on which a printed circuit board is manufactured. There are various kinds of copper foil laminates such as glass / epoxy copper foil laminate, heat resistant resin copper foil laminate, paper / phenol copper foil laminate, high frequency copper foil laminate, flexible copper foil laminate (polyimide film), and composite copper foil laminate. Glass / epoxy copper clad laminates are mainly used in the manufacture of multilayer printed circuit boards.

Next, a via hole 120 is formed in the copper foil laminate A (FIG. 2B).

The via hole 120 is formed through mechanical drilling or laser drilling, and in the case of using a laser drill, a laser drill using CO ₂ is mainly used, but a laser drill using UV-Yag may be used.

Subsequently, the via hole 120 is filled with the conductive paste 130 (FIG. 2C).

As the conductive paste 130, after adding a resin component such as epoxy and cellulose to a metal powder having high electrical conductivity such as gold (Au), nickel (Ni), silver (Ag), copper (Cu), and then using an organic solvent, Kneaded is used.

Since the conductive paste 130 has fluidity, it is preferable to fill the via hole 120 with the conductive paste 120 and then to harden the conductive paste 120.

Subsequently, the copper foil 113 is etched to form circuit patterns 140 on both surfaces of the insulating layer 110 (FIG. 2D). In this case, the circuit patterns 140 formed on the upper and lower surfaces of the insulating layer 110 are electrically connected through the conductive paste 130.

First, a photoresist is coated on the copper foil 113, and then the photoresist is patterned. After the copper foil 113 is etched using the patterned photoresist as an etch mask, the remaining photoresist is removed to form a circuit pattern 140 on the upper and lower surfaces of the insulating layer 110. .

The circuit pattern 140 should be designed in advance in the correct position and dimensions in consideration of the coupling with the interlayer connection layer to be described later.

After the circuit pattern 140 is formed, a process of inspecting the appearance of the circuit by a method such as automatic optical inspection and a black oxide process to check whether the circuit is properly formed. You can do more processing.

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. That is, the pattern information of the target circuit is read into the image sensor, and then compared with the reference data to read 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 laminate is required.

3A to 3C are cross-sectional views illustrating another embodiment of forming a first laminated plate and a second laminated plate on which a circuit pattern of the present invention is formed. As shown in FIG. 3, first, the via hole 220 penetrating the insulating layer 200 and the copper foil 210 is formed, and then the conductive paste 230 is filled in the via hole 220 (FIG. 3A).

Next, a plating layer 240 is formed on upper and lower surfaces of the copper foil 210 and the conductive paste 230 (FIG. 3B). The plating layer 240 is formed using an electrolytic plating method, the plating layer 240 is preferably made of copper (Cu).

The electroplating is preferably a copper sulfate 180-240 g / L, sulfuric acid 45-60 g / L and a thiourea, dextrin, or thiourea and molasses at a current density of 2-8 A / cm 2. It is carried out in a bath containing the same additives.

As described above, the reason why the plating layer 240 is formed on the upper and lower surfaces of the copper foil 210 and the conductive paste 230 is to increase the reliability of the electrical connection between the circuit patterns to be described later.

That is, in the case where voids occur because the conductive paste 230 is not properly filled in the via hole 220 in FIG. 3A, the electrical connection is properly formed between the circuit patterns formed on the upper and lower surfaces of the insulating layer 200. In this case, the plating layer 240 is formed on the upper and lower surfaces of the copper foil 210 and the conductive paste 230.

Subsequently, portions of the plating layer 240 and the copper foil 210 are etched to form circuit patterns 250 on the top and bottom surfaces of the insulating layer 200 (FIG. 3C).

4A to 4D are cross-sectional views illustrating a process of forming an interlayer connection layer for electrically connecting a first laminate and a second laminate of the present invention. As shown in the figure, first, copper foil 310 is formed on both surfaces of the insulating layer 300 (FIG. 4A).

The insulating layer 300 is made of a synthetic resin, preferably a form in which glass fiber is impregnated with the synthetic resin. The thickness of the insulating layer 300 is preferably 7 ~ 50㎛.

As said synthetic resin, the thermosetting resin or the thermoplastic resin of a semi-hardened state is used. In the semi-cured thermosetting resin, in the step of thermocompression bonding a plurality of laminates, polymerization proceeds to complete curing.

As the thermosetting resin in the semi-cured state, polyimide is mainly used, and since polyimide has a high melting point, it has excellent thermal stability and can withstand long-term use. In addition, since the mechanical strength, electrical properties, chemical resistance, radiation resistance and the like is good, it is widely used as an insulating layer of a multilayer printed circuit board.

The semi-cured thermosetting polyimide is formed by impregnating the glass fibers in a polyamic acid solution and then proceeding the polymerization at a relatively low temperature. The polyamic acid is an intermediate of the polyimide, and becomes a polyimide while the amidation reaction and the crosslinking reaction proceed.

In addition, as the thermoplastic resin, polyethylene, polymethyl methacrylate, polyethylene terephthalate, polypropylene, or the like may be used. The thermoplastic resin is easily flowable by heating, and it is necessary to proceed polymerization in the curing process. Therefore, there is an advantage that the workability is good as compared to the thermosetting resin in the semi-cured state.

Next, a via hole 320 penetrating the insulating layer 300 and the copper foil 310 is formed (FIG. 2B).

The via hole 320 is formed by mechanical drilling or laser drilling. When using a laser drill, a laser drill using CO ₂ is mainly used, but a laser drill using UV-Yag may be used. .

Subsequently, the conductive paste 330 is filled in the via hole 320 (FIG. 4C).

At this time, the conductive paste 330 is filled by using a screen printing method, the work environment at the time of screen printing is working at atmospheric pressure or vacuum.

The main component of the conductive paste 330 is a metal powder, which uses metals such as copper (Cu), silver (Ag), gold (Au), tin (Sn), and lead (Pb). It acts as a bond.

The conductive paste 330 should be able to secure the conductivity electrically or thermally in contact with each other when the metal powder is heated and pressed.

In the case of the conductive paste 330 filled in the via holes 320 of the interlayer connection layer, unlike the conductive pastes filled in the via holes of the first laminate and the second laminate, only the drying process is performed without completely curing. And when the second laminated plate and the interlayer connection layer are laminated together and thermocompressed, to facilitate the interlayer adhesion of the conductive paste 330 and to prevent thermal shock of the thermosetting resin.

Thereafter, the copper foil 310 is etched and removed (FIG. 4D).

That is, after forming a photoresist on the copper foil 310 and the conductive paste 330, patterning the photoresist, the copper foil 310 is etched using the patterned photoresist as an etching mask. Here, the copper foil 310 is preferably removed by wet etching using an etching solution.

In this case, when the copper foil 310 is removed, the conductive paste 330 filled in the via hole 320 protrudes from the surface of the insulating layer 300 by the thickness of the copper foil 310 to form a conductive bump. Such conductive bumps provide good electrical connection during thermocompression bonding of the first and second laminated plates and the interlayer connection layer.

As such, if the copper foil 310 is formed on both surfaces of the insulating layer 300 and then removed by etching to form the conductive bumps, the conductive bumps may be prevented from being damaged when the protective film is removed when the protective film is used. .

And, by adjusting the thickness of the copper foil 310 at the time of forming the copper foil 310, it is possible to adjust the height of the conductive bumps.

The interlayer connection layer should also be designed in precise position and pattern in advance in consideration of the circuit patterns of the first laminated board and the second laminated board to be bonded in the multilayer printed circuit board of the present invention. In addition, the number is determined depending on the number of layers of the multilayer printed circuit board to be manufactured.

5 is a cross-sectional view showing a state in which the first laminated plate and the second laminated plate and the interlayer connection layer of the present invention are collectively laminated.

As shown here, the interlayer connection layer C formed by the method of FIGS. 4A to 4D is positioned between the first laminated plate A and the second laminated plate B formed by the method of FIGS. 2A to 2D. . In this case, the via holes of the first laminated plate A, the second laminated plate B, and the interlayer connecting layer C may be connected on the same line.

Here, a thermocompression bonding method is used as a method of compressing the first laminated plate A, the second laminated plate B, and the interlayer connection layer C into a single printed circuit board. The lamination is carried out by placing the first laminated plate A, the second laminated plate B, and the interlayer connection layer C in a case and pressing and heating them by inserting them into hot plates above and below the 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.

Here, the insulating layer of the first laminated plate (A) and the second laminated plate (B) and the interlayer connection layer (C) is made of a thermoplastic resin or a thermosetting resin in a semi-cured state, in the case of the thermoplastic resin, the thermocompression bonding step At the glass transition temperature at and the flowability and adhesiveness is increased to bond each laminated plate, and in the case of the semi-cured thermosetting resin, the laminate is bonded while the polymerization proceeds in the thermocompression bonding process.

The pressure applied in the thermocompression process is preferably 80 to 120 kg / cm 2, and the heating temperature is preferably about 150 to 350 ° C.

6 is a cross-sectional view showing an embodiment of a multilayer printed circuit board of the present invention.

As shown in the drawing, the first insulating layer 400, the first circuit pattern 410 formed on both surfaces of the first insulating layer 400, the first insulating layer 400 and the first circuit pattern ( First via holes 420 penetrating through 410, conductive pastes filled in the first via holes 420 to contact the first circuit pattern 410, and formed on both surfaces of the first insulating layer 400. A first laminated plate comprising a first circuit pattern 410 and a first plating layer 430 formed above and below the conductive paste;

An interlayer connection layer including a second insulating layer 500, a second via hole 510 formed at a position corresponding to the first via hole 420, and a conductive paste filled in the second via hole 510; And

The third insulating layer 600, the second circuit pattern 610 formed at positions corresponding to the first circuit patterns 410 on both surfaces of the third insulating layer 600, and the third insulating layer 600. ) And a third via hole 620 penetrating through the second circuit pattern 610, a conductive paste filled in the third via hole 620 to contact the second circuit pattern 610, and the third insulating layer. A second laminated plate including a second circuit pattern 610 formed on both sides of the 600 and a second plating layer 630 formed on upper and lower portions of the conductive paste; and between the first laminated plate and the second laminated plate. An interlayer connection layer is interposed therebetween, and the conductive paste is pressed and electrically connected to each other.

Here, the second insulating layer 500 is made of a thermoplastic resin or a thermosetting resin in a semi-cured state, and the first plating layer 430 and the second plating layer 630 are preferably made of copper.

Although the present invention has been described in detail with reference to exemplary embodiments above, those skilled in the art to which the present invention pertains can make various modifications to the above-described embodiments without departing from the scope of the present invention. I will understand.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the present invention, copper foils are formed on both surfaces of the insulating layer and then removed by etching to form conductive bumps, thereby preventing the conductive bumps from being damaged when the protective film is removed when using a conventional protective film. The height of an electroconductive bump can be adjusted by adjusting the thickness of copper foil at the time of formation of copper foil.

In addition, according to the present invention, the first laminated plate, the second laminated plate and the interlayer connection layer are stacked together and thermally compressed to reduce the manufacturing time and improve the product yield.

Claims (10)

delete delete delete delete Circuit patterns are formed on upper and lower surfaces of the first insulating layer, and via holes penetrating through the first insulating layer and the circuit patterns are formed to electrically connect the circuit patterns, and conductive paste is formed in the via holes. Forming a filled first laminated plate and a second laminated plate; Forming an interlayer connection layer in which a via hole is formed in the second insulating layer, and in which the conductive paste protrudes from the upper and lower surfaces of the second insulating layer and is filled; And Interposing the interlayer connection layer between the first laminate and the second laminate, and positioning the via holes of the first laminate, the second laminate, and the interlayer connection layer to be connected on the same line, and then performing thermocompression bonding. , Forming the interlayer connection layer, Forming a copper foil on upper and lower surfaces of the second insulating layer, and then forming a via hole penetrating the second insulating layer and the copper foil; Filling a conductive paste into the via hole; And Method of manufacturing a multilayer printed circuit board comprising the step of removing the copper foil. The method of claim 5, Forming the first and second laminates; Forming copper foils on upper and lower surfaces of the first insulating layer, and then forming via holes penetrating the first insulating layer and the copper foil; Filling a conductive paste into the via hole; And Removing a portion of the copper foil to form circuit patterns electrically connected to upper and lower surfaces of the first insulating layer through conductive pastes filled in the via holes. Manufacturing method. The method of claim 5, Forming the first and second laminates; Forming copper foils on upper and lower surfaces of the first insulating layer, and then forming via holes penetrating the first insulating layer and the copper foil; Filling a conductive paste into the via hole; Forming a plating layer on the copper foil and the conductive paste; And And removing a portion of the copper foil and the plating layer to form circuit patterns electrically connected to upper and lower surfaces of the first insulating layer through conductive pastes filled in the via holes. Method of manufacturing a circuit board. delete The method of claim 5, The copper foil is removed using a wet etching method of manufacturing a multilayer printed circuit board. The method of claim 5, The thermocompression step may include; Method of manufacturing a multilayer printed circuit board, characterized in that the pressing by pressing at a pressure of 80 ~ 120 kg / ㎠ in a 150 ~ 350 ℃ atmosphere.

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