KR20190127471A - Method for forming cavity in pcb - Google Patents

Abstract

A method of forming a cavity of a printed circuit board according to the present invention includes a step of stacking a plurality of substrates including a circuit formed of copper foil, a step of stacking an outer layer forming substrate including copper foil on the outer layers of the substrates, and a step of pressing a dry film to the surface of the outer layer forming substrate, a step of developing and curing the dry film to open a cavity forming part, and a step of performing sandblasting on the cavity forming part. According to the present invention, it is possible to set the same as a cavity dimension actually required when the dimension of the cavity is designed, and to prevent an adhesive component from seeping out when the cavity is formed. In addition, the cavity can be easily processed. In addition, it is advantageous for mass production, thereby significantly reducing manufacturing costs, and preventing sedimentation of the prepreg and poor connection of components.

Description

Cavity Formation Method of Printed Circuit Board {METHOD FOR FORMING CAVITY IN PCB}

The present invention relates to a method for forming a cavity in a printed circuit board, and more particularly, the setting is equal to the cavity size actually required when designing the size of the cavity without exuding the adhesive component of the prepreg when the cavity is formed. The present invention relates to a cavity forming method of a printed circuit board capable of being easily processed and advantageous for mass production.

Recently, the technology related to electronic products is progressing in the trend of multi-function and high speed, and semiconductor chip manufacturing technology is also rapidly developing to cope with this trend.

In particular, the thickness of printed circuit boards (PCBs), which are applied to reduce the size and thickness of finished electronic products, has also been reduced, and related technologies for multilayer printed circuit boards having more circuit layers in printed circuit boards having the same thickness. Are being actively researched.

In general, a multilayer printed circuit board is obtained by stacking a plurality of printed circuit boards including a prepreg (insulator) formed by impregnating glass fiber with epoxy resin and a copper (cu) circuit formed on the surface thereof. It can form by heat-pressing in a state.

In some cases, a separate component such as a memory chip is connected to a specific region of the multilayer printed circuit board. In this case, a cavity (concave) is formed in the region to reduce the thickness of the entire circuit board. Will be placed.

1 is a side cross-sectional view of a state in which the cavity 120 is formed in a conventional multilayer printed circuit board 100.

Conventionally, the cavity is formed by using a laser drill method after forming the outermost layer substrate 130, a problem that the adhesive component is exuded from the adjacent prepreg 110 by the pressure applied during the lamination process of the outer layer substrate There is.

To prevent this phenomenon as much as possible, non-flow prepregs are prepared to minimize the flow of adhesive, but even non-flow prepregs, liquid components including adhesive components included in the prepregs during the cavity formation process are used. The fine melted and oozes out, and in consideration of this phenomenon, the design width of the cavity 120 is set to be somewhat larger than the width actually required.

Thus, even though some of the adhesive component flows out of the cavity 120 into the boundary portion (the corner portion of the cavity space) with the prepreg 110, the other space may be the actual cavity space size required for component mounting. I'm doing it.

This is a factor that increases the design dimension and the resulting machining dimensions of the cavity 120, and in addition to the work required for the formation of the cavity space that is actually required additionally required to reduce the work yield do.

In addition, as the liquid component oozes into the cavity 120 space from the prepregs 110 and 130 adjacent to the cavity 120 space, bending of the substrate due to sedimentation of the adjacent prepregs 110 and 130 is performed. Will be raised.

Thus, the circuit portion of the outermost layer substrate 130 located on the settled prepreg has a problem in that a defective rate is increased in connection with an electronic component connected thereto.

The present invention has been made to solve the above problems, an object of the present invention is to provide a cavity forming method of a printed circuit board is configured so that the adhesive component does not exude when forming the cavity.

Another object of the present invention is to provide a cavity forming method of a printed circuit board which can be set in the same way as the cavity dimension actually required when designing the dimension of the cavity, and is configured not to cause the prepreg to settle.

Another object of the present invention is to provide a cavity forming method of a printed circuit board which is easy to process and is configured to be advantageous for mass production.

Cavity forming method of a printed circuit board according to the present invention for achieving the above object is a step of laminating a plurality of substrates including a circuit formed of copper foil, and the outer layer forming substrate comprising a copper foil on the plurality of substrate outer layers And adhering a dry film to the surface of the outer layer forming substrate, exposing and developing the dry film to open a cavity forming portion, and sandblasting the cavity forming portion. do.

Preferably, the method may further include etching the cavity forming portion.

On the other hand, the cavity forming method of a printed circuit board according to another embodiment of the present invention comprises the steps of laminating a plurality of substrates including a circuit formed of copper foil, applying a photosolder resist to the cavity forming portion, and the photosolder Primary plating the resist surface, adhering the dry film to the outside of the primary plating layer, secondary plating the surface of the primary plating layer, removing the dry film, and removing the primary plating layer A quick etching step, stacking the substrates and forming an outer layer circuit, adhering the dry film to the surface of the outer layer forming substrate, and exposing and developing the dry film to open the cavity forming part. And blasting the cavity forming site, etching and removing the plating layer, and removing the photosolder resist. By a step of exposing the circuit.

Preferably, the primary plating is a chemical plating method.

In addition, the secondary plating may be made by an electroplating method.

The exposing the circuit by removing the photosolder resist may be performed by laser processing.

According to the present invention, it is possible to set the same as the cavity dimensions actually required when designing the dimensions of the cavity, and to prevent the adhesive component of the prepreg from seeping into the cavity space when the cavity is formed.

In addition, the cavity can be easily processed and advantageous to mass production, thereby significantly reducing the manufacturing cost.

In addition, it is possible to prevent defective parts connection due to the settling of the prepreg.

Since the accompanying drawings are for understanding the technical idea of the present invention together with the detailed description of the invention, the present invention should not be construed as limited to the matters shown in the following drawings.
1 is a side cross-sectional view of a circuit board formed by a conventional cavity forming method,
2 is a procedure flowchart of a cavity forming method according to a first embodiment of the present invention;
3 is a procedure flowchart of a cavity forming method according to a second embodiment of the present invention;
4 is a side sectional view of a circuit board formed according to the first embodiment;
5 and 6 are side cross-sectional views of a circuit board formed in accordance with the second embodiment.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

Prior to this, the terms used in this specification and claims should not be construed in a dictionary sense, and the inventors may properly define the concept of terms in order to explain their invention in the best way. It should be construed as meaning and concept consistent with the technical spirit of the present invention.

Therefore, the configurations shown in the embodiments and drawings described herein are only preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, and various equivalents may be substituted for them at the time of the present application. It is to be understood that water and variations may exist.

2 is a flow chart of a cavity forming method according to a first embodiment of the present invention, FIG. 3 is a flow chart of a cavity forming method according to a second embodiment of the present invention, and FIG. 4 is a flow chart according to the first embodiment. 5 and 6 are side cross-sectional views of the circuit board formed according to the second embodiment.

2 and 4, a cavity forming method of a printed circuit board according to the present invention includes stacking a plurality of substrates 10, 20, 30, 40, 50, and 60 including a circuit formed of copper foil (steps). 210 and stacking an outer layer forming substrate 70 including copper foil on an outer layer of the plurality of substrates 10, 20, 30, 40, 50, and 60 (step 220), and the outer layer forming substrate. Contacting the dry film 84 to the surface of the 70 (step 230), exposing and developing the dry film 84 to open the cavity 90 forming portion (step 240), and the cavity (90) sandblasting the forming site (step 250).

The plurality of substrates 10, 20, 30, 40, 50, and 60 are in contact with a dry film on the surface of the copper foil while the copper foil is disposed on the surface of the prepreg, and undergoes exposure, development, and copper foil etching. It is formed by laminating a plurality of individual substrates including a circuit formed by applying heat and pressure.

The outer layer forming substrate 70 disposed outside the plurality of substrates is also formed by forming a copper foil 72 on the surface of the prepreg.

The prepreg is formed by impregnating a polymer resin into a reinforcing base such as glass fiber, and as the reinforcing base, a glass fiber fabric, a glass fiber nonwoven fabric, a carbon fiber fabric, or an organic polymer fiber fabric is used.

In addition, the polymer resin for forming the prepreg is mixed with an additive such as a curing agent for controlling the dielectric constant, thermal expansion rate and the time required for curing.

Additives to be mixed in the polymer resin for controlling the above properties include inorganic fillers such as silica, aluminum hydroxide, calcium carbonate and organic fillers such as cured epoxy and crosslinked acrylic.

Circuit patterns 12 and 72 formed on the respective substrates by the copper foil may be formed to have a thickness of approximately 15 to 20 μm.

For convenience of description, a multilayer printed circuit board in which a total of seven layers of circuit patterns are stacked is illustrated, but the spirit of the present invention is not limited thereto.

Surfaces of the upper outer layer substrate 70 and the lower outer layer substrate 10 in the state in which the outer layer forming substrates 10 and 70 are loaded on the inner layer substrates 20 to 60 composed of a plurality of substrates as described above. Dry films 82 and 84 are brought into close contact with each other.

The dry films 82 and 84 may be disposed only on the surface of the outer layer substrate 70 disposed thereon.

In addition, through the exposure and development steps of the dry film 84, the dry film of the portion to form the cavity is removed.

Subsequently, the cavity space is formed by sandblasting the portion from which the dry film has been removed as described above.

The sand blasting process is a method in which fine sand or the like is sprayed from a nozzle together with high pressure air to impinge on the surface of a workpiece to be processed.

The dry films 82 and 84 disposed at the outermost part of the sand blasting process serve as a protective film to protect the outermost substrates 10 and 70, and at the same time, the cavity is formed by the sand sprayed during the sand blasting process. It serves as a guide tube to guide the to.

After the sandblasting process, the copper foil 62, which may be present in the bottom portion of the cavity 90 space, may be removed by etching.

3, 5, and 6 are side cross-sectional views of a process board and a circuit board of a cavity forming method according to a second embodiment of the present invention.

3, 5, and 6, the cavity forming method of the printed circuit board according to the second embodiment of the present invention includes a plurality of substrates 10, 20, 30, 40, and 50 including a circuit formed of copper foil. Stacking (step 10), applying a photosolder resist 64 to the cavity forming site (step 320), first plating the surface of the photosolder resist 64 (step 330), and Adhering the dry film 84 to the outside of the first plating layer 74 (step 340), second plating the surface of the first plating layer 74 (step 350), and the dry films 82 and 84. Removing the step (step 360), stacking the substrates 60, 70, and 80 and forming an outer layer circuit (step 370), and adhering the dry films 92 and 94 to the surface of the outer layer forming substrate. Step (380), exposing and developing the dry film 94 to open the cavity forming part 90 (step 390), and the cavity 9 0) sandblasting the formation site (step 400), etching and removing the plating layers 74 and 76 (step 410), and removing the photosolder resist 64 to expose the circuit 52. It comprises the step of.

The second embodiment is an embodiment in which it is necessary to form the chip connection circuit 52 in the cavity space. In the state where a plurality of substrates 10, 20, 30, 40, 50 are first stacked, A photo solder resist (PSR) is applied to the circuit copper foil of the portion where the cavity is to be formed (step 320).

By applying the photosolder resist 64, it is possible to prevent the circuit copper foil 52, which should be present in the cavity space, from being damaged by subsequent processes.

Then, the first surface of the applied photosolder 64 is thinly plated by chemical plating to form a primary plating layer 74.

The primary plating layer 74 then serves as a pre-plating layer for forming a thicker secondary plating layer 76 through electroplating.

After the formation of the primary plating layer 74 (step 330), the dry film 84 is closely adhered to the exterior of the primary plating layer 74.

Then, the dry film 84 disposed as described above is exposed and developed.

The exposure and development of the dry film 84 is for forming a thicker secondary plating layer 76 by an electroplating method, and the dry film 84 is exposed and developed to expose the secondary plating layer 76. Open the part to be formed.

As described above, after opening the portion to form the secondary plating layer 76 in the dry film 84, the secondary plating layer 76 is formed on the surface of the primary plating layer 74 by using an electroplating method.

The first and second plating layers 74 and 76 may mechanically and chemically protect the circuits 52 of the cavity forming part from various processes.

After the secondary plating layer 76 is formed, the dry films 84 and 82 are removed (step 360).

Then, Quick etching is performed to remove the primary plating layer 74 (step 370).

Subsequently, as illustrated in FIG. 5 (d), the substrates 60, 70, and 80 are stacked (step 380) to form an outer layer circuit (step 390), and as shown in FIG. 92, 94) (step 400).

Then, the dry film 94 is exposed and developed to open the cavity forming portion 90 (step 410).

Then, the open portion 90 of the dry film 94 is sandblasted to form a cavity space (step 420).

In addition, the plating layers 74 and 76 formed by the chemical plating and the electroplating are removed by etching.

The photosolder resist 64 is then drilled (removed) through laser processing to expose the circuit 52 (step 440).

By the cavity forming method according to the present invention as described above, it is possible to prevent the adhesive component of the prepreg from seeping into the cavity space when forming the cavity, it is possible to set the same as the actual cavity size required when designing the dimensions of the cavity Do.

In addition, when the number of cavities in the circuit board is large, when the cavity is formed by the laser processing method, the processing yield is reduced because the individual cavities must be processed separately, but according to the method according to the present invention, a plurality of cavities once Since it can be formed through sandblasting, the cavity can be easily processed and it is advantageous for mass production, thereby significantly reducing the manufacturing cost.

In addition, prepreg sedimentation does not occur due to processing, and the component connection failure rate can be significantly reduced.

As mentioned above, although the present invention has been described by way of limited embodiments and drawings, the technical idea of the present invention is not limited thereto, and a person having ordinary skill in the art to which the present invention pertains, Various modifications and variations may be made without departing from the scope of the appended claims.

10 to 70: substrate
12, 52: circuit part
64: photosolder resist
74, 76: 1st and 2nd plating layer
82, 84: dry film
92, 94: dry film

Claims (6)

Stacking a plurality of substrates comprising a circuit formed of copper foil;
Laminating a substrate for forming an outer layer including copper foil on the plurality of substrate outer layers;
Contacting a dry film to a surface of the substrate for forming an outer layer;
Exposing and developing the dry film to open a cavity forming portion;
The cavity forming method of the printed circuit board comprising the step of sandblasting the cavity forming portion.
The method of claim 1,
And etching the cavity forming portion.
Stacking a plurality of substrates comprising a circuit formed of copper foil;
Applying photosolder resist to the cavity forming site;
First plating the surface of the photosolder resist;
Contacting the dry film to the outside of the first plating layer;
Second plating the surface of the first plating layer;
Removing the dry film;
Quick etching step for removing the first plating layer;
Stacking substrates and forming an outer layer circuit;
Contacting the dry film to the surface of the substrate for forming an outer layer;
Exposing and developing the dry film to open a cavity forming portion;
Sandblasting the cavity forming portion;
Etching to remove the plating layer;
Removing the photosolder resist to expose the circuit.
The method of claim 3, wherein
The primary plating is a method of forming a cavity of a printed circuit board, characterized in that the chemical plating method.
The method of claim 3, wherein
The secondary plating is a cavity forming method of a printed circuit board, characterized in that the electroplating method.
The method of claim 1,
Exposing the circuit by removing the photosolder resist, wherein the cavity is formed by a laser processing method.

Images