KR100871031B1 - Forming method of bump for the printed circuit board - Google Patents

Abstract

A method for forming a bump of a PCB(Printed Circuit Board) is provided to reduce the number of printing conductive paste by forming a bump of a height that a user wants through one printing operation. A plate(11) which has a copper foil is prepared, and a first mask(31) which includes a hole at a portion where a bump of the plate is formed is placed on the plate. A second mask(33) which has a central point on a vertical line which passes through the center of a first mask hole and has a larger diameter than the hole of the first make hole is placed on the first mask. A conductive paste is placed on the second mask, and the conductive paste fills up the holes of the first and second mask holes by printing conductive paste with a squeezer.

Description

Forming method of bump for the printed circuit board

1A to 1C are cross-sectional views illustrating a bump forming method of a printed circuit board according to the prior art.

2A to 2C are cross-sectional views illustrating a bump forming method of a printed circuit board according to an exemplary embodiment of the present invention.

The present invention relates to a bump forming method of a printed circuit board, in particular, by using two masks to reduce the thickness of the mask to improve the omission characteristics of the conductive paste, and to reduce the number of printing of the conductive paste for bump formation process time and The present invention relates to a method for forming bumps of a printed circuit board which can reduce processing costs.

Due to the development of electronic components, there is a demand for a technology capable of improving performance of high density interconnection (HDI) substrates to which electrical patterns of circuit patterns and fine circuit wiring are applied for increasing the density of printed circuit boards. That is, in order to improve the performance of the HDI substrate, a technique for securing the electrical conduction technology and the degree of freedom of design between circuit patterns is required.

In the conventional multilayer printed circuit board, an inner layer circuit is formed by applying an additive method or a subtractive method to the surface of a core substrate such as a copper clad laminate (CCL), and an insulating layer and a metal layer are sequentially formed. It is manufactured by forming an outer layer circuit in the same way as an inner layer circuit while building up.

However, such a conventional multi-layer printed circuit board manufacturing process, such as the request for low cost (low cost) in accordance with the falling price of the application products such as mobile phones, the request for shortening the lead time (lead-time) to increase the mass production, etc. There is a problem that does not satisfy, there is a need for a new manufacturing process that can solve this problem.

On the other hand, in order to simplify the complicated process of the prior art and to manufacture a multilayer printed circuit board quickly and inexpensively by batch lamination, a paste is printed on the copper foil to form a bump, and an insulating material is laminated thereon. The B2it (Buried bumpinterconnection technology) method is commercially available, which allows a simple and easy lamination process by preparing a paste bump substrate in advance.

1A to 1C are cross-sectional views illustrating a method of forming bumps on a disc according to the prior art.

As shown in Fig. 1A, a mask 31 'is prepared which prepares a disc 11' on which a bump 53 'is to be formed and has holes at a position where a bump 53' of the disc 11 'is to be formed. Is placed on the disc 11 '. Thereafter, the conductive paste 51 'is placed on the mask 31' and the conductive paste 51 'is printed such that the conductive paste 51' is filled in the holes of the mask 31 'using a squeegee. Under pressure of the squeegee, the lower portion of the conductive paste 51 'is pressed against the original plate 11'.

Next, as shown in FIG. 1B, when the lower portion of the conductive paste 51 ′ is pressed against the disc 11 ′, the mask 31 ′ is lifted off from the disc 11 ′ to remove the mask 11 ′. A bump 53 'is formed in the').

However, in order to manufacture a high-density (0.4 mm pitch or less) substrate, the bump size should be reduced, and since the paste has a high viscosity, the smaller the hole of the mask, the better the characteristics. Therefore, when the above-described process is performed once, bumps having a desired height cannot be formed. Therefore, there was a need to increase the height of the bumps by repeatedly performing the above-described process and drying and curing the bumps.

Referring to Fig. 1C, a bump 55 'obtained by repeating the above-described process three times is shown.

According to this process, as the bump is formed by repeatedly performing the squeegee process and the hardening process to form the bumps, there is a problem in that the process time becomes longer and thus the time required for the manufacturing process of the entire printed circuit board becomes longer.

The present invention was created to solve the problems of the prior art as described above, by using two masks to reduce the thickness of the mask to improve the omission characteristics of the conductive paste, and to reduce the number of printing of the conductive paste for bump formation An object of the present invention is to provide a bump forming method of a printed circuit board which can reduce processing time and processing cost.

In order to achieve the above object, a method of forming a paste bump of a printed circuit board according to an embodiment of the present invention includes the steps of (A) preparing a disc; (B) positioning a first mask on the disc, the first mask having a hole in a position where a bump of the disc is to be formed; (C) positioning a second mask on the first mask, the second mask having a center on a vertical line passing through the center of the hole of the first mask and having a hole having a diameter larger than that of the hole of the first mask; And (D) filling a conductive paste into the holes of the first mask and the second mask to form bumps on the original plate.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to this, the terms or words used in this specification and claims are not to be interpreted in a conventional and dictionary sense, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Hereinafter, a preferred embodiment of a bump forming method of a printed circuit board according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view illustrating a method of forming a bump 53 of a printed circuit board according to an exemplary embodiment of the present invention.

First, as illustrated in FIG. 2A, a disc 11 on which bumps 53 are to be formed is prepared.

Here, the disc 11 may be any one of copper foil laminated plate (CCL), the copper foil, or one surface of the metal carrier in which the circuit pattern 15 is formed on one or both surfaces of the insulating layer.

This disc 11 is formed by any of the following methods.

In the first method, a dry film (not shown) is applied onto a copper foil of a single-sided copper clad laminate (RCC) in which copper foil is laminated on one or both sides of the first insulating layer, and then exposed and developed. The dry film of the remaining portion except for the portion where the circuit pattern is to be formed is removed.

Thereafter, the copper foil is etched with an etching solution to form a circuit pattern, and after the circuit pattern is formed, the dry film remaining on the circuit pattern is removed.

As a result, a disc 11 as shown in FIG. 2A is formed.

In a second method, an electroless copper plating layer and an electrolytic copper plating layer are formed on one or both surfaces of the first insulating layer through an electroless copper plating process and an electrolytic copper plating process.

After the electroless copper plating layer and the electrolytic copper plating layer are formed, a dry film is applied on the electrolytic copper plating layer, and then the dry film of the remaining portions except for the dry film of the portion where the circuit pattern is to be formed is subjected to exposure and development processes.

Thereafter, the copper foil is etched with the etching solution to form a circuit pattern, and the dry film remaining on the circuit pattern is removed.

Since the original plate 11 may be manufactured by any known technique, detailed description thereof will be omitted.

When the disc 11 on which the bump 53 is to be formed is prepared, a first mask 31 having a hole is formed on the disc 11 at a position where the bump 53 is to be formed, and the first mask ( A second mask 33 having a hole concentric with the hole of 31 is positioned on the first mask 31.

In this case, the diameter of the hole provided in the second mask 33 is larger than the diameter of the hole provided in the first mask 31 as shown in FIG. 2A. For this purpose, the diameter D1 of the hole provided in the first mask is preferably 130 to 150 μm, and the diameter D2 of the hole provided in the second mask is preferably 180 to 400 μm. In addition, when the original plate 11 is formed of a circuit pattern, the diameter of the hole provided in the first mask 31 is smaller than the width D2 of the land portion 15 on which the bumps 53 of the original plate 11 are to be formed. It is preferable.

The thickness of each of the first mask 31 and the second mask 33 is smaller than the height of the bump 53 to be formed. Preferably, the thickness H1 of the first mask 31 and the second mask 33 is 50-100 μm.

In general, when the mask 31 is separated from the disc 11 to form the bumps 53, the amount of the conductive paste 51 attached to the disc 11 by falling out of the hole of the mask 31 is determined by the amount of the mask 31. It is determined by the ratio of the diameter D1 of the hole to the thickness H3.

In other words, the thinner the thickness H3 of the mask 31 and the larger the diameter D1 of the hole, the better the missing characteristic of the conductive paste 51.

However, in order to fabricate a high-density substrate, since the diameter of the bump 53 must be small, there is a limitation in increasing the size of the hole formed in the mask 31.

In this regard, the thickness of the masks 31 and 33 according to the present invention can be reduced to improve the omission characteristics of the conductive paste 51.

When the original plate 11, the first mask 31, and the second mask 33 are arranged in this order, the conductive paste 51 is placed on the second mask 33, and then the conductive paste is printed with a squeegee to form the first mask 31. And the conductive paste 51 is filled in the holes provided in the second mask 33. When the conductive paste 51 is filled in the hole, the lower end of the conductive paste 51 is pressed onto the disc 11.

Next, as shown in FIG. 2B, the second mask 33 is separated from the original plate 11 and the first mask 31. As described above, since the diameter of the hole provided in the second mask 33 is larger than the diameter of the hole provided in the first mask 31, the omission property of the conductive paste 51 filled in the second mask 33 is reduced. It is better than one mask 31. When the second mask 33 is removed, the upper bumps 53a are formed at positions corresponding to the holes of the first mask 31. Since the diameter of the hole provided in the second mask 33 is larger than the diameter of the hole provided in the first mask 31, the diameter of the lower surface of the upper bump 53a is larger than the diameter of the hole provided in the first mask 31. do.

Next, as shown in FIG. 2C, the first mask 31 is separated from the original plate 11 after the second mask 33 is separated. Since the thickness of the first mask 31 is smaller than that of the mask used in the related art, the thickness of the first mask 31 is better, and the conductive paste 51 is forced downward by the weight of the upper bump 53a. The conductive paste 51 filled in the holes provided in 31 may be more easily pulled out. Among the upper bumps 53a that cover the holes of the first mask 31 while the first mask 31 is separated, the conductive paste 51, which is located outside the circumference of the holes of the first mask 31, is formed in the first mask 31. To be removed. When the first mask 31 is separated, the bump 11 including the upper bumps 53a and the lower bumps 53b is formed on the disc 11. The bumps 53 are completed by drying and curing the paste bumps 53 thus formed. In this way, a bump having a higher height than the diameter can be formed in one step.

When the bumps 53 are formed by the method according to the present invention, the process time can be shortened more effectively than the bumps 53 having the same height H4 are formed by the conventional method.

After forming the bumps, an insulating layer is laminated on the disc such that the paste bumps penetrate the insulating layer. In this process, the so-called 'B2it' method of forming a 'paste bump substrate' by forming an insulating layer on a substrate on which paste bumps are formed is applied, and the insulating layer is penetrated through the paste bump using a 'B2it' method penetrator. .

Next, the paste bumps are pressed in correspondence with the heights of the stacked insulating layers. This is to match the height of the paste bumps penetrating the insulating layer and protruding above the surface of the insulating layer to be equal to the height of the insulating layer. The compression of the paste bumps is done in a mechanical manner, and existing coining equipment can be applied. If the insulating layer is directly laminated without pressing the paste bump, a part of the paste bump may protrude over the surface of the insulating layer, thereby making it difficult to sequentially stack the circuit pattern layer.

In this way, the paste bump is pressed to flatten the surface of the insulating layer, and then a circuit pattern is formed. Through this process, one circuit pattern layer is formed. The process of forming the circuit pattern on the upper surface of the insulating layer laminated on the original plate is similar to the process of forming the circuit pattern on the original plate and can be made by a well-known technique, so a detailed description thereof will be omitted.

In order to form a multi-layered circuit pattern, paste bumps are again bonded to predetermined positions of the first circuit pattern layer, the insulating layers are laminated so that the paste bumps penetrate, and the paste bumps are pressed to the level of the insulating layer to form a flat surface. After that, a circuit pattern is formed. This results in repeating the process of forming the first circuit pattern layer again, and thus, in forming the multilayer printed circuit board, the multilayer process circuit board is manufactured by repeating the above-described processes by the number of circuit pattern layers.

When the circuit pattern layer of one layer is formed, the surface is formed of a circuit pattern, and in order to realize electrical conduction between the circuit pattern layers in the process of bonding the paste bumps to the predetermined position, the land portion of the circuit pattern is formed with the paste bumps. It is good practice to determine the bonding position of the paste bumps so that they are connected.

As such, when the land portion of the circuit pattern and the paste bump are continuously connected in the vertical direction, a via hole penetrating the entire printed circuit board, such as a 'stack via', may be realized. When a plurality of circuit pattern layers are stacked by repeating the above-described process, a multilayer printed circuit board is formed by pressing a batch.

The bump forming method of the printed circuit board according to the exemplary embodiment of the present invention can reduce the thickness of each mask by using two masks, thereby improving the omission characteristics of the conductive paste.

Accordingly, in the bump forming method of the printed circuit board according to the embodiment of the present invention, the bumping property of the conductive paste is improved, so that bumps having a desired height can be formed through one printing, thereby reducing the number of printing of the conductive paste. Thus, process time and process cost can be reduced.

As described above, the present invention improves the release characteristics of the conductive paste by reducing the thickness of each mask by using two masks, so that bumps having a desired height can be formed through one printing, thereby reducing the number of printing of the conductive paste. have.

Accordingly, the present invention can reduce the process time and the process cost for forming the bump in the printed circuit board.

Claims (6)

(A) preparing a disc provided with copper foil; (B) positioning a first mask on the disc, the first mask having a hole in a position where a bump of the disc is to be formed; (C) positioning a second mask on the first mask, the second mask having a center on a vertical line passing through the center of the hole of the first mask and having a hole having a diameter larger than that of the hole of the first mask; (D) placing a conductive paste on the second mask; (E) printing the conductive paste with a squeegee to fill the conductive paste in the holes of the first mask and the second mask; (F) separating the second mask; (G) separating the first mask; And (H) drying the conductive paste; Paste bump forming method of a printed circuit board to proceed sequentially. delete The method of claim 1, And the master plate comprises a copper foil having a circuit pattern formed on one surface of an insulating layer. The method of claim 1, And the master plate comprises a copper foil having circuit patterns formed on both surfaces of the insulating layer. The method of claim 1, The original plate is a paste bump forming method of a printed circuit board, characterized in that the copper foil is laminated on one surface of the metal carrier. The method of claim 1, The method of claim 1, wherein the original plate is copper foil.

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