KR100871028B1 - Process for surface treating printed circuit board - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a surface of a printed circuit board, wherein pre-etching is performed before desmearing the surface of the insulating layer of the printed circuit board by etching with permanganic acid etching solution, and after the desmear process, an alkali metal solution It is characterized by surface treatment.

According to the method of the present invention, before and after the desmear process, the pre-etching and alkali metal solution treatment processes are respectively performed to surface-treat the printed circuit board insulating layer, thereby forming the surface roughness suitable for forming the microcircuit under the environmentally friendly conditions. Can be secured.

Printed Circuit Board, Desmear, Etching, Permanganic Acid, Alkali Metals, Surface Treatment

Description

Process for surface treating printed circuit board

1 is a flowchart schematically showing a surface treatment process of a printed circuit board according to an exemplary embodiment of the present invention.

2 is a cross-sectional view schematically showing a change in the surface of the insulating layer treated in each process step in the surface treatment of a printed circuit board according to an embodiment of the present invention.

3 is a SEM photograph showing the surface state of a printed circuit board insulating layer surface-treated according to the first embodiment of the present invention.

Figure 4 is a SEM photograph showing the surface state of the printed circuit board insulating layer surface-treated according to Comparative Example 1 of the present invention.

5 is a flowchart schematically illustrating a general lamination process of a printed circuit board.

6 is a flowchart schematically illustrating a surface treatment process of a printed circuit board according to an exemplary embodiment of the prior art.

7 is a cross-sectional view schematically showing a change in the surface of the insulating layer treated in each process step in the surface treatment of a printed circuit board according to an embodiment of the prior art.

The present invention relates to the surface treatment of an insulating layer for forming a fine circuit of a printed circuit board. More specifically, the present invention relates to a surface treatment method of a printed circuit board capable of improving adhesion of a circuit and forming a fine circuit through surface treatment of an insulating layer.

In recent years, according to the strong demand for high density, high speed, and miniaturization, researches on a new packaging substrate that can cope with system in packaging have been actively conducted. In addition, in order to meet these demands, the implementation of microcircuits has also emerged as a major research subject.

Various methods have been proposed for the implementation of microcircuits, and many studies have been conducted to cope with high-layer and high speed. In particular, since the verification of the reliability has to be reproduced after the formation of the microcircuit, the importance of the product becomes more important because mass production is possible in the final stable state.

The semi-additive method, which has been widely applied to the realization of a microcircuit, realizes a microcircuit by accumulating electrolytic copper as a seed layer by electroless plating. In addition, recently, in preparation for mass production of fine circuits in the future, instead of the electroless plating, which is a conventional seed layer, surface modification by plasma and a method of forming a seed layer on the surface by sputtering them have also been studied.

5 is a flowchart illustrating a general lamination process of a printed circuit board.

Referring to FIG. 5, after the surface of the insulating material to be laminated is formed by pretreatment (for example, CZ treatment) to form roughness (S001), the substrate is laminated using a vacuum laminator under a predetermined pressure and temperature conditions (S002) and is preliminary. After curing (S003), via holes for interlayer connection are processed through a laser drill (S004). Subsequently, after removing the inner wall residues formed during the via hole processing and desmearing to secure adhesion in a later step (S005), electroless copper plating, dry film lamination, exposure / development, electroplating, and the like are performed. A circuit is formed (S006).

In particular, FIG. 6 is a flow chart illustrating a process of surface treating a printed circuit board through a desmear process according to an embodiment of the prior art.

Referring to FIG. 6, first, after swelling smear remaining on a printed circuit board having an insulating layer processed via holes in order to make an optimal state for etching (S011), for example, two-stage hot rinse, rinse, Wash through hot rinse or the like (S012), desmear with permanganic acid etching solution (S013). Subsequently, the insulating layer is washed through, for example, three-stage hot rinsing, two-stage rinsing (S014) and neutralized residual manganic acid in the neutralization stage (S015), and then again, for example, two-stage hot rinsing, Wash through three-step washing, hot rinse, etc. (S016).

The state change of the surface of the insulating layer before (a) and after (b) the desmear using such a permanganate etching liquid is shown in FIG.

The conventional desmear process is suitable for implementing circuits of general conditions, but it is difficult to implement fine circuits. For example, as shown in FIG. 7, in the case of a printed circuit board impregnated with a filler, a part of the filler is present after the desmear process and thus is not suitable for forming a fine circuit. Removing the filler component, in this case, there is a problem that the risk is increased because the F component.

Accordingly, in the present invention, as a result of extensive research in order to solve the above problems, the printed circuit board which can realize eco-friendly microcircuits by adding pre-etching and alkali metal solution treatment processes before and after the conventional desmear process, respectively. The surface treatment method of was found, and the present invention was completed based on this.

Accordingly, an aspect of the present invention is to provide a surface treatment method of a printed circuit board capable of forming a fine circuit under environmentally friendly conditions.

Another aspect of the present invention is to provide a method of treating a surface of a printed circuit board which can secure the formation and adhesion of surface roughness suitable for forming a fine circuit.

Surface treatment method of a printed circuit board according to an embodiment of the present invention is:

(a) providing a printed circuit board having an insulating layer having via holes formed on one or both surfaces thereof;

(b) pre-etching the surface of the insulating layer of the printed circuit board using permanganic acid etching solution;

(c) swelling the smear remaining on the surface of the insulating layer of the pre-etched printed circuit board, and then desmearing using the permanganic acid etching solution; And

(d) treating the surface of the insulating layer of the desmeared printed circuit board with an alkali metal solution of 0.1-5 N;

Characterized in that it comprises a.

Preferably, the pre-etching may be performed for 1 to 10 minutes.

The desmear is also preferably carried out for 5 to 30 minutes.

The alkali metal solution treatment may be preferably performed for 1 to 20 minutes.

The alkali metal solution treatment is also preferably carried out at a temperature of 20 to 80 ℃.

The alkali metal solution is preferably NaOH or KOH aqueous solution, the concentration is preferably 0.1 to 5N.

Meanwhile, after the pre-etching and the desmearing, the neutralization process is preferably performed, respectively. Further, the pre-etching, the desmearing, the neutralizing, the swelling, and the alkali metal solution treatment are performed before, after, or before and after each process. It is preferred that the procedure be carried out.

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

1 shows a schematic surface treatment process of a printed circuit board according to a preferred embodiment of the present invention, and FIG. 2 schematically shows changes in the surface of an insulating layer before and after each process step.

According to the surface treatment method of the present invention, a new application is applied to the removal of the inner wall of the hole in the existing desmear process and the part forming the rough surface. Conventional surface treatment conditions (desmear process) are suitable for implementing circuits of general conditions, but it is difficult to implement fine circuits. Therefore, in the present invention, as shown in FIG. 1, it is possible to create a surface treatment condition capable of realizing a fine circuit through a change of an existing process.

Referring to FIG. 1, first, an insulating layer surface of a printed circuit board having an insulating layer having via holes formed on one or both surfaces thereof is pre-etched using a permanganic acid etching solution (S101).

The type of insulating layer applicable in the present invention can be used without particular limitation, as long as it is commonly used as an insulating material in the art. In addition, the via hole may be processed through laser drilling or mechanical drill processing, but is not particularly limited thereto.

The conditions and process conditions of the permanganic acid in the pre-etching process are not particularly limited and may be used under the same conditions as those in the conventional desmear as known in the art.

For the formation of the microcircuits (5 to 15 mu m), it is necessary to form roughness in the substrate surface and in the hole because the pre-etching concept becomes more important. However, if the etching is excessive from the beginning, the roughness in the hole is intensified, which may cause difficulties in subsequent processes, and pre-etching for a short time may be appropriate since it may affect vias after the laser drill. Therefore, it is preferable to pre-etch for about 1 to 10 minutes, more preferably 1 to 3 minutes in the permanganic acid etching solution to minimize roughness on the surface of the insulating material while minimizing the influence on the vias.

After the pre-etching, the neutralization and washing processes applied in a conventional etching process such as a rinse-neutralization-rinse process may be performed without particular limitation.

Subsequently, as in the conventional desmear process, the smear remaining on the surface of the insulating layer is swollen (S102), and then desmeared using the permanganic acid etching solution (S103).

The smear swelling process serves as a conditioner for optimum etching at a pH of about 10 to 12 to inflate smear remaining on the surface of the insulating layer including the inside of the hole after laser processing for forming the via hole. The swelling process is not particularly limited as long as it is known in the art, all can be applied. Of course, after the swelling process, a washing process such as rinsing that is commonly applied may be further performed.

The conditions and process conditions of the permanganic acid to be applied in the desmear process are not particularly limited, and any ones known in the art may be applicable. Preferably, the desmear process is most preferably performed for 5-30 minutes in terms of economic efficiency and efficiency. In addition, after the desmearing, the neutralization and washing processes applied in a conventional etching process such as a three-stage hot rinse-neutralized two-stage hot rinse process may be further performed without being particularly limited.

Finally, the surface treatment is performed using an alkali metal solution (S104).

As the alkali metal solution, NaOH and KOH aqueous solutions are most preferred in terms of efficiency and economic efficiency. At this time, the concentration of the alkali metal solution is preferably 0.1 to 5N, more preferably 1.0 to 1.5N. If the concentration is less than 0.1N, the surface treatment effect is insignificant. If it exceeds 5N, it is not preferable because the physical properties of the insulating layer is changed and the degree of surface modification is increased so that it is difficult to control the microcircuit.

On the other hand, the filler component and the surrounding polymer component of the insulating material constituting the insulating layer by the alkali metal solution is required to have a desirable time to increase the adhesion by making the surface roughness is easy to form the roughness. The degree of surface modification may vary depending on the type of solution actually used, the concentration of the solution, and the treatment time. However, the increase of the treatment time does not result in continuous surface modification. Preferably, the treatment time is about 1 to 20 minutes. It is suitable. For example, in the case of 0.5-1.5N, a preferable time is about 3 to 8 minutes according to the component of an insulating material.

Optimum temperature conditions are required for the surface treatment of the insulating layer, but the chemical properties of the alkali metal compound may be changed at a temperature exceeding 80 ° C, preferably 20 to 80 ° C, more preferably about 45 to 55 ° C. ℃.

After surface treatment with the alkali metal solution, a washing process such as hot rinsing may be further performed.

As described above, according to the present invention, the surface modification effect as shown in FIG. 2 can be obtained by adding a surface treatment process using pre-etching and alkali metal solution, respectively, before and after the conventional desmear process.

That is, after slightly forming the residue and rough surface of the inner wall of the hole through pre-etching (Fig. 2 (a) and (b)), after performing a conventional desmear process (Fig. 2 (c)), alkali metal solution By completing the surface treatment of the insulating layer using (Fig. 2 (d)), it is possible to obtain the effect that not only the main component of the filler such as SiO ₂ constituting the insulating layer but also the surrounding polymers come off together. In general, in the case of performing the conventional desmear process, due to the presence of a filler component such as SiO ₂ having a large diameter, the filler component is removed through a separate treatment process, such as Arden, because it is not suitable for forming a fine circuit. As described above, there was a high risk of containing the F component. However, in the present invention, surface treatment using an alkali metal solution together with pre-etching can reduce the risk in the process and can form conditions suitable for the implementation of the microcircuit (5 to 15 μm) under environmentally friendly conditions.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

Example 1

Using an epoxy resin impregnated with SiO ₂ as the insulating material of the insulating layer, permanganic acid treatment in pre-etching was performed for about 3 minutes, swelling time was up to 10 minutes, and permanganic acid treatment was performed for about 20 minutes. In addition, after treatment for about 5 minutes at 50 ℃ using 1N KOH aqueous solution, the peel value and the etching amount of the treated insulating layer was measured and the results are shown in Table 1 below. . In addition, the surface roughness photograph of the insulating layer treated as described above is shown in FIG.

Comparative Example 1

Except for omitting the pre-etching and treatment with 1N KOH aqueous solution, the peel value and the etching amount of the insulating layer obtained in the same manner as in Example 1 were measured and the results are shown in Table 1 below. In addition, the surface roughness photograph of the insulating layer treated as described above is shown in FIG.

Example 2

By using (epoxy + phenol) resin impregnated with SiO ₂ as a filler of the insulating layer, permanganic acid treatment in pre-etching is about 3 minutes, swelling time is up to 10 minutes, and permanganic acid treatment is about 20 minutes after swelling. Was performed. In addition, after treatment for about 6 minutes at 55 ℃ using 1N KOH aqueous solution, the peel value and the etching amount of the treated insulating layer was measured and the results are shown in Table 1 below.

Comparative Example 2

Except for omitting the pre-etching and treatment with 1N KOH aqueous solution, the peel value and the etching amount of the insulating layer obtained in the same manner as in Example 2 were measured and the results are shown in Table 1 below.

Peel value (N / m) E.A (㎍ / ㎠) Example 1 492 887 Comparative Example 1 476 807 Example 2 677 383 Comparative Example 2 636 370

As shown in Table 1, Fig. 3 and Fig. 4, in the case of the insulating layer treated according to the general desmear process of the comparative example, although the filler component [SiO ₂ ] remains large, in the case of the insulating layer surface-treated according to the present invention, It can be seen that much of the filler component [SiO ₂ ] disappeared. In addition, in the case of the insulating layer surface-treated according to the present invention, it can be seen that exhibits sufficient fill value and roughness for the formation of the microcircuit.

Although the present invention has been described in detail through specific embodiments, this is for explaining the present invention in detail, and the method for treating the surface of a printed circuit board according to the present invention is not limited thereto, and it is within the technical spirit of the present invention. It is apparent that modifications and improvements are possible by those skilled in the art.

As described above, according to the method of the present invention, before and after the conventional desmear process, the pre-etching and alkali metal solution treatment processes are respectively performed to surface-treat the printed circuit board insulating layer to form microcircuits under environmentally friendly conditions. Formation and adhesion of suitable surface roughness can be ensured.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

Claims (10)

(a) providing a printed circuit board having an insulating layer having via holes formed on one or both surfaces thereof; (b) pre-etching the surface of the insulating layer of the printed circuit board using permanganic acid etching solution; (c) swelling the smear remaining on the surface of the insulating layer of the pre-etched printed circuit board, and then desmearing using the permanganic acid etching solution; And (d) treating the surface of the insulating layer of the desmeared printed circuit board with an alkali metal solution of 0.1-5 N; Surface treatment method of a printed circuit board comprising a. The method of claim 1, wherein the pre-etching is performed for 1 to 10 minutes. The method of claim 1, wherein the desmear is performed for 5 to 30 minutes. The method of claim 1, wherein the alkali metal solution treatment is performed for 1 to 20 minutes. The method of claim 1, wherein the alkali metal solution treatment is performed at a temperature of 20 ° C. to 80 ° C. 6. The method of claim 1, wherein the alkali metal solution is NaOH or KOH aqueous solution. The surface treatment method of a printed circuit board according to claim 1, wherein the concentration of the alkali metal solution is 0.1 to 5N. The method of claim 1, wherein a neutralization process is performed after each of the pre-etching and the desmearing. The method of claim 1, wherein the pre-etching, desmearing, swelling, and alkali metal solution treatment are performed before, after, or before and after each process. The method of claim 8, wherein the cleaning process is performed before, after, or after the neutralization process.

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