KR20130019211A - Surface treatment method of printed circuit board - Google Patents

Abstract

PURPOSE: A surface processing method for a printed circuit board is provided to improve the efficiency of a manufacturing process by reducing facility space through applying series processing which is not a batch type. CONSTITUTION: A printed circuit board comprises an insulating layer. The printed circuit board forms a micro circuit pattern. A junction part of anisotropic conductive film is formed at the insulating layer. The insulating layer performs a desmear process which is using permanganate etchant. The desmear process is implemented in the temperature of 60 to 95 °C for less than seven minutes.

Description

Surface treatment method of printed circuit board {SURFACE TREATMENT METHOD OF PRINTED CIRCUIT BOARD}

The present invention relates to a method for treating a surface of a printed circuit board which improves adhesion to the anisotropic conductive film.

In recent years, the application of an anisotropic conductive film (ACF) is increasing in accordance with the trend of miniaturization of electronic devices, reduction of manufacturing cost, and simplicity of manufacturing process. The application of ACF is expected to be wider in the future in that the application is relatively simple and enables the connection of fine patterns.

However, one of the problems of ACF is that the issue of adhesion is constantly being raised, which is typically applied to FOG (FPCB on Glass) part. FOG refers to bonding a flexible printed circuit board (FPCB) to an LCD module using an ACF. The adhesion between the polyimide and the ACF, which is mainly used as an insulator of the flexible printed circuit board (FPCB), is generally There is a problem of low. If the adhesive force is low, the connection by the ACF is poor, resulting in a failure of the electronic device, which includes a problem that may lead to a general quality defect.

In order to solve this problem, the FPCB manufacturing company is stably securing the adhesive strength to the ACF by treating the surface of the final product plasma. However, this plasma processing method has a disadvantage in that it takes not only a high process cost but also a long time since it is a batch type.

Therefore, the process can be applied to a continuous process rather than a batch type, thereby reducing equipment space and process cost, improving process efficiency, and manufacturing a printed circuit board with improved adhesion to anisotropic conductive films. Research on development is needed.

The present invention is to provide a method for treating the surface of a printed circuit board that can improve the adhesion with the anisotropic conductive film.

The present invention also provides a printed circuit board manufactured by surface treatment by the above method.

The present invention comprises the steps of manufacturing a printed circuit board including an insulating layer and a fine circuit pattern is formed; Desmearing the insulating layer to be an anisotropic conductive film (ACF) junction in the printed circuit board at a temperature of 60 to 95 ℃ less than 7 minutes using a permanganic acid etching solution; Surface treatment method of a printed circuit board comprising a To provide.

The present invention also provides a printed circuit board manufactured by surface treatment by the above method.

Hereinafter, a method for treating a surface of a printed circuit board and a printed circuit board manufactured therefrom according to a specific embodiment of the present invention will be described in detail. It will be apparent to those skilled in the art, however, that this is not intended to limit the scope of the invention, which is set forth as an example of the invention, and that various modifications may be made to the embodiments within the scope of the invention.

&Quot; Including "or" containing ", unless the context clearly dictates otherwise throughout the specification, refers to any element (or component) including without limitation, excluding the addition of another component .

The present inventors have investigated the method that can be applied during the FPCB manufacturing process to improve the adhesive strength, together with the cause of the decrease in the adhesive strength of the ACF and FPCB, by adding a step of removing the surface irregularities of the polyimide during the FPCB process The present invention has been completed to discover that the adhesion between ACF and FPCB can be significantly improved.

In particular, as shown in FIG. 1, air bubbles are generated inside the ACF when the FPCB is adhered to the ACF by the uneven surface of the polyimide, and thus the adhesion between the ACF and the FPCB may be reduced. . At this time, the cause of air bubbles in the ACF is caused by air or gold plating impurities remaining in the uneven portion of the polyimide, which is an insulator, at the interface with the ACF while expanding at a high temperature of 190 ° C. or higher during the ACF process. This is because air bubbles are formed. The photo showing the phenomenon of the internal air bubble (air bubble) when the ACF adhesion is shown in FIG. Therefore, if the process of removing the surface irregularities of the polyimide, which causes the air bubble, is inserted in the FPCB process, the adhesion between the ACF and the FPCB can be significantly improved. The printed circuit board manufactured in this manner can be effectively applied to an LCD module, a flying tail, and the like.

Accordingly, according to one embodiment of the invention, there is provided a surface treatment method of a printed circuit board that can improve the adhesion with the ACF. The surface treatment method of the printed circuit board of the present invention comprises the steps of manufacturing a printed circuit board including an insulating layer and a fine circuit pattern is formed; The insulating layer, which is a junction portion of the anisotropic conductive film (ACF) in the printed circuit board, may be desmeared at a residence time of 7 minutes or less at a temperature of 60 to 95 ° C. using an permanganic acid etching solution.

The present invention includes a step of manufacturing a printed circuit board including an insulating layer and a fine circuit pattern is formed, more specifically, desmear, PTH plating, patterning, and adhesion to ACF to improve drilling and adhesion to the conductor layer. Through the desmear, gold plating, etc., a printed circuit board having a fine circuit pattern may be manufactured.

In this case, the insulating layer may include one or more components, such as polyimide, LCP, Teflon, epoxy resin.

In addition, the printed circuit board on which the fine circuit pattern is formed may include at least one selected from the group consisting of copper, iron, and aluminum as a conductor.

The printed circuit board manufactured as described above is characterized by desmearing the insulating layer, which is a junction portion of the anisotropic conductive film (ACF), with a permanganic acid etching solution instead of the conventional plasma process, so as to improve adhesion to the anisotropic conductive film (ACF). do. In particular, the conventional desmear process is limited to the application after the drilling is performed in the pre-fine circuit formation step in order to improve the contact force between the copper and the insulating layer for the plating of conductors such as copper, but in the present invention The process is performed after the microcircuits are formed on the printed circuit board and before the ACF is attached, on the insulating layer which becomes the junction of the ACF on the printed circuit board.

At this time, the desmear step for the insulating layer which is the junction of the anisotropic conductive film (ACF) may be carried out at 60 to 95 ℃, preferably 65 to 90 ℃, more preferably 70 to 90 ℃. In addition, the desmearing step may be performed in the etching solution with a residence time of 7 minutes or less or 0.5 to 7 minutes, preferably 6 minutes or less, or 1 to 6 minutes, more preferably 5 minutes or less, or 1.5 to 5 minutes. have. In the desmear step, the residence time in the etchant can be adjusted to the extent that sufficient surface treatment is performed so that excellent adhesion to ACF can be exhibited, but less than 7 minutes in terms of preventing under cut. Can be done.

Through this desmearing process, the surface irregularities of the insulating layer such as polyimide can be effectively removed, thereby essentially blocking the generation of air bubbles in the ACF during adhesion with the ACF. The desmeared insulating layer has a surface roughness (Rz) of 2.0 μm or less, or 0.1 to 2.0 μm, preferably 1.8 μm or less, more preferably 1.5 μm or less, measured by atomic force microscope (AFM). Can be. The surface roughness of the insulating layer may be 2.0 μm or less in terms of showing good adhesion with ACF.

In addition, in the present invention, the desmear step for the insulating layer to which the anisotropic conductive film (ACF) is bonded may include at least one permanganate salt such as potassium permanganate (KMnO ₄ ), sodium permanganate (NaMnO ₄ ), sodium hydroxide (NaOH), and hydroxide. It can be performed using an etchant containing at least one alkali metal such as potassium (KOH). In particular, a mixed solution of sodium permanganate (NaMnO ₄ ) and sodium hydroxide (NaOH) or potassium hydroxide (KOH) can be used. In this case, the mixing ratio of the permanganate salt and the alkali metal may be 0.5: 1.0 to 3.0: 1.0, preferably 1.0: 1.0 to 2.0: 1.0, more preferably 1.1: 1.0 to 1.5: 1.0. In this case, the pH of the permanganic acid etching solution may be 12 or more.

Meanwhile, the insulating layer of the desmeared printed circuit board may further include a step of treating with an acid solution, wherein the acid solution includes one or more selected from the group consisting of sulfuric acid, hydrochloric acid, acetic acid, and the like. can do. However, it is preferable to use sulfuric acid, hydrochloric acid, or the like from the viewpoint of cleaning ability to water, the effect of acid treatment, and economical aspects.

The concentration of the acid solution may be 0.5 to 10 wt%, preferably 1.0 to 6.0 wt%, more preferably 1.3 to 5.0 wt%. In addition, the pH of the acid solution may be 1.0 to 7.0, preferably 2.0 to 6.0, more preferably 3.0 to 5.0.

The acid solution treatment may be carried out for 1 to 10 minutes, preferably 3 to 7 minutes, more preferably 4 to 6 minutes. In addition, the acid solution treatment may be carried out at 20 to 80 ℃, preferably 30 to 70 ℃, more preferably 40 to 60 ℃.

In particular, the conventional method of treating the plasma applied to remove the polyimide surface irregularities of the FPCB is not only high in manufacturing cost but also takes a long time in the process. On the other hand, the process of treating the desmear according to the present invention is not only a short process time, but also an effective method having a low process cost. Therefore, the present inventors have developed a method to significantly improve the adhesion with the ACF by adding a desmear process to the existing FPCB manufacturing process to improve the ACF tensile force.

On the other hand, according to another embodiment of the invention, there is provided a printed circuit board manufactured by surface treatment in the same manner as described above. The printed circuit board manufactured by surface treatment in this manner has a feature of reducing manufacturing cost and excellent adhesive strength with an anisotropic conductive film (ACF).

In particular, in the printed circuit board of the present invention, the anisotropic conductive film (ACF) is bonded to the surface-treated insulating layer by desmearing at a residence time of 7 minutes or less using a permanganic acid etching solution as described above. Can be.

For a printed circuit board manufactured through such a surface treatment process, the slide glass after releasing the FPCB, according to the microscopic observation, shows that the air bubble area is 30% or less, preferably 20% or less, of the total substrate area. More preferably, it may be 10% or less.

In addition, the printed circuit board of the present invention has an adhesive strength strength of 650 gf / cm or more or 650 to 1,500 gf / cm, preferably under test conditions for measuring peel strength, which is tested with a width of 1 cm. May be 800 gf / cm or more, more preferably 900 gf / cm or more.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

The present invention further provides an anisotropic conductive film by applying a step of desmearing an insulating layer, which becomes an anisotropic conductive film (ACF) junction, using a permanganic acid etching solution under a specific process condition after forming a fine circuit pattern on a printed circuit board. A printed circuit board having improved adhesion to ACF) can be effectively manufactured.

In particular, according to the present invention, the surface treatment process of the printed circuit board can be applied as a continuous process rather than a batch type, thereby reducing equipment space and process cost, and significantly improving the efficiency of the entire printed circuit board manufacturing process. have.

1 is a photograph showing an air bubble generation phenomenon during the ACF bonding process.
2 is a photograph showing a circuit portion and an insulator (polyimide) portion of an FPCB for ACF bonding.
3 is a photograph showing the surface of the insulator (polyimide) after desmearing the FPCB prepared according to Example 1 of the present invention.
Figure 4 is a photograph showing the insulator (polyimide) surface irregularities of the FPCB prepared according to Comparative Example 1 of the present invention.
Figure 5 is a photograph showing the phenomenon of internal air bubble (air bubble) generation when ACF adhesion.
FIG. 6 is a photograph showing a micrograph of a slide glass according to Example 1 of the present invention. FIG.
7 is a photograph showing a micrograph of a slide glass according to Comparative Example 1 of the present invention.

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

Example  One

One side of a flexible copper clad laminate (FCCL) consisting of 12 μm thick copper foil and 20 μm thick polyimide was completely etched and 100/100 circuits were formed on the opposite side. At this time, more specifically, a fine pattern was formed on the substrate through a desmearing, PTH plating, and patterning process for enhancing adhesion to copper foil.

Then, this fine circuit insulating layer is an anisotropic conductive film (ACF) joints in printed circuit board pattern is formed, that is, relative to the polyimide, NaMnO ₄ and NaOH mixture (NaMnO ₄ with NaOH weight ratio = 6: 4 ), The desmear process was carried out at 80 ° C. for 3 minutes. After the desmear process, a coverlay (HGCK-A305L) was attached to the opposite surface on which the circuit was formed. The product was attached to an ACF film on slide glass using an ACF bonding facility, and a final printed circuit board was prepared.

Example  2

As shown in Table 1, except that a double-sided flexible circuit board (FCCL, flexible copper clad laminate) made of a 12 μm thick copper foil and a 25 μm thick liquid crystal polymer (LCP, manufactured by Vurastar, Kuraray) was used. A printed circuit board was manufactured in the same manner as in Example 1.

Example  3 to 5

As shown in Table 1, except that the thickness of the insulating layer and the desmearing process conditions for the insulating layer were different, the printed circuit board was manufactured in the same manner as in Example 1.

Comparative example  1-2

As shown in Table 1 below, the desmearing process is not performed on the insulating layer serving as the anisotropic conductive film (ACF) junction in the printed circuit board on which the fine circuit pattern is formed (Comparative Example 1), or the desmearing process time. Except for the difference (Comparative Example 2), a printed circuit board was manufactured in the same manner as in Example 1.

Reference Example  One

Except for applying the plasma surface treatment process using a plasma apparatus under vacuum conditions, instead of the desmearing process, to the insulating layer serving as an anisotropic conductive film (ACF) junction in a printed circuit board having a fine circuit pattern, A printed circuit board was manufactured in the same manner as in Example 1.

In the manufacturing process of the printed circuit board according to Examples 1 to 5, Comparative Examples 1 to 2, and Reference Example 1, the insulating layer composition, the surface treatment process conditions, and the like are shown in Table 1 below.

division FCCL Insulation Desmearing for ACF Bonding Copper foil
thickness
(Μm) Insulating layer
ingredient Insulating layer
thickness
(Μm) drugs
Furtherance fair
Temperature
(℃) fair
time
(min) fair
shape Example 1 12 Polyimide 20 KMnO ₄ /
NaOH 80 3 continuity
fair Example 2 12 LCP 25 KMnO ₄ /
NaOH 80 3 continuity
fair Example 3 12 Polyimide 12 KMnO ₄ /
NaOH 80 3 continuity
fair Example 4 12 Polyimide 25 KMnO ₄ /
NaOH 80 3 continuity
fair Example 5 12 Polyimide 20 KMnO ₄ /
NaOH 80 3 continuity
fair Comparative Example 1 12 Polyimide 20 - - - - Comparative Example 2 12 Polyimide 20 KMnO ₄ /
NaOH 80 8 continuity
fair Reference Example 1 12 Polyimide 20 Pla
Zuma -
(vacuum) 20 arrangement
type

As shown in Table 1, as in Examples 1 to 5 according to the present invention, the desmearing process for the insulating layer serving as the anisotropic conductive film (ACF) junction in the printed circuit board having the fine circuit pattern is about 3 minutes. It can be carried out in a continuous process quickly in a short time. On the other hand, it can be seen that the plasma process of Reference Example 1 should be carried out by staying at a certain time for about 20 minutes under vacuum conditions. In addition, the plasma process of Reference Example 1 can not only be performed under vacuum conditions, but can be performed by limiting the reaction space to a separate batch type, which is difficult to apply to mass production.

On the other hand, for the printed circuit board manufactured according to Examples 1 to 5, Comparative Examples 1 and 2, and Reference Example 1, the physical properties were evaluated by the following method.

a) ACF Adhesive Insulation layer  Illuminance

For an insulating layer that becomes an anisotropic conductive film (ACF) junction in a printed circuit board on which a fine circuit pattern is formed, the surface roughness (AFM, Atomic Force MicroScope) device is used using the insulating layer sample before attaching the ACF film. Rz, μm) was measured.

b) ACF  Adhesion

In the printed circuit board on which the fine circuit pattern was formed, the ACF film was attached to the slide glass as a specimen, and the adhesive force of the anisotropic conductive film (ACF) was measured in the following manner.

First, the FPCB was attached to the slide glass by an ACF bonding machine, and then the FPCB was cut to have a width of 1 cm, and a tensile force of 1 cm was measured. At this time, the adhesive force was measured using a device called UTM (Zwick). At this time, the adhesive force between the FPCB (printed circuit board) and the slide glass (slide glass) was measured at an angle of 90 degrees. In measuring the tensile force, the ACF adhesive force was recorded as the highest value of the measured adhesive forces.

c) air bubble ( air bubble )

The presence of air bubbles was observed by observing slide glass after removing the FPCB using a microscope (OLYMPUS BX60).

At this time, when the total area occupied by the air bubble in the slide glass area exceeds 10% of the total slide glass area, it is evaluated that the air bubble exists (“is present”), and this air When the area of the bubble (air bubble) is 10% or less of the total slide glass area, it was evaluated that no air bubble ("none") was generated.

d) undercut ( under cut )

The under cut was measured by making a mold using an epoxy resin and polishing the cross section to observe the cross section of the circuit. Undercut is evaluated when the insulation layer and the copper foil are 3 micrometers or more ("is present"), and an under cut when the insulation layer and the copper foil is less than 3 micrometers. ) Was assessed as not occurring (“none”).

Measurement results of the physical properties of the printed circuit boards manufactured according to Examples 1 to 5, Comparative Examples 1 to 2, and Reference Example 1 are as shown in Table 2 below.

division Insulation layer surface roughness (Rz) for ACF bonding ACF Adhesion
(gf / cm) Air bubble Undercut Example 1 1.2 1,100 none none Example 2 1.1 1,000 none none Example 3 1.2 1,000 none none Example 4 1.2 1,300 none none Example 5 1.3 1,350 none none Comparative Example 1 2.5   600 has exist none Comparative Example 2 1.0 1,200 none has exist Reference Example 1 1.2 1,000 none none

On the other hand, as shown in Figure 3, after the desmear treatment of the FPCB prepared according to Example 1 of the present invention, the surface of the insulator (polyimide) can be seen that the roughness is cut off and the roughness is lowered. However, as shown in FIG. 4, it can be seen that the surface of the insulator (polyimide) of the FPCB manufactured according to Comparative Example 1 of the present invention remains unevenly severe and has high roughness.

In addition, as shown in Figure 6, through the micrograph of the slide glass (slide glass) according to the first embodiment of the present invention it can be seen that the air bubbles do not occur at all, ACF adhesion is high. However, as shown in FIG. 7, it can be seen that a large number of air bubbles are generated through the micrograph of the slide glass according to Comparative Example 1 of the present invention, which significantly reduces the ACF adhesion.

In addition, as shown in Table 2, the printed circuit boards of Examples 1 to 5 according to the present invention do not generate air bubbles and undercuts at the same time, and have excellent ACF adhesion strength of 1,100 to 1,350 gf / cm. It can be seen that.

On the other hand, in the printed circuit board of Comparative Example 1, the undercut did not occur, but air bubbles were generated, and the ACF adhesive force was also noticeably dropped to 600 gf / cm. In this case, if the ACF adhesive strength is less than 650 gf / cm, after the product is sold as a final product, if the user drops the electronic device in the process of using the electronic device or if the electronic device is bent, the ACF connection part may fall off, resulting in poor connection. This is not good because it can cause problems.

On the other hand, the printed circuit board of Comparative Example 2 does not generate air bubbles and the ACF adhesive strength is similar to those of Examples 1 to 5, but when the undercut occurs and the circuit is patterned into a fine circuit, the circuit copper foil and the insulator It turns out that there exists a problem that adhesive force with (polyimide) becomes weak and a circuit copper foil isolate | separates.

Claims (9)

Manufacturing a printed circuit board including an insulating layer and a fine circuit pattern formed thereon;
Desmearing the insulating layer to be a junction portion of the anisotropic conductive film (ACF) in the printed circuit board at a residence time of 7 minutes or less at a temperature of 60 to 95 ℃ using a permanganic acid etching solution;
Surface treatment method of a printed circuit board comprising a. The method of claim 1,
The surface roughness (Rz) of the insulating layer to be the junction of the anisotropic conductive film (ACF) after the desmear step is 2 ㎛ or less surface treatment method. The method of claim 1,
The desmear step is a surface treatment method of a printed circuit board is performed using an etching solution containing permanganate and alkali metal. The method of claim 1,
The insulating layer is a surface treatment method of a printed circuit board comprising one or more selected from the group consisting of polyimide, LCP, Teflon, and epoxy resin. The method of claim 1,
The printed circuit board on which the fine circuit pattern is formed includes at least one selected from the group consisting of copper, iron, and aluminum as conductors. A printed circuit board manufactured by surface treatment by the method according to any one of claims 1 to 5. The method according to claim 6,
A printed circuit board in which an anisotropic conductive film (ACF) is bonded to a surface-treated insulating layer by desmearing at a temperature of 60 to 95 ° C. using a permanganic acid etching solution for 7 minutes or less. The method according to claim 6,
A printed circuit board having an air bubble area of 30% or less of the total substrate area. The method according to claim 6,
Printed circuit board with 650 gf / cm adhesion to ACF film.

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