JP2006351646A - Circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which has a smoother surface for a liquid crystal polymer film than ever before, and has a strong adhesion between the film and a plating layer, and also to provide its manufacturing method. <P>SOLUTION: This circuit board includes an electroless plating layer and an electrolytic plating layer which are stacked in this order on at least one face of the liquid crystal polymer film. The surface of the liquid crystal polymer film has an arithmetic mean roughness Ra of 30 nm or less, and the plating layer has a 180° peel strength of 6 N/cm or above. The manufacturing method of the circuit board includes a first process wherein at least one face of the liquid crystal polymer film is so surface-reformed as to have a smaller contact angle with a liquid; a second process wherein the surface-reformed face of the liquid crystal polymer film is brought into contact with an alkali solution to apply alkali treatment to the face within such a range that the surface of the film is not roughed; a third process wherein the electroless plating layer is formed on the alkali-treated surface of the liquid crystal polymer film; and a fourth process wherein the electrolytic plating layer is formed on the surface of the electroless plating layer. Between the third and the fourth process and/or after the fourth process, a heat treatment is conducted for 5 min to 24 hours at a temperature not higher than the melting point of the liquid crystal polymer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board and a manufacturing method thereof, and more particularly to a circuit board using a liquid crystal polymer film as a substrate material and a manufacturing method thereof.

  Conventionally, many circuit boards are used in electronic devices. As this type of circuit board, for example, a flexible printed circuit board in which a circuit is formed on an insulating substrate made of polyimide film or the like, on which a copper foil or the like is bonded, or on which a copper layer or the like is formed by plating Is widely known.

  In recent years, along with miniaturization and high functionality of electronic devices, miniaturization and high density of circuits have progressed, and signals transmitted to circuits have also been increased in frequency.

  When a circuit is miniaturized and densified, a slight dimensional change due to moisture absorption of the film becomes a problem in circuit design. Further, since the transmission loss of the high-frequency signal involves not only the conductor loss but also the dielectric loss, it is advantageous to use a film having a dielectric loss as low as possible.

  Therefore, recently, as a substrate material, a liquid crystal polymer film having features such as (1) low water absorption and dielectric loss, and (2) small dimensional change and characteristic change due to moisture absorption, compared to conventional polyimide films. It is getting attention.

  For example, in Patent Document 1, the surface of the liquid crystal polyester film is sufficiently roughened using a specific etching solution having a very high etching rate, and then an electroless plating layer is formed. A technique is disclosed in which the anchoring effect is further enhanced by bonding the plating layer to the plating layer and further performing a heat treatment within a range of the liquid crystal transition temperature from 100 ° C. to ensure the adhesive strength between the two. .

  Patent Document 2 discloses that the surface of the liquid crystal polymer film is sufficiently roughened by immersing it in an alkaline etching solution having a concentration of 10 M or higher and a liquid temperature of 70 ° C. or higher for 60 minutes to 180 minutes. A technique for improving the adhesive strength between the two by forming is disclosed.

  Patent Document 3 discloses a technique for improving the adhesive strength between the two by sufficiently roughening the surface of the liquid crystal polymer film, forming an electroless plating layer, and then performing heat treatment at a temperature equal to or higher than the glass transition point. It is disclosed.

  Patent Document 4 discloses that the surface of the liquid crystal polymer film is irradiated with ultraviolet rays in an atmosphere containing a treatment agent such as an aqueous ammonia solution, and an electroless plating layer is formed on the surface, thereby improving the adhesive strength between the two. Technology is disclosed.

JP 2004-307980 A Japanese Patent Application Laid-Open No. 2004-143587 JP 2004-247425 A JP 2003-221456 A

  However, the conventional circuit board and its manufacturing method have the following problems.

  That is, the method for manufacturing a circuit board described in Patent Documents 1 to 3 is such that the film surface has an uneven shape enough to obtain an anchor effect in order to improve the adhesive strength between the liquid crystal polymer film and the electroless plating layer. It is roughened.

  For this reason, the surface roughness of the film surface is increased, and it is difficult to form a fine circuit.

  In addition, when an electroless plating layer is formed on the roughened film surface, the surface roughness of the film side interface in the electroless plating layer increases. Further, when the frequency of the signal is increased, a so-called skin effect is increased, in which current flows only on the conductor surface. For this reason, circuit conductor loss (= loss due to conductor roughness + loss due to skin effect) increases due to conductor roughness and skin effect, and the advantages of liquid crystal polymers such as low dielectric constant and dielectric loss are utilized. There were problems such as being lost.

  On the other hand, the circuit board manufacturing method described in Patent Document 4 uses a method of irradiating ultraviolet rays after diffusing a treatment agent such as an aqueous ammonia solution on the liquid crystal polymer film surface. The process is completely different from the manufacturing method.

  Furthermore, since the circuit board obtained by this manufacturing method does not mention anything about the surface roughness of the film surface, it is completely unclear whether or not the fine circuit formability is excellent.

  Accordingly, the problem to be solved by the present invention is to provide a circuit board having a smoother liquid crystal polymer film surface than the prior art and having excellent adhesion strength between the film and the plating layer, and a method for producing the circuit board.

To solve the above problems, a circuit board according to the present invention, an electroless plating layer on at least one surface of the liquid crystal polymer film, the electroless plating layer are laminated in this order, the arithmetic mean roughness R _a of the liquid crystal polymer film surface The gist is that it is 30 nm or less, and the 180 ° peel strength of the plating layer is 6 N / cm or more.

  On the other hand, in the method for producing a circuit board according to the present invention, the first step of modifying the surface of at least one surface of the liquid crystal polymer film so that the contact angle with the liquid is lowered, and the liquid crystal polymer film having the surface modified A second step of bringing the surface into contact with an alkali solution and subjecting it to an alkali treatment within a range in which the film surface is not roughened; a third step of forming an electroless plating layer on the surface of the alkali-treated liquid crystal polymer film; A fourth step of forming an electrolytic plating layer on the surface of the plating layer, and between the third step and the fourth step and / or after the fourth step, the melting point of the liquid crystal polymer or less The gist is to perform a heat treatment at a temperature for 5 minutes to 24 hours.

In this case, the arithmetic mean roughness R _a of the liquid crystal polymer film surface of the alkali treatment after the second step is preferably 30nm or less.

  In the circuit board manufacturing method according to the present invention, in the first step, the surface of the liquid crystal polymer film is surface-modified so that the contact angle with the liquid is lowered. Therefore, the film surface is easily wetted with the alkaline solution used in the next second step.

  Next, in the second step, the film surface with improved wettability is contacted with an alkali solution and subjected to an alkali treatment, so that the reaction by the alkali treatment is performed more uniformly, and hydrophilicity such as hydroxyl groups and carboxyl groups is formed on the film surface. A functional group exhibiting sex is generated. Further, since the alkali treatment is performed within a range in which the film surface is not roughened, a concavo-convex shape enough to obtain an anchor effect is not formed on the film surface as in the prior art.

In this case, the arithmetic mean roughness R _a of the film surface after the alkali treatment, when adjusted to 30nm or less, formation of fine circuit, a very good circuit board such as the transmission characteristic of the circuit is obtained .

  Next, in the third step, an electroless plating layer is formed on the surface of the alkali-treated film, and in the fourth step, an electrolytic plating layer is formed on the surface of the electroless plating layer, whereby a circuit board is obtained.

  Here, in the method for manufacturing a circuit board according to the present invention, between the third step and the fourth step and / or after the fourth step, at a temperature not higher than the melting point of the liquid crystal polymer for 5 minutes to Heat treatment is performed for 24 hours. Therefore, this heat treatment forms a strong chemical bond at the interface between the alkali-treated film surface and the electroless plating layer surface.

  Therefore, according to the method for manufacturing a circuit board according to the present invention, it is possible to manufacture a circuit board having a smoother liquid crystal polymer film surface and superior adhesive strength between the film and the plating layer.

  On the other hand, the circuit board according to the present invention can be obtained, for example, by suitably using the method for manufacturing a circuit board according to the present invention.

According to the circuit board according to the present invention, an electroless plating layer on at least one surface of the liquid crystal polymer film, the electroless plating layer are laminated in this order, the arithmetic mean roughness R _a of the liquid crystal polymer film surface be 30nm or less Since the 180 ° peel strength of the plating layer is 6 N / cm or more, the surface of the liquid crystal polymer film is smoother than before, and the adhesive strength between the film and the plating layer is excellent.

  Therefore, according to the circuit board according to the present invention, the surface of the liquid crystal polymer film is smoother than in the prior art, and therefore, the fine circuit formability is excellent. Therefore, it is easy to cope with miniaturization and high density of the circuit.

  Moreover, since it is excellent in the adhesive strength of a liquid crystal polymer film and a plating layer, it has high adhesive reliability. In particular, due to the gas impermeability of the liquid crystal polymer, it is difficult to form a fragile layer mainly composed of oxides of plated metal elements at the bonding interface, so not only the initial bonding strength but also the bonding strength after heat aging is excellent. High adhesion reliability can be exhibited over a long period of time.

  In addition, since the characteristics of the liquid crystal polymer can be utilized, it is easy to cope with high frequency transmission signals.

  A circuit board and a method for manufacturing the circuit board according to the present embodiment will be described in detail. Hereinafter, the circuit board according to the present embodiment may be referred to as “the present circuit board”, and the circuit board manufacturing method according to the present embodiment may be referred to as “the present manufacturing method”.

1. This circuit board This circuit board is formed by laminating an electroless plating layer and an electrolytic plating layer (hereinafter, collectively referred to as “plating layer”) in this order on at least one surface of a liquid crystal polymer film. The surface roughness of the film and the adhesive strength of the plating layer are within specific ranges.

  In addition, the circuit board said to this application includes both the thing in which the circuit is not yet formed in the plating layer, and the thing in which the circuit was formed in the plating layer.

1.1 Liquid Crystal Polymer Film In the present circuit board, specific examples of the liquid crystal polymer constituting the liquid crystal polymer film include, for example, a hot-melt type aromatic polyester.

  The thickness of the liquid crystal polymer film is not particularly limited, and may be appropriately selected in consideration of the space in the electronic device in which the circuit board is incorporated, the flexibility required for the circuit board, and the like. .

1.2 Plating layer In this circuit board, the plating layer may be formed on one side of the liquid crystal polymer film, or may be formed on both sides of the liquid crystal polymer film. Moreover, the electroplating layer may consist of a single layer, and may consist of multiple layers. When the electroplating layer is composed of a plurality of layers, each layer may be made of two or more different metals or alloys, or the same kind of metal or alloy, but the film quality such as composition is different. May be. Alternatively, a combination thereof may be used. Further, the plating layer may be formed at a time, or may be formed by being divided. Alternatively, a combination thereof may be used.

  Specific examples of the metal constituting the electroless plating layer include, for example, metals such as Ni, Cu, and Co or alloys containing these metals. On the other hand, as a metal which comprises an electroplating layer, specifically, metals, such as Cu and Ni, or an alloy containing these can be illustrated, for example.

  In addition, the thickness of the plating layer may be the same or different, and is not particularly limited. What is necessary is just to determine suitably considering a circuit shape, the etching property at the time of circuit formation, the total thickness of a board | substrate, etc.

1.3 Film surface roughness In conventional circuit boards, the surface of the liquid crystal polymer film is usually roughened to the extent that it physically meshes with the surface of the electroless plating layer, that is, the anchor effect is obtained. Met.

  On the other hand, this circuit board is characterized in that the surface of the liquid crystal polymer film is hardly roughened as compared to the conventional case, and the surface roughness of the film is in a specific range.

Here, the surface roughness of the film in the circuit board was determined from unevenness of the measured film surface using an atomic force microscope (AFM), it refers to the arithmetic mean roughness R _a in conformity to JIS B0601.

Preferred upper limit of the arithmetic mean roughness _{R a} of the film surface, can be exemplified 30 nm, 25 nm, 20 nm, and the like.

When the upper limit of the arithmetic mean roughness R _a of the film surface is more than 30 nm, the fragile layer is formed by alkali treatment, or the adhesive strength is lowered, the tendency of such transmission loss at the circuit formation increases seen.

On the other hand, the lower limit of the arithmetic mean roughness R _a of the film surface is not particularly limited. This is because it is advantageous to make the film surface as smooth as possible from the viewpoint of improving the formability of the fine circuit and reducing transmission loss.

If you dare illustrate preferred upper limit can be combined with the preferred lower limit of the arithmetic mean roughness R _a of the film surface, it can be exemplified 2 nm, 5 nm, 10 nm, and the like.

1.4 180 ° Peel Strength In this circuit board, the 180 ° peel strength of the plating layer is at least 6 N / cm or more. Preferably it is 6.5 N / cm or more, more preferably 7.0 N / cm or more.

  Here, the 180 ° C. peel strength in this circuit board refers to a tensile tester (tensile according to JIS C5016 using a 1 cm wide sample in which a liquid crystal polymer film, an electroless plating layer, and an electrolytic plating layer are joined. It means the initial peel strength (before heat aging) measured by peeling the plating layer at 180 ° C. at a speed of 50 mm / min.

  In this circuit board, if the 180 ° peel strength of the plating layer is less than 6 N / cm, it is not preferable because the adhesion reliability of the circuit is lowered.

  On the other hand, the upper limit value of the 180 ° peel strength of the plating layer is not particularly limited. This is because the higher the adhesive strength between the film and the plating layer, the better, and there is no problem.

2. This manufacturing method This manufacturing method has the 1st-4th process, Between the 3rd process and the 4th process, and / or after the 4th process, it is heat-processed for specific time at specific temperature. I do. Hereinafter, each process and heat treatment will be described in detail.

2.1 First Step In this production method, the first step is a step of modifying the surface of at least one surface of the liquid crystal polymer film so that the contact angle with the liquid is reduced.

  Since the kind of liquid crystal polymer film is the same as that described above, detailed description thereof is omitted. The film surface to be surface modified may be one side of the film or both sides of the film. What is necessary is just to select suitably in consideration of the form of the circuit board to manufacture.

  The surface modification of the film surface in the first step is mainly performed for the purpose of improving the wettability with the alkaline solution used in the next step. Therefore, the contact angle between the film surface after the surface modification and the liquid contained in the alkaline solution is at least lowered as compared with the contact angle between the film surface before the surface modification and the liquid. If so, you can reach that goal.

  Specific examples of such a surface modification method include ultraviolet treatment, plasma treatment, corona treatment, and the like. Of these methods, ultraviolet treatment is preferably used. This is because the ultraviolet treatment has advantages such as a high processing speed and uniformity compared with other processing methods, and therefore excellent in continuous productivity, etc., and inexpensive equipment.

  When the ultraviolet treatment is used, the wavelength of the ultraviolet ray is not particularly limited. However, since the energy is relatively high and the surface modification property of the film surface is excellent, it is preferable to mainly include a wavelength of 254 nm or less. . Such short wavelength ultraviolet rays can be generated using a low-pressure mercury lamp, an excimer lamp, or the like.

2.2 Second Step In the present production method, the second step is a step in which the surface of the liquid crystal polymer film whose surface has been modified in the first step is brought into contact with an alkali solution and the film surface is not roughened. This is a step of alkali treatment.

  This second step is not intended to roughen the film surface to the extent that an anchor effect is obtained as in the prior art, but mainly to generate functional groups on the liquid crystal polymer film surface. Therefore, it is sufficient to perform alkali treatment to such an extent that this purpose can be achieved.

  Specific examples of the alkaline solution include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide, and basic substances such as ammonia and ethylamine. One or two or more of these can be exemplified by a solution in which a suitable solvent such as water or alcohol is dissolved.

  Here, as a factor which the roughening of the film surface advances, generally the kind of alkaline solution, the density | concentration of the said solution, the temperature of the said solution, processing time, etc. can be illustrated. Therefore, it should be noted that the alkali treatment is performed by appropriately setting these factors so that more functional groups can be generated while maintaining the smoothness of the film surface as much as possible.

  If the alkali treatment is excessively performed, the surface roughness of the liquid crystal polymer film increases and a brittle layer is formed due to excessive treatment, and the adhesive strength between the liquid crystal polymer film and the electroless plating layer tends to decrease. In addition, when the alkali treatment is excessively reduced, there is a tendency that functional groups are not easily generated on the surface of the liquid crystal polymer film.

Estimated the alkali treatment, an arithmetic mean roughness R _a of the liquid crystal polymer film surface after providing alkali treatment, it may set to be within the range described above in "1.3."

  Specifically, for example, when an alkali metal hydroxide or a solution in which an alkaline earth metal hydroxide is dissolved in water is preferably used as the alkaline solution, the alkali metal hydroxide or alkaline earth metal hydroxide is used. Examples of the concentration include 8 mol / L, 7 mol / L, 6 mol / L and the like as preferable upper limit values. On the other hand, preferable lower limit values that can be combined with these preferable upper limit values include 2 mol / L, 3 mol / L, 4 mol / L, and the like.

  Moreover, as a solution temperature, 80 degreeC, 75 degreeC, 70 degreeC etc. can be illustrated as a preferable upper limit. On the other hand, examples of preferable lower limit values that can be combined with these preferable upper limit values include 40 ° C., 45 ° C., and 50 ° C.

  Moreover, as processing time, 30 minutes, 20 minutes, 10 minutes etc. can be illustrated as a preferable upper limit. On the other hand, examples of preferable lower limit values that can be combined with these preferable upper limit values include 1 minute, 2 minutes, and 3 minutes.

  Specifically, as a method of bringing the surface of the liquid crystal polymer film into contact with the alkaline solution, for example, a method of immersing the liquid crystal polymer film in the alkaline solution, a method of spraying the alkaline solution on the surface of the liquid crystal polymer film, a liquid crystal polymer Any method such as a method of applying an alkaline solution to the surface of the film can be used, and is not particularly limited.

2.3 Third Step In the manufacturing method, the third step is a step of forming an electroless plating layer on the surface of the alkali-treated liquid crystal polymer film.

  The electroless plating layer is formed, for example, by applying an appropriate catalyst to the surface of the alkali-treated liquid crystal polymer film and reducing it with an appropriate reducing agent, and then forming the electroless plating layer described above in “1.2”. For example, electroless plating may be performed using an electroless plating bath containing metal ions to be formed according to a conventional method. At this time, the electroless plating may be performed separately.

  In addition, the thickness of the electroless plating layer is not particularly limited, and may be determined as appropriate in consideration of the circuit shape, etching property at the time of circuit formation, and the like.

2.4 Fourth Step In this manufacturing method, the fourth step is a step of forming an electrolytic plating layer on the surface of the electroless plating layer.

  The electrolytic plating layer may be formed in accordance with a conventional method, for example, by performing electrolytic plating using an electrolytic plating bath containing metal ions constituting the electrolytic plating layer described in “1.2”. At this time, the electrolytic plating may be performed separately.

  Further, the thickness of the electrolytic plating layer is not particularly limited, and may be appropriately determined in consideration of the circuit shape, the etching property when forming the circuit, the total thickness of the circuit board, and the like.

2.5 Heat treatment In this manufacturing method, heat treatment is performed between the third step and the fourth step and / or after the fourth step. By this heat treatment, the functional group formed on the film surface by the alkali treatment in the second step and the electroless plating layer surface are chemically bonded, and high adhesive strength is obtained.

  The temperature range during the heat treatment basically varies depending on the type of liquid crystal polymer used. Generally, as a preferable upper limit of the temperature at the time of heat treatment, a temperature not higher than the melting point of the liquid crystal polymer to be used can be exemplified. On the other hand, examples of preferable lower limit values that can be combined with this preferable upper limit value include 100 ° C., 150 ° C., and 200 ° C.

  If the temperature during the heat treatment exceeds the melting point of the liquid crystal polymer used, the liquid crystal polymer film is deformed, and the dimensional stability of the resulting circuit board tends to decrease. On the other hand, when the temperature at the time of heat treatment is less than 100 ° C., the adhesive strength between the liquid crystal polymer film and the electroless plating layer is lowered, and there is a tendency that the practicality becomes poor.

  Moreover, as a heating time at the time of heat processing, 24 hours, 6 hours, 1 hour etc. can be illustrated as a preferable upper limit. On the other hand, examples of preferable lower limit values that can be combined with these preferable upper limit values include 5 minutes, 10 minutes, and 15 minutes.

  Therefore, when performing the heat treatment in the present production method, the heating temperature and the heating time may be appropriately combined so that the above is taken into consideration and the adhesive strength between the liquid crystal polymer film and the plating layer becomes an optimum value.

  The heat treatment may be performed in any atmosphere such as an oxidizing atmosphere or an inert gas replacement atmosphere.

  Specific examples of the heat treatment method include a batch method using a heat oven or the like, a line method using a heating roll or a continuous heat treatment furnace, and the like. It is possible to select various methods as appropriate.

  Hereinafter, the present invention will be described in detail using examples.

Example 1
First, a 20 cm × 20 cm × 25 μm liquid crystal polymer film (manufactured by Kuraray Co., Ltd., “Vecstar FA”, melting point 280 ° C.) is applied to an ultraviolet surface reformer (manufactured by Sen Engineering Co., Ltd., “low pressure mercury lamp EUV200WS”). And the surface of the liquid crystal polymer film was subjected to ultraviolet treatment. At this time, the conditions of the ultraviolet treatment were as follows: ultraviolet dominant wavelength 184.9 nm, 253.7 nm, ultraviolet illuminance 20 mW / cm ² , output 200 W, and treatment time 60 seconds.

  Further, the contact angle between the liquid crystal polymer film and water before and after the ultraviolet treatment was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., “contact angle meter CA-X type”). As a result, the contact angle of water before UV treatment was 90.3 °, and the contact angle of water after UV treatment was 36.6 °.

  Next, the surface of the liquid crystal polymer film treated with ultraviolet rays was subjected to alkali treatment by contacting with a 5 mol / L potassium hydroxide aqueous solution at 50 ° C. for 10 minutes.

Then, the arithmetic mean roughness R _a of the liquid crystal polymer film surface before and after the alkali treatment, an atomic force microscope (Seiko Instruments Co., Ltd., "SPI3800N") was measured using a. At this time, measurement conditions, the spring constant of 3N / m, scanning range 5 [mu] m × 5 [mu] m Shun Sumi to determine the arithmetical mean roughness _{R a} of the film surface from the roughness curve of the diagonal (5√2Myuemu length) of 5 [mu] m square. As a result, the arithmetic mean roughness _{R a} in the previous alkali treatment 10.3 nm, an arithmetic mean roughness _{R a} after the alkali treatment was 12.9 nm.

  Next, a catalyst (Okuno Pharmaceutical Co., Ltd., “OPC-50 inducer”) was applied to the surface of the alkali-treated liquid crystal polymer film at 40 ° C. for 5 minutes, and then a reducing agent (Okuno Pharmaceutical Co., Ltd.). , “OPC-150 Cryster”) at 25 ° C. for 5 minutes.

  Next, electroless Ni plating was performed at 40 ° C. for 6 minutes using an alkaline nickel solution (Okuno Pharmaceutical Co., Ltd., “TMP-chemical nickel”), and an electroless film having a thickness of 0.3 μm was formed on one surface of the liquid crystal polymer film. A Ni plating layer was formed.

  Subsequently, it was dried at 80 ° C. for 30 minutes using a drying oven.

Subsequently, electro Cu plating was performed for 50 minutes at a current density of 2 A / dm ² using a copper sulfate plating bath to form an electrolytic Cu plating layer having a thickness of 18 μm on the surface of the electroless Ni plating layer. The copper sulfate plating bath is prepared by mixing copper sulfate 70 g / liter, sulfuric acid 200 g / liter, chloride ion 50 mg / liter, brightener (Okuno Pharmaceutical Co., Ltd., “Top Lucina SF”) 5 g / liter. It is a thing.

  Next, heat treatment was performed at 250 ° C. for 10 minutes using an air circulation oven.

  As a result, a circuit board according to Example 1 in which the electroless Ni plating layer (0.3 μm) and the electrolytic Cu plating layer (18 μm) were laminated in this order on one surface of the liquid crystal polymer film (25 μm) was produced.

(Comparative Example 1)
A circuit board according to Comparative Example 1 was produced in the same manner as in Example 1 except that the surface of the liquid crystal polymer film was not subjected to ultraviolet treatment.

(Comparative Example 2)
A circuit board according to Comparative Example 2 was produced in the same manner as in Example 1 except that heat treatment was not performed.

(Adhesion test)
Next, 180 ° peel strength was measured using the circuit boards according to the obtained Examples and Comparative Examples.

  That is, using a sample obtained by cutting each circuit board into a width of 1 cm, the plating layers (electrolytic Cu plating layer and electroless Ni plating layer) were 180 by a tensile tester (tensile speed 50 mm / min) in accordance with JIS C5016. The peel was carried out and the 180 ° peel strength was measured.

  Each circuit board was oven-heated at 150 ° C. for 7 days, and the 180 ° C. peel strength was measured in the same manner. The results are shown in Table 1.

  According to Table 1, it can be seen that the circuit board according to Comparative Example 1 has an initial 180 ° C. peel strength of less than 6 N / cm and a low initial adhesive strength. This is presumably because the surface of the liquid crystal polymer film was poor in wettability because the surface was not modified beforehand by ultraviolet rays before the alkali treatment, and the alkali treatment was not performed uniformly.

  In addition, it can be seen that the circuit board according to Comparative Example 2 has significantly lower initial adhesive force than the circuit board according to Comparative Example 1. This is presumably because the heat treatment was not performed, so the functional groups at the interface between the film surface and the electroless Ni plating layer did not increase, and a strong chemical bond was not formed.

  On the other hand, as shown in FIG. 1, the circuit board according to Example 1 has an initial 180 ° C. peel strength despite the fact that the surface of the liquid crystal polymer film is very smooth compared to the conventional case. It can be seen that it greatly exceeds 6 N / cm and is excellent in initial adhesive strength.

  Therefore, it can be seen that the circuit board according to Example 1 is excellent in the formation of a fine circuit and has high adhesion reliability.

  Moreover, as shown in Table 1, the circuit board according to Example 1 is capable of maintaining the initial 180 ° peel strength even after heat aging as compared with the circuit board according to the comparative example. It can be seen that high adhesion reliability can be exhibited.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention.

It is a transmission electron micrograph which shows the cut surface of the circuit board based on a present Example.

Claims (3)

Electroless plating layer on at least one surface of the liquid crystal polymer film, the electroless plating layer are laminated in this order, the arithmetic mean roughness R _a of the liquid crystal polymer film surface is at 30nm or less, 180 ° peel strength of the plating layer is A circuit board characterized by being 6 N / cm or more. A first step of surface-modifying at least one surface of the liquid crystal polymer film so that a contact angle with the liquid is reduced;
A second step in which the surface of the surface-modified liquid crystal polymer film is brought into contact with an alkali solution and subjected to an alkali treatment within a range in which the film surface is not roughened;
A third step of forming an electroless plating layer on the surface of the alkali-treated liquid crystal polymer film;
A fourth step of forming an electrolytic plating layer on the surface of the electroless plating layer,
A circuit wherein heat treatment is performed between the third step and the fourth step and / or after the fourth step at a temperature not higher than the melting point of the liquid crystal polymer for 5 minutes to 24 hours. A method for manufacturing a substrate. The arithmetic mean roughness R _a of the liquid crystal polymer film surface of the alkali treatment after the second step, the manufacturing method of the circuit board according to claim 2, characterized in that at 30nm or less.