KR20070031811A - Manufacturing Method of Printed Wiring Board - Google Patents

Abstract

When performing the process which makes a copper layer thin to the desired thickness with respect to the laminated | multilayer film in which the copper layer was laminated | stacked on at least one surface of the insulating film, the manufacturing method of the printed wiring board is short and processing time and the thickness variation of the copper layer after a process is small is provided. The manufacturing method of the printed wiring board of this invention processes the laminated | multilayer film which the copper layer was laminated | stacked on at least one surface of the insulating film with the 1st etching liquid which contains a cupric chloride or ferric chloride as a main component, and reduces the thickness of a copper layer. And a step of thinning and adjusting the thickness of the copper layer by treating the laminated film treated with the first etching solution with a second etching solution containing sulfuric acid and hydrogen peroxide as main components.

Description

Manufacturing method of printed wiring board {METHOD FOR MANUFACTURING PRINTED WIRING BOARD}

[Patent Document 1] Japanese Patent Laid-Open No. 2003-78234

[Patent Document 2] Japanese Patent Application Laid-Open No. 2003-258411

[Patent Document 3] Japanese Patent Application Laid-Open No. 2004-95983

The present invention provides a printed wiring board on which electronic components such as semiconductor chips are mounted (for example, a tape automated bonding (TAB) tape, a chip on film (COF) tape, a ball grid array (BGA) tape, and a chip size package)). ) Tape, ASIC (Application Specific Integrated Circuit) tape, FPC (Flexible Printed Circuit) and the like. In addition, in this specification, the "printed wiring board" includes both the tape in which the wiring pattern was repeatedly formed in the longitudinal direction, and the thing made from the individual tape carrier from this long tape after electronic component mounting.

Various printed wiring boards are used to mount electronic components such as ICs (Integrated Circuits) and LSIs (large scale integrated circuits) in liquid crystal displays, printers, and the like. In recent years, there is a strong demand for miniaturization, weight reduction, and high functionality of such devices, and accordingly, miniaturization and high density of conductor wiring patterns of printed wiring boards are in progress. In recent years, the printed wiring board whose pitch width is less than 30 micrometers is also utilized.

In a printed wiring board having such a narrow pitch wiring pattern, a COF (Chip On Film) method or the like is used when mounting a semiconductor chip. Conventionally, a subtractive method, a semiadditive method, a full additive method, and the like have been used as a method of forming a wiring pattern on an insulating film when manufacturing a printed wiring board. In order to make it suitable, the semiadditive process attracts attention (patent documents 1-3).

Formation of the wiring pattern by the semiadditive process is performed as follows. First, a laminated film in which a thin base metal layer is laminated on an insulating film such as a polyimide film is prepared.

On the surface of this base metal layer, only a part which forms a wiring pattern forms a plating resist so that a base metal layer is exposed. The plating resist is formed by a method of exposing and developing a pattern using a photosensitive dry film or a liquid photoresist.

Next, a metal plating layer is formed by electroplating or the like on the portion where the base metal layer not covered with the plating resist is exposed. The thickness of this metal plating layer is formed so that it may be thick enough compared with the thickness of a base metal layer, for example, about 10 micrometers thick.

After removing the plating resist by an alkaline solution or the like, a wiring pattern is formed by removing the base metal layer remaining between the metal plating layers by flash etching.

When the base metal layer is thick, when the base metal layer is removed by flash etching, the bottom side of the wiring side is etched together with the base metal layer, and undercut is likely to occur during wiring. Therefore, it is necessary to make thickness of a base metal layer thin. For example, when using a commercially available copper foil laminated plate as a two-layer base material, what thinned the copper layer about 8 micrometers in thickness to 0.1-3 micrometers by chemical polishing is used.

If an etching solution of sulfuric acid-hydrogen peroxide or ammonium persulfate-based etching solution is used to obtain a thin base metal layer, the etching time is slow, and the etching time required until the base metal layer reaches a desired thickness becomes very long.

In addition, when the cupric chloride etching solution or the ferric chloride etching solution is used to obtain a thin base metal layer, the etching speed is high, so that it is difficult to control the base metal layer to have a uniform thickness. Therefore, the thickness variation of the base metal layer after the etching treatment is large.

Thus, in the surface state with large thickness variation, when the dry film resist which is a plating resist is coat | covered in a subsequent process, the adhesiveness of the dry film resist with respect to a base metal layer falls. If the adhesion of the dry film resist is not good, the plating liquid may invade between the dry film resist and the base metal layer during electrolytic plating, and a good wiring pattern may not be obtained.

On the other hand, even when the wiring pattern is formed by the subtractive method, the copper layer in the laminated film may be thinned to a desired thickness in advance before the wiring pattern is formed, but even in this case, the thickness variation There was a problem that it was difficult to obtain a copper layer of small desired thickness in a short time.

This invention is a manufacturing method of the printed wiring board which is short in processing time and small in thickness variation of the copper layer after a process, when performing the process which makes a copper layer thin to the desired thickness with respect to the laminated | multilayer film in which the copper layer was laminated | stacked on at least one surface of the insulating film. The purpose is to provide.

An object of this invention is to provide the manufacturing method of the printed wiring board which can obtain the thin base copper layer with favorable resist adhesiveness in a short process time, when forming a wiring pattern by the semiadditive process.

The manufacturing method of the printed wiring board of this invention processes the laminated | multilayer film which the copper layer was laminated | stacked on at least one surface of the insulating film with the 1st etching liquid which contains a cupric chloride or ferric chloride as a main component, and reduces the thickness of a copper layer. Thinning process,

And a step of adjusting the thickness of the copper layer by treating the laminated film treated with the first etching solution with a second etching solution containing sulfuric acid and hydrogen peroxide as main components.

The manufacturing method of the printed wiring board of this invention is a process of forming a plating resist so that only the part corresponding to a wiring pattern may be exposed on the copper layer in the laminated film processed with the 2nd etching liquid,

Forming a metal plating layer on the portion where the copper layer is exposed;

Removing the plating resist from the laminated film;

And removing the copper layer remaining between the metal plating layers serving as wirings by flash etching.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely. The laminated | multilayer film used in this invention is a laminated | multilayer film by which the copper layer was laminated | stacked on at least one surface of the insulating film. Specifically, the two-layer film which consists of an insulating film and the copper layer, or the three-layer film which laminated | stacked the insulating film and the copper layer through an adhesive agent can be used.

As a two-layer film which consists of an insulating film and a copper layer, after depositing thin metal layers, such as nickel and chromium, on the insulating film by sputtering method etc., the two-layer film which formed the copper layer by electroplating etc. on this metal layer, copper foil with carrier foil And the two-layer film obtained by peeling carrier foil or removing carrier foil by etching, the two-layer film obtained by the casting method, etc. are mentioned after thermocompression bonding to the insulating film. In the casting method, after apply | coating the resin solution of a polyimide precursor on copper foil, for example, a two-layer film can be obtained by drying, heating, and hardening.

Said three-layer film adhere | attaches an insulating film and copper foil through an adhesive bond layer. As an adhesive agent, an epoxy resin adhesive, an acrylic resin adhesive, a urethane resin adhesive, a polyimide adhesive, a polyamide adhesive, etc. are mentioned. The thickness of an adhesive bond layer is 3-50 micrometers normally, Preferably it is 6-25 micrometers.

The insulating film preferably has chemical resistance that does not corrode the acidic liquid used for etching, alkali liquid used for cleaning, and the like, and has heat resistance that does not significantly thermally deform by heating when mounting the electronic component by bonding or the like. Do.

As a specific example of an insulation film, a polyimide film, a polyimide amide film, a polyester film, a polyphenylene sulfide film, a polyether imide film, a fluororesin film, a liquid crystal polymer film, etc. are mentioned. In particular, it is preferable to use a flexible film made of polyimide.

The average thickness of an insulation film is 1-150 micrometers normally, Preferably it is 5-125 micrometers, More preferably, it is 15-75 micrometers. When a printed wiring board is COF, the polyimide film whose average thickness is 15-75 micrometers, Preferably 20-50 micrometers is mentioned as a specific example of an insulating film.

The copper layer laminated on the insulating film may be either an electrolytic copper foil or a rolled copper foil. Moreover, the layer which consists of a copper alloy which has copper as a main component may be sufficient.

Hereinafter, the case where a printed wiring board is manufactured by the semiadditive process using said laminated | multilayer film is demonstrated. As a laminated | multilayer film, the commercially available 2-layer film whose thickness of a copper layer is about 8 micrometers can be used, for example. A two-layer film having a thicker copper layer or a two-layer film having a thinner copper layer may be used, but a small one capable of thickness variation of the copper layer is preferable.

The laminated film is treated with a first etching solution containing cupric chloride or ferric chloride as a main component to reduce the thickness of the copper layer. It is preferable to make thickness of the copper layer thin to 2-5 micrometers with a 1st etching liquid.

The treatment with the first etching liquid is performed by spray etching. The laminated film is unwound from the unwinding reel and introduced into the etching chamber disposed between the unwinding reel and the unwinding reel at a constant speed.

In the etching chamber, the spray nozzle which sprays etching liquid is plurally arrange | positioned on one side or both sides of a laminated | multilayer film. The etching liquid from the etching liquid chamber is continuously supplied to the plurality of spray nozzles by the pump, and the etching liquid is uniformly sprayed from the spray nozzle onto the surface of the same layer. The spray nozzle may have a vibration function for performing uniform spraying. The laminated film is sprayed into the etching chamber while being vertically stood up or horizontally laid down in the etching chamber.

The etching liquid containing cupric chloride as a main component used as the first etching solution contains at least cupric chloride and hydrochloric acid (HCl). The content of cupric chloride is preferably 1 to 4 mol / L. Content of hydrochloric acid becomes like this. Preferably it is 2-8 mol / L.

The etching liquid may contain an oxidizing agent such as hydrogen peroxide. In addition, it may contain a small amount of additives.

The temperature of etching liquid becomes like this. Preferably it is 30-60 degreeC. The spray pressure is preferably 0.07 to 0.3 MPa. The spray amount to a copper surface becomes like this. Preferably it is 60-750 L / min * m <2>.

The etching solution containing ferric chloride as a main component used as the first etching solution contains at least ferric chloride and hydrochloric acid (HCl). The content of ferric chloride is preferably 1 to 4 mol / L. Content of hydrochloric acid becomes like this. Preferably it is 1-4 mol / L.

Said etching liquid may contain a small amount of additives in addition to this.

The temperature of etching liquid becomes like this. Preferably it is 30-60 degreeC. The spray pressure is preferably 0.07 to 0.3 MPa. The spray amount to a copper surface becomes like this. Preferably it is 60-750 L / min * m <2>.

After the laminated film is treated with the first etching solution, the laminated film is treated with a second etching solution containing sulfuric acid and hydrogen peroxide to adjust the thickness of the copper layer to a desired thickness. When forming a wiring pattern by the semiadditive process, it is preferable to adjust the thickness of a copper layer in the range of 0.1-2 micrometers with a 2nd etching liquid.

The treatment with the second etching liquid is performed by immersion etching. The laminated film is unwound from the unwinding reel and introduced into the etching chamber of the second etching liquid disposed between the unwinding reel and the unwinding reel. Spray etching with a 1st etching liquid and immersion etching with a 2nd etching liquid can also be performed in order between the same unwinding reel and the winding reel.

The second etching solution contains at least sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ). Content of sulfuric acid becomes like this. Preferably it is 1.5-4.5 mol / L. The content of hydrogen peroxide is preferably 1.0 to 4.0 mol / L.

In addition, the second etching liquid may contain an appropriate amount of copper ions, sulfates, and hydrogen sulfates. Moreover, you may contain a small amount of other additives, such as a stabilizer of hydrogen peroxide.

The temperature of the 2nd etching liquid becomes like this. Preferably it is 20-50 degreeC.

In the treatment with the first etching solution, since the etching rate is high, rapid etching is possible, but the thickness of the copper layer obtained here is about ± 1.0 to ± 2.0 μm from the average thickness. On the other hand, in the treatment with the second etching liquid, although the etching rate is slow, the faster the portion of the etching liquid flow (update of the etching liquid) is etched faster at the contact interface with the copper layer, the convex portion is faster than the concave portion on the surface of the copper layer. Is etched. Therefore, the thickness variation of the copper layer becomes small, and finally, the thickness variation can be about ± 0.1 to ± 8 .mu.m.

In this way, by treating in two steps using the first etching solution and the second etching solution, the surface having good adhesion of the plating resist can be finished in a short time, and the cost for obtaining the metal layer serving as the base of the semi-additive method can be reduced. Can be.

Using the laminated film which adjusted the thickness of the copper layer used as a base as mentioned above, plating resist is formed so that the copper layer may be exposed only in the part which will form a wiring pattern on the surface of the copper layer. A plating resist is formed by the method of exposing and developing a pattern using a photosensitive dry film or liquid photoresist.

After the plating resist is formed, a metal plating layer is formed on the portion where the copper layer is exposed without being coated with the plating resist. It is preferable to form this metal plating layer by electrolytic plating, For example, when forming the metal plating layer which consists of copper, electroplating which made the copper layer of laminated | multilayer film into a common electrode using copper sulfate bath etc. can be used. have. The thickness of this metal plating layer is 1-70 micrometers normally, Preferably it is 4-35 micrometers. In order to form the wiring pattern whose pitch is 30 micrometers or less, the wiring height as a total of the base copper layer and a metal plating layer is 12 micrometers or less normally, Preferably it is 10 micrometers or less.

Next, a wiring pattern is formed by removing a plating resist with an alkaline solution or the like and then removing the base metal layer remaining between the metal plating layers by flash etching. Although wiring pitch is generally 25-50 micrometers, while fine pitching progresses, a wiring pitch may become less than 25 micrometers in some cases. The method of the present invention is particularly suitable for forming a wiring pattern having a pitch of 30 µm or less.

After the wiring pattern is formed in this manner, the solder resist is coated so as to cover the area of the wiring pattern with one surface except for the internal lead connected to the terminals of the semiconductor chip and the external lead connected to external devices on the input side and the output side. Then, a printed wiring board is obtained by performing terminal plating on the internal lead and the external lead exposed from the soldering resist.

A soldering resist is formed by apply | coating and hardening a resist ink by a screen printing method, or coating a photosensitive dry film.

As terminal plating, tin plating, nickel plating, nickel-gold plating, Cu-Sn plating, Sn-Bi plating, etc. are mentioned, for example.

Although the case where the wiring pattern is formed by the semi-additive method has been described above, the present invention can be applied to the case where the wiring pattern is formed by the subtractive method. In this case, the above-mentioned various two-layer film and three-layer film can be used as the laminated film. For example, a commercially available laminated film can be used. The average thickness of the copper layer is usually 1 to 70 µm, preferably 4 to 35 µm.

The laminated film is treated with the above-described first etching solution containing cupric chloride or ferric chloride as a main component to make the thickness of the copper layer thin. It is preferable to make it thin to the average thickness + 1-5 micrometers which wants to finally obtain the average thickness of the copper layer with a 1st etching liquid.

After processing a laminated film with a 1st etching liquid, this laminated film is processed with the above-mentioned 2nd etching liquid containing a sulfuric acid and hydrogen peroxide, and the thickness of a copper layer is adjusted. As a result, a copper layer having a desired thickness having a thickness variation of, for example, about ± 0.1 to ± 0.8 μm is obtained.

Then, the dry film resist is coated on the copper layer of the laminated film or the liquid photoresist is applied, and the portion corresponding to the wiring pattern to be formed is cured by irradiating the resist with ultraviolet rays through a mask, and the uncured portion Is removed by dissolving the developer. In addition, the photoresist which can be melt | dissolved in a medium by exposure can also be used.

Next, the wiring pattern is formed on the surface of an insulating film by melt | dissolving and removing copper layers other than the part protected by the resist by the etching with an acid. The resist on the wiring pattern is removed with an alkaline solution or the like.

Electronic components, such as a semiconductor chip, are mounted by heat-pressing the inner lead of the printed wiring board obtained as mentioned above and the external terminal of a semiconductor chip using a bonding tool etc.

After mounting the semiconductor chip, resin such as epoxy is introduced into the device hole provided in the insulating film or in the case of a COF tape or the like between the insulating film and the semiconductor chip to cure the resin and the internal lead and the external terminal of the semiconductor chip. The connection part is sealed, and a semiconductor device is obtained in this way.

Hereinafter, although an Example demonstrates this invention, this invention is not limited to this Example.

[First Embodiment]

A commercial two-layer film (Spanex Shinnitetsu Chemical Co., Ltd. product, average thickness of 8 micrometers) in which the copper layer was laminated | stacked on the polyimide film was prepared.

While conveying this 2-layer film to a spray apparatus, it uses the 1st copper chloride type etching liquid (40 degreeC) containing 2 mol / L of cupric chlorides, and 4 mol / L of HCl, to the copper layer of a 2-layer film. On the other hand, the 1st etching liquid was sprayed uniformly by the spray pressure of 0.15 Mpa from the nozzle of a spray apparatus, and etching was performed for about 10 second.

The thickness of the copper layer after etching was measured by the following method. Using a contact film thickness gauge (manufactured by Nikon Co., Ltd., ME-50H), the thickness of the copper layer at a total of 5 points at 25 points spaced apart by 8 mm in the width direction and 50 mm spaced in the longitudinal direction. Was measured. The average thickness of the copper layer was 2.98 µm, the standard deviation σ of the thickness was 0.45 µm, and the thickness variation was 1.614 µm.

Next, the two-layer substrate was returned and immersed in an etching solution containing 3.0 mol / L of H ₂ SO ₄ , 2.8 mol / L of H ₂ O ₂ , and several tens of ppm of additives, and etching was performed at 30 ° C. for about 90 seconds. .

As a result of measuring the thickness of the copper layer after etching by the said method, the average thickness of the copper layer was 1.44 micrometers, the standard deviation (sigma) of thickness was O.162 micrometers, and the thickness deviation was 3 (sigma) and O.486 micrometers.

A dry film resist (ALPHO NIT 215 Nichigo Morton Co., Ltd.) having a thickness of 15 µm was laminated on the copper layer of this two-layer base material. Lamination conditions were the temperature of about 100 degreeC, the pressure of 0.3 Mpa, and the lamination rate of 2.0 m / min.

The pattern corresponding to the wiring was exposed to the dry film resist at about 80 mJ / cm 2, and then developed by spray using a 1% Na ₂ CO ₃ aqueous solution under conditions of a temperature of 30 ° C. for about 15 seconds.

Next, it was subjected to FR (trade name, Artech _{Inc.) 10% + 20% H 2} 18O seconds at a temperature of 40 ℃ as SO _4, continue to 60 minutes plating pre-treatment at a temperature of 30 ℃ to 10% H ₂ SO _4.

Then, in a plating solution containing 60 g / L of CuSO ₄ H ₂ O, 210 g / L of H ₂ SO ₄ , 50 ppm of chloride ions, and several ppm of additives, at a temperature of 23 ° C. and Dk = 2.0 A / dm ² . Electrolytic copper plating was performed for about 20 minutes to form a copper plating layer having a thickness of 9 µm.

Next, a 3% NaOH aqueous solution having a temperature of 50 ° C. was sprayed on the dry film resist for about 15 seconds by spraying to remove the resist.

Thereafter, using an etching solution containing 4.1 mol / L of H ₂ SO ₄ , 3.3 mol / L of H ₂ O ₂ , and several tens of ppm of additives, flash etching was performed for about 20 seconds by spraying under conditions of a temperature of 30 ° C. The copper layer which remained between the plating layers was removed. In this way, the wiring pattern of wiring pitch of 25 micrometers (line width; 13 micrometers, space width; 12 micrometers) was formed. Thereafter, the solder resist was coated so as to cover the wiring pattern leaving the lead portion, and the lead portion was subjected to terminal plating to obtain a printed wiring board.

Since this printed wiring board had few undercuts of wiring and the plating resist was fully in close contact with the copper layer surface, a good wiring pattern was obtained.

According to the present invention, the process of thinning the copper layer to a desired thickness can be performed in a short time, and the thickness variation of the copper layer after the treatment is small.

According to the present invention, when forming the wiring pattern by the semi-additive method, a thin base copper layer having good resist adhesion can be obtained in a short time.

Claims (2)

Treating the laminated film having the copper layer laminated on at least one surface of the insulating film with a first etching solution containing cupric chloride or ferric chloride as a main component to reduce the thickness of the copper layer; A process for manufacturing a printed wiring board, comprising: treating the laminated film treated with the first etching solution with a second etching solution containing sulfuric acid and hydrogen peroxide as main components to adjust the thickness of the copper layer. The method of claim 1, Forming a plating resist on the copper layer in the laminated film treated with the second etching solution so that only the portion corresponding to the wiring pattern is exposed to the copper layer; Forming a metal plating layer on the portion where the copper layer is exposed; Removing the plating resist from the laminated film; A method of manufacturing a printed wiring board, further comprising the step of removing the copper layer remaining between the metal plating layers serving as wirings by flash etching.