KR20090009692A - Method for preparation of metal-coated polyimide substrate - Google Patents

Abstract

A manufacturing method of a metallization polyimide substrate is provided to reduce a gap of a dimensional change when the metallization polyimide substrate is heated and to perform steadily bonding to added heat in case of being used as COF. A manufacturing method of a metallization polyimide substrate comprises steps of: forming a metal film on a surface of a polyimide film; returning the film(2) on the metal film of the manufactured polyimide film, including rollers(3,4) supplying electricity to the metal film and an anode(5) facing the metal film and forming a metal conductor using a continuous plating apparatus consisting of two plating baths(1). A ratio of a maximum value to a minimum value of cathodic current density in the plating bath is 1~5 and a film sending speed is 80~300 m/h. The anode is an insoluble anode.

Description

Method for Preparation of Metallized Polyimide Substrate {Method for Preparation of Metal-Coated Polyimide Substrate}

The present invention relates to a method for producing a metal-coated polyimide substrate, and more particularly, by reducing the gap of the dimensional change when heating the metal-coated polyimide substrate, it can be stably bonded when used in COF The present invention relates to a metal-coated polyimide substrate capable of improving a defective rate.

Background Art In recent years, metal-coated polyimide substrates have been widely used as semiconductor mounting substrates for mounting a driving semiconductor for displaying an image on a liquid crystal screen. The polyimide film used for the metal-coated polyimide substrate has not only excellent heat resistance but also no inferiority to other plastic materials in mechanical, electrical and chemical properties, for example, a printed wiring board (PWB), flexible (flexible) ) It is used as a material of the insulation board for electronic components, such as a printed wiring board (FPC), a tape automatic bonding tape (TAB), and a chip-on film (COF). Such PWB, FPC, TAB, and COF can be obtained by processing this using a metal-coated polyimide substrate coated with a metal layer on at least one side of the polyimide film.

Among them, in particular, COF attracts attention as a method of mounting the driver IC chip for liquid crystal display. COF is a fine pitch mounting method compared to the conventional mounting method (Tape® Carrier Package), and it is an easy mounting method for miniaturization and cost reduction of driver ICs. As a method of producing such a COF, a photolithography is performed using a polyimide film, which is a high heat resistance and high insulating resin, and a metal-coated polyimide substrate produced by bringing a copper layer, which is generally a good conductor, into close contact with a metal conductor. It is common to obtain fine patterning according to the method, and to obtain by coating tin plating and solder resist on additional desired areas.

In manufacturing the metal-coated polyimide substrate, as a method of forming a metal layer on the surface of the polyimide film, for example, first, a metal seed layer made of nickel, chromium, nickel chromium alloy, etc. is formed by sputtering, and In order to impart good conductivity thereon, a copper layer is formed to produce a metal film. Moreover, in order to thicken the conductive layer for circuit formation, the method of forming metal conductors, such as copper, is performed by the electroplating method or the method of using electroplating and electroless plating together.

On the other hand, the thickness of the metal film formed by the said sputtering method is generally 100-500 nm. In addition, as for the thickness of a metal conductor, when forming a circuit by a subtractive method, for example, 5-12 micrometers is common.

Here, in the case of forming the metal conductor by the electroplating method, for example, the plating bath in which the anode is provided so that the plating liquid is supplied to face the plating surface serving as the cathode inside the container may include at least two plural sets of films. By providing in the conveyance direction, the continuous plating apparatus containing the electric power supply part which supplies electric power to each plating tank, and the mechanism for conveying continuously a film-form board | substrate is used. For example, a plurality of plating tanks having an anode and an electrolytic solution are disposed, and an insulator film having a metal film having a thickness of 3 µm or less is continuously supplied to the plating bath in succession, and the amount of energization for each plating bath is controlled. The continuous plating method (for example, refer patent document 1) which continuously increases the electricity supply amount of each plating tank in the order which the said film is supplied, and forms a uniform and favorable electroplating film continuously is disclosed.

As described above, the metal-coated polyimide substrate having the metal layer formed by the sputtering method and the plating method is easy to thin the metal layer, and a technique of obtaining sufficient adhesion strength while maintaining the smooth interface between the polyimide film and the metal film has been established. The COF produced using is suitable for fine pitching of circuits. Accordingly, mass production of COFs having a 25 to 30 μm pitch in the inner lead portion has been started, and development of a very narrow pitch COF of 20 μm pitch or less is continued.

However, in the COF, the semiconductor chip is mounted by internal lead bonding, and then mounted on the liquid crystal panel by external lead bonding. In general, since the dimensions of the COF change due to the heat added at the time of bonding, the amount of change is predicted in advance, and the correction is added to the circuit formed in the COF in advance, in particular, the interval between the inner lead and the outer lead. In particular, since the 20 μm pitch COF is a very narrow pitch, precise correction of the lead spacing is required.

However, in the case of using a metal-coated polyimide substrate having a metal layer formed by the sputtering method and the plating method as described above, the rate at which the lead at the end deviates from the desired bonding position during bonding in a COF of 20 µm pitch is increased, so that the defective rate is increased. There was a problem of rising. This is considered to be the main reason for the difference in dimensional change when heating the metal-coated polyimide substrate. In such a situation, there is a demand for a metal-coated polyimide substrate capable of further reducing the gap in dimensional change during heating.

[Patent Document 1] Japanese Patent Laid-Open No. 7-22473 (claims 1 and 2)

SUMMARY OF THE INVENTION An object of the present invention is to grasp the problems of the prior art described above, reduce the dimensional change gap when heating a metal-coated polyimide substrate, and when used as a COF, it is possible to stably bond and improve the defective rate. It is to provide a method for producing a metal-coated polyimide substrate.

MEANS TO SOLVE THE PROBLEM The present inventors carried out in-depth study about the manufacturing method of a metal-coated polyimide board | substrate, in order to achieve the said objective, The sputtering process of forming a metal film on the surface of a polyimide film, and the metal film image of the obtained polyimide film A method for producing a metal-coated polyimide substrate, including an electroplating process of forming a metal conductor using a continuous plating apparatus, has been developed. This manufacturing method can form a metal film having a specific surface resistance to the sputtering process to suppress the heat history gap in sputtering, while reducing the difference in cathode current density during subsequent electroplating, In addition, in the above electroplating process, the specific cathode current density was controlled to uniformize the current density distribution, and at the same time, it was controlled at a specific film conveyance speed to suppress oxidation of the interface of the laminated structure. When the residual stress gap of the metal layer was reduced and the gap of the dimensional change during heating was reduced, and it was used as COF, it was found that the bonding can be performed stably and the defect rate can be improved. .

That is, according to the 1st invention of this invention, the sputtering process of forming a metal film on the surface of a polyimide film, and the roller which conveys a film and supplies electricity to a metal film on the metal film of the obtained polyimide film, and the said metal A manufacturing method of a metal-coated polyimide substrate comprising an electroplating step of forming a metal conductor using a continuous plating apparatus comprising an anode facing a film and composed of at least two plating baths, the following conditions (1) and The manufacturing method of the metal-coated polyimide board | substrate characterized by satisfy | filling (2) is provided.

(1) The surface resistance of the metal film formed in the said sputtering process is controlled to 0.1-1.0 ohm / square.

(2) In the electroplating step, the current density of the cathode is a ratio of the maximum value to the minimum value of the cathode current density in each plating bath, with the average cathode current density of the entire plating bath being 1 to 3 A / dm ² . To 1 to 5, and at the same time the conveying speed of the film is adjusted to 80 ~ 300 m / h.

According to a second aspect of the present invention, there is also provided a method for producing a metal-coated polyimide substrate, characterized in that, for the first aspect, the anode is an insoluble anode.

Further, according to the third invention of the present invention, in the second invention, the current density of the cathode is 1.5 to 3 A / dm ^{2 of the} average cathode current density of the entire plating bath. The ratio of the maximum value to the minimum value of the cathode current density in each plating tank is 1-3, and the conveyance speed of a film is 100-300 m / h, The manufacturing method of the metal-coated polyimide board | substrate characterized by the above-mentioned. do.

Further, according to the fourth invention of the present invention, according to the invention of any one of the first to the third, the metal film is composed of a metal seed layer and a copper layer formed on the surface thereof. It provides a manufacturing method.

Moreover, according to the 5th invention of this invention, with respect to any one of 1st-4th invention, it provides the manufacturing method of the metal-coated polyimide substrate characterized by the fact that a metal conductor is copper.

According to the manufacturing method of the metal-coated polyimide substrate of the present invention, the gap of the dimensional change during the heating of the produced metal-coated polyimide substrate is reduced, when using it as a COF, it is possible to stably bond, improve the defective rate Can be. In particular, in the case of using a narrow pitch COF represented by a pitch of 20 占 퐉, the rate at which the lead at the end deviates from the desired bonding position during bonding is reduced, and the defect rate is greatly improved, so the industrial value is very large.

Hereinafter, the manufacturing method of the metal-coated polyimide substrate of this invention is demonstrated in detail.

The manufacturing method of the metal clad polyimide board | substrate of this invention is the sputtering process of forming a metal film on the surface of a polyimide film; And a roller for conveying the film and supplying electricity to the metal film, and an anode facing the metal film, on a metal film of the manufactured polyimide film, using a continuous plating apparatus composed of at least two plating baths, An electroplating step of forming a conductor; as a manufacturing method of a metal-coated polyimide substrate comprising,

The following conditions (1) and (2) are satisfied.

(1) The surface resistance of the metal film formed in the said sputtering process is controlled to 0.1-1.0 ohm / square.

(2) In the electroplating step, the current density of the cathode is set to the average cathode current density of all the plating baths is 1 to 3 A / dm ² , and the ratio of the maximum value to the minimum value of the cathode current density in each plating bath is set. 1 to 5, and at the same time the conveying speed of the film is adjusted to 80 ~ 300 m / h.

In the production method of the present invention, the sputtering process and the electroplating process are performed to satisfy the above conditions (1) and (2) to control the surface resistance of the metal film to be formed, and together with the average cathode current density of the electroplating. By setting it to a certain range, the gap of the residual stress of the metal layer formed by making the difference of the current density for each layer of a laminated structure small is reduced, and further, the downtime of plating for current supply is reduced, and the interface of a laminated structure is suppressed from being oxidized. It is important to do. Thereby, when the gap of the dimensional change at the time of heating is reduced and it uses for COF, the metal-coated polyimide board | substrate which can bond stably can be obtained.

Below, the difference of the residual stress of the metal layer formed by a sputtering process and an electroplating process is explained in full detail about the operation | movement of the manufacturing method of this invention with the problem of the conventional method.

That is, in general, in order to form a lead of a COF using a metal-coated polyimide substrate, as described above, a constant correction is made to a pattern size formed on a photoresist exposure mask in consideration of a thermal history applied during lead formation. Is carried out. This is carried out to prevent the peeling by predicting in advance the extent to which the lead spacing changes due to thermal history, which is added until bonding to the IC chip and bonding to the liquid crystal panel.

In addition, the reason that the lead spacing changes is due to deformation due to thermal expansion, thermal contraction, or the like of a COF structural member such as a polyimide film, a metal layer, and a solder resist. The deformation due to these heat is a natural phenomenon, and the amount of deformation can be grasped experimentally in advance. However, the problem is that the amount of deformation is not constant and is dispersed, and furthermore, while the amount of deformation is irregular, the risk of the peeling increases as the lead spacing becomes a fine pitch. As a cause of the gap of such a COF structural member, the thermal history at the time of film-forming, the gap of extending | stretching, and the thickness gap of a film are main reasons for a polyimide film, and the thickness gap is a main factor for a soldering resist. On the other hand, the thickness irregularity is also a major factor for the metal layer, but it is also greatly influenced by the residual stress gap of the metal.

Here, the variation in the current density (hereinafter referred to as 'cathode current density') of the cathode formed on the polyimide film as a factor of the stress remaining in the plating film during the electroplating forming the metal conductor constituting the metal layer. This has the greatest impact. That is, when forming a metal conductor on the metal film formed by sputtering on the surface of the polyimide film by the electroplating method, generally, in the initial stage of electroplating, the metal film and the plated film formed thereon are thin. The high electrical resistance inevitably lowers the current density of the plating bath. Subsequently, in a step of growing to a certain thickness of the plating, a method of rapidly increasing the current density of the plating bath is performed with emphasis on productivity and economy. For example, in the conventional method, the plated film of the laminated structure formed through each plating bath has a current density of 0.001 to 0.01 A / dm ² at the immediately upper layer of the metal film formed by sputtering, and 0.5 to 1 at the outermost surface layer. It is formed at a current density of 0 A / dm ² . At this time, the average current density of the entire plating bath is 0.3 to 0.7 A / dm ² . In general, the residual stress of the plated film is proportional to the current density of the cathode. If the current density is high, the stress tends to increase. Therefore, in the conventional method, the difference in residual stress in each layer of the plated film formed in the laminated structure is significantly increased by the wide range of current densities as described above, and this causes a gap in the dimensional change.

As a means of suppressing the residual stress difference for each layer of the plated film, it may be considered to continue the plating at an extremely low current density state in the initial stage of the plating, but it may cause a significant obstacle to productivity and may lead to an excessively long production line. It is not realistic because it needs to be built. For example, when plating with an average current density of 0.1 A / dm ² to a thickness of 8 μm, the plating time requires about 5 hours. In addition, plating at very low current densities is effective in reducing residual stress, but it also affects elongation, tensile strength and bending resistance, which are important properties of other plating films. It is thought that the risk of generating troubles other than bonding increases in the assembling process using. In addition, in the plated film produced at a low current density, the bending resistance deteriorates, so that the risk of lead breakage or the like increases during the bonding of COF. Moreover, in terms of economics, the average current density needs to be secured above a certain value.

In this regard, the method for producing a metal-coated polyimide substrate of the present invention, as mentioned above, the surface of the metal film formed by performing a sputtering process and an electroplating process to satisfy the above conditions (1) and (2) By controlling the resistance and adjusting the average cathode current density of the plating to a certain range, the difference in current density is reduced for each layer of the laminated structure, thereby reducing the residual stress gap of the metal layer formed, and additionally plating for current supply. The time to stop the operation is reduced to suppress the oxidation of the interface of the laminated structure. In this way, productivity is improved.

The manufacturing method of the metal-coated polyimide substrate of this invention includes the sputtering process of forming a metal film on the surface of a polyimide film, and the electroplating process of forming a metal conductor on the metal film of the obtained polyimide film. That is, a very thin metal film is formed on the surface of the polyimide film so as to be formed to a predetermined thickness by the electroplating method.

One. Sputtering  fair

The sputtering step is not particularly limited except for the above condition (1), and is used under the conditions used in a method for producing a conventional metal-coated polyimide substrate which forms a metal film having a desired thickness on the surface of the polyimide film. Is performed. The apparatus used for the said sputtering is not specifically limited here, The magnetron sputtering apparatus etc. which have the target which consists of a predetermined composition containing the element which comprises a metal film are used.

The polyimide film used in the manufacturing method is not particularly limited, and Kapton EN (Kapton® EN; manufactured by Toray Dupont), Euphilex-S (Upilex S; manufactured by UBE), and Apical (made by Kaneka) Commercially available polyimide films such as these are used. In addition, the thickness of a polyimide film is not specifically limited, It is preferable that it is 25-50 micrometers in view of ensuring flexibility.

The metal film formed by the above sputtering is not particularly limited, and in order to secure reliability such as adhesion to the polyimide and heat resistance, the metal seed layer may be formed from a metal such as nickel, chromium, molybdenum, or an alloy such as a nickel chromium alloy. Although selected, nickel chromium alloys containing chromium in an amount of 5 to 30% by weight based on the total content are preferred. In addition, the thickness is preferably 5 to 50 nm. That is, when forming an electronic circuit by etching a metal layer when using for COF etc., alloy composition and thickness which differ greatly in etching property with copper which is a favorable conductor are unsuitable.

Moreover, it is preferable to form a copper layer on the surface of the metal film by sputtering continuously in order to reduce the surface resistance in order to secure the conductivity before electroplating. At this time, the copper layer controls the surface resistance to be a predetermined value that can satisfy condition (1). In other words, if the thickness is less than 50 nm, sufficient conductivity cannot be obtained, which adversely affects the uniformity of copper deposition by subsequent electroplating. On the other hand, if the thickness is more than 500 nm, it is advantageous in terms of imparting conductivity, but the thermal history of the polyimide film is increased by sputtering, resulting in dimensional change, deformation, etc. of the substrate, which adversely affects manufactured products such as COF. There is concern.

The condition (1) related to the manufacturing method is to control the surface resistance of the metal film formed in the sputtering step to 0.1 to 1.0? / ?. That is, by reducing the surface resistance of the metal film formed by sputtering, the current density can be improved from the initial stage of electroplating, and therefore the average cathode current density can be improved. On the other hand, reducing the surface resistance of the metal film increases the thickness of the metal film, and in this case, the amount of heat added to the polyimide film by sputtering increases, and the gap is naturally widened. Therefore, there is an increased risk that the lead position difference increases during bonding of the COF. Therefore, in the manufacturing method of the present invention, the surface resistance of the metal film is selected in such a range that the gap due to the increase in the amount of heat added by sputtering is not large.

That is, when the surface resistance of the metal film is less than 0.1 Ω / □, the gap in thermal history due to sputtering becomes large, and the positional difference at the time of bonding increases. On the other hand, when the surface resistance of the metal film exceeds 1.0 Ω / square, it is necessary to suppress the current density of the cathode too low in the initial stage of electroplating, and the difference in current density of the cathode increases for each laminated structure layer of plating. Alternatively, if the current density of the cathode is excessively increased in a state exceeding 1.0 Ω / □, the residual stress of the plated film increases. In addition, in order to reduce the thermal history gap due to sputtering and to reduce the difference in current density of the cathode, it is preferable to control the surface resistance of the metal film to 0.2 to 0.8? / ?.

In the method of controlling the surface resistance of the metal film, the surface resistance is influenced by the thickness, purity, crystal grain size, etc. of the metal film formed by sputtering, so that the sputtering conditions are set so as to obtain a desired surface resistance. . For example, in the case of forming the copper layer by sputtering through magnetron sputtering performed in a vacuum atmosphere, by adjusting the thickness of the copper layer to 300 to 10 nm, the surface resistance of the metal film is adjusted to 0.1 to 1.0 Ω / □. Can be.

2. Electroplating process

The electroplating step is not particularly limited except for the above condition (2), and the metal conductor is formed on the metal film satisfying the condition (1) formed on the polyimide film by using a continuous plating apparatus. It is performed on the conditions used for the manufacturing method of the normal metal coating polyimide substrate.

Further, the electrometal plating apparatus includes a roller for carrying the film and supplying electricity to the metal film, and an anode facing the metal film, and comprises at least two sets of plating baths. For example, since installation space can be largely reduced normally, what arrange | positioned and arrange | positioned the necessary number set in the conveyance line direction corresponding to the thickness etc. which plate the form of a plating tank is used. Here, the polyimide film of the predetermined width | variety which has a metal film is continuously supplied to a plating tank sequentially at a constant speed, and a plating layer is continuously formed on a metal film. That is, the plating tank provided with the electroconductive roller which can contact an metal film, and can supply electricity, and the anode provided in the position which opposes the said metal film, and the film conveyance mechanism which supplies a film in the said plating tank and conveys it while contacting with a plating liquid. The continuous plating apparatus used for the manufacturing method of the normal metal clad polyimide board | substrate provided with is used.

The metal conductor is not particularly limited, and COF is preferable as the circuit material. On the other hand, the coating by electroplating is preferably a metal or an alloy having excellent conductivity, but copper is preferred. As the plating liquid used at this time, a commercially available copper sulfate plating bath used for general electroplating may be used.

The condition (2) related to the manufacturing method described above is that for the electroplating process, the density of the cathode current is 1 to 3 A / dm ² of the average cathode current density of the entire plating bath, The conveyance speed of the film is controlled to 80 to 300 m / h while controlling the ratio of the maximum to the minimum. That is, by reducing the residual stress of the metal layer formed on the metal film that satisfies the condition (1), in order to suppress the positional difference during bonding, the average cathode current of each layer electroplated so that the current density difference is small for each layer of the laminated structure. It is to adjust the density to a certain range. On the other hand, the average cathode current density of electroplating is recommended to reduce the cathode current density difference for each layer of the laminated structure in order to suppress the positional difference during bonding, but the present invention is manufactured in consideration of securing bending resistance and productivity and economical efficiency The condition (2) above applies to the electroplating process of the method.

That is, as the cathode current density, the average cathode current density of the entire plating bath is 1 A / dm ² Below, it becomes difficult to ensure bendability. On the other hand, when the average cathode current density exceeds 3 A / dm ² , it is difficult to suppress the difference in residual stress. In addition, in order to secure reliability and economy, it is preferable that the average cathode current density of the entire plating bath is 1.5 to 3 A / dm ² .

In addition, by controlling the ratio of the maximum value to the minimum value of the cathode current density in each plating bath to 1 to 5, the residual stress of the metal conductor constituting the metal layer by uniformizing the current density distribution in each layer of the laminated structure. Further homogenization is achieved. Thereby, the residual stress in the laminated structure as a whole can be equalized and the gap can be suppressed. That is, when the ratio of the maximum value to the minimum value of the cathode current density exceeds 5, the difference in residual stress due to the difference in current density becomes large, and the gap becomes large. In addition, in order to make residual stress uniform, it is preferable to set ratio of the maximum value with respect to the minimum value of cathode current density to 1-3.

As the method for controlling the cathode current density, generally, in the initial stage of electroplating, that is, in the region where the surface resistance of the metal film is high, in each plating bath of the continuous plating apparatus, it is close to the roller which performs the electric supply. Since the current density tends to be extremely concentrated at the plating liquid inlet interface, on the contrary, the current density is greatly reduced in the lower part of the plating bath. Therefore, an appropriate current shielding plate is formed on the polyimide film to suppress the concentration of the current density at the plating bath inlet. The method provided between a film and an anode is preferable, and the method is not specifically limited. For example, as an electric current shielding plate, an opening is formed in the insulating plate, and the area of the opening is made small in the vicinity of the plating liquid interface where the current density is concentrated, and on the contrary, the method of adjusting the opening is made larger in the lower part of the plating bath where the current density is lowered. Can be.

Moreover, by adjusting the conveyance speed of a film to 80-300 m / h, when mounting a semiconductor chip in COF at the time of bonding and resin-sealing a semiconductor chip, the problem that the tin-plated film of a lead surface peels can be avoided. That is, since the continuous plating apparatus is composed of a plurality of plating baths, an electric supply portion and a conveyance mechanism, when the metal conductor is formed in a laminated structure by using the apparatus, in order to supply electricity to the metal film and the plating film formed thereon, The time during which the polyimide substrate is outside the plating liquid, that is, the plating stop time occurs between the layers of the laminated structure. When such a plating stop time is long, the lead is formed on the manufactured substrate by etching, and a tin plated film is formed on the surface by electroless plating, and then the semiconductor chip is mounted on the COF by bonding to resin seal the semiconductor chip. In this case, there was a problem that the risk that the tin-plated film on the lead surface can be peeled off.

More specifically, when a semiconductor chip is subjected to a heat load at 150 ° C. for about 3 hours when the semiconductor chip is resin-sealed, a void generated by a difference in diffusion rate when alloying of tin and copper in the lead surface layer occurs, so-called It is known that Kirkendall voids occur. In the laminated structure of the copper plating film obtained by the said continuous plating apparatus, supply of the copper ion required for alloying from a lower layer is delayed according to the interface state of a laminated structure. In a state where the supply of copper ions is delayed, copper is diffused to the tin side in a state in which the lead surface layer portion does not supply copper ions from the lower layer, and there is a risk that the voids may increase and expand rapidly. This risk increases as the interface of the laminated structure oxidizes, that is, the longer the downtime of the plating in the plating process. Therefore, the oxidation of the laminated structure interface is suppressed by controlling the stopping time of the plating within a predetermined time by carrying the conveyance speed of the film at a constant speed or more, thereby suppressing the peeling of the tin plating film on the lead surface.

That is, when the conveyance speed of a film is less than 80 m / h, even if the electrical supply part is made small, plating stop time will become about 30 second or more, and the risk of the said peeling becomes high. On the other hand, when the conveyance speed of a film exceeds 300 m / h, the risk which a wound etc. generate | occur | produce in a board | substrate arises. Moreover, it is preferable to make the conveyance speed of a film 100 m / h or more remove the peeling of the tin plating film on the lead surface.

The positive electrode used in the continuous plating apparatus is not particularly limited, and a soluble or insoluble positive electrode can be used. Among these, by using an insoluble positive electrode, it can be carried out under electroplating conditions having a more preferable effect. In this case, the average cathode current density of all the plating baths is set to 1.5 to 3.0 A / dm ² , and the conveyance speed of the film is controlled while controlling the ratio of the maximum value to the minimum value of the cathode current density in each plating bath to 1 to 3. Is preferably adjusted to 100 to 300 m / h. In addition, insoluble anodes are generally used to prevent the problem of sludge, etc., generated on the surface of phosphate-containing copper balls, which are a problem in soluble anodes in copper plating, being mixed in the plating solution and deteriorating the quality of the plating appearance. Although used for the purpose of manufacturing a metal-coated polyimide substrate, it is possible to optimize the plating current density condition and the substrate conveyance speed by using an insoluble anode from the viewpoint of suppressing the difference in residual stress, bendability in the plating film, and the like. This is because the uniformity of the surface potential of the insoluble anode and the uniformity of the distance between the electrodes are exerted to effect the uniformity of current density compared to the soluble anode.

The soluble anode is not particularly limited, and commercially available anodes containing the elements constituting the metal conductor to be formed are used. However, in the case of producing a copper conductor, one filled with a phosphorus-containing copper ball in a titanium box is used. .

The insoluble anode is not particularly limited, and a titanium-based surface or a thin film of an oxide thereof is formed on the surface of titanium, and the insoluble anode is, for example, preferably having a structure in which iridium oxide is coated on the surface of the titanium mesh.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples. In addition, the evaluation method at the time of using the surface resistance of a metal film using a Example and a comparative example and a metal-coated polyimide board | substrate as COF is as follows.

(1) Measurement of the surface resistance of the metal film: It carried out by the four probe method based on JISKK7194.

(2) Evaluation in the case of using a metal-coated polyimide substrate as a COF: Using a manufactured metal-coated polyimide substrate, a lead pattern having an inner lead portion of 20 mu m pitch and an outer lead portion of 35 mu m pitch by a subtractive method Was formed, and a tin film having a thickness of 0.6 mu m was formed on the lead surface by the electroless plating method. Then, for the purpose of suppressing whisker generation in the tin-plated film, heat treatment was performed at 120 ° C. for 60 minutes, and a solder resist layer having a thickness of 10 μm was formed on a desired portion, which was then thermally cured. Heat treatment was performed at 120 ° C. for 2 hours. In order to bond the internal lead part and the pad part of the IC chip after the heat treatment, the bonding part was thermocompressed at 420 ° C. for 1 second, and a thermosetting resin was further applied to the IC chip and its periphery, and then heat-treated at 150 ° C. for 3 hours. The IC chip was resin sealed. Thereafter, the bonding portion was thermocompression-bonded at 200 ° C. for 5 seconds in order to ACF bond the external lead portion and the liquid crystal panel ITO electrode.

After performing the above process, the joint part of the internal lead part and the external lead part was observed, and the incidence rate of defects, such as peeling by a position difference, was observed.

In addition, the index which shows the peelability of tin plating used the result evaluated by performing an acceleration test. That is, a tin plated film having a thickness of 0.6 µm was formed on the surface of the lead using an electroless plating solution Tinposit LT-34 manufactured by Rohm and Haas, and then treated at 160 ° C. for 24 hours to adhere the cellophane tape to the surface of the lead. After sticking, the tape was peeled off and the presence or absence of the peeling of a tin plating film was confirmed by the 200 times metal microscope.

In addition, the continuous plating apparatus used by the Example and the comparative example is as follows.

1 shows an example of a schematic structure of the continuous plating apparatus. In FIG. 1, the continuous plating apparatus has a positive electrode 5 by having a conveying roller 4 for conveying the film 2 inside the plating bath 1 and a stainless steel electric supply roller 3 for conveying the film 2 and supplying power to the metal film and the plated film. It is an example in which 17 tanks of the provided plating tank 1 were arranged in the conveyance direction.

On the other hand, in Examples and Comparative Examples, each plating bath is 3000 mm in the plating stage, that is, the plating liquid is immersed in the plating liquid, and the distance in which the substrate is conveyed in addition to the plating liquid in order to supply electric power to the plating surface between the plating tanks is 700 mm. In addition, the number of plating tanks used was optimized by each condition, and it was set as the number of tanks required. In addition, a current shielding plate having various shapes was provided between the anode, the metal film, and the plated film. The copper plating bath used what added predetermined amount of organic additives for the purpose of ensuring the smoothness of 180 g / L of sulfuric acid, 80 g / L of copper sulfate, 50 mg / L of chlorine ions, and a copper plating film.

Example 1

First, by a magnetron sputtering apparatus performed in a vacuum atmosphere, using a Kapton 150 EN (manufactured by Toray Dupont) as a polyimide film in a chamber kept at a vacuum degree of 0.01 to 0.1 Pa at 150 ° C. for 1 minute. Heat treatment was performed. Subsequently, a nickel chromium alloy layer having a thickness of 20 nm and a copper layer having a thickness of 300 nm were formed on the surface of the polyimide film using a nickel chromium alloy target containing 20 wt% of chromium and a copper target. The surface resistance of the formed metal film was 0.1 ohms / square.

Then, using the manufactured sputtering polyimide film, the metal plating polyimide board | substrate which laminated | stacked the copper plating layer on the copper film and formed the copper conductor by the said continuous plating apparatus (number of plating tanks: 17 sets) was obtained. . Here, as a positive electrode of the said continuous plating apparatus, the soluble positive electrode which filled the titanium box with the phosphorus containing copper ball and back-coated the polypropylene around the box was used. In addition, the average current density of the entire plating bath (hereinafter, also referred to as 'total average current density') 1.0 A / dm ² , and the ratio of the maximum value to the minimum value of the cathode current density in each plating bath are controlled to 5, The copper conductor which consists of a plating film of thickness 8micrometer was formed, adjusting the conveyance speed of a film to 80 m / h.

Then, using the obtained metal-coated polyimide substrate, according to the evaluation method at the time of using as a COF of the said metal-coated polyimide board | substrate, the position difference defect rate of a COF junction part, the lead disconnection occurrence rate, and the tin plating peeling incidence rate were observed, The results are shown in Table 1.

Example 2

The metal-coated polyimide was prepared using the metal-coated polyimide substrate obtained in the same manner as in Example 1 except that the ratio of the maximum value to the minimum value of the cathode current density in each plating bath was controlled to 3. According to the evaluation when the substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1.

Example 3

The number of plating tanks of the continuous plating apparatus was set to 12, the total average current density was controlled to 1.5 A / dm ² , and the ratio of the maximum value to the minimum value of the cathode current density in each plating tank was controlled to 3. Except for using the metal-coated polyimide substrate obtained under the same conditions as in Example 1, according to the 'evaluation when the metal-coated polyimide substrate is used as the COF', the incidence of defective position difference between the COF junctions and lead disconnection The incidence rate and the tin plating peeling incidence rate were observed, and the results are shown in Table 1.

Example 4

The number of plating tanks of the continuous plating apparatus is 6, and the total average current density is 3.0 A / dm.²The difference in the positions of the COF junctions according to the 'evaluation when the metal-coated polyimide substrate is used as the COF' using the metal-coated polyimide substrate obtained under the same conditions as in Example 1, except that the control was performed at Defective incidence, lead breakage incidence and tin plating peeling incidence were observed, and the results are shown in Table 1.

Example 5

The number of plating tanks of the continuous plating apparatus was set to 15 tanks, the point using an insoluble anode, the total average current density was controlled to 1.5 A / dm ^2, and the ratio of the maximum value to the minimum value of the cathode current density in each plating tank. The metal-coated polyimide substrate was obtained using the metal-coated polyimide substrate obtained by the same conditions as in Example 1, except that 3 was controlled to 3 and the conveyance speed of the film was adjusted to 100 m / h. By the evaluation method when used as COF, the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling were observed in the COF junction, and the results are shown in Table 1. In addition, the insoluble anode was coated with iridium oxide on the titanium mesh surface, and was installed so as to face the metal film and the plating film in the plating bath.

Example 6

The number of plating tanks of the continuous plating apparatus was set to 23, the ratio using the insoluble anode, the total average current density was controlled to 1.5 A / dm ^2, and the ratio of the maximum value to the minimum value of the cathode current density in each plating tank. Using the metal-coated polyimide substrate obtained under the same conditions as in Example 1, except that 2 was controlled to 2 and the conveyance speed of the film was adjusted to 150 m / h. According to the evaluation when the substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1. In addition, the insoluble anode was coated with iridium oxide on the titanium mesh surface, and was installed so as to face the metal film and the plating film in the plating bath.

Example 7

The number of plating tanks of the continuous plating apparatus is 8 sets, the point using an insoluble anode, the total average current density is controlled at 3.0 A / dm ^2, and the ratio of the maximum value to the minimum value of the cathode current density in each plating bath. Using the metal-coated polyimide substrate obtained in the same manner as in Example 1, except that the control was controlled to 3 and the conveyance speed of the film was adjusted to 100 m / h. According to the evaluation when the substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1. In addition, the insoluble anode was coated with iridium oxide on the titanium mesh surface, and was installed so as to face the metal film and the plating film in the plating bath.

Example 8

By using a metal-coated polyimide substrate obtained under the same conditions as in Example 1, except that a copper layer having a thickness of 10 nm was formed by sputtering, and the surface resistance of the metal film was 1.0? / Sq. According to the evaluation when the coated polyimide substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1 below.

Example 9

A copper layer having a thickness of 10 nm was formed by sputtering, the surface resistance of the metal film was 1.0 Ω / □, the number of plating baths of the continuous plating apparatus was 6 sets, and the total average current density was 3.0 A / dm ² . Except for the controlled point, the position difference of the COF junction was poor according to the above-mentioned 'Evaluation when using the metal-coated polyimide substrate as COF', using the metal-coated polyimide substrate obtained by the same conditions as in Example 1. The incidence rate, the lead breakage incidence rate, and the tin plating peeling incidence rate were observed, and the results are shown in Table 1.

Example 10

A copper layer having a thickness of 10 nm was formed by sputtering, the surface resistance of the metal film was 1.0 Ω / □, the number of plating baths of the continuous plating apparatus was set to 15 tanks, and the total average current density was controlled to 1.5 A / dm ² . Example 1 and conditions except that one point, the ratio of the maximum value to the minimum value of the cathode current density in each plating tank was controlled to 3, and the conveyance speed of the film was adjusted to 100 m / h. Using the metal-coated polyimide substrate obtained in the same manner, according to the 'evaluation when the metal-coated polyimide substrate is used as COF', the incidence of defective position difference, incidence of lead breakage, and induction of tin plating peeling were observed The results are shown in Table 1. In addition, the insoluble anode was coated with iridium oxide on the titanium mesh surface, and was installed so as to face the metal film and the plating film in the plating bath.

Example 11

A copper layer having a thickness of 10 nm was formed by sputtering, the surface resistance of the metal film was 1.0 Ω / □, the number of plating baths of the continuous plating apparatus was 8 sets, the point using an insoluble anode, and the total average current density was 3.0. Except that the point controlled by A / dm ² , the ratio of the maximum value to the minimum value of the cathode current density in each plating bath were controlled to 3, and the conveyance speed of the film was adjusted to 100 m / h. Using the metal-coated polyimide substrate obtained under the same conditions as in Example 1, according to the above-mentioned 'evaluation when the metal-coated polyimide substrate is used as COF', the incidence of defects in position difference, lead breakage occurrence rate and tin The incidence of plating peeling was observed, and the results are shown in Table 1. In addition, the insoluble anode was coated with iridium oxide on the titanium mesh surface, and was installed so as to face the metal film and the plating film in the plating bath.

Comparative Example 1

By using a metal-coated polyimide substrate obtained under the same conditions as in Example 1, except that a copper layer having a thickness of 1000 nm was formed by sputtering, and the surface resistance of the metal film was 0.09 Ω / square. According to the evaluation when the coated polyimide substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1 below.

Comparative Example 2

By using a metal-coated polyimide substrate obtained in the same manner as in Example 1 except that a copper layer having a thickness of 5 nm was formed by sputtering, and the surface resistance of the metal film was 1.1? According to the evaluation when the coated polyimide substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1 below.

Comparative Example 3

Using a metal-coated polyimide substrate obtained in the same manner as in Example 1, except that the number of plating tanks of the continuous plating apparatus was 20, and the total average current density was controlled to 0.9 A / dm ² . According to the 'evaluation in the case of using the metal-coated polyimide substrate as COF', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1.

[Comparative Example 4]

The number of plating tanks of the continuous plating apparatus is 5, and the total average current density is 3.5 A / dm.²Except for the control point, the difference in the positions of the COF junctions according to the above-mentioned 'Evaluation when using the metal-coated polyimide substrate as COF' using the metal-coated polyimide substrate obtained by the same conditions as in Example 1 Defective incidence, lead breakage incidence and tin plating peeling incidence were observed, and the results are shown in Table 1.

[Comparative Example 5]

Using the metal-coated polyimide substrate obtained in the same manner as in Example 1, except that the ratio of the maximum value to the minimum value of the cathode current density in each plating bath was controlled to 6, According to the evaluation when the mid substrate is used as the COF ', the incidence of defective position difference, incidence of lead breakage, and incidence of tin plating peeling of the COF junction were observed, and the results are shown in Table 1.

Comparative Example 6

Using the metal-coated polyimide substrate obtained in the same manner as in Example 1, except that the number of plating tides of the continuous plating apparatus was 16 trillion and the conveyance speed of the film was adjusted to 70 m / h, According to the evaluation when the metal-coated polyimide substrate is used as the COF ', the incidence of poor positional differences, the occurrence of lead breakage, and the incidence of tin-plating peeling of the COF junction were observed, and the results are shown in Table 1 below.

TABLE 1

In Examples 1-11 of Table 1, the surface resistance of the metal film formed in a sputtering process is controlled to 0.1-1.0 ohms / square, and the cathode current density in an electroplating process makes the average cathode current density of all the plating baths 1-1. By controlling the ratio of 3 A / dm ² and the maximum value to the minimum value of the cathode current density in each plating bath to 1 to 5, and controlling the conveying speed of the film to 80 to 300 m / h, the present invention Since the metal-coated polyimide substrate was manufactured according to the manufacturing method of the above, it can be judged that the position difference defective rate of the COF junction part, the lead disconnection generation rate, and the plating peeling generation rate of tin are all less than 0.01%, and are favorable.

On the other hand, in Comparative Examples 1 to 6, one of the surface resistance of the metal film, the average cathode current density of the entire plating bath, the ratio of the maximum value to the minimum value of the cathode current density in each plating bath, or the conveyance speed of the film is one of these conditions. In this case, one of the incidence of defective position difference, incidence of breakage of the lead, and incidence of tin plating peeling of the COF junction is 0.01% or more, and the metal-coated polyimide substrate obtained under these conditions is in terms of productivity, yield, and reliability. It is not good enough.

As described above, the metal-coated polyimide substrate obtained by the production method of the present invention is suitably used for a narrow pitch COF represented by an inner lead 20 μm pitch and an outer lead 35 μm pitch. Therefore, in the assembly process of the IC and the liquid crystal panel, problems such as peeling, problems such as lead disconnection, and tin plating peeling, etc., are sufficiently suppressed in the process of assembling the internal lead portion and the IC chip and the external lead portion and the liquid crystal panel. can do. Moreover, since the improvement of plating productivity can also be anticipated in the manufacturing method of this invention, productivity and economy are also effective. The metal-coated polyimide substrate obtained by the present invention can be suitably used for flexible substrates such as PWB, FPC, TAB, etc. other than COF.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of schematic structure of the continuous plating apparatus used in the manufacturing method of the metal clad polyimide board | substrate of this invention.

<Description of Major Codes in Drawings>

1: plating bath

2: film

3: electricity supply roller

4: conveying roller

5: anode

Claims (5)

A sputtering step of forming a metal film on the surface of the polyimide film; And a roller for conveying the film and supplying electricity to the metal film, and an anode facing the metal film, on the metal film of the produced polyimide film, using a continuous plating device composed of at least two plating baths, An electroplating step of forming a conductor; a method for producing a metal-coated polyimide substrate, comprising the following conditions (1) and (2): (1) the surface resistance of the metal film formed in said sputtering process is controlled to 0.1-1.0 ohm / square; (2) In the electroplating step, the current density of the cathode is set to the average cathode current density of all the plating baths is 1 to 3 A / dm ² , and the ratio of the maximum value to the minimum value of the cathode current density in each plating bath is set. 1 to 5, and at the same time the conveying speed of the film is adjusted to 80 ~ 300 m / h. The method of manufacturing a metal-coated polyimide substrate according to claim 1, wherein the anode is an insoluble anode. The current density of the cathode, the average cathode current density of the entire plating bath is 1.5 to 3 A / dm.² And the ratio of the maximum value to the minimum value of the cathode current density in each plating bath is 1 to 3, and the conveyance speed of the film is 100 to 300 m / h. The method for producing a metal-coated polyimide substrate according to any one of claims 1 to 3, wherein the metal film is made of a metal seed layer and a copper layer formed on the surface thereof. The method for producing a metal-coated polyimide substrate according to any one of claims 1 to 4, wherein the metal conductor is copper.

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