JP4865381B2 - Film metal laminate, method for producing the same, circuit board using the film metal laminate, and method for producing the circuit board - Google Patents

Description

  The present invention relates to a film metal laminate having excellent adhesion between the film and the metal layer and having good bending resistance, a method for producing the same, a circuit board using the film metal laminate, and a method for producing the circuit board. About.

  The flexible circuit board used a film metal laminate in which a metal layer (underlying metal (Ni etc.) layer / upper metal (Cu etc.) conductive layer) was formed on a polyimide resin film having excellent heat resistance. Since this film has high water absorption, there is a problem that the dimensional accuracy is lowered in a humid atmosphere.

  Therefore, as an alternative to the film, a liquid crystal polyester film having excellent heat resistance and low water absorption has been attracting attention. However, this film has poor adhesion to a metal layer (for example, Ni layer / Cu layer), and adhesion. When heat treatment for improving the properties was performed (Patent Document 1), there was a problem that the hardness of the Ni underlayer increased and the flex resistance of the film metal laminate decreased.

JP 2004-307980 A

  In view of such a situation, the present inventors first examined the adhesiveness between the liquid crystal polyester film and the metal layer, and found that Ni is superior in adhesiveness to the film than Cu as the base metal layer. Next, we examined the prevention of the increase in hardness of the Ni underlayer after heat treatment for improving adhesion, and by adding a predetermined amount of P to Ni in the underlayer, the Ni underlayer does not increase in hardness after the heat treatment. The obtained film metal laminate was found to have good adhesion and bending resistance, and further studies were made to complete the present invention.

  The present invention relates to a film metal laminate having excellent adhesion between the film and the metal layer and having good bending resistance, a method for producing the same, a circuit board using the film metal laminate, and a method for producing the circuit board. The purpose is to provide.

The invention according to claim 1 is a film metal laminate in which a base metal layer is formed on a flexible polymer film and an upper metal conductive layer is formed on the base metal layer, and the base metal layer contains 10% by mass of phosphorus. comprises a nickel alloy containing more,
The average thickness of the base metal layer is 0.03 μm or more and 0.3 μm or less,
The sheet metal layer has a sheet resistivity of 10 Ω / □ or more and 1 KΩ / □ or less, and the flexible polymer film is made of a thermoplastic polymer capable of forming an optically anisotropic melt phase. The film metal laminate is characterized by the above.

According to a second aspect of the present invention, there is provided a film metal laminate manufacturing method in which a base metal layer is formed on a flexible polymer film, and an upper metal conductive layer is formed on the base metal layer. The upper metal conductive layer is made of copper, and heat treatment is performed at a temperature of 150 ° C. to 310 ° C. after forming the base metal layer or after forming the upper metal conductive layer. The method for producing a film metal laminate.

According to a third aspect of the present invention, the upper conductive metal layer of the film metal laminate manufactured by the method of the first or second aspect is selectively removed to form a circuit, and the underlying metal layer is used as a resistor. A circuit board characterized by the above.

  In the film metal laminate of the present invention, a base metal layer of Ni alloy containing 10 mass% or more of P is formed on a flexible polymer film, and an upper metal conductive layer such as Cu is formed thereon. However, since the Ni-P alloy has excellent adhesion to the film, and the base metal layer does not increase in hardness during heat treatment for improving adhesion, the Ni-P alloy has good adhesion and bending resistance.

  By regulating the thickness of the base metal layer to 0.03 μm to 0.3 μm, the adhesion between the polymer film and the metal layer and the bending resistance are improved.

  By specifying the area resistivity of the base metal layer to be 10 Ω / □ or more and 1 KΩ / □ or less, particularly excellent adhesion and bending resistance can be obtained.

  If a thermoplastic polymer capable of forming an optically anisotropic melt phase is used for the polymer film, the thermoplastic polymer has high heat resistance, so that the film may deteriorate during heat treatment for improving adhesion. And a high-quality film metal laminate can be obtained.

  Since the manufacturing method of the film metal laminated body of Claim 5 performs heat processing at the temperature of 150 to 310 degreeC after base metal layer formation or upper metal conductive layer formation, the film metal laminated body obtained is a film, Excellent adhesion to the metal layer.

  The film metal laminate manufacturing method according to claim 6 is manufactured in a roll state since the residual stress of the metal layer can be reduced because the thickness of the metal layer when the heat treatment is first performed is reduced to 2 microns or less. In particular, the swelling of the plating and the peeling of the film and the metal can be prevented.

  Since the manufacturing method of the film metal laminate of the invention according to claim 7 increases the thickness of the upper conductive layer by electroplating after the heat treatment and again performs the heat treatment at 150 to 310 ° C., the residual stress of the electroplated layer can be reduced. The warpage of the film after etching can be reduced.

  In the circuit board according to claim 8, the upper conductive metal layer of the film metal laminate is selectively removed to form a circuit, and the base metal layer is used as a resistor. Low cost and compact.

  In the circuit board manufacturing method according to the ninth aspect of the invention, the upper metal conductive layer (copper) is removed by etching with an alkaline solution containing ammonia and copper, and the underlying metal layer is removed by etching using a solution containing copper chloride. The circuit board can be easily manufactured with high accuracy.

  The film metal laminate according to claim 1 is a post-heat treatment for improving adhesion by forming a Ni alloy layer containing 10% by mass or more of P as a base metal layer on a flexible polymer film. Since the increase in the hardness of the Ni underlayer is suppressed, the adhesion and bending resistance are excellent.

  In the present invention, the reason why P is added to Ni is that when P is added to Ni, an amorphous phase appears in a part of the precipitated phase, and the residual stress of the base metal layer is reduced. This is because the stress balance is improved, and as a result, an increase in the hardness of the underlying metal layer during heat treatment for improving adhesion is prevented.

  In the present invention, the reason why the content of P is specified to be 10% by mass or more is that when the content is less than 10% by mass, the amorphous phase does not sufficiently appear and the effect cannot be obtained. A particularly desirable P content is 11% by mass or more. Further, since the effect is saturated even if the content of P is increased, the upper limit is preferably set to 17% by mass.

  If the thickness (average thickness) of the base metal layer is too thin, there will be holes in the base metal layer and the adhesion to the film will decrease. If it is too thick, the flexibility of the film metal laminate is lowered. Therefore, the average thickness of the base metal layer is preferably 0.03 to 0.3 μm. When the thickness of the base metal layer is 10 Ω / □ to 1000 Ω / □ in terms of sheet resistivity, the adhesion and bending resistance of the film metal laminate are most improved.

  If the upper metal conductive layer such as copper is directly electroplated on the base metal layer, the current density cannot be increased, and thus a plating layer with good adhesion cannot be obtained. Therefore, a method of electroplating copper thickly after thinly (less than 2 μm) electroless plating of copper is recommended.

The adhesion strength between the polymer film and the underlying metal layer can be improved by heat treatment.
When winding the film metal laminate after plating into a roll, it is possible to prevent the metal layer from peeling off during winding by applying a heat treatment after electroless plating of the underlying metal layer or upper metal conductive layer. it can. In this case, the total thickness of the base metal layer and the upper metal conductive layer (such as copper) is preferably 2 μm or less in consideration of productivity. More preferably, 1 μm or less is suitable. If the metal layer is thin, it is possible to prevent plating swelling until the heat treatment step and peeling of the metal layer and the film. The upper metal conductive layer may be electroplated to a predetermined thickness as necessary after the heat treatment. Note that if the heat treatment is performed again after the electroplating in order to release the residual stress due to the plating, the warpage of the film can be reduced in the etching during circuit formation.

  If the heat treatment temperature for improving the adhesion is less than 150 ° C., the adhesion is not sufficiently improved, and if it exceeds 310 ° C., the amorphous phase may crystallize and the flex resistance of the film metal laminate may be lowered. Therefore, 150 ° C. to 310 ° C., particularly 200 ° C. to 250 ° C. is desirable.

  In the present invention, a polyimide film, a polyester film, or the like can be applied to the flexible polymer film. Among them, polyester naphthalate (PEN) is preferable because it has higher heat resistance than polyester terephthalate (PET).

  In particular, a thermoplastic polymer capable of forming an optically anisotropic melt phase, that is, a so-called thermoplastic liquid crystal polymer is optimal because it has a high heat resistance of around 300 ° C. and sufficiently withstands the heat treatment temperature. Although the heat resistance is slightly inferior, polyether ether ketone (PEEK) polymer is also suitable as the thermoplastic resin. All of the polymer films have low water absorption and can be used for wet plating.

  In the present invention, if the film surface is roughened, the adhesion between the base metal layer and the film is improved. The degree of roughening is desirably such that the maximum roughness Rz is 0.3 or more and 2.0 or less, and the average roughness Ra is 0.1 or more and 0.7 or less.

  As a method of roughening the film surface, a method of immersing the film in an etching solution is simple and desirable. As the etching solution, a strong alkaline solution, a permanganate solution, a chromate solution, or the like is used. In the case of a thermoplastic liquid crystal polymer film, it is effective to use a strong alkaline solution. A mechanical polishing method such as sandblasting is effective for a film that is difficult to etch.

  When the film metal laminate of the present invention is used as a circuit board, the conductive circuit exposes a metal layer in an area to be etched (removed) using a photoresist, and sprays an etching solution to remove metal in an unnecessary area. The layer is formed by etching away. As the photoresist, it is desirable to use a rubber-based photoresist that does not dissolve in an alkaline solution.

  Since the metal layer of the film metal laminate of the present invention is composed of a base metal layer and an upper metal conductive layer, the conductive circuit is usually formed by removing both of them by etching. In this case, the etching solution is preferably a cupric chloride solution. In particular, when etching a Ni-P alloy having a high P concentration, the iron chloride solution used in a lead frame or the like is not sufficiently etched. By appropriately adding hydrochloric acid to the cupric chloride solution, the etching rate is increased, side etching is reduced, and a circuit width of a predetermined dimension can be formed with high accuracy.

  For the metal layer, the upper metal conductive layer (copper) is first selectively removed using a ferric chloride solution, and then the underlying metal layer (Ni-P alloy layer) is removed using cupric chloride. it can.

  The film metal laminate of the present invention can be used as a resistor because the base metal layer of the Ni-P alloy has a high resistance value. In that case, only the upper metal conductive layer is selectively removed by etching, and then the underlying metal layer is selectively removed by etching, leaving a portion serving as a resistance. According to this method, a film metal laminate in which a resistor is embedded (embedded) in a circuit board can be obtained. In this case, a chip resistor or the like is not necessary, and the substrate size can be reduced.

  For etching only the upper metal conductive layer, a ferric chloride solution may be used. However, since an alkaline solution containing ammonia and copper does not dissolve the underlying metal layer relatively, a good resistance value can be obtained, and the side Etching with very little dimensional accuracy and high dimensional accuracy is possible. Examples of the alkali solution include ammonia copper complex salts (as copper concentration) of 135 to 145 g / L, ammonium chloride 100 to 250 g / L, ammonia 10 to 150 g / L, and pH 8.5 (pH adjustment with ammonia).

  The film metal laminate of the present invention can be used as a single-sided flexible substrate by forming a metal layer only on one side, or as a double-sided flexible substrate by forming a metal layer on both sides. Further, a plurality of laminated bodies in which a metal layer is formed only on one side can be overlapped and used as a multilayer substrate.

  Using a Vecstar (thickness 50 μm) manufactured by Kuraray Co., Ltd. as a polymer film, this film was immersed in an alkaline solution to form irregularities (surface roughness Rz = 0.8, Ra = 0.2) on the surface, and then conditioner treatment The film metal laminate was manufactured by applying each step of Ni-P alloy electroless plating, Cu electroless plating, heat treatment, and Cu electroplating in this order. Washing and drying were performed for each step. Metal layers (underlying metal layer + upper metal conductive layer) were formed on both sides of the film.

  Conditioner treatment was performed using an OPC-350 conditioner manufactured by Okuno Seiyaku Co., Ltd., and an OPC-80 catalyst manufactured by Okuno Seiyaku Co., Ltd. was used as a catalyst-providing solution containing palladium, and an OPC-500 accelerator was used as an activator.

  A top Nicolon NAC bath manufactured by Okuno Pharmaceutical Co., Ltd. was used for electroless plating of Ni-10 mass% to 14 mass% P alloy. The pH of the plating bath was adjusted to 3.5 to 5.5 using sulfuric acid or aqueous ammonia, and the bath temperature was adjusted to 70 ° C to 85 ° C. The plating thickness was variously changed in the range of 0.02 μm to 0.65 μm depending on the immersion time in the plating bath. The P concentration of the Ni—P alloy was varied in the range of 10% by mass to 18% by mass by adjusting the pH and temperature of the plating bath.

The following in-house bath was used for electroless plating with P concentration exceeding 14% and not exceeding 20%. The P concentration was varied by adjusting the pH and temperature of the plating bath, the concentration ratio of Ni and hypophosphorous acid, and the lead ion concentration.
In-house bath: nickel sulfate 20-30 g / L, sodium hypophosphite 10-80 g / L, sodium citrate 15 g / L, glycine 20 g / L, lead nitrate 2 ppm-20 ppm, pH 3.0-5.5 (dilute sulfuric acid And adjusted with aqueous ammonia), bath temperature 50 ° C. to 85 ° C.

Here, the sheet resistivity was measured by applying a probe using a low resistivity meter as the electrical characteristics of the underlying metal layer.

  The electroless plating of Cu is activated by immersing the surface of the base metal layer (Ni-P alloy layer) in a catalyst containing 0.1 g / L of palladium chloride and 10 mL / L of hydrochloric acid, followed by Rohm and Haas. This was carried out using a copper plating bath Cuposit 880 made by the manufacturer. The entire thickness of the base metal layer was covered with a plating thickness of 0.5 μm.

  The heat treatment for improving the adhesion between the film and the base metal layer was performed by heating the sample in a nitrogen atmosphere at 220 ° C. for 1 hour.

  Thereafter, Cu was electroplated using a copper sulfate bath so that the thickness of the metal layer (underlying metal layer + upper metal conductive layer) was 18 μm.

  About each obtained film metal laminated body, adhesiveness and bending resistance were investigated.

  The adhesion was evaluated by measuring the peeling strength (peel strength) of the metal layer based on a mechanical performance test (90 ° direction peeling method) described in JIS C5016.

  The bending resistance is described in JIS C6471, based on the MIT folding resistance test method without using a cover material, by forming a circuit by etching on the metal layers on both sides of the film so that line / space = 1 mm / 1 mm. In accordance with the test method, the load is 500 gf, the bending speed is 175 rpm, the bending angle is ± 135 °, the bending radius is 0.8 mm, and the number of times of bending until breakage is obtained and evaluated in an environment of an air temperature of 25 ° C. and a humidity of 50%. did.

The P concentration of the base metal layer (Ni—P alloy) was determined by measuring the mass of Ni and P using a fluorescent X-ray analyzer (SEA5120A manufactured by Seiko Precision Co., Ltd.). The thickness of the base metal layer was obtained by converting the mass measurement value into a thickness. That is, the value obtained by dividing the measured adhesion weight per unit area (total of P and Ni) by the density (approximately Ni density 8.90) was taken as the film thickness of the underlying metal layer.
The thickness of the upper metal conductive layer (Cu) was measured using a fluorescent X-ray film thickness meter SFT-3200.

  The electrical characteristics (area resistivity) of the base metal layer (Ni-P alloy) were measured with a four-short probe using a low resistivity meter (Lorestar GP manufactured by Mitsubishi Chemical Corporation). The sheet resistivity can also be measured by a four-terminal method by cutting out the pattern of the underlying metal layer by etching.

[Comparative Example 1]
A film metal laminate was produced in the same manner as in Example 1 except that the P concentration of the Ni—P alloy of the base metal layer was less than 10% by mass (hereinafter abbreviated as “%” where appropriate). We conducted a survey.
The base metal layer having a P concentration of 2% to 4% uses Chemical Nickel EXC manufactured by Okuno Pharmaceutical Co., Ltd., and the base metal layer having a P concentration of 4% to 6% uses Melplate NI-2250 manufactured by Meltex. In addition, the base metal layer having a P concentration of 6% to 8% is Melplate NI-871 manufactured by Meltex, and the base metal layer having a P concentration of 8% to 10% is Melplate NI-6575 manufactured by Meltex. Were used for electroless plating.
The test results of Example 1 and Comparative Example 1 are shown in Table 1. Table 1 also shows the sheet resistivity.

As is apparent from Table 1, all of the present invention examples (Example 1) have excellent peelability when the peel strength is 0.6 kN / m or more, and have high bending resistance when the number of folding times to break is 150 times or more. Also excellent. Especially when the plating thickness of the base metal layer was 0.03 μm or more (No. 1 to 15, 17, 19), the peel strength was as high as 0.8 kN / m. Furthermore, when the P concentration was 11 to 17% and the thickness of the base metal layer was 0.03 to 0.30 μm (Nos. 3 to 12), the number of times of bending until breakage was 200 times or more, indicating good bending resistance. . The sheet resistivity at that time was in the range of 10 Ω / □ or more and 1 kΩ / □.
On the other hand, since Comparative Examples 21-31 had a P concentration of less than 10%, the number of bending until breakage was 120 times or less, and the bending resistance was poor.

  A BIAC BC 50 μm thickness made by Japan Gore-Tex Co., Ltd. was used for the polymer film, the P concentration of the base metal layer was 11.3%, the plating thickness was 0.20 μm, and the heat treatment temperature was 150 ° C. to 310 ° C. A film metal laminate was produced in the same manner as in Example 1, and the same investigation as in Example 1 was performed.

[Comparative Example 2]
A film metal laminate was produced by the same method as in Example 2 except that the heat treatment temperature was less than 150 ° C. or more than 310 ° C., and the same investigation as in Example 2 was performed.
The test results of Example 2 and Comparative Example 2 are shown in Table 2.

  As is clear from Table 2, all of the inventive examples (Example 2) have a peel strength of 0.6 kN / m or more, and the number of times of bending until breakage is 100 times or more, showing good adhesion and bending resistance. It was. Among these, No. It can be seen that Nos. 34 to 36 have a peel strength of 0.8 kN / m or more, the number of bendings until breakage is 180 or more, and a heat treatment temperature of 200 to 250 ° C. is particularly preferable.

  On the other hand, no. Since the heat treatment temperature was low for Nos. 41 to 45, sufficient peel strength could not be obtained. In Comparative Examples 46 and 47, the amorphous phase disappeared due to the high heat treatment temperature, and sufficient bending resistance could not be obtained.

  The plating solution is not limited to that used in Examples 1 and 2, and a commercially available plating bath may be used as appropriate, or an in-house bath mixed with a reagent may be used. Further, the polymer film is not limited to the thermoplastic liquid crystal polymer, and resins such as PET, PEN, and PEEK may be used.

As a polymer film, a roll product (width: 625 mm) manufactured by Kuraray Co., Ltd. (width: 625 mm) was used, and in the same manner as in the example, this film was immersed in an alkaline solution to form irregularities on the surface, and nickel plating was performed. The P concentration of the base metal layer was 11.3%, and immediately after nickel plating, copper was formed as a part of the upper metal layer by electroless plating to a predetermined thickness. In this example, the roll film was immersed in a plating solution in order, and after the electroless copper plating, the water was blown off with warm air, and then the film was wound on a roll. The time of immersion in nickel plating and the time of immersion in electroless copper plating were changed, and the thickness of the metal layer including the base metal layer and the electroless copper plating layer as a part of the upper metal conductive layer was changed.
Thereafter, the surface of the roll film was observed, and the number of plating blisters and whether the metal layer was peeled off were observed. Table 3 shows the thickness and swelling of the metal layer before heat treatment and the presence or absence of peeling.

As is apparent from Table 3, if the metal layer thickness is 0.1 μm or more and 2.0 μm or less (No. 48 to 59 in Example 3), there is little swelling and no peeling occurs. Preferably, no blistering occurred at 0.1 μm or more and 1.0 μm. On the other hand, in Comparative Example 3, since the metal layer thickness was 0.1 μm or less (No. 60 to 62), swelling and peeling did not occur, but the resistance value was large and electroplating could not be performed in the subsequent process, and the upper metal The remainder of the conductive layer could not be formed. When the metal layer thickness was as thick as 2.0 μm or more (No. 63 to 68), swelling or peeling of the plating occurred.
Until the heat treatment is performed, the adhesion between the film and the metal layer is weak. Therefore, if the metal layer is thick, blisters are generated due to plating stress, and peeling is likely to occur due to the stress during the conveyance of the roll. The thickness of the metal layer before the heat treatment is suitably 0.1 to 2.0 μm.

  As the polymer film, BIAC BC 50μm thickness made by Japan Gore-Tex is used, the P concentration of the base metal layer is 11.3%, the plating thickness is 0.20μm, and electroless copper plating as part of the upper metal conductive layer 0.50 μm was performed. Then, after performing heat processing (heat processing 1) at each temperature of 150-310 degreeC in nitrogen atmosphere, electrolytic copper plating was performed and the remainder of the upper metal conductive layer was formed. After forming the upper metal conductive layer, heat treatment (heat treatment 2) was performed again at each temperature of 150 to 310 ° C. in a nitrogen atmosphere. Under each condition, metal layers were formed on both sides of the film.

  Next, a 200 mm × 200 mm size was cut out, and only one side of the metal layer formed on both sides was removed by etching. Only one side was etched and placed on a flat surface, and the amount of warpage of the film at the four corners was measured. Table 4 shows the amount of warpage after single-sided etching.

  As is apparent from Table 4, in the case where the remaining part of the upper electrode conductive layer was formed and then heat-treated (No. 69 to 75), the residual stress of the metal at the time of electroplating was released, and both were warped. The amount was as small as 10 mm or less.

  On the other hand, as a comparative example, after the remaining portion of the upper electrode conductive layer was formed, heat treatment was not performed (No. 76 to 82), and the one-side etching amount was as large as 20 mm or more.

A circuit board was produced using the film metal laminate produced in Examples 1 and 2, and the same investigation as in Example 1 was performed. The conductive circuit was formed by exposing a metal layer in an unnecessary region using a photoresist and removing the etching solution by spraying. As an etching solution, a solution (40 ° C. to 60 ° C.) obtained by adding 36% hydrochloric acid 50 to 300 mL / L to 50 g to 400 g / L of cupric chloride solution was used. As the photoresist, a rubber-based photoresist (solvent photoresist EPPRA manufactured by Tokyo Ohka Co., Ltd.) was used.
Each of the obtained circuit boards was excellent in adhesion between the film and the metal layer, and also excellent in bending resistance.

Claims (3)

In a film metal laminate in which a base metal layer is formed on a flexible polymer film and an upper metal conductive layer is formed thereon, the base metal layer includes a nickel alloy containing 10 mass% or more of phosphorus. ,
The average thickness of the base metal layer is 0.03 μm or more and 0.3 μm or less,
The thickness of the metal layer combining the base metal layer and the upper metal layer is 0.1 μm or more and 2.0 μm or less,
The area resistivity of the base metal layer is 10Ω / □ or more and 1KΩ / □ or less,
The film metal laminate, wherein the flexible polymer film is made of a thermoplastic polymer capable of forming an optically anisotropic melt phase . In the method for producing a film metal laminate in which a base metal layer is formed on a flexible polymer film and an upper metal conductive layer is formed thereon, the base metal layer contains 10 mass% or more of phosphorus. A film metal, which is an alloy, wherein the upper metal conductive layer is made of copper, and heat treatment is performed at a temperature of 150 ° C. to 310 ° C. after the formation of the base metal layer or at least part of the upper metal conductive layer. A manufacturing method of a layered product. A circuit board, wherein a circuit is formed by selectively removing an upper conductive metal layer of a film metal laminate produced by the method according to claim 1 or 2, and a base metal layer is used as a resistor.