JP4448610B2 - Circuit board manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a circuit board used for electronic equipment, electronic components, and the like.
[0002]
[Prior art]
As a circuit board manufacturing method, for example, using a metal support plate, an insulating layer having a predetermined shape is formed on the metal support plate, and a through-hole exposing the surface of the metal support plate is formed in the insulating layer. Then, in the through hole, metal is deposited by plating to form a conduction path, a conductor layer is formed with a predetermined circuit pattern on the insulating layer, and then the metal support plate is removed by etching. How to do is known.
[0003]
According to such a method, since each layer is formed on the metal support plate, it is possible to prevent a change in the dimensions of each layer during the manufacturing process, and because the handling during the manufacturing process is good, a very thin circuit board is manufactured. can do.
[0004]
More specifically, in a suspension board with circuit, for example, a stainless steel substrate is used as a metal support plate, and an insulating layer and a conductor layer having a predetermined circuit pattern are formed on the stainless steel substrate. Processing the substrate into a predetermined shape is performed by partially etching the substrate.
[0005]
[Problems to be solved by the invention]
However, in the above method, in the step of removing the metal support plate by etching, even the conduction path in contact with the metal support plate is etched, resulting in defects, and good connection reliability in the electrode portion. There is a defect that it cannot be obtained.
[0006]
The present invention has been made in order to solve such a problem, and an object of the present invention is to remove the metal support plate without causing a defect in the conduction path formed on the metal support plate. Another object of the present invention is to provide a circuit board manufacturing method capable of ensuring good connection reliability.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method of manufacturing a circuit board according to the present invention includes a step of forming a resin thin film on a metal support plate, and an insulating layer in which a through hole is formed in the thickness direction on the resin thin film. A step of forming a conduction path by plating in the through hole, a step of removing the metal support plate by etching, and a step of removing the resin thin film by etching.
[0008]
Moreover, in this method, it is preferable that the thickness of the said resin thin film is 1 micrometer or less, and it is preferable that the said resin thin film consists of a polyimide resin or a polyimide resin precursor.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
1 to 6 are process diagrams showing an embodiment of a circuit board manufacturing method of the present invention. Hereinafter, with reference to these FIGS. 1-6, the manufacturing method of the circuit board of this invention is demonstrated. In the method for manufacturing a circuit board according to the present invention, first, a resin thin film 2 is formed on a metal support plate 1 as shown in FIG.
[0010]
The metal support plate 1 is preferably a metal film in order to ensure rigidity during the manufacturing process. From the viewpoint of stiffness (waist strength), low coefficient of linear expansion, ease of etching, and the like, Copper, copper alloy, nickel, 42 alloy, etc. are preferably used. Moreover, especially the thickness of the metal support plate 1 is although it does not restrict | limit, It is preferable that it is 10-100 micrometers. If it is too thin, the stiffness (strength of the waist) will be insufficient, and if it is too thick, it will take time for etching and may cause a reduction in production efficiency.
[0011]
The resin thin film 2 is not particularly limited as long as it has resistance to the etching solution of the metal support plate 1 described later. For example, polyimide resin, polyimide resin precursor such as polyamic acid resin, epoxy resin, wholly aromatic polyester, aramid resin, Resins such as polycarbodiimide are used. The thickness of the resin thin film 2 is preferably 1 μm or less, and more preferably 0.01 to 0.5 μm. When the thickness of the resin thin film 2 exceeds 1 μm, it takes time for etching, which may cause a reduction in manufacturing efficiency. Moreover, there is no lower limit in particular in thickness, However, When it is thinner than 0.01 micrometer, it may become difficult to apply on the metal support plate 1 uniformly.
[0012]
The resin thin film 2 may be formed by, for example, applying a resin solution on the metal support plate 1 and drying it, or by laminating dry films. Preferably, as shown in FIG. 2, a polyimide resin precursor is applied onto the metal support plate 1 to form a polyimide resin precursor layer 2p, and then imidized to form a polyimide resin. The resin thin film 2 is formed. When the resin thin film 2 is formed of a polyimide resin using a polyimide resin precursor layer, the resin thin film 2 can be easily and reliably formed, and the insulating layer 4 described later is formed of a polyimide resin. The base resin (polyamic acid resin) having the same composition as that of the insulating layer 4 can be used.
[0013]
As the polyimide resin precursor, for example, a polyamic acid resin obtained by reacting acid dianhydride and diamine is used.
[0014]
Examples of the acid dianhydride include 3,3 ′, 4,4′-oxydiphthalic dianhydride (ODPA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic acid 2 Anhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) is preferably used. Examples of diamines include p-phenylenediamine (PPD), 1,3-bis (3-aminophenoxy) benzene, bisaminopropyltetramethyldisiloxane (APDS), 4,4′-diaminodiphenyl ether (DDE). ) Is preferably used. The polyamic acid resin is a suitable organic solvent, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, in such a ratio that the acid dianhydride and diamine are substantially equimolar. A polyamic acid resin solution can be obtained by reacting in a polar solvent such as N, N-dimethylformamide under normal temperature and pressure for a predetermined time. Furthermore, you may mix | blend an epoxy resin, bisallyl nadic imide, maleimide etc. with such a polyamic acid resin as needed.
[0015]
In order to form the polyimide resin precursor layer 2p on the metal support plate 1, for example, as shown in FIG. 2A, the polyimide resin precursor is formed on the metal support plate 1 with a certain thickness. After coating by a known method to form the polyimide resin precursor layer 2p, the polyimide resin precursor layer 2p is imidized as shown in FIG. What is necessary is just to form. The imidization may be performed by, for example, finally heating the polyimide resin precursor layer 2p to 300 ° C. or higher.
[0016]
Next, in the method of manufacturing a circuit board according to the present invention, as shown in FIG.
[0017]
As the insulating layer 4, the same resin as described above is used, and the thickness is not particularly limited, but is preferably 5 to 50 μm, for example.
[0018]
The insulating layer 4 may be formed by, for example, applying a resin solution on the resin thin film 2 and drying or by laminating a dry film. The through-hole 3 penetrating the thickness direction of the insulating layer 4 may be formed by a known opening method such as processing, laser processing, or etching so that the surface of the resin thin film 2 is exposed.
[0019]
Preferably, after forming a photosensitive polyimide resin precursor layer 4p on the resin thin film 2 as shown in FIG. 3 (a) using a photosensitive resin, especially a photosensitive polyimide resin precursor, this is used. As shown in FIGS. 3B and 3C, through holes 3 are formed at predetermined positions by exposure and development, and then, as shown in FIG. 3D, a photosensitive polyimide resin precursor is formed. The body layer 4p is preferably imidized to form the insulating layer 4 made of a polyimide resin layer.
[0020]
That is, in this method, as shown in FIG. 3A, first, a photosensitive polyimide resin precursor layer 4 p is formed on the resin thin film 2. The photosensitive polyimide resin precursor is obtained by blending a photosensitive agent with the polyamic acid resin described above. As the photosensitive agent, for example, a 1,4-dihydropyridine derivative is preferably used. -3,5-dimethoxycarbonyl-4- (2-nitrophenyl) -1,4-dihydropyridine is preferably used. Moreover, such a photosensitizer is normally mix | blended in the range of 0.1-1.0 mol with respect to the sum total of acid dianhydride and diamine, ie, 1 mol of polyamic acids.
[0021]
And in order to form the photosensitive polyimide resin precursor layer 4p on the resin thin film 2, for example, after coating the photosensitive polyimide resin precursor with a constant thickness on the resin thin film 2 by a known method The photosensitive polyimide resin precursor may be formed as a dry film with a certain thickness in advance, and this dry film may be laminated on the resin thin film 2.
[0022]
Next, in this method, as shown in FIG. 3 (b), the photosensitive polyimide resin precursor layer 4p is exposed through the photomask 6, and then exposed as necessary as shown in FIG. 3 (c). The portion is heated to a predetermined temperature and then developed to form a through hole 3 penetrating in the thickness direction in the photosensitive polyimide resin precursor layer 4p.
[0023]
The irradiation light for exposure has an exposure wavelength of 350 to 450 nm, more preferably 400 to 450 nm, and an integrated exposure light amount of 100 to 3000 mJ / cm. ² Furthermore, 200 to 1000 mJ / cm ² It is preferable that
[0024]
Further, the exposed portion of the irradiated photosensitive polyimide resin precursor layer 4p is solubilized (positive type) in the next development process by heating at, for example, 130 ° C. or more and less than 150 ° C. By heating at a temperature not lower than 180 ° C. and not higher than 180 ° C., it is insolubilized (negative type) in the next development processing. The development may be performed by a known method such as an immersion method or a spray method using a known developer such as an alkali developer. In this method, it is preferable to form the through-hole 3 with a negative type, and in FIG. 3, it is shown as an aspect of patterning with a negative type. The through hole 3 is a via hole for forming a conduction path 5 for conducting the circuit pattern of the conductor layer 7 to be formed next in the laminating direction, and a plurality of through holes 3 are formed at predetermined positions where such a conduction path 5 is formed. It is formed.
[0025]
Then, as shown in FIG.3 (d), the photosensitive polyimide resin precursor layer 4p is imidized, and the insulating layer 4 which consists of a polyimide resin layer is formed. The imidization may be performed by, for example, finally heating the photosensitive polyimide resin precursor layer 4p to 300 ° C. or higher. Thereby, the insulating layer 4 in which the through-hole 3 is formed in the thickness direction is formed on the resin thin film 2.
[0026]
Next, in the circuit board manufacturing method of the present invention, the conductive path 5 is formed in the through hole 3 by plating. More specifically, in this method, as shown in FIG. 1C, the conductive path 5 is formed in the through hole 3 by plating, and the conductor layer 7 is formed on the insulating layer 4 with a predetermined circuit pattern. Form.
[0027]
The plating is not particularly limited, and for example, a metal such as copper, nickel, gold, solder, or an alloy thereof is used, and copper is preferably used. Further, the method of forming the conductive path 5 in the through hole 3 and forming the conductor layer 7 with a predetermined circuit pattern on the insulating layer 4 is not particularly limited, and a known method is used. For example, a method of filling and baking a conductive paste, a method of forming a base layer of a metal thin film and then plating, a method of forming a thick film by vapor deposition, and the like are used. Among these, the method of plating after forming the base layer of the metal thin film is preferably used.
[0028]
In the method of filling and baking the conductive paste, for example, the conductive paste in which the fine metal particles are mixed in the binder is applied on the insulating layer 4 with a predetermined circuit pattern by a screen printing method or the like. 3 may be filled and fired.
[0029]
Further, in the method of plating after forming the base layer of the metal thin film, for example, as shown in FIG. 4A, first, sputtering deposition and vacuum deposition are performed on the entire surface of the insulating layer 4 including the through holes 3. A base layer 8 of a metal thin film such as chromium or copper is formed by the method or electroless plating, and then, as shown in FIG. 4B, on the base layer 8 where the through hole 3 is not formed. Then, a plating resist 9 is formed in a pattern reverse to the predetermined circuit pattern using a dry film resist or the like, and then, as shown in FIG. 5 and the conductor layer 7 may be formed as a predetermined circuit pattern on the base layer 8 on which the plating resist 9 is not formed. The plating may be either electrolytic plating or electroless plating, but electrolytic plating is preferably used. Then, as shown in FIG. 4D, the plating resist 9 and the underlying layer 8 on which the plating resist 9 has been formed may be removed by a known etching method such as chemical etching (wet etching). 1 and 5 to 8, the underlayer 8 is omitted. However, when the underlayer 8 is formed by this method, the underlayer 8 is exposed by etching the resin thin film 2 described later. To come.
[0030]
In the method of forming a thick film by vapor deposition, for example, the conductive path 5 is formed in the through hole 3 by increasing the thickness as it is by the above-described sputtering vapor deposition method, vacuum vapor deposition method, or the like, and a predetermined circuit is formed. The conductor layer 7 may be formed as a pattern.
[0031]
In the method of manufacturing a circuit board according to the present invention, basically, the metal support plate 1 is then removed by etching, and then the resin thin film 2 may be removed by etching. In the case of manufacturing as a single-layer circuit board having only one layer, more specifically, as shown in FIG. 5A, the insulating cover layer 11 on which the opening 10 is formed is formed on the conductor layer 7. Then, as shown in FIG. 5B, after the electrode layer 12 is formed in the opening 10, the metal support plate 1 is removed by etching as shown in FIG. As shown in FIG. 5D, the resin thin film 2 may be removed by etching.
[0032]
In FIG. 5A, there is no particular limitation on the formation of the insulating cover layer 11 on which the opening 10 is formed on the conductor layer 7, but, for example, on the surface of the conductor layer 7 by the same method as described above, After forming the photosensitive polyimide resin precursor layer and then forming the opening 10 by exposure and development, this may be finally heat-cured to, for example, 300 ° C. or higher.
[0033]
5B, in order to form the electrode layer 12 in the opening 10, the electrode layer 12 such as a bump may be formed in the opening 10 by, for example, copper plating or gold plating. The electrode layer 12 is used, for example, for connection with a terminal of an external circuit board, a terminal provided on a silicon wafer, or the like.
[0034]
In FIG. 5C, the metal support plate 1 is not particularly limited by etching, but it may be removed by chemical etching, for example. In chemical etching, for example, etching may be performed using an etching solution that etches metal and does not etch resin, such as ferric chloride / hydrochloric acid aqueous solution. The metal support plate 1 may be completely removed, but may be partially left and used as a circuit pattern or a suspension board. When used as a circuit pattern, it is preferable to further form an insulating cover layer for covering the circuit pattern. In this etching, the electrode layer 12 may be appropriately protected with a protective material so that the electrode layer 12 is not etched. For example, the electrode layer 12 is provided on a terminal of an external circuit board or a silicon wafer. These terminals may be connected in advance to a protective terminal.
[0035]
Next, in FIG. 5D, the method for removing the resin thin film 2 by etching is not particularly limited. For example, it may be removed by chemical etching or physical etching such as plasma etching. In the chemical etching, for example, etching may be performed using an etchant that etches the resin and does not etch the metal, such as a sodium permanganate aqueous solution or a strong alkaline aqueous solution. In plasma etching, for example, a circuit board may be disposed between the counter electrodes in an atmosphere filled with a predetermined gas to generate high-frequency plasma, and processing may be performed for a predetermined time corresponding to the etching thickness. . Examples of the predetermined gas include He, Ne, Ar, Xe, Kr, and N. ₂ , O ₂ , CF ₄ , NF ₃ These mixed gases are used, and the gas pressure (degree of vacuum) is preferably 0.5 to 200 Pa, more preferably 10 to 100 Pa, for example. Moreover, as conditions for generating the high-frequency plasma, the frequency is, for example, 10 kHz to 20 MHz, preferably 10 kHz to 100 kHz, and the processing power is, for example, 0.5 to 10 W / cm. ² Furthermore, 1 to 5 W / cm ² It is preferable that
[0036]
By using such an etching method, only the resin thin film 2 made of resin is etched without etching the conductive path 5 made of metal (or the base layer 8 when the base layer 8 is formed). be able to. Therefore, the surface of the conduction path 5 (when the underlayer 8 is formed, the surface of the underlayer 8) is satisfactorily exposed without being eroded by etching. In addition, the surface of the exposed conductive path 5 (when the underlayer 8 is formed, the underlayer 8) may be used as an electrode part as it is, or an electrode layer is formed on the surface. Also good.
[0037]
In the above-described method shown in FIG. 5, the cover insulating layer 11 is formed on the conductor layer 7, the electrode layer 12 is formed in the opening 10, and then the metal support plate 1 and the resin thin film 2 are removed by etching. The removal of the metal support plate 1 and the resin thin film 2 by etching may be performed in the middle of any process, and the metal support plate 1 and the resin thin film 2 do not need to be continuously etched. It may be carried out step by step.
[0038]
However, if the metal support plate 1 and the resin thin film 2 are removed by etching in the last step as in the method shown in FIG. 5, the dimensional change of each layer during the manufacturing process can be prevented and the manufacturing process is in progress. Handling can be improved, and a very thin circuit board can be manufactured.
[0039]
Further, when the circuit board is manufactured as a multilayer circuit board having a plurality of conductor layers, more specifically, as shown in FIG. As shown in FIG. 6B, the laminated side insulating layer 14 in which the through hole 13 is formed is formed, and at the same time the laminated side conductive path 16 is formed in the laminated side through hole 13, the laminated side insulating layer 14 After forming the laminated conductor layer 15 with a predetermined circuit pattern, a cover insulating layer 18 on which the opening 17 is formed is formed on the laminated conductor layer 15 as shown in FIG. 7 (d), an electrode layer 19 is formed in the opening 17, and then the metal support plate 1 is removed by etching as shown in FIG. 7 (e). The resin thin film 2 may be removed by etching as shown in FIG.
[0040]
In FIG. 6A, there is no particular limitation on the formation of the laminated side insulating layer 14 in which the laminated side through holes 13 are formed in the thickness direction on the conductor layer 7. For example, the same method as described above By forming a photosensitive polyimide resin precursor layer on the surface of the conductor layer 7 and then forming the laminated side through-hole 13 by exposure and development, then, for example, this is finally performed at 300 ° C. or higher It is sufficient to heat and cure.
[0041]
Further, in FIG. 6B, in order to form the lamination-side conductive path 15 in the lamination-side through hole 13 and at the same time to form the lamination-side conductor layer 15 with a predetermined circuit pattern on the lamination-side insulating layer 14, Although there is no limitation, for example, by a method similar to the above, first, an underlayer of a metal thin film is formed on the entire surface of the laminated side insulating layer 14 including the laminated side through hole 13, and then a plating resist is applied to a predetermined circuit. After forming in a pattern opposite to the pattern, metal is deposited in the lamination-side through hole 13 by plating to form the lamination-side conduction path 16, and the lamination-side conductor layer 15 is formed as a predetermined circuit pattern on the base layer. Then, the plating resist and the base layer on which the plating resist has been formed may be removed by etching.
[0042]
Next, in FIG. 6C, there is no particular limitation on the formation of the insulating cover layer 18 on which the opening 17 is formed on the laminated conductor layer 15. For example, the laminated conductor is formed by the same method as described above. After forming the photosensitive polyimide resin precursor layer on the surface of the layer 15 and then forming the opening 17 by exposure and development, this may be finally heat-cured to 300 ° C. or higher, for example. .
[0043]
7D, in order to form the electrode layer 19 in the opening 17, the electrode layer 19 such as a bump may be formed in the opening 17 by, for example, copper plating or gold plating. Similarly to the above, the electrode layer 19 is used, for example, for connection to a terminal of an external circuit board, a terminal provided on a silicon wafer, or the like.
[0044]
In FIG. 7E, there is no particular limitation on removing the metal support plate 1 by etching. For example, an etching solution such as ferric chloride / hydrochloric acid aqueous solution is used by the same method as described above. It may be removed by chemical etching or the like. The metal support plate 1 may be completely removed, but may be partially left and used as a circuit pattern or a suspension board. When used as a circuit pattern, it is preferable to further form an insulating cover layer for covering the circuit pattern. In this etching, the electrode layer 19 may be appropriately protected with a protective material so that the electrode layer 19 is not etched. For example, the electrode layer 19 may be connected to the terminal of the external circuit board or the like as described above. It is good also as connecting to the terminal etc. which were provided in the silicon wafer beforehand, and making them into a protective material.
[0045]
Next, in FIG. 7F, there is no particular limitation on removing the resin thin film 2 by etching. For example, an etching solution such as a sodium permanganate aqueous solution or a strong alkaline aqueous solution is used by the same method as described above. It may be removed by chemical etching or physical etching such as plasma etching. By using such an etching method, only the resin thin film 2 made of resin is etched without etching the conductive path 5 made of metal (or the base layer 8 when the base layer 8 is formed). be able to. Therefore, the surface of the conduction path 5 (when the underlayer 8 is formed, the surface of the underlayer 8) is satisfactorily exposed without being eroded by etching. In addition, the surface of the exposed conductive path 5 (the base layer 8 when the base layer 8 is formed) may be used as an electrode part as it is, or an electrode layer is further formed on the surface. May be.
[0046]
In the method shown in FIG. 6 described above, the cover insulating layer 18 is formed on the laminated conductor layer 15, the electrode layer 19 is formed in the opening 17, and then the metal support plate 1 and the resin thin film 2 are removed by etching. However, the removal of the metal support plate 1 and the resin thin film 2 by etching may be performed in the middle of any process, and the metal support plate 1 and the resin thin film 2 do not need to be continuously etched. You may carry out in steps, sandwiching the process.
[0047]
However, if the metal support plate 1 and the resin thin film 2 are removed by etching in the last step as in the method shown in FIG. 6, the dimensional change of each layer during the manufacturing process can be prevented and the manufacturing process is in progress. Handling can be improved, and a very thin circuit board can be manufactured.
[0048]
In the above description, the multilayer circuit board has been described by taking a two-layer circuit board as an example, but the number of layers is not particularly limited, and the multilayer insulating layer and the multilayer conductor layer are formed by the same method as described above. A multilayer circuit board having two or more layers may be manufactured by repeating sequentially.
[0049]
If a circuit board such as a single-layer circuit board or a multilayer circuit board is manufactured in this way, in the step of removing the metal support plate 1 by etching, the conduction path 5 (if the base layer 8 is formed, Since the resin thin film 2 is interposed between the base layer 8) and the metal support plate 1, the conductive path 5 (the base layer 8 is formed even if the metal support plate 1 is removed by etching. In addition, since the underlayer 8) is covered with the resin thin film 2, it is prevented from being removed by etching of the metal support plate 1, and also in the step of removing the resin thin film 2 by etching, Since the conductive path 5 (the base layer 8 when the base layer 8 is formed) is formed of metal, it is not removed by the etching of the resin thin film 2. I, the conductive paths 5 (if the underlying layer 8 is formed, the underlying layer 8) can effectively prevent the defects in occurs. Therefore, in the circuit board obtained by this method, it is possible to ensure good connection reliability in the electrode portion.
[0050]
The circuit board manufactured in this way is not particularly limited, and can be used as a circuit board for various electronic devices and electronic components. For example, it is also suitable as a suspension board with a circuit for a hard disk drive. Can be used.
[0051]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the examples and comparative examples.
[0052]
Example 1
100 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 31.2 g of p-phenylenediamine and 10.1 g of 4,4′-diaminodiphenyl ether are reacted in 800 g of N-methylpyrrolidone, A polyamic acid resin solution (A) was obtained.
[0053]
Further, 472 g of N-methylpyrrolidone was added to the polyamic acid resin solution (A) for dilution to obtain a polyamic acid resin solution (I) for forming a resin thin film.
[0054]
Next, 21.2 g of 1-ethyl-3,5-dimethoxycarbonyl-4- (2-nitrophenyl) -1,4-dihydropyridine was uniformly dissolved in the polyamic acid resin solution (A) separately prepared in the same manner. Thus, a photosensitive polyamic acid resin solution (II) for forming an insulating layer was obtained.
[0055]
The polyamic acid resin solution (I) was applied onto a stainless foil (thickness 25 μm, SUS304) using a spin coater and dried at 100 ° C. for 10 minutes to form a polyamic acid resin layer (FIG. 2A). reference). Next, a polyimide thin film having a thickness of 0.5 μm was formed on the stainless steel foil by heat treatment at 400 ° C. for 2 hours in a vacuum (see FIGS. 2B and 1A).
[0056]
Further, a photosensitive polyamic acid resin solution (II) was applied onto the polyimide thin film using a spin coater and dried at 100 ° C. for 15 minutes to form a photosensitive polyamic acid resin layer (FIG. 3 ( a)). Next, the photosensitive polyamic acid resin layer is exposed through a photomask having a predetermined pattern (see FIG. 3B), heated at 170 ° C. for 3 minutes, and then developed using an aqueous tetramethylammonium hydroxide solution. Thereby, the photosensitive polyamic acid resin layer in which the through-hole was formed in the predetermined position was formed (refer FIG.3 (c)). Furthermore, this photosensitive polyamic acid resin layer was heat-treated at 400 ° C. for 2 hours to form a 10 μm-thick polyimide insulating layer having through holes formed on the polyimide thin film (FIG. 3D, FIG. 1). (See (b)).
[0057]
Next, an approximately 500 mm chromium thin film and an approximately 1500 mm copper thin film were sequentially laminated on the entire surface of the polyimide insulating layer including the through holes by sputtering to form an underlayer (FIG. 4A). (See Fig. 4 (b)). Using a dry film resist, a plating resist is formed in a pattern opposite to the predetermined circuit pattern on the underlying layer (see Fig. 4 (b)), and then copper is deposited in the through hole by copper plating. Thus, a conductive path was formed, and a 10 μm conductor layer was formed as a predetermined circuit pattern (see FIG. 4C). Thereafter, the plating resist and the base layer on which the plating resist was formed were removed by chemical etching (see FIGS. 4D and 1C).
[0058]
Next, a photosensitive polyamic acid resin solution (II) is applied onto the conductor layer using a spin coater, and dried at 100 ° C. for 15 minutes to form a photosensitive polyamic acid resin layer. The photosensitive polyamic acid resin layer having a laminated side through-hole formed at a predetermined position by exposure through a photomask, heating at 170 ° C. for 3 minutes, and developing with an aqueous tetramethylammonium hydroxide solution Furthermore, this photosensitive polyamic acid resin layer was heat-treated at 400 ° C. for 2 hours, thereby forming a laminated polyimide insulating layer having a thickness of 10 μm and a laminated through hole formed on the conductor layer ( (See FIG. 6 (a)).
[0059]
Then, an about 500 mm chromium thin film and an about 1500 mm copper thin film are sequentially laminated on the entire surface of the layer side polyimide insulating layer including the layer side through-holes by a sputtering method to form a base layer. On the ground layer, using dry film resist, a plating resist is formed in a pattern opposite to the predetermined circuit pattern, and then copper is deposited in the lamination-side through hole by copper plating to form a lamination-side conduction path. Then, a 10 μm laminated conductor layer was formed as a predetermined circuit pattern. Thereafter, the plating resist and the base layer on which the plating resist was formed were removed by chemical etching (see FIG. 6B).
[0060]
Next, the photosensitive polyamic acid resin solution (II) is applied onto the laminated conductor layer using a spin coater and dried at 100 ° C. for 15 minutes to form a photosensitive polyamic acid resin layer. The photosensitive polyamic acid resin layer having an opening formed at a predetermined position is exposed through a photomask having a pattern of 1, heated at 170 ° C. for 3 minutes, and then developed with an aqueous tetramethylammonium hydroxide solution. Then, the photosensitive polyamic acid resin layer was heat-treated at 400 ° C. for 2 hours to form a cover polyimide insulating layer having a thickness of 10 μm and an opening formed on the laminated conductor layer (FIG. 6 ( c)).
[0061]
Then, after forming a 20 μm high bump in the opening by copper plating (see FIG. 7 (d)), the stainless steel foil was etched using a ferric chloride / hydrochloric acid aqueous solution (see FIG. 7 (e)). ). In this etching, the bumps were protected by a protective material so as not to be etched.
[0062]
Next, using a sodium permanganate aqueous solution, the polyimide thin film exposed by etching of the stainless steel foil was etched until the chromium thin film was exposed (see FIG. 7F) to obtain a two-layer circuit board.
[0063]
The surface of the exposed chromium thin film was observed with a microscope. As a result, the surface of the chromium thin film was not etched at all, and the surface of the copper thin film formed next was not observed at all.
[0064]
Example 2
After forming the conductor layer, without forming the laminated polyimide insulation layer and the laminated conductor layer, after forming the cover polyimide insulation layer on the conductor layer, the stainless steel foil was etched, and then the polyimide thin film was etched Except for the above, the single-layer circuit board shown in FIG.
[0065]
As shown in FIG. 8A, in the manufacture of this single-layer circuit board, an insulating layer 23, a conductor layer 24, and a cover insulating layer 25 are formed as predetermined patterns on the stainless steel foil 21 and the polyimide thin film 22. In the step of etching the stainless steel foil 21, as shown in FIG. 8B, the stainless steel foil 21 was partially etched only in the electrode portion 27 where the conduction path 26 was exposed and its periphery. In the process of etching the polyimide thin film 22, CF ₄ / O ₂ Plasma etching was performed under a predetermined condition using a mixed gas of (1: 2).
[0066]
When the surface of the chromium thin film (not shown) of the exposed electrode portion 27 of the obtained circuit board was observed with a microscope, the surface of the chromium thin film was not etched at all and was formed next. The surface of the copper thin film was not observed at all.
[0067]
Comparative Example 1
A two-layer circuit board was produced in the same manner as in Example 1 except that no polyimide thin film was formed. When the surface of the exposed chromium thin film was observed with a microscope with respect to this two-layer circuit board, the surface of the chromium thin film was etched, and erosion of the copper surface of the conduction path was confirmed.
[0068]
Comparative Example 2
A single-layer circuit board was manufactured in the same manner as in Example 2 except that no polyimide thin film was formed. When the surface of the exposed chromium thin film was observed with a microscope for this single-layer circuit board, the surface of the chromium thin film was etched, and erosion of the copper surface of the conduction path was confirmed.
[0069]
【The invention's effect】
As described above, according to the method for manufacturing a circuit board of the present invention, in the step of removing the metal support plate by etching, a resin thin film is interposed between the conduction path and the metal support plate. Even if the metal support plate is removed by etching, the conduction path is covered with the resin thin film, so that the metal support plate is prevented from being removed by etching, and the resin thin film is removed by etching. However, since the conductive path is formed by plating, it is not removed even by etching of the resin thin film. Therefore, these etchings effectively prevent defects in the conductive path, and the electrode portion has a good quality. Connection reliability can be ensured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part showing each step of an embodiment of a method for producing a circuit board of the present invention,
(A) is a step of forming a resin thin film on a metal support plate;
(B) is a step of forming an insulating layer in which a through hole is formed on the resin thin film;
(C) shows the process of forming a conductor layer with a predetermined circuit pattern on the insulating layer at the same time as forming a conduction path in the through hole.
FIG. 2 is a cross-sectional view of an essential part showing details of a step of forming a resin thin film on a metal support plate shown in FIG.
(A) is a step of forming a polyimide resin precursor layer on a metal support plate;
(B) shows the process of imidizing a polyimide resin precursor layer and forming the resin thin film which consists of a polyimide resin thin film.
FIG. 3 is a cross-sectional view of an essential part showing details of a step of forming an insulating layer in which a through hole is formed on a resin thin film shown in FIG.
(A) is a step of forming a photosensitive polyimide resin precursor layer on the resin thin film;
(B) is a step of exposing the photosensitive polyimide resin precursor layer through a photomask;
(C) is a step of forming a through hole in the photosensitive polyimide resin precursor layer by development, and (d) is a step of imidizing the photosensitive polyimide resin precursor layer to form an insulating layer made of the polyimide resin layer. Indicates.
FIG. 4 is a cross-sectional view of a main part showing details of a process of forming a conductive layer with a predetermined circuit pattern on an insulating layer at the same time as forming a conduction path in the through hole shown in FIG. 1 (c);
(A) is a step of forming an underlayer of a metal thin film on the entire surface of the insulating layer including the through hole;
(B) is a step of forming a plating resist in a pattern reverse to a predetermined circuit pattern on a base layer in which no through hole is formed;
(C) is a step of forming a conductive path by depositing a metal in the through hole by plating and forming a conductor layer as a predetermined circuit pattern on the underlayer,
(D) shows the process of removing the plating resist and the base layer in which the plating resist was formed by etching.
FIG. 5 shows a step of manufacturing a single-layer circuit board following the step of forming a conductive path in the through hole and forming a conductor layer with a predetermined circuit pattern on the insulating layer at the same time as shown in FIG. It is principal part sectional drawing which shows,
(A) is a step of forming a cover insulating layer in which an opening is formed on the conductor layer; (b) is a step of forming an electrode layer in the opening;
(C) is a step of removing the metal support plate by etching;
(D) shows the process of removing a resin thin film by an etching.
FIG. 6 shows a step of manufacturing a multilayer circuit board following the step of forming a conductive path in the through hole and forming a conductor layer with a predetermined circuit pattern on the insulating layer at the same time as shown in FIG. It is principal part sectional drawing shown,
(A) is a step of forming a laminated side insulating layer in which a laminated side through hole is formed on the conductor layer, and (b) is a laminated side insulating layer at the same time as forming a laminated side conduction path in the laminated side through hole. Forming a laminated conductor layer with a predetermined circuit pattern thereon,
(C) shows the process of forming the insulating cover layer in which an opening is formed on the lamination | stacking side conductor layer.
FIG. 7 is a cross-sectional view of a principal part showing a step of manufacturing a multilayer circuit board following FIG.
(D) is a step of forming an electrode layer in the opening;
(E) is a step of removing the metal support plate by etching;
(F) shows the process of removing a resin thin film by an etching.
FIG. 8 is a cross-sectional view of a principal part of a single-layer circuit board manufactured in Example 2,
(A) is a state in which an insulating layer, a conductor layer and a cover insulating layer are formed as a predetermined pattern on the stainless steel foil and the polyimide thin film,
(B) shows a state in which the stainless steel foil and the polyimide thin film are partially etched only in the electrode portion where the conduction path is exposed and its periphery.
[Explanation of symbols]
1 Metal support plate
2 Resin thin film
3 Through hole
4 Insulation layer
5 Conduction path

Claims (3)

Forming a resin thin film on a metal support plate;
Forming an insulating layer in which a through hole is formed in the thickness direction on the resin thin film;
Forming a conduction path by plating in the through hole;
A method for manufacturing a circuit board, comprising: a step of removing the metal support plate by etching; and a step of removing the resin thin film by etching. The method for manufacturing a circuit board according to claim 1, wherein the resin thin film has a thickness of 1 μm or less. The method for manufacturing a circuit board according to claim 1, wherein the resin thin film is made of a polyimide resin or a polyimide resin precursor.

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