JP2730218B2 - Manufacturing method of through-hole plated substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a method for producing a through-hole plated substrate by a novel gas phase method, and uniform plating adheres to a hole having a small hole diameter and a large aspect ratio. A plated through-hole plated substrate can be manufactured.

[Conventional technology and its problems]

In the fields of double-sided boards, multilayer boards, etc., due to the miniaturization of components and the development of surface mounting technology, through holes with a diameter of 0.8 mm to small holes of about 0.20 mm are used exclusively for interlayer conduction only. Is being demanded. However, in conventional through-hole plating by the electroless plating method, since the electroless plating solution is a liquid, when the diameter becomes 0.35 mm or less, for example, a small hole of about 0.20 mm, the plating solution reaches the inside of the hole. It is extremely difficult to uniformly form a copper film on the inner wall of the hole because it does not uniformly penetrate and the flow is difficult.

On the other hand, it is known that when copper formate is applied to ceramics and heat-treated in a non-oxidizing atmosphere, an article with a copper coating is obtained. It was difficult to manufacture it with high reliability. In addition, there is no example in which this method is applied to articles made of a thermoplastic resin or a thermosetting resin, and an electroless plating method is exclusively used.

[Means for solving the problem]

The present inventors have conducted intensive studies on a method for forming a copper film firmly bonded to polyimide without using an adhesive, using various copper compounds, and as a result, have previously found a method using copper formate. As a result of further study, they have found that this method is essentially a vapor phase method and can be suitably applied to through-hole plating, and based on this, the present invention has been completed.

That is, according to the present invention, a large number of through holes are formed in a copper-clad board or a double-sided copper-clad multilayer board to form a through-hole board (1), and copper formate is arranged or held at a position within 5 cm of the through-hole. 165 ° C under reduced pressure of 30 Torr or less
As described above, the through-hole substrate (1) is heated to a predetermined temperature in a range not more than the deformation deterioration temperature, and the temperature of the copper formate is raised at a rate of 1 ° C./min or more between at least 130 ° C. to 165 ° C.,
0.1μ thickness on through hole wall characterized by holding
This is a method of manufacturing a through-hole plated substrate formed with a copper film of m or more.

In the present invention, the through-hole substrate (1)
And the amount of copper formate per total surface area of the plating area to be heat-treated with copper formate is 0.003 to 0.3 g / cm ² , and the rate of temperature rise between 130 to 165 ° C. of copper formate is 1 to 50 ° C. / Min, the time between heating and holding the through-hole substrate (1) and copper formate is selected from the range of 1 to 60 minutes, and the pressure is 5 Torr.
It is as follows.

Further, the through-hole substrate (1) is continuously or intermittently supplied to a heating region at a predetermined temperature under reduced pressure and is taken out from the heating region. Are supplied on a plate-like body on which copper formate is thinly applied or laid, at least at a portion corresponding to a peripheral portion of the through-hole substrate (1) via a thin isolating piece. The substrate (1) is not subjected to a smear removal treatment after drilling the through-holes, but has been flattened. Further, the obtained through-hole plated substrate is subsequently subjected to electrolytic plating. This is a method for manufacturing a through-hole plated substrate by using electrolytic copper plating and using a plating rate of 0.1 μm / sec or less until the copper layer thickness becomes 5 μm or more.

 Hereinafter, the present invention will be described.

The through-hole substrate (1) of the present invention means a large number (usually 10,000 to 50,000) at a predetermined position of a copper-clad board or a double-sided copper-clad multilayer board, that is, a through-hole position of a desired printed wiring pattern based on a reference hole. those formed by the through holes drilled in pieces / m ² or so).

The deformation deterioration temperature of the through-hole substrate (1) is a limit temperature at which the holes are displaced due to a dimensional change and cannot be put to practical use when held at a predetermined temperature of 165 ° C. or higher. It varies depending on the residual stress of (1) and the like. In the present invention, it is preferable to improve the dimensional stability by performing an annealing process or the like before drilling a through-hole. In addition, smearing usually occurs when drilling a through-hole. However, when the matrix resin is an epoxy resin or the like, it is not necessary to perform a treatment for removing the smear. Further, it is preferable that the through-hole substrate (1) is subjected to surface preparation such as surface cleaning and drying using a cleaning liquid. Examples of the surface preparation solution include an acidic or alkaline aqueous solution of a degreasing agent, a volatile organic solvent, and washing with a volatile organic solvent solution containing an acid or an alkali. In the treatment under severe conditions, it is preferable to use a component solution or a solution containing the component that the resin is attacked, and to use the solution at a low temperature, a low concentration or in a short time, and to perform a cleaning process within a range where the surface state hardly changes. For example, when the composition is applied to a glossy resin surface, the washing treatment is performed under conditions within a range in which the gloss is not lost visually. In addition, as the flat surface, for example, a plasma treatment that is used in a normal vapor deposition method or the like, it is also possible to immediately perform a plating process, but equipment and operability are poor,
In the present invention, these need not be used.

A copper-clad board or a multilayer board having an inner layer printed wiring for manufacturing the through-hole board (1) is usually made of a thermosetting resin or a thermoplastic resin having solder heat resistance as a matrix resin and a glass (E-, T- , D-, S-, quartz-glass), wholly aromatic polyamide, super heat-resistant resin such as fluororesin, ceramics such as alumina, silica, nitrogen boron, aluminum nitride, silicon carbide, etc. Base material (= Base Mater
ial) and obtain a prepreg and integrate it with an electrolytic or rolled copper foil, or a printed wiring board for an inner layer in which printed wiring is formed on such a copper-clad board together with a prepreg and a copper foil. It is a multilayer board.

Here, as the thermosetting resin, phenol resin, diallyl phthalate resin, epoxy resin, polyamine-bismaleimide resin, polymaleimide-epoxy resin, polymaleimide-isocyanate resin, cyanate resin, cyanate-epoxy resin, cyanate-polymaleimide Resins, thermosetting resins such as cyanate-epoxy-polymaleimide resins; thermosetting resins and polyamides (nylons), aromatic polyesters, polyetherimides;
Thermosetting so-called "IPN" obtained by blending with engineering plastics such as polyetheretherketone, polysulfone and polyphenyleneether, and further adding catalysts as appropriate; polyolefins such as polyethylene, 1,2
-A resin such as polybutadiene, an organic peroxide as a cross-linking agent, a cross-linking curable resin obtained by further mixing a radically polymerizable polyfunctional compound, a thermosetting resin, etc., and the like. As the thermoplastic resin having properties, polyethylene-2,6-naphthalate, polyoxybenzoyl polyester, P-hydroxybenzoic acid, phthalic acid, wholly aromatic polyester having a main monomer such as bisphenol, and polyethylene terephthalate, etc. are grafted to these. Aromatic polyester liquid crystal polymer, polyetherimide, polysulfone, polysulfone, polyethersulfone, polyetheretherketone, polyphenyleneether, polyphenylenesulfide, polyimide, polybenzimidazole, polyphenylenesulfide, all Such as family polyamides.

The copper formate of the present invention is a cupric formate compound such as anhydrous copper formate, copper formate tetrahydrate or a mixture thereof, and any of them can be used. Is preferred.

The amount of copper formate used (the total amount of copper formate disposed) is mainly determined by the total surface area including the holes of the through-hole substrate (1) to be plated and the total surface area of the copper formate arrangement tool.
0.001 g / cm ² or more, preferably 0.002~0.3g / cm ^2, particularly 0.0
02 to 0.1 g / cm ² . When the through-hole substrate (1) to be plated and the copper formate are separately disposed or held, the distance is within 5 cm, preferably within 2 cm, and particularly within 1 cm, and plating is more uniform. Preferred for.

In addition, the disposition method includes a method of simply disposing copper formate in a hole of the through-hole substrate (1) and a method of disposing the copper formate at a distance within 5 cm from the hole so that copper formate vapor passes through the hole. There is.

From the standpoint of plating only in the through-holes, a dispersion in which copper formate is dispersed may be applied to the through-hole substrate (3) and heat-treated under reduced pressure, but this did not contribute to film formation. Since the copper generated from the anhydrous copper formate becomes a through-hole plated substrate adhered to the coated area of the anhydrous copper formate and requires a copper powder removing step, it is preferable to supply them separately using a copper formate arranging tool.

As the former arrangement method, copper formate is applied to the entire surface of the through-hole substrate (1) by brush coating, screen printing, roll coating, dipping, or the like, and then copper formate is applied to the holes using a roll, squeegee, or the like. For example, a method of indenting, removing copper formate on the surface as necessary, and drying is exemplified. In the latter method, copper formate is disposed on a plate-like body that can withstand the processing temperature, for example, a metal, resin, other sheet or film, and the through-hole substrate (1) is stacked so as not to come into direct contact with copper formate. And a method to configure
For example, a structure in which a large number of holes, grooves, and the like are formed on the surface of a plate-like body, copper formate is arranged in these holes and grooves, and a through-hole substrate (1) is stacked thereon; A method in which a thin insulator is overlapped on the laid plate-like body at least at a portion corresponding to the periphery of the through-hole substrate (1);
(2) The method of stretching by crossing the following ones in parallel, or the method of stretching the mesh with the width or diameter of the connecting part of the mesh thread or net wire less than 1/2 of the through hole hole diameter, etc. In addition, a horizontal arrangement or a vertical arrangement is appropriately selected for plating.

In addition, in the arrangement of copper formate, a solution obtained by dissolving or uniformly dispersing the powder in a solvent having a relatively low boiling point which does not substantially react with copper formate is applied by brushing, dipping, spray coating, bar coating, roll coating or other means. A preferred method is to apply it to the through-hole substrate (1) or the disposition tool, and to dry it under heating or reduced pressure at a temperature lower than the decomposition start temperature of copper formate, usually 130 ° C. or lower, particularly 110 ° C. or lower. Suitable solvents or dispersants for producing the copper formate liquid include water, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, and other suitable ones having a boiling point of 200 ° C. or lower. In the anhydrous copper formate used, a water-free organic solvent such as heptane, hexane, cyclohexane, octane, propanol, butanol, heptanol, benzene, toluene, xylene and the like are kneaded with a dispersion obtained by kneading fine powder of copper formate. It is preferred to use. In addition, the copper formate only needs to adhere to substantially the entire surface of the desired surface, and a slight variation does not cause any particular problem from the plating surface.
However, from the ratio of copper formate to be a copper film (film formation ratio), it is preferable to apply the film more uniformly and thinly.

The above-mentioned through-hole substrate (1) and copper formate are subjected to heat treatment to perform through-hole plating.

The plating treatment atmosphere is preferably under reduced pressure, and the degree of reduced pressure is 30 To.
rr or less, preferably 5 Torr or less. The method of reducing pressure is a method using a heating device capable of reducing pressure; a method of storing the through-hole substrate (1) and copper formate in a container capable of reducing pressure and reducing the pressure only in the container; Examples of the method include a method of arranging a decompression chamber capable of preheating, a decompression plating chamber heated to a predetermined temperature, and a decompression chamber capable of appropriately cooling at a take-out part, in the introduction portion of the through-hole substrate (1).
In particular, a semi-continuous type or a continuous type is preferable in terms of productivity, shortening of heating time, and the like.

For heating, infrared radiation, electron beam, radiation heating such as microwave, electric furnace, open, oil heating, pressurized steam heating, nichrome wire, and other means are appropriately selected. Further, from the viewpoint of reducing the dimensional change, it is preferable that the variation in the set temperature is small. It is also preferable from the viewpoint of productivity to increase the temperature raising rate and shorten the plating time to obtain a good copper film. In this case, a method of preheating to a temperature of 130 ° C. or less in advance and feeding it to a heating device having a hot plate as a heating unit set at a predetermined temperature; a method of heating using an infrared ray, particularly a far-infrared ceramic heater or the like A combination of the two, and in particular, the latter can efficiently heat only the plating surface.

Heating temperature is 165 ° C or more and the through-hole substrate (1)
The temperature is in the range of 170 ° C. to 300 ° C. and not higher than the deformation deterioration temperature of the through-hole substrate (1), and particularly preferably in the range of 170 ° C. to 230 ° C. On the other hand, copper formate is heated at a temperature of 130 ° C. to 165 ° C. at a rate of 1 deg / min or more, preferably 1 to 50 ° C./min, particularly 2 to 35 ° C./min, and kept at a predetermined temperature. The heating time is 3 hours or less, preferably 1 to 60 minutes, and it is preferable that the heating time is devised so as to be shorter. Temperature of copper formate 130 ℃ ～ 165 ℃
If the rate of temperature rise during this period is less than 1 ° C./min, the resulting plated film is not uniform or has poor adhesive strength, and the amount of copper powder produced tends to increase, which is not preferable. Although there is no particular problem from the generation of the plating film at the highest, it is not preferable because the tendency of the plating film to become non-uniform increases.

After heat treatment by the above method, the substrate is cooled to room temperature to obtain a through-hole plated substrate.

The through-hole plated substrate manufactured by the method of the present invention is used in a subsequent printed wiring board manufacturing process in the same manner as a through-hole plated substrate by a method such as a conventional electroless plating method, and has a hole and a land equivalent portion. A method of forming a resist pattern for the wiring pattern by etching the copper layer inside the hole by forming a resist layer, leaving only the resist layer, and electrolytic copper plating to increase the thickness of the copper film inside the hole; After thickening by copper plating, a printed wiring board is formed by a method of forming a resist pattern and etching. When performing electrolytic copper plating, plating at a plating rate of 0.1 μm / sec or less, particularly in the range of 0.003 to 0.05 μm / sec, until the copper layer thickness becomes 5 μm or more, is locally performed due to plating stress. It is preferable from the viewpoint of preventing the adhesive strength from being reduced due to stress concentration. After plating is completed, residual stress is removed by performing an annealing treatment or the like as necessary.

The through-hole plated substrate of the present invention produced by the above method, copper foil peel strength 0.4kg / cm or more when electrolytic copper plating and the thickness of the copper film is 10μm, preferably 0.5kg / cm
As described above, the value is particularly about 0.8 kg / cm.

Next, an example of the manufacturing method of the present invention will be described with reference to the attached device conceptual diagram.

FIG. 1 shows an example of an apparatus for through-hole plating a through-hole substrate (1) having a large aspect ratio by the semi-continuous method of the present invention, and FIG. 2 shows a through-hole between copper formate and the through-hole substrate (1). It is sectional drawing of the integrated material for plating.

FIG. 1 comprises a reduced-pressure plating chamber (A), a preliminary vacuum chamber for charging (B), and a preliminary vacuum chamber for removal (C). The reduced-pressure plating chamber A is provided with a lower heater (H1), an upper heater (H2) capable of adjusting the vertical position in accordance with an article to be plated, and a vacuum shutter (V1, V2) inside. Preliminary vacuum chamber (B, C)
Is equipped with tools (T1, T2) for loading or unloading articles to be plated. These chambers (A, B, C) are equipped with a vacuum pump (Vacuum
pump) to allow the desired degree of vacuum to be maintained. In the preliminary vacuum chambers (B, C), a preliminary heating device, a cooling device, and the like are appropriately installed. FIG. 2 shows a fixing portion of an aluminum separator provided at the edge of an aluminum plate having the same size as the through hole substrate (1) and having a thickness of 1 mm. An aluminum separator provided with a pin slightly smaller than the reference hole at a position corresponding to the reference hole in a shape corresponding to the edge of the through-hole substrate (1), and the reference hole of the through-hole substrate (1) is fitted into this pin. This is an integrated product for through-hole plating.

In FIG. 1, the integrated material shown in FIG. 2 is opened, the door of the preliminary vacuum chamber B for charging is opened, the door is closed, and vacuum suction is performed. The pre-vacuum chamber is used so that pre-heating can be appropriately performed. When the degree of vacuum reaches a predetermined degree, the vacuum shutter V1 of the reduced-pressure plating chamber A heated to a predetermined temperature is opened, and is put into the vacuum plating chamber A by the charging tool T1. Here, the integrated material is rapidly heated under reduced pressure, and the copper formate evaporates or sublimates, and diffuses to the vacuum pump side while passing through the holes. At this time, the copper formate that collides with the inner wall of the hole is decomposed to form a copper film and to become a formic acid gas or a formic acid decomposition gas. At this time, when the smear resin is an epoxy resin or the like, the smear and the like are decomposed and removed together. During this process, the next through-hole substrate is put into the preparatory vacuum chamber B and waits to be put into the reduced-pressure plating chamber A. After the predetermined processing is completed, the vacuum shutter V2 is opened, taken out of the vacuum plating chamber A by the take-out tool T2, and the vacuum shutter V2 is closed. The taken-out plated through-hole substrate is cooled as required and taken out of the take-out chamber B. Further, the following are charged into the vacuum plating chamber A.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples. Parts in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 100 parts of anhydrous copper formate powder and 50 parts of butyl alcohol were kneaded to obtain a dispersion solution in which the anhydrous copper formate powder was uniformly dispersed (hereinafter referred to as treatment liquid 1).

Using a 4-layer copper fiber-reinforced epoxy resin 4-layer board (manufactured by Mitsubishi Gas Chemical Co., Ltd.) with a board thickness of 1.6 mm and 300 mm x 300 mm,
After forming 30 rows of 0.35mm diameter through holes at 5mm intervals in a row of 5 rows and 30 rows at 10mm intervals, wash with alkaline degreasing agent solution at 60 ° C for 10 minutes and dry to obtain a 4-layer perforated plate. Was.

Treatment liquid 1 was applied to one side of an aluminum plate having the same size as a four-layer perforated plate, and dried to obtain about 0.02 g / cm ^{2 of} anhydrous copper formate.
The adhered aluminum plate was used.

An aluminum separator with a thickness of 1 mm and a width of 3 mm is placed around the edge of this aluminum plate, and the above-mentioned 4-layer perforated plate is placed on top of this, and placed between the hot plates of the heating equipment preheated to 200 ° C in advance. Then, the pressure inside the heating device was immediately reduced to several Torr, and the pressure was kept for 30 minutes. In addition, the temperature of anhydrous copper formate 130-165 ° C
The heating rate was 16 ° C./min.

After cooling the inside of the heating device to room temperature, air was introduced, and the four-layer perforated plate was taken out. The copper foil was thickened as it was and by electrolytic copper plating, sealed with a transparent liquid epoxy resin, cut, and the cut end face was observed with a microscope.

As a result, the inner wall of the hole and the inner layer copper foil had a thickness of 0.5
The copper film plated with copper formate of about 0.7 μm was in close contact, and the inner layer copper foil and the adhered copper film were completely in close contact. No resin dust was found between the inner layer copper foil and the plated copper film, and smear was completely removed.

Example 2 As a model multilayer board, a 6 mm-thick copper-clad board having both outer layers and two copper foil layers in an intermediate layer was manufactured using a glass nonwoven epoxy resin prepreg.

Using this copper-clad board, a board was obtained in the same manner as in Example 1 except that about 0.05 g / cm ^{2 of} copper formate was used, and through-hole plating was performed on through-holes having a hole diameter of 0.35 mm (aspect ratio: about 17). Observed similarly.

As a result, the inner wall of the hole and the inner layer copper foil had a thickness of 0.5
The copper film plated with copper formate of about 0.7 μm was in close contact, and the inner layer copper foil and the adhered copper film were completely in close contact. No resin dust was found between the inner layer copper foil and the plated copper film, and smear was completely removed.

Example 3 In Example 1, a glass fiber reinforced fluororesin four-layer plate was used instead of the glass fiber reinforced epoxy resin four-layer plate,
The procedure was the same except that the plating temperature was 250 ° C.

As a result, the inner wall of the hole and the inner layer copper foil had a thickness of 0.5
The copper film plated with copper formate of about 0.7 μm was in close contact, and the inner layer copper foil and the adhered copper film were completely in close contact.

Example 4 Example 1 was the same as Example 1, except that a glass fiber reinforced cyanate resin four-layer plate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used instead of the glass fiber reinforced epoxy resin four-layer plate.

As a result, the inner wall of the hole and the inner layer copper foil had a thickness of 0.5
The copper film plated with copper formate of about 0.7 μm was in close contact, and the inner layer copper foil and the adhered copper film were completely in close contact. No resin dust was found between the inner layer copper foil and the plated copper film, and smear was completely removed.

[Action and Effect of the Invention]

As described above, according to the method of the present invention, it is possible to perform through-hole plating in which a copper film is firmly and uniformly adhered, and it is extremely simple, in the case of a large aspect ratio, and in the case where those having different hole diameters are mixed. Also, a highly reliable plating film can be easily formed by devising the isolation piece. Also, in the case of a substrate where normal smear occurs, the smear removal step is not required, which is an extremely rational through-hole plating process.In addition, a copper film is formed by the conventional electroless through-hole plating. A copper film can be formed even on a fluorine resin that cannot be used.

The copper plating film can easily and uniformly form copper, nickel, chromium, silver, gold, and other plating by electroplating, electroless plating, or other means. Therefore, its industrial significance as a new, inexpensive and highly reliable through-hole plating method is extremely important.

[Brief description of the drawings]

FIG. 1 shows an example of an apparatus for through-hole plating a through-hole substrate (1) having a large aspect ratio by the semi-continuous method of the present invention, and FIG. 2 shows a through-hole between copper formate and the through-hole substrate (1). It is sectional drawing of the integrated material for plating.

Claims (10)

(57) [Claims] 1. A large number of through-holes are formed in a copper-clad board or a double-sided copper-clad multilayer board to form a through-hole board (1), and copper formate is placed or held at a position within 5 cm of the through-hole. Heating to a predetermined temperature in the range of 165 ° C. or higher and a temperature lower than the deformation deterioration temperature of the through-hole substrate (1) under a reduced pressure of 30 Torr or lower;
A method for producing a through-hole plated substrate comprising a through-hole wall having a copper film having a thickness of at least 0.1 μm, wherein the temperature is raised at a rate of 1 ° C./min or more and maintained at a temperature of up to 165 ° C. . 2. The amount of copper formate per total surface area of a plating area where the through-hole substrate (1) and copper formate are heat-treated is reduced.
0.003~0.3g / cm ² The process of through-hole plating substrate according to claim 1, wherein. 3. The method of manufacturing a through-hole plated substrate according to claim 1, wherein the rate of temperature rise of said copper formate between 130 and 165 ° C. is 1 to 50 ° C./min. 4. The method of manufacturing a plated through-hole substrate according to claim 1, wherein the heating and holding time of said through-hole substrate (1) and copper formate is selected from the range of 1 to 60 minutes. 5. The method according to claim 1, wherein said pressure is 5 Torr or less. 6. The through-hole plated substrate according to claim 1, wherein said through-hole substrate (1) is continuously or intermittently supplied to a heating area at a predetermined temperature under reduced pressure and taken out of said heating area. Manufacturing method of 7. The method according to claim 1, wherein said through-hole substrate (1) and copper formate are
The through-hole plating according to claim 1, wherein the through-hole plating is supplied as a structure in which a thin isolating piece is overlapped on at least a portion corresponding to a peripheral portion of the through-hole substrate on a plate-like body on which copper formate is thinly applied or spread. Substrate manufacturing method. 8. The method for manufacturing a plated through-hole substrate according to claim 1, wherein said through-hole substrate (1) is not subjected to a smear removal treatment after drilling said through-hole, and is surface-regulated. 9. A method of manufacturing a through-hole plated substrate, wherein the obtained through-hole plated substrate is subsequently subjected to electrolytic plating. 10. The method according to claim 1, wherein the electrolytic plating is electrolytic copper plating, and a plating rate of 0.1 μm / sec or less is used until the thickness of the copper layer becomes 5 μm or more.