JP5639465B2 - Method for producing metal pattern - Google Patents

Description

  The present invention relates to a method for producing a fine metal pattern using a subtractive method. Specifically, the present invention relates to a method for producing a fine metal pattern by performing exposure, development, and etching treatment after thinning a photocrosslinkable resin layer in a subtractive method.

  As a method of manufacturing printed wiring boards and lead frames, an etching resist layer is provided on an insulating substrate having a conductive layer on the surface or a circuit portion of the conductive substrate, and the exposed conductive layer of the non-circuit portion is removed by etching. There is a subtractive method for forming a circuit pattern. Compared to additive and semi-additive methods, this method has many advantages such as not only fewer manufacturing processes and cost advantages, but also a sufficiently large adhesive strength between the metal pattern and the insulating or conductive substrate. The current method of manufacturing printed wiring boards and lead frames has become the mainstream.

  In the subtractive method, the etching resist layer is formed by a screen printing method, a photofabrication method having an exposure development process using a photocrosslinkable resin, an ink jet method, or the like. Among these, a method using a sheet-like photocrosslinkable resin layer called a negative type dry film resist is generally preferably used since it is easy to handle and can protect through holes by tenting.

  Now, along with the recent downsizing and multi-functionalization of electronic equipment, printed wiring boards used inside the equipment are also being densified and miniaturized metal patterns, and the conductor width is now reduced by the subtractive method. A printed wiring board having a metal pattern of 50 to 80 μm and a conductor gap of 50 to 80 μm is manufactured. In addition, with higher density and finer wiring, ultrafine metal patterns with a conductor width or a conductor gap of 50 μm or less have been demanded. Along with this, the requirements for circuit pattern accuracy and impedance are also increasing. In order to form such a fine metal pattern, the semi-additive method has been studied instead of the subtractive method. However, there are problems such as a significant increase in the manufacturing process and insufficient adhesive strength of the electrolytically plated copper. was there.

  When producing a fine metal pattern using the subtractive method, it is of course necessary to improve the technical level and the management level of the entire production line, but the etching process is particularly important. This is because side etching that proceeds from the side of the conductor, which is a feature of the subtractive method, becomes a problem. In order to suppress the amount of side etching, it is necessary to adjust optimum etching conditions such as liquid composition management and the angle and strength of spraying the liquid onto the substrate. In addition, the side etching is affected not only by adjusting the etching conditions but also by the film thickness of the etching resist. That is, the thicker the etching resist film, the worse the circulation of the liquid in the gap portion of the fine resist pattern, and as a result, the side etching becomes larger. The film thickness of the dry film resist which is currently mainstream is around 25 μm, but in order to produce a fine metal pattern, it is necessary to make the resist film thickness as thin as possible, and in recent years the film thickness is 10 μm or less. Thin dry film resists have been developed and commercialized. However, such a thin dry film resist has a problem in that the mixing of bubbles with dust as a core and the unevenness followability become insufficient, and the resist is peeled off or disconnected.

  In order to solve such problems, a dry film resist having a film thickness of 25 μm or more is pasted on the substrate, and then the dry film resist is thinned to about 10 μm using a processing solution, and then exposure and development of a circuit pattern are performed. Has been proposed to form a resist pattern and subsequently etch a metal layer other than the resist pattern portion (see, for example, Patent Documents 1 and 2). However, when the 1% by mass sodium carbonate aqueous solution, which is the treatment liquid described in Patent Document 1, is used, there is a large difference in the dissolution rate of the resin layer within the surface, and it is difficult to uniformly control the dry film resist as a thin film. Improvements were necessary because of variations in conductor width.

  In addition, with the recent miniaturization and multi-functionalization of electronic devices, circuit boards are being further densified and wiring patterns are being miniaturized. In dry film resist pattern formation for high-density wiring, photocured resists are used. In some cases, a decrease in resolution caused by swelling of the developer with respect to the developing solution becomes a problem. In order to avoid such a problem, a resin composition is often designed in which a photocured resist hardly swells with respect to a developer. However, when attempting to thin such a resin using the inorganic alkaline treatment liquid by the methods disclosed in Patent Documents 1 and 2, the treatment may take time and productivity may be poor. It was.

JP 2004-214253 A International Publication No. 2009/096438 Pamphlet

  The present invention relates to a method for producing a metal pattern in which a photocrosslinkable resin layer is formed on a substrate, a photocrosslinkable resin layer is thinned, and then a circuit pattern is exposed, developed, and etched. Even if the crosslinkable resin is a resin that does not easily swell with respect to the developer, the photocrosslinkable resin layer can be evenly and thinly formed almost uniformly and with good productivity. A method for producing a pattern is provided.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have formed a photocrosslinkable resin layer on a substrate, a photocrosslinkable resin layer is thinned by an aqueous alkali solution containing an organic alkaline compound. It has been found that the above-mentioned problems can be solved by a metal pattern manufacturing method characterized by including a processing step, circuit pattern exposure, development, and etching in this order.

The concentration of the organic alkaline compound Ri 5-25% by mass, of manufacturing a patterned metal containing at least one kind of alkaline aqueous solution is selected tetramethylammonium hydroxide, from trimethyl-2-hydroxyethyl ammonium hydroxide the method was found to be able to solve the above Symbol challenges.

  In the metal pattern preparation method of the present invention, the photocrosslinkable resin layer is thinned with an aqueous alkali solution containing an organic alkaline compound, so that the photocrosslinkable resin layer is not unevenly uniform and has good productivity. A thin film can be formed, and a method for producing a uniform and fine metal pattern can be provided.

  Hereinafter, the method for producing a metal pattern of the present invention will be described in detail.

  First, a photocrosslinkable resin layer is formed on at least one surface of the substrate. The substrate may be subjected to pretreatment such as alkali degreasing and pickling. For the formation of the photocrosslinkable resin layer, for example, a thermocompression laminator device that presses and presses a rubber roll heated to 100 ° C. or higher can be used. After forming the photocrosslinkable resin layer, the carrier film of the photocrosslinkable resin layer is peeled off, and the photocrosslinkable resin layer is thinned with an aqueous alkali solution containing an organic alkaline compound. Next, the circuit pattern is exposed and developed to form an etching resist layer, and then a metal layer other than the etching resist layer is etched to produce a fine metal pattern.

  The substrate according to the present invention includes a printed wiring board or a lead frame substrate. Examples of the printed wiring board include a flexible substrate and a rigid substrate. The thickness of the insulating layer of the flexible substrate is 5 to 125 μm, and a metal layer of 1 to 35 μm is provided on both sides or one side, and the flexibility is large. As the material for the insulating layer, polyimide, polyamide, polyphenylene sulfide, polyethylene terephthalate, liquid crystal polymer, or the like is usually used. A material having a metal layer on an insulating layer is a thin conductive layer having a thickness of several nm formed on a resin film by an adhesion method in which an adhesive is bonded, a casting method in which a resin liquid is applied on a metal foil, or a sputtering or vapor deposition method. A material produced by any method such as a sputtering / plating method in which a metal layer is formed by electrolytic plating on the (seed layer), or a laminating method in which the metal layer is attached by hot pressing may be used. As the metal of the metal layer, any metal such as copper, aluminum, silver, nickel, chromium, or an alloy thereof can be used, but copper is generally used.

  A rigid substrate is made by stacking an insulating substrate in which an epoxy resin or phenolic resin is immersed in a paper base or glass base to form an insulating layer, and a metal foil is placed on one or both sides, and laminated by heating and pressing. And those provided with a metal layer. Moreover, the multilayer board which has a through-hole and a non-through-hole, and the multilayer shield board produced by laminating | stacking a prepreg, metal foil, etc. after an inner layer wiring pattern process is also mentioned. The thickness is 60 μm to 3.2 mm, and the material and thickness thereof are selected according to the final use form as a printed circuit board. Examples of the material for the metal layer include copper, aluminum, silver, and gold, but copper is the most common. Examples of these printed circuit boards are “Printed Circuit Technology Handbook-Second Edition” (edited by the Japan Society of Printed Circuits, published in 1987, published by Nikkan Kogyo Shimbun) and “Multilayer Printed Circuit Handbook” (JA Scarlet). 1992, published by Modern Chemical Co., Ltd.). Examples of the lead frame substrate include iron nickel alloy and copper alloy substrates.

  Examples of the photocrosslinkable resin layer according to the present invention include a negative dry film resist in which the light irradiation part is crosslinked and insolubilized in the developer. The dry film resist is composed of at least a photocrosslinkable resin, and a photocrosslinkable resin is coated on a carrier film such as polyester, and in some cases, the photocrosslinkable resin layer is covered with a protective film such as polyethylene. ing. The photocrosslinkable resin layer is composed of, for example, a binder polymer containing a carboxyl group, a photopolymerizable compound having at least one polymerizable ethylenically unsaturated group in the molecule, a photopolymerization initiator, a solvent, and other additives. . Their blending ratio is determined by a balance of required properties such as sensitivity, resolution, degree of cross-linking and tenting property. In the composition design of the photocrosslinkable resin for high resolution, it is effective to suppress swelling of the photocured resin in the photocured part by the developer, and for that purpose, a binder with a low acid value should be used. Is the most effective. Examples of photocrosslinkable resin compositions are “Photopolymer Handbook” (edited by Photopolymer Social Society, published in 1989, published by Kogyo Kenkyukai) and “Photopolymer Technology” (edited by Akio Yamamoto and Mototaro Nagamatsu, 1988). Published by Nikkan Kogyo Shimbun, etc.), and a desired photocrosslinkable resin composition can be used. The thickness of the photocrosslinkable resin layer is preferably 15 to 100 μm, and more preferably 20 to 50 μm. If the thickness is less than 15 μm, resist peeling or disconnection may occur due to mixing of bubbles with dust as a nucleus or uneven followability, and if it exceeds 100 μm, the amount dissolved and removed by thinning increases. The thinning time may be long.

  The step of thinning the photocrosslinkable resin layer with an aqueous alkali solution according to the present invention is a step of dissolving or swelling the photocrosslinkable resin with an aqueous alkali solution to remove the surface of the resin layer, thereby reducing the thickness. Further, it includes a process of washing away the photocrosslinkable resin that has not been removed or the remaining alkaline aqueous solution by washing with water. Examples of the organic alkaline compound according to the present invention include monoethanolamine, diethanolamine, triethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide (TMAH), and tetraethylammonium hydroxide. And organic alkaline compounds such as trimethyl-2-hydroxyethylammonium hydroxide (choline). The above organic alkaline compounds may be used alone or in combination.

  The content of the organic alkaline compound can be used in the range of 0.1% by mass to 50% by mass. In addition, in order to make the surface of the resin layer more uniform, sulfates and sulfites can be added to the alkaline aqueous solution. Examples of the sulfate or sulfite include alkali metal sulfates or sulfites such as lithium, sodium or potassium, and alkaline earth metal sulfates or sulfites such as magnesium and calcium.

  Among these, an alkaline aqueous solution having a content of the organic alkaline compound of 5 to 25% by mass can be preferably used because the surface of the alkaline aqueous solution can be made more uniform. Moreover, it is preferable for the same reason that at least any one of the organic alkaline compounds selected from TMAH and choline is included. If the content of the organic alkaline compound is less than 5% by mass, unevenness may easily occur in the thinning process. On the other hand, if it exceeds 25 mass%, the thinning rate may be slow. The content of the organic alkaline compound is more preferably 7 to 17% by mass, and further preferably 8 to 13% by mass. The pH of the alkaline aqueous solution is preferably in the range of 9-12. Further, a surfactant, an antifoaming agent, a solvent and the like can be added as appropriate.

  For the alkaline aqueous solution treatment, a dipping method, a paddle method, a spray method, brushing, scraping or the like can be used, and the spray method is most suitable from the viewpoint of the dissolution rate of the photocrosslinkable resin layer. In the case of the spray method, the treatment conditions (temperature, time, spray pressure) are appropriately adjusted according to the dissolution rate of the photocrosslinkable resin layer to be used. The treatment temperature is preferably 15 to 35 ° C. The spray pressure is preferably 0.02 to 0.3 MPa.

  In the thinning treatment according to the present invention, it is necessary to sufficiently wash with water after treating with an alkaline aqueous solution. There are a dip method, a battle method, a spray method, etc. as a method of washing with water, and the spray method is most suitable from the viewpoint of dissolution rate and uniformity.

  The circuit pattern exposure method according to the present invention includes reflection image exposure using a xenon lamp, high-pressure mercury lamp, low-pressure mercury lamp, ultra-high pressure mercury lamp, and UV fluorescent lamp as a light source, single-sided, double-sided contact exposure using a photo tool, and proximity. Examples include a method, a projection method, and laser scanning exposure. When performing scanning exposure, a laser light source such as a He—Ne laser, He—Cd laser, argon laser, krypton ion laser, ruby laser, YAG laser, nitrogen laser, dye laser, or excimer laser is used according to the emission wavelength. The exposure can be performed by wavelength conversion and scanning exposure, or by scanning exposure using a liquid crystal shutter and a micromirror array shutter.

  As a developing method according to the present invention, a developer corresponding to the photocrosslinkable resin layer to be used is used and sprayed from the vertical direction of the substrate toward the substrate surface to remove an unnecessary portion as a resist pattern, and a circuit pattern An etching resist layer corresponding to is formed. In general, a 1% by weight aqueous sodium carbonate solution is used.

  The etching according to the present invention is a method for removing an exposed metal layer other than an etching resist layer formed by development. In the etching process, a method described in “Handbook of Printed Circuit Technology” (edited by Japan Printed Circuit Industry Association, published in 1987, published by Nikkan Kogyo Shimbun) can be used. The etching solution may be one that can dissolve and remove the metal layer, and at least the etching resist layer has resistance. In general, when copper is used for the metal layer, a ferric chloride aqueous solution, a cupric chloride aqueous solution, or the like can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example. Examples 1, 2, 8, and 9 are reference examples.

(Examples 1 to 16)
Using a laminator for dry film resist on a glass substrate epoxy resin substrate (area 170 mm × 255 mm, copper foil thickness 12 μm, substrate thickness 0.1 mm, manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: CCL-E170) A dry film resist for resolution (manufactured by Hitachi Chemical Co., Ltd., trade name: RY3625, thickness 25 μm) was thermocompression bonded to form a photocrosslinkable resin layer.

  Next, after peeling off the carrier film, a thinning treatment was performed using an alkaline aqueous solution (liquid temperature 25 ° C.) shown in Table 1. The thinning treatment was performed by spraying an alkaline aqueous solution at a spray pressure of 0.05 MPa, and a thinned dry film was obtained by sufficient water washing treatment and cold air drying. Since the solubility of the solder resist in the aqueous alkali solution differs in each example, the treatment time was changed as shown in Table 1 for each solution.

  After thinning, the thickness of the thinned portion was measured at 10 points, and the maximum value and the minimum value were determined. As can be seen from the maximum and minimum values, 5 to 25% by mass of TMAH and choline and TMAH to which sodium sulfate and sodium sulfite were added had good film thickness uniformity of the dry film resist.

  Next, contact exposure was performed using an exposure original photomask having a minimum line & space of 20 μm. Subsequently, development processing was performed using a 1% by mass sodium carbonate aqueous solution (liquid temperature 30 ° C., spray pressure 0.15 MPa) to form an etching resist layer. Next, the substrate on which the etching resist layer was formed was treated with a ferric chloride solution (liquid temperature 40 ° C., spray pressure 0.20 MPa), and etching was performed by removing the copper foil other than the etching resist layer. Next, the remaining etching resist layer was removed with a 3% by mass sodium hydroxide solution at 40 ° C. to obtain a metal pattern. As a result of observing the obtained metal pattern with an optical microscope, no short-circuiting or disconnection occurred in the line and space 20 μm portions sparsely present in the surface, and a good metal pattern could be obtained.

(Comparative Examples 1-20)
A metal pattern was prepared in the same manner as described in Examples 1 to 16 except that the alkaline aqueous solution (liquid temperature 25 ° C.) shown in Table 2 was used. In any alkaline aqueous solution, the required treatment time was significantly increased.

  The present invention is widely used for producing a fine metal pattern using a subtractive method. For example, it can be used as a method for manufacturing a printed wiring board or a lead frame.

Claims (1)

Forming a photo-crosslinkable resin layer on a substrate, treating the thin film of the photo-crosslinkable resin layer with an alkaline aqueous solution comprising an organic alkaline compound, exposure of the circuit pattern, development, viewed including the etching processing in this order , the concentration of the organic alkali compound of the aqueous alkali solution is from 5 to 25 wt%, wherein the free Mukoto at least one kind of alkaline aqueous solution is selected tetramethylammonium hydroxide, from trimethyl-2-hydroxyethyl ammonium hydroxide A method for producing a metal pattern.