JP5588380B2 - Dry film resist thinning method - Google Patents

Description

  The present invention provides a DFR thinning method that can uniformly dry a dry film resist (hereinafter sometimes abbreviated as “DFR”) without unevenness.

  As a method for manufacturing a printed wiring board or a lead frame, there is a subtractive method in which an etching resist layer is formed on a substrate and a metal layer not covered with the etching resist layer is removed by etching. Compared to other methods, this method has advantages such as a shorter manufacturing process and lower cost, and stronger adhesion between the metal pattern and the insulating plate. It has become. And, as a method of providing an etching resist layer by a subtractive method, a method using a sheet-like photosensitive material called DFR and a liquid photoresist is mentioned, and among these, the handleability is excellent and a through hole by tenting is used. DFR is generally preferred because it can be protected.

  Nowadays, along with the recent downsizing and multi-functionalization of electronic devices, printed wiring boards used inside the devices are also being densified and metal patterns are being miniaturized. Printed wiring boards having a metal pattern of 50 to 80 μm and a conductor gap of 50 to 80 μm are manufactured. Further, with further progress in high density and fine wiring, ultra fine metal patterns of 50 μm or less are required. Along with this, the requirements for pattern accuracy and impedance are also increasing. In order to achieve such a fine metal pattern, a semi-additive method has been conventionally studied. However, there are problems such as a significant increase in the number of steps and poor adhesion of plated copper.

  In the case of forming such a fine metal pattern in the subtractive method, it is of course necessary to improve the technical level and management level of all production lines, but etching is a major point among them. 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, liquid composition management, the angle and strength of spraying the liquid onto the substrate, etc. It is necessary to adjust the optimum etching conditions. Further, side etching is influenced not only by adjusting the etching conditions but also by the film thickness of the etching resist layer. That is, the thicker the film, the more difficult the liquid circulates between the fine resist patterns, and as a result, the side etching increases. The thickness of DFR, which is currently the mainstream, is about 25 μm thick. On the other hand, in order to form a fine metal pattern, it is necessary to make the resist film thickness as thin as possible. DFR is being developed and commercialized. However, in such a thin DFR, there is a problem that the mixing of bubbles with dust as a nucleus and the follow-up of unevenness become insufficient, and resist peeling and disconnection occur.

In order to solve such a problem, in a method for producing a conductive pattern by a subtractive method, after DFR is pasted on a substrate, DFR is performed with a high-concentration alkaline aqueous solution having an inorganic alkaline compound content of 5 to 20% by mass. A method for forming a conductive pattern has been proposed, in which a thin film is processed by a method of removing the film at a time, and then a circuit pattern is exposed, developed, and etched (for example, a patent document) 1). In Patent Document 1, as a step of removing an unnecessary resist, a pH of 5 to 5 containing at least one of inorganic alkali compounds selected from alkali metal carbonates, alkali metal phosphates, and alkali metal silicates. A method of removing 10 aqueous solutions at a supply flow rate of 0.03 to 1 L / min per 1 cm ^{2 of} resist is described. The method of using the removing liquid is not described in detail in the cited document 1, but when it is once used and discharged as it is, or when a certain amount of removing liquid is stored in the tank in advance and repeatedly used. Can be considered. Although there is no specific description of the amount of the removal liquid discharged when it is discharged as it is, for example, a double-sided copper-clad laminate (area 510 mm × 340 mm, copper foil thickness 12 μm, substrate thickness 0.2 mm, Mitsubishi A description will be given of the results of an experiment conducted assuming that a 40 μm thick DFR attached to Gas Chemical Co., Ltd. (trade name: CCL-E170) is thinned to 20 μm. In this thinning process, a removal liquid corresponding to half the area of the substrate was constantly discharged as a minimum supply amount of the removal liquid necessary for removing unnecessary resist, and unnecessary DFR was removed. Considering the amount of discharge at that time, even if only one sheet (single side) is processed, the discharge amount is 26 to 867 L / min, and there is a problem in cost regarding the cost of the removal liquid, and the discharged removal liquid is discarded. There was also a problem that a separate wastewater treatment facility was required.

  Next, when a certain amount of removal liquid is stored in the tank in advance and used repeatedly, if the removal liquid is a new liquid after the bathing, thinning processing was possible without problems, but the removal liquid was circulated. If the concentration of the DFR dissolved material contained in the removal liquid exceeds a certain amount, regardless of the pH of the removal liquid, a phenomenon (cloudy unevenness) occurs in which the thinned DFR surface becomes cloudy white. There was a case. After performing the thinning process, a metal pattern is formed by performing exposure, development, and etching. However, where the cloudy unevenness occurs, the exposure amount is insufficient and the curing is insufficient, and the DFR is lower than the normal part in the development process. It becomes thin or DFR is completely dissolved. As described above, a portion where DFR should originally exist but a portion where DFR is not present or a portion where DFR is thinner than a normal portion is etched in the next etching process to obtain a metal pattern having no defect. In some cases, it becomes impossible to use the product at all.

International Publication No. 2009/096438 Pamphlet

  The present invention is an environmentally friendly DFR thinning method that can uniformly thin the DFR and can regenerate the removal liquid, thereby greatly reducing the amount of waste. It is an object of the present invention to provide a thin film processing method capable of greatly reducing the processing time for regeneration of the removal liquid.

  As a result of investigations by the present inventors, a DFR thin film comprising a step of treating the DFR on the substrate to which the DFR is attached with a treatment liquid, and then a step of removing unnecessary DFR on the surface using the removal liquid. In the chemical treatment method, before the DFR concentration contained in the removal liquid exceeds 0.5% by mass, the DFR dissolved in the removal liquid is aggregated and precipitated by lowering the pH once, as a filter aid. A DFR thin film characterized by using cellulose powder, solid-liquid separation using a pressure-type dehydration filter, returning the pH of the filtrate after separation to neutral, and reusing it as a removal liquid. The above problem could be solved by the conversion processing method.

  In the present invention, the DFR on the substrate is uniformly thinned with a processing solution and a removing solution without unevenness. As a thinning treatment method, first, a treatment step is performed with a treatment solution to insolubilize the DFR micelles once and make it difficult to dissolve and diffuse in the high-concentration alkaline aqueous solution. Then, after that, a step of removing unnecessary DFR on the surface is performed by a method of removing micelles at once, and thinning is performed. When the removal liquid is used repeatedly and the DFR concentration dissolved in the removal liquid increases, clouding unevenness occurs on the thinned DFR surface, and the DFR is dissolved in excess of 0.5% by mass. The liquid can no longer be used, and waste liquid treatment has been performed so far. However, even in this case, the burden of the amount of waste liquid is large and further reduction is necessary. As a prolongation of life, there is a method of removing DFR dissolved in the removal liquid using various filters. However, when an inexpensive rough filter is used, the dissolved fine DFR cannot be captured and cloudy unevenness may occur. However, when an expensive fine filter was used, the filter was severely clogged, and it was not appropriate considering the labor and cost of replacing the filter. As a result of intensive studies in the present invention, before the DFR concentration contained in the removal liquid exceeds 0.5 mass%, the DFR dissolved in the removal liquid is aggregated and precipitated by temporarily lowering the pH of the removal liquid. It was found that it was possible to perform solid-liquid separation using a pressure-type dehydration filter, return the pH of the filtered water after separation to neutral, and reuse it again as a removal liquid. Depending on the type of DFR, the regeneration of the removal liquid can be performed at least five times. By reusing the removal liquid in this way, the amount of waste liquid treatment can be further reduced. It became.

  Furthermore, the important point when performing the regeneration process of the removal liquid in the thinning process is the speed of the regeneration process. The speed of thinning differs depending on the type of DFR. When a DFR with a slow thinning speed is used, the speed of the regeneration process is faster than that of the thinning process. Reproduction is possible, but when a DFR with a high thinning process speed is used, the reproduction process speed is slower than the thinning process speed, and the reproduction process may not catch up. In particular, when performing double-sided processing in which DFR is pasted on both sides of the substrate, twice the amount of DFR is dissolved in the removal liquid compared to single-sided processing, and therefore it is necessary to increase the speed of the regeneration processing. It was. As a result of examining this point, it was found that the filtration rate can be greatly improved by performing a solid-liquid separation process using a pressure-type dehydration filter and adding cellulose powder as a filter aid. Further, it was found that dehydration filtration can be performed more efficiently by using a cellulose powder having a fiber diameter of 10 to 30 μm and a fiber length of 30 to 200 μm.

It is the schematic diagram which represented the structure of the thin film processing apparatus simply. It is a simple flowchart showing the process of reproducing | regenerating a removal liquid.

  The DFR thinning method of the present invention will be described in detail. The substrate to which the DFR is attached is obtained by attaching the DFR to at least one surface of the substrate. For the pasting, for example, a laminator device that presses and presses a rubber roll heated to 100 ° C. or higher is used. The substrate may be subjected to pretreatment such as pickling. After pasting, the DFR carrier film is peeled off, and the DFR film is thinned.

  After the DFR thinning method of the present invention, the circuit pattern is exposed, further developed to form an etching resist layer, and then a metal layer other than the etching resist layer is etched to form a conductive pattern. be able to.

  Examples of the substrate include a printed wiring board and a lead frame substrate. Examples of the printed wiring board include a flexible substrate and a rigid substrate. As the flexible substrate, polyester, polyimide, aramid, or polyester-epoxy base is usually used as a material for the insulating layer. 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 thereof, which is very flexible. The thickness of the insulating layer or metal layer may be outside this range. The flexible substrate may be in a sheet form or a roll form. If it is a roll-like form, steps such as thinning treatment, exposure, development, etching, etc. can be processed by a roll-to-roll method.

  As a rigid substrate, a necessary number of insulating substrates in which epoxy resin or phenol resin is dipped in a paper base material or glass base material are stacked to form an insulating layer, and a metal foil is placed on one or both sides, and heated and pressed. A laminated layer provided with a metal layer can be used. In addition, a multilayer shield plate produced by laminating prepreg, metal foil, etc. after processing the inner layer wiring pattern, and a multilayer plate having through holes and non-through holes are also included. 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, gold, silver, and aluminum, with copper being the most common. These printed circuit boards are, for example, “Printed Circuit Technology Handbook-Second Edition” (edited by the Printed Circuit Society of Japan, published by Nikkan Kogyo Shimbun) or “Multilayer Printed Circuit Handbook” (edited by JA Scarlet, Inc.). What is described in Modern Chemical Co., Ltd. can be used. Examples of the lead frame substrate include iron nickel alloy and copper alloy substrates.

  DFR is a commonly used photosensitive material for circuit formation, and includes a negative resist in which a light irradiation part is cured and insolubilized in a developer. The DFR is composed of at least a photocrosslinkable resin layer, and a photocrosslinkable resin layer is provided on a carrier film (transparent support) such as polyester. In some cases, the photocrosslinkable resin layer is covered with a protective film such as polyethylene. It has become the composition. The negative photocrosslinkable resin layer is composed of, for example, a binder polymer containing a carboxyl group, a photopolymerizable unsaturated compound, a photopolymerization initiator, a solvent, and other additives. Their blending ratio is determined by a balance of required properties such as sensitivity, resolution, hardness and tenting property. 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, the resist may be peeled off or disconnected due to the inclusion of bubbles with dust as a core or the uneven follow-up ability. If the thickness exceeds 100 μm, the amount removed by dissolution will increase. The processing time may become longer.

  The thinning process is a process for reducing the thickness of the DFR substantially uniformly, and is 0.05 to 0.9 times the thickness before the thinning process. The thinning process is roughly divided into two processes. First, a step of making the DFR photocrosslinkable resin component micelles insoluble once using a high-concentration alkaline aqueous solution as a treatment solution, making it difficult to dissolve and diffuse in the alkaline aqueous solution, and second, removing the insolubilized micelles. It is a process. Thereafter, a step of sufficiently washing the surface of the photocrosslinkable resin layer from which the micelles have been removed to form a thin film may be provided.

  Alkaline compounds used in the treatment liquid include alkali metal carbonates such as lithium, sodium or potassium carbonate or bicarbonate, alkali metal phosphates such as potassium and sodium phosphate, lithium, sodium or potassium An inorganic alkaline compound selected from alkali metal hydroxides such as hydroxides of alkali metal silicates such as potassium and sodium silicates. Examples of organic alkaline compounds include monoethanolamine, diethanolamine, triethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, trimethyl- Examples include organic alkaline compounds such as 2-hydroxyethylammonium hydroxide (choline). The above alkaline compounds according to the present invention may be used alone or in combination. Among these, particularly preferable compounds include alkali metal carbonates.

  The treatment liquid preferably contains 5 to 20% by mass of the alkaline compound with respect to the treatment liquid. If it is less than 5% by mass, micelles in the middle of dissolution and removal tend to dissolve and diffuse, and the thinning process may become non-uniform due to the flow of the treatment liquid. Moreover, when it exceeds 20 mass%, precipitation will occur easily and the temporal stability of the liquid and workability may be inferior. The pH of the solution is preferably in the range of 9-12. In addition, a small amount of a surfactant, an antifoaming agent, a solvent and the like can be added as appropriate.

  The step of once insolubilizing the micelles of the photocrosslinkable resin component using the treatment liquid is preferably performed by a so-called dip method in which the substrate on which DFR is attached is immersed in the treatment liquid. By performing the dip method, the photocrosslinkable resin surface can be uniformly micelle.

  Specifically as a temperature range of a process liquid, 10-50 degreeC is preferable, More preferably, it is 15-35 degreeC, More preferably, it is 15-25 degreeC. If the temperature of the treatment liquid varies greatly, the amount of micelles to be insolubilized becomes unstable, so it is desirable to keep the temperature of the treatment liquid constant.

  The removal liquid used in the step of removing insolubilized micelles in the present invention is an aqueous solution having a pH value in the range of 6.0 to 9.0 at a temperature of 20 ° C., and unnecessary DFR dissolved in the removal liquid. An aqueous solution having a concentration of 0.5% by mass or less is used. Using this removal liquid, the photocrosslinkable resin component insolubilized with the high-concentration alkaline aqueous solution is redispersed and dissolved and removed.

  The removal liquid used in the present invention preferably contains at least one of inorganic alkaline compounds selected from alkali metal carbonates, alkali metal phosphates, and alkali metal silicates. Further, the pH value of the removal liquid at a temperature of 20 ° C. is more preferably in the range of pH 7.0 to 8.5. If the pH is less than 6.0 in the unnecessary DFR removal step, the photocrosslinkable resin component dissolved by redispersion aggregates and becomes an insoluble sludge and adheres to the thinned DFR surface, and the dry film is thinned. White haze unevenness occurs on the surface. On the other hand, if the pH of the aqueous solution exceeds 9.0, dissolution and diffusion of the photocrosslinkable resin component is promoted and unevenness of the film thickness is generated in the surface. Similarly, the surface of the dry film subjected to thinning treatment is white. Cloudy unevenness occurs.

  The pH of the removal solution used in the present invention may be adjusted after adjusting the pH of the solution using sulfuric acid, phosphoric acid, hydrochloric acid or the like. In addition, if the pH value of the removal solution rises due to the introduction of alkaline compounds from the previous treatment step in the removal treatment step, the necessary amount is added as needed so that it falls within the prescribed range. After being within the range, the removal process can be started again. Furthermore, if the amount of acid added is automatically controlled in advance so that the pH falls within the specified range, the removal treatment can be performed continuously.

  As a method for measuring the pH of the removal liquid used in the present invention, a certain amount of the removal liquid can be collected and the temperature can be adjusted to 20 ° C. and then measured. It is preferable to measure the pH as it is. The removal solution is a solution in which a certain amount of removal solution is stored in the tank in advance and used repeatedly. Therefore, the temperature in the tank is controlled to 20 ° C. and measured at any time with a pH meter installed in the tank. It is preferable to do. Thus, by automatically controlling the temperature and measuring the pH as needed, it is possible to perform the removal process continuously by automatically controlling the amount of acid added as described above. As the pH meter, a commonly used aqueous solution measurement type pH meter can be used. For example, trade name: S650CD manufactured by Iwaki Co., Ltd. can be used.

  The range of the DFR concentration in the removal liquid used in the present invention is 0.5% by mass or less, preferably 0.3% by mass or less, and more preferably 0.2% by mass or less. When the range of the amount of DFR dissolved in the removal liquid is more than 0.5% by mass, white cloudiness unevenness occurs on the DFR surface subjected to the thinning treatment. For this reason, it is necessary to regenerate the removal liquid before the amount of DFR dissolved in the removal liquid exceeds 0.5% by mass.

  As a method for regenerating the removal solution used in the present invention, first, cellulose powder is added as a filter aid while thoroughly stirring the removal solution in which the resist is dissolved. As the filter aid, activated carbon, diatomaceous earth, and the like are generally used. However, although activated carbon can be separated, a long time is required to complete the filtration, which is not realistic. Although diatomaceous earth has a high separation speed, solid-liquid separation is not complete, and resist remains in the filtrate after filtration, or oxide compounds such as silicon oxide contained in diatomaceous earth adhere to the surface of the substrate. In the case of a product, defects may occur. Cellulose powder, on the other hand, is mainly composed of cellulose and does not adversely affect the final product of the substrate. Furthermore, cellulose powder is completely captured during filtration, and cellulose powder may remain in the removed liquid after filtration. Since there was almost nothing, it was possible to use it safely.

  There is no restriction | limiting in particular as addition amount of a cellulose powder, Although the optimal value exists in the addition amount also with the kind of cellulose powder, the range of 0.1-1.0 mass% with respect to the mass of a removal liquid exists. Preferably, the range of 0.2-0.6 mass% is more preferable. When the added amount is small, the filtration rate is not improved, and when the added amount is increased, the thickness of the resist solid formed on the filter after dehydration (hereinafter sometimes abbreviated as “cake layer”) increases. In some cases, it may be necessary to increase the number of times of dehydration filtration, or there may be a problem that the volume of the waste treatment product increases because the cake layer becomes bulky.

  Cellulose powder can be a commercially available one that is generally used, but more efficiently by using a cellulose powder having a fiber diameter in the range of 10 to 30 μm and a fiber length of 30 to 200 μm. Dehydration filtration can be performed. A more preferable fiber diameter is 15-30 micrometers, and a still more preferable fiber diameter is 15-25 micrometers. Moreover, a more preferable fiber length is 50 to 150 μm, and a more preferable fiber length is 100 to 150 μm. If the fiber diameter is too thin or too thick, the dehydration efficiency may deteriorate. If the fiber length is too short, the dehydration efficiency may deteriorate. If it is too long, the dewatering efficiency will deteriorate. In some cases, the bulk of the cake layer becomes high, which may cause a problem that the waste becomes bulky. Specific examples of cellulose powder used include KC Flock (registered trademark) manufactured by Nippon Paper Chemical Co., Ltd., ARBOCEL (registered trademark) manufactured by Toa Kasei Co., Ltd., and ashless pulp manufactured by ADVANTEC Co., Ltd. Examples thereof include filter paper powder and Selish (registered trademark) manufactured by Daicel Finechem Co., Ltd.

  The measuring method of the fiber length and the fiber diameter of the cellulose powder used in the present invention was measured using FQA; Fiber Quality Analyzer manufactured by OpTest Equipment Co., Ltd. The measurement conditions are fiber length: 0.04 to 10.0 mm, fiber width: 7 to 60 μm, and fine: 0.04 to 0.20 mm. For the fiber length, the value indicated by the term of the weighted average fiber length [LW] was used, and for the fiber diameter, the value indicated by the term [FiberWidth] was used.

  As the next step of the regeneration method of the removal liquid used in the present invention, an acid is added while the removal liquid is well stirred, and the pH is adjusted to 4.0 or lower. The range of pH is preferably in the range of 3.0 to 4.0, more preferably in the range of 3.0 to 3.5. The lower the pH, the easier the aggregation of DFR proceeds. However, it is necessary to return the pH to neutral again in the subsequent step, and an excessive alkaline solution is required at this time. It is preferable to keep it to 0. The acid used for lowering the pH can be used without any problem as long as it is a commonly used acid. For example, it is preferable to use sulfuric acid, hydrochloric acid, phosphoric acid or the like.

  As the next step of the regeneration method for the removal liquid used in the present invention, solid-liquid separation is performed using a pressure-type dehydration filter. The solid-liquid separation is a step of acidifying the removal liquid to separate the aggregated and precipitated DFR (solid component) and the removal liquid (liquid component). The equipment used in the solid-liquid separation process includes a cyclone type that uses centrifugal force, but the cyclone type has an important factor in the difference in specific gravity of the solid and liquid, and the specific gravity of DFR is the same as the removal liquid. There is no big difference and it takes a long time to completely separate. For this reason, a pressure filtration system is preferable as an apparatus used for solid-liquid separation because it enables efficient solid-liquid separation. Moreover, as a filter to be used, the thing made from paper, the thing made from a chemical fiber, a nonwoven fabric, etc. can be used suitably. Although there is no restriction | limiting in particular as a hole diameter, it becomes possible to filter efficiently by using a thing about several micrometers-tens of micrometers. The pressure-type dewatering filter is a pressure-type filtration method using a general filter, and is a method of promoting filtration by applying pressure to the liquid surface. As the pressure filtration system, for example, each company's filter press machine, others, Repressor (registered trademark) manufactured by Sanshin Seisakusho Co., Ltd., Autocus Spong Cleaner (Caspon Cleaner, registered trademark) manufactured by Mitaka Industrial Co., Ltd., An Exceller (registered trademark) filter manufactured by Sankyo Giken Co., Ltd. can be used.

  As the final step of the method for regenerating the removal liquid used in the present invention, an alkaline compound is added while thoroughly stirring the filtered removal liquid to return the pH to neutrality. As neutrality, it is most preferable to adjust the removal liquid to pH = 7 at a temperature of 20 ° C. However, if the removal liquid can be adjusted to 6.0 to 9.0, which is a pH in a range that can be used as the removal liquid, Can be used without any problem. Further, the pH range is more preferably 7.0 to 8.5. As an alkaline compound used for pH adjustment, at least any one of inorganic alkaline compounds selected from the same types of alkali metal carbonates, alkali metal phosphates, and alkali metal silicates as those used in the removal liquid is used. It is preferable to use seeds. Among these, particularly preferable compounds include alkali metal carbonates.

  The regeneration process for the removal liquid used in the present invention depends on the type of DFR used, but can be regenerated at least five times. However, if the regeneration process is further carried out, the reason has not yet been clarified, but the content of ionic species remaining in the removal liquid increases, so that it is more than necessary in the treatment process with the removal liquid. In some cases, excessive thinning processing may proceed, and a phenomenon may occur in which stable thinning processing cannot be performed. For this reason, the regeneration process can be performed at least five times. After that, it is necessary to determine the disposal time while confirming the type of DFR and the state of the thinning process.

  As a measuring method of the DFR concentration in the removal liquid used in the present invention, it can be measured from the absolutely dry mass. As a specific method, for example, 10 g of the removing solution in which DFR is dissolved is collected in a petri dish, put in a drier at a temperature of 100 ° C., and water is completely evaporated. Next, by measuring the mass after evaporation, the amount (% by mass) of DFR dissolved in 10 g of the removal liquid can be calculated.

  As the step of removing unnecessary DFR on the surface in the present invention, it is desirable to remove the micelles of the photocrosslinkable resin component once insolubilized using the treatment liquid at once, so that a spray method, a brushing method, a scraping method, etc. The spray method is most preferable 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 component to be used. Specifically, the treatment temperature is preferably 10 to 50 ° C, more preferably 15 to 35 ° C, and still more preferably 15 to 25 ° C. The spray pressure is preferably 0.01 to 0.5 MPa, more preferably 0.1 to 0.3 MPa. The spray is preferably ejected from a direction inclined with respect to a direction perpendicular to the surface of the photocrosslinkable resin layer, since it is preferable to remove unnecessary DFR at once without stagnation.

The supply flow rate of the removal liquid is preferably 0.030 to 1.0 L / min per 1 cm ^{2 of} DFR, more preferably 0.050 to 1.0 L / min, and still more preferably 0.10 to 1.0 L / min. When the supply flow rate is within this range, micelles can be removed substantially uniformly in the plane without leaving insoluble components on the surface of the photocrosslinkable resin layer after thinning. When the supply flow rate per 1 cm ^{2 of} DFR is less than 0.030 L / min, poor dissolution of the insolubilized photocrosslinkable resin component may occur. On the other hand, when the supply flow rate exceeds 1.0 L / min, parts such as a pump necessary for supply become enormous and a large-scale device may be required. Furthermore, when the supply amount exceeds 1.0 L / min, the effect of dissolving and diffusing the photocrosslinkable resin component may not change.

  In the thinning process according to the present invention, it is preferable that the DFR surface is sufficiently washed with water after the removal liquid is supplied, the photocrosslinkable resin component insolubilized with the treatment liquid is redispersed and dissolved and removed. The washing method includes a dip method, a paddle method, a spray method, and the like, and since the processing speed is fast, the spray method is most suitable.

  After performing the thinning process according to the present invention, a circuit pattern can be formed by performing exposure, development, and etching. Exposure methods include xenon lamps, high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, reflection image exposure using UV fluorescent lamps as light sources, single-sided and double-sided contact exposure using photo tools, proximity method, projection method, and laser scanning. Exposure is mentioned. 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 development method, a developer corresponding to the DFR to be used is used, and sprayed from the vertical direction of the substrate toward the substrate surface to remove unnecessary portions as a resist pattern, and an etching resist layer corresponding to a circuit pattern is formed. Form. In general, a 1 to 3% by mass aqueous sodium carbonate solution is used.

  Etching is a method of 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.

  Hereinafter, an apparatus used in the thinning method of the present invention will be described in detail.

  FIG. 1 is a schematic diagram simply showing the configuration of the thinning apparatus. In this figure, from the left side, the step (1) of once insolubilizing the micelles of the photocrosslinkable resin layer component using the treatment liquid to make it difficult to dissolve and diffuse in the treatment liquid, and then the step of removing the insoluble micelles ( 2) Next, the step (3) of thoroughly washing the surface of the photocrosslinkable resin layer from which micelles have been removed to make a thin film, and finally using the blower on the surface of the photocrosslinkable resin layer that has been made thin. 1 shows units 1 to 4 used in the step (4) for completely removing the remaining water.

  The substrate 5 with the DFR attached is first inserted from the carry-in entrance 6. The unit 1 in the step (1) is provided with a dip tank 7, and the transport roll 8 is installed in a pair in the dip tank 7. The DFR on the substrate 5 forms a micelle layer insolubilized in the dip tank 7. The processing liquid is supplied from the lower part of the dip tank by the processing liquid supply pump 9 and overflows. The overflowed processing liquid is recovered in the processing liquid storage tank 11 via the processing liquid recovery pipe 10 and reused. Further, a valve 12 is attached to the processing liquid recovery pipe 10, and the old processing liquid can be appropriately discharged from the waste liquid pipe 18 by switching this.

  Next, the substrate 5 is conveyed to the unit 2 in the next step (2) through the connection port 13. The unit 2 is provided with a spray nozzle 14 for removing micelles, and a removing liquid is supplied to and ejected from the spray nozzle to remove insoluble micelles formed on the substrate 5 at once. The spray nozzles 14 for removing micelles are installed on the upper and lower sides of the substrate 5 so as to enable double-side processing. As with the unit 1, the removal liquid is supplied from the storage tank 15 via the pump 16. At the lower part of the unit 2, there are a removed liquid collection pipe 10 and a waste liquid pipe 18 to which a valve 17 is attached. By operating these, it is possible to select collection and disposal.

  Unit 3 and unit 4 are units for the washing step (3) and the drying step (4), respectively. In the unit 3, water is supplied from the water supply pipe 26 to the spray nozzle 19 for washing, and the surface of the substrate 5 is cleaned cleanly. The washed water is discarded through the waste water treatment pipe 20. After washing with water, the substrate 5 is introduced into the unit 4. The unit 4 is provided with a turbo blower 21, a suction pipe 22 of the turbo blower 21 is connected to the unit 4, a plurality of air injection nozzles 24 are connected to the discharge pipe 23 of the turbo blower 21, and air is injected toward the surface of the substrate 5. It is the composition to do. Thereby, water droplets adhering to the substrate 5 are removed, the substrate 5 is unloaded from the carry-out port 25, and a series of thinning processes is completed.

  FIG. 2 is a simple flowchart showing the process of regenerating the removal liquid. First, the removal liquid in which DFR is dissolved is moved to a regeneration processing tank different from the main tank. Here, a required amount of cellulose powder is added while stirring the removal solution. Once the cellulose powder is well dispersed, acid is then added until the pH is in the range of 3.0-4.0. When the pH is completely within the range of 3.0 to 4.0, solid-liquid separation is started using a pressure-type dehydration filter. When the solid-liquid separation is completed, the pH is adjusted to a range of 6.0 to 9.0 by adding alkali to the separated removed liquid. When the pH adjustment is completed, the removal liquid is returned to the main tank to finish.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to this Example.

Comparative Example 1
Double film copper-clad laminate (area 510 mm x 340 mm, copper foil thickness 12 μm, substrate thickness 0.2 mm, manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: CCL-E170) and dry film resist (Asahi Kasei E-Materials Co., Ltd.) Manufactured, trade name: Sunfort (registered trademark) AQ-4038, thickness 40 μm). Next, after the carrier film was peeled off, a thinning treatment was carried out so that the average thickness of the DFR was 10 μm. As the conditions for the thinning treatment at this time, as described in Table 1, a 10 mass% sodium carbonate aqueous solution was used as the composition of the treatment liquid, and the thinning treatment was performed at a treatment speed of 3 m / min. The time required for one process was 1 min, and a thinning process of 10 μm was possible by one process. In addition, the temperature of the process liquid was 20 degreeC and processed by the dip method. The composition of the removal liquid is a sodium carbonate aqueous solution with pH = 7.5, the temperature of the removal liquid is 20 ° C., the spray pressure is 0.15 MPa, and the flow rate of the removal liquid is 0.3 L / min per 1 cm ² of DFR. It was carried out under conditions of pouring. For this reason, the amount of water of the removing liquid required for the thinning process was calculated by the area of the copper clad laminate × 0.3 L / min, and the amount of the removing liquid used was about 520 L / min, that is, 31200 L / hr.

Comparative Example 2
The same thinning treatment was repeated until 140 L of the removal liquid was laid and circulated until the unnecessary DFR concentration dissolved in the removal liquid reached 0.3% by mass, and then discarded. The removal solution is adjusted so that the pH value at 20 ° C. is always in the range of 7.0 to 8.5 by adding 0.5% by mass of sulfuric acid as necessary during the thinning process. did. The copper-clad laminate used in Comparative Example 1 required 80 thinning processes until the DFR concentration in the removal liquid reached 0.3% by mass, and the processing time required about 240 minutes. As a result, 140 L of the removal liquid was used for 240 minutes and then discarded, and finally the removal liquid usage amount was about 35 L / hr.

Comparative Example 3
The thinning treatment was performed in the same manner as in Comparative Example 2 except that the resist solution in the removal solution was repeatedly used until the resist concentration reached 0.6% by mass and then discarded. The amount of removal liquid used was about 18 L / hr, but when the resist concentration in the removal liquid exceeded 0.5% by mass, white cloudy unevenness occurred on the resist surface of the thinned substrate. Could not be used as.

Reference example 1
The same thinning process as in Comparative Example 2 was performed, and subsequently, the removal solution in which 0.3% by mass of DFR was dissolved was moved from the main tank to the regeneration processing tank in which the regeneration process was performed. In the regeneration treatment tank, 1% by mass of sulfuric acid was added while stirring the removal solution, and the pH of the removal solution was lowered to 3.5. In the removal solution with pH = 3.5, the dissolved resist was aggregated, and fine aggregates that were visible were confirmed. Subsequently, this removed liquid was subjected to solid-liquid separation using a fully automatic pressure dehydration filter Exceller (registered trademark) filter EF-10 type (filtration area 0.1 m ² ) manufactured by Sankyo Giken Co., Ltd. The filtration rate was about 40 L / hr, and it took about 210 min to process the removal liquid 140L. Subsequently, a 10% by mass aqueous sodium carbonate solution was added while thoroughly stirring the removed liquid after filtration, and the pH of the removed liquid was adjusted to 7.5. After the pH adjustment, the removal liquid was returned to the main tank, and the thinning treatment was performed again until 0.3% by mass of DFR was dissolved in the removal liquid, and the removal liquid was regenerated. This removal liquid regeneration cycle was repeated five times, after which the removal liquid was discarded. The amount of removal liquid used at this time was about 7 L / hr.

Examples 1-7
The thinning treatment was performed in the same manner as in Reference Example 1 except that cellulose powder was used as a filter aid in the addition amount shown in Tables 1 and 2 when the removal solution was regenerated.

Comparative Example 4
The thinning treatment is the same as in Reference Example 1 except that activated carbon (Nihon Enviro Chemicals Co., Ltd., Shirasagi C) is used as a filter aid in the amount of addition shown in Table 1 when the removal solution is regenerated. Went.

Comparative Example 5
A thinning treatment is performed in the same manner as in Reference Example 1 except that diatomaceous earth (manufactured by Showa Chemical Industry Co., Ltd., # R2000) is used as a filter aid in the amount of addition shown in Table 1 when the removal solution is regenerated. Went.

Reference example 2
The thinning process was performed in the same manner as in Reference Example 1 except that the resist was changed from single-sided to double-sided.

Example 8
A thinning process was performed in the same manner as in Example 1 except that the resist was changed from single-sided to double-sided.

Examples 9-16
A thinning treatment was performed in the same manner as in Example 1 except that the fiber diameter, fiber length, and addition amount of cellulose powder used as a filter aid were changed to the values shown in Table 2 when the removal solution was regenerated. It was.

  As is clear from the comparison between Comparative Examples 1 and 2 and Reference Example 1, the resist thinning method used by regenerating the removal liquid uses an extremely small amount of water and can greatly reduce the amount of waste liquid. It can be seen that this is a gentle thinning method.

  Moreover, as an effect of the addition amount of the cellulose powder as a filter aid, as shown in Examples 1 to 7, the treatment time required for regeneration of the removal liquid is shorter as the addition amount is increased, and an excellent regeneration treatment method is used. I know that there is. When the added amount of cellulose powder is less than 0.2% by mass, the treatment time is delayed, and when it is less than 0.1% by mass, the treatment time is further delayed, and improvement of the filtration rate is not recognized. When the amount is 0.6% by mass or more, the effect on the processing time becomes small, and when the amount exceeds 1.0% by mass, the effect on the processing time is eliminated. It is understood that an addition amount of 0.2 to 0.6% by mass is more preferable.

  When comparing Example 4 and Comparative Examples 4 and 5 with respect to the effect of the type of filter aid, Comparative Example 4 using activated carbon was separable, but no filter aid was added. As compared with Reference Example 1, the improvement in the processing speed was hardly recognized, and it could not be used. In Comparative Example 5 using diatomaceous earth, although the separation speed was fast, the separation was not complete, and DFR remained in the filtered liquid, and could not be used.

  Reference Example 2 and Example 8 show the state of thinning processing and regeneration processing when DFR is attached to both sides. Since DFR is pasted on both sides, compared to Example 1 pasted on one side, the number of processed sheets is half and the DFR concentration in the removal liquid reaches 0.3% by mass. Processing time is also halved. For this reason, in Example 9 in which the regeneration process was performed without adding the cellulose powder, the regeneration process could not catch up because the regeneration process took 210 min. On the other hand, in Example 10 in which the cellulose powder was added and the regeneration process was performed, the regeneration process time was shortened to 105 min, and the regeneration was sufficiently performed within 120 min, which is the time required for the thinning process in which the resist was pasted on both sides. It was possible to repeat the cycle of thinning and regeneration.

  Furthermore, the effects of fiber diameter and fiber length of cellulose powder are shown in Examples 9-12 and Examples 13-16. Regarding the fiber diameter, it can be seen that the processing ability is inferior even if it is too thin or too thick. As an optimal fiber diameter, the range of 10-30 micrometers can be said to be a preferable range. Regarding the fiber length, it can be seen that the treatment capacity improves as the fiber length increases, but gradually reaches a peak when a certain length is exceeded. As an optimal fiber length, it can be said that the range of 30-200 micrometers is a preferable range.

  As is clear from the above examples, reference examples, and comparative examples, the DFR thinning method that uses the removal liquid of the present invention by reprocessing allows the DFR to be uniformly thinned without unevenness. It can be seen that this is an environmentally friendly treatment method that uses very little water and can greatly reduce the amount of waste liquid. In addition, by using cellulose powder as a filter aid, it becomes possible to efficiently perform regeneration treatment, and thinning that enables smooth thinning treatment while repeating the thinning treatment and regeneration treatment cycles. It turns out that it is a processing method.

  The present invention is widely used for forming a metal pattern in a subtractive method, and can be used, for example, for producing a printed wiring board, a lead frame and the like.

1 Process (1) Unit 2 Process (2) Unit 3 Process (3) Unit 4 Process (4) Unit 5 Substrate with Dry Film Resist (DFR) Attached 6 Carrying Inlet 7 Dip Tank 8 Transport Roll 9 Unit 1 Treatment liquid supply pump 10 Treatment liquid (removal liquid) collection pipe 11 Treatment liquid storage tank 12 Valve 13 Connection port 14 Spray nozzle 15 for removing micelles Removal liquid storage tank 16 Removal liquid supply pump 17 Valve 18 Waste liquid pipe 19 Washing with water Spray nozzle 20 Wastewater treatment pipe 21 Turbo blower 22 Suction pipe 23 Discharge pipe 24 Air injection nozzle 25 Carrying out port 26 Water supply pipe

Claims (2)

  Thinning a dry film resist comprising a step of treating the dry film resist on a substrate to which the dry film resist is attached with a treatment liquid, and then a step of removing unnecessary dry film resist on the surface using a removal liquid. In the processing method, before the concentration of the dry film resist contained in the removal liquid exceeds 0.5% by mass, the dry film resist dissolved in the removal liquid is aggregated, precipitated, and filtered by lowering the pH once. Cellulose powder is used as an auxiliary agent, solid-liquid separation is performed using a pressure-type dehydration filter, the pH of the filtered water after separation is returned to neutral, and it is reused again as a removal liquid. A method for thinning a dry film resist.   2. The dry film resist thinning method according to claim 1, wherein the cellulose powder has a fiber diameter of 10 to 30 [mu] m and a fiber length of 30 to 200 [mu] m.