KR100628460B1 - Composition for forming circuit and method of forming circuits using the same - Google Patents

Abstract

The present invention relates to a wiring forming composition and a wiring forming method using the same. In forming wirings of a substrate used in various electronic or electrical devices, the manufacturing process is simplified by reducing the wiring forming process, thereby making a complicated wiring forming process. The present invention relates to a wiring forming composition capable of easily forming wirings, a wiring forming method using the same, and an apparatus including the wirings, so as to prevent various problems from occurring.

Nano metal precursor, inkjet printing, electronic tag, touch panel, lithography, IC card, display device

Description

Composition for wiring formation, wiring formation method using same {COMPOSITION FOR FORMING CIRCUIT AND METHOD OF FORMING CIRCUITS USING THE SAME}

Figure 1 is a photograph showing an embodiment of the RF-ID antenna wiring printed in a silkscreen method using the wiring forming composition of the present invention.

Figure 2 is a photograph showing another embodiment of the RF-ID antenna wiring printed in a silkscreen method using the wiring forming composition of the present invention.

3 is a photograph showing an embodiment of an electrode plate applied by spray coating to a glass substrate using the wiring forming composition of the present invention.

4 is an enlarged photograph of an embodiment of the electrode plate of FIG. 3.

The present invention relates to a wiring forming composition and a wiring forming method using the same. In forming wirings of a substrate used in various electronic or electrical devices, the manufacturing process is simplified by reducing the wiring forming process, thereby making a complicated wiring forming process. The invention relates to a wiring forming composition, a wiring forming method using the same, and an apparatus including the wiring. Or an antenna, an IC card, a display device, or a touch panel device.

Conventionally, in order to form wiring of an RFID tag, an antenna, or an IC card, a flexible copper clad laminate (FCCL), a copper clad laminate for a flexible substrate, which is a raw material thereof, is an essential raw material. In order to manufacture the FPCB (Flexible Printed Circuit Board) having the above-described wiring is manufactured through the following complex process. To introduce this briefly by process, first, the base of FCCL (Flexible Copper Clad Laminate) is either PI (Poly Imide) Film or PET (Poly Ethylene Terephatalate) Film, in order to attach copper foil to PI film or Epoxy adhesive is applied on PET film, copper foil is placed on it and it is made through hot pressing process. In order to make a circuit in the FCCL thus made, a lithography process is generally performed. This process is a process commonly used in semiconductor processes, including a photo mask for manufacturing a circuit, and a scene called a dry film register (DFR). Many expensive equipment such as photoresist, exposure equipment, etching equipment and etching solution, cleaning and drying equipment are required, and each process is complicated and manufactured by a large number of high difficulty processes, which inevitably increases manufacturing costs. There is this.

Also, in order to solve this problem, a new type of technology that is newly developed in recent years has introduced a dry type method of forming a wiring by depositing copper ions by introducing a deposition process during a printing process. Expensive equipment such as sputtering device is needed, and there is a lot of problems of lighting that requires pre-made master pattern.

The above problems in the manufacturing of FCCL not only occur in general PCB manufacturing, but also in various industrial fields such as the formation of wiring required for the manufacture of various display devices and touch panels and the formation of wiring of GOC (Glass On Chip). In the formation of the fine wiring has the same problem and there is a need for improvement.

In order to solve the problems of the prior art as described above, the present invention in forming the wiring of the substrate used in the electronic or electrical equipment, to simplify the process of forming the wiring to reduce the manufacturing cost, through which a complex wiring forming process It is an object of the present invention to provide a wiring forming composition, a wiring forming method using the same, and an apparatus including the wiring, in which various problems do not occur and which can easily form wiring.

Another object of the present invention is to enable a variety of metals with low resistivity as a wiring material to increase the selectivity of the wiring material, and to form a wiring forming composition capable of forming a highly integrated fine wiring having a fine line width and pitch, and using the same A wiring forming method and an apparatus including the wiring are provided.

The present invention to achieve the above object

a) a) a solution of metal salts at a concentration of 0.05 to 1 mol / L; And
B) prepared by reacting a hydrocarbon acid solution having a carboxyl group having 6 to 20 carbon atoms or a salt solution thereof having the same molar equivalent as the metal component of the metal salt, wherein the hydrocarbon acid having the carboxyl group surrounds the metal particle 10 to 90 weight percent of the metal precursor; And

b) 10 to 90% by weight of a dispersion solvent

It provides a wiring forming composition comprising a.

In addition, the present invention

Applying the wiring forming composition on a substrate; And

Drying the coated substrate

It provides a wiring forming method comprising a.

In addition, the present invention

Provided is an apparatus including a wiring manufactured by the wiring forming method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a wiring forming composition comprising 10 to 90% by weight of a nano metal precursor containing a metal particle and a hydrocarbon having a carboxyl group having 6 to 20 carbon atoms surrounding the metal particle and 10 to 90% by weight of a dispersion solvent. It is composed.

As the metal particles used in the present invention, any metal having conventional electrical conductivity may be used, and preferably silver (Ag), copper (Cu), nickel (Ni), aluminum (Al), platinum (Pt), Gold (Au), palladium (Pd), etc. can be used.

The hydrocarbon containing the carboxyl group used in the present invention includes both saturated hydrocarbons or unsaturated hydrocarbons, and preferably having 6 to 20 carbon atoms is more preferable for fluidity and nanoparticle formation of metal nanoparticles.

The nano metal precursor particles preferably have an average particle diameter of 1 to 50 nm, particularly preferably an average particle diameter of 2 to 10 nm, more preferably a distribution of these particles having a D ₁₀ (lower cumulative 10%). Diameter) 1.5 nm, and D ₉₀ (diameter that occupies 90% of the lower cumulative) preferably has a distribution of 25 nm. In the above range may be finely sprayed or coated for the formation of the micro-wiring, in the case of using a fine nozzle may be sprayed without blocking the nozzle may be properly coupled to the base.

In addition, the content of the nano metal precursor in the wiring forming composition of the present invention is not particularly limited, but is preferably included in 10 to 90% by weight, more preferably in 20 to 80% by weight. If it is in the said range, it is more favorable in formation of a conductive circuit wiring, dispersion stability, or apparatus suitability to injection apparatuses, such as an inkjet printer and a spray.

Preferably, the nano metal precursor is mixed with a solution of a metal salt, and a hydrocarbon acid solution having a carboxyl group or a salt solution thereof; And ii) cleaning and drying the nano metal precursor formed in step iii).

More preferably, the metal salt is silver nitrate (AgNO ₃ ), silver acetate (AgCH ₃ COO), copper nitrate (Cu (NO ₃ ) ₂ ), copper acetate (Cu (CH ₃ COO) ₂ ), copper chloride (CuCl ₂ ), nickel nitrate ( Ni (NO ₃ ) ₂ ), nickel acetate (Ni (CH ₃ COO) ₂ ), nickel sulfate (NiSO ₄ ), nickel chloride (NiCl ₂ ), chloroplatinic acid (H ₂ PtCl ₆ ), chlorochloric acid (HAuCl ₄ ), Water-soluble salts such as palladium chloride (PdCl ₂ ), aluminum nitrate (Al (NO 3) 3 .9H ₂ O), anhydrous aluminum chloride (AlCl 3), ammonium chloride (AlCl 3 · 6H 2 O), nickel acetylacetonate soluble in an organic solvent, Acetylacetonates such as copper acetylacetonate and aluminum acetylacetonate, and alkoxides such as nickel ethoxide, copper ethoxide, aluminum ethoxide, aluminum isopropoxide and aluminum butoxide which can be hydrolyzed It is preferable to use one or more selected from.

In addition, in the hydrocarbon acid solution having a carboxyl group or a salt solution thereof, which is a raw material necessary for synthesizing the precursor, the hydrocarbon acid or a salt thereof is a hydrocarbon having a carboxyl group (COO ^- Function) and includes both an acid or salt form and is saturated Both hydrocarbons and unsaturated hydrocarbons are applicable.

Preferably the hydrocarbon acids or salts thereof are citric acid, glutamic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, isostearic acid, sodium citrate, sodium glutamate, sodium laurate, sodium myristate, sodium Consists of palmitate, sodium stearate, sodium oleate, sodium isostearate, potassium citrate, potassium glutamate, potassium laurate, potassium myristate, potassium palmitate, potassium stearate, potassium oleate and potassium isostearate It is good to select at least 1 type from a group.

In addition, in preparing the nano-metal precursor particles of the wiring forming composition of the present invention, the content of the metal salt component in the reaction is preferably in the range of 0.05 mole / l to 1 mole / l. If the particle size is less than 0.05 mole / ℓ, the particle size is small, but the yield is low, the mass productivity is low, and if it is more than 1 mole / ℓ, the mass productivity is possible, but the size of the particle may be large, so within the above range It is good to be. More preferably, 0.5 mole / L to 0.7 mole / L is sufficient to satisfy the above conditions.

In addition, in the case of a hydrocarbon acid solution having a carboxyl group (COO ^- Function) which is the other raw material, it is preferable to react by mixing a molar equivalent number such as Mole number of the metal component of the metal salt. This means that when the amount of the metal salt is less than the Mole number, the unreacted material of the metal salt is present, the reaction loss occurs and the yield cannot be increased, and economical consideration is taken into consideration, and the amount of the metal salt is more than the Mole number of the metal salt. In this case, the unreacted carboxyl group remains, which causes the aggregation of the reactants to be severe, and to solve the difficulty in obtaining nanoparticles of a desired degree.

In addition, the nano-metallic precursor particles produced by the above reaction are washed to remove foreign substances such as water-soluble salts other than the reaction product, and are dried to obtain a dried body.

In addition, the step of heating the nano metal precursor formed in step ii) after step ii) in order to reduce the carboxyl group and increase the metal content while preventing agglomeration of the nano metal precursor formed by drying may be further performed. .

That is, a portion of the carboxyl groups on the surface of the nano metal precursor produces carbon dioxide and water while removing the nano metal precursor obtained by the reaction, washing, and drying in a range of about 200 to 300 ° C., thereby removing the nano metal precursor. The metal content can be increased, which is better.

Preferably, the metal content of the nano metal precursor of the wiring forming composition of the present invention is preferably 70% by weight or more.

In addition, the nano-metallic precursor of the present invention is a raw material for preparing the nano-metallic precursor particles having a structure similar to the result of the reaction, apart from the reaction, conventional fatty acid metal salts, more specifically silver stearate, nickel paratoluate It is also possible to utilize copper oleate, aluminum stearate, aluminum-12 hydroxy stearate and the like.

In addition, in the wiring forming composition of the present invention, a variety of known dispersion solvents may be used as the dispersion solvent, preferably aliphatic alcohols such as n-decanol, aromatic solvents such as n-Hexane, Toluene, Xylene, Phenol, Terpineol And Butyl Carbitol Acetate is one or more selected from the group consisting of. Terpineol and Butyl Carbitol Acetate, in particular, have high boiling points and are more viscous.

In addition, the content of the solvent is not particularly limited, but is preferably included in 10 to 90% by weight, more preferably 20 to 80% by weight in the wiring forming composition of the present invention. When it is in the said range, it is more favorable in formation of a conductive circuit wiring, dispersion stability, or apparatus suitability to injection apparatuses, such as an inkjet printer and a spray.

The wiring forming composition of the present invention may have a sol or paste phase, and may further include 0.01 wt% to 10 wt% of a conventional dispersant, thickener, or additive as necessary to improve physical properties.

In another aspect, the present invention provides a method for forming a wiring using the wiring forming composition. That is, the wiring forming method comprising the step of applying the wiring forming composition on a substrate and drying the coated substrate.

The substrate refers to any substrate capable of forming a conductor wiring, including a resin substrate, a glass substrate, or a semiconductor substrate including a known PCB, FPCB, and the like. In addition, the application form includes not only the application in the form of wiring, but also the entire application of the substrate.In order to form the wiring, the composition for forming a wiring in the form of a sol or paste can be used for inkjet printing, , Wiring using inkjet printer, sol or paste for silk screen use, wiring using silk screen machine, sol or paste for spray use, and spray gun And the method of coating.

In the case of the spray method, the whole may be applied, or the wiring forming method may be applied in which a mask film is applied in a predetermined pattern and then sprayed on the entire surface, and then the mask film is removed to form a pattern.

In addition, by applying a conventional lithography method, the photoresist is coated on the entire surface of the substrate, and then exposed and cured using Photo-Mask designed for the wiring to be formed, followed by etching, thereby removing the uncured photoresist. A method of filling the thin recesses in the thin recesses, which are thin grooves in which the photoresist is removed, may be applied to the thin recesses. As a result, a wiring having a thickness of 15 to 30 μm thicker than the printing method described above can be obtained. Similarly, a film having a pattern formed thereon is laminated on the substrate through adhesion or the like, or after laminating the film on the entire surface to remove only the film of the portion to be wired to form the thin recessed parts as described above. The composition may also be filled.

The formed wiring may have a fine wiring width and pitch according to the miniaturization of the metal precursor particles, and thus the wiring formed and coated may have a line width of 1 to 30 μm. In addition, a protective layer may be formed by stacking a protective film in a single layer or a double layer before applying the wiring forming composition.

The substrate is coated as described above is subjected to a drying process. The drying process is preferably maintained for 10 to 30 minutes at 120 to 300 ℃.

In addition, in the drying step, the weight loss ratio at the time of ignition loss of the nano metal precursor may be 2 to 20% by weight or less. More preferably, it is more than 3 to 5 weight%. When the weight loss ratio is less than 2% by weight, the dispersion is not properly performed in the solvent, but agglomeration occurs. When the weight loss rate is 20% by weight or more, the processing time in the heat treatment process for converting the metal after wiring becomes long, Even if the wire is processed for a long time, the wiring is poorly formed and filling is not performed properly, which may cause the specific resistance of the formed wiring to be increased.

In addition, after the wiring molding is completed, the coated substrate is laminated in a single or double protective film after the drying process step to form a protective layer for preventing oxidation of the wiring, penetration of external moisture and contamination by this. have.

In another aspect, the present invention provides a device comprising a wiring manufactured by the wiring forming method. The device may include any device including electric wiring, and preferably, an electronic tag (RF-ID Tag), an antenna, an IC card, a display device (especially, a mobile phone, a PDA, It can be applied to a method for forming wiring of various electronic circuits including a portable such as a notebook) or a touch panel device.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1 Formation of Wiring on Heat Resistant Film

In preparing the nano-metal precursor particles were prepared by the following method. First, in order to prepare a 0.1 mole / L solution by weighing silver nitrate (AgNO ₃ ), 16.98 g of commonly used reagent grade nitrate was quantified and dissolved in ultrapure water to adjust the total amount to 1 L. Also on the other hand, the reagent grade sodium stearate was weighed to make a 0.1 mole / L solution, and then the two solutions were mixed in an apparatus equipped with a stirrer. The material produced was Silver Stearate. Silver Stearate, a reactant, was obtained from the filter and washed with ultrapure water until no Na ⁺ ions and NO ₃ ⁻ ions were detected. After washing, drying was performed in a drier set at 80 ° C for 12 hours.

10 g of the organic compound thus obtained was placed in a 500 ml glass beaker placed on a hot plate, and heated at atmospheric pressure and air to maintain 250 ° C. As heating the silver stearate of white melted from the surface gradually turned to brown, and after 1 hour after the start of heating turned dark brown. The powder thus obtained was 2.5 g. When the powder was added to 100 ml of n-Hexane and stirred for 15 minutes, 100 ml of nano metal precursor sol (Sol) dispersed in n-Hexane (viscosity: 4 cPs, specific gravity: 0.89, Loss on ignition: 11.8 wt%). Apply this to PI (Poly Imide) Film using Spin Coating Machine, pre-dry it with a dryer of about 60 ℃, put it in the high temperature dryer set at 220 ℃, hold it for 15 minutes, take it out of the dryer, and measure the resistivity by measuring with resistance measuring device 3.5 * 10 ^-5 Ωcm, the color of the wiring was silvery wiring.

[Examples 2 to 11]

The same method as in Example 1 was performed, but it was different depending on the type and content of the solvent and the type and content of the thickener to disperse the nano metal precursors as shown in Table 1 below. In Table 1, the unit of the input amount of the nano metal precursor and the thickener is weight%, the remaining amount is a solvent, and the thickener used was nitro cellulose (Nitro Cellulose, molecular weight 150,000).

In the experiments of Examples 2 to 11, the following results were obtained. The wiring formation method at this time was performed by the silk screen method. The result of this is as shown in Figs.

TABLE 1

division  Nano Metal Precursor Type of solvent Thickener Type ^* Thickener input Heat Treatment Condition ^** (℃ * min) Viscosity (cP) Wiring thickness (㎛) Properties after coating Resistivity (Ωcm) Adhesion Example 2 30 Terpineol-Butyl Carbitol Acetate Mixture N.C 0.5 220 * 30 170,000 2.0 6.8 * 10 ^-5 No dropout Example 3 40 Terpineol-Butyl Carbitol Acetate Mixture " " 220 * 30 200,000 2.2 2.2 * 10 ^-5 " Example 4 50 Terpineol-Butyl Carbitol Acetate Mixture " " 220 * 30 200,000 2.2 1.2 * 10 ^-5 Somewhat eliminated Example 5 60 Terpineol-Butyl Carbitol Acetate Mixture " " 220 * 30 200,000 2.2 2.2 * 10 ^-6 " Example 6 70 Terpineol-Butyl Carbitol Acetate Mixture " " 220 * 30 200,000 2.2 2.2 * 10 ^-6 " Example 7 30 Terpineol-Butyl Carbitol Acetate Mixture - - 220 * 30 70,000 2.0 8.3 * 10 ^-6 Somewhat eliminated Example 8 30 Terpineol-Butyl Carbitol Acetate Mixture N.C 0.1 220 * 30 130,000 2.2 2.5 * 10 ^-3 Somewhat eliminated Example 9 30 Terpineol-Butyl Carbitol Acetate Mixture " 0.3 220 * 30 150,000 2.3 3.8 * 10 ^-3 No dropout

Example 12

In preparing the nano metal precursor particles, it could be prepared by the following method. In order to prepare a solution of 0.08 mole / L by weighing silver nitrate (AgNO ₃ ), 13.59 g of commonly used reagent grade nitrate was quantified and dissolved in ultrapure water to adjust the total amount to 1 L. On the other hand, reagent grade potassium stearate was weighed to make a 0.08 mole / L solution, and the two solutions were mixed in an apparatus equipped with a stirrer. The material produced was Silver Stearate. Silver Stearate, a reactant, was obtained in a filter and washed with ultrapure water until no K ⁺ ions and NO ₃ ⁻ ions were detected. After washing, drying was performed in a drier set at 80 ° C for 12 hours.

10 g of the metal organic compound thus obtained was placed in a 500 ml glass beaker placed on a hot plate, and heated at atmospheric pressure and air to maintain 250 ° C. The white silver stearate melted from the surface as the heating was turned, and the color gradually changed to brown, and the color became dark brown for 1 hour after the start of heating. The powder thus obtained was 2.1 g. When the powder was added to 20 ml of n-Hexane and stirred for 15 minutes, 20 ml of nano metal precursor sol (Sol) dispersed in n-Hexane (viscosity: 6 cPs, specific gravity: 0.89, Loss on ignition: 11.8 wt%).

The nano-metal precursor sol (Sol) thus obtained was placed in a container of a spray apparatus equipped with a spray gun having a nozzle diameter of 0.2 mm, and adjusted so that the air pressure during spraying was 1 to 2 Kg / cm ² . After that, the surface is well cleaned in advance, and the surface temperature of the glass plate is set to about 40 ° C., and 10 wt% of the nano metal is placed on the 0.7 mm thick flat glass plate having the mask film attached to the surface other than the wiring. The precursor sol (Sol) was sprayed so that it could be dried as soon as the nano metal precursor sol (Sol) on the glass surface.

Through this process, the wiring formed on the glass plate is dried by passing through a dryer set at 70 ° C. in advance, and then the mask film is removed. Then, the film is heat-treated in a hot air dryer for 30 minutes at 220 ° C. for a thickness of about 1.80 μm. Could make.

At this time, the specific resistance was 2.8 * 10 ^-6 and the silver (Ag) glow appeared as shown in FIGS.

Example 13

In preparing the nano metal precursor particles, it could be prepared by the following method. To prepare a 0.08 mole / L solution by weighing silver nitrate (AgNO ₃ ), 13.59 g of commonly used reagent grade nitrate was quantified and dissolved in ultrapure water to adjust the total amount to 1 L. On the other hand, reagent grade potassium stearate was weighed to make a 0.08 mole / L solution, and the two solutions were mixed in an apparatus equipped with a stirrer. The material produced was Silver Stearate. Silver Stearate, a reactant, was obtained in a filter and washed with ultrapure water until no K ⁺ ions and NO ₃ ⁻ ions were detected. After washing, drying was performed in a drier set at 80 ° C for 12 hours.

10 g of the organic compound thus obtained is placed in a 500 ml glass beaker placed on a hot plate, and heated at atmospheric pressure and air to maintain 250 ° C. As the heating was turned off, the white silver stearate melted from the surface and gradually turned brown, and after 1 hour of initiation of heating, the color turned dark brown. The powder thus obtained was 2.1 g, and 100 g of the powder obtained by performing the same process several times was added to 400 ml of a mixed solvent in which α-Terpineol and Butyl Carbitol Acetate having a boiling point of 216 ° C. were mixed in a weight ratio of 1: 1. Paste was made using a stirring mixing device (Kurabo K-300) capable of empty electron transfer. The viscosity of the paste obtained at this time was 1,000 cPs.

In using these pastes, the lithography method used in the past was applied. As in the conventional lithography method, the photoresist is coated on the entire surface and then exposed and cured using Photo-Mask designed for wiring, followed by etching to remove the uncured photoresist, and then the paste prepared in the above process. After entering the place where the photoresist is removed and pre-dried at 70 ℃, and heat treatment for 220 ℃, 30 minutes. After that, the existing cured photoresist was removed with an etchant to form a fine pattern of wiring.

As described above, according to the composition for forming a wiring of the present invention, the wiring forming method using the same, and an apparatus including the wiring, the present invention provides a method for forming wiring of a substrate used in an electronic or electrical apparatus. By simplifying the process, the manufacturing cost is lowered, and various problems that occur in the complicated wiring forming process do not occur, and wiring can be easily formed, and fine wiring can be formed without the need for expensive equipment. There is an effect that wiring formation is possible.

In addition, according to the present invention, it is possible to minimize the amount of usage in the case of the noble metal through printing only the fine wiring width and the necessary portion, and it is possible to use a variety of metals with low specific resistance as a wiring material as a variety of materials can be selected It is possible to form a highly integrated fine wiring having a fine line width and a pitch, thereby increasing the selectability of the present invention, thereby making it possible to manufacture a thin and simple electrical and electronic device.

The present invention described above is not limited to the above-described embodiments and detailed description, and various modifications and changes by those skilled in the art without departing from the spirit and scope of the present invention described in the claims below. Of course it is also included within the scope of the present invention.

Claims (12)

a) a) a solution of metal salts at a concentration of 0.05 to 1 mol / L; And   B) prepared by reacting a hydrocarbon acid solution having a carboxyl group having 6 to 20 carbon atoms or a salt solution thereof having the same molar equivalent as the metal component of the metal salt, wherein the hydrocarbon acid having the carboxyl group surrounds the metal particle 10 to 90 weight percent of the metal precursor mixture; And b) 10 to 90% by weight of a dispersion solvent Wiring forming composition comprising a. The method of claim 1, The nano metal precursor is mixed with a solution of a metal salt having a concentration of 0.05 to 1 mol / L and a hydrocarbon acid solution having a carboxyl group having 6 to 20 carbon atoms having the same molar equivalent as the metal component of the metal salt, or a salt solution thereof, followed by washing and Wiring forming composition, characterized in that it is manufactured by drying. delete The method of claim 1, The wiring forming composition further comprises a dispersing agent, a thickener, or an additive in the wiring forming composition. a) applying the wiring forming composition of claim 1 on a substrate; And b) drying the applied substrate Wiring formation method comprising a. The method of claim 5, The drying temperature is a wiring forming method, characterized in that at 120 to 300 ℃. The method of claim 5, The coating method is characterized in that the silkscreen method, inkjet printing method, spray coating method or fill in the thin recessed filling method. The method of claim 5, And the thin recess is formed by a lithography process of a photocurable resin or is formed by film lamination. The method of claim 5, The wiring formed by forming the wiring line, characterized in that the line width of 1 to 30 ㎛. The method of claim 5, And drying the protective film in one or two layers after drying the wiring forming composition. delete delete

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