KR20090006249A - Acrylic adhesive compositions to be manufactured a double sided flexible printed circuit board and method of manufacturing the same - Google Patents

Abstract

An acrylic adhesive composition is provided to ensure stable adhesion value and to reduce the manufacturing costs by manufacturing two products through one process. A method for manufacturing an acrylic double-sided adhesive composition comprises a step for performing the second crosslinking reaction of a blocked-isocyanate cross-linking agent in an adhesive resin in a hot press process to reduce adhesion and a step for easily releasing a cross section flexible substrate from the adhesive after the process. The acrylic double-sided adhesive composition has the molecular weight of 60~1,000,000, molecular weight distribution of 3.5~5, viscosity of 5~200,000 cps and glass transition temperature (Tg) of -10~20 °C. The evaporation temperature of the adhesive solvent is 100~110 °C, the first crosslinking time is 3 minutes at 90~100 °C and 12 hours at 60 °C.

Description

ACRYLIC ADHESIVE COMPOSITIONS TO BE MANUFACTURED A DOUBLE SIDED FLEXIBLE PRINTED CIRCUIT BOARD AND METHOD OF MANUFACTURING THE SAME}

1 illustrates a manufacturing process of a flexible printed circuit board (FPCB).

1: base material, 2: surface treatment layer, 3: secondary crosslinkable pressure-sensitive adhesive layer, 4: release film.

Figure 2 shows the basic concept of application of the weak adhesive sheet.

Figure 3 shows the crosslinking reaction path of the blocked cross-isocyanate, the secondary crosslinking agent.

Figure 4 shows the reaction path of acrylic weak adhesive for FPCB fixing.

5 shows the FT-IR change of the internal polymer over time.

   The present invention relates to a method of manufacturing an acrylic weak sheet that can be used by double-sided flexible printed circuit board in the manufacturing process of single-sided FPCB, in particular to produce a new weak sheet that can be used for fixing in the single-sided FPCB manufacturing process Using the weakness sheet, the effect on the cross-sectional FPCB manufacturing process was confirmed. The acrylic weak adhesive according to the present invention has a molecular weight of 60 to 1 million, a molecular weight distribution of 3.5 to 5, a viscosity of 5 to 200,000 cps, a glass transition temperature (Tg) of -10 ° C to 20 ° C, and a pressure-sensitive adhesive solvent volatilization temperature at 100 to 110 ° C. Within 3 minutes, the primary crosslinking time was prepared by aging at 90 ~ 100 ℃ for 3 minutes and at 60 ℃ for 12 hours. In the hot press process, the crosslinking reaction with the blocked-isocyanate crosslinking agent in the adhesive resin It is characterized in that the method to give a decrease in the adhesive force by the generation of carbon dioxide during the crosslinking reaction to facilitate the peeling of the flexible substrate in the adhesive after the process.

Flexible Printed Circuit Boards are thin, freely flexible and very light, unlike rigid Printed Circuit Boards, in which copper foil is laminated on a sheet of thermosetting resin such as epoxy or phenol. . Because of these features, efficient arrangements are possible in the narrow space of electronic devices, and the design and the design of small size and light weight are very high. have. Its main uses are notebook computers, cameras, mobile phones, AV devices, etc., and are particularly used for small precision electronics. In particular, Korea is emerging as a global supply base for information and communication devices such as mobile phones, TFT-LCDs, and D-STBs, and the market for flexible circuit boards is growing at more than 15% annually.

   In order to give flexibility in the process of producing a multilayered flexible printed circuit board, it is inevitably manufactured as a single side flexible printed circuit film. The conventional manufacturing process of the flexible printed circuit board is fixed by using adhesive tape on a substrate called a carrier or a backup board due to the bending or wrinkle of the flexible printed circuit board. By using a double-sided adhesive sheet, the double-sided FPCB can be attached to both sides, so that both sides can be processed at the same time, thereby increasing the productivity twice. Therefore, in order to shorten this process, all the processes of FPCB have recently been developed, namely, YEON-D / F adhesion-exposure-D / F development-Cu corrosion-drying-winding-roll cutting-welding-coverlay molding process Various methods have been studied for smooth peeling of adhesive tapes and flexible printed circuit boards after the process of surface treatment-electroless plating-punching process.

  Current manufacturing facilities can work on both single-sided and double-sided FPCB at the same time, but in the case of single-sided FPCB, only one side can be processed, there is a limit in productivity improvement. After manufacturing the sheet with the adhesive resin containing the microsphere foaming agent, after passing through all the processes of FPCB and foaming at 190 ° C or higher to lose the adhesive strength, peeling method or special adhesive resin with no change over time at high temperature with polyimide, etc. The method etc. which apply and apply to the same base material are tried. However, these adhesive sheets have a disadvantage in that the manufacturing cost is increased to another cost increase factor.

  Conventionally, the pressure-sensitive adhesive used in the processed product as the pressure-sensitive adhesive sheet is mostly used an acrylic pressure-sensitive adhesive and a crosslinking agent, and such pressure-sensitive adhesive has a constant ratio of the crosslinking functional group and the crosslinking agent in order to impart cohesive force and adhesion force to the substrate during sheet processing. Used. In particular, it is possible to prepare a weakness sheet by controlling the combination of various monomers well, but if the temperature is raised for a long time after adhering to the adherend has a disadvantage that it is difficult to separate from the adherend. The double-sided adhesive sheet adopted to advance the single-sided FPCB to the double-sided process should not cause thermal deformation under the conditions of more than 40 minutes at a temperature of 160 ° C and a pressure of 40㎏ / ㎠, and it is resistant to chemicals encountered during the flexible circuit board manufacturing process. Chemical property is required, peeling occurs easily after completion of the flexible circuit board manufacturing process, and contamination of the flexible circuit board should not occur due to transfer of adhesive resin during the manufacturing process of the flexible circuit board. At such high temperatures, stable acrylic adhesive resins with no change over time are difficult to manufacture. In particular, after 40 minutes at 160 ℃, pressure 40㎏ / ㎠ to increase the adhesive strength significantly. Loss of adhesion at this temperature is easy for the latent crosslinking agent to react and lose adhesion at this temperature.

   Isocyanate crosslinking agent is used in two-component type due to the reactivity at room temperature after mixing with the adhesive resin, and in order to compensate for this disadvantage, recently, a blocked-isocyanate crosslinking agent having a storage stability has been used. Isocyanate (-N = C = O) is easily used as a crosslinking agent for hydroxy and amine functional groups because it reacts easily with a compound having active hydrogen or water, but many studies have been conducted to solve this problem because it is not storage. . In particular, one-component polyurethane resin coating, powder coating, water-based coating, etc. are a problem. In this case, when the isocyanate group rich in reactivity is reacted with a blocking agent in advance, it becomes a stable state as a crosslinking agent, and in the step of forming a coating film, the blocking agent is decomposed by heating to reproduce the original free isocyanate group. Therefore, the dissociated free isocyanate group is used as a curing agent for oligomers or polymers having an active hydrogen group in the resin.

   Therefore, the present inventors are developing a new weak sheet which can produce two products in one process without changing the existing process of single-sided FPCB, and have excellent heat resistance and do not require a large amount of additives. The present invention is made by manufacturing a new acrylic double-sided adhesive which can improve productivity by reducing the FPCB manufacturing process by adjusting the molecular weight, the degree of crosslinking and the crosslinking method, by using an acrylic adhesive capable of retaining the performance of no foreign matter remaining on the part. It was completed.

   In order to solve the above problems, the present invention provides excellent adhesive strength by using blocked-isocyanate as a secondary crosslinking resin, and at the same time, crosslinking proceeds by heat treatment at 180 ° C. or higher, thereby easily peeling off the adherend. It is to provide a method for producing FPCB using the weak sheet that can be produced.

   It is still another object of the present invention to provide chemical resistance in which no liquid penetrates in the etching and peeling processes in the manufacturing process of the flexible circuit board, and the hot press process under high temperature and high pressure conditions of 160 ° C, 40㎏ / ㎠ and 40 minutes or more. By using the secondary cross-linked weakness sheet that maintains the adhesive strength, in the conventional single-sided FPCB production process, it is possible to produce two pieces of single-sided FPCB simultaneously in a single process to provide a method of manufacturing FPCB that can improve the productivity of the FPCB manufacturing process It is.

In order to achieve the above object, the present invention uses a block-isocyanate crosslinking agent in the pressure-sensitive adhesive of the double-sided adhesive sheet for the double-sided of the flexible printed circuit board (FPCB) two in one process without changing the existing process Provided is a method of manufacturing an acrylic double-sided adhesive capable of producing a product.

   In the general FPCB process for advancing single-sided FPCB to double-sided process, the dry film process is a process in which a photosensitive film, which is cured by ultraviolet rays, is adhered to the copper foil film to form a circuit. It is a process of oxidizing and removing this exposed part. After that, the temporary welding process is performed, which refers to a process of temporarily bonding a copper foil film and a coverlay, and the hot press process, which is the most vulnerable to an adhesive, is a process of completely fixing them by applying heat and pressure. As such, the FPCB should not be contaminated due to the transfer of the adhesive resin during the manufacturing process of the FPCB. Therefore, it is very important to control the physical properties of the adhesive resin constituting the adhesive layer of the weak sheet. In addition to the preparation of the resin liquid having a crosslinking functional group and the selection of a crosslinking agent, a blending technique thereof is very important.

Pressure sensitive adhesives include rubber pressure sensitive adhesives, acrylic pressure sensitive adhesives and styrene-conjugated diene block copolymers, but rubber and styrene-conjugated diene-based adhesives require the blending of a large amount of waxes, tackfiers and other additives. Therefore, when used in electrical and electronic parts, problems such as transfer of foreign materials to the parts may occur, and heat resistance is poor. On the other hand, acrylic adhesives have excellent heat resistance, do not require tackifiers such as rubber and a large amount of additives, and are capable of retaining performance in which foreign substances do not remain in the parts at all by controlling the type of monomer, the component ratio of the monomers, the molecular weight and the degree of crosslinking. There is this. Therefore, in the present invention, using an acrylic pressure-sensitive adhesive to prepare a pressure-sensitive adhesive having a different physical properties than the pressure-sensitive adhesive for general adhesive sheets.

The present invention provides a crosslinking functional group that increases the high elasticity of the pressure-sensitive adhesive.

In order to impart high elastic properties of the pressure-sensitive adhesive, the degree of crosslinking must be high in addition to the method of increasing the molecular weight. The crosslinking functional groups of existing adhesives are mainly acrylic acid, itaconic acid and methacrylic acid having -COOH group, 2-hydroxyethyl methacrylate (HEMA) or 2-hydroxyethyl acrylate (HEA) and 4-hydride having -OH group. Roxybutyl acrylate (HBA) etc. are used. However, in the case of -COOH group, since the polarity is very strong, the adhesive force may be increased, and as a result, re-peelability may be deteriorated. Therefore, in the present invention, a small amount of a monomer having a carboxyl group is used, and a pressure-sensitive adhesive is prepared using a monomer having a hydroxyl group such as HEMA, HEA, and HBA, and used as a crosslinking functional group. In this case, some of the hydroxy groups are crosslinked by isocyanate during the primary crosslinking, and the remaining hydroxy groups and the carboxyl groups are secondary crosslinked during the hot press process, thereby greatly reducing the adhesive force, and amide and carbon dioxide are generated to help reduce the adhesive force.

The present invention provides a method of lowering the adhesive ability of the pressure-sensitive adhesive.

Isocyanates, epoxies, melanin, urea and metal chelates are used as crosslinking agents used in general adhesive sheet production. It is important to select the crosslinking temperature and catalyst because the type and application amount of the crosslinking agent should consider the pot life for uniform coating properties and physical properties. Therefore, in the present invention, by adding two kinds of crosslinking agents, the first crosslinking agent is added to prepare a pressure-sensitive adhesive in a method of reducing pressure, and the crosslinking reaction is carried out by 70%, and the second crosslinking agent is added during a heat press process to advance the crosslinking reaction by 30%. The reaction was carried out in steps to increase the degree of crosslinking and to lower the adhesive ability of the pressure-sensitive adhesive.

The higher the crosslinking degree of the adhesive force of the acrylic adhesive, the lower the adhesive force. Therefore, the method of adding a crosslinking agent of the present invention maintains a low crosslinking degree before the hot press process, that is, the nicking process and the peeling process, but in the hot press process, as the crosslinking reaction proceeds due to high heat, the adhesive force is lowered and then the peeling of the flexible substrate is completed after the process. This is an easy way to do it.

In the present invention, a blocked isocyanate-based crosslinking agent was used as the second crosslinking agent. When DURANATE (TPA-B or MF-B) is used as the secondary crosslinking agent, only the first crosslinking proceeds during adhesive coating and the second crosslinking hardly proceeds, but in the hot press process at high temperature, carbon dioxide during crosslinking reaction and crosslinking reaction Adhesion decreases by generation (see FIG. 3).

Hereinafter, the present invention will be described in more detail with reference to Examples. Since these examples are only for illustrating the present invention, the scope of the present invention is not to be construed as being limited by these examples.

1. Material synthesis and experimental method

  In the present invention, the monomers used in the synthesis include methyl acrylate (MA) 99%, butyl acrylate (BA) 99%, acrylic acid (AA) 99%, 2-hydroxyethyl acrylate, and the like. The isocyanate used as a primary crosslinking agent was an isocyanate crosslinking agent (AK-75, Aekyung Chemical), and the secondary crosslinking agent was a blocked isocyanate (DURANATE, TPA-B) crosslinking agent. Ethyl acetate, toluene, cyclohexane, and isopropyl alcohol were used as the solvent during the polymerization, and 99.5% of Duksan Chemical used the reagent, and α, α'-azobisisobutyronitrile used as the initiator used the 99% reagent. It was.

 Infrared spectra were obtained using a BIO RAD FTS135 spectrometer. The adhesive thickness was measured using Digimicro MF-501 (Nikon, Japan), and the automatic coating machine used in the manufacture of weak adhesive film was used as a trade trade (Korea) product, and Instron 4442 was used as the adhesion tester. Used.

2. Synthesis of Adhesive Resin

<Manufacture example 1>

 Methyl acrylate (63 g) as a monomer, n-butyl acrylate (64 g) as a monomer, hydroxyethyl acrylate (14 g) in a 2 L glass reactor equipped with a stirrer, a cooler, a dropping funnel, a thermometer, and a jacket And acrylic acid (0.8 g) were mixed, and an initiator α, α'-azobisisobutyronitrile (0.01 g) was added to ethyl acetate (200 g) and toluene (60 g), and the radical polymerization was performed at 70 ° C. . After 30 minutes in the growth step, methyl acrylate (182 g), comonomer n-butyl acrylate (191 g), hydroxyethyl acrylate (33 g) and acrylic acid (1.8 g) were mixed, and the initiators α, α ' -Azobisisobutyronitrile (0.05 g) was added dropwise using ethyl acetate (120 g) and toluene (20 g) for about 90 minutes using a funnel. After dropping, the temperature was constantly adjusted, and after the reaction was completed, a radical initiator (0.25 g) was dissolved in toluene (150 g) and added dropwise for 60 minutes so as to leave unreacted monomer. .

 The polymerization was carried out while maintaining the external temperature of 85 ~ 87 ℃. In the radical initiation step, the proportion of solids was added by weight of 25% by weight relative to the total solids and proceeded using a small amount of AIBN initiator. The internal temperature was continuously increased. After about 15 minutes, the reaction was started to increase the molecular weight of the polymer when the temperature was slightly decreased (see FIG. 4). The solid content in the radical growth step of increasing the molecular weight of the acrylic polymer was added to 75% by weight relative to the total solid to prepare an adhesive resin having the physical properties of the acrylic weak adhesive for FPCB, and the viscosity and adhesion results are shown in Table 2.

<Manufacture example 2>

  Prepared as in Preparation Example 1 except that hydroxyethyl acrylate (14 g) and acrylic acid (0.4 g) were used in the initiation step, and hydroxyethyl acrylate (33 g) and acrylic acid (0.9 g) were used in the growth step. It was.

<Manufacture example 3>

  Prepared as in Preparation Example 1, except that hydroxyethyl acrylate (14 g) and acrylic acid (1.6 g) were used in the starting step, and hydroxyethyl acrylate (33 g) and acrylic acid (3.6 g) were used in the growth step. It was.

<Comparative Production Example 1>

  Hydroxyethyl acrylate (14 g) was added at the start step, and was prepared in the same manner as in Preparation Example 1 except that hydroxyethyl acrylate (33 g) was used in the growth step.

<Comparative Production Example 2>

Hydroxyethyl acrylate (21 g) was added at the start step, and was prepared in the same manner as in Preparation Example 1 except that hydroxyethyl acrylate (49 g) was used in the growth step.

3. Film production

<Example 1>

Into the adhesive resin solution prepared in Preparation Example 1, 24 g of an isocyanate crosslinking agent (AK-75) and 12 g of a block isocyanate crosslinking agent (DURANATE, TPA-B), which is a secondary crosslinking agent, were stirred for 2 hours, followed by stirring for 2 hours. The resin composition liquid was prepared. The adhesive was applied to a PET film (50 μm) to form an adhesive layer of 22 μm, prepared by attaching 36 μm of release paper, and then, the prepared weak sheet was aged for 7 days. Adhesion results of the prepared secondary crosslinked weakness sheet are shown in Table 2. The whole process of double-sided flexible circuit board was carried out in the following order. Lamination of FCCL and weak sheet-Front treatment-Dry film laminate-Exposure-Developing process-Etching process-Dry film peeling-Tempering process-Hot press process-Surface treatment-Punching process-Weak process of weak sheet Performance was evaluated in each process.

<Example 2>

A double-sided pressure-sensitive adhesive sheet was manufactured in the same manner as in Example 1, except that 12 g of an isocyanate crosslinking agent (AK-75) and 24 g of a blocked isocyanate crosslinking agent (DURANATE, TPA-B) were used as secondary crosslinking agents.

<Example 3>

A double-sided pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that 30 g of an isocyanate crosslinking agent (AK-75) and 6 g of a blocked isocyanate crosslinking agent (DURANATE, TPA-B) were used as secondary crosslinking agents.

Comparative Example 1

Except for using 24g of the isocyanate crosslinking agent (AK-75) in the adhesive resin solution prepared in Comparative Preparation Example 1 was prepared in the same manner as in Example 1.

Comparative Example 2

Except for using 36 g of the isocyanate crosslinking agent (AK-75) in the adhesive resin solution prepared in Comparative Preparation Example 2 was prepared in the same manner as in Example 1.

For the double-sided test of the single-sided flexible circuit board, the adhesive resin and the weakness sheet manufactured according to the above-described manufacturing examples, comparative manufacturing examples and comparative examples, adopting the following materials and process conditions as a high-temperature weakness sheet flexible circuit board Reliability was investigated throughout the process.

1.Structure analysis and synthesis result of synthesized acrylic weak adhesive (Preparation Example 1)

In order to analyze the structure of the acrylic weak adhesive (Preparation Example 1) synthesized in the present invention, first the FT-IR change of the polymer with time was measured. In FIG. 5, a total of 5 times of the polymerization reactions were collected and analyzed, and the D1-30 graph shown in the graph refers to an IR graph that sampled the material of the reaction tank after 30 minutes after the start of the propagation step D1, followed by D1-Out represents the sample after the end of D1 dropping. D2 also measured the same sample as D1, and looking at the FT-IR spectrum, it can be seen that as the reaction proceeds, the width of the -CH2- peak of the alkane becomes wider at 1450 cm ^-1 . As the polymerization proceeds, the molecular structure of the alkane form is increased to show the result as shown in FIG. 5.

In addition, as a result of analyzing ¹ H-NMR of the reaction monomers, it was confirmed that the hydrogen peaks of alkenes disappeared at around 6 ppm. These results indicated that the π bond was broken and the alkane was formed in the double bond. In addition, the acrylic-butyl acrylate been used as a monomer-CH ₂ - 4.15ppm, acrylic _{-CH 2 - CH 2 - 1.5 ppm} , acryl-butyl-terminal of _{CH 3 -, CH 3 - CH} 2 - is at 0.96, 1.3 ppm, respectively The presence of the peak was confirmed. The acryl- CH ₃ hydrogen peak at the methyl acrylate terminal was confirmed at 3.8 ppm, and the methyl group of the acryl- CH ₂ -CH ₂ -OH of HEA having a functional group reactive with a crosslinker was 4.1 ppm and 3.8 ppm, respectively. The -OH peak at the terminal was confirmed at 3.6 ppm and it was confirmed that an acrylic polymer adhesive was synthesized.

In addition, in the step of increasing the average molecular weight of the weak adhesive synthesized in the present invention more than 400,000, there are many problems due to the high viscosity of the polymer to adjust the content of solids from 45% to 35%. Therefore, in the present invention, the solvent was selected in the direction of increasing the polymerization chain transition to compensate for the above problems, and by adding a small amount of IPA in the initiation step and increasing the proportion of ethyl acetate, the viscosity of the weak adhesive is slightly lowered. By adjusting the result can be obtained about 20,000 cps / 25 ℃.

2. Selection of Fabric

Fabric for the weak sheet is to be used in the flexible circuit board process, it should be flexible considering the workability or roll to roll (roll to roll) method, it is possible to use PET film between 25 to 100㎛. Furthermore, heating to high temperatures and cooling to room temperature are repeated, so thermal dimensional deformation should not occur. In order to satisfy these conditions, the base material was used as 50 micrometers and 36 micrometers thickness as a release film.

3. Reliability Assessment

Using a total of five weakness sheet prepared in the present invention was carried out a chemical resistance test for each process. If the adhesive of the weakness sheet is dissolved and penetrated, it is impossible to proceed due to separation of the weakness sheet and FCCL due to the decrease in adhesive force of the adhesive and contamination of FCCL due to infiltration of liquid may occur. Drugs used in the individual process in the present invention are shown in Table 1.

Chemical Resistance Condition by Detailed Process fair Details process Drug used Temperature condition Processing time Processing method Reverse Circuit formation face H ₂ SO ₄ , H ₂ O ₂ solution 25 ～ 28 ℃ About 20 seconds Spray Copper foil surface front Photoresist Na ₂ CO ₃ solution 30 ～ 35 ℃ About 30 seconds Spray Dissolution of Photosensitive Resin Etching CuCl ₂ , HCl, H ₂ O ₂ 38 ～ 42 ℃ 60 seconds Spray Copper surface corrosion gold plating Cleaning Surfactants 36 ~ 40 ℃ About 3 minutes Dipping Oxide film removal and cleaning Activation PdCl _2, HCl solution 25 ～ 28 ℃ About 3 minutes Dipping PCB Copper Pd Substitution Nickel Plating NiCl ₂ , H ₂ PO ₂ , Complexing Agent 80 ～ 90 ℃ About 10 minutes Dipping Electroless Ni Plating Mountain deposition H ₂ SO ₄ 25 ～ 28 ℃ About 4 minutes Dipping Acid treatment gold plating K [Au (CN) ₄ .1 / 2H ₂ O] 80 ～ 90 ℃ About 8 minutes Dipping Electroless Au Plating

On the other hand, the composition and the adhesion test results of the secondary crosslinked adhesive resin are as shown in Table 2.

Adhesive resin composition and adhesion test Adhesive resin Film production Sample step BA (g) MA (g) AA (g) HEA (g) Viscosity (cps, 25 ℃) Sample Before film production After film making AK -75 (g) TPA -B (g) Initial adhesive force (gf / 25mm) Late adhesive force (gf / 25mm) Manufacture example One Start 64 63 0.8 14 20,500 Example One 24 12 37 14 growth 191 182 1.8 33 2 Start 64 63 0.4 14 11,500 2 12 24 49 26 growth 191 182 0.9 33 3 Start 64 63 1.6 14 52,000 3 30 6 26 19 growth 191 182 3.6 33 Comparative Production Example One Start 64 63 0 14 6,500 Comparative example One 24 X 76 87 growth 191 182 0 33 2 Start 64 63 0 21 8,500 2 36 X 54 68 growth 191 182 0 49

After confirming the penetration of the solution through these processes are shown in Table 3.

Performance analysis result according to the whole process Sample process Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Lamination (lamination) ○ ○ ○ ○ ○ Frontal treatment ○ ○ ○ ○ ○ Dry Feel Laminate ○ ○ ○ ○ ○ Exposure ○ ○ ○ ○ ○ Developing process ○ ○ ○ ○ ○ Etching process ○ ○ ○ ○ ○ Dry Film Peeling ○ ○ ○ ○ ○ Temporary Process ○ ○ ○ ○ ○ Hot press ○ ○ ○ ○ ○ Surface treatment ○ ○ ○ ○ ○ Punching Process ○ ○ ○ ○ ○ Weakness Sheet Peeling ○ ○ ○ Ｘ Ｘ Condition: ○ Good, △ Normal, Bad

Laminating was carried out by maintaining the FCCL 70 ℃ on both sides of the weak sheet. Bubbles and wrinkles of the polyimide film did not occur in the adhered product during the lamination process. In particular, in the FPCB production process, the adhesive state was checked so that various chemicals did not penetrate due to the decrease in the adhesive strength of the outer portion, but showed strong adhesive force. Even if it rolled and bent in the roll, the weakness sheet and the stripping phenomenon of the copper foil were not found. It was confirmed that the mixture of sulfuric acid and hydrogen peroxide solution used in the front treatment process did not penetrate the weak sheet and the surface adhered to it. In this process, the weak sheet and FCCL are attached to both sides, which makes it unnecessary to use a subsidiary carrier film. When laminating both sides of the dry film at the same time, it can be seen that the airflow is reduced by 50%. In the exposure process, the exposure machine is irradiated with ultraviolet rays from the top to the bottom so that it can be exposed simultaneously. No factor affecting the quality of the product was found, and it was confirmed that the ease of operation was increased due to the thickening of the product during production. In the development process, no separation phenomenon due to penetration of the developer was found in the adhesion between the weak sheet and the FCCL. In the etching process, it is a strong acid solution. Like the developing process, the possibility of separation at the contact surface between the FCCL and the weak sheet by the penetration of the liquid may be a problem, but in the actual test, the separation phenomenon was not found. In the welding process, the soldering iron is used, and the weak work sheet is operated in the same way, and there is a requirement that the damage of the weakening sheet caused by the iron does not occur. I could confirm it.

In addition, the results of measuring the change in the adhesive strength according to the cross-linking aging day after the addition of a crosslinking agent in the present invention is shown in Table 4, the second cross-linking of the blocked-isocyanate at 120 ℃ and the change in the cohesion according to the aging time 5 is shown.

Changes in Adhesion According to Cross-linking Aging Date after Addition of Primary Crosslinking Agent Aging day 4 5 7 8 9 10 0223-1st (gf / 25mm) 136 129 76 63 47 44 0223-2nd (gf / 25mm) 156 151 82 76 53 55

Secondary Crosslinking of Blocked Isocyanate at 120 ℃ and Changes of Adhesion According to Aging Time Aging time (min) One 3 5 7 9 11 0228-1st (gf / 25mm) 63 60 35 21 12 15 0228-2nd (gf / 25mm) 55 53 37 28 19 16

The manufacturing process using the synthetic acrylic weak adhesive of the present invention as a weak sheet of the FPCB and PCB manufacturing process has not been reported so far, the present invention is a new method for the manufacturing of FPCB can take advantage of the competition among the competition countries and manufacture FPCB This has the advantage of reducing process costs.

Claims (3)

For the double-sided flexible PCB (FPCB), the adhesive strength is reduced by using blocked-isocyanate as the secondary crosslinking agent in the hot press process without changing the existing process. Method for producing an acrylic double-sided pressure-sensitive adhesive, characterized in that to produce two products in one process. The acrylic double-sided pressure sensitive adhesive according to claim 1, wherein the acrylic double-sided adhesive has a molecular weight of 60 to 1 million, a molecular weight distribution of 3.5 to 5, a viscosity of 5 to 200,000 cps, a glass transition temperature (Tg) -10 ° C to 20 ° C, and a pressure-sensitive adhesive solvent volatilization temperature of 100 to 110. Within 3 minutes at ℃, the first crosslinking time is a method of producing an acrylic double-sided adhesive, characterized in that 3 minutes at 90 ~ 100 ℃, 12 hours at 60 ℃. Acrylic double-sided pressure-sensitive adhesive produced by the method of claim 1 or 2.

Images