WO2006095955A1

WO2006095955A1 - Cover tape for packaging electronic parts and method for preparing the cover tape

Info

Publication number: WO2006095955A1
Application number: PCT/KR2005/004360
Authority: WO
Inventors: Hee-Sik Han; Young-Hee Kim; Heon-Moo Kim; Sung-Ki Min; Kwan Young Park
Original assignee: Youl Chon Chemical Co., Ltd.
Priority date: 2005-03-11
Filing date: 2005-12-16
Publication date: 2006-09-14
Also published as: KR100614449B1; CN101142869A; CN101142869B

Abstract

Disclosed are a cover tape for packaging electronic parts comprising heat-seal layer formed by gravure-coating and a method for preparing the cover tape. The cover tape according to the present invention is excellent in heat-seal property, peel-off strength, anti-blocking property, haze, etc. and to this end also in work efficiency.

Description

COVER TAPE FORPACKAGING ELECTRONIC PARTS AND METHOD FOR PREPARING THE COVER TAPE

Technical Field

[1] The present invention relates to a cover tape for packaging electronic parts and a method for preparing the cover tape. In particular, the present invention relates to a cover tape for packaging electronic parts and a method for preparing the cover tape, which has a uniform heat seal layer formed by gravure-coating (concave printing). Background Art

[2] Small sized electronic parts such as transistor, condenser and diode are carried by means of a carrier tape, which is heat-sealed with a cover tape. The cover tape is peeled from the carrier tape when the electronic parts are removed from the carrier tape after carried.

[3] The cover tape should have desired properties such as low temperature heat-sealing property, anti-blocking property and low haze property in order to be suitable for packaging electronic parts. Especially, the cover tape needs to have a uniform peel-off strength since nonuniform peel-off strength may cause the small electronic parts to be separated from a carrier tape thereby increasing a defective proportion.

[4] According to the prior art, a heat sealing layer film is formed using a T-die or a circular die for manufacturing a cover tape.

[5] However, in case of forming a heat sealing layer using such methods, there are problems that the heat sealing layer has a fish-eye pattern, in which a bubble and an unmelted material are present together if the heat sealing layer are not properly mixed or melted with additives, as well as a nonuniform thickness, and further its appearance is not good since the peel-off strength becomes nonuniform due to the exposure of the small molecule additives when the cover tape is removed from the carrier tape.

[6] Furthermore, there are also such problems that a time-dependent change of the properties is caused during a long time storage and a delamination as well as a high haze are caused. Disclosure of Invention Technical Problem

[7] The present invention has been made to solve the foregoing problems, and an object of the invention is to provide a cover tape for packaging electronic parts and a method for preparing the cover tape, which has excellent properties such as heat-sealing property, peel-off strength, anti-blocking property, haze, etc. and to this end an excellent work efficiency without having such problems of the conventional cover tape and the method for preparing the same as high cost, fish eye phenomena resulting from the insufficient mixing and melting with additives, nonuniform peel-off strength, time- dependent change in properties, delamination, high haze and the like. Technical Solution

[8] In order to solve the objects, the present invention provides a cover tape for packaging electronic parts comprising a heat sealing layer formed by gravure-coating.

[9] In the present invention, the cover tape preferably comprises a substrate film; an intermediate layer composed of thermoplastic resin formed on the substrate film; and a heat sealing layer of heat sealing agent which is gravure-coated on the intermediate layer.

[10] In the present invention, the heat sealing layer is preferably made by gravure- coating of the heat sealing agent 2-3 times and the gravure-coating thickness is 2~5D for each one time coating.

[11] In the present invention, the heat sealing agent preferably comprises thermoplastic elastomer and solvent.

[12] In the present invention, the thermoplastic elastomer is preferably styrene- ethylene-butadiene-styrene block copolymer or styrene-butadiene-styrene block copolymer.

[13] In the present invention, the solvent is preferably toluene.

[14] In the present invention, the heat sealing agent preferably further comprises antiblocking agent.

[15] In the present invention, the substrate film is preferably composed of one or stack of biaxially oriented film made of polyethyleneterephthalate, polyolefin or nylon.

[16] In the present invention, the substrate film is preferably surface-treated with corona or plasma.

[17] In the present invention, the substrate film preferably has a thickness of 10-25D.

[18] In the present invention, the thermoplastic resin of the intermediate layer is preferably polyolefin resin such as linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, etc., and more preferably, linear low density polyethylene.

[19] In the present invention, the linear low density polyethylene is preferably octene- based linear low density polyethylene in which its comonomer is octene.

[20] In the present invention, the intermediate layer preferably has a thickness of 10-40D.

[21] In order to solve the objects, the present invention also provides a method for preparing the cover tape for packaging electronic parts comprising steps of: (Sl) forming an intermediate layer of thermoplastic resin on a substrate film; and (S2) gravure-coating heat sealing agent onto the intermediate layer to form a heat sealing layer. [22] In the step (Sl), it is preferable to form the intermediate layer by lamination using one-part adhesive or two-part adhesive. [23] In the step (Sl), it is preferable to use polyurethane resin or acrylic resin as the adhesive. [24] In the step (S2), it is preferable to gravure-coat the heat sealing agent 2-3 times with a coating thickness of 2~5D for each one time. [25] In the step (S2), it is preferable to use thermoplastic elastomer solved into toluene as the heat sealing agent. [26] In the step (S2), it is preferable to use styrene-ethylene-butadiene-styrene block copolymer or styrene-butadiene-styrene block copolymer as the thermoplastic elastomer.

[27] In the step (S2), it is preferable to use the heat sealing agent further added with antiblocking agent.

Advantageous Effects

[28] According to the present invention, contrary to such cover tape and method for preparing the cover tape in the prior art, it is possible to provide a cover tape for packaging electronic parts and a method for preparing the cover tape, which has excellent properties such as heat-sealing property, peel-off strength, anti-blocking property, haze, etc., and to this end an excellent work efficiency. Brief Description of the Drawings

[29] FlG. 1 is a schematic view illustrating a cover tape for packaging electronic parts according to an example of the present invention. Mode for the Invention

[30] According to the present invention, in a cover tape for packaging electronic parts, a heat sealing layer can be formed uniformly by gravure-coating.

[31] FlG. 1 is a schematic view illustrating a cover tape for packaging electronic parts according to an example of the present invention.

[32] As shown in FlG. 1, a cover tape 50 for packaging electronic parts according to an example of the invention comprises a substrate film 10, an intermediate layer 20 composed of thermoplastic resin adhered onto the substrate film by means of an adhesive 15 and a heat sealing layer 30 of heat sealing agent which is gravure-coated three times on the intermediate layer 20.

[33] The substrate film is formed with one or stack of film which is biaxially oriented film made of such resin as nylon, polyolefin such as polypropylene etc., polyethyleneterephthalate(PET) and the like. In the present invention, it is especially preferable to use the polyethyleneterephthalate resin film. [34] That is, it is difficult to use nylon due to its sensitivity to moisture even though nylon has no problem in thermal resistance. In case of using polyolefin, since sealing process is performed with a seal bar having a temperature of 150~200°C, heat may be transferred to the cover tape and thus the cover tape may be thermally deformed when a relevant machine stops to work. Accordingly, it is preferable to use PET resin film for the substrate film.

[35] Further, it is preferable to use the substrate film having a thickness of 10-25D, and more preferable to use the substrate film having a thickness of 15-20D. If the thickness is under 10D, curling may be caused in the lamination process performed using thermoplastic resin of the intermediate layer such as LLDPE film etc. and adhesive (refer to the step Sl which will be described later), and thermal deformation of thermoplastic resin of the intermediate layer such as LLDPE, etc. may be caused since the heat can not be blocked when a relevant machine stops to work during the process. If the thickness is over 25D, the cost may be increased.

[36] In order to enhance adhesion strength in adhering the intermediate layer 20 to the substrate film 10 as will be described later, it is preferable to perform the surface treatment such as corona treatment and plasma treatment of the substrate film 10. Further, if necessary, it is preferable to apply anchor coat (AC) agent after surface treatment. Furthermore, additives such as oxidizing agent, crocking agent, UV stabilizer and slipping agent may be added in order to provide a function corresponding to the respective additive.

[37] Meanwhile, anti-electrification agent is coated on a cover tape used for a carrier tape packaging electrically chargeable or light electronic parts.

[38] GMS (Glycerol Mono-Stearates) having an immediate effect and amines having a continuing effect are used together for the anti-electrification agent, and specifically, ethoxylated alkylamines, alkylsulfonates, fatty acid esters, quaternary ammonium compound etc. are mainly used for the anti-electrification agent.

[39] The intermediate layer 20 enhances the strength of the cover tape, uniformly transfers heat during the heat sealing and acts as a buffer for another layer, and is made of thermoplastic resin, e.g. polyolefin resin such as linear low density polyethylene, medium density polyethylene and high density polyethylene etc.

[40] In the present invention, it is preferable to use linear low density polyethylene

(LLDPE) which is excellent in tensile strength and low temperature heat-sealing property among the thermoplastic resin. In order to prevent rusting of electronic parts, it is more preferable to use LLDPE wherein amide, chloride, dioctyl phthalate (DOP) or silicon oil is not added and its comonomer is octene.

[41] Furthermore, it is preferable not to add additives, e.g. oxidizing agent, crocking agent, UV stabilizer and slipping agent in order to prevent any exposure of such low molecule additives.

[42] It is preferable to use the intermediate layer 20 having a thickness of 10-40D, and more preferable to use the inetermediate layer 20 having a thickness of 25-35D. If the thickness is under 10D, maufacturing can become difficult due to a sheet tearing and difficulty of thickness control since the thermoplastic resin film is manufactured by bubble method (blown method). If the thickness is over 4OD, the cost may be increased.

[43] Meanwhile, the intermediate layer 20 is formed on the substrate film 10 according to the following process (Sl).

[44] The intermediate layer 20 may be formed on the substrate film 10 by coextrusion or junction through dry lamination process. The present invention preferably adopts lamination using one-part adhesive or two-part adhesive. For example, polyurethane resin or acrylic resin can be used for the adhesive. In case of adhesion, tension should be adjusted to prevent curling so as to be free of vertical or horizontal creases. After the junction, curing is performed at a room temperature (25°C) for 7 days or more.

[45] The heat sealing layer 30 is formed by gravure-coating of heat sealing agent. The heat sealing agent is obtained by solving thermoplastic elastomer into solvent. The thermoplastic elastomer is suitable for heat sealing agent since it is viscous, aging- resistant, plastic, highly elastic, excellent in low temperature sealing property and has no need for vulcanization.

[46] For the thermoplastic elastomer, styrene-ethylene-butadiene-styrene block copolymer (SEBS) or styrene-butadiene-styrene block copolymer (SBS) is used in the present invention.

[47] SEBS has good transparency as well as excellent weathering-resistance, deposition property and strength. Since SEBS maintains its good propreties even at a high temperature of 150°C or a low temperature of -60°C, there is such advantage that it is possible to raise the packaging rate by reducing the thermal adhesion temperature.

[48] Solvent for solving the thermoplastic elastomer may include methylethylketone

(MEK), toluene, ethyl acetate (EA) and so on. In case of using MEK or EA, since gelling may be caused after main ingredient is solved, it is preferable to use toluene for preventing such gelling.

[49] Meanwhile, it is preferable to add anti-blocking agent to the heat sealing agent in order to prevent the closely sticking phenomena between films or sheets. Examples of such anti-blocking agent may include inorganic silica, calcium carbonate, talc, clay, polyethylene powder, cross-linked acrylic resin, cross-linked styrene resin powder and so on.

[50] Heat sealing agent is gravure-coated as follows (S2).

[51] That is, heat sealing agent is coated with a gravure-coater preferably 2-3 times to form a heat seal layer preferably having a total thickness of 4-15D, and more preferably, 10-15D. Using such gravure-coater makes uniform coating distribution and low cost obtained.

[52] Meanwhile, it is preferable to make one time coating thickness of the heat sealing agent 2~5D. If the thickness is over 5D, druying problems may occur. If the thickness is under 2D, the overall coating times may be increased and thus the cost may be increased.

[53] In case that coating is performed 2-3 times with the gravure-coater so as to have the thickness for one time, heat sealing agent becomes uniformly coated without leaving any area that is not coated and also there becomes no such problem of drying and cost increase. Further, the coating can be performed in a wide temperature range. Furthermore, uniform peel-off strength can be obtained and to this end work efficiency can be increased greatly.

[54] Hereinafter, the present invention will be described further in detail by describing the preferred examples and experiments of the present invention. However, the present invention is not limited to the following examples, and various modification can be realized in the scope of the accompanying claims. The following examples are just for making those skilled in the art carry out the present invention with ease and the complete disclosure of the present invention.

[55] [Experiment 1 : Evaluation of gelling according to solvent of heat sealing agent]

[56] Experiment 1 was performed to observe gelling according to solvent of heat sealing agent.

[57] First, SEBS and solvents were solved at a weight ratio of 1 :3 to prepare solutions.

The solvents were respectively methylethylketone (Example 1 of Experiment 1), toluene (Example 2 of Experiment 1) and ethyl acetate (Example 3 of Experiment 1).

[58] Then, SBS and solvents were solved at a weight ratio of 1 :3 to prepare solutions.

The solvents were methylethylketone (Example 4 of Experiment 1), toluene (Example 5 of Experiment 1) and ethyl acetate (Example 6 of Experiment 1).

[59] The solutions were added with anti-blocking agent [used was YMAB- 12 (trade name); composed of 7% of vinyl resin, 20% of extender, 5% of PE wax. and the remainders of matting agent, CL-PP and supporting resins] at a weight ratio of 7:1, and agitated with an agitator at a temperature of 40°C for 3 hours.

[60] After agitated, the solutions were left for 1 hour and then measured for viscosity with a brookfield rotary viscometer. Table 1 shows the measurement results of the viscosity.

[61] Table 1

[62] As shown in Table 1, gelling was occurred as like tofu all in the heat sealing agents of Examples 1, 4 using MEK for the solvent and those of Examples 3, 6 using ethyle acetate for the solvent, among Examples 1-3 using SEBS and Examples 4-6 using SBS.

[63] However, the viscosities of the heat sealing agents of Example 2, 5 using toluene for the solvent were 2000~3,000cps and there was no gelling.

[64] Therefore, it is concluded that it is preferable to use toluene for the solvent in gravure-coating, and such heat sealing agent using toluene for the solvent has no problems in properties such as mixing property, storability, blocking property, heat- sealing property and the succeeding processing.

[65] [Experiment 2: Evaluation of characteristics according to number and thickness of coating]

[66] In this experiment, the peel-off strength and haze of cover tapes were measured according to the number and thickness of gravure-coating.

[67] <Example 1 of Experiment 2>

[68] Heat sealing agent with SEBS solved into toluene solvent was gravure-coated three times onto a cover film (PET film + acrylic adhesive (Product 9600 of Sungdo Chemical, Co., Ltd.) + LLDPE film) with a thickness of 5D for the first coating, 5D for the second coating and 5D for the third coating.

[69] <Example 2 of Experiment 2>

[70] Gravure-coating was carried out in the same process as that of Example 1 three times with a thicknesses of 4D for the first coating, 3D for the second coating and 3D for the third coating.

[71] <Example 3 of Experiment 2>

[72] Gravure-coating was carried out in the same process as that of Example 1 two times with a thicknesses of 5D for the first coating and 5D for the second coating.

[73] <Comparative Example 1 of Experiment 2>

[74] Gravure-coating was carried out in the same process as that of Example 1 three times with a thicknesses of 8D for the first coating, 4D for the second coating and 3D for the third coating.

[75] <Comparative Example 2 of Experiment 2> [76] Gravure-coating was carried out in the same process as that of Example 1 two times with a thicknesses of 7D for the first coating and 2D for the second coating.

[77] <Comparative Example 3 of Experiment 2> [78] Gravure-coating was carried out in the same process as that of Example 1 one time with a thicknesses of 2OD for the coating.

[79] <Comparative Example 4 of Experiment 2> [80] Gravure-coating was carried out in the same process as that of Example 1 one time with a thicknesses of 1OD for the coating.

[81] <Comparative Example 5 of Experiment 2> [82] Gravure-coating was carried out in the same process as that of Example 1 one time with a thicknesses of 5D for the coating.

[83] Table 2 shows the number and thickness of coating of the above examples and comparative examples of this experiment. [84] Table 2

[85] Since the heat sealing agents of the examples and comparative examples of this experiment were gravure-coated with different amounts, drying temperature and coating rate should be controlled accordingly. Table 3 shows the drying temperature and coating rate of the examples and comparative examples in gravure-coating.

[86] Table 3

[87] As shown in Table 3, in case of coating the heat sealing agent onto the cover film

(PET film + adhesive + LLDPE film) with a thickness larger than 5D as in Comparative Examples 1-4, sufficient drying time and temperature become needed (therefore drying temperature should be raised up to the extent of 10~20°C) and coating rate also becomes slowed down, thereby lowering productivity.

[88] The prepared cover tapes of Examples 1-3 and Comparative Examples 1-5 were heat-sealed onto transparent carrier tapes (available from Denka). The heat sealing condition was at a temperature of 150°C and a pressure of 2kgf/cm² for 0.5sec. Then, peeling was carried out at an angle of 180° with a rate of 300mm/min and a pressure of 3kgf/cm².

[89] The peel-off strength and haze of the cover tapes heat-sealed to the carrier tapes were measured.

[90] The peel-off strength required for peeling off the cover tapes heat-sealed to the carrier tapes was about 20~50gf/1.2mm. Smaller difference in peel-off strength was more preferable. Meanwhile, haze (%) should be in a desired range (i.e., 40% or less) to the extent that electronic parts can be checked with the naked eye even if packaged with cover tape. Table 4 shows the measured results of the peel-off strength and haze.

[91] Table 4

[92] As shown in Table 4, in case of Examples 1-3, the differences between maximum and minimum peel-off strengths were smaller compared to Comparative Examples 1-5. Furthermore, in case of Examples 1-3, hazes were in such a range that electronic parts packaged in the carrier tapes can be checked with the naked eye.

[93] Moreover, in case of Examples 1-3 wherein coating was carried out at a thickness of 5D or less for one time and the heat sealing agent was completely dried and then the coating was repeated 2-3 times so as to produce a total thickness of 10-15D, heat sealing property was excellent and there were no such blocking problems.

[94] However, in case of Comparative Examples 1, 3, 4, high haze (%) disabled identification of electronic parts. In case of Comparative Examples 1-5, the overall peel- off strengths were nonuniform. With such nonuniform peel-off strength, it is very difficult to produce products since electronic parts may separate from a carrier tape while being carried thereon, thereby increasing defective proportion of products.

[95] Meanwhile, although only one time coating is preferable in terms of cost saving, such a single coating makes it difficult to achieve uniform distribution at all the parts of the coated heat sealing agent so that large difference in peel-off strengths may occur. In case of coating the heat sealing agent with a thickness over 5D for one time, longer drying time or higher drying temperature may be needed.

[96] In the above case, if line speed is lowered in order to prolong the drying time, the intermediate layer (linear low density polyethylene film) may shrink due to the hot air drying, thereby creating problems such as sheet curling and creases. Further, in that case, even though drying temperature is increased, heavy blocking and severe de- lamination also may occur. In case that the heat sealing agent was coated only one time with a thickness of 5D as in Comparative example 5, heat sealing property dropped and blocking problems also occurred. Therefore, the most preferable is to gravure-coat the heat sealing agent 2-3 times with a thickness of 1-5D for each one time. Industrial Applicability

[97] The present invention provides a cover tape for packaging electronic parts and a method for preparing the cover tape, which is excellent in heat sealing property, peel- off strength, anti-blocking property, haze, etc. and to this end also in work efficiency.

Claims

[I] A cover tape for packaging electronic parts comprising a heat sealing layer formed by gravure-coating.

[2] The cover tape according to claim 1, wherein the cover tape comprises a substrate film; an intermediate layer composed of thermoplastic resin formed on the substrate film; and a heat sealing layer of heat sealing agent which is gravure-coated on the intermediate layer. [3] The cover tape according to claim 1 or 2, wherein the heat sealing layer is made by gravure-coating of heat sealing agent 2-3 times and the gravure-coating thickness is 2~5D for each one time coating. [4] The cover tape according to claim 3, wherein the heat sealing agent comprises thermoplastic elastomer and solvent. [5] The cover tape according to claim 4, wherein the thermoplastic elastomer is styrene-ethylene-butadiene-styrene block copolymer or styrene- butadiene-styrene block copolymer.

[6] The cover tape according to claim 4, wherein the solvent is toluene.

[7] The cover tape according to claim 4, wherein the heat sealing agent further comprises anti-blocking agent. [8] The cover tape according to claim 2, wherein the substrate film is composed of one or stack of biaxially oriented film made of polyethyleneterephthalate, polyolefin or nylon. [9] The cover tape according to claim 8, wherein the substrate film is surface-treated with corona or plasma. [10] The cover tape according to claim 8 or 9, wherein the substrate film has a thickness of 10-25D.

[II] The cover tape according to claim 2, wherein the thermoplastic resin of the intermediate layer is linear low density polyethylene, low density polyethylene, medium density polyethylene or high density polyethylene.

[12] The cover tape according to claim 2, wherein the thermoplastic resin of the intermediate layer is linear low density polyethylene.

[13] The cover tape according to claim 12, wherein the comonomer of the linear low density polyethylene is octene.

[14] The cover tape according to one of claims 11 to 13, wherein the intermediate layer has a thickness of 10-40D.

[15] A method for preparing the cover tape for packaging electronic parts comprising steps of:

(51) forming an intermediate layer of thermoplastic resin on a substrate film; and

(52) gravure-coating heat sealing agent onto the intermediate layer to form a heat sealing layer.

[16] The method according to claim 15, wherein, in the step (Sl), the intermediate layer is formed by lamination using one-part adhesive or two-part adhesive. [17] The method according to claim 16, wherein, in the step (Sl), polyurethane resin or acrylic resin is used as the adhesive. [18] The method according to one of the claims 15 to 17, wherein, in the step (S2), the heat sealing agent is gravure-coated 2-3 times with a coating thickness of

2~5D for each one time. [19] The method according to claim 18, wherein, in the step (S2), thermoplastic elastomer solved into toluene is used as the heat sealing agent. [20] The method according to claim 19, wherein, in the step (S2), styrene- ethylene-butadiene-styrene block copolymer or styrene-butadiene-styrene block copolymer is used as the thermoplastic elastomer. [21] The method according to claim 19, wherein, in the step (S2), the heat sealing agent is further added with anti-blocking agent.