JP2002355935A - Conductive sheet for carrier tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive sheet for a carrier tape having an excellent wear resistance without powder drop or the like of carbon in a constitution in which the carbon is filled to impart conductivity to a surface of a material for the tape. SOLUTION: The conductive sheet for the carrier tape comprises an ABS arranged on an intermediate layer to supplement an impact weakness of a resin of a conductive surface layer, and, in addition to an HIPS, carbon, an ethylene vinyl acetate copolymer and a water-added block copolymer blended in the conductive surface layer. Thus, a problem of dropping the carbon of the conductive surface layer due to rubbing of leads of an IC with a body of the IC of a prior art product can be solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier tape material used for transporting electronic parts and the like, and more particularly, to a material having a surface provided with conductivity.

[0002]

2. Description of the Related Art As a material for a carrier tape used for transporting electronic parts, thermoforming such as vacuum forming, pressure forming and press forming is required. (Hereinafter referred to as PC), polyester resin (hereinafter referred to as PET), and polystyrene resin (hereinafter referred to as PS) have been used.

[0003] In particular, in the case where the electronic component as a content is a carrier tape for packaging an IC or the like which is more expensive than the case where the electronic component is a resistor or a component, the IC itself is easily damaged by static electricity. BACKGROUND ART A conductive material (generally inexpensive carbon) kneaded into a resin or a resin coated on the surface is used as a conductive carrier tape.

[0004] The term "conductivity" as used herein is a common name used for general-purpose sheets in the electronic parts industry, food packaging materials, and the like, and has a surface resistivity of 1 × 10 ⁴ to 1 × 10 ⁸ [Ω]. Point to. By the way, among these plastics for carrier tapes, the use rate of PS has recently increased from the viewpoints of environmental consideration, low specific gravity, low cost, and the like.

[0005] There have been several applications in the past that have imparted conductivity to PS. Initially, for example, as shown in FIG. 2), and carbon coated on the surface as shown in FIG. In addition, as shown in FIG. 3, there is also a structure including three layers of a conductive surface layer made of a carbon-containing resin, an intermediate layer, and a conductive surface layer made of a carbon-containing resin.

Further, even in the same three-layer structure, an ABS resin is disposed in an intermediate layer, and carbon and HIPS are disposed as a conductive surface layer.
This is the result of trying to improve PS, which is inferior in impact and weather resistance compared to PVC, PET, PC, etc., to a range that can withstand practical use. In the three-layer type with ABS in the middle layer, there are some items that are inferior in performance as compared with other resins,
It is almost at a usable level. However, even this type has the following serious disadvantages.

That is, since the surface of the conductive surface layer is formed by kneading carbon into a GPS or HIPS base, the IC is filled, and a vibration test is performed assuming a transportation condition. As a result, as shown in FIG. There is also rubbing of the surface layer and rubbing of the IC body and the conductive surface layer.
The fallout may adhere to the lead and eventually lead to poor conduction. This is considered to be due to the fact that the carbon holding power of PS of the base resin also serving as a binder is weak.

[0008]

SUMMARY OF THE INVENTION In a configuration in which carbon is added to impart conductivity to the surface of a tape material, a conductive sheet for a carrier tape which is excellent in abrasion resistance without carbon powder falling off or the like. I will provide a.

[0009]

According to the present invention, an ABS is provided in an intermediate layer to compensate for the impact weakness of a resin in a conductive surface layer, an HIPS is provided in the conductive surface layer, and an ethylene / vinyl acetate copolymer is used in addition to carbon. By blending the hydrogenated block copolymer, it is possible to overcome the problem of carbon falling off of the conductive surface layer due to friction with the IC body and the lead of the IC, which is a conventional product.

That is, an intermediate layer made of ABS resin,
(A) 98 to 60% by weight of a polystyrene resin (b) 1 to 20% by weight of an ethylene / vinyl acetate copolymer (c) At least the terminal polymer block A mainly composed of a vinyl aromatic compound One or more and at least one or more polymer blocks B mainly composed of a conjugated diene compound, and the content of the vinyl aromatic compound is in the range of 5 to 50% by weight; Is 70% or more of a hydrogenated block copolymer having a number average molecular weight of 100,000 to 200,000 and an average particle size of 10 to 70 n with respect to 100 parts by weight of a mixture of 1 to 20% by weight.
A conductive surface layer composed of 10 to 40 parts by weight of carbon having a thickness of m is produced by a co-extrusion method, and has a thickness composition ratio of 2 to 20% of the conductive surface layer / 96 to 60% of the intermediate layer / 2 to 2
It is a conductive sheet for a carrier tape, which is 20%. A further preferred embodiment is a conductive sheet for a carrier tape in which the polystyrene resin is a high impact styrene resin and the carbon is acetylene black.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The ABS resin used for the intermediate layer of the present invention is not particularly limited, and for example, a terpolymer or an acrylonitrile-styrene binary copolymer obtained by polymerizing polybutadiene is used. it can. ABS
Resin is used to improve the strength of the entire sheet.

Next, as the resin for the conductive surface layer, a PS-based resin is preferable in terms of cost. As the PS resin, for example, a GPS resin or a HIPS resin can be used. More preferable in terms of strength.
An ethylene / vinyl acetate copolymer (hereinafter referred to as E)
VA). This is to prevent carbon falling when carbon black is kneaded and to improve the heat sheet property with the cover tape.
EVA is 1 to 20% by weight, preferably 3 to 15% by weight, with respect to 60% by weight. If the amount of EVA added is less than 1% by weight, there is no effect on carbon dropout and 2
If it exceeds 0% by weight, there is a problem that the mechanical strength is reduced.

Further, a hydrogenated block copolymer is added to the PS resin. This is to prevent carbon falling when carbon black is kneaded and to improve the heat sheet property with the cover tape. The amount of the hydrogenated block copolymer is PS9.
The hydrogenated block copolymer is 1 to 2 with respect to 8 to 60% by weight.
0% by weight, preferably 3 to 15% by weight. If the added amount of the hydrogenated block copolymer is less than 1% by weight, there is no effect on the removal of carbon, and if it exceeds 20% by weight, there is a problem that the mechanical strength is reduced.

The term "hydrogenated block copolymer" as used herein means at least one terminal polymer block A mainly composed of a vinyl aromatic compound and at least one polymer block B mainly composed of a conjugated diene compound. And the content of the vinyl aromatic compound is in the range of 5 to 50% by weight, and 70% or more of the conjugated diene compound portion is obtained by hydrogenation. As the vinyl aromatic compound in the hydrogenated block copolymer, styrene, α
-Methylstyrene, o, m and p-methylstyrene,
Examples thereof include 1,3-dimethylstyrene, vinylnaphthalene, and vinylanthracene. Incidentally, the polymer A is a polymer composed of these homopolymers or a mixture thereof. The conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3 butadiene, 1,3-butadiene,
Examples thereof include pentadiene and 1,3-hexadiene, and the polymer block B is a homopolymer or a mixture thereof.

The number average molecular weight of the hydrogenated block copolymer (M
n) is 30,000 or more, preferably 50,000 to
The molecular weight distribution Mw / Mn is 10 or less (Mw: weight average molecular weight), preferably 5 or less, more preferably 2 or less. Number average molecular weight is 3
When the number average molecular weight exceeds 200,000, the fluidity is extremely lowered and the appearance of the molded article is deteriorated. Further, the hydrogenated block copolymer has a conjugated diene moiety of 70%.
% Or more is hydrogenated. If the hydrogenation ratio of the conjugated diene portion is less than 70%, the weather resistance is extremely poor and the use is greatly restricted, which is not preferable. The structure of the hydrogenated block copolymer may be linear or branched. Further, the hydrogenated block copolymer used in the present invention may be a further modified one, that is, one having a polar group such as a hydroxyl group, a carboxyl group, or an epoxy group at a molecular terminal or a molecular chain.

Carbon is added to the resin of the surface layer in order to impart conductivity. Resin component 10 consisting of PS and EVA
The amount of carbon added is 10 to 40 parts by weight, preferably 15 to 30 parts by weight, based on 0 parts by weight. If the added amount of carbon is less than 10 parts by weight, the conductivity is insufficient, and if the added amount of carbon exceeds 40 parts by weight, it becomes difficult to prepare a sheet, the flow is poor at the time of extrusion, and so-called “bubbles” due to carbon aggregation. This results in poor molding and poor appearance when molding a storage pocket for electronic components. In addition, mechanical strength such as bending strength is reduced.

The carbon used in the present invention is not particularly limited, but carbon black is preferred from the viewpoint of cost.
Further, acetylene black is more preferred. The average particle size of the carbon used in the present invention is 10 to 70 nm,
If it is less than nm, handling becomes difficult, and there is a problem that compounding and sheeting cannot be performed.
If it exceeds 70 nm, there is a problem that the surface resistivity cannot be obtained with a predetermined number of parts, and it is preferably 30 to 60 nm.

The development of conductivity is generally as shown in FIG.
This is achieved by the fact that the carbon is caught on the seat surface. In other words, the more carbon that is caught, the better the conductivity and the lower the surface resistivity. However, the more carbon that is caught, the more carbon is removed. Therefore, the carbon contained in the conductive surface layer is preferably as small as possible within a range where the conductive effect can be obtained.

By the way, the electrical conductivity generally required of a carrier tape is such that if it is too good, some current from the outside is transmitted to the electronic components of the content as it is, causing damage to the content, and if it is too bad, static electricity is generated. , Which also leads to content damage. At present, the surface resistivity is less than 1 × 10 ¹² [Ω], preferably 1 ×, even in the portion where the thickness is reduced when the carrier tape is formed after molding.
It is less than 10 ¹⁰ [Ω], and a surface resistivity of about 1 × 10 ⁴ to 1 × 10 ⁶ [Ω] is required as a carrier tape material as a base material thereof. Therefore, 10 to 40 parts of carbon is required for 100 parts by weight of the base resin. Carbon is usually used as a mere black colorant, but it is not more than 10 parts by weight. Compared with them, the amount of carbon used in this application is large. It is not possible to reduce the amount of carbon, and it is required that carbon does not fall off even if it is rubbed.

The thickness ratio of the conductive surface layer to the intermediate layer is 2 to 20% / 96 to 60% / conductive surface layer / intermediate layer / conductive surface layer.
2-20%, 7-15% / 86-70% / 7-1
5% is more preferred. The thickness ratio on one side of the conductive surface layer is 5
%, The thickness of the heated and stretched portion, particularly at the corners, is reduced at the time of molding, and the carbon structure in the conductive surface layer is destroyed. On the other hand, if it exceeds 20%, there arises a problem that mechanical properties such as tensile strength deteriorate. The production of the conductive sheet of the present invention is preferably performed by a co-extrusion method from the viewpoint of cost.

[0021]

EXAMPLES Conductive sheets for carrier tapes of Examples 1 to 10 and Comparative Examples 1 to 8 were prepared by a coextrusion method using an extruder with the composition and thickness shown in Table 1.

[0022]

[Table 1]

The prepared sheet was evaluated, and the evaluation results are shown in Table 2.

[0024]

[Table 2]

The evaluation was performed as follows. Regarding the abrasion resistance, as a test 1, the surface of each sheet was checked for carbon falling off by using an abrasion resistance tester (manufactured by Sumitomo Bakelite) as shown in FIG. Each sheet was attached to a rubbing tester, and the surface thereof was reciprocated 200 times with a gauze under a load of 500 g for 200 times, and it was determined whether or not the sheet became black, that is, whether or not carbon was removed. In Test 2, a carrier tape was prepared from each sheet using a vacuum drum forming machine (manufactured by Sumitomo Bakelite), and the pockets were filled with ICs as contents, and a cover tape 7301 made by Sumitomo Bakelite was placed thereon. Covered and heat sealed. Further, the sealed material is subjected to VOREX-GENIE 2 Model: G-5 manufactured by SCIENTIFIC INDUSTRIES.
Attached to a 60E vibration tester and vibrated at 450 rpm,
Judgment was made based on whether the bottom of the IC main body and the lead portion were darkened, that is, whether carbon was removed.

Other tests were carried out in the following manner. The conductivity is MODE manufactured by ADVANTEST
L: Using a two-point type 2 mm square electrode with an R8340A measuring instrument,
Measure the surface resistance (Ω / □) at the corner of the bottom of each molded product (carrier tape) pocket.
That is, it was determined whether it was less than 1 × 10 ⁹ [Ω / □]. As a strength judgment, the strength in the sheet state is determined by a tensile test (JIS
K6734), and the strength of the molded product (carrier tape) is determined to be the bending strength (bending strength) (JISP81).
15). The workability was determined based on whether sheeting was possible.

[0027]

According to the present invention, the present invention is a conductive carrier tape which has overcome the problem of carbon detachment in conventional products by a low cost method and is suitable as a material for a carrier tape for transporting electronic parts. is there.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structure in which carbon is kneaded into a base material.

FIG. 2 is a schematic diagram showing a configuration in which the surface of a base material is coated with carbon.

FIG. 3 is a schematic diagram showing a structure including three layers: a conductive surface layer made of a carbon-containing resin, an intermediate layer, and a conductive surface layer made of a carbon-containing resin.

FIG. 4 is a schematic cross-sectional view when a surface layer contains carbon (conductive surface layer).

FIG. 5 is a schematic diagram showing a state in which an IC is stored in a carrier tape.

FIG. 6 is a schematic diagram showing an implementation state of test 1;

[Explanation of symbols]

 Reference Signs List 1 base material 2 carbon 3 carbon coating layer 4 carbon-containing surface resin layer (conductive surface layer) 5 IC 6 lead 7 intermediate layer 8 gauze-wound weight 9 sample 10 counter 11 motor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) // B65D 85/86 C08L 23:08 (C08L 25/06 53:02 23:08 B65D 85/38 S 53:02) F-term (reference) 3E096 AA06 BA08 CA15 EA02 FA07 GA01 4F100 AA37B AA37C AA37H AK12B AK12C AK68B AK68C AK73B AK73C AK74A AL02B AL02C AL05B AL05C AL06B AL06C BA03 BA06 BA10A BA10B BA10C BA15 EH20 GB90 JA07B JA07C JG01A JG01C JK09 JK10B JK10C YY00 YY00B YY00C YY00H 4J002 BB062 BC031 BN141 BP013 DA036 FD116 GQ00

Claims (3)

[Claims] 1. An intermediate layer made of an ABS resin, and (a) 98 to 60% by weight of a polystyrene resin (b) 1 to 20% by weight of an ethylene / vinyl acetate copolymer (c) It has at least one or more terminal polymer blocks A mainly composed of vinyl aromatic compounds and at least one or more polymer blocks B mainly composed of conjugated diene compounds, and has a content of vinyl aromatic compounds. Is a hydrogenated block copolymer having a number average molecular weight of 100,000 to 200,000 and a mixture of 1 to 20% by weight, wherein 70% or more of the conjugated diene compound portion is hydrogenated. 10
A conductive surface layer comprising 10 to 40 parts by weight of carbon having an average particle diameter of 10 to 70 nm with respect to 0 parts by weight is produced by a co-extrusion method, and the thickness constituting ratio is 2 to 20.
% / Intermediate layer 96 to 60% / conductive surface layer 2 to 20%. 2. The conductive sheet for a carrier tape according to claim 1, wherein the polystyrene resin is a high impact styrene resin. 3. The conductive sheet for a carrier tape according to claim 1, wherein the carbon is acetylene black.