JP2798727B2 - Bottom material of conductive carrier for electronic parts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bottom material for a conductive carrier for electronic components used for taping and packaging of electronic components such as ICs, and particularly to a conductive material having good conductivity, The present invention relates to a bottom material for a conductive carrier for electronic components, which has good adhesion to a lid material having a vinyl acetate copolymer resin as a seal layer and has good adhesion.

[Problems to be solved by conventional technology and invention]

In recent years, electronic components have been automatically mounted on circuit boards for the purpose of automating the production of electronic devices.In this case, in order to facilitate the handling of the electronic components, the individual electronic components are transferred to a carrier tape. The electronic components are automatically picked up while sequentially sending out the carrier, and are automatically mounted at predetermined positions on the circuit board.

A carrier used for automatic mounting of such electronic components generally includes a tape-shaped bottom member and a cover (cover tape), and the bottom member has electronic component accommodating recesses formed at regular intervals. In addition, a feed hole having a constant pitch is formed on one or both sides thereof. Also,
The lid has a width that completely covers the recess that houses the electronic component, and is bonded to the bottom material by heat sealing or the like on both sides.

As a bottom material of such a carrier of electronic components, usually,
Polystyrene, polyvinyl chloride, in terms of strength and cost,
Polyethylene etc. are used, and as the lid material,
Ethylene-vinyl acetate copolymer (EVA) is used in terms of adhesiveness.

By the way, with the miniaturization and precision of electronic components, it is becoming increasingly important to prevent dielectric breakdown and the like due to high voltage. For this purpose, it is necessary to make the carrier conductive and to prevent accumulation of electric charge.

For the purpose of imparting such conductivity, a large amount of fine particles of a conductive substance such as carbon is blended in a polyvinyl chloride resin as a bottom material of the carrier, and the surface resistance is 10 ⁸ Ω /
□ Some of them use a resin sheet of the following.

However, since the bottom material of this carrier has a single-layer structure and contains a conductive material such as carbon black in all the resins forming the bottom material, the amount of the material is inevitably large and the mechanical strength is low. In addition to a decrease in workability and a decrease in workability, there is a problem that the cost is high.

Therefore, as a sheet for packaging electronic parts provided with conductivity without lowering the mechanical strength and workability, one or both sides of a polystyrene or ABS resin sheet base material contains 5 to 50% by weight of carbon black. There has been proposed a composite plastic sheet obtained by integrally laminating a polystyrene or ABS resin film or sheet having a surface resistance of 10 ¹⁰ Ω or less by co-extrusion (Japanese Patent Laid-Open No. 57-57).
205145).

However, when this composite plastic sheet is used as a bottom material of an electronic component carrier (carrier tape), an ethylene-vinyl acetate copolymer for improving the heat sealing property with a lid (containing an ethylene-vinyl acetate copolymer) on the surface layer. There is a problem that the heat seal with the lid is not sufficient because no coalesce or vinyl chloride-vinyl acetate copolymer is contained.

Therefore, the object of the present invention is to have sufficient conductivity, good adhesion to the lid, and high mechanical strength,
An object of the present invention is to provide an inexpensive base material for an electronic component carrier.

[Means for solving the problem]

As a result of intensive studies in view of the above object, the present inventor has found that even if the entire bottom material of the carrier is not made conductive, providing a conductive layer at least on the side in contact with the electronic component is sufficient for protection of the electronic component. In addition, the present inventors have found that it is possible to achieve both improvement in heat sealability, prevention of reduction in mechanical strength, and reduction in cost by reducing the amount of conductive resin used, and arrived at the present invention.

That is, the bottom material of the conductive carrier for electronic components of the present invention, a conductive polypropylene layer is laminated at least on the side in contact with the electronic component, the conductive polypropylene layer is 65 to 85 wt% of polypropylene, 5-10% by weight of ethylene-vinyl acetate copolymer and 10-25% by weight of carbon
Wherein the bottom material has a total thickness of 0.2 to 2.0 mm, and the conductive polypropylene layer has a thickness of 30 to 100 μm.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is a plan view of a conductive carrier according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view taken along line AA of FIG.

The conductive carrier comprises a tape-like bottom material 1 and a tape-like lid 2 heat-sealed to the tape-like bottom material 1. The bottom material 1 has concave parts 11 for component loading arranged at a predetermined interval (a), and one side part. And feed holes 12 provided at a constant pitch (b). Further, the lid 2 is adhered to the upper surface of the bottom member 1 by heat sealing or the like so as to completely cover the concave portion 11. In such a conductive carrier, the electronic component 6 is loaded as shown by a dashed line in FIGS.

In the embodiment shown in FIG. 2, the bottom material 1 of the conductive carrier of the present invention has a conductive polypropylene layer 3 and a polypropylene layer 4 as essential components, and further, if necessary, a lower side of the polypropylene layer 4. Further has a conductive polypropylene layer 5.

In the present invention, the conductive polypropylene resin composition is
It contains 65 to 85% by weight of polypropylene, 5 to 10% by weight of ethylene-vinyl acetate copolymer (EVA), and 10 to 25% by weight of carbon.

In the present invention, the blending ratio of the polypropylene in the conductive polypropylene resin composition is 65 to 85% by weight, particularly preferably 70 to 80% by weight. If the blending ratio of polypropylene is less than 65% by weight, the adhesion to the polypropylene layer 4 is not sufficient, and if it exceeds 85% by weight, the blending amounts of EVA and carbon are too low.

In the present invention, the ethylene-vinyl acetate copolymer (EV
A) is not particularly limited, but as described later, since the content of vinyl acetate is preferably 2% by weight or more based on the whole composition, it depends on the mixing ratio of EVA in the composition. Therefore, it is preferable to select one having an appropriate vinyl acetate content.

The blending ratio of the ethylene-vinyl acetate copolymer (EVA) is generally 5 to 10% by weight, and particularly preferably in the range of 7 to 10% by weight. If the compounding ratio of EVA is less than 5% by weight, the adhesion to the lid will decrease over time, and if it exceeds 10% by weight, blending with polypropylene will be difficult.

The content of vinyl acetate (VA) in EVA depends on the amount of EVA used, as described above, and it is generally preferable that the content be 2% by weight or more based on the whole composition. Therefore, for example, when EVA is 5% by weight, the content of VA may be 40% by weight or more, and when EVA is 10% by weight,
May be 20% by weight or more. In general, when the content of vinyl acetate is too low, the storage stability of the heat seal strength with the lid is significantly reduced. It is meaningless if the content of vinyl acetate is too large.

The conductive polypropylene resin composition contains the above-mentioned polypropylene and EVA, and further contains carbon.
The compounding ratio of carbon in the conductive polypropylene resin composition is 10 to 25% by weight, and particularly preferably 10 to 20% by weight. If the proportion of carbon is less than 10% by weight, the conductivity of the conductive polypropylene resin composition is not sufficient,
If the content is more than 10% by weight, when the bottom material is stored at a high temperature for a long period of time, the carbon bleeds out to the surface of the bottom material, so that the preservability of the heat seal strength with the lid material decreases. Thus, the surface resistance of the conductive polypropylene layer containing an appropriate amount of carbon is 10 ⁸ Ω / □ or less, preferably 10 ⁶ Ω / □ or less.

In particular, in the present invention, in order to improve the compatibility between polypropylene and ethylene-vinyl acetate copolymer (EVA), the propylene-α-olefin copolymer is added in an amount of 5 to 15% by weight based on the whole composition. % Is preferably added. When the content of the propylene-α-olefin copolymer is less than 5% by weight, the effect of the addition is not remarkable, and
There is no point in exceeding the weight percentage.

In addition, if necessary, a heat stabilizer, an antioxidant, a light stabilizer, a flame retardant, a plasticizer, an antistatic agent, and the like may be added in appropriate amounts in addition to the components described above.

The polypropylene layer 4 is not limited to a homopolymer of propylene, but may be a layer obtained by appropriately copolymerizing a monomer such as ethylene.

In the present invention, the conductive polypropylene layer 3
It is sufficient if is provided on the electronic component side, but in order to obtain better conductivity, it is preferable to provide a conductive polypropylene layer 5 also on the outside as shown in FIG.

The total thickness of the bottom member composed of each layer as described above can be appropriately changed according to the size and weight of the electronic component to be loaded, but is generally 0.2 to 2.0 mm.

The conductive polypropylene layer 3 has a thickness of 30 to 100 μm in order to obtain sufficient conductivity. If the thickness exceeds 100 μm, the amount of the conductive polypropylene resin composition to be used increases, and the mechanical strength and workability of the electronic component carrier are lowered, and the cost is disadvantageous. When the conductive polypropylene layer 5 is also provided on the lower side,
The thickness of the conductive polypropylene layer 5 may be the same as the thickness of the conductive polypropylene layer 3.

The bottom material of the conductive carrier having such a multilayer structure is
It can be manufactured by the following method.

First, polypropylene of the above composition range, ethylene-
A vinyl acetate copolymer (EVA), carbon, and a propylene-α-olefin copolymer and additives, etc., which are blended as necessary, are kneaded at 180 to 250 ° C., and then extruded from a die, followed by inflation. Alternatively, a sheet of the conductive polypropylene composition is formed into a film by a T-die method or the like.

Next, a laminated sheet is manufactured using the sheet of the conductive polypropylene composition by an apparatus as shown in FIG. The apparatus comprises an extruder (not shown), a die 33 at the end of the extruder for feeding a polypropylene sheet 31,
Guide rolls 34, 34 'for guiding the conductive polypropylene sheets 32, 32', a heating roll 35, and a pressure roll
36, cooling rolls 37 and 38, and a winding roll 39.

In such an apparatus, the sheet for each layer is fed to the heating roll 35 and the pressure roll 36 for thermal lamination. Subsequently, the lamination sheet is cooled by a cooling roll 37,
It is cooled by 38 and wound up by a winding roll 39.

At this time, the temperature of the heating roll 35 is preferably set to 60 to 150 ° C., and the temperature of the cooling rolls 37 and 38 is set to 30 to
If the temperature is set to about 0 ° C., cooling can be performed efficiently.

When a conductive polypropylene sheet is provided only on one side of the polypropylene sheet 31, the conductive polypropylene sheet 32 'need not be simply fed.

Next, a concave portion 11 is formed in the obtained laminated sheet, a perforation hole 12 is formed in a side portion, and the laminated sheet is wound around a reel. Thus, the bottom material of the conductive carrier can be obtained.

The lid heat-sealed to the bottom material of the conductive carrier has (a) a small variation in peel strength when heat-sealed to the bottom material, (b) antistatic properties, and (c) constant It is necessary to have the above mechanical strength.

FIG. 4 shows an example of a lid satisfying such conditions. The lid 2 includes a base sheet 21 and a sealing material layer 22, and an anchor coat layer 23 is provided between the two layers as needed. The sealing material layer 22 has a two-layer structure of a polyethylene layer 22a and an ethylene-vinyl acetate copolymer (EVA) layer 22b.

For the base sheet 21, it is preferable to use polyester such as polyethylene terephthalate from the viewpoint of mechanical strength. The EVA layer 22b contains an antistatic agent in addition to EVA. As the above EVA, the same E as used for the aforementioned bottom material
VA is fine. As the antistatic agent, it is preferable to use a nonionic surfactant or a nonionic surfactant plus a monoester of glycerin and a carboxylic acid (for example, stearic acid or the like).

The content of the antistatic agent is 0.2 to 0.5% by weight based on 100% by weight of the composition of the EVA layer 22b. The amount added is 0.
If it is less than 2% by weight, the surface resistance value of the lid cannot be sufficiently reduced, and if it exceeds 0.5% by weight, it is meaningless. Due to the addition of antistatic agent, the surface resistance of this lid is 10 ¹¹ Ω / □
Or less, preferably 10 ⁹ Ω / □ or less. Since the surface resistance of EVA when no antistatic agent is added is 10 ¹⁶ Ω / □ or more, it can be seen that the conductivity is significantly improved.

When the anchor coat layer 23 is provided between the base sheet 21 and the sealing material layer 22, a general-purpose anchor coat agent such as polyethyleneimine, urethane, and isocyanate can be used.

The thickness of such a lid material is in the range of 47 to 145 μm as a whole. If the thickness of the lid material is less than 47 μm, there is a problem in strength, and if the thickness is more than 145 μm, the heat transfer during heat sealing deteriorates. The thickness of each layer is 12 to 50 for the base sheet.
μm, the sealing material layer is 35 to 95 μm,
Preferably, the EVA layer is between 15 and 50 μm. More preferably, the sealing material layer is 40 to 60 μm, and the EVA layer is 20 to 30 μm.
m. Note that the thickness of the base sheet is determined for the purpose of reinforcement, and if not within the above range, the strength is impaired. If the thickness of the sealing material layer is less than 35 μm, the dispersion of the peel strength becomes large, making it difficult to open the conductive carrier softly.

The lid 2 having such an EVA layer 22b has a peel strength of 10 to 70 gf or less with respect to the bottom material 1 (strength when peeled at a speed of 300 mm / min from a heat-sealed one having a width of 1 mm). Also, the peel strength has little variation throughout,
The difference between the maximum and the minimum is only within 30gf.

The lid 2 can be obtained, for example, by extruding and laminating polyethylene between a polyethylene terephthalate base sheet and an antistatic agent-containing EVA composition sheet. When an anchor coat layer is provided, an anchor coat agent is applied to the polyethylene terephthalate base sheet to form an anchor coat layer, and then the same extrusion lamination may be performed.

(Operation)

The bottom material of the conductive carrier of the present invention has a sufficiently small surface resistance because the conductive polypropylene resin composition is laminated on the side in contact with the electronic component, and the amount of the conductive polypropylene resin composition used. Requires less. For this reason, it is an inexpensive conductive carrier bottom material.

In addition, polypropylene, which is a component of the conductive polypropylene resin composition, is more EVA than propylene homopolymer.
And good compatibility. Moreover, due to the EVA in the composition, the adhesiveness with the polypropylene layer as the base material is also good.

Furthermore, since the conductive polypropylene resin composition forming the conductive polypropylene layer contains EVA in which the ratio of vinyl acetate to the entire composition is within a desired range, the sealing surface can be applied to a lid having an EVA layer. Shows good heat sealability and extremely small variation in seal strength.

〔Example〕

The present invention will be described in more detail with reference to the following specific examples.

Examples 1 to 4 and Comparative Examples 1 to 4 Preparation of Sheet for Bottom Material Four types of ethylene-vinyl acetate copolymers (EVA (1) to (4)) having different contents of vinyl acetate, polypropylene, and carbon And a propylene-α-olefin copolymer in the proportions shown in Table 1 and kneaded at 240 ° C. for 30 minutes. The kneaded product was extruded from a T-die and a sheet of a conductive polypropylene resin composition having a thickness of 50 μm. I got

The resulting conductive polypropylene resin composition sheets were used as the upper layer and the lower layer, and the polypropylene sheet having a thickness of 0.2 mm was used as the intermediate layer. A sheet for bottom material was created.

The vinyl acetate contents of EVA (1) to EVA (4) are as shown below.

EVA (1): Vinyl acetate content 20% by weight EVA (2): Vinyl acetate content 25% by weight EVA (3): Vinyl acetate content 30% by weight EVA (4): Vinyl acetate content 35% by weight Surface resistance Measurement of value Upper layer of obtained bottom material sheet (side in contact with electronic components)
Was measured using a Mitsubishi Loka Co., Ltd. Lorester.

 The measurement results are shown in Table 1.

As shown in Table 1, the surface resistance value of the sheet for the bottom material of Examples 1 to 4 is 10 ⁸ Ω required for the bottom material of the conductive carrier.
/ □ or less (preferably 10 ⁶ Ω / □ or less).

Measurement of peel strength and evaluation of uniformity of peel strength For a peel strength storage test, an isocyanate anchor coating agent was applied to polyethylene terephthalate to form an anchor coat layer as a lid for heat sealing to the bottom material of the present invention. And an ethylene-vinyl acetate copolymer (EVA) -based resin were extruded and laminated with polyethylene to prepare a laminated sheet having a polyethylene terephthalate layer of 25 μm, a polyethylene layer of 20 μm, and an EVA layer of 30 μm.

The EVA-based resin is obtained by adding 0.5% by weight of a nonionic surfactant (Staticide manufactured by Tokyo Denki Kagaku Kogyo Co., Ltd.) as an antistatic agent, with the whole being 100% by weight. The surface resistance of this lid was 10 ⁸ Ω / □.

For each base material sheet, cover the above with a width of 1mm and 170 ℃
For 1 second, and measured the maximum value and the minimum value of the peel strength immediately after the heat sealing, and the maximum value and the minimum value of the peel strength after storing at 40 ° C. and 90% humidity for 14 days.

 The conditions for measuring the peel strength were as follows.

Peeling angle: 180 ° with respect to the tape surface Peeling speed: 300 mm / min The uniformity was evaluated from the measured peel strength.
The uniformity of peel strength depends on the difference between the maximum and minimum peel strength.
If it is larger than 30 gf, since the electronic parts are likely to jump when opening the carrier, the maximum value and the minimum value are both 10 gf or more, and the difference between the maximum value and the minimum value is 30 gf or less, ○, When the maximum value or the minimum value was less than 10 gf or the difference between the maximum value and the minimum value exceeded 30 gf, it was evaluated as x.

 The results are shown in Table 1.

Peel strength storage test The lid was heat-sealed to the sheet for bottom material of Examples 1 to 4, and the peel strength immediately after heat sealing, the temperature of 60 ° C, and the humidity of 90
The peel strength after storage for 14 days and the peel strength after storage for 28 days were measured in%.

The peel strength was indicated by the average of the maximum value and the minimum value. The peel strength immediately after heat sealing is an average of the maximum value and the minimum value in the column of the measurement of the peel strength.

 The results are shown in Table 2.

From Table 2, it can be seen that the sheet for the bottom material of the conductive carrier of the present invention has little change in peel strength even under an environment where storage conditions are severe.

[Effects of the Invention] As described above in detail, the bottom material of the conductive carrier of the present invention,
Since the contact surface with the electronic component is made of a conductive polypropylene layer, it has good conductivity, and the amount of the expensive conductive resin composition used can be reduced. In addition to having good heat sealing properties with respect to a lid having EVA as a sealing layer, the dispersion of peel strength (difference between maximum and minimum) is extremely small. For this reason, the lid of the electronic component carrier can be stably peeled off with a constant force, and automatic handling of the electronic component can be reliably and easily performed. Furthermore, since the preservability of the heat seal strength is good, there is almost no change in the peel strength due to the length of the preservation period.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a bottom material of the conductive carrier of the present invention, FIG. 2 is an enlarged sectional view taken along the line AA of FIG. 1, and FIG. 3 is a conductive carrier of the present invention. FIG. 4 is a schematic view showing a manufacturing process of a body bottom material, and FIG. 4 is a cross-sectional view showing a layer structure of a lid heat-sealed to the bottom material of the conductive carrier of the present invention. DESCRIPTION OF SYMBOLS 1 ... Bottom material 11 ... Component mounting concave part 12 ... Sending hole 2 ... Lid 3,5 ... Conductive polypropylene layer 4 ... Polypropylene layer 6 ... Electronic component 21 ... Base sheet 22 ... Seal material Layer 22a Polyethylene layer 22b Ethylene-vinyl acetate copolymer resin layer 23 Anchor coat layer 31 Polypropylene sheet 32, 32 'Conductive polypropylene sheet 33 Die 34, 34' Guide Roll 35 Heating roll 36 Pressure roll 37, 38 Cooling roll 39 Winding roll

Continuation of front page (72) Inventor Kimiaki Momome 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. (56) References JP-A-62-271858 (JP, A) 62-171486 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H05K 13/02

Claims (2)

(57) [Claims] 1. A bottom of a tape-shaped conductive carrier for electronic parts, which has recesses for loading electronic parts at regular intervals, and has perforations at one or both sides thereof at a constant pitch. In the material, a conductive polypropylene layer is laminated at least on a side in contact with the electronic component, and the conductive polypropylene layer is composed of 65 to 85% by weight of polypropylene and 5 to 10% by weight of an ethylene-vinyl acetate copolymer. ,
It is formed of a conductive polypropylene resin composition containing 10 to 25% by weight of carbon, and the total thickness of the bottom material is
0.2 to 2.0 mm, and the conductive polypropylene layer has a thickness of 30 to 100 μm. 2. The bottom material of a conductive carrier for electronic parts according to claim 1, wherein said conductive polypropylene resin composition further contains 5 to 15% by weight of a propylene-α-olefin copolymer. A bottom material for a conductive carrier for electronic parts, characterized by the following.