Cover tape for sealing the chip-holding parts of a carrier tape

Abstract: A cover tape (10) for sealing chips (4) in chip-holding parts (3) of a carrier tape (1) having said parts provided discontinuously and longitudinally of said carrier tape, which cover tape comprises a base tape (11), an adhesive layer (12) formed on one surface of said base tape and a non-adhesive coat (13) formed on said adhesive layer along the longitudinal direction of said base tape so that said non-adhesive coat has a width broader than that of the chips and narrower than that of said adhesive layer. When the cover tape is used in combination with the carrier tape, the chip-holding parts are sealed by the cover tape having the non-adhesive coat and in consequence the chips held in the chip-­ holding parts do not come in contact with the adhesive layer although they might come in contact with the non-adhesive coat. Accordingly, the chips are not stained by the adhesive in the adhesive layer.

Description: The present invention relates to a chip carrying cover tape according to the preamble of claim 1 (FR-A-2 445 273). The invention also relates to a process for the preparation of such a cover tape. Recently, electronic parts such as resistances, condensers and integrated circuits have been miniaturized and used in the form of chips. To cope with such a tendency, various devices for packaging such chips suitable for use in storage, transportation and automatic taking out of the packaged chips have been proposed. Among others, devices based on a carrier tape appear to have the most promising prospects. Such devices may be roughly classified into two types: (a) one using a carrier tape having apertures punched out, as disclosed in Japanese Utility Model Laid-open Publication No. 58-7.399, and (b) the other using an embossed carrier tape, as disclosed in Japanese Utility Model Laid-open Publication Nos. 62-65,959 and 61-202,362. In the first type of devices, use is made as a carrier tape of a relatively thick tape of paper having a row of apertures of a required dimension formed along the center line of the tape with a predetermined interval between successive apertures. Normally, another row of holes is provided along one of the side edges of the carrier tape for delivery purposes. A bottom tape is attached to one surface of the carrier tape so that each aperture may form a chip-holding room or recess. After chips have been placed in respective chip-holding recesses, a cover tape is attached to the other surface of the carrier tape so as to seal the chips in position. In the second type of devices use is made as a carrier tape of an embossed plastic tape having a row of recesses or depressed parts (chip-holding parts) of a required dimension embossed along the center line of the tape with a predetermined interval between successive parts. Normally, another row of holes is provided along one of the side edges of the carrier tape for delivery purposes. After chips have been placed in respective chip-holding parts, a cover tape is attached to the surface of the carrier tape so as to seal the chips in position. In both the types of devices, use is made of a cover tape, which normally comprises a base plastic tape and a layer of a heat sensitive adhesive formed on the base tape, which adhesive is inactive at ambient temperature and becomes active only when heated. Such a cover tape is adhered to the carrier tape by application of heat and pressure particularly to those areas adjacent to the chip-holding parts. The cover tape is required to firmly adhere to the carrier tape on the one hand. On the other hand, upon taking out the stored chips, it is required that the cover tape can be peeled off from the carrier tape by a relatively weak force. Further, the chips must not be stained by the adhesive constituting the adhesive layer. In other words, the chips should not come in contact with the adhesive layer at least under conditions where the adhesive is active. For these requirements, hot melt adhesives have heretofore been generally employed to constitute the adhesive layer. However, problems have been associated with the hot melt adhesives in that the cover tape must be adhered to the carrier tape under heat along both side edges of the cover tape of a width of on the order of about one millimeter, frequently resulting in non-uniform adhesion. The step of adhesion under heat is also disadvantageous from the view point of the productive speed of the production line, and might invite undesirable heat deformation of the carrier tape. Further, in a case wherein the chips are stored or transported at an elevated temperaure, the hot melr adhesive is reactivated and might come in contact with the chips to stain them. Document FR-A-2 445 273 discloses a carrier tape having electronic component holding parts along its length and a cover tape to overlie the components in the carrier tape, said cover tape having an adhesive layer on one surface, but this document does not teach having a further, continuous non-adhesive coat along the length of the cover tape which has a width narrower than that of the adhesive layer. Although the cited document mentions the problem of the electronic components coming into contact with the adhesive layer of the cover tape, the only solution suggested therein is to provide heat locally only along the edges of the cover tape. In such tapes, heat must be applied in a very narrow strip along the edges The strip must be sufficiently wide to ensure proper adhesion of the cover tape but care must be taken that the adhesive does not spread to the chip holding region. Thus, it is difficult to provide uniform adhesion in this way, particularly for long strips of tape and thus such tape is not suitable for mass production. Further, if the carrier strips containing chips are stored and transported at high temperatures, the adhesive in the chip holding regions may become activated and contact the chips. The present invention does away with the need to apply heat accurately along the edges of the strip and thus overcomes the above problems and facilitates mass production. With regard to documents US-A-4 211 329 and US-A-3 760 856 these documents disclose a carrier tape with cavities along its length for holding items, in particular pills or medicaments, the cavities being sealed by a strip of cover tape to the carrier tape by adhesive. The area of cover tape in contact with the carrier tape is provided with an adhesive coating the area covering the cavity has a non-adhesive surface. This surface is provided by circular portions of non-adhesive liner located over each article-holding unit to prevent the article disposed therein from adhering to the adhesive of the cover sheet. Documents US-A-4 211 329 and US-A-3 780 856 are concerned with a very different field to that of the present invention. These documents are concerned with storing and packaging drugs and medicaments. It is essential to provide adhesion between the cover tape and the carrier tape in between cavities to keep the medicaments stored in the cavities separate. The present invention provides a novel tape for carrying electronic components. Tapes for carrying medicaments must clearly satisfy very different requirements and criteria from tapes for carrying electronic components and there would be no reason to consider such tapes as having any relevance to the field of electronics. According to a first aspect of the invention there is provided; a chip carrying cover tape for sealing chips in a carrier tape having chip-holding parts provided discontinuously and longitudinally along said carrier tape, said cover tape comprising a base tape, and an adhesive layer formed on one surface of said base tape characterized by further comprising a non-adhesive coat formed from a radiation-cured ink formed by pattern printing on said adhesive layer, and being continuous along the longitudinal direction of said base tape so as, in use, to overlie chips in said chip-holding parts of a carrier tape and wherein said non-adhesive coat has a width narrower than that of said adhesive layer. According to a second aspect of the invention there is provided; a process for the preparation of a chip carrying cover tape for sealing chips in a carrier tape having chip-holding parts provided discontinuously and longitudinally along said carrier tape, comprising the step of forming an adhesive layer on one surface of a base tape, characterized by further comprising the steps of pattern-printing a radiation-curable ink on said adhesive layer, and irradiating light to cure said radiation-curable ink, thereby forming a non-adhesive coat on said adhesive layer said non-adhesive coat being continuous along the longitudinal direction of said base tape so as, in use, to overlie chips in said chip-holding parts of a carrier tape and wherein said non-adhesive coat has a width narrower than that of said adhesive layer. By using the present invention the chip-holding parts of the carrier tape are sealed by the non-adhesive coat of the cover tape so that the chips placed in the chip-holding parts of the carrier tape do not come in contact with the adhesive layer of the cover tape although they might come in contact with the non-adhesive coat of the cover tape, and in consequence the chips are not stained by the adhesive constituting the adhesive layer of the cover tape. Further. those portions of the adhesive layer of the cover tape which are not covered by the non-adhesive coat can uniformly and effectively adhere to those parts of the carrier tape other than the chip-holding parts to provide stable adhesion and peeling, and in consequence adhesion and peeling of the cover tape is easy and simple. In cases wherein an antistatic agent is incorporated in the non-adhesive coat, the cover tape is prevented from being charged with static electricity, thereby effectively preventing damage of the chips by static charge and attraction of the chips to the cover tape upon peeling the cover tape, which attraction might inadvertently cause removal of the chips. Further, in cases wherein a pressure-sensitive adhesive which is sticky at ambient temperature is used to constitute the adhesive layer of the cover tape, adhesion of the cover tape to the carrier tape can be effected without using heat and pressure, ensuring not only easy processing but also uniform adhesion without a risk of heat deformation of the carrier tape. Embodiments of the invention will now be described in detail by way of example with reference to the attached drawings in which: Fig. 1 (A) is a partly cross-sectional perspective view of a cover tape according to one embodiment of the invention; Fig. 1 (B) is a partly cross-sectional perspective view of a cover tape according to another embodiment of the invention; Fig. 2 is a partly cross-sectional perspective view of an assembly comprising an embossed carrier tape and a cover tape according to the invention. Fig. 3 is a partly cross-sectional perspective view of an assembly comprising a carrier tape having apertures and two cover tapes according to the invention, and Fig. 4 is a partly cross-sectional perspective view of an assembly comprising an embossed carrier tape and a cover tape according to the prior art. As shown in Fig. 1 (A), a cover tape 10 according to one embodiment of the invention comprises a transparent base tape 11, an adhesive layer 12, which is preferably sticky at ambient temperature, formed all over one of the surfaces of the base tape 11 and a non-adhesive coat 13 having a predetermined width formed on the adhesive layer 12. While the non-adhesive coat 13 extends along the longitudinal direction of the cover tape 10, the width of the non-adhesive coat 13 is wider than that of chips 4 held in chips-holding parts 1 of a carrier tape 3 and narrower than that of the adhesive layer 12, as shown in Fig. 2. The width of the non-adhesive coat should preferably be as same as the width of the chips-holding parts 1 of the carrier tape 3, as shown in Fig. 2. By doing so the chips 4 held in the parts 1 will be almost completely prevented from being brought in contact with the adhesive layer 12 of the cover tape 10. For example, in a case wherein the carrier tape 3 has a width of 8 mm, the cover tape 10 has a width of 5.3 mm, and the chips have a width of not greater than 3 mm, the width of the non-adhesive coat may be on the order of 3.3 mm. The cover tape 10 according to this embodiment can be prepared by forming an adhesive layer 12 on one surface of a base tape 11, and pattern-printing a non-adhesive coat 13 on said adhesive layer 12 so that the non-adhesive coat may extend continuously along the longitudinal direction and may have a predetermined width. Materials of the base tape 11 include polyethylene terephthalate (PET), polypropylene (PP), high density polyethylene, polystyrene, polyimide and polyvinyl chloride. Of these, PET is particularly preferred. The thickness of the base tape 11 is normally from 6 to 200 µm, preferably from 10 to 100 µm. Preferred pressure-sensitive-adhesives which can be used to form the adhesive layer 12, are those which are sticky at ambient temperature, such as acrylic and methacrylic adhesives and rubber-based adhesives. Examples of (meth) acrylic adhesives include, for example, homopolymers and copolymers of (meth) acrylic acid esters such as ethyl, butyl, 2-ethylhexyl, glycidyl and 2-hydroxyethyl acrylates and methacrylates, and copolymers of at least one of such (meth) acrylates with at least one copolymerizable monomer such as vinyl acetate, acrylic acid, methacrylic acid, styrene and acrylonitrile. Examples of the rubber-based adhesives include, for example, natural rubbers (NR), polyisobutylene rubbers (IR), butadiene robbers (BR), styrene-butadiene rubbers (SBR) and styrene-isoprene-styrene block copolymer (SIS), alone or in combination, as well as blends of at least of such robbers with at least one other tackifiers such as rosin and terpene resins. The thickness of the adhesive layer 12 is normally from 5 to 100 µm, preferably from 10 to 50 µm. The non-adhesive coat 13 is advantageously formed by pattern-printing with radiation-curable inks based on urethane acrylate, epoxy acrylate, polyester acrylate and polyethers. The ink used may be colored or may not be colored. Radiation-curable inks, in particular ultraviolet ray-curable inks, which are curable to a high crosslink density, are generally preferred. After a predetermined pattern of the coat 13 has been printed on the adhesive layer 12 with a radiation curable ink, the printed pattern is subjected to irradiation, in particular ultraviolet ray-irradiation, to cure the ink, rendering the pattern-printed coat non-adhesive. The non-adhesive coat 13 so formed does not stain chips, even if it comes in contact with the chips. The thickness of the non-adhesive coat 13 is normally from 0.1 to 20 µm, preferably from 1 to 10 µm. The ink, and in turn the non-adhesive coat 13 made therefrom, may contain an antistatic agent such as surfactants. By doing so, the non-adhesive coat 13 becomes antistatic, and thus it is possible to prevent damage of chips by static charge and static attraction of chips which might cause chips to fall off. Suitable antistatic agents which can be used herein include, for example, quarternary ammonium salts, aliphatic sulfonates, salts of higher alcohol sulfates, salts of higher alcohol phosphates, ethylene oxide adducts to higher alcohols and polyethylene glycol esters of fatty acids. In cases wherein an antistatic agent is incorporated in the non-adhesive coat 13, the cover tape 10 is prevented from being charged with static elecricity, thereby effectively preventing damage of the chips 4 by static charge and attraction of the chips 4 to the cover tape 10 upon peeling the cover tape which attraction might be a cause of falling off of the chips 4. Further, in cases wherein a pressure-sensitive adhesive which is sticky at ambient temperature is used to constitute the adhesive layer 12 of the cover tape 10, adhesion of the cover tape 10 to the carrier tape 3 can be effected without using heat and pressure, ensuring not only easy processing but also uniform adhesion without a risk of heat deformation of the carrier tape 3. While the invention has been described with reference to Fig. 1 (A) and Fig. 2, it is not restricted thereto. For example, the carrier tape 10 according to the invention can be used in combination with an embossed carrier tape, as illustrated in Fig. 2. Likewise, as shown in Fig. 3, it can be used in combination with a carrier tape 3a having a row of apertures (chip-holding parts 1a) of a required dimension formed along the center line of the tape with a predetermined interval between successive apertures. In this case two cover tapes 10 are adhered to both surfaces of the carrier tape 3a, respectively. In both cases, a row of holes 2 are provided for transportation or delivery purposes. Further, as shown in Fig. 1 (B), a cover tape according to an embodiment of the invention may comprise a base tape 11, an adhesive layer 12 formed on one surface of said base tape 11, a non-adhesive coat 13 formed on said adhesive layer 12 along the longitudinal direction of said base tape so that said non-adhesive coat 13 has a width broader than that of the chips and narrower than that of said adhesive layer 12, and a layer of a releasing agent 14 formed on the opposite surface of said base tape 11. The cover tape 10a is stored in the form of a roll before use. At this state, the layer 14 advantageously provides the adhesive layer 12 of the rolled cover tape 10a with a releasing surface. Examples of the releasing agent which can be used to form the layer 14 include, for example, silicone, stearyl acrylate and stearyl maleate; and copolymers thereof with acrylic acid, methyl acrylate, acrylonitrole, maleic acid or styrene. Of these, copolymers of stearyl acrylate are particularly preferred. Chips 4 that can be placed in the chip-holding parts 1, 1a of the carrier tape 3. 3a may be small mechanical items and pharmaceutical tablets as well as small electronic components. While the invention has been described on the cases wherein the adhesive layer 12 is composed of a pressure-sensitive adhesive which is sticky at ambient temperature, the adhesive layer 12 may comprises a heat-sensitive adhesive. Examples of the heat-sensitive adhesive which can be used herein include, for example, ethylenevinyl acetate rubber (EVA), styrene-butadiene rubber (SBR), ionomeric rubber, polybutadiene rubber (BR), styrene-isoprene-styrene block copolumer (SIS) and styrene-ethylene-butadiene-styrene block copolumer (SEBS). The invention, which is defined by the claims will now be further described by the following examples. Example 1 One of the surfaces of a polypropylene film having a thickness of 40 µm was coated with a terpolymer of 2-ethylhexyl acrylate, vinyl acetate and acrylic acid forming a pressure-sensitive adhesive layer having a thickness of 20 µm. On the adhesive layer so formed a pattern of a predetermined width extending longitudinally of the tape was printed with a transparent, ultraviolet ray-curable, polyester acrylate-based ink. The printed coat was cured by ultraviolet ray irradiation. The cured coat had a thickness of about 6 µm. The effect of the invention is confirmed with the cover tape so prepared. Example 2 One of the surfaces of a polyethylene terephthalate film having a thickness of 25 µm was coated with a styrene-butadiene block copolymer forming a heat-sensitive adhesive layer having a thickness of 20 µm. On the adhesive layer so formed a pattern of a predetermined width extending longitudinally of the tape was printed with a transparent, ultraviolet ray-curable, epoxy acrylate-based ink. The printed coat was cured by ultraviolet ray irradiation. The cured coat had a thickness of about 6 µm. The effect of the invention is confirmed with the cover tape so prepared.

Claims: A chip carrying cover tape (10) for seating chips (4) in a carrier tape (3) having chip-holding parts (1) provided discontinuously and longitudinally along said carrier tape (3), which cover tape (10) comprises a base tape (11), and an adhesive layer (12) formed on one surface of said base tape (11), characterized by further comprising a non-adhesive coat (13) formed from a radiation-cured ink formed by pattern printing on said adhesive layer (12), and being continuous along the longitudinal direction of said base tape (11) so as, in use, to overlie chips (4) in said chip-holding parts (1) of a carrier tape (3) and wherein said non-adhesive coat (13) has a width narrower than that of said adhesive layer (12). The cover tape (10) according to Claim 1 wherein said adhesive layer (12) comprises a pressure-sensitive adhesive. The cover tape (10) according to Claim 1 wherein said adhesive layer (12) comprises a heat-sensitive adhesive. A cover tape (10) according to any of the preceding claims wherein said non-adhesive coat (13) contains an antistatic agent. A cover tape (10) according to any preceding claim further comprising a layer of a releasing agent (14) formed on the other surface of said base tape (11). A process for the preparation of a chip carrying cover tape (10) for sealing chips (4) in a carrier tape (3) having chip-holding parts (1) provided discontinuously and longitudinally along said carrier tape (3), which process comprises the step of forming an adhesive layer (12) on one surface of a base tape (11), characterized by further comprising the steps of pattern-printing a radiation-curable ink on said adhesive layer (12), and irradiating light to cure said radiation-curable ink, thereby forming a non-adhesive coat (13) on said adhesive layer (12), said non-adhesive coat (13) being continuous along the longitudinal direction of said base tape (11) so as, in use, to overlie chips (4) in said chip-holding parts (1) of a carrier tape (3) and wherein said non-adhesive coat (13) has a width narrower than that of said adhesive layer (12). The process according to Claim 6 wherein said adhesive layer (12) comprises a pressure-sensitive adhesive. The process according to Claim 6 wherein said adhesive layer (12) comprises a heat-sensitive adhesive. A process according to any of Claims 6 to 8 wherein said non-adhesive coat (13) contains an antistatic agent. An assembly for storing and transporting chips (4) comprising a carrier tape (3) having chip-holding parts (1) containing chips (4), arid a cover tape (10) as defined in any of Claims 1 to 5 or formed by a process as defined in any of Claims 7 to 9, wherein said cover tape (10) includes a non-adhesive coat (13) having a width broader than that of the chips (4).

Inventors: EBE KAZUYOSHI, ITOU KAZUMI, MINAGAWA TOSHIO, EBE, KAZUYOSHI, ITOU, KAZUMI, MINAGAWA, TOSHIO
Applicants: LINTEC CORP, LINTEC CORPORATION
Application year: 1988
Main classification: B65D73
IPC codes: B65D75, H05K13, B65D73