Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
1998-11-30
2001-01-09
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S041800, C428S042200, C428S042300, C428S352000
Reexamination Certificate
active
06171672
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cover tape for sealing a carrier tape which is employed to individually pack small items (hereinafter also referred to as “chips”) such as small electronic parts without causing them to contact each other and hence used in the storage, transportation and automatic takeout of the chips. Moreover, the present invention relates to a sealed structure in which use is made of the above cover tape.
BACKGROUND OF THE INVENTION
In recent years, the movement toward miniaturizing electronic parts such as resistors, capacitors and integrated circuits into chips is rapid. Accordingly, various methods which enable simultaneously carrying out the storage, transportation and automatic takeout of chips have been proposed, of which the tape carrier method is regarded as being the most promising.
The conventional tape carrier method is classified into the method in which a substrate furnished with through holes is used as the carrier tape and the method in which a substrate furnished with recessed parts is used as the carrier tape.
In the method in which use is made of a carrier tape furnished with through holes, a carrier tape composed of, for example, a thick strip of paper is furnished with a multiplicity of through holes at given intervals by punching or other means to thereby provide accommodating parts. Separately, the carrier tape is furnished with a multiplicity of feeding holes. A bottom tape is stuck to one side surface of the carrier tape, and small electronic parts or other chips are accommodated in the accommodating parts. Thereafter, the other side surface of the carrier tape is laminated with a cover tape so that the chips are sealed in the accommodating parts.
In the method in which a substrate furnished with recessed parts is employed as the carrier tape, use is made of a carrier tape produced by furnishing a stripform plastic tape with a multiplicity of recessed parts at given intervals to thereby provide accommodating parts and further furnishing the stripform plastic tape with a multiplicity of feeding holes. Small electronic parts or other chips are accommodated in the accommodating parts, and, thereafter, the carrier tape is laminated with a cover tape so that the chips are sealed in the accommodating parts.
In both the above methods, use is made of the cover tape. A tape comprising a tape-shaped substrate and adhesive layers disposed at both edges along the lengthwise direction on one side of the tape-shaped substrate is used as the above cover tape. The tape-shaped substrate is composed of, for example, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, a nylon or an ionomer. The conventional general-purpose acrylic, polyester or rubber pressure sensitive adhesive is used as the above adhesive. On the other hand, the carrier tape furnished with recessed parts is composed of, for example, polystyrene, a polycarbonate, polyvinyl chloride or an amorphous polyethylene terephthalate.
However, the use of the above conventional cover tape and carrier tape encounters the problems that the lifting and separation (wrinkle) of the cover tape from the carrier tape occurs during the transportation thereof, depending on the circumstance experienced during the transportation and that the peeling of the cover tape from the carrier tape after the transportation causes adhesive transfer (adhesive residue) onto the carrier tape side.
Illustratively, the cover tape and carrier tape may be exposed to high temperatures such as 50° C. or above, occasionally, 70° C. or above during the transportation in the summer or on the sea. In this high temperature atmosphere, the polystyrene tape generally used as the carrier tape shrinks by about 2%. On the other hand, the shrinkage ratio of polyethylene terephthalate generally employed as a substrate of cover tape is 0.1% or less, so that a shrinkage ratio difference occurs between the cover tape and the carrier tape. Therefore, the cover tape is in excess and the cover tape is lifted from the carrier tape so that the cover tape and the carrier tape are separated from each other.
The above problem would be solved by increasing the bonding strength of the adhesive layer of the cover tape. However, the increase of the bonding strength invites the problem that adhesive residue occurs on the carrier tape when use is made of a carrier tape with relatively high polarity, such as a polycarbonate, polyvinyl chloride or an amorphous polyethylene terephthalate. When the adhesive remains on the carrier tape, conveyance failure occurs at the time of chip mounting, and the adhesive sticks to the takeup machine to thereby disenable smooth winding operation at the time of winding the carrier tape after use. Further, there is the disadvantage that the carrier tape cannot be recycled.
The inventors have conducted extensive and intensive studies with a view toward solving the above problems. As a result, it has been found that the above problems can be solved by employing a specified silicone pressure sensitive adhesive to constitute the adhesive layer of the cover tape. The present invention has been completed on the basis of this finding.
Japanese Patent No. 2,500,879 discloses a cover tape using a silicone pressure sensitive adhesive. However, the patent does not disclose the silicone pressure sensitive adhesive containing a phenyl group as required in the present invention.
Further, when the polydimethylsiloxane pressure sensitive adhesive described in Japanese Patent No. 2,500,879 is used on the cover tape, it has been inevitable to apply an expensive release agent such as a fluorosiloxane release agent to the cover tape. If the ordinary release agent is used, large unwinding force is required at the time of sealing the same to the carrier tape to thereby increase the load on the sealing apparatus.
The present invention has been made taking the above prior art into account. An object of the present invention is to avoid the lifting/separation of the cover tape from the carrier tape which is caused by a difference in thermal shrinkage ratio when a polystyrene carrier tape is used. Another object of the present invention is to avoid the adhesive residue occurring on the carrier tape when a carrier tape with relatively high polarity, such as a polycarbonate, a polyvinyl chloride or an amorphous polyethylene terephthalate tape is used. A further object of the present invention is to ensure small unwinding force, irrespective of the type of release agent employed, so that the load on sealing apparatus is reduced and sealing operation can be efficiently performed.
SUMMARY OF THE INVENTION
The cover tape for chip transportation according to the present invention is one stuck to a surface of a carrier tape which has parts for accommodating chips formed intermittently in its lengthwise direction, to thereby seal the chip accommodating parts, wherein said cover tape comprises a tape-shaped substrate and pressure sensitive adhesive parts superimposed on one surface of the tape-shaped substrate so that the pressure sensitive adhesive parts do not face the chip accommodating parts,
the above pressure sensitive adhesive parts comprising a silicone pressure sensitive adhesive and a crosslinking agent (C) capable of crosslinking therewith,
the above silicone pressure sensitive adhesive comprising:
(A) a silicone resin component and
(B) a silicone rubber component with a structure represented by the formula:
wherein R
1
, R
2
, R
3
and R
4
may be identical with or different from each other and represent a methyl group, an ethyl group or a propyl group;
either of X and Y represents a hydroxyl group and the other represents a hydroxyl group, hydrogen or an alkyl group having 1 to 13 carbon atoms;
each of R
1
, R
m
, R
n
, R
1′
, R
m′
and R
n′
independently represents a phenyl group, an alkyl group having 1 to 13 carbon atoms, CF
3
CH
2
CH
2
— or a vinyl group, provided that at least one of R
1
, R
m
, R
n
, R
1′
, R
m′
and R
n′
is a phenyl group w
Ebe Kazuyoshi
Koike Hiroshi
Taguchi Katsuhisa
Lintec Corp.
Morris Terrel
Singh Arti R.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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