Process for producing two-layered tape for tab

Details Process for producing two-layered tape for tab Process for producing two-layered tape for tab

1994-01-12

1996-04-16

Simmons, David A.

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

156230, 156231, 156249, 156253, B32B 3104, B32B 3118, B32B 3126

Patent

active

055079032

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for producing a tape for TAB (tape automated bonding), used for mounting semiconductor elements thereon, particularly to a process for producing a two-layered tape for TAB.


BACKGROUND ART

Semiconductor mounting techniques have accomplished remarkable progress in recent years. TAB, in particular, is under active development in order to respond to the current requirement for high-density mounting technique, because TAB enables formation of conductor pattern at a very high density, making it easy to connect multiple pins, and moreover TAB enables simultaneous bonding of all leads with semiconductor chips (gang bonding) without using any wire.
There are two kinds of tapes for TAB, i.e. a tape for TAB having a two-layered structure and a tape for TAB having a three-layered structure. The tape for TAB having a three-layered structure (hereinafter abbreviated as three-layered tape for TAB) is generally a laminate obtained by laminating a conductor foil (e.g., copper foil) with a heat-resistant resin film using an adhesive and has an adhesive layer of poor heat resistance; hence, the three-layered tape for TAB has been unable to fully exhibit the superior properties even when there is used, as the resin film, a polyimide film superior in properties such as heat resistance, chemical resistance and the like.
Meanwhile, the tape having a two-layered structure for TAB (hereinafter abbreviated as two-layered tape for TAB) generally has excellent heat resistance as a tape for TAB because the base film has no adhesive layer; however, the two-layered tape for TAB has found only very limited applications because of difficulty in production. That is, the two-layered tape for TAB is produced by two processes, i.e., the one process which comprises forming a conductor layer on a heat-resistant film made of a polyimide or the like by a thin-film-forming technique such as sputtering, vapor deposition, plating or the like, and then applying an etching treatment to the base film and the conductor layer to form desired holes (device holes, sprocket holes) and a desired conductor pattern, and the other process which comprises coating a varnish of a heat-resistant resin (e.g., polyimide) directly on a conductor foil (e.g., copper foil), drying the coated varnish to form a two-layered base board, and then applying an etching treatment to the resin layer and the conductor foil to form desired holes and a desired conductor pattern. In the former process, however, there is a problem that a rolled foil of excellent flexibility, a Fe--Ni alloy foil of excellent modulus, etc. cannot be used; moreover, the base film holes must be formed by an etching method, resulting in significantly reduced productivity as compared with the case employing the punching method applied to three-layered tapes for TAB. Meanwhile in the latter process, it is necessary that the linear thermal expansion of the resin used be nearly the same as that of the copper foil (conductor layer) in order to prevent formation of curls and wrinkles; however, such resins are generally rigid and have excellent solvent resistance, making it difficult to apply alkali etching in many cases and requiring use of dry etching (e.g. excimer laser) in order to form holes in the film layer, which results in disadvantageous productivity and cost.
Meanwhile, two-layered flexible materials for printed circuit, having no adhesive layer are finding increased applications, as electronic appliances become smaller and lighter. Similarly, film cover layers having no adhesive layer are in active development. Further, not only conventional flexible materials for wiring but also materials having a supporting film with holes, such as the above-mentioned carrier tape for TAB have found increased applications recently.
In the two-layered flexible base board for printed circuit, obtained by a process which comprises coating a polyamic acid on a conductor foil, followed by curing, there is no problem caused by an adhesive layer; however, the fi

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