Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2001-06-22
2003-02-04
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S559340
Reexamination Certificate
active
06515295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for exposure of a peripheral area of a film circuit board provided with perforation holes, such as a TAB strip, by which unnecessary resist is exposed.
2. Description of Related Art
In a liquid crystal substrate, a portable phone, a camera, a pocket calculator, an IC card, or the like, a film circuit board is used in which an integrated circuit is deposited to an insulating film, such as a polyester film, a polyimide film or the like, with a thickness of roughly 25 to 125 microns.
FIG.
8
(
a
) shows part of a TAB strip as one of the film circuit boards. The TAB strip TP is a strip workpiece, for example, with a width of 35 mm to 70 mm and a length of a few hundred meters, which is ordinarily wound onto a spool.
The circuit is produced on the TAB strip TP by a conductive foil (for example, a copper foil) being cemented to the above described insulating film and by the following processes and the like being repeated:
deposition process of the resist
projection printing process of the desired circuit pattern
development process of the resist
etching process in which the unnecessary conductive foil is removed. In the respective process, the film circuit board is unwound from the spool, is treated and processed, and wound back onto a spool.
The TAB strip (TP) (hereinafter also called the strip) is provided on both sides with perforation holes (PH) (also called sprocket holes) which are located at the same distance to one another (for example, with a pitch of 4.75 mm) and which are used for positioning and transport of the strip in the above described process. The strip TP is transported, for example, by rotating rollers with projections which fit into the perforation holes PH. Furthermore, in treatments such as exposure and the like, the strip TP is positioned such that the pins which are located at given positions of the device are inserted into the perforation holes PH.
As was described above, in the etching process, an unnecessary conductive foil (hereinafter also called copper (Cu) foil) is removed. When the conductive foil is not sufficiently removed, there are cases in which insulation faults and the like, and thus scrap, result. Furthermore. there is the disadvantage that the appearance is poor.
FIG.
8
(
b
) shows a state in which a resist R has been deposited to the copper foil of the TAB strip TP. FIG.
8
(
b
) is a cross section relative to the strip as shown in FIG.
8
(
a
). The area shown by the double dot-dash line designates the resist R.
As was described above, the copper foil was cemented to the insulating film. On the edge of the copper foil (hereinafter also called the peripheral area), the deposited resist R protrudes as a result of the surface tension, by which the edge is thicker than the remaining area.
Conventionally, a circuit pattern is formed such a peripheral area of the copper foil is not used. The area (the area which is cross-hatched) in which a circuit pattern is formed is shown in FIG.
8
(
a
) as the “effective pattern area”.
Conventionally, the peripheral area of the copper foil is removed in the etching process. However, since the resist R in the peripheral area of the copper foil is thick, as was described above, a greater amount of exposure is needed than in the remaining area (in the area in which the pattern is formed) in order to expose completely. With one-time exposure (exposure when the pattern is being formed), the amount of exposure is inadequate, as a result of which, in the development in the peripheral area, unexposed resist remains, and in the etching process, the copper foil is not eliminated. This unnecessarily remaining copper foil is ultimately unnecessary for attachment of the element. Thus, cutting off or the like must be performed with a cutting tool.
In order to completely expose the unnecessary resist in the peripheral area of the copper foil, it is therefore necessary to repeatedly expose only the resist in the peripheral area of the copper foil using an exposure device.
On the other hand, a process for exposing the peripheral area of a TAB strip in which only the resist in the peripheral area of the copper foil is exposed was proposed in Japanese patent disclosure document HEI 3-78237. In this publication, using
FIG. 1
, a process for exposure of a peripheral area is described in which UV (ultraviolet) radiation is emitted from a light source lamp through an optical fiber onto the two edges of the film and is focused by means of an exit optics unit, and in which the resist in the peripheral area of a moving film is exposed. In this process, the TAB strip is transported by a film transport device which has a friction roller and a sprocket roller. Since the TAB strip is made of a thin resin, as was described above, a serpentine is often formed during transport. The above described sprocket roller has protrusions which engage with the perforation holes of the film substrate. This prevents the film from slipping or twisting during transport.
As was described above, for the TAB strip, a copper foil is cemented to the film. But it is difficult to cement the copper foil to the film with high precision. The copper foil undulates with respect to the film roughly ±0.3 mm.
FIG. 9
schematically shows the above described snaking of the copper foil.
FIG. 9
shows in zone (b) the case in which the copper foil is located on the position (standard position) to be cemented.
FIG. 9
shows in zone (a) a case in which the copper foil is located towards the outside of the strip TP. Zone (c) of
FIG. 9
shows a case in which the copper foil is located towards the inside of the strip TP relative to the standard position.
Also in the case of transport of a TAB strip TP by the sprocket roller, between the two, an amount of play of roughly 0.1 mm is required to prevent the perforation holes from colliding with the protrusions of the sprocket roller, thus being abraded and damaged. There are therefore cases in which in the TAB strip TP, a wiggle of roughly ±0.1 mm is formed during transport. The peripheral area of the copper foil with a maximum width of roughly ±0.4 mm meanders during transport through the snaking of the copper foil with respect to the TAB strip TP and through the snaking of the TAB strip TP on itself during transport.
It depends on the user who produces the film circuit boards. The region which is to be subjected to exposure of the peripheral area extends, however, from the edge of the copper foil by a width of roughly 0.3 mm (hereinafter this width is called the exposure width). The exposure width should have few faults. But the following problems must be considered:
(1) When the exposure width is less than or equal to 0.2 mm from the edge of the copper foil, it is smaller than the projecting area of the resist R, as a result of which, during development, unexposed resist remains. Therefore, an exposure width of greater than or equal to 0.2 mm is needed.
(2) The area in which the pattern is formed is fixed independently of the snaking of the copper foil as a result of the perforation holes (PH) (for example, by 1 mm to the inside from the edges of the perforation holes as shown in FIG.
9
). When the copper foil is located towards the inside of the strip TP, as is shown in zone (c) of
FIG. 9
, the distance between the edge of the copper foil and the area in which the pattern is formed is therefore only roughly 0.4 mm. At an exposure width at least equal to 0.4 mm, the exposure light enters the area for forming the pattern and exposes the resist R which is necessary for pattern formation, resulting in possible formation of scrap.
(3) Based on (1) and (2), an exposure width of 0.3 mm±0.1 mm must be ensured for exposure of the peripheral area.
U.S. Pat. No. 4,899,195 suggests a technology of exposure of a peripheral area in which exposure takes place from the edge of the workpiece with a stipulated width. Here, it is described that, using an optical detector having an emission element and a light receiving eleme
Murakami Satoshi
Sato Masanori
Le Que T.
Nixon & Peabody LLP
Safran David S.
Ushiodenki Kabushiki Kaisha
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