Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1998-11-24
2001-02-27
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S792000, C361S807000, C174S254000, C257S669000
Reexamination Certificate
active
06195260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a flexible printed circuit board unit wherein electronic parts such as semiconductor devices are mounted on a flexible printed circuit board.
2. Description of the Related Art
A conventional circuit board unit of the type mentioned is disclosed in Japanese Patent Laid-Open No. 220736/1991 which has a structure shown in FIG.
1
.
This circuit board unit
101
includes reinforcing plates
109
provided on the reverse side of flexible printed circuit board
102
on which semiconductor devices
106
are mounted. Reinforcing plates
109
are provided particularly on the reverse side of flexible printed circuit board
102
at locations at which semiconductor devices
106
are mounted in order to increase the rigidity of the portions of flexible printed circuit board
102
at the locations at which semiconductor devices
106
are mounted, thereby enhancing the reliability of electric connection between semiconductor devices
106
and flexible printed circuit board
102
. Semiconductor devices
106
are encapsulated in encapsulating resin
108
.
Japanese Patent Laid-Open No. 220736/1991 mentioned above further discloses circuit board unit
111
wherein, on a front surface of flexible printed circuit board
112
on which semiconductor devices
116
are mounted, reinforcing frames
119
which surround regions in which semiconductor devices
116
are mounted are provided as shown in FIG.
2
. In the example shown, encapsulating resin
118
is flowed into and hardened in regions surrounded by reinforcing frames
119
to provide a rigidity to the portions of flexible printed circuit board
112
at which semiconductor devices
116
are mounted and simultaneously encapsulate semiconductor devices
116
.
However, the conventional circuit board units described above do not sometimes present a sufficient reinforcing function to enhance the reliability of electric connection between the semiconductor devices and the flexible printed circuit board.
When an assembling process for a circuit board unit is taken into consideration, an organic material such as a glass epoxy material is preferably used for reinforcing members for a flexible printed circuit board. However, organic materials do not provide a sufficient rigidity. If an organic material of a comparatively great thickness is used to assure a sufficient rigidity, then a great difference in thickness will be produced between a location of the flexible printed circuit board at which the reinforcing member is provided and another location at which the reinforcing member is not provided. This makes handling of the flexible printed circuit board in the assembling process difficult. Thus, it may be proposed to alternatively use, for the reinforcing member, a metal plate having a sufficient rigidity with a comparatively small thickness. In this instance, however, since the metal plate is heavier than an organic material, it is difficult to transport the circuit board unit in the assembling process. Further, since the metal plate has a high thermal conductivity, condition setting such as temperature setting when a semiconductor device is to be connected to the flexible printed circuit board becomes severe.
In short, if it is tried to assure a high rigidity of a flexible printed circuit board in order to stabilize the electric connection between semiconductor devices and the flexible printed circuit board, then such disadvantages as described above occur in the assembling process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a flexible printed circuit board unit which is easy to handle in its assembling process while assuring a sufficiently high rigidity for a portion of a flexible printed circuit board at which a semiconductor device is mounted.
A flexible printed circuit board unit according to the present invention includes one or more electronic parts mounted on a front surface of a flexible printed circuit board. Further, a reverse side reinforcing plate is provided on a reverse side of the flexible printed circuit board in a region in which the electronic parts are mounted, and an upper reinforcing structure is provided on the flexible printed circuit board in such a manner as to cover at least one of the electronic parts.
In the flexible printed circuit board unit according to the present invention constructed above, the reverse side reinforcing plate provides a rigidity to the region of the flexible printed circuit board in which the electronic parts are mounted. Besides, since the electronic parts mounted on the flexible printed circuit board are covered with the upper reinforcing structure, the rigidity of the flexible printed circuit board after the electronic parts are mounted is provided by the reverse side reinforcing plate and the upper reinforcing structure, and the electronic parts themselves are protected by the upper reinforcing plate. Accordingly, since it is required to take into consideration only the rigidity of the flexible printed circuit board upon mounting of the electronic parts, the reverse side reinforcing plate need not be provided with an unnecessarily great thickness and need not be made of a metal. Consequently, handling of the flexible printed circuit board during mounting of the electronic parts onto the flexible printed circuit board and mounting of the electronic parts are facilitated.
According to a preferred embodiment of the present invention, the flexible printed circuit board includes a film-like base member made of an organic material, and a conductor layer formed on the base member and electrically connected to the electronic parts. In this instance, the reverse side reinforcing plate is preferably made from the same material as that of the base member of the circuit board in order to suppress warpage or deflection of the flexible printed circuit board.
Further, the flexible printed circuit board unit may be constructed such that the electronic parts are semiconductor devices, and the upper reinforcing structure includes an encapsulating resin for encapsulating the semiconductor devices and an upper reinforcing plate provided on the semiconductor devices with the reinforcing resin interposed therebetween. In this instance, it is preferable that the upper reinforcing plate has a recess or recesses formed therein for accommodating the semiconductor devices and the upper reinforcing plate is securely mounted on the flexible printed circuit board by the encapsulating resin in a condition wherein the semiconductor devices are positioned in the recess or recesses in order to protect the semiconductor devices mounted on the flexible printed circuit board. Further, it is preferable that the upper reinforcing plate is made of a metal in order to radiate heat generated by operation of the semiconductor devices efficiently.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.
REFERENCES:
patent: 56-62387 (1981-05-01), None
patent: 57-57575 (1982-04-01), None
patent: 57-146347 (1982-09-01), None
patent: 63-67278 (1988-05-01), None
patent: 1-303781 (1989-12-01), None
patent: 228342 (1990-01-01), None
patent: 3-123040 (1991-05-01), None
patent: 3220736 (1991-09-01), None
patent: 4-214654 (1992-08-01), None
patent: 4-251968 (1992-09-01), None
patent: 5-267561 (1993-10-01), None
patent: 6-326151 (1994-11-01), None
patent: 8-279576 (1996-10-01), None
patent: 10-154862 (1998-06-01), None
Yoshio Iinuma; Citizen Watch Co., Ltd., Technical Laboratory;IC Packaging Technology for Electronic Watch; pp. 41-44 (No Date).
Gandhi Jayprakash N.
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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