Electric lamp and discharge devices – With character display
Reexamination Certificate
2001-11-27
2003-09-23
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With character display
C313S495000
Reexamination Certificate
active
06624573
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a fluorescent display device adapted to impinge electrons emitted from an electron emission source such as a filamentary cathode, a field emission cathode (FEC) or the like on a phosphor to carry out desired display, and more particularly to a fluorescent display device in the form of a tube which facilitates mounting thereof on a circuit board (printed circuit board) on which various circuit parts are mounted and minimizes a variation in pitches of lead terminals and deformation thereof.
Now, a conventional fluorescent display device which has been widely known in the art will be described with reference to
FIGS. 7 and 8
.
The conventional fluorescent display device generally designated at reference numeral
1
, as shown in
FIG. 7
, includes an envelope
2
which is formed into a box-like shape and has an interior hermetically kept at a high vacuum. The envelope
2
includes a lid-like casing
6
constituted by an insulating substrate
3
, an insulating and light-permeable front cover
4
, and an insulating frame-like side plate
5
.
The substrate
3
of the envelope
2
, as shown in
FIG. 8
, is formed on an inner surface thereof with a wiring layer
7
of a predetermined pattern corresponding to a display pattern
8
and wirings between segments or picture cells
10
. The wiring layer
7
has an insulating layer
9
laminatedly formed thereon. The insulating layer
9
is formed by subjecting an insulating glass paste consisting of, for example, a lead borosilicate glass powder, a powder of an inorganic material such as a heat-resistant pigment or the like, and a vehicle to thick film printing. The insulating layer
9
is formed at a portion thereof corresponding to each of the segments or picture cells
10
of the display pattern
8
with a through-hole
11
, through which the wiring layer
7
is exposed. The through-hole
11
through which the wiring layer
7
is exposed is closed with a conductor layer
12
by printing of a conductive paste.
The insulating layer
9
, as shown in
FIG. 8
, is formed thereon with anode conductors
13
, each of which is discretely allocated for every segment
10
of the display pattern
8
so as to be electrically connected through each of the conductor layers
12
to the wiring layer
7
. The anode conductors
13
each are formed of, for example, a graphite paste consisting of a graphite powder and an inorganic binder or Al paste by thick film printing. The anode conductors
13
each have a phosphor layer
14
deposited thereon. The phosphor layers
14
each are made of a phosphor paste consisting of a phosphor powder and a vehicle by printing and formed into the same configuration as each of the picture cells or segments
10
of the display pattern
8
. This results in the anode
15
being provided for every segment
10
of the display pattern
8
. Arranged above each of the anodes
15
of the display pattern
8
is a grid or control electrode
16
. The fluorescent display device
1
also includes filamentary cathodes
17
arranged above the grids
16
.
The conventional fluorescent display device
1
constructed as described above is operated in such a manner that the filamentary cathodes
17
are driven for heating, resulting in thermions being emitted from the filamentary cathodes
17
. Then, the thus-generated thermions are accelerated by the grids
16
having a positive voltage applied thereto while being controlled thereby, to thereby be impinged on the phosphor layer
14
of each of the anodes
15
positioned below the grids, resulting in the phosphor layer
14
being excited for luminescence, leading to desired display.
The fluorescent display device is mounted on a circuit board having various circuit parts mounted thereon. Such mounting, as shown in
FIG. 9
, is carried out by downwardly bending each of lead terminals
21
of various electrodes (anodes
15
, grids
16
, cathodes
17
and GNDs) led out of the envelope
2
in a horizontal direction along the substrate
3
by an angle of 90 degrees, inserting each of the lead terminals
21
in each of the through-holes
23
of the circuit board
22
electrically connected to the wiring pattern on a circuit board
22
, and then fixing each lead terminal
21
in each through-hole
23
of the circuit board
22
by soldering in a reflow oven.
However, the above-described soldering in the reflow oven causes the fluorescent display device
1
to be introduced into the reflow oven being heated while being controlled, so that the fluorescent display device
1
is increased in temperature. This causes gas adhering to the cathodes
17
and phosphor layers
14
in the envelope
2
to be driven out thereof, resulting in a reduction vacuum in the envelope
2
, leading to a deterioration in luminance of the fluorescent display device. In order to eliminate the problems, it is required to carry out an aging step of continuously driving the fluorescent display device
1
again. Mounting of the circuit parts on the circuit board
22
is carried out by surface mounting without introducing the circuit parts into the reflow oven, so that it is required to carry out soldering of the fluorescent display device
1
to the circuit board
22
in a step separate from that of mounting the circuit parts on the circuit board
22
. This causes an increase in assembling cost of the fluorescent display device and a deterioration in operating efficiency.
Also, a fluorescent display device recently developed is generally increased in the number of lead terminals depending on desired display and reduced in pitches between the lead terminals in order to carry out complicated graphic display. This causes soldering in the reflow oven to be highly hard to form the lead terminal-inserting through-holes via the circuit board.
In view of the above, techniques of surface-mounting the fluorescent display device on the circuit board which are carried out without requiring formation of the through-hole via the circuit board are proposed as substitution for the above-described soldering in the reflow oven. The techniques proposed are practiced in such a manner as shown in FIG.
10
. More particularly, lead terminals
21
of various electrodes including anodes
15
, grids
16
, cathodes
17
and GNDs each are led out of an envelope
2
of a fluorescent display device in a manner to horizontally extend along a substrate
3
and then bent at an intermediate portion thereof into an inverted L shape. Then, the lead terminals
21
each are formed at a distal end thereof with a substantially horizontal portion, which is provided thereon with a preliminary solder
24
. Thereafter, the preliminary solders
24
each are arranged so as to face each of solder pads
25
positioned on connections on a wiring pattern of a circuit board
22
. Then, soldering is carried out by means of a hot bar or manually between the solders
24
and the solder pads
25
, resulting in the fluorescent display device
1
being mounted on the circuit board.
However, in the case that the fluorescent display device is so constructed that a lot of such lead terminals
21
are arranged and pitches between the lead terminals
21
are reduced, soldering by means of the hot bar causes short-circuiting between the lead terminals
21
adjacent to each other when the amount of solder used is increased. Also, a reduction in amount of solder leads to a failure in electrical connection between the connections on the wiring pattern and the lead terminals.
Also, manual soldering requires to solder the lead terminals
21
of the fluorescent display device to the circuit board one by one, resulting the soldering being not only time-consuming but highly troublesome.
In the prior art, when the fluorescent display device is to be shipped to a customer while being kept mounted on the circuit board, it is generally carried out to mount the circuit parts on the circuit board and then solder the lead terminals of the fluorescent display device to the circuit board in a last step. However, this causes mounting of the circuit boards
Heynen Klaus
Shinya Soichi
Suzuki Toshio
Tojo Kazuhiko
Futaba Corporation
Leurig Sharlene
Patel Nimeshkumar D.
LandOfFree
Fluorescent display device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluorescent display device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluorescent display device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3014583