Coating processes – Nonuniform coating
Reexamination Certificate
2000-09-28
2003-05-13
Talbot, Brian K. (Department: 1762)
Coating processes
Nonuniform coating
C118S410000, C118S663000, C118S684000, C118S688000, C118S712000
Reexamination Certificate
active
06562406
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and a method for applying a viscous fluid, e.g., used in applying an adhesive onto a circuit board to bond electronic components to the circuit board.
BACKGROUND ART
Such an adhesive applying apparatus
30
as shown in
FIG. 26
has conventionally been employed to apply an adhesive onto a circuit board to bond electronic components to the circuit board. The adhesive applying apparatus
30
includes an adhesive application head unit
15
which will be described later, a Y-table
20
loading the circuit board thereon to which the adhesive is to be applied and moving the circuit board in a Y-direction, an X-robot unit
21
moving the adhesive application head unit
15
in an X-direction orthogonal to the Y-direction, and a controller
22
controlling operations of at least the adhesive application head unit
15
, Y-table
20
and X-robot unit
21
.
As indicated in
FIGS. 27 and 28
, the adhesive application head unit
15
has three sets of application mechanism portions for extruding and applying the adhesive with compressed air. Each application mechanism portion comprises a syringe
2
in which the adhesive
13
is stored and from which a predetermined amount of the adhesive
13
is discharged from a nozzle
1
through the injection of compressed air, a compressed air feed system
9
for feeding the compressed air to the syringe
2
, and a lift mechanism
3
for moving the syringe
2
up and down in a thicknesswise direction of the circuit board so as to apply the adhesive
13
discharged to a leading end of the nozzle
1
onto the circuit board. The compressed air feed system
9
is provided with a piping
10
connected to the syringe
2
for feeding the compressed air into the syringe
2
, and a valve
11
for controlling the supply of the compressed air to the syringe
2
. The lift mechanism
3
is provided with a lift shaft
4
coupled to the syringe
2
and allowing the compressed air to pass through the lift shaft
4
, a lever S rotating about a supporting shaft
14
and having one end
5
a coupled to the lift shaft
4
and the other end brought into contact with a driving shaft of a nozzle selection cylinder
7
, a cam follower
6
set to the lever
5
in a state to be rotatable, and a cam
8
engaged with the cam follower
6
. In the lift mechanism
3
, when the cam
8
rotates, at the lever
5
where the cam follower
6
and cam
8
are brought into contact with each other by the nozzle selection cylinder
7
, the one end
5
a
of the lever
5
rotates about the supporting shaft
14
, thereby moving the lift shaft
4
in the above thicknesswise direction.
The conventional adhesive applying apparatus
30
constituted as above operates in the following manner.
Before the adhesive
13
is started to be applied to the circuit board, the application head unit
15
carries out a test application of the adhesive
13
on a test tape
16
as shown in FIG.
27
. More specifically, the valve
11
of the compressed air feed system
9
operates for a predetermined time, thereby pressing a float
12
in the syringe
2
down by the supplied compressed air, and consequently the adhesive
13
stored in the syringe
2
is discharged by a predetermined amount from a leading end la of the nozzle
1
. The nozzle selection cylinder
7
then acts thereby bringing the cam follower
6
and cam
8
of the lever
5
into contact with each other. As a result of the rotation of the cam
8
, the one end
5
a
of the lever
5
rotates as described above, lowering the syringe
2
in the thicknesswise direction via the lift shaft
4
. The adhesive
13
discharged to the leading end
1
a
of the nozzle
1
is hence applied onto the test tape
16
. After the test application, the cam
8
rotates and the syringe
2
moves up to an original position.
An application state of the adhesive
13
at the test application is picked up by a recognition camera
19
. The controller
22
measures an area of the test application on the basis of image information output from the recognition camera
19
, thereby judging whether or not a preliminarily set target-application-diameter is satisfied. The above test application and image pick-up operation are conducted until a diameter of the test application is kept within an allowance of the target-application-diameter. The adhesive
13
is started to be applied to the circuit board after the diameter of the test application is within the allowance of the target-application-diameter.
In the conventional adhesive applying apparatus
30
as above, as the amount of the compressed air supplied to the syringe
2
increases, the adhesive
13
in the syringe
2
decreases. The application diameter becomes smaller in accordance with a decrease of the adhesive
13
in the syringe
2
if the adhesive
13
is extruded with the same amount of air and the same pressure of the air at all times. so, in order to obtain a constant application diameter irrespective of the amount of the adhesive
13
remaining in the syringe
2
, it is not enough to simply control the pressure of the compressed air and the amount of the air supplied to the syringe
2
. The pressure of the compressed air and the amount of the air are required to be controlled also in accordance with a temperature of the adhesive
13
and a state of the test tape
16
. Furthermore, these four conditions, namely, the pressure of the compressed air, the amount of the air, the temperature of the adhesive and the state of the tape should be selected for each kind of the adhesive and for each nozzle to be used in the conventional apparatus
30
. Therefore, not everyone can handle the conventional adhesive applying apparatus
30
. The conventional apparatus consumes much time in discharging the adhesive, and exhibits a loss of a cycle time in correcting the application diameter.
An apparatus disclosed in U.S. Pat. No. 5,564,606 proposes a solution to the above problem. According to the disclosed apparatus as shown in
FIG. 29
, a screw
33
is fitted to a sleeve
34
in a state where the screw can be rotated about an axis thereof by a motor
32
and, a nozzle
31
is disposed coaxially with the screw
33
. A viscous material is supplied to the sleeve
34
through a path
35
, sent to the nozzle
31
as a result of the rotation of the screw
33
about the axis, and discharged from a leading end of the nozzle
31
. A constituting portion including the nozzle
31
is moved in an axial direction of the nozzle
31
, whereby the viscous material discharged from the leading end of the nozzle
31
is applied to a member.
Since the above apparatus is adapted to discharge the viscous material through the rotation of the screw
33
, the aforementioned problem caused by the amount of the remaining viscous material is eliminated.
As indicated by a chain double-dashed line,
FIG. 29
also proposes another type of the apparatus, wherein a nozzle stopper
36
is erected at a portion of the sleeve
34
to form a predetermined gap between the leading end of the nozzle
31
and a face of the circuit board, for instance, when the viscous material is applied to the circuit board. The nozzle stopper is set adjacent to the nozzle
31
, having a slightly larger length than a total length of the nozzle
31
, with a leading end of the nozzle stopper
36
maintained in contact with the face of the circuit board.
However, an arrangement position of the nozzle stopper
36
relative to the nozzle
31
cannot be changed in the above prior art of the screw type equipped with the nozzle stopper
36
. when the nozzle
31
moves in the axial direction to apply the viscous material, the leading end of the nozzle stopper
36
comes into contact with a wiring pattern, etc. formed on the face of the circuit board, and possibly damages the wiring pattern, etc.
The present invention is devised to solve the above-described problems, and has for its object to provide an apparatus and a method for applying a viscous fluid, which enables anyone to handle the apparatus with ease while obtaining a constant applicatio
Chikahisa Naoichi
Iizuka Akira
Inaba Yuzuru
Miyake Hiroyuki
Sasaki Takashi
Talbot Brian K.
Wenderoth , Lind & Ponack, L.L.P.
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