Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2001-01-22
2004-06-08
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C029S701000, C101S123000, C414S277000, C425S110000
Reexamination Certificate
active
06748289
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control method for improving the productivity of a screen printer for an electronics-mounting machine.
BACKGROUND ART
A screen printer for an electronics-mounting machine prints cream solder on a circuit board of an electronic part. There are several problems to be solved in order to improve the productivity of this printer. A first problem is the correction of locational offset between a printed pattern of a screen and a pattern on the circuit board. A procedure for improving the printing accuracy of a conventional screen printer is described with reference to
FIGS. 8
to
11
.
FIG. 8
is a perspective view of a screen printer. A circuit board loaded by a loader
1
is fixed to a stage section
2
. A recognition camera
3
recognizes a circuit board target mark, and a stage moving section
4
and a stage elevating section
5
position the circuit board in a screen
6
. Subsequently, a print head section
7
moves in the lateral direction for printing and the stage elevating section
5
lowers to perform a print separating operation. Then, a cleaner section
8
moves forward and backward to clean the rear surface of the screen, but at this point, the stage moving section
4
on the rear surface of the screen is located so as to contact the cleaner section
8
, so the stage moving section must retreat to the loader
1
side together with the circuit board. Once the cleaning operation is finished, the stage moving section
4
moves to an unloader
9
side, where the circuit board is unloaded to the unloader
9
.
FIG. 9
is a flowchart describing a process of a conventional general screen printer.
The operation of each step is described based on the flowchart with reference to FIG.
9
.
When the program starts at #
1
and a circuit board waiting state (upstream side) is exited at #
2
, a circuit board is loaded by the loader
1
at #
3
and fixed to the stage section
2
at #
4
, and the recognition camera
3
recognizes the circuit board target mark. At #
5
, the stage moving section
4
and the stage elevating section
5
position the circuit board at a screen target mark that has been already recognized, and at #
6
, the print head section
7
performs a printing operation. At #
7
, the stage elevating section
5
retreats the stage, and at #
8
, the cleaner section
8
cleans the rear surface of the screen. When the circuit board waiting state (downstream side) is exited at #
11
, the stage moving section
4
moves at #
12
to unload the circuit board, thereby finishing the production of the single one circuit board. Furthermore, if production is to be continued, the process returns to #
2
from #
13
to repeat the same steps. If production is to be finished, the process finishes at #
14
.
The occurrences of #
2
and #
11
depend on the production conditions of the mounting machine on the upstream and downstream sides.
FIG. 10
is a flowchart describing a procedure for improving the printing accuracy of a conventional screen printer having no inspection function. Steps #
1
to #
8
, #
11
, and #
12
are the same as in FIG.
9
and their description is omitted. When a circuit board is unloaded at #
12
, the machine is stopped at #
15
, and an operator uses a microscope to measure the results of printing at #
16
and registers the locational difference between a screen pattern and a circuit board pattern, in the machine as an offset to reflect the measured offset in the subsequent printing correction operation at #
17
. At #
18
, the operator re-operates the machine, and the subsequent steps are the same as in FIG.
9
.
FIG. 11
is a flowchart describing a procedure for improving the printing accuracy of a conventional screen printer having a function for inspecting the results of printing. Steps #
1
to #
8
are the same as in FIG.
9
. When the cleaning operation is finished at #
8
, the machine inspects the results of printing at #
9
and registers the locational difference between the screen pattern and the circuit board pattern at #
10
to reflect it in the subsequent printing correction operation. The subsequent steps are the same as in FIG.
9
.
In the process executed by the conventional screen printer having no inspection function, the machine must be halted to measure the offset between the screen pattern and the circuit board pattern, and a step is required in which the operator inspects the results of printing, thereby reducing productivity.
In addition, in the conventional screen printer having a function for inspecting the results of printing, a step for inspecting the results of printing is required that follows the cleaning operation. The inspection of the results of printing requires a large amount of time, thereby reducing the productivity of the printer.
A second problem relates to an automatic solder supply method executed by the conventional screen printer.
FIG. 12
is a perspective view of a screen printer. A used screen is collected from the inside of a printer body
10
by a stocker section
12
in an automatic screen replacing apparatus
11
. In addition, a plurality of unused screens are stored beforehand in the stocker section
12
in the automatic screen replacing apparatus
11
so that a screen corresponding to a produced circuit-board type is loaded in the printer body
10
from the automatic screen replacing apparatus
11
to switch the circuit-board type. Cream solder must be filled on an unused screen by an automatic solder supply apparatus
13
. In addition, cream solder remains filled on a used screen that has been used for production once and that has been stored in the stocker section
12
unless the screen is cleaned of the solder.
FIG. 13
is a flowchart describing an automatic solder supply method carried out after automatic screen replacement in a screen printer having the automatic screen replacing apparatus
11
and the automatic solder supply apparatus
13
. At #
1
, the program starts, and at #
2
, the production of a circuit board starts. If it is determined at #
3
that the production of a different circuit board is to be continued, the screen is replaced at #
4
. At #
8
, the machine is halted, and at #
9
, the operator determines whether cream solder must be supplied to the screen for use. If the screen for use is unused and solder must be supplied, the operator issues a command to the automatic solder supply apparatus
13
at #
10
, and an automatic solder supply operation is performed at #
6
. If the screen is a used one, cream solder remains on the screen so the automatic solder supply operation is not performed. At #
11
, the operator issues a production restart command, and the process returns to #
2
to resume production. In addition, if it is determined at #
3
that production is not to be continued, it is finished at #
7
.
In the screen printing method of the conventional electronics-mounting machine, the operator must determine whether solder must be supplied to a screen for use after automatic screen replacement, resulting in an unwanted increase in the number of required steps. Thus, the machine must be halted and re-operated regardless of the presence of the solder supply operation, thereby reducing the productivity of the printer.
A third problem relates to a screen replacing method of a screen printer. The screen replacing method carried out by the conventional screen printer is described with reference to
FIGS. 12 and 14
. A screen
14
in the printer body
10
is fixed and unfixed by a screen fixing/unfixing section
15
. In the automatic screen replacing apparatus
11
, a lifter section
16
elevates to position the stocker section
12
in order to house a screen in a desired stocker of the stocker section
12
or to supply a desired screen in the stocker section
12
to the printer body
10
. A screen transfer section
17
transfers a screen
14
from the printer body
10
to the automatic screen r
Nishikawa Noboru
Saito Hiroyoshi
Wachi Akihiko
Lee Douglas S.
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
Picard Leo
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