Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
2000-10-26
2003-01-28
Nguyen, Vinh P. (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S758010, C324S761010
Reexamination Certificate
active
06512363
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an inspection method and inspection apparatus wherein a board that has been conveyed to the inspection position is photographed with a line sensor camera and inspected.
BACKGROUND OF THE INVENTION
When electronic components are mounted to printed circuit boards, various kinds of inspections are performed. These include inspections of print conditions after solder printing, inspections of mounting conditions of mounted components, and inspections of conditions of components and solder after the solder has hardened.
One method for performing such inspections is the method of inspecting by using a line sensor camera to photograph boards that have been conveyed to an inspection position.
A conventional inspection apparatus is shown in
FIGS. 7
to
10
.
As shown in
FIGS. 7 and 8
, the inspection apparatus is configured such that an inspection is made by causing a line sensor camera
3
to photograph a printed circuit board
1
conveyed to an inspection position, by scanning that printed circuit board
1
in a direction (direction indicated by arrow C) along the direction of board conveyance.
More specifically, the printed circuit board
1
in the inspection position is held by a pair of rails
2
being constant in breadth and constituting a pair of holding members. The line sensor camera
3
is movable in the direction of arrow C by a movement shaft
8
, and photographs the surface of the printed circuit board
1
through a reflecting mirror
10
.
In an inspection apparatus configured in this way, the movement shaft
8
is sometimes caused to expand and contract or the printed circuit board
1
to expand and contract due to factors such as heat.
For this reason, in the printed circuit board
1
being inspected, as shown in
FIG. 9
, a first correction mark
6
e
and a second correction mark
6
f
are provided on the side where the line sensor camera
3
starts reading and on the side where it ends reading, respectively, such that these correction marks
6
e
and
6
f
are positioned on a diagonal line passing through the board
1
. Using the correction marks in these two places, any discrepancy in the movement shaft
8
or printed circuit board
1
described above is corrected.
In more specific terms, when the printed circuit board
1
is photographed by the line sensor camera
3
, the correction marks
6
e
and
6
f
are first recognized with the line sensor camera
3
and center positions therefor are found respectively. Coordinate positions for the correction marks
6
e
and
6
f
thus obtained by the recognition with the line sensor camera
3
are defined as (x
e
, y
e
) and (x
f
, y
f
) respectively.
Here, coordinate positions for the first and second correction marks
6
e
and
6
f
have been pre-taught as (X
e
, Y
e
) and (X
f
, Y
f
), respectively, and distances between the first correction mark
6
e
and the second correction mark
6
f
in the X axis direction and the Y axis direction have been known, so that based on the distances and the recognition with the line sensor camera, the ratios of the distances between the first and second correction marks
6
e
and
6
f
in the X axis direction and the Y axis direction are found, respectively, as &ggr;
x
and &ggr;
y
, that may be expressed as;
&ggr;
x
=|x
e
−x
f
|/|X
e
−X
f
|and &ggr;
y
=|y
e
−y
f
|/|Y
e
−Y
f
|.
When the ratios in the X axis direction and the Y axis direction are both valued 1, it can be judged that there is no expansion or contraction in the movement shaft
8
or the printed circuit board
1
. When the ratio is other than
1
, however, it is judged that there is expansion or contraction in the movement shaft
8
and/or printed circuit board
1
, whereupon adjustments are made to respective coordinate positions in an image so that the recognized positions of the correction marks become the taught values, and the position of the printed circuit board
1
is also adjusted.
More specifically, assuming that the expansion and contraction are uniform, respective X-coordinate and Y-coordinate values in the recognized image are divided by &ggr;
x
and &ggr;
y
to produce corrected values so that a corrected image can be presented.
However, as will be explained below, there is a problem with the inspection method described in the foregoing in that it cannot be used when the printed circuit board
1
is so large in the breadth direction of the rails
2
that it cannot be thoroughly scanned by the line censor camera.
When the printed circuit board
1
is too large as mentioned above, one possibility is to provide the printed circuit board
1
with a screw shaft that is movable in the breadth direction of the rails
2
. By rotating the screw shaft, the printed circuit board
1
is moved in the breadth direction of the rails
2
a
while photographs are taken with the line sensor camera
3
a plural number of times.
When the printed circuit board
1
is photographed two times with the line sensor camera
3
, for example, first, as shown in FIG.
10
(
a
-
1
), the line sensor camera
3
is moved from a first scan start position
5
c
in the direction indicated by arrow E
1
, whereupon a first scan area
7
a
wherein a first inspection point
11
a
is provided is photographed.
Next, as shown in FIG.
10
(
a
-
2
), the printed circuit board
1
is moved in the direction indicated by arrow E
2
by the screw shaft, and a second scan area
7
b
wherein a second inspection point
11
b
is provided is photographed from a second scan start position
5
d.
The printed circuit board
1
, after photographing is concluded, is moved in the direction indicated by arrow F by the screw shaft, as shown in FIG.
10
(
a
-
3
), and returned to the original position.
When there is contained a process step for moving the printed circuit board
1
by a screw shaft in the breadth direction of the rails
2
, as described above, there is a problem in that when printed circuit boards
1
are conveyed successively and each printed circuit board undergoes inspection, even if the position of the printed circuit board
1
is altered by rotating the screw shaft for the same amount each time, the resulting amount of movement will not be constant in actual practice because of the influence of the thermal expansion of the screw shaft.
FIGS.
10
(
b
-
1
) to
10
(
b
-
3
) show the inspection method for a case where there has been thermal expansion in the screw shaft.
FIG.
10
(
b
-
1
), where photographing is done in the same manner as shown in FIG.
10
(
a
-
1
), shows a reference position for moving the printed circuit board
1
with the screw shaft, so that the first scan start position
5
c
and the first scan start position
5
e
are at the same position, and there is no discrepancy between the first scan area
7
a
and the first scan area
7
c
photographed by the line sensor camera
3
.
However, when thermal expansion occurs in the screw shaft, the moved printed circuit board
1
, as shown in FIG.
10
(
b
-
2
), even though the screw shaft is rotated for the same amount as shown in FIG.
10
(
a
-
2
), exhibits a discrepancy between the second scan start position
5
f
and the second scan start position
5
d
in the breadth direction of the rails
2
.
As a result, the distance from the second scan start position
5
d
to the second correction mark
6
f
as shown in FIG.
10
(
a
-
2
) differs from the distance from the second scan start position
5
f
to the second correction mark
6
h
as shown in FIG.
10
(
b
-
2
). Likewise, the distance from the second scan start position
5
d
to the second inspection point
11
b
as shown in FIG.
10
(
a
-
2
) differs from the distance from the second scan start position
5
f
to the second inspection point lid as shown in FIG.
10
(
b
-
2
). Accordingly, overall dislocation has occurred between the image including the first scan area
7
c
and the second scan area
7
d
as shown in FIG.
10
(
b
-
3
), and the image including the first scan area
7
s
and the second scan
Kajiyama Masayuki
Tanaka Suehiro
Tsujikawa Toshihiko
Yamauchi Satoshi
Matsushita Electric - Industrial Co., Ltd.
Nguyen Vinh P.
Parkhurst & Wendel L.L.P.
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