JP2757490B2 - Screen mask pattern matching method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a pattern matching method for a screen mask, and more particularly, to a method for optimally matching a pattern hole formed in a screen mask with a land formed on a substrate. About the method.

(Prior art) For electronic components such as IC chips and capacitor chips, paste solder is applied by a screen printing machine onto lands (electrodes) formed on a substrate, and then the electrodes of the electronic components are placed on the paste solder. Landed on and glued. In this case, if the paste solder is displaced from the land, the electronic component cannot be bonded properly, so the paste solder must be accurately applied to a predetermined position of the land.

FIG. 6A shows an ideal application position of the paste solder 100.
Smaller than one of the lands 101 (right side in this example)
And applied. Therefore, in this state, their centroids G1 and G2 do not match.

By the way, pattern matching is generally performed by detecting the centroids of two persons to be matched with each other by a camera, and matching the centroids with the centroids. However, when such a general pattern matching method is used, as shown in FIG. 6B, the paste solder 100 is applied to the center of the land 101, and from the ideal position shown in FIG. It will shift considerably.

FIG. 7 shows a conventional means for solving the above-mentioned problem. In a screen mask 102, apart from a pattern hole 103 for applying paste solder, a diagonal line far from a printing area 105 is provided. Are formed with two small holes 104 for pattern matching. This camera detects the position of the small holes 104, 104 by a camera, and
The paste solder is applied so that 04 and 104 match the matching marks formed on the substrate (not shown).

(Problems to be Solved by the Invention) If the small holes 104, 104 are formed in a process different from that of the pattern holes 103, the relative positional accuracy of the two holes 103, 104 is deviated.
They must be formed together in the same step. Therefore, this conventional means can be applied when a new screen mask is formed, but cannot be applied to an existing screen mask in which pattern holes are already formed.

Therefore, the present invention provides a screen mask and a substrate without forming a special matching means such as the small holes.
An object of the present invention is to provide a method capable of performing ideal pattern matching as shown in FIG.

(Means for Solving the Problems) In the present invention, as shown in FIG. 6 (a), the centroids G1 and G2 of the individual lands and the paste solder do not match,
The midpoint of the two lands and the midpoint of the two cream solders corresponding to the lands of the two lands are focused on matching. For this purpose, the present invention
Two lands for bonding leads on two sides of an electronic component are selected from two opposing land rows of a land portion of a substrate formed by arranging a plurality of lands, and these two lands are separated. The camera detects the midpoint of the connecting line and detects the midpoint of the line connecting the two pattern holes corresponding to the two lands formed on the screen mask, and matches the two midpoints. For this purpose, the XY table is driven to move the substrate relative to the screen mask. Also preferably,
As the two lands, two lands on the diagonal of the two land portions facing each other are selected.

(Operation) In the above configuration, the midpoint of the two lands and the midpoint of the two pattern holes are detected, and the two midpoints are matched to apply the paste solder to an ideal position on the land. I do.

Example Next, an example of the present invention will be described with reference to the drawings.

4 and 5 are a perspective view and a front view, respectively, of a screen printing machine. This apparatus comprises an XYZ table device 1, a board observation device 2 provided above one side thereof, and an XYZ table device 1 provided above the other side. And a screen device 3 provided in the device.

The XYZ table device 1 has an X table on a base plate 4.
5, a Y-table 6, a rotary table 7, and a Z-table 8 are mounted in stages. The X table 5 is mounted on an X-direction rail 11 provided on the base plate 4 via a slider 12, and reciprocates in the X direction by a motor MX and a feed screw 13.

The Y table 6 is mounted via a slider 16 on a Y-direction rail 15 provided on the X table 5, and reciprocates in the Y direction by a motor MY and a feed screw 17. The rotary table 7 is rotatably mounted on the Y table 6 via a rotary shaft 18 at a corner thereof. A motor Mθ and a feed screw 19 are provided on the Y table 6. 20 is a nut screwed on the feed screw 19, 21 is the rotary table 7
The roller is attached to the distal end of the arm 22 extending from the nut and fitted to the nut portion 20. Therefore, the motor Mθ
When the nut is driven and the nut portion 20 slides along the feed screw 19, the turntable 7 rotates horizontally about the shaft portion 18.

The Z table 8 is attached to an actuator MZ composed of a cylinder provided at the center of the rotary table 7. 23 is a guide rod part. Reference numeral 24 denotes a substrate positioned on the Z table 8, which is a reference point for observing positional deviation.
J1 and K1 are provided. Reference numeral 25 denotes a mask observation camera, which is integrally mounted on a side of the Y table 6.

The board observing apparatus 2 is configured by attaching a board observing camera 31 to a column 30, and observes reference points J1 and K1 of the board 24 that has moved below the camera 31 from above.

The screen device 3 includes a mask supported by the frame 32.
33, a squeegee 34 driven by a driving device (not shown) to slide on the mask 33, and the mask 33 is provided with reference points J2, K2.

FIG. 1A is a plan view of the substrate 24, on which a large number of lands A1 to AN are formed. Each land A1-AN
Is formed by juxtaposing a plurality of lands (electrodes) a to which a large number of leads of an electronic component are grounded. The land a is precisely formed by etching using a conductive material such as a copper foil. FIG. 1B is an enlarged view of the land portion A1. Land part A1 has four land rows A11, A12, A1
It consists of 3, A14. Each land row A11 to A14 is composed of four elongated lands a. Each land row
A11 to A14 are formed at positions corresponding to the four sides of the electronic component to be bonded thereto. As will be described later, two diagonal lands a are selected as observation targets from four lands a of two land rows (for example, the land row A11 and the land row A13) facing each other. In FIG. 1 (b), two lands a to be selected are hatched.

FIG. 2A is a plan view of the screen mask 33, in which a large number of pattern holes B1 to BN are formed. The pattern holes B1 to BN correspond to the lands A1 to AN, respectively, and the pattern holes B1 to BN have pattern holes b corresponding to the lands a. The pattern holes b are smaller than the lands a, and the pattern holes b are matched with the lands a, and the squeegee 34 is slid to apply paste solder on the lands a. FIG. 2B is an enlarged view of the pattern hole B1. The pattern hole portion B1 has four pattern hole rows B11, B12, B13,
Consists of B14. Each pattern hole array B11 to B14 is composed of four elongated pattern holes b. The pattern hole rows B11 to B14 correspond to the land rows A11 to A14, respectively. Then, as described later, a pattern hole b corresponding to the two lands a with hatching is selected as an observation target.

This screen printing machine has the above configuration,
Next, the operation will be described.

The motor MX is driven to move the camera 25 below the mask 33 (see the broken line in FIG. 5), and then the motors MX and MY are driven to move the camera 25 in the XY direction.
Observe 33 reference points J2 and K2. Next, the motor MX is driven to move the board 24 below the camera 31, and then the motors MX and MY are driven to move the board 24 in the X and Y directions, so that the two reference points J1 and Observe K1 (see chain line in FIG. 5). Next, the substrate 2 with respect to the reference points J2 and K2 of the mask 33
The position shift of the reference points J1 and K1 in the XYθ direction is calculated. Such calculation and control of each motor are performed by a control device such as a computer.

Next, in order to match the reference points J1 and K1 of the substrate 24 with the reference points J2 and K2 of the
4 is moved directly below the mask 33. Next, actuator M
By driving Z, the substrate 24 is raised and pressed against the lower surface of the mask 33, and then the squeegee 34 is slid to print cream solder on the circuit pattern of the substrate 24 (see the chain line in FIG. 5). When printing is completed, the substrate 24 returns to its original position and is conveyed to the next step by a conveyor (not shown).

Next, a pattern matching method will be described with reference to FIG.

As a mark for matching, for example, land A
1, AN and the pattern holes B1, BN are selected. This selection is optional, but in order to increase the matching accuracy, particularly in the θ direction (rotational direction), as in this embodiment, the land portions A1 that are diagonal and that are far apart from each other are used. , A
It is desirable to select N and the pattern holes B1 and BN.

Now, by operating the XY tables 5 and 6 and moving the substrate 24 in the XY directions, the two lands a11.a19, a21, and a27 in the selected lands A1 and AN are selected by the camera 31. Observe. The selection of the land is arbitrary, but it is desirable to select the lands a11, a19, a21, a27 that are diagonal and separated from each other for the same reason as described above. Then detect the respective centroids G11, G19, G21, G27,
Further, the midpoints Q1, N2 of the lines N1, N2 connecting the centroids G11, G19 and G21, G27.
Find Q2.

Similarly, while moving the camera 25 in the X and Y directions, the lands a11, a19, and a2
Observe pattern holes b11, b19, b21, b27 corresponding to 1, a27,
The respective centroids g11, g19, g21, and g27 and the midpoints q1 and q2 of the lines n1 and n2 connecting these centroids are detected.

As described with reference to FIG. 6 (b), when the centroid G of the land a matches the centroid g of the pattern hole b,
Paste solder cannot be printed at the ideal position shown in FIG. 6 (a). However, as is clear from FIG.
When the midpoints Q1 and Q2 coincide with the midpoints q1 and q2, the pattern holes b can be ideally matched with the lands a, and paste solder can be applied to ideal positions shown in FIG. 6A. . The present invention has been made in view of the fact that the land a and the pattern hole b have such unique matching characteristics.

Then, in order to make each midpoint Q1, Q2 coincide with each midpoint q1, q2, the XY tables 5, 6 are operated to move the substrate 24 directly below the screen mask 33. Can be applied. In FIG. 3, M is a line connecting the midpoints Q1, q1 and Q2, q2,
From this, the displacement in the θ direction is detected. In the above embodiment, the substrate 24 is moved in the XY direction, and the matching of the midpoints Q1 to q2 is performed. However, the screen mask 33, or both 24, 33, may be moved in the XY direction to perform matching. Good.

By the way, if paste solder is applied to a predetermined number of substrates 24 using the screen mask 33, the screen mask 33 is removed from the printing machine and stored in a storage separately, and a new screen mask is printed. The printer is set on the machine and printing is performed on another type of substrate. Then, at a later date, when the same printing is to be performed again on the same kind of substrate 24 using the screen mask 33, the screen mask 33 is taken out of the storage and set in the printing machine. However, in this case, another screen mask may be erroneously set on the printing press, or the front, rear, left and right directions of the screen mask 1 may be erroneously set on the printing press. Defective products will be produced. Therefore, means for preventing such mistakes will be described next.

As described above, the land a1 of the substrate 24 observed by the camera 31
The coordinates of the centroids G11, G19, G21, G27 of 1, a19, a21, a27 and the camera 25
Centroids g11, g19, g of pattern holes b11, b19, b21, b27 observed in
The coordinates of 21, g27 are registered in the computer as unique feature points of the substrate 24 and the screen mask 33, respectively. That is, lands a11 to a11 having the centroids G11 to G27.
The fact that the pattern hole b having the centroids g11 to g27 is present in the computer is stored in the computer in the screen mask used for the substrate 24 in which 27 is present. By doing so, if another screen mask is set by mistake or the direction of the screen mask 33 is set by mistake, the centroids g11 to g27 corresponding to the centroids G11 to G27 are not observed. Thus, the alarm can be issued to the operator by issuing an alarm sound or an alarm light.

The feature points are not limited to the centroids described above, but may be anything that can be observed by a camera and is unique to the substrate or the screen mask. Also, the number of feature points is arbitrary, but if it is increased to some extent, erroneous determination can be more reliably prevented.

(Effect of the Invention) As described above, according to the present invention, the pattern holes of the screen mask can be correctly matched with the lands of the substrate, and the paste solder can be applied to the ideal positions.
Further, by selecting two lands on a diagonal line of two land rows facing each other as the two lands, the matching accuracy can be further improved. In particular, the present method has an advantage that it does not require any special modification or the like to a screen mask or a substrate and can be applied to an existing screen mask as it is.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is a plan view of a screen mask, FIG. 2 is a plan view of a substrate, FIG. 3 is a plan view of a main part during observation, and FIG. FIG. 5 is a front view of the printing press, FIG. 5 is a front view thereof, FIGS. 6 (a) and 6 (b) are plan views of lands and paste solder, and FIG. 7 is a plan view of a conventional screen mask. 33 ... Screen mask 25,31 ... Camera 24 ... Substrate 5,5 ... XY table a ... Land b ... Pattern hole Q1, Q2, q1, q2 ... Middle point

Claims (2)

(57) [Claims] 1. Two lands to which leads on two sides of an electronic component are bonded are selected from two opposing lands in a land portion of a substrate formed by arranging a plurality of lands in parallel. The midpoint of the line connecting the two lands is detected by the camera, and the two points formed on the screen mask are detected.
The midpoint of the line connecting the two pattern holes corresponding to the two lands is detected by the camera, and the XY table is driven so that the two midpoints match, and the substrate is moved relative to the screen mask. A pattern matching method for a screen mask, wherein the pattern is moved. 2. A pattern matching method for a screen mask according to claim 1, wherein two lands on a diagonal line of said two land rows facing each other are selected as said two lands.