JPH03187746A - Screen printing machine - Google Patents

Abstract

PURPOSE:To perform precise printing by amending shift in printing by a method wherein a correction part which amends a relative position of a screen to a printing surface by introducing shift data to a printing mechanism according to a transfer direction of a squeegee in printing is provided. CONSTITUTION:A pattern shift detection part 51 detects shift to a copper pattern on the first substrate 10 of the substrate 10 on and after the second one based on image output of a target mark 10 with video cameras 36, 37. A printing shift detection keeping part 53 detects shift in printing of cream solder to be generated principally in a transfer direction of a squeegee 45 in printing based on outputs of the video cameras 36, 37. A correction part 52 receives data of the pattern shift detection part 51 and the printing shift detection keeping part 53 each completion of setting of a substrate 10, and deduces a correction data to be added to an initial value (X,Y,Z) to an adder 54, at that time, a directional signal L/R of the squeegee 45 is bonded to an output data of the pattern shift detection part 51 by selecting the printing shift data in the direction R and the direction L.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a screen printing device, and is suitable for use in printing cream solder onto a circuit board. This is a screen printing device that corrects dynamic printing misalignment in accordance with the direction of squeegee movement and enables precise printing.

[Conventional technology]

In the technology of mounting electronic components on printed circuit boards, in order to achieve high-quality soldering, cream-like solder is applied onto the board using a printing machine, and then melted in a furnace to solder the components. Flow technology is becoming mainstream. In order to realize even higher-density parts, the development of technology to precisely print cream solder on fine copper patterns is remarkable. An example of this is the introduction of a visual recognition device.

The basic idea of this device is as follows.

In general printing machines, the printed circuit board is fixed by inserting pins into the external shape of the printed circuit board or mechanically drilled holes to print, so the actual positional relationship between the copper pattern on the board and the printed solder is There is a limit to reproducibility due to slight deviations in the copper pattern on the board and mechanical play. Therefore, in the visual recognition device, as shown in FIG. 5, target marks 11 are provided on the substrate 10 by simultaneous processing with the copper pattern 12,
The pattern deviation between the first substrate 10 in which the substrate 10 and the screen 13 are perfectly aligned and the second and subsequent substrates to be printed is defined as the deviation of the target mark 11.
Corrected by recognizing with V camera etc., cream solder 14
This makes it possible to print with high precision.

[Problem to be solved by the invention]

However, with this method alone, no consideration is given to the direction of printing, and printing misalignment caused by sagging of the printing screen still remains.For a large screen with a printing area of 300+uX300+u, printing misalignment of O91 to 0.2 mm will occur. may occur.

Particularly in the case of reciprocating printing, as shown in FIG. 6, the substrates are alternately shifted in two directions, forward and backward.

In view of this problem, it is an object of the present invention to make it possible to correct dynamic printing misalignment caused by movement of a squeegee.

[Means for Solving the Problems] The screen printing device of the present invention includes a printing mechanism that is movable to move the relative position between the screen and the printing surface at least in the direction of movement of the squeegee, and a printing position on the printing surface that is detected in advance. A deviation data storage unit holds the deviation amount corresponding to the moving direction of the squeegee, and the deviation data is derived to the printing mechanism corresponding to the moving direction of the squeegee during printing, and the deviation data is stored between the screen and the printing surface. and a correction section that corrects the relative position.

[Effect]

Print misalignment caused by sagging of the screen was unavoidable due to the clearance that must be maintained between the screen and the printing surface, but by correcting the position according to the printing direction, it is possible to completely correct misalignment. .

〔Example〕

FIG. 1 schematically shows a solder printing apparatus to which the present invention is applied.

The substrates 10 are placed one by one on the X table 20. X
The table 20 has a slide shaft 22a on the Y table 21.
, 22b so as to be slidable in the X-axis direction;
It is driven by an X-axis pulse motor 23 and feed screw 24 mounted on the table 2.1.

The Y table 21 has a sliding shaft 26 on a fixed base 25.
a and 26b so as to be slidable in the Y-axis direction,
It is driven by a Y-axis pulse motor 27 and a feed screw 26 attached to the base 25. The Y-axis element extends to the bottom of the printing section, which will be described later, and the Y-table 25 is reciprocated for each substrate IO exchange and printing process.

A slider 31 screwed to the feed screw 30 is provided inside the X table 20, and this slider 3I
is engaged with the side end portion 10a of the substrate IO. The substrate lO is pivoted by a fulcrum pin 32, and the feed screw 3
By driving the θ-axis pulse motor 33 coupled to the θ axis, the substrate 10 is rotated in the θ direction.

Two video cameras 36 and 37 are arranged above the board 10, and each takes an image of the target mark 11 on the board. The captured images are displayed on two monitors TV 38 and 39.

The printing section has four vertical slide shafts 41a to 41d.
The printer includes a frame 42 supported by a frame 42 and a printing screen 43 attached to the frame 42.

The screen 43 is provided with an opening 43a for printing cream solder onto the substrate 10. The frame body 42 is raised and lowered by a pair of linear actuators 44a, 44b, and during printing, the actuators 44a, 44b are operated so that the screen 43 is placed on the substrate IO with a predetermined clearance.

Printing is performed by supplying cream solder onto the screen 43 and moving the squeegee 45 in the Y-axis direction (or X-axis direction). In order to increase work efficiency, the squeegee 45 is alternately moved in the forward direction (+Y) and backward direction (-Y) every time the substrate IO is replaced. In other words, 2 in one round trip.
Printing is performed on two substrates 10.

FIG. 2 is a block diagram of a control section that controls the screen printing apparatus of FIG. 1.

In FIG. 2, the initial value setting unit 50 moves the first substrate 10 as a reference below the screen 43, and initializes each axis l (X, Y , θ) are set and held, respectively.

The pattern deviation detection unit 51 detects deviations of the copper patterns of the second and subsequent substrates 10 from the first substrate using the video camera 36.
Detection is performed based on the image output of the target mark 11 by the target mark 37. Pattern deviations include deviations in the setting of base+ff1lO on the X table 20 and deviations during manufacturing of the copper pattern on the board IO, and are detected for each board 10 and output to the correction data generator 52 before printing. be done.

The printing deviation detection holding unit 53 detects the printing deviation of the cream solder that occurs mainly in the moving direction of the squeegee 45 during printing based on the outputs of the video cameras 36 and 37. This shift occurs because, as shown in FIG. 3, there is a clearance between the substrate IO and the screen 43, which causes the screen 43 to sag during printing. Therefore, two types of printing deviation occur corresponding to the moving direction (reciprocating) of the squeegee 45 during printing.

These printing deviations can be solved by forming an opening in the screen 43 corresponding to the same position as the target mark 11 provided on the board IO shown in FIG. 4, and actually performing solder printing on the two test boards IO. Can be detected. That is, if the printed mark 11' is misaligned as shown in FIG. 4, the printing misalignment (Δ
X, Δy, Δθ). The printing deviation is detected in each of the forward movement R and backward movement of the squeegee 45, and is stored in the memory of the detection unit 53 as (ΔXR%Δy3, Δθ
R) (ΔXt, ΔyL%ΔθL). Although the printing deviation generally occurs only in the sliding direction of the squeegee 45 (for example, +Y and -Y), deviations in the X direction and the θ direction are also included if necessary.

Since the detected printing misalignment is a fixed value unique to the same screen 43, it is sufficient to detect and hold it for the dummy substrate in advance.

The correction unit 52 receives the data from the pattern deviation detection unit 51 and the print deviation detection holding unit 53 every time the board 10 is stamped, and outputs correction data to be added to the initial setting values (X, Y, Z) to the adder 54. . At this time, the direction signal L/R of the storage 45 is received from the device shown in FIG. In this way, the movement data sent to the pulse motors 23, 27, and 33 of each axis immediately before each printing is X+Δχ+ΔxR Y+ΔY+ΔyR θ+Δθ+Δθ8 when the squeegee 45 moves in the R direction, and when the squeegee 45 moves in the L direction, In case, X+
Δχ+ΔXt Y+ΔY+ΔyL θ+Δθ+Δθ.

becomes.

〔Effect of the invention〕

As described above, the present invention corrects dynamic printing misalignment that occurs in response to the direction of movement of the squeegee, thus making it possible to perform high-precision printing without being affected by screen sag or the like. Therefore, it is possible to accurately print cream solder for soldering electronic components with extremely small terminal pitches onto a board.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a screen printing apparatus to which the present invention is applied, Fig. 2 is a block diagram of the control system, Fig. 3 is a diagram showing the clearance between the substrate and the screen, and Fig. 4 is a diagram showing the target mark on the substrate and FIG. 5 is a diagram showing the principle of conventional printing misalignment correction, and FIG. 6 is a diagram showing printing misalignment corresponding to a difference in printing direction. In addition, in the symbols used in the drawings, 10-・--1----------1 substrate 11--・-11------
--------Target ma 1-ri 12-・--1--・
−1−−−・−・−Copper pattern 13−・−−−−−・−
-Screen 14----------11--Cream solder 50--1--Initial value setting section 51--1- ------Pattern shift detection section 52----------Correction section 5
3----------1---------Printing shift detection and holding section.

Claims (1)

[Claims] A printing mechanism that is movable to move the relative position between the screen and the printing surface at least in the direction of movement of the squeegee, and a previously detected amount of deviation of the printing position on the printing surface corresponding to the direction of movement of the squeegee. and a correction unit that derives the deviation data to the printing mechanism in accordance with the direction of movement of the squeegee during printing and corrects the relative position between the screen and the printing surface. Screen printing equipment.