JPH0135516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an automatic masking device for a printed circuit board, which is applied when components are mounted on a printed circuit board using a solder dip.

BACKGROUND ART Nowadays, it is common for components to be mounted on printed circuit boards automatically using solder dips. However, many of the components mounted on the board must be individually soldered and fixed without using solder dips. Therefore, it is necessary to mask the patterned surface of the printed circuit board to which such components are soldered prior to the solder dip to prevent the solder from adhering to the patterned surface of the printed circuit board to which such components are soldered. Conventionally, this masking has been performed by pasting a masking tape such as paper adhesive tape at a predetermined position on the pattern surface. However, according to this method, a separate process is required to remove the tape pasted after the solder dip, and furthermore, the pasting and removal of the tape is done entirely by hand. Since the parts are generally scattered not only in one place but in multiple places, the work is complicated and extremely difficult, as well as being inefficient and lacking in workability. Furthermore, after the tape is removed, the adhesive remains on the patterned surface of the board, and this cannot be completely removed even in the subsequent board cleaning process, so the solder "glue" may be removed during subsequent soldering. In some cases, the solderability deteriorated, adversely affecting solderability and reducing soldering reliability.

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to enable masking to be performed automatically, easily, efficiently, and reliably on masking locations on a printed circuit board that are scattered at multiple locations. That is.

The purpose of this is to support a metal screen in the middle of the printed circuit board transfer line so that it can rotate up and down with respect to the board installation surface, and to use the squeegee surface provided on the top surface of the metal screen to detect masking points scattered at multiple locations on the patterned surface of the printed circuit board. A plurality of corresponding openings are formed so that the masking resin can be supplied to the masking area through these openings, and a squeegee is provided on the top surface of the metal screen to move the squeegee surface, and the masking resin and organic This can be achieved by providing a means for dispensing a fixed amount of the solvent, and configuring the masking resin and the organic solvent to be automatically dropped at predetermined locations on the squeegee surface of the metal screen.

According to the present invention, when the printed circuit board is transferred to a predetermined position in the middle of the printed circuit board transfer line, the metal screen is rotated and lowered onto the board surface.
The masking resin and organic solvent dropped onto the squeegee surface flow from one side to the other by the squeegee movement. During the flow process, the masking resin and organic solvent are stirred and supplied to the corresponding masking location on the substrate pattern surface through the opening provided on the squeegee surface. Therefore, the masking points scattered at multiple locations on the pattern surface of the board can be masked using a mixture of resin and solvent automatically and reliably during the board transfer process, and moreover, efficiently with one stroke of the squeegee. It becomes easy to do. As a result, the masking process can be fully automated and labor-saving.

Furthermore, since the mixture used for masking contains an organic solvent, it can be easily removed from the substrate in a subsequent cleaning step.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a transfer line consisting of a conveyor for transferring the printed circuit board A. The printed circuit board A is placed on this transfer line 10, and is automatically moved from the starting end to the ending end at a constant timing. It is starting to be sent. In the middle of the transfer line 10, there is an automatic reversing mechanism that turns the printed circuit board A upside down, an automatic insertion machine that inserts and temporarily attaches components onto the substrate A, an automatic soldering tank that solders and fixes the inserted and temporarily attached components with a solder dip, or A cooling fan and the like are incorporated, and a cleaning device for automatically cleaning the solder-dipped printed circuit board A is disposed on the rear end side. Then, the printed circuit board A is installed on the transfer line 10,
The solder dips are fed into each part in sequence, and components are thereby mounted on the mounting surface using solder dips.

In the embodiment, for the sake of simplicity, only the main parts of the transfer line are shown, and other parts are omitted.

A printing device 20 equipped with a printing plate made of a metal material such as stainless steel, that is, a metal screen is disposed at one side of the starting end of the transfer line 10, and the pattern surface of the printed circuit board A is automatically masked here. It is becoming more and more like this.

The printing device 20 consists of a main body 21 and a metal screen 22 supported on the main body 21 so as to be vertically rotatable. The metal screen 22 is formed into a substantially rectangular frame shape, and a squeegee surface 23 is provided on the upper surface thereof. A squeegee 24 is attached to the side of this squeegee surface 23 so as to be able to slide back and forth. The squeegee 24 has a brush 25 that comes into sliding contact with the squeegee surface 23.
is provided. The squeegee 24 is reciprocated by an air cylinder (not shown) built into the device. The squeegee surface 23 is provided with a plurality of openings 26 that correspond to and match the masking locations 100 provided on the pattern surface of the printed circuit board A, and the masking resin is supplied to the masking locations 100 through the openings 26. It's becoming like that. Note that the metal screen 22 is rotated up and down about a fulcrum provided on the base end side by a driving means (not shown) such as an air cylinder provided on the main body 21.

On the other hand, above the metal screen 22 there is provided a metering discharge device 27 that automatically drips masking resin onto the squeegee surface 23 . The masking resin is, for example, vinyl-based and has a resin of 5000~
A pre-adjusted viscosity of about 10,000 CPS (centipoise) is discharged onto the squeegee surface 23 in the required amount. The viscosity adjustment is performed using a viscometer built into the device. Further, above the metal screen 22, there is provided a quantitative dispensing device 28 for automatically dropping an organic solvent such as (1-1-1)-trichloroethane onto the squeegee surface 23. This organic solvent is used to maintain fluidity so that the dropped masking resin does not dry out, and is discharged and dropped in a required amount onto the squeegee surface together with the masking resin.

Note that various organic solvents can be used depending on the drying speed and workability of the masking resin. Further, several types of metal screens 22 are prepared in advance according to the types of printed circuit boards having different shapes, sizes, numbers, etc. of masking portions, and these can be used by replacing them as appropriate.

On the other hand, as shown in FIG. 2, masking portions 100...
A positioning section is defined in advance, and the masking resin is printed and masked here avoiding the solder dip portion.

The printed circuit board A is turned upside down and placed on the transfer line 10 with the pattern side facing upward, and is sent toward the end. Then, the printing device 20 is positioned relative to the metal screen 22, feeding is stopped, and the masking portions 100... are masked.

Next, the procedure will be explained.

Note that the transfer line 10 may be driven or stopped, or the metal screen 22 or squeegee 2 of the printing device 20 may be
The operations of each part such as 4 are automatically performed in a predetermined order set in advance under the control of a control device built into the device.

First, when the printed circuit board A is positioned and stopped below the metal screen 22 as shown in FIG. 3, the metal screen 22 rotates downward and the printed circuit board A
is placed in close contact with the patterned surface of the As a result, the opening 26... is the masked portion 1 of the substrate A.
00..., respectively (see Fig. 4). Next, the quantitative discharge devices 27 and 28 are activated, and a required amount of the masking resin B is automatically discharged and dropped together with the organic solvent C onto the squeegee surface 23 in the vicinity of the squeegee 24 . At this time, the squeegee 24 is located on the screen base end side on the squeegee surface 23. Thereafter, the squeegee 24 is driven, and the arrow 11 in FIG.
As shown by 0, the squeegee reciprocates on this surface a required number of times while making sliding contact with the squeegee surface 23. As a result, the masking resin B passes through the openings 26 on the squeegee surface 23 and into the masking portions 100 on the substrate pattern surface.
...is supplied in the required quantity. At that time, use squeegee 24
The reciprocating motion of the organic solvent C provides a constant stirring action to the resin B dropped onto the squeegee surface 23.
Combined with this action, resin B is prevented from drying during printing masking, and its fluidity is maintained.

Thus, as shown in FIG. 5, only the masking portions 100 on the pattern surface are printed and masked, avoiding the other solder dip portions, and a layer of masking resin B is formed. At this time, consideration is given to keeping the screen 22 in close contact with the pattern surface of the substrate so that the masking resin B does not flow into the solder dip portion.

Thereafter, the metal screen 22 is rotated upward again, and then the printed circuit board A is sent into the solder bath by driving the transfer line 10. During this process, masking resin B is completely cured so that it will not peel off during soldering. Also, in the middle of this process, the reversing mechanism is activated, and the printed circuit board A is reversed and sent with the component mounting side upward to an automatic insertion machine, where components a, b, c, etc. are subjected to solder dip. is first inserted and tacked. Next, the board A is immersed in a solder bath, and the inserted and temporarily attached parts a, b, c, . . . are fixed onto the board A (see FIG. 6). At this time, the masking part 100
The layer 200 of resin B formed on the layer 200 effectively and reliably prevents the solder D from adhering to the soldering parts 100 of parts that are not subjected to the soldering process, that is, parts to be individually soldered in subsequent steps. and its protection will be sought.

Thereafter, the printed circuit board A is cooled in a cooling process and sent to the next automatic cleaning device, where it is automatically cleaned with an organic solvent. During this cleaning process, the printed circuit board A is immersed in the solvent E, so that the layer of resin B formed on the masking portion 100 is dissolved by the solvent E and eluted from the substrate A. Therefore, the resin B is completely removed without remaining on the masking portion 100 (see FIG. 7). Therefore, individual soldering can be performed in a clean state without leaving any resin B behind.

Thereafter, as shown in FIG. 8, components A, B, etc. which are not subjected to soldering are inserted into the board A, and the leads protruding from the back surface thereof are fixed by soldering.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an automatic masking device for printed circuit boards according to the present invention, FIG. 2 is a perspective view showing the back structure of a printed circuit board to which the device is applied, and FIG. 3 is a printed circuit board using the device of the present invention. 4 is a sectional view showing the procedure of printing masking on a substrate, FIG. 5 is a sectional view showing the same procedure of masking, and FIG. 6 is a protection of the pattern surface by the masked resin layer. FIG. 7 is a cross-sectional view explaining the operation of removing masking resin during the board cleaning process. FIG. 8 is a cross-sectional view showing a state in which components that are not subjected to solder dip are mounted by individual soldering. It is. A... Printed circuit board, 22... Metal screen, 23... Squeegee surface, B... Masking resin, C... Organic solvent, 24... Squeegee, 26...
...Opening (part), 100... Masking portion (position), 27, 28... Meter discharge device.

Claims (1)

[Claims] 1. An automatic masking device placed in the middle of a transfer line in the soldering process of printed circuit boards, which supports a metal screen in the middle of the transfer line so as to be rotatable up and down with respect to the board installation surface, and is provided on the top surface of the metal screen. A plurality of openings are formed on the squeegee surface to correspond to masking points scattered at a plurality of places on the pattern surface of the printed circuit board, and masking resin can be supplied to the masking points through the openings, and the masking resin can be supplied to the masking points on the upper surface of the metal screen. A squeegee that slides on the squeegee surface is provided, a means for dispensing a fixed amount of masking resin and an organic solvent is provided above the metal screen, and both the masking resin and the organic solvent are automatically dropped at predetermined locations on the squeegee surface. An automatic masking device for printed circuit boards, which is characterized by the following features: