KR20090103429A - Screen printer and cleaning method thereof - Google Patents

Abstract

PURPOSE: A screen printer and a cleaning method thereof are provided to maximize cleaning effect and prevent the defect of SMT by wiping removed solder balls using a cleaning paper. CONSTITUTION: The screen printer(100) contains a holding unit, a stencil, a screen printer head, and a pneumatic cleaner. The holding unit clamps and supports a printed circuit board. The stencil(120) is located on the top of the printed circuit board by pouring the solder cream on the top surface of the printed circuit board. A plurality of openings are formed for the input of the solder cream. The screen printer head(130) has a squeegee blade(133) and moves horizontally and downwardly from the top of the stencil. The pneumatic cleaner(140) is installed on the screen printer head to spray the air toward the opening of the stencil.

Description

Screen printer and cleaning method thereof

TECHNICAL FIELD The present invention relates to a screen printer and a cleaning method thereof, and more particularly, to a screen printer and a cleaning method thereof, which can prevent clogging of an opening of a stencil.

Generally, the screen printer is a soldering pretreatment process of a printed circuit board for SMT (Surface mounting technology) process. It is equipment to apply lead.

When the chip is placed on the coated solder cream and passed through the reflow oven, the solder cream is melted and solidified to fix the component on the PCB, thereby completing the SMT operation.

In general, a squeegee blade method is used to apply solder cream onto a printed circuit board pattern.

The screen printer places a stencil (metal mask) having an opening that is the same as or similar to the pattern of the printed circuit board above the printed circuit board, and squeezes the solder cream applied to the stencil using a squeegee blade. When the printed circuit board is separated, solder cream is applied to the upper surface of the printed circuit board pattern.

The main function of a screen printer is to apply the appropriate amount of solder cream to the correct location on the printed circuit board before the component is mounted on the printed circuit board.

Solder cream is a gel-type chemical that consists of solder balls and fluxes as a medium used to attach components on printed circuit boards. For the electronics to work properly, the circuits and components on the printed circuit board must be connected properly.

Therefore, it is important that the solder cream connecting the printed circuit board and the component be applied at the correct position, but it is also important to apply an appropriate amount in order to perform good printing.

1 is a longitudinal sectional view showing a conventional screen printer of the squeegee blade method.

Referring to FIG. 1, in the conventional screen printer 10, the squeegee blade 14 is attached to the lower end of the screen printer head 13, and after the user applies solder cream onto the stencil 12, the screen printer head 13 is applied. By moving back and forth, the solder cream S can be applied onto the printed circuit board P. FIG.

The backup pin 11 supports the printed circuit board P at the lower part of the screen printer, and the backup pin 11 is raised so that the printed circuit board P can be brought into contact with the lower surface of the stencil 12. It is.

In addition, a plurality of openings 15 are formed in the stencil 12, and the solder cream S is filled in the openings 15 so that the amount of the solder cream S is appropriate for the correct position of the printed circuit board P. This is to be applied.

However, in the conventional screen printer, if the printing is repeated several times, the solder balls and the flux are buried at the bottom of the stencil 12 by the solder cream S leaked into the gap between the bottom of the stencil 12 and the printed circuit board P.

If screen printing is continued in this state, a bridge phenomenon in which solder creams applied on a pattern of a printed circuit board adheres to each other is generated, which causes product defects.

In order to prevent the bridge phenomenon, the debris on the lower part of the stencil was wiped off using a cleaning paper.

However, as the screen printing operation proceeds more, the solder balls stick to the wall surfaces of the openings, and even if they are wiped off with the cleaning paper, the solder balls adhered to the walls are not easily removed. If this phenomenon persists, the solder may be clogged and the solder may be insufficient in the amount of solder cream applied to the printed circuit board pattern.

In order to prevent such a defect, the stencil was conventionally cleaned using a cleaning method using a pneumatic part and a solvent. At this time, the solvent is wiped off the cleaning paper and the pneumatic part is located under the cleaning paper to blow out the flux on the lower surface of the stencil, or remove the solder ball between the openings.

However, such a conventional method also causes a problem of discharging the solder balls and the flux back to the upper surface of the stencil, thereby causing a problem when performing printing after cleaning.

The present invention has been devised to solve the above-described problems, and the present invention is to place a pneumatic cleaner on the top of the stencil, not the bottom of the printing paper, and to spray the air toward the opening of the stencil to remove the solder ball stuck in the opening and The purpose of the present invention is to provide a screen printer and a cleaning method thereof by wiping the removed solder balls with a cleaning paper, thereby maximizing the cleaning effect and preventing SMT defects.

In order to achieve the above object, the present invention provides a screen printer and a screen cleaning method.

The screen printer of the present invention comprises: a holding unit for clamping and supporting a printed circuit board; A stencil positioned on an upper portion of the printed circuit board to apply solder cream on the upper surface of the printed circuit board, and having a plurality of openings formed therein; A screen printer head having a squeegee blade and moving down and horizontally on top of the stencil; And a pneumatic cleaner installed at the screen printer head to inject air toward the opening of the stencil.

The holding unit may include a clamp supporting both side surfaces of the printed circuit board; And a support pin for supporting a lower surface of the printed circuit board. And the pneumatic cleaner is preferably located higher than the squeegee.

In addition, the cleaning method of the screen printer of the present invention comprises the steps of supporting and lifting the printed circuit board to contact the bottom of the stencil; Moving the screen printer head down and horizontally, using a squeegee blade of the screen printer head to roll the solder cream applied to the upper surface of the stencil to fill the opening of the stencil; Lowering the printed circuit board; And a pneumatic cleaner spraying air into the opening of the stencil to clean the opening.

As described above, according to the present invention, the printing performance for producing a component having a small pattern size, such as a micro component, a narrow pitch QFP (quad flat package) component, or a chip scale package (CSP), is improved.

In addition, by placing a pneumatic cleaner on the top of the stencil, not the bottom of the printing paper, and spraying air toward the opening of the stencil to remove the solder ball stuck in the opening, while cleaning the removed solder ball with a cleaning paper, cleaning By maximizing the effect of the SMT can be prevented in advance, and screen printing efficiency can be improved.

Figure 1 is a longitudinal cross-sectional view showing a conventional screen printer

2 is a perspective view showing a screen printer according to a preferred embodiment of the present invention

3 is an enlarged view of portion “A” of FIG. 2;

4 and 5 are longitudinal cross-sectional views showing screen printing of the screen printer shown in FIG.

6 is a longitudinal sectional view illustrating cleaning of the screen printer shown in FIG.

7 is a flowchart illustrating a cleaning method of a screen printer according to an exemplary embodiment of the present invention.

* Description of main parts

P: printed circuit board

S: solder cream

100: screen printer

110: holding unit

111: clamp

112: support pin

120: stencil

121: opening

130: screen printer head

131: lifting unit

132: forward and backward movement unit

133: squeegee blade

140: pneumatic cleaner

150: cleaning paper

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a perspective view showing a screen printer according to a preferred embodiment of the present invention, Figure 3 is an enlarged view "A" of Figure 2, Figures 4 and 5 shows the screen printing of the screen printer shown in FIG. 6 is a longitudinal sectional view for explaining the cleaning of the screen printer shown in FIG.

2 to 6, a screen printer 100 according to a preferred embodiment of the present invention includes a holding unit 110 for clamping and supporting a printed circuit board (P); In order to apply the solder cream S to the upper surface of the printed circuit board P, the printed circuit board P is positioned on the upper portion, and a plurality of openings 121 for inputting the solder cream S are formed. Stencils 120; A screen printer head (130) having a squeegee blade (133) and descending and moving horizontally above the stencil (120); And a pneumatic cleaner 140 installed in the screen printer head 130 to inject air toward the opening 121 of the stencil 120.

More specifically, the screen printer head 130 is installed to be moved up and down by the lifting unit 131 and the front and rear movement unit 132 to move in the front and rear directions.

The front and rear movement unit 132 is rotated by the drive motor (M) as a ball screw, the screen print head 130 is configured to be slidably moved forward and backward by the rotation of the ball screw 132. .

The holding unit 110 may include a clamp 111 supporting both sides of the printed circuit board P; And a support pin 112 supporting the lower surface of the printed circuit board P. Here, the pneumatic cleaner 140 is preferably located higher than the squeegee blade 133.

The stencil 120 is supported by a base frame (not shown) so as to be positioned on the upper surface of the printed circuit board P as a metal mask.

Referring to the operation of the screen printer according to an embodiment of the present invention configured as described above are as follows.

The clamp 111 and the support pin 112 are raised while supporting the printed circuit board P, and the printed circuit board P is brought into contact with the bottom surface of the stencil 120.

The elevating unit 131 then lowers the screen printer head 130 so that the blade 133 is in contact with the stencil 120 at an appropriate pressure.

When the driving motor (M) is driven, the ball screw 132 is rotated to move the screen printer head 130 in the front and rear directions.

At this time, the solder cream S supplied to the stencil 120 is applied to the correct position of the printed circuit board P through the opening 121 of the stencil 120.

After the screen printing is performed several times, the cleaning paper 150 is transferred to the lower portion of the stencil 120 to clean the lower surface of the stencil 120 in which the solder balls and the flux are embedded.

At the same time, the solder ball stuck in the opening 121 of the stencil is removed using the pneumatic cleaner 140 attached to the screen printer head 130.

The pneumatic cleaner 3 attached to the screen printer head 130 is located above the squeegee blade 133 in the normal printing state and does not interfere with printing, and the opening 121 of the stencil 120 only when cleaning is performed. Located on the upper surface of the pneumatic pressure to remove the solder ball stuck in the opening 121. The solder ball thus removed is wiped off by the cleaning paper 150 to complete the cleaning.

On the other hand, Figure 7 is a flow chart illustrating a cleaning method of the screen printer according to an embodiment of the present invention.

Referring to FIG. 7, a cleaning method of a screen printer according to an exemplary embodiment of the present invention includes a step of supporting and raising a printed circuit board to contact a lower portion of a stencil (S110); Moving the screen printer head down and horizontally, and rolling the solder cream applied to the upper surface of the stencil using a squeegee blade of the screen printer head to fill the opening of the stencil (S120); Lowering the printed circuit board (S130); And pneumatic cleaner spraying air into the opening of the stencil to clean the opening (S140).

In the opening cleaning step, the screen print head and the cleaning paper must be controlled so that the cleaning paper and the sprin print head can be driven simultaneously at the same speed.

Normally, in the case of manual cleaning, after cleaning the stencil using cleaning paper and solvent, the air gun is used to remove the solder balls stuck between the flux and the openings on the upper part of the stencil. By switching from manual to automatic, production automation of SMT is possible, which can double the user convenience.

As described above, in the detailed description of the present invention has been described with respect to preferred embodiments of the present invention, those skilled in the art to which the present invention pertains various modifications can be made without departing from the scope of the present invention Of course.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below, but also by the equivalents of the claims.

Claims (5)

A holding unit for clamping and supporting a printed circuit board; A stencil positioned on an upper portion of the printed circuit board to apply solder cream on the upper surface of the printed circuit board, and having a plurality of openings formed therein; A screen printer head having a squeegee blade and moving down and horizontally on top of the stencil; And And a pneumatic cleaner installed on the screen printer head to inject air toward the opening of the stencil. The method of claim 1, The holding unit Clamps supporting both sides of the printed circuit board; And And a support pin supporting a lower surface of the printed circuit board. The method of claim 1, And the pneumatic cleaner is positioned higher than the squeegee. Supporting and lifting the printed circuit board to contact the bottom of the stencil; Moving the screen printer head down and horizontally, using a squeegee blade of the screen printer head to roll the solder cream applied to the upper surface of the stencil to fill the opening of the stencil; Lowering the printed circuit board; And And a pneumatic cleaner spraying air into the openings of the stencil to clean the openings. The method of claim 4, wherein In the cleaning of the opening, the screen printer head and the cleaning paper are controlled so that the cleaning paper and the sprinkler print head can be driven simultaneously at the same speed.