JP2007125764A - Solder printing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solder printing machine which copes with making density of an LSI high, and can prevent a solder in a solder printing head from solidifying and sticking. <P>SOLUTION: The solder printing machine (1) is equipped with the printing head (2) for printing a solder paste (23) on a body (4) to be printed. The printing head is equipped with a nozzle part (24) for passing the solder paste through and delivering it toward the body to be printed, a nozzle opening (25) provided at the tip of the nozzle part and delivering the solder paste therefrom, and an agitating wire (22) stored in the nozzle part and has an elasticity. The agitating wire is characterized in that it is extended toward the body to be printed from the nozzle opening so as to be protruded therefrom. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solder printing machine, and more particularly to a solder sticking prevention method and a solder sticking prevention apparatus in a sealed type print head of a solder printer, and is suitable for being applied to solder printing on an electronic circuit board. .

  Solder printers are widely used for solder printing on electronic circuit boards. An example of such a solder printer is shown in FIG. The structure of the solder printer 1 shown in FIG. 1 is general, and the solder printer of the present invention may have a similar structure. The solder printer 1 includes a work jig 5, a screen mask 7, a sealed print head 2, a drive unit (mask up / down drive unit 8) that moves the screen mask 7 up and down, and a drive that reciprocates the print head 2 up and down. (Head up / down drive unit 11 and head reciprocation drive unit 10).

  A conventional print head 200 shown in FIG. 8 includes a nozzle portion 24 and a piston 21, and a nozzle port 25 that is an opening is provided at the tip of the nozzle portion 24, and the piston 21 is driven. Thus, the solder paste 23 filled in the print head 200 is pushed out from the nozzle opening 25. In the solder printing process, first, the screen mask 7 is overlaid on the work 4 that is the printing object. The print head 200 reciprocates while being pressed onto the screen mask 7, and the solder paste 23 inside the print head is pressurized by the piston 21 and discharged or pushed out from the nozzle port 25, passing through the mask hole 71 of the screen mask 7. The solder paste 23 is applied on the work 4. Thereafter, when the screen mask 7 is raised, a solder having a mask hole shape is formed on the land 72.

  Here, since the solder paste 23 is a substance in which granular solder and a solvent flux are mixed, only the flux 31 oozes out from the nozzle opening 25 in the vicinity of the nozzle opening 25 due to the dilatancy effect as shown in FIG. The phenomenon that the remaining solder is fixed to the vicinity of the nozzle opening 25 (fixed solder 32) occurs. When the solder fixing 32 occurs, the nozzle opening 25 is blocked, so that a printing faint defect occurs. Further, in order to remove the fixed solder 32, it is necessary to remove the nozzle portion 24 and discard the fixing portion. Work is required, and resource loss of the solder paste 23 and a decrease in the operating rate of the solder printer have been problems.

  In the prior art, as shown in FIG. 10, the intermediate bar 33 is provided inside the print head to prevent this problem, thereby preventing the sticking by generating a flow that agitates the entire inside of the print head. However, due to the recent increase in LSI density, the mask hole diameter for solder printing has become finer, the amount of solder paste used in a single printing has decreased, and the amount of solder paste flowing inside the print head has decreased. In the conventional intermediate bar 33 method, the stirring effect is thin, and there is no other way of dealing with the problem that the solder is fixed at the interface between the screen mask and the nozzle opening, except for dismantling cleaning.

  The present invention has been made in view of the above problems, and paying attention to the need for a mechanism for stirring the solder paste fixed to the interface between the screen mask and the nozzle opening, and solder printing corresponding to LSI densification. It is an object of the present invention to provide a method for preventing solder sticking inside a nozzle of a head and a solder printer having a solder sticking preventing structure.

  According to the first aspect of the present invention, in order to achieve the above-mentioned object, a solder printing machine comprising a print head (2) for printing a solder paste (23) on a substrate (4) to be printed. In (1), the print head is provided at the tip of the nozzle portion (24) for the solder paste to pass through and ejected toward the substrate, and the solder paste is ejected therefrom. A nozzle port (25) and an elastic stirring wire (22) housed in the nozzle part. The stirring wire extends so as to protrude from the nozzle port toward the printing medium.

  With this configuration, conventionally, there is a problem that the solder is fixed at a portion having poor fluidity (dilatancy phenomenon) in a sealed type print head of a solder printer, and the fixed solder is discarded by removing the nozzle portion. On the other hand, in the solder printer of the present invention, the stirrer wire is provided by an elastic stirrer wire provided inside the print head, so that the nozzle part is pressed away and reciprocated during printing. By moving the nozzle in and out of the nozzle port, it is possible to agitate the solder paste near the nozzle port, and by preventing the formation of fixed solder near the nozzle port, remove the nozzle and discard the fixed solder This provides a highly productive printing process that saves resources and is maintenance-free without unnecessary operations. Furthermore, since the stirring effect is independent of the flow rate of the solder paste, it can cope with the recent solder printing in which the mask hole diameter is miniaturized as the LSI density is increased. In the stirring mechanism of the present invention, the stirring wire is operated by the reciprocating motion of the print head during printing. Therefore, a mechanism such as a shaft or a guide for stirring is unnecessary, and the structure is simple. The print head size can also be kept small.

According to a second aspect of the present invention, in the form according to the first aspect, the print head further comprises a piston (21). The piston is capable of reciprocating and is characterized in that the solder paste is pressed and discharged from the nozzle port.
According to this embodiment, the configuration of the print head that discharges the solder paste is further clarified.

According to a third aspect of the present invention, in the form according to the first or second aspect, the stirring wire is disposed so as to be freely movable in the nozzle portion. Features.
According to this embodiment, since the solder paste is stirred by the stirring wire freely moving in the nozzle portion, the solder paste is prevented from being separated into solder and flux, and the solder paste is fixed to the inner wall of the nozzle portion. Can also be suppressed.

According to a fourth aspect of the present invention, in the form according to the third aspect, the maximum dimension of the stirring wire is smaller than the minimum dimension of the nozzle portion.
According to this embodiment, since the maximum dimension of the stirring wire is smaller than the minimum dimension of the nozzle portion, the stirring wire can freely move in the nozzle portion, and the stirring effect can be exhibited.

According to a fifth aspect of the present invention, in the form according to the fourth aspect, the maximum diameter of the stirring wire is smaller than the minimum dimension of the nozzle portion.
According to this embodiment, since the maximum diameter of the stirring wire is smaller than the minimum dimension of the nozzle portion, the stirring wire can move freely within the nozzle portion, and the stirring effect can be exhibited.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the solder printer is used for solder printing of an electronic circuit board.
According to this form, the form which actualizes the use of the solder printer of this invention more is disclosed.
In the above description of the present invention, symbols or numbers in parentheses () are attached to show correspondence with the embodiments described below.

  Hereinafter, a solder printer according to an embodiment of the present invention will be described in detail with reference to the drawings. 1 to 7 schematically show one embodiment of a solder printer according to the present invention, and FIG. 1 schematically shows the overall configuration of the solder printer 1 according to one embodiment of the present invention. FIG. 2 is an enlarged front cross-sectional view of the solder printing machine 1 according to one embodiment of the present invention as viewed from the traveling direction of the print head 2, and FIG. 3 is a solder according to the first embodiment of the present invention. The enlarged side sectional view seen from the side side to the advancing direction of printing head 2 of printing machine 1 is shown. 4 to 7 are explanatory views for explaining the operation of the print head according to the first embodiment of the present invention. FIG. 4 is a front sectional view similar to FIG. 2, and FIGS. 5 to 7 are similar to FIG. FIG. Referring to FIGS. 2-7, the element parts of FIGS. 2-7 that are the same as or similar to the element parts of the prior art shown in FIGS. 8-10 are designated by the same reference numerals.

  The basic solder printer function of the present invention is the same as that of a conventional machine, and the overall configuration is basically the same as that of the conventional solder printer already described, and is shown in FIG. The structure of the solder printer 1 of the present embodiment is also general, and the solder printer 1 supplies a work jig 5 for holding the work 4 and a solder pace and 23 to the land 72 of the work 4. Screen mask 7 for sealing, sealed type print head 2 for performing solder printing, drive unit for moving up and down the screen mask 7 (mask up / down drive unit 8), and drive unit for moving the print head 2 up and down (head up / down drive) Part 11 and a head reciprocating drive part 10).

  The print head 2 of the present embodiment shown in FIGS. 2 and 3 also includes a nozzle portion 24 and a piston 21, and a nozzle port 25 that is an opening is provided at the tip of the nozzle portion 24. . In the present embodiment, the print head 2 is driven by compressed air supplied from an air supply port 26 by the piston 21 and moves downward in the figure (in the direction of arrow A) to fill the inside of the print head 2. The solder paste 23 is pushed out of the nozzle port 25 through the nozzle portion 24. The piston 21 may be driven by a hydraulic pressure other than pneumatic pressure or by another electrical and / or mechanical means. The solder paste 23 may be supplied to the nozzle portion 24 from a supply port (not shown). Similar to the above-described conventional technology, in the solder printing process of the present embodiment, first, the screen mask 7 is overlaid on the work 4 that is the printing medium. Next, the print head 2 reciprocates while being pressed onto the screen mask 7, and the solder paste 23 inside the print head is pressurized by the piston 21 and ejected so as to be pushed out from the nozzle port 25, and the mask of the screen mask 7. The solder paste 23 is applied on the workpiece 4 through the hole 71. Thereafter, when the screen mask 7 is raised, a solder having a mask hole shape is formed on the land 72.

  Since the present invention is characterized by the print head 2 in the solder printer 1, the configuration of the print head 2 of the present embodiment will be described below. As can be seen from FIGS. 2 and 3, the opening of the nozzle port 25 of the print head 2 has a rectangular shape with a high ratio of length to width (for example, 1:20), and the solder paste 23 is stirred and dispersed inside. A stirring wire 22 is provided as a mechanism to do this. The stirring wire 22 has a spring shape that is narrower than the width inside the print head, and has a function of expanding and contracting in the vertical direction with respect to the nozzle opening 25 of the print head 2. In the present embodiment, as can be seen from FIG. 2, the stirring wire 22 has a shape in which a plurality of V-shaped springs connected in parallel is connected in parallel. It can be expanded and contracted so as to be guided along the inner wall. However, the stirring wire 22 of the present invention is not limited to the above-described form, and can be elastically expanded and contracted in the vertical direction of the nozzle port 25, such as a coil spring, for example, and can freely move in the lateral direction in FIG. Any elastic form known to those skilled in the art can be used as long as it is dimensionally and shapely movable. Furthermore, the stirring wire 22 may not have a shape in which two springs are connected. Further, as can be seen from FIGS. 2 and 3, a part of the stirring wire 22 extends so as to protrude outside the nozzle opening 25 of the print head 2.

Next, the operation of the present application will be described with reference to FIGS. 4 to 7 in the above embodiment.
First, when the print head 2 is pressed onto the screen mask 7 so that the nozzle opening 25 is in contact with the screen mask 7 in order to perform solder printing, as shown in FIGS. 4 and 5, an elastic stirring wire 22 is used. Is shrunk so as to be pushed by the screen mask 7, and the portion of the stirring wire 22 protruding from the nozzle opening 25 completely enters the inside of the print head as shown in FIG. Subsequently, since the wire diameter of the stirring wire 22 is smaller than the thickness inside the head when the print head 2 moves forward, the portion of the stirring wire 22 in contact with the screen mask surface is caused by friction with the screen mask surface. As shown in FIG. 4, the print head 2 moves in the direction opposite to the moving direction.

  Next, when the print head moves backward, as shown in FIG. 6, the portion of the stirring wire 22 that is in contact with the screen mask 7 moves in the direction opposite to the moving direction of the print head 2. In this way, when the stirring wire 22 moves inside the print head, the solder paste 23 is stirred, and separation of solder and flux is prevented. Finally, when the print head 2 is lifted away from the screen mask 7, the stirring wire 22 expands by its own spring force and returns to its original shape, and a part of the stirring wire 22 is more than the nozzle opening 25 as shown in FIG. The fixed solder 35 sticking out of the screen mask 7 and the nozzle opening is dispersed outside.

  In a specific example, the workpiece 4 is □ 38 mm, the thickness of the screen mask 7 is 50 μm, the mask hole diameter is 100 μm, the mask hole pitch is 150 μm, the number of mask holes is 4000, the print head 2 has an internal width (B) of 40 mm, The internal thickness (T) was 2 mm (see FIGS. 2 and 3). When the solder paste 23 was bump-printed with a lead-free solder having a content flux weight ratio of 10%, in the printing process using the nozzle without the stirring wire 22 of the present invention, a faint defect occurred in the number of printings of 10 sets or less. Moreover, the printing process which requires nozzle cleaning could enable continuous printing of 100 sets or more by adopting the configuration of the present invention having the above specifications.

Next, effects and operations of the above embodiment will be described.
The following effects can be expected from the solder printer according to the above embodiment of the present invention.
-With the above configuration and operation (the operation of entering and exiting the stirring wire from the nozzle port and swinging), the solder paste at the interface between the screen and the nozzle port can be stirred and dispersed to prevent its sticking. Since the agitation effect is independent of the flow rate of the solder paste, it can cope with the recent solder printing in which the mask hole diameter is miniaturized as the LSI density is increased.
・ In addition, the stirring mechanism of the present application does not require a mechanism such as a shaft or a guide for stirring because the operation of the stirring wire is performed by the reciprocating motion of the print head during printing, and the structure is simple. The print head size can also be kept small.

  In the embodiments described above, the values of dimensions of the print head and the like, the composition of the solder, and the like are examples, and the present invention is not limited to these.

  The embodiment described above or shown in the drawings is the minimum configuration necessary for carrying out the present invention, and therefore known to those skilled in the art in the print head or the solder printer of the above embodiment. Various additional configurations may be added. These configurations may be, for example, valves in a constant pressure line for driving the piston, a spring for reciprocating the piston, and the like.

  The above-described embodiment is an example of the present invention, and the present invention is not limited by the embodiment, and is defined only by matters described in the claims, and other embodiments are also possible. It can be implemented.

FIG. 1 is an explanatory diagram schematically showing the overall configuration of a solder printing machine according to an embodiment of the present invention. FIG. 2 is a schematic enlarged front sectional view of the solder printing machine according to one embodiment of the present invention as viewed from the direction of travel of the print head. FIG. 3 is an illustrative enlarged side sectional view seen from the side with respect to the traveling direction of the print head of the solder printing machine according to one embodiment of the present invention. FIG. 4 is a front sectional view similar to FIG. 2 for explaining the operation of the print head according to one embodiment of the present invention, and shows a state in which the print head is pressed against the screen mask. FIG. 5 is a side sectional view similar to FIG. 3 for explaining the operation of the print head according to one embodiment of the present invention, and shows a state when the print head is advanced. FIG. 6 is a side sectional view similar to FIG. 3 for explaining the operation of the print head according to one embodiment of the present invention, and shows a state when the print head is retracted. FIG. 7 is a side sectional view similar to FIG. 3 for explaining the operation of the print head according to one embodiment of the present invention, and shows a state in which the print head is separated from the screen mask. FIG. 8 is a front sectional view similar to FIG. 2 of a print head of a conventional solder printer. FIG. 9 is an explanatory diagram of a solder sticking phenomenon that occurs in the print head of the conventional solder printer of FIG. FIG. 10 is a front sectional view similar to FIG. 2 of another print head of a conventional solder printing machine, and includes an intermediate bar.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solder printer 2 Print head 4 Work 5 Work jig 7 Screen mask 8 Mask vertical drive part 10 Head reciprocation drive part 11 Head vertical drive part 21 Piston 22 Stirring wire 23 Solder paste 24 Nozzle part 25 Nozzle opening

Claims (6)

In a solder printer (1) comprising a print head (2) for printing a solder paste (23) on a substrate (4),
The print head is
A nozzle portion (24) for allowing the solder paste to pass through and ejected toward the substrate;
A nozzle opening (25) provided at the tip of the nozzle portion, from which the solder paste is discharged;
An elastic stirring wire (22) housed in the nozzle section;
It has
The solder printing machine, wherein the stirring wire extends so as to protrude from the nozzle opening toward the printing medium.   The solder printing machine according to claim 1, wherein the print head further includes a piston (21), the piston is capable of reciprocating, and the solder paste is pushed and discharged from the nozzle port. .   The solder printing machine according to claim 1, wherein the stirring wire is disposed so as to be freely movable in the nozzle portion.   The solder printing machine according to claim 3, wherein a maximum dimension of the stirring wire is smaller than a minimum dimension of the nozzle portion.   The solder printer according to claim 4, wherein a maximum diameter of the stirring wire is smaller than a minimum dimension of the nozzle portion.   6. The solder printing machine according to claim 1, wherein the solder printing machine is used for solder printing of an electronic circuit board.

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