JP4775133B2 - Screen printing apparatus and printing method therefor - Google Patents

Description

  The present invention relates to a screen printing apparatus for printing a solder paste or the like on a substrate through a screen mask and a printing method thereof, and more particularly to a screen printing apparatus and a printing method suitable for obtaining screen printing of a high-density and high-multilayer board. About.

  In general, as a technique for connecting a printed circuit board and a semiconductor chip, a method of joining using a solder bump (a fine solder protrusion) called a flip chip (FC) method is employed. Since this method can connect several thousand to several tens of thousands of connection points at a time by arranging solder bumps in a plane, the connection conditions of semiconductor chips that are becoming more and more functional with the advance of IT are fine, high density, The increase in the number of points is progressing rapidly. Due to the trend toward higher functionality and higher integration of semiconductors in recent years, further miniaturization of printed bumps has been required for solder bumps on package substrates.

The solder bump printing device is a device that performs printing by placing a screen mask S with holes S ₁ in accordance with a printing pattern on a work W and filling the mask holes S ₁ with solder paste P using a print head. Conventionally, a screen printing apparatus as shown in FIG. 4 is used. The screen printing apparatus 1 includes a workpiece alignment unit 2 that positions a workpiece (substrate) W, a mask vertical drive unit 3 that moves a screen mask S up and down, a print head 4, and a head up and down that moves the print head 4 up and down. It is basically composed of a drive unit 5 and a head reciprocating drive unit 6 that reciprocally moves the print head 4 left and right (lateral direction). In this printing apparatus 1, after the work W is placed on the table of the work alignment unit 2, the work W is positioned, and then the screen mask S is overlaid on the work W by the mask vertical drive unit 6 of the solder printing apparatus 1. Then, the print head 4 is moved by the head reciprocating drive unit 6 and the head vertical drive unit 5 to apply the solder paste P onto the work W through the screen mask S, thereby printing the solder bumps B on the work W. Yes.

  In this conventional printing apparatus 1, a squeegee type print head shown in FIG. 5 or a sealed type print head shown in FIG. 6 is generally used as the print head 4. The squeegee type print head 4 is used to perform bump printing on the work W by moving the solder paste P between the squeegee 41 and moving on the screen mask S. On the other hand, the sealed type print head 4 has a nozzle 42 at its tip. The nozzle 42 for discharging the solder paste P is moved in a state where the nozzle 42 is in contact with the screen mask S, and bump printing is performed on the workpiece W.

In recent years, the mask hole S ₁ of the screen mask S is also miniaturized in accordance with the miniaturization of the print bumps, and the solder paste P is also increased in viscosity to prevent drooling. Therefore, the squeegee 41 of the conventional squeegee type print head 4 is used. by the printing pressure becomes difficult filling of the mask holes S ₁ paste, fillable sealed printhead is becoming the mainstream at high pressure. However, as compared with the squeegee type print head, the sealed print head 4 has a problem that the solder paste P at the tip of the nozzle 42 is fixed and a printing defect occurs.

FIG. 7 is a diagram for explaining (a) a state before the solder paste P adheres to the tip of the nozzle and (b) a state after the adhering occurs. That is, the solder paste P is a mixture of solid solder particles and a flux solvent, and the space between the solder particles is filled with the flux solvent as shown in FIG. Yes. In this regard, in the squeegee type print head, as shown in FIG. 5, the solder paste P is flowed and agitated as a whole by the printing operation, so that aggregation is prevented and fluidity is maintained. Therefore, the solder particles near the nozzle tip hardly flow, and only the liquid flux solvent is used as the contact surface between the nozzle 42 and the screen mask S or the screen mask S. Since it flows out from the gap with the workpiece W, as shown in FIG. 7B, the solder particles aggregate and adhere to each other and lose fluidity. The solder paste P that has lost its fluidity does not sufficiently flow into the mask hole S ₁ of the screen mask S during printing, causing a defective chipping of the bump.

  In the conventional screen printing apparatus, the above problem has been dealt with by periodically scraping and discarding the solder paste P fixed to the tip of the nozzle. However, even at present, this disposal work is required every 50 printing operations. In addition, a small print head that supports fine bumps requires a disposal operation every 10 printings, which significantly reduces productivity. In the future, as bumps become further miniaturized, it is required to make the solder particles of solder paste P finer and have higher functionality, and there is a problem of lowering solder costs and productivity in the conventional fixing method due to disposal work. Therefore, there is a need for a solder bump printing method that does not require disposal and that is more productive and resource-saving.

  The present invention has been made in view of the above problems, and its purpose is to eliminate the need for the conventional disposal work of scraping and discarding the solder paste fixed to the nozzle tip of the print head on a regular basis. The present invention provides a screen printing apparatus and a printing method thereof that can be maintenance-free and can improve soldering costs and productivity.

The present invention provides a screen printing apparatus and a screen printing method according to each of the claims as means for solving the problems.
Screen printing apparatus according to claim 1, the paste supply mechanism 7 for supplying a solder paste P to the print head 4, have to be supplied from the nozzle 42 leading end of the printing head 4 a solder paste P to the print head 4 The paste supply mechanism 7 is disposed on the opposite side of the print head 4 with respect to the screen mask S. As a result, the printing surface solder paste P that is reduced by the flux solvent being lost during printing is replaced with a new solder paste P. As a result, the flux concentration is maintained in a normal state, and printing defects are prevented. Therefore, it is possible to perform continuous printing 100 times or more without maintenance without performing a disposal operation for discarding the solder paste agglomerated at the nozzle tip. Also, the solder paste P can be supplied from the nozzle tip by connecting the paste supply mechanism 7 and the print head 4 in the vertical direction.

The printing apparatus according to claim 2 is provided such that the supply port 71a of the paste supply mechanism 7 is in close contact with the surface of the screen mask S on the side in contact with the workpiece W, and the screen mask S penetrates the position of the supply port 71a. A hole S ₂ is formed, which allows the print head 4 to be moved to the solder paste P supply region of the screen mask S every several printings, and through the through hole S ₂ of the screen mask S. Thus, the solder paste P supplied from the supply port 71a of the paste supply mechanism 7 can be easily supplied to the print head 4 from the tip of the nozzle.

In the printing apparatus according to the third aspect , the paste supply mechanism 7 is provided with a pressure piston 73 for extruding the solder paste P, so that an appropriate pressure is applied to the solder paste P and supplied. The printing surface solder paste P, which can be pushed out from the opening 71a and decreased due to flux loss during printing, is effective for pushing into the print head 4 and mixing with the new solder paste P.
The printing apparatus according to claim 4 further includes a cleaning mechanism 8 including a cleaning paper 81 and a paper feed roller 82 provided on the lower surface of the screen mask S and penetrates the screen mask S at a position corresponding to the cleaning mechanism 8. The opening S ₃ is provided, so that even when the deteriorated solder paste P (solder paste with reduced flux) is accumulated in the nozzle 42 of the print head 4, the print head 4 is opened to the opening S of the screen mask S. _By moving to the position ₃ , it is possible to automatically discard the deteriorated solder paste P, and it is possible to continuously print without maintenance.

A screen printing method according to a fifth aspect is obtained by changing the apparatus invention according to the first to third aspects into a method invention, and the function and effect thereof are the same as those of the first to third aspects.
The printing method of claim 6 is the method invention of the apparatus invention of claim 4 , and the operation effect is the same as that of claim 4 .

  Hereinafter, a screen printing apparatus and a printing method according to an embodiment of the present invention will be described with reference to the drawings. Since the basic configuration of the screen printing apparatus 1 of the present invention is the same as that of the conventional screen printing apparatus of FIG. 4, the overall configuration will be briefly described based on FIG. The screen printing apparatus 1 basically includes a work alignment unit 2 that positions a work W, which is a package substrate placed on a table 21, in the X axis, Y axis, and θ directions, and a screen mask S (hereinafter referred to as “screen”). The mask up / down drive unit 3 that moves up and down, the print head 4 that discharges the solder paste P, the head up / down drive unit 5 that moves the print head 4 up and down, and the print head 4 in the horizontal direction (left and right in the figure). The head reciprocating drive unit 6 and the like reciprocally move.

  The workpiece alignment unit 2 has a table 21 on which the workpiece W is placed and held, an X-direction moving table 22 that moves the table 21 in the X-axis direction, a Y-direction moving table 23 that moves in the Y-axis direction, and a rotation in the θ direction. The rotating table 24 is configured to move, and these are combined together and placed on the base 11 of the printing apparatus 1. The upper surface of the table 21 is an adsorption surface having a number of suction holes (not shown), and can be adsorbed and positioned in a state where the workpiece W is placed. These suction holes are connected to a vacuum pump (not shown). The table 21 is supported on an X direction moving table 22, the X direction moving table 22 is supported on a Y direction moving table 23, and the Y direction moving table 23 is further supported on a rotating table 24. As a result, the position of the workpiece W on the table 21 can be corrected in the X axis, Y axis, and θ directions. The movement in the X-axis and Y-axis directions and the rotation in the θ-direction are performed by the servo motor 25, respectively.

The screen S is a concept including a mask on which a predetermined pattern (mask hole S ₁ ) is formed, for example, a metal mask or a narrowly defined screen mask. The screen S can be moved up and down by the mask vertical drive unit 3. That is, the mask vertical drive unit 3 includes a lift cylinder 31 attached to a lift guide body 12 erected on the base 11, a piston body 32 that slides in the lift cylinder 31, and the piston body. The lifting member 33 is fixed to 32 and the holding member 34 that is coupled to the lifting member 33 and holds the screen S on both sides. The lifting member 33 is moved up and down by the holding member 34. The held screen S moves up and down. The elevating member 33 is operated by a fluid introduced into the elevating cylinder 31, for example.

  A horizontal frame 13 is provided between the left and right lifting guide bodies 12 erected on the base 11 of the printing apparatus 1. The horizontal body 13 is provided with a horizontal guide body 14 in parallel therewith. The guide body 14 is fitted with a reciprocating member 15 that can slide back and forth in the lateral direction along the guide body 14, and the head vertical drive unit 5 is attached to the reciprocating member 15. A head reciprocating drive unit 6 is installed on the horizontal body 13, and the head vertical drive unit 5 is attached to the tip of a reciprocating member 61 of the head reciprocating drive unit 6. In FIG. 4, a ball screw mechanism is employed as the head reciprocating drive unit 6. Therefore, the head vertical drive unit 5 also moves in the horizontal direction as the reciprocating member 61 is moved forward / backward in the horizontal direction by the operation of the head reciprocating drive unit 6.

  The head vertical drive unit 5 includes a cylinder part 51 fixed to the tip of the reciprocating member 61 of the head reciprocating drive part 6 and a piston part 52 that slides in the cylinder part 51. A print head 4 is attached to the tip portion. In this way, the print head 4 can move up and down in the vertical direction and reciprocate in the left and right direction (lateral direction). In the above description, the mask vertical drive unit 3 and the head vertical drive unit 5 are a piston-cylinder mechanism and the head reciprocating drive unit 6 is a ball screw mechanism. In this case, a known mechanism such as a piston-cylinder mechanism, a ball screw mechanism, a rack-pinion mechanism, or a linear motor mechanism can be appropriately employed.

Next, a configuration that characterizes the present invention will be described with reference to FIG.
The print head 4 includes a cylindrical first cylinder 42 having a small diameter corresponding to the nozzle 42, a cylindrical second cylinder 43 having a larger diameter than the first cylinder 42, and the first and second cylinders 42 and 43. And a first pressurizing piston 44 that slides. That is, the first pressurizing piston 44 is composed of a small-diameter piston 44a that slides in the first cylinder 42 and a large-diameter piston 44b that slides in the second cylinder 43 by a rod 44c that passes through both cylinders 42 and 43. It has a connected barbell shape. The second cylinder 43 is in communication with an air supply source. When air as working fluid is introduced into the second cylinder 43, the first pressurizing piston 44 is lowered and the nozzle (first cylinder) 42. The solder paste P inside is pushed out from the tip of the nozzle 42.

  The print head 4 is provided on the upper side of the screen S, while the paste supply mechanism 7 is provided on the lower side of the screen S. The basic structure of the paste supply mechanism 7 is the same as that of the print head 4, and a third cylinder 71 having a supply port 71 a for supplying the solder paste P, a fourth cylinder 72 for working fluid, and the solder paste P And a second pressurizing piston 73 that applies a supply pressure to the main body. The second pressure piston 73 also has a barbell shape in which a piston 73a that slides in the third cylinder 71 and a piston 73b that slides in the fourth cylinder 72 are connected by a rod 73c that penetrates both the cylinders 71 and 72. I am doing. The fourth cylinder 72 is in communication with an air supply source, and the second pressurizing piston 73 is raised by introducing air, which is a working fluid, into the fourth cylinder 72, and the supply port 71 a of the third cylinder 71. Further, the solder paste P is extruded.

In order to avoid the portion of the screen S where the mask hole S ₁ is formed, the screen S is provided with a through hole S ₂ having approximately the same size as the nozzle hole. When the screen S is positioned on the work W mounted on the table 21, so that the supply port 71a of the paste supply mechanism 7 coincides with the through-hole S ₂ of the screen S, the paste supply mechanism 7 is fixed or adjustable It is installed in the printing apparatus 1 as possible. In this way, the paste supply mechanism 7 is provided so as to be in close contact with the surface on which the ink supply port 71a is in contact with the workpiece W of the screen S, the through-hole S ₂ is open to the position of the supply port 71a to the screen S since, by moving the print head 4 directly above the supply port 71a, a structure that a supply port 71a of the nozzle 42 distal port and the paste supply mechanism 7 of the print head 4 is directly connected via a through-hole S ₂ Yes.

  The operation (printing method) of the screen printing apparatus 1 of the present embodiment having the above-described configuration will be described. 2A and 2B are diagrams for explaining the operation of the screen printing apparatus according to this embodiment. FIG. 2A shows the supply of solder paste, FIG. 2B shows the solder printing, and FIG. 2C shows the solder paste. It is a figure explaining each re-supply. In the screen printing apparatus 1 of the present invention, the workpiece W is placed on the table 21 and the alignment operation is performed in the same manner as in the normal operation. Thereafter, the screen S is lowered by the operation of the mask vertical drive unit 3, and the workpiece is moved. It is arranged in close contact with W.

First, as shown in FIG. 2A, the print head 4 is moved directly above the paste supply mechanism 7 by the head reciprocating drive unit 6, and the nozzle 42 of the print head 4 is passed through the screen S through the head vertical drive unit 5. Adhere to the hole S ₂ . In this case, the supply port 71a of the paste supply mechanism 7 is disposed in close contact from the lower surface to the through-hole S ₂ screens S. Thus, the nozzle 42 distal port and a supply port 71a is communicated via a through-hole S _2. In this state, the pressurizing force of the first pressurizing piston 44 of the print head 4 is turned off and the second pressurizing piston 73 of the paste supply mechanism 7 is pressurized, whereby a certain amount of solder paste P is applied to the print head 4 (nozzle 42). ) Is supplied.

Next, as shown in FIG. 2B, the print head 4 is moved in the horizontal direction by the head reciprocating drive unit 6 while the print head 4 is in close contact with the upper surface of the screen S by the head vertical drive unit 5. The first pressure piston 44 is pressurized to supply solder paste P to the mask hole S ₁ of the workpiece W, thereby performing solder printing. This printing operation is performed several times while shifting the position in the front and back direction of the paper.

  After several times of printing, the print head 4 is moved directly above the paste supply mechanism 7 as shown in FIG. 2C, so that the same state as described in FIG. The solder paste P is supplied again from the supply port 71a into the print head 4 (nozzle 42). By re-supplying the solder paste P, the solder paste P remaining at the tip portion of the nozzle 42 by several printing operations and pushed out is reduced and mixed with the newly supplied solder paste P.

  As described above, in this embodiment, since the solder paste P is newly supplied from the nozzle tip every several times of printing, the printed surface solder paste P that is decreased due to flux loss during printing is mixed with the new solder paste P. Thus, the flux concentration is maintained in a normal state, and printing failure is prevented. Specifically, when the paste supply mechanism of the present embodiment is not used as in the prior art, the solder paste on the nozzle printing surface is fixed when printing is performed about 10 times, as shown in FIG. In contrast to the occurrence of printing failure, if the solder paste is supplied from the tip of the nozzle 42 from the paste supply mechanism 7 every five printings, printing failure does not occur, and continuous printing can be performed 100 times or more without maintenance.

FIG. 3 is a diagram for explaining a main part of the screen printing apparatus according to the second embodiment of the present invention. In the second embodiment, in addition to the paste supply mechanism 7 of the first embodiment, a cleaning mechanism 8 for cleaning the nozzle tip is provided. The paste supply mechanism 7 has the same configuration, arrangement, and operation as those in the first embodiment, and a description thereof will be omitted. The cleaning mechanism 8 includes a cleaning paper 81 and a feed roller 82 that moves the cleaning paper 81. The cleaning mechanism 8 is arranged on the lower surface side of the screen S like the paste supply mechanism 7 so as to face the paste supply mechanism 7 with the workpiece W interposed therebetween. In addition, an elongated hole-shaped opening S ₃ is formed at a position corresponding to the cleaning mechanism 8 of the screen S. Therefore, when the print head 4 is moved by the head reciprocating drive portion 6 and the head vertically driving portion 5 on the cleaning paper 81 of the cleaning mechanism 8, since the opening S ₃ is open on the screen S on the cleaning paper 81, the print head The front end surface of the four nozzles 42 can be brought into close contact with the cleaning paper 81.

In the operation of the screen printing apparatus of the second embodiment, in addition to the operation of the first embodiment shown in FIG. 2, the print head 4 is periodically cleaned by the head reciprocating drive unit 6 and the head vertical drive unit 5. Solder inside the nozzle 42 is moved to the area (position of the opening S ₃ ), the nozzle 42 of the print head 4 is brought into close contact with the cleaning paper 81, and the first pressure piston 44 of the print head 4 is pressurized. The paste P is discarded on the cleaning paper 81. The portion of the cleaning paper 81 to which the waste solder paste is attached is fed by the feed roller 82.

  In the second embodiment, in addition to the effects of the first embodiment described above, even when the deteriorated solder paste P accumulates inside the nozzle 42, the deteriorated solder paste is automatically discarded and continuously maintained without maintenance. It becomes possible to print.

  In the present invention, in addition to the effects described above, the print head does not need to accumulate the solder paste supplied to the nozzles, and is an amount necessary for several printings performed between the supply of the solder paste. Since it is only necessary to hold the solder paste, it is possible to reduce the size of the device compared to the past, and even when cleaning the print head after the production of the device, only a small amount of solder paste is discarded. Contributes to

It is sectional drawing explaining the principal part of the screen printing apparatus of 1st Embodiment of this invention. It is a figure explaining operation | movement of the screen printing apparatus of 1st Embodiment, (a) is supply of solder paste, (b) is solder printing, (c) is a figure explaining resupply of solder paste. is there. It is sectional drawing explaining the principal part of the screen printing apparatus of 2nd Embodiment of this invention. It is a whole block diagram of the conventional screen printing apparatus. It is a figure explaining the conventional squeegee type print head. It is a figure explaining the conventional sealed printing head. It is a figure explaining the solder paste and the printed state inside the conventional sealed type print head before (a) adhesion occurrence and (b) after adhesion occurrence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screen printer 14 Guide body 15 Reciprocating member 2 Work alignment part 21 Table 3 Mask vertical drive part 4 Print head 42 Nozzle (1st cylinder)
43 2nd cylinder 44 1st pressurization piston 5 Head vertical drive part 6 Head reciprocation drive part 7 Paste supply mechanism 71 3rd cylinder 71a Supply port 72 4th cylinder 73 2nd pressurization piston 8 Cleaning mechanism 81 Cleaning paper 82 Feeding roller W Work S Screen mask (screen)
S ₁ mask hole S ₂ through hole S ₃ opening P Solder paste

Claims (6)

A workpiece alignment unit (2) for placing and positioning the workpiece (W);
A mask up / down drive unit (3) for moving the screen mask (S) up and down;
A print head (4) having a nozzle (42) for printing the solder paste (P) on the workpiece (W);
A head reciprocating drive unit (6) for reciprocating the print head (4) in the lateral direction;
A head up-and-down drive unit (5) for moving the print head (4) up and down;
The screen mask (S) on which the predetermined pattern is formed is overlaid on the workpiece (W) on which the predetermined pattern is printed, and the solder paste (P) is applied to the workpiece via the screen mask (S). (W) In a screen printing apparatus for printing on,
A paste supply mechanism (7) for supplying a solder paste (P) to the print head (4) is provided, and the paste supply mechanism (7) is soldered from the tip of the nozzle (42) of the print head (4). The paste (P) is supplied to the print head (4) ,
The screen printing apparatus, wherein the paste supply mechanism (7) is located on the opposite side of the print head (4) with respect to the screen mask (S) . A supply port (71a) of the paste supply mechanism (7) is provided so as to be in close contact with the surface of the screen mask (S) that contacts the work (W), and the supply port is provided in the screen mask (S). located in the through hole of (71a) (S ₂₎ screen printing apparatus according to claim 1, characterized in that is formed. The screen printing apparatus according to claim 1 or 2 , wherein the paste supply mechanism (7) is provided with a pressure piston (73) for extruding the solder paste (P). Further, a cleaning mechanism (8) comprising a cleaning paper (81) and a paper feed roller (82) is provided on the lower surface of the screen mask (S), and the screen is located at a position corresponding to the cleaning mechanism (8). the mask (S), through the opening (S ₃₎ screen printing apparatus according to any one of claims 1 to 3, characterized in that is formed. A screen mask (S) on which a predetermined pattern is formed is superimposed on a work (W) on which a predetermined pattern is printed, and solder paste (P) discharged from the nozzle (42) of the print head (4) is applied to the screen mask ( In the screen printing method of printing on the workpiece (W) via S),
A paste supply mechanism (7) for supplying the print head (4) and a solder paste (P) to the print head is disposed across the screen mask (S), and the paste is provided on the screen mask (S). A through hole (S ₂ ) is formed at a position corresponding to the supply port (71a) of the supply mechanism (7),
When supplying the solder paste, the print head (4) is moved to the position of the through hole (S ₂ ) of the screen mask (S), and the through hole is supplied from the supply port (71a) of the paste supply mechanism (7). Solder paste (P) is supplied to the print head (4) from the tip of the nozzle (42) of the print head (4) via (S ₂ ). Further, a cleaning mechanism (8) comprising a cleaning paper (81) and a paper feed roller (82) is provided on the lower surface of the screen mask (S) and is located at a position corresponding to the cleaning mechanism (8). In the screen mask (S), a through opening (S ₃ ) is formed,
The nozzle (42) of the print head is brought into close contact with the cleaning paper (81), and the pressurizing piston (44) of the print head (4) is pressurized, so that the waste paste inside the nozzle (42) is removed. The screen printing method according to claim 5 , wherein the screen printing method is discarded.

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