KR20080055715A - Screen printing machine and bump forming method - Google Patents

Abstract

A screen printing machine and a bump forming method are provided to reduce a facility cost by configuring a plurality of soldering bumps at a high speed. A screen printing machine includes a sheave shape body(45), and a vibrator(47). The screen printing machine provides and prints a soldering ball using a printing unit by installing a mask on an electrode formed on a substrate. The sheave shape body has a metal plane having a plurality of apertures. The vibrator applies a vibration to the sheave shape body. The aperture is widened by vibrating the sheave shape body with the vibrator. A soldering ball received in the sheave shape body is provided to an electrode of the substrate by installing the mask.

Description

SCREEN PRINTING MACHINE AND BUMP FORMING METHOD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing apparatus, and more particularly, to a bump forming method by solder ball printing.

In the ball bump formation (diameter 80-100 micrometers) of pitch 180-150 micrometers, there exists the printing method which reflows cream solder after printing using said high precision screen printing apparatus, and performs solder ball formation. . As an example of a screen printing apparatus, a board | substrate carrying conveyor, a board | substrate carrying conveyor, the table part provided with the lifting mechanism, the skid head provided with the mask which has a transfer pattern as an opening part, skis, a skid lifting mechanism, and a horizontal movement mechanism, The control apparatus which controls these mechanisms is provided. After bringing in a board | substrate from an import conveyor part into a apparatus, the board | substrate is temporarily fixed to a printing table part, and after that, the mark of both masks of a mask which has an opening corresponding to a board | substrate and a circuit pattern is recognized with a camera, and both shift amounts Position correction, position the substrate on the mask, raise the printing table so that the substrate is in contact with the mask, and fill the paste, such as cream solder, in the opening of the mask while contacting the mask by the skid, The paste is lowered, the paste is transferred onto the substrate by removing the substrate and the mask, and then printing is performed by carrying out the substrate from the apparatus.

In addition, a ball shaking method is known in which a solder ball is shaken into a jig processed with high precision and fine drilling, aligned at a predetermined pitch, directly mounted on a substrate, and then formed into a solder ball by reflow after loading. Further, according to Japanese Patent Laid-Open No. 2000-49183, there is a method of filling a solder ball in a predetermined opening by swinging or vibrating a mask, or a method of heating after filling by a translational motion of a brush or the like.

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-49183

The printing method by cream solder has the advantage that the equipment cost is low, and a large amount of bumps can be formed collectively, so that the throughput is high and the manufacturing cost is low. However, in the printing method, it is difficult to secure the uniformity of the transfer volume, and a plating process is performed to press the solder bumps after reflow to smooth the height. In addition, when the micronization is advanced at a pitch of 150 to 120 占 퐉 or the like with the increase in the density of the device, there exists a point that the print yield is poor and the productivity is not good. On the other hand, the ball shaking method is suitable for miniaturization because it is possible to form bumps with a stable height by securing the classification accuracy of the solder balls, but the solder balls are mounted by a robot using a high precision solder ball adsorption jig, There exists a problem of the increase of the bump formation cost by the increase of tact in a case, and the rise of jig | tool price.

In addition, in the method of filling a solder ball in a predetermined opening by oscillating or vibrating a mask according to Japanese Patent Application Laid-Open No. 2000-49183, adhesion between particles occurs due to the small hardening of the solder ball particle diameter. If the diameter is less than 1.3 times the particle diameter, there is a problem that the adhesion between the particles is larger than the particle weight so that the opening cannot be filled. Similarly, the same problem exists in filling by skidding or brush translation.

An object of the present invention is to print bumps at an ultra-fine pitch in a large amount, such as a printing method, in which a large amount of bumps can be formed, and a bump can be formed at a stable height like a ball shaking method. It is to provide a high productivity solder ball filling printing apparatus and a bump forming method that enable filling.

In order to achieve the above object, the following means were implemented in the present invention. First, a low cost and high precision screen printing technique used in the printing method was developed, and a solder ball filling printing apparatus capable of filling and printing solder ball fine particles with stable bump height at high speed and high accuracy was developed. Moreover, in order to use solder ball microparticles | fine-particles efficiently, filling and printing were implemented, maintaining a solder ball in a sealed state. In addition, it has developed a stable and high quality bump formation method by suppressing poor filling of solder balls.

As described above, according to the present invention, it is possible to form a large amount of solder bumps in which the solder bump height accuracy is stable at a low cost and at a high speed. In addition, the device also has a simple configuration, and the equipment cost can be kept low.

1 shows an example of a metal mask used for forming bump electrodes. 1A shows an example of an opening pattern 20p corresponding to an electrode group printed on one device while the entire mask is shown. That is, the mask 20 is provided in the plate frame 21. Hereinafter, the entirety including the plate frame 21 will be referred to as a mask 20. As an example of using this mask, bump formation is performed by a printing method for a plurality of take-up substrates having a diameter of 120 µm and a pitch of 150 µm and a plurality of electrode pad groups having a number of pads of one CPU chip. It is used for. The square shape in Fig. 1A shows one electrode pattern group 20a. That is, the mask opening part 20c provided corresponding to one electrode pad group is open by the diameter corresponding to the magnitude | size of an electrode pad. Printing is performed using this mask 20, after completion of printing, the printing table 10 is lowered, and the substrate 5 fixed to the printing table 10 is lowered to perform a plate separation operation and print.

Fig. 2 shows the configuration of the screen printing apparatus in the present invention. Fig. 2A shows the configuration and system configuration view seen from the front of the screen printing apparatus. 2B, the structure which looked at the screen printing apparatus from the side surface is shown. 3 (a) and 3 (b) show a state in which the screen printing apparatus is viewed from the side and printing.

The frame frame which is not shown in figure is provided in the main body frame, The mask frame is comprised so that the mask 20 which covers the screen which has a printing pattern as an opening part is set. The filling / printing head 2 is disposed above the mask 20, and the filling / printing head 2 is composed of skids (in the present invention, a sheave shaped body 45, a scraper 3, etc. instead of skids). Charging unit) is mounted. The filling / printing head 2 is configured to be movable in the horizontal direction by the filling / printing head moving mechanism 6. The charging unit can move in the vertical direction by the charging unit elevating mechanism 4. Below the mask 20, the printing table 10 which mounts and holds the board | substrate 5 which is a printing object so that the mask 20 may be provided is provided. This printing table 10 receives the XYθ table 11 which moves the board | substrate 5 in a horizontal direction, and performs alignment with a mask, and receives the board | substrate 5 from the carrying-in conveyor 25, and also the board | substrate 5 ) Is provided with a table elevating mechanism (12) for bringing or close to the mask 20 surface. The substrate receiving conveyor 26 is provided in the upper surface of the printing table 10, and the board | substrate 5 carried in by the board | substrate loading conveyor 25 is received on the printing table 10, and when printing is complete, the board | substrate carrying out is carried out. The substrate 5 is discharged to the conveyor 27.

The printing unit main body 1 is equipped with the function which performs alignment of the mask 20 and the board | substrate 5 automatically. That is, the CCD camera 15 picks up the alignment mark provided on each of the mask 20 and the board | substrate 5, image-processes, calculates the position shift amount, and corrects the shift amount. The table 11 is driven to perform alignment.

In addition, the printer control unit 30 which performs the printing control unit 36 for each sub-drive, the image input unit 37 which processes the image signal from the CCD camera 15, etc. is provided in the inside of the printer main body frame, A data input unit 50 for rewriting control data, changing a printing condition, and the like, and a display unit 40 for monitoring the printing status or the like and accepted recognition marks are disposed outside the printing press.

The printer control unit 30 has a charging unit control unit 36 that controls the filling unit, and simply selects an appropriate filling / printing mode according to the pitch of the produced bumps, the difference in the solder ball particle diameter, and the type of metal mask to be used. Can be set. Moreover, the correlation value calculation part 31 which calculates a correlation value according to an input image, the shape estimation part 32 which calculates a shape based on the received image or the data from the dictionary 38, and the position coordinate which calculates a position coordinate The calculation unit 33 and the dimension calculation unit 34 are provided, and based on the position recognition marks provided on the substrate and the mask from the data captured by the CCD camera 15, the position shift amount is obtained, and the position of the XYθ table is driven. It is a structure which performs alignment.

Next, the operation of the printing apparatus of the present invention will be described.

The substrate 5 on which the bumps are to be formed is supplied to the substrate receiving conveyor 26 by the substrate loading conveyor 25 and fixed to a predetermined position on the printing table 10. After the substrate is fixed, the CCD camera 15 is moved to a substrate mark position which is set in advance. Subsequently, the CCD camera 15 picks up the position recognition mark (not shown) provided in the board | substrate 5 and the mask 20, and transmits it to the printer control part 30. FIG. In the image input unit 37 in the control unit, the position shift amount between the mask 20 and the substrate 5 is obtained from the image data, and based on the result, the printer control unit 30 controls the XYθ table for moving the print table 10 ( 35 is operated to correct and position the position of the substrate 5 relative to the mask 20. After completion of the alignment operation, the CCD camera 15 is evacuated by a predetermined amount to a position where it does not interfere with the print table 10. After completion of evacuation of the CCD camera 15, the print table 10 is raised to bring the substrate 5 into contact with the mask 20. After that, by operating the charging unit elevating mechanism, the sheave shaped body provided in the filling / printing head 2 is brought into contact with the mask 20 surface. Next, a solder ball is supplied to the electrode part of a board | substrate through the opening formed in the mask surface from the opening of a sieve body, moving on a mask surface, having a sieve shape.

The filling / printing head 2 rises after a fixed distance stroke in the horizontal direction. Then, the printing table 10 is lowered, the mask 20 and the substrate 5 are separated, and the solder balls filled in the openings of the mask 20 are transferred to the substrate. And the board | substrate 5 on which the solder ball was printed is sent to the next process via the board | substrate carrying conveyor 27.

Moreover, two or more recognition mark alignment marks are provided in the substrate 5 and the mask 20 at relatively the same positions, and each of these marks is placed on a special CCD camera 15 having two views in the vertical direction. Thus, the mark of the mask 20 is recognized from below, the mark of the substrate 5 is recognized from above, and the position coordinates of all the marks provided at predetermined positions are read, and the substrate (with respect to the mask 20) ( The shift amount of 5) is calculated and corrected to position the substrate 5 with respect to the mask 20.

Next, the print head of the present invention will be described.

Fig. 4 shows a schematic diagram when the filling / printing head on the mask moves while filling the mask with solder balls. Fig. 5 is a sectional view of the filling and printing head.

As shown in Fig. 4, the filling / printing head 2 has a sieve-shaped body 45 for mounting a solder ball, and a sieve-shaped fixing bracket 3a and a means for imparting vertical or horizontal vibration to the sieve-shaped body 45. And a scraper 3 which is supplied onto the screen surface and which can be scraped off without leaving unfilled solder balls. In addition, in FIG. 4, the sieve-shaped body is provided in the scraper 3, but as shown in FIG. 5, the sieve-shaped body is installed in the sieve-shaped fixing bracket 3a, and the scraper 3 is provided outside thereof. It is good also as a structure. Moreover, you may be set as the structure which attaches a brush to the sheave-shaped fixing bracket 3a, and omits the scraper 3. The sieve shaped body 45 is formed of an extremely thin metal plate having a mesh-shaped opening 46 or an opening 46 such as a continuous circular, elliptical, rectangular, or slit. In addition, the mesh opening 46 can be formed integrally with a metal plate by electroforming or the like. The solder ball 48 placed on the upper side of the sieve shaped body 45 vibrates by the means 47 having the sieve shaped body 45 in the vertical or horizontal direction, or a combination thereof (the direction of the arrow 42). In this way, it is possible to reduce and diffuse the adhesion between the solder balls and to apply the rotational force to the solder balls. Due to the rotational force generated in the solder ball 48, the force of the vertical downward component is generated in the solder ball 48. By this downward force, the solder ball 48 can be filled in the predetermined opening position of the mask 20 through the opening 46 of the sieve body 45. That is, the filling / printing head 2 has the sieve-shaped body 45 on the surface of the mask 20, and moves and winds the solder ball 48 continuously in the horizontal direction so that the surface of the substrate 5 can be rotated. The upper electrode portion 5p is charged and printed.

As shown in Fig. 5, the filling / printing head 2 is formed of a solder ball storage means capable of holding the solder balls 48 in a sealed state by the sieve-shaped body 45 in a sealed state. The filling / printing head 2 was configured to cause the sieve-shaped body 45 containing the solder balls 48 to vibrate with the opposed scraper 3 during the printing operation. That is, the excitation means 47 which has the sheave shape fixing bracket 3a and the scraper 3 is provided, and it is comprised so that the scraper 3 and the sheave shape 45 may vibrate synchronously.

6 shows a sieve structural diagram having a connecting vibration action. As described above, the sieve shaped body 45 is made of an extremely thin metal plate, and an opening 46 such as a mesh shape is formed on the bottom thereof. Both ends are bent in accordance with the inclination of the sieve-shaped fixing bracket 3a, and the bent portion is provided on the surface of the sieve-shaped fixing bracket 3a. Since the sheave body 45 can be easily stretched and deformed, in the case of the solder ball diameter> opening dimension + extension deformation dimension, the solder ball 48 cannot pass and the solder ball 48 is made using the shape characteristic thereof. ) Can be maintained. On the other hand, in the case of solder ball diameter <opening dimension + expansion-deformation dimension, the clearance which the solder ball 48 can pass through is ensured, and a solder ball can be filled. The expansion and contraction of this sieve shaped body 45 can be generated with the sieve shaped body 45 or by external force, such as a magnetic force.

Fig. 7 shows an explanatory diagram of the filling / printing mechanism of the solder ball by the filling / printing head through the sieve-shaped body 45 (not shown). In the figure, the sieve-shaped fixing bracket 3a sets the attack angle θ to about 60 degrees. The filling / printing head 2 is moved in the direction of the arrow 41 while exciting the sieve-shaped fixing bracket 3a in the inclined direction (attack angular direction) using the excitation means 47 (not shown). This vibration is transmitted to the sieve body 45 through the sheave body fixing bracket 3a. When this vibration is transmitted to the solder ball 48 accommodated in the bottom face of the sieve body 45, the rotational force in the direction of the arrow 41r will generate | occur | produce in the solder ball 48. As shown in FIG. By this rotation, the solder ball 48 generates a force in the direction of the arrow 41 (horizontal direction) and a force in the direction of the arrow 41a (vertical direction). That is, downward force is generated in the solder ball 48 by the rotational force. In this state, when the sieve-shaped body 45 is stretched and repeated, and the sieve-shaped body 45 is extended, the opening formed in the bottom face part is largely opened, and the solder ball falls and moves to the mask surface therefrom. . The solder ball dropped to the opening of the mask is pressed into the mask opening by the bent corner of the sieve-shaped body or the scraper. The solder ball dropped in addition to the opening on the mask surface is scraped off by the bent corner of the sheave body 45, the scraper 3, or the like.

In addition, in the above description, a scraper is provided to scrape the solder balls remaining on the mask surface. However, a brush is provided at a portion in contact with the mask surface at the bottom of the sheave-shaped fixing bracket 3a without installing the scraper. You may sweep a solder ball with a brush. In addition, although it is set as the structure which arrange | positions a sieve body to the main-body part of a sole, it is good also as above-mentioned. You may provide a scraper and a brush separately from a sieve body. In this case, an excitation apparatus having a sieve shaped body and an excitation apparatus having a scraper or a brush are required.

8 shows an example of a situation where a solder ball is filled in a mask opening portion used in the present invention. 9 shows the arrangement of the suction flow path provided in the resin layer portion under the mask. 10 shows an enlarged view of the mask opening.

As shown in FIG. 8, the mask 20 is made into the mask shape of the two-layer structure which provided the resin layer 20n under the metal layer 20s which consists of magnetic materials. In addition, although reference | standard 20n was made into the resin layer in order to give adhesiveness and flexibility, even if it is made from thin metals, such as nickel, when it considers durability, it can implement | achieve. The upper part of the electrode pad 5P is supplied with a flux 5f (paste) for increasing the adhesion of the solder ball. Further, a plurality of magnet pads 10b are fixed to the substrate receiving surface of the print table 10 so as to be the same surface as the print table 10 surface. It is for increasing the adhesiveness of the surface of each of the mask 20 and the board | substrate 5 by attracting the metal layer 20s of a mask by the magnetic force of this magnet pad 10b.

In this embodiment, as shown in Fig. 9, a groove for sucking air flow from an opening formed in the mask surface is roughly formed in the resin layer 20n of the metal layer 20s.目) It is installed in the shape. This groove serves as an exhaust passage 52 through which air is discharged when a mask is mounted on the substrate. Moreover, the exhaust flow path 52 is formed so that the exhaust groove 51 which consists of the groove | channel formed so that the electrode group may be connected may be connected. Although not shown, a pump for sucking air is arranged, and a pipe connecting the pump and the exhaust passage 52 is provided. In the above description, the air is sucked from the mask opening via the exhaust flow path 52 using a pump, but the pressurized air supply means for spraying air onto the mask surface is provided on the printing / filling head side. After printing the solder balls, the compressed balls may be compressed air sprayed onto the mask surface to press the solder balls into the electrode pads from the mask openings. Also in this case, by forming an exhaust flow path in the resin layer constituting the mask and pushing out air from the periphery of the mask, the solder balls can be easily supplied to the mask openings.

As shown in Fig. 10, the mask 20 is formed so that the opening on the resin layer 20n side becomes larger than the opening on the metal layer 20s side. In this way, the resin layer is provided on the side of the mask in contact with the substrate, thereby increasing the adhesion of the mask to the substrate, preventing damage to the substrate, and reliably supplying solder balls to the electrode portions of the substrate. . Interval (pitch) L of opening of mask, diameter Rs of opening on metal layer 20s side, diameter Rr of opening on resin layer 20n side (= 1.1Rs), exhaust groove 52 Width R1 (about 0.4Rr). The opening diameter of the mask is determined by the diameter of the solder balls to be fed.

1 illustrates one example of a metal mask.

2 illustrates one example of a screen printing apparatus.

3 is a view for explaining an outline of a printing operation of the screen printing apparatus.

4 is a diagram showing an example of solder ball filling in a filling / printing head.

5 is a view showing a cross section of an example of a filling / printing head.

Fig. 6 is a diagram showing one example of the retractable sheave shape of the filling and printing head.

Fig. 7 is a diagram showing a filling / printing mechanism.

8 is a structural conceptual view of a metal mask.

9 illustrates an example of an exhaust passage of a metal mask.

Fig. 10 is a diagram showing an outline of an opening of the metal mask and an exhaust passage.

<Explanation of symbols for the main parts of the drawings>

1: Print unit body

2: filling / printing head

3: scraper

5: substrate

10: printing table

11: XYθ table

15: camera

20: mask

45: sheave

Claims (8)

A bump forming method using a solder ball, comprising: a screen having an opening for filling and transferring a solder ball in a predetermined pattern, a screen fixing means for loading and fixing the screen, and a substrate for forming bumps, for which predetermined printing is carried out Substrate fixing means to be carried out after the transfer is completed, recognition positioning means for aligning the screen and the substrate by image processing the reference marks of the screen and the substrate, adhesion means for bringing the substrate into close contact with the screen, and through the screen. Printing means for filling the solder ball at a predetermined position, parallel movement means for moving the printing means in parallel with the screen surface, and transfer means for fixing the solder ball filled in the screen opening onto the substrate and transferring the plate by separation. A printing apparatus having: a sieve-shaped body for loading solder balls, and perpendicular or vertical to the sieve-shaped body The method of forming a bump having a vibrating means for applying vibration. The bump according to claim 1, further comprising a solder ball storage means capable of holding a solder ball of a quantity necessary for printing in a sealed state in said sheave shape, and vibrating said sheave shape containing the solder ball during a printing operation. Forming method. The printing apparatus and bump forming method according to claim 1, wherein the printing means is provided with a brush-like body or scraper means parallel to or separate from the sheave body, and vibrates the brush-like body or the scraper means during a printing operation. 2. The screen according to claim 1, wherein the total thickness of the step formed integrally with the resin material around the pattern opening on the back surface of the screen by 1 to 1.2 times the solder ball diameter and 1/2 or less the solder ball diameter. And a step, a suction path formed when a slit is formed in the stepped portion of the screen to be in close contact with the substrate, and a screen adsorption means. The bump forming method as claimed in claim 1, wherein the printing means is provided with solder ball pressurizing means for pressing downward from an upper portion of the screen to apply pressure by using the flexibility of the screen after the solder ball filling operation. A screen printing apparatus for supplying and printing a solder ball by using a printing means through a mask on an electrode formed on a substrate, The printing means includes a sieve shaped body having a metal surface having a plurality of openings, and a means for applying vibration to the sieve shaped body, and the sieve shaped body widens the opening by having a sieve shaped body by the exciting means. The soldering ball accommodated in the said screen printing apparatus is characterized by the structure which supplies an electrode on a board | substrate through the said mask. A screen printing apparatus for supplying and printing a solder ball by using a printing means through a mask on an electrode formed on a substrate, The printing means includes a sieve shaped body having a metal surface having a plurality of openings, a means for applying vibration to the sieve shaped body, and a substrate holding means for supporting and fixing a substrate, wherein the substrate holding means includes a magnet. When the printing means moves parallel to the mask surface, a magnetic force is applied to the metal mask and the metal sheave through the substrate to widen the sheave opening, and the solder ball housed on the sheave body is placed on the substrate via the mask. The screen printing apparatus characterized by the configuration of supplying to an electrode. The screen according to claim 6 or 7, wherein the filling unit is provided with the sieve shape or is provided separately with the brush shape or the scraper means, and the screen is provided with a vibrating means for vibrating the brush shape during the printing operation. printer.

Images