JP2005088528A - Screen printing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent dimensions of a ball-shaped electrode and a height-direction dimension from varying due to an air lock in the application of a paste-like substance by screen printing, when conductive paste 45 is applied to a surface of a circuit board 25 through an opening 27 of a screen 26 by a screen printing method and the ball-shaped electrode is formed by using surface tension by a reflow. <P>SOLUTION: A retaining recess 37 and a recess 38 for negative pressure are preformed in such a manner as to face a jointing surface 36 of a squeegee 30; the conductive paste 45 is supplied to the retaining recess 37 by a paste supply pipe 39; and the conductive paste 45 is pressurized by a pressure regulating pipe 40. Contrary to this, the recess 38 is decompressed by a pressure-reducing suction pipe 41. When the squeegee 30 is moved on the screen 26, the opening 27 is decompressed by the recess 38 which is brought into contact with the opening 27 in advance, and the conductive paste 45, which is retained in the retaining recess 37 in this state, is infilled into the opening 27. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a screen printing apparatus, and more particularly to a screen printing apparatus in which a squeegee is moved on a screen having an opening at a predetermined position, and a paste-like substance is applied to a work through the opening of the screen.

  Screen printing technology is widely applied in the manufacturing process of electronic circuit devices. In particular, with the miniaturization and high-density mounting of circuit boards, the need for high aspect ratio screen printing with high-viscosity pastes and the filling of fine areas by screen printing is increasing. Is required.

  For example, in a ball grid array (BGA) type semiconductor device package in which ball-shaped electrodes are mounted on one surface of a package covering a semiconductor chip in a matrix, the conductive balls as the external connection terminals are packaged. It is necessary to form on the outer surface. Conventionally, the following three types of methods are used for forming such conductive balls.

  In the first method, a conductive ball such as a solder ball formed in a spherical shape in advance is attached to a predetermined position of the package. In this case, flux or solder paste is applied in advance to a predetermined position of the package by screen printing. Then, the conductive ball is mounted by a ball mounter. Since the conductive balls are temporarily fixed to the outer surface of the package by the adhesive force of the flux or solder paste, if the conductive balls are gently guided into the reflow furnace after that, the conductive balls are formed into electrodes by melting the flux or the solder paste. It is fixed in a state of being connected to.

  Such a ball mount requires a dedicated ball mounter. However, due to the recent high-density mounting, the mounter for mounting the required small-diameter ball is very expensive, which causes the cost increase of the ball grid array package using the small-diameter conductive ball having a small diameter. It has become.

  Further, a structure shown in FIG. 7 has been proposed as a ball grid array that satisfies both the reliability of the temperature cycle and the low profile with a small size in the height direction. In this structure, the semiconductor chip 1 is mounted on the reinforcing plate 2 in a state opposite to the state shown in FIG. 7, and the electrodes of the semiconductor chip 1 and the electrodes of the reinforcing plate 2 are connected by the connecting wires 3 and sealed. It is sealed with the resin 4. Then, an electrode opening 5 is formed on the surface side of the reinforcing plate 2 for forming an external electrode, and a solder ball 6 is introduced into the opening 5.

  Such a ball mount method employs an electrode having a structure in which the conductive ball 6 is formed in the opening 5 of the reinforcing plate 2, and the mounting reliability of the conductive ball 6 to the external electrode opening 5 is improved. It is difficult to ensure the connection between the electrode of the semiconductor chip 1 and the conductive ball 6. In other words, the conductive ball 6 mounted on the opening 5 of the reinforcing plate 2 may not be correctly connected to the electrode of the semiconductor chip 1 at the reflow stage, which causes defective products.

  In the second method, electroplating with a large thickness is performed in advance at the position where the electrode is to be attached. Thereafter, the metal layer formed by plating is melted to form a ball by surface tension. However, plating with a large dimension in the thickness direction takes a long time, and in order to form a ball-shaped electrode of a desired size, it is necessary to perform plating for about 2 hours, for example. For this reason, there is a disadvantage that the time required for the process increases and the cost increases.

  The third method is the method shown in FIG. Here, a work such as a circuit board 11 is placed on the base 10, the screen 12 is overlaid thereon, and the conductive paste 15 is applied by the squeegee 14 held at the tip of the squeegee holder 13. The conductive paste 15 is applied to the surface of the circuit board 11 through the opening 16. That is, the conductive paste 15 is applied on the circuit board 11 by screen printing, and the applied conductive paste 15 is melted to form a ball by its surface tension.

  This third method is composed of two steps of printing the conductive paste 15 and melting (reflow) as shown in FIG. 8, and has higher productivity than the first and second methods. Thus, a printing machine and a reflow apparatus necessary for the process can be an inexpensive general-purpose apparatus. Therefore, a low-cost BGA (Ball Grid Array) package can be provided.

  However, as shown in FIGS. 8 and 9A, the high-aspect-ratio printing in which the dimension in the thickness direction of the screen with respect to the opening of the screen is large and the conductive paste 15 is printed in a hole having a small diameter and a bottom, as shown in FIGS. There is a problem that an air pocket 17 is formed at the bottom of the conductive paste 15 to be formed. When the air pool 17 is generated, the supply amount of the conductive paste 15 is reduced by an amount corresponding to the volume of the air pool 17. Therefore, if reflow is performed in such a state, the size of the partial ball-shaped electrode 18 corresponding to the volume of the air pool 17 is reduced as shown in FIG. 9B. That is, the sizes and heights of the ball-shaped electrodes 18 formed on the circuit board 11 are not uniform due to the presence of the air reservoir 17 and may cause a connection failure in some cases.

  In addition, as an example of the fine area filling printing of the high-viscosity paste material, in addition to the printing of the conductive paste 15 for forming the ball-shaped electrode as shown in FIG. 8 and FIG. There is a demand for printing a conductive paste in a via hole for connecting various formed wiring layers and filling an insulating resin paste in a hole connected to a via by plating. As for via hole filling, a technique is widely used in which a thermosetting resin or a photocurable resin is filled into a through hole by screen printing or the like, and then the resin is cured by heat, light, or a combination of heat and light. .

  However, with the downsizing of electronic equipment, the density of wiring layers of circuit boards to be used has increased, and the demand for small diameter vias has increased. According to the conventional printing technique, it is difficult to fill the paste without leaving air inside the small-diameter via. For example, in Japanese Patent Laid-Open No. 6-39998, residual air is obtained by vacuum suction from the bottom of the through hole. However, this method cannot be applied to bottomed holes.

  As a further example of the fine portion filling printing of the high-viscosity paste material, there is a demand for printing a sealing resin on an electronic component such as a semiconductor element mounted on a substrate (see FIG. 6). Regarding the sealing resin printing on the electronic component on the substrate, the resin filling of the lower surface of the flip-chip connected semiconductor element and the wire bonded wire becomes a technical problem. And as the solution, the method of removing residual air with a vacuum degassing apparatus after resin sealing printing, the vacuum printing method, etc. are used.

  The method using the vacuum deaerator takes time required for deaeration. Further, since the volume of residual air is not constant, the printed paste volume decreases non-uniformly, and there is a problem that the thickness of the sealing resin is not constant.

  On the other hand, the vacuum printing method is a method for solving the problem of the above-mentioned method by vacuum defoaming. However, as disclosed in Japanese Patent No. 3203345, the apparatus becomes larger and the price is increased. Since printing is performed in the printing medium, there is a problem that it is difficult to observe the printing status for setting printing conditions.

Japanese Patent Laid-Open No. 6-39998 Japanese Patent No. 3203345

  The subject of this invention is providing the screen printing apparatus which can apply | coat a paste-form substance on a workpiece | work with high precision.

  Another object of the present invention is to provide a screen printing apparatus capable of high aspect ratio printing of a high viscosity paste material.

  Still another object of the present invention is to provide a screen printing apparatus which can solve the problem of fine portion filling printing.

  Still another object of the present invention is to provide a screen printing apparatus that removes non-uniformity in the coating amount due to air remaining in a paste-like substance.

  Still another object of the present invention is to provide a screen printing apparatus in which a conductive paste for forming ball-shaped electrodes is uniformly applied on a workpiece.

  Still another object of the present invention is to provide a screen printing apparatus capable of uniformly and uniformly applying a sealing resin for sealing a semiconductor chip.

A main invention of the present application is a screen printing apparatus in which a squeegee is moved on a screen having an opening at a predetermined position, and a paste-like substance is applied to a work through the opening of the screen.
A concave portion for holding the paste-like substance at a portion in contact with the screen of the squeegee and a decompression means for decompressing the opening of the screen are provided, and the paste-like substance is removed from the recess after being decompressed by the decompression means. The present invention relates to a screen printing apparatus characterized by being supplied to the opening of the screen.

  Here, it is preferable that the recess of the squeegee holding the pasty substance includes a pressurizing unit, and the pasty substance supplied by the pressurizing unit is pressurized. Further, the means for reducing the opening of the screen of the squeegee is a recess provided in front of the recess for holding the paste-like substance in the traveling direction of the squeegee, and the inside is reduced by the suction means. Is preferred. Moreover, it is preferable that the recessed part which decompresses the opening part of the said screen is provided in the both sides of the stroke direction of the said squeegee with respect to the recessed part holding the said paste-like substance. Moreover, it is preferable that the thickness in the stroke direction of the partition wall between the concave portion for holding the paste-like substance of the squeegee and the concave portion for decompressing the opening of the screen is larger than the dimension in the stroke direction of the opening of the screen. . Further, it is preferable that the paste-like substance is a conductive paste, and the conductive paste is remelted to form a ball-shaped electrode. Moreover, it is preferable that the paste-like substance is a sealing resin and a semiconductor chip mounted on a substrate is sealed.

  A preferred embodiment of the present invention is for printing having a structure in which a plurality of recesses are provided in a portion on the tip side of a squeegee that is in contact with a printing surface of screen printing, and a paste-like substance to be printed in at least one of these recesses is supplied It is a squeegee. Here, it is preferable to have a pressure structure for extruding the paste-like substance supplied to the recess from the tip of the squeegee. In addition, it is preferable to provide a decompression structure in another recess adjacent to the recess to which the squeegee paste-like substance is supplied.

  According to the above-described aspect, uniform printing of the paste-like substance and internal residual voids can be achieved by making the opening of the screen negative before printing and supplying and printing the paste-like substance at a pressure higher than atmospheric pressure. Occurrence is reduced. In addition, since the pressurization and normal pressure of the paste-like substance are performed in a series of processes during printing, the generation of voids in the paste-like substance is reduced, and no special vacuum defoaming device is required, or vacuum defoaming is also possible. Work is unnecessary and productivity is improved.

  In the above-described aspect, since the paste-like substance is supplied from the concave portion inside the squeegee, the rolling phenomenon of the paste-like substance in front of the squeegee due to the movement operation of the squeegee does not occur. Accordingly, air can be prevented from being entrained in the paste-like substance due to the rolling phenomenon, and high-quality printing with less voids can be performed. Further, the above-described excellent operational effects can be obtained with a simple structure without using an apparatus such as a so-called vacuum printing apparatus that performs a vacuum on the printing stage or the entire printing apparatus.

  The main invention of the present application is provided with a recess for holding the paste-like substance at a portion of the squeegee in contact with the screen and a decompression means for decompressing the opening of the screen. It is what I did.

  Therefore, according to such a screen printing apparatus, the paste-like substance is supplied after being depressurized in advance by the depressurizing means, and for this reason, air pockets are generated inside the paste-like substance applied by printing. Is prevented. Accordingly, non-uniformity in the amount of the paste-like substance due to air accumulation is prevented, and high-precision printing is possible.

  The present invention will be described below with reference to embodiments shown in the drawings. 1 and 2 show an example of a screen printing apparatus according to the present embodiment. Here, a screen 26 is overlaid on a circuit board 25, and a paste-like substance is applied from an opening 27 of the screen 26. FIG. This is a screen printing apparatus.

  The screen 26 in which the opening 27 is formed at a predetermined position is stretched on the four sides by a frame body 28. Then, the squeegee 30 moving on the squeegee 30 is held in a concave portion below the squeegee holder 31. The circuit board 25 overlapped with the screen 26 is placed on the base plate 32 as shown in FIG. A spacer 33 is disposed on the peripheral edge of the circuit board 25 so that no gap is generated between the screen 26 and the base plate 32.

  A major feature of such a screen printing apparatus is the squeegee 30. FIG. 3 shows the squeegee 30 in the reverse manner, and a holding recess 37 is formed so as to open to the joint surface 36 that contacts the screen 26, and a stroke is formed with respect to the holding recess 37. Negative pressure recesses 38 are formed on both sides in the direction. Then, a paste supply pipe 39 for supplying the paste-like substance to the holding recess 37 and a pressure adjusting pipe 40 for applying pressure to the paste-like substance are connected as shown in FIG. On the other hand, as shown in FIG. 2, the negative pressure recess 38 is connected to a vacuum suction pipe 41 for making the inside of the negative pressure concave.

  Next, the printing operation of the conductive paste 45 by such a screen printing apparatus will be described with reference to FIG. When the printing squeegee 30 is moved from the position shown in FIG. 5A to the position shown in FIG. 5B, the opening 27 of the screen 26 communicates with the negative pressure recess 38. Accordingly, the opening 27 of the screen 26 has a pressure reduced to the same pressure as the pressure in the negative pressure recess 38.

  Thereafter, when the squeegee 30 is further moved from the position (c) to the position (d), the holding recess 37 is applied to the opening 27 of the screen 26 which is in a negative pressure, and the negative pressure of the opening 27 and the pressure adjusting tube 40 are applied. The conductive paste 45 is extruded by the differential pressure of the pressure of the conductive paste 45 applied by, and the conductive paste 45 flows into the opening 27 of the screen 26, and the opening 27 of the screen 26 is filled with the conductive paste 45. It is.

  As the squeegee 30 further moves to the left, as shown in (e) and (f), the above printing operation is sequentially performed on the openings 27 of the other screens 26, and all the openings 27 are moved. A conductive paste 45 is filled. Therefore, the conductive paste 45 is applied onto the circuit board 25 so as to correspond to the openings 27 of the screen 26 by gently lowering the circuit board 25 with respect to the screen 26 thereafter. Thereafter, when the circuit board 25 is guided to a reflow furnace, the conductive paste 45 is remelted and becomes spherical due to surface tension, and a ball-shaped electrode is formed on the circuit board 25.

  The squeegee 30 is formed with negative pressure recesses 38 on both sides in the stroke direction with respect to the holding recesses 37, that is, on both the left and right sides in FIGS. Therefore, the pressure reducing operation may be performed by the holding recess 38 in a position preceding the holding recess 37. Therefore, the conductive paste 45 is applied by both the leftward movement and the rightward movement of the squeegee 30.

  Further, the wall thickness of the partition wall in the stroke direction between the holding recess 37 and the negative pressure recess 38 of the squeegee 30, that is, in the left and right directions in FIGS. 2 and 5, is larger than the dimension in the same direction of the opening 27 of the screen 26. It needs to be set to a large value. When the partition between the holding recess 37 and the negative pressure recess 38 is smaller than the dimension of the opening 27 in the stroke direction, the holding recess 37 of the squeegee 30 and the negative pressure recess 38 are formed by the opening 27 of the screen 26. This is because the conductive paste 45 flows into the negative pressure recess 38 and the negative pressure recess 38 is blocked.

  Next, another embodiment will be described with reference to FIG. This embodiment is a screen printing apparatus for sealing the semiconductor chip 49 by applying a sealing resin 48 on the upper side of the semiconductor chip 49 mounted on the circuit board 25. The basic structure of the squeegee 30 is the same as that in the first embodiment.

  Electronic components such as a semiconductor chip 49 are mounted on the circuit board 25 in advance. Then, the electrodes of the semiconductor chip 49 and the electrodes of the circuit board 25 are connected in advance by connecting means. The circuit board 25 is overlapped with the screen 26 and the semiconductor chip 49 on the circuit board 25 is aligned with the opening 27 of the screen 26.

  In such a state, when the squeegee 30 is moved from the position shown in FIG. 5A to the position shown in FIG. 5B, the negative pressure recess 38 which is the negative pressure of the squeegee 30 covers the opening 27 of the screen 26. Thus, the opening 27 of the screen 26 has the same atmospheric pressure as the pressure in the negative pressure recess 38.

  Thereafter, when the squeegee 30 is further moved from the position (c) to the position (d), the squeegee 30 is applied to the holding recess 37 holding the sealing resin 48 in the opening 27 of the screen 26 in a negative pressure. The sealing resin 48 is extruded by the pressure difference between the pressure of the reduced opening 27 of the screen 26 and the pressure of the conductive paste 45 pressurized by the pressure adjusting tube 40, and sealed in the opening 27 of the screen 26. The stop resin 48 flows in, and the opening 27 of the screen 26 is filled with the sealing resin 48.

  By further moving the squeegee 30 in the traveling direction, the above-described printing operation to the other openings 27 of the screen 26 is continuously performed, whereby the sealing resin 48 is applied to all the openings 27 of the screen 26. Sealed. Accordingly, after the squeegee has moved completely to the left after that, the sealing resin 48 is covered on the circuit board 25 so that the sealing resin 48 covers the semiconductor chip 49 by gently separating the circuit board 25 from the screen 26 downward. 48 is applied. Therefore, after that, the sealing operation of the semiconductor chip 49 is performed by curing the sealing resin 48 with heat, light, or heat and light.

  Although the present invention has been described above with reference to the illustrated embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea of the present invention. For example, the above embodiment relates to the application of the conductive paste 45 or the sealing resin 48, but the present invention is widely applicable to the application of other various paste-like substances.

  The present invention is widely applicable to screen printing for applying paste-like substances with high accuracy, and is particularly suitable for high-precision printing of conductive pastes and sealing resins in the production of electronic circuit devices. Is done.

It is a principal part perspective view which shows the outline of a screen printing apparatus.

It is a principal part longitudinal cross-sectional view of the same screen printing apparatus.

It is a perspective view of the state which made the squeegee reverse.

It is the sectional view on the AA line in FIG.

It is process drawing which shows the printing operation of an electrically conductive paste.

It is process drawing which shows printing operation of sealing resin.

It is a longitudinal cross-sectional view of the BGA package provided with the pole-shaped electrode.

It is a longitudinal cross-sectional view which shows the printing operation | movement of the conventional electrically conductive paste.

It is a principal part longitudinal cross-sectional view which shows formation of the ball-shaped electrode by the conventional printing operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor chip, 2 ... Reinforcement board, 3 ... Connection wire, 4 ... Sealing resin, 5 ... Opening, 6 ... Solder ball, 10 ... Base, 11 ... Circuit board (workpiece) , 12 ... Screen, 13 ... Squeegee holder, 14 ... Squeegee, 15 ... Conductive paste, 16 ... Opening, 17 ... Air trap, 18 ... Ball electrode, 25 ... Circuit board, 26 Screen, 27 Opening, 28 Frame, 30 Squeegee, 31 Squeegee holder, 32 Base plate, 33 Spacer, 36 Joining surface, 37 Retaining recess, 38 ... Negative pressure recess, 39 ... Paste supply pipe, 40 ... Pressure adjusting pipe, 41 ... Vacuum suction pipe, 45 ... Conductive paste, 48 ... Sealing resin, 49 ... Semiconductor chip

Claims (7)

In a screen printing apparatus in which a squeegee is moved on a screen having an opening at a predetermined position, and a paste-like substance is applied to a work through the opening of the screen,
A concave portion for holding the paste-like substance at a portion in contact with the screen of the squeegee and a decompression means for decompressing the opening of the screen are provided, and the paste-like substance is removed from the recess after being decompressed by the decompression means. A screen printing apparatus, characterized by being supplied to the opening of the screen.   2. The screen printing apparatus according to claim 1, wherein the recess of the squeegee holding the paste-like substance includes a pressurizing unit, and pressurizes the paste-like substance supplied by the pressurizing unit.   The means for decompressing the opening of the screen of the squeegee is a recess provided in front of the recess for holding the paste-like substance in the traveling direction of the squeegee, and the inside is decompressed by the suction means. The screen printing apparatus according to claim 1, wherein:   The screen printing apparatus according to claim 3, wherein recesses for decompressing the openings of the screen are provided on both sides in the stroke direction of the squeegee with respect to the recesses for holding the paste-like substance.   The thickness in the stroke direction of the partition wall between the concave portion for holding the paste-like substance of the squeegee and the concave portion for decompressing the opening of the screen is larger than the dimension in the stroke direction of the opening of the screen. The screen printing apparatus according to claim 3 or 4.   The screen printing apparatus according to claim 1, wherein the paste-like substance is a conductive paste, and the conductive paste is remelted to form a ball-shaped electrode. The screen printing apparatus according to claim 1, wherein the paste-like substance is a sealing resin and seals a semiconductor chip mounted on a substrate.

Images