JP2009032722A - Method of mounting conductive ball and tool for attracting conductive ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of mounting conductive balls by an attraction head, which reliably mounts the balls on a warped substrate without the balls biting into an attraction hole to completely disturb the mounting of the balls on the substrate, even if the conductive balls have small diameters; and to provide an attracting tool of conductive balls used in such a method. <P>SOLUTION: In the conductive ball mounting method, the attraction head 30 having an attraction surface 32 with the attraction hole 31 that can attract the conductive balls 40 is prepared at a position corresponding to each pad 14b; the attraction surface 32 is allowed to turn upward; and the conductive balls 40 are attracted by the attraction hole 31. The attraction head 30 where the conductive balls 40 are attracted, and a substrate 10' that has the pad 14b coated with flux 18 and has the side of the pad 14b turned downward are approached, and gas is discharged out of the attraction hole 31 of the attraction head 30, thereby launching the conductive balls 40 upward and making them adhere to the flux 18 applied to the pad 14b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for mounting a conductive ball on a substrate. More specifically, the present invention relates to a conductive ball using adsorption on a pad for external connection provided on a substrate (for example, a wiring substrate, a package substrate, a wafer, etc.). And a conductive ball adsorption jig that can be used in such a method.

  As a method of forming solder bumps for connecting to other electronic components on pads formed on a substrate such as a wiring board or wafer, a conductive ball such as a solder ball is adsorbed to an adsorption head and mounted on the substrate There is.

  For example, in Patent Document 1, a container in which solder balls are put is used, and air is blown out from the bottom of the container to blow up the ball, or the container is shaken to float the ball, and is arranged above the container. A technique is described in which a ball is adsorbed by the adsorbing head, and then the adsorbing head is arranged above a substrate having a pad to which flux is attached, and the suction for adsorbing is stopped and a solder ball is mounted on the substrate.

  Further, in Patent Document 2, a mask is used, a ball is transferred to the suction jig through the mask while sucking from below, and then the mask is removed, and the ball is mounted from below onto the bump with the substrate flux attached thereto. It is described to do.

JP 2001-358451 A JP 2005-328017 A

  When using the upper suction head that picks up the ball that has been blown up or floated from below, and using the technique of mounting the solder ball on the board, the ball is held with a large suction force in order to hold the ball firmly on the head. It is necessary to adsorb. Since the ball is adsorbed in a suction hole having a smaller diameter than that of the head, in the case of a small ball such as 200 μm or less, or 100 μm or less, if the ball is adsorbed with a large suction force, the ball is adsorbed. It becomes easy to bite into the hole for use, and the problem arises that the bited ball is not mounted on the substrate. Furthermore, with a small ball, a plurality of balls are easily adsorbed in one suction hole. In this case, it is necessary to redo the ball adsorbing process or to add a process of removing an extra ball, thereby reducing productivity. It becomes easy to invite.

  When the ball is swung through the mask while sucking from below, and then the mask is removed and the ball is mounted on the substrate from below, the suction force can be reduced, thus avoiding the problem of the ball biting into the suction hole. In other words, a plurality of balls are not attracted to one suction hole. However, in the case of a warped substrate, it becomes difficult to mount all the balls on the substrate from the suction head, particularly when the ball diameter is reduced.

  The object of the present invention is to prevent the ball from biting into the suction hole even in the case of a conductive ball having a small diameter, and preventing the ball from being completely mounted on the substrate. An object is to provide a method for mounting a conductive ball by a suction head that can be reliably mounted, and a conductive ball suction jig used in such a method.

The conductive ball mounting method of the present invention is a method of mounting a conductive ball using a suction head on a substrate provided with a pad,
Preparing an adsorption head having an adsorption surface with an adsorption hole capable of adsorbing a conductive ball at a position corresponding to each pad, and adsorbing the conductive ball into the adsorption hole with the adsorption surface facing upward;
A step of bringing a suction head that sucks a conductive ball, and a substrate having a pad coated with a flux, with the pad side facing downward,
Discharging the conductive ball upward by ejecting gas from the suction hole of the suction head and attaching it to the flux applied to the pad;
It is characterized by mounting a conductive ball.

  Preferably, the suction pressure when sucking the conductive ball into the suction hole of the suction head is −0.1 to −50 kPa.

  When the conductive balls are sucked into the suction holes of the suction head, a mask having an opening corresponding to each suction hole and into which the conductive balls can enter can be used. Instead of using a mask, use a suction head equipped with a suction tool that also has a mask function and has a recess opened on the top surface at a position corresponding to each pad of the substrate and a suction hole opened on the bottom surface of this recess. May be.

  The conductive ball adsorption jig of the present invention has a concave portion opened on the upper surface of the jig at a position corresponding to each pad of the substrate on which the conductive ball is to be mounted, and an adsorption hole opened on the bottom surface of the concave portion. In addition, one conductive ball is accommodated in each recess, and the conductive ball is held by the suction hole by a suction action.

  The conductive ball adsorption jig of the present invention can be made of, for example, metal, silicon, or glass.

According to the conductive ball mounting method of the present invention, even in the case of a conductive ball having a small diameter, the suction head is used to prevent the ball from biting into the suction hole to prevent complete mounting of the ball on the substrate. In addition, the ball can be reliably mounted on a warped substrate.
Since the conductive ball adsorption jig of the present invention has the function of a mask, it can be used without the necessity of aligning the mask and the jig at the time of ball adsorption. It can also be handled as a single part, thus simplifying part management.

  In the present invention, the conductive balls adsorbed by the adsorption head are supplied by discharging from below toward the substrate arranged with the pad coated with the flux facing downward, and the conductive balls are attached to the flux to thereby form the substrate. Conductive balls are mounted on

  The substrate on which the conductive ball is mounted may be various substrates that are connected to an external circuit using bumps formed from the mounted conductive ball. Examples of such a substrate include a wiring substrate, a package substrate, and a wafer. The package substrate also includes a ball grid array (BGA) package and the like.

  The substrate has a pad formed in a predetermined pattern, and flux is applied to the upper surface of the pad. A flux corresponding to the type of conductive ball to be mounted is used.

  FIG. 1 shows an example of a substrate on which conductive balls are mounted according to the present invention. The substrate in this figure is manufactured as an aggregate of a plurality (three in this figure) of individual substrates 10 to be separated later. The individual substrate 10 is separated at a broken line indicated by A in FIG. Each individual substrate 10 has an upper wiring 12 a and a lower wiring 12 b formed on the upper surface and the lower surface of the core substrate 11, respectively, and the upper wiring 12 a and the lower wiring 12 b are connected by vias 13 penetrating the core substrate 11. . The upper wiring 12a and the lower wiring 12b include pads 14a and 14b for external connection as a part thereof. Except for the pads 14a and 14b, the upper wiring 12a and the lower wiring 12b are covered with solder resist layers 15a and 15b. According to the present invention, the flux 18 is applied to the surface of the lower wiring pad 14b on which the conductive ball 20 is mounted.

  In the present invention, conductive balls may be mounted on a single substrate corresponding to one individual substrate 10 in FIG.

  A representative example of the conductive ball mounted on the substrate is a solder ball. However, in the present invention, as other conductive balls, for example, a resin core material coated with a solder material can be used.

  Next, the mounting of the conductive ball on the substrate according to the present invention will be described with reference to the drawings. Here, an example will be described in which conductive balls are mounted on one side of a substrate on which wiring has been formed on both sides described above with reference to FIG. 1, but in the drawings referred to below, Only the wiring 12b formed on the mounting surface (lower surface), the pad 14b, the solder resist layer 15b, and the flux 18 on the pad 14b are shown, and the other members are not shown. Further, a single substrate 10 ′ corresponding to one individual substrate 10 described with reference to FIG. 1 is used as a substrate on which balls are mounted.

  As shown in FIG. 2A, a suction head 30 having a suction surface 32 with a suction hole 31 capable of sucking a conductive ball at a position corresponding to each pad of the substrate is prepared. The opening diameter of the suction hole 31 is smaller than the diameter of the conductive ball to be attracted to the suction hole 31 later (see FIG. 2B). The suction head 30 is constituted by a suction jig 34 having a suction hole 31 and a suction surface 32, and a porous member 35 connected to a suction source (not shown) such as a vacuum pump. The conductive ball can be sucked into the suction hole 31 by being sucked by the through suction source.

  As shown in FIG. 2B, a mask 37 having an opening 38 corresponding to the suction hole 31 is aligned, placed on the suction head 30, and conductive in the opening 38 of the mask 37. The sexual balls 40 are transferred, and are sucked and held in the suction holes 31. The conductive ball 40 can be transferred by dropping the ball from the top of the mask into each opening 38 using, for example, a squeegee or brush while sucking with a suction source (not shown), or swinging the ball on the mask. Alternatively, it can be performed by dropping into each opening 38 by vibration or the like. Suction is not performed when the conductive ball 40 is transferred, and suction can be started after the conductive ball 40 is transferred.

  Adsorption of the conductive ball is performed only to ensure that the position of the ball and the position of the opponent's pad coincide with each other, and it is not necessary to prevent the ball from falling as in the case where the adsorption surface of the adsorption head faces downward. Therefore, the suction pressure for that purpose may be small. For example, a suction pressure of the ball of about −0.1 to −50 kPa is sufficient.

  After the transfer of the conductive ball 40 is completed, the mask 37 is removed. Removal of the mask 37 is not essential, and it may not be removed in some cases. By leaving the mask on the suction head, the steps of aligning, arranging, and removing the mask become unnecessary when working continuously.

  After removing the mask 37, as shown in FIG. 2C, the substrate having the suction head 30 that sucks the conductive balls 40 and the pad 14b to which the flux 18 is applied, with the pad 14b facing downward. 10 'is aligned so that the flux 18 and the adsorption jig 34 do not come into contact with each other.

  Subsequently, the conductive ball 40 is discharged upward by ejecting gas (for example, air) from the suction hole 31 of the suction head 30, and the conductive ball 40 is fed to the flux 18 as shown in FIG. And is mounted on the substrate 10 '.

  In the present invention, a suction head using a suction jig that also functions as a mask can be used, and this aspect will be described next.

  An adsorption head 50 as shown in FIG. 3A is prepared, and the adsorption head 50 is positioned on a porous member 55 connected to a suction source (not shown) such as a vacuum pump, It is constituted by an adsorption jig 54 having an adsorption surface 52 with an adsorption hole 51 capable of adsorbing a conductive ball at a position corresponding to each pad of the substrate. The adsorption jig 54 has an upper surface 56 located above the adsorption surface 52, and the adsorption surface 52 is formed on the bottom surface of a recess 57 formed by digging from the upper surface 56 at a position corresponding to each pad of the substrate of the jig 54. The upper surface 56 corresponds to the upper surface of a normal mask. The concave portion 57 is formed to have an opening diameter that is about 10 to 30 μm larger than the diameter of the conductive ball to be transferred into the concave portion 57 and a depth that is about 50 to 140% of the diameter of the conductive ball, as in a normal mask. The The suction hole 51 is formed to have an opening having a diameter of about 10 to 80% of the diameter of the ball to be sucked, as in a normal suction jig. The jig 54 having such a structure can be easily manufactured from a material such as metal, silicon, and glass using an etching technique. Moreover, if this jig is used, the alignment between the jig and the mask, which is necessary when using a jig without a mask function, can be omitted.

  Next, as shown in FIG.3 (b), the conductive ball | bowl 60 is thrown into the recessed part 57 of the jig 54, and they are hold | maintained by adsorption | suction. The conductive ball 60 can be transferred as described above with reference to FIG.

  Subsequently, as shown in FIG. 3C, a suction head 50 that sucks the conductive ball 60, and a substrate 10 ′ having a pad 14b coated with the flux 18 and the pad 14b side facing downward. Are aligned so that the flux 18 and the adsorption jig 54 do not come into contact with each other. Next, the conductive ball 60 is discharged upward by ejecting gas (for example, air) from the suction hole 51 of the suction head 50, and the conductive ball 60 is fed to the flux 18 as shown in FIG. And is mounted on the substrate 10 '.

The following examples further illustrate the invention.
[Comparative Example 1]
Using a method in which a ball blown from below described in Patent Document 1 is adsorbed by an adsorption head on a wiring board provided with 3000 pads (applied with flux) having a diameter of 200 μm at a pitch of 200 μm. Sn / Ag solder balls were mounted. The hole diameter of the suction jig attached to the suction head was 60 μm, and the suction pressure for sucking the ball was −80 kPa. Four mounting experiments were performed, and the number of pads that could not be mounted due to the balls biting into the suction holes of the jig was examined.

[Example 1]
According to the present invention, the same experiment as in the comparative example was repeated except that the suction head with the suction surface facing upward was used and the sucked solder balls were discharged from below by air injection and mounted on the substrate. The mask used in Comparative Example 1 was used for sucking the ball onto the suction head. The hole diameter of the adsorption jig was 60 μm, the same as in the comparative example, but the suction pressure for adsorbing the ball was −10 kPa.

  The results of Comparative Example 1 and Example 1 are shown in Table 1.

  As is apparent from this result, according to the present invention, it is possible to prevent the small-diameter ball from getting into the suction hole and to reliably mount the ball on the substrate.

[Comparative Example 2]
A wiring board with a warp of 0.1 mm (a difference of 0.1 mm is observed when the height of the upper surface of the wiring board is horizontally arranged and observed) is disclosed in Patent Document 2. A test was performed under the same conditions as in Comparative Example 1 except that the ball adsorbed by the adsorption jig was mounted on the substrate from below by the described method, and the number of pads on which the ball could not be mounted was examined.

[Example 2]
Similarly, the procedure of Example 1 was repeated except that a wiring board having a warp of 0.1 mm was used, and the number of pads on which a ball could not be mounted was examined.

  The results of Comparative Example 2 and Example 2 are shown in Table 2. In the second experiment of Comparative Example 2, the number of unmounted pads was very large, so the experiment was stopped without checking the number.

  As is clear from this result, according to the present invention, the ball can be reliably mounted on the substrate even in the case of a wiring substrate having a large warp.

It is a schematic diagram explaining the example of the board | substrate which mounts an electroconductive ball. It is a figure explaining the example of mounting of the conductive ball to the board | substrate by this invention. It is a figure explaining another example of mounting of the conductive ball to the substrate by the present invention.

Explanation of symbols

10, 10 'substrate 11 core substrate 12a upper wiring 12b lower wiring 13 via 14a, 14b pad 15a, 15b solder resist layer 18 flux 20, 40, 60 conductive ball 30, 50 suction head 31, 51 suction hole 32, 52 suction Surface 34, 54 Adsorption jig 35, 55 Porous member 37 Mask 56 Upper surface (of adsorption jig)
57 recess

Claims (6)

A method of mounting a conductive ball using a suction head on a substrate having a pad,
Preparing an adsorption head having an adsorption surface with an adsorption hole capable of adsorbing a conductive ball at a position corresponding to each pad, and adsorbing the conductive ball into the adsorption hole with the adsorption surface facing upward;
A step of bringing a suction head that sucks a conductive ball, and a substrate having a pad coated with a flux, with the pad side facing downward,
Discharging the conductive ball upward by ejecting gas from the suction hole of the suction head and attaching it to the flux applied to the pad;
A conductive ball mounting method comprising mounting a conductive ball by the method described above.   The conductive ball mounting method according to claim 1, wherein a suction pressure when the conductive ball is sucked into the suction hole of the suction head is −0.1 to −50 kPa.   3. The conductive material according to claim 1, wherein when the conductive ball is sucked into the suction hole of the suction head, a mask having an opening corresponding to each suction hole and capable of containing the conductive ball is used. How to mount sex balls.   3. The conductive member according to claim 1, wherein the suction head includes a jig having a concave portion opened on an upper surface at a position corresponding to each pad of the substrate and a suction hole opened on a bottom surface of the concave portion. How to mount sex balls.   A concave portion opened on the upper surface of the jig at a position corresponding to each pad of the substrate on which the conductive ball is to be mounted, an adsorption hole opened on the bottom surface of the concave portion, and one conductive ball in each concave portion And the conductive ball is held by the suction hole by a suction action.   The conductive ball adsorption jig according to claim 5, which is made of metal, silicon or glass.

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