JP2002141366A - Method for mounting conductive ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for aligning conductive balls in a prescribed array on a ball grid array base plate or the like. SOLUTION: A method for mounting the conductive ball comprises a first step of displacing and superposing perforated parts of an aligning mask 21 and a supply mask 21 having substantially the same arrays and same opening shapes, a second step of introducing the balls 1 into holes 23 of the aligning mask, and a third step of bringing the opening parts 23 and 24 of the masks 21 and 22 into coincidence and disposing the balls 1 in the prescribed array on the base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a conductive ball for forming a bump on an electrode of a ball grid array substrate, a semiconductor element, or a wafer on which the semiconductor element is disposed, and a method of mounting the conductive ball. It relates to a mounting device.

[0002]

2. Description of the Related Art FIGS.
This will be described with reference to FIG.

There are roughly two types of conductive ball mounting methods. The first is a method in which flux and conductive balls are separately supplied to electrodes on a substrate. The second method is to apply a flux to the conductive balls and then supply and mount the conductive balls together with the flux. FIG. 1 shows the former process flow, and FIG. 2 shows the latter process flow.

First, a method of separately supplying a flux and conductive balls will be described with reference to FIG.

[0005] First, there is a step of applying a flux on the electrodes of the substrate. There are many flux coating methods such as a pin transfer method, a screen printing method, and a dispensing method. Here, the pin transfer method will be described as a representative example with reference to FIG.

First, the flux 2 is squeezed on the flux tank 7 using a squeegee 8 to form a flux film having a constant thickness. Thereafter, the pin 9 is moved up and down, and the flux 2 is attached to the tip of the pin. Next, the pin 9 is moved onto the substrate, the electrode 4 on the substrate is aligned with the pin 9, and then moved up and down to transfer the flux 2 onto the electrode 4, completing the flux application. .

Second, there is a conductive ball alignment step in parallel with the flux application step. The conductive ball alignment step will be described with reference to FIG.

The conductive ball alignment is a process of using the mounting head 5 to vacuum-suck the conductive balls 1 in the same arrangement as the electrodes 4 of the substrate 3. The mounting head 5 has electrodes 4 on the substrate 3.
The suction holes 17 having the same arrangement as those described above are provided, and the inside of the mounting head is depressurized by the air suction means 11 to suck and suck the conductive balls in the conductive ball storage tank 6. At this time, the air flow path opening / closing means (suction side) 15 is open, and the air flow path opening / closing means (exhaust side) 16 is closed.

After the conductive balls are sucked and aligned, it is checked whether a specified number of balls are sucked to the mounting head. This method generally includes an image recognition method and a laser sensor method.

Finally, there is a conductive ball mounting step. The conductive ball mounting step will be described with reference to FIG.

The conductive ball mounting is a process of mounting the conductive ball 1 on the electrode 4 on the substrate 3 via the mounting head 5 on which the conductive ball 1 is sucked. After moving the position of the conductive ball 1 onto the electrode 4 of the substrate 3 while holding the conductive ball 1, the mounting head is opened to the atmosphere by the air flow generating means 12 so that the mounting head is aligned with the suction hole 17. The conductive ball 1 is cut off and mounted on the electrode 4. At this time, the air flow path opening / closing means (exhaust side) 16 is open, and the air flow path opening / closing means (suction side) 15 is closed.

After the balls are mounted, there is a mounting inspection step for inspecting whether or not the conductive balls on the substrate are mounted at a specified number and in a specified position by image recognition or the like. Here, if there is no abnormality, it is put into a reflow furnace and melt-bonded to form an external electrode.

Next, a method (FIG. 2) of supplying and mounting the conductive balls together with the flux after applying the flux to the conductive balls (FIG. 2) will be described with reference to an example of FIG.

This is a typical example of a ball transfer method. First, a flux 2 is squeezed on a flux tank 7 using a squeegee 8 to form a flux film having a constant thickness. Then, the flux 2 is applied to the conductive balls 1 by vertically moving the mounting head 5 in which the conductive balls 1 are aligned in a film shape. Next, while moving the position of the conductive ball 1 onto the substrate 3 while holding the conductive ball 1,
The conductive balls 1 are mounted together with the flux 2.

[0015]

In such a conductive ball mounting method, as the conductive balls are consumed during alignment of the conductive balls, as shown in FIG. The conductive ball 1 in the inside cannot be completely absorbed, and a ball defect occurs. If the number of the conductive balls in the conductive ball storage tank 6 is too large, a large number of the conductive balls 1 stick to the suction holes 17 as shown in FIG.

Further, when the conductive balls 1 in the storage tank are running low and new conductive balls are poured over the old conductive balls, the conductive ball storage tank 5 as shown in FIG. When the old conductive balls 18 accumulated in the bottom of the inside deteriorate and become aligned with the new conductive balls 19 and are mounted on the mounting head 5, it is determined that there is no ball in the subsequent mounting inspection process, and Will be excluded. Occurrence of these phenomena and inconveniences lowers the operation rate of the apparatus and causes a decrease in productivity.

Further, when the conductive balls are consumed and cannot be completely absorbed, at present, it is troublesome to discard the conductive balls in the conductive ball storage tank and replace them with new conductive balls. Is discarded, and as a result, there is a problem that the productivity is lowered and the cost is increased.

[0018]

According to the present invention, in order to solve the above-mentioned problems, the opening portions of the alignment mask and the supply mask having substantially the same arrangement and the same opening shape are shifted and overlapped. A first step, a second step of inserting conductive balls into the openings of the alignment mask, and matching the openings of the alignment mask and the supply mask with the conductive mask in a predetermined arrangement on the substrate. And a third step of arranging the conductive balls.

In another embodiment, the alignment mask has a ratio of an opening diameter to a conductive ball diameter of 1.1.
And the ratio of the thickness of the alignment mask to the diameter of the conductive ball is in the range of 1.1 to 1.47, and the supply mask further comprises: The ratio of the diameter of the opening to the diameter of the conductive ball is 1.1 to 1.
26. A method for mounting a conductive ball, the method comprising:

In another embodiment, the second step is a step of inserting the conductive ball into an opening of the alignment mask by a skinning operation. provide.

In another embodiment, the third step is to align the openings of the alignment mask with the supply mask and to arrange the conductive balls in a predetermined arrangement on the substrate. In addition, the present invention provides a method for mounting a conductive ball, characterized in that the material of the supply mask is made of a transparent portion, and the alignment inspection of the conductive ball is performed simultaneously from the lower surface of the supply mask using a sensor.

In another embodiment, a transparent material such as glass is used as the material of the supply mask so as to check the filling of the conductive balls into the openings of the alignment mask. A method and an apparatus for mounting a conductive ball, wherein alignment inspection is performed simultaneously with alignment of the conductive ball by a CCD camera.

As another embodiment, an air blow generating means and a moving means for the air blow are provided, and when the conductive balls are mounted on the electrodes of the substrate, the conductive balls remaining in the openings are removed by air blow. Provided are a method and an apparatus for mounting a conductive ball, characterized in that the conductive ball is forcibly separated by being sprayed more vertically.

Further, as another embodiment, a vibration generating means and a moving means therefor are provided, and when the conductive balls are mounted on the electrodes of the substrate, the conductive balls remaining in the openings are removed.
Provided is a method and apparatus for mounting a conductive ball, characterized in that the conductive ball is forcibly separated by being applied vertically from above a vibration mask.

Further, as another embodiment, as means for responding to the diversity of the arrangement pattern of the electrodes on the substrate, a supply mask provided with openings in a full grid arrangement is provided. A method and an apparatus for mounting a conductive ball, characterized in that it is possible to use a supply mask provided with an opening and to cope with a substrate of a new type by replacing only an alignment mask when coping with substrates having different electrode arrangements. provide.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

In this embodiment, as shown in FIG.
In a conductive ball mounting method in which a flux and conductive balls are separately supplied to the electrodes on the substrate, as shown in FIG. 10, the alignment mask 21 and the supply mask 22 are overlapped with each other. The conductive ball 1 filled between the squeegees 8 is dropped into the alignment mask opening 23 by squeezing. At this time, the alignment mask 21 is shifted from the supply mask 22 by half the pitch P of the openings. Thereafter, as shown in FIG. 11, the position of the supply mask opening 24 and the position of the electrode 4 of the substrate 3 are aligned, and then the alignment mask 21 is slid by ピ ッ チ pitch, so that the alignment mask 21 and the supply The openings of the mask 22 are connected to each other, and the conductive balls 1 in the mask opening 23 for alignment are cut off and mounted on the electrodes 1 of the substrate 3.

According to the above-described process, the conductive balls inserted first can be supplied first, so that it is possible to mount conductive balls of a certain quality. In addition, since it is forcibly replenished to the alignment mask opening by squeezing,
Even if the remaining amount of the conductive balls in the storage tank is low,
Since the conductive balls can be arranged, highly efficient consumption of the conductive balls in the storage tank can be realized.

At this time, the alignment between the opening of the supply mask and the electrode of the substrate is performed by image recognition using a CCD camera, and the alignment is performed by recognizing the mask position and the substrate position. However, the recognition method is not limited as long as the mask position and the substrate position can be recognized and alignment can be performed.

As a result, the ball can be mounted with a highly accurate mounting position of the conductive ball.

Here, the conductive balls are designed and manufactured so that the conductive balls are held one by one in all the openings of the alignment mask. Also in the supply mask, the conductive ball is designed and manufactured so as to be mounted so that the amount of displacement of the conductive ball falls within the process conditions.

FIG. 12 shows an example of a sectional view of the alignment mask 21 and the supply mask 22. The key points in the design are the opening diameter D1 of the alignment mask 21, the thickness T of the alignment mask 21, and the opening D2 of the supply mask 22, with respect to the diameter d of the conductive ball 1. is there.

First, FIG. 13 shows the relationship between the opening diameter (diameter) in the alignment mask and the number of balls in the opening. The horizontal axis indicates the ratio of the alignment mask opening diameter D1 / ball diameter d (hereinafter, referred to as D1 / d ratio), and the vertical axis indicates the number Bi of balls in the opening (the number of balls in all openings / the number of openings).

As shown in the figure, when the D1 / d ratio is 0.9 or less, there is no ball in the opening, and the ball sharply falls within the range of 0.9 to point A (D1 / d ratio 1.1). Rise to point A to point B
A specified number of balls exist in the opening within the range of the point (D1 / d ratio 1.65). In addition, an ascending curve is drawn again from the point B. In a range beyond the point B, an excessive number of conductive balls are present in the opening with respect to the specified number.

Therefore, the D1 / d ratio is determined by A to D in FIG.
The range between the points B (1.1 to 1.65) is in an appropriate range.

Next, FIG. 14 shows the relationship between the mask thickness in the alignment mask and the number of balls in the opening. The horizontal axis indicates the ratio of the alignment mask thickness T / ball diameter d (hereinafter referred to as the T / d ratio), and the horizontal axis indicates the number Bi of balls in the opening (the number of balls in all openings / the number of openings).

As shown in the figure, when the T / d ratio is 0.9 or less, no ball exists in the opening, and the ball sharply falls within the range of 0.9 to point C (T / d ratio 1.1). , And a specified number of balls exist in the range from the point C to the point D (T / d ratio 1.47). In addition, an ascending curve is drawn again from the point D. In the range above the point D, an excessive number of conductive balls are present in the opening with respect to the specified number.

Therefore, the T / d ratio can be determined by comparing C to D in FIG.
The appropriate range is between the points (1.1 to 1.47).

Third, FIG. 15 shows the relationship between the opening diameter (diameter) in the supply mask and the amount of ball displacement during mounting. The horizontal axis is the supply mask opening diameter D2 / ball diameter d.
(Hereinafter referred to as D2 / d ratio), and the vertical axis indicates the ratio of ball displacement R / ball radius r (hereinafter referred to as R / r ratio).

As shown, as the D2 / d ratio increases, the R / r ratio also increases. That is, the displacement of the ball becomes large. As a result, it comes into contact with the adjacent ball, and a defective external electrode is formed. There are certain conditions for the formation of the external electrodes to be established, and it is necessary to suppress the ball position shift amount within the conditions to be established. The supply mask opening diameter D2 must be as small as possible. However, if the supply mask opening diameter D2 is too small, the ball cannot be separated from the opening due to tolerance. The opening diameter for separating the ball is described in the appropriate range of the mask opening diameter for alignment.
The point E (D2 / d ratio 1.1) is obtained from the condition for aligning the prescribed number of balls in the opening. Further, the range in which the condition for establishing the ball position deviation amount is satisfied is determined by F
Up to the point (D2 / d ratio 1.26).

Accordingly, the D2 / d ratio is determined by the values of E to F in FIG.
The appropriate range is between the points (1.1 to 1.26).

By optimizing the shapes of the alignment mask and the supply mask as described above, it is possible to realize the ball mounting with a high number of conductive balls and the mounting position.

By applying the ball mounting method and apparatus of this embodiment, it is possible to reduce the production cost and mount the ball with high accuracy.

The object on which the balls are mounted may be a wafer instead of a substrate.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, when the conductive balls 1 are squeezed to align the conductive balls in the mounting of the conductive balls of the first embodiment, the alignment mask 21 is used for some reason.
This is a solution to the case where the conductive balls 1 are not filled and aligned in all the openings 23 of the first embodiment.

As shown in FIG. 16, when an unfilled portion is generated by one squeezing, the same area is squeezed a plurality of times to fill and align the conductive balls 1 in all openings. Can be.

Here, the number of times of squeezing may be repeated any number of times and is not limited.

Next, a third embodiment of the present invention will be described with reference to FIG.

This embodiment is an alignment inspection method after the conductive balls 1 are aligned in the alignment mask openings 23 in the conductive ball mounting of the first and second embodiments.

As shown in FIG. 17, the transparent supply mask 3 is formed.
By using the CCD camera 1, the presence or absence of the conductive ball 1 in the alignment mask opening 23 can be inspected by the CCD camera 32, similarly to the squeezing operation for aligning the conductive ball.

By adding this means to the first and second embodiments, a more accurate method and apparatus for supplying conductive balls can be realized.

Here, the material of the transparent supply mask is as follows:
There is no limitation as long as it is transparent.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the conductive ball 1 remaining in the alignment mask opening 23 or the supply mask opening 24 is forcibly cut off and mounted on the electrode 4 in the conductive ball mounting step. A method and apparatus for supplying a conductive ball to which means are added.

As a solution to this, a method shown in FIG. 18 is proposed.

In the conductive ball mounting method of the present embodiment, after the alignment mask 21 is slid, an air blow 42 is generated by the air blow generation means 41, and the alignment mask opening 23 and the supply mask are formed from above the alignment mask 21. The conductive ball remaining in the opening is forcibly cut off by spraying the mask onto the mask opening 24 in the vertical direction, and mounted on the electrode 4.

By adding this means to the first and second embodiments, a more accurate conductive ball supply method and apparatus can be realized.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the conductive balls 1 remaining in the alignment mask opening 23 or the supply mask opening 24 are forcibly cut off in the conductive ball mounting step, similarly to the fourth embodiment. 4 is a method and apparatus for supplying a conductive ball to which a solution to be mounted on the conductive ball is added.

As shown in FIG. 19, alignment mask 2
1 is slid, and the vibration 5
2 is generated, and the conductive balls remaining in the openings are forcibly cut off by spraying vertically from above the alignment mask 21 onto the alignment mask opening 23 and the supply mask opening 24, and onto the electrode 4. Mount.

By adding this means to the first and second embodiments, a more accurate method and apparatus for supplying conductive balls can be realized.

Next, a sixth embodiment of the present invention will be described with reference to FIG.

The present embodiment uses the method shown in FIG. 20 as a means for responding to the diversity of the arrangement pattern of the electrodes 4 on the substrate 3 in the conductive ball mounting of the first and second embodiments. suggest.

In the conductive ball mounting method of this embodiment, the supply mask 22 having openings in a full grid arrangement is provided.
On the other hand, the alignment mask 21 is provided with openings in the same arrangement as the electrodes 4 of the substrate 3, so that a new type of substrate can be handled by replacing only the alignment mask 21. Also, since the replacement jig is only the alignment mask 21, the investment required for the production of new varieties can be reduced.

The effects of the embodiment of the present invention will be summarized below.

As described above, after the alignment masks are overlapped, the conductive balls are squeezed thereon to fill the openings, and then the alignment masks are slid to provide the quality of the conductive balls to be supplied. Can be stabilized, and material can be first-in-first-out.

Further, since the conductive balls are forcibly filled into the openings by squeezing, the conductive balls can be efficiently consumed, and the production cost can be reduced.

Further, by designing and manufacturing the shape of the alignment mask within the optimum range, it is possible to realize high-precision ball mounting.

Further, by using a transparent material such as glass as the material of the supply mask, the presence or absence of conductive balls in the opening can be inspected from the lower surface of the supply mask in parallel with the alignment of the conductive balls. Therefore, the index can be reduced.

Further, when the conductive balls are mounted, the conductive balls remaining in the mask openings are forcibly cut off by air blow or vibration from the upper portion of the mask, so that more accurate ball mounting becomes possible.

Further, by using a supply mask provided with a full-grid opening and an alignment mask provided with openings of the same arrangement as the electrodes of the substrate, it is possible to cope with substrates having different electrode arrangements. By replacing only the alignment mask, a new type of substrate can be handled. Also, since the replacement jig is only the alignment mask, the investment required for the production of new varieties can be reduced.

[0073]

According to the present invention, by adopting the above structure,
After overlaying the alignment mask and squeezing the conductive balls onto the openings to fill the openings, the alignment mask is slid to stabilize the quality of the conductive balls to be supplied, and to first-in, first-out materials. Can be realized.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of a conductive ball mounting method for separately supplying a flux and conductive balls.

FIG. 2 is a process flow diagram of a conductive ball mounting method for supplying a flux through conductive balls.

FIG. 3 is a schematic cross-sectional view of a flux coating method using a pin transfer method.

FIG. 4 is a schematic cross-sectional view of a conductive ball suction method.

FIG. 5 is a schematic cross-sectional view of a conductive ball mounting method.

FIG. 6 is a schematic sectional view of a flux supply method using a ball transfer method.

FIG. 7 is a schematic cross-sectional view of a ball defect suction failure in a ball alignment step.

FIG. 8 is a schematic cross-sectional view of a ball excessive suction failure in a ball alignment step.

FIG. 9 is a schematic cross-sectional view of a defective ball suction failure in a ball alignment process.

FIG. 10 is a schematic sectional view of a method for aligning conductive balls according to the first embodiment.

FIG. 11 is a schematic cross-sectional view of a method for mounting a conductive ball according to the first embodiment.

FIG. 12 is a schematic cross-sectional view of an alignment mask and a supply mask.

FIG. 13 is a diagram showing the relationship between the alignment mask opening diameter and the number of balls in the opening.

FIG. 14 is a view showing the relationship between the thickness of an alignment mask and the number of balls in an opening.

FIG. 15 is a diagram showing a relationship between a supply mask opening diameter and a ball position shift amount.

FIG. 16 is a schematic sectional view of a method for aligning conductive balls according to a second embodiment.

FIG. 17 is a schematic cross-sectional view of the method for inspecting the alignment of balls in an opening in the third embodiment.

FIG. 18 is a diagram showing a means for separating conductive balls in an opening using an air blow according to the fourth embodiment.

FIG. 19 is a view showing a means for solving conductive ball separation in an opening using vibration according to the fifth embodiment.

FIG. 20 is a schematic cross-sectional view of a conductive ball mounting method corresponding to a variety of electrode arrangement patterns according to the sixth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conductive ball 2 ... Flux 3 ... Substrate 4 ... Electrode 5 ... Mounting head 6 ... Ball storage tank 7 ... Flux tank 8 ... Squeegee 9 ... Kenzan pin 10 ... Stage 11 ... Air suction means 12 ... Air flow disposal means 13 ... Air flow path (suction side) 14 ... Air flow path (discard side) 15 ... Air flow path opening / closing means (suction side) 16 ... Air flow path opening / closing means (disposal side) 17 ... Suction hole 18 ... Old conductive ball 21 ... Alignment mask 22 ... Supply mask 23 ... Alignment mask opening 24 ... Supply mask opening 31 ... Transparent supply mask 32 ... CCD camera 41 ... Air blow generating means 42 ... Air blow 51 ... Vibration generating means 52 ... Vibration

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuya Yamamoto 800 Yamano Isshiki-cho, Yokkaichi, Mie Prefecture F-term in Toshiba Yokkaichi Plant (reference)

Claims (4)

[Claims] 1. A first step in which opening portions of an alignment mask and a supply mask having substantially the same arrangement and the same opening shape are shifted and overlapped, and a conductive ball is provided in the opening of the alignment mask. And a third step of aligning the opening portions of the alignment mask and the supply mask and disposing the conductive balls in a predetermined arrangement on a substrate. Mounting method for conductive balls. 2. The alignment mask according to claim 1, wherein a ratio between an opening diameter of the alignment mask and a diameter of the conductive ball is in a range of 1.1 to 1.65. The supply mask has an opening shape having a ratio in the range of 1.1 to 1.47, and the supply mask has a ratio of the opening diameter to the diameter of the conductive ball in the range of 1.1 to 1.26. 2. The method according to claim 1, wherein the conductive ball is mounted. 3. The method of claim 1, wherein the second step is a step of inserting the conductive ball into an opening of the alignment mask by a skidding operation. 4. The method according to claim 3, wherein the aligning mask and the supply mask are aligned with each other in an opening portion, and when arranging the conductive balls in a predetermined arrangement on a substrate, the supply mask is formed. 2. The method for mounting conductive balls according to claim 1, wherein the material is formed of a transparent member, and the alignment inspection of the conductive balls is performed simultaneously from the lower surface of the supply mask using a sensor.