JPH11297902A - Flip chip mounting body and method for under-filling it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an under-filling method by which the space between the IC chip and substrate of a flip flop mounting body can be filled with a resin solution for sealing even when the substrate has no through hole for air vent. SOLUTION: A resin solution 11 for sealing is applied to the peripheral area of a flip chip mounting body 1 on the upper surface of a substrate 3 by the stencil printing, etc., in a vacuum atmosphere. Then, the space 12 formed between an IC chip 2 and the substrate 3 is filled up with the resin solution 11 by lowering the degree of vacuum of the vacuum atmosphere or returning the vacuum atmosphere to a normal atmospheric atmosphere. In other words, the space 12 is filled up with the solution 11 by utilizing a differential pressure. When the space 12 is filled up with the solution 11, the air remaining in the space 12 is pushed out and confined in a non-through hole 13 made into the substrate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a flip chip package and an underfill method thereof.

[0002]

2. Description of the Related Art Conventionally, in a flip-chip mounting body in which an IC chip is aligned with a substrate face-down and then bonded, a substrate and an IC chip are firmly fixed, and the substrate and the IC are fixed. A gap formed between the IC chip and the substrate to prevent thermal stress generated due to the mismatch of the linear expansions of the chip from concentrating on the joint and inducing a crack easily. Is filled with a sealing resin liquid, that is, underfill is performed, and various underfill methods have already been proposed.

[0003] For example, JP-A-8-241900,
JP-A-7-130794 and JP-A-9-1720
In Japanese Patent No. 35, a so-called decompression method is used in which a gap formed between an IC chip and a substrate is depressurized to suck and fill the sealing resin liquid supplied to the side of the IC chip into the gap. Type differential pressure filling has been proposed.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 8-2
In the reduced pressure differential pressure filling disclosed in Japanese Patent No. 41900, an encapsulating resin solution is applied to one area around the side of an IC chip under a normal atmospheric atmosphere, and then, while being heated in a container. By forcibly evacuating the air in the vessel to reduce the pressure, the sealing resin liquid
Since the gap is formed to fill the gap formed between the C chip and the substrate, a portion where the bumps of the IC chip are formed at a high density (see FIG. 2) and a central portion where the bumps are not formed (see FIG. 2). In other words, the filling state tends to be non-uniform, that is, the filling of the portion where the bumps are formed with high density is prioritized, and the filling amount in the central portion is insufficient or not filled. There was a disadvantage that uniformity was easily generated.

[0005] Further, in the pressure reducing type differential pressure filling disclosed in Japanese Patent Application Laid-Open Nos. 7-130794 and 9-172035, air is suctioned from a suction hole penetrated through an IC chip mounting portion of a substrate. By reducing the pressure in the gap between the IC chip and the substrate, the gap is filled with the stencil-printed sealing resin liquid over the entire area around the side of the IC chip under a normal atmosphere. A disadvantage that underfill non-uniformity is likely to occur similarly to the former depending on the control state of such intake, that is, in the case of excessive intake, excessive sealing resin liquid is transferred to the suction hole side. Insufficient amount of resin to be filled into the gap makes it difficult to seal with a sufficient amount,
On the contrary, in the case of under-suction, a sufficient amount of the sealing resin liquid stencil-printed on the substrate is not filled into the gap (from the side periphery of the IC chip). Therefore, even in this case, there is a disadvantage that it is difficult to seal with a sufficient amount.

[0006] Further, with recent high-density mounting of IC chips, further higher density of bump formation and further miniaturization of the gap formation (the gap between the substrate and the IC chip) are required. As a result, the filling time becomes longer, and the filling of the resin mixed with the filler becomes more difficult.

[0007] Therefore, by performing the differential pressure filling by increasing the pressure instead of performing the differential pressure filling by reducing the pressure as described above, it is possible to prevent the occurrence of non-uniformity of the underfill. It has been proposed in the prior application (Japanese Patent Application No. 10-44440) that it can be quickly filled. However, in this prior invention, when filling by differential pressure by pressurization, the gap between the IC chip and the substrate is reduced. Because of the so-called air vent, the through-holes are provided in the board, so it cannot be applied to flip-chip mountings that do not have such through-holes in the board. Had.

In view of the above drawbacks, the present invention has been intensively studied to solve the drawbacks. As a result, after applying a sealing resin liquid on a substrate in a vacuum atmosphere, the present invention discloses a method of applying a pressure higher than atmospheric pressure as in the prior application. By reducing the degree of vacuum in such a vacuum atmosphere or by making it a normal atmospheric pressure atmosphere and performing differential pressure filling without using a pressurized atmosphere, the substrate is not provided with a through hole for air release. The present inventors have found that the flip-chip mounted body can be favorably underfilled, and the present invention has been completed based on the finding.

[0009]

According to a first aspect of the present invention, there is provided an underfill method according to the present invention, wherein a sealing resin solution is filled in a gap formed between an IC chip of a flip-chip mounted body and a substrate. In the underfill method of filling the resin, the sealing resin liquid is mixed with the I under a vacuum atmosphere.
After applying over the entire area around the side of the C chip, differential pressure filling is performed by lowering the degree of vacuum in the vacuum atmosphere or changing the vacuum atmosphere to a normal atmospheric pressure atmosphere.

The application of the sealing resin liquid and the filling with the differential pressure are preferably performed a plurality of times, and the application of the sealing resin liquid is preferably performed by stencil printing. It is preferable that the substrate is provided with a non-through hole that is opened in a gap formed between the IC chip and the substrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, which is a longitudinal sectional view, a flip-chip mounted body 1 has an IC chip 2 positioned face-down on a substrate 3 and then bonded, that is, bonded. It is configured. Although not shown, a plurality of IC chips 2 are bonded in a predetermined pattern, and the IC chips 2 are formed by forming bumps 4 at a high density as shown in FIG. 2 which is a plan view. And a central portion 6 where no bump is formed.

Further, the flip chip mounting body 1 is supported by the horizontal stage 7, the stencil 8 is supported by the substrate 3, and the IC chip 2 is arranged in a resin reservoir 9 formed in the stencil 8. Have been. In addition, the upper surface of the stencil 8
It is located slightly above the upper end surface of the IC chip 2, but is not limited to this, and may be located at the same level as the upper end surface of the IC chip 2 or slightly above the upper end surface of the IC chip 2. Is selected as needed.

The stencil 8 has a resin reservoir 9 formed in a predetermined pattern corresponding to the mounting pattern of the IC chip 2, and the resin reservoir 9 is provided on the IC chip 2 as shown in FIG. It is provided in a shape similar to.

For this purpose, the stencil 8 is supported on the horizontal stage 7 with the resin reservoir 9 positioned at a predetermined position with respect to the IC chip 2, and a sealing resin solution 11 is provided on the upper surface of the stencil 8.
Is supplied and the squeegee (not shown) is moved, whereby the sealing resin liquid 11 can be pushed into the resin reservoir 9 and applied onto the substrate 2. At this time, the amount of resin applied is controlled to a predetermined value, which is determined by the squeegee speed and the size of the frontage of the resin reservoir 9.

Although this state is shown in FIG. 1, the stencil printing is performed in a vacuum chamber (not shown). That is, before the stencil printing, the inside of the vacuum chamber is, for example, 0.1 torr or more.
The degree of vacuum is maintained at about 2 torr, and when the sealing resin liquid 11 is supplied to the upper surface of the stencil 8 under this vacuum atmosphere, the squeegee moves to perform stencil printing.

The squeegee is reciprocated as required, and the squeegee moves in, for example, the direction shown in FIG.
When the sealing resin liquid 11 is supplied to the right end of the stencil 8, the stencil 8 moves from the right side to the left side by a predetermined stroke, and then moves from the left side to the right side.

The reason why the sealing resin liquid 11 is applied on the substrate 2 in a vacuum atmosphere is that it is advantageous to prevent the generation of voids. Is applied on the substrate 2 by stencil printing.
This is because it can be quickly applied over one surface.

Therefore, as shown in FIG. 1, the sealing resin liquid 11 can be applied to the substrate 3 over the entire area around the side of the IC chip 2. The sealing resin liquid 11 is not sufficiently filled in the minute gap 12 between the IC chip 2 and the substrate 3.

Then, as shown in FIG. 4, subsequently, the degree of vacuum of the vacuum atmosphere at the time of stencil printing is reduced, or the vacuum atmosphere is changed to a normal atmospheric pressure atmosphere, and differential pressure filling is performed. In addition, reducing the degree of vacuum in the vacuum atmosphere is, for example, 0.1 torr during stencil printing.
A vacuum atmosphere of about r to 2 torr is set to 10 torr to 50 torr.
What is necessary is just to control it to a vacuum atmosphere of about torr.

As a result, the sealing resin liquid 11 in the resin reservoir 9 shown in FIG. 1 is pressurized to a predetermined pressure, and as shown in FIG. It can be forcibly filled into the minute gap 12 (for example, 50 μm) formed between the substrate 2 and the substrate 3.

At this time, a small amount of air remaining there is extruded by the sealing resin liquid 11 which is pressurized from the entire area around the side of the IC chip 2 and filled in the minute gap 12, and A so-called void is formed by being collected and sealed in the central portion 6 of the chip 2. However, since the voids are kept in a vacuum atmosphere, they are very small, and the bumps 4 are not formed in the central portion 6. Therefore, the voids can be ignored in quality control of the underfill.

It is to be noted that air remains in the minute gap 12 because the vacuum atmosphere for applying the sealing resin liquid 11 is not a completely degassing atmosphere. This is because if the coating is applied on the substrate 2 over the entire area around the side, the air in the minute gap 12 is trapped therein.

Therefore, as shown in FIG. 2, the IC chip 2 has a bump-forming portion 5 where bumps 4 are formed at a high density and a central portion 6 where no bump is formed. Even if there is, both portions can be filled with the sealing resin liquid 11 uniformly, so that the occurrence of underfill non-uniformity can be almost completely prevented, and the filling time is greatly reduced. Thus, efficient production can be achieved.

The pressure in the differential pressure filling is set to a predetermined value in consideration of various conditions such as the type of the sealing resin liquid 11, the size of the gap 12, and the manner of forming the bumps 4. Also, the application of the sealing resin liquid 11 by the stencil printing method is suitable for mass production of components, and the resin liquid can be supplied around the IC chip 2 almost at the same time. There is an advantage that it is formed at the central position of the central portion 6 that is not formed (the central position of the IC chip 2).

As described above, the sealing resin liquid 11 is applied on the substrate 3 by stencil printing over the entire area around the side of the IC chip 2 in a vacuum atmosphere, and then the degree of vacuum in the vacuum atmosphere is reduced or Although the mode in which the vacuum atmosphere is set to the normal atmospheric pressure atmosphere and the differential pressure filling is performed has been described, in the present invention, unlike the above, the sealing resin liquid 11 is applied to the side periphery of the IC chip 2 under the vacuum atmosphere. May be applied on the substrate 3 using a dispenser (or a nozzle) over the entire region, and then the vacuum degree of the vacuum atmosphere may be reduced or the vacuum atmosphere may be changed to a normal atmospheric pressure atmosphere to perform differential pressure filling. .

Further, if necessary, the application of the sealing resin liquid 11 and the differential pressure filling may be performed a plurality of times. This is because, in one application and differential pressure filling, the resin liquid filling amount in the minute gap 12 may be insufficient. The sealing resin liquid 11 may be any liquid such as one containing a filler. Further, as shown in FIG. 4, the flip chip mounting portion of the substrate 3, that is, the IC chip 2 is bonded. A non-through hole 13 may be provided at the location where the hole is provided, more specifically, at the center portion 6.

By providing this non-through hole 13, I
The small gap 1 is pressed from the whole area around the side of the C chip 2.
A small amount of air remaining there is pushed out by the sealing resin liquid 11 filled into the inside 2, collected in the central portion 6 of the IC chip 2, and can be sealed in the non-through hole 13. It is. The non-through hole 13 is
A plurality may be provided as needed.

Therefore, according to the present invention, the sealing resin liquid 1
1 is applied on the substrate 3 over the entire area around the side of the IC chip 2 in a vacuum atmosphere, and then the degree of vacuum in the vacuum atmosphere is reduced, or the vacuum atmosphere is changed to a normal atmospheric pressure atmosphere, and the differential pressure is reduced. Based on the filling, it is possible to satisfactorily underfill even the flip-chip mounted body 1 in which the substrate is not provided with a so-called air vent through hole.

Further, since the sealing resin liquid 11 can be forcibly filled into the minute gap 12 formed between the IC chip 2 and the substrate 3 of the flip chip mounting body 1,
As shown in FIG. 2, even if the C chip 2 has a bump forming portion 5 where the bumps 4 are formed at a high density and a central portion 6 where no bumps are formed, The sealing resin liquid 11 can be uniformly filled, and the occurrence of underfill non-uniformity can be almost completely prevented, and can be filled in a short time.

In the present invention, the term "non-through hole" generally includes a hole called a blind via hole or a blind through hole, and the "substrate" includes a multilayer substrate (or a build-up substrate). Includes

[0031]

As described above, according to the present invention, it is possible to satisfactorily underfill even a flip-chip mounted body in which a so-called air vent through-hole is not provided in a substrate, and in addition to the underfill, The occurrence of non-uniformity can be prevented, and moreover, even the sealing resin mixed with the filler can be quickly filled, and the filling time can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a sealing resin liquid is stencil-printed in a vacuum atmosphere.

FIG. 2 is a plan view of an IC chip.

FIG. 3 is a plan view of FIG. 1;

FIG. 4 is a longitudinal sectional view showing a state in which the degree of vacuum in the vacuum atmosphere is reduced or the vacuum atmosphere is changed to a normal atmospheric pressure atmosphere and differential pressure filling is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 flip chip mounted body 2 IC chip 3 substrate 4 bump 7 horizontal stage 8 stencil 9 resin reservoir 11 sealing resin liquid 12 gap 13 non-through hole

Claims (5)

[Claims] 1. A flip chip mounted body, wherein a non-through hole is provided in the substrate to be opened in a gap formed between the IC chip and the substrate. 2. An underfill method for filling a gap formed between an IC chip and a substrate of a flip-chip mounted body with a sealing resin liquid, wherein the sealing resin liquid is applied to the IC chip under a vacuum atmosphere. An underfill method comprising: applying the pressure over the entire area around the side; and reducing the degree of vacuum in the vacuum atmosphere or setting the vacuum atmosphere to a normal atmospheric pressure atmosphere and performing differential pressure filling. 3. The underfill method according to claim 2, wherein the application and the differential pressure filling of the sealing resin liquid are performed a plurality of times. 4. The underfill method according to claim 2, wherein the sealing resin liquid is applied by stencil printing. 5. The underfill method according to claim 2, wherein the flip chip mounted body is the flip chip mounted body according to claim 1.