JP3243449B2 - Flip chip package and underfill method thereof - Google Patents

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. The disadvantage that underfill non-uniformity is likely to occur similarly to the former depending on the control state of the 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 the recent high-density mounting of IC chips, further higher density of bump formation and further miniaturization of the gap formation (spacing 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.

[0008] The present invention has been made in view of the above drawback, a result of intensive studies to solve it, after applying the sealing resin solution on a substrate in a vacuum atmosphere, prior application above atmospheric pressure as Instead of a pressurized atmosphere, reduce the degree of vacuum in such a vacuum atmosphere or make it a normal atmospheric pressure atmosphere and perform differential pressure filling to form a gap between the IC chip and the substrate.
The remaining air in the gap is
By enclosing in a through-hole, it was found that a flip-chip mounted body having no through-hole for bleeding air on the substrate could be favorably underfilled, and based on this point, the present invention could be completed. Things.

[0009]

Means for Solving the Problems That is, the underfill process according to the present invention, filling the sealing resin in the gap formed between the IC chip and the substrate of the flip chip mounting body
An underfill method in which the sealing resin is applied over the entire area around the side of the IC chip in a vacuum atmosphere, and then the degree of vacuum in the vacuum atmosphere is reduced or the vacuum atmosphere is reduced to a normal level. Underfill method that performs differential pressure filling even at atmospheric pressure
The residual air in the gap by the differential pressure filling,
It is located at the center of the IC chip surrounded by the bumps.
And the base is opened only to the gap.
It is characterized by being sealed in a non-through hole provided in a plate .

[0010] Incidentally, the coating and the differential pressure filling of the sealing resin solution is preferably carried out several times, also, the coating of the sealing resin solution is preferably carried out by stencil printing, further, the under
-The flip chip package to be filled is
At the center of the mounted IC chip surrounded by bumps
The non-through hole which is opened only for the formed clearance between the IC chip and the substrate to be positioned, which is provided with such a substrate is preferable.

[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, prior to the stencil printing, the inside of the vacuum chamber is, for example, 13.3 Pa-2.
The degree of vacuum is maintained at about 66 Pa. When the sealing resin 11 is supplied to the upper surface of the stencil 8 in 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. It is to be noted that decreasing the degree of vacuum in the vacuum atmosphere is performed, for example, in 13.3 Pa at the time of stencil printing.
A vacuum atmosphere of about 266 Pa to 1330 Pa to 6650
What is necessary is just to control it to a vacuum atmosphere of about Pa .

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.
The sealing resin liquid 11 to be filled into 2, the air traces remaining there in bump 4 groups of IC chip 2
It can be collected in the enclosed central part 6 and extruded therefrom and sealed in the non-through hole 13 . Note that a plurality of non-through holes 13 may be provided as necessary. As mentioned above
Thus, the residual air in the minute gap 12 is sealed in the non-through hole 13.
The sealing resin liquid 11 is filled
Formation of voids in the region of the minute gap 12
It can be completely prevented. Therefore, the non-through hole 13
This is more advantageous than the above-mentioned non-provided example.

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.

Further, by the differential pressure filling, the minute gap 1
The remaining air in 2 is transferred to a non-through hole provided in substrate 3
13, the sealing resin liquid 11 was filled.
Almost completely prevents voids from forming in the minute gap 12 region.
Can be prevented. In the present invention, “non-through hole” generally includes a hole called a blind via hole or a blind through hole, and “substrate” includes a multilayer substrate (or a build-up substrate). It is.

[0031]

As described above, according to the present invention, it is possible to satisfactorily underfill even a flip-chip mounted body having no so-called air vent through-hole in the substrate . That is, it is possible to prevent the occurrence of underfill non-uniformity and to quickly fill even the sealing resin mixed with the filler, thereby greatly shortening the filling time , and furthermore, Filled with resin solution
Formation of voids in the micro-gap area almost completely
Can be prevented.

[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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/28 H01L 21/56 H01L 21/60

Claims (4)

(57) [Claims] An IC chip mounted on a substrate and the substrate
Is not filled with the sealing resin.
In a flip-chip package, the IC chip
Flip chip mounting body, characterized in that is provided with a non-through hole in the substrate on which the is opened only for the gap to be positioned in a central portion surrounded by the pump group. 2. A underfilling method in the gap formed between the IC chip and the substrate of the flip chip mounting body Ru is filled with the sealing resin, the sealing resin, wherein a vacuum atmosphere After applying over the entire area around the side of the IC chip, in the underfill method of lowering the degree of vacuum of the vacuum atmosphere or changing the vacuum atmosphere to a normal atmospheric pressure atmosphere and performing differential pressure filling,
By filling, the remaining air in the gap is removed from the IC chip.
Located in the central portion surrounded by the bumps of the
Provided on the substrate so as to be opened only to the gap
An underfill method characterized by being sealed in a non-through hole . 3. The underfill method according to claim 2, wherein the application and the differential pressure filling of the sealing resin are performed a plurality of times. 4. The underfill method according to claim 2, wherein the sealing resin is applied by stencil printing.