JP2003100960A - Bga package mounting structure and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the connection reliability of a BGA package mounting structure with an IVH. SOLUTION: A seal resin 6 fills the gap between a mounting board 5 with an IVH 4 and a BGA package 3 connected through solder bumps 2 on the board 5 and a buffer frame 8 is disposed so as to surround the BGA package 3 for relaxing stresses in fillets 7 extruding out of the package 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a BGA (Ball Grid Array) via bumps on a mounting substrate.
The present invention relates to a BGA package mounting structure in which packages are connected and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a BGA package mounting structure in which a BGA package is connected to a mounting substrate via solder bumps, a BGA package is sealed between the mounting substrate and the BGA package in order to improve connection reliability against thermal shock. There is one in which a resin is filled so that the area around the solder bump is filled with the resin.

A BGA package mounting structure of this type is manufactured through the following steps, as described in, for example, Japanese Patent Laid-Open No. 10-74868. First, connect the BGA package to the mounting board via solder bumps, then B
The sealing resin is applied on the mounting substrate located in a part of the periphery of the GA package. Then, the sealing resin is spread and filled between the mounting substrate and the BGA package due to the capillary phenomenon. Then, the filled sealing resin is cured to complete the BGA package mounting structure.

In the BGA package mounting structure in which the sealing resin is filled between the mounting substrate and the BGA package as described above, the solder bumps are caused by the difference in the linear expansion coefficient of the constituent materials when an environmental temperature load is applied. The distortion caused by the above is alleviated by the sealing resin, and the entire BGA package mounting structure is bent together with the sealing resin, so that the stress caused by the difference in the linear expansion coefficient of the constituent materials is alleviated.

Further, in the case of the conventional BGA package mounting structure manufactured by the conventional manufacturing method, the surplus sealing resin remains around the BGA package at the portion where the sealing resin is applied on the mounting substrate, and the sealing is performed. Even in the area where the stop resin is not applied, the sealing resin spread by the capillary phenomenon protrudes around the BGA package and remains on the mounting substrate. Then, the extra sealing resin remaining around the BGA package is cured to form the fillet portion. This fillet part is mounted on the mounting board and the BG.
It is bonded to the upper surface of the mounting substrate integrally with the resin that is filled and cured between the A package and the A package.

[0006]

By the way, in the BGA package mounting structure, if the pin pitch of the BGA package becomes narrow, the connection will be limited only by using the lead-out from the terminal or using the surface layer or the through hole. There is a case in which a cylindrical member called IVH (Inner Via Hole) is installed in the wiring, and the wiring is pulled out to the lower side of the mounting substrate through the IVH. However, when a thermal shock test is performed on the BGA package mounting structure in which the sealing resin is filled between the mounting substrate and the BGA package and the IVH is provided, the IVH is distorted and accumulated, and the IVH is damaged. A new problem arose.

As a result of diligent research by the present applicant regarding this cause, it has been found that one of the causes for causing the IVH to be distorted is the presence of the fillet portion. To be more specific, when the thermal shock test was performed with various lengths of the portion of the fillet portion joined to the mounting board (hereinafter referred to as the leg length of the fillet portion), it was found that the longer leg length was shorter than the shorter one. Was also found to have poor thermal shock resistance to IVH and a short life. The reason is that the larger the area where the sealing resin and the mounting substrate are bonded is, the larger the stress generated in the IVH due to the difference in the linear expansion coefficient of the constituent materials when the environmental temperature load is applied. It is presumed that. Therefore, the present invention provides a BGA package mounting structure which is less likely to be damaged by bumps and IVHs and has high connection reliability, and a manufacturing method thereof.

[0008]

In order to solve the above-mentioned problems, the invention described in claim 1 has a structure in which a mounting substrate having an IVH and a BGA package connected to the mounting substrate via bumps are provided. In the BGA package mounting structure in which the sealing resin is filled in, the fillet portion of the sealing resin protruding to the outside of the BGA package is provided with a buffer for relaxing stress in the fillet portion.
The BGA package mounting structure is characterized by being installed so as to surround the GA package. With this configuration, when the environmental temperature load is applied, due to the difference in the linear expansion coefficient of the constituent materials, the force in the direction away from the fillet portion is applied to the mounting substrate located below the fillet portion. When applied, or when a force is applied to the mounting substrate located below the fillet portion in the direction of compressing the fillet portion, the stress generated in the fillet portion is relaxed by the buffer, and the stress generated in the IVH is reduced. Can be made smaller

According to a second aspect of the invention, in the first aspect of the invention, the buffer body is made of a material that is softer and more elastic than the sealing resin. With this configuration, when the environmental temperature load is applied, due to the difference in the linear expansion coefficient of the constituent materials, the force in the direction away from the fillet portion is applied to the mounting substrate located below the fillet portion. When applied, or when a force is applied to the mounting substrate located below the fillet portion in the direction to compress the fillet portion, the stress generated in the fillet portion is relaxed by elastic deformation of the cushioning body, IVH
It is possible to reduce the stress generated in the.

According to a third aspect of the present invention, in the first or second aspect of the invention, the buffer body is formed in an annular frame shape, and the bottom of the buffer body is placed on the mounting substrate. It is characterized in that they are brought into contact with each other and arranged in a substantially upright posture with respect to the mounting board. With this configuration, the fillet portion located outside the cushioning body is
It can be separated from the sealing resin filling the lower side of the A package, and the force is directly transmitted from the fillet portion located outside the buffer to the sealing resin filling the lower side of the BGA package. Can be prevented.

According to a fourth aspect of the present invention, in the third aspect of the invention, one of the inner surface and the outer surface of the shock absorber is separable from the fillet portion. . With this configuration, when the environmental temperature load is applied, due to the difference in the linear expansion coefficient of the constituent materials, the force in the direction away from the fillet portion is applied to the mounting substrate located below the fillet portion. When applied, one surface of the cushioning body is separated from the fillet portion, stress is hardly generated in the fillet portion and the sealing resin located inside the cushioning body, and the stress generated in IVH is extremely small.

According to a fifth aspect of the present invention, in the invention according to the third aspect, the buffer body has a double frame structure in which an annular inner frame and an outer frame are superposed, and the buffer body is provided near the bottom portion of the buffer body. The inner frame and the outer frame are openably and closably connected. With this configuration, when the environmental temperature load is applied, due to the difference in the linear expansion coefficient of the constituent materials, the force in the direction away from the fillet portion is applied to the mounting substrate located below the fillet portion. When applied, the outer frame of the cushioning body opens outward and separates from the inner frame, and almost no stress is generated in the fillet portion and the sealing resin located inside the inner frame of the cushioning body, and the stress generated in the IVH is reduced. It becomes extremely small.

According to a sixth aspect of the present invention, the step of connecting the BGA package to the mounting substrate having the IVH via bumps, and the sealing resin is filled between the mounting substrate and the BGA package. BGA comprising: a step, and a step of inserting and attaching a frame-shaped buffer body to the protruding sealing resin before the sealing resin protruding outside the BGA package is cured.
It is a method of manufacturing a package mounting structure. With this configuration, it is possible to easily manufacture the BGA package mounting structure according to any one of claims 1 to 5 in which the fillet portion is provided with the buffer body.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings of FIGS. [First Embodiment] First, a first embodiment of the present invention will be described with reference to the drawings of FIGS. FIG. 1 is a BGA package mounting structure 1 according to the first embodiment.
It is sectional drawing of A. This BGA package mounting structure 1A
Is a BG made of an LSI or the like having solder bumps 2 on the lower surface.
A package 3 and IVH4 made of, for example, a copper cylinder
A mounting substrate 5 having an upper part, a sealing resin 6 filled between the BGA package 3 and the mounting substrate 5 and cured,
A fillet portion 7 formed of the same material as the sealing resin 6 formed around the GA package 3, and a buffer frame (buffer body) 8 installed in the fillet portion 7 so as to surround the outside of the BGA package 3. Is equipped with.

The IVH 4 of the mounting board 5 is arranged directly under the solder bumps 2 of the BGA package 3, and both are electrically connected. The solder bumps 2 are, for example, Pb and S
The mounting board 5 is composed of eutectic solder having an n ratio of 37:63.
Is made of, for example, a glass epoxy substrate, and the sealing resin 6 is made of, for example, silica-containing epoxy resin.

The fillet portion 7 is the same as the fillet portion formed in the manufacturing process of the conventional BGA package mounting structure. As will be described later, the sealing resin 10 before curing is applied to the BGA package 3 and the mounting substrate 5. The initial application portion of the sealing resin 10 and the sealing resin 1 when filled between
0 is formed by curing the portion protruding outside the periphery of the BGA package 3.

As shown in FIG. 4, the buffer frame 8 has a rectangular annular frame shape having upper and lower openings, and is made of a material that is softer and more elastic than the sealing resin 6. The cushion frame 8 is installed in a posture in which the bottom portion of the cushion frame 8 abuts on the upper surface 5a of the mounting substrate 5 and stands upright with respect to the mounting substrate 5, and the top portion of the cushion frame 8 slightly projects from the fillet portion 7. The inner size of the buffer frame 8 is set to be substantially the same as or slightly larger than the outer size of the BGA package 3 (for example, about 5% larger than the BGA package 3). The inner surface and the outer surface of the buffer frame 8 installed in the fillet portion 7 are joined to the fillet portion 7. In this embodiment, since the bottom of the buffer frame 8 is in contact with the mounting substrate 5, the fillet portion 7 located outside the buffer frame 8 is filled with the sealing resin 6 below the BGA package 3. From the fillet portion 7 that is located outside the buffer frame 8 and is filled in the lower side of the BGA package 3.
It is possible to prevent the force from being directly transmitted to.

Next, this BGA package mounting structure 1A
The manufacturing method of will be described with reference to FIGS. [First Step] First, the IVH 4 of the mounting board 5 and the solder bumps 2 of the BGA package 3 are connected to each other and B is mounted on the mounting board 5.
Install the GA package 3.

[Second Step] Next, as shown in FIG.
The sealing resin 10 before curing is applied on the mounting substrate 5 on one side of the GA package 3 along the outer edge of the BGA package 3, and the sealing resin 10 before curing is mounted on the BGA package 3 with its surface tension. It is filled between the substrate 5 and the substrate 5. The uncured encapsulating resin 10 that has spread between the BGA package 3 and the mounting substrate 5 protrudes from the other side of the BGA package 3 onto the mounting substrate 5, but this protrusion size is a predetermined value. The filling of the sealing resin 10 is completed so as to be within the range.

[Third Step] Next, as shown in FIG. 3, before the encapsulating resin 10 is cured, the buffer frame 8 is provided on the BGA package 3 and the encapsulating resin for the fillet portion 7 is formed. The bottom portion of the buffer frame 8 is abutted against the upper surface 5a of the mounting substrate 5 as it is inserted into the mounting frame 10.

[Fourth Step] After this, the filled sealing resin 1
By curing 0, a cured sealing resin 6 is formed between the BGA package 3 and the mounting substrate 5, and a fillet portion 7 is formed on the entire outer periphery of the BGA package 3 to surround the BGA package 3. Thus, the buffer frame 8 is fixed upright in the fillet portion 7. Then, when the filled sealing resin 10 cures, the inner surface and the outer surface of the buffer frame 8 are joined to the fillet portion 7. As described above, the BGA package mounting structure 1A of the form shown in FIG.
Can be manufactured.

In the BGA package mounting structure 1A thus configured, the mounting substrate located below the fillet portion 7 due to the difference in the linear expansion coefficient of the constituent materials when an environmental temperature load is applied, for example. Fillet part 5
When a force is applied in a direction away from (i.e., the X direction in FIG. 1), the fillet portion 7 is pulled by the mounting substrate 5, and thus the pulling force acts on the buffer frame 8. Since it is softer than the portion 7, it elastically deforms and swells, whereby the stress generated in the fillet portion 7 and the sealing resin 6 located inside the buffer frame 8 is relaxed, and the stress generated in the IVH 4 is reduced.

On the other hand, the direction in which the fillet portion 7 is compressed to the mounting substrate 5 located below the fillet portion 7 (that is,
When a force in the Y direction in FIG. 1 is applied, the compressing force acts on the buffer frame 8 because the fillet portion 7 is pressed, but the buffer frame 8 is softer than the fillet portion 7 and is elastically deformed. By being compressed, the stress generated in the fillet portion 7 and the sealing resin 6 located inside the buffer frame 8 is relaxed, and the stress generated in the IVH 4 is reduced.
Therefore, when force is applied in either direction, IV
H4 is less likely to be damaged, and BGA package mounting structure 1
The connection reliability of B is improved and the life is extended.

The BGA package mounting structure 1A
Also in the above, since the sealing resin 6 is present between the mounting substrate 5 and the BGA package 3, the solder bumps 2 are less likely to be damaged, the connection reliability of the BGA package mounting structure 1A is improved, and the life is extended. Of course.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to the drawings of FIGS. 5 and 6. BGA package mounting structure 1 of the second embodiment
B is the BGA package mounting structure 1A of the first embodiment.
The only difference is that the outer surface of the buffer frame 8 is not joined to the fillet portion 7. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

In this BGA package mounting structure 1B, in the third step of the method of manufacturing the BGA package mounting structure 1A of the first embodiment, a release agent is applied to the entire outer surface of the buffer frame 8 in advance, and Can be manufactured by inserting into the portion of the sealing resin 10 where the fillet portion 7 is formed before the sealing resin 10 is cured.

In the BGA package mounting structure 1B thus configured, the mounting substrate located below the fillet portion 7 due to the difference in the linear expansion coefficient of the constituent materials when an environmental temperature load is applied, for example. Fillet part 5
When a force is applied in a direction away from the buffer frame (that is, the X direction in FIG. 5), the fillet portion 7 located outside the buffer frame 8 is separated from the buffer frame 8 as shown in FIG. Almost no stress is generated in the fillet portion 7 and the sealing resin 6 located inside the buffer frame 8, and the IVH
Almost no stress is generated in 4.

On the other hand, the direction in which the fillet portion 7 is compressed to the mounting substrate 5 located below the fillet portion 7 (that is,
When a force in the Y direction in FIG. 5 is applied, it is the same as in the case of the first embodiment. That is, since the fillet portion 7 is pressed, a compressive force acts on the buffer frame 8. However, since the buffer frame 8 is softer than the fillet portion 7, it is elastically deformed and compressed, whereby the buffer frame 8 is placed inside the buffer frame 8. The stress generated in the positioned fillet portion 7 and the sealing resin 6 is relaxed, and the stress generated in IVH 4 is reduced.

Therefore, when the force is applied in any direction, the IVH 4 is less likely to be damaged, the connection reliability of the BGA package mounting structure 1B is improved, and the life is extended.
In this example, a release agent is applied to the outer surface of the buffer frame 8,
Although the outer surface can be separated from the fillet portion 7, the same effect as described above can be obtained even when the inner surface of the buffer frame 8 is coated with a release agent so that the inner surface can be separated from the fillet portion 7.

[Third Embodiment] Next, a third embodiment of the present invention will be described with reference to the drawings of FIGS. 7 to 10. BGA package mounting structure 1 of the third embodiment
C is the BGA package mounting structure 1A of the first embodiment
The only difference is that the buffer frame 8 has a double frame structure. More specifically, the buffer frame 8 has the same structure as that shown in FIGS.
As shown in 0, the inner frame 8a and the outer frame 8b are configured to be overlapped with each other, and the inner frame 8a and the outer frame 8b are joined to each other with an adhesive 9 around the lower ends thereof over the entire circumference. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

The BGA package mounting structure 1C can be manufactured by the same manufacturing method as the manufacturing method of the BGA package mounting structure 1A of the first embodiment.
Since the inner frame 8a and the outer frame 8b are joined to each other in the vicinity of their lower ends over the entire circumference, the buffer frame 8 is sealed with the sealing resin 1 before being cured.
The sealing resin 10 does not enter between the inner frame 8a and the outer frame 8b when it is inserted into 0.

In the BGA package mounting structure 1C thus configured, the mounting substrate located below the fillet portion 7 due to the difference in the linear expansion coefficient of the constituent materials when an environmental temperature load is applied, for example. Fillet part 5
When a force is applied in the direction away from the inner frame 8 (that is, the X direction in FIG. 7), the outer frame 8b of the buffer frame 8 is separated from the inner frame 8a as shown in FIG. Almost no stress is generated in the fillet portion 7 and the sealing resin 6 located inside, and almost no stress is generated in the IVH 4.

On the other hand, the direction in which the fillet portion 7 is compressed to the mounting substrate 5 located below the fillet portion 7 (that is,
When a force in the Y direction in FIG. 7 is applied, it is the same as in the case of the first embodiment. That is, since the fillet portion 7 is pressed, the inner frame 8a and the outer frame 8b are superposed and a compressive force acts on the buffer frame 8. However, since the buffer frame 8 is softer than the fillet portion 7, it is elastically deformed and compressed. As a result, the stress generated in the fillet portion 7 and the sealing resin 6 located inside the inner frame 8a is relaxed, and the stress generated in the IVH 4 is reduced. Therefore, the IVH4 is less likely to be damaged when a force is applied in any direction,
The connection reliability of the A package mounting structure 1B is improved and the life is extended.

The present invention is not limited to the above embodiment. For example, in the above-described respective embodiments, the bottom portion of the buffer frame 8 is brought into contact with the upper surface 5a of the mounting substrate 5, but the bottom portion of the buffer frame 8 may be slightly floating above the upper surface 5a of the mounting substrate 5. The mounting substrate 5 may be made of a resin other than glass epoxy, and the sealing resin 6 may be made of a resin other than silica-containing epoxy resin. Further, it goes without saying that the BGA package 3 does not have to be a square in plan view. Further, the material and thickness of the buffer frame 8 can be selected as appropriate.

[0035]

As described above, according to the first aspect of the present invention, the stress generated in the fillet portion is relieved by the buffer and the stress generated in the IVH can be reduced, so that the IVH is damaged. It becomes difficult, the connection reliability of the BGA package mounting structure is improved, and the excellent effect of extending the life is exhibited.

According to the second aspect of the invention, the stress generated in the fillet portion is relaxed by the elastic deformation of the buffer body, and the stress generated in the IVH can be reduced, so that the IVH is less likely to be damaged. , The connection reliability of the BGA package mounting structure is improved and the life is extended.

According to the third aspect of the present invention, it is possible to prevent the force from being directly transmitted from the fillet portion located outside the cushioning body to the sealing resin filling the lower side of the BGA package. Therefore, the stress generated in the IVH can be reduced, the IVH is less likely to be damaged, and the connection reliability of the BGA package mounting structure is improved.
The excellent effect of extending the life is exhibited.

According to the invention described in claim 4, when one surface of the cushioning body is separated from the fillet portion, stress hardly occurs in the fillet portion and the sealing resin located inside the cushioning body, and the IVH Since the stress generated in the IC is extremely small, the IVH is less likely to be damaged, the connection reliability of the BGA package mounting structure is improved, and the life is extended, which is an excellent effect.

According to the fifth aspect of the present invention, when the outer frame of the shock absorber is opened outward and separated from the inner frame, stress is applied to the fillet portion and the sealing resin located inside the inner frame of the shock absorber. Hardly occurs, and the stress generated in IVH becomes extremely small, so that IVH is less likely to be damaged, and B
The excellent effect that the connection reliability of the GA package mounting structure is improved and the life is extended is exhibited.

According to the invention described in claim 6, there is an excellent effect that the BGA package mounting structure according to any one of claims 1 to 5 in which the fillet portion is provided with a buffer can be easily manufactured. To be done.

[Brief description of drawings]

FIG. 1 is a sectional view of a BGA package mounting structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the method of manufacturing the BGA package mounting structure according to the first embodiment.

FIG. 3 is a cross-sectional view for explaining the method of manufacturing the BGA package mounting structure according to the first embodiment.

FIG. 4 is a perspective view of a buffer frame (buffer body) used in the BGA package mounting structure according to the first embodiment.

FIG. 5 is a sectional view of a BGA package mounting structure according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view for explaining the operation of the BGA package mounting structure according to the second embodiment.

FIG. 7 is a sectional view of a BGA package mounting structure according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating the operation of the BGA package mounting structure according to the third embodiment.

FIG. 9 is a perspective view of a buffer frame (buffer body) used in the BGA package mounting structure according to the third embodiment.

FIG. 10 is a cross-sectional view of a buffer frame (buffer body) used in the BGA package mounting structure according to the third embodiment.

[Explanation of symbols]

1A, 1B, 1C BGA package mounting structure 2 Solder bump 3 BGA package 4 IVH 5 mounting board 6 Sealing resin (after curing) 7 Fillet part 8 Buffer frame (buffer) 10 Sealing resin (before curing)

Claims (6)

[Claims] 1. A BGA package mounting structure in which a sealing resin is filled between a mounting substrate provided with IVH and a BGA package connected to the mounting substrate via bumps, the BGA package mounting structure comprising: A BGA package mounting structure in which a fillet portion of the encapsulating resin protruding outside is provided with a cushioning body that relieves stress in the fillet portion so as to surround the BGA package. 2. The BGA package mounting structure according to claim 1, wherein the buffer body is made of a material that is softer and more elastic than the sealing resin. 3. The buffer body is formed in an annular frame shape, and is arranged in a substantially upright posture with respect to the mounting board with the bottom portion of the buffer body abutting on the mounting board. The BGA package mounting structure according to claim 1 or 2. 4. The BGA package mounting structure according to claim 3, wherein either one of the inner surface and the outer surface of the buffer body is separable from the fillet portion. 5. The buffer body has a double frame structure in which an annular inner frame and an outer frame are overlapped with each other, and the inner frame and the outer frame are openably and closably connected in the vicinity of a bottom portion of the buffer body. The BGA package mounting structure according to claim 3, which is characterized in that. 6. A step of connecting a BGA package on a mounting board having IVH via bumps, a step of filling a sealing resin between the mounting board and the BGA package, and And a step of inserting a frame-shaped cushioning body into the protruding sealing resin before hardening the sealing resin protruding outside, and manufacturing the BGA package mounting structure.