JPH09307022A - Surface mount semiconductor package, printed wiring board and module substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface mount semiconductor package capable of preventing defective soldering, a printed wiring board and a module substrate. SOLUTION: A semiconductor package 3 is provided with a rectangular package body 15. A large number of solder balls 22 covered each with a semiconductor layer 23 are arranged in a matrix shape on the rear 16b of the package main body and solder balls 22 are reflowed and soldered on the pads of a printed wiring board 2. Of the solder balls 22, at least those solder balls 22 to be positioned on the outermost periphery of their arranging areas have a larger diameter than the other solder balls.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount semiconductor package having a large number of solder balls connected to an IC chip, a printed wiring board suitable for mounting the semiconductor package, and a ball grid array on the printed wiring board. The present invention relates to a module substrate on which a semiconductor package of mold is mounted.

[0002]

2. Description of the Related Art As a surface mount type semiconductor package, a ball grid array type (hereinafter referred to as BGA) semiconductor package is known. This type of semiconductor package includes types such as a plastic BGA whose package base material is a printed circuit board, a ceramic BGA whose package base material is ceramic, and a tape BGA whose package base material is a film-shaped member. Is used according to the purpose.

[0003] Of these BGAs, the plastic B
The GA has an IC chip bonded to the printed circuit board and a synthetic resin molding material for molding the IC chip, and the molding material and the printed circuit board form a rectangular package body. A large number of solder balls are arranged in a matrix on the back surface of the printed circuit board. The solder ball functions as an external terminal of the semiconductor package,
It is soldered to the pad on the back surface of the printed circuit board.

Such a BGA type semiconductor package is mounted on a printed wiring board. The printed wiring board has a mounting surface on which a semiconductor package is mounted, and on this mounting surface, a large number of pads are arranged in a matrix. The pads are electrically connected to the conductor patterns of the printed wiring board, and the solder balls of the semiconductor package are joined to these pads.

Incidentally, the semiconductor package having the above configuration is mounted on a printed wiring board by, for example, a reflow soldering method. To mount this semiconductor package on a printed wiring board, first, a solder paste is printed on the pads of the printed wiring board. Next, the semiconductor package is mounted on the printed wiring board, and its solder balls are brought into contact with the pads. In this state, the printed wiring board is housed in a reflow furnace, and the printed wiring board and the semiconductor package are heated to melt the solder paste.
As a result, the solder balls and the pads are joined to each other, and the semiconductor package is electrically and mechanically connected to the printed wiring board.

[0006]

However, when soldering a BGA type semiconductor package to a printed wiring board,
Since this semiconductor package is heated together with the printed wiring board, if the thermal expansion coefficient of the package main body and the thermal expansion coefficient of the printed wiring board are different, the outer peripheral portion of the package main body including the printed board is printed wiring board. There may be a case where it is deformed so as to warp in the direction away from the mounting surface. The amount of warpage of the package body tends to increase as the size of the package body increases.

Therefore, among the solder balls arranged in a matrix, a mechanical stress is applied to the soldering portion of the pad and the soldering portion of the outermost peripheral portion near the outer peripheral portion of the package body, and the soldering portion is cracked or the like. Is likely to occur. In particular, in a BGA type semiconductor package, a soldering portion between a solder ball and a pad enters a minute gap between the package body and a printed wiring board. It is not possible to visually inspect whether there is an abnormality in the soldered portion.

Even when no abnormality is visually recognized in the soldered portion, the presence of the stress may cause fine cracks in the soldered portion. The existence of these cracks is difficult to find even in the functional test of the semiconductor package, and there is a problem that the reliability of soldering is lowered together with the occurrence of the soldering failure.

The present invention has been made under such circumstances, and an object thereof is a surface-mounting type semiconductor package which is capable of preventing a soldering failure and is excellent in soldering reliability, and a surface-mounting type semiconductor package. The purpose is to obtain a printed wiring board used for, and a module board.

[0010]

In order to achieve the above object, a surface mount semiconductor package according to a first aspect of the present invention has a rectangular package body having a back surface covered with a solder layer and a printed wiring board. Many solder balls to be soldered to the pads are arranged side by side in a matrix,
Among these solder balls, at least the solder ball located at the outermost periphery of the arrangement area has a larger diameter than other solder balls.

According to the semiconductor package having such a structure, as the diameter of the solder balls on the outermost circumference increases, the amount of solder covering the solder balls increases, so that the solder balls on the outermost circumference are bonded to the pads. Therefore, the amount of solder is larger than the amount of solder for joining other solder balls and pads. Therefore, the outermost solder balls can be firmly bonded to the pads.

Moreover, as the diameter of the solder ball increases,
When the package body is mounted on the printed wiring board, the height dimension from the back surface of the package body to the printed wiring board becomes large. Therefore, when soldering the semiconductor package, if a load due to the difference in thermal expansion coefficient between the package body and the printed wiring board acts on the soldering portion of the outermost solder ball, a solder ball with a large diameter may be generated. It deforms to absorb the above load. Therefore, the joint between the outermost solder ball and the pad is strengthened, and the soldered portion is less likely to be defective.

According to a second aspect of the surface mount type semiconductor package, a large number of solder balls to be reflowed and soldered to the pads of the printed wiring board are arranged in a matrix on the back surface of the rectangular package body. The solder balls are composed of eutectic solder, and at least the solder balls located at the outermost periphery of the arrangement area have a larger diameter than other solder balls. It has a feature.

According to the semiconductor package having such a structure, the amount of solder of the outermost solder ball itself increases,
The amount of solder that melts during reflow and soldering becomes larger than the amount of solder in other solder balls. Therefore, the outermost solder balls are firmly bonded to the pads.

Moreover, as the diameter of the solder ball increases,
When the package body is mounted on the printed wiring board, the height dimension from the back surface of the package body to the printed wiring board becomes large. Therefore, when a semiconductor package is reflowed and soldered, and the load resulting from the difference in the coefficient of thermal expansion between the package body and the printed wiring board acts on the soldering part of the outermost solder ball, the solder with a large diameter is used. The ball is deformed to absorb the load. Therefore, the joint between the outermost solder ball and the pad is strengthened, and the soldered portion is less likely to be defective.

Further, as described in claim 3, when the solder balls having a large diameter are arranged at the positions corresponding to the four corners of the package body, the package body is firmly bonded to the printed wiring board at the four corners. Therefore, it is possible to more reliably prevent defects in the soldered portion.

According to another aspect of the surface mount semiconductor package of the present invention, the back surface of the rectangular package body is covered with a solder layer, and a large number of external terminals to be soldered to the pads of the printed wiring board are arranged in a matrix. Are arranged side by side, and these external terminals are provided with at least a columnar first terminal portion located at the outermost periphery of the arrangement area and these first terminals.
And a ball-shaped second terminal portion located inside the terminal portion, and the shape of the first terminal portion is set to be larger than the shape of the second terminal portion. It has a feature.

According to the semiconductor package having such a structure, the amount of solder covering the first terminal portions located at the outermost periphery increases, so that the amount of solder for joining the first terminal portions to the pads is The amount is larger than the amount of solder for joining the second terminal portion to the pad. Therefore, the first terminal portion can be firmly joined to the pad, and the load caused by the difference in thermal expansion coefficient between the package body and the printed wiring board acts on the soldered portion between the first terminal portion and the pad. Even in this case, the soldered portion is less likely to have a defect.

According to a fifth aspect of the surface mount type semiconductor package, a large number of external terminals are arranged in a matrix on the back surface of a rectangular package body, and these external terminals are provided at least on the outermost periphery of the arrangement area. A columnar first terminal portion positioned and a ball-shaped second terminal portion positioned inside the first terminal portion;
The terminal portion is formed of eutectic solder, and the shape of the first terminal portion is set to be larger than the shape of the second terminal portion.

According to the semiconductor package having such a structure, since the amount of solder in the first terminal portion itself located at the outermost periphery increases, the amount of solder that melts during reflow / soldering is the solder in the second terminal portion. More than the amount. Therefore, the first terminal portion can be firmly joined to the pad, and the load caused by the difference in thermal expansion coefficient between the package body and the printed wiring board acts on the soldered portion between the first terminal portion and the pad. Even in this case, the soldered portion is less likely to have a defect.

If the pads of the printed wiring board are each covered with a solder layer as described in claim 6, the amount of solder for joining the first terminal portion and the pad is increased, The soldering strength between the first terminal portion and the pad is increased.

A printed wiring board according to a seventh aspect has a mounting surface on which a ball grid array type semiconductor package having a large number of solder balls is mounted, and the mounting surface is covered with a solder layer and the solder A large number of pads to which the balls are soldered are arranged side by side in a matrix, and the plane shape of at least the pad located at the outermost periphery of the arrangement area is set to be larger than the plane shapes of other pads. It is characterized by that.

According to the printed wiring board having such a structure, in the case of a pad having a large planar shape, the amount of solder covering the pad increases, so that the amount of solder for joining these pads and the solder balls is different from that of other pads. The amount is larger than the amount of solder for joining the pad and the solder ball. Therefore, the outermost peripheral pad can be firmly soldered to the solder ball, and the load caused by the difference in thermal expansion coefficient between the package body and the printed wiring board is applied to the soldering portion between the outermost peripheral pad and the solder ball. Even if it works, it is difficult for a defect to occur in the soldered portion.

Further, as described in claim 8,
By arranging the large planar pads at the positions corresponding to the four corners of the layout area, the semiconductor package can be firmly bonded to the printed wiring board at the four corners, and defects in the soldered part can be prevented more reliably. it can.

A printed wiring board according to a ninth aspect has a mounting surface on which a ball grid array type semiconductor package having a large number of solder balls is mounted, and a large number of pads are arranged side by side in a matrix on the mounting surface. At the same time, among these pads, at least the pad located on the outermost periphery of the arrangement area is formed to have a wall thickness thicker than the other pads.

According to the printed wiring board having such a structure, when the semiconductor package is mounted on the mounting surface, the height dimension from the semiconductor package to the mounting surface becomes large. Therefore, when a load caused by the difference in thermal expansion coefficient between the semiconductor package and the printed wiring board acts on the soldering portion between the pad and the solder ball, the thick pad is deformed to absorb the load. As a result, it becomes difficult for a defect to occur in the soldered portion.

Further, as described in claim 10, when at least the pads located at the outermost periphery are covered with the solder layer, a large amount of solder joins the pads at the outermost periphery and the solder balls. Therefore, these pads and the solder balls can be firmly bonded.

A module substrate according to claim 11 is a printed wiring board having a mounting surface on which a large number of pads are arranged side by side in a matrix; and a ball grid array type semiconductor package mounted on the mounting surface of the printed wiring board. And; And, the semiconductor package is
A package body including a back surface facing the mounting surface,
A large number of solder balls, which are arranged side by side in a matrix on the back surface of the package body, are covered with a solder layer, and are soldered to the pads of the printed wiring board, of which at least The solder balls located on the outermost periphery of the placement area are
It is characterized by having a larger diameter than other solder balls.

According to the module board having such a structure, as the diameter of the outermost solder balls increases, the amount of solder in the solder layer covering the solder balls increases, so that the outermost solder balls and pads are separated from each other. The amount of solder for joining is larger than the amount of solder for joining other solder balls and pads. Therefore, the outermost solder balls can be firmly bonded to the pads.

Moreover, as the diameter of the solder ball increases,
When the semiconductor package is mounted on a printed wiring board, the height dimension from the back surface of the semiconductor package to the printed wiring board increases. Therefore, when a semiconductor package and a printed wiring board are soldered, a load resulting from a difference in thermal expansion coefficient between the semiconductor package and the printed wiring board acts on the soldering portion of the solder ball having a large diameter. Deforms and absorbs the above load. Therefore, the joint between the outermost solder ball and the pad is strengthened, and the soldered portion is less likely to be defective.

A module board according to a twelfth aspect of the present invention is a printed wiring board having a mounting surface on which a large number of pads are arranged side by side in a matrix; and a ball grid array type mounted on the mounting surface of the printed wiring board. And a semiconductor package. The semiconductor package has a package body including a back surface facing the mounting surface, and a large number of solder balls arranged in a matrix on the back surface of the package body, and these solder balls are eutectic solder. Of these solder balls, the solder balls located at the outermost periphery of at least the arrangement area have a larger diameter than other solder balls. It is characterized by having.

According to the module board having such a configuration, the amount of solder of the outermost solder ball itself increases,
The amount of solder that melts during reflow and soldering becomes larger than the amount of solder in other solder balls. Therefore, the outermost solder balls can be firmly bonded to the pads.

Moreover, as the diameter of the solder ball increases,
When the package body is mounted on the printed wiring board, the height dimension from the back surface of the package body to the printed wiring board becomes large. Therefore, when a semiconductor package is reflowed and soldered, and the load resulting from the difference in the coefficient of thermal expansion between the package body and the printed wiring board acts on the soldering part of the outermost solder ball, the solder with a large diameter is used. The ball is deformed to absorb the load. Therefore, the joint between the outermost solder ball and the pad is strengthened, and the soldered portion is less likely to be defective.

Further, when the pads of the printed wiring board are covered with the solder layer as described in claim 13, the amount of solder for joining the solder balls and the pads is increased, and these solders are used. The soldering strength between the ball and the pad is increased.

Further, as described in claim 14, if the plane shape of the pads to be soldered to the solder balls having a large diameter is set to be larger than the plane shapes of the other pads, it melts with these pads. Since the contact area with the solder is increased, the outermost solder ball can be soldered more firmly to the printed wiring board than in the case where all the pads have the same planar shape.

A module board according to a fifteenth aspect of the invention is a printed wiring board in which a large number of pads covered with a solder layer are arranged side by side in a matrix on a mounting surface; and the pads are mounted on the mounting surface of the printed wiring board and the pads are mounted on the mounting surface. And a ball grid array type semiconductor package having a large number of solder balls bonded to each other.

Among the pads of the printed wiring board, at least the pads located at the outermost periphery of the arrangement area have a plane shape larger than other pads, and the solder balls are soldered to these pads. It is characterized by

According to the module board having such a structure, in the case of a pad having a large planar shape, the amount of solder covering this pad increases, so that the amount of solder for joining these pads and the solder balls is different from that of other pads. Is larger than the amount of solder for joining the solder ball with the solder ball. Therefore, the pads on the outermost periphery can be firmly soldered to the solder balls, and the load caused by the difference in the thermal expansion coefficient between the package body and the printed wiring board acts on the soldering portion between the pads and the solder balls. Even in this case, the soldered portion is less likely to be defective.

A module board according to a sixteenth aspect comprises a printed wiring board having a mounting surface; and a ball grid array type semiconductor package mounted on the mounting surface of the printed wiring board.

The printed wiring board has a large number of pads arranged in a matrix on the mounting surface,
And a plurality of dummy pads arranged outside the area where these pads are arranged, and the semiconductor package has
It has a large number of solder balls corresponding to the pad, and a plurality of dummy balls corresponding to the dummy pad, wherein the pad and the solder ball and the dummy pad and the dummy ball are soldered to each other. There is.

According to the module board having such a structure, the semiconductor package and the printed wiring board are bonded to each other outside the outermost solder balls, so that the thermal expansion coefficient of the semiconductor package and the printed wiring board is large. Most of the load caused by the difference is the soldering portion of the dummy pad and the dummy ball. for that reason,
It becomes difficult for the above-mentioned load to directly act on the soldered portion between the solder ball and the pad, and a defect is less likely to occur at the soldered portion between the solder ball and the pad.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the module substrate 1 according to the present invention comprises a printed wiring board 2 and a ball grid array type semiconductor package 3 mounted on the printed wiring board 2.

The printed wiring board 2 is an insulating substrate 5 made of, for example, glass epoxy or polyimide.
And a conductor pattern 6 formed on the insulating substrate 5. The surface of the insulating substrate 5 forms a flat mounting surface 5a. A large number of pads 8 are arranged side by side in a matrix on the mounting surface 5a. The pad 8 is electrically connected to the conductor pattern 6. The pads 8 each have a circular planar shape, and the shapes of the pads 8 are the same as each other. The surface of the pad 8 is covered with a solder layer 9, and the solder layer 9 is formed by printing a solder paste on the surface of the pad 8.

As shown in FIG. 3, the insulating substrate 5 is covered with the solder resist layer 11. The solder resist layer 11 has been removed at a portion corresponding to the pad 8. Therefore, the pad 8 is exposed outside the printed wiring board 2.

On the other hand, as shown in FIGS. 1 and 2, the semiconductor package 3 has a package body 15.
The package body 15 has a flat rectangular shape having four corners 15a to 15d. This package body 1
Reference numeral 5 denotes a printed board 16 as a package base material, an IC chip 17 mounted on the surface 16a of the printed board 16, and a molding material 18 made of synthetic resin or ceramic for molding the IC chip 17 on the printed board 16. It has and. Before the IC chip 17 is molded on the printed board 16,
Is wire-bonded to the wiring pattern 19 on the surface 16a.

As shown in FIG. 3, the back surface 16b of the printed board 16 is exposed without being covered with the molding material 18. A large number of connection pads 20 are arranged on the back surface 16b in a matrix. The connection pad 20 is electrically connected to the conductor pattern 19.

The connection pad 20 of the printed board 16 is
The spherical solder balls 22 are joined to each other. The solder balls 22 function as external terminals of the semiconductor package 3, and are arranged in a matrix on the back surface 16b of the printed circuit board 16 so as to correspond to the pads 8 of the printed wiring board 2. These solder balls 2
2 is bonded to the connection pad 20 via the solder layer 23, and the outer peripheral surface of each solder ball 22 is covered with the solder layer 23.

The solder balls 22 are made of solder having a melting point higher than that of the solder layers 9 and 23.

As shown in FIGS. 2 and 3, among the solder balls 22 arranged in the matrix, all the solder balls 22a located at the outermost periphery of the arrangement area have the diameter D1 of other solder balls 22a. It is set to be larger than the diameter D2 of 22. Therefore, all the solder balls 22a located on the outermost periphery of the arrangement area have a larger protrusion amount from the back surface 16b of the printed board 16 than the other solder balls 22.

The semiconductor package 3 having the above structure is
It is mounted on the printed wiring board 2 by a reflow / solder method. That is, to mount the semiconductor package 3 on the printed wiring board 2, the semiconductor package 3 is mounted on the mounting surface 5 a of the printed wiring board 2 such that the solder balls 22, 22 a are located on the desired pads 8. At this time, of the solder balls 22 arranged in a matrix,
All solder balls 2 located on the outermost periphery of the placement area
Since 2a has a larger diameter than other solder balls 22,
These solder balls 22a come into contact with the solder layer 9 on the pad 8, and the other solder balls 22 are kept slightly lifted from the solder layer 9 of the pad 8.

Then, in this state, the printed wiring board 2 on which the semiconductor package 3 is mounted is housed in a reflow furnace and the entire printed wiring board 2 and the semiconductor package 3 are heated. The heating temperature may be a temperature sufficient to melt the solder layers 9 and 23, and is set lower than the melting point of the solder balls 22 and 22a.

By this heating, the solder layers 9 and 23 are melted and integrated, and the solder balls 22 and 22a and the pad 8 are bonded via the solder layers 9 and 23. As a result,
The semiconductor package 3 is electrically connected to the pads 8 and is fixed to the printed wiring board 2.

According to the first embodiment having such a structure, the diameter D1 of all the solder balls 22a located at the outermost periphery of the arrangement area among the many solder balls 22 is equal to that of the other solder balls 22. It is formed larger than the diameter D2. Therefore, the surface area of the outermost solder balls 22a becomes large, and the amount of solder in the solder layer 23 covering these solder balls 22a increases. Therefore, the outermost solder balls 22
The amount of solder that joins a with the pad 8 is equal to that of the other solder balls 2.
The amount of solder is larger than the amount of solder that bonds 2 to the pad 8, and the outermost solder ball 22a can be firmly bonded to the pad 8.

Moreover, according to the above configuration, the solder ball 2
Since the melting points of the solder balls 22 and 22a are set higher than the heating temperature at the time of reflow and soldering, the solder balls 22 and 22a should be crushed even when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2. Maintain a certain height without.

From this, the outermost solder balls 22a
Since the diameter of the package is large, the back surface 16b of the package body 15
The height dimension H from to the mounting surface 5a of the printed wiring board 2 increases. As a result, at the time of reflow / soldering, when a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the solder ball 22a on the outermost periphery and the pad 8, The solder balls 22a having a large diameter are deformed so as to absorb the load.

Accordingly, the solder ball 22a and the pad 8 are firmly joined together, and the soldered portion between the solder ball 22a and the pad 8 is less likely to be defective, and the reliability of soldering is improved. To do.

The present invention is not limited to the first embodiment described above, and FIG. 4 shows a second embodiment of the present invention.

The second embodiment is different from the first embodiment in the arrangement of the solder balls 22a having a large diameter, and the other structures are the same as those in the first embodiment. is there.

As shown in FIG. 4, of the solder balls 22 positioned at the outermost periphery of the arrangement area, the package body 15
Three solder balls 2 corresponding to the respective corners 15a to 15d of
The diameter 2a of 2a is set to be larger than the diameter D2 of the other solder balls 22. Therefore, the package body 1
Solder balls 22a located at corners 15a to 15d of No. 5
Has a larger protrusion amount from the back surface 16b of the printed circuit board 16 than the other solder balls 22.

Also in the second embodiment having such a structure, the package main body 15 has four corners 15a to 15d.
At, it can be firmly joined to the mounting surface 5a of the printed wiring board 2. Therefore, as in the case of the above-described first embodiment, the soldering portions between the outermost solder balls 22 and 22a and the pads 8 are less likely to have defects, and the reliability of soldering is improved.

5 and 6 disclose a third embodiment of the present invention.

The third embodiment is different from the first embodiment mainly in the shape of the external terminals of the semiconductor package 3, and the other structures are the same as those in the first embodiment. It is the same.

As shown in FIG. 5, a large number of external terminals 31 are arranged in a matrix on the back surface 16b of the package body 15. The external terminal 31 has a plurality of prismatic first terminal portions 31a and a large number of ball-shaped second terminal portions 31b. The first terminal portion 31a is
It is located at the outermost periphery of the area where the external terminals 31 are arranged and at positions corresponding to the corners 15 a to 15 d of the package body 15.

As shown in FIG. 6, the outer peripheral surfaces of the first and second terminal portions 31a and 31b are covered with the solder layer 23, respectively. The surface area of each of the first terminal portions 31a is set to be larger than the surface area of each of the second terminal portions 31b, and the tips of the first terminal portions 31a are abutted against the pad 8. A flat mating surface 32 is formed.

The first terminal portion 31a and the total length L are set to be equal to the diameter D of the second terminal portion 31b.

According to the third embodiment having such a configuration, the first terminal portions 31a located at the corner portions 15a to 15d of the package body 15 have different corners from the second terminal portion 31b. It has a columnar shape, and these first terminal portions 3
The surface area of 1a is larger than the surface area of the second terminal portion 31b.

Therefore, the amount of solder in the solder layer 23 covering the first terminal portions 31a increases, so that the first terminal portions 31
The amount of solder that joins a with the pad 8 is equal to the second terminal portion 31
The amount is larger than the amount of solder that joins b and the pad 8. Therefore, the first terminal portion 31a can be firmly bonded to the pad 8, and the semiconductor package 3 and the printed wiring board 2 can be connected.
And the bonding with the solid.

In the third embodiment, the first terminal portion 31a, the total length L, and the diameter D of the second terminal portion 31b are set to be equal, but the present invention is not limited to this. The first terminal portion 31a and the total length L may be set to be slightly larger than the diameter D of the second terminal portion 31b.

According to this structure, since the total length L of the first terminal portion 31a is long, the back surface 16b of the package body 15 is increased.
The height dimension from to the mounting surface 5a of the printed wiring board 2 increases. Therefore, during reflow / soldering, when a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the first terminal portion 31a and the pad 8, First terminal portion 31a
The load is absorbed by the deformation of. Therefore, a defect is less likely to occur in the soldered portion between the first terminal portion 31a and the pad 8.

7 and 8 disclose a fourth embodiment of the present invention.

In the fourth embodiment, the shape of the pad 8 of the printed wiring board 2 is mainly different from that of the first embodiment. That is, the mounting surface 5a of the printed wiring board 2
Has an arrangement area 7 in which a large number of pads 8 are arranged in a matrix. The arrangement area 7 has a rectangular shape that follows the outline of the semiconductor package 3 shown by the chain double-dashed line in FIG. 7, and the arrangement area 7 has four corners 7a to 7a.
d. Of the many pads 8, the four pads 8a located at the outermost corners 7a to 7d of the arrangement area 7 have the diameter d1 set to be larger than the diameter d2 of the other pads 8, These pads 8 a are covered with a solder layer 9.

Further, in the case of the fourth embodiment, the solder balls 2 of the semiconductor chip 3 bonded to the pads 8 and 8a.
No. 2 has the same diameter and shape.

In the fourth embodiment having such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2, the solder layers 9 and 23 are melted and integrated, and these solder layers 9 and 23 are integrated. The solder ball 22 and the pads 8 and 8a are bonded via the. At this time, since the diameters of the four pads 8a located at the corners 7a to 7d of the arrangement area 7 are larger than the diameters of the other pads 8, the solder amount of the solder layer 23 covering these pads 8a is large. Increase. As a result,
The amount of solder that bonds the four pads 8a located at the corners 7a to 7d of the arrangement area 7 and the solder balls 22 becomes larger than the amount of solder that bonds the other many pads 8 and the solder balls 22, These four pads 8a and solder balls 2
2 can be firmly joined.

Therefore, at the time of reflow / soldering, the load caused by the difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldering portion between the outermost pads 8, 8a and the solder ball 22. Even in this case, the joining force due to the soldering opposes the load, and the soldered portion between the outermost peripheral pads 8 and 8 and the solder ball 22 is less likely to be defective.

In the fourth embodiment described above, the diameter d1 of the four pads 8a located at the corners 7a to 7d of the arrangement area 7 is formed to be large, but the present invention is not limited to this, and FIG. As in the fifth embodiment of the present invention shown in FIG. 3, three pads 8a are provided at each of the corners 7a to 7d of the arrangement area 7.
The diameter d1 of the pad 8a may be formed to be large so that the total number of the enlarged pads 8a is 12.

According to this structure, the bonding force between the semiconductor package 3 and the printed wiring board 2 is further increased, and it is possible to reliably prevent defective soldering.

In the fourth and fifth embodiments, the pad 8a having a large diameter d1 is formed on the corner portion 7 of the arrangement area 7.
Although they are partially arranged in a to 7d, the present invention is not limited to this, and the diameters of all pads located at the outermost periphery of the arrangement area 7 may be set larger than the diameters of the other pads.

Furthermore, FIG. 10 discloses a sixth embodiment of the present invention.

The sixth embodiment is a development of the fourth embodiment.

In the sixth embodiment, FIG.
(A), the diameter D1 of the solder ball 22a corresponding to the pad 8a having a large diameter d1 is formed larger than the diameter D2 of the solder ball 22 corresponding to the other pad 8.

According to this structure, the corner portion 7 of the arrangement area 7 is
amount of solder in the solder layer 9 covering the pads 8a located at a to 7d and solder balls 22 bonded to these pads 8a
Since the amount of solder in the solder layer 23 that covers a increases together, the amount of solder that joins the pads 8a and the solder balls 22 is
It is significantly larger than the amount of solder that joins the other many pads 8 and solder balls 22. Therefore, placement area 7
The pads 8 at the four corners and the solder balls 22 can be joined more firmly, and the effect of reinforcing the soldered portion is increased.

At the same time, as shown in FIG. 10B, the solder ball 22a has a large diameter, and the mounting surface 5a of the printed wiring board 2 from the back surface 16 of the package body 15 is increased.
Since the height H up to the point increases, when a load generated during reflow / soldering acts on the soldered portion between the solder ball 22a and the pad 8a, the solder ball 22a is deformed to absorb the load. .

As a result, the solder balls 22a and the pads 8a
It is possible to reliably prevent the occurrence of defects in the soldered part with
The reliability of soldering is improved.

In the fifth and sixth embodiments, the diameter of a part of the pads located at the corners of the arrangement area is set large, but the present invention is not limited to this. Not limited to this, the diameters of all pads located at the outermost periphery of the arrangement area may be set to be large.

Further, FIG. 11 discloses a seventh embodiment of the present invention.

The seventh embodiment is different from the fourth embodiment in the shape of the pad 8 of the printed wiring board 2, and the other structure is the same as that of the fourth embodiment. Is.

As shown in FIG. 11A, flat disc-shaped bumps 41 are formed on the four pads 8a located at the corners 7a to 7d of the arrangement area 7.
The bump 41 includes a disc-shaped high melting point solder layer 42 and a eutectic solder layer 43 stacked on the high melting point solder layer 42. The high melting point solder layer 42 is laminated on the pad 8a, the melting point of the high melting point solder layer 42 is equal to that of the solder ball 22, and the eutectic solder layer 43 is formed.
Higher than the melting point of.

Then, the four pads 8 including the bumps 41
The wall thickness T1 of a is set to be larger than the wall thickness T2 of the other pads 8.

In the seventh embodiment having such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2, the thick pad 8a is
The solder layer 9 and the eutectic solder layer 43 are melted and integrated with each other, and the solder ball 22 and the bump 4 are interposed via the solder layers 9 and 43.
The high melting point solder layer 42 of No. 1 is joined. Similarly, in the other pads 8, the solder layers 9 and 23 are melted and integrated, and the solder balls 22 are inserted through these solder layers 9 and 23.
And the pad 8 are joined.

At this time, since the melting points of the high melting point solder layer 42 and the solder balls 22 are set higher than the heating temperature at the time of reflow / soldering, the high melting point solder layer 42 and the solder balls 22 are crushed. Maintain a certain height without. Therefore, the plurality of pads 8a located at the corners 7a to 7d of the arrangement area 7 have an increased protrusion height from the mounting surface 5a of the printed wiring board 2 by the amount of the bump 41. After being mounted on the pad 8a via 41, the height dimension H from the mounting surface 5a to the back surface 16b of the package body 15 increases.

Therefore, during reflow / soldering, when a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the solder ball 22 and the pad 8a, the above-mentioned high The melting point solder layer 42 and the solder balls 22 are deformed to absorb the load. Therefore, the solder ball 22 and the pad 8a are less likely to be defective in the soldered portion, and the reliability of soldering is improved.

12 and 13 disclose the eighth embodiment of the present invention.

The eighth embodiment is an example suitable for the case where the number of pads 8 arranged on the mounting surface 5a is small and the arrangement area 7 of these pads 8 is considerably smaller than the back surface 16b of the package body 15. Shows.

As shown in FIG. 12, on the mounting surface 5a of the printed wiring board 5, in addition to the large number of pads 8, four dummy pads 51a to 51d are arranged. The dummy pads 51a to 51d are located outside the arrangement area 7 and are adjacent to the corners 7a to 7d of the arrangement area 7, respectively. The dummy pads 51a to 51d are covered with the solder layer 52, and the dummy pads 51a
The solder resist layer 11 is removed at the portions corresponding to 51d.

Four connection pads 53 are arranged on the back surface 16b of the package body 15. Connection pad 53
Are arranged outside the arrangement area of the connection pads 20, and spherical dummy balls 54 are joined to the connection pads 53, respectively. The dummy balls 54 correspond to the dummy pads 51a to 51d when the semiconductor package 3 is mounted on the mounting surface 5a. These dummy balls 54 are bonded to the connection pads 53 via the solder layer 55, and each dummy ball 5
The outer peripheral surface of No. 4 is covered with the solder layer 55.

The dummy balls 54 are made of solder having a higher melting point than the solder layers 52 and 55, and the diameters of the dummy balls 54 are the same as the diameters of the other solder balls 22.

In the eighth embodiment having such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2, the solder layers 52 and 55 are melted and integrated in the dummy ball 54 portion. , These solder layers 5
2, 55 through dummy ball 54 and dummy pad 51
a-51d are joined. In the other solder ball 22, the solder layers 9 and 23 are melted and integrated, and the solder ball 22 and the pad 8 are bonded via the solder layers 9 and 23.

In the case of this structure, the joints between the dummy balls 54 and the dummy pads 51a to 51d are located just corresponding to the corners 7a to 7d of the arrangement area 7, and
Since the outermost solder ball 22 and the connection pad 8 are displaced to the outside of the joint, the reflow / soldering process
When a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the package body 15 and the printed wiring board 2, most of the load is the dummy ball 54 and the dummy. Pads 51a-5
The soldering portion with 1d will bear the load.

Therefore, it is possible to prevent the load from directly acting on the soldered portion between the pad 8 and the solder ball 22, and it becomes difficult for the soldered portion between the pad 8 and the solder ball 22 to have a defect.

FIG. 14 discloses a ninth embodiment of the present invention.

The ninth embodiment is very similar to the first embodiment, and its main configuration is the same as that of the first embodiment. In the ninth embodiment, the solder balls 22 and 22a of the semiconductor package 3 are made of eutectic solder.
Cream solder 61 is applied to the surface of the pad 8 to which 22a is joined. The melting point of the cream solder 61 and the melting point of the eutectic solder forming the solder balls 22 and 22a are
It is almost the same.

The solder balls 22 and 22a are connected to the connection pads 2 of the printed circuit board 16 by the reflow soldering method.
It is joined to 0. That is, the solder balls 22, 22
To solder a to the connection pad 20,
The solder balls 22 and 22a are placed on the semiconductor chip 0, and in this state, the semiconductor package 3 is housed in a reflow furnace and heated. This heating melts the solder balls 22 and 22a,
It is integrally bonded to the connection pad 20. In this case, the solder balls 22 and 22a are deformed by heat and are bonded to the connection pad 20 in a state of being crushed into a substantially elliptical shape.

The semiconductor package 3 having such solder balls 22 and 22a is mounted on the printed wiring board 2 by the reflow soldering method. In mounting the semiconductor package 3, first, the cream solder 61 is applied to the pad 8 of the printed wiring board 2. Then, the semiconductor package 3 is mounted on the mounting surface 5 of the printed wiring board 2 so that the solder balls 22 and 22a are located on the desired pads 8.
The printed wiring board 2 is mounted together with the semiconductor package 3 in a reflow furnace and heated. By this heating, the solder balls 22 and 22a and the cream solder 61 are melted and integrated, and the solder balls 22 and 22a and the pad 8 are joined.

According to this structure, the solder balls 22a on the outermost circumference have a large diameter, and therefore the solder balls 22a
Since the amount of solder of a itself increases, the amount of solder that melts during reflow / soldering becomes greater than the amount of solder that joins the other solder balls 22 and the pads 8. Therefore, the bonding strength between the outermost solder ball 22a and the pad 8 is increased.

Since the diameter of the outermost solder ball 22a is large, the height H from the back surface 16b of the package body 15 to the mounting surface 5a of the printed wiring board 2 is large. Therefore, during reflow / soldering, when a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the solder ball 22a on the outermost periphery and the pad 8, the diameter is reduced. Big solder ball 2
2a is deformed so as to absorb the load. Therefore, as in the first embodiment, the solder ball 22a and the pad 8 are less likely to be defective in the soldered portion.

In the ninth embodiment described above,
Although the cream solder is applied to the pads, the cream solder may be omitted and the solder balls themselves may be melted at the time of reflow / soldering to bond the solder balls to the pads.

FIG. 15 discloses a tenth embodiment of the present invention.

The tenth embodiment is very similar to the third embodiment, and its main structure is the same as that of the third embodiment. In the tenth embodiment, the first terminal portion 31a of the semiconductor package 3 is made of eutectic solder.
a is reflowed to the connection pad 20 of the printed wiring board 2.
It is soldered. The cream solder 71 is applied to the surface of the pad 8 joined to the first terminal portion 31a. The melting point of the cream solder 71 and the melting point of the eutectic solder forming the first terminal portion 31a are substantially the same.

According to this structure, when the printed wiring board 2 on which the semiconductor package 3 is mounted is housed in the reflow furnace and heated, the terminal portion 31a and the cream solder 71 are removed at the first terminal portion 31a. It is melted and integrated, and the solder layers 9 and 23 are formed at the second terminal portion 31b.
Are melted and integrated. In this case, the prismatic first
The surface area of the terminal portion 31a of the second terminal portion 3a is spherical.
Since it is larger than the surface area of 1b, the amount of solder of the first terminal portion 31a that melts during reflow / soldering becomes larger than the amount of solder that joins the second terminal portion 31b and the pad 8. Therefore, the bonding strength between the outermost first terminal portion 31a and the pad 8 is increased.

In addition, in the tenth embodiment,
As shown in FIG. 15 (A), if the total length L of the first terminal portion 31a is slightly larger than the diameter D of the second terminal portion 31b, the printed wiring board can be removed from the back surface 16b of the package body 15. The height dimension H to the second mounting surface 5a increases. Therefore, during reflow / soldering, if a load caused by a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the first terminal portion 31a and the pad 8, The first terminal portion 31a is deformed so as to absorb the load, and the first terminal portion 3
A defect is less likely to occur in the soldered portion between the 1a and the pad 8.

In the tenth embodiment, the cream solder is applied to the pad, but the cream solder is omitted and the first terminal portion itself is melted at the time of reflow / soldering, so that the first solder You may make it join the terminal part and pad.

FIG. 16 discloses an eleventh embodiment of the present invention.

The eleventh embodiment is very similar to the fourth embodiment, and its main structure is the same as that of the fourth embodiment. In the eleventh embodiment, the solder balls 22 of the semiconductor package 3 are made of eutectic solder. These solder balls 22 are reflowed and soldered to the connection pads 20 of the printed board 16. Further, cream solder 81 is applied to the surfaces of the pads 8 and 8a to which the solder balls 22 are joined. The melting point of the cream solder 81 and the melting point of the eutectic solder forming the solder balls 22 are substantially the same.

With such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2,
The solder ball 22 and the cream solder 81 are melted and integrated, and the solder ball 22 and the pads 8 and 8a are joined. At this time, since the four pads 8a located at the four corners of the arrangement area 7 have a larger diameter than the other pads 8, the amount of cream solder 81 applied to these pads 8a increases.

Therefore, the amount of solder for joining the pads 8a located at the four corners of the arrangement area 7 and the solder balls 22 is
The amount of solder is larger than the amount of solder that bonds the other many pads 8 and the solder balls 22, and the pads 8a located at the four corners of the arrangement area 7 can be firmly bonded to the solder balls 22.

In the eleventh embodiment as well, the cream solder is applied to the pads, but this cream solder is omitted and the solder balls themselves are melted at the time of reflow and soldering, so that the solder balls and pads You may make it join.

FIG. 17 discloses a twelfth embodiment of the present invention.

The twelfth embodiment is a further development of the eleventh embodiment, in which the diameter of the solder ball 22a corresponding to the pad 8a having a large diameter d1 is
The diameter is larger than the diameter of the solder ball 22 corresponding to the other pad 8. The solder balls 22 and 22a are made of eutectic solder, respectively.
2a is reflowed and soldered to the connection pad 20 of the printed board 16.

With such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2,
The solder balls 22, 22a and the cream solder 81 are melted and integrated, and the solder balls 22, 22a and the pad 8,
8a is joined. At this time, the solder amount of the cream solder 81 covering the four pads 8a located at the four corners of the arrangement area 7 and the solder ball 2 that melts at the time of reflow / soldering
The amount of solder of 2a itself is significantly larger than the amount of solder that joins the other solder balls 22 and pads 8. Therefore, the pads 8a located at the four corners of the placement area 7 and the solder balls 22a can be joined more firmly, and the reliability of soldering is improved.

In the twelfth embodiment, the cream solder is applied to the pads, but the cream solder is omitted and the solder balls themselves are melted during reflow / soldering, thereby You may make it join.

FIG. 18 discloses a thirteenth embodiment of the present invention.

The thirteenth embodiment is very similar to the seventh embodiment, and its main configuration is the same as that of the seventh embodiment. In the thirteenth embodiment, the solder balls 22 of the semiconductor package 3 are made of eutectic solder. These solder balls 22 are reflowed and soldered to the connection pads 20 of the printed board 16.

The bumps 41 located at the four corners of the arrangement area 7
Has cream solder 91 applied to the surface of the high melting point solder layer 42. The same cream solder 91 is also applied to the surface of the other pads 8 that do not have the bumps 41. The melting point of the cream solder 91 is equal to the melting point of the eutectic solder forming the solder balls 22 and lower than the melting point of the high melting point solder layer 42.

In such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2,
The solder ball 22 and the cream solder 91 are melted and integrated, and the solder ball 22 is bonded to the pads 8 and 8a.

At this time, since the melting point of the high melting point solder layer 42 of the bump 41 is higher than the melting points of the solder balls 22 and the cream solder 91, even if the printed wiring board 2 is housed in a reflow furnace and heated, The high melting point solder layer 42 maintains a constant height without being crushed. Therefore, the plurality of pads 8a located at the four corners of the arrangement area 7 have an increased protrusion height from the mounting surface 5a of the printed wiring board 2 by the amount of the high melting point solder layer 42, and the mounting surface 5a is packaged. The height dimension H to the back surface 16b of the main body 15 becomes large.

As a result, at the time of reflow / soldering, when a load due to a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the solder ball 22 and the pad 8a, The high melting point solder layer 42 and the solder balls 22 are deformed so as to absorb the load, and the soldered portions between the solder balls 22 and the pads 8a are less likely to be defective.

In the thirteenth embodiment, cream solder is applied to the surface of the high melting point solder layer, but this cream solder is omitted and the solder balls themselves are melted during reflow / soldering so that these solders can be melted. You may make it join a ball and a high melting point solder layer.

Furthermore, FIG. 19 discloses a fourteenth embodiment of the present invention.

The fourteenth embodiment is very similar to the eighth embodiment, and its main structure is the same as that of the eighth embodiment. In the fourteenth embodiment, the solder balls 22 and the dummy balls 54 of the semiconductor package 3 are each made of eutectic solder.
The solder balls 22 and the dummy balls 54 are reflow-soldered to the connection pads 20 and the connection pads 53 of the printed board 16.

Cream solder 101 is applied to the surfaces of the pads 8 to which the solder balls 22 are joined and the surfaces of the dummy pads 51a to 51d to which the dummy balls 54 are joined. The melting point of the cream solder 101 and the melting points of the eutectic solder forming the solder balls 22 and the dummy balls 54 are substantially the same.

With such a structure, when the semiconductor package 3 is reflowed and soldered to the printed wiring board 2,
In the portion of the dummy ball 54, the dummy ball 54 and the cream solder 101 are melted and integrated, and the dummy ball 54 and the dummy pads 51a to 51d are joined. Further, at the solder ball 22 portion, the solder ball 22
And the cream solder 101 is melted and integrated, and the solder balls 22a and the pads 8 are joined.

Therefore, during reflow / soldering, when a load due to a difference in thermal expansion coefficient between the package body 15 and the printed wiring board 2 acts on the soldered portion between the package body 15 and the printed wiring board 2, Most of this load is due to the dummy balls 54 and the dummy pads 51a-5.
Since the soldering portion with 1d bears the load, it becomes difficult for the above load to directly act on the soldering portion between the solder ball 22 and the pad 8.

Although cream solder was applied to the surfaces of the pads and dummy pads in the fourteenth embodiment, the cream solder was omitted and the dummy balls and solder balls themselves were melted during reflow and soldering. The dummy ball and the dummy pad, and the solder ball and the pad may be bonded to each other.

Further, in each of the above embodiments, the printed wiring board is used as the package base material of the semiconductor package, but the present invention is not limited to this, and the package base material is made of a flexible film or ceramic. You may.

[0136]

According to the surface mount type semiconductor package of the first or second aspect, the solder balls on the outermost periphery of the arrangement area can be firmly bonded to the pads. Moreover, even if a load due to heat during soldering acts on the soldering portion between the outermost solder ball and the pad, the solder ball having a large diameter is deformed to absorb the load, so that the soldering portion is not defective. This can be surely prevented, and the reliability of soldering is improved.

According to the surface mount semiconductor package of the fourth or fifth aspect, the first terminal portion located at the outermost periphery of the arrangement area can be firmly bonded to the pad. Therefore, even when a load due to heat during soldering acts on the soldered portion between the first terminal portion and the pad, the soldered portion is less likely to have a defect, and the reliability of soldering is improved.

According to the printed wiring board of the seventh aspect, the solder balls can be firmly bonded to the pads located at the outermost periphery of the arrangement area. Therefore, even when a load due to heat during soldering acts on the soldering portion between the outermost peripheral pad and the solder ball, a defect is less likely to occur in this soldering portion, and the reliability of soldering is improved.

According to the printed wiring board of the ninth aspect, when a load due to heat during soldering acts on the soldering portion between the outermost pad and the solder ball in the arrangement area, the thick pad is deformed. By doing so, the load is absorbed, so that a defect is less likely to occur in the soldering portion, and the reliability of soldering is improved as compared with the conventional case.

According to the module substrate of the tenth or eleventh aspect, the solder balls on the outermost periphery of the arrangement area can be firmly bonded to the pads. In addition, when a load due to heat during soldering acts on the soldering portion between the outermost solder ball and the pad, the solder ball having a large diameter is deformed to absorb the load, resulting in a defective soldering portion. Can be reliably prevented and the reliability of soldering is improved.

According to the module board of the fourteenth aspect, the solder balls can be firmly bonded to the pads located at the outermost periphery of the arrangement area. Therefore, even when a load due to heat during soldering acts on the soldering portion between the outermost peripheral pad and the solder ball, a defect is less likely to occur in this soldering portion, and the reliability of soldering is improved.

According to the module board of the fifteenth aspect, most of the load due to heat during soldering is carried by the soldering portion of the dummy pad and the dummy ball.
It becomes difficult for the load to directly act on the connection portion between the solder ball and the pad. Therefore, the solder ball-pad pad is less likely to be defective in the soldered portion, and the reliability of soldering is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a printed wiring board and a semiconductor package mounted on the wiring board according to a first embodiment of the present invention.

FIG. 2 is a plan view of a semiconductor package showing an arrangement of solder balls.

FIG. 3A is an enlarged sectional view showing a relationship between a solder ball and a pad. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 4 is a plan view of a semiconductor package showing an arrangement of solder balls according to a second embodiment of the present invention.

FIG. 5 is a plan view of a semiconductor package showing an arrangement of solder balls according to a third embodiment of the present invention.

FIG. 6A is an enlarged cross-sectional view showing the relationship between external terminals and pads. FIG. 6B is a cross-sectional view showing a state in which the external terminal and the pad are soldered.

FIG. 7 is a plan view showing an arrangement of pads on a printed wiring board according to a fourth embodiment of the present invention.

FIG. 8A is an enlarged cross-sectional view showing a relationship between a solder ball and a pad. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 9 is a plan view showing an arrangement of pads on a printed wiring board according to a fifth embodiment of the present invention.

FIG. 10A is an enlarged cross-sectional view showing the relationship between solder balls and pads in the sixth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 11A is an enlarged sectional view showing the relationship between solder balls and pads in the seventh embodiment of the invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 12 is a plan view showing an arrangement of pads on a printed wiring board according to an eighth embodiment of the present invention.

FIG. 13A is a cross-sectional view showing an enlarged relationship between a solder ball and a pad. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 14A is an enlarged cross-sectional view showing the relationship between solder balls and pads in the ninth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 15A is an enlarged cross-sectional view showing the relationship between external terminals and pads in the tenth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the external terminal and the pad are soldered.

FIG. 16A is an enlarged cross-sectional view showing the relationship between solder balls and pads in the eleventh embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 17A is an enlarged cross-sectional view showing the relationship between solder balls and pads in the twelfth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 18A is an enlarged cross-sectional view showing the relationship between solder balls and pads in the thirteenth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

FIG. 19 (A) is an enlarged sectional view showing the relationship between solder balls and pads in the fourteenth embodiment of the present invention. FIG. 6B is a cross-sectional view showing a state in which the solder ball and the pad are soldered.

Claims (16)

[Claims] 1. A back surface of a rectangular package body,
In a surface mount type semiconductor package in which a large number of solder balls covered with a solder layer are arranged side by side in a matrix, and these solder balls are soldered to pads of a printed wiring board, at least the placement area of at least the placement area of the solder balls is the highest. The surface-mount type semiconductor package characterized in that the solder balls located on the outer periphery have a larger diameter than other solder balls. 2. On the back surface of the rectangular package body,
In a surface mount type semiconductor package in which a large number of solder balls are arranged side by side in a matrix, and these solder balls are reflowed and soldered to the pads of the printed wiring board, the solder balls are composed of eutectic solder. Of these, at least the solder balls located at the outermost periphery of the arrangement area have a larger diameter than other solder balls. 3. The package body according to claim 1 or 2, wherein the package body has four corners, and the solder balls having the large diameter are arranged at positions corresponding to these corners. Surface mount semiconductor package. 4. On the back surface of the rectangular package body,
In a surface-mount type semiconductor package in which a large number of external terminals covered by a solder layer are arranged side by side in a matrix, and these external terminals are soldered to pads of a printed wiring board, the external terminals are at least the outermost periphery of the arrangement area. Has a columnar first terminal portion and a ball-shaped second terminal portion located inside the first terminal portion, and the first terminal portion has the shape described above. A surface-mount type semiconductor package characterized in that the shape is set larger than the shape of the second terminal portion. 5. On the back surface of the rectangular package body,
In a surface-mount type semiconductor package in which a large number of external terminals are arranged side by side in a matrix form and these external terminals are reflowed and soldered to pads of a printed wiring board, the external terminals are located at least at the outermost periphery of the arrangement area. It has a columnar first terminal portion and a ball-shaped second terminal portion positioned inside the first terminal portion, and the first terminal portion is made of eutectic solder. In addition, the surface mounting semiconductor package is characterized in that the shape of the first terminal portion is set to be larger than the shape of the second terminal portion. 6. The surface mount semiconductor package according to claim 4 or 5, wherein the pad is covered with a solder layer. 7. A mounting surface on which a ball grid array type semiconductor package having a large number of solder balls is mounted, and a large number of pads covered with a solder layer are arranged side by side in a matrix on the mounting surface, and In a printed wiring board in which the solder balls are soldered to these pads, at least the pad located at the outermost periphery of the arrangement area of the pads has a larger planar shape than other pads. And a printed wiring board. 8. The pad arrangement area according to claim 7, wherein the pad arrangement area has a rectangular shape having four corners, and the large pad having the planar shape is arranged at a position corresponding to these corners. A printed wiring board characterized in that 9. A mounting surface on which a ball grid array type semiconductor package having a large number of solder balls is mounted, a large number of pads are arranged side by side in a matrix on the mounting surface, and the solder balls are provided on these pads. In the printed wiring board for soldering, at least the pad located on the outermost periphery of the arrangement area is thicker than the other pads among the pads. 10. The printed wiring board according to claim 9, wherein at least the pad located at the outermost periphery of the arrangement area is covered with a solder layer. 11. A module comprising: a printed wiring board having a mounting surface on which a large number of pads are arranged side by side in a matrix; and a ball grid array type semiconductor package mounted on the mounting surface of the printed wiring board. On the board, the semiconductor package is arranged in a matrix form on the back surface of the package body including the back surface facing the mounting surface, is covered with a solder layer, and is soldered to the pads of the printed wiring board. Characterized in that at least the solder balls located at the outermost periphery of the arrangement area have a larger diameter than other solder balls. Module board to be. 12. A module comprising: a printed wiring board having a mounting surface on which a large number of pads are arranged side by side in a matrix; and a ball grid array type semiconductor package mounted on the mounting surface of the printed wiring board. In the substrate, the semiconductor package includes a package body including a back surface facing the mounting surface, and a large number of solder balls arranged side by side in a matrix on the back surface of the package body,
These solder balls are made of eutectic solder, are reflowed and soldered to the pads of the printed wiring board, and at least the solder balls located at the outermost periphery of the placement area of these solder balls. The module substrate is characterized in that the balls have a larger diameter than other solder balls. 13. The method according to claim 11 or 12,
A module substrate, wherein the pad is covered with a solder layer. 14. The module board according to claim 13, wherein the pad to be soldered to the solder ball having the large diameter has a larger planar shape than the other pads. 15. A printed wiring board having a mounting surface on which a large number of pads covered with a solder layer are arranged side by side in a matrix; and a large number of solders mounted on the mounting surface of the printed wiring board and joined to the pads. A ball grid array type semiconductor package having balls; and, in a pad of the printed wiring board, at least the pad located at the outermost periphery of the arrangement area is a plane larger than other pads. A module substrate having a shape, wherein the solder balls are soldered to these pads. 16. A module board comprising: a printed wiring board having a mounting surface; and a ball grid array type semiconductor package mounted on the mounting surface of the printed wiring board, wherein the printed wiring board has the mounting surface. A plurality of pads arranged side by side in a matrix on the surface and a plurality of dummy pads arranged outside the arrangement area of the pads, and the semiconductor package has a large number of solder balls corresponding to the pads. And a plurality of dummy balls corresponding to the dummy pads, wherein the pads and the solder balls and the dummy pads and the dummy balls are soldered to each other.