JP2003060336A - Method for mounting semiconductor device and semiconductor package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce heat damages to a semiconductor package and peripheral components and to improve connection reliability. SOLUTION: Solder balls 8 are loaded on multiple lands 6, arranged on a circuit board 3 via the solder paste 7 of a low-melting point. Preliminary heating is performed, solder paste 7 is melted and caked, and the semiconductor package 2 is positioned and loaded in a state with the balls 8 being fixed to the circuit board 3. Reflow soldering is performed, the solder balls 8 are melted and caked, and the semiconductor package 2 is mounted on the circuit board 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device obtained by surface-mounting a semiconductor package having surface electrodes on a circuit board and a method for mounting the semiconductor package. More specifically, the present invention relates to a ball grid array (BGA: Ba
ll Grid Array) The present invention relates to a semiconductor device in which a semiconductor package is mounted by a mounting method and a mounting method of the semiconductor package.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have been required to be smaller and thinner, a method for mounting a semiconductor package and a circuit board is to provide an electrode on the bottom surface and directly contact the electrode on the circuit board. A BGA surface mounting method, which is designed to be miniaturized by connecting, has been used. As shown in FIG. 4, a semiconductor device 30 by the BGA surface mounting method includes a semiconductor package 33 having a surface 31 provided with a number of surface electrodes 32, and a circuit board 35 having a number of lands 34 corresponding to the surface electrodes 32. And a solder ball 36 for soldering the semiconductor package 33 and the circuit board 35.

The semiconductor package 33 covers the electronic parts with an insulating resin in order to protect the chips and the like from the external environment such as temperature and humidity, and is arranged in a grid pattern on the surface 31 for electrical connection with the circuit board 35. Many surface electrodes 3
Two are provided. In the semiconductor package 33, solder balls 36 are mounted on the surface electrodes 32 via a solder paste 37. In the semiconductor package 33, the solder balls 36 are melted and solidified by, for example, a reflow soldering process, so that the surface electrode 32 and the circuit board 3
5 lands 34 are electrically connected and surface-mounted on the circuit board 35.

The solder ball 36 has conventionally been made of Sn / P, which is made of tin and lead having a low melting temperature as a material of a solder alloy.
Although b-type metals have been used, lead-free metal has been used in recent years from the standpoints of impact on the human body and environmental protection. Therefore, as a material of the solder alloy, an alloy containing Sn such as Sn / Zn system has come to be used from the viewpoint of being compatible with all mounting methods and being low in cost.

In the method of mounting the semiconductor package 33, first, the solder paste 37 is applied to the surface electrode 32 provided on the surface 31, and the solder balls 36 are mounted through the solder paste 37. The mounting method is such that a large number of lands 34 are arranged corresponding to the surface electrodes 32 with the surface 31 on which the solder balls 36 are provided facing the circuit board 35, that is, with the solder balls 36 facing down. After the semiconductor package 33 is placed on the circuit board 35, the reflow soldering process is performed. The mounting method is
The reflow soldering process melts the solder balls 36
The semiconductor package 33 is solidified and mounted on the circuit board 35.

In the method of mounting the semiconductor package 33, since the mounting portion 38 is present between the semiconductor package 33 and the circuit board 35, the mounting portion 38 is below the semiconductor package 33.
Hide in. In the mounting method, therefore, the reflow soldering process described above may be performed without noticing the missing or misalignment of the solder balls 36.

When the solder balls 36 are missing or misaligned as described above, in the semiconductor device 30, the semiconductor package 33 is not mounted at a predetermined position on the circuit board 35, and thus the semiconductor package 33 and the semiconductor package 33 are not mounted. A connection failure or the like occurs in the mounting portion 38 between the circuit board 35 and the mounting portion 38. In such a case, the semiconductor device 30 is found to be a defective product such as a defective connection in the quality inspection process, and the semiconductor package 33 is re-mounted on the product determined to be a defective product.

In the method of remounting the semiconductor package 33, the semiconductor device 30 is heated to melt the solder, the semiconductor package 33 is removed from the circuit board 35, and the circuit board 3 is removed.
5 and the solder remaining on the semiconductor package 33 are removed. Then, the remounting method is performed by the semiconductor package 33.
The solder paste 37 is applied again to the front surface electrode 32 provided on the front surface 31, and the solder ball 36 is attached to the front surface electrode 32 through the solder paste 37. In the remounting method, the semiconductor package 33 is mounted on a circuit board 35 provided with a large number of lands 34 corresponding to the surface electrodes 32, and flux 39 is applied to the circuit board 35 to prevent metal oxidation. To be done. In the remounting method, the semiconductor package 33 is mounted on the circuit board 35 by performing a reflow soldering process.

[0009]

The conventional method for remounting the semiconductor package 33 described above is the same as the method for initially mounting the semiconductor package 33 on the circuit board 35. Since the surface 31 on which the 32 is provided is downward, the mounting portion 38 is provided between the semiconductor package 33 and the circuit board 35.
Therefore, in the remounting method, the heat generated by the reflow soldering is melted by the heat conduction from the semiconductor package 33 to mount the solder balls 36, so that more heat needs to be supplied. Further, since the solder material tends to be lead-free, Sn / Cu-based or Sn / Ag-based containing tin having a melting point of about 220 ° C. is used from the viewpoint of bonding reliability as compared with the conventional lead-containing solder material. Doing is becoming mainstream. Therefore, in the conventional remounting method, there is a problem that the heating temperature during reflow soldering becomes high and damages not only the semiconductor package 33 having low heat resistance but also the electronic components and the like incorporated in the circuit board 35. there were. There is a problem that the function of the semiconductor device 30 is deteriorated.

Further, in the conventional mounting method, since the mounting portion 38 is provided between the semiconductor package 33 and the circuit board 35, when the semiconductor package 33 is mounted on the circuit board 35, the solder balls 36 are missing or positioned. If a shift occurs, it is difficult to find it at the time of implementation. Therefore, the conventional mounting method has a problem that a defective product may be produced in the semiconductor device 30, the yield is reduced, and the re-mounting of the semiconductor package 33 is repeated, which causes a reduction in work efficiency and an increase in cost. It was

Further, in the semiconductor device 30, there is a difference in the coefficient of thermal expansion between the Si chip in the semiconductor package 33 and the circuit board 35 made of resin, and due to the difference, solder cracks such as bending and distortion may occur. Occurs. Semiconductor device 30
Since there is several times the difference between the coefficient of thermal expansion of the Si chip and the coefficient of thermal expansion of the circuit board 35, solder cracks may occur in the mounting portion 38 due to this difference, and problems such as poor connections may occur. The heating temperature during soldering is extremely important.

Therefore, according to the present invention, it is possible to prevent the solder balls from being dropped or misaligned, to shorten the reflow soldering time, and to reduce the influence of heating on the semiconductor package and peripheral components. It provides the implementation method of.

[0013]

In order to achieve the above-mentioned object, in a semiconductor device according to the present invention, a semiconductor package having a large number of surface electrodes arranged in a grid pattern on the surface is provided on each of the surface electrodes. It is mounted by a ball grit array surface mounting method on a circuit board provided with a corresponding large number of lands. A semiconductor device has, on the circuit board, a large number of solder balls mounted on a large number of lands formed corresponding to the surface electrodes of the semiconductor package through a solder paste having a melting point lower than that of the solder balls. By melting and solidifying the solder paste, reflow solder is applied with the solder balls fixed on the circuit board to melt and solidify the solder balls, and the semiconductor package is mounted on the circuit board. Become.

Also, in the method for mounting a semiconductor package according to the present invention, a semiconductor package having a large number of surface electrodes arranged in a grid pattern on the surface is provided with a large number of lands corresponding to the surface electrodes. It is mounted on the circuit board by the ball grit array surface mounting method.
The semiconductor package mounting method includes a solder paste applying step of applying a solder paste having a melting point lower than that of the solder balls on the respective lands provided on the circuit board, and a step of mounting the solder balls on the solder paste. And a solder ball mounting step of mounting the solder balls by heating at a temperature that melts only the solder paste, and arranging the land and the surface electrode facing the semiconductor package with respect to the circuit board so as to face each other. The method includes an assembling step of a semiconductor package to be assembled and a reflow soldering step of performing reflow soldering on the assembly of the semiconductor package and the circuit board.

According to the present invention, a solder paste having a melting point lower than that of the solder ball is previously melted and solidified and applied to the circuit board to mount the solder ball, and the solder ball is fixed. Missing and misalignment are prevented. Therefore, according to the present invention, the semiconductor package is precisely mounted on the circuit board.

Further, according to the present invention, the solder paste having a melting point lower than that of the solder balls is previously heated and melted on the circuit board to fix the solder balls, so that this heating is a state in which the solder balls are preheated. . Therefore, according to the present invention, since the solder balls are preheated, reflow soldering treatment is performed to melt the solder balls.
It is possible to shorten the heating time and the temperature when solidifying and mounting the semiconductor package.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. The semiconductor device 1 is
As shown in FIG. 1C, it is composed of a semiconductor package 2 and a circuit board 3. The semiconductor package 2 is
In order to protect electronic parts such as chips from the external environment such as temperature and humidity, the electronic parts are covered with insulating resin. The semiconductor package 2 is provided with a large number of surface electrodes 4 arranged in a grid pattern on the surface 2a for electrical or mechanical connection with the circuit board 3.

As shown in FIGS. 1 (a) and 1 (b), the circuit board 3 is obtained by subjecting a copper foil bonded on an insulating substrate to photolithography and etching, and to the mounting surface 5. A large number of lands 6 corresponding to the surface electrodes 4 provided on the surface 2a are formed. The circuit board 3 is coated with the solder paste 7 on the lands 6 and the solder balls 8 are mounted through the solder paste 7. Then, the circuit board 3 is coated with a solder flux 9 for preventing metal oxidation caused by heating of soldering by reflow solder and improving solder wetting.

As the solder ball, a solder alloy having a melting point of about 220 ° C. is used from the viewpoint of the lead-free tendency of the metal material and the bonding reliability. Further, the solder paste 7 has a melting point near 200 ° C. which is lower than the melting point of the solder ball 8 so that the height of the solder ball 8 does not vary when the solder ball 8 is mounted on the land 6. A mixture of a granular solder alloy such as Sn / Zn system or Sn / Bi system and flux is used. The solder paste 7 is melted and solidified by being heated at a temperature at which the solder balls 8 are not melted, and is fixed onto the lands 6 while maintaining the initial shape of the solder balls 8. In addition, the granular solder alloy contains Sn / Zn and Sn / B in terms of protecting the human body and the environment.
Although it is preferable to use i-type or the like, it is not limited to lead-free and can be used for those containing Pb.

The semiconductor device 1 includes a semiconductor package 2 and a surface 2 of the semiconductor package 2 on which surface electrodes 4 are provided.
It is obtained by placing a on the solder balls 8 fixed in advance on the lands 6 of the circuit board 3 and soldering by reflow soldering.

As described above, the semiconductor device 1 heats the solder paste 7 having a melting point lower than that of the solder ball 8.
Since the solder balls 8 are melted to fix the mounting of the solder balls 8 on the lands 6 in advance, the solder balls 8 are preheated when the semiconductor package is mounted. Therefore, in the semiconductor device 1, the heating time for soldering by reflow soldering can be shortened and the number of times of heating during mounting can be reduced. In the semiconductor device 1, by shortening the heating time and the number of times of heating, distortion and bending due to the difference in the coefficient of thermal expansion between the electronic component such as the chip and the circuit board are improved, and
It is possible to suppress heat damage to electronic parts such as chips. Further, the semiconductor device 1 has the solder balls 8
Since the solder balls 7 are mounted in advance by solder paste 7, the solder balls 8 are prevented from dropping or misaligned, and defective products such as defective connections are not produced, so that the working efficiency is improved and the device is manufactured.

Next, a second embodiment for remounting the semiconductor package will be described. The remounting method is shown in Fig. 2.
And the steps shown in FIG. In the remounting method, in step S1 shown in FIG.
The semiconductor device 22 is manufactured by performing the reflow soldering on the surface 1. In the remounting method, in step S2, the quality of the obtained semiconductor device 22 is inspected, and the semiconductor device 22 determined to be defective is sorted.

In the remounting method, in step S3, the semiconductor package 20 of the semiconductor device 22 determined to be defective is removed from the circuit board 21, and in step S4, the existing solder is removed from the semiconductor package 20 and the circuit board 21. I do.

The remounting method is performed in step S5 as shown in FIG.
As shown in (b), a new solder paste 24 is applied on the land 23 of the circuit board 21 from which the solder has been removed. As shown in FIG. 2 (c), the remounting method is performed by connecting the solder ball 25 to the land 2 through the solder paste 24.
3, the flux 26 is applied between the lands 23 in order to prevent metal oxidation due to heating at the time of mounting, the solder paste 24 is melted, and the solder balls 25 are attached to the circuit board 2.
Implemented on 1.

In the remounting method, as shown in FIG. 2D, at step S7, the land 23 provided on the circuit board 21 and the semiconductor package 2 corresponding to the land 23 are provided.
The semiconductor package 20 is assembled to the circuit board 21 by combining it with the surface electrode 27 provided on the surface 20 a of 0. The remounting method is step S8 in which the solder balls 25
Soldering by reflow soldering is performed to melt and solidify the solder balls 25, and the semiconductor package 2
Implement 0.

The semiconductor package 20 having the above steps
In the remounting method, the solder paste 24 having a melting point lower than that of the solder balls 25 is heated and melted, and the reflow soldering is performed while the solder balls 25 are heated on the circuit board 21 in advance. Since the solder balls 25 are preheated, the heating time at the time of reflow soldering can be shortened, and the number of times of heating at the time of mounting can be reduced. In the remounting method of the semiconductor package 20, since the solder balls 25 are mounted in advance by the solder paste 24, the solder balls 25 are prevented from dropping or misaligned, and the heating time is shortened or the heating temperature is lowered. As a result, distortion and bending due to the difference in thermal expansion coefficient between the electronic component such as a chip and the circuit board are also improved. Further, in the method of remounting the semiconductor package 20, thermal damage to the semiconductor package 20 and peripheral components can be suppressed, dropping and displacement of the solder balls 25 can be prevented, and the semiconductor package 20 can be remounted. The process is unnecessary and the work efficiency is improved.

[0027]

As described above in detail, according to the present invention, the solder balls are mounted via the low-melting-point solder paste, and the reflow solder is fixed with the solder paste fixed by melting and solidifying the solder paste. Since the heating is performed, the heating time for mounting the semiconductor package can be shortened, and the solder balls can be prevented from being lost or displaced. Further, according to the present invention, by shortening the heating time, it is possible to suppress the thermal damage to the semiconductor package and peripheral components, and the remounting can be repeated because there is no missing or misaligned solder ball. The work efficiency is reduced and the reliability is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a semiconductor package mounting process according to the present invention, in which (a) is a sectional view of a circuit board coated with a solder paste and (b) is a sectional view of a circuit board mounted with solder balls. And (c) is a cross-sectional view of the semiconductor device.

2A and 2B are explanatory views of a remounting process of a semiconductor package according to the present invention, FIG. 2A is a cross-sectional view of a BGA mounted semiconductor device, and FIG. 2B is a circuit board in which a solder paste is applied on a land. 2C is a cross-sectional view of a circuit board in which solder balls are mounted on a solder paste, and FIG. 3D is a cross-sectional view of a semiconductor device.

FIG. 3 is a flowchart showing a remounting process of a semiconductor package.

FIG. 4 is a sectional view of a conventional semiconductor device.

[Explanation of symbols]

1 semiconductor device, 2 semiconductor package, 2a surface,
3 circuit board, 4 surface electrode, 5 mounting surface, 6 land, 7 solder paste, 8 solder ball, 9 flux

Claims (2)

[Claims] 1. A ball-grid array surface on a circuit board having a plurality of lands corresponding to the surface electrodes, the semiconductor package having a plurality of surface electrodes arranged in a grid pattern on the surface. In the semiconductor device mounted by the mounting method, the circuit board is mounted on a large number of lands formed corresponding to the surface electrodes of the semiconductor package through a solder paste having a melting point lower than that of a solder ball. Of the semiconductor package, by melting and solidifying the solder paste, the reflow solder is applied in a state where the solder ball is fixed on the circuit board to melt and solidify the semiconductor package. A semiconductor device that is mounted. 2. A ball-grid array surface-mounting a semiconductor package having a plurality of surface electrodes arranged in a grid pattern on the surface thereof on a circuit board provided with a plurality of lands respectively corresponding to the surface electrodes. In a method of mounting a semiconductor package to be mounted by a method, a solder paste applying step of applying a solder paste having a melting point lower than that of a solder ball on each of the lands provided on the circuit board, A step of mounting a solder ball on each land, a step of heating the solder paste only at a temperature that melts the solder paste, and a step of fixing the solder ball through the solidified solder paste; The semiconductor package is assembled with the land and the surface electrode facing each other facing each other. Mounting method of a semiconductor package and having a assembling process of the semiconductor package attached, and a reflow soldering step of performing reflow soldering in the assembly of the semiconductor package and the circuit board.