JP3173547B2 - Method of forming solder bumps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a solder bump for mounting a semiconductor device face down on a circuit board.

[0002]

2. Description of the Related Art Conventionally, as a method of forming solder bumps on a semiconductor element, for example, as shown in Japanese Patent Application Laid-Open No. 4-236433, a support substrate having a concave portion on the surface thereof opposed to an electrode of the semiconductor element. Some use.

In FIG. 3, reference numeral 1 denotes a support substrate made of aluminum, stainless steel, or the like, and a cylindrical recess 2 is formed on the surface thereof so as to face an electrode of a semiconductor element. The concave portion 2 is filled with a metal material 3 made of a low-melting alloy or metal containing flux as a component by sliding a squeegee 4. Then, as shown in FIG. 3C, the semiconductor device 5 is placed such that the protruding electrodes 6 formed on the semiconductor element 5 face the concave portions 2 of the support substrate 1. In this state, a reflow process is performed in an atmosphere of heated air to heat the protruding electrodes 6 of the semiconductor element 5 and melt the metal material 3 to form the solder bumps 7 on the semiconductor element 5 as shown in FIG. I do.

[0004]

However, the above-mentioned conventional method has the following problems. That is, conventionally, the projection electrode 6 is heated to melt the metal material 3 in an atmosphere in which hot air is blown by a fan to force convection of the air. Since the semiconductor element 5 was thin and lightweight, the semiconductor element 5 mounted on the support substrate 1 was displaced, and the solder bump was not transferred normally.

[0005] Then, although an infrared ray reflow treatment with reduced convection of hot air, as used for mounting components on a printed circuit board, was performed, the semiconductor element 5 composed of a silicon base material transmits infrared rays. Therefore, the semiconductor element itself did not generate heat, and as a result, only unmelted solder bumps were transferred as shown in FIG.

As described above, it is extremely difficult to form a solder bump on a thin and lightweight semiconductor element by the conventional method.

Therefore, in the present invention, by placing a heat transfer plate on a semiconductor element, a load is applied to the semiconductor element by the weight of the heat transfer plate, and very good heat transfer is performed on the semiconductor element made of a silicon base material. To form a completely molten solder bump on a thin and lightweight semiconductor element.

[0008]

According to the present invention, there is provided a method of forming a solder bump, comprising: forming a projection electrode formed on a semiconductor element on a support substrate in which a concave portion formed on the surface is filled with a metal material; The semiconductor element is placed on a support substrate so as to face the recess, and a heat transfer plate formed of a material that absorbs infrared rays and generates heat is placed on the semiconductor element,
The metal material is melted in an atmosphere heated by hot air while being heated by infrared rays, so that solder bumps are formed on the protruding electrodes of the semiconductor element.

[0009]

According to the above method, the heat transfer plate placed on the semiconductor element generates heat by infrared rays when it is heated and melted in a reflow furnace with infrared rays, and subsequently, the heat transfer plate is connected to the semiconductor element. Heat is well transmitted to the semiconductor element due to the contact, and as a result, the protruding electrode on the semiconductor element also generates heat, and the metal melted in the concave portion of the support substrate is completely melted on the protruding electrode on the semiconductor element. Is transcribed.

Further, since the heat transfer plate applies a load on the semiconductor element by its own weight, there is no displacement of the semiconductor element due to convection due to hot air, a decrease in viscosity of a solvent component in the flux or bumping. is there.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram showing a method for forming a solder bump in one embodiment of the present invention, and FIG. 2 is a sectional view of a semiconductor device on which a solder bump is formed.

FIG. 1 is different from the prior art in that the support substrate 1 is formed of a sintered body of carbon (manufactured by IBIDEN Co., Ltd.), and in FIG. It is composed of the same material.

The support substrate 1 has a concave portion 2 in which a metal material is filled in a position facing a protruding electrode of a semiconductor element by machining or etching on a surface of a carbon sintered body plate.
Is formed. The heat transfer plate 8 may have the same shape as the support substrate 1 in which the recess 2 is not formed.

First, as shown in FIGS. 1A and 1B, a squeegee 4 slides a metal paste 3 made of a low melting point alloy or a metal into a concave portion 2 provided on the surface of a support substrate 1. Fill with In this embodiment, a cream solder containing 9% by weight of a flux and containing a Sn-37Pb eutectic alloy having an average particle diameter of 10 μm or less was used as the metal paste 3.

Next, as shown in FIG. 1C, a bump electrode 6 previously formed on the semiconductor element 5 by a stud bump bonding method using a gold wire, and a concave portion 2 formed on the surface of the support substrate 1 are formed. Align and align. Then Figure 1
The heat transfer plate 8 is disposed on the upper surface of the semiconductor element 5 as shown in FIG.

In this state, the metal paste 3 is melted by heating in a reflow furnace combined with infrared rays, and the protruding electrode 6 is melted.
Around the solder bumps. At this time, the semiconductor element 5
Since the heat transfer plate 8 is placed on the heat transfer plate, heat is transferred from the heat transfer plate 8 to the semiconductor element 5 and then to the protruding electrodes 6 on the semiconductor element. The metal melted in the concave portion 2 is transferred around the bump electrode 6 in a completely melted form.

Further, since the heat transfer plate 8 applies a load on the semiconductor element 5 by its own weight, displacement of the semiconductor element due to convection due to hot air, a decrease in the viscosity of the solvent component in the flux, bumping, or the like is prevented. There is nothing.

In the above embodiment, since the support substrate 1 and the heat transfer plate 8 are made of the same material and have substantially the same shape, the temperature distribution is uniform above and below the semiconductor element 5 and good transfer can be performed.

The metal paste 3 used was a Sn-37Pb eutectic alloy having an average particle diameter of the metal particles of 10 μm or less, but the material of the metal particles was Sn, Pb, Bi, S
An alloy mainly containing b or In or a simple substance may be used.

[0020]

As described above, according to the present invention, a semiconductor element is arranged on a supporting substrate in which a concave portion formed on the surface is filled with a metal paste so that projecting electrodes are opposed to each other. A plate is arranged. The projecting electrode of the semiconductor element can be sufficiently heated by the heat transfer plate. Further, since the heat transfer plate applies a load to the semiconductor element by its own weight, it is possible to prevent displacement due to hot air during reflow, buoyancy due to solvent, and displacement due to bumping.

Thus, the completely melted solder bumps are collectively transferred onto the semiconductor element, so that not only solder bumps having low connection resistance can be obtained, but also semiconductor elements having a high transfer yield can be obtained, which is extremely advantageous in practical use. Become.

[Brief description of the drawings]

FIG. 1 is a process diagram showing one embodiment of a method for forming a solder bump of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor device having solder bumps formed by the same method.

FIG. 3 is a process chart showing a conventional method of forming a solder bump.

FIG. 4 is a cross-sectional view of a semiconductor device on which solder bumps are formed by the same method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support substrate 2 Depression 3 Metal paste 4 Squeegee 5 Semiconductor element 6 Protruding electrode 7 Bump 8 Heat transfer plate

Claims (1)

(57) [Claims] 1. A semiconductor device is mounted on a support substrate having a recess formed on a surface thereof filled with a metal material such that a projection electrode formed on the semiconductor device faces the recess.
A heat transfer plate formed of a material that absorbs infrared rays and generates heat is placed on the semiconductor element, and the metal material is melted in an atmosphere heated by hot air while being heated by infrared rays, and is applied to the projecting electrodes of the semiconductor element. A method for forming a solder bump in which a bump is formed.