JPH04369227A - Electrode formation method and mounting method of semiconductor device - Google Patents

Abstract

PURPOSE:To provide the electrode structure and the mounting structure, of a semiconductor device, wherein the semiconductor device and a circuit board can be connected easily and with good reliability. CONSTITUTION:In a mounting method, the upper part of an aluminum electrode pad 2 on an IC substrate 1 for a semiconductor device is provided with a protrusion-shaped bump electrode 3, a low-melting-point alloy foil 5 is brought into contact with the top part of the bump electrode 3, the IC substrate 1 is heated, a low-melting-point alloy bonded layer 8 is formed only on the bump electrode 3 and the semiconductor device is connected electrically to a terminal electrode on the circuit board via the bonded layer 8. When the bonded layer is formed by a transfer operation, it is possible to avoid the contamination of the semiconductor device, the spread of the bonded layer can be regulated by the protrusion-shaped bump electrode 3, and a bonding operation at a fine pitch can be realized.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for forming electrodes of a semiconductor device when the device is mounted on a circuit board and a method for mounting the same, and particularly to a method for forming electrodes of a semiconductor device mounted face-down. and how to implement it.

0002

[Prior Art] In the past, soldering was often used to mount semiconductor devices on circuit boards, but in recent years, as semiconductor device packages have become smaller and the number of connection terminals has increased, the spacing between connection terminals has become narrower. It has become increasingly difficult to deal with this problem using conventional soldering techniques.

[0003]Recently, therefore, a method has been devised in which a bare semiconductor device is directly attached to a circuit board in order to reduce the mounting area and to achieve efficient use.

In particular, when connecting a semiconductor device to a circuit board, an electrode structure consisting of a vapor-deposited film of an adhesive metal or a diffusion-preventing metal and a solder layer formed by plating on the aluminum electrode pad of the semiconductor device is prepared in advance. The mounting structure, in which the semiconductor device is placed face down and heated to a high temperature to fuse the solder to the terminal electrodes of the circuit board, is effective because it has strong mechanical strength after connection and can be connected all at once. It is said to be a method. (For example, Kogyo Kenkyukai, January 15, 1980, edited by Japan Microelectronics Association, "IC Mounting Technology") Below, with reference to the drawings, is an example of the electrode formation method and mounting method of the conventional semiconductor device described above. I will explain about it.

(FIG. 5) is a schematic explanatory diagram of a method for forming an electrode of a semiconductor device having a conventional solder bump electrode.
) is a schematic explanatory diagram of the electrode structure of the solder bump electrode, and (FIG. 7) is a schematic explanatory diagram of the mounting structure of the semiconductor device.

In (FIG. 5), 19 is the I of the semiconductor device.
C substrate, and 20 is an aluminum electrode pad. 21 is a close contact metal film, and 22 is a diffusion prevention metal film. 23
is a passivation film, and 24 is a photoresist film. 25 is a solder bump after plating, and 26 is a solder bump after reflow. (Figure 7), 27
is a circuit board, and 28 is a terminal electrode.

A method for forming an electrode and a method for mounting a conventional semiconductor device having solder bump electrodes configured as described above will be briefly described below.

First, as shown in (a) of FIG. 5, Cu is deposited on the aluminum electrode pad 20 of the IC substrate 19 of the semiconductor device.
A close contact metal film 21 such as Cr and a diffusion prevention metal film 22 such as Cr are formed by vapor deposition. After that, (b) of (Figure 5)
As shown in the figure, the area other than the electrode part is covered with photoresist 24,
Solder is deposited on the diffusion prevention metal film 22 by a plating method to obtain mushroom-shaped solder bumps 25 shown in (c) of FIG. 5. Finally, by performing solder reflow (Fig. 5
), the solder bumps 26 are formed as shown in (d) to obtain a solder bump electrode having the electrode structure shown in FIG. 6.

Furthermore, after aligning the semiconductor device having the solder bump electrodes obtained as described above to a predetermined position on the circuit board 27 and loading it face down,
The semiconductor device is mounted in the mounting structure shown in FIG. 7 by heating to a high temperature of 00 to 300° C. to melt the solder bumps 26 and fusing them to the terminal electrodes 28.

0010

[Problem to be Solved by the Invention] However, in the electrode forming method and mounting method of a semiconductor device as described above,
1. In order to form solder bumps by plating, it is necessary to prevent contamination of the semiconductor device from the plating solution by cleaning, making the electrode formation method complicated and lacking in versatility. 2. When heating the IC board to a high temperature to melt the solder and connect it to the terminal electrode, it is not possible to maintain a gap between the IC board and the circuit board, so there is a risk that the solder will spread and cause a short circuit with the adjacent circuit board. There were issues such as these.

The present invention has been made in view of the above problems, and its purpose is to easily connect a semiconductor device and a circuit board with high reliability and at a fine pitch. An object of the present invention is to provide a method for forming electrodes and a method for mounting semiconductor devices.

0012

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a semiconductor device mounted face-down on a circuit board, in which a protruding bump electrode is provided on an aluminum electrode pad portion of the semiconductor device, and a heated bump electrode is provided on an aluminum electrode pad portion of the semiconductor device. After adsorbing the back side of the semiconductor device with a suction device equipped with the device, the bump electrodes on the front surface of the semiconductor device are brought into contact with the low melting point alloy foil, and the semiconductor device is heated with a heating device to cool the contact area between the bump electrode and the alloy foil. After transferring the low melting point alloy onto the bump electrode, it is aligned and stacked on the terminal electrode of the circuit board, and the semiconductor device is heated again by the heating device to bond the low melting point alloy on the bump electrode and the terminal electrode. It is characterized by mounting semiconductor devices, and attempts to realize highly reliable mounting of semiconductor devices on circuit boards.

[0013]

[Operation] The present invention prevents contamination of a semiconductor device by melting a low melting point alloy foil on a protrusion-shaped bump electrode formed on an aluminum electrode pad portion of a semiconductor device to form a bonding layer of a low melting point alloy. When bonding a semiconductor device to a terminal electrode on a circuit board, the bonding layer can be bonded at a fine pitch without shorting with the adjacent layer.
Moreover, a highly reliable semiconductor device mounting structure can be realized.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of forming electrodes and a method of mounting a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

(FIG. 1) is a schematic explanatory diagram of a method for forming electrodes of a semiconductor device according to an embodiment of the present invention, and (FIG. 2)
3 is a schematic explanatory diagram of an electrode structure of a semiconductor device according to the electrode forming method of the above embodiment, and (FIG. 3) is a schematic explanatory diagram of a mounting method of a semiconductor device according to an embodiment of the present invention.
(FIG. 4) is a schematic explanatory diagram of a mounting structure of a semiconductor device mounted according to the above embodiment.

In (FIG. 1), 1 is an IC of a semiconductor device.
It is a substrate, and 2 is an aluminum electrode pad. 3 is a protruding bump electrode, and 4 is a passivation film. 5 is a low melting point alloy foil, and 6 is an adsorption device. 7 is a heating device, and 8 is a bonding layer of a low melting point alloy. (Figure 3
), 9 is a semiconductor device on which the electrode of this example is formed. 10 is an adsorption device, and 11 is a heating device. 12 is a supply reel of rolled low melting point alloy foil, and 13 is a take-up reel. 14 is a horizontally stretched low melting point alloy foil, and 15 is a transfer stage. 16
is a stage for positioning the semiconductor device and the circuit board. 17 is a circuit board, and 18 is a terminal electrode.

A method of forming electrodes and a method of mounting the semiconductor device configured as above will be explained below with reference to the drawings.

First, as shown in FIG. 1A, protruding bump electrodes 3 are formed on aluminum electrode pads 2 of an IC substrate 1 of a semiconductor device by a known method.

Next, as shown in (b) of (FIG. 1), the top of the protruding bump electrode 3 is brought into contact with the low melting point alloy foil 5 made of solder, and then (c) of (FIG. 1) is made. As shown in FIG.
℃ to melt the low melting point alloy at the contact portion between the bump electrode 3 and the low melting point alloy foil 5, and transfer the bonding layer 8 of the low melting point alloy onto the bump electrode 3.

By the above method, an electrode structure consisting of a protruding bump electrode 3 and a bonding layer 8 of a low melting point alloy can be easily formed on an aluminum electrode pad 2 of a semiconductor device as shown in FIG. 2.

Furthermore, in the method for mounting a semiconductor device of this embodiment, as shown in (a) of FIG. After that, as shown in (b) of FIG. 3, a semiconductor device is applied to a low melting point alloy foil 14 made of solder that is supplied from a roll-shaped low melting point alloy foil supply reel 12 and stretched horizontally on a transfer stage 15. A protruding bump electrode formed on the surface of 9 is brought into contact.

In this state, the semiconductor device 9 is heated to 200 to 300° C. by the heating device 11 to transfer the low melting point alloy onto the bump electrodes.

Thereafter, the transferred low melting point alloy foil is taken up by the take-up reel 13.

Furthermore, the semiconductor device 9 onto which the bonding layer of the low melting point alloy has been transferred as described above is placed on a stage 16 for positioning at a predetermined position on the circuit board 17, as shown in (c) of FIG. After positioning and loading face down, the heating device 11 of the suction jig 10 heats the bonding layer of the low melting point alloy to 200 to 300°C again, melting the bonding layer of the low melting point alloy, and bonding the semiconductor to the terminal electrode 18. Implement the equipment.

By the above method, when the bonding layer of the low melting point alloy is bonded to the terminal electrode 18 as shown in FIG.
The gap between the C substrate 1 and the circuit board 17 can be maintained by the protruding bump electrodes 3, and since the bonding layer 8 of a low melting point alloy is formed only on the top, the spread of the bonding layer is restricted. This makes it possible to obtain a semiconductor device mounting structure that allows connection at fine pitches without the risk of short-circuiting with adjacent devices.

The semiconductor device mounting structure of the present invention is extremely stable because the protruding bump electrodes can control the spread of solder, which was impossible in the conventional mounting structure using solder bump electrodes. Semiconductor devices can be mounted with high reliability and high density.

In this embodiment, if the shape of the bump electrode is a two-stage protrusion, the effect can be more pronounced.

Further, in this embodiment, the protruding bump electrodes are formed using a plating method, but as long as the bump electrodes have a protruding shape, they may be formed by other methods such as wire bonding.

Furthermore, although the semiconductor device is heated by the pulse heater only when necessary, it may be heated by a normal heater all the time.

Further, although the low melting point alloy foil is made of solder, its material is not limited to solder, and may be formed of other metals as long as it is made of a low melting point alloy.

[0031]

Effects of the Invention As explained above, according to the electrode forming method and mounting method for a semiconductor device of the present invention, a low melting point alloy foil is placed on a protruding bump electrode formed on an aluminum electrode pad portion of a semiconductor device. By melting and forming a bonding layer of a low-melting point alloy, it is possible to form an electrode consisting of a bump electrode and a bonding layer on a semiconductor device without contaminating the semiconductor device with plating liquid, etc., making it extremely versatile. expensive.

Furthermore, by having an electrode structure in which a bonding layer of a low melting point alloy is formed only on the top of the protruding bump electrode, it is possible to control the spread of the bonding layer when bonding a semiconductor device to a terminal electrode of a circuit board. This makes it possible to bond at a fine pitch without causing short-circuits between the bonding layers and adjacent ones, making it possible to mount semiconductor devices extremely stably, reliably, and at high density.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a method for forming electrodes of a semiconductor device in an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of an electrode structure of a semiconductor device according to the electrode forming method of the present invention.

FIG. 3 is a schematic explanatory diagram of a method for mounting a semiconductor device in an embodiment of the present invention.

FIG. 4 is a schematic explanatory diagram of a mounting structure of a semiconductor device mounted according to an embodiment of the present invention.

FIG. 5 is a schematic explanatory diagram of a method of forming an electrode of a semiconductor device having a conventional solder bump electrode.

FIG. 6 is a schematic explanatory diagram of the electrode structure of a conventional solder bump electrode.

FIG. 7 is a schematic explanatory diagram of a mounting structure of a semiconductor device mounted using conventional solder bump electrodes.

[Explanation of symbols]

1 IC substrate for semiconductor devices 2 Aluminum electrode pad 3. Protruding bump electrode 4 Passivation film 5 Low melting point alloy foil 6 Adsorption device 7 Heating device 8 Low melting point alloy bonding layer 9 Semiconductor device 10 Adsorption device 11 Heating device 12 Supply reel 13 Take-up reel 14 Low melting point alloy foil 15 Transfer stage 16 Stage for positioning 17 Circuit board 18 Terminal electrode 19 IC board 20 Aluminum electrode pad 21 Adhesive metal film 22 Diffusion prevention metal film 23 Passivation film 24 Photoresist film 25 Solder bump after plating 26 Solder bump after reflow 27 Circuit board 28 Terminal electrode

Claims (9)

[Claims] [Claim 1] A method for forming electrodes of a semiconductor device mounted face-down on a circuit board, comprising: providing a protruding bump electrode on an aluminum electrode pad portion of the semiconductor device; and bringing the bump electrode into contact with a low melting point alloy foil. A method for forming an electrode for a semiconductor device, comprising: heating the semiconductor device to melt the contact portion between the bump electrode and the alloy foil to transfer a low melting point alloy onto the bump electrode to form a bonding layer. 2. The method of forming an electrode for a semiconductor device according to claim 1, wherein the protruding bump electrode has a two-step protrusion shape. 3. The method of forming an electrode for a semiconductor device according to claim 1, wherein the material of the protruding bump electrode is made of Au. 4. The method of forming electrodes for a semiconductor device according to claim 1, wherein the material of the low melting point alloy foil is solder. 5. The method of forming electrodes for a semiconductor device according to claim 1, wherein the low melting point alloy foil is a foil having a thickness of 20 to 100 μm. 6. The method of forming electrodes for a semiconductor device according to claim 1, wherein the semiconductor device is heated with a pulse heater to transfer the low melting point alloy. 7. In a method for mounting a semiconductor device face-down on a circuit board, after the back side of the semiconductor device is suctioned by a suction device equipped with a heating device, the bump electrodes formed on the surface of the semiconductor device are bonded to a low melting point alloy. contact with foil,
After the semiconductor device is heated with a heating device to transfer the low melting point alloy onto the bump electrodes, the semiconductor device is aligned and stacked on the terminal electrodes of the circuit board, and the semiconductor device is heated again with the heating device to transfer the low melting point alloy onto the bump electrodes. A method for mounting a semiconductor device, characterized by mounting the semiconductor device by bonding a melting point alloy and a terminal electrode. 8. The method of mounting a semiconductor device according to claim 7, wherein the low melting point alloy foil is in the form of a roll, and the low melting point alloy foil is continuously supplied by a supply section and a winding section. 9. The method for mounting a semiconductor device according to claim 7, wherein the low melting point alloy is made of solder.