JP2002057261A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which has a reliable solder bonding with no solder cracks, without having to conduct surface treatment, such as Ni plating on the metal base plate. SOLUTION: In the semiconductor device, a metal base board 6 formed of copper or copper-based alloy, and an insulating substrate 5 having a rear face pattern 4 formed of copper or copper-shaped alloy on a face opposite to the metal base board 6 are bonded by soldering. The rear face pattern 4 is surface- treated, while a solder bonding face 11 of the metal base board 6 is not surface- treated. A ten-point surface roughness (Rz) of the solder bonding face 11 is 4 μm or smaller. The rear face pattern 4 and the solder bonding face 11 are bonded by solder 8 with flux mixed in.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor device in which an insulating substrate and a metal base plate as a heat sink are joined by solder, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, when soldering a metal base plate and an insulating substrate, a surface treatment such as Ni plating is applied to the metal base plate in order to improve solderability and secure solder joint strength. Was. Table 1 shows combinations of the respective surface treatments of the metal base plate and the insulating substrate for performing the solder joining.

[0003]

[Table 1]

[0004] As shown in Table 1, conventionally, a metal base plate made of copper or a copper-based alloy as a base material with a Ni plating or the like on the surface, and a Ni plating or the like with the same surface. A combination of an insulating substrate having a circuit pattern and a back surface pattern based on copper or a copper-based alloy, or an insulating substrate on which the surface of the circuit pattern and the back surface pattern is not subjected to Ni plating or the like; Was a combination of The joining method in the above two combinations is to join in air using flux-filled solder (flux-filled solder + atmospheric reflow), or in reducing gas using non-flux solder, or in reducing gas and inert gas. Joining in mixed gas (Non-flux solder +
Atmosphere reflow).

[0005] Further, regarding a related solder joining technique,
For example, Japanese Patent Application Laid-Open No. 11-12714 discloses joining using non-flux solder. Table 2 shows that of
1 shows the concept of the effect of the surface roughness and the oxide film in JP-A No. 1-2714.

[0006]

[Table 2]

Japanese Patent Application Laid-Open No. H11-12714 discloses that the surface roughness of a lead frame material and the thickness of an oxide film are controlled to improve the direct wire bonding property and the solderability as shown in Table 2. Has been disclosed. However, although it discloses that the direct wire bonding property depends on the surface roughness and that the solderability depends on the oxide film, it does not disclose the relationship between the surface roughness and the solder crack.

[0008]

The conventional metal base plate has been subjected to a surface treatment such as Ni plating, and has a problem that the cost of the member is high due to the cost of the plating process. The present invention has been made in order to solve the above-mentioned problems, and a surface treatment of a metal base plate is omitted to alleviate the above-mentioned cost problem, and a semiconductor having a highly reliable solder joint that prevents solder cracks. A device and a method for manufacturing a semiconductor device are provided.

[0009]

In order to solve the above problems, a semiconductor device according to a first aspect of the present invention includes a metal base plate formed of copper or a copper-based alloy, and a metal base plate facing the metal base plate. In a semiconductor device in which an insulating substrate having a back surface pattern formed of copper or a copper-based alloy on a surface is bonded by solder, the back surface pattern is subjected to a surface treatment, and a solder bonding surface of the metal base plate is provided. Has not been subjected to a surface treatment, and has a ten-point surface roughness (R
z) is 4 μm or less, and the back surface pattern and the solder joint surface are joined by flux-filled solder.

Next, a semiconductor device according to a second invention of the present application is the semiconductor device according to the first invention of the present application, wherein the back surface pattern is not subjected to surface treatment, and the back surface pattern has ten points. The surface roughness (Rz) is 4 μm or less.

Next, a method for manufacturing a semiconductor device according to a third aspect of the present invention is a method for manufacturing a semiconductor device, comprising: a metal base plate formed of copper or a copper base alloy; and a copper or copper base alloy formed on a surface facing the metal base plate. In a method of manufacturing a semiconductor device in which an insulating substrate having a formed back surface pattern is joined by soldering, the solder joint surface of the metal base plate has a ten-point surface roughness (Rz) of 4
μm or less, subjected to a surface treatment on the back surface pattern, without surface treatment on the solder joint surface, using a non-flux solder, in a reducing gas, or in a reducing gas and an inert gas The method is characterized in that the back surface pattern and the solder joint surface are soldered in a mixed gas.

Next, a method for manufacturing a semiconductor device according to a fourth invention of the present application is the method for manufacturing a semiconductor device according to the third invention of the present application, wherein the back surface pattern is not subjected to a surface treatment. With a ten-point surface roughness (Rz) of 4μ
m or less.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of the semiconductor device according to the first embodiment. In FIG.
The semiconductor device includes a semiconductor element 1, an insulating substrate 5, a metal base plate 6 made of copper or a copper-based alloy, and an aluminum wire 10. The insulating substrate 5 includes the circuit pattern 3, the insulating base 2, and the back pattern 4. The circuit pattern 3 and the back surface pattern 4 are formed of copper or a copper-based alloy, and have been subjected to a surface treatment such as Ni plating. Solder joint surface 11 of metal base plate 6 not subjected to surface treatment such as Ni plating, and back surface pattern 4
Are joined using a solder material 8 containing a flux.

Further, the semiconductor element 1 is mounted on a circuit pattern 3 which has been subjected to a surface treatment such as Ni plating with a solder material 7. The aluminum wire 10 has one end bonded to the semiconductor element 1 and the other end bonded to the circuit pattern 3 by an ultrasonic method. As a result, the aluminum wire 10
Electrically connects the semiconductor element 1 and the circuit pattern 3. Also, as shown in FIGS. 1 and 2, the surface of the metal base plate 6 usually has a solder joint surface 11 where solder is easily wetted.
And a resist-coated surface 9 to which solder is hardly wetted. The resist coating surface 9 can prevent the solder material 8 from flowing out from the solder joint surface 11 because the solder is hard to wet.

Hereinafter, a method for manufacturing a semiconductor device will be described. First, the metal base plate 6 is rolled so that the ten-point surface roughness (Rz) of the solder joint surface 11 becomes 4 μm or less. Next, a surface treatment such as Ni plating is performed on the back surface pattern 4.

Next, in order to fix the back surface pattern 4 of the insulating substrate 5 to the metal base plate 6, a flux-containing cream solder is applied to a place where the insulating substrate 5 is to be mounted. After applying the cream solder, the insulating substrate 5 is mounted on the metal base plate 6.

Next, the applied cream solder is melted in the air using, for example, an atmospheric reflow furnace. When the molten solder cools, the back surface pattern 4 of the insulating substrate 5 is securely soldered to the metal base plate 6. When soldering,
The part to be soldered (in the first embodiment, the solder joint surface 1
It is generally known that when 1) is oxidized, the solderability deteriorates. When soldering in air, the portion to be soldered by oxygen contained in air is easily oxidized, but the flux contained in the solder prevents the solder joint surface 11 of the metal base plate 6 from being oxidized. The oxide film on the solder joint surface 11 can be removed.

At the same time that the insulating substrate 5 and the metal base plate 6 are soldered, the semiconductor element 1 is soldered to the circuit pattern 3 by the same method as described above or a conventional method.
Thereafter, the aluminum wire 10 is wire-bonded to the circuit pattern 3 and the semiconductor element 1 by an ultrasonic method.

The reason why the ten-point surface roughness (Rz) of the surface not subjected to the treatment such as Ni plating (the solder joint surface 11 of the metal base plate 6 and the surfaces 3 and 4 of the insulating substrate) is set to 4 μm or less. Will be described. FIG. 3 shows experimental data showing the degree of development of solder cracks under a substrate in a heat cycle with respect to the ten-point surface roughness (Rz) of a metal base plate (or the surface of an insulating substrate) whose surface is not subjected to Ni plating or the like. FIG. FIG. 3 shows the ten-point surface roughness (R
When z) exceeds 4 μm, the degree of development of solder cracks is rapidly increased.

FIG. 4 shows that the ten-point surface roughness (Rz) is 4
FIG. 4 is an enlarged schematic view of a solder joint when the diameter is larger than μm;
FIG. 5 is an enlarged schematic view of the solder joint when the ten-point surface roughness (Rz) is smaller than 4 μm. When the ten-point surface roughness (Rz) is smaller than 4 μm, the intermetallic compound layer 1
When the ten-point surface roughness (Rz) is larger than 4 μm while the surface of No. 2 is stable, the intermetallic compound layer 12 is not stable, and a part of the intermetallic compound non-forming layer 13 is exhibited. Furthermore, there is a possibility that solder cracks may develop early due to the concentration of stress generated at the solder fillet tip 14. From the above, the surface not subjected to the treatment such as Ni plating (the solder joint surface 11 of the metal base plate 6 and the surface 3 of the insulating substrate,
The ten-point surface roughness (Rz) of 4) is preferably 4 μm or less.

In the first embodiment, the solder material 8
Although cream solder was used as (and / or solder material 7), it is not limited to cream solder, and any solder can be used as long as it can join back pattern 4 and metal base plate 6. It is. further,
Ni plating is applied to improve solderability and secure solder joint strength. For example, Ag plating may be used as long as a similar effect is obtained. The same applies to the following Embodiments 2 to 4.

In the semiconductor device having the above configuration,
Ten-point surface roughness (R) of a metal base plate 6 based on copper or a copper-based alloy not subjected to surface treatment such as Ni plating
z) is rolled to Rz ≦ 4 μm,
A highly reliable solder joint can be performed, and the degree of development of a solder crack under the substrate in a heat cycle is not different from that of a metal base plate subjected to a surface treatment such as Ni plating.

Embodiment 2 FIG. Embodiment 2 of the present invention will be described. Here, the description of what is the same as the first embodiment is omitted to avoid duplication. First, a semiconductor device according to the second embodiment will be described. The semiconductor device according to the second embodiment is the same as the semiconductor device according to the first embodiment except that the solder material 8 (FIG. 1) is not flux-filled solder but non-flux solder. That is, the semiconductor element 1, the insulating substrate 5,
The metal base plate 6, the solder material 7, and the aluminum wire 10
This is the same as that of the semiconductor device in the first embodiment.

Next, a method of manufacturing a semiconductor device according to the second embodiment will be described. First, the metal base plate 6 is rolled so that the ten-point surface roughness (Rz) of the solder joint surface 11 becomes 4 μm or less. Next, a surface treatment such as Ni plating is performed on the back surface pattern 4.

Next, in order to fix the back surface pattern 4 of the insulating substrate 5 to the metal base plate 6, a non-flux cream solder is applied to a place where the insulating substrate 5 is mounted. After applying the cream solder, the insulating substrate 5 is mounted on the metal base plate 6.

Next, the applied cream solder is melted in a reducing gas (for example, hydrogen) or a mixed gas of a reducing gas and an inert gas by using, for example, a reflow furnace. When the molten solder cools, the back surface pattern 4 of the insulating substrate 5 is securely soldered to the metal base plate 6. It is generally known that at the time of soldering, when a portion to be soldered (the solder joint surface 11 in the second embodiment) is oxidized, the solderability deteriorates. In the second embodiment, since soldering is performed in a reducing gas or a mixed gas of a reducing gas and an inert gas, oxidation of the solder joint surface 11 of the metal base plate 6 can be prevented. Further, the reducing gas can remove the oxide film on the solder joint surface 11.

At the same time that the insulating substrate 5 and the metal base plate 6 are soldered, the semiconductor element 1 is soldered to the circuit pattern 3 by the same method as described above or a conventional method.
Thereafter, the aluminum wire 10 is wire-bonded to the circuit pattern 3 and the semiconductor element 1 by an ultrasonic method.

In the semiconductor device having the above configuration,
Ten-point surface roughness (R) of a metal base plate 6 based on copper or a copper-based alloy not subjected to surface treatment such as Ni plating
z) is rolled to Rz ≦ 4 μm,
A highly reliable solder joint can be performed, and the degree of development of a solder crack under the substrate in a heat cycle is not different from that of a metal base plate subjected to a surface treatment such as Ni plating.

Embodiment 3 Embodiment 3 of the present invention will be described. Here, the description of what is the same as the first embodiment is omitted to avoid duplication. First, a semiconductor device according to the third embodiment will be described. The back surface pattern 4 (FIG. 1) is not subjected to a surface treatment such as Ni plating, and the ten-point surface roughness (Rz) of the back surface pattern 4 is 4 μm or less. This is a difference from the semiconductor device according to the first embodiment.

Next, a method of manufacturing the semiconductor device according to the third embodiment will be described. First, the back surface pattern 4 and the metal base plate 6 are rolled so that the ten-point surface roughness (Rz) of the back surface pattern 4 and the solder joint surface 11 is 4 μm or less. Other steps in the method for manufacturing a semiconductor device are the same as those in the method for manufacturing a semiconductor device in the first embodiment.

In the semiconductor device having the above configuration,
The ten-point surface roughness (Rz) of the back surface pattern 4 and the metal base plate 6 based on copper or a copper-based alloy not subjected to surface treatment such as Ni plating is rolled to Rz ≦ 4 μm. Therefore, a highly reliable solder joint can be performed, and the degree of development of solder cracks under the substrate in a heat cycle is also subjected to a surface pattern such as Ni plating and a surface treatment such as Ni plating. It is no different from a metal base plate.

Embodiment 4 FIG. Embodiment 4 of the present invention will be described. Here, the description of what is the same as the second embodiment is omitted to avoid duplication. First, a semiconductor device according to the fourth embodiment will be described. The semiconductor device according to the fourth embodiment is different from the first embodiment in that surface treatment such as Ni plating is not performed on rear surface pattern 4 (FIG. 1) and ten-point surface roughness of rear surface pattern 4 is 4 μm or less. 2 is different from the semiconductor device of FIG.

Next, a method of manufacturing a semiconductor device according to the fourth embodiment will be described. First, the back surface pattern 4 and the metal base plate 6 are rolled so that the ten-point surface roughness (Rz) of the back surface pattern 4 and the solder joint surface 11 is 4 μm or less. Other steps in the method for manufacturing a semiconductor device are the same as those in the method for manufacturing a semiconductor device in the second embodiment.

In the semiconductor device having the above configuration,
The ten-point surface roughness (Rz) of the back surface pattern 4 and the metal base plate 6 based on copper or a copper-based alloy not subjected to surface treatment such as Ni plating is rolled to Rz ≦ 4 μm. Therefore, a highly reliable solder joint can be performed, and the degree of development of solder cracks under the substrate in the heat cycle is also subjected to a surface treatment such as Ni plating and a back surface pattern subjected to surface treatment such as Ni plating. It is no different from a metal base plate.

In order to reduce the ten-point surface roughness (Rz) of the back surface pattern 4 and the solder joint surface 11 to 4 μm or less, the metal base plate 6 and the back surface pattern 4 may be polished instead of rolling.

[0036]

According to the semiconductor device according to the first aspect of the present invention, highly reliable solder bonding can be performed without performing surface treatment on the solder bonding surface of the metal base plate. The effect is that an excellent and inexpensive metal base plate can be used.

According to the semiconductor device of the second aspect of the present invention, not only the surface treatment is not performed on the solder joint surface of the metal base plate, but also the highly reliable solder joint can be performed without performing the surface treatment on the back surface pattern. Since it can be performed, there is an effect that an extremely inexpensive semiconductor device with excellent productivity can be provided.

According to the method of manufacturing a semiconductor device according to the third aspect of the present invention, since the non-flux solder is used for soldering in a reducing gas or a mixed gas of a reducing gas and an inert gas, metal Highly reliable solder bonding can be performed without performing surface treatment on the solder bonding surface of the base plate.
This has the effect of being able to use an inexpensive metal base plate with excellent productivity. In addition, the use of non-flux solder eliminates the need for cleaning after solder joining, thereby improving productivity and reducing manufacturing costs.

According to the method of manufacturing a semiconductor device according to the fourth aspect of the present invention, highly reliable solder bonding can be performed without performing surface treatment not only on the solder bonding surface of the metal base plate but also on the back surface pattern. , So it is extremely productive,
This has the effect of providing an extremely inexpensive semiconductor device. In addition, the use of non-flux solder eliminates the need for cleaning after solder joining, thereby improving productivity and reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a semiconductor device according to a first embodiment;

FIG. 2 is a plan view of a metal base plate according to the first embodiment.

FIG. 3 is a graph showing experimental data showing the degree of development of solder cracks under a substrate in a heat cycle with respect to ten-point surface roughness (Rz) of a metal base plate whose surface is not subjected to Ni plating or the like.

FIG. 4 is an enlarged schematic view showing a solder joint under a substrate when ten-point surface roughness (Rz) is larger than 4 μm;

FIG. 5 is an enlarged schematic view showing a solder joint under the substrate when the ten-point surface roughness (Rz) is smaller than 4 μm.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Semiconductor element, 2 Insulating base material, 3 Circuit pattern, 4 Back pattern, 5 Insulating substrate, 6 Base plate, 7 Solder material, 8 Solder material, 9 Resist application surface, 10 Aluminum wire, 11 Solder joint surface,
12 intermetallic compound layer, 13 intermetallic compound non-forming layer, 14 solder fillet tip.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Takao 1-1-1 Imajuku Higashi, Nishi-ku, Fukuoka City, Fukuoka Prefecture Inside Fukuryo Semicon Engineering Co., Ltd. (72) Hideaki Nakama 2-2-2 Marunouchi, Chiyoda-ku, Tokyo No. 3 Mitsubishi Electric Corporation F-term (reference) 5F036 AA01 BB01 BC06 BC22 BD01

Claims (4)

[Claims] 1. A metal base plate formed of copper or a copper-based alloy and an insulating substrate having a back surface pattern formed of copper or a copper-based alloy on a surface facing the metal base plate by soldering. In the semiconductor device, a surface treatment is applied to the back surface pattern, a surface treatment is not applied to a solder joint surface of the metal base plate, and a ten-point surface roughness (Rz) of the solder joint surface is provided. Is 4 μm or less, and the back surface pattern and the solder joint surface are joined by flux-filled solder. 2. The semiconductor device according to claim 1, wherein no surface treatment is performed on the back surface pattern, and the back surface pattern has a ten-point surface roughness (Rz) of 4 μm or less. 3. A semiconductor in which a metal base plate made of copper or a copper-based alloy is joined to an insulating substrate having a back surface pattern made of copper or a copper-based alloy on a surface facing the metal base plate by soldering. In the method for manufacturing a device, a solder joint surface of the metal base plate may have a ten-point surface roughness (Rz).
Is processed so as to be 4 μm or less, a surface treatment is performed on the back surface pattern, and a surface treatment is not performed on the solder joint surface.
A method of manufacturing a semiconductor device, comprising: using a non-flux solder to solder-bond the back surface pattern and the solder bonding surface in a reducing gas or a mixed gas of a reducing gas and an inert gas. 4. The back surface pattern having a ten-point surface roughness (Rz) of 4 μm without subjecting the back surface pattern to a surface treatment.
4. The method according to claim 3, wherein the processing is performed as follows.