JP3199028B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a composite metal plate as a heat radiating plate, and more particularly to a semiconductor device having improved heat radiating characteristics with improved reliability of a heat radiating plate and mounting strength of a semiconductor element, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art A ceramic frame is mounted on a heat radiating plate composed of a metal plate in order to enhance the heat radiation of heat generated by a semiconductor device, and the semiconductor element is mounted on the surface of the heat radiating plate in the ceramic frame. Semiconductor devices have been proposed. FIG. 6 is a view showing an example of the heat radiating plate 1 made of metal.
The semiconductor element 3 is mounted on the surface of the heat sink 1 in a region surrounded by the ceramic frame 2. A lead 4 made of a thin metal plate is brazed to the upper surface of the ceramic frame 2, and the semiconductor element 3 and the lead 4 are electrically connected by a thin metal wire or metallized wiring (not shown).
Further, although not shown, for example, the ceramic frame 2
The semiconductor element is sealed in the ceramic frame by being covered with a cap made of a metal plate and brazing to the ceramic frame. The cap may be made of ceramic, and the sealing may be filled with a sealing resin in the ceramic frame.

In such a semiconductor device, the semiconductor element 3
Is immediately transmitted to the heat radiating plate 1 and dissipated, so that extremely high heat dissipation can be obtained, which is advantageous in realizing a high-output semiconductor device. In such a semiconductor device, since the ceramic frame 2 is directly joined to the metal radiator plate 1, a thermal stress is generated due to a difference in thermal expansion coefficient between the metal and the ceramic, and the ceramic frame 2 Cracks may occur, and the sealing characteristics of the semiconductor element 3 may be degraded. In recent years, as shown in FIG. 6, both sides of a Mo (molybdenum) plate 11 having a relatively small coefficient of thermal expansion are used as the heat radiating plate 1 by using Cu, which is a metal having a high thermal conductivity and a soft material. It has been proposed to be composed of a CuMoCu composite metal plate clad with a (copper) plate 12. For example, JP-A-5-29507.
In this composite metal plate, the coefficient of thermal expansion is approximately equal to the coefficient of thermal expansion of the ceramic, which is advantageous in solving the above-mentioned problem.

[0004] As described above, the CuMoCu composite metal plate is formed by cladding a Cu plate on both sides of the Mo plate and punching the Cu plate into a predetermined outer shape by press working. Since the bonding force at the interface between the plate and the Mo plate is weak, a minute gap is formed between the Cu plate and the Mo plate on the peripheral end surface which is the outer side surface of the CuMoCu composite metal plate due to the punching or the subsequent processing step. Then, there is a problem that the Cu plate and the Mo plate are separated from each other by the above-mentioned thermal stress from the gap as a starting point.
When such peeling occurs, peeling proceeds due to heat history, temperature cycle test, and the like at the time of assembling the semiconductor device,
The heat radiating effect of the heat radiating plate is reduced, and the heat radiating characteristics of the semiconductor device are deteriorated. In order to prevent such peeling at the end face between the Cu plate and the Mo plate, conventionally, Cu
There has been proposed a technique of plating the surface of a MoCu composite metal plate, filling a gap between the Cu plate and the Mo plate with a formed plating film, and preventing the above-mentioned peeling from occurring or progressing. For example, in Japanese Patent Application No. 9-314088 previously proposed by the present applicant, an electroless nickel-phosphorous plating layer is formed on the surface of a CuMoCu composite metal plate, and the Cu layer The gap at the interface is buried.

[0005]

As described above, the Cu plate and the M
The present inventor evaluated a CuMoCu composite metal plate in which an electroless nickel-phosphorous plating layer was formed on an o-plate composite metal plate. By forming the plating layer, it was possible to effectively separate the Cu plate and the Mo plate. However, since this plating layer is formed not only on the end surface of the composite metal plate where the joining surface of the Cu plate and the Mo plate exists but also on the surface of the Cu plate, the following problems occur. Was found to occur. That is, as schematically shown in FIG. 13, a cross section of the heat sink 1 made of a CuMoCu composite metal plate, when Ni (nickel) is plated on the surface of the Cu plate, an alloy layer of Cu and Ni is formed on the surface of the Cu plate. 13 are formed. Since the alloy of Cu and Ni has a lower thermal conductivity than Cu, the CuM
An Au (gold) plating layer 14 is formed on the heat sink 1 made of an oCu composite metal plate, and the semiconductor element 3 is made of a metal brazing material 15.
When a semiconductor device is configured by mounting the semiconductor device 3, the heat generated in the semiconductor element 3 is less likely to be transferred to the heat sink 1 due to the low thermal conductivity of the alloy layer 13, and the heat dissipation is reduced.

Further, the alloy with Ni formed on the surface of Cu of the CuMoCu composite metal plate has a higher hardness than Cu, so that the surface of the radiator plate is hard, and fine irregularities are formed on the surface. When the heat radiating plate 1 is connected to a device radiator 16 such as a device housing or a chassis by screws or the like, the contact area between the heat radiating plate 1 and the device radiator 16 is reduced. The efficiency of heat conduction from the semiconductor device to the equipment radiator 16 is reduced, and the heat dissipation of the semiconductor device is also reduced in this aspect. In addition, in the above-mentioned Japanese Patent Application No. 5-29507, in order to increase the bonding strength when brazing a semiconductor element to a CuMoCu composite metal plate, one to one surface is used.
Although a Ni plating layer of about 5 μm is formed, by forming such a relatively thick Ni plating layer on the surface of a Cu plate, an alloy of Cu and Ni is formed remarkably. It is undeniable that such problems will arise.

The present invention effectively prevents the peeling of the bond in the CuMoCu composite metal plate, increases the brazing bond strength of the semiconductor element mounted on the heat sink, and further increases the CuMo
It is an object of the present invention to provide a semiconductor device in which a heat radiating plate composed of a Cu composite metal plate has improved a heat radiating effect and a method of manufacturing the same.

[0008]

According to the present invention, there is provided a semiconductor device comprising:
Radiating plate in CuMoCu composite metal plate clad with Cu plate on both sides of the Mo plate is formed, the primary on the surface of the heat radiating plate
Ni plating layer is formed of, and on the surface of the heat sink with a ceramic frame is bonded, the semiconductor element is a mounting configurations on the surface of the heat radiating plate in said ceramic frame, further wherein the 1 following Ni plating layer Ri der is 0.5μm or less and the thickness thereof, said semiconductor element is the release
Form on the secondary nickel plating layer formed on the surface of the hot plate
It is characterized in that it is brazed on the surface of the formed gold plating layer . In this case, it is preferable that the first nickel plating layer is formed thicker than 0.1 μm. The primary nickel plating layer is formed at least on the peripheral end surface of the heat radiating plate in a region where the end surfaces of the Mo plate and the Cu plate are exposed.

Further, the semiconductor device according to the present invention is characterized in that molybdenum
CuMoCu composite metal plate with copper plate clad on both sides of the plate
A radiator plate is formed on the surface of the radiator plate.
Kel plating layer is formed, and on the surface of the heat sink
The ceramic frame is joined and the ceramic frame
Semiconductor having a semiconductor element mounted on the surface of the heat sink therein
In the apparatus, the primary nickel plating layer is the semiconductor layer.
Formed in a region excluding the region where the body element is mounted, and
The end surfaces of the molybdenum plate and the copper plate on the peripheral surface of the heat sink are exposed.
It is formed only in the presented region.

In any of the above semiconductor devices, a secondary nickel plating layer is formed on a surface of the heat sink including a region where the primary nickel plating layer is formed, and a gold plating is formed on the surface. A plating layer is formed, and the semiconductor element is brazed on the surface of the gold plating layer. And the primary nickel plating layer is 0.1
It is formed to a thickness of ５5 μm.

Further, a method of manufacturing a semiconductor device according to the present invention
Forming a primary Ni plating layer having a thickness of 0.5 μm or less on the surface of a heat sink formed of a CuMoCu composite metal plate, and forming a ceramic frame on the surface of the primary Ni plating layer; A step of brazing the leads to the frame with a metal brazing material, a step of sequentially forming a secondary Ni plating layer and a Au plating layer on the conductive surfaces of the heat sink and the ceramic frame, and A
brazing the semiconductor element on the surface of the u plating layer with a metal brazing material.

Further, another method of manufacturing a semiconductor device according to the present invention includes a step of forming a mask covering at least a region for mounting a semiconductor element on a surface of a heat sink formed of a CuMoCu composite metal plate; A step of forming a primary Ni plating layer having a thickness of 0.1 to 5 μm on the surface of the heat radiating plate in a region other than the area where the ceramic frame is formed; A step of brazing with a metal brazing material, a step of sequentially forming a secondary Ni plating layer and a Au plating layer on the conductive surfaces of the heat sink and the ceramic frame, and a step of forming the Au plating layer in the ceramic frame. Brazing a semiconductor element with a metal brazing material on the surface. In addition,
In this manufacturing method, the mask may be formed so as to cover the entire surface of the heat radiation plate on the side on which the semiconductor element is mounted and the surface on the opposite side.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. In this embodiment, as shown in FIG. 6, the ceramic frame 2 is brazed to the surface of the heat sink 1, and the semiconductor element 3 is mounted on the surface of the heat sink 1 inside the ceramic frame 2. An example in which the present invention is applied to a semiconductor device having a configuration in which a metal lead 4 is attached to the upper surface of the ceramic frame 2 and a semiconductor element is electrically connected to the lead is shown. FIGS. 1 to 5 are views showing a first embodiment of the present invention in the order of steps, and are cross-sectional views along the line AA in FIG. First, as shown in FIG. 1, 0.75 mm thick C
CuMoCu which is clad on the u-plate 12 and press-bonded by press working
After the composite metal plate is formed, the heat dissipation plate 1 made of the CuMoCu composite metal plate is formed by stamping into a predetermined outer shape, here a rectangular shape, by press punching.
In this press punching, small holes 5 for mounting are simultaneously opened at positions near both ends of the heat sink 1.

Next, the heat sink 1 is subjected to Ni electroplating to form a primary Ni plating layer 21 having a thickness of 0.5 μm or less on the entire surface of the heat sink 1. The primary Ni plating layer 21 enables the peripheral end face of the heat radiator 1 to be
That is, the end face of the joint between the Mo plate 11 and the Cu plate 12 on both sides of the composite metal plate is covered with the Ni plating layer 21, and the Mo plate 11 and the Cu plate 12
Even if a gap is formed in the joint surface with the Ni plating layer, the gap is covered with the Ni plating layer 21 and reinforced. Therefore, even if an external force is applied to the heat radiating plate 1 or an internal stress is generated thereafter, the spread of the peeled portion at the joint between the Mo plate 11 and the Cu plate 12 is prevented.

Next, as shown in FIG. 2, the above-described ceramic frame 2 formed in a rectangular frame shape is prepared, and a W (tungsten) metallized layer 22 is formed on upper and lower surfaces thereof. 2 by electrolytic plating on the surface of
The Ni plating layer 23 having a thickness of about 4 μm is formed. Further, a lead 4 made of a metal piece such as Cu or 42 alloy or Kovar is prepared. Then, Ag (silver) brazing material is formed in a thin film shape on the upper surface of the heat radiating plate 1 on the area where the ceramic frame 2 is mounted and on the upper surface of the ceramic frame 2 where the leads 4 are mounted. Reforms 24, 25 are placed, and these preforms 24, 2
The ceramic frame 2 is placed on the heat radiating plate 1 so as to sandwich the lead 5, and the lead 4 is placed on the ceramic frame 2, and then heated at about 850 ° C. while applying a required pressure thereon, as shown in FIG. As described above, the Ag brazing material preforms 24 and 25 are melted, and the heat radiating plate 1, the ceramic frame 2, and the lead 4 are respectively set to A.
g Braze.

Further, as shown in FIG. 4, the heat sink 1, the ceramic frame 2, and the leads 4 are electrolytically plated.
A secondary Ni plating layer 26 is formed. Therefore, the secondary Ni plating layer 26 is formed by the primary Ni of the heat sink 1.
The exposed surface of the plating layer 21, the exposed surface of the W metallized layer 22 and the Ni plated layer 23 of the ceramic frame 2, the surface of the lead 4, and the exposed surfaces of the Ag brazing materials 24 and 25 are respectively formed. The thickness of the secondary Ni plating layer 26 is arbitrary, and is formed, for example, to a thickness of about 0.5 μm to 3 μm, which is the same as that of the primary Ni plating layer 21. Further, an Au (gold) plating layer 27 is formed on the secondary Ni plating layer 26.

Then, as shown in FIG. 5, an AuSn (gold tin) solder 2 previously cut and formed on the surface of the Au plating layer 27 of the heat sink surrounded by the ceramic frame.
The semiconductor element 3 is placed on the AuSn braze 28 and heated at 320 ° C., so that the semiconductor element 3 is brazed on the heat sink 1. Thereafter, although not shown, the semiconductor element 3 and the lead 4 are electrically connected by a thin metal wire, and a cap made of metal or alumina ceramic is put on the ceramic frame 2. The semiconductor element 3 is sealed between the ceramic frame 2 and the metal cap by joining and sealing the cap and the ceramic frame with each other. As a result, the semiconductor device is completed, and the completed semiconductor device uses the small-diameter hole 5 provided in the radiator plate 1 so that the lower surface of the radiator plate is a device radiator such as a device housing or a chassis. It is mounted by screws so as to be in close contact with.

In the semiconductor device manufactured as described above, the primary Ni plating layer 21 is noted.
In this embodiment, the thickness of the primary Ni plating layer 21 is set to 0.1.
The feature is that the thickness is 5 μm or less. That is,
By forming a primary Ni plating layer 21 on the surface of the heat radiating plate 1 made of a CuMoCu composite metal plate,
Although the separation of the bond with the u-plate 12 is prevented, about 8 mm in the Ag brazing step immediately after that is prevented.
By heat treatment at a high temperature of 50 ° C., N
i and Cu in the Cu plate 12 react with each other. At this time, if the thickness of the Ni plating layer 21 is 1 μm or more,
Ni and Cu are interdiffused by the high-temperature heat treatment at about 850 ° C. to form an alloy layer having a high Ni concentration.
An alloy of Cu and Ni is formed on the surface of the plate 12. As described in the related art, the heat dissipation of the heat sink 1 is reduced by this alloy.

On the other hand, when the thickness of the Ni plating layer 21 is 0.5 μm or less as in this embodiment, the absolute amount of Ni required to be alloyed with Cu is small, so
By the high-temperature heat treatment at ℃, Ni diffuses into the Cu layer and is diluted, and an alloy layer having a high Ni concentration is not formed. Therefore, an alloy layer with Cu having a high Ni concentration is not formed on the surface of the Cu plate 12, that is, on the surface of the Cu plate 12 on the surface side of the heat radiating plate 1, and the heat conductivity of the alloy layer is low. Deterioration of the heat radiation characteristics of the heat radiation plate is prevented. Also, since the alloy layer of Cu and Ni is not formed on the surface of the Cu plate 12 on the back side of the heat sink 1, the hardness of the back surface of the heat sink 1 is not increased,
When the semiconductor device is mounted on the equipment heat radiator by using the screw for inserting the small-diameter hole 5, the close contact between the back surface of the heat sink 1 and the equipment heat radiator is improved, and the thermal conductivity from the heat radiator to the equipment heat radiator is improved. And the heat radiation characteristics of the semiconductor device can be improved.

Here, the present inventor has made the primary Ni plating layer 2
7 (a) and 7 (b) show measured values of the thermal resistance of the heat sink 1 made of a CuMoCu composite metal plate when the thickness of the heat sink 1 was changed, and graphs thereof. As you can see from the figure,
When the primary Ni plating layer 21 is 0.5 μm or less, the thermal resistance R
It was confirmed that when the value of "th" was low and the thickness was larger than 0.5 μm, the thermal resistance was rapidly increased. Conversely, when the Ni plating layer 21 is formed thin, it becomes difficult to form a uniform plating layer on the entire surface of the heat sink due to the concentration of the plating solution and the plating time.
Pinholes missing are more likely to occur. Incidentally, according to the experiment of the present inventor, as shown in the figure, when the primary Ni plating layer 21 is made thinner than 0.1, the pinhole generation rate is sharply increased and the Ni plating layer 21 Is impaired, that is, the effect of preventing the separation of the Mo plate and the Cu plate from each other is prevented. Therefore, from the above results, the primary Ni plating layer 21 has a thickness of 0.1 to 0.5 μm.
It is preferable that the thickness be in the range of m. In this range, the occurrence of pinholes can be suppressed, and peeling of the Cu and Mo plates in the CuMoCu composite metal plate can be effectively prevented.

In the embodiment shown in FIGS.
While the secondary Ni plating layer 21 is formed to a thickness of 0.1 to 0.5 μm, the secondary Ni plating layer 26 (thickness 1 to 3 μm) and the Au plating layer 27 formed after the Ag brazing 24 is assembled. (Thickness: 1 to 3 μm). The Au plating 27 is used for mounting the semiconductor element 3.
For the purpose of securing the leakage of the AuSn brazing solder 28 for the purpose of improving the connectivity of an Au wire (not shown) for leading the electrodes of the semiconductor element 3 to the outside, the lead 4 is made of PbSn alloy or the like. It is installed for the purpose of securing the brazing property when soldering and mounting. Further, the secondary Ni plating layer 26 is formed of the AuSn solder 2 of the semiconductor element 3 to be mounted.
Au plating layer 2 by heating (approximately 320 ° C.) at the time of brazing assembly and heating (240-360 ° C.)
It is provided as a barrier layer for preventing the diffusion of the components (Ag, Cu) of the Ag solder 24 on the surface of the metal alloy 7. If the secondary Ni plating layer 26 is not provided, the components (Ag, Cu) of the Ag solder 24 easily diffuse to the surface of the Au plating layer 27, and a small amount of Ag or Cu diffused on the surface is completed. In particular, in environments where water is used, adhesion of water and trace ionic impurities (Cl, Na, K, sulfur oxides, etc.)
In addition, due to the synergistic effect of the application of an electric field, the metal is dissolved and precipitated on the ceramic frame 2, and the insulating property of the ceramic frame 2 is easily damaged.
In particular, this secondary Ni plating layer 26 is applied to ensure the reliability of products that require long-term reliability (guaranteed for 5 to 30 years). If the thickness of the secondary Ni plating exceeds 5 μm, the surface of the heat radiating plate 1 becomes rough, and this surface roughening easily causes air bubbles in the AuSn braze 24 to which the semiconductor element 3 is fixed. This is not preferable because heat dissipation of the semiconductor device is impaired.

In the present embodiment, the thicknesses of the Mo plate 11 and the Cu plate 12 of the CuMoCu composite metal plate constituting the heat sink 1 are set to 0.5 μm: 0.75 μm, and the thickness of the Cu plate with respect to the thickness of the Mo plate. Ratio (hereinafter referred to as Cu / Mo ratio)
Is set to about 1.5. This is shown in FIGS. 8A and 8B.
As shown in the graph, the relationship between the Cu / Mo ratio and the cracks in the ceramic frame 2 was examined and the results were clarified.
When a temperature cycle test at 5 ° C. was performed, the crack generation rate in the ceramic frame was lowest when the Cu / Mo ratio was around 1.5. Therefore, as shown in FIG. 8C, the primary Ni plating layer 21 is
Ag brazing on top of being formed to a thickness of μm 2
5 Ag is passed through the Ni plating layers 26 and 27 to form CuMoC.
Even if it diffuses into the Cu plate 12 of the u composite metal plate, it is possible to prevent the occurrence of cracks in the ceramic frame 2 due to the above-mentioned temperature cycle. Therefore, as described in Japanese Patent No. 2675397, A
It is not necessary to form a Ni plating layer with a thickness of 1 to 3 μm in order to prevent g from diffusing into the Cu plate, and it is possible to enjoy the heat dissipation effect of the present embodiment described above.

As described above, in the semiconductor device using the CuMoCu composite metal plate as a heat sink, the thickness of the CuMoCu composite metal plate is 0.5 μm or less, preferably 0.1 μm or less.
By forming a primary Ni plating layer having a thickness of 0.5 μm, the Ni plating layer and the CuMoCu
The formation of an alloy layer with Cu having a high Ni concentration between the plate and the alloy layer is prevented, the formation of an alloy layer having low thermal conductivity and high hardness is prevented, and a semiconductor device having high heat dissipation can be obtained.
On the other hand, the generation of pinholes in the primary Ni plating layer can be suppressed, and peeling of the Cu plate and the Mo plate in the CuMoCu composite metal plate, which is the original purpose of the Ni plating layer, can be prevented. Further, by forming a secondary Ni plating layer and an Au plating layer to a required thickness on the primary Ni plating layer, the diffusion of the Ag brazing component to the surface of the Au plating layer is prevented, and the assembly is performed at the time of assembly. It is possible to provide a semiconductor device which is excellent in brazing / wire bonding properties and brazing properties in mounting and is excellent in long-term reliability.

FIGS. 9 to 11 show a second embodiment of the present invention in the order of manufacturing steps. Note that parts equivalent to those in the first embodiment are denoted by the same reference numerals. In FIG. 9, a heat radiating plate 1 made of a CuMoCu composite metal plate similar to the first embodiment is formed. Then, the mask 30 is formed on the mounting area of the semiconductor element on the surface of the heat sink 1 or a wider area including the mounting area, for example, an area surrounded by the ceramic frame 2 to be mounted. As the mask 30, a paint film or a resin film which is formed of an insulating material and which is not peeled off even by Ni electrolytic plating can be employed. Then, the heat sink 1 is plated with Ni and the mask 3 of the heat sink 1 is formed.
A primary Ni plating layer 21 having a thickness of 0.1 to 5 μm is formed in a region other than 0. Due to the primary Ni plating layer 21, the peripheral end surface of the radiator 1, that is, the CuMoCu
Mo plate 11 constituting a composite metal plate and Cu plates 1 on both sides thereof
2 is covered with the Ni plating layer 21, and even if a gap is formed in the joining surface between the Mo plate 11 and the Cu plate 12, this gap is covered with the Ni plating layer 21. And buried. For this reason,
Thereafter, even when an external force is applied to the heat radiating plate 1 or internal stress is generated, it is possible to prevent the joint between the Mo plate 11 and the Cu plate 12 from peeling off.

Next, as shown in FIG.
Is removed, the above-mentioned ceramic frame 2 formed in a rectangular frame shape is prepared, and W (tungsten) is formed on upper and lower surfaces thereof.
Forming a metallized layer 22 and forming the W metallized layer 2
2 having a thickness of 2 to 4 μm by electrolytic plating on the surface of
After the plating layer 23 is formed, the ceramic frame 2 is further formed on the heat radiating plate 1 and the ceramic frame 2 is further formed thereon by using a preform in which the Ag brazing material is formed in a thin film shape as in the first embodiment. The leads 4 are brazed with Ag brazes 24 and 25, respectively.

Further, as shown in FIG. 11, the exposed surface of the primary Ni plating layer 21 of the heat sink, the Ni plating of the ceramic frame 2, The exposed surface of layer 23, the surface of lead 4,
Further, secondary Ni plating layers 26 are formed on the exposed surfaces of the Ag brazing layers 24 and 25, respectively. The thickness of the secondary Ni plating layer 26 is arbitrary, but may be formed thinner than in the first embodiment. Further, the second order N
An Au plating layer 27 is formed on the i plating layer 26. Subsequently, A of the heat sink 1 surrounded by the ceramic frame 2
Au cut and formed in advance on the u-plated layer 27
The semiconductor element 3 is mounted on the Au solder 28 and heated at 320 ° C. to braze the semiconductor element 3 on the heat sink 1. The subsequent steps are the same as those in the first embodiment, and a description thereof will not be repeated.

In this embodiment, the primary Ni plating layer 2
Since the thickness of the heat sink 1 is 0.5 to 5 μm, by forming the Ni plating layer 21 to be thick, the CuMoCu
The joint surface between the Mo plate 12 and the Cu plate 12 on the peripheral end surface of the composite metal plate can be suitably covered with the Ni plating layer 21, and peeling at these joints can be effectively prevented. On the other hand, when the Ni plating layer 21 is formed thick, the surface of the Cu plate 12
It is inevitable that an alloy layer of Ni and Ni is formed. However, since the primary plating layer 21 does not exist in the region of the heat sink 1 where the semiconductor element 3 is mounted by using the mask 30, alloying of Cu and Ni is prevented in this region, No alloy layer is formed. Note that a secondary Ni plating layer is also formed in this region.
Since the i-plated layer is formed after Ag brazing, it does not undergo high-temperature treatment and does not alloy with Cu. Therefore, at least the semiconductor element 3 of the heat sink 1
No alloy layer of Cu and Ni having poor thermal conductivity does not exist in the region where the semiconductor device 3 is mounted, and the heat generated in the semiconductor element 3 is well conducted to the heat sink 1, and the heat is efficiently emitted from the heat sink 1. The heat will be dissipated. In this embodiment, an alloy layer with the thick primary Ni plating layer 21 is formed on the surface of the Cu plate on the back side of the heat sink 1 to increase the hardness. Is used to mount the heat sink to the equipment radiator with a heat conductive resin or metal brazing material, the back surface of the heat sink and the equipment radiator can be brought into close contact with the resin or brazing material. Can be configured.

As a modification of the second embodiment, as shown in FIG. 12, a primary Ni plating layer 2 is formed only on the peripheral end surface of a heat radiating plate 1 composed of a CuMoCu composite metal plate.
1 may be formed. That is, the mask 30 in the step of FIG. 10 of the second embodiment is formed on the entire surface of the heat sink 1 and the back surface.
The primary Ni plating layer 21 is formed only on the exposed surface, that is, on the peripheral end surface of the heat sink 1. This primary plating layer 2
1 has a thickness of 0.5 to 5 μm as in the second embodiment. If formed in this way, the joint surface between the Mo plate 11 and the Cu plate 12 at the peripheral end surface of the CuMoCu composite metal plate is N
It is possible to suitably cover with the i-plated layer 21,
Needless to say, peeling in the CuMoCu composite metal plate can be effectively prevented.

On the other hand, the primary plating layer 21 does not exist on the front surface of the heat sink 1 on which the semiconductor element 3 is mounted and on the rear surface of the heat sink 1 mounted in contact with the device heat sink. . Therefore, after that, the secondary Ni plating layer 26 is formed on each of the front and back surfaces of the heat sink 1, but since this Ni plating layer is formed after Ag brazing,
No high-temperature treatment is performed, and no alloying with Cu occurs. Thereby, the semiconductor element 3 on the surface of the heat sink 1
Since there is no alloy layer of Cu and Ni with poor thermal conductivity in the area where the The heat will be dissipated. Further, Cu on the back side of the heat sink 1
Since the alloy layer of Ni and Cu is not formed on the surface of the plate, the hardness of the surface of the Cu plate is not increased, and when the semiconductor device is mounted on the device heat radiator,
A close contact state between the back surface of the heat sink and the device heat radiator can be ensured, and an effective heat dissipation structure can be configured.

In the second embodiment and its modifications, the primary Ni plating layer 21 is formed to have a thickness of 0.1 μm or more, so that the generation of pinholes can be suppressed. Further, by forming the secondary Ni plating layer and the Au plating layer to a required thickness, the diffusion of the Ag brazing component to the surface of the Au plating layer is prevented, and the brazing / wire bonding property during assembly and the mounting property are reduced. A semiconductor device having excellent brazing properties and excellent long-term reliability. Further, Cu / Cu constituting the CuMoCu composite metal plate is
By setting the Mo ratio to around 1.5 (preferably 1.5 ± 0.3), cracks in the ceramic frame 2 can be effectively prevented.

Also, in each of the above embodiments, the preform 24 used when Ag brazing the ceramic frame to the heat radiating plate is used.
Although the one formed according to the shape of the ceramic frame 2 is used, a preform having an area covering the entire surface of the heat sink may be used. In this case, the molten preform is the primary Ni plating layer 2 formed on the surface of the heat sink 1.
1 to cover the peripheral end face from the surface of the heat sink. Therefore, the Mo plate of the CuMoCu composite metal plate and C
The joint surface at the end face of the u-plate is covered with the primary Ni plating layer 21 and the Ag braze 24, and the Ag braze 24 accumulates in a concave portion (not shown) due to minute peeling of the Mo plate 11 and the Cu plate 12. Since the portion is formed and is reinforced satisfactorily, it is possible to more effectively prevent the progress and expansion of the peeling. Also, by forming the secondary Ni plating layer 26 and the Au plating layer 27 to a predetermined thickness, the components of the Ag solder 24 can be prevented from diffusing to the surface of the Au plating layer 27, and brazing and soldering during assembly can be prevented. It is possible to provide a semiconductor device which is excellent in wire bonding property and brazing property in mounting and is excellent in long-term reliability. Further, by providing the secondary Ni plating layer 26, in the case of a semiconductor device that does not require long-term reliability, the Au plating layer 27 can be formed thin, which is advantageous in reducing costs.

[0032]

As described above, the present invention provides CuMo
1 formed on the surface of a heat sink composed of a Cu composite metal plate
The thickness of the next Ni plating layer is 0.5μm or less, the release
Form on the secondary nickel plating layer formed on the surface of the hot plate
Brazing the semiconductor device on the surface of the formed gold plating layer
With this configuration, the C of the CuMoCu composite metal plate
Alloying between u and Ni can be prevented, and the formation of an alloy layer having low thermal conductivity and high hardness on the surface of the heat sink can be prevented, so that a semiconductor device having excellent heat dissipation properties can be obtained. . A secondary Ni plating layer is formed on the primary Ni plating layer.
By forming the Au plating layer to a required thickness,
The component of the brazing material for joining the mic frame to the heat sink is A
prevents diffusion to the surface of the u-plated layer,
Brazing and wire bonding when attaching to a heat sink
Provides semiconductor devices with excellent reliability and long-term reliability
it can. Furthermore, by forming the primary Ni plating layer thicker than 0.1 μm, peeling of the joint between the Cu plate and the Mo plate on the peripheral end surface of the CuMoCu composite metal plate can be prevented, and high reliability and high heat dissipation can be achieved. A semiconductor device having a heat sink can be obtained.

Further, a region of the surface of the heat sink composed of the CuMoCu composite metal plate excluding at least a region where the semiconductor element is mounted, for example, the entire surface of the semiconductor element mounting surface or the surface on which the semiconductor element is mounted, and By forming a primary Ni plating layer in a region excluding the entire opposite surface, alloying of Cu and Ni can be reliably prevented at least in a surface region of a heat sink on which a semiconductor element is mounted. In addition, it is possible to prevent the formation of an alloy layer having low thermal conductivity and high hardness, and to obtain a semiconductor device excellent in heat dissipation. In this case , by forming the primary Ni plating layer to a thickness of 0.1 to 5 μm, CuMoC
The peeling of the joint between the Cu plate and the Mo plate on the peripheral end surface of the u composite metal plate can be prevented, and a semiconductor device having a highly reliable and highly heat-dissipating heat sink can be obtained. Furthermore, this
In this case, the secondary Ni plating may be formed on the primary Ni plating layer.
To form the required thickness of the pin layer and the Au plating layer
The brazing material used to join the ceramic frame to the heat sink
Prevents components from diffusing to the Au plating layer surface
Brazing and wire bonding when attaching the body element to the heat sink
Semiconductor device with excellent mounting characteristics and long-term reliability.
Can be provided.

Further, the CuMoCu composite metal plate is
By setting the thickness ratio (Cu / Mo ratio) of the plate and the Mo plate to about 1.5, cracks in the ceramic frame can be effectively prevented. For this reason, it is not necessary to form a thick Ni plating layer in order to prevent the Ag brazing for brazing the ceramic frame from diffusing into the Cu plate, and an alloy layer with Cu having a high Ni concentration immediately below the semiconductor element 3 is not required. This is also advantageous in preventing the formation, and can further promote the effects of the present invention described above.

[Brief description of the drawings]

FIG. 1 is a first sectional view of a manufacturing step according to a first embodiment of the present invention.

FIG. 2 is a second sectional view of the manufacturing process according to the first embodiment of the present invention.

FIG. 3 is a third sectional view of the manufacturing process according to the first embodiment of the present invention.

FIG. 4 is a fourth cross-sectional view of the manufacturing process of the first embodiment of the present invention.

FIG. 5 is a fifth sectional view of the manufacturing process of the first embodiment of the present invention.

FIG. 6 is a schematic perspective view of a semiconductor device to which the present invention is applied.

FIG. 7 is a diagram showing the relationship between the thickness of a Ni plating layer, thermal resistance and pinholes.

FIG. 8 is a diagram showing a relationship between a Cu / Mo ratio and a ceramic crack, and a relationship between diffusion of an Ag solder and a ceramic crack.

FIG. 9 is a first cross-sectional view of a manufacturing step according to the second embodiment of the present invention.

FIG. 10 is a second sectional view illustrating a manufacturing step according to the second embodiment of the present invention;

FIG. 11 is a third sectional view of the manufacturing process according to the second embodiment of the present invention.

FIG. 12 is a cross-sectional view of a modification of the second embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view for explaining a problem caused by a Ni plating layer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 radiator plate (CuMoCu composite metal plate) 2 ceramic frame 3 semiconductor element 4 lead 11 Mo plate 12 Cu plate 21 primary NI plating layer 22 W metallization layer 23 Ni plating layer 24, 25 Ag solder 26 secondary Ni plating layer 27 Au Plating layer 28 AuSn brazing 30 Mask

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/36

Claims (10)

(57) [Claims] 1. A radiator plate is formed of a CuMoCu composite metal plate in which a copper plate is clad on both surfaces of a molybdenum plate, a primary nickel plating layer is formed on a surface of the radiator plate, and In a semiconductor device in which a ceramic frame is joined and a semiconductor element is mounted on the surface of the heat sink in the ceramic frame, the primary nickel plating layer has a thickness of 0.5 μm or less;
The semiconductor device, wherein the semiconductor element is brazed on a surface of a gold plating layer formed on a secondary nickel plating layer formed on a surface of the heat sink. 2. The primary nickel plating layer has a thickness of 0.1 μm.
The semiconductor device according to claim 1, wherein the semiconductor device is formed to be thicker than m. 3. The semiconductor device according to claim 1, wherein the primary nickel plating layer is formed at least on a peripheral end surface of the heat sink at a region where end surfaces of the molybdenum plate and the copper plate are exposed. 4. The semiconductor device according to claim 1, wherein said ceramic frame is brazed on a surface of said primary nickel plating layer with a brazing metal. 5. A radiator plate is formed of a CuMoCu composite metal plate in which a copper plate is clad on both sides of a molybdenum plate, a primary nickel plating layer is formed on a surface of the radiator plate, and a radiator plate is formed on the surface of the radiator plate. Is a semiconductor device having a ceramic frame bonded thereto and a semiconductor element mounted on the surface of the heat sink in the ceramic frame, wherein the primary nickel plating layer is a region excluding a region where the semiconductor element is mounted. Formed around the heat sink.
Surface where the end surfaces of the molybdenum plate and the copper plate are exposed.
A semiconductor device formed only in the region . 6. A secondary nickel plating layer is formed on a surface of the heat sink including a region where the primary nickel plating layer is formed, and a gold plating layer is formed on the surface. The semiconductor device according to claim 5 , wherein the surface of the gold plating layer is brazed. 7. The method according to claim 7, wherein the primary nickel plating layer is 0.1 to
7. The semiconductor device according to claim 6 , which is formed to a thickness of 5 μm. 8. A step of forming a primary nickel plating layer having a thickness of 0.5 μm or less on a surface of a heat sink formed of a CuMoCu composite metal plate, and forming a ceramic on the surface of the primary nickel plating layer. A step of brazing a lead to the ceramic frame with a metal brazing material; a step of sequentially forming a secondary nickel plating layer and a gold plating layer on the conductive surface of the heat sink and the ceramic frame; Brazing a semiconductor element on a surface of the gold plating layer in a frame with a brazing metal material. 9. A step of forming a mask covering at least a region for mounting a semiconductor element on a surface of a heat sink formed of a CuMoCu composite metal plate, and forming a mask on a surface of the heat sink in a region other than the region covered by the mask. 1 with a thickness of 0.1-5 μm
A step of forming a next nickel plating layer, a step of brazing a ceramic frame on the surface of the radiator plate, and a step of brazing a lead to the ceramic frame with a metal brazing material. A step of sequentially forming a secondary nickel plating layer and a gold plating layer, and a step of brazing a semiconductor element on a surface of the gold plating layer in the ceramic frame with a metal brazing material. Manufacturing method. 10. The method of manufacturing a semiconductor device according to claim 11, wherein the mask covers the entire surface of the heat radiation plate on the side on which the semiconductor element is mounted and the opposite surface. .