JPH11297909A - Metallic plate for radiating heat and package for electronic parts using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic plate for radiating heat having an appropriate coefficient of thermal expansion and a high coefficient of thermal conductivity. SOLUTION: A metallic plate 10 for radiating heat is composed of a molybdenum plate 11 coated with plated copper films 12 on both surfaces. The ratio t2/t1 of the thickness t2 of each plated copper film 12 to the thickness t1 of the molybdenum plate 11 is adjusted to <=2.5. Consequently, the metallic plate 10 can absorb the heat generated from a semiconductor element 30 and, at the same time, can well radiate the absorbed heat to the outside. Therefore, the semiconductor element 30 can be operated stably in a normal state for a long period. Moreover, since the occurrence of thermal stress between the metallic plate 10 and a package main body 20 due to the difference between the coefficients of thermal expansion of the plate 10 and main body 20 can be prevented and, at the same time, the warping of the metallic plate is suppressed to a relatively small value, the main body can be firmly bonded to the metallic plate 10 and the semiconductor element 30 can be firmly fixed to the semiconductor element mounting section 31 of the metallic plate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal plate for heat radiation and a package for electronic parts using the same.

[0002]

2. Description of the Related Art In semiconductor devices, Si chips and Ga
Electronic components such as a semiconductor element such as an As chip and a chip capacitor are mounted on an electronic component mounting portion provided in an electronic component package and are put to practical use. Ceramics such as alumina are excellent in heat resistance, durability, thermal conductivity, etc.
It is suitable as a material for the main body of the electronic component package, and ceramic electronic component packages are currently in active use.

[0003] In order to reduce the package size, increase the mounting density on a mounting board, and improve the electrical characteristics, this ceramic electronic component package is generally formed by laminating and firing a plurality of green sheets to form a ceramic. A package body is manufactured. Further, in the case where a semiconductor element such as a power module generates a large amount of heat, the semiconductor device may not operate normally due to heat generation if the semiconductor element is mounted only by a normal method. Therefore, as a package for an electronic component that satisfactorily dissipates heat generated during operation of a semiconductor element to the atmosphere, for example, a ceramic package having a heat-dissipating metal plate made of a metal having excellent heat conductivity is known. I have.

[0004]

The heat dissipating metal plate used for the ceramic package according to the prior art described above has, for example, a thermal expansion coefficient close to that of the ceramic package body and a thermal conductivity of about 200 W / mK. A composite material formed by impregnating a porous sintered body of tungsten or molybdenum with molten copper is known.

However, in recent years, semiconductor devices used in the field of high density and high integration and power electronics in the field of power electronics have been rapidly advanced, and heat generated per unit area or unit volume generated when the semiconductor device is operated. The amount tends to increase rapidly. For this reason, in the above-mentioned conventional ceramic package, since the thermal conductivity of the heat-dissipating metal plate is about 200 W / mK, the heat generated during operation of the semiconductor element is completely dissipated to the outside through the heat-dissipating metal plate. It is difficult to make. Therefore, there has been a problem that a semiconductor element becomes high in temperature due to heat generated during operation of the semiconductor element, and the semiconductor element is physically destroyed or a characteristic of the semiconductor element undergoes a thermal change, thereby causing a malfunction of the semiconductor element. .

The present invention has been made to solve such a problem, and an object of the present invention is to provide a metal plate for heat radiation having an appropriate coefficient of thermal expansion and a high thermal conductivity.
Another object of the present invention is to provide an electronic component package capable of satisfactorily dissipating heat generated during operation of the electronic component to the outside.

[0007]

According to the heat dissipating metal plate of the present invention, molybdenum, copper-molybdenum,
A copper plating film is formed on one or both surfaces of any metal plate selected from copper-tungsten. Therefore, by using a metal plate of molybdenum, copper-molybdenum or copper-tungsten having an appropriate coefficient of thermal expansion, by applying copper plating to this metal plate, it has an appropriate coefficient of thermal expansion and a high thermal conductivity. A heat-dissipating metal plate can be obtained.

[0008] By forming a copper plating film on a metal plate,
Compared with the case where the copper plate is integrally joined to the metal plate by rolling, the thickness of the metal plate and the copper plating film does not vary, and the heat-dissipating metal plate has a predetermined uniform thickness. Therefore, since the coefficient of thermal expansion of the heat-dissipating metal plate does not partially differ, for example, the heat-dissipating metal plate and the insulator such as ceramics are brazed using a brazing material such as silver brazing, and When the semiconductor element is mounted on the heat dissipating metal plate, the heat dissipating metal plate does not deform, the heat dissipating metal plate and the insulator can be firmly joined, and the semiconductor element is firmly fixed on the heat dissipating metal plate. be able to.

A heat-dissipating metal plate formed by forming a copper plating film on both sides of a metal plate has a thermal stress caused by a difference in thermal expansion between the metal plate and the copper plating film. Since both sides cancel each other out, the heat dissipating metal plate can always be flat. Therefore, when the semiconductor element is mounted on the metal plate for heat radiation, the semiconductor element can be firmly fixed on the metal plate for heat radiation.

When a semiconductor element is mounted on a heat-dissipating metal plate, the thermal conductivity of the heat-dissipating metal plate is higher than that of the entire heat-dissipating metal plate by the value of the upper layer of the heat-dissipating metal plate immediately below the semiconductor element. Is important, a copper plating film may be formed only on one surface of the metal plate corresponding to a portion directly below the semiconductor element. Copper plating methods include an electrolytic plating method and an electroless plating method.Either plating method can be used, but the electrolytic plating method has a shorter plating time than the electroless plating method. This is preferable because the quality of the plating film is stable, the production yield is high, and the production cost can be reduced. The above-described electrolytic plating method or electroless plating method can be performed by a known method, and is not particularly limited.

According to the heat-dissipating metal plate according to the second aspect of the present invention, since the thickness ratio between the copper plating film and the metal plate is 2.5 or less, the coefficient of thermal expansion of the heat-dissipating metal plate is moderate. Thus, it is possible to prevent the occurrence of thermal stress due to the difference in the coefficient of thermal expansion between the copper plating film and the metal plate. Therefore, the metal plate for heat dissipation can always be made flat, and when the semiconductor element is mounted on the metal plate for heat dissipation,
The semiconductor element can be firmly fixed on the metal plate for heat radiation.

The thickness ratio between the copper plating film and the metal plate is 2.
When the value exceeds 5, the thermal expansion coefficient of the heat-dissipating metal plate becomes large, and the heat-dissipating metal plate and the insulator are brazed using a brazing material such as silver brazing, and the semiconductor element is mounted on the heat-dissipating metal plate. In this case, the brazing strength between the heat-dissipating metal plate and the insulator may be reduced, or the heat-dissipating metal plate may be warped, and the semiconductor element may not be firmly fixed on the heat-dissipating metal plate. is there.

The ratio of the thickness of the copper plating film to the thickness of the metal plate is preferably 0.1 or more. If the thickness ratio between the copper plating film and the metal plate is less than 0.1, the thermal conductivity of the heat radiating metal plate becomes low, and when the semiconductor device is mounted on the heat radiating metal plate, There is a risk that the heat generated during operation may not be sufficiently removed. According to the electronic component package of the third aspect of the present invention,
Since the electronic component is mounted on the metal plate for heat radiation according to claim 1 or 2, the heat generated during operation of the semiconductor element can be satisfactorily dissipated to the outside, and the semiconductor element operates normally and stably for a long period of time. Can be done.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. (First Embodiment) A first embodiment in which the present invention is applied to, for example, a surface-mount type ceramic semiconductor package will be described with reference to FIGS.

As shown in FIG. 1, a semiconductor package 100 made of ceramics includes a metal plate 10 for heat radiation, a package body 20 made of alumina, a lead frame 50 and the like. The heat-dissipating metal plate 10 has a semiconductor element mounting part 31 on which the semiconductor element 30 is mounted and fixed, and the semiconductor element 30 is mounted on the semiconductor element mounting part 31.
It is mounted and fixed using an adhesive such as glass, resin, or brazing material.

The heat dissipating metal plate 10 has a structure in which a copper plating film 12 is formed on both upper and lower surfaces of a molybdenum plate 11 as a metal plate. In the heat-dissipating metal plate 10, a ratio t 2 between the thickness t 2 of the copper plating film 12 and the thickness t 1 of the molybdenum 11.
/ T1 is limited to 2.5 or less. A package body 20 made of alumina and formed in a frame shape is joined to the upper surface of the heat-dissipating metal plate 10 using a brazing material 15 such as silver braze so as to surround the entire periphery of the semiconductor element mounting portion 31. I have.
A space for mounting the semiconductor element 30 is formed by the metal plate 10 for heat dissipation and the package body 20. This space is
A lid or the like (not shown) is joined to the upper surface 21 of the package body 20 with a sealing material such as solder, low-melting glass, resin, brazing material, or the like, so as to be airtightly sealed.

The package body 20 has a bonding pattern 23 made of tungsten, molybdenum, or the like, which is bonded to the metal plate 10 for heat dissipation via the brazing material 15 on the lower surface 22. And the like. Joining pattern 2
3 and the surface of the wiring pattern 24 are plated with nickel, gold, or the like. One end of the wiring pattern 24 is electrically connected to the electrode portion of the semiconductor element 30 via the bonding wire 40, and the other end of the conductor wiring layer 24 is connected to an external electric circuit such as a printed circuit board.
0 is electrically connected.

Next, a method of manufacturing the metal plate 10 for heat radiation will be described. (1) As shown in FIGS. 2 and 3, for example, a copper plating film 12 is formed on both upper and lower surfaces of a molybdenum plate 11 by an electrolytic plating method using a plating solution mainly containing copper sulfate, copper nitrate or the like. Thus, the metal plate 10 for heat radiation is obtained. The thickness of the heat-dissipating metal plate 10 shown in FIG.
Ratio t2 between thickness t2 of Mo2 and thickness t1 of molybdenum plate 11
/ T1 is 2.5 or less.

Next, a method of manufacturing the package body 20 will be described. (2) Magnesia, silica, calcined talc, alumina powder
Powder to which a small amount of a sintering aid such as calcium carbonate and a coloring agent such as titanium oxide, chromium oxide, and molybdenum oxide are added,
A plasticizer such as dioxyl phthalate, a binder such as an acrylic resin or a butyral resin, and a solvent such as toluene, xylene and alcohol are added, and the mixture is sufficiently kneaded to obtain a viscosity of 200.
A slurry of 0 to 40000 cps is produced, and a plurality of 0.3 mm-thick alumina green sheets, for example, are formed by a doctor blade method.

(3) Each green sheet is processed into a desired shape using a punching die, a punching machine, or the like, and further, a plurality of via holes are punched to form a conductor layer using tungsten powder, molybdenum powder, or the like for each via hole. The vias are filled to form vias. An inner layer pattern is formed on the green sheet corresponding to the inner layer of the package body using the same conductive paste as the via. A conductor pattern is screen-printed on the green sheet corresponding to the front and back layers of the package body using the same conductor paste as the via.

(4) A green sheet corresponding to an inner layer having a via and an inner layer pattern formed thereon and a green sheet corresponding to a surface layer on which a conductor pattern is screen-printed are laminated.
This green sheet laminate is heated to, for example,
It is integrated by thermocompression bonding under the condition of 0 to 250 kg / cm ² . (5) The integrated green sheet laminate is fired at 1500 to 1600 ° C. in a nitrogen-hydrogen mixed gas atmosphere. As a result, the resin component in the conductive paste is decomposed and eliminated, a wiring pattern is formed on the surface of the package body made of alumina, and a bonding pattern is formed on the back surface.

(6) The electrode portion and the bonding pattern of the formed wiring pattern are plated with nickel, gold, or the like to obtain the package body 20 shown in FIG. Next,
The heat-dissipating metal plate 10 produced in the step (1) and the above-mentioned (2)
To the package body 20 manufactured in the steps (6) to (6) using a brazing material such as silver brazing, electrically connecting a lead frame to an electrode portion of the wiring pattern, and mounting a semiconductor device on a semiconductor element mounting portion of the semiconductor package. The device is mounted, and the electrode portion of the semiconductor device and the electrode portion of the wiring pattern are electrically connected by wire bonding. Thereafter, the semiconductor element mounting portion is hermetically sealed with a lid or the like, and then mounted on an external electric circuit such as a printed circuit board.

Next, Table 1 shows the results of measuring the thermal conductivity, the coefficient of thermal expansion, and the warpage of the metal plate 10 for heat radiation shown in FIG. Table 1 shows the results of measuring the thermal conductivity, the coefficient of thermal expansion, and the warpage of Comparative Example 1 in which the copper plating film was not formed on the molybdenum plate 11. Comparative Example 1
It has the same configuration as the molybdenum plate 11 of the first embodiment shown in FIG. 2, and substantially the same parts are denoted by the same reference numerals. Further, as shown in FIG. 6, the molybdenum plate 11 is
Table 1 shows the results of measuring the thermal conductivity, the coefficient of thermal expansion, and the warpage of Comparative Example 2 in which Sample No. 4 was integrally joined by rolling. Note that the warp values shown in Table 1 are all length x
It is the result of measurement for the dimensions of width × thickness = 30 mm × 30 mm × 1 mm.

[0024]

[Table 1]

As shown in Table 1, in Comparative Example 1,
Thermal conductivity is 150 W / mk and thermal expansion coefficient is 6 × 10
⁻⁶ / ° C., and warpage is 5 μm. Therefore, when the semiconductor element is mounted on the molybdenum plate 11, it is difficult to completely dissipate the heat generated during operation of the semiconductor element to the outside via the metal plate for heat radiation. Therefore, the temperature of the semiconductor element becomes high due to the heat generated during the operation of the semiconductor element, and the semiconductor element may be physically damaged, or the characteristics of the semiconductor element may change in heat, and the semiconductor element may malfunction. In Comparative Example 2, the thermal conductivity was 27%.
0 W / mk, the coefficient of thermal expansion is 9.5 × 10 ⁻⁶ / ° C., and the warpage is 70 μm. For this reason, the molybdenum plate 1
A brazing material, such as silver brazing, is used to braze a heat-dissipating metal plate and an insulator such as ceramics to which the copper plates 13 and 14 have been integrally joined by rolling, and a semiconductor element is mounted on the heat-dissipating metal plate. When mounted, the metal plate for heat dissipation has a large warp, so that the metal plate for heat dissipation and the insulator cannot be firmly joined, and the semiconductor element cannot be firmly fixed on the metal plate for heat dissipation.

On the other hand, in the first embodiment, as shown in Table 1, the thermal conductivity is 280 W / mk, the thermal expansion coefficient is 8.5 × 10 ⁻⁶ / ° C., and the warpage is 8 μm. . Therefore, as shown in FIG. 1, even when the semiconductor element 30 is placed and fixed on the semiconductor element mounting portion 31, the heat-dissipating metal plate 10 absorbs the heat generated by the semiconductor element 30 and transfers the absorbed heat to the outside. Can be satisfactorily dissipated. Therefore, the semiconductor element 30 can be normally and stably operated for a long time.

Further, in the first embodiment, the thermal expansion coefficient of the package body 20 made of alumina shown in FIG.
× 10 ⁻⁶ / ° C., and the coefficient of thermal expansion of the heat-dissipating metal plate 10 is close to the coefficient of thermal expansion of the package body 20. Therefore, as shown in FIG. 1, even if the metal plate 10 for heat dissipation and the package body 20 are joined by the brazing material 15 and the semiconductor element 30 is placed and fixed on the semiconductor element mounting portion 31, It is possible to prevent the occurrence of thermal stress due to the difference in the coefficient of thermal expansion between the package and the package body 20, and to firmly join the heat-dissipating metal plate 10 and the package body 20. , Semiconductor element mounting part 31
The semiconductor element 30 can be firmly fixed.

Further, in the first embodiment, the metal plate 10 for heat radiation has a smaller warp than that of the metal plate for comparative example 2, so that the metal plate 10 for heat radiation and the package body 20 can be more firmly joined. The semiconductor element 30 can be further firmly fixed to the semiconductor element mounting portion 31. In the first embodiment, the present invention is applied to a surface mount type semiconductor package. However, in the present invention, the present invention may be applied to an insert type package such as a PGA (Pin Grid Array) or another type package.

In the present invention, the present invention is not limited to the electronic component package made of alumina, but may be applied to any ceramic electronic component package such as aluminum nitride, mullite, low temperature fired glass ceramic, and the like. (Second Embodiment) A heat radiation metal plate according to a second embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 5, the heat dissipating metal plate 110 of the second embodiment is the same as the molybdenum plate 1 of the first embodiment shown in FIG.
1 is replaced with a copper-tungsten plate 111 formed by impregnating a porous sintered body of tungsten with molten copper, and other portions that are substantially the same as those in the first embodiment are denoted by the same reference numerals.
Copper plating films 12 are formed on both upper and lower surfaces of a copper-tungsten plate 111 as a metal plate. The thickness t2 of the copper plating film 12 and the copper-tungsten plate 111 shown in FIG.
The ratio t2 / t11 to the thickness t11 is limited to 2.5 or less.

Next, the results of measuring the thermal conductivity, the coefficient of thermal expansion and the warpage of the metal plate 110 for heat radiation shown in FIG. 5 are shown in Table 1. In the second embodiment, as shown in Table 1, the thermal conductivity is 270 W / mk, and the thermal expansion coefficient is 9.
5 × 10 ⁻⁶ / ° C., and warpage is 13 μm. Therefore, when the semiconductor element is mounted and fixed on the heat radiating metal plate 110, the heat radiating metal plate 110 can absorb the heat generated by the semiconductor element and satisfactorily dissipate the absorbed heat to the outside. Therefore, the semiconductor element can be normally and stably operated for a long time.

Further, in the second embodiment, since the coefficient of thermal expansion of the metal plate for heat dissipation 110 is close to the coefficient of thermal expansion of an insulator such as alumina, the metal plate for heat dissipation 110 and the insulator are brazed. When the semiconductor element is mounted and fixed on the heat-dissipating metal plate 110, thermal stress caused by the difference in the coefficient of thermal expansion between the heat-dissipating metal plate 110 and the insulator is prevented. Thus, the heat radiating metal plate 110 and the insulator can be firmly joined, and the semiconductor element can be firmly fixed on the heat radiating metal plate 110.

Further, in the second embodiment, the warpage of the heat-dissipating metal plate 110 is kept relatively small.
When the heat-dissipating metal plate 110 and the insulator such as alumina are joined by a brazing material, the heat-dissipating metal plate 110 and the insulator can be more firmly joined, and the semiconductor element is further mounted on the heat-dissipating metal plate 110. Can be fixed firmly. (Third Embodiment) A heat-dissipating metal plate according to a third embodiment of the present invention is the copper-tungsten plate 111 of the second embodiment shown in FIG.
Is replaced by a copper-molybdenum plate obtained by impregnating a porous sintered body of molybdenum with molten copper, and copper plating films are formed on both upper and lower surfaces of the copper-molybdenum plate as a metal plate. The ratio of the thickness of the copper plating film to the thickness of the copper-molybdenum plate is limited to 2.5 or less.

Next, the results of measuring the thermal conductivity, the coefficient of thermal expansion, and the warpage of the metal plate for heat radiation according to the third embodiment are shown in Table 1. In the third example, as shown in Table 1, the thermal conductivity was 310 W / mk, and the thermal expansion coefficient was 9.
It is 8 × 10 ⁻⁶ / ° C., and the warpage is 12 μm. Therefore, when the semiconductor element is mounted and fixed on the metal plate for heat dissipation,
The heat-dissipating metal plate can absorb the heat generated by the semiconductor element and satisfactorily dissipate the absorbed heat to the outside. Therefore, the semiconductor element can be normally and stably operated for a long time.

Further, in the third embodiment, since the coefficient of thermal expansion of the metal plate for heat dissipation is close to the coefficient of thermal expansion of an insulator such as alumina, the metal plate for heat dissipation and the insulator are joined by brazing. However, when the semiconductor element is placed and fixed on the heat-dissipating metal plate, it is possible to prevent the occurrence of thermal stress between the heat-dissipating metal plate and the insulator due to the difference in the coefficient of thermal expansion between the two. In addition, the metal plate for heat radiation and the insulator can be firmly joined, and the semiconductor element can be firmly fixed on the metal plate for heat radiation.

Furthermore, in the third embodiment, since the warp of the heat-dissipating metal plate is relatively small, when the heat-dissipating metal plate and the insulator such as alumina are joined by a brazing material, The plate and the insulator can be more firmly joined, and the semiconductor element can be more firmly fixed on the heat-dissipating metal plate. In the embodiments of the present invention described above, molybdenum, copper-molybdenum, copper-
A copper plating film is formed on one or both surfaces of any metal plate selected from tungsten. Therefore, by setting the thickness ratio between the copper plating film and the metal plate to 2.5 or less, it is possible to obtain a heat-dissipating metal plate having an appropriate coefficient of thermal expansion and high thermal conductivity. Therefore, the semiconductor element can be normally and stably operated for a long period of time by mounting and fixing the semiconductor element on the metal plate for heat radiation.

In the embodiments of the present invention, the heat-dissipating metal plate has a structure in which copper plating films are formed on both surfaces of the metal plate. In the present invention, however, the semiconductor element is mounted on the heat-dissipating metal plate. When fixed, a copper plating film may be formed only on one surface of the metal plate corresponding to a portion directly below the semiconductor element.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor package according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a method of manufacturing a metal plate for heat dissipation according to a first embodiment of the present invention and showing a molybdenum plate.

FIG. 3 is a cross-sectional view illustrating a heat-dissipating metal plate according to a first embodiment of the present invention.

FIG. 4 is a sectional view showing a package body according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a metal plate for heat dissipation according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a heat-dissipating metal plate according to Comparative Example 2 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 heat-dissipating metal plate 11 molybdenum plate (metal plate) 12 copper plating film 15 brazing material 20 package body 30 semiconductor element 31 semiconductor element mounting unit 50 lead frame 100 semiconductor package 110 heat-dissipating metal plate 111 copper-tungsten plate (metal plate) )

Claims (3)

[Claims] 1. A heat dissipation device comprising: a metal plate selected from molybdenum, copper-molybdenum, and copper-tungsten; and a copper plating film formed on one or both surfaces of the metal plate. Metal plate. 2. The heat radiating metal plate according to claim 1, wherein a ratio of a thickness of the plating film to a thickness of the metal plate is 2.5 or less. 3. A package for an electronic component, wherein the electronic component is mounted on the heat-dissipating metal plate according to claim 1.