JP4227610B2 - Manufacturing method of heat dissipation base - Google Patents

Description

The present invention relates to a method for manufacturing a heat dissipation base that dissipates heat, and in particular, high reliability with excellent heat dissipation characteristics in which a semiconductor element having high heat generation such as gallium arsenide (GaAs), indium phosphorus (InP), or silicon (Si) is mounted. The present invention relates to a method for manufacturing a heat dissipation base used in a package for housing a semiconductor element for use.

  Conventionally, a package for housing a semiconductor element for housing a semiconductor element is generally made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, or a glass ceramic sintered body, and houses the semiconductor element on the upper surface. An insulating base having a concave portion for forming, a plurality of wiring layers made of a metal powder such as tungsten, molybdenum, manganese, copper, silver, etc., deposited from the concave portion to the outer surface of the insulating base, and a lid The semiconductor element is bonded and fixed to the bottom surface of the concave portion of the insulating substrate via an adhesive such as glass, resin, or brazing material, and each electrode of the semiconductor element is electrically connected to the wiring layer via a bonding wire. Thereafter, the lid is joined to the insulating base via a sealing material made of glass, resin, brazing material, etc., and a semiconductor element or the like is placed inside the container consisting of the insulating base and the lid. A semiconductor device as a product by housing the heat component.

  In this conventional package for housing semiconductor elements, since the thermal conductivity of the aluminum oxide sintered body constituting the insulating base is low (about 15 W / mK), the semiconductor element accommodated in the insulating base generates a large amount of heat during operation. If generated, the heat cannot be dissipated well into the atmosphere, and as a result, the semiconductor element becomes high temperature due to the generated heat, causing the semiconductor element to be thermally destroyed, causing a thermal change in characteristics, and malfunctioning. It had the fault of producing.

  Therefore, in a semiconductor element housing package that accommodates a semiconductor element that generates high heat, a heat radiating component made of a composite metal material such as copper-tungsten / copper-molybdenum in order to dissipate the heat of the semiconductor element through an insulating substrate. Is provided directly under the semiconductor element.

  For example, a heat dissipation component made of a copper-tungsten composite material is composed of tungsten and copper in a matrix, and the thermal conductivity of the copper-tungsten composite material varies depending on the ratio, but is generally about 150 to 200 W / mK. .

  However, with the development of semiconductor devices that require large currents such as power ICs and high-frequency transistors, the amount of heat generated by the semiconductor devices tends to increase year by year, and at present, heat dissipation components having a thermal conductivity of 250 W / mK or more. Is required.

  In order to solve this problem, a clad material of a first member (base material) made of molybdenum and a second member made of copper is used as a heat dissipation substrate for a semiconductor device. M.M. C. The thing of (Cu / Mo / Cu) structure is disclosed (for example, refer patent document 1). This C.I. M.M. C. The thermal conductivity of the semiconductor device heat dissipation substrate made of the clad material having a structure is as high as 200 W / mK or more.

A second member made of a metal material mainly composed of copper on both principal surfaces of a first member (base material) made of at least one metal material selected from the group consisting of a tungsten-copper alloy and a molybdenum-copper alloy. There has been proposed a heat dissipation substrate for a semiconductor device in which these members are joined by either a hot uniaxial pressing method or a rolling method (see, for example, Patent Document 2). This semiconductor substrate heat dissipation substrate achieves a thermal conductivity of 250 W / mK or more.
JP-A-6-268115 JP-A-6-268117

  However, the heat dissipation substrates for semiconductor devices disclosed in Patent Document 1 and Patent Document 2 have a very high thermal conductivity of about 250 W / mK. However, as a manufacturing method, the base layer is formed by a rolling method or a hot uniaxial processing method. Since the copper layer is bonded together, for example, when an insulating frame is bonded to this heat dissipation base, there is a problem that cracks are likely to occur at the interface between the base material layer and the copper layer due to thermal stress during bonding.

  In addition, since there is an interface between the copper layer and the base material layer, there is a problem that the thermal conductivity is lowered due to the contact resistance of both layers.

  The present invention has been devised in view of the above-described problems in the prior art, and the object thereof is to dissipate heat generated from a semiconductor element mounted on a mounting surface, and The object is to propose a heat dissipating substrate capable of operating a semiconductor element normally and stably over a long period of time.

  In the method for manufacturing a heat dissipation base according to the third aspect of the present invention, a porous material of tungsten or molybdenum is impregnated with copper to form a composite material layer, and the upper and lower surfaces of the composite material layer are covered. A copper layer is formed by leaving a part of the copper.

  In the manufacturing method of the heat dissipation base of the present invention, when the thickness of the composite material layer is t1 and the thickness of the copper layer is t2, 30 μm ≦ t2 ≦ 300 μm and t2 ≦ 0.15 × t1 are satisfied. It is preferable to polish the surface of the copper layer.

  The heat dissipating substrate of the present invention is continuous with a composite material layer formed by impregnating copper into a porous body of tungsten or molybdenum, and copper located on the upper and lower surfaces of the composite material layer and impregnated with the composite material layer. And a copper layer made of copper. Therefore, in the present heat dissipation base, the heat generated in the semiconductor element placed on the surface of the heat dissipation base is less than that of the heat dissipation base composed only of a composite material layer in which a porous body of tungsten or molybdenum is impregnated with copper. In addition to being able to escape more in the horizontal direction in the plane by the copper layer in the vicinity, the copper layer and the copper in the composite material layer are continuously connected, so the heat conduction loss is reduced, and the inside of the composite material layer More heat can be released.

  In this heat dissipation base, the copper layers formed on the upper and lower surfaces of the composite material layer can be formed simultaneously with impregnating the porous body with copper. For this reason, in the present heat dissipation base, unlike the case where the copper layer bonded by the hot uniaxial method or the rolling method is provided, for example, the copper layer and the composite material layer are caused by the thermal stress when the insulating frame is joined to the heat dissipation base. There is almost no crack at the interface. Therefore, in the optical semiconductor element housing package, the semiconductor element placed on the heat dissipation base and housed in the package can be operated normally and stably over a long period of time.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an example of an embodiment of a package for housing a semiconductor element using a heat radiating substrate of the present invention. 1 is an insulating frame, 2 is a lid, 3 is a heat radiating substrate, and 4 is a semiconductor. It is an element. The heat dissipating base 3 has a mounting portion on which the semiconductor element 4 is mounted at the center of the upper surface, and the insulating frame 1 is attached to the upper surface of the heat dissipating base 3 so as to surround the mounting portion. The insulating frame 1, the lid 2 and the heat radiating base 3 constitute a container for housing the semiconductor element 4.

  The heat dissipating substrate 3 of the present invention has a composite material layer 3a formed by impregnating copper into a porous body of tungsten or molybdenum and a copper layer formed on the upper and lower surfaces thereof as shown in a sectional view in FIG. 3b. The heat dissipation base 3 has a function of absorbing heat generated by the operation of the semiconductor element 4 and dissipating it into the atmosphere.

The heat radiating substrate 3 is produced by melting and impregnating copper from the upper and lower surfaces into a previously formed porous body of tungsten or molybdenum to form a composite material layer 3a. At that time, the upper and lower surfaces of the composite material layer 3a are formed. Since the copper remaining in this layer becomes the copper layer 3b and covers the upper and lower surfaces, the copper layer 3b is polished so as to leave a thickness of 30 to 200 μm. Thereafter, if necessary, a plating layer (not shown) such as nickel is provided on the exposed surface for the purpose of improving the corrosion resistance of the surface of the copper layer 3b and improving the wettability with the brazing material 6 and the adhesive material 7. Apply.
In the heat radiating base 3, the tungsten or molybdenum porous body constituting the composite material layer 3a is, for example, about 10 kN / cm ³ after mixing an appropriate amount of binder with tungsten powder or molybdenum powder having a center particle diameter of several μm to 100 μm. It can be obtained by molding a press body at a moderate pressure, and firing and sintering the press molded body at a temperature of about 1500 ° C.

The composite material layer 3a is formed by impregnating the porous body with copper, and the copper layer 3b is formed on the upper and lower surfaces thereof. The copper layer 3b is usually formed by placing the remaining part of the copper impregnated in the composite material layer 3a from the upper and lower surfaces of the porous body on the upper and lower surfaces of the composite material layer 3a. Is done.
In the heat radiating base 3, as shown in FIG. 2, when the thickness of the upper and lower copper layers 3b is t2, and the thickness of the composite material layer 3a is t1, 30 μm ≦ t2 ≦ 300 μm and t2 ≦ It is important to set it to 0.15 × t1. When t2 <30 μm, it becomes difficult to dissipate the heat generated by the semiconductor element 4 well into the atmosphere because more heat cannot be released in the in-plane horizontal direction by the copper layer 3b near the surface. There is a tendency for the semiconductor element 4 to be thermally destroyed or to cause a malfunction due to a thermal change in characteristics. On the other hand, when t2> 300 μm, the proportion of copper in the mounting portion of the semiconductor element 4 becomes too large, the coefficient of thermal expansion becomes large, the semiconductor element 4, the heat dissipation base 3 and the bonding material 7, and the insulating frame 1 and the heat dissipating substrate 3 and the bonding material 6 tend to be easily broken or peeled off.
Further, when t2> 0.15 × t1, as described above, the proportion of copper in the mounting portion of the semiconductor element 4 becomes too large, the thermal expansion coefficient becomes large, and the semiconductor element 4 and the heat dissipation base 3 are joined. There is a tendency that breakage or peeling easily occurs between the material 7 and between the insulating frame 1 and the heat radiation base 3 and the bonding material 6.
Further, the content of copper impregnated in the porous material of tungsten or molybdenum in the composite material layer 3a is such that the thermal expansion coefficient of the heat dissipation base 3 is 6.5 to 9 × 10 ⁻⁶ / ° C., and the sintered glass ceramics. In order to obtain a value in the vicinity of the thermal expansion coefficient of the insulating frame 1 formed, it is preferably set to 10 to 25% by weight. When the copper content is less than 10% by weight, the thermal expansion coefficient of the heat radiating base 3 becomes 6 × 10 ⁻⁶ / ° C. or less, so that the semiconductor element 4, the heat radiating base 3 and the bonding material 7 are insulated and insulated. There is a tendency that breakage and peeling are likely to occur between the frame body 1 and the heat dissipation base 3 and the bonding material 7. On the other hand, if it exceeds 25% by weight, the thermal expansion coefficient of the heat radiating base 3 becomes 9 × 10 ⁻⁶ / ° C. or more, and therefore, between the semiconductor element 4 and the heat radiating base 3 and the bonding material 7 and the insulating frame 1 and There is a tendency that breakage or peeling is likely to occur between the heat dissipation base 3 and the bonding material 7.

The insulating frame 1 in the package for housing a semiconductor element having such a heat dissipation base is composed of a glass ceramic sintered body (linear thermal expansion coefficient: 6 to 8 × 10 ⁻⁶ / ° C.) having a relative dielectric constant of 7 or less, Specifically, 1) Sintered glass ceramics (relative dielectric constant 5-6) manufactured from raw powder obtained by adding alumina or mullite to borosilicate glass 2) Alumina or mullite on cordierite crystallized glass Glass ceramics sintered body (relative dielectric constant 5-6) manufactured from raw material powders added with 3) Sintered glass ceramics manufactured from raw material powders formed by adding alumina or mullite to mullite crystallized glass It is formed of a body (relative dielectric constant 5-6) or the like.

  The insulating frame 1 is bonded and fixed via a heat dissipation base 3 and a brazing material 6. Note that a brazing metal layer (not shown) is formed at a joint portion between the insulating frame 1 and the heat dissipation base 3.

When the insulating frame 1 is made of a glass ceramic sintered body made of a raw material powder formed by adding alumina or mullite to borosilicate glass, for example, the composition of the raw material powder is 72 to 76% by weight of silica. Borosilicate powder consisting of 2-3% of boron oxide, 2-4% aluminum oxide, sodium oxide, potassium oxide and titanium oxide in total amount of alumina, quartz and cordierite powder, organic binder, A slurry is made by adding a solvent and the like, and this slurry is made into a ceramic green sheet (ceramic raw sheet) by adopting a doctor blade method or a calender roll method, and then suitable for these ceramic green sheets. In addition to punching and stacking multiple sheets, firing at a temperature of about 900 ° C It is prepared me.

  In addition, the insulating frame 1 is formed with a wiring layer 8 led out from a portion surrounding the mounting portion of the semiconductor element 4 inside to the outer surface, and the wiring layer 8 exposed to the inside of the insulating frame 1 is formed. Each electrode of the semiconductor element 4 is electrically connected to one end via a bonding wire 5, and an external lead pin 9 connected to an external electric circuit is silver at a portion led to the upper surface of the insulating frame 1. It is brazed and attached via a brazing material such as brazing.

  The wiring layer 8 functions as a conductive path for connecting each electrode of the semiconductor element 4 to an external electric circuit, and is formed of a metal powder such as copper, silver, or gold.

  The wiring layer 8 is formed by adding a metal paste obtained by adding and mixing an appropriate organic binder, solvent, or the like to a metal powder such as copper, silver, or gold on a ceramic green sheet serving as the insulating frame 1 in advance. By printing and applying to a predetermined pattern by the above, the insulating frame 1 is deposited from the inner side to the outer surface.

  Although the melting point of copper, silver, gold, etc. forming the wiring layer 8 is as low as about 1000 ° C., the sintering temperature of the glass ceramic sintered body constituting the insulating frame 1 is low. It is possible to form a film on the substrate.

  Further, since the electrical resistivity of copper, silver, gold, etc. forming the wiring layer 8 is as low as 2.5 μΩ · cm or less, the semiconductor element 4 and the external electric circuit accommodated inside the container via the wiring layer 8 Even if the electrode signal is taken in and out between, the electric signal is not greatly attenuated in the wiring layer 8, and as a result, the semiconductor element 4 can be operated accurately and reliably.

Further, the wiring layer 8 has a low dielectric constant of 7 or less (room temperature, 1 MHz), preferably 5.5-6, because the insulating frame 1 to which the wiring layer 8 is applied is low. As a result, even if an electric signal is taken in and out between the semiconductor element 4 accommodated in the container and the external electric circuit via the wiring layer 8, the electric signal is propagated. Thus, an electronic signal can be input / output accurately and reliably to / from the semiconductor element 4.
When the wiring layer 8 is made of copper or silver, a metal having excellent corrosion resistance such as nickel and gold and excellent bonding property of the bonding wire 5 is deposited on the exposed surface to a thickness of 1 to 20 μm by a plating method. By doing so, the oxidative corrosion of the wiring layer 8 can be effectively prevented and the connection of the bonding wire 5 to the wiring layer 8 can be strengthened. Therefore, it is desirable that the wiring layer 8 be coated with a metal having excellent corrosion resistance such as nickel / gold and excellent bonding properties on the exposed surface to a thickness of 1 to 20 μm.

  The external lead pins 9 that are brazed to the wiring layer 8 attached to the insulating frame 1 are made of a metal material such as iron-nickel-cobalt alloy or iron-nickel alloy, and each electrode of the semiconductor element 4 is connected to the external electricity. It has a function of electrically connecting to a circuit.

  The external lead pin 9 is formed in a predetermined shape by subjecting an ingot made of a metal such as an iron-nickel-cobalt alloy to a conventionally known noble processing method such as a rolling method or a punching method.

  The heat dissipating base 3 has a mounting portion for the semiconductor element 4 on its upper surface, and the semiconductor element 4 is fixed to the mounting portion via an adhesive material 7 such as resin, glass, or brazing material. In the case where a brazing material is used as the adhesive material 7, a brazing metal layer (not shown) is usually formed at a joint portion of the heat dissipation base 3 with the semiconductor element 4. The insulating frame 1 and the heat radiating base 3 are joined by using a brazing material 6 made of silver-copper alloy or the like, melting the brazing material 6 in a reducing atmosphere at 600 ° C. to 900 ° C., and then cooling and solidifying it. Is done.

In contrast to such a heat radiating base 3, the insulating frame 1 has a thermal expansion coefficient of 6 from the viewpoint of setting the thermal expansion coefficient of the heat radiating base 3 to a value close to the thermal expansion coefficient of the insulating frame 1. To 8 × 10 ⁻⁶ / ° C. (room temperature to 800 ° C.). It is preferably made of a glass ceramic sintered body.

Thus, according to the semiconductor element storage package of the present invention described above, the semiconductor element 4 is bonded and fixed to the mounting portion on the upper surface of the heat radiating base 3 through the adhesive material 7 made of glass, resin, brazing material, or the like. At the same time, each electrode of the semiconductor element 4 is connected to a predetermined wiring layer 8 through a bonding wire 5, and then the lid 2 is sealed on the upper surface of the insulating frame 1 with glass, resin, brazing material or the like. The semiconductor element 4 is hermetically accommodated in a container composed of the insulating frame 1, the heat dissipating base 3, and the lid 2, and a semiconductor device as a product is obtained.

(Example 1) First, after mixing an appropriate amount of binder with tungsten powder having a center particle diameter of several μm to 100 μm, a press body was formed at a pressure of about 10 kN / cm ³ . A sintered porous body made of tungsten obtained by firing at a temperature was prepared. Next, 15% by weight of copper was infiltrated into the porous body at a temperature of 1200 ° C., and the thicknesses of the upper and lower copper layers were 0, 0.015, 0.030, 0.050, 0.10, 0.20, 0.30. , 0.50 mm, and a heat-radiating substrate sample for evaluation was produced.

For these evaluation heat dissipation substrate samples, the thermal conductivity (W / mK) of the evaluation heat dissipation substrate sample is determined based on the thermal diffusion, specific heat capacity, and thermal conductivity test method by the fine ceramic laser flash method specified in JIS R1611. Measure the amount of elongation of the evaluation heat dissipation substrate sample for each temperature while raising the temperature of the evaluation heat dissipation substrate sample by the TMA (Thermomechanical Analysis) method, and divide that value by the value of the temperature increase width The expansion coefficient (× 10 ⁻⁶ / ° C.) was measured. Further, the interface of the bonded interface was observed with a microscope having a magnification of 40 times. Thereafter, the same observation was performed with an ultrasonic flaw detector.

As for the results, Table 1 shows the physical property values of the thermal expansion coefficient and thermal conductivity of the heat-dissipating substrate when the thickness ratio between the composite material layer composed of tungsten and copper and the upper and lower copper layers is changed, and the temperature cycle. The size after the test (TCT: -65 / + 150 ° C, 1000 cycles) is 10 mm □, the thickness is 0.6 mm, the bonding interface between the silicon semiconductor element and the heat dissipation base, the outer size is 20 mm □, and the cavity size is 12 shows a bonding interface state between an insulating frame having a thickness of 1 mm and a heat dissipation base.

  As can be seen from the results shown in Table 1, in the heat radiating substrates No. 1 to No. 8, when the thickness of the composite material layer is fixed to 2 mm and the thickness of the copper layer is changed from 0 to 0.50 mm, the composite material The layer / copper layer thickness ratio (t2 / t1 ratio) increases from 0 to 0.25, and accordingly, the thermal conductivity and the thermal expansion coefficient also show large values. In particular, t2 / t1 = 0.015 or more and a value of 250 W / mK or more was shown. However, although the thermal conductivity does not change greatly when the copper layer thickness is 0.30 mm or more, it has been confirmed that if t2 / t1 = 0.15, cracks occur at the bonding interface between the heat dissipation base and the insulator. As the heat dissipating substrate, the thickness ratio of the composite material layer and the copper layer, which has a high heat dissipating property of 250 W / mK or more and can ensure reliability with the insulator, is preferably 0.15 or less.

In the heat dissipation bases No. 9 to No. 10, even when the thickness of the composite material layer is changed to 1 mm and 3 mm and the thickness of the copper layer is changed to 0.10 mm and 0.30 mm, the thermal conductivity is 250 W / mK. From the above, it can be seen that the coefficient of thermal expansion also shows a value of 8.0 × 10 ⁻⁶ / ° C. or less.

  In addition, also as a result when using molybdenum for a porous body, as shown in No. 11, it has confirmed that it showed favorable thermal conductivity of 250 W / mK or more.

(Example 2) After mixing an appropriate amount of binder with tungsten powder having a center particle diameter of several μm to 100 μm, a press body is formed at a pressure of about 10 kN / cm 3, and this press formed body is fired at a temperature of about 1500 ° C. A sintered porous body made of tungsten was prepared. Next, the porous body is infiltrated and impregnated at a temperature of 1200 ° C. so that the content of copper is 10 to 40% by weight (the amount of tungsten is 90 to 60% by weight). A heat radiation base sample for evaluation was prepared so that the copper layer had a thickness of 0.10 mm. And evaluation similar to Example 1 was performed.

Table 2 shows the results of the heat dissipation substrate when the amount of copper in the composite material layer when the thickness ratio of the composite material layer and the upper and lower copper layers is 0.05 is changed between 10 wt% and 60 wt%. Physical property values of coefficient of thermal expansion and thermal conductivity, bonding interface state between semiconductor element and heat dissipation base and temperature interface test (TCT: -65 / 150 ° C, 1000 cycles) and bonding interface state between insulator and heat dissipation base Indicates.

  As can be seen from the results shown in Table 2, in the heat radiating bases No. 1 to No. 8, the copper content of the copper-tungsten composite material layer was changed within the range of 10 to 60% by weight. The coefficient of thermal expansion gradually increases by increasing the copper content ratio. In particular, when the copper ratio is 30% by weight or more, the thermal expansion coefficient is 9 × 10 −6 / ° C. or more, and cracks are generated at the interface between the heat dissipation base and the insulator. Therefore, the ratio of the copper material in the composite material layer that can ensure reliability is preferably 10 to 25% by weight.

  Moreover, it shows about the result at the time of using molybdenum instead of tungsten for No.9. From this, it can be seen that a good thermal conductivity of 250 W / mK or more is obtained.

Note that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

It is sectional drawing which shows an example of embodiment of the package for semiconductor element accommodation provided with the thermal radiation base | substrate of this invention. It is sectional drawing which shows an example of embodiment of the thermal radiation base | substrate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation frame 2 ... Lid 3 ... Radiation base 3a ... Composite material layer 3b ... Copper layer 4 ... Semiconductor element 8: Wiring layer

Claims (2)

Forming a composite material layer by impregnating copper into a porous body of tungsten or molybdenum, and forming a copper layer by leaving a part of the copper so as to cover the upper and lower surfaces of the composite material layer; A method for manufacturing a heat dissipation base. The surface of the copper layer is polished so that 30 μm ≦ t2 ≦ 300 μm and t2 ≦ 0.15 × t1 when the thickness of the composite material layer is t1 and the thickness of the copper layer is t2. 2. A method for producing a heat dissipating substrate according to 1.

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