JPH0657381A - Fe-ni-co low thermal expansion alloy - Google Patents

Abstract

PURPOSE:To approximate the thermal expansion of an Fe-Ni-Co low thermal expansion alloy to that of a package material such as silicon and to enable its joining use with the package material by specifying the compsn. of Ni, Co and Fe, the average thermal expansion coefficient, the variation point of its thermal expansion or the like. CONSTITUTION:This Fe-Ni-Co low thermal expansion alloy is formed with a compsn. consisting of, by weight, 30.6 to 34.5% Ni and 7.8 to 11.5% Co as well as 40.5 to 43.5% Ni+Co, and the balance Fe. Furthermore, the average thermal expansion coefficient at 30 to 350 deg.C is regulated to 3.5X10<-6>/ deg.C and the variation point of its thermal expansion is regulated to 300 deg.C or above. Moreover, its gamma alpha' transformation temp. is regulated to -70 deg.C or below, and its thermal expansion coefficient is approximated to that of a package material such as silicon, aluminum nitride and glass-ceramic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Fe-Ni-Co based alloy materials used for semiconductor packages such as IC lead frame materials, PGA seal ring materials, PGA lead pin materials, and the like. The thermal expansion coefficient of aluminum nitride and glass
The present invention relates to a Fe-Ni-Co-based low thermal expansion alloy that approximates the thermal expansion coefficient of a package material such as ceramics.

[0002]

2. Description of the Related Art Conventionally, as a metal material used for an IC lead frame material, a PGA seal ring material, a PGA lead pin material, etc., 29 wt% Ni-17 wt% Co-
Fe (ASTM F15) alloy and 41 wt% Ni-Fe
(ASTM F30) alloy or the like is used. 29w
The average thermal expansion coefficient (30 to 300 ° C.) of the t% Ni-17 wt% Co-Fe alloy is 4.6 to 5.4 × 10 ⁻⁶ / ° C.,
Average thermal expansion coefficient of 41 wt% Ni-Fe alloy (30-3
00 ° C.) is 4.0 to 4.7 × 10 ⁻⁶ ° C.

With the recent increase in size of semiconductor packages,
Average thermal expansion coefficient of silicon chips 3.0 to 3.3 × 10
^{Since the difference between −6} / ° C. and the average coefficient of thermal expansion of the Fe—Ni—Co based alloy and the Ni—Fe based alloy described above is large, joining becomes difficult.

Further, aluminum nitride having high thermal conductivity and glass-ceramics having a low dielectric constant have begun to be used as the ceramic material of the ceramic package, but their average thermal expansion coefficient (30 to 300 ° C.) is
Aluminum nitride is 2.6 to 3.3 × 10 ⁻⁶ / ° C. and glass / ceramics is 2.5 to 3.0 × 10 ⁻⁶ / ° C., which are very small, and the Fe—Ni—Co alloy Ni— Joining is difficult with Fe-based alloys.

[0005]

Therefore, an Fe-Ni-Co alloy in which the average coefficient of thermal expansion of the material has been reduced (Japanese Patent Laid-Open No. Sho 5).
7-23830, JP-A-59-198741 and the like) have been developed. However, JP-A-59-19
The Fe-Ni-Co based alloy described in Japanese Patent No. 8741 has insufficient reduction in thermal expansion.

The Fe-Ni-Co alloy described in JP-A-57-23830 is subjected to specific processing and heat treatment in order to reduce thermal expansion, but it is industrially used for various purposes. Cause problems. That is, 30 to 90
% Cold working, then annealing and heat treatment at 200 ~ 600 ℃, a thermal expansion coefficient of 35 × 10 ^-7 / ℃ or less can be obtained, but customers can apply it for various purposes and various uses. There is a problem that the previously given characteristics cannot be exhibited due to the processing and heat treatment performed for this purpose.

The present invention has been made in view of the above problems of the Fe-Ni-Co alloy material used for the semiconductor package.
The thermal expansion coefficient changes depending on the thermal expansion coefficient of the packaging material such as aluminum nitride, glass, ceramics, etc., and the processing and heat treatment performed by the customer to apply it for various purposes, or the ambient temperature. The purpose is to provide an Fe—Ni—Co-based low thermal expansion alloy.

[0008]

The inventor has found that Fe-Ni-
As a result of various studies on the composition in which the coefficient of thermal expansion does not change even by working or heat treatment at the same time as reducing the thermal expansion of the Co-based alloy, in particular, the total content of Ni and Co is set within a specific range, The inventors have completed the present invention by finding that their thermal expansions are very similar to those of aluminum nitride and glass ceramics and do not change due to heat treatment.

That is, the present invention satisfies Ni 30.6 to 34.5 wt%, Co 7.8 to 11.5 wt%, and 40.5≤Ni + Co≤43.5 wt%,
The balance consists of Fe and unavoidable impurity elements, and is 30 to 35
It is characterized in that the average coefficient of thermal expansion at 0 ° C. is 3.5 × 10 ⁻⁶ / ° C. or less, the transition point of thermal expansion is 300 ° C. or more, and the γ → α ′ transformation temperature is −70 ° C. or less. Fe-Ni-
It is a Co-based low thermal expansion alloy.

Reason for limiting the composition Ni is a basic component of this system composition, and if it is less than 30.6 wt%, the thermal expansion becomes large, and the γ → α 'transformation temperature becomes high, and if it exceeds 34.5 wt%, the thermal expansion becomes large. Therefore, the range is set to 30.6 to 34.5 wt%.

Co is a basic component of this system composition, and is 7.8.
If it is less than wt%, the transition point of thermal expansion becomes less than 300 ° C., and at the same time, the thermal expansion at a temperature exceeding the transition point becomes large, and if it exceeds 11.5 wt%, the thermal expansion becomes large. The range is 0.5 wt%.

As shown in FIG. 1, when the Ni + Co content is less than 40.5 wt%, the thermal expansion transition temperature is less than 300 ° C. Expansion increases, the γ → α ′ transformation temperature rises, and when it exceeds 43.5 wt%, thermal expansion increases, so that Ni + Co is 40.5 to 43.
The range is 5 wt%.

The additive element is not particularly limited, but C is 0,
If it exceeds 02 wt%, smut is likely to occur during pickling treatment and foaming is likely to occur during glass sealing, so 0.0
2 wt% or less is desirable. When Si is more than 0.25 wt%, internal grain boundary oxidation becomes severe and non-metallic inclusions increase and the bendability of the material decreases when Si is pickled. desirable. Mn is
If it exceeds 0.5 wt%, the amount of non-metallic inclusions increases and the bendability of the material decreases, so 0.5 wt% or less is desirable. Further, Fe is a basic component of this system composition, and accounts for the remaining content of Ni, Co, etc.,

The Fe—Ni—Co low thermal expansion alloy according to the present invention has an average thermal expansion coefficient of 3.5 × at 30 to 350 ° C.
It is characterized in that it is 10 ^-6 / ° C or less, but when considering joining such as IC package assembly, high temperature solder or Au is used.
-Si brazing material may be used for joining. In this case, the solidification temperature is high, about 360 ° C.
It is necessary to specify the average coefficient of thermal expansion of 350 ° C., and if the average coefficient of thermal expansion exceeds 3.5 × 10 ⁻⁶ / ° C., silicon,
Since the thermal expansion difference with aluminum nitride, glass ceramics, etc. becomes too large, the average thermal expansion coefficient at 30 to 350 ° C. is limited to 3.5 × 10 ⁻⁶ / ° C. or less.

In the present invention, when the transition point is less than 300 ° C., in joining with high temperature solder or Au-Si brazing material,
Since it is difficult to ensure the linearity of thermal expansion up to the joining temperature and the residual stress after joining increases, the transition point is set to 300 ° C or higher.

In the present invention, the γ → α ′ transformation temperature is −
If the temperature is higher than 70 ° C, the γ → α 'transformation may occur during use or transportation in an extremely cold region and the thermal expansion may increase, so the α'transformation temperature is limited to -70 ° C or lower.

[0017]

According to the present invention, in the Fe-Ni-Co based alloy, the total amount of Ni and Co regulated to the respective specific contents is set within the specific range, so that silicon, aluminum nitride, glass ceramics can be obtained over 30 to 350 ° C. And the thermal expansion can be made extremely close to each other, and the transition point is 3
The temperature is not lower than 00 ° C and the transformation temperature is not higher than -70 ° C, and the coefficient of thermal expansion does not change depending on the processing or heat treatment performed by the consumer for application to its purpose or various uses, or further the ambient temperature of use.

[0018]

EXAMPLES As shown in Table 1, Fe-Ni-Co alloy samples of various compositions with different amounts of Ni and Co were melted in a high frequency vacuum melting furnace. After hot rolling the ingot, cold rough rolling,
After intermediate annealing, it was cold-rolled to a plate thickness of 0.5 mm. After the final finish annealing was performed at 900 ° C., the thermal expansion characteristics were measured. Also, 15mm x 15 from the finished plate
mm test piece was cut out and kept at −70 ° C. for 3 hours, then γ →
The presence or absence of α'transformation was confirmed. Table 1 shows each measurement result.

Further, according to the invention alloy No. 4, No. 5 and comparative alloy No. 13, further known silicon,
The thermal expansion curves of aluminum nitride and glass ceramics are shown in FIG. In FIG. 2, solid line 4 indicates the alloy No. of the present invention in the example. In the case of No. 4, the solid line 5 is the alloy No. of the present invention in the example. In the case of No. 5, the small broken line indicates the comparative alloy No. In the case of No. 13, the large broken line shows the case of silicon and aluminum nitride, and the one-dot chain line shows the case of glass ceramics.

[0020]

[Table 1]

[0021]

The Fe-Ni-Co alloy according to the present invention has a total content of Ni and Co regulated to specific contents within a specific range, and as shown in FIG. The thermal expansion of silicon, aluminum nitride, and glass ceramics can be made extremely close to each other, and the transition point is 300 ° C. or higher and the transformation temperature is −70.
It becomes below ℃, even if plastic processing such as cutting, bending, bending, etc., which is carried out by the customer to apply it for various purposes and purposes, or heat treatment, or even thermal expansion due to the operating environment temperature Fe-Ni-, which has the characteristic that the coefficient does not change, can be used by bonding with packaging materials such as silicon, aluminum nitride and glass ceramics.
It is a Co-based low thermal expansion alloy.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of Ni and the amount of Co, showing the regulation of the total amount of Ni and Co, which is a feature of the present invention.

FIG. 2 is a graph showing the relationship between temperature and coefficient of thermal expansion,
The solid line 4 indicates the alloy No. of the present invention in the examples. In case of 4,
The solid line 5 is the alloy No. of the present invention in the examples. In case of 5,
The small broken line indicates the comparative alloy No. In case of 13,
The large broken line shows the case of silicon and aluminum nitride, and the alternate long and short dash line shows the case of glass ceramics.

Claims (1)

[Claims] 1. Ni 30.6-34.5 wt%, Co
7.8 to 11.5 wt% and 40.5 ≦ Ni + Co
Satisfying ≦ 43.5 wt%, consisting of balance Fe and unavoidable impurity elements, having an average coefficient of thermal expansion of 3.5 × 10 ⁻⁶ / ° C. or less at 30 to 350 ° C. and a transition point of thermal expansion of 300 ° C. or more. And a γ → α ′ transformation temperature of −70 ° C. or lower, an Fe—Ni—Co based low thermal expansion alloy.