JPH04120245A - High strength lead frame material and its production - Google Patents

Abstract

PURPOSE:To produce a high strength lead frame material without deteriorating solderability, etc., by subjecting an alloy having a specific composition consisting of Co, Ni, Mn, Si, Nb, etc., and Fe to respectively specified solution treatment, cold working, and final annealing. CONSTITUTION:An alloy having a composition which consists of, by weight, 0.5-22% Co, 22-32.5% Ni, <=1.0% Mn, <=0.5% Si, further 0.1-3.0% of one or more elements among Nb, Ti, Zr, Mo, V, W, and Be, and the balance Fe with inevitable impurities and in which Ni is regulated to 27-32.5% when Co is less than 12% and 66<=2Ni+Co<=74% is satisfied when Co exceeds 12% and, further, the contents of C, S, O, and N among the impurities are limited, preferably, to <=0.02%, <=0.015%, <=150ppm, and <=100ppm, respectively, is subjected to solution treatment at a temp. not lower than the austenitization finishing temp., to cold working at 40-90% draft, and then to final annealing at a temp. not higher than the austenitization finishing temp., by which a dual-phase structure consisting of >=50% of inversely transformed austenitic phase and martensitic phase is formed. By this method, the high strength lead frame material excellent in solderability, plating suitability, and thermal expansion characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to lead frame materials for semiconductor devices that have higher strength than conventional materials.

[Conventional technology]

In recent years, as semiconductor devices such as logic devices have become higher in capacity and higher in integration, and packages have become thinner, there has been a tendency for lead frames to have more bins and become thinner. For this reason, higher strength lead frame materials are required than ever before.

Conventionally, Fe-42Ni and Fe-29Ni-17Co (copal) are known as Fe-based lead frame materials for multiple bins. Proposals for improved materials for these Fe-Ni and Fe-N1 to Co systems include Japanese Patent Laid-Open No. 55
~131155 or high-strength Fe-Ni alloys with various reinforcing elements added, and Fe-N1-C
For improved o-based alloys, see JP-A-55-128565.
No., JP-A-57-82455, JP-A-61-6251
No. 1-817, Japanese Patent Publication No. 1-15562, and Japanese Patent Application Publication No. 1-61042, which was previously proposed by the applicant of the present invention.

[Problem to be solved by the invention]

Multi-bin lead frames are mainly manufactured using a photo-etching method that allows fine processing. However, these finely processed Fe-42N i or Fe-29N 1-17
Co thin plate multi-pin lead frames are prone to warping, bending, and other variations in the leads during package assembly, transportation, and mounting due to insufficient strength of the leads, and also to buckling due to impact during use. There was a problem.

Regarding the improvement of Fe-Ni-based or Fe-Ni-Co-based alloys, attempts have been made to strengthen them by incorporating Si, Mn, and Or (Japanese Patent Application Laid-Open No. 131155/1983), or proposals to increase strength by using other strengthening elements. , related to thermal expansion of Fe-Ni-Co alloys ((a) JP-A-1983-1
No. 28565, (b) JP-A-57-82455, (C
) JP-A-61-6251, (d) JP-A-1-817, (e) JP-A-1-15562, (f) JP-A-1-6
No. 1042), but since the former contains an excessive amount of reinforcing elements in addition to the main elements, surface oxidation is likely to occur and there is a problem that the solderability and plating performance, which are the main characteristics of lead frames, are significantly deteriorated. Of the latter, none of the methods other than (a) are intended to actively improve the strength of the lead frame.6 Note that the material in (a) above has a reinforcing mechanism different from that of the present invention material. be.

[Means to solve the problem]

Therefore, the present inventors focused on Fe-N1-Co alloys whose austenite phase is unstable at room temperature, and conducted various experiments regarding the composition and manufacturing conditions. It was discovered that by precipitating the reversely transformed austenite phase during subsequent annealing to form a two-phase structure at a specific ratio, it was possible to increase the strength of the lead frame without impairing its various properties, especially its solderability and plating properties. .

However, the reverse transformation from the martensitic phase to the austenite phase is sensitive to temperature, so the strength is highly dependent on the annealing temperature, which causes many problems in terms of stable production. Therefore, in addition to the reverse transformation of the martensite phase to the austenite phase, solid solution hardening or precipitation strengthening is used to alleviate the dependence on annealing temperature, thereby achieving high strength without impairing solderability, plating properties, and thermal expansion characteristics. We have discovered that it can be converted into

The material of the present invention is characterized by its structure control and solid solution strengthening or precipitation strengthening by specific elements, but in the process of evaluating the solderability and plating properties of the alloy of the present invention, it was added as a deoxidizing agent and remained. Mn, Si, and carbon, sulfur,
It has been found that when impurities such as oxygen and nitrogen are regulated to below a specific value, the under-order properties and plating properties are significantly improved, and the practical properties required in addition to strength and thermal expansion properties are improved. In other words, the material of the present invention is a completely new material in terms of the combination of alloy composition and structure control.
It is a lead frame material with excellent strength and thermal expansion characteristics.
Furthermore, by using a material in which the impurities mentioned above are controlled to be below a specific value, it is possible to further facilitate the manufacture of a lead frame, which is the application of the material of the present invention.

To explain the present invention more specifically, the first aspect of the present invention
The invention contains, in weight percent, C:, o O, 5-22%, Ni
22-32.5%, Mn 1.0% or less, Si 0.5% or less, and the content of N1 and Co is Ni 27-32.5% if Co is less than 12%, and 66%≦ if it is 0012% or more.
2Ni+Co≦74%, and also Nb, T
i, Zr, Mo, V, W.

0.1 to 3.0% of any one or two or more types of Be
The structure is composed of two phases: a reversely transformed austenite phase (with a retained austenite phase) and a martensite phase, and the austenite phase accounts for 50% or more. The second invention is a high-strength lead frame material characterized by Co 0.5-22%, Ni 22-
32.5%, Mn 1.0% or less, Si 0.5% or less, and the content of Ni and CO is less than 12% Co.
27-32.5%, 66%≦2N for Co 12% or more
It satisfies the relationship of i+Co≦74%, and further contains Nb and Ti.

Contains 0.1 to 3.0% of one or more of Zr, Mo, V, W, and Be, with the balance consisting of Fe and unavoidable impurities, and among the unavoidable impurities,
C is 0.02% or less, S is 0.015% or less, O is 15
0 ppm or less, N is 1100 pp or less, and the structure is composed of two phases: a reversely transformed austenite phase (accompanied by a retained austenite phase) and a martensite phase, and the austenite phase accounts for 50% or less. The third invention is a high-strength lead frame material having a weight percentage of Co of 0.5 to 22% and Ni of 22 to 32.
5%, Mn 0.1-0.8%, Si 0.5% or less, and the content of Ni and Co is less than 12% Co, Ni
27-32.5%, 66%≦2N for Go12% or more
It satisfies the relationship of i+Co≦74%, and furthermore, Nb, Ti,
Zi, Mo, V, W.

0.1 to 3.0% of any one or two or more types of Be
and has a composition with the balance consisting of Fe and unavoidable impurities, of which C is 0.015% or less,
S is 0.010% less than 10% 1100pp or less, N is 5
0 ppm or less, and the composition is composed of two phases: a reverse transformed austenite phase (with a residual austenite phase) and a martensite phase, and the austenite phase accounts for 50% or more. The fourth invention is a material, and the average thermal expansion coefficient from room temperature to 300°C is (3 to 9) A high-strength lead frame material according to any one of the first to third inventions, characterized in that the fifth invention is characterized in that the alloy having the composition of any one of the first to third inventions is heated to a temperature equal to or higher than the austenitization finish temperature. Then, part of the austenite phase is transformed into strain-induced martensite by 40 to 90% cold working, and then final annealing is performed at a temperature not exceeding the austenitization finish temperature to precipitate the reversely transformed austenite phase. This is a method for manufacturing a high-strength lead frame material.

[Effect]

Next, the reason for limiting the numerical values of the present invention will be described.

The Co content is optimal for minimizing the thermal expansion coefficient of the present material at around 17% and around 5%, and 0.
．． When it is less than 5% or more than 22%, the coefficient of thermal expansion becomes large and the thermal expansion matching with the silicon chip deteriorates. Therefore, the Co content is limited to a range of 0.5 to 22%.

The Ni content is determined in relation to the Co content.

Co less than 12% and N1 less than 27% or Co
If it is 12% or more and (2Ni+Co) is less than 66%,
The martensite initiation temperature is high, the austenite becomes unstable, martensite transformation occurs during the cooling process during solution treatment, and a sufficient amount of austenite cannot be obtained. Also, if Co is less than 12% and Ni exceeds 32.5%, or Co
If (zNi + CO) exceeds 74% at 12% or more,
The austenite phase becomes too stable at room temperature, making it difficult for deformation-induced transformation to occur. For this reason, when Co is less than 12%, Ni is 27-32.5%, and when Co is 12% or more, 66
Ni so as to satisfy the relationship of %≦2Ni+Co≦74%
limited. Further, for the optimum composition, it is important to adjust the Ni and Co contents so that the martensite initiation temperature is 0° C. or lower.

Nb, Ti, Zr, Mo, V, W, and Be are important elements that strengthen the matrix by solid solution strengthening or precipitation strengthening of the alloy of the present invention. The alloy of the present invention is strengthened by precipitation of a reversely transformed austenite phase during final annealing, but from the viewpoint of thermal expansion characteristics, it is desirable to have a large amount of austenite, and the final annealing temperature must be as high as possible. but,
As shown by the solid line in FIG. 1, in Fe-Ni-Co yarn, as the annealing temperature increases, the hardness, which influences the mechanical properties, decreases rapidly. Therefore, in order to stabilize production, it is necessary to stabilize the mechanical properties on the high temperature annealing side.

The present invention has discovered that by adding these solid solution strengthening or precipitation strengthening elements, it is possible to improve the fluctuation in hardness due to final annealing on the high temperature side, that is, the decline in mechanical properties, as shown by the dotted line in Figure 1. This is due to the fact that

If the amount of these elements added is less than 0.1%, it has no stabilizing effect, and if it exceeds 3%, it promotes surface oxidation and improves solderability.
Since these elements significantly impair plating properties and act on the austenite formation side, if the amount added increases, the austenite in the matrix becomes too unstable, so the content is limited to 0.1 to 3%.

Mn acts as a deoxidizing agent, but if it exceeds 1.0%, it increases the coefficient of thermal expansion and also deteriorates solderability and plating properties, so it is limited to 1.0% or less. The desirable range of Mn is 0.1 to 0.8%.

Si is added as a deoxidizing agent, and it is preferable that it not remain in the material, but Si up to 0.5% is acceptable because it does not cause an extreme increase in the coefficient of thermal expansion or extreme deterioration of solderability and plating performance.

When C exceeds 0.02%, etching perforation performance deteriorates.
Further, excessive precipitation of carbides impairs solderability and plating performance, so the content is set to 0.02% or less. The desirable range of C is 0.015% or less.

When S exceeds 0.015%, excessive MnS is formed and surface defects are likely to occur, and solid solution S deteriorates hot workability, so it is limited to 0.015% or less. S
The desirable range of is less than 0.010%.

When O exceeds 150 ppm, excessive oxides are formed with the deoxidizing agent Si and unavoidably mixed elements such as AI and Mg, which have a strong affinity with ○, which impairs surface cleanliness and reduces solderability. In order to reduce the plating property, the content should be iooppm or less. The desirable range for ○ is 1100 pp or less.

Since N has an austenite stabilizing effect, 1100p
When added in excess of p, the austenite phase becomes too stable and deformation-induced transformation becomes difficult to occur. Further, since nitrides precipitate excessively and deteriorate solderability and plating performance, the preferable amount of N is 50 ppm or less.

In addition, the final structure is determined by the retained austenite phase during solution treatment, the deformation-induced martensite phase, and the reversely transformed austenite phase that precipitates during final annealing, but if the residual and reversely transformed austenite is less than 50%, thermal expansion The coefficient becomes large and the thermal expansion matching with the silicon chip deteriorates. In addition, the strength of the matrix decreases significantly as the austenite phase approaches 100%, so the structure consists of two phases: a retained austenite phase, a reversely transformed austenite phase, and a martensite phase, and the total austenite phase is limited to 50% or more. did.

Note that the Ji (%) of the austenite phase in the present invention is a value determined from the X-ray diffraction intensity, which will be explained in Examples below.

Next, in the method for producing the material of the present invention, if the solution treatment before cold working is performed at a temperature below the austenitization end temperature, the austenite phase will not be in sufficient amount, so the solution treatment temperature is set at a temperature equal to or higher than the austenitization end temperature. . However, since it is necessary to make the crystal grains as fine as possible in the next step, the temperature of this solution treatment is preferably 1050° C. or lower.

If the cold working rate is less than 40%, a sufficient amount of deformation-induced martensitic transformation will not occur, and if it exceeds 90%, material anisotropy will become strong and dimensional accuracy will deteriorate, so the cold working rate should be 40 to 90%. limited to.

Furthermore, when the final annealing temperature exceeds the austenitization end temperature, all the deformation-induced martensite phase transforms into reverse-transformed austenite, and the desired precipitation strengthening due to the two-phase structure cannot be obtained. limit.

In addition, α8. T. . (Average coefficient of thermal expansion from room temperature to 300°C), hardness, and tensile strength were determined to be αR4-3° after examining the package assembly process and usage environment. teeth(
3-9) It was found that a product with a hardness of X 104/'C1 Hv≧260 and a tensile strength of 80 bag f/dish or more can be used satisfactorily.

〔Example〕

The material of the present invention will be explained using examples. An alloy having the composition shown in Table 1 was melted and cast in a vacuum induction melting furnace, and
Forged at 150℃, hot rolled to 3-thickness, rolled to 9.
After solution treatment at 50° C. for 1 hour (water cooling), cold rolling was performed to a thickness of 0.35 mm.

These materials are 0.35mm→750℃ solution treatment→
Cold rolling up to 0.1 cylinder (71%) → 500-650'
C After performing a series of final annealing treatments, various properties were investigated, and the results are shown in Table 2. Regarding the conventional alloy material 2, the characteristics were investigated for two materials: material Z-1, which was subjected to the above series of treatments using the method of the present invention, and material Z-2, which was finished to a thickness of 0.1 mm using the conventional method. I did it.

Further, the amount (%) of the austenite phase is a value determined as follows.

1 IFIT (IIIl+ ITtzoo++ITtzao
++ IT+s+o+ITn2z+I7 (+++1 etc. is the Xta diffraction intensity of austenite 1α2 engineering αC]eo)
+Iα+zoo) +Iα+211) Engineering α. According to the X-ray diffraction intensity tree table of martensite, 101 grade shows that the conventional alloy Z has Co of 12% or more and (2Ni+Co) of 7%.
Material Z to which the production method of the present invention is applied to exceed 4%
Even in the case of -1, the austenite becomes a single phase (austenite amount: 100%) and high mechanical properties cannot be obtained. On the other hand, the materials A-Q of the present invention contain appropriate amounts of Ni and Co, and by adding one or more of Nb, Ti, Zr, Mo, V, W, and Be, they can be heated to 500°C. Even if the final annealing is performed at a temperature above, an appropriate coefficient of thermal expansion and high mechanical properties can be obtained at the same time.

Since Comparative Material However, as shown in FIG. 1, in the temperature range of 500 DEG to 550 DEG C., where the final annealing is performed, the mechanical properties rapidly deteriorate, so there is a problem that stable properties cannot be obtained.

In addition, if the Ni or Ni+Co of the comparative materials R~■ is high, the austenite phase becomes too stable and high mechanical properties cannot be obtained; The disadvantage is that it gets bigger. Furthermore, material (2) containing more than 3% of solid solution strengthening or precipitation strengthening elements has significantly reduced plating and solderability.

Among the materials of the present invention, materials A-L are particularly low in impurity elements such as C, S, O, and N in addition to Si and Mn, and materials M-Q
It can be seen that the plating and soldering properties are superior compared to the above. On the other hand, comparative material W has a high Mn content, and comparative material Y
Because of the high Si content, the plating and soldering properties are significantly reduced.

〔Effect of the invention〕

As stated above, the material of the present invention has F e-N 1 to C
In the specific composition of o-type, the final cold working and final annealing combine deformation-induced martensitic transformation and precipitation of reverse transformed austenite, and further stabilize the strength on the high temperature side by solid solution strengthening or precipitation strengthening with specific elements. This allows us to maintain the high hardness (lv≧260) and high strength of 80 kgf/mi” or more required for a thin multi-bin lead frame with an appropriate thermal expansion coefficient range (3~9x1o=/
'c) is what you can get. Further, by controlling specific impurities in the material of the present invention, there is an effect that manufacturing of lead frames, such as plating and soldering properties, becomes stable and easy.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between final annealing temperature and mechanical properties.

Claims (1)

[Claims] 1% by weight, Co0.5-22%, Ni22-32
．． 5%, Mn 1.0 or less, Si 0.5% or less,
When the content of Ni and Co is less than 12%, Ni27~
32.5%, 66%≦2Ni+Co for Co12% or more
Satisfies the relationship of ≦74%, and also contains Nb, Ti, Zr, M
o, V, W, and Be at 0.0 or more.
The content is 1 to 3.0%, the balance is Fe and unavoidable impurities, and the structure is composed of two phases: a reversely transformed austenite phase (accompanied by a retained austenite phase) and a martensite phase, and the austenite phase is % or more. 2% by weight, Co0.5-22%, Ni22-32
．． 5%, Mn 1.0% or less, Si 0.5% or less, and the content of Ni and Co is less than 12% Co, Ni27
~32.5%, 66%≦2Ni+C for Co12% or more
satisfies the relationship o≦74%, and further contains Nb, Ti, Zr,
One or more of Mo, V, W, Be 0
．． 1 to 3.0%, with the balance consisting of Fe and unavoidable impurities, of which C is 0.0%.
0.02% or less, S 0.015% or less, O 150ppm
Hereinafter, the N content is 100 ppm or less, and the structure is composed of two phases: a reversely transformed austenite phase (accompanied by a retained austenite phase) and a martensite phase, and the austenite phase accounts for 50% or more. High strength lead frame material. 3% by weight, Co0.5-22%, Ni22-32
．． 5%, Mn0.1-0.8%, Si0.5% or less, and the content of Ni and Co is less than 12%, Ni2
7 to 32.5%, 66%≦2Ni+ for Co12% or more
Satisfies the relationship of Co≦74%, and also contains Nb, Ti, and Zi.
, Mo, V, W, and Be in an amount of 0.1 to 3.0%, with the balance consisting of Fe and unavoidable impurities, in which C is the unavoidable impurity. 0
．． 015% or less, S less than 0.010%, O 100p
pm or less, N is 50 ppm or less, and the composition is composed of two phases: a reversely transformed austenite phase (accompanied by a retained austenite phase) and a martensite phase, and the austenite phase accounts for 50% or more. High strength lead frame material. 4 The average coefficient of thermal expansion from room temperature to 300°C is (3 to 9)
The high-strength lead frame material according to any one of claims 1 to 3, characterized in that the lead frame material has a hardness of 260 or more in Hv, and a tensile strength of 80 kgf/mm^2 or more. . 5. The alloy having the composition according to any one of claims 1 to 3 is solution-treated at a temperature equal to or higher than the austenitization finish temperature, and then a part of the austenite phase is transformed into strain-induced martensite by 40 to 90% cold working. A method for producing a high-strength lead frame material, comprising: final annealing at a temperature not exceeding the austenitization finish temperature to precipitate a reversely transformed austenite phase.