JPH04221039A - Alloy material for lead frame and its production - Google Patents

Abstract

PURPOSE:To improve etching characteristic, sealing characteristic, and formability by subjecting an alloy stock, in which respective contents of Ni, Co, Ti, Al, B, Fe, etc., are specified, to final annealing, cold rolling, and aging heat treatment under respectively prescribed conditions. CONSTITUTION:An alloy having a composition consisting of, by weight, 15-55% Ni, 2-30% Co, 0.2-3% Ti, 0.1-3% Al, 0.001-0.1% B, <=0.015% C, 0.001-0.15% Si, 0.1-1% Mn, <=0.01& P, <=0.005% S, <=0.01% 0, <=0.01% N, and the balance Fe is refined. Rolling is performed at 40-90% draft by using this alloy as a stock and final annealing is exerted under the conditions for regulating crystalline grain size to <=30mum. Subsequently, after the draft in the final cold rolling is regulated to 15-85%, aging heat treatment is performed at 300-800 deg.C.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention provides etching processability,
The present invention relates to an alloy material for lead frames that has excellent sealing properties and moldability and high strength, and a method for manufacturing the same.

0002

[Prior Art] In general, it is known that the characteristics of the lead material used in semiconductor devices have a large effect on their performance and cost. For this purpose, Fe--Ni alloys have been preferably used, which have a low coefficient of thermal expansion and exhibit relatively good adhesion and sealing properties with semiconductor elements and ceramics. but,
For example, thermal stress can occur between the resin and lead material during the cooling process after the resin molding process in the "LSI plastic packaging process", during mounting on a printed circuit board, and when subjected to temperature cycles in the usage environment. Although this cannot be avoided, if this stress becomes excessive, the lead material used should be made of a Fe-Ni alloy (e.g. 42%
Even if the package is made of Ni--Fe alloy), it is difficult to avoid problems such as cracks occurring in the package or peeling of the adhesive interface, which deteriorates the moisture resistance reliability of the package. This problem is caused by the difference in thermal expansion coefficient between the mold resin and the lead material. When the above-mentioned microcracks or peeling interface occur due to the difference in thermal expansion coefficient, moisture can enter from the outside through this and cause damage to the internal semiconductor elements. There was a risk of damaging the Therefore, in order to improve the moisture resistance reliability of LSI, it is necessary to use a lead frame material having a chemical composition whose coefficient of thermal expansion is as close as possible to that of mold resin. On the other hand, recently, the above-mentioned types of LSIs are also becoming more highly integrated.
This trend has resulted in an increase in the number of pins in the lead frame used, but in order to cope with the increase in the number of pins in the lead frame, it is required to use a material with higher strength. This is because when a lead frame has a large number of pins, the pin spacing inevitably becomes narrower and the width of the pin itself becomes smaller, but achieving this requires etching or press processing with even higher precision. There is also a concern that the thickness will become thicker than the pin width, making processing even more difficult. Therefore, in order to deal with this, it becomes necessary to reduce the material thickness, but in order to make the material thinner, it is necessary to increase the strength (resistance against lead deformation) than before.
Therefore, a lead frame material with the following characteristics is required. In addition, especially for lead frame materials for high-pin count and ultra-high-pin count, etching is the main process for molding.
'Excellent etching processability' has also become an important required property. In general, the etching process for Fe-Ni alloy lead frame materials involves applying photoresist to both sides of a degreased lead frame material, baking and developing a pattern, and then using ferric chloride as the main component. Usually, the resist is etched using an etching solution, and then the resist is removed. The factors that determine the etching performance at this time are:
Among these factors, the etching speed of the material is the most important factor, and as the etching speed increases, the pin width and pin formed on the lead frame material increase. Since the interval can be easily controlled, it is no exaggeration to say that the evaluation of etching processability is largely determined by the etching rate.

0003

[Problems to be Solved by the Invention] Therefore, as the degree of integration of semiconductor devices increases, lead frame materials must not only have excellent sealing properties and strength properties, but also ``faster etching speed characteristics (i.e., good etching processability). However, there is still a need for etching processability,
At present, no material has been found that fully satisfies all of the sealing properties, strength, and moldability. Therefore, in order to improve the moisture resistance reliability of LSI, it is necessary to use a lead frame material having a chemical composition whose coefficient of thermal expansion is as close as possible to that of mold resin. Therefore, recently, in addition to Ni, Co is also used as a main component,
By adjusting the content of Ni and Co, the coefficient of thermal expansion of Ni is made as close as possible to that of the mold resin.
-Co-Fe alloy lead frame materials have also been developed, and their performance is attracting attention. Therefore, the purpose of the present invention is to apply it to highly integrated semiconductor devices that have high strength and also have excellent etching processability, sealing performance, and moldability. The objective was to establish an industrial means for mass production of lead frame materials that would exhibit sufficient performance even when

0004

[Means for Solving the Problems] In order to achieve the above object, the present inventors have focused particularly on the relatively high strength characteristics and low coefficient of thermal expansion of the Fe-Ni-Co alloy lead frame material, and As a result of repeated research into a manufacturing method that would further improve its strength, significantly improve its etching processability and moldability, and enable stable production, we were able to obtain the following new knowledge. That is, (a) Fe-N, which has been considered relatively preferable as a lead frame material;
In an i-Co alloy, if the contents of C, Si, and P, as well as the N content, are limited to specific low values, the etching rate of the alloy will be significantly improved. (b) Moreover, by subjecting the above alloy to aging heat treatment, the strength of the material can be effectively improved without any particular adverse effect on the properties as a lead frame material, and the Ni content can be reduced. Addition of the above-mentioned specific elements under careful control is an extremely effective means for bringing the coefficient of thermal expansion closer to that of the mold resin. (c) Also, in the above alloy materials, the crystal grain size has a considerable effect on strength and formability, but by taking measures to suppress the crystal grain size below a certain value, lead frames with a large number of pins can be made. ``Further improvement in material strength'' can be expected, which is preferable for many people, and moldability is also improved. (d) In the above-mentioned alloy system, in order to stably manufacture the crystal grain size without making the grains mixed, it is necessary to control the degree of rolling before final annealing within a specific range. (e) Furthermore, in order to improve the strength without increasing the anisotropy, it is necessary to control the degree of rolling in the final cold rolling within a specific range. (f) Therefore, while comprehensively adjusting the content of Ni, C, Si, P, etc. in the alloy containing Fe-Ni-Co as the basic component, specific alloying elements are added to this as necessary, Furthermore, if the degree of rolling before the final annealing, the grain size during the final annealing, the degree of workability of the final rolling, and the aging heat treatment conditions are controlled within appropriate ranges, properties such as strength, coefficient of thermal expansion, sealing property, and formability will be excellent. Moreover, it becomes possible to stably manufacture a lead frame material having very good etching processability.

The present invention was completed based on the above-mentioned findings, etc.; (1) Ni 15 to 55% by weight;
Co2~30%, Ti0.2~3.0%, Al0.1~
3.0%, B0.001%~0.1%, C0.015%
Below, Si0.001-0.15%, Mn0.1-1.
0%, P0.010% or less, S0.005% or less, O0
．． 0.010% or less, N0.010% or less, and the balance consists of Fe and other unavoidable impurities, and the polymerization ratio is 15 to 55% Ni,
Co2~30%, Ti0.2~3.0%, Al0.1~
3.0%, B0.001%~0.1%, C0.015%
Below, Si0.001-0.15%, Mn0.1-1.
0%, P0.010% or less, S0.005% or less, O0
．． The material is an alloy containing 0.010% or less, N0.010% or less, and the balance consisting of Fe and other unavoidable impurities, and after final annealing and rolling with a workability of 40 to 90%, the crystal grain size is 30 μm or less. After adjusting the workability of the final cold rolling to 15 to 85%,
This is a method for producing a high-strength lead frame material having excellent etching processability, molding processability, and sealing property, which is characterized by performing aging heat treatment in a temperature range of 0 to 800°C. In addition,
In this invention, (a) C content is 0.005%
(b) Si content is adjusted to below 0.001 to 0.
(c) adjusting the P content to 0.003% or less, alone or in combination, the effect of improving the moldability and etching processability of the resulting lead frame material is even more remarkable. This makes it possible to more fully support the production of multi-lead frame materials.

[0006]

[Operation] Next, in the present invention, the composition of the material alloy,
The reason why the working degree of rolling before final annealing, the grain size at the time of final annealing, and the working degree of final cold rolling are numerically limited as described above will be explained together with their effects. A) Composition of material alloy Ni: Ni is an important component in determining the thermal expansion coefficient of the lead frame material, and it reduces the difference in thermal expansion with the package during and after sealing, resulting in excellent sealing. In order to ensure adhesion and moisture resistance reliability, it is necessary to adjust the Ni content to 15 to 55%. Therefore, the Ni content is 15-55%
I decided. Co: Co is also an important component in determining the coefficient of thermal expansion of the lead frame material. In order to reduce the difference in thermal expansion with the package during and after sealing and to ensure excellent sealing performance and moisture resistance reliability, it is necessary to adjust the Co content to 2 to 30%. . Therefore, the Co content was determined to be 2 to 30%. Ti: Ti has a remarkable effect on improving strength through aging strengthening, but when the amount added is 0.
If it is less than 2%, precipitation hardening cannot be obtained, and if it is added in excess of 3%, etching processability and molding processability will deteriorate, and the coefficient of thermal expansion will become too large, resulting in poor sealing properties. The content was determined to be 0.2% to 3.0%. Al:A
L also has a remarkable effect on improving strength through aging strengthening, but if the amount added is less than 0.1%, precipitation hardening will not be obtained, and if it is added in excess of 3%, etching processability and molding processability will be affected. The Al content deteriorates and the thermal expansion coefficient becomes too large, resulting in poor sealing properties.
I decided on %. Further, by adding Ti and Al at the same time, the effect of increasing strength is more remarkable than when each is added individually, so it is desirable to add them in combination. C: When the C content in the lead frame material exceeds 0.015%, iron carbide is generated, which impairs the etchability of the lead frame material. Therefore, the upper limit of the C content was set at 0.015%, but since solid solution C also has a negative effect on etching processability, the lower the C content, the better, and it is best to suppress it to 0.005% or less if possible. desirable. S
i:Si is an element necessary as a dispersant, but it is also an element that has a large effect on the etching processability of the lead frame material. That is, as the Si content increases, the etching rate slows down and etching processability deteriorates. Therefore, in order to ensure good etching processability, S
It is necessary to adjust the i content to 0.15% or less. In particular, in the case of a multi-pin type lead frame material, even better etching processability is required, so it is desirable to reduce the Si content to 0.05% or less. However, if the Si content is reduced to less than 0.001%, the deoxidizing effect will no longer be observed. Therefore, although the Si content was determined to be 0.001 to 0.15%, it is desirable to adjust it to 0.001 to 0.05% if possible as described above. Mn: Mn is a component added to ensure deoxidation and hot workability of lead frame materials, but if its content is less than 0.1%, not only will the desired deoxidizing effect not be obtained, but Hot workability also becomes poor. On the other hand, 1
．． If the content exceeds 0%, the hardness of the lead frame material will increase too much, resulting in deterioration of workability and furthermore, the coefficient of thermal expansion will increase. Therefore, the Mn content is 0.1-1
．． It was set as 0%. P: Like Si, P is an element that harms the etching processability of lead frame materials when its content increases. Since the adverse effect on the etching processability becomes more apparent when the P content exceeds 0.01%, the P content is set to be 0.01% or less. However, P
When the content is reduced to 0.003% or less, the effect of improving etching processability becomes even more remarkable, and even when applied to multi-pin type lead frames, it becomes possible to stably secure sufficiently satisfactory results. , preferably 0
．． It is preferable to adjust it to 0.003% or less. S: S content is 0
．． If it exceeds 0.005%, sulfide-based inclusions will increase in the lead frame material, causing defects during etching, such as pin breakage. Therefore, the S content is 0
．． It was limited to 0.005% or less. O: O content is 0.010
%, oxide-based inclusions increase in the lead frame material, resulting in perforation defects during etching. Therefore, the O content was limited to 0.010% or less. N: If the N content exceeds 0.010%, the etching processability and molding processability of the lead frame material will deteriorate.
The content shall be 0.010% or less. B: B is added because the addition of B improves the ductility of the material and improves the moldability. If the B content is less than 0.001%, the effect cannot be obtained, and if it is added in excess of 0.1%, the ductility and etching processability will deteriorate. % to 0.1%.

B) Rolling degree before final annealing The degree of rolling before final annealing is important in ensuring the desired strength of the lead frame material, but the degree of rolling is particularly important when the degree of rolling is 40 to 90.
The reason why it is limited to % is that if the degree of rolling is less than 40%, the desired fine grains cannot be stably obtained during final annealing, resulting in mixed grains, whereas if the degree of rolling is less than 90%, If the temperature reaches a certain degree, the cubic structure will develop too much during the final annealing, resulting in an abnormal structure, and as a result, anisotropy will develop, making it impossible to obtain the desired strength even if final cold rolling and strain relief annealing are performed. . C) Crystal grain size during final annealing The final annealing conditions are also important in ensuring the desired strength of the lead frame material, and are also factors that greatly affect etching properties and press workability. The reason for carrying out the final annealing under the conditions that the diameter is 30 μm or less is as follows.
Reducing the grain size greatly contributes to high strength, and also produces good results in etching and press workability, which is effective in realizing high-precision frames.
This is because if the thickness exceeds 0 μm, these effects cannot be ensured. Note that the grain size during final annealing can be easily adjusted by adjusting the annealing temperature and time, as is well known. D) Working degree of final cold rolling The working degree of the final cold rolling also has a large effect on the strength of the lead frame material, but the reason why the working degree is particularly limited to 15 to 85% is that the working degree of the final cold rolling is 15%. If it is less than 85%, no significant effect on strength improvement will be obtained, whereas if it exceeds 85%, anisotropy in strength will become noticeable and moldability will deteriorate. E) Aging heat treatment By performing appropriate aging heat treatment after final rolling, Kb
The value is improved, the anisotropy is also dramatically improved, and the molding processability and sealing properties are improved.
Aging heat treatment is performed in a temperature range of ~800°C. At temperatures below 300° C., it takes more than 10 hours for the aging phenomenon to occur, and a sufficient increase in strength cannot be obtained. When aging at a temperature exceeding 800°C, a peak strength is obtained within 1 hour, but the strength at that peak is 300°C.
The aging temperature is lower than when aging heat treatment is performed in the temperature range of 300℃ to 800℃.
00℃.

[0008]

[Example] Next, the effects of the present invention will be explained in more detail with reference to Examples. First, Fe-Ni-Co alloy ingots having the chemical composition shown in Table 1 were obtained by vacuum melting and casting, then hot rolled and pickled, and then cold rolled and annealed repeatedly. A cold-rolled plate having a plate thickness of 0.1 mm was produced, and after the final cold rolling, an aging heat treatment was performed at 600°C for 3 hours. In addition, "cold rolling before final annealing" at this time
The working degree, the grain size at the final annealing, and the working degree at the final cold rolling were as shown in Table 2 above.

[0009]

[Table 1]

0010

[Table 2] Next, the ``mechanical properties'', ``etchability'', ``formability'', and ``sealability'' of the Fe-Ni-Co alloy lead frame material manufactured in this way were investigated. The results are also shown in Table 2.

As for the mechanical properties, the strength of the material against bending moment was evaluated using the Kb value (spring limit value). Regarding etching properties, after degreasing each of the manufactured plate samples with a thickness of 0.1 mm, a resist film was applied, a pattern was baked and developed, and dichloride dichloride was applied.
A 128-pin lead frame made of iron was etched under the same conditions, and the outer lead pin width and its variation were measured and evaluated. The moldability is
Evaluation was performed by conducting a 90 degree repeated bending test. The sealability was evaluated by applying a thermal cycle after resin sealing and examining whether cracks were generated. The following points are clear from the results shown in Table 2. That is, invention example No. The materials related to Nos. 1 to 5 are Comparative Example No.
Compared to Nos. 6 to 14, they have excellent mechanical properties, etching properties, moldability, and sealing properties. Among them, present invention example No.
．． Inventive Example No. 1, the C, Si, and P contents are all controlled within a more preferable range. The etching properties are even better than those related to Nos. 2 to 5. On the other hand, comparative example No. Regarding No. 6, because the rolling workability before final annealing is too low, it is not possible to achieve a small grain size by subsequent annealing, and Kb
The value is low. Comparative example no. Regarding 7,
The Kb value is low because the final rolling degree is too small. Comparative example no. Those related to 8 are Ti and Al
Because it does not contain any additives, its strength is low. Comparative example no. In the case of No. 9, the etching processability, molding processability, and sealing property are poor because of the large Ti content. Comparative example no. Items related to 10 are A.
Since the content of 1 is large, the etching processability, molding processability, and sealing properties are poor. Comparative example. 11-1
The material related to No. 2 has a high content of C, Si, and P, and therefore has poor etching processability, molding processability, and sealing property. In addition, FIG. 1 shows the example No. of the present invention. 1 and comparative example no. It is a graph showing "the relationship between the bending moment and the amount of settling" regarding No. 13 and No. 14. Here, comparative example No. Items related to 13 have a plate thickness of 0.1m.
m, Comparative Example No. For those related to 14, the plate thickness is 0.15
mm, and all were manufactured using conventional manufacturing methods. From FIG. 1, it can be seen that the lead frame material manufactured under the conditions specified in the present invention has a plate thickness of 0.
．． Even if the thickness is reduced from 15 mm to 0.1 mm, the amount of settling for the same bending moment is small, and it can be confirmed that the material has strong strength against deformation.

0012

[Effect of the invention] According to this invention, etching processability,
It is possible to stably produce lead frame materials with excellent sealing properties, moldability, and high strength, and extremely effective industrial effects are brought about, such as enabling even higher integration of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amount of bending moment sag in an example of the present invention and a comparative example.

Claims (5)

[Claims] Claim 1: Ni 15-55%, C
o2~30%, Ti0.2~3.0%, Al0.1~3
．． 0%, B0.001% to 0.1%, C0.015% or less, Si0.001 to 0.15%, Mn0.1 to 1.0
%, P0.010% or less, S0.005% or less, O0.
0.010% or less, N0.010% or less, and the balance is F.
An alloy material for lead frames consisting of e and other unavoidable impurities. 2. The alloy material for lead frames according to claim 1, wherein the C content is 0.005% or less. [Claim 3] Si content is 0.001 to 0.05%
The alloy material for lead frames according to claim 1 or 2. 4. The alloy material for a lead frame according to claim 1, wherein the P content is 0.003% or less. Claim 5: Polymerization ratio of 15 to 55% Ni, C
o2~30%, Ti0.2~3.0%, Al0.1~3
．． 0%, B0.001% to 0.1%, C0.015% or less, Si0.001 to 0.15%, Mn0.1 to 1.0
%, P0.010% or less, S0.005% or less, O0.
0.010% or less, N0.010% or less, and the balance is F.
Made from an alloy consisting of e and other unavoidable impurities,
Final annealing is carried out under conditions such that the grain size becomes 30 μm or less after rolling with a working degree of 40 to 90%, and after adjusting the working degree of the final cold rolling to 15 to 85%,
A method for producing a high-strength lead frame material having excellent etching processability, molding processability, and sealing property, the method comprising performing aging heat treatment in a temperature range of ~800°C.