JPH04231418A - Production of lead frame material - Google Patents

Abstract

PURPOSE:To improve etching characteristic, sealing characteristic, and formability by specifying respective contents of Ni, Si, and P in an Fe-Ni-base alloy and also specifying the draft at rolling before final annealing, the crystalline grain size at the time of final finish annealing, and the draft at final cold rolling, respectively. CONSTITUTION:The lead frame material has a composition consisting of, by weight, 0.015-0.2% C, 0.001-0.15% Si, 0.1-1.0% Mn, <=0.01% P, <=0.005% S, <=0.010% O, <=0.005% N, 33-55% Ni, and the balance Fe with inevitable impurities. After rolling is applied to this alloy stock at 40-90% draft, final annealing is exerted under the conditions where crystalline grain size is regulated to <=30mum. By this method, the lead frame material having high strength can stably be produced, and semiconductor equipment can highly be integrated.

Description

[Detailed description of the invention]

0001

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

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, 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 alloy lead frame material, and have developed As a result of repeated research on a manufacturing method that can further improve the processability, markedly improve the etching processability and molding processability, and enable stable production, we were able to obtain the following new knowledge. (a) In Fe-Ni alloys that have been considered relatively preferable as lead frame materials, if the Si and P contents and also the N content are limited to specific low values, The etching rate of the alloy becomes significantly improved. (b) Moreover, when the above alloy contains one or more selected specific elements in a predetermined ratio,
In addition to being able to effectively improve the strength of the material without any particular negative effect on its properties as a lead frame material, the addition of the above specific elements under careful control of the Ni content improves its thermal expansion coefficient. This is an extremely effective means of bringing the quality close to that of mold resin. (c) Also, in the above materials, the crystal grain size has a considerable influence on the strength and moldability, but by taking measures to keep the crystal grain size below a certain value, it is possible to increase the number of pins in the lead frame. Not only can a desirable "further improvement in material strength" be expected, but 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, the content of Ni, Si, P, etc. in the alloy containing Fe-Ni as a basic component is adjusted comprehensively, and at the same time, specific alloying elements are added to this as necessary, and furthermore, before final annealing. If the degree of rolling, grain size during final annealing, and degree of final rolling are controlled within appropriate ranges, it will have excellent properties such as strength, coefficient of thermal expansion, sealing properties, and formability, as well as very good etching processability. It becomes possible to stably manufacture lead frame materials that also have high properties.

[0005] The present invention was completed based on the above-mentioned findings, etc.;
．． 2%, Si0.001-0.15%, Mn0.1-1
．． 0%, P 0.010% or less, S 0.005% or less, O
0.010% or less, N0.005% or less, Ni33-5
5%, or further contains Mg, Ca, Al, Cu
, 0.01 to 5.0% in total of one or two types of Co
Or contains one or both of Cr, Mo, W, V, Nb, Ta, Ti, Zr and Hf in a total amount of 0.01 to 5.0%, and contains Fe and other unavoidable impurities. After rolling 40-90%, final annealing is performed under conditions such that the grain size becomes 30 μm or less, followed by final cold rolling with a working degree of 40-85%. This is a method for manufacturing a high-strength lead frame material with excellent sealing properties at 300-800° C. after adjusting the degree of final cold rolling to 15-85%. In addition, in the present invention, strain relief annealing is performed after the final cold pressing, S
By adjusting the i content to 0.001 to 0.05% and/or the P content to 0.003% or less, either alone or in combination, the effect of improving the etching processability of the resulting lead frame material becomes even more prominent, and it becomes possible to more fully cope with 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 33 to 55%. Therefore, the Ni content is 33-55%
I decided. C: If the C content in the lead frame material is 0.015% or less, no improvement in strength due to C is observed, and if it is added in excess of 0.2%, the material becomes brittle and the bending workability becomes poor. In addition, Cr, Co, Mo, W, V, Nb, which will be described later
When , Ta, Ti, Zr, Hf, etc. are added together, carbides are formed, and dispersion strengthening due to carbide formation and strength improvement due to crystal grain refinement can be obtained. The C content is 0.015-0.2% to improve strength without impairing bending workability.
And so. Si: Si is an element necessary as a dispersing agent, but it is also an element that greatly affects the etching processability of lead frame materials. That is, as the Si content increases, the etching rate slows down and etching processability deteriorates. Therefore, in order to ensure good etching processability, it is necessary to adjust the Si 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, Si
Although the content was determined to be 0.001 to 0.15%, it is desirable to adjust the content 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, if the content exceeds 1.0%, 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 was determined to be 0.1 to 1.0%. P: Like Si, P is an element that harms the etching processability of lead frame materials when its content increases. The above-mentioned adverse effect on etching processability occurs when the P content is 0.
Since P content becomes more obvious when it exceeds 0.01%, the P content was set at 0.01% or less. However, the P content is 0.00
When it is reduced to 3% or less, the effect of improving etching processability becomes even more remarkable, and even when applied to a multi-pin type lead frame, a sufficiently satisfactory result can be stably ensured, so it is preferably 0. It is preferable to adjust it to 0.003% or less. S: If the S content 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 was limited to 0.005% or less. O: If the O content exceeds 0.010%, oxide-based inclusions will increase in the lead frame material, which will also cause drilling defects during etching processing, so the O content should be reduced to 0.010%.
Limited to the following. N: Even if the N content exceeds 0.005%, the etching processability of the lead frame material deteriorates, so the upper limit of the N content was set at 0.005%. Mg, Ca, Al, Cu, Co, Cr, Mo, W, V,
Nb, Ta, Ti, Zr, and Hf: These elements all have the effect of increasing the strength and thermal expansion coefficient of the lead frame material, so they can improve the material strength and increase the thermal expansion coefficient to improve resin molding. If necessary, one or more types may be included for the purpose of further improving the sealing property by bringing the composition closer to that of . In particular, Cr, Co, Mo, W, V
, Nb, Ta, Ti, Zr, and Hf form carbides and reduce solid solution carbon, so they have an etching effect, and dispersion of carbides makes crystal grains finer, increasing strength and improving bendability. It also brings about the effect of However, if the total content of these is less than 0.01%, the desired effect of the above action cannot be obtained, and on the other hand, if the total content is less than 5.
If it exceeds 0%, the material will become too hard, leading to deterioration in moldability, and it will also be difficult to secure an appropriate coefficient of thermal expansion, so the total content of the above components should be 0.01 to 0. 5
．． It was set as 0%.

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, and 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 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 40 to 85% is that the working degree of the final cold rolling is 40%. 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 Proper strain annealing after final rolling improves the Kb value, dramatically improves its anisotropy, and improves bending workability and sealing properties. I do. For example, the above effects can be obtained by heat treatment in a continuous annealing furnace in a reducing atmosphere at a furnace temperature of 500 to 900° C. and a residence time of the material in the furnace of 10 seconds to 120 seconds.

[0008]

[Example] Next, the effects of the present invention will be explained in more detail with reference to Examples. First, Fe-Ni 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 to achieve a thickness of : A cold rolled sheet of 0.125 mm was produced, and after the final cold rolling, it was heated at 700°C for 3 hours in a reducing atmosphere.
A strain relief heat treatment was performed for seconds. In addition, the working degree of "cold rolling before final annealing" at this time, the grain size at the time of final annealing, and the working degree of final cold rolling were as shown in Table 2.

[0009]

[Table 1]

0010

[Table 2] Next, the "mechanical properties" and "etchability" of the Fe-Ni alloy lead frame material manufactured in this way are described.
, "bending workability" and "sealability" were investigated, and 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 4 are Comparative Example No.
Compared to Nos. 22 to 35, it has excellent mechanical properties, etching properties, bending properties, and sealing properties. Among them, the present invention example N
o. 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 4. Moreover, the present invention example No. In the case of Nos. 5 to 21, the strength is further improved due to the addition of Nb, Mo, Ti, etc. On the other hand, comparative example No. In the case of No. 22, since the degree of rolling before final annealing was too low, it was not possible to achieve a small grain size through subsequent annealing, resulting in a low Kb value. On the contrary, comparative example No. Regarding No. 23, the degree of rolling before final annealing was too large, resulting in the development of a cubic structure during subsequent annealing, resulting in K
The b value is low. Comparative example no. In the case of No. 24, the Kb value is low because the final rolling degree is too small. Comparative example no. Regarding No. 25, the Kb value was low because the crystal grain size at the time of final annealing was large. Comparative example no. In the case of No. 26, the final rolling degree is too large and the bending workability is poor. Comparative example.
In the case of No. 27, the bending workability and sealing properties are poor due to the high content of C. Comparative example no. 2
In the case of Nos. 8 to 29, the etching workability, bending workability, and sealing performance are poor due to the large contents of Si and P. Comparative example no. Regarding items 30 to 33,
Since the amounts of W, Mo, Co, etc. added are too large, the bending workability and sealing properties are poor. 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. 34 and No. 35. Here, comparative example No. Regarding No. 34, the plate thickness was 0.125 mm and Comparative Example No. No. 35 has a plate thickness of 0.15 mm, and was manufactured by a conventional manufacturing method. From FIG. 1, it can be seen that the lead frame material manufactured under the conditions specified in the present invention has a small amount of settling under the same bending moment even if the plate thickness is reduced from 0.15 mm to 0.125 mm. 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 a lead frame material 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 settling in an example of the present invention and a comparative example.

Claims (6)

[Claims] Claim 1: C0.015 to 0.2 in weight proportion
%, Si0.001-0.15%, Mn0.1-1.0
%, P0.01% or less, S0.005% or less, O0.0
The material is an alloy containing 10% or less, 0.005% or less N, 33-55% Ni, and the balance consisting of Fe and other unavoidable impurities, and after being rolled 40-90%, the crystal grain size is 30 μm or less. Final annealing was carried out under the conditions of
A method for producing a high-strength lead frame material with excellent etching workability and sealing properties, which comprises then performing final cold rolling at a working degree of 40 to 85%. Claim 2: C0.015 to 0.2 in weight proportion
%, Si0.001-0.15%, Mn0.1-1.0
%, P0.01% or less, S0.005% or less, O0.0
10% or less, N0.005% or less, Ni33-55%, and also contains one or more of Mg, Ca, Al, and Cu in a total of 0.01-5.0%, and the balance is Fe.
and other unavoidable impurities,
After rolling 40 to 90%, final annealing is carried out under conditions such that the grain size is 30 μm or less, and then 40 to 85%
1. A method for producing a high-strength lead frame material with excellent etching workability and sealing properties, characterized by performing final cold rolling at a working degree of . Claim 3: C0.015 to 0.2 in weight proportion
%, Si0.001-0.15%, Mn0.1-1.0
%, P0.01% or less, S0.005% or less, O0.0
Contains 10% or less, N0.005% or less, and 33 to 55% Ni, as well as Cr, Co, Mo, W, V, Nb,
One or more of Ta, Ti, Zr and Hf in total 0.01
~5.0%, with the balance consisting of Fe and other unavoidable impurities. After rolling 40 to 90%, final annealing is performed under conditions such that the grain size is 30 μm or less. A method for producing a high-strength lead frame material having excellent etching processability and sealing properties, the method comprising: followed by final cold rolling at a workability of 40 to 85%. Claim 4: C0.015 to 0.2 in weight proportion
%, Si0.001-0.15%, Mn0.1-1.0
%, P0.01% or less, S0.005% or less, O0.0
10% or less, N0.005% or less, Ni33-55%, and also contains a total of 0.01-5.0% of one or more of Mg, Ca, Al, and Cu, and furthermore, C
Contains a total of 0.01 to 5.0% of one or more of r, Co, Mo, W, V, Nb, Ta, Ti, Zr and Hf, with the remainder consisting of Fe and other inevitable impurities. The alloy is used as a material, and after being rolled 40 to 90%, final annealing is performed under conditions such that the grain size becomes 30 μm or less, and then final cold rolling is performed at a workability of 40 to 85%. A method for manufacturing a high-strength lead frame material with excellent etching processability and sealing properties. 5. The method for producing a high-strength lead frame material with excellent etching processability and sealing properties according to claim 1, wherein strain relief annealing is performed after the final cold rolling. [Claim 6] Si content is 0.001 to 0.05%
The method for producing a high-strength lead frame material having excellent etching processability and sealing properties according to any one of claims 1 to 5, wherein an alloy having a P content of 0.003% or less is used.