JP3000154B2 - Lead frame material manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a lead frame material having excellent etching workability, sealing property and molding workability and having high strength.

<Background technology and its problems> In general, in semiconductor devices, it is known that the characteristics of the lead material used have a large effect on the performance and cost. As the lead material, an Fe-Ni-based alloy having a low coefficient of thermal expansion and showing relatively good adhesion and sealing properties to semiconductor elements and ceramics has been preferably used.

However, for example, during the cooling process after the resin molding process in the “LSI plastic packaging process”, during mounting on a printed circuit board, or when subjected to a temperature cycle in the usage environment, the heat between the resin and the lead material Although it is unavoidable that stress is applied, if the stress becomes excessive, the lead material to be used may be a “Fe—Ni alloy (eg, 42
% Ni-Fe alloy), it is difficult to avoid the problem that cracks occur in the package and the bonding interface is peeled off, thereby lowering the moisture resistance reliability of the package. Is caused by the difference in the thermal expansion coefficient between the mold resin and the lead material.If the minute cracks and the peeling interface occur due to the difference in the thermal expansion coefficient, moisture enters from outside through this and the semiconductor elements etc. There was a risk of damage.

Therefore, in order to improve the humidity resistance reliability of the LSI, it is necessary to use a lead frame material having a chemical composition whose thermal expansion coefficient is as close as possible to that of the mold resin.

On the other hand, recently, high integration has been promoted in the above-mentioned type of LSI, and this tendency has resulted in promoting the use of more pins in the lead frame to be used. Requires the use of higher strength materials.

This is because when the number of pins in the lead frame is increased, the distance between the pins is inevitably reduced, and the width of the pins themselves is also reduced. However, in order to achieve this, etching or pressing with higher precision is required. In addition, there is a concern that the thickness becomes thicker than the pin width, and the processing becomes more difficult. In order to cope with this, it is necessary to reduce the thickness of the material. However, in order to make the material thinner, a lead frame material having strength (resistance to lead deformation) higher than before is required.

In particular, in the case of a lead frame material for a multi-pin or super-multi-pin device, "excellent etching processability" has also become an important required characteristic because the process for molding mainly involves etching.

Here, the etching process of the Fe-Ni alloy lead frame material is generally performed by applying a photoresist on both surfaces of a degreased lead frame material, baking and developing a pattern, and then using ferric chloride as a main component. In general, the method comprises a step of etching with an etching solution to be removed and then removing the resist. The factor that determines the etchability at this time is "resist adhesion"
And the "etching rate", among which the etching rate of the material is the most important factor. As the etching rate increases, the controllability of the pin width and pin spacing formed on the lead frame material increases. It was not an exaggeration to say that the evaluation of the etching processability was generally determined by the etching rate because of the simplification.

Accordingly, as the degree of integration of semiconductor devices increases, "faster etching rate characteristics (that is, better etching processability)" is required for lead frame materials in addition to excellent sealing properties and strength characteristics. However, at present, there has not been found any material which sufficiently satisfies all of the etching workability, the sealing property, the strength, and the moldability.

In view of the above, an object of the present invention is to apply the present invention to a highly integrated semiconductor device having high strength and excellent etching processability, sealing property, and moldability. The objective was to establish a means for industrial mass production of lead frame materials that exhibited sufficient performance even in such cases.

<Means for Solving the Problems> In order to achieve the above object, the present inventors have paid particular attention to the relatively high strength characteristics and low thermal expansion coefficient of Fe-Ni alloy lead frame materials, and As a result of repeated research on a manufacturing method that can further stably manufacture while further improving the etching processability and forming processability, and further improving the processability,
The following new findings were obtained. That is, (a) In the case of Fe-Ni alloy which has been considered to be relatively preferable as a lead frame material, when the contents of C, Si and P, and also the N content are restricted to specific low values, The result is that the etching rate of the alloy is significantly improved.

(B) In addition, when one or more selected specific elements are contained in the above alloy in a predetermined ratio, the properties as a lead frame material are significantly adversely affected. In addition to improving the strength of the material effectively, the addition of the above specific element under careful adjustment of the Ni content is a very effective means to bring the coefficient of thermal expansion close to that of the mold resin .

(C) Also in the above alloy material, the crystal grain size has a considerable effect on the strength and formability, but by taking measures to suppress the crystal grain size to a specific value or less, it is possible to increase the number of pins in the lead frame. In addition to the above, “further improvement in material strength” can be expected, and moldability is also improved.

(D) In the above-mentioned alloy system, in order to stably produce a fine grain size without mixing grains, it is necessary to control the rolling degree before final annealing to a specific range.

(E) Further, in order to improve the strength without increasing the anisotropy, it is necessary to control the rolling degree of the final cold rolling to a specific range.

(F) Therefore, in an alloy containing Fe-Ni as a basic component,
At the same time as adjusting the contents of Ni, C, Si and P, etc., at the same time, adding specific alloying elements to this, if necessary, further reduce the degree of rolling before final annealing, the crystal grain size during final annealing, By controlling the workability of the final rolling to an appropriate range, it is possible to stably produce leadframe materials with excellent properties such as strength, coefficient of thermal expansion, sealing properties, and formability, and also with very good etching workability. It can be manufactured.

The present invention has been completed based on the above findings and the like, `` When manufacturing a Fe-Ni-based alloy lead frame material,
C: 0.015% or less by weight (hereinafter,% representing the weight is referred to as% by weight), Si: 0.001 to 0.15%, Mn: 0.1 to 1.0%, P: 0.01% or less, S: 0.005% or less, O: 0.010% or less, N: 0.005% or less, Ni: 33 to 55% or Co, Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Cu, A, Be , Mg and Ca 1
Species or more: The alloy contains 0.01 to 5.0% in total, the balance being Fe and other unavoidable impurities, and the final annealing has a workability of 40 to 9%.
0% (preferably 50 to 85%) rolling is carried out to obtain a fine grain structure having a crystal grain size of 30 μm or less (preferably 20 μm or less). %
(Preferably 50 to 80%) to stably produce a lead frame material having both excellent etching processability, sealing property and molding processability, and high strength. " Has features.

In this case, (a) strain relief annealing is performed after final cold rolling, (b) C content is regulated to 0.005% or less, (c) Si content is adjusted to 0.001 to 0.05%, (d) If the P content is regulated to 0.003% or less, the conditions for improving the formability and etching processability of the obtained lead frame material become more remarkable, and the effect of the multi-pin lead frame material is improved. It will be possible to more fully cope with manufacturing.

Next, the reasons for limiting the numerical values of the component composition of the base alloy, the workability of rolling before final annealing, the crystal grain size at the time of final annealing, and the workability of final cold rolling as described above in the present invention are as follows. It is explained together with.

<Action> A) Composition of the material alloy Ni Ni is an important component in determining the thermal expansion coefficient of the lead frame material, and has excellent sealing properties and a small thermal expansion difference with the package after sealing. It is necessary to adjust the Ni content in the range of 33 to 55% in order to secure the sealing property and the moisture resistance reliability. Therefore, the Ni content is determined to be 33 to 55%, but a particularly preferred range is 40 to 53%.

C When the C content in the lead frame material exceeds 0.015%, iron carbide is generated, which impairs the etching property of the lead frame material. Therefore, the upper limit of the C content is 0.015
However, since the dissolved C also has an adverse effect on the etching processability, the C content is preferably as low as possible, and is desirably suppressed to 0.005% or less if possible.

Si Si is an element necessary as a deoxidizing material, but is also an element that has a great effect on the etching processability of a lead frame material. That is, as the Si content increases, the etching rate decreases, and the etching processability deteriorates. Therefore, it is necessary to adjust the Si content to 0.15% or less in order to ensure good etching processability. In particular, in the case of a multi-pin type lead frame material, since even better etching workability is required, it is desirable to reduce the Si content to 0.05% or less. However, the Si content is 0.00
When it is reduced to a region of less than 1%, the deoxidizing effect is not recognized. Therefore, Si content is 0.001-0.15%
However, it is desirable to adjust to 0.001 to 0.05% if possible as described above.

Mn Mn is a component added to ensure deoxidation and hot workability of the lead frame material, but its content is 0.1%
If it is less than 1, not only the desired deoxidizing effect cannot be obtained, but also the hot workability becomes poor. On the other hand, when Mn is contained in excess of 1.0%, the hardness of the lead frame material is excessively increased, thereby causing deterioration in workability and further increasing the coefficient of thermal expansion. Therefore, the Mn content is set to 0.1 to 1.0%.

PP, like Si, is an element that, if its content increases, impairs the etching processability of the lead frame material. And
Since the adverse effect on the etching processability becomes more remarkable when the P content exceeds 0.01%, the P content is set to 0.01% or less. However, when the P content is reduced to 0.003% or less, the effect of improving the etching workability becomes more remarkable, and a sufficiently satisfactory result can be stably secured even when applied to a multi-pin type lead frame. Preferably, it is adjusted to 0.003% or less.

If the SS content exceeds 0.005%, sulfide-based inclusions increase in the lead frame material, which becomes a defect during etching and causes pin breakage and the like. Therefore, S
The content was limited to 0.005% or less.

If the O 2 O content exceeds 0.010%, oxide-based inclusions increase in the lead frame material, which also causes drilling defects at the time of etching, so the O content was limited to 0.010% or less.

Even if the N content exceeds 0.005%, the etching processability of the lead frame material deteriorates.
0.005%.

Co, Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Cu, A, Be, Mg, and Ca All of these elements have the effect of increasing the strength and thermal expansion coefficient of the lead frame material. Therefore, one or two or more kinds may be contained as necessary for the purpose of improving the material strength and increasing the thermal expansion coefficient to approach that of the resin mold to further improve the sealing property. In particular, Co, Cr,
Mo, W, V, Nb, Ta, Ti, Zr and Hf have the effect of improving the etchability to form carbides and reduce the amount of solute carbon. In addition, it also has effects of increasing strength and improving bendability.

However, if their contents are less than 0.01% in total, the desired effects of the above-mentioned effects cannot be obtained. On the other hand, if the total content exceeds 5.0%, the material becomes too hard and the moldability increases. In addition to causing deterioration, it is also difficult to secure an appropriate coefficient of thermal expansion, so the content of the above components is 0.
01-5.0%.

B) Degree of Rolling Before Final Annealing The degree of rolling before final annealing is important for securing the desired strength to the lead frame material.
The reason for limiting to 90% is that if the degree of rolling is less than 40%, the desired fine crystal grains are not obtained stably during final annealing, resulting in mixed grains. When the working degree is reached, the cubic structure develops too much during the final annealing, resulting in an abnormal structure. As a result, anisotropy develops and the final cold rolling,
The desired strength may not be obtained even when the strain relief annealing is performed.

C) Grain size during final annealing The final annealing conditions are also important in ensuring the desired strength of the lead frame material, and also have a significant effect on the etching properties and press workability. The reason why the diameter is adjusted to be 30 μm or less is that the refinement of the crystal grain size greatly contributes to high strength, and good results are also obtained in etching and press workability, realizing a high precision lead frame. On the other hand, if the crystal grain size exceeds 30 μm, these effects cannot be secured. The crystal grain size during the final annealing can be easily adjusted by adjusting the annealing temperature and the processing time as is well known.

D) Degree of work in final cold rolling The degree of work in final rolling also has a significant effect on the strength of the lead frame material. The reason for limiting the degree of work especially to 40 to 85% is that the degree of work in rolling is 40%. If it is less than 85%, a remarkable effect on strength improvement cannot be obtained, while if it exceeds 85%, strength anisotropy becomes remarkable.

E) Strain relief annealing By performing appropriate strain relief annealing after final rolling, Kb
The value has been improved and its anisotropy has been dramatically improved.
Since the bending property and the sealing property are also improved, the strain relief annealing is performed. For example, in a continuous annealing furnace in a reducing atmosphere, furnace temperature: 500 to 900 ° C., residence time of material in the furnace: 10 to 120
The above effect can be obtained by performing the heat treatment in seconds.

Next, the effects of the present invention will be described more specifically with reference to examples.

<Examples> First, Fe-Ni-based alloy ingots having the chemical composition shown in Table 1 were obtained by vacuum melting and casting, and then hot-rolled and pickled, and then cold-rolled. Annealing was repeated to produce a cold-rolled sheet having a sheet thickness of 0.125 mm. At this time, the working ratio of "cold rolling before final annealing", the crystal grain size at the time of final annealing, and the working ratio of final cold rolling were as shown in Table 1 above.

Subsequently, the “mechanical properties”, “etching properties”, “bending workability” and “sealability” of the Fe—Ni-based alloy lead frame material thus manufactured were investigated, and the results were taken as the first. It is also shown in the table.

Here, regarding the mechanical properties, the strength of the material with respect to the bending moment was evaluated based on the Kb value (spring limit value).

Regarding the etching properties, each of the manufactured cold-rolled sheets was degreased, then a resist film was applied, and after baking and developing the pattern, the lead frame of 128 pins was all etched with ferric chloride under the same conditions. The processed one was evaluated by measuring the outer lead pin width and its variation.

The bending workability was evaluated by performing a 90 ° repeated bending test.

The sealing property was evaluated by examining whether a crack was generated by applying a heat cycle after sealing the resin.

The following items are apparent from the results shown in Table 1.

That is, the materials according to Examples 1 to 4 of the present invention are superior to those according to Comparative Examples 22 to 35 in all of mechanical properties, etching properties, bending workability, and sealing properties. Among them, those according to Inventive Examples 1 to 4 were controlled in a more preferable range for each of the contents of C, Si, and P.
The etching properties are further superior to those according to the above.

Further, those according to Examples 5 to 21 of the present invention have further improved strength because Nb, Mo, Ti and the like are added.

On the other hand, in the case of Comparative Example 22, the workability of the rolling before final annealing was too low, so that a small crystal grain size could not be realized by subsequent annealing, and the Kb value was low.

On the other hand, in the case of Comparative Example 23, since the workability of the rolling before final annealing was too large, the cubic structure was developed by the subsequent annealing, and the Kb value was low.

In the case of Comparative Example 24, the Kb value was low because the workability of final cold rolling was too small.

In the case of Comparative Example 25, the Kb value was low because the crystal grain size at the time of final annealing was large.

In the case of Comparative Example 26, the bending workability was inferior because the final rolling degree was too large.

In the case of Comparative Examples 27 to 29, since the contents of C, Si and P are large, the etching workability, bending workability and sealing property are inferior.

In the cases of Comparative Examples 30 to 33, since the added amounts of W, Mo, Co and the like were too large, the bending workability and the sealing property were inferior.

FIG. 1 is a graph showing the “relationship between bending moment and sag amount” of Example 1 of the present invention and Comparative Examples 34 and 35. Here, those according to Comparative Example 34 had a plate thickness of 0.
125 mm, the one according to Comparative Example 35 has a thickness of 0.15 mm,
Each of them was prepared 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 plate thickness of 0.15 mm or less.
Even if the thickness is reduced to 0.125 mm, the amount of sag for the same bending moment is small, and it can be confirmed that the material strength against deformation is strong.

<Summary of Effects> As described above, according to the present invention, it is possible to stably produce a high-strength lead frame material which is excellent in etching workability, sealing property, and moldability, and is suitable for semiconductor devices. Industrially extremely useful effects such as higher integration can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph comparing the relationship between the bending moment and the set amount between the material according to the present invention and the material according to the comparative method.

Continuation of the front page (56) References JP-A-61-279628 (JP, A) JP-A-61-210127 (JP, A) JP-A-2-270941 (JP, A)

Claims (7)

(57) [Claims] When manufacturing a lead frame material of an Fe-Ni alloy, C: 0.015% or less, Si: 0.001 to 0.15% Mn: 0.1 to 1.0%, P: 0.01% or less, S: 0.005% by weight %, O: 0.010% or less, N: 0.005% or less, Ni: 33 to 55%, and the balance is made of an alloy consisting of Fe and other unavoidable impurities. ~ 90
% To obtain a fine grain structure with a crystal grain size of 30 μm or less.
A method for producing a high-strength lead frame material excellent in etching processability and sealing property, characterized in that the material is adjusted to: (2) Co, Cr, Mo, W, V, Nb, Ta, Ti,
The high-etching and sealing property according to claim 1, wherein an alloy containing at least one of Zr and Hf in a total amount of 0.01 to 5.0% by weight and the balance being Fe and other unavoidable impurities is used. Manufacturing method of strength lead frame material. 3. The material further comprises one of Cu, A, Be, Mg and Ca.
3. A high-strength lead frame according to claim 1 or 2, wherein the alloy contains at least 0.01 to 5.0% by weight of a seed and the balance is Fe and other unavoidable impurities. The method of manufacturing the material. 4. The method for producing a high-strength lead frame material excellent in etching workability and sealing property according to claim 1, wherein strain relief annealing is performed after final cold rolling. 5. The method for producing a high-strength lead frame material excellent in etching workability and sealing property according to claim 1, wherein an alloy having a C content of 0.005% by weight or less is used as a material. . 6. The material has a Si content of 0.001 to 0.05% by weight.
The method for producing a high-strength lead frame material excellent in etching processability and sealing property according to any one of claims 1 to 5, using an alloy of (1). 7. The method for producing a high-strength lead frame material excellent in etching workability and sealing property according to claim 1, wherein an alloy having a P content of 0.003% by weight or less is used as a material. .