JPH04231421A - Production of lead frame material - Google Patents

Abstract

PURPOSE:To produce a high strength lead frame material excellent in etching characteristic, sealing characteristic, etc., by applying, after final cold rolling, stress relief heat treatment and skin pass rolling to an Fe-Ni-Cr alloy material having a specific composition. CONSTITUTION:After final annealing and final cold rolling are applied to a lead frame material composed of an Fe - 33-55wt.% Ni - 2-15wt.% Cr alloy, this material is subjected to stress relief heat treatment and further to skin pass rolling at <=5% draft. It is preferable that the above lead frame material has a composition containing, e.g. 0.001-0.15% Si, 0.1-1.0% Mn, 2-15% Cr, 33-55% Ni, 0.01-5.0% of one or more elements among Co, Mo, W, V, Nb, Ta, Ti, Zr, and Hf, <=0.015% C, <=0.01% P, <=0.005% S, <=0.010% O, and <=0.005% N. Further, it is preferable that, after the above material is rolled at 40-90% draft, final annealing is exerted under the conditions where a crystalline grain size of <=30mum is reached and also the draft at successive final cold rolling is regulated to 40-85%.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to Fe, which has excellent etching processability, sealing property, and molding processability, and has high strength.
-33 to 55 wt% Ni-2 to 15 wt% Cr alloy lead frame material manufacturing method.

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 favorably used, which have a low coefficient of thermal expansion and exhibit relatively good adhesion and sealing properties with semiconductor elements and ceramics.

However, for example, during the cooling process after the resin molding process in the plastic packaging process for LSIs, during mounting on printed circuit boards, and even when subjected to temperature cycles in the usage environment, the relationship between the resin and lead material may deteriorate. If thermal stress cannot be avoided and this stress becomes excessive, the lead material used may be a Fe-Ni alloy (e.g. 42% 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,
This is caused by the difference in thermal expansion coefficient between the mold resin and the lead material. If 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 damage the internal semiconductor elements. There was fear. Therefore, in order to improve the moisture resistance reliability of LSI,
It was necessary to use a lead frame material with a chemical composition whose coefficient of thermal expansion was as close as possible to that of the mold resin.

[0004] Therefore, recently, Ni-Cr-Fe alloys have been developed that contain Cr as a main component in addition to Ni, and have a coefficient of thermal expansion as close as possible to that of mold resin by adjusting the contents of Ni and Cr. Lead frame materials made from aluminum have also been developed, and their performance is attracting attention.

On the other hand, recently, the above-mentioned types of LSIs have been becoming more highly integrated, and this trend has resulted in the promotion of increasing the number of pins in the lead frames used. To cope with this, it is necessary to use stronger materials. because,
When a lead frame has a large number of pins, the pin spacing inevitably becomes narrower and the width of the pins themselves becomes smaller, but to achieve this, etching or press processing with even higher precision is required, and the pin spacing becomes narrower. There is also a concern that the thickness will become thicker than the width, making processing even more difficult. Therefore, in order to cope with this, it becomes necessary to reduce the material thickness, and in order to make the material thinner, a lead frame material with higher strength (resistance against lead deformation) than conventional ones is required.

[0006] In addition, especially for lead frame materials for high-pin count and extremely high-pin count, the processing for molding is mainly etching process, so excellent etching processability has also become an important required property. . Here, in the etching process of lead frame materials made of Fe-Ni alloy or Fe-Ni-Cr alloy, generally, photoresist is applied to both sides of the degreased lead frame material, and a pattern is baked and developed. It usually consists of a step of etching with an etching solution containing ferric chloride as a main component, and then removing the resist. Factors that determine the etching performance at this time include resist adhesion and etching speed, but among these, the etching speed of the material is the most important factor, and as the etching speed increases, the lead It is no exaggeration to say that the evaluation of etching workability is largely determined by the etching speed since the pin width and pin spacing formed on the frame material can be easily controlled. Therefore, as the degree of integration of semiconductor devices increases, lead frame materials are required to not only have excellent sealing properties and strength properties, but also faster etching speed properties (i.e., good etching processability). That's why.

However, etching processability,
The reality is that no material or manufacturing method has been found that fully satisfies all of the sealing properties, strength, and moldability.

[0008] From this point of view, the present applicant first developed Fe
- As a method for manufacturing a Ni-Cr alloy lead frame material, Si: 0.001 to 0.15 wt%, Mn: 0.
1 to 1.0 wt%, Cr: 2 to 15% and Ni: 33
-55% as a basic component, the remainder consists of Fe and unavoidable impurities, and C: 0.015wt% or less, P: 0.01wt% or less, S: 0.005wt% or less, O: 0.010wt % or less and N: 0.005w
The lead frame material is made of an alloy regulated to be t% or less, and when performing strain relief heat treatment after final annealing and final cold rolling, rolling is performed at a working degree of 40 to 90% before final annealing,
Etching workability, molding workability, and sealing property characterized by carrying out final annealing under conditions such that the crystal grain size is 30 μm or less, and adjusting the workability of the subsequent final cold rolling to 40 to 85%. We have proposed a manufacturing method for superior high-strength lead frame materials, and have achieved many results.

[0009]

[Problem to be solved by the invention] In view of the above requirements, it is important to further improve the strength without impairing the forming (bending) workability in future application to highly integrated semiconductor devices. Gender has become more recognized.

[0010] Therefore, an object of the present invention is to apply it to highly integrated semiconductor devices that have excellent etching processability, sealing property, and moldability as well as higher strength. The object of the present invention is to establish an industrial mass production method for Fe-Ni-Cr alloy lead frame materials that exhibit sufficient performance even when intended for

[0011]

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present inventors have proposed a method for manufacturing Fe-Ni-Cr alloy lead frame materials that further improves the strength without impairing workability. We have conducted repeated research on how to measure this.

[0012] Here, the main points of the proposed method are as follows: (a) In the Fe-Ni-Cr alloy, which has been considered to be relatively preferable as a lead frame material, C, Si,
If the S, P and O contents, and also the N content, are limited to certain low values, the etching rate of the alloy will be significantly improved. (b) Moreover, when the above alloy contains one or more selected specific elements such as Co, Mo, W, and V in a predetermined ratio, various elements as a lead frame material can be used. Besides being able to effectively improve the strength of the material without any particular negative effect on its properties, the addition of the above-mentioned specific elements under careful control of the Ni and Cr contents increases its thermal expansion coefficient to that of the mold resin. This is an extremely effective means of approaching that goal. (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 to below a certain value, lead frames with a large number of pins can be created. Further improvement in material strength, which is favorable for materials, can be expected, and molding processability is also improved. (d) In the above-mentioned alloy system, in order to stably manufacture the crystal grain size without creating mixed grains, it is necessary to control the degree of rolling before final annealing within a specific range. (e) 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.

Under these means and requirements, in order to improve the strength without impairing bending workability, strain relief heat treatment is performed after the final cold rolling, and then skin pass rolling of 5% or less is performed. was found to be the most effective.

[0014] In this way, the content of Ni, C, Si, P, etc. in the alloy containing Fe-Ni-Cr as a basic component is comprehensively adjusted, and at the same time, specific alloying elements are added thereto as necessary. Furthermore, by controlling the rolling workability before final annealing, the grain size during final annealing, and the workability during final rolling within appropriate ranges, and performing skin pass rolling of 5% or less after strain relief heat treatment, the coefficient of thermal expansion and sealing can be improved. This makes it possible to stably produce a high-strength lead frame material that has excellent properties such as hardness and moldability, and also has very good etching processability.

The present invention was completed based on the above findings, and includes Fe-33-55wt% Ni-2-15%
When manufacturing Cr-based alloy lead frame materials, Fe-
A 33-55 wt% Ni-2-15% Cr alloy lead frame material is subjected to strain relief heat treatment after final annealing and final cold rolling, and is then further subjected to skin pass rolling of 5% or less, The present invention provides a method for manufacturing a high-strength lead frame material with excellent etching workability, bending workability, and sealing performance.

More specifically, in the present invention, the lead frame material contains Si: 0.001 to 0.15 wt% and Mn: 0.
．． 1 to 1.0 wt%, Cr: 2 to 15% and Ni: 33
~55wt, or further contains Co, Mo, W, V
, Nb, Ta, Ti, Zr and Hf in a total of 0.01 to 5.0% by weight and/or Cu, A
0.0 in total of one or more of l, Be, Mg and Ca
Contains 1 to 5.0 wt%, and C: 0.015 wt% or less, P: 0.01 wt% or less, S: 0.005 wt% or less, O: 0.010 wt% or less, and N: 0.005 w.
The alloy is regulated to be less than t%, and 4
Rolling is performed at a working degree of 0 to 90%, preferably 50 to 85%, final annealing is carried out under conditions such that the grain size becomes 30 μm or less, preferably 20 μm or less, and the subsequent final cold rolling is performed with a working degree of 40%. A high-strength lead frame material with excellent etching workability, bending workability, and sealing property, which is adjusted to ~85%, preferably 50 to 80%, and then subjected to skin pass rolling of 5% or less. The present invention provides a method for manufacturing.

[0017] In this case, (a) the C content is 0.0
(b) Si content should be regulated to 0.05% or less.
If the conditions of (c) regulating the P content to 0.01 to 0.05% and (c) regulating the P content to 0.003% or less are adopted alone or in combination, the moldability and etching processability of the resulting lead frame material will be improved. The effect of improving the properties becomes even more remarkable, and it becomes possible to more fully cope with the production of multi-pin lead frame materials.

[0018]

[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 properties. Therefore, in order to ensure excellent moisture resistance reliability, N
It is necessary to adjust the i content to 33-55%. Therefore, the Ni content was determined to be 33 to 55%.

Cr: Cr 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 ensure excellent sealing performance and moisture resistance reliability, C
It is necessary to adjust the r content to 2-15%. Therefore,
The Cr content was determined to be 2 to 15%.

Si: Si is an element necessary as a deoxidizing 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, the Si content was set at 0.001 to 0.15%, but as mentioned above, the Si content was set at 0.001 to 0.00%.
．． It is desirable to adjust it to 0.05%.

Mn: Mn is a component added to ensure deoxidation and hot workability of the lead frame material, but if its content is less than 0.1%, the desired deoxidation effect cannot be obtained. Not only is this not possible, but the hot workability is also inferior. 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 is 0
．． It was set at 1 to 1.0%.

C: The C content in the lead frame material is 0.
If it exceeds 0.015%, iron carbides will be formed, which will impair 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 desirable to suppress it to 0.005% or less. .

P: Similar to 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, when the P content is reduced to 0.003% or less, the effect of improving etching processability becomes even more remarkable, making it possible to stably secure sufficiently satisfactory results even when applied to multi-pin type lead frames. Therefore, 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.

[0027] O: When the O content exceeds 0.010%,
The O content was limited to 0.010% or less because oxide-based inclusions increase in the lead frame material, resulting in perforation defects during etching and causing pin breakage, etc.

N: 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%.

Co, Mo, W, V, Nb, Ta, Ti,
Zr and Hf and Cu, Al, Be, Mg and C
a: All of these elements have the effect of increasing the strength and coefficient of thermal expansion of the lead frame material. For the purpose of further improving properties, one or more types may be contained as necessary. especially,
The former group Co, Mo, W, V, Nb, Ta
, Ti, Zr, and Hf form carbides and reduce solid solution carbon, which has the effect of improving etching properties.Also, dispersion of carbides makes crystal grains finer, which increases strength and improves bendability. It also has an effect. but,
If their total content is less than 0.01%, the desired effect of the above action cannot be obtained, while if their total content exceeds 5.0%, the material becomes too hard. In addition to causing deterioration in moldability, it is also difficult to ensure an appropriate coefficient of thermal expansion, so the total content of the above components should be reduced to 0.
．． It is set at 01 to 5.0%.

B) Degree of rolling before final annealing: The degree of rolling before final annealing is important in ensuring the desired strength of the lead frame material.
The reason why it is limited to 90% is that if the degree of rolling is less than 40%, it will not be possible to stably obtain the desired fine grains during final annealing, resulting in mixed grains; This is because when the degree of deformation is reached, the cubic structure develops too much during final annealing, resulting in an abnormal structure, and as a result, anisotropy develops, making it impossible to obtain the desired strength even after final cold rolling and strain relief annealing. be.

C) 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 and press workability. The reason why the final annealing is carried out under conditions such that the obtained crystal grain size is 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 property and press workability. This is because, while it is effective in realizing a highly accurate frame, if the crystal grain size exceeds 30 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) Degree of work in final cold rolling: The degree of work in final rolling also has a great effect on the strength of the lead frame material, but the reason why the degree of work is particularly limited to 40 to 85% is that the degree of work in final cold rolling is If it is less than 40%, no remarkable effect on strength improvement will be obtained, whereas if it exceeds 85%, the anisotropy of strength will become noticeable.

E) Strain relief heat treatment: By performing appropriate strain relief heat treatment after final rolling, the Kb value is improved, the anisotropy is also dramatically improved, and the bending workability and sealing properties are improved. Therefore, strain relief annealing is performed. for example,
In a continuous annealing furnace in a reducing atmosphere, furnace temperature: 500
℃~900℃ and residence time of material in furnace: 10 seconds~1
The above effect can be obtained by heat treatment for 20 seconds.

F) Skin pass rolling: By performing skin pass rolling at an appropriate working degree after strain relief heat treatment, it is possible to improve the strength without impairing bending workability. The reason why the degree of rolling is particularly limited to 5% or less is that if the degree of rolling is more than 5%, the bending workability will deteriorate, residual stress will increase, and deformation will occur during lead frame processing. .

Next, the effects of the present invention will be explained in more detail with reference to Examples and Comparative Examples.

[0036]

[Examples and Comparative Examples] First, Fe-Ni-C with the chemical composition shown in Tables 1 and 2 was prepared by vacuum melting and casting.
After obtaining R-based alloy ingots, they are hot rolled and pickled, then cold rolled and annealed repeatedly to obtain a plate thickness of 0.
．． A 125 mm cold rolled plate (with the exception of sample No. 36, the plate thickness was 0.15 mm) was produced, and after the final cold rolling, it was subjected to strain relief heat treatment at 700° C. for 30 seconds in a reducing atmosphere. At this time, the "working degree of cold rolling before final annealing", "crystal grain size at final annealing", "working degree of final cold rolling" and "working degree of skin pass rolling" are shown in Table 3. and 4.

[0037] Next, the Fe-N produced in this way
Regarding the i-Cr alloy lead frame material, "mechanical properties", "etching properties", "bending properties", and "sealing properties" were investigated, and the results are also shown in Tables 3 and 4.

As for the mechanical properties, the strength of the material against bending moment was evaluated using the Kb value (spring limit value). The anisotropy of the Kb value is expressed by the ratio of the Kb value in the perpendicular direction to the Kb value in the parallel direction when the longitudinal direction of the sample is parallel to and perpendicular to the rolling direction. In other words, the anisotropy of Kb value = “K in the perpendicular direction
b value/[Kb value in parallel direction], and the closer this value is to 1, the less anisotropy is.

Regarding etching properties, after degreasing each of the produced cold-rolled plates, applying a resist film, and baking and developing the pattern, all 128-pin lead frames were etched with ferric chloride under the same conditions. The outer lead pin width and its dispersion were measured and evaluated for the ones etched below.

Bending workability was evaluated by conducting a 90 degree repeated bending test.

[0041] The sealing property was evaluated by applying a heat cycle after resin sealing and examining whether cracks were generated.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046] All the examples of the present invention in which skin pass rolling was performed at a workability of 5% showed an improvement in strength of approximately 10% compared to those in which skin pass rolling was not performed without impairing bending workability.

For reference, the following points are clear from the results shown in the table.

Invention Example No. The materials related to Nos. 1 to 4 are Comparative Example No. Compared to Nos. 22 to 36, it has excellent mechanical properties, etching properties, bending properties, and sealing properties. Among them, the 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 4.

[0049] Furthermore, inventive 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. Regarding 22,
Since the degree of rolling before final annealing is too low, it is not possible to achieve a small grain size through subsequent annealing, resulting in a low Kb value.

On the contrary, Comparative Example No. In the case of No. 23, since the degree of rolling before final annealing was too large, a cubic structure developed during subsequent annealing, resulting in a low Kb value.

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 No. Regarding items 27 to 29,
Since the content of C, Si, and P is large, the etching workability, bending workability, and sealing performance are poor.

Comparative Example No. Those related to 30-33 are:
Since the amounts of W, Mo, Co, etc. added are too large, the bending workability and sealing properties are poor.

Comparative Example No. In the case of No. 34, since the degree of workability of the skin pass rolling after the strain relief heat treatment was as large as 25%, the anisotropy of the Kb value was large and the bending workability was poor.

Note that FIG. 1 shows the example No. 1 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. 35 and No. 36. here,
Comparative example no. For those related to 35, the plate thickness is 0.125m.
m, Comparative Example No. For those related to 36, 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 0.1
It can be confirmed that even when the thickness is reduced to 25 mm, the amount of settling against bending moment is small, and the material strength against deformation is strong.

[0059]

[Effects of the Invention] As explained above, according to the present invention,
N, C in alloys with Fe-Ni-Cr as basic components
, Si, P, etc., and at the same time, add specific alloying elements as necessary. Furthermore, the degree of rolling before final annealing, the grain size at final annealing, and the final rolling 5 after controlling the processing degree within the appropriate range and heat treatment to remove distortion.
By adopting a skin pass rolling step of less than 30%, we can stably produce high-strength lead frame materials with excellent properties such as thermal expansion coefficient, sealing properties, and moldability, as well as very good etching processability. It has become possible to manufacture semiconductor devices in a number of steps, and has extremely effective industrial effects, such as enabling even higher integration of semiconductor devices.

[Brief explanation of the drawing]

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

Claims (7)

[Claims] [Claim 1] Fe-33-55wt% Ni-2-1
When manufacturing the 5 wt% Cr alloy lead frame material, the Fe-33 to 55 wt% Ni-2 to 15 wt% Cr alloy lead frame material is subjected to final annealing and final cold rolling, then subjected to strain relief heat treatment, and then further processed. A method for producing a high-strength lead frame material having excellent etching workability, bending workability, and sealing property, the method comprising performing skin pass rolling of 5% or less. [Claim 2] The lead frame material is Si: 0.00.
1 to 0.15 wt%, Mn: 0.1 to 1.0 wt%, C
r: 2 to 15 wt% and Ni: 33 to 55 wt%, the balance consists of Fe and unavoidable impurities, and C
: 0.015wt% or less, P: 0.01wt% or less, S
: 0.005 wt% or less, O: 0.010 wt% or less, and N: 0.005 wt% or less,
Then, before final annealing, rolling was performed at a working degree of 40 to 90%, final annealing was carried out under conditions such that the grain size was 30 μm or less, and the working degree of the subsequent final cold rolling was adjusted to 40 to 85%. The method for manufacturing a lead frame material according to claim 1, characterized in that: [Claim 3] The lead frame material is Si: 0.00.
1 to 0.15 wt%, Mn: 0.1 to 1.0 wt%, C
Contains r: 2 to 15 wt% and Ni: 33 to 55 wt%, and further contains Co, Mo, W, V, Nb, Ta, Ti, Zr.
and Hf in a total of 0.01 to 5.0% by weight, and C: 0.015wt% or less, P: 0.0
1wt% or less, S: 0.005wt% or less, O: 0.0
The alloy is regulated to 10wt% or less and N: 0.005wt% or less, and is rolled with a workability of 40 to 90% before final annealing, and final annealing is carried out under conditions such that the grain size is 30μm or less. , the working degree of the subsequent final cold rolling was set to 40
2. The method for manufacturing a lead frame material according to claim 1, wherein the lead frame material is adjusted to 85%. [Claim 4] The lead frame material further includes Cu and Al.
, Be, Mg and Ca in total of 0.01
The method for producing a lead frame material according to claim 2 or 3, wherein the lead frame material contains 5.0% by weight. 5. C content of the lead frame material is 0.
5. The method for producing a lead frame material according to claim 2, wherein the lead frame material has a content of 0.005% by weight or less. [Claim 6] The lead frame material has a Si content of 0.
．． 6. The method for manufacturing a lead frame material according to claim 2, wherein the content is 0.001 to 0.05% by weight. Claim 7: The P content of the lead frame material is 0.
7. The method for producing a lead frame material according to claim 2, wherein the content is 0.003% by weight or less.