JPH04224631A - Manufacture of lead frame material - Google Patents

Abstract

PURPOSE:To stably manufacture a high strength lead frame combining excellent etching workability, sealability and formability by regulating the rolling conditions in an Fe-Ni-Co alloy stock having a limited compsn. CONSTITUTION:Alloy stock constituted of, by weight, <=0.015% C, 0.001 to 0.15% Si, 0.1 to 1.0% Mn, <=0.01% P, <=0.005% S, <=0.010% O, >0.005 to 0.2% N, >5 to 30% Co, 15 to 55% Ni and the balance iron with inevitable impurities is manufactured. This stock is rolled and is then subjected to final annealing under the condition where its grain size will be regulated to <=30mum, and the draft in the subsequent final cold rolling is regulated to 40 to 85% to manufacture the above lead frame. Furthermore, after the final annealing, stress relieving annealing is preferably executed.

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] Generally speaking, it is known that the characteristics of the lead material used in semiconductor devices have a large effect on their performance and cost. For lead materials, 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 ``process of plastic packaging LSI'', during mounting on a printed circuit board, and even when subjected to temperature cycles in the usage environment, the resin removal process is difficult. It is unavoidable that thermal stress will be applied between the lead material and the lead material, but if this stress becomes excessive, the lead material used may be
Even if the package is made of Ni-based alloy (e.g. 42% Ni-Fe alloy), cracks may occur in the package or the adhesive interface may peel off, reducing the moisture resistance reliability of the package. It was difficult to avoid this problem. This problem is caused by the difference in thermal expansion coefficient between the mold resin and the lead material. When the above-mentioned microcracks and peeling interface occur due to the difference in thermal expansion coefficient, moisture infiltrates from the outside through this and enters the inside. There was a risk of damaging semiconductor devices and other components.

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 thermal expansion coefficient is as close as possible to that of mold resin. Therefore, recently, Ni-Co-Fe alloys have been developed that contain Co as a main component in addition to Ni, and have a thermal expansion coefficient as close as possible to that of mold resin by adjusting the contents of Ni and Co. Lead frame materials have also been developed, and their performance is attracting attention. On the other hand, recently, the above-mentioned types of LSIs are also becoming more highly integrated, and this trend has resulted in the promotion of increasing the number of pins in the lead frames used.
In order to cope with the increase in the number of pins in the system, it is required to use materials with higher strength.

[0005] 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. In addition, there is a concern that the thickness will be thicker than the pin width, making processing even more difficult. Therefore, in order to deal with this, it is necessary to reduce the thickness of the material, but in order to make the material thinner, a lead frame material with higher strength (resistance against lead deformation) than before is required. This is the reason. In addition, especially for lead frame materials for high-pin count and ultra-high-pin count, etching is the main processing for forming, so ``excellent etching processability'' is also an important required property. It's here.

[0006] Here, a lead frame made of Fe-Ni alloy
Generally, the etching process for lead frame materials involves coating both sides of a degreased lead frame material with photoresist, baking and developing the pattern, and then etching with an etching solution containing ferric chloride as the main component. It usually consists of steps of processing 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. It is not an exaggeration to say that the evaluation of etching processability is largely determined by the etching speed, as it becomes easier to control the pin width and pin spacing formed on the lead frame material as the lead frame material becomes larger. .

Therefore, as the degree of integration of semiconductor devices increases, lead frame materials are required to have "faster etching speed characteristics (that is, better etching processability)" in addition to excellent sealing and strength characteristics. However, the current situation is that no material has yet been found that fully satisfies etching processability, sealing properties, strength, and even moldability. Ta.

[0008]

Problems to be Solved by the Invention In view of the above, the object of the present invention is to provide a material that has high strength and also has excellent etching processability, sealing property, and moldability. The objective was to establish an industrial means for mass production of lead frame materials that can exhibit sufficient performance even when intended for application to highly integrated semiconductor devices.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have particularly focused on the relatively high strength characteristics and low thermal expansion coefficient of the Fe-Ni-Co alloy lead frame material. As a result of research into a manufacturing method that further improves its strength, significantly improves its etching processability and moldability, and enables stable production, we have obtained the following new knowledge. was completed. That is,

0010
(a) In a Fe-Ni-Co alloy that has been considered relatively preferable as a lead frame material, when the Si and P contents and the C content are limited to specific low values. In this case, the etching rate of the alloy is significantly improved.

(b) Moreover, when the above alloy contains one or more selected specific elements in a predetermined ratio, various properties as a lead frame material are improved. In addition to being able to effectively improve the strength of the material without any particular negative effects, the addition of the above-mentioned specific elements under careful control of the Ni content can bring its coefficient of thermal expansion closer to that of mold resin. This is an extremely effective means.

(c) Also, in the above-mentioned alloy materials, the crystal grain size has a considerable influence on the strength and formability, but by taking measures to suppress the crystal grain size below a specific value, lead distortion can be reduced. ``Further improvement in material strength,'' which is favorable for increasing the number of pins in the -m, can be expected, and molding processability is also improved.

(d) In the above-mentioned alloy system, in order to stably produce grain size refinement without mixing grains, 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-Co as a basic component is adjusted comprehensively, and at the same time, specific alloying elements are added to this as necessary. Furthermore, if the degree of rolling before final annealing, 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, sealability, and formability.
Moreover, it becomes possible to stably produce a lead frame material having very good etching processability.

The present invention was completed based on the above-mentioned knowledge, etc., and it is based on the above-mentioned findings.
5%, Mn 0.1-1.0%, P 0.0
1% or less, S 0.005% or less, O 0.010% or less, N
More than 0.005% -0.2%, Co more than 5% -30%, Ni 15-55%, or in addition, Mg,
Ca, Al, Be, Cu, Cr, Mo, W, V, Nb,
The material is an alloy containing 0.01-5.0% of one or more of Ta, Ti, Zr, and Hf, with the balance consisting of Fe and unavoidable impurities.
- After rolling by 90%, preferably 50-85%, final annealing is performed under conditions such that the grain size becomes 30 μm or less, preferably 20 μm or less, and the working degree of the subsequent final cold rolling is 40-85%. Provided is a method for stably producing a lead frame material having excellent etching processability, sealing property, moldability and high strength, characterized in that the lead frame material is preferably adjusted to 50-80%. It is something to do.

In this case, (a) strain relief annealing is performed after final cold rolling, (b) C content is adjusted to 0.005% or less, (c) Si content is 0.001-0. (d) regulating the P content to 0.003% or less, either alone or in combination, improves the molding processability and etching processability of the resulting lead frame material. The effect 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 raw material alloy Ni Ni is an important component in determining the thermal expansion coefficient of the lead frame material, and the difference in thermal expansion with the package during and after sealing. In order to ensure sealing properties and moisture resistance reliability by reducing the Ni content, it is necessary to adjust the Ni content to 15-55%. Therefore, the Ni content was determined to be 15-55%.

Co Co is also an important component in determining the coefficient of thermal expansion in the lead frame material. In order to ensure excellent sealing performance and moisture resistance reliability by reducing the difference in thermal expansion with the package during and after sealing, the Co content must exceed 5%.
It is necessary to adjust it to 30%. Therefore, the Co content is 5
I decided to exceed -30%.

C When the C content in the lead frame material exceeds 0.015%, iron carbides are generated, which impairs the etchability of the lead frame material. Therefore, the upper limit of the C content is set to 0.
However, since solid solution C also has an adverse effect on etching processability, the lower the C content, the better, and it is desirable to suppress it to 0.005% or less if possible.

Si Si is an element necessary as a deoxidizing agent, 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, 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, S
If the i 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 0.001-0.15%, it is desirable to adjust it to 0.001-0.05% if possible as described above.

MnMn 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 will it not be possible to reduce the heat, but the hot workability will also be poor. On the other hand, if the content exceeds 1.0%, the hardness of the lead frame material will increase too much, leading to deterioration of workability.
Furthermore, the coefficient of thermal expansion also increases. Therefore, Mn
The content was determined to be 0.1-1.0%.

[0024] P Like Si, P is an element that harms the etching processability of the lead frame material when its content increases. and,
The above-mentioned negative effect on etching processability is due to P content of 0.01
If the P content exceeds 0.0%, the P content becomes more obvious.
It was set as 0.01% or less. However, the P content is 0.003%
If it is reduced to below, 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. It is best to adjust it to .003% or less.

[0025] If the SS 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.

[0026] O If the O content exceeds 0.010%, oxide 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%. It was limited to 0.010% or less.

[0027] N When the N content is 0.005% or less, no improvement in strength is observed due to the N content, and when it exceeds 0.2%, lead flaking
Since the etching workability and bending workability of the material deteriorated, the N content was set at -0.2%, exceeding 0.005%.

Mg, Ca, Al, Be, Cu, Cr, M
o, W, V, Nb, Ta, Ti, Zr, and Hf These elements all have the effect of increasing the coefficient of thermal expansion of the lead frame material, so they improve the material strength and reduce thermal expansion. By increasing the coefficient to bring it closer to that of the resin mold, type 1 or 2 can be used as needed to further improve the sealing properties.
More than one species can be contained. However, if the total content is less than 0.01%, the desired effect cannot be obtained due to the above action, while if the total content exceeds 5.0%, the material becomes too hard. In addition to causing deterioration in moldability, it also becomes difficult to secure an appropriate coefficient of thermal expansion, so the content of the above components was determined to be 0.01-5.0% in total.

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, but it is especially important to increase the degree of rolling to 40-90%. The reason for this limitation is that if the rolling degree is less than 40%, the desired fine crystal grains cannot be stably obtained during final annealing, resulting in mixed grains, and conversely, if the rolling degree is less than 90%, In this case, the cubic structure develops too much during final annealing, resulting in an abnormal structure.
As a result, anisotropy develops and the desired strength cannot be obtained even after final cold rolling and strain relief annealing.

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 properties and press workability. In particular, the reason why the final annealing is carried out under conditions such that the obtained crystal grain size is 30 μm or less is as follows.
Reducing the crystal 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. is 3
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 great influence on the strength of the lead frame material, but the reason why the working degree is particularly limited to 40-85% is that This is because when the rolling degree is less than 40%, no remarkable effect on strength improvement can be obtained, whereas when it exceeds 85%, the anisotropy of strength becomes remarkable.

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

[0033]

[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, and then hot rolled and pickled, and then cold rolled and annealed repeatedly. A cold-rolled plate with a plate thickness of 0.125 mm was produced, and after the final cold rolling, it was rolled at 700 mm in a reducing atmosphere.
A strain relief heat treatment was performed at ℃ for 30 seconds.

[0034]

[Table 1]

[0035] At this time, "cold rolling before final annealing"
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.

[0036]

[Table 2]

[0037] Next, the Fe-Ni produced in this way
- "Mechanical properties" of Co-based alloy lead frame material
, "etchability", "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, each cold-rolled plate produced above was degreased, a resist film was applied, a pattern was baked and developed, and a 128-pin lead frame was etched with ferric chloride. The width of the outer lead pin and its variation were measured and evaluated for all the films etched under the same conditions.

[0040] In Table 2, No. 35 only, plate thickness 0.
15 mm, and all other plate thicknesses are 0.125 mm. Regarding the anisotropy of the Kb value, the longitudinal direction of the sample is taken in the direction parallel to rolling and the direction perpendicular to rolling, and the anisotropy is expressed by the ratio of the Kb value in the perpendicular direction to the Kb value in the parallel direction. That is, K
Anisotropy of b value = (Kb value in perpendicular direction) / (K in parallel direction
b value). The closer this value is to 1, the less anisotropy there is.

Bending workability was evaluated 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 material related to Comparative Example No. 1-4 is Comparative Example No. Compared to No. 22-35, it has excellent mechanical properties, etching properties, bending properties, and sealing properties. Among them, the present invention example No. Inventive Example No. 1 has the C, Si, and P contents controlled within more preferable ranges. The etching properties are even better than those related to No. 2-4.

[0043] Also, inventive example No. In the case of No. 5-21, the strength is further improved because Nb, Mo, Ti, etc. are added. On the other hand, comparative example No. In the case of No. 22, because the degree of rolling before final annealing was too low, it was not possible to achieve a small grain size through subsequent annealing.
Kb value is low. On the contrary, comparative example No. In cases related to 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 Kb
The 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 No. The material related to No. 27 has a low strength due to a low N content. Comparative example no. The material related to No. 28 had poor bending workability and etching property because of its large N content. Comparative example no. Those related to 29 are C, Si and P
Since the content of is large, etching workability, bending workability, and sealing performance are poor. Comparative example no. 3
In the case of No. 0-33, the amount of W, Mo, Cr, etc. added was too large, resulting in poor bending workability and sealing performance.

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. 34 and No. 35. here,
Comparative example no. For those related to 34, the plate thickness is 0.125m.
m, Comparative Example No. For those related to 35, 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 0.125 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.

[0048]

[Effects of the Invention] As explained above, according to the present invention, it is possible to stably produce a lead frame material that has excellent etching processability, sealing performance, and moldability, and has high strength. This will bring about extremely useful effects industrially, such as enabling even higher integration of semiconductor devices.

[Brief explanation of the drawing]

[0049]

[Figure 1]

[0050] This is a graph comparing the ``relationship between bending moment and amount of settling'' between materials related to the method of the present invention and materials related to the comparative method.

Claims (7)

[Claims] [Claim 1] C 0.015% or less, Si
0.001-0.15%, Mn 0.1-1.
0%, P 0.01% or less,
S 0.005% or less, O 0.010
% or less, N more than 0.005% -0.2
%, Co over 5% -30%, Ni 15-55
%, the balance consisting of Fe and unavoidable impurities
Using i-Co alloy as material, it has a processing degree of 40-90.
%, final annealing is performed under conditions such that the grain size is 30 μm or less, and the working degree of the subsequent final cold rolling is 40 μm.
- A method for manufacturing a high-strength lead frame material with excellent etching processability and sealing properties, characterized by adjusting the lead frame material to 85%. [Claim 2] The Fe-Ni-Co alloy material contains Mg
2. Etching processability according to claim 1, further comprising 0.01-5.0% by weight of one or more elements selected from the group consisting of and a method for manufacturing a high-strength lead frame material with excellent sealing properties. [Claim 3] The Fe-Ni-Co alloy material is Cr
, Co, W, V, Nb, Ta, Ti, Zr and Hf.
further containing 1-5.0% by weight,
A method for producing a high-strength lead frame material having excellent etching processability and sealing properties according to claim 1 or 2. 4. The high-strength lead frame with excellent etching workability and sealing properties according to any one of claims 1 to 3, characterized in that strain relief annealing is performed after final cold rolling.
A method of manufacturing mu materials. [Claim 5] The Fe-Ni-Co alloy material has a carbon content of 0.
．． 5. 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 4, characterized in that the content is 0.05% by weight or less. 6. Etching processability and sealing according to claim 1, wherein the Fe-Ni-Co alloy material contains 0.001-0.05% by weight of Si. A method for manufacturing a high-strength lead frame material with excellent properties. [Claim 7] The Fe-Ni-Co alloy material has P of 0.
．． 7. 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 6, characterized in that the content is 0.03% by weight or less.