JPH03197641A - Lead frame material - Google Patents

Abstract

PURPOSE:To obtain a high strength lead frame material excellent in etching characteristic and sealing characteristic by specifying a composition consisting of C, Si, P, S, O, N, Co, Ni, elements for improving strength and thermal expansion coefficient, such as Cu, and Fe. CONSTITUTION:A lead frame material having high strength and hardness and excellent in etching characteristic, sealing characteristic, and formability can be obtained by providing a composition which consists of, by weight, <=0.015%, preferably <=0.005%, of C, 0.001-0.15%, preferably 0.001-0.05%, of Si, <=0.01%, preferably <=0.003%, of P, <=0.005% S, <=0.010% O, <=0.005% N, 5-30% Co, 15-55% Ni, further 0.01-5.0% of one or more elements among Cu, Mn, Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, B, Be, Mg, and Ca, and the balance Fe with inevitable impurities and also providing a structure in which crystalline grain size at the time of the final annealing is regulated, preferably, to <=50mum.

Description

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

Background technology and its issues> It is generally known that the characteristics of lead materials in semiconductor devices have a large impact on their performance and cost. Conventionally, lead materials for such semiconductor devices include Fe--Ni alloys have been favorably used because they have a low coefficient of thermal expansion and exhibit relatively good adhesion and sealing properties with semiconductor elements and ceramics.

However, recently, the degree of acceleration of LSI has been increasing
The trend toward higher integration has resulted in the use of lead frames with a greater number of bins, but thinner materials are advantageous for increasing the number of pins in lead frames, so thinner materials are being used to accommodate thinner boards. Therefore, lead frame materials with higher strength and hardness are required than ever before.

Further, when a lead frame is made to have a large number of bins, the intervals between the bins inevitably become narrower, and the width of the bins themselves also become smaller. To cope with this, etching processing with higher precision is required. Therefore, in addition to high strength and hardness, lead frame materials used for multiple bins must also have excellent etching workability, which allows control over the width of the formed pins and the spacing between the bins. It had become a characteristic.

By the way, the etching process for lead frame materials made of Fe-Ni alloys is generally carried out by applying photoresist to both sides of the degreased lead frame material, baking and developing the resist, and then etching the lead frame material mainly using ferric chloride. It usually consists of a step of etching with a liquid and then removing the resist. The factor that determines the etching performance at this time is "resist adhesion."
Among these factors, the etching speed of the material is the most important factor, and as the etching speed increases, the controllability of the bin width and bin spacing formed on the lead frame material increases. It is no exaggeration to say that the evaluation of etching processability is generally determined by the etching speed.

Therefore, as the degree of integration of semiconductor devices increases, lead frame materials are required to have "faster etching speed (that is, better etching processability)" properties in addition to strength properties, but this is still insufficient. At present, no material has been found that has satisfactory etching processability, strength and hardness, as well as sealability and moldability.

For these reasons, the object of the present invention is to provide a material that has high strength and hardness, as well as excellent etching processability.

Established a means to industrially stably provide lead frame materials that have both sealing properties and moldability and can exhibit sufficient performance even when intended for application to highly integrated semiconductor devices. It was put to do.

Means for Solving the Problems> In order to achieve the above objects, the present inventors have specifically developed FeNi-
Focusing on the relatively high strength and low coefficient of thermal expansion of Co-based alloy lead frame materials, we have discovered the possibility of further improving these properties as well as significantly improving its etching processability and moldability. As a result of repeated research, we were able to obtain the following new knowledge. That is, (a) In a Fe alloy whose main components are Ni and Co, if the contents of C, Si and P, and even the N content are limited to specific low values, etching of the alloy Speed will be noticeably improved.

(b) However, if the above-mentioned alloy contains one or more selected specific elements in a predetermined ratio, it will have a particularly negative effect on the properties required as a lead frame material. In addition, the addition of the above-mentioned specific elements under careful control of the Nt and Co contents can bring the thermal expansion coefficient closer to that of mold resin and semiconductor chips. This is an extremely effective method.

(C) In addition, the crystal grain size of the alloy materials mentioned above has a considerable influence on strength and formability, but by taking measures to suppress the crystal grain size to below a certain value, lead frames can be made with a large number of bins. ``Further improvement in material strength'' can be expected, which is preferable for many people, and molding processability is also improved.

(d) Therefore, it is necessary to comprehensively adjust the content of Ni, Co, C, Si, P, etc. in the alloy whose basic component is Fe-Ni-Co, and at the same time add specific alloying elements to it, or Furthermore, by adjusting the crystal grain size, it is possible to create a lead frame material that has excellent properties such as strength, coefficient of thermal expansion, sealing properties, and moldability, and also has very good etching processability. .

The present invention was completed based on the above-mentioned findings, etc., and it is based on the above-mentioned findings.
).

Si: 0.001-0.15%, P: 0.0
Less than 1%.

S: 0.005% or less, O: 0.010%
below.

N: 70.005% or less, Co: 5-30%.

Ni: 15-55%, further containing Cu, Mn, Cr, Mo, L
V, Nb+Ta.

Ti, Zr, Hf, B+ Be, Mg and Ca
By configuring the composition to include one or more of the following in a total of 0.01 to 5.0%, with the remainder consisting of Fe and unavoidable impurities, excellent etching processability, sealing property and molding processability can be achieved. It is characterized by having both high strength and hardness.

In addition, in the lead frame material according to the present invention, a) C content is 0.005% or less.

b) Adjust the Si content to o,ooi~0.05%.

c) P content is 0.003% or less.

If the following conditions are adopted alone or in combination, the effect of improving etching workability obtained will be particularly remarkable;
Adjust as below.

Since the strength and formability are further improved and stabilized by the plain text, it is possible to sufficiently respond to the production of multi-pin lead frames by applying one or more of these as necessary. be.

Next, in the present invention, the reason why the component composition of the lead frame material is limited as described above will be explained in detail together with the effects of each component.

Ni 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 and moisture resistance. In order to ensure buccal properties, it is necessary to adjust the Ni content to 15-55%. In addition, Ni has the effect of improving the strength and hardness of lead frame materials, but the Ni content is 15%.
If it is less than that, it will be difficult to secure the desired strength and hardness. Therefore,
The Ni content was determined to be 15 to 55%.

O 2 Co is also an important component in determining the coefficient of thermal expansion of the lead frame material, and is also an effective component in improving the strength and hardness of the material. However, the Co content is 5
If it is less than %, not only will the coefficient of thermal expansion become larger than the desired value, but it will also be difficult to ensure the desired strength and hardness of the lead frame material.

On the other hand, even if Co is contained in an amount exceeding 30%, the coefficient of thermal expansion becomes larger than the desired value. Therefore, the Co content was determined to be 5 to 30%.

When the C content in the lead frame material exceeds 0.015%, iron carbides are generated, which impairs the etching processability 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 recommended to suppress it to 0.005% or less if possible. is desirable.

St 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 machining/nching workability, it is necessary to adjust the Si content to 0.15% or less. In particular, in the case of a multi-pin type glued frame material, even better etching processability is required, so the Si content is preferably reduced 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 o,oot~0.15%, it is preferable to adjust it to 0.001~0.05% if possible as described above.

Like St, P is also an element that harms the etching processability of the lead frame material if it is contained in excess. The above-mentioned negative effect on etching processability is caused by P content of 0.0.
Since it becomes more pronounced when 1% is added, the P content is 0.
．． It was set as 0.01% or less. However, the P content is 0.003
If the content is reduced to 0.003% or less, the effect of improving etching processability becomes even more remarkable, so it is preferable to adjust the content to 0.003% or less.

If the S content exceeds 0.005%, sulfide-based inclusions will increase in the lead frame material, causing defects during etching and causing bottle breakage, etc. Therefore, the S content was limited to 0.005% or less.

If the 0 content exceeds o, oio%, there will be a lot of oxide inclusions in the lead frame material, which will also cause drilling defects during etching processing, so the 0 content will be reduced to 0.010%.
limited to.

Since the etching processability of the lead frame material deteriorates even if the N content exceeds 0.005%, the upper limit of the N content was set at 0.005%.

Cu Mn Cr Mo W V Nb T
a Ti Zr Of B.

All of these elements have the effect of increasing the strength and thermal expansion coefficient of the lead frame material, so by improving the material strength and increasing the thermal expansion coefficient to approach that of a resin mold, the sealing performance can be improved. Type 1 or 2 for the purpose of improvement
More than one species can be contained. However, if the total content is less than 0.01%, the desired effect of the above action cannot be obtained, while if the total content exceeds 5.0%, the material becomes too hard. In addition to causing deterioration in molding processability, 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 to 5.0% in total.

As explained earlier, controlling the crystal grain size at the final annealing to 50- or less leads to effective improvement of strength and formability, so it is preferable to control the grain size at the final annealing to The crystal grain size is 50J! It is better to take measures to adjust the plain text to 11 or less. Here, the grain size is controlled by the working degree and annealing temperature before annealing.

It goes without saying that this is possible by adjusting the annealing time and the like.

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

<Example> First, a material prepared by vacuum melting was cast, and after hot rolling and pickling, cold rolling and annealing were repeated, and after the final annealing, cold rolling was performed at a workability of 40%, and further 500%
Strain relief annealing was performed at ℃ for 1 hour to produce a cold-rolled plate (thickness = 0.15 mm) having the composition shown in Table 1.

Next, after degreasing these cold-rolled sheets, a resist film is applied, a prescribed pattern is baked and developed, and then an etching process is performed using a ferric chloride solution under the same conditions.
A 28-pin lead frame was created.

For the obtained lead frame, we evaluated the ``outer lead pin width and its variation after etching'' as an evaluation of ``etchability,'' and the ``tensile strength'' and ``Vickers hardness'' as evaluations of mechanical properties. ” and “processability (bending property)” and for evaluation of “sealability”, the presence or absence of cracks was investigated when thermal cycles (80′CX 60m1nX once) were applied after resin sealing. The evaluation of the workability (bendability) was carried out according to a 90-degree repeated bending test (bending radius: 0.15 mm).

These investigation results were combined with the grain size at the final annealing to
Also listed in the table.

As is clear from the results shown in Table 1, the materials of the present invention all have sufficient strength and hardness, and exhibit excellent etching, molding, and sealing properties. It can be seen that the comparative materials whose compositions do not meet the conditions specified in the present invention are inferior in any of the characteristics required of the above lead frame materials.

That is, it can be confirmed that inventive materials 1 to 26 have narrower pin widths and higher etching speeds than comparative materials 28 to 30. It can also be seen that the standard deviation (S, D,) of the pin width formed by etching is small, and a lead frame product with excellent dimensional accuracy can be obtained.

Among the present invention materials, particularly present invention materials 1 to 18 are C
, St, and P are all controlled within a more preferable range, and it can be confirmed that these materials exhibit even better etching properties than Invention Materials 19 to 25.

Further, from a comparison between Inventive Material 8 and Comparative Material 34, it can be seen that sufficient strength (hardness) cannot be ensured if the crystal grain size of the lead frame material greatly exceeds 5 On.

On the other hand, comparative materials 28 to 30 were Sit P and C, respectively.
Because of the high content of etching, the width of the pins formed by etching is wide and the variation is large.

Comparative material 27 does not have sufficient strength because no strength-improving or thermal expansion coefficient increasing component is added, and the thermal expansion coefficient is too small, resulting in poor sealability.

Comparative material 31 had a high S content, so the bottle broke in the bending test.

Comparative materials 32 and 33 have poor bending workability and poor etching workability because the content of strength improving components is too large.

Comparative material 35, on the other hand, does not exhibit sufficient strength (hardness) because the content of the strength improving component is small.

Summary of Effects> As explained above, according to the present invention, it is possible to produce a lead frame material that has excellent etching processability, sealability and moldability, as well as high strength and hardness.
This will bring about useful effects on the industrial landscape, such as facilitating higher integration of semiconductor devices.

Claims (5)

[Claims] (1) C: 0.015% or less, Si: 0.001 to 0.15% by weight
, P: 0.01% or less, S: 0.005% or less, O: 0
．． 0.010% or less, N: 0.005% or less. Co: 5-30%, Ni: 15-55%, further containing Cu, Mn, Cr, Mo, W, V, Nb
, containing one or more of Ta, Ti, Zr, Hf, B, Be, Mg and Ca in a total of 0.01 to 5.0%, with the balance consisting of Fe and unavoidable impurities.
High-strength lead frame material with excellent etching processability and sealing properties. (2) The lead frame material according to claim 1, wherein the C content is 0.005% by weight or less. (3) The lead frame material according to claim 1 or 2, having a Si content of 0.001 to 0.05% by weight. (4) The lead frame material according to any one of claims 1 to 3, wherein the P content is 0.003% by weight or less. (5) The lead frame material according to any one of claims 1 to 4, wherein the crystal grain size at the time of final annealing is 50 μm or less.