JPH03197647A - Lead frame material - Google Patents

Abstract

PURPOSE:To stably obtain a high strength lead frame material excellent in etching characteristic, sealing characteristic, and formability by specifying a composition consisting of C, Si, Mn, P, S, O, N, Ni, 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, 0.1-1.0% Mn, <=0.01%, preferably <=0.003%, of P, <=0.005% S, <=0.010% O, <=0.005% N, 43-55% Ni, 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. By using this lead frame material, the high integration of semiconductor equipment can be facilitated.

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> In general, it is known that the characteristics of lead materials in semiconductor devices have a large impact on their performance and cost. 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, for example, during the cooling process after the resin molding process in the "LSI plastic packaging process", during mounting on a printed circuit board, and even when subjected to temperature cycles in the usage environment, thermal stress is generated between the resin and the lead material. However, when this stress becomes excessive, the lead material becomes
- How can we solve the problem that even if the package is made of Ni-based alloy (e.g. 42% Ni-Fe alloy), cracks occur in the package or the adhesive interface peels off, reducing the moisture resistance of the package? In other words, there is a risk that moisture may infiltrate from the outside through the above-mentioned microcracks and peeled interfaces caused by the difference in thermal expansion coefficient between the mold resin and the lead material, and damage the internal semiconductor elements. Therefore, in order to improve the moisture resistance reliability of LSI, it is necessary to use a lead frame material whose coefficient of thermal expansion is close to that of mold resin.

On the other hand, recently, the above-mentioned types of LSIs have been becoming more highly integrated, and this trend has resulted in the further increase in the number of bins of lead frames used. Since thinner materials are more advantageous, lead frame materials with higher strength and hardness than ever before are required to accommodate thinner plates.

Furthermore, when a lead frame has a large number of pins, the spacing between the pins inevitably becomes narrower, and the width of the pin itself also becomes smaller. To cope with this, etching processing with higher precision is required. Therefore, in addition to high strength and hardness, it is important for lead frame materials used for multiple bins to have excellent etching workability, which allows control over the pin width and pin spacing. It was a required 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 a degreased lead frame material, baking a pattern, and developing it, followed by etching using ferric chloride as the main component. It usually consists of a step of etching with a liquid 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 no exaggeration to say that the evaluation of etching workability 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.

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)" in addition to excellent sealing and strength properties. However, the etching processability is still quite satisfactory.

At present, no material has been found that has sealing properties, strength, hardness, 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 Fe-Ni.
Focusing on the relatively high strength characteristics and low coefficient of thermal expansion of the alloy lead frame material, we have further improved its strength, made the coefficient of thermal expansion more similar to that of mold resin, and improved its etching processability and molding process. As a result of repeated research exploring the possibility of significantly improving sexual performance, we were able to obtain the following new findings. That is, (
a) In Fe-Ni alloys that have been considered relatively preferable as lead frame materials, C, St, and P
If the content of N, and even the N content, is limited to a certain low value, the etching rate of the alloy will be significantly improved.

(b) However, by carefully adjusting the Ni content of the alloy, the strength of the material can be improved without any particular adverse effect on the properties required for lead frame materials, and the adjustment of the Ni content is This is a very effective means of bringing the expansion coefficient closer to that of mold resin.

(C) Also, the crystal grain size of the alloy materials mentioned above has a considerable influence on strength and formability, but by taking measures to keep the crystal grain size below a certain value, it is possible to increase the number of bins in lead frames. Not only can a desirable "further improvement in material strength" be expected, but moldability is also improved.

(dl) Therefore, if the content of Ni, C+ St, P, etc. in an alloy with Fe-Ni as a basic component is adjusted comprehensively, and the crystal grain size is also adjusted, the strength, thermal expansion coefficient, sealing It becomes possible to realize a lead frame material that has excellent characteristics such as hardness and moldability, and also has very good etching workability.

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: 0.01% or less.

0: 0.010% or less.

Ni: 43-55% Mn: 0.1-1.0%.

S: 0.005% or less.

N: 0.005% or less.

By configuring the component table so that the proportion is by weight and the remainder is Fe and unavoidable impurities, it has excellent etching processability, sealing property, and molding processability, as well as high strength and hardness. ” is characterized by

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

b) Adjust the St content to 0.001-0.05%.

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 to below m.

Strength and formability are further improved and stabilized by this method, so by applying one or more of these methods as necessary, it is possible to sufficiently respond to the production of multi-bin lead frames. .

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.

(Function) 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 performance and moisture resistance reliability. In order to ensure the properties, it is necessary to adjust the Ni content to 33% to 55%.Ni also has the effect of improving the strength and hardness of the board frame material, but if the Ni content is 43%
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 43 to 55%.

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 best to suppress it to below o, oos% if possible. is desirable.

St St is an element necessary as a deoxidizer, but it is also an element that has a large effect on the etching processability of lead frame materials. That is, as the St 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 St 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 the St content is preferably reduced to 0.05% or less. just,
If the St content is reduced to a region of less than 0.001%, the deoxidizing effect will no longer be recognized. Therefore, the St content was set at 0.001 to 0.15%. It is preferable to adjust it to 0.001 to 0.05%.

Mn Mn is used to deoxidize lead frame materials and ensure hot workability Φ
', but its content is 0.1
If it is less than %, not only the desired deoxidizing effect cannot be obtained, but also the hot workability becomes poor. On the other hand, if it exceeds 1.0%, M
If n is included, the hardness of the lead frame material will increase too much, resulting in deterioration of workability and furthermore, the coefficient of thermal expansion will increase. Therefore, the Mn content was determined to be 0.1 to 1.0%.

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 it exceeds 1%, 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.

Note that the Si content is 0.1% and the P content is 0.0%.
Although it is not yet fully clear why the etching processability of the lead frame material is impaired when 1% of each is added, St inhibits etching.

This is thought to be due to variations in the microscopic components of P.

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.

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

As explained earlier, controlling the crystal grain size during final annealing to 50n or less leads to effective improvement of strength and formability, so it is preferable to control the crystal grain size during final annealing to 50n or less. It is preferable to take measures to adjust the grain size to 50 ps or less. Here, it goes without saying that the crystal grain size can be controlled by adjusting the degree of working before annealing, the annealing temperature, and the annealing time.

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%. A cold-rolled plate (thickness: 0.15 IIm) having the composition shown in Table 1 was manufactured.

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 manufactured.

For the obtained lead frame, the "outer lead bin width and its variation after etching" were evaluated for "etchability", and the "Vickers hardness" and "workability (bending)" were evaluated for "mechanical properties". In addition, as an evaluation of "sealability", heat cycles (8
The presence or absence of cracks was investigated when applying a temperature of 0°C x 60m1n x 100 times. Note that the processability (
The evaluation of bendability was carried out according to a 90 degree repeated bending test (bending radius: 0.15 fin).

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 7 have narrower pin widths and higher etching speeds than comparative materials 8 to 10. Also, the standard deviation (S) of the pin width formed by etching is
, D, ) are also small, and it can be seen that a lead frame product with excellent dimensional accuracy can be obtained.

Among the materials of the present invention, materials 1 to 3 of the present invention in particular have lower contents of C, St, and P than materials 4 to 6 of the present invention, and thus exhibit better etching processability. There is.

On the other hand, Comparative Materials 8 to 10 each have a high content of St, P, and C, so the pin width formed by etching is wide and the variation is large.

Comparative materials 11 and 12 both have low hardness (strength) (and poor sealing properties) due to low Ni content.Comparative material 12 also has high C content, so it has poor etching processability. is also inferior.

Comparative material 13 had a high S content, so pin breakage occurred in the bending test.

Comparative material 14 has both 0 content and N content higher than the specified values of the present invention, and therefore is inferior in both etching workability and molding workability (bending workability).

Furthermore, when comparing Inventive Materials 1 and 2 or Comparative Materials 15 and 16, it was found that the smaller the grain size during rolling after final annealing (final rolling), the higher the strength (hardness). You can check it. In addition, it can be seen that especially when the crystal grain size becomes large as in Comparative Material 16, the molding workability (bending workability) becomes inferior.

Summary of Effects> As explained above, the present invention provides a lead frame that has excellent etching processability, sealability and moldability, high strength and hardness, and a sufficiently low coefficient of thermal expansion. This will bring about extremely useful effects industrially, such as making it possible to provide materials and making it easier to further integrate semiconductor devices.

Claims (5)

[Claims] (1) C: 0.015% or less, Si: 0.001 to 0.15% by weight
, Mn: 0.1-1.0%, P: 0.01% or less, S:
0.005% or less, O: 0.010% or less, N: 0.0
A high-strength lead frame material having excellent etching processability and sealing property, characterized in that Ni: 43 to 55%, and the remainder consisting of Fe and unavoidable impurities. (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.