JPS63137148A - Manufacture of high-strength iron-copper alloy foil for lead frame - Google Patents

Abstract

PURPOSE:To improve strength and thermal and electric conductivities, by subjecting an Fe-Cu alloy in which respective contents of Cu, O, Si, Al, Ti and Fe are specified to casting and aging treatment under the prescribed conditions. CONSTITUTION:The alloy which has a composition consisting of, by weight, 20-90% Cu, 0.03-0.2% O, 0.012-0.2% Si, 0.015-0.25% Al, 0.02-0.3% Ti, and the balance Fe and satisfying (8/7Si+8/9Al+2/3Ti)>=0.013% and (8/7Si+8/9 Al+2/3Ti)/O<=1 is refined. This molten alloy is continuously cast at >=100 deg.C/sec cooling rate. The resulting thin alloy slab is cold rolled and then subjected to aging treatment at 450-650 deg.C for 20-500min.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a low-cost semiconductor I with excellent thermal and electrical conductivity.
This invention relates to a method for producing iron-copper alloy ribbon for high-strength lead frames used in C, LSI, etc.

(Prior art) Lead frame materials for semiconductor ICs, LSIs, etc.
For example, an alloy containing 26 to 30% by weight of nickel and 11 to 16% by weight of cobalt in iron (kovar alloy) disclosed in JP-A-59-198741, and JP-A-60-1987-
An alloy containing 30 to 55% by weight of nickel in iron as shown in Publication No. 111447 (42% Ni alloy is a typical component)
etc. are used because their thermal expansion characteristics match those of glass sealants and Si. On the other hand, copper and copper alloys have also gradually come to be used in ICs that require high thermal and electrical conductivity.

In other words, the Kovar alloy and 42Ni alloy mentioned above have excellent strength and heat resistance, but have poor thermal and electrical conductivity (,
Due to poor workability and high cost, there has been a trend in recent years to shift to copper alloys, which are inexpensive and have good thermal and electrical conductivity and workability, due to the demand for heat dissipation as ICs become more highly integrated.

(Problems to be Solved by the Invention) However, since copper alloys generally have poor heat resistance and strength, for example, the CA-195 alloy or the alloy described in JP-A-60-218442 aims to improve these drawbacks. These alloys contain tin, iron, silicon, phosphorus, cobalt, etc., but the addition of these elements increases the cost of the alloy and also causes problems such as deterioration of thermal and electrical conductivity.

The present invention provides an iron-copper alloy with appropriate amounts of oxygen, silicon, aluminum,
The object of the present invention is to provide an iron-copper alloy ribbon for lead frames that has sufficient thermal and electrical conductivity, high strength, and good workability as a lead frame by adding titanium.

(Means for Solving the Problems) The present invention overcomes the problems of these prior art techniques, and in order to produce an iron-copper alloy ribbon having excellent properties as a material for lead frames, the inventors have developed a direct casting method. We conducted a lot of research on material improvement using iron-copper alloy thin slabs, and came up with the invention of a method for manufacturing iron-copper alloy thin strips for high-strength lead frames.

The gist of the present invention is as follows.

(11Cu is 20% by weight or more and 90% by weight or less, 0 is 0.
03% by weight or more and 0.2% by weight or less, Si, Aj, T
One or more types of i each have Si of 0.012 to 0.
．． 2 wt%, IV 0.015-0.25 wt%, Ti
8/7 S
t +8/9 A1+2/3 Ti is 0.013% by weight
Above, (8/7 St +8/9 A!+2/3 Ti
)/O is included in the range of 1 or less, and the remainder is mainly Fe.
An iron-copper alloy thin slab with a composition of
A method for producing a high-strength iron-copper alloy ribbon for lead frames, which comprises subjecting it to an aging treatment for 0 minutes or more and 500 minutes or less.

(2) Cu from 20% by weight to 901iffi%, 0 from 0.03% by weight to 0.2% by weight, St,
One or more of N and Tl and 0.0 Si each
12~0.2ffl amount%, Al 0.015~0.25
% by weight, Ti in the range of 0.02 to 0.3% by weight, and 8/7 Si + 8/9 A1 + 2/3 Ti is 0.02 to 0.3% by weight.
013% by weight or more, (8/7 Si +8/9 A!+
An iron-copper alloy thin slab having a composition containing 2/3 Ti)/O in a range of 1 or less and the remainder mainly consisting of Fe was heated at 100°C.
Continuously cast at a cooling rate of /sec or more, and after cold rolling 650 ~
Annealed at 1050°C for 5 minutes or more and 60 minutes or less, and
A method for producing a high-strength iron-copper alloy ribbon for lead frames, which comprises subjecting it to an aging treatment at ~650°C for 20 minutes or more and 500 minutes or less.

(3) Cu from 20% by weight to 90% by weight, O from 0.03% by weight to 0.2% by weight, Sl, Al,
One or more types of Tl and 0.012 Si each
~0.2 wt%, 0.015-0.25 wt% IV,
Contains Ti in the range of 0.02 to 0.3% by weight and 8/T
Si +8/9 jV+2/3 Ti is 0.013x4 type, (8/7 Si +8/9 N+2/3Ti
) An iron-copper alloy thin slab having a composition in which 10 is in the range of 1 or less and the remainder mainly consists of Fe is continuously cast at a cooling rate of 100 ° C / sec or more, and after cold rolling at 650 to 1050 ° C for 5 minutes or more Anneal for 60 minutes or less at 450-650℃ for 20 minutes.
1. A method for producing an iron-copper alloy ribbon for high-strength lead frames, which comprises performing an aging treatment for at least 500 minutes and then final cold rolling at a reduction rate of 15 to 60%.

The reasons for limiting this configuration requirement will be explained below.

First, the reason for limiting the chemical composition of the alloy is as follows.

A higher content of copper is preferable in order to improve thermal and electrical conductivity, but if the application requires strong strength, it is desirable to increase the content of iron.

If the copper content is less than 20% by weight, the thermal and electrical conductivity necessary for an IC lead frame cannot be obtained, so this is set as the lower limit. Also, the upper limit is 90% by weight because the iron content is 1
This is because if the content is 0% by weight, the distribution of the iron phase, which effectively works to refine the structure, will be insufficient, or it may be preferable to set an upper limit to some extent in order to alleviate the heat shock caused by soldering.

Next, 0.03% by weight or more of oxygen is added to Si and Aff in iron due to the relationship with the following oxide-forming elements.

Ti and Si+Aj in copper or steel! This is because it forms an oxide with +Tt, iron, etc., exhibits a dispersion strengthening effect, and improves thermal and electrical conductivity by reducing the amount of these solid solution elements. Further, the upper limit is set to 0.2% by weight because at the same time as the above effects are saturated, the deterioration of workability becomes noticeable due to an increase in the amount of oxides.

Next, one or more of Si, AJ, and Ti are mixed with Si in an amount of 0.012 to 0.2% by weight and Al in an amount of 0.012 to 0.2% by weight.
8/7 St +8/9 A (1
+2/3 The reason why Ti is added to be 0.013% by weight or more is that these are strong oxide-forming elements, and they cause fine particles to form at or immediately after the solidification of the copper-rich phase of the slab. This is because forming an oxide is extremely effective in preventing a decrease in conductivity due to solid solution elements and increasing strength.

The amounts of these elements to be added are determined from stoichiometric considerations for oxide formation. Among these restrictions, the lower limit is the amount necessary for one or more of these oxides to exist finely dispersed in the iron-enriched phase/caved phase,
The upper limit is determined in relation to the amount of oxygen, but this is because the oxide becomes too coarse and not only does not contribute to strengthening, but also significantly reduces ductility, so each amount is determined accordingly.

In addition, it is often useful to add a small amount of Cr + Z n + S n + N b, etc., so it may be added, but this is not particularly stipulated. Other elements are impurity elements that are unavoidably mixed in raw materials, melting, and other processes.

Next, the manufacturing process of the present invention will be explained.

First, an iron-copper alloy thin slab is produced by continuous casting, but the secondary cooling rate at this time is limited to 100° C./second or more.

The reason for this is generally that the larger the cooling rate after solidification, the finer the size of the solidified structure, and the effect is preserved even if heat treatment or cold rolling-annealing is performed thereafter. This limit is due to the fact that the values required for high-strength lead frame materials can be obtained even when it is relatively difficult to obtain high strength when the alloy contains 70% or more of copper. If the cooling rate is less than 100°C/second, the thickness of the slab will increase, and the cold rolling rate required to achieve the thickness required for the final use will be high (which will reduce production efficiency). Therefore, this is an important limitation.

Furthermore, cold rolling and aging treatment are subsequently performed. The main purpose of cold rolling is to obtain the required plate thickness for the lead frame, but the reduction rate of the next cold rolling depends on the combination of chemical composition, casting thickness, and final cold rolling process. These are the conditions for obtaining thickness, strength, and workability. The effective rolling reduction range is 30-95%.

Aging treatment is essential in the manufacturing process in order to improve thermal and electrical conductivity, and an appropriate temperature should be selected depending on the chemical composition and pre-process conditions.

In general, if the temperature is too low, distortion will occur around the precipitates, deteriorating the properties of the base material, and increasing the heating time, resulting in
This becomes a constraint on manufacturing efficiency. If the temperature is too high, not only will the amount of precipitate decrease and good properties will not be obtained, but the precipitates will also become coarse, which is disadvantageous in terms of ensuring strength.
Appropriate conditions include aging treatment at 0° C. for 20 minutes or more and 500 minutes or less.

In addition, if workability is particularly required as a lead frame, annealing is performed for a practical time of 5 minutes to 60 minutes at a temperature range of 650 to 1050 degrees Celsius before aging treatment. It is possible to improve workability by removing processing strain, recrystallization, and grain growth.

The present invention is suitable for applications where strength is required as a lead frame, but when further workability and high strength are required,
After performing the above-mentioned annealing, cold rolling is performed at a reduction rate of 15 to 60% to increase the strength by introducing working strain. In this case, the lower limit at which the effect becomes noticeable is 15%, and the upper limit is 50% of the rolling reduction, which increases workability and thermal/electrical conductivity (no reduction occurs).

In addition, when containing 70 MM% or less of copper, or when the subsequent cold rolling reduction exceeds 50%, measures are required to prevent cracking during cold rolling.

Effective methods include slow cooling in a constant temperature range after casting and reheating after cooling to room temperature.

The conditions for this are a temperature range of 850 to 750℃ after casting.
Cool at a cooling rate of 0-100°C/sec or 850-4
Heat treatment is performed in a temperature range of 50° C. for 20 minutes or more and 60 minutes or less. If it is less than 10° C./sec, a sufficient crack prevention effect cannot be obtained, and if it exceeds 100° C./sec, the grains become coarser or the degree of supersaturation obtained by rapid cooling is rather unfavorably reduced, so there are limitations. This effect prevents the generation of residual austenite or martensite that occurs during cooling after casting, or
Or by reducing the hardness difference between iron and copper structures through tempering softening.

(Example) The effects of the present invention will be explained below using examples.

Example 1 Table 1 shows the chemical compositions of alloy BE in the composition range of the present invention and comparative materials A and F in the comparative composition range.

Table 2 shows the material properties of the iron-copper alloy ribbon when treated under the following conditions. Casting is done using a twin roll casting machine, 3.5
A sheet of 2.0 mm was continuously cast at a cooling rate of 9.
It was rolled to 3 mm.

After cold rolling, aging treatment was performed at 490° C. for 180 minutes and air cooling was performed. Sample No. 6 has parameter X (see Table 1) below the lower limit, and both strength and conductivity are insufficient. Sample No. 6 has parameter・Low conductivity. In the table, Fe-N
The properties of i and Cu-Fe-5 Tsuru alloys were also included in the comparison.

From this, it is clear that the properties of the material of the present invention are excellent.

Table 2 Example 2 Table 3 compares the case where sample material B having the composition range of the present invention was cast using a twin roll casting machine and the cooling rate was low, which was outside the range of the present invention, with the case of the present invention. Here, the processing conditions after casting are as shown in Example 1.
is the same as It is clear from this that the cooling rate during casting has a large effect.

Table 3 Example 3 Table 4 compares sample material C having the composition range of the present invention with the case of the present invention in which the effect of annealing before aging treatment after cold rolling is not performed. It is clear from this that adding annealing before aging treatment has a significant effect of improving ductility and electrical conductivity.

Table 4 Example 4 Table 5 shows the test materials containing the composition range of the present invention after cold rolling.
The material is shown after annealing at 30 minutes at 490 degrees Celsius and aging at 490 degrees Celsius for 180 minutes, followed by final cold rolling at 25%. It is clear from this that final cold rolling is an effective means of increasing strength without significantly impairing electrical conductivity.

Table 5 Example 5 Table 6 shows that sample material E having the composition range of the present invention was prepared using a twin roll casting machine at a cooling rate of 2.5 x 103/sec to a plate thickness Q of 3.
Continuously cast to am, and after casting, the direct reduction rate is 48% and it is 0.4
After rolling to 2 ml and cold rolling, it was aged at 490°C for 180 minutes, air cooled, and then final cold rolled by 30%. After casting, the material was held at 820°C for 30 minutes during cooling. This was done to prevent cracking during cold rolling, then rolled to 0.3 am at a reduction rate of 85%, and then heated to 490°C after cold rolling.
A comparison is shown with a material that was aged for 180 minutes and cooled in air.

It can be seen from this that an iron-copper alloy ribbon for lead frames having excellent properties can be produced by either method.

Table 6 (Effects of the Invention) The present invention makes it possible to obtain a material with excellent strength and thermal and electrical conductivity by using continuously cast thin slabs in the production of iron-copper alloy ribbons for high-strength lead frames. It is an industrially valuable invention that can economically produce a material that can replace conventional Fe-Ni alloys and copper alloys for high-strength lead frames.

Procedural amendment (voluntary) March 5, 1986

Claims (3)

[Claims] (1) Cu content: 20% by weight or more and 90% by weight or less, O: 0.
03% by weight or more and 0.2% by weight or less, one or more of Si, Al, and Ti, each containing 0.012 to 0.2 of Si
wt%, Al 0.015 to 0.25 wt%, Ti 0
．． Contains in the range of 02 to 0.3% by weight and 8/7Si+8
/9Al+2/3Ti is 0.013% by weight or more, (8/
An iron-copper alloy thin slab having a composition containing 7Si+8/9Al+2/3Ti)/O in a range of 1 or less and the remainder mainly consisting of Fe is continuously cast at a cooling rate of 100°C/second or more, and after cold rolling it has a temperature of 450°C to A method for producing a high-strength iron-copper alloy ribbon for lead frames, which comprises subjecting it to an aging treatment at 650° C. for 20 minutes or more and 500 minutes or less. (2) Cu content: 20% by weight or more and 90% by weight or less, O: 0.
03% by weight or more and 0.2% by weight or less, one or more of Si, Al, and Ti, each containing 0.012 to 0.2 of Si
wt%, Al 0.015 to 0.25 wt%, Ti 0
．． Contains in the range of 02 to 0.3% by weight and 8/7Si+8
/9Al+2/3Ti is 0.013% by weight or more, (8/
An iron-copper alloy thin slab having a composition containing 7Si+8/9Al+2/3Ti)/O in a range of 1 or less and the remainder mainly consisting of Fe is continuously cast at a cooling rate of 100°C/second or more, and after cold rolling, it has a temperature of 650°C to A method for producing a high-strength iron-copper alloy ribbon for lead frames, which comprises annealing at 1050°C for 5 minutes or more and 60 minutes or less, and aging at 450-650°C for 20 minutes or more and 500 minutes or less. (3) Cu content of 20% by weight or more and 90% by weight or less, O content of 0.
03% by weight or more and 0.2% by weight or less, one or more of Si, Al, and Ti, each containing 0.012 to 0.2 of Si
wt%, Al 0.015 to 0.25 wt%, Ti 0
．． Contains in the range of 02 to 0.3% by weight and 8/7Si+8
/9Al+2/3Ti is 0.013% by weight or more, (8/
An iron-copper alloy thin slab having a composition containing 7Si+8/9Al+2/3Ti)/O in a range of 1 or less and the remainder mainly consisting of Fe is continuously cast at a cooling rate of 100°C/second or more, and after cold rolling, it has a temperature of 650°C to After annealing at 1050°C for 5 minutes to 60 minutes and aging at 450 to 650°C for 20 minutes to 500 minutes, final cold rolling is performed at a reduction rate of 15 to 60.
%.A method for producing iron-copper alloy ribbon for high-strength lead frames.