JPH0413421B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has high strength and excellent heat resistance,
The present invention relates to a method for manufacturing an iron- and tin-containing copper alloy suitable for use as a lead frame material for ICs and LSIs. [Prior art] In recent years, the lead width of lead frames has become narrower due to the improvement in the degree of integration of semiconductor circuits, and the cost of expensive Kovar (54Fe-29Ni
-17Co), Fe-42Ni alloy to relatively inexpensive copper alloy, it has become a lead frame material with higher strength, higher heat resistance, and easier workability than before. There are increasing demands for copper alloy materials. Specifically, the tensile strength is
65Kg/mm2 or ^more , heat resistance is 80% of tensile strength before heating
The optimal material is said to satisfy the following conditions: heating temperature (heating time: 60 minutes) that provides a tensile strength of , that is, a semi-softening temperature of 500°C or higher. Traditionally, copper alloys were used as lead frame materials.
CDA (Copper Development Association) Alloy 194, Phosphor Bronze, Copper
There are iron-tin-phosphorus alloys, copper-zinc-iron-tin-phosphorus alloys, etc. However, none of these satisfies all of the above conditions. That is, C.D.A.
Alloy 194 has a tensile strength of 45 Kg/mm ² and a heat resistance of 420° C., neither of which fully satisfies these two properties. Phosphor bronze has the above characteristics of 70 kg/mm ² and 375°C, respectively, and although the strength is satisfactory, the heat resistance is quite low. Next, for example, a copper-iron-tin-phosphorus alloy containing 0.15 to 1% by weight of heat, 3 to 9% by weight of tin, and 0.03 to 0.3% by weight of phosphorus is intended to be strengthened by precipitation of a compound of iron and phosphorus. However, the tensile strength is 55Kg/mm ² and the heat resistance
400℃, which does not satisfy either of the two characteristics. Furthermore, for example, zinc 0.5-3.0% by weight, iron 0.5-1.5%
wt%, tin 1.6-3.0 wt%, phosphorus 0.005-0.2 wt%
The copper-zinc-iron-tin-phosphorus alloy contained is intended to strengthen through fine aging precipitation of iron.
It has a tensile strength of 60 Kg/mm ² and a heat resistance of 480°C, both of which are slightly unsatisfactory. The above-mentioned copper-iron-tin-phosphorus alloy and copper-zinc-iron-tin
Iron in phosphorus alloys, iron in tin-containing copper alloys,
The addition of iron has the effect of improving strength and heat resistance, so the amount of iron added should be 1 to 1.5.
It is conceivable that both of the above two characteristics can be satisfied by further increasing the weight percentage. However, conventionally, the above-mentioned iron and tin-containing copper alloys are produced by heating the ingot to 700 to 950°C, hot working, cooling the hot worked material with water, further cold working, and then subjecting it to aging treatment. It is manufactured using a method. When such a method is adopted, even if the amount of iron in the iron-tin-containing copper alloy is increased to more than 1 to 1.5% by weight, the above-mentioned effect of iron is hardly exhibited. That is, not only the strength is almost saturated, but also the size and distribution of precipitates tend to fluctuate. Consequently, such materials eventually require solution treatment, resulting in economical problems. [Problems to be solved by the invention] The present invention has been made in view of the above circumstances, and
Iron made by finely precipitated iron with excellent properties such as tensile strength of 65Kg/mm2 or ^more and heat resistance of 500℃ or more.
The present invention provides a manufacturing method capable of industrially manufacturing a tin-containing copper alloy as an inexpensive mass-produced product. [Means for solving the problem] The manufacturing method of the present invention uses 1.5 to 3.0% by weight of iron and 0.8% by weight of tin.
After hot-working an ingot containing ~2.5% by weight and 0.005-0.1% by weight of phosphorus, the remainder consisting essentially of copper, the hot-worked material is heated to 780°C or higher for 20 minutes.
The purpose is to cool the material at a cooling rate of .degree. C./second or more, then cold work it, and after aging treatment, further cold work it. [Function] The function and effect of each component element of the alloy used in the manufacturing method of the present invention and the reasons for limiting each composition will be explained below. If it is less than 1.5% by weight of iron, no improvement in tensile strength or heat resistance can be expected due to aging precipitation of iron, and if it exceeds 3.0% by weight, coarse primary crystals of γ iron will be formed non-uniformly during casting, making it difficult to maintain a uniform composition. Since it is difficult to obtain an ingot and, therefore, the variation in mechanical properties of the manufactured lead frame material becomes larger than permissible, the iron content was set in the range of 1.5 to 3.0% by weight. In addition, if the tin content is less than 0.8% by weight, the tensile strength will not be sufficient, and if the tin content is less than 0.8% by weight, the tensile strength will not be sufficient.
If it exceeds this amount, cracks will occur during hot working, making it impossible to continue the working, so the tin content is set in the range of 0.8 to 2.5% by weight. Further, if the phosphorus content is less than 0.005% by weight, it is difficult to obtain a sound ingot, and if the phosphorus content exceeds 0.1% by weight, the electrical conductivity decreases significantly, so the phosphorus content is set in the range of 0.005 to 0.1% by weight. Next, to explain the method of the present invention, when hot working a copper alloy ingot having the above-mentioned composition, the heating temperature was limited to 880 to 99°C. tin does not form a solid solution in the copper alloy matrix, making it difficult to obtain a copper alloy with sufficient tensile strength and heat resistance.When the temperature exceeds 990℃, tin diffuses into the grain boundaries of the alloy and becomes concentrated. Grain boundary embrittlement is likely to occur. In extreme cases, partial melting may occur there, resulting in cracking or destruction during the subsequent hot working. Cooling after hot working must be carried out at a cooling rate of 20°C/sec or more from 780°C or above, but if cooling is performed after the temperature drops below 780°C or at a cooling rate of less than 20°C/sec, the steel This is because the precipitation of copper cannot be sufficiently inhibited, and it is ultimately difficult to obtain a copper alloy having sufficient tensile strength and heat resistance. The material obtained by cooling after hot working as described above can be subjected to aging treatment after cold working to finely precipitate iron in the copper alloy matrix, thereby achieving sufficient It is possible to obtain a copper alloy that provides heat resistance and has sufficient tensile strength through subsequent cold working. In addition, the aging treatment is a well-known method, for example, 350
Processing within 4 hours at ~550°C is sufficient. [Example] Next, the method for producing a copper alloy of the present invention will be explained with reference to Examples. Example 1 After melting ordinary piece-shaped electrolytic copper in a graphite crucible in a high-frequency atmospheric melting furnace, the surface of the molten metal was immediately coated with a charcoal flux. Next, iron and tin according to the target value are added and dissolved in this order as electrolytic iron and granular metal tin, respectively, and phosphorus according to the target value is added as an intermediate alloy of copper and phosphorus (15% by weight of phosphorus). After melting, it is cast into multiple molds to create a product with a width of 105 mm and a thickness of 35 mm.
Multiple ingots with a length of 210 mm were obtained. The composition of the ingot was as shown in Table 1. The quality of these ingots was determined by
Judgment was made by observing the milled surface using the color check method and observing the microstructure of a microscopic specimen taken from the ingot. The obtained judgment results are also shown in Table 1. In addition, in Table 1, the ○ marks are
No surface defects observed by color check method.
In addition, microstructural observation revealed that coarse primary crystals of γ iron were not formed, and the x marks indicate other cases.

[Table] From Table 1, ingots containing an appropriate amount of phosphorus are of good quality unless the amount of iron is excessive (ingots No. 1 to 13), and ingots containing too little phosphorus are of good quality. (Ingot No. 14) and an ingot with an excessive amount of iron (Ingot No. 15) are found to be of poor quality. Example 2 A specimen with a width of 30 mm, a thickness of 25 mm, and a length of 100 mm was taken from an ingot that had been milled by 5 mm per side in the thickness direction in Example 1. These specimens are 850, 900, 950, 980 and
It was heated to 1000°C and hot rolled to a thickness of 12mm.
During hot rolling, the temperature of the material was measured with an infrared thermometer, and hot rolling was carried out at a temperature of 800°C or higher. Therefore, when it was determined that hot rolling was to be performed at a temperature lower than 780°C, hot rolling was performed after heating to the initial heating temperature again. This heating and rolling process was repeated as necessary until a plate thickness of 12 mm was obtained. The obtained hot-rolled materials were treated with the exception of materials that cracked or broke during rolling and were abandoned for further processing.
Immediately water cooling was performed by shower cooling. The cooling rate of this shower water cooling was 60 to 70°C/sec. This cooled hot-rolled material was further face-milled and then cold-rolled from 11 mm to a thickness of 0.8 mm. This was aged at 550°C for 1 hour, and the tensile strength was measured. The results obtained are shown in Table 2.

【table】

[Table] From Table 2, 900 of the invention examples (ingot Nos. 1 to 9)
The samples heated to ~980°C and hot rolled had tensile strengths greater than 50 Kg/mm ² compared to other samples that could be hot rolled to the end.
Since the above sample was heated at 550℃ for 1 hour, it has good insulation properties, and both tensile strength and heat resistance are further improved.The tensile strength of samples other than the above is presumed to be due to poor quality of the ingot. It can be seen that the measured values showed large variations, or cracks or fractures occurred during hot rolling, which forced the abandonment of further processing. Example 3 Three pieces separately collected in Example 2, width 30 mm, thickness 25
mm, length 100 mm of the ingot specimen of the present invention example, each was divided into two in the length direction, and six 30 mm wide and 25 mm thick,
A specimen with a length of 50 mm was prepared. These specimens were heated to 900° C. and hot-rolled to a thickness of 12 mm in the same manner as in Example 2. For cooling of specimens after hot rolling, the cooling start temperature should not be less than 780℃, and the cooling temperature should be about 750℃ below 780℃.
There are two types of cooling rates: air cooling in the atmosphere (0.5 to 1.5 degrees Celsius/second), water cooling by spray water (10 to 15 degrees Celsius/second), and water cooling by shower (25 to 15 degrees Celsius).
35℃/sec) and water quenching in a water bath (100~150℃)
The experiment was carried out under four types of conditions: (°C/sec). The hot-rolled material cooled in this way was prepared in Example 2.
Tensile strength was measured in the same manner as above. The results obtained are shown in Table 3.

[Table] From Table 3, approximately 750
℃, sufficient tensile strength cannot be obtained, and the faster the cooling rate, the greater the tensile strength obtained.
In addition, when the cooling start temperature is 780℃ or higher and the cooling rate is 25 to 35℃/sec and 10 to 150℃/sec, the tensile strength is both greater than 50Kg/ ^mm2 , and the heat resistance is also good. It can be seen that both the heat resistance and the heat resistance are much improved compared to the case under other conditions. Example 4 After obtaining a hot-rolled material that was heated to 900°C in Example 2 and subsequently face-milled in the same manner (excluding materials that cracked or broke during rolling and abandoned further processing), Furthermore, the following processing was performed. That is, this hot rolled material was cold rolled from 11 mm to a thickness of 3 mm, aged at 550° C. for 1 hour, and then cold rolled to a thickness of 0.25 mm. Obtained plate material and three commercially available conventional alloys {CDA
Alloy 194 (2.3 wt% Fe, 0.12 wt% Zn, 0.003 wt% P, balance Cu), phosphor bronze type 2 (6.0 wt% Sn, 0.1 wt%
(wt% P, balance Cu) and Fe-42Ni alloy}, the tensile strength, hardness, semi-softening temperature (heat resistance), and electrical conductivity were measured. The results obtained are shown in Table 4.

〔Effect of the invention〕

From the above, the method of the present invention is similar to the conventional Kovar and
This makes it possible to manufacture iron and tin-containing copper alloys as relatively inexpensive mass-produced products, which can replace expensive non-copper lead frame materials such as Fe-42Ni alloys, and is highly effective for industrial use. The value is extremely large.

[Brief explanation of drawings]

The figure is an electron micrograph (magnification:
100,000 times).

Claims (1)

[Claims] 1 1.5-3.0% by weight, tin 0.8-2.5% by weight, phosphorus 0.005
After heating and hot working a copper alloy ingot containing ~0.1% by weight and the remainder consisting essentially of copper to 880-990°C, the hot-processed material is cooled from 780°C or higher at a rate of 20°C/second or more. A method for producing a high-strength, high-heat-resistant copper alloy, which comprises cooling at a high speed, followed by cold working, aging treatment, and then further cold working.