JP3344700B2 - High-strength, high-conductivity copper alloy sheet for leadframes with excellent heat treatment during press punching - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength, high-conductivity copper alloy plate used for a lead frame , and more particularly, to a lead frame formed by a plurality of shearing processes including a punching process. The present invention relates to a high-strength, high-conductivity copper alloy plate for a lead frame , which can easily remove residual stress generated at the time of shearing by annealing at the time of manufacturing, and is hardly softened.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned lead frames generally have strength, elongation, conductivity, heat resistance, Ag plating property, Sn plating,
It is required to have features such as heat-peelability of plating and solder. From these facts, for example, C19400 (Cu-2.3 wt% Fe-
0.03 wt% P-0.1 wt% Zn) and C19210
Many other copper alloys, including (Cu-0.1 wt% Fe-0.03 wt% P), are used for their production.

[0003]

On the other hand, in response to recent demands for reduction in the weight and thickness of various electric and electronic devices and improvement in mounting density, the use of smaller parts and a shorter distance between leads have been accelerated. For this reason, for example, in punching of a lead frame by pressing, it is required that a lead twist, a lead shift, a lead level difference, and the like after punching be small. In order to ensure the performance which can be called the flatness of these leads, it is required that residual stress generated by shearing during press punching be small.

Further, a technique for reducing the residual stress generated along with this has been developed. This technology occurs when the lead side is punched out, after a side surface of the lead is punched out, a short time heat treatment (annealing) for a few seconds to several minutes is performed once in a state where the lead ends are not cut off and bundled, and the lead side surfaces are punched out. Then, the residual stress is released, and then, when the residual stress becomes small, the lead tip is cut off to ensure flatness. When applying this technology,
It is necessary that the residual stress is easily removed by annealing during the punching process, and that the lead frame material itself is not softened. If the material itself softens, it may be deformed due to insufficient strength at the time of cutting off the lead tip after this, or it may be easily deformed in the subsequent IC assembly process even if it can be processed into a lead frame Handling becomes difficult, leading to a decrease in productivity. Therefore, there is a need for a material that has a small residual stress generated by press punching, easily removes the residual stress by annealing during the punching process, and is unlikely to be softened during the annealing.

[0005] Recently, in Japanese Patent Application Laid-Open No. Hei 2-111829, Fe and Sn and P, Zn, Si, Sb,
A heat-resistant copper alloy for lead frames, which has a composition containing at least one of In, Al, Mn, Ni, and Mg, and controls the size of Fe precipitates, has been proposed. In Japanese Patent No. 2673967, Fe, P, Z
A Cu alloy lead frame material for a semiconductor device having high strength, in which the composition of n, Mg, and Sn is controlled, has been proposed. However, JP-A-2-111829 describes that the copper alloy is rich in heat resistance, but it has strength, conductivity, residual stress at the time of punching, and furthermore,
No mention is made of characteristics such as ease of removal of residual stress generated by punching. Also,
Japanese Patent No. 2673967 describes that the copper alloy has high strength, high conductivity and heat resistance. However, it is also easy to remove residual stress at the time of punching and residual stress generated by punching. No such property is mentioned at all.

The present invention relates to a method for producing a copper alloy sheet for a lead frame, which maintains the properties such as strength, conductivity, solderability, and plating properties that are higher than those of an ordinary copper alloy sheet. It is an object of the present invention to obtain a copper alloy plate which has a small residual stress, which is easily removed by the annealing during the punching process during the punching process, and which is not easily softened during the annealing and has good heat resistance.

[0007]

The copper alloy plate for a high-strength, high-conductivity lead frame according to the present invention has a Fe: 0.05 to
3.0 wt%, P: 0.01 to 0.4 wt%, Ni:
0.001 to 0.5 wt%, Sn: 0.005 to 2.0
wt%, Zn: 0.005 to 5.0 wt%, Si: 0.
Less than 01 wt%, O: 100 ppm or less, H: 10 pp
m or less, the balance substantially consists of Cu and unavoidable impurities ,
In particular, annealing for removing residual stress is performed during press stamping.
This is a copper alloy plate used for a lead frame. The copper alloy further contains one or more of Mn, Zr, Cr, Al, and In in a total amount of 0.001 to 0.1 wt.
%, Can be contained. In the above copper alloy, Mg, Co, Ca, Ag, Cd, B
e, Ti, Au, Pt, Hf, Th, Li, Na, K,
Sr, Pd, W, S, C, Nb, V, Y, Mo, Pb,
Ga, Ge, As, Se, Sb, Bi, Te, B, C
e, it is desirable that the total amount of misch metal is limited to 0.005 wt% or less.

[0008]

Next, the reasons for limiting the components in the alloy of the present invention as described above will be described below. <Fe> Fe has a function of forming a compound with P and precipitating in the alloy or precipitating Fe alone in the alloy, thereby ensuring the strength and heat resistance of the alloy. However, if the content is less than 0.05 wt%, desired strength and heat resistance cannot be obtained, while if the content is more than 3.0 wt%, coarse Fe precipitates are formed in the alloy. As a result, the workability during hot rolling is reduced, and the bending workability and electrical conductivity of the product are significantly reduced, which is not preferable.
Therefore, the Fe content is set to 0.05 to 3.0 wt%.

<P> P forms a compound with Fe and precipitates in the alloy to improve strength and heat resistance. In addition, a compound with Ni, which will be described later, is generated and precipitates in the alloy to improve the shearing property. When the content of P is less than 0.01 wt%, precipitation of the compound is insufficient, so that the desired strength,
Heat resistance and shearability cannot be obtained. On the other hand, if the content of P exceeds 0.4 wt%, it is not preferable because the workability during hot working is lowered and the conductivity is lowered. Therefore, the content of P is 0.01 to 0.4 wt.
%.

<Ni> Ni forms a compound with P and precipitates in the alloy to improve the shear workability, and as a result, reduces the residual stress generated during press punching. When this compound is dispersed in the alloy, there is no metallurgical continuity with the base material, so stress is intensively received during shearing and becomes a source of microcracks, significantly improving shearing workability, Consequently, the residual stress can be kept low. Ni
When the content of is less than 0.001 wt%, the compound precipitates only very finely, and the desired shear workability cannot be obtained. On the other hand, when the content of Ni exceeds 0.5 wt%, it precipitates as a coarse compound of Ni—P, which contributes to the improvement of the shearing workability but decreases the bending workability. In addition, the conductivity is undesirably reduced. Therefore, the content of Ni is set to 0.001 to 0.5 wt%.

<Sn> Sn not only improves the strength by forming a solid solution in the alloy, but also forms an Fe—P precipitate or Fe.
Improves heat resistance in the state of coexistence with precipitates. On the other hand, S
Since the processing temperature for removing the residual stress does not rise even if n is added, it is possible to remove the residual stress without excessively softening during annealing for removing the residual stress during shearing. it can. This property is not sufficient if the Sn content is less than 0.005 wt%. On the other hand, if the Sn content exceeds 2.0 wt%, the conductivity is drastically reduced, which is not preferable. Therefore, the content of Sn is 0.005 to 2.
0 wt%. <Zn> Zn improves the heat-peeling resistance of copper alloy solder and Sn plating. However, if the content is less than 0.005 wt%, the desired effect cannot be obtained. On the other hand, if the content exceeds 5.0% by weight, the solder wettability decreases. In addition, the decrease in conductivity also becomes severe. Therefore, the content of Zn is set to 0.005 to 5.0 wt%.

<Si> Si forms a compound with Ni and precipitates in the alloy. However, when the content of Si is 0.1.
If the content exceeds 01 wt%, Ni is used to form a compound with Si, and inhibits the formation of a Ni-P compound. As a result, the shearing property that would be obtained by the Ni-P compound is impaired. In addition, the electric conductivity is drastically reduced, which is not preferable. Therefore, the content of Si is 0.01 w
Limit to less than t%. For this purpose, O may be blown into the molten metal as necessary to float the impurity Si and remove it together with the slag. <O> O easily reacts with P. When O exceeds 100 ppm, the reacted P cannot form the above-mentioned compound with Ni. As a result, the effect of improving the shearability cannot be obtained. Therefore, the content of O is set to “100 ppm or less”. <H content> When H content exceeds 10 ppm, H is combined with O in the cooling process during casting to form steam, and this steam becomes blowhole in the ingot. It causes defects. Therefore, the content of H is "10 ppm or less, preferably 4 ppm or less,
More preferably, it is 2 ppm or less. As for the reduction of O and H, Ar bubbling may be performed on the molten metal under charcoal coating as necessary.

<Mn, Zr, Cr, Al, In> Mn,
Zr, Cr, Al, and In also exhibit the same effects of removing residual stress and improving heat resistance as Sn. If the amount is less than 0.001% by weight, the effect is not sufficient, and if it exceeds 0.1% by weight, the electric conductivity is greatly reduced, which is not preferable. Therefore, the content of these elements is set to 0.001 to 0.1 wt% in total.

<Others> Mg, Co, Ca, Ag, C
d, Be, Ti, Au, Pt, Hf, Th, Li, N
a, K, Sr, Pd, W, S, C, Nb, V, Y, M
o, Pb, Ga, Ge, As, Se, Sb, Bi, T
When the total content of e, B, Ce, and misch metal exceeds 0.005 wt%, it is considered that these solid-dissolved atoms hinder the interaction between Sn atoms and dislocations. This prevents the effect of improving the heat resistance of the Sn atoms and makes it difficult to remove the residual stress without softening the material during annealing for removing the residual stress during shearing. Therefore, the content of these elements is 0.005 in total.
wt% or less.

[0015]

Next, a high-strength, high-conductivity lead according to the present invention.
Examples of a copper alloy plate for a frame will be described together with comparative examples and a conventional example. A copper alloy having a composition shown in Tables 1 to 3 was melted in the air under a charcoal coating in a kryptor furnace, and cast into a book mold to produce an ingot of 50 mm × 80 mm × 200 mm. This ingot is hot-rolled at about 900 ° C.
Immediately, it was quenched in water to produce a hot-rolled material having a thickness of 15 mm.
In order to remove the oxide scale on the surface of the hot-rolled material, the surface was lightly cut, cold-rolled and heat-treated repeatedly at least once, and then cold-rolled to a thickness of 0.25 mm and a width of 60 mm.
mm strips were made.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

The obtained strips were measured for strength, electrical conductivity, heat resistance temperature and solder heat resistance peeling properties in the following manner, and were also subjected to a press punching test, a residual stress removal test and a bending workability test. The results are shown in Tables 4 and 5. The strength was measured by processing a JIS No. 5 test piece from the strip and measuring the tensile strength, and the conductivity was measured using a double bridge based on the method specified in JIS H0505. Heat resistant temperature is 5 minutes after heating, Hv decrease amount before heating
10% of the temperature. This was designated as heat-resistant temperature 1. The soldering heat-peeling resistance was 150 seconds after soldering 6Sn / 4Pb solder at 245 ± 5 ° C. × 5 seconds.
Heated to 1000 hr in an oven at ℃. This test piece was processed by bending it back by 180 °, and it was observed whether the solder in the processed portion was peeled off.

In the press punching test, first, as shown in FIG. 1, (a) one side of the lead is processed by etching (the hatched portion 1 is removed by etching... At this time, the residual stress is zero). (B) The other side is processed by a press (press-punching of the hatched portion 2 ... residual stress occurs at this time), length 20 mm, width 0.3 mm, interval 1 mm
(A), (B) and (C) and (D) were processed into a state where the ends were connected, and (c) the ends were cut off with a press as it was (press-punching the arrow 3). At this time, the intervals between the tips of the leads A and B, and C and D change according to the generated residual stress. The absolute value of the changed amount was used as an index of the residual stress generated by the shearing process of press punching.

In the test for removing residual stress, annealing is performed at 300 to 500 ° C. for 5 minutes in the state shown in FIG. 1B of the press punching test, that is, with the tips connected, and thereafter, as shown in FIG. The tip was cut off by pressing. When the lead is cut off, the interval between the tips of the leads changes according to the residual stress that could not be removed by annealing. This interval is plotted against the annealing temperature, and the change in the tip interval is 30 μm.
m was obtained. This was designated as heat-resistant temperature 2. The heat resistant temperature 2 is compared with the heat resistant temperature 1, and the difference can be used as an index of the easiness of removing residual stress generated by shearing. That is, as the heat-resistant temperature 1 is higher than the heat-resistant temperature 2, the residual stress can be easily removed. In the bending test, W bending was performed using a W-shaped bending jig having a bending radius equivalent to the plate thickness according to the method of JIS-H3130. The W-bent portion after processing was visually observed, and workability was evaluated based on the presence or absence of cracks.

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

[Table 6]

From Table 4, it can be seen that N falling within the specified range of the present invention.
o. The alloys 1 to 10 have properties required for electric and electronic components such as strength, electrical conductivity, heat resistance temperature, bending workability, etc., and are excellent in shear workability (small residual stress). It is higher than the heat resistance temperature 2, and the residual stress can be easily removed. On the other hand, Tables 5 and 6 show that Comparative Example Nos. 11-
It can be seen that No. 25 has no material adjustment or one of the characteristics is inferior.

[0026]

According to the present invention, a copper alloy for a lead frame is provided.
The residual stress generated at the time of punching is small, while maintaining the properties such as strength, conductivity, solderability, plating properties, bending workability etc. required as a metal plate more than ordinary copper alloys,
Further, the residual stress generated by the punching can be easily removed by annealing during the punching, and a copper alloy that is hard to be softened during the annealing and has good heat resistance can be obtained.
Therefore, it is possible to meet strict requirements for dimensional accuracy due to miniaturization of various electric and electronic devices.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a procedure of a press punching test.

[Explanation of symbols]

 1 Locations removed by etching 2, 3 Locations stamped out A to D Lead

Claims (3)

(57) [Claims] 1. A method for removing residual stress during press punching.
A copper alloy sheet for a lead frame to be subjected to annealing,
e: 0.05 to 3.0 wt%, P: 0.01 to 0.4 w
t%, Ni: 0.001 to 0.5 wt%, Sn: 0.0
05 to 2.0 wt%, Zn: 0.005 to 5.0 wt%
%, Si: less than 0.01 wt%, O: 100 ppm or less, H: 10 ppm or less, the balance being substantially high strength lead frame excellent in the heat treatment at the time of stamping, characterized in that it consists Cu and inevitable impurities , High conductivity
Copper alloy plate . 2. Mn, Zr, Cr, Al, In
0.001 to 0.1 w in total of one or two or more
2. The lead frame according to claim 1, which is excellent in heat treatment during press punching.
For high strength, high conductivity copper alloy plate . 3. Mg, Co, Ca, Ag, Cd, Be,
Ti, Au, Pt, Hf, Th, Li, Na, K, S
r, Pd, W, S, C, Nb, V, Y, Mo, Pb, G
a, Ge, As, Se, Sb, Bi, Te, B, Ce,
The high-strength, high-conductivity copper alloy sheet for a lead frame according to claim 1 or 2, wherein the total amount of the misch metal is 0.005 wt% or less.