JP3296709B2 - Thin copper alloy for electronic equipment and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy applied to a lead material, a terminal material, a connector material, a switch material and the like for electronic and electric equipment, and more particularly to a lead material (lead frame material) for a semiconductor element such as an IC. It relates to a suitable copper alloy.

[0002]

2. Description of the Related Art Conventionally, lead frame materials for semiconductor devices,
As the terminal material, in addition to the iron-based material, a copper-based material having excellent electrical conductivity and thermal conductivity is often used. In recent years, high integration and miniaturization of semiconductor devices have progressed, and copper alloys used in these devices have often used copper-based materials having excellent electrical conductivity and thermal conductivity.

[0003] In general, the characteristics required for a lead frame material include a noble metal (Ag or the like) in addition to electric conductivity and heat conductivity.
Since plating and solder plating are performed, excellent plating properties and solder bonding properties are also required. In addition, lead frame materials are usually strictly required, for example, higher surface smoothness is required than terminal materials. Also, since lead frames are usually manufactured by punching or etching,
It is also important to have excellent etching properties. Materials that satisfy such a wide range of properties are desired, but it is also important that they be practical in terms of price.

As a copper-based material meeting such a wide range of requirements, Cu-Sn-based materials, Cu-Fe-based materials, and the like have been widely used. However, at present, the above-mentioned wide-ranging requirements are becoming more stringent in response to recent high integration, miniaturization, and high packaging density of semiconductor devices. In particular, in recent years, the number of pins in a lead frame has been increased, and improvements in strength characteristics and the like have been strongly demanded, and more excellent punching workability or etching properties have been demanded.

In response to such demands, precipitation hardening type Cu-Cr-based, Cu-Cr-Zr-based, Cu-Cr-S
Alloys such as n-based have come to be used. An object of the present invention is to provide a copper alloy for electronic equipment which is particularly suitable for a multi-pin lead frame material and a method for producing the same.

[0006]

The above-mentioned precipitation hardening type copper alloy utilizes precipitation of Cr and Zr, and exhibits an excellent balance in strength, conductivity and the like. However, further miniaturization and higher density of semiconductor devices have been remarkable, and in recent years lead pins have been increased in number, and conventional lead frame materials have become unable to cope.

In recent years, higher densification has further progressed, and as a result, problems such as short-circuiting between lead frames and poor conduction due to poor plating of noble metal (Ag or the like) have become apparent. Specifically, if a crystallized substance or a precipitate is exposed on the punched end face or the etched end face, the adhesion of the plating layer such as Ag is partially deteriorated, or the precipitate (needle) extended by processing is removed. Protrusion of shaped or plate-shaped precipitates) may cause a short circuit.

During plating, whiskers grow from exposed portions of the precipitate, which also causes a short circuit. Furthermore, minute burrs at the time of punching also cause deterioration of plating property and short circuit.

[0009] The precipitation hardening type copper alloy utilizing the precipitation of Cr or Zr described above is not good in workability. Therefore, when a lead frame is manufactured by punching, generation of punching powder, burrs and the like occur. As a result, this may cause a short circuit between the lead frames. If the workability is poor, the dimensional accuracy of the formed lead frame is degraded, and the production yield is greatly reduced. In addition, there was a problem that the life of the mold was shortened. This is remarkable especially in the case of a multi-pin lead frame.

[0010]

DISCLOSURE OF THE INVENTION In view of the above problems, the present invention has developed a precipitation hardening type copper alloy which has solved these problems, and has realized a thin copper alloy for electronic equipment such as a lead frame material which has realized excellent characteristics. The purpose is to provide. That is, according to the present invention, Cr is 0.1 to 0.4% by weight, Sn
Is 0.05 to 2% by weight, Zn is 0.05 to 2% by weight, P
at least one of b or Ca has a total of 0.005 to
0.2 wt%, P is less than 0.01 wt%, S is 0.00
A copper alloy containing less than 5% by weight, less than 0.005% by weight of O ₂ , and a balance of Cu and unavoidable impurities, wherein the size of a crystallized substance or a precipitate is less than 3 μm and the crystal grain size is less than 3 μm. Is less than 5 μm. Further, in addition to the above-mentioned elements, 0.01 to 0.2% by weight of Zr is further added.
It is a thin copper alloy for electronic equipment included.

As a manufacturing method, an alloy having the above-mentioned composition is cast at a cooling rate of 5 ° C./sec or more,
After hot working at 0 to 1000 ° C., cooling at a rate of 10 ° C./sec or more, and then cold working at a working rate of 80% or more;
Heat treatment at 400 to 500 ° C for 10 minutes to 24 hours, cold working at a working rate of 50% or less, 300 to 600 ° C for 10 seconds to 1
A final heat treatment of 2 hours is sequentially applied to reduce the size of a crystal or a precipitate to less than 3 μm and the crystal grain size to less than 5 μm.
A manufacturing method is provided.

Although the copper alloy for electronic devices of the present invention is particularly suitable for lead frame materials, it is also applicable to copper alloys for electronic devices such as terminal materials and connector materials.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The alloy of the present invention obtains appropriate strength and electrical conductivity by precipitation hardening of Cr and Zr. The present inventors have specified the contents of these Cr and Zr and the contents of other components, and have further specified the size of a crystallized substance or a precipitate to realize a practically excellent lead frame material. Have been found, and as a result, the present invention has been obtained. The reasons for limiting the components of the alloy of the present invention will be described below.

Cr is an element that precipitates in copper to improve the strength without significantly lowering the conductivity of copper, but if its content exceeds 0.4% by weight, it contributes to the improvement in strength. In addition to saturating, the size of crystallized substances or precipitates tends to increase, and these precipitates may protrude from the end face of the lead frame and cause a short circuit such as a short circuit with an adjacent lead frame. On the other hand, 0.
If it is less than 1% by weight, the strength and heat resistance become insufficient, and it is not suitable for use in lead frames.

In the case of the alloy of the present invention containing Zr, like Zr, Zr is precipitated in copper to improve the strength without significantly lowering the conductivity of copper. Its content is 0.0
1 to 0.2% by weight is preferred. If the content exceeds 0.2% by weight, the contribution to the improvement in strength is saturated, and the crystallization or the precipitate tends to become coarse, which may cause a short circuit phenomenon of the lead frame. On the other hand, if it is less than 0.01% by weight,
Insufficient strength and heat resistance make it unsuitable for lead frame applications.

Sn enhances its strength by being added to copper, but its content is desirably 0.05 to 2% by weight. If it exceeds 2% by weight, the solid solution amount of Cr or Zr in copper is reduced, and the size of a crystal or a precipitate containing Cr or Zr is increased. For this reason, as described above, this causes a short circuit phenomenon of the lead frame. In addition, the conductivity is also lowered. On the other hand, when the content is 0.05% by weight, the strength is insufficiently improved.

[0017] Zn improves the solder plating property of the lead frame material and contributes to the prevention of peeling due to the deterioration with time of the solder joint surface when soldered. Its content is 0.05
~ 2% by weight is good. If too much Zn is contained, the solderability deteriorates, so the upper limit is suitably 2% by weight. On the other hand, the lower limit is suitably 0.05% by weight, and if less than 0.05%, the improvement of the solder plating property is insufficient, and the peeling prevention of the solder joint surface becomes insufficient.

Further, by adding Pb or Ca, press formability of the lead frame is improved. In particular, in recent years, the distance between pins has been narrowing, and the demand for a multi-pin type lead frame having a very large number of pins has been increasing. For this reason, improvement of the precision of the press end face is also desired. Pb or Ca is at least one of a total of 0.001 to 0.
When added at a content of 2% by weight, the end face of the press becomes precise and the formation of burrs is suppressed, contributing to press formability. In addition, it is possible to obtain a product having stable dimensions and shape after pressing, and it is expected that the life of the pressing die is prolonged. When the content is less than 0.001% by weight, the contribution to the improvement of press formability is poor, while the excessive content deteriorates the workability such as the occurrence of defects such as cracks.
2% by weight is suitable.

In addition, usually, P,
Although a small amount of S, O _{2 and the} like are contained, the present invention, by suitably restricting the contents thereof, realizes excellent properties in combination with the above-mentioned alloy components and the later-described crystallization or precipitate specification. It is intended.

The content of P is 0.01% by weight.
By specifying that the content of Cr-P in the alloy of the present invention is less than
And the like to suppress the coarsening of the crystallized material and realize excellent characteristics. It is particularly desirable that the content of P be less than 0.005% by weight, and the performance thereof such as prevention of short circuit of the lead frame is further improved.

By defining the content of S to be less than 0.005% by weight, coarsening of crystallized substances such as Cr-S and Zr-S is suppressed, and the occurrence of short circuit as a lead frame is suppressed. . Further, by making S less than 0.005% by weight, hot workability is improved. It is particularly desirable that the content of S be less than 0.002% by weight, and the performance such as prevention of short circuit of the lead frame is further improved.

If the content of O ₂ is 0.005% by weight or more, Cr and Zr are oxidized, so that the precipitation hardening action becomes insufficient and the solderability decreases. It is particularly desirable that the O ₂ content be less than 0.002% by weight.

Although P, S, and O ₂ described above are usually contained in trace amounts in copper-based materials, they are particularly important in the alloy of the present invention containing Cr and Zr. Have found that by defining the preferred content, a copper alloy suitable for a lead frame is realized.

Next, the size of a crystal or a precipitate will be described. These sizes are desirably less than 3 μm. If it is larger than these, these crystallized substances and precipitates are formed into needles or plates in the rolling process, and these crystallized substances,
This is because the precipitates protrude from the end surface of the lead frame and easily cause a short circuit with the adjacent lead frame.

In the structure of the present invention described above, it is necessary to reduce the crystal grain size to less than 5 μm in order to suitably realize the characteristics. In particular, the addition of Pb or Ca has the effect of improving press formability as described above, but this effect becomes insufficient when the crystal grain size is 5 μm or more.
If the crystal grain size is less than 5 μm, when etching is employed, the end face after the etching becomes smooth, which contributes to improvement in plating property.

A preferred method for producing the alloy of the present invention is described below. First, the above-mentioned copper alloy of the present invention is cast at a cooling rate of 5 ° C./sec or more. This means that at a rate of less than 5 ° C./sec, large crystals or precipitates (Cr, Cr-P, Cu-Zr, Zr-
S) is generated. Then 850-1
Hot working at 000 ° C. This is because if the temperature of hot working is lower than 850 ° C., the compounds of Cr and Zr become large,
Finally, it becomes difficult to satisfy the conditions of the present invention. 1000 ° C
Is carried out at a temperature exceeding 1000 ° C., there is an industrial problem of growth of an oxide film, and the energy cost is increased.

After hot working, cooling is performed at a rate of 10 ° C./sec or more.
This is for suppressing the compound from becoming coarse. At a cooling rate lower than this, large crystallized substances or precipitates exceeding 3 μm (Cr, Cr—P, Cu—Zr, Zr—S, etc.) are likely to be generated.

After the cooling, cold working is performed at a working rate of 80% or more. It is better not to include a heat treatment step before this cold working. The working ratio of the cold working is preferably 80% or more, and if it is less than 80%, the heat treatment in the next step will be insufficient in the precipitation hardening ability of Cr and Zr, resulting in insufficient strength and electrical conductivity.

The heat treatment performed before the final cold working after the cold working is preferably performed at 400 to 500 ° C. for 10 minutes to 24 hours. If the temperature is lower than 400 ° C., fine precipitation of Cr and Zr dissolved in the copper alloy is not sufficient, and the strength and the electrical conductivity are insufficient. If the heat treatment time is less than 10 minutes, fine precipitation of Cr and Zr similarly dissolved in the alloy is not sufficient, and the strength and electrical conductivity are insufficient. On the other hand, if the temperature exceeds 500 ° C., the crystal grain size becomes too large,
Punching workability and the like deteriorate. The heat treatment time is suitably 24 hours or less. Heat treatment beyond this does not contribute much to the property improvement and is not economical in terms of manufacturing cost.

The final cold working is desirably performed at a working ratio of 50% or less. If it exceeds 50%, the strength is improved, but the soldering heat-peeling resistance is deteriorated, and it becomes unsuitable especially for a multi-pin type lead frame.

After the final cold working, a final heat treatment is applied at 300 to 600 ° C. for 10 seconds to 12 hours. The heat treatment may be a batch process or a running process such as tension annealing. The heat treatment improves the solder heat-peelability and the bending workability. In addition, the anisotropy related to characteristics and workability is also reduced, which contributes to a reduction in internal stress. If the temperature of this heat treatment is lower than 300 ° C., the above-mentioned improvement becomes insufficient. The same applies when the heat treatment time is less than 10 seconds. On the other hand, when this heat treatment is performed at a temperature exceeding 600 ° C., the crystal grain size increases, and the punching workability and the like deteriorate. The heat treatment time is suitably 12 hours or less. Heat treatment beyond this does not contribute much to the property improvement and is not economical in terms of manufacturing cost.

In addition, if necessary, after the heat treatment, a straightening treatment may be performed by a tension leveler, a roller leveler or the like.

[0033]

【Example】

Example 1 Using a high-frequency melting furnace, a copper alloy having the composition shown in Table 1 (S and O ₂ are expressed in ppm) was melted and cooled at a cooling rate of 6%.
Casted at ° C / sec. The size of the ingot is 30mm thick and 1 width
It is 00 mm and 150 mm in length. Next, these ingots were hot-rolled at 980 ° C. and then rapidly cooled at a cooling rate of 30 ° C./sec. In order to remove the oxide film on the surface, the surface was cut to a thickness of about 9 mm. Next, a thickness of 0.
It was processed to 33 mm. After this, 42 in an inert atmosphere
After a heat treatment of 0 ° C. × 2 hours, it was further cold-rolled to a thickness of 0.2 mm. Final annealing is performed at 350 ° C. × 2 hours. Various evaluations were made by sampling from the lead material thus manufactured. Comparative Example 22 could not be manufactured due to cracking during hot working.

[0034]

[Table 1]

The crystal grain size was measured by observing the test piece with a microscope (200 times). The size of the crystallized substance or the precipitate was measured in the same manner. Table 2 shows these average values. Tensile strength is JISZ2241, conductivity is J
The measurement was performed according to ISH005, and the results are also shown in Table 2.

[0036]

[Table 2]

The test piece was etched by using a ferric chloride solution, and the width was 0.5 m in the direction perpendicular to the rolling direction.
m lead portions were formed. The etched end face was observed under a microscope (50 times), and the presence or absence of a protrusion was examined. In the case where protrusions were clearly observed by this microscopic observation, the presence was described in Table 2.

The solderability was evaluated by examining the wettability of the solder and the peelability of the solder. Evaluation of solder wettability was performed as follows. First 10mm x 5
A rosin-based (RMA)
After immersion in a flux of 5 seconds, the eutectic solder (P
b-63 wt% Sn) for 5 seconds, and evaluated by examining the degree of solder wetting. The degree of wetting of the solder was determined by visual observation.
% Is shown in Table 2 as defective.

The condition of the peeling of the solder due to the heating of the solder was as follows.
After being heated for 180 hours in the air and then subjected to 180 ° close contact bending and bending back, evaluation was made by examining the degree of solder peeling at that portion. If peeling of the solder is visually observed,
Table 2 indicates that there is.

The punching property was examined by performing a punching test (providing a square hole of 1 mm × 5 mm) with a mold (manufactured by SKD11). And from the 5001th to 10,000
The size (height) of burrs of 20 randomly sampled samples from the second punching was observed, and the average value is shown in Table 2. The thickness of the fractured part was measured by observing the punched surface. Table 2 shows the ratio of the thickness of the fractured part to the thickness of the test piece (fracture part / plate thickness x 100) in%.

From Table 2, it can be seen that Examples 1 to 13 of the present invention all show excellent characteristics. Comparative Example 14 with a small amount of Cr and Comparative Example 17 with a small amount of Sn have lower strength than the inventive examples. Comparative Example 1 having a large content of Cr and Zr
In Nos. 5 and 16, protrusions after etching are observed, which may cause short-circuiting, which is inconvenient for a lead frame.

Comparative Example 18, which has a large amount of Sn, has a high strength, but has a low electrical conductivity, and a protrusion after etching is recognized, which is inconvenient for use as a lead frame as described above. Zn improves the solder plating properties and the peeling resistance of the solder. However, in Comparative Example 19 containing less Zn, the solder peeling was observed. Conversely, in Comparative Example 20 containing a large amount of Zn, the solder wettability was deteriorated.

Although Pb and Ca improve the press formability,
In Comparative Example 21 having a small total content, it was found that the evaluation of the punching property described above resulted in a large burr. Further, the ratio of the fractured surface on the punched surface was small, and it was found that the molding was not so precise. On the other hand, in Comparative Example 22 having a large total amount, the workability was poor, and cracks occurred during hot working, so that subsequent property evaluation could not be performed.

In addition, in Comparative Examples 23 and 24 in which P and S are out of the range of the present invention, protrusions after etching are recognized, and are inconvenient for use as a lead frame as described above. Also O ₂
Comparative Example 25, which has a large content, has insufficient precipitation hardening action, has low strength, and is not excellent in solder wettability.

Example 2 Using the alloys 3, 6, 9 and 13 of the present invention in Table 1, casting, hot rolling, cooling, heat treatment and cold rolling were performed under the conditions shown in Table 3. Table 3 shows Examples 3 and 6 of the present invention.
9 and 13 are repeated. Comparative Examples 52-55, 57, 5
8, 60 to 62 are comparative examples with respect to claims 3 and 4.
Regarding the present invention examples and comparative examples to be displayed, similarly to Example 1, the crystal grain size , the size of the crystallized substance (precipitate), the tensile strength, the conductivity, the presence or absence of protrusions after etching, the height of burrs, Investigations were made on the ratio of the fractured portion of the punched surface and the heat peeling of the solder. The results are shown in Table 4.

[0046]

[Table 3]

[0047]

[Table 4]

Tables 3 and 4 show that Examples 3, 9, and 31 to 40 of the present invention all show excellent characteristics. On the other hand, in Comparative Example 51 in which the cooling rate at the time of casting was low, the crystallized substance became large, and the large crystallized substance became acicular or plate-like in hot working or cold working. Things were found.

In Comparative Example 52 in which the temperature of the hot working was low, the crystallized product also became large, and the large crystallized product became acicular or plate-shaped in hot working or cold working. A protrusion was observed in the sample. In Comparative Example 53 in which the cooling rate after the hot working was slow, a protrusion was also observed on the end face after the etching. These Comparative Examples 52 and 53 also had low tensile strengths.

In Comparative Example 54 in which the working ratio of the cold working after the hot working is low, the strength and the electric conductivity are inferior, and thus it is not suitable as a lid frame material.

In Comparative Example 56 in which the temperature of the annealing (heat treatment) performed before the final cold working after the cold working is high, the crystal grain size is large, and the strength is insufficient and large burrs are generated as compared with the present invention. And a decrease in the fractured portion ratio was observed. Also, the tensile strength was reduced. Conversely, in Comparative Examples 55 and 60 where the annealing (heat treatment) temperature is low, the peeling resistance of the solder is deteriorated.

Comparative Example 5 in which the working ratio of the final cold working is high
In Nos. 7 and 61, the peeling resistance of the solder is deteriorated.

In Comparative Example 59, in which the final annealing (heat treatment) temperature was high, the crystal grain size was large, generation of large burrs and reduction in the ratio of fractured parts were observed, and tensile strength was low. Conversely, Comparative Example 5 having a low final annealing (heat treatment) temperature
In Nos. 8 and 62, the crystal grain size is large and the peeling resistance of the solder is deteriorated. Comparative Example 5 in which such solder has poor peeling resistance
5, 57, 58, 60, 61 and 62 are not particularly suitable for a multi-pin type lead frame.

Although not described in the examples, even if hot working is performed at a temperature exceeding 1000 ° C., it does not particularly contribute to the improvement of characteristics, and when hot working at a high temperature, an oxide film is remarkably formed on the copper surface. It is not very desirable, for example, Further, since the treatment is performed at a high temperature, it is not economical in terms of energy. That is, from the viewpoint of manufacturing cost, it is understood that the temperature of the hot working is preferably 1000 ° C. or less.

[0055]

As described in detail above, the copper alloy for electronic equipment and the method of manufacturing the same according to the present invention are excellent in strength and electrical conductivity, solderability, punching workability, heat-peelability of solder and the like. Therefore, it is possible to suitably cope with the recent trend of high density and high integration of electronic devices. The copper alloy for electronic devices provided by the present invention has a particularly large number of pins, and can be suitably applied to a multi-pin lead frame.
In addition, they are also suitable as general conductive materials such as terminals, connectors, and electrode materials. As described above, the present invention has a remarkable industrial contribution.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-198439 (JP, A) JP-A-63-38561 (JP, A) JP-A-3-199355 (JP, A) JP-A-63-1984 143230 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 1/00-49/14 C22F 1/00-3/02 H01L 23/50

Claims (4)

(57) [Claims] 1. Cr is 0.1 to 0.4% by weight, Sn is 0.05 to 2% by weight, Zn is 0.05 to 2% by weight, Pb
Or at least one of Ca has a total of 0.005 to
0.2 wt%, P is less than 0.01 wt%, S is 0.00
A copper alloy containing less than 5% by weight, less than 0.005% by weight of O ₂ , and a balance of Cu and unavoidable impurities, wherein the size of a crystallized substance or a precipitate is less than 3 μm and the crystal grain size is less than 3 μm. electronic equipment sheet copper alloy but is less than 5 [mu] m. 2. Cr is 0.1 to 0.4% by weight, Sn is 0.05 to 2% by weight, Zn is 0.05 to 2% by weight, Zr is
Is 0.01 to 0.2% by weight, at least one of Pb and Ca is 0.005 to 0.2% by weight in total, and P is 0.1 to 0.2% by weight.
A copper alloy containing less than 01% by weight, less than 0.005% by weight of S, less than 0.005% by weight of O ₂ , and a balance of Cu and unavoidable impurities; electronic equipment sheet copper alloy grain size of less than 5μm with but less than 3 [mu] m. 3. Cr is 0.1 to 0.4% by weight, Sn is 0.05 to 2% by weight, Zn is 0.05 to 2% by weight, Pb
Or at least one of Ca has a total of 0.005 to
0.2 wt%, P is less than 0.01 wt%, S is 0.00
A copper alloy containing less than 5% by weight and less than 0.005% by weight of O ₂ and a balance of Cu and unavoidable impurities is cooled at a cooling rate of 5%.
Casting at a cooling rate of at least ℃ / sec, hot working at 850-1000 ° C, cooling at a rate of at least 10 ° C / sec, then cold working at a working rate of 80% or more, 400-500 ° C
For 10 minutes to 24 hours, cold working at a working rate of 50% or less, and final heat treatment at 300 to 600 ° C. for 10 seconds to 12 hours, and the size of a crystallized substance or a precipitate is 3 μm.
Crystal grain size be less than 5μm the method for producing a thin copper alloy for an electronic device with less than. 4. Cr is 0.1 to 0.4% by weight, Sn is 0.05 to 2% by weight, Zn is 0.05 to 2% by weight, Zr
Is 0.01 to 0.2% by weight, at least one of Pb and Ca is 0.005 to 0.2% by weight in total, and P is 0.1 to 0.2% by weight.
Less than 01 wt%, S less than 0.005 wt%, O ₂ is contained less than 0.005 wt%, the cast copper alloy consisting of the remainder Cu and unavoidable impurities at a cooling rate of 5 ° C. / sec or more cooling rate After hot working at 850-1000 ° C.
Cooling at a rate of at least ℃ / sec, then cold working at a working rate of 80% or more, heat treatment at 400 to 500 ° C for 10 minutes to 24 hours, cold working at a working rate of 50% or less, 300 to 600
A method for producing a sheet copper alloy for electronic equipment, in which a final heat treatment at 10 ° C. for 10 seconds to 12 hours is sequentially performed so that the size of a crystallized substance or a precipitate is less than 3 μm and the crystal grain size is less than 5 μm.