JP3404278B2 - Cu-Ni-Si based copper base alloy with improved annealing cracking - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cu-Ni-Si-based copper-based alloy having improved annealing cracking resistance.

[0002]

2. Description of the Related Art A Cu-Ni-Si-based copper-based alloy for electronic equipment is manufactured by a process of once hot rolling a large ingot in order to reduce the manufacturing cost. afterwards,
Although it is processed into a thin plate by cold working, in terms of manufacturability, how to obtain a hot rolled plate with high efficiency and high yield is very important.

By the way, due to the demand for miniaturization of electronic equipment, the demand for high-density mounting of semiconductor elements on a substrate is increasing more and more. Recently, SO which is advantageous for high packaging density improvement
Surface mount packages such as J, SOP, and QFP are the mainstream. Recently, in these packages, the lead pitch has been further reduced due to the demand for more pins, and TSO
Thinning plates represented by P, TQFP, etc. are in progress.
Multi-pin, narrow-pitch of the frame created by etching
But are the are the majority, etching not only the plate thickness direction, since the side-etched also occur to the plate width direction, processing limit of the lead width and lead spacing are dependent on the plate thickness, plate thickness thinner working on Be advantageous. Also, due to the demand for thinner package, it is necessary to make the lead frame material thinner,
As a result, the thickness is 0.15mm and 0.125m recently.
Thin materials such as m are the mainstream. Such thinning of the lead frame and narrowing of the leads reduce the rigidity of the entire frame and the leads, causing deformation of the inner leads during the assembly process and deformation of the outer leads during device mounting. In order to prevent such trouble, higher strength is required for the lead frame material used. On the other hand, since the power consumption increases as the processing speed of the IC increases and the number of pins increases, measures to dissipate the heat generated from this become an important issue in IC design.

Copper alloys are advantageous in terms of heat dissipation, since copper has a property of thermal conductivity far exceeding 42 alloy. Therefore , there is an increasing demand for a copper-based lead frame material which has strength capable of coping with thinning and is excellent in heat dissipation. The requirements are as follows: 1) The leads must have mechanical strength so that they are not easily deformed. 2) It has excellent etching property and press workability in the pattern formation of the lead frame. 3) It has a high thermal conductivity capable of efficiently dissipating the heat generated by the chip. 4) Excellent current-carrying characteristics. 5) Excellent solderability in mounting High reliability of solder joint. 6) Excellent silver plating property for bonding. 7) The oxide layer on the surface of the alloy generated in the heating step is difficult to peel off. 8) Excellent workability during lead bending. 9) The price is reasonable. Etc., and various characteristics are required.

Further, for electronic parts such as various terminals, connectors, relays and switches, materials such as inexpensive brass, phosphor bronze having excellent spring characteristics or nickel silver having excellent spring characteristics and corrosion resistance have been conventionally applied. It was However, in recent years, electronic devices and their parts are required to be smaller and thinner, and in the case where they are used in a high temperature environment such as electric parts of automobiles, they can withstand harsh environments. There is a demand for reliable components that can be used. In order to meet such requirements, the material must have a) sufficient strength to generate a high contact pressure even at a thin plate thickness. b) The stress relaxation rate is low, and the contact pressure does not decrease even after long-term use at high temperature. c) The conductivity is high, and Joule heat is unlikely to be generated when energized. Also, the heat generated should be easily dissipated. d) No cracking or roughening of the bent portion occurs even after severe bending. e) It is required that the material does not fatigue-fracture even if a large amount of bending deformation is repeatedly applied within the elastic region.

In recent years, precipitation-type copper alloys are often used in applications requiring high strength and conductivity such as copper alloys for electronic devices. The Cu-Ni-Si alloy is a typical precipitation-type copper alloy having both high strength and high conductivity, and has been put to practical use as a material for electronic devices. For example,
As a material suitable for use in lead frames or connectors, Cu-Ni-Si alloys having the following component compositions have been published. Japanese Patent Publication No. 60-058783: Ni = 1.0 to 4.0% by weight, Si = 0.3 to 1.0% by weight, and if necessary, P, As, Sb, Fe, Co, Cr, Sn. , A
1, 0.001 to 2.0% of at least one of Ti, Zr, Mg, Be, Zn, and Mn, and the balance Cu and its unavoidable impurities, Japanese Patent Publication No. 7-88549: Ni = 1. 0 to 4.0% by weight, Si = 0.2 to 1.0% by weight, Ag = 0.0005
.About.0.5% by weight, and further contains Zn, Mn, Mg, S
n, Sb, Cr, B, Y, rare earth, Co, Ti, Zr,
An alloy containing 2.0% or less of one or more of V and the balance Cu and its unavoidable impurities.

However, it is known that such an ingot of a Cu--Ni--Si alloy causes brittle cracking in the heating step before hot rolling due to the effect of residual stress during casting (Japanese Patent Laid-Open No. Hei 10-1999). No. 4-210439, Japanese Patent Laid-Open No. 4-41039
No. 2750), hot rolling an ingot having such cracks causes problems such as an increase in manufacturing cost due to a decrease in productivity and a decrease in yield, and instability of quality. On the other hand, as a measure to avoid this heat cracking, a method of reducing the cross-sectional area of the ingot to reduce the residual stress,
A method for reducing the grain size of the ingot, a method for hot rolling after rolling the ingot at a low temperature, and the like have been published (JP-A-4-210439, JP-A-4-4-2).
750).

Further, when a Cu-Ni-Si alloy thin plate is subjected to strong cold working and then annealed, it is accumulated in the cold working.
Strain fine cracks causing was found <br/> that may occur. This crack breaks the material in the subsequent rolling and causes a significant yield loss. Even if no fracture occurs in rolling, cracks remain until the end, and cracks may occur when the material is pressed into parts.

[0009]

As a countermeasure against annealing cracks, productivity is lowered, and there is an industrial limit to refining the crystal grain size of the ingot, both of which improve the annealing cracks of the ingot. Could not be an effective means of The present invention has been made in view of such problems, and Cu- which eliminates the annealing cracks of ingots and thin plates without lowering productivity and increasing manufacturing cost.
It is intended to provide a Ni-Si alloy.

[0010]

The present invention provides Ni: 1.0.
.About.4.8 wt%, Si: 0.2 to 1.4 wt% as a basic component, and the balance is Cu--Ni which is substantially Cu.
In the —Si-based copper-based alloy, by controlling the hydrogen concentration to 0.0001% by weight or less and the sulfur concentration to 0.0020% by weight or less, the conventional problem of Cu—Ni
A major feature is that the hot workability and heat treatment of the Si-based alloy are improved. In addition, Cu-Ni-Si referred to here
The system is a general term for copper-based alloys characterized by incorporating basic properties such as strength and electrical conductivity by precipitating Ni and Si compound particles (Ni ₂ Si) by appropriate aging treatment. is there. Of course, for the purpose of improving various characteristics as an electronic material, the above-mentioned P, As, S
b, Fe, Co, Cr, Sn, Al, Ti, Zr, M
g, Be, Zn, Mn, Ag, B, Y, rare earth, Co,
Even when elements such as Ti, Zr and V are added as auxiliary components, the effect of improving hot workability can be obtained by reducing the hydrogen and sulfur concentrations.

The alloy according to claim 2 of the present application has a shape and dimensions that are industrially hot worked. Specifically, the present invention can be preferably applied to those having a sectional area of 10 ⁴ mm ² or more. The hot working of the large ingot is mainly performed by rolling, but the same effect can be obtained in the case of hot forging. Further, the same effect can be obtained in the case of hot rolling a slab or bloom in the case of hot working an ingot for two heats.

There is no particular limitation on the shape of the alloy having a tempered state annealed after cold working according to claim 3 of the present application, and a rolled sheet material that has been annealed after cold rolling or has a similar tempered state after final rolling. It may be a new lead frame material. Next, the reason why the composition of the copper alloy is determined as described above in the present invention will be explained. The compositional percentages are expressed in% by weight.

Ni and Si Ni and Si also have the effect of increasing the alloy strength by forming a solid solution in the alloy, but by performing an appropriate aging treatment, Ni and Si mutually precipitate the Ni ₂ Si composition. It forms a substance and significantly increases the strength of the alloy and also significantly increases the thermal conductivity. Therefore, if the contents of these elements are extremely low, these properties deteriorate and the alloy becomes undesired for electronic devices. Therefore, N
The i content is 1.0 % or more and the Si content is 0.2% or more. The Ni content is 4.8% or more or the Si content is 1.
If it is 4% or more, in addition to the desired electrical conductivity not being obtained, the size and frequency of the compound particles of Ni and Si generated at the grain boundaries of the ingot increase, which promotes annealing cracking of the ingot. . Therefore, the Ni content is 1.
0 to 4.8% and the Si content were set to 0.2 to 1.4%. In order to increase the thermal conductivity after the aging treatment, the concentration ratio of Ni and Si in the alloy, Ni ₂ Si precipitate that takes closer to the concentration ratio of Ni and Si in desirable. Ni to Si concentration for good thermal conductivity
The concentration ratio (Ni concentration / Si concentration) is 2 to 8.

S S is segregated to the grain boundaries in the atomic state to reduce the binding force of the grain boundaries, and also the starting point of void generation when crystallized or precipitated at the grain boundaries as a sulfide with Cu or an alloy element. Becomes Therefore, it is desirable that the S concentration is as low as possible. However, if it is 0.0020% or less, this adverse effect can be ignored industrially, so the S content was made 0.0020% or less.

H H gathers in the voids and grain boundaries where stress concentrates, and promotes annealing cracking of a work material such as an ingot. Therefore, it is desirable that the H concentration is as low as possible.
If the content is 0001% or less, this adverse effect can be ignored industrially, so the H content was set to 0.0001% or less.

[0016]P, As, Sb, Fe, Co, Cr, A
l, Ti, Zr, Mg, B, Y, rare earth, Co, V These elements, which are optional additional components, have a solid solubility in Cu.
Precipitation, which is a relatively small element and is the origin of voids
It is necessary to limit the upper limit because it is easy to form particles at grain boundaries.
is there. The total amount is 2% or less.

Zn, Mn, Ag, Sn These elements are elements that have a relatively high solid solubility in Cu and do not form precipitated particles, but between the alloy components and impurities such as Ni and Si. Thus, the intermetallic compound particles and the non-metallic inclusion particles are formed, and these cause the generation of grain boundary voids. Therefore, the upper limit of the content limited for the same reason as P is 2% or less.

In order to produce the above-described copper alloy having an extremely low H content, it is necessary to reduce the amount of hydrogen absorbed by the copper alloy during melting and pouring. In particular, it is important to suppress the absorption of the former, and for this purpose, make sure to use sufficiently dry charcoal just before use.
It is preferably used as a molten metal coating layer having a thickness of 20 to 200 mm. When this charcoal coating is used in combination with a coating of a molten salt composed of oxides, chlorides or fluorides, a higher hydrogen absorption suppressing effect can be obtained. There is also a method of producing a copper alloy having a low H content by degassing the molten metal. The solubility of H in liquid Cu ([% H]) is
The hydrogen partial pressure (P _H2 ) in the atmosphere gives the relationship of [% H] = K√P _H2 . Here, K is a constant determined by the temperature. When the temperature is 1200 ° C., the solubility of H in Cu under P _H2 = 1 atm is 6 ppm. Therefore, in order to reduce the H concentration to 1 ppm or less, equilibrium P _H2 should be 0.028 atm or less. You can do this. This also <br/> relatively easily achieved industrially, particularly a method for its, vacuum melting, vacuum degassing, manufactured by Vacuum Metallurgical methods such as vacuum casting, the molten metal of a melting furnace or in a launder not There is a method of blowing active gas. Similarly, in order to produce a copper alloy having an extremely low S content, it is necessary to prevent the incorporation of S from the raw material, the refractory that comes into contact with the molten metal, the molten metal coating agent, etc. However, it is necessary to add a desulfurizing agent such as Na ₂ CO ₃ to the molten metal to remove S contained in the molten metal.

[0019]

As a result of intensive studies on the annealing cracks of Cu-Ni-Si alloys, the present inventors found that the cracks occur at around 500 ° C in the process of raising the temperature of a copper alloy in which strain such as an ingot has accumulated. It was found that intergranular cracking occurs, which is a phenomenon corresponding to the intermediate temperature brittleness generally known in copper alloys. That is, the cast ingot and strength
Residual stress in cold-worked materials
It was found that grain boundary slip occurs due to the thermal stress generated in the material, and a void is generated at the grain boundary accompanying this, and the voids are connected and united to cause cracking. Further research has been conducted, and the factors that promote this cracking are as follows: (1) N of grain boundaries formed by crystallization or precipitation during casting.
i-Si compound particles (becomes the origin of generation of voids) (2) Grain boundary segregation of sulfur (sulfur segregates at the grain boundaries to reduce the bond strength of the grain boundaries) (3) Hot rolling material such as ingot Hydrogen contained in (reduces the energy required for crack generation by gathering in the stress concentration area and being released inside the crack)
I found that For the above reason, N
The amount of i, Si, H and S was determined to improve the annealing cracks of ingots. Hereinafter, the present invention will be described in more detail with reference to examples.

[0020]

Example 1 Electrolytic copper, Ni, Si, Mg, Zn, and Cu ₂ S were mixed to obtain a molten raw material so that the molten alloy had the following six types of copper alloys. Here, the reason why Mg is added is that Mg has a strong affinity with sulfur, and therefore, by forming a compound with sulfur, an effect of reducing segregation of the elemental sulfur into grain boundaries can be expected. Zn is an alloying element that is often added to copper alloys for electronic materials for the purpose of improving properties such as heat resistance peeling resistance and migration resistance.
It is added to investigate the effect of the alloy on annealing cracking. Cu-3% Ni-0.6% Si-0.0005% S Cu-3% Ni-0.6% Si-0.0025% S Cu-3% Ni-0.6% Si-0.1% Mg-0.
0005% S Cu-3% Ni-0.6% Si-0.1% Mg-0.
0025% S Cu-3% Ni-0.6% Si-0.2% Zn-0.
0005% S Cu-3% Ni-0.6% Si-0.2% Zn-0.
0025% S

Next, dissolve the raw material was dissolved with loading city high-frequency induction furnace in a graphite crucible, by performing a process of mixing hydrogen in the process or oil additives reduce hydrogen by vacuum degassing, various molten metal After adjusting the hydrogen concentration to 1, the ingot was manufactured by pouring the molten metal into a mold. The ingot has a thickness of 60 mm, a width of 90 mm and a height of 150 mm. No cracking occurred even when the ingot was annealed at 850 ° C. for 1 hour. This is because the cross-sectional area of the ingot is small and the residual stress generated in casting, which is the driving force for annealing cracking, is small. Therefore, as shown in FIG. 1, after ingot 10 was cut into four pieces (1 to 4), cold rolling was performed on 1 to 3 to add residual stress. For No. 4, hydrogen analysis was performed by melt extraction in an inert gas-thermal conductivity measurement method. 12 is a feeder. Cold rolling is 1, 3 and 5%
However, no cracks were observed in the sample after cold rolling. Next, the sample after cold rolling is set to 850
After heating for 1 hour at 0 ° C. and cooling, the presence or absence of surface cracks was observed by a penetrant flaw detection method. FIG. 2 shows the dimensions and macrostructure of the rolled test material.

Tables 1 to 6 show the relationship between the hydrogen concentration in each of the alloys 1 to 6 and the occurrence of cracks observed by the penetrant flaw detection method. In all alloys, the hydrogen concentration is high,
It can be seen that the greater the rolling workability, that is, the residual stress, the more remarkable the occurrence of cracks. Also, compared to the and cracking and to compare the occurrence of cracking ,,, and the among the alloys - is vigorously generated. this is,
In addition to hydrogen, sulfur also has an adverse effect on cracking, and it is shown that when Mg is contained, the grain boundary segregation of sulfur is reduced and cracking is improved. Similar to Mg, Ti, Zr, Al, Mn, rare earth elements, and the like are elements that have a strong affinity with sulfur and reduce sulfur grain boundary segregation. On the other hand, from the possible cracking and is almost the same level cracking and of, on the order of 0.2% Zn
It can be seen that the addition of does not affect the occurrence of cracks. Elements other than Zn, such as P and A described above, do not affect the cracking in a relatively low concentration range.
s, Sb, Fe, Co, Cr, Sn, B, Y, Co, V
And Ag can be mentioned up. The cracks observed in this experiment occurred at the grain boundaries. 4 and 5 show the occurrence of cracks and the cross-section of cracks for typical cracks. The cracks were generated on the rolled surface of the sample, and this is considered to be because tensile residual stress was generated on the rolled surface. Further, in comparison with FIG. 2, it can be seen that cracks mainly occur along columnar crystals. Furthermore, by observing the ends of the cracks microscopically, it was confirmed that the cracks were generated by the generation and growth of voids at the grain boundaries.

[0023]

[Table 1] ○: No cracks, △: Fine cracks occurred, ×: Large cracks occurred

[0024]

[Table 2] ○: No cracks, △: Fine cracks occurred, ×: Large cracks occurred

[0025]

[Table 3] ○: No cracks, △: Fine cracks occurred, ×: Large cracks occurred

[0026]

[Table 4]

[0027]

[Table 5] ○: No cracks, △: Fine cracks occurred, ×: Large cracks occurred

[0028]

[Table 6] Occurrence of cracks Cu-3% Ni-0.6% Ni-0.2% Zn-0.
(0025% S) ○: No cracks, △: Fine cracks occurred, ×: Large cracks occurred
Raw

Cu- (2.0-3.0%) Ni- (0.
4 to 0.8%) The dry state of the charcoal powder coating the molten alloy when the Si alloy was melted in the low frequency melting furnace was adjusted in advance. The cross-sectional shape obtained by casting is an ingot with a width of 500 mm and a thickness of 200 mm, which is 2 at 850 ° C. before hot rolling.
It was heated for an hour and then hot rolled to 10 mm. Annealing cracking of the ingot becomes apparent as hot rolling cracking. Cracks generated by hot rolling must be removed by cutting or grinding in the next grinding step. Therefore, using the hot rolling yield calculated by the formula (1) as an index, the effect of hydrogen and sulfur concentrations on annealing cracks was investigated. Hot rolling yield (%) = (weight of material after grinding) / (weight of ingot) × 10 0 ········ (1) The hot rolling yield is shown in FIG. Show.

When the sulfur concentration is 0.0020% or less and the hydrogen concentration is 0.0001% or less, the hot rolling yield is 80% or more. The yield reduction of about 20% is inevitably caused by surface oxidation of the material. On the other hand, when the hydrogen concentration exceeds 0.0001%, the hot rolling yield is 80.
It shows a low value of less than%. Also, the sulfur concentration is 0.0
If it exceeds 02%, the hot rolling yield is low regardless of the hydrogen concentration.

[0031]

As described above, Cu related to the present invention
The -Ni-Si-based copper-based alloy achieves excellent properties by controlling the amounts of H and S, and specifically, has the following advantages. (1) Since the hot rolling yield of the ingot is high, the productivity is excellent and the cost is reduced. (2) Grinding of the hot rolled plate becomes unnecessary, or the grinding allowance is small even when grinding is performed. (3) The means for obtaining the extremely low H and S can be widely applied to various Corson alloy materials regardless of the size of the ingot and the alloy components, and thus has a wide range of industrial application. Further, the conditions for processing the material once having extremely low H and S are not limited. On the other hand, in the method of preventing annealing cracks by fine crystal grains, casting conditions are limited, and it is desirable to avoid processing conditions that coarsen the crystal grains during processing. (4) Since it is possible to prevent fine cracks in the material annealed after cold working, it is possible to meet severe quality requirements for electronic equipment parts.

[Brief description of drawings]

FIG. 1 is a view showing an ingot used in Example 1 and a cutting line thereof.

FIG. 2 is a diagram showing a macrostructure of a rolled material cut from an ingot.

FIG. 3 is a view showing a weaving hot rolling yield investigated in Example 2.

FIG. 4 is a view showing a typical crack occurrence situation on a rolled surface.

FIG. 5 is a view of a crack observed from a cross section.

[Explanation of symbols]

1-3: Rolled material 4: Part used for hydrogen analysis 10: Ingot 12: Hot water

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Claims (3)

(57) [Claims] 1. Ni: 1.0 to 4.8 wt%, Si: 0.2 to 1.4 wt% as a basic component, the balance is substantially Cu,
Hydrogen concentration is 0.0001% by weight or less, sulfur concentration is 0.0020% by weight
Cu-N with improved annealing cracking characteristics characterized by:
i-Si-based copper-based alloy. 2. The C according to claim 1, which is a material for hot working.
u-Ni-Si-based copper-based alloy. 3. The Cu-Ni-Si-based copper-based alloy according to claim 1, which has a tempered state that is annealed after cold working.