JP4447300B2 - Phosphor bronze strip with excellent bendability - Google Patents

Description

  The present invention relates to a phosphor bronze strip used for electronic parts such as terminals and connectors, which has high strength and good bending workability, and further relates to a terminal, connector or relay using the same.

  In general, copper alloys are used for electronic parts such as terminals, connectors, and relays from the viewpoints of mechanical strength and electrical conductivity, as well as solderability and plating properties. Among them, phosphor bronze has high mechanical strength and superiority. Widely used because of its excellent bending workability.

On the other hand, with the recent progress of remarkable thinning and shortening of electronic parts, thinner materials are required. However, when the thickness is reduced, the contact pressure of the connector is lowered, so that it is necessary to increase the strength of the material. Similarly, along with the high-density mounting of cellular phones and the like, finer processing is performed, so it is necessary to improve workability, particularly bendability.
International Publication WO02 / 053790

  In response to this requirement, it has been reported that bendability is improved by reducing the crystal grain size (WO02 / 053790), but it has not always been possible to stably obtain excellent bendability.

  An object of the present invention is to provide a phosphor bronze strip capable of stably obtaining excellent bendability.

The present inventor investigated the relationship between crystal orientation and bendability with respect to the above problems, and the following knowledge was obtained.
(1) by removing the sample surface by etching, it was measured crystal orientation (plate surface direction) for etching surface of the inner thick. As a result, the phosphor bronze strip, the surface (rolled surface) of the (220) intensity (I S ₍₂₂₀₎₎ is, the internal thickness of the etched surface of the (220) intensity (I C ₍₂₂₀₎₎ that is lower than I found.
(2) Further, if (220) the strength of the etched surface of the internal thickness of the same, the lower the (220) intensity of the surface (rolled surface), it found that good bending properties are obtained. That is, in order to stably obtain excellent bendability, the ratio of I _{S (220)} to I _{C (220)} (I _{S (220)} / I _{C (220)} ) is regulated to a predetermined level or less. I found out that there is a need to do.
(3) phosphorus generally predetermined thickness at final rolling bronze from (t _0), in the course of processing to a predetermined thickness (t), is rolling in multiple passes. I _{C (220)} is determined by the total degree of rolling from t ₀ to t, and I _{C (220)} increases as the total degree of processing increases. On the other hand, _{IS (220)} is affected not only by the total workability but also by various rolling conditions.
a. The smaller the number of rolling times (the higher the degree of processing in one rolling _), the lower the I _{S (220)} .
b. The lower the viscosity of the rolling oil, the lower is I _{S (220)} .
c. The lower the rolling temperature, the lower is _{IS (220)} .
It has been found.
(4) The bendability of the copper alloy strip is usually improved when the rolling degree is lowered. On the other hand, both I _{C (220)} and I _{S (220)} are generally reduced when the rolling degree is lowered. From these two relationships, it has been publicly announced that bending of a copper alloy _strip having a low IS ₍₂₂₀₎ is excellent. However, no bending improvement measures focusing on the ratio of I _{C (220)} and I _{S (220)} have been reported in the past.
(5) In addition to the crystal orientation control in the thickness direction, by refining the crystal grains, better bending properties are obtained. The bendability of phosphor bronze deteriorates as the degree of processing increases. When the crystal grain size is refined, the strength increases due to grain boundary strengthening, so that the bendability is improved because the degree of rolling work for obtaining the strength required for the product can be set low.

As described above, the measures of the crystal orientation control in the thickness direction was now found, by combining the measures of grain refinement has been reported conventionally, so that good bending properties can be stably obtained Became. The phosphor bronze strip of the present invention is suitable as a material for terminals, connectors or relays used in small electronic components, can be manufactured at the same cost as conventional phosphor bronze, and has properties other than strength and bendability. Is equivalent to conventional phosphor bronze, it is extremely useful industrially.

  Details of the present invention will be described below.

Phosphor bronze ratio <br/> present invention (220) intensity of the rolling surface and the thickness etched surface of the central intensity of the (220) plane of the rolled surface (I S ₍₂₂₀₎₎ and a thickness of the central portion The relationship with the strength (I _{C (220)} ) of the etched surface is that I _{S (220)} / I _{C (220)} ≦ 0.8.

When the crystal grain size is the same, the strength of the product has a correlation with the total workability of the final rolling. Moreover, I _{C (200)} has a correlation with the total processing degree in the final rolling. That is, I _{C (220)} is determined by the strength required for the product. On the other hand, I _{S (220)} is defined for the purpose of obtaining good bendability.

In the range of I _{S (220)} / I _{C (220)} > 0.8, the bendability improves as I _{S (220)} decreases. This effect is saturated when I _{S (220)} = 0.8, and the bendability hardly changes even if it is further reduced. Therefore, I _{S (220)} / I _{C (220)} ≦ 0.8 is specified.

Average crystal grain size and maximum crystal grain size The average crystal grain size is set to 2 μm or less. When the average crystal grain size is set to 2 μm or less, the strength increases due to grain boundary strengthening, and a desired strength is obtained with a smaller degree of rolling work. Because it becomes possible. The maximum crystal grain size is set to 10 μm or less because when large crystal grains are localized in small crystal grains, the deformation concentrates on large crystal grains (low stress at which plastic deformation starts) during bending. This is because cracks occur early in large crystal grains. Therefore, it is also important to control the crystal grain size uniformly.

Sn concentration In this invention, Sn concentration is prescribed | regulated in the range of 3.5 to 11%. If the Sn concentration is less than 3.5%, the necessary strength for the terminal / connector material cannot be obtained. If the Sn concentration exceeds 11%, the necessary conductivity for the terminal / connector material cannot be obtained, and the raw material cost increases. There is a problem that Sn segregation of the ingot is increased and productivity is lowered. Therefore, the Sn concentration is determined in consideration of various characteristics required for the material, acceptable cost, and the like.

P concentration P concentration is in the range of 0.03 to 0.35% in accordance with JIS standards and ASTM standards. When the P concentration is too low, deoxidation of the molten metal becomes insufficient when melting phosphor bronze, the viscosity of the molten metal becomes high, and a healthy ingot cannot be manufactured. Further, even if the strip can be manufactured, coarse oxide inclusions are generated, and the bendability is lowered.

When a small amount of the trace alloy elements Mg, Si, Fe, Co, Ni is added, these elements and P form an intermetallic compound, and the intermetallic compound is precipitated and dispersed in the matrix. When intermetallic compounds such as Fe-P are precipitated and dispersed, the strength is increased by precipitation strengthening of the alloy itself, and crystal grains grow due to the pinning effect of the crystal grain boundaries due to residual particles of precipitates or crystallized substances. This makes it difficult to achieve crystal refinement. Moreover, when Zn is added, thermal peeling of tin and solder plating is suppressed.

However, if the addition amount of these elements exceeds 0.5 mass%, (220) a change that cannot be ignored appears and the bending workability deteriorates. Therefore, in the present invention, the total addition amount of these elements is 0.5 mass% or less. It is prescribed.

Since the thickness of the thick <br/> conditions becomes difficult than thicker the fine bending 0.4mm, to limit the thickness of the material to 0.4mm or less.

Sn concentrations of different thicknesses 30 mm, and melted various phosphor bronze ingot width 60 mm. In Table 1, data corresponding to each Sn concentration is divided into groups 1 to 5 and displayed. Next, homogenization annealing is performed at 600 ° C. to 800 ° C. for 0.5 hours to 3 hours in a 75% N ₂ + 25% H ₂ atmosphere, and the reverse segregation of Sn on the surface layer is mechanically removed by 2 mm on the surface, Rolling to 1.3 mm was performed by hot rolling, and the first recrystallization annealing was performed here. After that, each group A and B of the examples shown in Table 1 is further rolled to 0.25 mm by cold rolling, followed by recrystallization annealing so that the crystal grains become fine, and C and D are rolled to 0.3 mm. After that, normal recrystallization annealing was performed, and E was rolled to 0.25 mm and then subjected to normal recrystallization annealing.

  The fine crystal grains after recrystallization annealing were adjusted according to WO02 / 053790.

Next, a 0.2 mm plate was finished by cold rolling. 10cSt viscosity of rolling oil in the cold rolling, the rolling temperature of 25 ° C., the thickness of the annealing raises the by changing the rolling count in the process of rolling up _{0.2mm, I S (220) /} I C ( ₂₂₀₎ was changed. That is,
Group A: Total rolling degree 20%, rolling number 1 time Group B: Total rolling degree 20%, rolling number 3 times Group C: Total rolling degree 33%, rolling number 1 time Group D: Total Rolling degree 33%, rolling times 3 times Group E: Total rolling degree 20%, rolling times 3 times

Subsequently, a bending test and a crystal grain size measurement were performed on the plate material as an evaluation of bendability. Moreover, (220) peak intensity was calculated | required with the X-ray-diffraction apparatus.

In the bending test, badway W-bending (JIS H 3110) was performed at various bending radii, and the minimum bending radius ratio (r (bending radius) / t (test specimen thickness)) at which no crack was generated was obtained.

  The crystal grain size was measured in a cross section parallel to the rolling surface. After the observation surface was finished to a mirror surface by mechanical polishing, crystal grain boundaries were revealed by etching. The average grain size was determined by a method of counting the number of crystal grains that are completely cut by a line segment of a predetermined length according to the cutting method (JIS H 0501, 1999). The average particle size was determined by drawing line segments in the direction parallel to and perpendicular to the rolling direction, and the average of the measured values in both directions was defined as the average particle size. The maximum grain size was defined as the diameter of the smallest circle containing crystal grains.

  (220) The peak intensity was measured using a Rigaku X-ray diffractometer RINT2500, using a Co tube (λ = 1.7889 mm), tube voltage: 30 kV, tube current: 100 mA, divergence slit: 1 °, Divergence length limiting slit: 10 mm, scattering slit: 1 °, light receiving slit: 0.3 mm, monochrome light receiving slit 0.8 mm, scanning speed 7 ° / min, step width 0.05 °, scanning axis: 2θ / θ, scanning range : Measurement was performed under conditions of 83 ° to 93 °, and after smoothing and background removal, the maximum intensity in the measurement range was defined as the (220) peak intensity.

Table 1 shows the evaluation results of each sample. Each group A in the examples was prepared by adjusting both the crystal grain size and the (220) peak intensity, and it can be seen that all have good bendability. On the other hand, each group B of the examples was only adjusted for the crystal grain size (220), and the bendability was slightly inferior because the ratio of peak intensities was the same. In addition, each group C in the examples was only adjusted for the (220) peak intensity, and the bendability was slightly inferior because the average crystal grain size and the maximum crystal grain size were large. For each group D of the examples, the strength is the same as that of the invention example, but the bendability is the worst because the crystal grain size and (220) peak intensity are not adjusted. The bendability of each group E in the examples is equal to that of the invention example, but the crystal grain size and (220) peak intensity are not adjusted, so that the desired strength is not obtained.

Claims (3)

Sn the 3.5～11Mass%, a P containing 0.03～0.35Mass%, balance being phosphor bronze strip consisting of Cu and unavoidable impurities, and the average crystal grain size in this rolling surface at 2μm or less The maximum crystal grain size is 10 μm or less, and the (220) plane peak intensity (I _{S (220)} ) measured on the rolled surface by X-ray diffraction and one side of the rolled surface are etched away to the center of the thickness. The relationship with the peak intensity (I _{C (220)} ) of (220) plane measured for
I _{S (220)} / I _{C (220)} ≦ 0.8
A phosphor bronze strip excellent in bendability characterized by being. 0.05 to 0.5 mass in total of at least one selected from Sn to 3.5 to 11 mass%, P to 0.03 to 0.35 mass % , Mg, Si, Fe, Co, Ni, and Zn The balance is phosphor bronze strips composed of Cu and inevitable impurities, the average crystal grain size on this rolled surface is 2 μm or less and the maximum crystal grain size is 10 μm or less, and measured on the rolled surface by X-ray diffraction. (220) peak intensity (I S ₍₂₂₀₎₎ of the surface and removed by etching to a thickness of the central portion of one side of the rolling plane, the peak intensity of the measured for etching surface (220) plane (I C ₍₂₂₀₎₎ Relationship
I _{S (220)} / I _{C (220)} ≦ 0.8
A phosphor bronze strip excellent in bendability characterized by being. A terminal, connector, or relay using the phosphor bronze strip according to claim 1 or 2.