TWI599665B - LED lead frame with copper alloy strip - Google Patents

Description

Copper lead strip for LED lead frame

The present invention relates to, for example, copper alloy slats (plates and strips) used as lead frames for LEDs and copper alloy slats having Ag-coated films.

In recent years, a light-emitting device using a light-emitting diode (LED) as a light source has been widely used in a wide range of fields due to energy saving and long life. The LED element is fixed to a copper alloy lead frame excellent in thermal conductivity and electrical conductivity, and assembled in a package. In order to efficiently extract light emitted from the LED element, an Ag plating film is formed on the surface of the copper alloy lead frame as a reflection film. Since the LED package is used as a backlight for illumination and personal computers and mobile phones, illumination and a brighter picture are required, and the demand for higher brightness of the LED package is also increasing.

In order to increase the brightness of the LED package, there is a method of increasing the luminance of the LED element itself and a method of improving the quality of the Ag plating film (high reflectance). However, the high luminance of LED elements is approaching the limit, but a slight increase in brightness will result in a significant increase in component cost. Therefore, in recent years, the demand for high reflectance of the Ag plating film is also stronger. As a copper alloy for a lead frame which is subjected to an Ag plating treatment, a polishing and polishing product having an arithmetic mean roughness Ra of about 0.08 μm and a purified rolled product having an arithmetic mean roughness Ra of about 0.06 μm have been conventionally used. However, the reflectance after the Ag plating treatment is at most about 91%, and it is still required to have a higher reflectance.

On the other hand, the high-intensity LED, which is mainly used for illumination, is unexpectedly large in heat, which dissipates the LED element itself and the surrounding resin, so that it does not damage the long life of the LED. Special attention is paid to the heat dissipation measures of LED components. As a copper alloy for a lead frame of an LED, C194 having a strength of 450 MPa and a conductivity of about 70% IACS is often used (refer to Patent Documents 1 and 2).

[Previous Technical Literature]

Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-252215

Patent Document 2: Japanese Laid-Open Patent Publication No. 2012-89638 (paragraph 0058)

An object of the present invention is to improve the reflectance of an Ag-plated reflective film formed on a surface of a C194 slat which is mostly used as a copper alloy for a lead frame of an LED to achieve high brightness of the LED package. Chemical.

In order to improve the reflectance of the Ag-plated reflective film, it is considered to reduce the surface roughness of the lead frame material, that is, the copper alloy strip, but only by doing so, the reflectance of the Ag-plated reflective film cannot be improved. According to the inventors' inventors, fine defects such as oil pits and strip-like lines are formed on the surface of the copper alloy strip during cold rolling, or a work-affected layer is formed by grinding and polishing, which is to be plated. The surface roughness, crystal grain diameter, and the like of the Ag reflective film affect the reflectance of the Ag-plated reflective film. The present invention has been developed based on this novelty.

The copper alloy strip (plate and strip) for the lead frame of the LED of the present invention contains Fe: 1.8 to 2.6% by mass, P: 0.005 to 0.20% by mass, Zn: 0.01 to 0.50% by mass, and the rest is Cu and not Cu-Fe-based copper alloy slab composed of impurities to be avoided, if necessary, contains 0.02 to 0.3% by mass of one or two of Sn, Co, Al, Cr, Mg, Mn, Ca, Pb, Ni, Ti, and Zr. More than one species. The copper alloy strip has a surface roughness in the vertical direction of the rolling, an arithmetic average roughness Ra of less than 0.06 μm, a ten-point average roughness R _{zJIS of} less than 0.5 μm, and an atomic force microscope (AFM: Atomic Force Microscope) on the roll. The area of the trough portion in the range of 50 μm in the roughness curve (AFM profile) obtained by rolling in the vertical direction is 1.3 μm ² or less, and the thickness of the work-affected layer composed of fine crystal grains on the surface is 0.5 μm or less.

In the copper alloy strip of the present invention, the surface roughness of the Ag-plated reflective film formed on the surface can be ten points average roughness R _zJIS : 0.3 μm or less, and as a result, the reflectance of the Ag-plated reflective film can be improved. When it is 92% or more, the brightness of the LED package can be increased.

Fig. 1 is an AFM profile (AFM profile) showing the surface state of the copper alloy strip of Test No. 1.

Fig. 2 is an AFM profile showing the surface state of the copper alloy strip of Test No. 15 of the Example.

Next, the present invention will be more specifically described.

(Chemical composition of copper alloy)

The copper alloy of the present invention contains Fe: 1.8 to 2.6% by mass, P: 0.005 to 0.20% by mass, and Zn: 0.01 to 0.50% by mass, and the balance is composed of Cu and unavoidable impurities, and contains 0.02 to 0.3 mass in total as needed. One or two or more of Sn, Co, Al, Cr, Mg, Mn, Ca, Pb, Ni, Ti, and Zr.

In the above copper alloy, Fe forms a compound with P, and has an effect of improving strength and electrical conductivity characteristics. However, when the content of Fe is more than 2.6% by mass, Fe which is not completely dissolved at the time of melting remains as a precipitate, and the larger particle diameter of the precipitate is also several tens of μm or more, which is in the copper alloy strip. The surface is exposed, which causes a defect in the Ag plating film. In addition, when the content of Fe is less than 1.8% by mass, it cannot be obtained as an LED. The required strength of the lead frame. On the other hand, when the content of P is more than 0.2% by mass, the thermal conductivity and electrical conductivity of the lead frame for LEDs are deteriorated. When the content is less than 0.005% by mass, the strength required for the frame for LEDs cannot be obtained. Therefore, the content of Fe is set to 1.8 to 2.6% by mass, and the content of P is set to be 0.005 to 0.20% by mass.

Zn has an effect of improving the heat-resistant peeling property of the solder, and has a function of maintaining solder joint reliability when the LED package is assembled to the chassis. However, when the content of Zn is less than 0.01% by mass, it is not sufficient to meet the heat-resistant peeling resistance of the solder, and if it is more than 0.50% by mass, the electrical conductivity and thermal conductivity of the copper alloy are deteriorated.

As an accessory component, Sn, Co, Al, Cr, Mg, Mn, Ca, Pb, Ni, Ti, and Zr added as needed may also improve the strength and heat resistance of the copper alloy, and may also improve hot rolling during production. The role of sex. In order to obtain the aforementioned effects by adding these elements to the copper alloy, it is preferred to contain 0.02% by mass or more. However, if these components are contained in a total amount of more than 0.3% by mass, the thermal conductivity and the electrical conductivity are deteriorated. Therefore, when these subcomponents are added, the content thereof is set to be 0.02 to 0.3% by mass in total.

(surface properties of copper alloy strips)

As the material to be plated, that is, the surface property of the copper alloy plate, specifically, the area of the valley in the surface roughness and roughness curve, and the thickness of the work-affected layer formed on the surface, all affect the Ag-plated reflection. The reflective properties of the film.

The surface roughness of the copper alloy strip is set to: the arithmetic mean roughness Ra in the direction in which the surface roughness is maximized (usually the vertical direction of the rolling): less than 0.06 μm, ten-point average roughness R _zJIS : lower than 0.5 μm. The arithmetic mean roughness Ra and the ten point average roughness R _zJIS were measured according to the method specified in Japanese Industrial Standard JIS B0601:2001. When the arithmetic mean roughness Ra is 0.06 μm or more, or the ten-point average roughness R _{zJIS is} higher than 0.5 μm, the surface roughness of the Ag-plated reflective film is increased, and the reflectance of the Ag-plated reflective film cannot be made 92% or more. . The arithmetic mean roughness Ra and the ten point average roughness R _zJIS were obtained from the roughness curve (AFM profile) obtained by atomic force microscopy (AFM) measurement in the vertical direction of the rolling.

The area of the trough portion in the roughness curve, more specifically, the area of the portion between the X-axis (average line) of the AFM profile obtained by measuring in the vertical direction of the roll and the curve located on the lower side of the X-axis. . According to the inventors of the present invention, the area of the trough portion obtained from the AFM profile has a correlation with the reflectance of the Ag-plated reflective film formed on the surface of the copper alloy sheet. In the present invention, the area of the trough portion in the range of 50 μm (X-axis length) of the AFM profile is set to 1.3 μm ² or less. When the area of the trough portion is higher than 1.3 μm ² , the Ag-plated reflective film is likely to be recessed or the like, and the reflectance of the Ag-plated reflective film cannot be made 92% or more. The reason for this is presumed to be that if the area of the valley portion of the roughness curve of the surface of the copper alloy strip is increased, the Ag-plated reflective film is likely to have irregularities. The length of the trough portion 50μm area range of the AFM profile of 1.0μm ² or less is better. Further, the area of the trough portion can be reduced to about 0.5 μm ² by using a production method to be described later. Also, by using an atomic force microscope (AFM), a finer surface morphology can be measured as compared with the measurement by a conventional stylus type roughness meter.

On the surface of the cold-rolled copper alloy strip, sequentially formed from the surface are: (1) amorphous Beilby layer; (2) fiber and fine layer (fine grain layer (3) elastic strain layer. In general, these three layers are collectively referred to as a processing metamorphic layer. On the other hand, in the present invention, in particular, the above (1) and (2) are collectively referred to as "a work-affected layer composed of fine crystal grains". The layers of the above (1) and (2), and the layer and the base material of the above (3) are easily recognized because the grain structure is significantly different. The affected layer affects the properties of the Ag-plated reflective film. If the total thickness of the processed metamorphic layer composed of the fine crystal grains (the layers of the above (1) and (2)) is higher than 0.5 μm, the Ag-reflected film is plated. The surface roughness will increase, and the reflectance of the Ag-plated reflective film cannot be made 92% or more. Therefore, the thickness of the work-affected layer composed of fine crystal grains is set to 0.5 μm or less. The thickness of the work-affected layer is preferably 0.3 μm or less. Further, in the copper alloy slab which has been subjected to grinding after the final cold rolling, the thickness of the work-affected layer composed of fine crystal grains is much higher than 0.5 μm.

(Ag plating film)

The surface morphology of the Ag-plated reflective film is largely affected by the surface properties of the copper alloy strip as a material. When the surface properties of the copper alloy strip (surface roughness, the area of the trough portion in the roughness curve, and the thickness of the work-affected layer formed on the surface) fall within the above range, the surface roughness of the Ag-plated reflective film can be made. Ten point average roughness, falling below R _zJIS : 0.3 μm. The reflectance of the Ag-plated reflective film is generally considered to be affected by the grain diameter of the Ag-plated reflective film and the orientation of the coating. When the surface roughness of the Ag-plated reflective film is set to ten-point average roughness R _zJIS : 0.3 μm or less, the crystal grain diameter of the Ag-plated reflective film can be 13 μm or more, and the coating orientation ((001) orientation) is 0.4. As described above, the reflectance of the Ag-plated reflective film can be increased to 92% or more. On the other hand, when the ten-point average roughness R _{zJIS of the} Ag-plated reflective film is higher than 0.3 μm, the crystal grain diameter of the Ag-plated reflective film cannot be 13 μm or more, or the orientation of the coating film ((001) orientation) is 0.4. As described above, the reflectance of the Ag-plated reflective film cannot be increased to 92% or more.

(Manufacturing method of copper alloy strip)

The C194 copper alloy strip is usually produced by subjecting the ingot to surface turning, hot rolling, hot rolling, quenching or solution treatment, followed by cold rolling and precipitation annealing, followed by final cold rolling. The cold rolling and precipitation annealing are repeated as needed, and after the final cold rolling, low temperature annealing is performed as needed. In the case of the copper alloy slab of the present invention, it is not necessary to significantly change the manufacturing process itself. On the other hand, coarse Fe, Fe-P, and Fe-PO particles are mainly formed during melt casting and hot rolling, and cause the increase in the area of the valley portion in the roughness curve of the surface of the copper alloy strip product. Therefore, it is necessary to select suitable conditions for melt casting and hot rolling. Specifically, it is as follows.

In the melt casting, Fe is added to a molten copper alloy of 1200 ° C or higher to be melted, and thereafter, the temperature of the melt is maintained at 1200 ° C or higher to carry out casting. In order to prevent coarse Fe particles and Fe-based inclusion particles from entering the ingot, it is effective to completely melt the added Fe, prevent oxidation of iron by controlling the gas phase atmosphere during melting, and melt the casting. Liquid filtration. The cooling of the ingot is carried out at a cooling rate of 1 ° C /sec or more during solidification (when solid-liquid coexisting) and after solidification. For this reason, in the case of continuous casting or semi-continuous casting, it is necessary to sufficiently cool the primary cooling in the casting mold and the secondary cooling directly under the casting mold. In the hot rolling, the homogenization treatment is carried out at 900 ° C or higher, more preferably at a temperature of 950 ° C or higher, and hot rolling is started at this temperature, and the hot rolling end temperature is set to 650 ° C or higher, more preferably 700 ° C or higher, hot rolling. Immediately after the completion, the water was rapidly cooled to 300 ° C or less with a large amount of water.

After the precipitation annealing, in order to remove the oxide formed on the surface of the material, the surface of the material is generally mechanically polished. At this time, when the stripe-shaped unevenness (abrasive mark) is introduced into the surface of the material, and then the final cold rolling is performed, the unevenness is crushed, and the strip-like grain is likely to remain on the product (copper alloy strip). Due to the strip-like texture, the above-mentioned surface roughness of the copper alloy strip and the area of the trough portion in the roughness curve of the surface cannot be met. Therefore, it is preferable that the mechanical polishing is not performed after the precipitation annealing. should. Precipitation annealing is performed in a reducing gas phase atmosphere so that an oxide film is not formed on the surface of the material during annealing, and mechanical polishing performed after precipitation annealing can be omitted.

The surface roughness of the copper alloy strip is formed by transferring the surface shape of the roll to the surface of the material in the final cold rolling. Since the surface roughness (arithmetic mean roughness Ra and ten point average roughness R _zJIS ) of the copper alloy strip of the present invention is extremely small, the final cold rolled roll needs to correspond to the surface roughness of the target copper alloy strip. Mirror polishing. As the roll, a high speed steel roll made of super steel or a tantalum nitride type roll such as SIALON is preferably used. Among them, the Sialon ceramic roll has a Vickers hardness of about 1600, and can stably transfer the surface morphology of the roll to the surface of the material. Further, the surface roughness (arithmetic mean roughness Ra) of the surface of the copper alloy sheet before the final cold rolling is preferably 0.20 μm or less.

As the rolling conditions for the final cold rolling, it is necessary to appropriately combine: the lubricating oil, the number of revolutions of the rolls, the rolling reduction ratio, and the tensile tension (tension at the outlet side of the roll), and can be produced by performing the final cold rolling in accordance with the following conditions. A copper alloy strip having a desired surface property (surface roughness, trough area in a roughness curve, and a work-affected layer).

As the lubricating oil to be finally cold-rolled, a paraffin-based lubricating oil having a light transmittance of 90% or more with respect to incident light having a wavelength of 550 nm is used, and it is preferable to carry out rolling at a temperature of about 40 °C. In addition, the transmittance refers to the relative transmittance of the lubricating oil when the transmittance of xylene to incident light having a wavelength of 550 nm is 100%. By using the lubricating oil, the formation of the oil sump can be suppressed.

Final cold rolling, a roll diameter of about 20 ~ 100mm rolls, the rotational speed is set roll was 200 ~ 700mpm, the drawing tension (outlet-side tension) is set to 50 ~ 200N / mm is about ^2, single pass or Multi-pass pass, and the total processing rate is 20~70% cold rolling. In the final cold rolling, if the pass is performed in multiple passes, it is preferable to set the thickness of the roll after the second pass to be smaller than the thickness of the roll of the first pass, and after the second pass. The rolling speed is set to be slower than the rolling speed of the first pass. The method has the advantages of slow rotation speed, small tensile tension and large rolling reduction, and it is possible to transfer the roll well to the surface of the material, and to ensure a small and stable surface roughness and roughness curve on the copper alloy strip. The area of the trough is also reduced. However, if the rolling reduction ratio is large, it is easy to form a work-affected layer. On the other hand, the rotation speed of the rolls is fast, the tensile tension is large, and the reduction ratio is small, which tends to be opposite. The processing rate of the final cold rolling is determined according to the mechanical properties as the target.

(Manufacture of lead frame for LED)

The lead frame for LEDs is produced by subjecting copper alloy strips (product strips) after final cold rolling to Ag plating, and then forming a lead frame pattern by punching. Alternatively, the lead frame pattern is formed by punching or etching the copper alloy strip (product strip) after the final cold rolling, and then an Ag plating treatment is performed.

[Example 1]

Using a small electric furnace, the copper alloy (alloy No. 1 to 24) of the composition shown in Tables 1 and 2 was melted in the atmosphere under the cover of charcoal, and melted to a thickness of 50 mm, a width of 80 mm, and a length of 180 mm. Ingot. 5 mm surface turning for each of the surface and the back surface of the ingot to be produced Thereafter, the mixture was homogenized at 950 ° C for 1 hour, and then hot rolled to form a sheet having a thickness of 12 mm, and was rapidly cooled from a temperature of 750 ° C or higher. Surface turning of about 1 mm was performed on the front and back surfaces of the sheet. These sheets were repeatedly cold rolled and subjected to precipitation annealing at 500 to 550 ° C for 2 to 5 hours, and then a 50 mm diameter Sialon ceramic roll after mirror polishing was used to carry out final cold rolling at a processing rate of 40%. A copper alloy strip having a thickness of 0.2 mm was produced. In the final cold rolling, the aforementioned lubricating oil is used, and the rotational speed and tensile tension of the rolls fall within the aforementioned ranges.

Test materials were taken from each of the produced alloy sheets, and various measurement tests of tensile strength, electrical conductivity, and solder heat-resistant peelability were carried out in accordance with the following procedures. The measurement results are shown in Tables 1 and 2.

(Measurement of tensile strength)

A Japanese Industrial Standard JIS No. 5 test piece having a longitudinal direction parallel to the rolling direction was taken from the test piece, and a tensile test was carried out in accordance with the specifications of Japanese Industrial Standard JIS Z2241, and the tensile strength was measured. Those with tensile strength above 400 MPa are acceptable.

(Measurement of conductivity)

The electrical conductivity was measured in accordance with the regulations of Japanese Industrial Standard JIS H0505. Conductivity above 65% IACS is acceptable.

(Measurement of solder heat-resistant peelability)

The soldering method is a test in which a commercially available Sn-3 mass% Ag-0.5 mass% Cu solder is kept at 260 ° C to keep the solder in a molten state, and then the surface is cleaned to a length of 10 mm × 35 mm. The sheet was immersed in molten solder under the conditions of a soaking speed of 25 mm/sec, a soaking depth of 12 mm, and a soaking time of 5 seconds. As the soldering device, a solderer (type SAT5100) was used. Flux uses an active flux. The test piece after the soldering was subjected to a heating test at 175 ° C for 72 hours in the air. Further, for these heated test pieces, the bending and reverse folding test were performed at normal temperature. In the reverse foldback section, the sticker sold on the market After the tape, the tape was peeled off from the test piece. The tape after the peeling was visually observed, and if it was not confirmed that the solder was peeled off, it was evaluated as pass (○), and when it was confirmed that the solder was peeled off, it was evaluated as unacceptable (×).

As shown in Table 1, the alloy composition of Alloy Nos. 1 to 13 conforms to the regulations of the present invention, and has high tensile strength, high electrical conductivity, and excellent heat resistance and peelability of the solder, and is suitable for use as a copper alloy for lead frames of LEDs. .

On the other hand, as shown in Table 2, the content of any one of Fe, P, Zn or a subcomponent is deviated from the alloy Nos. 14 to 24 specified in the present invention, and the tensile strength, electrical conductivity, and solder heat-resistant peelability are One or more of the characteristics are poor. The Fe content of Alloy Nos. 14 and 20, the P content of Alloy No. 16, the Zn content of Alloy No. 18, and the total content of the subcomponents of Alloy Nos. 22 to 24 were all excessive, and the electrical conductivity was low. The Fe content of Alloy No. 15 and the Fe and P contents of No. 21 were small, respectively, and the tensile strength was insufficient. No. 17 has a small P content and a poor electrical conductivity. Alloy No. 19 has a small Zn content and is inferior in solder heat-resistant peelability.

[Example 2]

A copper alloy (alloy No. 1) having the composition shown in Table 1 was melted in a small electric furnace under the cover of charcoal in the atmosphere, and melted to obtain an ingot having a thickness of 50 mm, a width of 80 mm, and a length of 180 mm. The surface and the back surface of the produced ingot were subjected to surface turning of 5 mm, and then homogenized at 950 ° C for 1 hour, followed by hot rolling to form a sheet having a thickness of 12 mm, and the temperature was rapidly increased from 750 ° C or higher. cool down. Further, the surface of the sheet and the back surface were separately turned by about 1 mm. For these boards The material is repeatedly subjected to cold rolling and precipitation annealing at 500 to 550 ° C for 2 to 5 hours, and then the surface of the plate is mechanically ground (test No. 1 to 5) or not polished (test No. 6, 7). A copper alloy strip having a surface roughness (arithmetic average roughness Ra) as shown in Table 3 was obtained.

The measurement of the surface roughness (arithmetic mean roughness Ra) of the copper alloy strip (before final cold rolling) was carried out in accordance with the following procedure. The results are shown in Table 3.

(Measurement of surface roughness)

The surface of the test material was observed in the vertical direction of the roll using an atomic force microscope (AFM) using a test material taken from a copper alloy strip before final cold rolling (No. 1 to 5 was after grinding) to obtain a roughness curve. (AFM profile), the arithmetic mean roughness Ra is obtained from the AFM profile.

Next, any one or more of three Sialon ceramic rolls (roll A, roll B, and roll C) having a surface roughness of 50 mm having various surface roughnesses are processed by mirror polishing in one or more passes. Cold rolling was carried out to prepare a copper alloy strip having a thickness of 0.2 mm. In the case of performing multi-pass rolling, the roller A is used in the first pass, the roller B is used in the second pass, and the roller C is used in the third pass. The Sialon ceramic rolls used in the final cold rolling were indicated by ○ marks in Table 3. In addition, Table 3 also shows the total processing rate of the final cold rolling and the type of lubricating oil. The rotational speed and tensile tension of the rolls, as well as the transmittance of the lubricating oil, fall within the aforementioned ranges. Further, the surface roughness (arithmetic average roughness Ra of the roll axis direction) of the three Sialon ceramic rolls is reduced in the order of the rolls A, B, and C, and all of them are compared with the final cold rolling. The surface roughness (arithmetic mean roughness Ra) of the plate is smaller.

The surface roughness (arithmetic mean roughness Ra and ten point average roughness R _zJIS ) of the copper alloy strip after the final cold rolling, and the valley of the range of 50 μm in the roughness curve (AFM profile) were carried out in the following manner. Measurement test of the area. These results are shown together in Table 3.

(Measurement of surface roughness)

Using the test piece taken from the copper alloy strip after the final cold rolling, the surface state of the test piece was observed in the vertical direction of the roll using an atomic force microscope (AFM), and a roughness curve (AFM profile) was obtained, which was obtained from the AFM profile. Arithmetic mean roughness Ra and ten point average roughness R _zJIS .

(measurement of the area of the trough)

The area of the trough portion in the range of 50 μm in length of the X-axis (average line) of the AFM profile was measured based on the measured AFM profile of the surface roughness. The area of the trough portion refers to the area of the portion between the X-axis (average line) of the AFM profile and the curve on the lower side of the X-axis. The AFM outline of Test No. 1 is shown in Fig. 1.

As shown in Table 3, in the copper alloy sheets of No. 1, 2, 4, and 6, the surface roughness before the final cold rolling was relatively small (arithmetic average roughness Ra ≦ 0.20 μm), and the total processing rate of the final cold rolling was as follows. Larger (processing rate ≧ 20%). The copper alloy sheets of Nos. 1, 2, 4, and 6 have surface roughness (arithmetic average roughness Ra and ten point average roughness R _zJIS ) and a trough portion area in accordance with the regulations of the present invention.

On the other hand, in the copper alloy sheets of No. 3 and 7, the total processing rate of the final cold rolling is small (processing rate < 20%), and the copper alloy sheet of No. 5 has a relatively large surface roughness before final cold rolling (arithmetic The average roughness Ra>0.20 μm). In the copper alloy sheets of Nos. 3, 5, and 7, the surface roughness (arithmetic average roughness Ra and ten point average roughness R _zJIS ) and the area of the trough portion are larger than the specifications of the present invention.

[Example 3]

Using a small electric furnace, in the atmosphere, under the cover of charcoal, the copper alloys (alloy No. 1, 2, 3, 12, 15, 24) of the compositions shown in Tables 1 and 2 are melted and melted to a thickness. Ingot of 50mm, width 80mm and length 180mm. For the surface and back of each of the above-mentioned ingots produced After 5 mm surface turning, the mixture was homogenized at 950 ° C for 1 hour, and then hot rolled to form a sheet having a thickness of 12 mm, and was rapidly cooled from a temperature of 750 ° C or higher. Surface turning of about 1 mm was performed on the front and back surfaces of the sheet. These sheets were repeatedly cold rolled and subjected to precipitation annealing at 500 to 550 ° C for 2 to 5 hours, and then a 50 mm diameter Sialon ceramic roll after mirror polishing was used to carry out final cold rolling at a processing rate of 40%. A copper alloy strip having a thickness of 0.2 mm was prepared as a test material. In the final cold rolling, the number of passes, the surface roughness of the Sialon ceramic rolls in the final and intermediate passes, and the rotational speed of the rolls were obtained to obtain copper alloy strips with various surface roughness (test in Table 4). No.8~28). Further, only for Test No. 15, the surface of the copper alloy sheet was mechanically polished after the final cold rolling.

A test material was taken from each of the prepared copper alloy strips, and the surface roughness (Ra, R _zJIS ) and the measurement of the area of the trough portion were carried out in accordance with the method described in the above [Example 2]. The AFM outline of Test No. 15 is shown in Fig. 2. Further, a test for measuring the thickness of the affected layer was carried out in accordance with the following procedure. The results of these measurements are shown in Table 4.

(Measurement of thickness of processing metamorphic layer)

A cross section (length: 20 mm) parallel to the rolling direction and the thickness direction was cut out from each of the test materials as an observation sample. With respect to each of the observation samples, the cross section was observed by SEM (scanning electron microscope) at a magnification of 40,000 times, and the maximum value of the thickness of the work-affected layer composed of fine crystal grains at each observation portion was determined, and this was regarded as the sample. The thickness of the processed metamorphic layer consists of "fine grains". Further, when the thickness of the work-affected layer is about 0.1 μm or less, since the thickness cannot be accurately measured, it is indicated by "-" in the column of the thickness of the work-affected layer in Table 4.

Next, the prepared copper alloy strip was subjected to Ag plating treatment under the following conditions, and the Ag plating material was subjected to the following methods: surface roughness, Ag plating orientation, Ag coating diameter, and reflection. Rate, measurement test of brightness after packaging and assembly. The measurement results are shown in Table 4.

(Ag plating conditions)

Each copper alloy strip was subjected to electrolytic degreasing (5 Adm ² × 60 seconds), pickling (20% by mass sulfuric acid × 5 seconds), and after 0.1 to 0.2 μm thick Cu flash plating, an Ag plating treatment having a thickness of 2.5 μm was performed. The composition of the Ag plating solution is as follows. Ag concentration: 80 g/L, free KCN concentration: 120 g/L, potassium carbonate concentration: 15 g/L, additive (trade name: Ag20-10T (manufactured by Metalor Technology Co., Ltd.)): 20 ml/L.

(Measurement of surface roughness of Ag plated material)

Using the produced Ag-plated material, the surface state of the test _{piece was} observed in the vertical direction by rolling using AFM, and a surface roughness curve (AFM profile) was obtained, and a ten-point average roughness R _{zJIS was} obtained from the AFM profile.

(Measurement of the orientation of the Ag-coated film and the particle size of the Ag-coated film)

The orientation of the Ag plating film and the particle size of the Ag plating film were measured by EBSD (Electron Backscatter Diffraction) analysis using the prepared Ag plating material. The EBSD analysis was carried out using MSC-2200 manufactured by TSL Corporation to measure steps: 0.2 μm, measurement area: 60 × 60 μm. Further, when the average particle diameter (equivalent circle diameter) of the Ag plating film is obtained, and the difference in orientation between adjacent measurement points is 5 or more, it is regarded as a grain boundary of the Ag plating film, and the grain boundary is The completely enclosed area is a grain.

(Measurement of reflectance of Ag plated material)

The total reflectance (positive reflectance + diffuse reflectance) of the produced Ag-plated material was measured using a spectrophotometer CM-600d manufactured by Konica Minolta. Those with a total reflectance of 92% or more are considered qualified.

(Measurement of brightness after package assembly)

The LED package was assembled using the produced Ag plating material, and the LED package was placed in a small integrating sphere to measure the total luminous flux. The size of the small integrating sphere is: Model made by Spectra Co., Ltd.: SLM series, size 10 inches. The brightness after packaging and assembly is 2.05 lm or more.

As shown in Table 4, Test Nos. 8 to 14, 20, 22, and 24, the alloy composition, the surface roughness (Ra, R _zJIS ) of the copper alloy sheet, the thickness of the work-affected layer, and the area of the concave portion are in accordance with the present invention. It is prescribed that the reflectance after Ag plating is 92% or more, and the brightness (total luminous flux) after package assembly is 2.05 lm or more. Ag plating material which surface roughness _R zJIS are 0.3μm or less, Ag plating film orientation ((001) orientation) of 0.4 or more, the crystal grain size of the Ag plating film of 13μm or more.

On the other hand, the alloy composition is in accordance with the provisions of the present invention, but one of the surface roughness (Ra, R _zJIS ), the thickness of the work-affected layer, and the area of the trough portion of the copper alloy sheet does not conform to the test No. specified in the present invention. .15~19, 21, 23, 25, the reflectance after Ag plating and the brightness (total luminous flux) after package assembly are poor. The surface roughness R _{zJIS of the} Ag-plated material is higher than 0.3 μm, the orientation of the Ag-coated film ((001) orientation is less than 0.4, and the grain diameter of the Ag-coated film is less than 13 μm.

The alloy composition does not conform to the provisions of the present invention, but the surface roughness (Ra, R _zJIS ) of the copper alloy sheet, the thickness of the work-affected layer, and the area of the trough portion conform to the test No. 26 and 28 of the present invention, and the Ag plating is performed. The reflectance after that was 92% or more, and the brightness (total luminous flux) after package assembly was 2.05 lm or more. The surface roughness R _zJIS of the Ag plating material is 0.3 μm or less, the orientation of the Ag plating film ((001) orientation) is 0.4 or more, and the crystal grain diameter of the Ag plating film is 13 μm or more.

The alloy composition and the surface roughness (Ra, R _{zJIS) of the} copper alloy sheet did not conform to Test No. 27 of the present invention, and the reflectance after Ag plating and the brightness (total luminous flux) after package assembly were inferior. In addition, Ag plating a surface roughness _R zJIS material is higher than 0.3 m Test No.27, Ag plating film orientation ((001) orientation) is less than 0.4, Ag-plated film grain diameter of less than 13μm.

Claims (5)

A copper alloy strip for a lead frame of an LED, characterized in that it contains Fe: 1.8 to 2.6% by mass, P: 0.005 to 0.20% by mass, Zn: 0.01 to 0.5% by mass, and the balance is composed of Cu and unavoidable impurities. The surface roughness is: the arithmetic mean roughness Ra is less than 0.06 μm, the ten-point average roughness R _{zJIS is} less than 0.5 μm, and the length of the obtained roughness curve is measured in the range of 50 μm in the vertical direction by the atomic force microscope. The area of the trough portion is 1.3 μm ² or less, and the thickness of the work-affected layer composed of fine crystal grains on the surface is 0.5 μm or less. A copper alloy strip for a lead frame of the LED according to claim 1, wherein the total of 0.02 to 0.3% by mass of Sn, Co, Al, Cr, Mg, Mn, Ca, Pb, Ni, Ti, and Zr is contained. One or two or more. A copper alloy strip having an Ag-plated coating, characterized in that the surface of the copper alloy strip according to claim 1 or 2 is subjected to an Ag plating treatment, and is measured in the vertical direction of the rolling of the copper alloy strip. The surface roughness is: ten point average roughness R _zJIS is 0.3 μm or less. A lead frame for LEDs is produced by punching a copper alloy strip having an Ag-plated film according to claim 3. A lead frame for LEDs is produced by punching or etching a copper alloy strip according to claim 1 or 2, and then performing an Ag plating process, and measuring the vertical direction of the rolled copper alloy strip. have a surface roughness: _R zJIS ten point average roughness of 0.3μm or less.