A copper-iron alloy strip for lead frame and a method for manufacturing the same

Abstract

The application relates to a copper-iron alloy strip for a lead frame, which comprises, in percentage by mass: P 0.010wt%-0.100wt%; Fe 2.0wt%-3.0wt%; RE 0.005wt%-0.05wt%; Cu and impurities; wherein the RE is selected from La or / and Ce. The copper-iron alloy strip for the lead frame of the application controls the particle size of the Fe3P second phase by controlling the mass percentage of P and Fe elements, and refines the grain by adding La elements or / and Ce elements; and the preparation method of the application can significantly reduce the surface roughness and gloss of the strip, thereby meeting the performance parameter requirements for application to the lead frame.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper alloy, in particular to a copper-iron alloy strip for lead frame and a preparation method thereof. BACKGROUND

[0002] The copper-iron alloy has high strength, good electrical conductivity, good thermal conductivity, electroplating property and high-temperature softening resistance, but has the following problems: firstly, the copper-iron alloy with high iron content (for example, C19400) has a large tolerance fluctuation in the rolling process due to the existence of iron-rich phase, so that the final strip has poor plate shape and uneven performance, which is not conducive to subsequent etching processing; secondly, the surface roughness and glossiness of the copper-iron alloy strip obtained by processing are high due to unreasonable design of the roughness of the roller in the rolling process or unreasonable design of the cleaning brush roller pitch and ratio in the cleaning process, which affects the plating strength and uniformity of the subsequent electroplated product.

[0003] The copper-iron alloy strip is the mainstream base material of the lead frame at present, and the surface roughness and glossiness of the base material directly affect the effect of the lead frame in etching and electroplating processing; the lead frame is the carrier of various electronic integrated circuits and an important medium for connecting internal electronic elements such as chips and external wires in the integrated circuit, and the effect of the lead frame in etching and electroplating processing affects the quality of the final product.

[0004] Therefore, there is an urgent need for a copper-iron alloy strip for lead frame and a preparation method thereof. SUMMARY

[0005] The present application aims at the deficiencies in the prior art and provides a copper-iron alloy strip for lead frame and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] The first aspect of the present application is to provide a copper-iron alloy strip for lead frame, which comprises, by mass percentage:

[0008] P0.010wt%~0.100wt%;

[0009] Fe2.0wt%~3.0wt%;

[0010] RE0.005wt%~0.05wt%;

[0011] Cu and impurities in balance;

[0012] Wherein, the RE is selected from La or / and Ce.

[0013] Preferably, the lead frame copper-iron alloy strip comprises a Fe3P second phase with a particle size of 100nm-200nm.

[0014] By controlling the mass percentage of P element and Fe element, the particle size of the Fe3P second phase formed after the cold rolling treatment and annealing treatment of the lead frame copper-iron alloy strip is controlled, thereby improving the tensile strength and high-temperature softening resistance of the strip; specifically, the Fe3P second phase hinders the dislocation slip in the strip to improve the tensile strength of the strip, and the Fe3P second phase mainly distributed in the lattice effectively inhibits the growth of the grains under the heat treatment condition above 450℃ to improve the high-temperature softening resistance of the strip; in addition, the mass percentage of P element and Fe element can make the Fe3P second phase spherical or ellipsoidal with a particle size of 100nm-200nm, if the mass percentage of Fe element is higher than 3.0wt%, the Fe3P second phase will grow and agglomerate to a certain extent, becoming hard points in the rolling process, resulting in cracks or peeling of the strip, and if the mass percentage of Fe element is lower than 2.0wt%, the high-temperature softening resistance of the strip is significantly reduced.

[0015] By adding La element or / and Ce element, the high-temperature softening resistance of the strip is further improved; specifically, the addition of La element or / and Ce element can refine the grains in the strip, and after the grains are refined, the proportion of grain boundaries increases significantly, according to the Hall-Petch formula and dislocation theory, under the action of external stress, the dislocation source continuously emits dislocations, causing the crystal in the strip to slip, and after the proportion of grain boundaries increases, the dislocation will be inhibited when moving along the slip surface, and a dislocation network is formed, which increases the driving force required for the growth of the grains after being heated, thereby improving the high-temperature softening resistance of the strip; at the same time, by adding La element or / and Ce element, the oxygen content in the strip can be reduced from 10ppm-15ppm to 5ppm, reducing the risk of welding cracking, i.e. improving the welding performance of the strip.

[0016] Preferably, the hardness of the lead frame copper-iron alloy strip is 100-130(HV1), the tensile strength of the lead frame copper-iron alloy strip is 350MPa-450MPa, the elongation after fracture of the lead frame copper-iron alloy strip is not less than 10%, the high-temperature softening temperature of the lead frame copper-iron alloy strip is not less than 550℃, the surface roughness of the lead frame copper-iron alloy strip parallel to the rolling direction is less than 0.120μm, the surface gloss of the lead frame copper-iron alloy strip parallel to the rolling direction is less than 500GU, the surface roughness of the lead frame copper-iron alloy strip perpendicular to the rolling direction is less than 0.100μm, and the surface gloss of the lead frame copper-iron alloy strip perpendicular to the rolling direction is less than 300GU.

[0017] The second aspect of the present application provides a preparation method of the copper-iron alloy strip for lead frame as described above, and the steps include:

[0018] S1, providing an electrolytic copper plate and completely melting the electrolytic copper plate;

[0019] S2, after adding the copper-iron intermediate alloy, heating to a first temperature and keeping for a first time;

[0020] S3, after adding the phosphor copper intermediate alloy and the rare earth intermediate alloy, heating to a second temperature and keeping for a second time, and then performing semi-continuous casting to obtain the copper-iron alloy;

[0021] S4, sequentially performing hot rolling treatment, face milling treatment, multiple intermediate treatments, last cold rolling treatment, and last cleaning treatment on the obtained copper-iron alloy to obtain the copper-iron alloy strip; wherein,

[0022] Each intermediate treatment includes sequentially performing cold rolling treatment and annealing treatment;

[0023] The adjacent intermediate treatments further include cleaning treatment, or the adjacent intermediate treatments do not include the cleaning treatment.

[0024] Preferably, the hot rolling treatment is performed to control the distribution of the formed Fe3P second phase.

[0025] Preferably, multiple intermediate treatments are performed to control the particle size of the Fe3P second phase to be 100nm-200nm.

[0026] By controlling the feeding step sequence, the uniformity of Fe elements in the strip can be ensured; at the same time, the P elements can be ensured not to be seriously burned to generate a suitable proportion of Fe3P second phase, on the one hand, and to reduce the content of O elements in the strip through P elements, on the other hand; in addition, the rare earth elements can also be ensured not to be seriously burned to play a role in refining grains.

[0027] Preferably, the first temperature is 1200℃-1250℃.

[0028] Preferably, the first time is 30min-90min.

[0029] Preferably, the second temperature is 1250℃-1300℃.

[0030] Preferably, the second time is 30min-90min.

[0031] Preferably, in the hot rolling treatment, the heating temperature is 840℃-900℃.

[0032] Preferably, in the hot rolling treatment, the keeping time is 3h-4h.

[0033] Preferably, the total processing rate in the hot rolling treatment is not less than 90%.

[0034] The temperature of the hot rolling treatment can ensure sufficient solid solution of Fe element, and can control the distribution of Fe3P second phase, further avoid the aggregation of strip or block, and lay a foundation for controlling the particle size of Fe3P second phase in subsequent treatment.

[0035] Preferably, the plurality of intermediate treatments comprises: a first cold rolling treatment, a first annealing treatment, a first cleaning treatment, a second cold rolling treatment, a second annealing treatment, a third cold rolling treatment, and a third annealing treatment performed in sequence.

[0036] Preferably, in the first cold rolling treatment, the roughness of the roller is 0.8-1.0 μm.

[0037] Preferably, in the first cold rolling treatment, the processing rate is 75%-85%.

[0038] The roughness of the roller in the first cold rolling treatment can meet the roughness requirement of subsequent cold rolling treatment. If the roughness of the roller is higher than 1.0 μm, the subsequent treatment cannot reduce the roughness of the strip. If the roughness of the roller is lower than 0.8 μm, the processing efficiency is significantly reduced, and the surface will appear bruising and wire scratching. The processing rate can ensure that the recrystallized grains after the hot rolling treatment are completely broken, laying a foundation for subsequent grain refinement.

[0039] Preferably, in the first annealing treatment, a bell-type furnace annealing is adopted.

[0040] Preferably, in the first annealing treatment, the annealing temperature is 500-550 °C.

[0041] Preferably, in the first annealing treatment, the holding time is 8-12 h.

[0042] The parameters of the first annealing treatment can eliminate the processing stress caused by the first cold rolling treatment, reduce the hardness of the strip to facilitate subsequent processing, and also ensure that the grains will not grow too much.

[0043] Preferably, in the first cleaning treatment, three groups of cleaning brushes with mesh numbers of 400, 600, and 1200 are adopted.

[0044] Preferably, in the first cleaning treatment, the walking speed is 15-35 m / min.

[0045] Preferably, in the second cold rolling treatment, the roughness of the roller is 0.2-0.3 μm.

[0046] Preferably, in the second cold rolling treatment, the processing rate is 60%-70%.

[0047] Preferably, in the second annealing process, a spread annealing is adopted.

[0048] Preferably, in the second annealing process, the annealing temperature is 600-700°C.

[0049] Preferably, in the second annealing process, the strip speed is 15-45 m / min.

[0050] Preferably, in the third cold rolling process, the roughness of the roller is 0.15-0.2 μm.

[0051] Preferably, in the third cold rolling process, the reduction is 50-60%.

[0052] Preferably, in the third annealing process, a spread annealing is adopted.

[0053] Preferably, in the third annealing process, the annealing temperature is 600-700°C.

[0054] Preferably, in the third annealing process, the strip speed is 60-85 m / min.

[0055] Preferably, in the last cold rolling process, the roughness of the roller is 0.12-0.15 μm.

[0056] Preferably, in the last cold rolling process, the reduction is 30-40%.

[0057] The roughness of the roller in the second, third and last cold rolling processes is gradually reduced to reduce the roughness of the strip and maximize the production efficiency; the reduction in the second, third and last cold rolling processes is gradually reduced to ensure that the desired strength, hardness and elongation after fracture are obtained while the plate shape of the strip does not significantly warp to affect the subsequent processing.

[0058] The second and third annealing processes can control the particle size of the Fe3P second phase to be 100-200 nm and the Fe3P second phase is uniformly distributed.

[0059] Preferably, in the last cleaning process, three groups of cleaning brushes with mesh numbers of 400, 600 and 1200 are adopted.

[0060] Preferably, in the last cleaning process, the strip speed is 50-70 m / min.

[0061] The first and last cleaning processes can brush off the surface oxide film to reduce the surface glossiness without forming obvious cleaning marks to avoid affecting the quality of the lead frame product.

[0062] Compared with the prior art, the present application has the following technical effects:

[0063] The lead frame copper-iron alloy strip of the present application controls the particle size of the Fe3P second phase by controlling the mass percentage of P element and Fe element, and refines the grain by adding La element and / or Ce element; the preparation method of the present application can significantly reduce the surface roughness and gloss of the strip, thereby meeting the performance parameter requirements for application in lead frames. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0065] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0066] The present application will be further described below in combination with specific embodiments, but is not limited to the present application.

[0067] Embodiment 1

[0068] The present embodiment provides a lead frame copper-iron alloy strip, which comprises, by mass percentage:

[0069] P0.010wt%~0.100wt%;

[0070] Fe2.0wt%~3.0wt%;

[0071] RE0.005wt%~0.05wt%;

[0072] Cu and impurities in balance;

[0073] The RE is selected from La or / and Ce.

[0074] It should be noted that, due to the influence of sampling position and other factors in the actual preparation process, the mass percentage of each element meets the above range, that is, the chemical composition is considered to be the same, otherwise it is different.

[0075] Embodiment 2

[0076] The present embodiment provides a preparation method of the lead frame copper-iron alloy strip as described in embodiment 1, comprising the following steps:

[0077] S1, providing an electrolytic copper plate and completely melting the electrolytic copper plate;

[0078] S2, after adding copper-iron intermediate alloy, heating to 1200-1250 DEG C and holding for 30-90 min;

[0079] S3, after adding phosphor copper intermediate alloy and rare earth intermediate alloy, heating to 1250-1300 DEG C and holding for 30-90 min, and then semi-continuous casting to obtain a copper-iron alloy;

[0080] S4, sequentially performing hot rolling treatment, milling surface treatment, first cold rolling treatment, first annealing treatment, first cleaning treatment, second cold rolling treatment, second annealing treatment, third cold rolling treatment, third annealing treatment, last cold rolling treatment, and last cleaning treatment on the obtained copper-iron alloy to obtain the copper-iron alloy strip;

[0081] In steps S1-S3, the copper liquid is covered with roasted charcoal;

[0082] In the semi-continuous casting, the casting temperature is 1250-1300 DEG C, the casting speed is 50-80 mm / min, and the ingot thickness is 230 mm;

[0083] In the hot rolling treatment, step furnace hot rolling is used, the heating temperature is 840-900 DEG C, the holding time is 3-4 h, and the total processing rate is not less than 90%;

[0084] In the milling surface treatment, the milling thickness of the upper surface and the lower surface is 0.5-1.0 mm;

[0085] In the first cold rolling treatment, the roughness of the roller is 0.8-1.0 μm, and the processing rate is 75-85%;

[0086] In the first annealing treatment, cover furnace annealing is used, the annealing temperature is 500-550 DEG C, and the holding time is 8-12 h;

[0087] In the first cleaning treatment, three groups of cleaning brushes with mesh numbers of 400, 600, and 1200 are used, the reduction is 5-20%, and the running speed is 15-35 m / min;

[0088] In the second cold rolling treatment, the roughness of the roller is 0.2-0.3 μm, and the processing rate is 60-70%;

[0089] In the second annealing treatment, spread annealing is used, the annealing temperature is 600-700 DEG C, and the running speed is 15-45 m / min;

[0090] In the third cold rolling process, the roughness of the roller is 0.15 μm-0.2 μm, and the processing rate is 50%-60%;

[0091] In the third annealing process, the annealing temperature is 600°C-700°C, and the running speed is 60 m / min-85 m / min;

[0092] In the last cold rolling process, the roughness of the roller is 0.12 μm-0.15 μm, and the processing rate is 30%-40%;

[0093] In the last cleaning process, three groups of cleaning brushes with mesh numbers of 400, 600, and 1200 are used, the reduction is 5%-20%, and the running speed is 50 m / min-70 m / min.

[0094] Application Examples 1-10 and Comparative Examples 1-14

[0095] The quality percentages and preparation methods of Examples 1-2 are used to obtain the application examples 1-10 and the comparative examples 1-14;

[0096] The quality percentages of the application examples and the comparative examples are shown in the following table:

[0097]

[0098] The preparation parameters of the application examples and the comparative examples are shown in the following table:

[0099]

[0100]

[0101]

[0102]

[0103]

[0104] In the application examples 1-10 and the comparative examples 1-14, the casting temperature for semi-continuous casting is 1280℃ and the casting speed is 60mm / min, unless otherwise specified; the holding time for hot rolling treatment is 3.5h and the total reduction is 92%; the milling thickness of the upper surface for face milling treatment is 0.5mm and the milling thickness of the lower surface is 0.5mm; the holding time for the first annealing treatment is 10h; the reduction for the first cleaning treatment is 15% and the running speed is 25m / min; the annealing temperature for the second annealing treatment is 670℃ and the running speed is 35m / min; the reduction for the last cleaning treatment is 20%;

[0105] In the comparative example 12 and the application example 1, the difference lies in that two groups of cleaning brushes with mesh numbers of 600 and 1200 are used in the last cleaning treatment.

[0106] In the comparative example 13 and the application example 1, the difference lies in that the reduction for the last cleaning treatment is 25%.

[0107] Detection example

[0108] The hardness, tensile strength, electrical conductivity, roughness, gloss, high-temperature softening temperature, grain size, and Fe3P second phase particle size of each application example and comparative example are detected, wherein,

[0109] Hardness detection: according to GB / T 4340.0-2009, Vickers Hardness Test for Metallic Materials, Part 1: Test Method, the strip size is 30mm×30mm;

[0110] Tensile strength detection: according to GB / T 228.1-2010, Tensile Test for Metallic Materials, Part 1: Room Temperature Test Method, on an electronic universal mechanical property testing machine, the test sample is dumbbell-shaped, the tensile sample width is 20mm, and the tensile speed is 5mm / min;

[0111] Electrical conductivity detection: according to GB / T 32791-2016, Copper and Copper Alloy Electrical Conductivity Eddy Current Test Method, the strip size is 100mm×100mm;

[0112] Roughness detection: according to GB / T 1031-1995, Surface Roughness Parameters and Their Numerical Values, on a Japanese Sanfeng SJ-210 stylus roughness meter, the strip size is 200mm×200mm;

[0113] Gloss detection: According to "DIN 67530-1982 as a supplementary means for assessing the brightness of smooth coatings (plating) and plastic surfaces" and "ASTM D523-2014 Test Method for Specular Gloss", on the German BYK AG-4561 metal triangular gloss meter, the test strip size is 100 mm x 100 mm;

[0114] High temperature softening temperature detection: According to "GB / T 33370-2016 Test Method for Softening Temperature of Copper and Copper Alloy", the sample length is 40 mm and the width is 40 mm;

[0115] Grain size detection: According to the intercept method of "GB / T 6394-2007 Metal Average Grain Size Determination Method", the grain size in the photo collected by the 100 times metallographic microscope is tested, and the test strip size is 10 mm x 10 mm;

[0116] Fe3P second phase particle size detection: on the field emission scanning electron microscope JSM-IT700HR.

[0117] The detection results of grain size and Fe3P second phase particle size are shown in the above table, and the detection results of hardness, tensile strength, electrical conductivity, roughness, gloss, and high temperature softening temperature are shown in the following table:

[0118]

[0119]

[0120]

[0121] According to the analysis and comparison in the above table:

[0122] Comparative example 1 does not add rare earth elements, and the average grain size of the prepared strip is higher, and the softening temperature is lower;

[0123] In comparative example 2, the P element is added too much, the particle size of Fe3P second phase of the prepared strip increases obviously, about 1200 nm, although the tensile strength and hardness increase, the electrical conductivity, elongation after fracture and softening temperature decrease;

[0124] In comparative example 3, the hot rolling temperature is 700℃, the Fe3P second phase of the prepared strip is unevenly distributed, and part of the aggregation appears, and cracking appears during the first cold rolling treatment;

[0125] In comparative example 4, the processing rate of the first cold rolling treatment is 70%, the grain size of the prepared strip is higher, the mechanical properties are deviated, and the softening temperature decreases;

[0126] The hardness and tensile strength of the strip prepared in Comparative Example 5 are low because the reduction ratio of the last cold rolling treatment is 20%;

[0127] The roughness of the strip prepared in Comparative Examples 6-9 is obviously increased, and the gloss is affected because of the change of the roughness of the roller;

[0128] The Fe3P second phase of the strip prepared in Comparative Examples 10-11 is obviously grown, and the conductivity and softening temperature are decreased because of the increase of the annealing temperature;

[0129] The gloss of the strip prepared in Comparative Examples 12-14 is obviously increased because of the change of the cleaning parameters.

[0130] In summary, the copper-iron alloy strip for lead frame of the present application can control the particle size of the Fe3P second phase by controlling the mass percentage of P element and Fe element, and can refine the grain by adding La element and / or Ce element. The preparation method of the present application can significantly reduce the surface roughness and gloss of the strip, thereby meeting the performance parameter requirements for application in lead frame.

[0131] The above only describes the preferred embodiments of the present application, and does not limit the implementation and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacement and obvious change made according to the content of the present application should be included in the protection scope of the present application.

Claims

1. A copper-iron alloy strip for lead frames, characterized in that, By weight percentage, including: P 0.010wt%~0.100wt%; Fe 2.0wt%~3.0wt%; RE 0.005wt%~0.05wt%; Cu and impurity balance; Wherein, the RE is selected from: La and / or Ce; The preparation steps of the copper-iron alloy strip for the lead frame include: S1. Provide an electrolytic copper plate and completely melt the electrolytic copper plate; S2. After adding the copper-iron intermediate alloy, heat to the first temperature and hold for the first time; S3. After adding phosphorus copper master alloy and rare earth master alloy, the temperature is raised to the second temperature and held for the second time, and then semi-continuous casting is carried out to obtain copper-iron alloy. S4. The obtained copper-iron alloy is subjected to hot rolling, milling, multiple intermediate treatments, final cold rolling, and final cleaning in sequence to obtain the copper-iron alloy strip; wherein, The multiple intermediate processes include: a first cold rolling process, a first annealing process, a first cleaning process, a second cold rolling process, a second annealing process, a third cold rolling process, and a third annealing process performed sequentially. In the first cold rolling process, the roll roughness is 0.8μm~1.0μm, and the processing rate is 75%~85%. In the second cold rolling process, the roll roughness is 0.2μm~0.3μm, and the processing rate is 60%~70%. In the third cold rolling process, the roll roughness is 0.15μm~0.2μm, and the processing rate is 50%~60%. In the final cold rolling process, the roll roughness is 0.12μm~0.15μm, and the processing rate is 30%~40%.

2. The copper-iron alloy strip for lead frames according to claim 1, characterized in that, The copper-iron alloy strip for the lead frame includes Fe3P second phase with a particle size of 100nm~200nm.

3. The copper-iron alloy strip for lead frames according to claim 1, characterized in that, The hot rolling process is performed to control the distribution of the formed Fe3P second phase.

4. The copper-iron alloy strip for lead frames according to claim 3, characterized in that, The aforementioned multiple intermediate processing steps are performed to control the particle size of the Fe3P second phase to be 100 nm to 200 nm.

5. The copper-iron alloy strip for lead frames according to claim 1, characterized in that, The first temperature is 1200℃~1250℃; the first time is 30min~90min; the second temperature is 1250℃~1300℃; the second time is 30min~90min.

6. The copper-iron alloy strip for lead frames according to claim 1 or 3, characterized in that, In the hot rolling process, the heating temperature is 840℃~900℃, the holding time is 3h~4h, and the total processing rate is not less than 90%.

7. The copper-iron alloy strip for lead frames according to claim 1 or 4, characterized in that, In the first annealing process, a bell-type furnace is used for annealing, the annealing temperature is 500℃~550℃, and the holding time is 8h~12h; In the second annealing process, an open-type annealing is used, with an annealing temperature of 600℃~700℃ and a belt speed of 15m / min~45m / min; In the third annealing process, an open-type annealing is adopted, with an annealing temperature of 600℃~700℃ and a conveyor speed of 60m / min~85m / min.

8. The copper-iron alloy strip for lead frames according to claim 1 or 4, characterized in that, In the first cleaning process, three sets of cleaning brushes with mesh sizes of 400 mesh, 600 mesh and 1200 mesh are used, and the conveyor belt speed is 15m / min~35m / min; In the final cleaning process, three sets of cleaning brushes with mesh sizes of 400 mesh, 600 mesh, and 1200 mesh are used, and the conveyor belt speed is 50m / min to 70m / min.

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