A processing method for submicrocrystalline phosphorus copper balls

Abstract

The present invention relates to the technical field of copper processing, and in particular to a method for processing submicrocrystalline phosphor copper balls. The method comprises the following processing methods: uncoiling and straightening treatment, torsion and stretching treatment, cold extrusion treatment, upsetting treatment, and post-treatment; after performing three multi-directional plastic deformations of strong shearing, radial cold shrinkage, and axial cold pressing, no significant temperature rise occurs inside the product, phosphorus volatilization is not caused, and the alloy composition is stable; the multi-directional deformation makes the alloy structure more uniform and dense, and the average sub-grain size is less than 5 μm; no surface defects are formed during the forming process, and the yield rate is close to 100%. The phosphor copper balls obtained by the present invention have a finer grain size than microcrystalline phosphor copper balls prepared by the "continuous extrusion + upsetting forging" method, and have better surface quality, more stable composition, and higher yield rate.

Description

Technical Field

[0001] The invention relates to the technical field of copper processing, and in particular to a processing method of submicrocrystalline phosphor copper balls. Background Art

[0002] Phosphor copper balls are a raw material used in the electroplating of various products, including PCBs, LED components, and hardware parts. Microcrystalline phosphor copper balls feature a fine, uniform grain structure, resulting in superior electroplating performance and are commonly used for high-end circuit board plating. Practice has shown that the optimal size of phosphor copper balls for electroplating anodes is less than 10μm. Conventional phosphor copper balls in the industry are typically made from T2 copper rods produced through continuous casting, which are then forged into spheres. However, this process results in a low deformation rate and larger grain sizes, typically ranging from 30 to 60μm. By subjecting the continuous casting rods to a continuous extrusion process followed by cold forging, microcrystalline phosphor copper balls with fine grains, ranging from 5 to 20μm, can be obtained. These microcrystalline phosphor copper balls exhibit significantly fewer columnar crystals and more equiaxed crystals, resulting in a denser crystal structure, a more uniform phosphorus distribution, and less segregation. This allows for more uniform dissolution of the phosphor copper anode during the electroplating process, resulting in higher utilization rates. The demand for microcrystalline phosphor copper balls from downstream users has driven technological advancement among phosphor copper ball manufacturers.

[0003] However, in the existing technology, the main process used to produce microcrystalline phosphor copper balls is the "continuous extrusion + cold heading" process. This technology has the following problems:

[0004] 1) Due to the intense friction during the continuous extrusion process, the temperature of the phosphor copper rod billet rises as high as 400-600°C, causing some phosphorus elements in the rod billet to volatilize and the product composition to be unstable;

[0005] 2) It is difficult to directly connect with the upsetting ball and post-processing process after continuous extrusion, resulting in a discontinuous production process and difficulty in achieving continuous and automated production;

[0006] 3) After continuous extrusion, the rod blank is prone to surface defects such as peeling and bubbles, which affect the quality of the final phosphor copper ball product. Summary of the Invention

[0007] According to the problems raised in the background technology, the present invention provides a processing method of submicrocrystalline phosphor copper balls to solve the problems. The present invention will be further explained below.

[0008] A method for processing submicrocrystalline phosphor copper balls, comprising the following processing methods:

[0009] Step 1: Uncoiling and straightening: The φ16-25mm phosphor copper coiled rod produced by the upward continuous casting method is uncoiled from the material rack through the first set of five-roller vertical straightening system to complete the first straightening operation;

[0010] Step 2: Pull and twist treatment: The phosphor copper rod, which has been straightened for the first time, is pulled forward and twisted to a certain angle by the second set of seven-roll horizontal straightening systems. It is then introduced into the drawing die to achieve pull and twist deformation. After passing through the die, the phosphor copper rod is straightened for the second time by the five-roll horizontal straightening system.

[0011] Step 3: Cold extrusion treatment: Push the phosphor bronze rod that has been subjected to tension and twisting treatment into a set of extrusion dies through a pair of traction rollers to achieve cold extrusion deformation;

[0012] Step 4: Ball upsetting: The phosphor copper rod of a certain length extruded from the cold extrusion die is cut by a special device and quickly transferred to the cold upsetting die. It is cold-forging formed by a high-speed ball upsetting machine to obtain phosphor copper balls of the required specifications.

[0013] Step 5: Post-processing: The phosphor bronze balls formed by cold heading undergo a series of fully automated post-processing steps and are processed into finished products;

[0014] Preferably, the twisting treatment in step 2 is to change the holding angle between the two straightening systems so that the phosphor copper rod is twisted 15° along the axis, with a maximum equivalent effect of 0.08;

[0015] Preferably, a drawing die is set between the two straightening systems, and the phosphor copper rod is introduced into the drawing die to achieve drawing and twisting deformation, wherein the drawing deformation rate is 19%; the equivalent effect of drawing and twisting deformation is 0.4-0.5;

[0016] Preferably, in the cold extrusion treatment in step 3, the cold extrusion ratio is 1.2-1.3; the equivalent effect of the cold extrusion deformation is 0.3-0.6;

[0017] Preferably, the degree of deformation of the cold heading ball treatment in step 4 is determined according to the product specifications, the equivalent effect of the cold heading ball deformation is 0.5-1.2, and the average deformation rate is 37.5%;

[0018] Preferably, the post-processing steps in step 5 include collecting, cleaning, drying, inspecting, weighing, and packaging;

[0019] Beneficial effects: Compared with the prior art, the present invention obtains phosphor copper balls with smaller grain size than the microcrystalline phosphor copper balls prepared by the "continuous extrusion + upsetting" method, and has better surface quality, more stable composition and higher yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : A low-magnification microscopic photograph of the submicrocrystalline phosphor copper ball prepared by the present invention;

[0021] Figure 2 : A high-magnification microscopic photograph of the submicrocrystalline phosphor copper ball prepared by the present invention; DETAILED DESCRIPTION

[0022] Next, a specific embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0023] A method for processing submicrocrystalline phosphor copper balls, comprising the following processing methods:

[0024] Step 1: Uncoiling and straightening: The φ16-25mm phosphor copper coiled rod produced by the upward continuous casting method is uncoiled from the material rack through the first set of five-roller vertical straightening system to complete the first straightening operation;

[0025] Step 2: Pull and twist treatment: The phosphor copper rod, which has been straightened for the first time, is pulled forward and twisted to a certain angle by the second set of seven-roll horizontal straightening systems. It is then introduced into the drawing die to achieve pull and twist deformation. After passing through the die, the phosphor copper rod is straightened for the second time by the five-roll horizontal straightening system.

[0026] Step 3: Cold extrusion treatment: Push the phosphor bronze rod that has been subjected to tension and twisting treatment into a set of extrusion dies through a pair of traction rollers to achieve cold extrusion deformation;

[0027] Step 4: Ball upsetting: The phosphor copper rod of a certain length extruded from the cold extrusion die is cut by a special device and quickly transferred to the cold upsetting die. It is cold-forging formed by a high-speed ball upsetting machine to obtain phosphor copper balls of the required specifications.

[0028] Step 5: Post-processing: The cold-forged phosphor bronze balls undergo a series of fully automated post-processing steps to be processed into finished products. These steps include collection, cleaning, drying, inspection, weighing, packaging, etc.

[0029] In this embodiment, the pulling and twisting treatment is achieved by changing the holding angle between the two straightening systems, causing the phosphor copper rod to be twisted 15° along the axis, with a maximum equivalent effect of 0.08; a drawing die is set between the two straightening systems, and the phosphor copper rod is introduced into the drawing die to achieve pulling and twisting deformation, wherein the drawing deformation rate is 19%; the equivalent effect of the pulling and twisting deformation is 0.4 to 0.5;

[0030] In this embodiment, the cold extrusion treatment in step 3 has a cold extrusion ratio of 1.2-1.3. The equivalent effect of cold extrusion deformation is 0.3-0.6;

[0031] In this embodiment, the degree of deformation of the cold heading ball treatment in step 4 is determined according to the product specifications, the equivalent effect of the cold heading ball deformation is 0.5 to 1.2, and the average deformation rate is 37.5%;

[0032] The key process differences between the embodiment and the comparative example are shown in Table 1. The phosphorus copper balls obtained by different processes were cut radially to observe their grain structures, and the results are shown in Table 1.

[0033] Table 1 Process and tissue analysis results of examples and comparative examples

[0034]

[0035] As can be seen from Table 1, according to the process scheme of the present invention (Examples 1 and 2), the grain structure of the phosphor copper balls is effectively refined, and the average subgrain size is basically less than 5 μm; however, if only cold extrusion and cold heading are performed without tensile-torsional deformation (Comparative Example 1), the degree of grain structure fragmentation is significantly reduced because the phosphor copper alloy does not undergo strong shear deformation, and the final average subgrain size reaches 36.72 μm; if only one heading deformation is performed according to the conventional phosphor copper ball production process (Comparative Example 2), coarse-grained phosphor copper balls with a grain size of more than 50 μm will be obtained.

[0036] The main technical principle is to achieve grain refinement and processing of phosphor copper balls through multi-pass multi-directional severe plastic deformation. The grain refinement technology of metal materials generally includes three categories, namely grain refinement in the crystallization and solidification process, grain refinement in large plastic deformation, and grain refinement by heat treatment. The phosphor copper balls involved in the present invention belong to a class of intermediate products and generally do not require heat treatment after forming; and the cost of achieving its grain refinement in the casting process is relatively high. Therefore, the present invention only performs grain refinement treatment on the upward continuous casting phosphor copper rod billets that have been crystallized and solidified into a solid state. Through three passes of multi-directional plastic deformation, namely strong shearing, radial shrinkage, and axial cold pressing, the cumulative equivalent plastic strain reaches more than 2.0, so that the cast structure of the continuous casting rod billet is effectively broken, and the deformation is uniformly penetrated, and the grain refinement and processing of the phosphor copper balls are simultaneously achieved, and submicrocrystalline phosphor copper balls with an average grain size of 4.64μm are obtained.

[0037] Ordinary phosphor copper balls generally only undergo plastic deformation during the ball upsetting step, resulting in coarse grains with a typical grain size of 30 to 60 μm. Existing microcrystalline phosphor copper ball processing technology involves a single continuous extrusion of the upper guide rod blank prior to ball upsetting. Continuous extrusion is a commonly used technique for achieving large deformation, so after continuous extrusion and ball upsetting, microcrystalline phosphor copper balls with grain sizes of 5 to 20 μm can be obtained. However, as mentioned above, the large plastic deformation during continuous extrusion not only leads to a high temperature rise, causing alloy composition instability (phosphorus volatilization), but also causes a certain degree of dynamic recrystallization and grain growth in the phosphor copper balls. Furthermore, continuous extrusion often causes defects such as peeling and bubbles in the phosphor copper balls, reducing the yield rate. Furthermore, using continuous extrusion technology for phosphor copper rod pretreatment makes it difficult to achieve continuous and automated production of phosphor copper balls.

[0038] The present invention continuously realizes the deformation of phosphor copper rod billets produced by upward continuous casting by stretching and twisting, cold extrusion and cold heading on a set of equipment. The deformation processes adopted include stretching and twisting, cold extrusion and cold heading. Through three multi-directional plastic deformations, no significant temperature rise is generated, phosphorus volatilization is not caused, and the alloy composition is stable. The multi-directional deformation makes the alloy structure more uniform and dense, with an average subgrain size of less than 5μm. No surface defects are formed during the forming process, and the yield rate is close to 100%.

[0039] Compared with the existing technology, the present invention obtains phosphor copper balls with smaller grain size than the microcrystalline phosphor copper balls prepared by the "continuous extrusion + upsetting" method, and has better surface quality, more stable composition and higher yield.

[0040] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for processing submicrocrystalline phosphor copper balls, characterized by: The following processing methods are included: Step 1: Uncoiling and straightening: The φ16-25mm phosphor copper coiled rod produced by the upward continuous casting method is uncoiled from the material rack through the first set of five-roller vertical straightening system to complete the first straightening operation; Step 2: Pull and twist treatment: The phosphor copper rod, which has been straightened for the first time, is pulled forward and twisted to a certain angle by the second set of seven-roll horizontal straightening systems. It is then introduced into the drawing die to achieve pull and twist deformation. After passing through the die, the phosphor copper rod is straightened for the second time by the five-roll horizontal straightening system. Step 3: Cold extrusion treatment: Push the phosphor bronze rod that has been subjected to tension and twisting treatment into a set of extrusion dies through a pair of traction rollers to achieve cold extrusion deformation; Step 4: Ball upsetting: The phosphor copper rod of a certain length extruded from the cold extrusion die is cut by a special device and quickly transferred to the cold upsetting die. It is cold-forging formed by a high-speed ball upsetting machine to obtain phosphor copper balls of the required specifications. Step 5: Post-processing: The phosphor bronze balls formed by cold heading are subsequently processed into finished products through a series of fully automated post-processing steps.

2. The method for processing submicrocrystalline phosphor copper balls according to claim 1, characterized in that: The pulling and twisting treatment in step 2 is achieved by changing the holding angle between the two sets of straightening systems, so that the phosphor bronze rod is twisted 15° along the axis, with a maximum equivalent effect of 0.

08.

3. The method for processing submicrocrystalline phosphor copper balls according to claim 2, characterized in that: A drawing die is set between the two sets of straightening systems, and the phosphor bronze rod is introduced into the drawing die to achieve drawing and twisting deformation, wherein the drawing deformation rate is 19%; the equivalent effect of drawing and twisting deformation is 0.4-0.

5.

4. The method for processing submicrocrystalline phosphor copper balls according to claim 1, characterized in that: In the cold extrusion treatment in step 3, the cold extrusion ratio is 1.2-1.3; the equivalent effect of the cold extrusion deformation is 0.3-0.

6.

5. The method for processing submicrocrystalline phosphor copper balls according to claim 1, characterized in that: The degree of deformation of the cold heading ball treatment in step 4 is determined according to the product specifications. The equivalent effect of the cold heading ball deformation is 0.5-1.2, and the average deformation rate is 37.5%.

6. The method for processing submicrocrystalline phosphor copper balls according to claim 1, characterized in that: The post-processing steps described in step five include collection, cleaning, drying, inspection, weighing, and packaging.

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