Structure capable of reducing proportion of bulk crystals of electrolytic copper foil and use method

Abstract

The invention discloses a structure capable of reducing the proportion of bulk crystals of an electrolytic copper foil and a using method.The structure comprises shielding plates which are detachably installed at the positions, corresponding to liquid return openings, of the upper sides of titanium plates at the two ends in an electrolytic bath so as to improve the liquid level of the positions, corresponding to the liquid return openings, of the titanium plates, and the length of the shielding plates is matched with the width of the titanium plates; the liquid level of the electrolyte liquid return opening can be raised through the arrangement of the shielding plate, so that the surface of the titanium roller is wetted by the electrolyte in advance; under the action of a weak electric field, copper can be deposited on the roller more uniformly and more tightly, the microstructure of the copper foil is optimized fundamentally, the proportion that the copper foil becomes blocky crystals is reduced during subsequent pressing of the CCL substrate, the conversion degree of the blocky crystals of the copper foil on the two faces of the substrate is more consistent, internal stress is released uniformly, the situation that one face is tight and the other face is loose is avoided, and the quality of the CCL substrate is improved. The warping risk of the CCL substrate is directly reduced, and the requirements of circuit board production can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolytic copper foil manufacturing, in particular to a structure capable of reducing the proportion of blocky crystals of electrolytic copper foil and a use method thereof. BACKGROUND

[0002] Electronic circuit foil is a thin copper layer deposited on the base layer of a circuit board, mainly used as a conductor on a printed circuit board (PCB). As the base material of a PCB, CCL is processed through etching, drilling, etc. to make a PCB (printed circuit board), and such a substrate provides the PCB with conductive, insulating and mechanical support functions. As one of the core raw materials of CCL, copper foil is combined with resin and glass fiber cloth through processes such as impregnation and hot pressing to form a CCL substrate. The CCL substrate after high-pressure and high-temperature pressing is prone to warping abnormalities. In simple terms, the CCL substrate requires high temperature and high pressure during pressing, which will cause changes in the crystals in the copper foil. The originally long and thin "columnar crystals" will change into "blocky crystals". The copper foils on both sides of the CCL substrate will not be the same in terms of the degree of blocky crystal transformation, for example, one side will have more blocky crystals and the other side will have fewer blocky crystals, resulting in uneven "internal stress" release on both sides of the substrate, and finally the substrate will warp and cannot be normally used on a circuit board. Generally, the smaller the degree of crystal structure change, the lower the risk of CCL substrate warping. The conventional method mainly achieves the purpose of reducing the proportion of blocky crystals in copper foil by increasing the content of additives and adjusting the parameters of electrolyte, but increasing the content of additives will cause the roughness of the copper foil surface to be too high, and will also bring other appearance abnormalities, with limited control effect and ability, and large fluctuations between different devices, which cannot meet the requirements of stable production. SUMMARY

[0003] The present application provides a structure capable of reducing the proportion of blocky crystals in electrolytic copper foil and a use method thereof, which can avoid the abnormal warping of the board caused by different degrees of blocky crystal transformation or too high a proportion of blocky crystals in the copper foil in the downstream.

[0004] To achieve the above-mentioned purpose, in a first aspect, the present application provides the following technical solution: a structure capable of reducing the proportion of blocky crystals in electrolytic copper foil, comprising a shielding plate, which is detachably installed on the upper side of the titanium plate at the position corresponding to the liquid return port at both ends inside the electrolytic cell to raise the liquid level at the position corresponding to the liquid return port of the titanium plate. The length of the shielding plate matches the width of the titanium plate. The shielding plate can raise the liquid level of the electrolyte liquid return port and wet the surface of the titanium roller in advance. Under the action of a weak electric field, copper will be more uniformly and closely deposited on the drum, which optimizes the microstructure of the copper foil from the root cause. When the CCL substrate is subsequently pressed, the proportion of blocky crystals in the copper foil will be reduced, and the degree of blocky crystal transformation of the copper foil on both sides of the substrate will be more consistent, the internal stress will be evenly released, and the situation of one side being tight and the other side being loose will not occur. The risk of CCL substrate warping is directly reduced, which can meet the requirements of circuit board production.

[0005] Preferably, the shielding plate is L-shaped in cross section and is arranged at the upper side corner of the titanium plate, which is beneficial to the shielding plate to block the electrolyte and raise the liquid level, and is also beneficial to the installation and positioning of the shielding plate.

[0006] Preferably, a plurality of mounting holes are arranged on the shielding plate along the length direction, and the shielding plate is connected to the titanium plate through screws passing through the mounting holes, and the shielding plate can be uniformly and firmly installed through the mounting holes.

[0007] Preferably, the thickness of the shielding plate is 3-5 mm.

[0008] Preferably, the transverse width of the shielding plate is 30-70 mm, and different widths of the shielding plate can be selected according to different thickness requirements of the copper foil.

[0009] Preferably, the shielding plate is made of PVC material.

[0010] In a second aspect, the application further provides a use method of the structure capable of reducing the proportion of blocky grains of electrolytic copper foil according to the first aspect, comprising the following steps: S1, selecting the width and length of the shielding plate according to the titanium plate, the electrolytic cell and the thickness of the copper foil to be made, and manufacturing the shielding plate; S2, installing the shielding plate at the edge of the titanium plate along the length direction, and adjusting the installation position of the shielding plate so that the distance between the shielding plate and the surface of the titanium roller of the electrolytic copper foil is 2-3 cm; S3, according to the requirement of making the copper foil, the electrolyte is blocked when flowing to the position of the shielding plate, so as to raise the liquid level, so that the electrolyte can cover the surface of the titanium roller just entering the electrolysis area to perform early wetting; S4, blocky grain proportion detection, the copper foil sample is converted into blocky grains by high-temperature baking, and the baked copper foil sample is sliced to read the proportion of blocky grains.

[0011] Compared with the prior art, the application has the following beneficial effects: The liquid level at the return liquid outlet position of the electrolytic cell is raised by the shielding plate, the surface of the titanium roller is wetted in advance, the deposition speed and density of the copper foil are changed in advance under the action of a weak electric field, so as to optimize the deposition density, uniformity and texture state of the copper foil; for the difference between different machines in the same group, the size and installation position of the shielding plate can be flexibly adjusted, so as to avoid the influence of system adjustment additives on the physical properties of other machines. Therefore, the microstructure of the copper foil is changed by ingenious and simple mechanical operation, and the abnormal plate warping caused by different blocky grain conversion degrees or too high blocky grain proportion in the downstream is effectively avoided. BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1is a perspective view of a shielding plate according to the present application; Fig. 2 is a schematic view of a mounting state of a shielding plate according to the present application; Fig. 3 is a block diagram of experimental results according to various embodiments of the present application.

[0013] Reference signs: 1, shielding plate, 11, mounting hole, 2, electrolytic cell, 3, titanium plate, 4, liquid return port, 5, connecting wire. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0015] The present application avoids the problem of plate warping caused by different conversion degrees of block crystals or too high proportion of block crystals in copper foil downstream. Figs. 1-3 As shown, the following technical solution is provided: a structure capable of reducing the proportion of block crystals of electrolytic copper foil, comprising a shielding plate 1, which is detachably mounted on the upper side of the titanium plate 3 at the position corresponding to the liquid return port 4 inside the electrolytic cell 2 to raise the liquid level at the position corresponding to the liquid return port 4 of the titanium plate 3. The length of the shielding plate 1 matches the width of the titanium plate 3. The shielding plate 1 is arranged to raise the liquid level of the electrolyte liquid return port and wet the surface of the titanium roller in advance. Under the action of a weak electric field, copper is more uniformly and closely deposited on the roller, which optimizes the microstructure of the copper foil from the root cause. When the CCL substrate is subsequently pressed, the proportion of copper foil that becomes block crystals is reduced, and the conversion degree of block crystals on both sides of the substrate is more consistent. The internal stress is uniformly released, and there is no situation of tight on one side and loose on the other side. The risk of CCL substrate warping is directly reduced, which can meet the requirements of circuit board production.

[0016] In the prior art, the root cause of CCL substrate warping is uneven conversion or too high proportion of block crystals during high-temperature pressing of copper foil. The key to block crystal conversion depends on the initial microstructure of copper foil during production, which includes deposition density, uniformity, and crystal arrangement state. The principle of the shielding plate 1 is to mechanically intervene in the contact state of the electrolyte and the cathode roller to optimize the initial microstructure of the copper foil from the source and ultimately block abnormal block crystal conversion.

[0017] Specifically, the production principle of the electrolytic copper foil is that when the cathode roller (titanium roller) rotates, the surface adsorbs copper ions in the electrolyte, and under the action of the electric field, the copper foil is reduced and deposited. Among them, the "initial contact state" of the cathode roller (titanium roller) just entering the electrolysis area directly determines the deposition quality of the outermost layer of the copper foil (that is, the area most prone to block crystal transformation during subsequent pressing). In the existing production, the liquid level height of the electrolyte return port of the electrolytic tank is fixed, which causes the cathode roller (titanium roller) to only partially contact the electrolyte at the inlet position, resulting in the problem of partial contact and partial contact. The area that is not wetted in advance will quickly deposit copper ions when it enters the strong electric field, forming a loose and uneven initial copper layer. One of the main functions of the shielding plate 1 is to raise the electrolyte liquid level of the return port by its physical structure: since the shielding plate 1 is installed on the upper side of the titanium plate 3 at the position corresponding to the return port 4 of the electrolytic tank 2, it forms a physical barrier at the return port, forcing the electrolyte liquid level to rise until it completely covers the surface of the cathode roller (titanium roller) just entering the electrolysis area, thereby solving the basic problem of uneven initial wetting and allowing the titanium roller surface to form a uniform electrolyte film before entering the strong electric field, laying the foundation for subsequent uniform deposition.

[0018] The block crystal transformation trend of the copper foil is directly related to the density and crystal arrangement state of the initial copper layer: if the initial copper layer is loose and the crystal arrangement is chaotic, the columnar crystals will quickly coarsen into block crystals during high-temperature pressing, and the transformation speed will vary greatly in different areas; if the initial copper layer is dense and the crystal arrangement is regular, the block crystal transformation will be slower and more uniform. Therefore, after the cathode roller (titanium roller) is wetted by the electrolyte, it just enters the electrolysis area, the distance from the anode is far, and the electric field strength is weak, which is much lower than the strong electric field in the core electrolysis area. If in the strong electric field, copper ions will quickly rush to the surface of the titanium roller, and the layer will be formed without orderly arrangement, which is easy to form a loose and chaotic crystal direction structure; in the weak electric field, the movement speed of copper ions slows down, and there is enough time for uniform adsorption and orderly arrangement on the surface of the titanium roller, and the finally deposited copper layer is more dense and the crystal arrangement direction is more consistent. Therefore, this step changes the initial microstructure of the copper foil from the source, forms a dense and uniform initial copper layer, reduces the possibility of rapid transformation of columnar crystals into block crystals, and makes the crystal arrangement state of each area of the copper foil consistent.

[0019] Therefore, the shielding plate 1 mechanically intervenes in the contact state of the electrolyte without changing the composition of the electrolyte, so it will not cause the rough surface of the copper foil like additives, while optimizing the microstructure, it ensures the appearance quality of the copper foil.

[0020] In the present embodiment, the shielding plate 1 is L-shaped in cross-section and is arranged at the upper side corner of the titanium plate 3, which is conducive to the shielding plate 1 blocking and raising the liquid level of the electrolyte, and also conducive to the installation and positioning of the shielding plate 1.

[0021] Meanwhile, the shielding plate 1 is provided with a plurality of mounting holes 11 along its length. The shielding plate 1 is connected to the titanium plate 3 by screws passing through the mounting holes 11. The shielding plate 1 can be installed evenly and firmly through the mounting holes 11.

[0022] In this embodiment, the shielding plate 1 is made of PVC material, with a thickness of 3-5mm and a lateral width of 30-70mm. Different widths of shielding plate 1 can be selected based on the required copper foil thickness. The shielding plate is installed at the edge of the anode groove at the inlet of the cathode roller (titanium roller), precisely on the electrolyte return path of the return port. When the electrolyte flows out of the return port, it is physically blocked by the shielding plate. The wider the shielding plate 1, the larger its blocking area on the return path, resulting in a slower electrolyte return speed and more electrolyte accumulating near the return port, naturally raising the liquid level higher. Conversely, the narrower the shielding plate 1, the smaller its blocking area, allowing the electrolyte to flow away from the return port more quickly, resulting in less accumulation and a smaller rise in liquid level.

[0023] As a specific implementation method: Example 1: S1. Fabrication of the shielding plate: A PVC shielding plate is fabricated for installation. Specific parameters: shielding plate thickness 3mm, length 1360mm, width 30mm. Six mounting holes 11 are equally spaced along the length to facilitate the installation of the shielding plate. S2. Shielding plate installation: Install shielding plate 1 above titanium plate 3 at the inlet position of the anode tank of the electrolytic foil machine. Ensure that the shielding plate is installed with uniform force and keep the distance between it and the titanium roller at 2-3mm to prevent scratching the surface of the titanium roller. S3 is made of 35um copper foil and uses the specified production parameters for 35um copper foil, specifically: copper concentration 95±3.5g / l, 130±8g / L, electrolysis current 28000A; S4. Bulk crystal ratio detection: Bulk crystal transformation is achieved through high-temperature baking. Specific operation: Cut the electrolytically generated copper foil into 10*20cm samples, and cut a total of 5 samples. Bake the cut samples in an oven at 200℃ / 60min. After baking, perform metallographic sectioning and micro-etching, and then read the bulk crystal ratio under a super depth-of-field microscope.

[0024] Example 2: The only difference from Example 1 is that the width of the shielding plate 1 in step S1 is 50mm, while the other dimensions and installation method remain unchanged, and the experiment is carried out according to the same process as in Experiment 1.

[0025] Example 3: The only difference from Example 1 is that the width of the shielding plate in step S1 is 70mm, while the other dimensions and installation method remain unchanged, and the experiment is carried out according to the same process as in Experiment 1.

[0026] Example 4: The only difference from Example 1 is that the copper foil with a specification of 70um is produced in step S3. The other shielding plate dimensions, installation, and production parameters remain unchanged, and the experiment is carried out according to the same process as in Experiment 1.

[0027] Example 5: The only difference from Example 1 is that the copper foil produced in step S3 is 105um in size. The other shielding plate dimensions, installation, and production parameters remain unchanged, and the experiment is carried out according to the same process as in Experiment 1.

[0028] The specific embodiments can be summarized in Table 1 below: Table 1 Experimental test results are as follows Fig. 3 As shown, different shielding plate widths and specifications result in different proportions of bulk crystals after baking.

[0029] from Fig. 3 The results show that in Examples 1, 2, and 3, all used 35µm copper foil. Under the same conditions, as the height of the shielding plate increased from 30mm, 50mm, and 70mm, the proportion of bulk crystals in the copper foil after baking was 75%, 60%, and 45%, respectively, showing a decreasing trend. Increasing the height of the shielding plate has a significant effect on reducing the proportion of bulk crystals in the copper foil.

[0030] Comparative Examples 1, 4, and 5 all use shielding plates with a width of 30mm. The proportions of bulk crystals of 35um, 70um, and 105um are 75%, 40%, and 25%, respectively. This shows that the same width of shielding plate has different effects on the proportion of bulk crystals of copper foils of different specifications. As the specifications increase, the proportion of bulk crystals decreases significantly.

[0031] In summary, the shielding plate is effective in reducing the proportion of bulk crystals in copper foil. The wider the shielding plate, the better the effect of reducing the proportion of bulk crystals in copper foil. However, it is necessary to consider the installation position of the cathode roller to prevent scratching the cathode roller and to prevent electrolyte backsplashing.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0033] Furthermore, in this invention, descriptions involving terms such as "primary," "secondary," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "primary" or "secondary" may explicitly or implicitly include at least one of that feature. In the description of this invention, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

Claims

1. A structure capable of reducing the proportion of bulk grains of electrolytic copper foil, characterized by The utility model relates to a shielding plate for electrolytic tank, which comprises: A shielding plate (1) is detachably installed on the upper side of the titanium plate (3) at the position corresponding to the liquid return port (4) of the electrolytic tank (2) to improve the liquid level at the position corresponding to the liquid return port (4) of the titanium plate (3).

2. The structure capable of reducing the proportion of bulk grains of electrolytic copper foil according to claim 1, characterized by: The shielding plate (1) is L-shaped in cross section and is arranged at the upper corner of the titanium plate (3).

3. The structure capable of reducing the proportion of bulk grains of electrolytic copper foil according to claim 1, characterized by: A plurality of mounting holes (11) are arranged on the shielding plate (1) along the length direction, and the shielding plate (1) is connected to the titanium plate (3) through screws passing through the mounting holes (11).

4. The structure capable of reducing the proportion of bulk grains of electrolytic copper foil according to claim 1, characterized by: The thickness of the shielding plate (1) is 3-5 mm.

5. The structure for reducing proportion of bulk grains of electrolytic copper foil according to claim 1, characterized by: The transverse width of the shielding plate (1) is 30-70 mm.

6. The structure for reducing proportion of bulk grains of electrolytic copper foil according to claim 1, characterized by: The shielding plate (1) is made of PVC material.

7. A method of using a structure for reducing the proportion of blocky grains of electrolytic copper foil according to any one of claims 1 to 6, characterized by, The method comprises the following steps: S1. Select the width and length of the shielding plate (1) according to the thickness of the titanium plate (3), the electrolytic tank (2) and the copper foil to be produced, and produce the shielding plate (1); S2. Install the shielding plate (1) along the length direction at the edge of the titanium plate (3), and adjust the installation position of the shielding plate (1) so that it is kept at a distance of 2-3 cm from the surface of the titanium roller of the electrolytic copper foil; S3. According to the production of the copper foil, the electrolyte flowing to the position of the shielding plate (1) is blocked, thereby raising the liquid level, so that the electrolyte can cover the surface of the titanium roller just entering the electrolysis area to perform early wetting; S4. Block crystal proportion detection, the copper foil sample is converted into block crystal by high-temperature baking, and the baked copper foil sample is sliced to read the block crystal proportion.

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