Carrier copper foil and preparation method of copper-clad plate thereof

Abstract

The invention relates to a carrier copper foil and a preparation method of a copper-clad plate thereof, which are different from a conventional carrier copper foil structure, the carrier copper foil only comprises a carrier copper layer, a stripping layer and a roughening treatment layer, the carrier copper foil is stripped after being laminated with a resin plate, only roughening copper nodules embedded in the resin are reserved, and the stripping layer and the carrier copper layer are separated from the resin. According to the method, the compatibility of the same carrier copper foil is expanded, the step of separating the ultrathin copper layer from the carrier copper layer is avoided, surface defects caused by separation of the ultrathin copper layer are reduced, and the method has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the field of copper foil processing, and in particular relates to a preparation method of a carrier copper foil and a copper-clad plate thereof. Background Art

[0002] Since the invention of the electronic computer in 1946, the functions of electronic equipment terminals have been continuously enriched, and the computing power of equipment has also been rapidly improved. High integration and precision have always been the goals pursued by the electronic circuit industry. As the basic material of PCB circuit boards, the thickness, roughness, tensile strength, elongation, etc. of copper foil will affect the processing and performance of PCB. Among them, the thickness of copper foil has a particularly significant impact on the line width and line spacing of PCB products. Today, the development of carrier copper foil technology with a thickness of less than 5μm has brought the production of integrated and precise circuit boards to a new level.

[0003] Limited by the production process of rolled copper foil and traditional electrolytic copper foil, when the thickness of copper foil is less than 5μm, due to its own insufficient mechanical properties, the production, storage and transportation of copper foil will become extremely difficult. Therefore, people consider producing ultra-thin copper foil with a thickness of less than 5μm by attaching it to conventional copper foil (such as 18μm). When the copper foil is transported to downstream manufacturers for use, the conventional copper foil is peeled off to complete the use of ultra-thin copper foil. This kind of copper foil is called carrier copper foil.

[0004] After decades of development, the current carrier copper foil has a variety of specifications such as 35+5μm, 18+1.5μm, 18+2μm, and 18+3μm. Its structure includes a carrier copper layer as a support, a peeling layer that provides peelable performance, an ultra-thin copper layer as the main body of use, and a copper nodule treatment layer on its surface. The thickness specifications of the carrier copper foil have been finalized during the production of the copper foil, and the thickness of the ultra-thin copper layer cannot be flexibly adjusted during downstream processing. It is conceivable that when the thickness of the ultra-thin copper foil continues to be thinned or other surface treatment processes begin to be differentiated, the specifications of the carrier copper foil will increase. Coupled with the high price of the carrier copper foil, the test cycle and the threshold for use will be greatly extended. Secondly, the core technology of the carrier copper foil lies in the construction of the peeling layer. The excellent peeling layer structure has uniform interlayer separation force at room temperature and after high-temperature pressing, and the ultra-thin copper layer is subjected to small tearing force and no defects. Improper peeling layer structure can easily cause problems such as the inability to separate the copper layers and uneven separation force, which causes the ultra-thin copper layer to be torn during the peeling process, resulting in local pinholes or abnormal separation interface. This situation that affects the peeling performance can only be solved by adjusting the peeling layer under the existing structure, but there is not much related research at present. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a carrier copper foil and a copper-clad laminate thereof, which avoids the step of peeling off an ultra-thin copper layer from a carrier copper layer and reduces the generation of surface defects and anomalies of the ultra-thin copper layer.

[0006] The present invention provides a method for preparing a carrier copper foil, comprising the following steps:

[0007] (1) preparing a carrier copper layer as a support, and pretreating the carrier copper layer with a mixed solution of sulfuric acid and hydrogen peroxide;

[0008] (2) electrochemically depositing a release layer on the surface of the carrier copper layer using a non-copper metal electroplating process;

[0009] (3) performing a roughening treatment on the surface of the carrier copper layer on which the release layer is deposited, and finally performing a silane coating treatment on the surface of the carrier copper layer to obtain a carrier copper foil.

[0010] Preferably, the thickness of the carrier copper layer in step (1) is between 12-35 μm, and the surface roughness Rz of the copper layer is between 0.9-1.5 μm.

[0011] Preferably, the concentration of the mixed solution of sulfuric acid and hydrogen peroxide in step (1) is between 40-80 g / L, the volume ratio of hydrogen peroxide to sulfuric acid is between 0.1-0.3, and the pretreatment time is between 5-10 s.

[0012] Preferably, the non-copper metal electroplating treatment technology in step (2) is specifically: using a DC power supply to deposit the non-copper metal on the surface of the pretreated carrier copper layer 2-5 times, with a current density between 0.15-1.00A / dm 2 The electrolyte temperature is 40-50°C; after the non-copper metal deposition is completed, an organic peeling layer is coated on its surface, and the hot air oven baking temperature is 150-180°C.

[0013] Preferably, the organic release layer is one or more of chromium chloride methacrylate, molybdenum dialkyl dithiophosphate, and ethyl aluminum dichloride, and the concentration of each additive is between 5-40 ppm.

[0014] Preferably, the roughening treatment in step (3) is specifically: performing a roughening and curing treatment on the surface of the carrier copper layer in an electroplating solution containing an additive for 2-6 times, with a roughening current density of 14-30A / dm 2 The curing current density is between 12-45A / dm 2 The ratio of coarsening and curing current is between 0.7-1.5.

[0015] Preferably, the process conditions of the silane coating treatment in step (3) are: silane concentration is 0.9±0.1wt%, and hot air oven baking temperature is 120-130°C.

[0016] Preferably, the silane coupling agent used in the silane coating treatment is one or more of KH-550, KBM-403, and KBM-903.

[0017] Preferably, the roughness Rz of the treated surface of the carrier copper layer is between 0.6-1.5 μm, the roughness Rz after the peeling layer is attached to the treated surface is between 0.6-1.6 μm, and the roughness Rz of the roughened treated surface of the finished carrier copper foil is between 1.3-2.5 μm.

[0018] Preferably, the copper nodules on the roughened surface of the carrier copper foil are densely distributed, the average curvature radius Spc of the surface characteristic peak is between 57.7-112.1 1 / mm, and the surface characteristic density Spd of the peak point is between 33100-74100 1 / mm 2 The copper tooth height is between 0.5-1.5μm.

[0019] The present invention also provides a method for preparing a copper clad laminate, comprising the following steps:

[0020] (1) laminating the obtained carrier copper foil to a resin sheet and performing a sheet heat pressing process;

[0021] (2) peeling off the carrier copper foil and the resin sheet, retaining the roughened copper nodules embedded in the resin, and obtaining a resin sheet embedded with the roughened copper nodules;

[0022] (3) An ultra-thin copper layer is electrodeposited on the surface of the resin sheet embedded with the roughened copper nodules to obtain a copper-clad laminate.

[0023] Preferably, the process conditions of the hot pressing treatment in step (1) are: temperature of 200-240°C, pressure of 40-45 kgf / m 2 .

[0024] Preferably, the peeling process conditions in step (2) are: an angle of 90° and a peeling line speed of 40-60 mm / min.

[0025] Preferably, the ultra-thin copper layer in step (3) has a thickness of 1.0-5.0 μm.

[0026] Preferably, the process conditions for the electrodeposition in step (3) are: the electrolyte temperature is 50±1°C, the electrodeposition current density is between 150-400A / dm 2 between.

[0027] The present invention also provides a copper clad plate, which is prepared by the above preparation method.

[0028] Beneficial Effects

[0029] The carrier copper foil of the present invention only comprises a carrier copper layer, a peeling layer and a surface-treated copper layer. The ultra-thin copper layer is obtained by electrodeposition after lamination with resin and peeling. The preparation technology proposed by the present invention has the following characteristics: 1. High compatibility of the thickness of the carrier copper layer. The thickness of the carrier copper layer is between 12-35 μm, and the surface roughness Rz is between 0.6-1.5 μm, which broadens the use types of the carrier; 2. Simplified carrier copper foil structure reduces the lengthy production process. Different from the conventional carrier copper foil structure, the finished copper foil of the present invention only includes a carrier copper layer, a peeling layer and a roughening treatment layer. After being pressed with the resin plate, only the copper nodules of the surface treatment layer are embedded in the resin, and the peeling layer and the carrier copper layer are separated from the resin; 3. Dense surface copper nodules are distributed. In order to ensure the stability of the subsequent thickening process, the roughened copper nodule structure is compact, and its roughness Rz is between 1.3-2.5μm, Sz is between 1.2-4.0μm, the average curvature radius Spc of the surface characteristic peak is between 57.7-112.1 1 / mm, and the surface characteristic density Spd of the peak point is between 33100-74100 1 / mm 2 The copper tooth height is between 0.5-1.5μm; 4. High peel strength, the finished foil and bismaleimide triazine BT resin sheet at 240℃, 45kgf / m 2 The copper clad laminate obtained after 4 hours of pressure lamination is thickened to 35μm, and its peel strength is not less than 0.6N / mm; 5. Excellent ultra-thin copper layer performance regulation. The construction of the ultra-thin copper layer is carried out after the plate is pressed. According to the needs of the mSap process, its thickness can be flexibly thickened to between 1.5-5.0μm, which expands the compatibility of the same carrier copper foil, avoids the separation step of the ultra-thin copper layer and the carrier copper layer, and reduces the surface defects of the ultra-thin copper layer caused by separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a comparison diagram of the process of preparing carrier copper foil in the present invention and the prior art; wherein, 1 is a roughening layer; 2 is an ultra-thin copper layer; 3 is a peeling layer; and 4 is a carrier copper layer.

[0031] Figure 2 The figure is a comparison diagram of the process of preparing copper clad laminates according to the present invention and the prior art; wherein, 5 is a resin sheet.

[0032] Figure 3 These are pinhole photographs of the ultra-thin copper layers prepared in Example 1(a) and Comparative Example 1(b). DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0034] Example 1

[0035] 1. Preparation of carrier copper layer

[0036] A mixed solution of H2SO4, CuSO4 and HCl was used as the electrolyte, and a DC power supply was used to electrolytically deposit the carrier copper layer on the cathode roller surface at a certain temperature. The thickness of the prepared carrier copper layer was 18 μm, and the surface roughness of the copper layer Rz was less than 2.5 μm. The parameters of the electrolytic process were as follows:

[0037] H2SO4 concentration: 125g / L

[0038] Cu 2+ Ion concentration: 100g / L

[0039] Cl － Ion concentration: 10mg / L

[0040] Current size: 38A / dm 2

[0041] Electrolyte temperature: 55°C

[0042] Electrolyte flow rate: 15m 3 / h

[0043] Cathode roller linear speed: 9.0m / min.

[0044] 2. Pretreatment of carrier copper layer

[0045] The combined solution of H2SO4 and H2O2 is used as the pretreatment solution to immerse the copper foil in surface pretreatment to remove the surface oxide layer and impurities. After treatment, the copper foil copper layer thickness remains unchanged, and the surface roughness Rz is less than 2.5μm. The pretreatment process parameters are as follows:

[0046] H2SO4 concentration: 60g / L

[0047] H2O2 concentration: 25wt%

[0048] Processing liquid temperature: 35℃

[0049] Processing liquid flow rate: 10m 3 / h

[0050] Processing time: 15s.

[0051] 3. Peel-off layer construction

[0052] The peeling layer is constructed from non-copper metal and organic coupling agent to provide stable peeling performance. The specific parameters of the peeling layer deposition and coating process are as follows:

[0053] (1) Electrodeposition of nickel-containing release layer

[0054] Ni 2+ Concentration: 0.5g / L

[0055] K4P2O7 concentration: 10g / L

[0056] pH value: 11

[0057] Current density: 0.15A / dm 2

[0058] Electrolyte temperature: 40℃.

[0059] (2) Electrodeposition of zinc-containing peeling layer

[0060] Zn 2+ Concentration: 0.5g / L

[0061] K4P2O7 concentration: 20g / L

[0062] pH value: 11

[0063] Current density: 0.3A / dm 2

[0064] Electrolyte temperature: 40℃.

[0065] (3) Organic release layer coating

[0066] Methacrylate Chromium Chloride Concentration: 30ppm

[0067] Coating time: 5s

[0068] Solution temperature: 45°C

[0069] Baking temperature: 130℃.

[0070] 4. Surface roughening

[0071] In the present invention, the surface roughening copper nodules are not only used to enhance the bonding force between the copper foil and the resin sheet, but also will be embedded in the resin sheet as an ultra-thin copper layer electrodeposition substrate after the carrier copper layer is peeled off. The surface roughening process is divided into a roughening treatment and a curing treatment. The roughening treatment is used to generate fine copper nodule crystals on the surface of the peeling layer, and the curing treatment is used to allow the crystals to continue to grow. The two roughening treatments are carried out in different electrolytes, and the roughening and curing treatments are repeated alternately twice. The specific parameters of the roughening process are as follows:

[0072] (1) Roughening parameters

[0073] Cu 2+ Ion concentration: 13g / L

[0074] H2SO4 concentration: 110g / L

[0075] Roughening liquid temperature: 30℃

[0076] Roughening fluid flow rate: 11.0m 3 / h

[0077] Average current density: 14A / dm 2

[0078] Processing time: 10s.

[0079] (2) Curing process parameters

[0080] Cu 2+ Ion concentration: 45g / L

[0081] H2SO4 concentration: 90g / L

[0082] Curing liquid temperature: 50℃

[0083] Roughening fluid flow rate: 11.0m 3 / h

[0084] Average current density: 12A / dm 2

[0085] Processing time: 10s.

[0086] In addition to surface roughening, in order to extend the oxidation resistance and shelf life of copper foil, non-copper metals need to be electroplated on the surface of the roughened copper nodules. The specific parameters of the treatment process are as follows:

[0087] Electrodeposition of nickel-containing anti-oxidation layer

[0088] Ni 2+ Concentration: 1.5g / L

[0089] K4P2O7 concentration: 20g / L

[0090] pH: 11

[0091] Current density: 0.5A / dm 2

[0092] Electrolyte temperature: 40°C

[0093] Processing time: 10s.

[0094] 5. Silane coupling agent coating

[0095] Silane coupling agent coating is mainly used to further enhance the bonding strength between copper foil and resin sheet. In the present invention, the silane coupling agent is coated on the roughened surface by spraying + roller coating. The specific parameters of the coating process are as follows:

[0096] KH-550 silane concentration: 0.9wt%

[0097] Silane liquid temperature: 27°C

[0098] Silane liquid flow rate: 4.0m 3 / h

[0099] Baking temperature: 140℃.

[0100] 6. High temperature pressing of copper foil and resin sheet

[0101] The high-temperature pressing of copper foil and resin sheet is mainly used to embed the roughened copper nodules. Under high temperature conditions, the resin sheet shows fluidity and adheres closely to the copper foil. After cooling, it forms an embedded structure with the roughened copper nodules. The specific parameters of the high-temperature pressing process are as follows:

[0102] Prepreg Model: Bismaleimide triazine BT resin

[0103] Lamination temperature: 240℃

[0104] Insulation time: 180min

[0105] Pressure per unit area: 45kgf / m 2 .

[0106] 7. Separation of copper foil and resin sheet

[0107] In the present invention, the separation process will separate the carrier copper layer and the roughened copper nodules in the carrier copper foil structure from the peeling layer interface, and the roughened copper nodules will remain in the cured resin sheet. The specific parameters of the separation process are as follows:

[0108] Peeling angle: 90°

[0109] Peeling speed: 50mm / min

[0110] Foil surface tension: 60N.

[0111] 8. Ultra-thin copper layer electrodeposition

[0112] In the present invention, the ultra-thin copper layer is produced in this process. The roughened copper nodules embedded in the resin sheet are used as a seed layer to electroplate the ultra-thin copper layer to produce a copper-clad laminate. The specific parameters of the electrodeposition are as follows:

[0113] Cu 2+ Ion concentration: 85g / L;

[0114] H2SO4 concentration: 100g / L;

[0115] Cl - Ion concentration: 30mg / L;

[0116] Gum Arabic: 40ppm.

[0117] Example 2

[0118] The difference between this embodiment and embodiment 1 is that (1) the current density of the carrier copper layer is adjusted, and the thickness of the carrier copper layer is 12 μm; (2) the current density when preparing the metal stripping layer is adjusted from 0.15 A / dm 2 Change to 1.00A / dm 2 (3) The type of organic release layer material was adjusted to dialkyl dithiophosphate oxymolybdenum; (4) The type of silane coating on the surface of the finished foil was adjusted: KH-550 was changed to KBM-403.

[0119] Example 3

[0120] The differences between this embodiment and embodiment 1 are as follows: (1) the current density of the carrier copper layer is adjusted, and the thickness of the carrier copper layer is 35 μm; (2) the type of the organic stripping layer material is adjusted to dialkyl dithiophosphorothioate oxymolybdenum and dichloroethylaluminum; (3) the type of silane coating on the surface of the finished foil is adjusted: KH-550 is changed to KBM-903; (4) the thickness of the ultra-thin copper layer is adjusted from 2 μm to 1.5 μm.

[0121] Example 4

[0122] The difference between this embodiment and embodiment 1 is that (1) the roughening copper nodule treatment process is adjusted, wherein the roughening current density is 30A / dm 2 , curing current density is 45A / dm 2 (2) The type of organic stripping layer material was adjusted to chromium chloride methacrylate and molybdenum dialkyl dithiophosphate; (3) The thickness of the ultra-thin copper layer was adjusted from 2μm to 5μm.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 1 is that (1) the ultra-thin copper layer deposition in step 8 is moved between step 3 peeling layer construction and step 4 surface roughening treatment, that is, the ultra-thin copper layer is electroplated on the surface of the peeling layer instead of the copper nodule surface embedded in the resin after pressing.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 2 is that (1) the ultra-thin copper layer deposition in step 8 is moved between step 3 peeling layer construction and step 4 surface roughening treatment, that is, the ultra-thin copper layer is electroplated on the surface of the peeling layer instead of the copper nodule surface embedded in the resin after pressing.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 3 is that (1) the ultra-thin copper layer deposition in step 8 is moved between step 3 peeling layer construction and step 4 surface roughening treatment, that is, the ultra-thin copper layer is electroplated on the surface of the peeling layer instead of the copper nodule surface embedded in the resin after pressing.

[0129] Comparative Example 4

[0130] The difference between this comparative example and Example 4 is that (1) the ultra-thin copper layer deposition in step 8 is moved between step 3 peeling layer construction and step 4 surface roughening treatment, that is, the ultra-thin copper layer is electroplated on the peeling layer surface instead of the resin-embedded copper nodule surface after lamination.

[0131] Table 1 Main parameters of embodiments and comparative examples

[0132]

[0133]

[0134] Table 2 Comparison of copper foil performance prepared in Example and Comparative Example

[0135]

[0136] The preparation method of the carrier copper foil and the copper clad laminate of the present invention focuses on that the ultra-thin copper layer as the main body is prepared after the copper foil and the resin are pressed together. The specific implementation process is as follows Figure 1 , Figure 2 As shown. The main preparation processes of the comparative examples are all existing technical processes, and the main preparation processes of the embodiments are all processes of this patent. It can be seen from Table 2 that the carrier copper foil samples used in each embodiment meet the requirements of the preparation method of the present invention. Under this manufacturing method, the peeling process between the ultra-thin copper layer and the carrier copper layer can be avoided, and good results can be obtained in the pinhole test process. In comparative examples 1, 2, 3, and 4, except for the adjustment of the preparation sequence of the ultra-thin copper layer, the remaining steps correspond to embodiments 1, 2, 3, and 4 one by one. As a result, the results in the pinhole test are not good, and there are a large number of pinholes such as Figure 3 As shown, this creates a great risk of short circuits when manufacturing fine circuits on copper-clad laminates and PCBs.

Claims

1. A method for preparing a carrier copper foil, comprising the following steps: (1) preparing a carrier copper layer as a support, and pretreating the carrier copper layer with a mixed solution of sulfuric acid and hydrogen peroxide; (2) electrochemically depositing a release layer on the surface of the carrier copper layer using a non-copper metal electroplating process; (3) performing a roughening treatment on the surface of the carrier copper layer on which the release layer is deposited, and finally performing a silane coating treatment on the surface of the carrier copper layer to obtain a carrier copper foil.

2. The preparation method according to claim 1, characterized in that: The thickness of the carrier copper layer in the step (1) is between 12-35 μm, and the surface roughness Rz of the copper layer is between 0.9-1.5 μm.

3. The preparation method according to claim 1, characterized in that: The non-copper metal electroplating treatment technology in step (2) is specifically: using a DC power supply to deposit the non-copper metal on the surface of the pre-treated carrier copper layer 2-5 times, with a current density of 0.15-1.00A / dm 2 The electrolyte temperature is 40-50°C; after the non-copper metal deposition is completed, an organic peeling layer is coated on its surface, and the hot air oven baking temperature is 150-180°C.

4. The preparation method according to claim 1, characterized in that: The roughening treatment in step (3) is specifically: performing a roughening and curing treatment on the surface of the carrier copper layer in an electroplating solution containing an additive for 2-6 times, with a roughening current density of 14-30A / dm 2 The curing current density is between 12-45A / dm 2 The ratio of coarsening and curing current is between 0.7-1.

5.

5. The preparation method according to claim 1, characterized in that: The process conditions of the silane coating treatment in step (3) are: silane concentration is 0.9±0.1wt%, and hot air oven baking temperature is 120-130°C.

6. A method for preparing a copper clad laminate, comprising the following steps: (1) laminating the carrier copper foil obtained as claimed in claim 1 to a resin sheet and subjecting the sheet to a thermal pressing treatment; (2) peeling off the carrier copper foil and the resin sheet, retaining the roughened copper nodules embedded in the resin, and obtaining a resin sheet embedded with the roughened copper nodules; (3) An ultra-thin copper layer is electrodeposited on the surface of the resin sheet embedded with the roughened copper nodules to obtain a copper-clad laminate.

7. The preparation method according to claim 6, characterized in that: The process conditions of the heat pressing treatment in step (1) are: temperature of 200-240°C, pressure of 40-45kgf / m 2 .

8. The preparation method according to claim 6, characterized in that: The thickness of the ultra-thin copper layer in step (3) is 1.0-5.0 μm.

9. The preparation method according to claim 6, characterized in that: The process conditions of the electrodeposition in step (3) are: the electrolyte temperature is 50±1°C, the electrodeposition current density is between 150-400A / dm 2 between.

10. A copper clad laminate, characterized in that: Prepared by the preparation method according to any one of claims 6 to 9.

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