A method for surface treatment of electrolytic copper foil

Abstract

The present application relates to a kind of electrolytic copper foil surface treatment method, in the production process of surface treatment rough solidification, special morphology is generated, the top of copper foil rough surface peak and waist are " sea urchin " roughening organization morphology, each pointed copper tumor is formed by the stacking of multiple small copper tumor.The special surface of the present application is treated with electrolytic copper foil and has the characteristics of thin copper foil, special micro-morphology and wide coverage area, low roughness of treatment surface, sufficient anti-peeling performance, low conductor insertion loss, etc., suitable for packaging carrier board and high-frequency high-speed circuit manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of copper foil processing, and specifically relates to a method for surface treatment of electrolytic copper foil. Background Technology

[0002] Copper foil has become a key raw material for PCBs in electronic products, playing a crucial role in supporting and interconnecting components. It is often likened to the "neural network" of signal and power transmission and communication in electronic products. Since the beginning of the 21st century, the rapid development of IT products, especially in recent years with the advancements in smartphones, IC chips and packaging, servers, and 5G base stations, has driven PCBs towards multi-layering, thinning, high density, and high speed. This has also demanded that copper foil, entering a new era of technological development, possess even higher performance, higher quality, and higher reliability.

[0003] For IC packaging substrates, the substrate materials include copper foil, substrate, dry film, wet film, and metal materials. The minimum copper foil thickness required for IC substrates can be 1.5μm, typically 2-18μm. High-frequency, high-speed circuits also use copper foil with thicknesses of 12 / 15 / 18μm. Furthermore, resin substrates are becoming increasingly thinner, with some even featuring low resin content. These changes in copper foil and resin substrates reflect the adaptation of PCBs to multilayer and thinner designs. PCBs are manufactured by laminating resin substrates and copper foil to form a "sandwich" structure, followed by hot pressing. Generally, thinner copper foil has lower roughness. Lower roughness results in fewer mechanical bonding points between the copper foil and resin substrate at the microscopic level, leading to lower macroscopic adhesion (peel strength) at the interface. This can pose risks and hazards during downstream PCB drilling or reflow soldering processes, making the peel strength of copper foil a crucial concern for the copper foil industry and downstream customers.

[0004] The peel strength of the copper foil was quantified according to IPC-TM 650 2.4.8C measurements. Based on elasticity theory, the factor affecting mechanical adhesion P is the tensile strength σ of the resin. N The ratio of copper foil modulus E to resin modulus Y, and the thickness y of the deformed resin. o Copper foil thickness δ. From the formula, we can see that "mechanical adhesion P" is positively correlated with "copper foil thickness δ". The thinner the copper foil, the smaller its P value will be.

[0005]

[0006] During the hot-pressing process, the thickness of the deformed resin is directly related to the roughness of the copper foil. Generally speaking, the increase of the roughness of the copper foil is beneficial to the improvement of the peel strength, and it is necessary to point out that the excessively high roughness will cause the following problems: when the distance between two copper conductors is too narrow, there may be a short circuit risk between the adjacent conductors due to residual copper. As the thickness of the resin substrate becomes thinner, the copper foil with large roughness may pierce the substrate and cause the upper and lower copper foils to be connected and short-circuited. In high-frequency high-speed circuits, there is a phenomenon called'skin effect', that is, when the frequency of the transmitted signal is higher, the current is more concentrated on the outer layer of the conductor, and the'skin effect' is more obvious, and the roughness of the copper foil is larger, the conductor loss is higher. Therefore, the copper foil with excessively high roughness will cause the signal attenuation to be more serious and even distorted.

[0007] In summary, the copper foil suitable for the field of high-frequency high-speed circuit boards needs to be designed with appropriate roughness to balance the peel strength and signal transmission performance. However, for very thin copper foils, the roughness is naturally low, and it is difficult to improve the peel strength. This bottleneck also brings challenges to the development of related industries. Therefore, it is practical to study the micro-morphology of thin copper foil products without significantly changing the roughness, so as to provide more mechanical riveting force and improve the peel strength. It is of great significance to promote the development of high-end copper-clad plate industry, especially for the current 5G communication high-end copper-clad plate or PCB. SUMMARY

[0008] In view of the technical bottleneck that the copper foil with low roughness must be used in IC packaging boards to ensure sufficient peel strength, the present application aims to develop a new improved electrolytic copper foil surface treatment technology to meet the requirements of packaging boards and its application in printed circuit boards.

[0009] The electrolytic copper foil surface treatment method of the present application comprises:

[0010] (1) Pre-treatment of the green foil to obtain a pre-treated green foil;

[0011] (2) Roughening: immersing the pre-treated green foil in a roughening solution for electroplating;

[0012] (3) Solidification: immersing the roughened copper foil in a solidification solution for electroplating;

[0013] (4) Whisker treatment (micro-roughening): immersing the solidified copper foil in a roughening solution for electroplating;

[0014] (5) Ashing and passivation: ashing and passivation treatment on the surface of the whisker-treated copper foil to form a metal barrier layer;

[0015] (6) Coating, drying: coating the surface of the copper foil after ashing and passivation treatment with silane coupling agent, and drying.

[0016] The preferred mode of the above preparation method is as follows:

[0017] The pretreatment parameters in step (1) are H2SO4 90-110 g / L, electrolyte temperature: 27-35°C; treatment time: 8-15 s. The roughening solution in step (2) comprises: Cu 2+ 9-13 g / L, H2SO4: 120-160 g / L, and the additive is at least two of sodium tungstate, sodium molybdosilicate, sodium molybdate, sodium molybdovanadate, sodium thiomolybdate, and sodium thiosilicate; the additive concentration is 10-60 ppm; the plating parameters are: current density 10-40 A / dm 2 , time 8-15 s.

[0018] Preferably, the roughening solution in step (2) comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, sodium tungstate additive concentration: 5-30 ppm, sodium molybdate or sodium thiomolybdate additive concentration: 5-30 ppm; electrolyte temperature 27-35°C.

[0019] Further preferably, the roughening solution comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, sodium tungstate additive concentration: 10-30 ppm, sodium molybdate or sodium thiomolybdate additive concentration: 10-30 ppm.

[0020] The solidification solution in step (3) comprises: Cu 2+ 50-70 g / L, H2SO4 100-130 g / L, solidification solution temperature: 45-53°C; the plating parameters are: current density 15-50 A / dm 2 , time 8-15 s.

[0021] The roughening and then solidification are repeated 1-4 times.

[0022] The roughening solution in step (4) comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, and the additive is at least two of sodium tungstate, sodium molybdosilicate, sodium molybdate, sodium molybdovanadate, sodium thiomolybdate, and sodium thiosilicate; the additive concentration is 10-60 ppm; the plating parameters are: current density 5-10 A / dm 2 , time 8-15 s.

[0023] Preferably, the roughening solution in step (4) comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, sodium tungstate additive concentration: 5-30 ppm, sodium molybdate or sodium thiomolybdate additive concentration: 5-30 ppm; electrolyte temperature: 27-35℃.

[0024] Further preferably, the roughening solution in step (4) comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, sodium tungstate additive concentration: 10-30 ppm, sodium molybdate or sodium thiomolybdate additive concentration: 10-30 ppm.

[0025] The ashing treatment parameters in step (5) are: Ni 2+ 0.6-2.0 g / L, Zn 2+ 1.2-2.5 g / L, K4P2O7 110-145 g / L, pH value: 9-11, current density: 0.4-1.0 A / dm 2 , electrolyte temperature: 42-48℃, treatment time: 8-15 s;

[0026] The parameters of the passivation layer are: Cr 6+ 0.5-1.5 g / L, pH value: 11-13, current density: 0.4-1.0 A / dm 2 , electrolyte temperature: 27-33℃, treatment time: 8-15 s.

[0027] The silane coupling agent in step (6) is one of acrylic-based silane coupling agent, epoxy-based silane coupling agent, amino silane coupling agent, and mercapto silane coupling agent; the concentration of the silane coupling agent is 0.3-1.0 wt%; the drying temperature is 150-250℃.

[0028] The copper foil prepared by the method of the present application has a "urchin-shaped" roughening tissue morphology on the peak top and waist of the copper foil, and each sharp conical copper tumor is formed by stacking a plurality of small copper tumors; there are about 5-15 sharp conical copper tumors on each peak top and waist, the height of the sharp conical copper tumor is between 500-1300 nm, and the width is between 200-450 nm; the diameter of a single small copper tumor tissue is between 50-180 nm.

[0029] The copper-clad plate of the present application contains the copper foil prepared by the method.

[0030] The copper-clad plate is prepared by first referring to a "sandwich" structure, laminating the two surfaces of the prepreg against the rough surface of the copper foil prepared by the method, and then performing hot pressing, wherein the hot pressing temperature is between 180-220 DEG C, the surface pressure is between 20-25 kg / m2, and the holding time is between 130-160 min.

[0031] The application of the copper-clad plate in packaging carrier boards and printed circuit boards.

[0032] The production process in the application comprises the following steps: a. surface treatment (coarse solidification treatment, whisker treatment, ashing treatment, passivation treatment, silane coating), b. FCCL preparation of the copper-clad plate, c. PCB printed circuit board processing, testing, etc.

[0033] The coarse solidification surface treatment process uses direct current electrochemical deposition assisted by two-component additives to form a plurality of scattered sharp cone-shaped copper tumor morphologies. The additives used in the coarse solidification surface treatment process are, for example, sodium tungstate + sodium molybdenum phosphate or sodium thiomolybdate two-component additives, the concentration of the sodium tungstate additive is 5-30 ppm, and the concentration of the sodium molybdenum phosphate or sodium thiomolybdate additive is 5-30 ppm; the coarse solidification sequence is: coarse solidification -> solidification -> coarse solidification -> solidification -> whisker.

[0034] The current density in the process of treating the plurality of scattered sharp cone-shaped copper tumor morphologies is between 10-40 A / dm 2 , and the treatment time is between 8-15 s.

[0035] The application aims to develop a new type of electrolytic copper foil surface treatment technology to enable the copper foil to meet the requirements of packaging carrier boards and its application in printed circuit boards. A series of surface treatments are performed on the rough surface of the electrolytic copper foil: (1) first, an acid solution is used to pretreat the light / rough surface of the copper foil to remove the surface oxide layer; (2) two-component composite additives are added to the coarse liquid, and a two-coarse-two-solid treatment process is used to perform "urchin-shaped" coarse organization special morphology roughening treatment on the rough surface of the copper foil; (3) the coarse treatment layer is subjected to whisker treatment to expand the mechanical riveting action points on the "main stem" to further improve the mechanical bonding force; (4) then, nickel, zinc, and chromium metal barrier layer water plating treatment is performed, the nickel-containing layer can improve the etching resistance, the zinc-containing layer can improve the high-temperature oxidation resistance, and the chromium-containing layer can improve the weather resistance; (5) finally, a matching silane coupling agent is coated on the rough surface of the copper foil and subjected to drying treatment to improve the chemical bonding force between the copper foil and the board.

[0036] Further, the application is implemented by the following steps:

[0037] Step one, light / rough surface pretreatment of the copper foil: first, an acid solution is used to pretreat the light / rough surface of the copper foil to remove the surface oxide layer, and the pretreatment time is between 8-15 s;

[0038] Step two, roughening solidification treatment of the foil surface: adding a certain concentration of new two-component composite additives such as sodium tungstate + sodium molybdenum phosphate (sodium thiomolybdate) to the roughening solution, immersing the pre-treated raw foil surface in the roughening solution, and using a direct current power source to electroplate, forming a roughening structure on the surface, the current density is between 10-40 A / dm 2 , the plating time is between 8-15 s, then solidification treatment, immersing the roughened copper foil surface in the solidification solution, using a direct current power source to electroplate, forming a solidified copper layer on the roughened copper layer to prevent copper powder from falling off, the current density is between 15-50 A / dm 2 , the plating time is between 8-15 s; the sequence of roughening and solidification is: roughening → solidification → roughening → solidification.

[0039] Step three, whisker treatment: due to the solidification deposition of some metal precipitates filling the small grooves of the roughening layer to reduce the specific surface area, causing the adhesion to decrease slightly, in order to make up for the loss of adhesion, whisker treatment is needed. Whisker treatment, i.e. micro-roughening treatment, can grow many small copper tumors on the outside of the roughened copper tumors, and through strict control of the deposition rate and deposition amount of copper ions, a more ideal roughening effect is obtained, and the specific surface area of the surface is increased. Immersing the copper foil surface of "step two" in the roughening solution, using a direct current power source to electroplate, forming side branch copper tumors on the surface of the copper foil, the current density is between 5-10 A / dm 2 , the plating time is between 8-15 s;

[0040] Step four, water electroplating of non-copper metal barrier layer: ashing and passivation treatment of the copper foil of "step three" is performed to form a nickel / zinc / chromium metal barrier layer on the surface of the copper foil, improving the oxidation resistance of the copper foil at high temperature and room temperature, etc. The current density during the treatment process is between 0.4-1.0 A / dm 2 , the plating time is between 8-15 s;

[0041] Step five, silane coupling agent coating: selecting a silane coupling agent matched with the downstream resin to coat on the surface of the copper foil, and performing drying treatment to provide chemical bonding force between the copper foil and the resin;

[0042] The copper foil prepared based on the above implementation steps of the present application is tested for relevant performance:

[0043] Step six, preparation of copper-clad plate: first, referring to the "sandwich" structure, laminating the copper foil surface prepared in the steps of the present application on both sides of the prepreg, and then hot pressing, wherein the hot pressing temperature is between 180-220℃, the surface pressure is between 20-25 kg / m 2 , and the holding time is between 130-160 min.

[0044] Step seven, anti-peeling strength test: first, the copper-clad plate after hot pressing is cut into a sample with a width of 3.0 mm using a cutting knife; then the copper foil on one side of the sample is peeled off 1-2 cm from the clamping position by means of an art knife, the copper foil in the clamping position is fixed on the anti-peeling machine clamp, and finally the anti-peeling strength test is carried out on the peeling strength tester by moving the clamp upwards to drive the copper foil sample to slide.

[0045] Step eight, signal transmission performance test: the copper-clad plate after hot pressing is used to make a sample for transmission characteristic determination, and the transmission loss in the high frequency bandwidth is determined. In the evaluation of transmission characteristics, the vector network analyzer VNA is used to determine the insertion loss of the PCB board at 4GHz by using the band line resonator method (microstrip line structure: dielectric thickness of 50μm, conductor length of 1.0mm, conductor thickness of 12μm, conductor circuit width of 120μm, characteristic impedance of 50Ω, and no cover layer film, the method of determining S21 parameter), and the average value of 5 tests is taken as the final test result of the sample. The greater the insertion loss of the board, the greater the negative absolute value.

[0046] Advantages

[0047] The present application adopts this surface treatment technology to form a special "urchin-like" roughening organization morphology on the rough surface of the copper foil, and grow side branch tumors on the sharp conical copper tumors, and have certain deep plating ability, which increases the specific surface area. The larger specific surface area improves the contact area of the copper foil and the resin, which is a prerequisite for ensuring the anti-peeling strength. The numerous scattered sharp conical copper tumors and side branch tumors can better root in the resin and form a rivet structure to further ensure the mechanical bonding force. In addition, the coating of silane can further improve the chemical bonding force between the copper foil and the board. Finally, the above three conditions can better ensure the sufficient anti-peeling strength and stability of the copper foil. And this special copper tumor roughening structure slightly reduces the roughness of the finished foil, the signal transmission loss is small, and it is suitable for IC packaging board and high frequency and high speed circuit manufacturing.

[0048] The present application provides a new type of electrolytic copper foil with "urchin-like" roughening organization morphology roughening surface treatment technology, using this new type of additive compared with traditional additives, the copper foil rough surface treatment surface roughening organization morphology is special, has the following characteristics: (1) the top and waist of the copper foil rough surface organization presents "urchin-like" roughening organization morphology, each sharp conical copper tumor is formed by stacking multiple small copper tumors; each peak top and waist about 5-15 sharp conical copper tumors, the height of the sharp conical copper tumor is between 500-1300 nm, the width is between 200-450 nm; the diameter of a single small copper tumor organization is between 50-180 nm; (2) wide coverage, sharp conical copper tumors are distributed on the peak top and waist of the copper foil rough surface; (3) the roughness of the treated surface is low, the contact type roughness Rz of the 12 micron finished foil is between 3.0-4.5 μm, the non-contact type roughness Rz is between 4.5-5.5 μm, the surface roughness Sz is between 7-9.5 μm, the peak density Spd is between 20000-27000 mm -2 , the surface area ratio is between 1.30-1.60, the peak curvature Spc is between 200-350 mm -1 , the interface expansion area ratio Sdr is between 60-80%; (4) sufficient peel resistance, the peel resistance of the 12 micron finished foil and the wlm1 resin substrate prepreg after hot pressing is not less than 0.7 kgf / cm; (5) low conductor insertion loss, the PCB processed from the 12 micron finished foil and the wlm1 resin substrate prepreg has an insertion loss between -1.10--2.00 dB / in at a signal frequency f=4 GHz. Therefore, the special surface morphology of the electrolytic copper foil of the present application has the characteristics of thin copper foil thickness, special micro-morphology of the rough surface, low roughness, sufficient peel resistance, low conductor insertion loss and the like. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 Figure (a) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 1; (b) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 2;

[0050] Figure 2 Figure (a) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 1; (b) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 2;

[0051] Figure 3 Figure (a) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 1; (b) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 2;

[0052] Figure 4 Figure (a) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 1; (b) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 2;

[0053] Figure 5 Figure (a) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 1; (b) is the SEM morphology of the treatment surface of the finished copper foil of Comparative Example 2;

[0054] Figure 6Laser confocal nephogram of surface roughness of the treated surface of the finished copper foil of Example 1;

[0055] Figure 7 Schematic diagram of the roughening structure of a spherical morphology;

[0056] Figure 8 Schematic diagram of the roughening structure of a special sharp cone-shaped copper tumor morphology. DETAILED DESCRIPTION

[0057] The application is further described in conjunction with the specific embodiments. It should be understood, however, that these embodiments are intended to illustrate the application and not to limit the scope of the application. Moreover, it should be understood that various modifications and changes can be made to the application by those skilled in the art upon reading the contents of the present application, and such equivalent forms are also within the scope of the appended claims.

[0058] Example 1

[0059] Basic process: green foil pretreatment → roughening → solidification → roughening → solidification → whisker → ashing → passivation → silane coupling agent → drying → copper-clad plate preparation → peel resistance test → processing of copper-clad plate into printed circuit board.

[0060] The copper foil for packaging board and the method for preparing the printed circuit board thereof are described in detail as follows:

[0061] S1. Green foil pretreatment

[0062] The specific parameters in the green foil pretreatment process are as follows:

[0063] H2SO4 concentration: 100 g / L;

[0064] Treatment temperature: 31℃;

[0065] Liquid flow rate: 5.0 m 3 / h;

[0066] Treatment time: 9 s;

[0067] S2. Additive-assisted roughening treatment / solidification treatment

[0068] The specific parameters in the roughening process are as follows:

[0069] Cu 2+ ion concentration: 12 g / L;

[0070] H2SO4 concentration: 140 g / L;

[0071] Sodium tungstate concentration: 10 ppm, sodium molybdate concentration: 15 ppm;

[0072] Electrolyte temperature: 33℃;

[0073] Roughening solution flow rate: 5.0 m 3 / h;

[0074] Average current density: 25 A / dm 2 ;

[0075] Treatment time: 9 s;

[0076] The specific parameters for the solidification stage are as follows:

[0077] Cu 2+ Ion concentration: 55 g / L;

[0078] H2SO4concentration: 120 g / L;

[0079] Solidification solution temperature: 52°C;

[0080] Solidification solution flow rate: 8.0 m 3 / h;

[0081] Solidification current density: 45 A / dm 2 ;

[0082] Treatment time: 9 s;

[0083] The S2 roughening treatment / solidification treatment was repeated once;

[0084] S3. Additive-assisted whisker treatment

[0085] The specific parameters during the whisker treatment are as follows:

[0086] Cu 2+ Ion concentration: 9 g / L;

[0087] H2SO4concentration: 120 g / L;

[0088] Sodium tungstate concentration: 10 ppm, sodium molybdate concentration: 20 ppm;

[0089] Electrolyte temperature: 30°C

[0090] Roughening solution flow rate: 5.0 m 3 / h;

[0091] Average current density: 5 A / dm 2 ;

[0092] Treatment time: 9 s;

[0093] S4. Non-copper metal ashing / passivation layer treatment

[0094] The parameters during the nickel / zinc ashing layer process are as follows:

[0095] Ni 2+ Concentration: 1.0 g / L;

[0096] Zn 2+ Concentration: 1.5 g / L;

[0097] K4P2O7 concentration: 125 g / L;

[0098] pH: 10;

[0099] Current density: 0.55 A / dm 2

[0100] Electrolyte temperature: 45°C;

[0101] Treatment time: 9 s;

[0102] The parameters in the passivation layer process are as follows:

[0103] Cr 6+ Concentration: 1.0 g / L;

[0104] pH: 12;

[0105] Current density: 0.85 A / dm 2 ;

[0106] Electrolyte temperature: 30°C;

[0107] Treatment time: 9 s;

[0108] S5. Silane coupling agent coating and drying

[0109] The parameters in the construction of the chemical bonding layer process are as follows:

[0110] Acrylic base silane concentration: 0.8 wt%;

[0111] Silane solution temperature: 30°C;

[0112] Silane solution flow rate: 4.0 m 3 / h;

[0113] Oven temperature: 180°C;

[0114] S6. Preparation of copper-clad plate

[0115] The process parameters in the plate pressing process are as follows:

[0116] Prepreg model: wlm1 (low resin content)

[0117] Pressing temperature: 195°C

[0118] Soaking time: 140 min

[0119] Unit area pressure: 20 kgf / m 2

[0120] S7. Peel strength test parameters are as follows (standard IPC-TM 650 2.4.8C):

[0121] Spline width: 3.175 mm

[0122] Peel length: 1 cm

[0123] Peel angle: 90°

[0124] Peel speed: 50 mm / min

[0125] Number of tests per spline: 3

[0126] S8. Signal transmission performance test: The copper-clad board using thermal compression is used to make a sample for transmission characteristic measurement, and the transmission loss in the high frequency bandwidth is measured by a vector network analyzer VNA. The parameters of the signal transmission performance test process are as follows:

[0127] Test spline structure: microstrip line

[0128] Electrolyte thickness: 50 pm

[0129] Conductor length: 1.0 mm

[0130] Conductor thickness: 12 pm

[0131] Conductor circuit width: 120 pm

[0132] Characteristic impedance: 50 W

[0133] Test frequency: 4 GHz

[0134] Number of tests per sample: 5.

[0135] Example 2

[0136] The difference between this example and Example 1 is that the type and concentration of silane coupling agent used in the chemical bonding layer process are adjusted, the acrylic-based KBM503 silane coupling agent is replaced with an amino-based KBM903 silane coupling agent, and the silane concentration is changed from 0.8 wt% to 1.0 wt%.

[0137] Example 3

[0138] The difference between this example and Example 1 is that the type of silane coupling agent used in the chemical bonding layer process is adjusted, and the acrylic-based KBM503 silane coupling agent is replaced with an epoxy-based KBM403 silane coupling agent.

[0139] Example 4

[0140] The difference between this example and example 1 is that the concentration of the additive in the roughening process is adjusted. The concentration of sodium tungstate used in the roughening process is adjusted from 10 ppm to 5 ppm, and the concentration of sodium molybdate phosphate is adjusted from 15 ppm to 5 ppm.

[0141] Example 5

[0142] The difference between this example and example 1 is that the concentration of the additive in the roughening process is adjusted. The concentration of sodium tungstate used in the roughening process is adjusted from 10 ppm to 30 ppm, and the concentration of sodium molybdate phosphate is adjusted from 15 ppm to 30 ppm.

[0143] Example 6

[0144] The difference between this example and example 1 is that the concentration of the additive in the roughening process is adjusted. The concentration of sodium tungstate used in the roughening process is adjusted from 10 ppm to 5 ppm, and the concentration of sodium molybdate phosphate is adjusted from 15 ppm to 5 ppm.

[0145] Example effect: The physical property parameters of the finished product foil produced by the parameter processing of this example for packaging board are as follows: (1) the roughening organization morphology of the copper foil surface is "urchin-shaped" on the peak top and waist of the copper foil, and each sharp cone-shaped copper tumor is formed by stacking multiple small copper tumors; there are about 5-15 sharp cone-shaped copper tumors on each peak top and waist, the height of the sharp cone-shaped copper tumor is between 500-1300 nm, and the width is between 200-450 nm; the diameter of a single small copper tumor organization is between 50-180 nm; (2) the coverage area is wide, and the sharp cone-shaped copper tumors are distributed on the peak top and waist of the copper foil surface; (3) the roughness of the treated surface is low, the contact type roughness Rz of the 12 micron finished product foil is between 3.0-4.5 μm, the non-contact type roughness Rz is between 4.5-5.5 μm, the surface roughness Sz is between 7-9.5 μm, the peak density Spd is between 20000-27000 mm -2 , the surface area ratio is between 1.30-1.60, the peak curvature Spc is between 200-350 mm -1 , the interface expansion area ratio Sdr is between 60-80%; (4) sufficient peel resistance, the peel resistance of the 12 micron finished product foil after hot pressing with the wlm1 resin substrate prepreg is not less than 0.7 kgf / cm; (5) low conductor insertion loss, the PCB processed from the 12 micron finished product foil and the wlm1 resin substrate prepreg has an insertion loss between -1.10-2.00 dB / in at a signal frequency f=4 GHz. Therefore, the special surface morphology electrolytic copper foil of the present application has the characteristics of thin copper foil thickness, special micro-morphology, low roughness of the treated surface, sufficient peel resistance, and low conductor insertion loss.

[0146] Comparative example 1

[0147] The difference between this comparative example and Example 1 is that the process parameters in the roughening process are adjusted, and no additive is introduced into the roughening electrolyte.

[0148] Cu 2+ Ion concentration: 12 g / L

[0149] H2SO4 concentration: 140 g / L

[0150] Electrolyte temperature: 33°C

[0151] Roughening solution flow rate: 5.0 m 3 / h

[0152] Average current density: 25 A / dm 2

[0153] Treatment time: 9 s

[0154] Comparative example effect:

[0155] The physical property parameters of the 12 μm finished copper foil treated by the parameters of this comparative example are as follows: the contact roughness Rz is 4.53 μm, the non-contact roughness Rz is 6.15 μm, the root mean square roughness Rq is 1.12 μm, the surface roughness Sz is 10.88 μm, the interface expansion area ratio Sdr is 51.03%, the peak curvature Spc is 326.53 mm -1 , and the peak density Spd is 26050 mm -2 . The peel strength between the 12 μm finished foil produced by the parameters of this comparative example and the wlm1 resin substrate is 0.55 kgf / cm. The PCB material processed by pressing the 12 μm finished copper foil produced by the parameters of this comparative example and the wlm1 resin substrate is tested at a frequency of 4 GHz, and the insertion loss obtained is -2.55 dB / inch.

[0156] Comparative example 2

[0157] The difference between this comparative example and Example 1 is that the type of additive in the roughening process is adjusted, and a commonly used single-component additive, sodium molybdate phosphate, is used.

[0158] Cu 2+ Ion concentration: 12 g / L

[0159] H2SO4 concentration: 140 g / L

[0160] Sodium molybdate phosphate concentration: 25 ppm

[0161] Electrolyte temperature: 33°C

[0162] Roughening solution flow rate: 5.0 m 3 / h

[0163] Average current density: 25 A / dm 2 ;

[0164] Processing time: 9 s;

[0165] Comparative Example Effect:

[0166] The physical properties of the 12 μm finished copper foil after processing with the parameters of this comparative example are as follows: contact roughness Rz is 4.18 μm, non-contact roughness Rz is 6.37 μm, root mean square roughness Rq is 1.09 μm, surface roughness Sz is 10.20 μm, interface expansion area ratio Sdr is 57.18%, peak curvature Spc is 307.93 mm -1 , and peak density Spd is 27800 mm -2 . The peel strength between the 12 μm finished foil produced with the parameters of this comparative example and the wlm1 resin substrate is 0.64 kgf / cm. The PCB material processed by pressing the 12 μm finished copper foil produced with the parameters of this comparative example and the wlm1 resin substrate has an insertion loss of -2.23 dB / inch at a frequency of 4 GHz.

[0167] The finished copper foils prepared by surface treatment in the above examples and comparative examples were tested for performance, and the results are shown in Table 1.

[0168] Table 1. Performance comparison of copper foils prepared in examples and comparative examples

[0169]

[0170] Observation Figure 1 -a and Figure 1 -b, the comparative example copper foil rough surface produced a serious sharp discharge effect, copper particles were mainly deposited on the top of the copper foil peaks, resulting in high roughness, which had a large impact on the insertion loss, and the morphology was coarse spherical morphology, the size of the copper tumor was 800-1300 nm. Compared with Comparative Example 1, the number of copper tumors in Comparative Example 2 increased, but the Sdr values of both were small, and the peel resistance was low.

[0171] And the rough surface of the copper foil of embodiment 1 forms a special "urchin-like" roughening organization pattern, and grows out of the side branch copper tumor on the sharp conical copper tumor, and has a certain deep plating ability, which increases the specific surface area. Larger specific surface area increases the contact area of copper foil and resin, which is a prerequisite to ensure its peel strength. Numerous scattered sharp conical copper tumors and side branch copper tumors can better root in the resin and form a rivet structure to further ensure the mechanical bonding force. In addition, the coating of silane can further improve the chemical bonding force between the copper foil and the plate. Finally, the above three conditions can better ensure the peel strength and stability of the copper foil. And this special copper tumor roughening structure slightly reduces the roughness of the finished foil, the signal transmission loss is small, and it is suitable for IC packaging and high-frequency high-speed circuit manufacturing.

Claims

1. A method for treating the surface of electrolytic copper foil, comprising: (1) pre-treating the green foil to obtain pre-treated green foil; (2) roughening: immersing the pretreated raw foil in a roughening solution to perform electroplating; wherein the roughening solution comprises: Cu 2+ 9-13 g / L, H2SO4: 120-160 g / L, and an additive being at least two of sodium tungstate, sodium molybdate, sodium molybdate silicate, sodium molybdate phosphate, sodium molybdate cobaltate, sodium thiomolybdate, and sodium thiosilicate; the additive concentration is 10-60 ppm; (3) solidification: immersing the roughened copper foil in a solidification solution to perform electroplating; (4) whisker treatment: immersing the solidified copper foil in a roughening solution to perform electroplating; (5) graying and passivation: performing graying and passivation treatment on the surface of the copper foil after whisker treatment to form a metal barrier layer; (6) coating and drying: coating the surface of the copper foil after graying and passivation treatment with silane coupling agent and drying.

2. The process of claim 1 wherein, In step (1), the pre-treatment parameters are H2SO4: 90-110 g / L, treatment temperature: 27-35℃, and treatment time: 8-15 s; The plating parameters in step (2) are: current density 10-40 A / dm 2 , time 8-15 s.

3. The method of claim 1 wherein, the additive is sodium tungstate with a concentration of 5-30 ppm or sodium molybdate or sodium thiomolybdate with a concentration of 5-30 ppm.

4. The method of claim 1 wherein, The solidification liquid in the step (3) includes: Cu 2+ 50-70 g / L, H2SO4: 100-130 g / L, solidification liquid temperature: 45-53 °C; the electroplating parameters: current density 15-50 A / dm 2 , time 8-15 s; The roughening and solidification are repeated 1-4 times.

5. The method of claim 1 wherein, The roughening solution in the step (4) comprises: Cu 2+ 9-13 g / L, H2SO4 120-160 g / L, and an additive is at least two of sodium tungstate, sodium molybdate silicate, sodium molybdate phosphate, sodium molybdate cobaltate, sodium thiomolybdate, and sodium thiosilicate. The additive concentration is 10-60 ppm; the electroplating parameters: current density 5-10 A / dm 2 , time 8-15 s.

6. The process of claim 1 wherein, The ashing treatment parameters in step (5) are: Ni 2+ 0.6-2.0 g / L, Zn 2+ 1.2-2.5 g / L, K4P2O7 110-145 g / L, pH value: 9-11, current density: 0.4-1.0 A / dm 2 , Electrolyte temperature: 42-48℃, treatment time: 8-15 s; The parameters of the passivation: Cr 6+ 0.5-1.5 g / L, pH 11-13, current density 0.4-1.0 A / dm 2 , electrolyte temperature 27-33 °C, treatment time: 8-15 s.

7. The method of claim 1 wherein, In step (6), the silane coupling agent is one of acrylic-based silane coupling agent, epoxy-based silane coupling agent, amino silane coupling agent, and mercapto silane coupling agent; the concentration of the silane coupling agent is 0.3-1.0 wt%; and the drying temperature is 150-250℃.

8. The copper foil produced by the method of claim 1, wherein The peak top and waist of the copper foil roughen into urchin-shaped roughening tissue morphology, and each sharp conical copper tumor is formed by stacking multiple small copper tumors; each peak top and waist has 5-15 sharp conical copper tumors, the height of the sharp conical copper tumor is between 500-1300 nm, and the width is between 200-450 nm; and the diameter of a single small copper tumor tissue is between 50-180 nm.

9. A copper clad plate characterized by, The copper-clad plate contains the copper foil prepared by the method of claim 1.

10. Use of the copper-clad plate of claim 9 in packaging boards and printed circuit boards.

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