CN114900975A - A kind of ultra-thin copper foil for electronic circuit and preparation method thereof - Google Patents

Abstract

The invention relates to an ultrathin copper foil for an electronic circuit and a preparation method thereof, wherein the copper foil sequentially comprises the following components from bottom to top: a carrier layer, a peeling layer, a non-metal layer, a metal compound layer, a sputtering seed layer, an electrodeposition layer and a surface treatment layer. The invention realizes the support function of the carrier and the peeling function of the peeling layer at the same time by introducing the carrier layer and the peeling layer, and combining the peeling layer coated on the carrier layer with the vacuum sputtering metal layer.

Description

A kind of ultra-thin copper foil for electronic circuit and preparation method thereof

technical field

The invention belongs to the field of copper foil, in particular to an ultra-thin copper foil for electronic circuits and a preparation method thereof.

Background technique

Electrolytic copper foil is an important material for the manufacture of copper clad laminates (CCL) and printed circuit boards (PCB). With the thinning of electronic products and the development of high-frequency and high-speed signal transmission, terminal products have higher and higher requirements for PCBs. PCB performance largely depends on the quality of copper foil, so copper foil must be developed to higher quality and thinner. At present, the thickness of copper foil used in the electronic circuit industry is mainly 12 to 70 μm, while the ultra-thin copper foil less than 9 μm mainly depends on imports. There is no technology that can stably mass-produce ultra-thin copper foil for electronic circuits in China. The technical methods for the production and application of ultra-thin copper foil are the focus of the current work of practitioners in my country's copper foil industry.

Since the traditional electrolytic copper foil is mainly prepared by electrolysis, the cathode roll is used as the electrolytic cathode, and the copper foil is electrolyzed in the acid high-concentration copper sulfate solution to form the copper foil. The thickness of the copper foil is mainly determined by the speed of the cathode roll and the electrolytic current. The thickness of the electrolytic Cu foil can be reduced by increasing the rotation speed or reducing the current. However, the lower the thickness, the easier it is to break and wrinkle. At the same time, electronic circuit copper foil generally needs complex surface roughening and anti-oxidation treatment, and the lengthy processing line must require copper foil to have a certain tensile strength. Therefore, ultra-thin copper foil cannot be produced by traditional production processes, and new production technologies must be developed.

In order to solve the problem of insufficient strength of ultra-thin copper foil, an ultra-thin copper foil with a carrier came into being. The key technical difficulty of copper foil with carrier is that proper bonding force must be maintained between the carrier layer and the peeling layer, that is, the bonding force is not too strong to achieve peeling, and the bonding force is not too weak to achieve a series of subsequent processing such as surface treatment as a whole process. In addition, a barrier layer needs to be introduced between the carrier layer with the carrier copper foil and the ultra-thin copper foil to prevent the adhesion of the ultra-thin copper layer and the carrier layer. At present, in some successful cases abroad, the stripping function is realized by coating a layer of conductive organics (BTA benzotriazole, MBT mercaptobenzothiazole) on the surface of the carrier copper layer. On the one hand, the conductive organic matter can maintain the peeling ability between the ultra-thin copper layer and the carrier layer; However, this method has many problems in practical operation. On the one hand, the conductive organic matter is physically adsorbed on the surface of the carrier copper layer to form a film, and the thickness is not uniform, which often leads to poor uniformity in the subsequent electrodeposition process. On the other hand , the introduction of organic matter often has an important impact in the subsequent electroplating process, affecting the growth of ultra-thin copper foil and the quality of surface treatment, seriously affecting product quality and appearance. Therefore, in recent years, the vacuum coating technology with finer and more controllable control process has been introduced into the manufacturing process of ultra-thin copper foil. However, at present, the preparation of ultra-thin copper foil by vacuum coating technology also faces the problems of poor peeling layer stability and poor barrier effect of the barrier layer. Therefore, selecting a suitable peeling layer and preparing a strict barrier layer is the current vacuum coating to prepare ultra-thin copper for electronic circuits. Foil key.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an ultra-thin copper foil for electronic circuits and a preparation method thereof. By introducing a carrier layer and a peeling layer, applying a peeling layer on the carrier layer and combining the vacuum sputtering coating technology, the The support function of the carrier and the peeling function of the peeling layer are realized at the same time.

The invention provides an ultra-thin copper foil for electronic circuits. The copper foil includes, from bottom to top, a carrier layer, a peeling layer, a non-metallic layer, a metal layer, a metal compound layer, a sputtering seed layer, an electrodeposited layer and a Surface treatment layer.

The carrier layer is one of copper foil, aluminum foil, nickel foil, and polymer film (such as polyimide), with a thickness of 15-35 μm.

The peeling layer is a thermoplastic organic adhesive layer with a thickness of 4-8 μm. The thermoplastic organic adhesive is one of polyacrylic resin and polyurethane resin.

The non-metallic layer is a carbon layer or a silicon layer, and the thickness is 30-50 μm.

The metal layer is a titanium layer, a tantalum layer or a chromium layer; the metal compound layer matches the metal layer, and is a titanium nitride layer, a tantalum nitride layer or a chromium nitride layer. The thicknesses are 20-40 μm and 30-50 μm, respectively.

The sputtering seed layer is a copper layer with a thickness of 50-80 μm.

The electrodeposited layer is a copper layer, a nickel layer, a zinc layer or a chromium layer, and is used for surface roughening and anti-oxidation treatment.

The surface treatment layer is a silane coupling layer, which can improve the peel strength.

The invention provides a preparation method of ultra-thin copper foil for electronic circuits, comprising:

(1) The carrier layer is subjected to surface pretreatment, pickled, washed with water, sprayed with pure water, and dried;

(2) use the coating machine to evenly coat the peeling layer on the single side of the carrier layer, and then transfer to the vacuum condition to continue curing after preliminary curing in the oven;

(3) then send into PVD coating sputtering chamber, and sputter non-metallic layer, metal layer, metal compound layer, sputtering seed layer successively;

(4) Finally, it is transferred to an electroplating machine, thickened by pickling and electroplating, and finally surface-treated to form a surface-treated layer, that is, an ultra-thin copper foil for electronic circuits is obtained.

The pickling in the step (1) is a mixture of one or more of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, oxalic acid and oxalic acid. Sulfuric acid is preferred, the concentration is 150-300g/L, and the time is 5-45s.

The preliminary curing temperature in the step (2) is 80-100°C, the curing time is 30-120min, and then the curing is continued for 1-2h under the condition that the vacuum degree is 1.0×10-1-1.0×10-2Pa.

In the step (3), the working gas Ar is introduced to adjust the vacuum degree of the coating to be controlled between 0.1 and 0.6 Pa. The vacuum sputtering process needs to ensure the constant temperature of the coating substrate. The substrate is placed on the cooling roller, and the substrate is continuously cooled. Cool down. The temperature of the cooling roll is controlled at -15 to 25°C.

The thickening method in the step (4) may be chemical plating, electroplating or vacuum evaporation, and the target thickness is 0.5-9 μm.

The surface treatment in the step (4) includes roughening, curing, blackening, ashing, and passivation on the surface of the ultra-thin copper foil, and coating a silane coupling agent. The treatment process is the same as the surface treatment process in the copper foil industry. .

The invention mainly adopts the combination of coating the peeling layer on the carrier layer and the vacuum sputtering coating technology, so as to achieve the support function of the carrier and the peeling function of the peeling layer at the same time. The peeling layer is mainly a thermoplastic organic adhesive, which has good adhesion with the carrier layer, and at the same time, the interlayer bonding force with the vacuum sputtering layer on the other side is weak, which ensures its peelability. Using vacuum sputtering technology, a non-metallic layer, a metal layer, a metal compound layer and a sputtering seed layer are sequentially sputtered on the surface of the organic layer. The adhesion between the sputtered non-metallic layer and the adhesive is weak, and the metal layer and the metal compound layer jointly realize the anti-diffusion function to prevent the mutual adhesion between the carrier layer and the ultra-thin copper foil. The sputtered seed layer provides "seeds" for the subsequent thickening of electroplating in the subsequent section to ensure the smooth progress of subsequent electroplating. The preparation method can break through the thickness limit of conventional electronic circuit foils, produce ultra-thin copper foils of a series of thicknesses, break through the technical bottleneck in mass production of ultra-thin copper foils in my country, and has important market value.

beneficial effect

(1) The present invention proposes to use a thermoplastic organic adhesive as the peeling layer, and before vacuum sputtering, perform linear curing on one side of the carrier layer to ensure the bonding force with the carrier layer. Since the adhesive has been cured before sputter coating, the adhesive force between the adhesive and the sputtered non-metallic layer is low, which ensures the peeling between the adhesive and the non-metallic layer.

(2) The present invention adopts vacuum sputtering coating to deposit a non-metallic layer and a conductive composite layer of metal and metal compound on the surface of the organic layer. The anti-expansion capability of a single metal layer is limited, and the film structure of the metal compound layer is introduced to enhance its resistance to Cu. Diffusion ability, it is important to ensure its peelable stability to ensure peeling from the non-metallic layer and the adhesive layer.

(3) The present invention achieves both the support function of the carrier and the peeling function of the peeling layer by introducing the carrier layer and the peeling layer, and combining the peeling layer coated with the vacuum sputtering metal layer on the carrier layer.

Description of drawings

1 is a cross-sectional view of the structure of the present invention and the prepreg after high temperature lamination;

2 is a cross-sectional view of the structure when the above-mentioned structural peeling layer is peeled off;

Among them, 1 is the carrier layer, 2 is the peeling layer, 3 is the non-metallic layer, 4 is the metal layer, 5 is the metal compound layer, 6 is the sputtering seed layer, 7 is the electrodeposition layer, 8 is the surface treatment layer, and 9 is the Prepreg.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not 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 also fall within the scope defined by the appended claims of the present application.

Example 1

The copper foil with a width of 1000mm and a thickness of 18μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform layer of thermoplastic adhesive polyacrylate of 5 μm, cured at 80 ° C for 60 minutes, transferred to a vacuum oven, and the baking conditions are 1.0 × 10 ^-1 Pa, 80℃, 120min baking. The baked carrier layer is sent into the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2-0.6Pa, and then the Si target, Ti target, TiN target, and Cu target are sputtered successively. PVD composite film structure of Si-Ti-Ti _x N _y -Cu deposited on the surface, PVD film thickness is plated to 170nm, and the carrier copper foil with conductive layer is electrodeposited in Cu salt solution to thicken to 3μm, 5μm, 7μm , 9μm, and then pass through Cu, Ni, Zn, Cr salt solution, electrodeposit multi-metal layer, rough surface anti-oxidation treatment. The silane coupling agent is coated and dried to obtain an ultra-thin copper foil with a carrier.

Example 2

The copper foil with a width of 1000mm and a thickness of 18μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform thermoplastic adhesive polyurethane of 5 μm, cured at 90 ° C for 60 min, transferred to a vacuum oven, and baked with air extraction, and the baking condition is 1.0×10 ^-1 Pa, 90 ℃, 120min baking. The baked carrier layer is sent into the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2-0.6Pa, and the reaction gas N ₂ is introduced to sputter Si target, Cr target, and Cu target successively. The PVD composite film structure of Si-Cr-Cr _x N _y -Cu is deposited on the surface of the organic adhesive, the PVD film thickness is plated to 170nm, and the carrier copper foil with a conductive layer is electrodeposited and thickened to 3μm, 5μm, 7μm , 9μm, successively through the salt solution of Cu, Ni, Zn, Cr, electrodeposited multi-metal layer. It can roughen the surface and improve the bonding strength with the prepreg. Ni plating on the surface prevents the diffusion of Cu atoms. The surface coating of Zn and Cr mainly plays the role of anti-oxidation. The silane coupling agent is coated and dried to enhance the bonding strength with the prepreg to obtain an ultra-thin copper foil with a carrier.

Example 3

The PI film with a width of 1000 mm and a thickness of 15 μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform layer of thermoplastic adhesive polyacrylate of 5 μm, cured at 80 ° C for 60 minutes, transferred to a vacuum oven, and the baking conditions are 1.0 × 10 ^-1 Pa, 80℃, 120min baking. The baked carrier layer is sent to the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2-0.6Pa to sputter Si target, Ti target, TiN target, Cu target successively, and then sputter Si target, Ti target, TiN target and Cu target on the surface of the organic adhesive. The PVD composite film structure of Si-Ti-Ti _x N _y -Cu was deposited, and the PVD film thickness was plated to 170nm. 9μm, and has undergone Cu, Ni, Zn, Cr salt solution, electrodeposited multi-metal layer, rough surface anti-oxidation treatment. The silane coupling agent is coated and dried to obtain an ultra-thin copper foil with a carrier.

Comparative Example 1

The copper foil with a width of 1000mm and a thickness of 18μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform layer of thermoplastic adhesive polyacrylate of 5 μm, cured at 80 ° C for 60 minutes, transferred to a vacuum oven, and the baking conditions are 1.0 × 10 ^-1 Pa, 80℃, 120min baking. The baked carrier layer is sent to the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2-0.6Pa, then the Si target, Ti target and Cu target are sputtered successively, and Si is deposited on the surface of the organic adhesive. - PVD composite film structure of Ti-Cu, PVD film thickness is plated to 130nm, the carrier copper foil with conductive layer is electrodeposited in Cu salt solution to thicken to 3μm, 5μm, 7μm, 9μm, and then pass through Cu successively, In the salt solution of Ni, Zn, Cr, the multi-metal layer is electrodeposited, and the surface is rough and anti-oxidation treatment. A silane coupling agent is coated and dried to obtain an ultra-thin copper foil with a carrier.

Comparative Example 2

The copper foil with a width of 1000mm and a thickness of 18μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform thermoplastic adhesive polyurethane of 5 μm, cured at 90 ° C for 60 min, transferred to a vacuum oven, and baked with air extraction, and the baking condition is 1.0×10 ^-1 Pa, 90 ℃, 120min baking. The baked carrier layer is sent to the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2~0.6Pa, and the Si target, Cr target, and Cu target are sputtered successively, and Si is deposited on the surface of the organic adhesive. - Cr-Cu PVD composite film structure, PVD film thickness is plated to 130nm, the carrier copper foil with conductive layer is electrodeposited and thickened to 3μm, 5μm, 7μm, 9μm, successively through Cu, Ni, Zn, Cr Electrodeposited polymetallic layers in salt solutions. It can roughen the surface and improve the bonding strength with the prepreg. Ni plating on the surface prevents the diffusion of Cu atoms. The surface coating of Zn and Cr mainly plays the role of anti-oxidation. The silane coupling agent is coated and dried to enhance the bonding strength with the prepreg to obtain an ultra-thin copper foil with a carrier.

Comparative Example 3

The copper foil with a width of 1000mm and a thickness of 18μm was passed through a sulfuric acid pickling tank and a water washing tank successively. And under the action of the coating machine, the surface is coated with a uniform layer of thermoplastic adhesive polyacrylate of 5 μm, cured at 80 ° C for 60 minutes, transferred to a vacuum oven, and the baking conditions are 1.0 × 10 ^-1 Pa, 80℃, 120min baking. The baked carrier layer is sent to the PVD coating chamber for vacuum sputtering coating, and Ar is introduced to adjust the vacuum to 0.2-0.6Pa to sputter Ti target, TiN target, and Cu target successively, and deposit Ti- on the surface of the organic adhesive. PVD composite film structure of Ti _x N _y -Cu, PVD film thickness is plated to 140nm, the carrier copper foil with conductive layer is electrodeposited in Cu salt solution to thicken to 3μm, 5μm, 7μm, 9μm, and then pass through successively In the salt solution of Cu, Ni, Zn, Cr, the multi-metal layer is electrodeposited, and the surface is rough and anti-oxidation treatment. The silane coupling agent is coated and dried to obtain an ultra-thin copper foil with a carrier.

The ultra-thin copper foil with carrier prepared in the 6 groups of examples is pressed and cured at high temperature with the base prepreg. Due to the variety of products corresponding to the carrier copper foil, different products have different pressing processes, and they are tested at the highest pressing temperature. (180 ℃ and 240 ℃, 2h), GB/T29847-2013 method to test its peel strength.

It can be seen from the experimental results that when Cu foil carrier and PI film are used as carriers, the peel strength between the peeling layer and the barrier layer shows a certain regularity. When resin PI film is used as carrier, the peel strength is 0.14-0.2N/15mm, which is higher than that of copper foil carrier. The peel strength was as low as 0.15 to 0.35 N/15mm. The main reason is that during vacuum sputtering coating, PI resin volatilizes impurities under high vacuum conditions, which affects the adhesion between PVD film and adhesive.

The combination of different adhesives and PVD film structure has a certain influence on the peel strength. From the analysis of the experimental results, the combination of polyacrylic resin and PVD film (Si-Ti-Ti _x N _y -Cu) structure, peeling The strength is 0.17~0.25N/15mm; under the condition of high temperature lamination (180℃ or 240℃, 2h), it not only ensures stable peelability, but also has certain adhesion. It is more suitable for the application of carrier peelability between ultra-thin copper foils.

Under the condition of 180 ℃, 2h lamination, single metal layer or composite film layer (metal and metal compound layer) as the barrier layer can achieve stable peeling, and its peel strength meets the requirements. The carrier copper foil has different types of products, and different products have different high-temperature lamination processes. A single metal is used as a barrier layer. After 2 hours of lamination at 240 ° C, the diffusion effect of copper atoms is stronger. During the peeling process of the carrier, adhesion between the carrier layer and the ultra-thin copper layer occurs, resulting in the tearing of the ultra-thin copper foil and the appearance of peeling. instability. The composite film layer or the single metal layer is the barrier layer, and the barrier effect is not very different at lower temperature; however, at higher temperature, the composite film layer has better anti-diffusion effect and provides stable peeling effect.

The composite film layer (metal and metal compound) is a barrier layer, and the lamination temperature is 240°C and 180°C. The higher the lamination temperature, the lower the peel strength.

Compared with Example 1 and Comparative Example 3, the non-metallic layer is removed, and the peel strength is increased from 0.17 to 0.25N/15mm to 0.65 to 0.75N/15mm. Easy to tear, resulting in product failure and unstable peeling.

To sum up: the present invention can meet the production requirements of producing ultra-thin copper foil by introducing organic adhesive and PVD coating technology, which not only ensures a certain adhesiveness, but also has peelability. The invention has simple steps and easy operation, can produce stable ultra-thin copper foil, and has broad technical development and application prospects.

Claims (10)

1. An ultra-thin copper foil for electronic circuits, characterized in that: the copper foil sequentially comprises from bottom to top: a carrier layer, a release layer, a non-metallic layer, a metallic compound layer, a sputtered seed layer, an electrodeposited layer, and a surface treatment layer.

2. The ultra-thin copper foil according to claim 1, wherein: the carrier layer is one of copper foil, aluminum foil, nickel foil and polymer film.

3. The ultra-thin copper foil according to claim 1, wherein: the stripping layer is a thermoplastic organic adhesive layer.

4. The ultra-thin copper foil according to claim 1, wherein: the non-metal layer is a carbon layer or a silicon layer.

5. The ultra-thin copper foil according to claim 1, wherein: the metal layer is a titanium layer, a tantalum layer or a chromium layer; the metal compound layer is matched with the metal layer and is a titanium nitride layer, a tantalum nitride layer or a chromium nitride layer.

6. The ultra-thin copper foil according to claim 1, wherein: the sputtering seed layer is a copper layer.

7. The ultra-thin copper foil according to claim 1, wherein: the electrodeposition layer is a copper layer, a nickel layer, a zinc layer or a chromium layer.

8. The ultra-thin copper foil according to claim 1, wherein: the surface treatment layer is a silane coupling layer.

9. A method for preparing an ultra-thin copper foil for electronic circuits as claimed in claim 1, comprising:

(1) carrying out surface pretreatment on the carrier layer, carrying out acid washing and water washing, spraying by pure water, and drying;

(2) uniformly coating a stripping layer on one side of the carrier layer by using a coating machine, primarily curing in an oven, and finally turning to a vacuum condition for continuous curing;

(3) then sending the mixture into a PVD coating sputtering cavity, and sequentially sputtering a non-metal layer, a metal compound layer and a metal copper seed layer;

(4) and finally, transferring the copper foil to an electroplating machine, performing acid washing and electroplating thickening, and finally performing surface treatment to form a surface treatment layer to obtain the ultrathin copper foil for the electronic circuit.

10. The method for producing according to claim 9, characterized in that: the primary curing temperature in the step (2) is 80-100 ℃, the curing time is 30-120min, and then the vacuum degree is 1.0 multiplied by 10 ^-1 -1.0×10 ^-2 And continuously curing for 1-2h under the condition of Pa.

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