CN114845480A - A kind of flexible copper clad laminate graphene oxide hole metallization method - Google Patents

Abstract

The invention provides a method for metallizing graphene oxide holes of a flexible copper-clad plate. The hole wall produced by the hole metallization method is smooth and flat, has no flaws, and does not have the problem of plating leakage.

Description

A kind of flexible copper clad laminate graphene oxide hole metallization method

technical field

The invention relates to a method for metallizing graphene oxide holes of a flexible copper clad plate, and belongs to the technical field of flexible circuit boards.

Background technique

Flexible Printed Circuit (FPC for short) is a highly reliable and excellent flexible printed circuit board made of polyimide or polyester film as the base material. It has the characteristics of high wiring density, light weight, thin thickness and good bendability, and is widely used in LCD and plasma flat panel displays in the fields of electronics and communications.

Flexible circuit boards are prepared on flexible copper clad laminates through a certain process. Flexible circuit boards can generally be divided into single-sided, double-sided and multi-layer circuit boards. Double-sided and multi-layer circuit boards have two layers of copper plates and multi-layer copper plates, respectively, and the copper plates and the copper plates are separated by a non-conductive base material. Therefore, through holes are required between different copper layers to conduct the lines between layers. Since the substrate is a non-conductive material, copper cannot be plated on the substrate during electroless plating. Therefore, the hole wall of the through hole needs to be metallized (hole metallization) so that it can conduct electricity, so that the electroless copper plating can be carried out smoothly.

At present, there are three main processes for hole metallization: the first is to form a conductive layer from graphite or carbon black; the second is to use a layer of metal palladium as a seed layer; the third is to use pyrrole, thiophene, furan and aniline The conductive polymer layer is formed by polymerizing on the hole wall. However, the conductive layer formed by graphite or carbon black has poor conductivity, and due to the large particle size, it is difficult to attach when the size of the through hole is small; metal palladium is difficult to use in mass production due to its high cost; the polymer conductive layer is currently the most widely used However, the polymerization process requires potassium permanganate solution for oxidation treatment, which pollutes the environment to a certain extent, and the conductive ability of the formed polymer conductive layer is relatively limited. When these traditional hole metallization processes are applied to some more complex high-frequency circuit boards, the hole wall of the circuit board often has the phenomenon of missing conductive layer, which seriously affects the subsequent chemical plating and leads to waste products. Therefore, there is still much room for improvement in the hole metallization process.

SUMMARY OF THE INVENTION

The present invention provides a method for metallizing graphene oxide holes of flexible copper clad laminates, which can effectively solve the above problems.

The present invention is realized in this way:

A method for metallizing graphene oxide holes of a flexible copper clad laminate. The copper clad laminate with a through hole is soaked in an aqueous solution of graphene oxide and then electroless copper is plated.

As a further improvement, the concentration of the graphene oxide aqueous solution is 18-24wt%, and the processing time is 2-10min.

As a further improvement, ultrasonic treatment is also performed during the soaking treatment.

As a further improvement, the frequency range of the ultrasonic wave in the ultrasonic treatment is 20-60 kHz.

As a further improvement, before the immersion treatment, the through hole of the flexible copper clad laminate is also treated with a hole-forming agent.

As a further improvement, after the immersion treatment, a micro-etching solution is also used to perform a micro-etching process on the through holes of the flexible copper clad laminate.

As a further improvement, the through holes are formed by drilling holes on the surface of the flexible copper clad laminate by using an ultraviolet laser drilling machine.

As a further improvement, the power of the ultraviolet laser drilling machine is 4.5W, the scanning speed is 50mm/s, and the number of repeated drilling is 4 times.

As a further improvement, the graphene oxide is formed by the sufficient oxidation reaction of potassium permanganate and graphite powder in concentrated sulfuric acid.

A flexible copper clad laminate prepared by the above method.

The beneficial effects of the present invention are:

In the present invention, graphene oxide solution is used for hole metallization treatment, and the microstructure of graphene oxide is sheet-like. When dispersed in the solution, sheet-like graphene oxide is easily adsorbed on the surface of the copper hole wall, and has a strong electrostatic adsorption force at this time. , the entire pore wall can be completely adsorbed. With the increase of the hole metallization treatment time, that is, the black hole time of the flexible copper clad laminate in the graphene oxide solution increases, the carboxyl group in the graphene oxide molecule undergoes a complex reaction with copper to form an intermetallic complex. The graphene oxide layer directly forms a molecular bond with strong binding force, which will not fall off in the subsequent copper plating process. After the inner wall of the through hole is immersed in copper, the hole wall is smooth and flat, flawless, and there will be no leakage plating problem. In addition, compared with other hole metallization processes, graphene oxide hole metallization has a thinner conductive layer thickness, which is more suitable for high-frequency circuit board production.

The pore metallization method of the invention does not contain formaldehyde carcinogens and the use of chemical liquids that harm the ecological environment, the entire production process is harmless to people, and the graphene oxide waste water can be reused to avoid waste and environmental pollution. At the same time, the technological process is simple, the efficiency is improved, the cost of human resources can be saved, and higher economic benefits can be obtained.

Description of drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Example 1 of the present invention after the graphene oxide black hole is treated for 2 minutes.

2 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Example 2 of the present invention after the graphene oxide black hole is treated for 4 minutes.

3 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Example 3 of the present invention after the graphene oxide black hole is treated for 6 minutes.

4 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Example 4 of the present invention after the graphene oxide black hole is treated for 8 minutes.

5 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Comparative Example 1 of the present invention after traditional carbon black black hole treatment for 4 minutes.

6 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Comparative Example 2 of the present invention.

7 is a metallographic microscope image of a section of the electroplated copper layer of the flexible copper clad laminate provided in Comparative Example 3 of the present invention.

8 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Comparative Example 4 of the present invention.

9 is a metallographic microscope image of a slice of the electroplated copper layer of the flexible copper clad laminate provided in Comparative Example 5 of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, the terms "first" and "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

Embodiments of the present invention provide a method for metallizing graphene oxide holes of a flexible copper clad laminate, wherein the copper clad laminate of a flexible copper clad laminate with through holes is soaked in a graphene oxide aqueous solution and then electroless copper is plated.

As a further improvement, the concentration of the graphene oxide aqueous solution is 18-24wt%, and the processing time is 2-10min. The graphene oxide is formed by the sufficient oxidation reaction of potassium permanganate and graphite powder in concentrated sulfuric acid. Further, graphene oxide is prepared by adding graphite solid powder in concentrated sulfuric acid with a concentration of 98% and stirring evenly. After the mixed liquid is cooled, potassium permanganate is slowly added in 5 times. After the mixed liquid is cooled to room temperature, centrifugal precipitation is obtained to obtain oxidation. Graphene flakes. Wherein, the ratio of concentrated sulfuric acid, graphite solid powder and potassium permanganate is 180-220mL:1.5-2.5g:8-12g, preferably 200mL:2g:10g. The graphene oxide solution prepared by this method has good dispersibility, can be uniformly dispersed in the aqueous solution and does not agglomerate after being placed for a long time. went well. At the same time, potassium permanganate is added in 5 times, and the addition method is that the amount added is first small, then gradually increased, and finally reduced. This way of adding makes graphene oxide molecules with carboxylic acid groups on the edge of the carbon ring and phenolic hydroxyl groups and epoxy groups on the plane of the carbon layer. At the same time, the carboxyl groups are very rich, and the carboxyl groups are complexed with copper to produce intermetallic groups. At this time, the pore wall and the graphene oxide layer directly form a strong molecular bond force, which will not fall off in the subsequent copper plating process.

As a further improvement, ultrasonic treatment is also performed during the soaking treatment, so that the graphene oxide is more uniformly dispersed in the solution, so that the graphene oxide sheets are more uniformly adsorbed on the pore walls. Preferably, the frequency range of the ultrasonic wave in the ultrasonic treatment is 20-60 kHz, preferably 40 kHz, which is most conducive to the dispersion of graphene oxide.

As a further improvement, before the immersion treatment, the through hole of the flexible copper clad laminate is also treated with a hole-forming agent. The whole hole is also called degreasing, the purpose is to remove the oil or other impurities on the surface of the CCL, and make the through holes of the flexible CCL with electronegativity; the flexible CCL after the whole hole treatment is easy to adhere to the conductive layer, and the CCL is soaked. In the graphene oxide suspension with ultrasonic vibration, the hole metallization can be completed for a certain period of time. An ultrasonic generating device is provided in the hole-forming step, so that the negative charge of the hole wall is more uniform. Further, the frequency range of ultrasonic waves is 40-60 kHz. Preferably, when the frequency of the ultrasonic wave is 45 kHz, the dispersion of graphene oxide is most favorable.

The main component of the pore-forming agent is an anionic surfactant, such as polyacrylamide. Due to the combination of polyacrylamide hydrogen bonds and oxygen-containing functional groups in graphene oxide to form van der Waals bonds, the adhesion of graphene oxide to the pore wall is further improved. The pore-forming agent is used in a concentration range of 15-30 wt %, a pH value in a range of 9-12, and is most likely to form hydrogen bonds in the polyacrylamide surfactant at this concentration and pH, and a temperature in the range of 30-40° C. , this temperature is beneficial for hydrogen bonding and oxygen-containing functional group bonding.

As a further improvement, after the immersion treatment, a micro-etching solution is also used to perform a micro-etching process on the through holes of the flexible copper clad laminate. The micro-etching solution is a mixed solution of 60-90 g/L sulfuric acid and 30-50 g/L sodium persulfate. The micro-etching temperature of the micro-etching solution is 30-35° C., and the micro-etching time is 40-90s. The micro-etching solution has good compatibility with graphene oxide and will not cause damage to the GO adhesion layer; the temperature and time are based on the consideration of the protection of the GO adhesion layer.

As a further improvement, the through holes are formed by drilling holes on the surface of the flexible copper clad laminate by using an ultraviolet laser drilling machine. The ultraviolet laser drilling machine is a 355 nm picosecond ultraviolet laser drilling machine, the drilling power is 4.5 W, the scanning speed is 50 mm/s, and the number of repeated drilling is 4 times. Under this drilling condition, the hole wall has a special texture, which is conducive to the attachment of graphene oxide.

As a further improvement, the temperature of the electroless copper plating is 30-42° C., and the copper plating time is 5-15 minutes. The electroless copper plating process can control the thickness of copper plating more accurately, and there is little leakage of the hole wall. The thickness of the copper plating is 15-20 μm, preferably 18 μm.

The embodiment of the present invention also provides a flexible copper clad laminate prepared by the above method. The flexible copper clad laminate can be a double-sided copper clad laminate or a multi-layer copper clad laminate. After the inner wall of the through hole is immersed in copper, the hole wall is smooth and flat, without flaws, and there is no problem of leakage plating; at the same time, the graphene oxide hole is metallized. Compared with other hole metallization processes, the thickness of the conductive layer is thinner, which is very suitable for the production of flexible circuit boards, especially for the production of high frequency circuit boards.

Example 1

The specific process steps of metallizing the graphene oxide holes of the flexible copper clad laminate of the present invention are as follows:

The first step is to use ultraviolet laser drilling to drill several through holes on the flexible copper clad plate; use a 355nm picosecond ultraviolet laser drilling machine, the power of the ultraviolet laser drilling machine is 4.5W, the scanning speed is 50mm/s, repeat The number of drillings is 4 times.

In the second step, the perforated flexible copper clad laminate is washed with circulating water, and then the through hole of the flexible copper clad laminate is processed with a hole-forming agent polyacrylamide. The concentration range of the pore-forming agent is 20wt%, the pH value range is 10, and the set temperature is 35°C. Ultrasonic treatment was used during the whole hole treatment, and the frequency was 45 kHz.

The 3rd step, add the graphite solid powder of 2g in the sulfuric acid of 98% concentration of 200 milliliters and stir well, after waiting for the mixed liquid problem to cool, slowly add 10g potassium permanganate in 5 times (1.5g for the first time, 1.5g for the second time) 2g, 3g for the 3rd time, 2g for the 4th time, 1.5g for the 5th time), centrifugal precipitation after the mixture is cooled to room temperature to obtain graphene oxide flakes, and pure water is added to form a 20wt% graphene oxide solution.

In the fourth step, the flexible copper clad laminate is immersed in the graphene oxide suspension for black hole treatment for 2 minutes. The immersion process was sonicated at a frequency of 40 kHz.

In the fifth step, the flexible copper clad laminate after the black hole is soaked and sprayed in a mixed solution of a micro-etching solution of 80g/L sulfuric acid and 40g/L sodium persulfate to achieve the purpose of micro-etching. The temperature of the micro-etching solution is 32°C, and the micro-etching time of the copper clad laminate is 60s.

The sixth step is to perform chemical copper plating on the washed flexible copper clad laminate. The temperature of the electroless copper plating was 36° C., and the copper plating time was 10 minutes.

The hole wall of the flexible copper clad laminate is treated with black hole for two minutes by graphene oxide. The copper plating layer on the hole wall is shown in Figure 1. The hole bottom is round and complete, without black spots, the hole copper thickness is uniform, and there are a few defects at the hole. Empty, without layers.

Example 2

The difference from Example 1 is that the black hole treatment time is 4 minutes, and other operations are the same as those of Example 1.

The hole wall of the flexible copper clad laminate was treated with black hole for 4 minutes by graphene oxide. The copper plating layer on the hole wall is shown in Figure 2. The hole bottom is round and complete without black spots. The best set of black holes.

Example 3

The difference from Example 1 is that the black hole treatment time is 6 minutes, and other operations are the same as those of Example 1.

The hole wall of the flexible copper clad laminate was treated with black hole for 6 minutes by graphene oxide. The copper plating layer on the hole wall is shown in Figure 3. The hole bottom is round and complete, with a few black spots. The hole copper thickness is uniform, without voids and delamination. There are some defects at the orifice.

Example 4

The difference from Example 1 is that the black hole treatment time is 8 minutes, and other operations are the same as those of Example 1.

The hole wall of the flexible copper clad laminate is treated with black hole for 8 minutes by graphene oxide. The copper plating layer on the hole wall is shown in Figure 4. The hole bottom is round and complete with black spots. There are some defects in the mouth.

Comparative Example 1

The traditional carbon black suspension is used for metallization of the through holes of the flexible circuit board, and other operations are performed at the same time as Example 1.

The carbon black suspension is prepared by adding carbon black powder and dispersant sodium tripolyphosphate into DI water, the mass fraction of carbon black powder is 3%, the mass fraction of dispersant is 4%, and it is fully dispersed by ultrasonic vibration. After the carbon black suspension is made.

The carbon black suspension is used to black hole the hole wall of the flexible copper clad laminate for four minutes. The copper plating layer on the hole wall is shown in Figure 5. The hole wall plating layer is more than 6um, but the residual copper in the hole accumulates to the hole, and the hole bottom plating layer There is delamination with base copper.

Comparative Example 2

The power of the ultraviolet laser drilling machine is 10W, the scanning speed is 60mm/s, the number of repeated drilling is 1 time, and other operations are the same as those in Example 1.

The electroplated copper layer on the hole wall is shown in Figure 6. Since the laser drilling parameters are not optimal parameters, the drilled hole has a lot of residue. During copper plating, copper is deposited on the residue, resulting in copper nodules in the hole.

Comparative Example 3

The pore-forming agent adopts ethylene oxide propylene oxide copolymer, and other operations are the same as those in Example 1.

The copper electroplating layer on the hole wall is shown in Figure 7. Due to the poor adsorption of ethylene oxide and propylene oxide copolymer with GO, it cannot provide hydrogen bonds to bond with GO, GO cannot be uniformly attached to the hole wall, and GO is in the hole. deposition, resulting in an electroplated copper layer depositing thick copper inside the hole.

Comparative Example 4

In the preparation of graphene oxide, potassium permanganate was added at one time, and other operations were the same as in Example 1.

The electroplated copper layer on the hole wall is shown in Figure 8. Due to the one-time addition of potassium permanganate, GO cannot form enough carboxyl groups, and the complex reaction between carboxyl groups and copper is reduced, resulting in GO deposition at the bottom of the hole, and the copper plating layer at the bottom is too thick.

Comparative Example 5

The micro-etching solution is 40g/L sulfuric acid and 80g/L sodium persulfate, and the others are the same as in Example 1.

The copper plating layer on the hole wall is shown in Figure 9. The micro-etching solution has poor compatibility with GO at this concentration, and some GO and GO will be carried out of the hole wall by the micro-etching solution, resulting in poor charging of the hole wall and poor copper plating effect. too thin.

As can be seen from Examples 1-4 and Comparative Examples 1-5, the method for metallizing the graphene oxide holes of the flexible copper clad laminate according to the embodiment of the present invention is mainly to perform hole metallization treatment on the flexible copper clad laminate by using a graphene oxide solution, and at the same time. , and also through the adjustment of the drilling process, the selection and use process of the pore-forming agent, the preparation and use process of graphene oxide, the micro-etching process and the copper plating process, so that each process interacts with graphene oxide and exerts a synergistic effect. , to promote the adhesion of graphene oxide to the hole wall and the formation of the copper-plated layer, thereby forming a uniform, meticulous, and firmly bonded conductive layer, the reliability of the copper-plated layer is higher, and the hole wall is smooth and smooth after copper sinking on the inner wall of the through hole. , and there will be no leakage plating problem.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for metallizing graphene oxide holes of a flexible copper-clad plate is characterized in that the flexible copper-clad plate with through holes is immersed in a graphene oxide aqueous solution and then subjected to electroless copper plating.

2. The flexible copper clad laminate graphene oxide hole metallization method according to claim 1, wherein the concentration of the graphene oxide aqueous solution is 18-24 wt%, and the treatment time is 2-10 min.

3. The flexible copper clad laminate graphene oxide hole metallization method according to claim 1, wherein ultrasonic treatment is further performed in the soaking treatment process.

4. The flexible copper clad laminate graphene oxide hole metallization method according to claim 3, wherein the frequency range of the ultrasonic wave of the ultrasonic treatment is 20-60 kHz.

5. The method for metallizing graphene oxide holes on a flexible copper clad laminate according to claim 1, wherein the through holes of the flexible copper clad laminate are further subjected to hole arrangement treatment by using a hole arrangement agent before the soaking treatment.

6. The method for metallizing graphene oxide holes on a flexible copper clad laminate according to claim 1, wherein after the soaking treatment, the through holes on the flexible copper clad laminate are further microetched with a microetching solution.

7. The method for metallizing graphene oxide holes on a flexible copper clad laminate according to claim 1, wherein the through holes are formed by drilling the surface of the flexible copper clad laminate by using an ultraviolet laser drilling machine.

8. The flexible copper clad laminate graphene oxide hole metallization method according to claim 7, wherein the power of the ultraviolet laser drilling machine is 4.5W, the scanning speed is 50mm/s, and the number of repeated drilling is 4.

9. The flexible copper clad laminate graphene oxide hole metallization method according to claim 1, wherein the graphene oxide is formed by sufficient oxidation reaction of potassium permanganate and graphite powder in concentrated sulfuric acid.

10. A flexible copper clad laminate prepared by the method of any one of claims 1 to 9.

Images