TWI688674B - Liquid crystal polymer metallization method - Google Patents

Abstract

The invention discloses a metallization method of liquid crystal polymer. First, the liquid crystal polymer material is subjected to alkali treatment to clean and roughen the surface of the liquid crystal polymer material. Next, the liquid crystal polymer material is activated to provide metal ions attached to the surface of the liquid crystal polymer material using an activator, and the surface is modified. Next, the liquid crystal polymer material is subjected to reduction treatment, and the reduced metal ion is used as the metal catalyst. Finally, in accordance with the catalytic activity of the metal catalyst, a nickel layer or a nickel alloy layer is formed by electroless plating to form a copper electroplated layer on the nickel layer or nickel alloy layer. The present invention does not need to additionally use a physical method to treat the surface of the liquid crystal polymer material, but directly uses a wet process for the purpose of using nickel to improve the peel strength of the copper foil.

Description

Liquid crystal polymer metallization method

The present invention relates to a metallization method, and particularly to a metallization method for liquid crystal polymers.

Liquid crystal polymer (LCP) material has the characteristics of acid and alkali resistance and high temperature resistance. Compared with polyimide (PI), it has lower water absorption, dielectric constant and thermal expansion coefficient, so the liquid crystal polymer film becomes the main One of the flexible board substrates for high-speed transmission. The traditional LCP soft board is made by high-temperature copper foil lamination, the lamination temperature is close to the LCP melting temperature, and it is difficult to grasp the production yield.

In Taiwan Patent I607866, it is disclosed that the metallization process is carried out on a liquid crystal polymer substrate, in which the liquid crystal polymer material needs to undergo an additional treatment, that is, a C=O functional group with a content of 0.01% or more is formed on the surface, and then undergoes pretreatment and chemical plating The copper and electroplated copper processes are metallized, which requires a longer process and higher cost. In addition, the diffusion between the polymer and the metal interface increases the adhesion between the two through the high temperature environment. The electroless copper plating is easily oxidized to form a copper oxide layer under a high temperature environment. As the thickness of the copper oxide layer increases, the adhesion decreases. The separation of the copper foil and the substrate causes the circuit to peel off or fail to form a circuit during the circuit manufacturing process. In Taiwan Patent I563886, it is disclosed that the trigger particles are added to the resin as an insulating material, and the trigger particles in the hole are activated by laser, and then the metal layer can be plated on the hole, because the trigger particles need to be added, so this process is also required Longer time and higher cost. Another traditional method is sputtering, in which a conductive layer is first sputtered on the substrate, and then copper foil is produced by electroplating. As shown in FIG. 1, this sputtering method can use the sputtering target 10 to form a conductive layer on the liquid crystal polymer material 12, but under the influence of multi-directional and multi-angle scattering of sputtering atoms, the liquid crystal polymer material 12 It is not easy to form a uniform and continuous conductive layer under the non-horizontal surface, even in the case of tiny blind holes 14 or through holes or even sealing holes. Since the liquid crystal polymer material is mainly used for the production of flexible circuit boards, blind holes or through holes are necessary structures for circuit manufacturing. The main function is to conduct double-sided or double-layer circuits. The hole sealing causes the conductive layer in the hole to be uneven or unable to conduct electricity. Subsequent electroplated copper will not be plated.

Therefore, in order to solve the above-mentioned problems, the present invention proposes a metallization method of liquid crystal polymer to solve the problems caused by the prior art.

The main object of the present invention is to provide a metallization method for liquid crystal polymer, which does not require additional physical treatment of the surface of the liquid crystal polymer material, but directly uses a wet process for treatment, in order to use the chemical with excellent oxidation resistance Nickel plating enhances the peel strength of copper foil, provides the thickness required for the formation of electroplated copper, and shortens the manufacturing process and reduces costs. In addition, the isotropic characteristics of the wet process can simultaneously form a uniform conductive layer on non-horizontal surfaces such as blind holes or through holes.

In order to achieve the above object, the present invention provides a method for metallizing a liquid crystal polymer. First, an alkali treatment is performed on the liquid crystal polymer material to clean and roughen the surface of the liquid crystal polymer material. Next, the liquid crystal polymer material is activated to provide metal ions attached to the surface of the liquid crystal polymer material using an activator, and the surface is modified. Next, the liquid crystal polymer material is subjected to reduction treatment, and the reduced metal ion is used as the metal catalyst. Finally, in accordance with the catalytic activity of the metal catalyst, a nickel layer or a nickel alloy layer is formed by electroless plating to form a copper electroplated layer on the nickel layer or nickel alloy layer.

In one embodiment of the present invention, the alkali treatment is to immerse the liquid crystal polymer material in an alkali treatment agent with a concentration of 50 to 500 grams/liter (g/L) for 1 to 30 minutes, and the temperature of the alkali treatment agent is 40 to 80 degrees Celsius.

In one embodiment of the present invention, the alkali treatment agent includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and calcium hydroxide.

In one embodiment of the present invention, the activation process is to immerse the liquid crystal polymer material in the activator for 1 to 10 minutes, and the temperature of the activator is 20 to 70 degrees Celsius, and the concentration of the activator is 0.01 to 5 grams/liter. (g/L).

In one embodiment of the present invention, the metal ion is palladium ion, and the activator includes palladium chloride, dichlorodiammonium palladium, dichlorotetraammine palladium, palladium sulfate, or diammine palladium nitrite.

In one embodiment of the present invention, the reduction process is to immerse the liquid crystal polymer material in a reducing agent with a concentration of 2 to 100 grams/liter (g/L) for 1 to 10 minutes, and the temperature of the reducing agent is 20 degrees Celsius ~70 degrees.

In one embodiment of the present invention, the reducing agent comprises at least one of sodium hypophosphite, sodium dihydrogen hypophosphite, formaldehyde, sodium borohydride, dimethylamine borane, hydrazine, glucose, and ascorbic acid.

In one embodiment of the present invention, the chemical plating method is to immerse the liquid crystal polymer material in a chemical plating solution for 1 to 5 minutes, and the temperature of the chemical plating solution is 30 to 70 degrees Celsius.

In one embodiment of the present invention, the chemical plating solution contains 0.5 to 5 weight percent of water-soluble nickel salt, 1 to 10 weight percent of sting agent, 0.5 to 5 weight percent of reducing agent, and 0.00001 to 0.01 weight percent of stabilizer. , 0.005 to 0.1 weight percent additives, 3 to 10 weight percent acid-base regulator and the remaining weight percent water.

In one embodiment of the present invention, after the step of forming the nickel layer or nickel alloy layer, the nickel layer or nickel alloy layer is baked to form a copper plating layer for power supply on the nickel layer or nickel alloy layer.

In order to make your reviewer have a better understanding and understanding of the structural features and achieved effects of the present invention, I would like to use the preferred embodiment drawings and detailed descriptions, the explanations are as follows:

The embodiments of the present invention will be further explained in the following with the related drawings. As much as possible, in the drawings and the description, the same reference numerals represent the same or similar components. In the drawings, the shape and thickness may be exaggerated for simplicity and convenience. It can be understood that the elements that are not specifically shown in the drawings or described in the specification have a form known to those skilled in the art. Those of ordinary skill in the art can make various changes and modifications according to the content of the present invention.

Please refer to FIG. 2 and FIG. 3 below to introduce the metallization method of the liquid crystal polymer of the present invention. First, as shown in step S10, the liquid crystal polymer material 16 is subjected to alkali treatment to clean and roughen the liquid crystal polymer The surface of the material 16 further increases the adsorption capacity of the catalyst and the adhesion between metals. Specifically, the alkali treatment is to immerse the liquid crystal polymer material 16 in an alkali treatment agent with a concentration of 50 to 500 grams/liter (g/L) for 1 to 30 minutes, and the temperature of the alkali treatment agent is 40 to 80 degrees Celsius degree. The alkali treatment agent includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and calcium hydroxide. Next, as shown in step S12, the liquid crystal polymer material 16 is activated to provide metal ions attached to the surface of the liquid crystal polymer material 16 using an activating agent, and the surface of the liquid crystal polymer material 16 is modified. Specifically, the activation process is to immerse the liquid crystal polymer material 16 in the activator for 1 to 10 minutes, and the temperature of the activator is 20 to 70 degrees Celsius, and the concentration of the activator is 0.01 to 5 grams per liter (g/L ). The metal ion is palladium ion, and the activator includes palladium chloride, dichlorodiammonium palladium, dichlorotetraammine palladium, palladium sulfate, or diammine palladium nitrite. Next, as shown in step S14, the liquid crystal polymer material 16 is subjected to a reduction process to use reduced metal ions as a metal catalyst, that is, palladium metal. Specifically, the reduction process is to immerse the liquid crystal polymer material 16 in a reducing agent with a concentration of 2 to 100 grams/liter (g/L) for 1 to 10 minutes, and the temperature of the reducing agent is 20 to 70 degrees Celsius. The reducing agent includes at least one of sodium hypophosphite, sodium dihydrogen hypophosphite, formaldehyde, sodium borohydride, dimethylamine borane, hydrazine, glucose, and ascorbic acid. After step S14, step S16 is performed.

In step S16, in accordance with the catalytic activity of the metal catalyst, a nickel layer 18 or a nickel alloy layer is formed by electroless plating. In this embodiment, the nickel layer 18 is taken as an example. Specifically, the chemical plating method is to immerse the liquid crystal polymer material 16 in a chemical plating solution for 1 to 5 minutes, and the temperature of the chemical plating solution is 30 to 70 degrees Celsius. The chemical plating solution contains 0.5 to 5 weight percent of water-soluble nickel salt, 1 to 10 weight percent of sting mixture, 0.5 to 5 weight percent of reducing agent, 0.00001 to 0.01 weight percent of stabilizer, 0.005 to 0.1 weight percent of additives, 3 to 10 weight percent of the acid-base regulator and the rest of the weight percent of water, the sum of all component ratios must be 100 weight percent. The concentration of the water-soluble nickel salt is 5 to 50 grams per liter (g/L). The water-soluble nickel salt includes nickel sulfate, nickel chloride and nickel hypophosphite. The concentration of the mixture is 10~100g/L. The mixture contains malic acid, succinic acid, adipic acid, lactic acid, oxalic acid, gluconic acid, citric acid and other carboxylic acids and their salts, glycine, alanine, imine Amino acids such as diacetic acid, arginine and glutamic acid. The concentration of the reducing agent is 5~50g/L. The reducing agent includes hypophosphorous acid and its salts, boron compounds and amine borane compounds. The hypophosphorous acid salts include sodium hypophosphite or potassium hypophosphite. The boron compound includes sodium borohydride Or boron hydride compounds such as potassium borohydride, amine borane compounds include dimethylamine borane (DMAB), trimethylamine borane or triethylamine borane. The concentration of the stabilizer is 0.0001~0.1g/L. The stabilizer contains soluble lead salts or sulfur compounds. Soluble lead salts such as lead acetate and sulfur compounds such as thiourea or thioglycolic acid. The concentration of the additive is 0.05~1g/L. The additive contains the commonly used wetting agent or gloss agent. The pH value of the chemical plating solution is preferably 6-10, and the acid-base adjusting agent includes ammonia water, sodium hydroxide, potassium hydroxide, sulfuric acid and hydrochloric acid. Finally, as shown in step S18, the nickel layer 18 or nickel alloy layer is baked to form a copper plating layer 20 formed on the nickel layer 18 or nickel alloy layer. Specifically, the baking temperature is 200°C to 300°C, and the time is 10 to 60 minutes. Through the baking process, the nickel layer 18 polymerizes with the liquid crystal polymer material 16 in a diffusion manner to form a strong bond, thereby improving adhesion. As the baking temperature increases or the time increases, a higher peel strength is obtained. In this case, the surface of the liquid crystal polymer material 16 does not need to be physically treated, such as forming functional groups or adding trigger particles, and is directly processed by the chemical plating method of the wet process, to use chemical nickel plating with excellent oxidation resistance to promote copper The peel strength of the foil provides the thickness required for the formation of electroplated copper, while shortening the manufacturing process and reducing costs. In addition, the isotropic characteristics of the wet process, if the liquid crystal polymer material 16 is used as the material of the flexible circuit board, a uniform conductive layer can be formed on the non-horizontal surface of the blind hole or through hole of the flexible circuit board at the same time, and the sputtering method It is not easy to form a uniform conductive layer.

The baking process in the above step S18 can also be omitted, so that in step S16, after the nickel layer 18 or the nickel alloy layer is formed, the direct power supply copper plating layer 20 is formed on the nickel layer 18 or the nickel alloy layer, and no additional physical use is required The surface of the liquid crystal polymer material is processed by a wet process, and the peel strength of the copper foil is improved by chemical nickel plating with excellent oxidation resistance to provide the thickness required for the formation of copper plating, while shortening the process and reducing costs .

The experiment was conducted with a liquid crystal polymer film, after alkaline treatment at a temperature of 80°C for 5 minutes, activation treatment at an activation agent, temperature of 50°C and time of 3 minutes, and reduction treatment at a reducing agent, temperature of 25°C and time of 3 minutes Then, electroless nickel plating and copper electroplating were carried out at a temperature of 45°C for 3 minutes. The thickness of the electroplated copper was 18 microns (μm). After drying, the baking process is carried out. Tested on a 10 mm wide copper surface, the peel strength can reach 951 grams per square centimeter (g/cm ² ). After 6 times of bleaching tin treatment according to the IPC TM-650 test method, the peel strength can reach 894g/cm ² .

The experiment was carried out on a liquid crystal polymer copper foil substrate with blind holes with a pore diameter of 100 μm. After an alkali treatment at a temperature of 80° C. for 5 minutes, an activation treatment at an activation agent, a temperature of 50° C. and a time of 3 minutes, a reducing agent and a temperature The reduction treatment was carried out at 25°C for 3 minutes, followed by electroless nickel plating and copper electroplating at a temperature of 45°C for 3 minutes. The thickness of the electroplated copper was 6 μm. After drying, the observation hole and the hole wall can be completely plated to form a continuous conductive layer.

In summary, the present invention can improve the peel strength of copper foil, provide the thickness required for the formation of electroplated copper, and shorten the manufacturing process and reduce the cost.

The above is only a preferred embodiment of the present invention and is not intended to limit the scope of the implementation of the present invention. Therefore, all changes and modifications based on the shape, structure, features and spirit described in the patent application scope of the present invention are cited. , Should be included in the scope of the patent application of the present invention.

10: Sputtering target 12: Liquid crystal polymer material 14: Blind hole 16: Liquid crystal polymer material 18: nickel layer 20: Electroplated copper layer

FIG. 1 is a schematic diagram of a conductive layer formed on a non-horizontal surface of a liquid crystal polymer material by a sputtering target of the prior art. Figure 2 is a flow chart of the metallization method of the liquid crystal polymer of the present invention. FIG. 3 is a cross-sectional view of the structure of the liquid crystal polymer material, nickel plating layer and electroplated copper layer of the present invention.

Claims (9)

A metallization method of liquid crystal polymer, comprising: performing alkaline treatment on liquid crystal polymer material to clean and roughen the surface of the liquid crystal polymer material; performing activation treatment on the liquid crystal polymer material to provide metal with an activator Ions attach to the surface of the liquid crystal polymer material and modify the surface; perform reduction treatment on the liquid crystal polymer material to reduce the metal ion as a metal catalyst; and cooperate with the catalytic activity of the metal catalyst, Forming a nickel layer or a nickel alloy layer by electroless plating, and baking the nickel layer or the nickel alloy layer at a baking temperature of 200° C. to 300° C. to form an electroplated copper layer on the nickel layer or On the nickel alloy layer. The metallization method of liquid crystal polymer according to claim 1, wherein the alkali treatment is to immerse the liquid crystal polymer material in an alkali treatment agent with a concentration of 50 to 500 g/L (g/L) 1 to 30 Minutes, and the temperature of the alkali treatment agent is 40 to 80 degrees Celsius. The method for metallizing a liquid crystal polymer according to claim 2, wherein the alkali treatment agent comprises at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide and calcium hydroxide. The metallization method of liquid crystal polymer according to claim 1, wherein the activation treatment is to immerse the liquid crystal polymer material in the activator for 1-10 minutes, and the temperature of the activator is 20-70 degrees Celsius, The concentration of the activator is 0.01-5 grams per liter (g/L). The method for metallizing a liquid crystal polymer according to claim 4, wherein the metal ion is palladium ion, and the activator comprises palladium chloride, dichlorodiammonium palladium, dichlorotetraammine palladium, palladium sulfate or diammonium nitrite palladium. The metallization method of liquid crystal polymer according to claim 1, wherein the reduction treatment is to immerse the liquid crystal polymer material in a reducing agent with a concentration of 2~100 g/L (g/L) 1~ 10 minutes, and the temperature of the reducing agent is 20 to 70 degrees Celsius. The metallization method of liquid crystal polymer according to claim 6, wherein the reducing agent comprises sodium hypophosphite, sodium dihydrogen hypophosphite, formaldehyde, sodium borohydride, dimethylamine borane, hydrazine, glucose and ascorbic acid At least one of them. The metallization method of liquid crystal polymer according to claim 1, wherein the chemical plating method is to immerse the liquid crystal polymer material in a chemical plating solution for 1~5 minutes, and the temperature of the chemical plating solution is 30~C 70 degrees. The metallization method of liquid crystal polymer according to claim 8, wherein the plating solution contains 0.5 to 5 weight percent water-soluble nickel salt, 1 to 10 weight percent padding agent, 0.5 to 5 weight percent reducing agent, 0.00001~0.01% by weight of stabilizer, 0.005~0.1% by weight of additives, 3~10% by weight of acid-base regulator and the remaining weight of water.

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