KR20020057507A - Method of improving adhesion between polymer and metal - Google Patents

Abstract

The present invention relates to a method for improving adhesion between a polymer and a metal. The ion assist reaction method provides a hydrophilic group to the surface of the polymer and performs electroless plating or electroplating, thereby improving adhesion between the polymer and the metal film or plating itself. Metal film is easily formed on the polymer. Specifically, a reactive gas is injected into the vacuum chamber to irradiate the polymer with an ion beam having energy to partially destroy the bonds of the polymer surface, and a reactive gas is injected into the vacuum chamber to atomize the atoms on the polymer surface where the bond is broken. By reacting with the polymer to change the surface of the polymer to hydrophilic, and to provide a method for improving the adhesion between the polymer and the metal consisting of depositing a metal film on the surface of the polymer changed to hydrophilic. According to the present invention, the metal film is easily formed on the polymer which promotes adhesion between the polymer and the metal film or the plating itself is difficult, and in particular, by modifying the surface of the polymer with an ion beam, plating is possible on the polymer without a metal culture layer. The process can be shortened.

Description

METHOD OF IMPROVING ADHESION BETWEEN POLYMER AND METAL}

The present invention relates to a method for improving adhesion between a polymer and a metal.

Electroless plating and electroplating are a method of easily obtaining a metal thick film with a large area, and are mainly applied to wiring of electrodes and printed circuit boards of various electrical components. In the case of forming a metal film on the polymer by electroless plating or electroplating, the adhesion between the polymer and the metal is generally weak even if the plating itself is not well made or the metal film is formed. Has a number of polymeric surface treatment method is proposed to solve this problem, as a representative of which after the chemical treatment of the surface with sodium-naphthalenide, or surface treated with UV, X-ray radiation or the RF plasma, such as SnCl ₂ or PdCl ₂ After precipitation in the solution to form a thin Pd or Sn film to form a metal culture layer there is a method of electroless plating and electroplating the metal film thereon.

However, such a surface treatment method for electroless or electrolytic plating has to be accompanied by several stages of surface treatment processes, and requires an additional facility for wastewater treatment by using a chemical aqueous solution.

Therefore, an object of the present invention is to improve the adhesion between the polymer and the metal film or to easily form a metal film without a metal culture layer on the polymer that is not well plating itself.

In addition, an object of the present invention is to provide an economical manufacturing process by simplifying a complex surface treatment process when forming a metal film on a polymer by electroless plating or electroplating.

1 is a conceptual diagram of an apparatus for ion beam surface treatment in accordance with the present invention.

Figure 2 is a photograph showing the degree of plating of copper formed on PE and untreated PE modified in an oxygen atmosphere with 1.0 kV argon ions in the present invention.

Figure 3 is a photograph showing the results of the 3M Scotch tape test the adhesion of the modified PP and untreated PP and copper in the present invention.

Figure 4 is a photograph showing the results of the modified PET and untreated PET and copper adhesion test 3M Scotch tape test in the present invention.

Figure 5 is a photograph showing the results of the 3M scotch tape test the adhesion of the modified PTFE and untreated PTFE and copper in the present invention.

6 is an XPS C1s spectrum showing chemical bonds of modified and untreated PTFE in the present invention.

*** Explanation of symbols for main parts of drawing ***

1: vacuum chamber 2: reactive gas inlet

3: ion source 4: substrate

5: vacuum exhaust port

The present invention provides a simplified and environmentally free manufacturing process through the surface treatment using an ion beam instead of the conventional complex surface treatment process in the deposition of a metal film on the polymer and a polymer film deposited by the method. To this end, the present invention provides a hydrophilic group on the surface of the polymer by an ion assist reaction method and performs electroless plating or electroplating to enhance adhesion between the polymer and the metal film or to easily form a metal film on the polymer which is not well plated itself.

Specifically, a reactive gas is injected into the vacuum chamber to irradiate the polymer with an ion beam having energy to partially destroy the bonds of the polymer surface, and a reactive gas is injected into the vacuum chamber to atomize the atoms on the polymer surface where the bond is broken. By reacting with the polymer to change the surface of the polymer to hydrophilic, and to provide a method for improving the adhesion between the polymer and the metal consisting of depositing a metal film on the surface of the polymer changed to hydrophilic.

The ions may be used alone or in combination with a gas capable of ionizing such as argon, nitrogen, hydrogen, helium, oxygen, ammonia, the reactive gas may be used alone or in combination with oxygen, nitrogen, ammonia, hydrogen.

According to the present invention, polymers irradiated with an ion beam having energy and blown with a reactive gas and adhered to a surface-treated metal film may be polyethylene, polypropylene, polytetrafluoroethylene, polyethylene. Thermoplastic or thermosetting resins such as terephthalate (polyethylene terephtalate), silicone rubber (silicon rubber), polystylene (polystylene), polycarbonate (polycabonate), epoxy (epoxy).

In general, the surface of the polymer is hydrophobic. The hydrophobic surface is characterized in that the polymer surface is made hydrophilic by reacting with an atmospheric gas after partially breaking the bond of the polymer surface with an ion beam having acceleration energy in a vacuum chamber. In particular, by controlling the appropriate acceleration voltage and the amount of ions reached per unit area to increase the hydrophilicity of the surface of the polymer, it is possible to reduce the contact angle with distilled water to about 30 ° or less.

Generating hydrophilic functional groups on the surface of the polymer increases the affinity for the electrons on the surface of the polymer, thereby increasing donor-acceptor interaction between the metal atom and the surface of the polymer that readily emit electrons. This donor-upceptor interaction can increase the reactivity with the metal atoms to facilitate the plating of the metal thin film and can improve the adhesion between the plated metal thin film and the polymer substrate. As a result of performing the 3M Scotch tape test as described below to measure the adhesion, the metal film formed on the polymer specimen having the improved hydrophilicity was also found to increase the adhesion.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In the embodiment of the present invention, oxygen was used as the argon ion beam and the atmosphere gas to surface-modify the polymer. Various materials suitable for increasing the hydrophilicity of the surface of the polymer may be used as the kind of ions or the atmosphere gas. A cold hollow ion gun was used as an ion source of the argon ion beam, and metal deposition was performed using an electroless plating method. Electrolytic plating may also be used for metal deposition.

An example of the ion source for polymer surface modification used in the present invention is as follows. 1 is a conceptual diagram of an apparatus for ion beam surface treatment in the present invention, as shown, a portion (2) for introducing a reactive gas into the interior of the vacuum chamber (1), ionize the gas and accelerate the ionized gas ion And an ion source (3), a substrate (4), and a vacuum exhaust port (5) for extracting ions.

Example.

The surface of the polymer was modified under the following experimental conditions.

Experimental vacuum degree: 1 × 10 ^-6 Torr

Acceleration voltage: 300 ~ 2000 V

Inflow oxygen amount: 8 sccm

Surface Modification Materials: Polypropylene (PP), Polytetrafluoroethylene (PTFE), Polyethylene (PE), Polyethylene terephtalate (PET)

Ion Implantation: 1 × 10 ¹⁴ ~ 1 × 10 ¹⁷ ions / cm ²

The metal was deposited on the surface-modified polymer under the following conditions.

Deposition Method: Electroless Plating

Bath temperature: 50 ~ 60 ℃

Solution pH: 11 to 13

Metal Thickness: 20000 ~ 30000 Å

The electroless plating solution composition used is as follows.

CuSO ₄ · 5H ₂ O 6 ~ 10g / l, EDTA 15 ~ 30g / l, TMAH 100 ~ 140g / l, PEG (polyethyleneglycol) 1 ~ 2g / l, 2,2′-Bipyridine 1 ~ 3g / l, HCHO ( 37%) 6 ~ 10g / l, KOH 0 ~ 1.5g / l

TMAH and KOH were used to control the pH of the electrolyzer and 2,2′-Bipyridine was used as a stabilizer to prevent spontaneous deposition of Cu in the plating solution. PEG is also a surfactant that reduces surface energy and prevents the formation of hydrogen droplets on the deposited Cu surface.

In order to determine the degree of hydrophilicity improvement of the surface-modified polymer by ion beam, the acceleration voltage of the ion was fixed at 1000V, and the change in contact angle between the polymer surface and water according to the amount of ions is shown in Table 1.

Change of Contact Angle between Polymer Surface and Water According to Ion Content PE PP PET PTFE Contact angle before treatment 85。 75。 68。 102。 Contact angle after treatment 25。 24。 15。 71。 Processing conditions 1 × 10 ¹⁷ Ar + / cm ² 5 × 10 ¹⁶ Ar + / cm ² 1 × 10 ¹⁶ Ar + / cm ² 1 × 10 ¹⁵ Ar + / cm ²

The contact angle of PE to water decreased from 85 ° before treatment to about 25 ° at 1 × 10 ¹⁷ Ar ⁺ / cm ² treatment conditions. In the case of PP, it decreased from about 75 ° to about 24 ° at 5 × 10 ¹⁶ Ar ⁺ / cm ² treatment conditions. In the case of PET, it was reduced to about 15 ° at the treatment condition of 1 × 10 ¹⁶ Ar ⁺ / cm ² at 68 ° before treatment. And the contact angle of PTFE was reduced to about 71 ° at the treatment condition of 1 × 10 ¹⁵ Ar ⁺ / cm ² at 102 ° before treatment. Decreasing the contact angle means increasing the hydrophilicity of the polymer surface.

When ions having appropriate energy are irradiated on the surface of the polymer, free radicals are formed on the surface, and when the free end reacts with a reactive gas introduced around the surface of the polymer, ether groups, carbonyl groups, carboxyl groups, etc. The functional groups are formed to increase the surface energy of the polymer. Increasing the surface energy means that the surface hydrophilicity is increased, so that the contact angle with respect to water of the polymer surface with increased hydrophilicity is reduced.

2 is a photograph showing the plating degree of copper formed on PE (a) surface-treated in an oxygen atmosphere with 1.0 kV argon ions and PE (b) not surface-treated according to the present invention. As shown in FIG. 2, the copper was hardly plated on the untreated PE, and the plated portion was almost peeled off. However, it can be seen that the copper is plated on the entire surface deposited in the plating solution on the surface-modified PE. By modifying the surface of the polymer with an ion beam, plating on the PE can be performed without a metal layer, thereby shortening the plating process.

Figure 3 is a photograph showing the results of testing the adhesion of the surface modified PP (b) and the untreated PP (a) and copper by 3M Scotch tape according to the present invention. As can be seen in Figure 2, the copper plated on the untreated PP can be seen that most of the peeling off by Scotch tape. On the other hand, the copper plated on the surface-modified PP did not peel off or bucking at all even after testing with Scotch tape. In the case of PP, since there is no polar functional group in the polymer as in PE, it can be seen that this increase in adhesion is due to polar functional groups such as carboxyl groups, carbonyl groups, and ether groups formed by ion assist reactions.

Figure 4 is a photograph showing the results of testing the adhesion of the copper plated on the surface-modified PET (b) and untreated PET (a) by the present invention 3M Scotch tape. Since PET has a carboxyl group and a carbonyl group in the chain of the polymer, the contact angle is relatively low and the surface energy is large, so that the adhesive force with the metal is easy. However, the polar functional groups on the surface of the polymer rearrange in the bulk direction in the air to lower the energy of the whole system. As shown in Fig. 4A, some of the electroless plated copper is peeled off. On the other hand, the copper (b) treated by the ion assisted ion reaction method can be seen that the adhesion is enhanced because there is no peeled part. Therefore, it can be seen that the ion assisted reaction method is also applied to polymers having polar functional groups.

Figure 5 is a photograph showing the results of testing the adhesion of the surface modified PTFE (b) and untreated PTFE (a) and copper by 3M Scotch tape according to the present invention. The copper thin film plated on the PTFE after the ion beam treatment did not peel off as compared with the entire copper thin film plated on the PTFE before the treatment. As described above, the polar functional groups formed by the ion assisted reaction method on the polymer enhance donor-acceptor interaction, thereby improving adhesion. PTFE rapidly changes its surface shape as the ion beam is irradiated. This change in surface shape serves to promote adhesion with the metal through interlocking. In the case of PTFE, since the surface roughness does not change significantly at an ion dosage of 1 × 10 ¹⁵ Ar ⁺ / cm ² or less, the adhesion of the plated copper is improved by the interaction of the polar functional groups, and 1 × 10 ¹⁶ Ar ⁺ / cm ² In the above ion dosage, it can be seen that the plated copper improves adhesion due to the interaction of the polar functional groups and the cohesion of the rough surface.

This adhesion was thought to be due to the enhancement of the donor-acceptor interaction by the ion-assisted reaction of atmospheric oxygen and was analyzed through XPS. FIG. 6 is a Cls spectra of PTFE specimens of (b) before reforming (a) and by irradiating 1 × 10 ¹⁵ / cm ² argon ions at an acceleration voltage of 1000 V and an oxygen flow rate of 8 sccm. Compared with the pre-modified specimens, the bonds between CF _{2 and} CF ₂ were broken and transferred into complex forms. In addition, since there is a peak at the position of various bonds between CF _x , CF ₁ , and CO, it is thought that cross linking, chain scission, etc. occurred.

In conclusion, the surface of the polymer can be activated with accelerated ions to induce the reactive gas to chemically bond. The hydrophilic bond formed by this reaction can be used as an acceptor when forming a thin metal film on the polymer by electroplating or electroless plating. As a result, the plating of the metal film is possible without the intermediate metal culture layer between the polymer and the deposited metal, and the adhesion between the plated metal film and the polymer is enhanced.

According to the present invention, the metal film is easily formed on the polymer which promotes adhesion between the polymer and the metal film or the plating itself is difficult, and in particular, by modifying the surface of the polymer with an ion beam, plating is possible on the polymer without a metal culture layer. The process can be shortened.

Claims (7)

Injecting a reactive gas into the vacuum chamber and irradiating an ion beam with energy to the polymer to destroy some of the bonds on the surface of the polymer, and injecting a reactive gas into the vacuum chamber to react atoms on the surface of the polymer with the bond with the reactive gas. Thereby changing the surface of the polymer to be hydrophilic and depositing a metal film on the surface of the polymer to be hydrophilic. The method of claim 1, wherein the acceleration voltage of the ion beam is 300 to 2000V. The method of claim 1, wherein the ions are a single or mixed form of a gas capable of ionizing argon, nitrogen, hydrogen, helium, oxygen, ammonia, and the like. The method of claim 1, wherein the reactive gas is in the form of a single or mixed form of oxygen, nitrogen, ammonia, hydrogen, and the like. The method of claim 1, wherein the deposition of the metal film is performed by electroless plating or electroplating. A polymer in which a metal film is adhered onto a surface after irradiating an ion beam with energy and blowing a reactive gas to perform a surface treatment. The method of claim 6, wherein the polymer is polyethylene, polypropylene, polytetrafluoroethylene, polyethylene terephtalate, silicone rubber, polystylene, poly A polymer bonded to a metal film, characterized in that the thermoplastic or thermosetting resin such as carbonate (polycabonate), epoxy (epoxy).