JP2010077467A - Electroless plating method of polyimide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the electroless plating method of a polyimide resin by which an electroless metal plated film is formed on the polyimide resin with excellent adhesiveness, expensive Pd or Sn exhibiting large environmental load is not needed for a pretreatment and remarkable productivity and practical performance are attained since an independent reducing step is not needed. <P>SOLUTION: The method of electroless plating the polyimide resin by which the metal plated film is formed on the surface of the polyimide resin includes: immersing the polyimide resin into an alkaline aqueous solution; successively immersing the polyimide resin into a solution containing metal ion; drying the polyimide resin; and next, immersing the polyimide resin into an electroless plating bath. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for electroless plating of a polyimide resin.

  Polyimide resin is an important electronic device component material as a typical engineer plastic, and there is a great need for flexible printed wiring boards and electromagnetic shielding materials for metallization of its surface. It is an effective surface metallization method with excellent productivity.

  By the way, although it has been difficult to perform highly adhesive plating on a polyimide resin so far, in recent years, for example, an electroless plating method as disclosed in Patent Document 1 has been proposed. In this electroless plating method, a polyimide resin is immersed in an alkaline aqueous solution to modify the surface, and this polyimide resin is immersed in a solution containing metal ions to form metal ions (metal salts) that serve as catalysts on the surface of the polyimide resin. After carrying out the reduction treatment by dipping in a reducing solution (for example, a solution containing sodium borohydride) that does not spontaneously cause electroless plating reaction, the electroless plating bath in which electroless plating reaction occurs By dipping, a plating film with high adhesion is formed on the polyimide surface.

JP 2002-256443 A

  In view of the present situation as described above, the present invention has been completed as a result of various experiments in order to further improve the adhesion of the plating film and simplify the treatment process. Electrolytic metal plating film can be formed, and pre-treatment does not require expensive Pd or environmentally high Sn, and because it does not require a reduction process independently, it has excellent practicality with excellent productivity. An electroless plating method for a polyimide resin is provided.

  The gist of the present invention will be described with reference to the accompanying drawings.

  A method of electroless plating of a polyimide resin that forms a metal plating film on the surface of the polyimide resin, wherein the polyimide resin is immersed in an alkaline aqueous solution, and then this polyimide resin is immersed in a solution containing metal ions, The polyimide resin is dried, and then the polyimide resin is immersed in an electroless plating bath.

  Also, a method for electroless plating of a polyimide resin that forms a metal plating film on the surface of the polyimide resin, wherein the polyimide resin is immersed in an alkaline aqueous solution to open a imide ring on the surface of the polyimide resin to generate a carboxyl group Subsequently, the polyimide resin is immersed in a solution containing metal ions so that the metal ions are adsorbed on the carboxyl groups, and then the polyimide resin is dried to form a metal salt with the carboxyl groups. Is then fixed to the surface of the polyimide resin, and then the polyimide resin is immersed in an electroless plating bath to reduce the metal salt to form a metal nucleus and to perform an electroless plating reaction using the metal nucleus as a catalyst. The present invention relates to a method for electroless plating of a polyimide resin, which is performed.

  Moreover, in the electroless plating method of the polyimide resin according to any one of claims 1 and 2, the polyimide resin is dried by removing moisture on the surface of the polyimide resin until there is no free water on the surface. The present invention relates to a method for electroless plating of polyimide resin.

  4. The method for electroless plating of polyimide resin according to claim 3, wherein the polyimide resin is dried by removing water of 30% or more on the surface of the polyimide resin. It is related to.

  5. The polyimide resin electroless plating method according to claim 1, wherein the electroless plating bath is an electroless copper plating bath or an electroless nickel plating bath. This relates to the electroless plating method.

  The method for electroless plating of a polyimide resin according to any one of claims 1 to 5, wherein the alkaline aqueous solution is a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution. It concerns the method.

  The polyimide resin electroless plating method according to any one of claims 1 to 6, wherein the metal ions are silver, copper, palladium, nickel, cobalt, gold, or platinum. This relates to the electroless plating method.

  Since the present invention has been described above, an electroless plating film can be formed on a polyimide resin with good adhesion, and pretreatment does not require expensive Pd or environmentally high Sn, and the reduction process is independent. Therefore, it is an electroless plating method of a polyimide resin that is extremely practical and excellent in productivity because it is not necessary.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  The polyimide resin is immersed in an alkaline aqueous solution to open the imide ring on the surface of the polyimide resin to generate a carboxyl group, and then the polyimide resin is immersed in a solution containing metal ions to add metal ions to the carboxyl groups. Next, the polyimide resin is dried to form a metal salt by the carboxyl group, the metal salt is fixed on the surface of the polyimide resin, and then the polyimide resin is immersed in an electroless plating bath. Thus, the metal salt is reduced to generate a metal nucleus, and the electroless plating reaction is continuously performed using the metal nucleus as a catalyst (starting point).

  At this time, the metal salt can be firmly fixed on the surface of the polyimide resin by performing a drying treatment, and the leaching of metal ions from the polyimide resin surface to the plating bath is prevented during the electroless plating treatment. The fixing amount of metal ions on the resin surface increases, and an electroless plating film is formed with extremely good adhesion using a metal nucleus generated from the metal ions as a catalyst.

  Also, the amount of fixing of metal ions increases, so that the modification treatment time by immersing in an alkaline aqueous solution can be shortened, the polyimide resin is less painful, the swelling is reduced, and the dimensional stability of the polyimide resin is improved. .

  Furthermore, by removing the water on the surface, (1) a plating bath that causes the adsorbed metal ions to be firmly fixed on the surface of the resin that has been swollen by immersion in an alkaline aqueous solution, which causes decomposition of the plating bath when immersed in an electroless plating bath (2) Phenomenon in which a part of the metal film is oxidized by the residual moisture and dissolved in the residual moisture after the metal film is formed. Therefore, by removing the moisture on the surface, it is not necessary to perform the reduction process independently as in the prior art. It becomes possible to perform processing efficiently with the number of steps.

  Specific embodiments of the present invention will be described with reference to the drawings.

  This example is a method for electroless plating of a polyimide resin that forms a metal plating film on the surface of the polyimide resin. The polyimide resin is immersed in an alkaline aqueous solution, and then the polyimide resin is immersed in a solution containing metal ions. Immersion is followed by drying the polyimide resin, and then dipping the polyimide resin in an electroless plating bath.

  Specifically, as illustrated in FIG. 1, a film-like polyimide resin (thickness 12) is obtained by sequentially performing four steps of a reforming treatment step, an ion exchange treatment step, a drying treatment step, and a reduction / plating treatment step. An electroless plating film is formed on the surface of about 100 μm.

  First, a polyimide resin (Kapton 200H manufactured by Toray DuPont Co., Ltd.) is immersed in an aqueous potassium hydroxide (KOH) solution to open the imide ring on the surface of the polyimide resin to generate a carboxyl group (—COOH). In addition, H in —COOH is replaced by K by a neutralization reaction between an acidic carboxyl group (—COOH) and basic potassium hydroxide.

  In this example, the sample was immersed in an aqueous potassium hydroxide solution at 5M (volume molar concentration) at 40 ° C. for 1 minute and then washed with pure water.

  In this embodiment, a potassium hydroxide aqueous solution is employed as the alkaline aqueous solution, but other aqueous solutions such as a sodium hydroxide (NaOH) aqueous solution may be employed.

Subsequently, (allowed to replace the K of -COOK and Ag) of the polyimide resin silver (Ag) nitrate containing ions (AgNO ₃₎ was immersed in an aqueous solution allowed to adsorb silver ions to the carboxyl group.

  In this example, the film was immersed in an aqueous solution of silver nitrate at 0.05 M and 40 ° C. for 1 minute, and then washed with pure water.

  In this embodiment, silver ions are used as metal ions, but copper (Cu), palladium (Pd), nickel (Ni), cobalt (Co), gold (Au) or platinum (Pt) ions. Similarly, not only the aqueous silver nitrate solution but also other aqueous solutions may be adopted.

  Subsequently, the polyimide resin is dried to form a metal salt (—COOAg) by the carboxyl group, and the metal salt is fixed to the surface of the polyimide resin.

  Specifically, the drying treatment is a treatment for removing at least 30% or more of water adhering to the surface (surface on which the plating film is formed) until there is no free water (water that can move freely) on the surface of the polyimide resin. In the present embodiment, the polyimide resin is dried by performing the moisture removal treatment on the surface of the polyimide resin for 10 seconds or more at room temperature using a strong wind (air blow by compressed air) that splashes water droplets.

  In this embodiment, when removing moisture on the surface of the polyimide resin, the amount of moisture removed from the surface on which the plating film is formed is set by placing the polyimide resin in a vacuum of about 0.2 Torr for 1 hour or more. When it is 100%, 30% or more is removed.

  The drying treatment is not limited to the above method, and may be other methods such as evaporating by leaving (heating) at 25 ° C. for 5 minutes or more, at 50 ° C. for 3 minutes or more, or at 75 ° C. for 2 minutes or more.

  Moreover, by removing 30% or more of the moisture on the surface of the polyimide resin, it is possible to prevent re-dissolution of adsorbed metal ions in the plating bath that causes decomposition of the plating bath when immersed in the electroless plating bath, and further, a metal film is formed. After film formation, it has been confirmed that it is possible to prevent the phenomenon that part of the metal film is oxidized by residual moisture and dissolved in the residual moisture and the film thickness is reduced, and a plating film with good adhesion can be formed. In order to completely eliminate free water on the resin surface, it is particularly preferable to remove 40% or more (40 to 100%). In this embodiment, about 40% of water is removed.

  Subsequently, the polyimide resin is immersed in an electroless copper plating bath containing formaldehyde (HCHO) as a reducing agent, thereby reducing a metal salt with the reducing agent to form a metal nucleus and using the metal nucleus as a catalyst. The electrolytic copper plating reaction is continuously performed to form an electroless copper plating film having a desired thickness.

  The electroless copper plating bath is not limited to other plating baths such as electroless nickel (Ni) plating bath containing dimethylamine borane as a reducing agent, and is not limited to formaldehyde or dimethylamine borane. Other reducing agents such as phosphinates may be employed.

  Confirmed that the surface of the polyimide resin obtained as described above has an electroless copper plating film having a thickness of several hundreds of nanometers (100 to 500 nm) and free from swelling, peeling or uneven plating. did.

  FIG. 2 shows a plating film (left side) obtained by the present embodiment and a plating film (left side) obtained by a conventional example in which the reduction process and the plating process are separated without including the drying process as disclosed in Patent Document 1. From FIG. 2, it can be confirmed from FIG. 2 that the plating film obtained by this example is a uniform plating film without unevenness as compared with the plating film obtained by the conventional example.

  Further, although deformation is seen in the conventional polyimide resin, no deformation is seen in the polyimide resin of this embodiment (see FIGS. 2 and 3), and this embodiment has excellent dimensional stability and uniform plating. It can be confirmed that this is a method for obtaining a film.

  Further, FIG. 4 is a photograph showing the result of a peel test by the JIS H8504 tape test method, and no peeling is seen even when a tape test is performed on a notched plating film. It can be confirmed that the plating film is excellent.

  Since the present embodiment is as described above, the metal salt can be firmly fixed on the surface of the polyimide resin by performing the drying process, and the leaching of metal ions from the polyimide resin surface to the plating bath during the electroless plating process. As a result, the fixed amount of metal ions on the surface of the polyimide resin is increased, and an electroless plating film is formed with extremely good adhesion using a metal nucleus formed from the metal ions as a catalyst.

  Also, the amount of fixing of metal ions increases, so that the modification treatment time by immersing in an alkaline aqueous solution can be shortened, the polyimide resin is less painful, the swelling is reduced, and the dimensional stability of the polyimide resin is improved. .

  Furthermore, by removing the water on the surface, (1) a plating bath that causes the adsorbed metal ions to be firmly fixed on the surface of the resin that has been swollen by immersion in an alkaline aqueous solution, which causes decomposition of the plating bath when immersed in an electroless plating bath (2) Phenomenon in which a part of the metal film is oxidized by the residual moisture and dissolved in the residual moisture after the metal film is formed. Therefore, by removing the moisture on the surface, it is not necessary to perform the reduction process independently as in the prior art. It becomes possible to perform processing efficiently with the number of steps.

  Therefore, in this example, an electroless plating film can be formed on polyimide resin with good adhesion, and pretreatment does not require expensive Pd and environmentally high Sn, and a reduction process is required independently. Therefore, it is an electroless plating method of polyimide resin with excellent practicality and excellent productivity.

It is a schematic explanatory drawing of a present Example. It is a comparative photograph with the polyimide resin with a plating film which concerns on a present Example, and the polyimide resin with a plating film which concerns on a prior art example. It is a one part enlarged photograph of the polyimide resin with a plating film which concerns on the present Example of FIG. It is a photograph which shows the result of a peeling test.

Claims (7)

  A method of electroless plating of a polyimide resin that forms a metal plating film on the surface of the polyimide resin, wherein the polyimide resin is immersed in an alkaline aqueous solution, and then this polyimide resin is immersed in a solution containing metal ions, A method of electroless plating of a polyimide resin, comprising drying the polyimide resin and then immersing the polyimide resin in an electroless plating bath.   A method for electroless plating of a polyimide resin that forms a metal plating film on the surface of the polyimide resin, wherein the polyimide resin is immersed in an alkaline aqueous solution to open a imide ring on the surface of the polyimide resin to generate a carboxyl group, Subsequently, the polyimide resin is immersed in a solution containing metal ions so that the metal ions are adsorbed to the carboxyl groups. Subsequently, the polyimide resin is dried to form metal salts with the carboxyl groups, and the metal salts are Fixing on the surface of the polyimide resin, and subsequently immersing the polyimide resin in an electroless plating bath to reduce the metal salt to form a metal nucleus and to perform an electroless plating reaction using the metal nucleus as a catalyst. A method for electroless plating of a polyimide resin.   The method for electroless plating of a polyimide resin according to any one of claims 1 and 2, wherein the polyimide resin is dried by removing moisture on the surface of the polyimide resin until free water is eliminated. A method for electroless plating of a polyimide resin.   4. The method for electroless plating of polyimide resin according to claim 3, wherein the polyimide resin is dried by removing moisture of 30% or more on the surface of the polyimide resin.   5. The method for electroless plating of a polyimide resin according to claim 1, wherein the electroless plating bath is an electroless copper plating bath or an electroless nickel plating bath. Electroplating method.   6. The method for electroless plating of a polyimide resin according to claim 1, wherein the alkaline aqueous solution is a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution.   The method for electroless plating of a polyimide resin according to any one of claims 1 to 6, wherein the metal ion is silver, copper, palladium, nickel, cobalt, gold, or platinum. Electroplating method.