JPH09102668A - Method for forming circuit with laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form a conductive circuit accurately on a molding of synthetic resin with a complex shape in a simple method by forming a metallic thin film with given brightness on the surface of the molding and carrying out a laser beam machining step. SOLUTION: A metallic coating step for a molding is carried out to form a metallic thin film 2 on the surface. In this case, the metallic film 2 on the molding 1 has a thickness of 1 to 2μm, and preferably made of copper in a chemical plating, sputtering, vacuum deposition or ion plating step. When the surface of the metallic thin film 2 has brightness of 40 or below, preferably 30 or below, a laser beam machining step with laser can be carried out directly. As an example, when an electroless copper plating solution containing organic sulfur compound is used, the brightness of the surface of the copper foil deposited thereon becomes 40 or below, so the laser beam machining step can be carried out directly. In addition, thiol-based material like 2- mercaptobenzoimidazole may be used as the organic sulfur compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a conductive circuit on the surface of a synthetic resin molded product, which is used as a circuit component in the field of electric / electronic equipment and has a precise conductive circuit on the surface. The present invention relates to a method for efficiently manufacturing a product.

[0002]

2. Description of the Related Art
As a circuit forming method using laser light, a metal film with a sufficient thickness for a conductive circuit is previously formed on the surface of a molded product, and the metal film other than the conductive circuit is scattered and removed by laser light, and the conductive circuit is used as it is. (Japanese Patent Laid-Open No. 64-833
However, according to this method, the thickness of the conductor metal layer needs to be a relatively thick layer (for example, 10 μm or more) so that the conductivity of the circuit is sufficient. When removing the unnecessary part of the metal layer, it is necessary to increase the output of the laser beam, as a result, the underlying synthetic resin molded product will be damaged and the appearance shape of the formed circuit will be significantly impaired. In addition, there is a problem in that the synthetic resin is carbonized to impair the insulating property. In addition, a method of forming a metal thin film on the surface of a molded product, removing the metal thin film in a portion other than the conductive circuit portion to form a circuit pattern, and performing electroplating to form a conductive circuit (JP-A-6-164105) is disclosed. It is considered that according to this method, the synthetic resin is not carbonized because there is no output of the laser light and irradiation is performed, so there is no problem of insulation, but since the output of the laser light is reduced, the thickness of the metal thin film is reduced. Due to the variation, the metal thin film cannot be partially removed and remains, resulting in a new problem that the conductive circuit is short-circuited.

[0003]

SUMMARY OF THE INVENTION The present inventors have solved the problems of the above-mentioned conventional methods, and are capable of accurately forming a conductive circuit on a molded article having a complicated shape by using a laser beam by a simple method. As a result of detailed examination of the above, as a metal thin film formed on the surface of the molded product, a metal thin film having a surface brightness (L value) of 40 or less was used, and by performing laser processing, metal due to variation in thickness of the metal thin film No thin film remains,
The inventors have found that the conductive circuit can be formed without short-circuiting, and have completed the present invention. Here, using a metal thin film having a surface brightness (L value) of 40 or less means
A metal thin film whose surface lightness (L value) is 40 or less may be used originally, or the surface lightness (L value) is 40 or less by an appropriate means.
It may be changed to the following. That is, the present invention is a method for removing a metal thin film formed on the surface of a synthetic resin molded product by laser light to form a circuit, wherein the surface brightness (L value) is 40%.
A circuit forming method using a laser, which is characterized in that the following metal thin film is used, or the lightness (L value) of the surface of the metal thin film is set to 40 or less, and then laser processing is performed.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described below step by step with reference to the drawings. The material of the synthetic resin molded product (base molded product) used in the present invention may be either a thermoplastic resin material or a thermosetting resin material as long as it is a synthetic resin capable of firmly adhering a metal thin film. Considering that the molded product will later undergo severe processing such as soldering,
A resin having high heat resistance and excellent mechanical strength is preferable, and a thermoplastic resin capable of injection molding is preferable from the viewpoint of mass production. If the example is given, aromatic polyester, polyamide, polyacetal, polyarylene sulfide, polysulfone, polyphenylene oxide,
Polyimide, polyetherketone, polyarylate and their compositions, etc., and the lightness (L value) of the metal thin film surface
The heat distortion temperature of 20
A thermoplastic resin having a temperature of 0 ° C. or higher is preferable, and particularly from the viewpoint of high melting point, high strength, high rigidity, moldability, etc., a liquid crystalline polymer (eg, liquid crystalline polyester, polyester amide),
Polyarylene sulfide is particularly preferred, but not limited to. Moreover, in order to enhance the adhesion of the metal thin film, an appropriate substance may be added to the material, if necessary. The base molded product 1 (FIG. 1) is molded by injection molding or the like, and in order to improve the adhesion of the metal thin film on its surface, chemical etching with acid, alkali or the like,
Alternatively, physical surface treatment such as corona discharge or plasma treatment may be performed.

Next, the surface of this molded product is subjected to a metal coating process to form a metal thin film 2 (FIG. 2). If the thickness of the metal thin film 2 provided here is too thick, a laser beam having a strong output is required for forming a circuit pattern by the laser beam in the next step, which causes damage to the base molded article 1 as described above. Therefore, it is not preferable. On the other hand, if it is too thin, electricity for plating will not flow in the metal layer adding step by electroplating in the subsequent step, which is not preferable. From this point of view, the metal thin film 2 applied to the surface of the base molded article 1
The thickness is preferably in the range of about 0.1 to 2 .mu.m, more preferably 0.3 to 1 .mu.m. If the thickness is in this range, the circuit pattern formation by the laser light can be accurately performed with a comparatively weak output without causing damage to the base molded product 1. Examples of the method of forming the metal thin film 2 include chemical plating, sputtering, vacuum deposition, ion plating, transfer method, conductive agent coating, etc.
Any known method may be used, but chemical plating (electroless plating), sputtering, vacuum deposition, or ion plating is suitable for forming a uniform metal thin film 2. The metal used here is copper, silver, nickel, or the like.
As described below, any metal may be used as long as it is a metal that changes to dark brown color due to a chemical reaction or the like, but copper is preferable for forming a metal thin film that is inexpensive and has good conductivity. here,
If the lightness (L value) of the surface of the metal thin film is 40 or less, more preferably 30 or less, laser processing may be performed as it is. For example, when the organic sulfur compound is added to the electroless copper plating solution, the brightness (L value) of the surface of the deposited copper thin film is 40 or less, so that laser processing can be performed as it is. Here, examples of the organic sulfur compound include thiols such as 2-mercaptobenzimidazole, disulfides such as dimethyldisulfide, sulfides such as 1,2-bis (2-hydroxyethylthio) ethane, thioacetone, thiourea and the like. Examples thereof include thioketones, sulfoniums such as 1-ethylthiazolium chloride, and sulfolanes such as sulfolane, and one or more of these can be used. The brightness (L value) of the electroless plating surface is 40
When the value exceeds L, the surface of the metal thin film 2 of the substrate molded product 1 (FIG. 2) having the metal thin film 2 formed on the surface thereof has the lightness (L value).
It may be changed to a dark color so that the value becomes 40 or less (Fig. 3). The lightness in the present invention means L measured by a color difference meter.
It is a value. As a method for changing the lightness (L value) of the surface of the metal thin film to 40 or less, a chemical reaction is suitable, specifically, a known method such as oxidation or sulfurization, and any method suitable for the metal. For example, in the case of a copper thin film, a method of forming a dark oxide on the thin film surface by oxidation by heating is simple and suitable. Further, the setting of the heating temperature here is important, and the metal thin film 2 is less likely to be oxidized at a low temperature, and conversely, at a high temperature, a defect such as deformation of the base resin molded product occurs, which is not preferable. From this point of view, when the metal thin film is oxidized by heating, the heating temperature is 100 to 200 ° C., preferably 140 to 200 ° C., and the heating time is 0.5 to 3 hours.

Generally, regarding the processability of the metal and the synthetic resin by the laser, since the synthetic resin is processed by the laser having a lower output, the laser is processed by the laser with the lowest possible output in order to prevent the synthetic resin from being damaged. There is a need to. According to the present invention, when the lightness (L value) in the color difference meter is set to 40 or less, the absorption of the laser light to the metal thin film is increased, and the metal thin film of the unnecessary part is not damaged by the low output laser which does not damage the synthetic resin. It has been found that a conductive circuit that can be completely removed and that does not short-circuit can be formed. In other words, when the lightness (L value) in the color difference meter is greater than 40, the absorption of the laser light to the metal thin film deteriorates, and it is necessary to process with a high-power laser, so when removing the metal thin film, the underlying synthetic resin This is not preferable because problems such as carbonization may occur.

Next, with respect to the molded product (FIG. 3) on which the metal thin film having the surface brightness (L value) of 40 or less is formed, the unnecessary portion other than the conductive circuit portion is irradiated with the laser beam 4 whose output is appropriately adjusted. As a result, only the metal thin film 2 in this portion is selectively scattered and removed to form the conductive circuit pattern 5 of the metal thin film 2 (FIG. 4). Here, the laser light 4 to be irradiated may be any laser as long as it can remove the chemically reacted metal thin film, but in consideration of the removal performance of the metal thin film, a YAG laser having a wavelength in the infrared region,
Carbon dioxide gas laser and the like are preferable. Such lasers
A preset circuit pattern is selectively irradiated by a laser marker having a scanning mechanism in XY directions controlled by a computer. If it is necessary to form a circuit on a complicated three-dimensional molded product, laser light 4
The optical fiber, prism, etc.
It is possible to accurately irradiate a predetermined area by computer control. Alternatively, an XY that moves in synchronization with a computer with a laser marker having an XY scanning mechanism.
It is also possible to irradiate three-dimensionally by combining a 5-axis table of Z direction, rotation, and inclination. Further, according to this method, the creation and modification of the pattern can be easily performed only by changing the drawing program in the laser irradiation area.

After that, the conductive circuit portion of the circuit pattern 5 formed by removing the unnecessary portion of the metal thin film 2 whose surface brightness (L value) is 40 or less is further electroplated to a desired thickness (eg, , 10-100 μm) to form a target conductive circuit 6 (FIG. 5). The metal layer is 10 μm
With the above thickness, there is no problem in terms of conductivity or damage such as breakage due to friction during use, and since it is not necessary to make the thickness more than necessary, the thickness may be about 100 μm.
In addition, the brightness (L value) of the surface of compound 3 such as oxide is 40
In the metal thin film 2 described below, the adhesion of the metal layer 6 formed by electroplating on the metal thin film 2 is not good. Therefore, the metal thin film surface layer is removed as a pretreatment for forming the metal layer 6 by electroplating. It is better to do. As the method, any known method may be used, but a method of immersing the molded product in an acid such as hydrochloric acid or sulfuric acid to dissolve and remove the surface layer is convenient.

[0009]

EFFECTS OF THE INVENTION According to the present invention, it is possible to avoid the adverse effects on the appearance, shape, insulating property, etc. due to the damage of the synthetic resin molded product due to the use of laser light.
Since the metal thin film does not remain due to the variation in the thickness of the metal thin film, there is no short circuit of the conductive circuit, and the range of processing conditions is wide, resulting in excellent mass productivity and having a precise conductive circuit of the desired thickness with a simple method. A conductive circuit component can be obtained, which is economically advantageous.

[0010]

EXAMPLES Examples of the present invention will now be described with reference to the drawings, but the present invention is not limited thereto. In addition, the brightness (L value) is measured by a color difference meter (“Z-300” manufactured by Nippon Denshoku Industries Co., Ltd.).
A)) is a value obtained by measuring the plating surface of a molded product using a 30φ projection lens so as not to be affected by external light. Example 1 A three-dimensional molded article 1 was prepared by injection molding using a metal adhesive (plating) resin composition mainly composed of liquid crystalline polyester (trade name "Vectra", manufactured by Polyplastics Co., Ltd.). (Figure 1). Next, this is degreased, and after etching the almost entire surface with a KOH aqueous solution,
After neutralization and washing with an aqueous HCl solution, a catalyst is applied to activate the surface, and then a chemical copper plating solution (Okuno Pharmaceutical Co., Ltd. O
It is dipped in PC-750, a mixed solution of solution A, solution B and solution C), and a metal thin film 2 of 0.3 μm thick is formed on the surface by chemical copper plating.
Was formed, washed well, and then dried (FIG. 2). next,
A molded product (Fig. 2) whose surface is chemically copper-plated at 120 ° C
When heated for 1 hour, the chemical copper plating surface changed to dark brown oxide 3 due to a chemical reaction (FIG. 3). The brightness (L value) of this surface was 26.23. Then, the laser output is 0.
A conductive circuit pattern 5 was formed by irradiating 4 W of YAG laser light 4 to remove unnecessary chemical copper plating other than the conductive circuit part (FIG. 4). After that, the molded product having the conductive circuit pattern 5 formed thereon is dipped in a 5% aqueous solution of sulfuric acid to dissolve and remove the discolored oxide on the surface, and then the conductive circuit pattern portion is subjected to electrolytic copper plating with a thickness of 10 μm. After washing, it was dried to obtain a circuit-formed product (FIG. 5) having an accurate and three-dimensional conductive circuit portion 6. Table 1 shows the results of measuring the yield rate of 50 circuit-formed products manufactured in the above process.
Shown in

Examples 2 to 8 and Comparative Examples 1 to 6 The thickness of the metal thin film, the heating temperature for forming a dark-colored compound (oxide) on the surface of the metal thin film, and the surface temperature of the molded article formed as a result. A circuit-formed article was manufactured in the same manner as in Example 1 except that the laser output of the laser light for removing unnecessary portions other than the brightness and the conductive circuit portion was changed as shown in Table 1, and the same measurement was performed. It was Table 1 shows the results.

[0012]

[Table 1]

Example 9 Three-dimensional molded article 1 by injection molding using a metal adhesive (plating) resin composition mainly composed of liquid crystalline polyester (trade name "Vectra", manufactured by Polyplastics Co., Ltd.) Was created (Fig. 1). Next, this is degreased, and after etching the almost entire surface with a KOH aqueous solution,
After neutralizing and washing with an aqueous HCl solution, a catalyst is applied to activate the surface, and then thiourea is added to a mixed solution of the electroless chemical copper plating solution OPC-750 manufactured by Okuno Chemical Industries Co., Ltd. Immersion in a chemical copper plating solution containing 6 ppm to form a 0.5 μm-thick chemical copper plating metal thin film 2 on the surface,
After thorough washing, it was dried (Fig. 2). The brightness (L value) of this surface was 23.76. Then, the molded product on which the chemical copper plating is formed is irradiated with YAG laser light 4 having a laser output of 0.7 W to remove the chemical copper plating on unnecessary portions other than the conductive circuit portion, thereby forming the conductive circuit pattern 5. Formed (FIG. 4). After that, a thickness of 10 is formed on the conductive circuit pattern portion of the molded product on which the conductive circuit pattern 5 is formed.
A circuit-formed product (FIG. 5) having an accurate and three-dimensional conductive circuit portion 6 was obtained by applying electrolytic copper plating of μm, washing and drying. Table 2 shows the results of measuring 50 non-defective products by manufacturing 50 circuit-formed products in the above process. Example 10 A circuit formed article was manufactured in the same manner as in Example 9 except that the thickness of the metal thin film was changed, and the same measurement was performed. Table 2 shows the results.

[0014]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a perspective view of a base molded product that is a molded product of a three-dimensional circuit as an example of the present invention.

FIG. 2 is a perspective view showing a state where a copper thin film is formed by performing chemical copper plating on the surface of the base molded article shown in FIG.

FIG. 3 is a perspective view showing a state in which a molded product having the copper thin film shown in FIG. 2 is heated to form an oxide having a lightness (L value) of 40 or less on the surface of the copper thin film.

FIG. 4 is a perspective view showing a state in which a copper thin film other than a conductive circuit portion of a molded product is removed by a YAG laser to form a conductive circuit pattern.

5 is a perspective view showing a state in which a circuit is formed by performing electrolytic copper plating on a conductive circuit portion of a molded product on which the conductive circuit pattern shown in FIG. 4 is formed.

[Explanation of symbols]

 1 ... Base molded product 2 ... Metal thin film by chemical metal plating 3 ... Metal whose lightness (L value) is changed to 40 or less 4 ... Laser light 5 ... Conductivity formed by laser light Circuit pattern 6 ... Conductive circuit formed by electrolytic copper plating

Claims (11)

[Claims] 1. A method for removing a metal thin film formed on the surface of a synthetic resin molded article by laser light to form a circuit, using a metal thin film having a surface brightness (L value) of 40 or less to perform laser processing. A method for forming a circuit using a laser, characterized in that 2. A method of forming a circuit by removing a metal thin film formed on the surface of a synthetic resin molded product by laser light, after setting the lightness (L value) of the surface of the metal thin film to 40 or less,
A method for forming a circuit using a laser, which comprises performing laser processing. 3. The circuit forming method according to claim 2, wherein the surface of the metal thin film is heated at a temperature of 100 to 200 ° C. for 0.5 to 3 hours to change the lightness (L value) to 40 or less. 4. The circuit forming method according to claim 1, wherein the metal thin film is made of copper. 5. The circuit forming method according to claim 1, wherein the metal thin film surface is treated with an acid after laser processing. 6. The metal thin film having a brightness (L value) of 40 or less on the surface is a copper thin film obtained from an electroless copper plating solution containing an organic sulfur compound. Circuit forming method. 7. The circuit forming method according to claim 6, wherein the organic sulfur compound is one or more selected from thiols, disulfides, sulfides, thioketones, sulfoniums and sulfolanes. 8. A synthetic resin molded product has a heat distortion temperature of 200 ° C.
The circuit forming method according to any one of claims 1 to 7, which is the above. 9. A synthetic resin molded article is formed by using polyether sulfone, polyether imide, liquid crystalline polyester, polyester amide, polyphenylene sulfide, polysulfone, and compositions thereof. The circuit forming method according to claim 1. 10. The circuit forming method according to claim 1, wherein laser processing is performed with a YAG laser. 11. The circuit forming method according to claim 1, wherein the synthetic resin molded product has a three-dimensional shape.