JP2001009862A - Production of metal inserted resin composite molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and inexpensively produce a metal inserted resin molded article while ensuring airtightness sufficient to protect the electric circuit or contact in a part even if there is a severe environmental change. SOLUTION: In a method for producing a resin composite molded article having a metal part inserted therein, a needle-like or porous uniform metal fine structure is preformed to the whole or part of the surface of the metal part and this metal part is inserted in the mold of an injection molding machine to perform the injection molding of a thermoplastic resin material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin composite molded product in which a metal component is inserted.

[0002]

2. Description of the Related Art Resin composite parts obtained by insert molding of metal parts are used in a wide variety of industrial fields, mainly in the fields of electrics and automobiles. There are various types of such resin composite molded parts, and the purpose of inserting a metal part also differs depending on the function and use of the product, but for example, it is used for various sensor parts such as a speed sensor used in automobiles and home electric appliances. Button type switch parts.
In the former example, generally, a metal terminal is inserted into a metal mold for injection molding together with a wound coil bobbin and the like, and is integrally molded with resin. At this time, since the metal terminal has a function of electrically connecting the inside and the outside of the molded product, a part of the metal terminal is molded so as to be exposed from the surface of the resin molded product. As is well known, automobile parts are used in a harsh environment, and in particular, electric and electronic parts are susceptible to moisture and moisture, so that it is necessary to prevent them from easily entering the inside. However, it is generally difficult to bond a metal and a resin. In particular, in metal insert molding using a thermoplastic resin, almost no adhesion between the metal and the resin is obtained, and moisture and water are not easily absorbed through the interface between the metal and the resin. Moisture easily enters the interior. For this reason, conventionally, countermeasures such as applying a thermosetting adhesive to the boundary portion between the metal terminal and the resin by post-processing, or assembling and sealing a rubber-like protected component have been taken.

On the other hand, in the latter example, a hoop-shaped copper lead frame is sequentially fed into an injection molding die, inserted, and continuously and integrally molded with resin. Next, bending, trimming, assembling, and the like of the externally exposed terminal portion are sequentially performed, and the completed switch component is finally soldered to a printed circuit board or the like, thereby constituting a part of a home appliance or the like. . One of the problems in the process of manufacturing such a switch component is that flux enters the switch during the soldering process. In other words, the solder flux previously applied to the metal terminals as a solder adhesion improver reduces the viscosity due to the heat during soldering, and a part of the flux conveys the interface between the metal and the resin and contaminates the internal contacts of the switch. Poor electrical contact may occur. For this reason, conventionally, flux penetration has been prevented by applying a fluorine-based water repellent or the like to the base of the terminal in advance and then soldering.

[0004]

A problem common to the above-mentioned examples is that, in order to protect an electric circuit and an electric contact inside the part from external influences such as moisture and humidity, the parts are not easily assembled during the assembly process. Secondary processing and installation of protection parts are necessary,
This complicates the production process and increases the cost of the product. The root cause of this problem is that it is originally difficult to obtain a strong chemical interaction (such as a chemical bond) between a thermoplastic resin and a metal such as copper, and therefore, it is merely an injection molding die. Even if hot melted resin is poured into the inside and the insert metal is coated, it is practically possible to prevent the formation of extremely minute gaps at the resin / metal interface during the cooling process of the molded product and subsequent changes in the use environment. Was difficult.

Accordingly, an object of the present invention is to provide a metal insert resin composite molded product which is easy to manufacture and which can secure sufficient airtightness for protecting electric circuits and electric contacts inside components even under severe environmental changes. It is an object of the present invention to provide an inexpensive method for producing a.

[0006]

Means for Solving the Problems The present inventor has made intensive studies in view of such circumstances, and as a result, has previously formed a needle-like or porous uniform metal microstructure on all or a part of the surface of a metal part, By inserting this metal part into the mold of the injection molding machine and performing injection molding using a thermoplastic resin material, it is possible not only to secure the initial airtightness, but also after severe environmental degradation tests such as cooling and heating cycle tests. The present inventors have found that a composite molded article that maintains high airtightness can be easily obtained, and have reached the present invention.

That is, the present invention relates to a method for producing a resin composite molded article in which a metal part is inserted, wherein a needle-like or porous uniform metal microstructure is previously formed on all or a part of the surface of the metal part. Then, a metal insert-resin composite molded product is characterized in that the metal component is inserted into a mold of an injection molding machine and injection-molded using a thermoplastic resin material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail.

First, a method for forming a needle-like or porous metal microstructure on the surface of a metal component used in the present invention will be described. The acicular or porous metal microstructure defined in the present invention is a fine or acicular microporous structure having a micrometer (micron meter) order or less, which is uniformly and densely formed on the metal surface. is there. As a specific example, as a method of forming a uniform acicular fine structure, a zinc phosphate treatment method widely used as a pretreatment for coating an automobile body steel plate, and a republished patent WO 97/4673.
No. 1 discloses an electroless copper plating method.
The former is mainly used as a pre-coating treatment for the purpose of improving the adhesion with the cationic electrodeposition paint used for rust-preventive undercoating of steel sheets, and the latter is mainly used for copper-clad laminates such as multilayer printed circuit boards It has been devised for the purpose of improving the adhesion between the copper foil and the thermosetting resin (prepreg). FIGS. 1 and 2 show examples of observation results of the metal surface treated by each method using an electron microscope.

On the other hand, as a technique for forming a uniform porous fine structure on a metal surface, for example, Japanese Patent Application Laid-Open No. 10-23766
There is an electroless copper plating method disclosed in Japanese Patent Publication No. This method is also devised mainly for the purpose of improving the adhesion between a copper foil and a thermosetting resin (prepreg) in a copper-clad laminate or the like. FIG. 3 shows an example of the observation result of the metal surface treated by this method using an electron microscope.

[0011] The metal part for insert in the present invention is
A metal insert part in which a needle-like or porous uniform metal microstructure as described above is previously formed on all or part of the surface of the metal part is used, and the insert part forms a part of an electric circuit. For example, in the case of an electric terminal, copper or a copper alloy is preferable as the insert metal, and as a technique for forming a needle-like or porous uniform metal microstructure defined by the present invention on the surface of these metals, The electroless copper plating method is preferably used.

By utilizing the metal having a needle-like or porous uniform microstructure surface for metal insert molding of a thermoplastic resin, the airtightness is remarkably improved as will be described in the embodiments of the present invention described later. An effect was found.
On the other hand, when the adhesion and releasability between the metal having the fine structure surface and the thermoplastic resin were evaluated, no remarkable improvement was observed as much as the airtightness. Therefore, it is considered that there is a mechanism other than the adhesive force at the resin / metal interface in achieving good airtightness when insert molding a metal part having such a fine structure surface with a thermoplastic resin. Regarding this mechanism, according to the study of the present inventor, a needle-like or porous microstructure densely formed on a metal surface results in an extremely large contact area with the resin, which results in It is presumed that the airtightness required for practical use is secured because the passage for moisture and moisture to enter the inside of the component through the metal / resin interface is significantly extended.

The microstructure formed in a uniform needle shape is not particularly limited in diameter, length, direction, shape, number, etc.
It is preferable that the direction of formation is inclined with respect to the vertical direction of the surface of the metal component because the anchor effect is increased.

In the microstructure formed in a uniform porous shape, the single pore diameter is preferably 100 μm or less, and more preferably the pores are substantially in the range of 0.01 to 10 μm.

Next, the thermoplastic resin material used in the present invention will be described. The thermoplastic resin used in the present invention, polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene copolymer resin, polyvinyl chloride resin, polycarbonate resin, polyamide resin,
Polyacetal resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, liquid crystalline polyester resin, polyimide resin, syndiotactic polystyrene resin, polycyclohexane dimethylene terephthalate resin and the like, and more preferably, molding processing Polyacetal resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polyamide resin, liquid crystalline polyester resin, polyimide resin, syndiotactic polystyrene resin, polycyclohexane dimethylene terephthalate, which is easy and has excellent electrical and mechanical properties Thermoplastic resin containing as a main component at least one resin selected from the group consisting of resins is preferably used. It is.

As the thermoplastic resin material used in the present invention, in addition to the above-mentioned thermoplastic resin, various conventionally known inorganic and organic fillers, flame retardants, flame retardant assistants, and ultraviolet absorbers as long as the airtightness is not deteriorated. Of course, it may contain additives such as a heat stabilizer, a light stabilizer, a colorant, carbon black, a processing aid, a nucleating agent, a release agent, and a plasticizer.

Next, an injection molding apparatus is generally used to insert-mold the above-mentioned metal part having the needle-like or porous uniform metal microstructure formed thereon using the above-mentioned thermoplastic resin material. The injection molding apparatus used in the present invention is not special, and a commercially available injection molding machine can be used. There is no particular limitation on the molding method and molding conditions in the present invention, but as common general knowledge in insert molding, it is desirable to adjust the conditions so that the molten resin comes into firm contact with the insert metal and a sufficient holding pressure is applied.

[0018]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to these examples unless departing from the gist of the present invention.

FIG. 4 shows the shape of an insert metal part used for resin molding in the embodiment, and a resin molded article obtained by inserting the metal part into an injection mold and injection molding with a thermoplastic resin. Is shown in FIG.

FIG. 6 is a schematic view of a test apparatus for airtightness evaluation performed using the above resin molded product.

Further, in the examples, the method used for evaluating the airtightness is as follows. (1) Airtightness test Using the resin molded product shown in Fig. 5 as a sample for evaluation,
The airtightness was evaluated using the test device shown in FIG. First, a method of setting an evaluation sample is as follows. A resin molded product is set in a metal container portion of a pressure-resistant airtight container via a rubber O-ring, and then fixed so that the resin molded product is sandwiched between metal upper lids (container The male part and the female part are cut into the upper part and the upper lid part, respectively, so that they are fixed). The pressure-resistant airtight container was put into a water tank, and the pressure in the pressure-resistant airtight container was gradually increased by gradually opening the compressed air valve until a desired pressure was reached. If there is no air leakage in a still state for 1 minute under a predetermined pressure, the airtightness under the pressure is determined to be OK.
The test was started at 0.1 MPa, and if OK, the test was sequentially increased by 0.1 MPa, and the test was performed up to a maximum of 0.6 MPa.

With respect to the sample which was OK at 0.6 MPa in the airtightness test in the initial state, after performing a heat shock resistance test described below for a predetermined cycle, the airtightness test was similarly performed. In addition, the test was performed with the sample of n = 5. (2) Heat shock resistance test A commercially available heat shock tester was used.
hr to 180 ° C. × 2 hr) as one cycle, and the resin molded product was taken out of the tank every 20 cycles and subjected to the above airtightness test to evaluate heat shock resistance.

Example 1 A brass insert part having the shape shown in FIG. 4 was subjected to ordinary pretreatment for electroless copper plating, and was immersed in a plating solution A having the following composition at a temperature of 70 ° C. for 10 minutes. When the surface condition of the insert part after immersion was observed with an electron microscope, a uniform needle-like crystal was obtained as shown in FIG. (Electroless copper plating solution composition A) Copper sulfate 8.0 g / L Citric acid 11.0 g / L 50% hypophosphorous acid solution 38.8 g / L Boric acid 31.0 g / L Nickel sulfate 0.6 g / L Surfynol 465 0.1 g / L L Lithium hydroxide 28.8 g / L Next, this insert part was set in a mold for injection molding, and a polyphenylene sulfide resin containing 30% by weight of glass fiber and 30% by weight of calcium carbonate was used. Injection molding was performed under the conditions, and a sample for evaluation having a shape shown in FIG. 5 was obtained, and the above-mentioned airtightness test was performed. Table 3 shows the results.

Example 2 A polybutylene terephthalate resin containing 15% by weight of glass fiber and 15% by weight of glass flake was used as a molding resin, and injection molding was performed under the molding conditions shown in Table 2. A sample for evaluation was prepared in the same manner as in Example 1,
The above airtightness test was performed. Table 3 shows the results.

Example 3 A brass insert part having the shape shown in FIG. 4 was subjected to ordinary electroless copper plating pretreatment, and then immersed in a plating solution B having the following composition at a temperature of 70 ° C. for 10 minutes. When the surface condition of the insert component after immersion was observed with an electron microscope, microporous crystals were obtained as shown in FIG. (Electroless copper plating solution composition B) Copper sulfate 8.0 g / L Sodium citrate 11.0 g / L Sodium hypophosphite 23.8 g / L Boric acid 31.0 g / L Nickel sulfate 0.6 g / L Surfynol 104 1.0 g / L Next, the insert part was set in a mold for injection molding, and injection molding was performed under molding conditions shown in Table 1, using a polyphenylene sulfide resin containing 30% by weight of glass fiber and 30% by weight of calcium carbonate. An evaluation sample having the shape shown in FIG. 5 was obtained, and the above airtightness test was performed. Table 3 shows the results.

Example 4 A polybutylene terephthalate resin containing 15% by weight of glass fiber and 15% by weight of glass flake was used as a molding resin, and injection molding was performed under the molding conditions shown in Table 2. A sample for evaluation was prepared in the same manner as in Example 3,
The above airtightness test was performed. Table 3 shows the results.

Comparative Examples 1 to 4 Evaluation samples were prepared in the same manner as in Examples 1 to 4, except that the brass insert parts were not subjected to the electroless copper plating treatment, and the above airtightness test was performed. Table 3 shows the results.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

As is apparent from the above description and Examples, the metal insert resin molded product obtained by the method of the present invention has extremely high airtightness at the resin / metal interface and is exposed to a severe environment. Can maintain its excellent airtightness, so that a highly reliable product can be provided for a long period of time.

Therefore, the resin composite molded article produced by the production method of the present invention can be used for metal inserts in a wide range of fields, including various sensor parts for automobiles, various switch parts for home appliances, capacitor parts for various industrial equipments, and the like. It can be suitably used for resin parts.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing an example of a needle-like crystal formed on a metal surface treated by a zinc phosphate treatment method.

FIG. 2 is an electron micrograph showing an example of a needle-like crystal formed on a metal surface treated by an electroless copper plating method.

FIG. 3 is an electron micrograph showing an example of a porous crystal formed on a metal surface treated by an electroless copper plating method.

FIG. 4 is a view showing the shape of an insert metal part used in the example, where (a) is a top view and (b) is a front view.

FIG. 5 is a view showing the shape of a resin molded product obtained by injection-molding a thermoplastic resin material on an insert metal part used in Examples, (a) is a top view, and (b) is a perspective view. It is.

FIGS. 6A and 6B are schematic views of a test device in an airtightness evaluation performed in an example, in which FIG. 6A is an overall view, and FIG.

FIG. 7 is an electron micrograph showing a needle-like crystal formed on a metal surface treated by the electroless copper plating method of Example 1.

FIG. 8 is an electron micrograph showing a porous crystal formed on a metal surface treated by the electroless copper plating method of Example 3.

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Claims (9)

[Claims] 1. A method for producing a resin composite molded article having a metal part inserted therein, wherein a uniform needle-like metal microstructure is formed on all or a part of the surface of the metal part in advance, and then the metal part is formed. A method for producing a metal insert resin composite molded product, wherein the molded product is inserted into a mold of an injection molding machine and injection molded using a thermoplastic resin material. 2. The method for producing a metal insert-resin composite molded product according to claim 1, wherein the uniform needle-like metal microstructure is formed to be inclined from the vertical direction of the surface of the metal component. 3. A method for producing a resin composite molded product in which a metal component is inserted, wherein a uniform porous metal microstructure is previously formed on all or a part of the surface of the metal component. A method for producing a metal insert resin composite molded product, wherein the molded product is inserted into a mold of an injection molding machine and injection molded using a thermoplastic resin material. 4. The method for producing a metal insert-resin composite molded article according to claim 3, wherein the uniformly porous metal microstructure substantially comprises micropores having a diameter of 0.01 to 10 μm. 5. A thermoplastic resin material comprising: a polyacetal resin, a polyethylene terephthalate resin, a polybutylene terephthalate resin, a polyphenylene sulfide resin,
The polyamide resin, a liquid crystalline polyester resin, a polyimide resin, a syndiotactic polystyrene resin and a polycyclohexane dimethylene terephthalate resin as a main component, at least one resin selected from the group consisting of: A method for producing a metal insert resin composite molded product according to any one of the preceding claims. 6. A resin composite molded article having substantially airtightness, produced by the production method according to claim 1. Description: 7. A resin composite molded article substantially forming a part of an electric circuit device, produced by the production method according to claim 1. 8. The resin composite molded article according to claim 6, wherein the metal component substantially has a function as an electrical connection terminal. 9. The resin composite molded product according to claim 6, which is a component of any one of a sensor, a switch, and a capacitor.