JP4875595B2 - Synthetic resin spring with conductive circuit - Google Patents

Description

  The present invention relates to a synthetic resin spring in which a conductive circuit is formed on the surface of a synthetic resin spring base.

  Conventionally, in a three-dimensional conductive circuit or the like in which a plurality of substrates are laminated at a predetermined interval, spring-like connection terminals have been used as means for electrically connecting the electrodes of each layer to each other. (For example, refer patent documents 1-3.).

  That is, Patent Document 1 discloses a configuration in which a metal plate-like terminal pin 2 is implanted on a synthetic resin support 1. The upper end portion of the terminal pin 2 protrudes from the upper surface of the support body 1, and the lower end portion of the terminal pin has a bifurcated shape and protrudes from the lower surface of the support body. Therefore, when the support body 1 is stacked up and down, the upper end part of the terminal pin protruding from the upper surface of the lower support body is inserted and engaged with the bifurcated lower end part of the terminal pin 2 protruding from the lower surface of the upper support body. Both are electrically connected.

  On the other hand, in Patent Document 2, a bonding pad 1a formed on a semiconductor chip 1 and an electrode 3a formed on a substrate 3 are formed by a spring-like protruding electrode 2 formed on the surface of the electrode. A configuration for electrical connection is disclosed. In addition to a metal spring such as nickel, the protruding electrode 2 is formed by laminating a plurality of layers of photocurable resin on the surface of the electrode 3a to form a spring-shaped protrusion, and electroless plating is applied to the outer surface of the conductor. And a material in which a plurality of layers of a photo-curing resin mixed with a metal material is laminated to form a spring-like protrusion.

In Patent Document 3, a lead-like spring mechanism 3b is integrally projected on one side portion of a locating housing 3 made of synthetic resin, and this spring mechanism is brought into contact with a side surface of the opposing housing 4, A configuration for electrically connecting the two is described. The locating housing 3 made of synthetic resin has a surface plated so as to have conductivity, thereby taking measures against electromagnetic interference.
JP-A-8-31492 (FIG. 7 etc.) Japanese Unexamined Patent Publication No. 2005-11845 (FIG. 5 etc.) Japanese Utility Model Laid-Open No.2-129689 (FIG. 1 etc.)

  The inventor of the present application has found that the conventional conductive spring member described above has the following points to be further improved. That is, since these conductive spring members are all conductive on the entire surface, for example, when connecting highly conductive circuits to each other, in order to electrically isolate them from peripheral components, It is necessary to sandwich an insulating layer such as an insulating film on the side surface of the conductive spring member.

  In addition, the conductive spring members described in Patent Document 2 and Patent Document 3 describe a configuration in which electroless plating is applied to the entire surface of a spring member made of an insulating synthetic resin to ensure conductivity. Yes. None of the patent literature describes the details of the electroless plating method, but the surface of this spring member is etched to ensure the adhesion between the electroless plating and the spring member made of synthetic resin. It is necessary to roughen by such as.

  By the way, the use of the spring member is intended to cause the spring member to exhibit a function of repeatedly elastically deforming, and therefore, it is necessary to ensure sufficient fatigue strength. However, when the surface of the spring member made of synthetic resin is roughened, the adhesion of the electroless plating is improved by the anchor effect, but on the other hand, minute unevenness generated on the roughened surface becomes a notch, resulting in a decrease in fatigue strength. To do. In particular, in the current situation where the degree of integration of conductive circuits is increasing and miniaturization of components is progressing, it is necessary to make the spring member as small as possible. Therefore, in order to ensure the fatigue strength, it is difficult to increase the cross-sectional area of the spring member because it is against this minute requirement.

  Accordingly, a first object of the present invention is to provide a synthetic resin spring having a conductive circuit that facilitates electrical isolation from peripheral components. The second object is to provide a synthetic resin spring having a conductive circuit that can prevent a reduction in fatigue strength of a spring member made of synthetic resin.

  A feature of the synthetic resin spring having the conductive circuit according to the present invention is that an adhesive layer having excellent adhesion to electroless plating is provided on the surface of the synthetic resin spring base. Another feature is that a conductive circuit by electroless plating is selectively formed on the adhesive layer. Yet another feature resides in the use of a synthetic resin spring base having excellent adhesion to the adhesive layer.

  In other words, a synthetic resin spring having a conductive circuit according to the present invention is made of a synthetic resin spring base formed by injection molding, an adhesive layer covering the entire surface of the spring base, and a surface selective to the adhesive layer. And a conductive circuit formed by electroless plating. The adhesive layer is formed by coating a solution in which a polypyrrole resin in a dedope state is dispersed with a binder mixed in advance.

  The synthetic resin constituting the spring base is preferably one of polyetheretherketone (PEEK) resin, polyetherimide (PEI), or a copolymer of polyetherimide and polyimide (PI). .

  Here, as the “spring base”, a coiled helical spring, a plate-shaped spring, and the like are applicable. In addition to a single spring base, a single spring base is also included as a part of another part. The “electroless plating selectively formed on the surface of the adhesive layer” is not the entire surface of the adhesive layer, for example, the connection terminals are formed by electroless plating on both ends of the plate-like spring member, This means that the passage connected to the connection terminal of the part is formed by electroless plating only on one side of the plate-like spring member.

  The “undoped polypyrrole resin” means a state in which a so-called charge carrier is reduced and removed from the polypyrrole resin. That is, the polypyrrole resin is polymerized by oxidizing pyrrole to grow into a conductive polymer. This conductive polymer has charge carriers which are so-called free electrons and holes, and exhibits conductivity. The “dedoped state” means a state in which the conductive polymer is reduced, the charge carriers are removed, and the conductivity is lost. “Binder” means an adhesive component for adhering a polypyrrole-based resin to an adhesive layer, for example, an epoxy resin. Further, “application” means spraying, applying on a shoe, or dipping in a solution.

  The following effects can be obtained by covering the entire surface of the synthetic resin spring base with an adhesive layer in which a polypyrrole resin is dispersed and applying electroless plating to the adhesive layer. That is, the polypyrrole-based resin has a strong electrochemical affinity with the electroless plating and can provide strong adhesion with the electroless plating. Therefore, the step of roughening the surface of the spring base before electroless plating can be omitted.

  Further, in addition to the labor saving of the above process, the fatigue strength of the spring base can be prevented from decreasing by not roughening the surface of the spring base. Furthermore, when the surface of the synthetic resin is roughened, it is necessary to mix a filler or the like that is dissolved in the etching solution into the synthetic resin, and the synthetic resin mixed with such a filler is in a dissolved state. As a result, the fluidity of the resin deteriorates, making it difficult to injection-mold minute products. In the present invention, since it is not necessary to mix such a filler or the like, it becomes easy to injection mold a minute product. Further, an etching solution such as chromic acid is used for roughening the surface of the spring base, but this etching solution causes environmental pollution and requires a large amount of cost for disposal. In this invention, since it does not have such an etching process, it is excellent in environmental resistance.

  By selectively forming a conductive circuit by electroless plating on the surface of the adhesive layer, the following effects can be obtained. That is, since the use of the spring member is intended to be elastically deformed, the position of the outer surface varies somewhat during assembly to the circuit board or the like or during use. In the case of a helical spring member, it is necessary to support the center hole and the periphery of the spring member with a guide member so that the axis of the spring member is not excessively displaced. In such a case, in the conventional spring member whose entire surface is conductive, in order to surely avoid electrical contact with the adjacent conductive circuit, support member, etc., the surface of the spring member, etc. is insulated with an insulating film or the like. Must be covered by means. Providing such an insulating means significantly hinders circuit integration.

  In the present invention, by selectively forming a conductive circuit only on one surface, for example, not on the entire surface of the spring base made of an insulator, the insulation of the spring member on both sides is provided. Can be secured easily. Therefore, it is not necessary to provide an insulating means such as an insulating film in order to avoid electrical contact with adjacent conductive circuits and components, and circuit integration and cost reduction are possible. In addition, by forming a plurality of conductive circuits on the surface of a spring base made of an insulator, a single spring member can be electrically connected to a plurality of connection terminals, etc., further enabling circuit integration and cost reduction. become.

  By using one of polyether ether ketone (PEEK) resin, polyether imide (PEI), or a copolymer of polyether imide and polyimide (PI) as the spring base, it is excellent as a spring member. The characteristics can be exhibited. That is, since these synthetic resins all have high fatigue strength and excellent heat resistance and chemical resistance, they are extremely suitable for spring members used in conductive circuits and the like.

  In addition, these synthetic resins all have excellent adhesiveness with an epoxy resin or the like that is a binder of the adhesive layer, and it is possible to ensure strong adhesiveness between the adhesive layer and the spring base.

  The structure of a synthetic resin spring (hereinafter referred to as “the spring of the present invention”) having a conductive circuit according to the present invention will be described with reference to FIGS. In addition, the manufacturing process of the spring of this invention is mentioned later in FIG. FIG. 1 shows the spring of the present invention formed into a helical spring 1. First, the helical spring 1 is formed by injection-molding a polyether ether ketone (PEEK) resin, which is a thermoplastic resin, into a helical spring base 2 having a square wire cross section. The entire surface of the helical spring base 2 is covered with an adhesive layer 3 to which a non-doped polypyrrole resin is dispersed and a binder made of an epoxy resin is applied.

  A conductive circuit 4 by electroless plating is formed on the surface of the adhesive layer 3 only on the outer surface of the helical spring 1. Both end surfaces of the helical spring base 2 are also formed with electroless plating 2 to enable electrical connection with electrodes facing each other. The strand cross section is not limited to a square but may be a circle, not limited to a circular spiral, but may be an elliptical or hexagonal other helical shape.

  FIG. 2 shows the spring of the present invention configured as a plate-like spring 101. The plate-like spring 101 includes two side leads 111 that are curved in a substantially S shape, and one end 112 that connects the two side leads. In the plate-like spring 101, first, polyether ether ketone (PEEK) resin, which is a thermoplastic resin, is injection-molded on the plate-like spring base 102. The entire surface of the plate-like spring base 102 is covered with an adhesive layer 103 coated with a mixture of an undoped polypyrrole resin dispersed with an epoxy resin binder.

  Conductive circuits 104 are formed by electroless plating on the upper surface of the lead 111 on the two sides and on the surface of the adhesive layer 103. The conductive circuit 104 is also formed around the front side surface and the back surface of the one end 112 of the plate-like spring 101, and enables electrical connection with electrodes facing each other. The two-sided leads 111 may be single or three or more sides. In addition, the lead 111 is not limited to a substantially S shape, and may be a lateral U shape, a zigzag plate member, or the like.

  FIG. 3 shows an integrally formed spring according to the present invention as a part of another part. The spring of the present invention is composed of a lead-like spring 201 that is curved in a substantially S-shape and protrudes from one end of a plate-like panel 205 at a predetermined interval. The lead-shaped spring 201 is formed by injection-molding polyether ether ketone (PEEK) resin, which is a thermoplastic resin, integrally with the plate-shaped panel 205 to form the lead-shaped spring base 202. The entire surface of the lead-shaped spring base body 202 is covered with an adhesive layer 203 coated with a mixture of an undoped polypyrrole resin dispersed with an epoxy resin binder.

  On one side of each lead-like spring base 202 and on the surface of the adhesive layer 203, a conductive circuit 204 is formed by electroless plating. Note that the conductive circuit 204 extends to the surface of the plate-like panel 205 and is electrically connected to electrodes and the like. The lead-shaped spring 201 is not limited to two or more sides, but may be a single shape, not limited to a substantially S shape, but may be a U shape, a substantially C shape, or the like.

  FIG. 4 shows an example of a mold for injection-molding the helical spring base 2 described in FIG. That is, this mold has an outer mold A having an opening hole having the same diameter as the inner peripheral diameter of the helical spring base 2 and divided into two at 180 degrees, and a circle fitted and inserted into the opening hole. It consists of a columnar core B. On the inner peripheral surface of the outer mold A, a groove C having a wire cross-sectional shape of the helical spring base 2 is formed in a helical shape, each half a circumference. Then, in a state where the two outer molds A are overlapped, a cylindrical core B is fitted and inserted into the central opening hole. The helical spring base 2 is formed by injecting a thermoplastic resin into a cavity formed by the outer peripheral surface of the core B and the helical groove C.

  FIG. 5 shows an example of a mold for injection molding the plate-like spring base 102 described in FIG. That is, this mold is composed of an upper mold D and a lower mold E which are divided into two vertically along the lower surface of the plate-shaped spring base 102. The upper mold includes the plate-shaped spring. A recess F is formed so that the base is embedded. Then, the upper mold D and the lower mold E are overlapped, and a thermoplastic resin is injected into the cavity formed by the depression F and the lower mold of the upper mold.

  FIG. 6 shows an example of how the plate-like spring 101 described in FIG. 2 is used. The plate-like spring 101 is inserted while being compressed between the substrates 106 and 107 facing each other at a predetermined interval. That is, a conductive circuit 141 is formed on the upper surface of the upper substrate 106, and a connection terminal 143 is formed on the lower surface. The conductive circuit 141 and the connection terminal 143 are electrically connected by a through hole 142 subjected to conductive plating. A conductive circuit 151 is formed on the upper surface of the lower substrate 107. An electronic component 108 is mounted on the lower surface of the upper substrate 106.

  One end 112 of the plate-like spring 101 is mounted on the upper surface of the conductive circuit 151 formed on the lower substrate 107, and both are coupled by soldering. On the other hand, the tips of the leads 111 on the two sides of the plate-like spring 101 are in pressure contact with the connection terminals 143 formed on the lower surface of the upper substrate 106, respectively. Thus, the conductive circuit 141 formed on the upper surface of the upper substrate 106 and the conductive circuit 151 formed on the upper surface of the lower substrate 107 are electrically connected to each other via the plate-like spring 101. Connected. In addition, since the electroless plating is not formed on both side surfaces of the plate-like spring 101, insulation with the adjacent electronic component 108 is ensured. Therefore, it is not necessary to provide an insulating film or the like between the plate-like spring 101 and the adjacent electronic component 108.

  Next, a specific example of the spring manufacturing method of the present invention will be described with reference to FIG. FIG. 7 shows a cross section AA of the plate-like spring 101 shown in FIG. First, polyether ether ketone (PEEK) resin, which is a thermoplastic resin, is injection-molded to produce a plate-like spring base 102 (A). Next, the entire surface of the plate-like spring base 102 is covered with the adhesive layer 103. The adhesive layer 103 is formed as follows.

  First, pyrrole, which is an organic material, is polymerized by oxidizing it chemically or electrochemically to produce a polypyrrole resin, which is a conductive polymer. Since the produced polypyrrole resin has electrical conductivity, it is electrically or chemically reduced to remove charge carriers and lose electrical conductivity (this operation is referred to as “de-doping”). Next, the dedoped polypyrrole resin is made into a fine powder and dispersed in either an inorganic solvent or an organic solvent to form a solution. Next, an epoxy resin as a binder is mixed into the polypyrrole resin solution. The adhesive layer 103 is formed by immersing or applying the plate-like spring base 102 in a polypyrrole resin solution mixed with an epoxy resin. After forming the adhesive layer 103, the adhesive layer is sufficiently dried (C).

  Next, the surface of the adhesive layer 103 is partially covered with a covering material a, leaving a portion where a conductive circuit is to be formed (D). As the covering material a, a simple substance of polylactic acid is used, but not limited thereto, a simple substance of polyglycolic acid, a mixture of polylactic acid and an aliphatic polyester, or a copolymer may be used. These resins have a property of hydrolyzing with an alkaline aqueous solution and have a property of being resistant to an acidic aqueous solution. As a covering method, a plate-like spring base 102 covered with an adhesive layer 103 is set in an injection mold, and a portion of the plate-like spring base where a predetermined conductive circuit is to be formed. Is covered with a mold or the like, and a polylactic acid resin is injected into a cavity other than that portion, so that the covering material a is integrally formed on the surface of the first substrate. The thickness of the covering material a is preferably 0.1 to 1 mm, and more preferably 0.3 to 0.5 mm.

  Next, a catalyst b made of palladium, gold or the like is applied to the entire surface of the plate-like spring base 102 coated with the coating material a (E). The application of the catalyst b is performed by a known method. For example, after the spring base 102 coated with the coating material a is immersed in a mixed catalyst solution of tin and palladium, the surface is activated with an acid such as hydrochloric acid or sulfuric acid. To deposit palladium. Alternatively, a relatively strong reducing agent such as stannous chloride is adsorbed on the surface and immersed in a catalyst solution containing noble metal ions such as gold to deposit gold on the surface. What is necessary is just to immerse the temperature of a liquid at 15 to 23 degreeC for 5 minute (s).

  Of the surface of the plate-like spring base 102, an exposed portion that is not covered with the covering material a, that is, a portion where a predetermined conductive circuit is to be formed is exposed by the adhesive layer 103, and this adhesive layer is hydrophilic. Therefore, the catalyst b adheres firmly. On the other hand, since the coating material a is hydrophobic, the catalyst b does not adhere firmly.

  Therefore, when the plate-like spring base 102 coated with the coating material a is washed with water, the catalyst b remaining on the surface of the coating material a is completely removed and removed (F). On the other hand, as described above, the catalyst b is firmly attached to the portion where the predetermined conductive circuit is to be formed, so that the catalyst does not fall off even by washing with water. This water cleaning is performed by immersing the workpiece in a water bath at a temperature of 15 ° C. to 25 ° C. and swinging the workpiece for 5 to 30 seconds.

  Next, electroless nickel plating with an acidic bath composition is performed on the surface of the plate-like spring base 102 that is not covered with the covering material a, thereby forming a conductive circuit 104 (G). For example, the electroless nickel plating is performed by immersing in an acidic bath having a pH of 4.7 and a temperature of 90 ° C. for 35 minutes. In addition, the electroless gold plating may be performed by neutralizing the electroless copper plating, the second electroless nickel plating, and the bath composition in this order on the electroless nickel plating. In addition, since electroless nickel plating, electroless copper plating, and electroless gold plating are performed with an acidic or neutral bath composition, the coating material a having acid resistance as described above does not dissolve in the plating solution. The conductive circuit 104 can be formed precisely.

  Next, the covering material a covering the surface of the plate-like spring base 102 is removed (H). As described above, the polylactic acid or the like of the coating material a is resistant to an acidic aqueous solution, but is easily hydrolyzed by an alkaline aqueous solution, so that the plate-like spring base 102 coated with the coating material a has a concentration of 2 to 2. The coating material is removed by immersing in a caustic (NaOH, KOH, etc.) aqueous solution of 15% by weight and a temperature of 25 ° C. to 70 ° C. for about 1 to 120 minutes. Therefore, the working efficiency is remarkably improved as compared with the manual mask removal.

Note that either before or after the removal of the covering material a, electrolytic plating with an acidic or neutral bath composition is performed on the conductive circuit 104 by electroless nickel plating to form a secondary plating layer. The thickness may be increased. This electrolytic plating uses, for example, an acidic copper sulfate bath, and the bath composition is CuSO ₄ .5H ₂ O (75 g) / lH ₂ SO ₄ (190 g) / lCl (60 ppm) / additive (appropriate amount). The anode material is phosphorous copper, the bath temperature is set to 25 ° C., and the cathode current density is 2.5 A / dm 2. Even before the removal of the covering material a, this covering material has acid resistance, so that it does not dissolve in the acidic electrolytic copper plating solution and is accurately formed on the surface of the conductive circuit 104 formed with electroless plating. A secondary plating layer can be formed on the substrate.

  Further, a fibrous or particulate filler may be added to polyether ether ketone (PEEK) resin or the like which is a material of the plate-like spring base 102. Examples of the fiber include glass fiber, carbon fiber, calcium titanate whisker, aluminum borate whisker, and carbonated whisker whisker. Examples of the particulate filler include calcium carbonate and wollastonite.

  A synthetic resin spring having a conductive circuit according to the present invention improves the fatigue strength of the spring, facilitates integration of the conductive circuit, and is excellent in environmental resistance, and can be widely used in industries related to electronic devices and the like. .

It is a perspective view of a helical spring. It is a perspective view of a plate-shaped spring. It is a perspective view of the plate-shaped spring protrudingly provided at one end of the plate-shaped panel. It is the schematic of the metal mold | die for injection molding of a helical spring. It is the schematic of the metal mold | die for injection molding of a plate-shaped spring. It is a partial cross section figure which shows the usage condition of a plate-shaped spring. It is a manufacturing-process figure of the spring made from a synthetic resin.

Explanation of symbols

1, 101, 201 Spring 2, 102, 202 Spring base 3, 103, 203 Adhesive layer 4, 104, 204 Conductive circuit a Coating material b Catalyst

Claims (2)

A spring base made of synthetic resin formed by injection molding;
An adhesive layer covering the entire surface of the spring base;
A conductive circuit by electroless plating selectively formed on the surface of the adhesive layer,
The adhesive layer is formed by applying a solution in which a polypyrrole resin in a dedope state is dispersed and mixing a binder ,
The conductive circuit is made of a polylactic acid or polyglycolic acid simple substance, a mixture of polylactic acid and aliphatic polyester, or a copolymer, leaving the surface where the conductive circuit is to be formed. Coating the covering material in part, applying a catalyst to the entire surface of the spring base coated with the covering, removing the catalyst remaining on the surface of the covering with water, The conductive layer is formed by performing electroless plating with either an acidic or neutral bath composition on a portion that is not covered with a coating material, and removing the coating material with an alkaline aqueous solution. Synthetic resin spring with circuit. 2. The synthetic resin constituting the spring base according to claim 1, wherein the synthetic resin is one of polyetheretherketone (PEEK) resin, polyetherimide (PEI), or a copolymer of polyetherimide and polyimide (PI). A synthetic resin spring having a conductive circuit.

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