JP2019181711A - Metal-resin bonded product - Google Patents

Abstract

To provide a metal-resin bonded product with a high joint strength.SOLUTION: A metal-resin bonded product is made by bonding a metallic body and a resin body. The bonded surface of the metallic body is unlevel with a surface roughness (Ra) ranging 0.3-10 μm. At least a part of convex parts forming the unlevel surface has metallic particles with size ranging 100-1000 nm joined together at the tip. Spiry projections are distributed like a pinholder on the unlevel surface, and, preferably the metallic particles are joined together at the top of projections. The unlevel surface of this sort is obtained, for example, by roughened plating. The metallic particles, at least partially, are preferably swollen in a tuft-like state from tips of the projections to the bonded surface. In this way the surface area of the bonded interface increases, and the resin penetrated into the concave part is locked with the swollen metallic particles, to provide the metal-resin bonded product with a particularly high joint strength.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a metal-resin joined body obtained by joining a metal and a resin.

  In recent years, with the need for weight reduction in the automotive field and the aircraft field, a highly reliable metal / resin bonding member is required. For example, electronic devices and power devices packaged with a resin often require high airtightness at the bonding interface between the resin and metal.

  In general, the airtightness at the bonding interface between the metal and the resin is ensured by an O-ring, caulking, an adhesive, or the like. The use of the O-ring causes an increase in the size of the member and an increase in the number of parts. Caulking causes an increase in processing man-hours. The adhesive may cause peeling due to aging. Also, the use of an adhesive often involves the use of an adhesive solvent, which is an environmentally hazardous substance.

  Therefore, it is desired to secure the airtightness between the two while directly joining the metal and the resin. Various proposals have been made to join such a metal and a resin. For example, there are descriptions related to the following patent documents.

WO2009 / 093668 WO2009 / 151099 Japanese Unexamined Patent Publication No. 2015-100959 Japanese Patent Laid-Open No. 2006-65267 JP 2012-214027 A JP 2014-4773 A

  In patent document 1 and patent document 2, resin is joined to the metal surface roughened by the etching process. In patent document 3, resin is joined to the metal surface in which the recessed part was formed by laser irradiation. In Patent Document 4, a resin film is bonded to a copper foil having a roughened copper plating layer, a small protrusion copper plating layer, and the like.

  In Patent Documents 5 and 6, a resin (PPS) is bonded to an uneven surface formed by bonding Ag nanoparticles to the surface of electropolished metal (Cu, Al, etc.). However, the bonding strength is only about 10 MPa at most.

  The present invention has been made under such circumstances, and an object thereof is to provide a new metal-resin joined body and the like that can exhibit high joint strength.

  As a result of diligent research to solve this problem, the present inventors have succeeded in selectively bonding metal particles to the tips of minute convex portions on the surface to be joined of the metal body, and through the surface to be joined. It was newly found that the metal-resin bonded body bonded in this way exhibits high bonding strength. By developing this result, the present invention described below has been completed.

《Metal-resin bonded body》
(1) The present invention is a metal-resin joined body obtained by joining a metal body and a resin body, and a surface to be joined of the metal body is an uneven surface having a surface roughness (Ra) of 0.3 to 10 μm. The metal resin bonded body has metal particles having a particle size of 100 to 1000 nm bonded to the tip side of at least some of the convex portions constituting the uneven surface.

(2) The metal-resin bonded body of the present invention (simply referred to as “bonded body”) can exhibit high bonding strength or high adhesion and sealing properties. Therefore, the joined body of the present invention can be used for various products in various fields. The reason why the bonded body of the present invention can exhibit such excellent effects is considered as follows.

  First, the surface to be joined of the metal body according to the present invention is not a smooth surface obtained by electropolishing but an uneven surface having a predetermined roughness. For this reason, a large contact area is ensured between the metal body and the resin body, and a high bonding strength is generated between them due to a so-called anchor effect.

  Furthermore, the metal particle is couple | bonded with the convex part of the uneven surface. The metal particles are almost selectively bonded to the tip side of the convex portion. That is, there is almost no coupling near the base of the convex portion or the bottom surface of the concave portion. For this reason, the metal particles do not smooth the uneven surface described above, and further increase the contact area between the metal body and the resin body or make the interface form more complicated, thereby increasing the bonding strength due to the anchor effect.

  Thus, it is thought that the joined body of the present invention has exhibited high joint strength by the synergistic action of the uneven surface having a predetermined surface roughness and the metal particles bonded to the projecting portion. .

<< Method for producing metal-resin bonded body >>
The present invention can also be grasped as a method for manufacturing a joined body. That is, the present invention includes a bonding step of bonding a resin to a bonded surface of a metal body, and the bonded surface includes an uneven surface having a surface roughness (Ra) of 0.3 to 10 μm. A metal resin joined body manufacturing method in which metal particles having a particle diameter of 100 to 1000 nm are bonded to the front end side of at least some of the convex portions constituting the surface may be used.

<Others>
Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. A range such as “a to b” can be newly established with any numerical value included in various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.

It is a schematic diagram which shows the cross section of the to-be-joined surface of a metal body. It is the SEM image which observed the nickel plating surface before the coupling | bonding of a silver nanoparticle. It is the SEM image which observed the nickel plating surface after the coupling | bonding of a silver nanoparticle.

  The contents described in this specification can be appropriately applied not only to the joined body of the present invention but also to the manufacturing method thereof. One or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. A component related to the manufacturing method can also be a component related to an object. Which embodiment is the best depends on the target, required performance, and the like.

《Metal body surface to be joined》
(1) Surface roughness The to-be-joined surface of the metal body joined to a resin body consists of an uneven surface. The uneven surface preferably has an arithmetic average roughness (Ra / JIS B 0601) of 0.3 to 10 μm, more preferably 0.4 to 4 μm. If the surface roughness of the uneven surface is too small or too large, the increase in surface area and bonding strength due to the bonding of metal particles will be insufficient.

  The surface roughness here is determined as the surface roughness (Ra) in a randomly extracted region (110 μm × 145 μm) with respect to the uneven surface after the metal particles are bonded. When specifying the surface roughness of the metal body from the bonded body, the surface roughness (Ra) may be measured after the resin is melted or burned out.

(2) Form It is preferable that the concavo-convex surface has convex portions that are substantially spire-shaped (or substantially cone-shaped) projections, and the projections are distributed in a sword mountain shape (see FIGS. 1 and 2A). The metal particles bonded to the top of the protrusion (tip on the resin body side) form an undercut in cooperation with the concave portion of the concave and convex surface (see FIGS. 1 and 2B). That is, the metal particles act like a so-called “reverse taper” or “barbage”. With such metal particles, the resin that has entered the recesses is mechanically locked. As a result, a stronger anchor effect is produced at the joint interface between the metal body and the resin body, and both are joined more firmly. This tendency becomes more prominent as the extent to which at least a part of the metal particles bulge in the lateral direction (bonded surface direction) from the tip side of the convex portion is within a range in which the concave portion is not blocked.

(3) Metal particles As long as the metal particles can be bonded to the tip (top) of the nano-sized to micro-sized convex portions, only the primary particles may be used, or fine primary particles aggregate to a desired size. Secondary particles may also be used.

  The particle size of the metal particles bonded to the convex portion is preferably 100 to 1000 nm, more preferably 300 to 600 nm. If the metal particles are too small, the surface area of the bonding interface cannot be increased sufficiently. Excessive metal particles are likely to fall off the convex portion. When the metal particles are composed of secondary particles in which primary particles are aggregated, the primary particles preferably have a particle size of 1 to 500 nm, more preferably 50 to 300 nm. When the metal particles are composed of such nanoparticles (primary particles or secondary particles), metal particles having a desired shape that are selectively bonded to the tip side of the convex portion are easily formed.

  Unless otherwise specified, the particle size referred to in the present specification is specified by arithmetically averaging the maximum lengths of 100 particles arbitrarily extracted in a region observed with a scanning electron microscope (SEM).

  The metal particles may be made of a material that can be bonded to the tip (top) of the convex portion, and may be selected from pure metals or alloys such as Ag, Au, Cu, Pt, Ru, Pd, Ir, Os, and Rh. The The material of the metal particles is preferably selected according to the material of the concavo-convex surface in order to improve the bonding strength between the metal particles and the convex portion, and hence the bonding strength between the metal body and the resin body. For example, when the uneven surface is made of nickel (Ni) or an alloy thereof, the metal particles are preferably made of silver (Ag) or an alloy thereof. Note that the metal particles and the concavo-convex surface may be made of the same material as long as the desired bonding strength is ensured. Further, the bonding layer of the metal particles and the convex portions may be various depending on their materials and processing. For example, as the bonding layer, a sintered layer, an alloy layer, an intermetallic compound layer, or the like can be considered.

(4) Formation of concavo-convex surface The concavo-convex surface may be formed directly on the surface of the base material constituting the metal body or may be formed on a coating layer (plating or the like) provided on the surface of the base material. The uneven surface can be formed by, for example, roughening plating, (wet) etching, laser processing, pressing, die casting, cutting, blasting, sputtering, various types of vapor deposition (CVD, PVD) or the like. However, since the uneven surface can be efficiently formed by using rough plating, the uneven surface is preferably a rough plating layer.

《Metal body》
The metal body may be of any material or form as long as an uneven surface (bonded surface) to which metal particles are bonded is obtained. The metal body is, for example, copper or copper alloy (copper metal), iron or iron alloy (including iron metal / steel materials (carbon steel, alloy steel, stainless steel, etc.)), aluminum or aluminum alloy (aluminum metal). ), Magnesium or magnesium alloy (magnesium-based metal), titanium or titanium alloy (titanium-based metal), or the like. Further, it may be made of nickel, nickel alloy (nickel metal), tin, tin alloy (tin metal), silver, silver alloy (silver metal), gold or the like. Furthermore, a composite material including a dispersion material using these metals as a matrix may be used.

<Resin body>
As long as the resin body can be bonded to the bonded surface of the metal body, the material and the form thereof are not limited. In the case of the present invention, since the bonding strength is basically secured by the anchor effect, a wide variety of resins can be bonded to the bonded surfaces of the metal bodies.

  The resin may be a thermoplastic resin or a thermosetting resin. Specifically, polyphenylene sulfide (PPS) resin, epoxy resin, polybutylene terephthalate (PBT) resin, silicone resin, polyamide (PA) resin, polyacetal (POM) resin, diallyl phthalate (PDAP) Resin (diallyl phthalate, allyl resin, etc.), aromatic polyamide (APA) resin, fluorine resin (PTFE, PFA, EPA), polyimide (PI) resin, polypropylene (PP) resin, polyacetal (POM) Resin, polyethylene terephthalate (PET) resin, phenol (PF) resin, unsaturated polyester (UP) resin, polyurethane (PUR), melamine (MF), aromatic polyester (APES) resin, polycarbonate (PC) Resin, polyamideimide ( AI) resin, polysulfone (PSU) resin, polyethersulfone (PES) resin, polyphenylene ether (PPE) resin, can be used any of such modified Noryl resins (PPE + PS, etc.).

  As long as the resin exists in the region in contact with the surface to be joined (uneven surface) of the metal body, the resin body may be composed entirely of resin or a composite material in which various fillers are dispersed in the resin. Good. Examples of the filler include soft particles (for example, silicone rubber, crosslinked NBR, acrylic rubber, crosslinked olefin rubber), hard particles (carbon, ceramics, etc.), and fibers (carbon, ceramics, glass, etc.). The resin is not limited to a single type, and may be a mixture of a plurality of types.

"Production method"
The joining step for joining the resin to the surface to be joined of the metal body is performed, for example, by solidifying the softened or melted resin on the surface to be joined. This joining step is performed by, for example, a supplying step of supplying a softened or melted resin to the surfaces to be joined and a solidifying step of solidifying the resin to obtain a resin body. The supplying step is performed, for example, by containing or setting a metal body in a mold and injecting a softened or molten resin into the mold so as to come into contact with the surface to be joined of the metal body. It is efficient if the metal body and the resin body are joined together by so-called insert molding. The resin body may be molded by any of injection molding, extrusion molding, blow molding, vacuum molding, transfer molding, compression molding, and the like.

  The joining step may be performed by separately thermally welding a resin body that has already been formed into a desired shape to a metal body. This joining process includes, for example, a heating process in which the resin in the vicinity of the surface to be joined of the resin body is heated directly or indirectly to soften or melt, and the molten or softened resin is brought into contact with the surface to be joined of the metal body. (Or pressure contact) and a cooling step of cooling and solidifying.

《Joint body》
Since the bonded body of the present invention exhibits high bonding strength, it can be used for various products in various fields. The joint strength of the joined body obtained by the shear test can be, for example, 20 MPa or more, 25 MPa or more, or 30 MPa or more.

  Moreover, in the joined body of the present invention, the resin is in close contact with the surface to be joined having a large surface area (and the uneven surface that has been reversely tapered by the metal particles). For this reason, the bonded body of the present invention has not only high bonding strength but also high airtightness (sealability) at the bonding interface. Therefore, the joined body of the present invention is suitable for a member or the like in which the joining interface between the metal body and the resin body serves as a fluid sealing surface.

  An example of such a member is a gas or fluid pressure sensor. The pressure sensor includes a sensing portion and a terminal portion (metal body) that transmits an electric signal to the external connector (metal body), and a case portion and a package portion (resin body) that secure their retention and insulation. In this case, even if fluid pressure acts near the joint interface, peeling along the joint interface, fluid leakage, etc. are suppressed, and in combination with the rust prevention effect of the metal part, the reliability of the pressure sensor is improved. Figured.

  (Roughening) nickel plating was performed on the base material (metal body), and silver nanoparticles (metal particles) were further bonded on the nickel plating. The resin was integrally formed on the base material via this treated surface (surface to be joined). The bonding strength of the obtained bonded body was measured and its treated surface was observed. The present invention will be described in more detail through such specific examples.

<Production of sample>
(1) Base material (metal body)
As a base material, an oxygen-free copper plate (20 mm square × 3 mm thickness / JIS C1020) was prepared. In order to improve the adhesion of the plating, the surface of the base material was electrolytically degreased and washed, then etched in a persulfuric acid solvent, and further acid-activated in hydrochloric acid (10% by volume).

(2) Nickel plating Electrolytic nickel plating was applied to the surface of the pretreated substrate (unevenness forming step). A Watt bath (an aqueous solution of nickel sulfate, nickel chloride and boric acid) was used as the plating bath. No other additives were used in the preparation of the plating bath. Nickel sulfate and nickel chloride were used as a source of Ni ions, and boric acid was used as a pH buffer. The pH of the plating bath thus obtained was 6.

The substrate was immersed in a plating bath maintained at 60 ° C., and a current density of 0.5 to 1 A / dm ² was applied. The processing time was 90 minutes. At this time, plating was performed in a static bath without stirring. Thus, a nickel plated surface having a surface roughness (Ra) of 0.35 μm was formed on the substrate surface. The calculation of the surface roughness will be described later.

(3) Bonding of silver nanoparticles Silver nanoparticles (metal particles) were bonded to a nickel-plated surface (uneven surface) (particle bonding step). This process was performed according to the description in Japanese Patent Application Laid-Open No. 2014-4773 or Japanese Patent Application Laid-Open No. 2012-214027. The outline is as follows.

  An Ag particle-containing dispersion was prepared using an aqueous silver nitrate solution and an aqueous trisodium citrate solution. As described in the above publication, the particle size of Ag particles contained in the dispersion was about 3 nm. A cationic polymer solution comprising an aqueous solution of polyethyleneimine (PEI) was also prepared. The nickel-plated surface was alternately immersed in a dispersion containing Ag particles and a cationic polymer solution, and silver nanoparticles were supported on the nickel-plated surface.

  The base material subjected to the above-described treatment on the nickel plating surface was heated in a hydrogen gas atmosphere at 250 ° C. for 1 hour (firing step). In addition, the organic modification process as described in Unexamined-Japanese-Patent No. 2014-4773 is not performed after this process.

  Incidentally, the description in Japanese Patent Application Laid-Open No. 2014-4773 or Japanese Patent Application Laid-Open No. 2012-214027 constitutes a part of this specification, and the detailed contents not described in this specification depend on the description of those publications.

(4) Resin bonding The non-reinforced polyphenylene sulfide resin (PPS / A900 manufactured by Toray Industries, Inc.) melted by heating to 330 ° C. into the molding die in which the base material after the above-described treatment (base material after the firing step) is disposed. Injected (supply process). Thereafter, the molding die was cooled to solidify the resin (solidification step). By this insert molding, a joined body (metal resin joined body) in which a resin body (5 mm square × 4 mm thickness) was joined to the base material via the treated surface was obtained. The contact region (junction) of the substrate and the resin member was 25mm ² ~40mm ^2. This joined body is referred to as Sample 1.

(5) Comparative sample Resin was directly joined to the surface of the nickel-plated surface in the same manner as Sample 1 except that the silver nanoparticles were not bonded. The joined body thus obtained is referred to as Sample C1.

  A base material having a nickel-plated surface having a surface roughness (Ra) of 0.15 μm was also prepared. In the same manner as in the case of Sample 1, this nickel plating surface was subjected to silver nanoparticle bonding treatment and resin bonding. The joined body thus obtained is referred to as Sample C2.

<Shear test>
The joining strength concerning each sample was calculated | required by the shear test. The bonding strength was calculated by measuring the shear resistance and fracture area for each joined body and dividing the shear resistance by the fracture area.

  The shear resistance was measured by a die shear test measurement method using a universal bond tester (4000PLUS manufactured by Nordson Advanced Tester). At this time, the height of the share tool: 50 μm, tool speed: 50 μm / min, conformity standard: Department of Defense, Test method standard microcircuits, MIL STD-883E, Dec. 31, 1996. METHOD 2019.5, May 29, 1987. did.

  The fracture area was measured by image processing of an optical micrograph of the base-side fracture surface after the shear test (software: ImageJ, National Institutes of Health). Table 1 shows the bonding strength of each sample thus obtained.

《Measurement and observation of bonded surface》
(1) Observation About the base material which concerns on the sample 1, the nickel plating surface before the coupling | bonding of a silver nanoparticle and the nickel plating surface after the coupling | bonding of a silver nanoparticle were observed by SEM. The respective SEM images are shown in FIGS. 2A and 2B.

(2) Surface roughness About the base material which concerns on each sample, the surface roughness (Ra) of the nickel plating surface before the coupling | bonding of a silver nanoparticle and the nickel plating surface after the coupling | bonding of a silver nanoparticle was measured (calculated). The results are also shown in Table 1.

  The surface roughness (arithmetic average roughness: Ra / JIS B 0601) is a roughness curve in a measurement area of 110 μm in length and 145 μm in width with a magnification of 100 times using a laser microscope (VK-X manufactured by Keyence). Based on (Z (x, y)).

(3) Particle Size of Metal Particle Based on the SEM image of FIG. 2B, the (average) particle size of silver nanoparticles (mainly secondary particles) was calculated by the method described above. The results are also shown in Table 1. In addition, the particle diameter of the primary particle which concerns on the sample 1 was 100 nm.

<Evaluation>
(1) Bonding strength As is clear from Sample 1 shown in Table 1, a bonded body in which silver nanoparticles are bonded and a resin is bonded to a bonded surface having a predetermined surface roughness is a very high bond. It was found to exert strength. On the other hand, as can be seen from Sample C1 and Sample C2, when the bonding surface of the silver nanoparticles is not applied to the surfaces to be bonded or when the surface roughness of the surfaces to be bonded is not within the desired range, the high bonding strength as in Sample 1 is obtained. Was not obtained.

(2) Consideration As can be seen from FIG. 2A, it can be seen that the surface after nickel plating is a concavo-convex surface in which spire-like protrusions are distributed in a sword mountain shape. Further, as can be seen from FIG. 2B, it can be seen that the surface after the silver nanoparticle binding treatment is selectively bonded with the silver nanoparticle only at the tip (top) of the protrusion. It can also be seen that the silver nanoparticles swell in a tuft shape in the lateral direction (direction along the bonded surface) from the top of each protrusion.

  The area of the bonding interface is increased by such silver nanoparticles, and the resin that has entered the concave portion of the nickel plating is in a state of being hooked on the silver nanoparticles swelled in a tuft shape. It is considered that the joined body of Sample 1 exhibited very high bonding strength due to the synergistic action of these. This is also clear from the comparison of the bonding strength between sample 1 and sample C1.

  Moreover, although the sample C2 was subjected to the silver nanoparticle bonding treatment, its bonding strength was relatively small. From this, it can be said that the surface roughness after the treatment must be within a predetermined range in order to obtain a high bonding strength. For this purpose, it is considered that the surface roughness of the nickel-plated surface before processing is also important. As can be seen from Table 1, the surface roughness after the treatment is about 0.1 μm higher than the surface roughness before the treatment. Therefore, it is preferable that the surface roughness before the treatment is also approximately the same as the surface roughness after the metal particle bonding treatment defined in the present invention.

  Thus, it has been clarified that the metal body and the resin body can be firmly bonded through the bonded surface defined in the present invention.

Claims (9)

A metal-resin joined body obtained by joining a metal body and a resin body,
The bonded surface of the metal body is an uneven surface having a surface roughness (Ra) of 0.3 to 10 μm,
A metal-resin bonded body in which metal particles having a particle size of 100 to 1000 nm are bonded to the tip side of at least some of the convex portions constituting the irregular surface. The convex portion is composed of a substantially spire-shaped protrusion,
The uneven surface has the protrusions distributed in a sword mountain shape,
The metal resin bonded body according to claim 1, wherein the metal particles are bonded to the tops of the protrusions.   The metal-resin joined body according to claim 1 or 2, wherein at least a part of the metal particles bulge from a tip side of the convex portion.   The metal resin joined body according to any one of claims 1 to 3, wherein the metal particles are formed of secondary particles in which primary particles are aggregated. The uneven surface is made of nickel,
The metal resin joined body according to claim 1, wherein the metal particles are made of silver.   The metal-resin joined body according to any one of claims 1 to 5, wherein the uneven surface includes a roughened plating layer.   The resin body includes polyphenylene sulfide resin, epoxy resin, polybutylene terephthalate resin, silicone resin, polyamide resin, polyacetal resin, diallyl phthalate resin, aromatic polyamide resin, fluorine resin, polyimide resin. Polypropylene resin, polyacetal resin, polyethylene terephthalate resin, phenol resin, unsaturated polyester resin, polyurethane, melamine, aromatic polyester resin, polycarbonate resin, polyamideimide resin, polysulfone resin, polyethersal The metal resin joined body according to any one of claims 1 to 6, comprising any one of a phon resin, a polyphenylene ether resin, and a modified noryl resin.   The metal-resin joined body according to any one of claims 1 to 7, wherein a joining strength obtained by a shear test is 20 MPa or more.   The metal-resin joined body according to claim 1, wherein a joint interface between the metal body and the resin body serves as a fluid sealing surface.