JPH08186016A - Bonded magnet having plating film and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To provide the title bonded magnet having plating film and manufacturing method thereof in simple procedures having excellent corrosion resistance as well as dimentional precision and beautiful appearance and formable into any complicated shape. CONSTITUTION: The title bonding magnet mainly comprising a magnetic particle body 1 and a binder represented by R-T-B (where R represents Nd or a part thereof substituted with a rare earth element, T represents Fe or a part thereof substituted with a transition element is painted with a mixture of resin 4 and conductive materials 5 so as to form a conductive film layer B on the bonding magnet base material A surface and then the surface of the conductive film layer B is smoothed to electroplate the surface of the smoothed conductive film layer B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonded magnet having a plating film and a method for producing the same, and more specifically, it is excellent not only in corrosion resistance and aesthetics but also in dimensional accuracy.
Further, the present invention relates to a bond magnet having a plating film which can be used for a complicated shape and has a simple manufacturing procedure, and a method for manufacturing the bond magnet.

[0002]

2. Description of the Related Art Alloy magnets containing rare earth metals and transition metals as main components (hereinafter referred to as "rare earth magnets") have excellent magnetic properties as compared with conventional ferrite-based and alnico-based magnets, and thus have been widely used in recent years. Although it is used in various fields, it has a drawback that it is easily oxidized, and this tendency is remarkable especially in Nd-Fe-B magnets. The resin-bonded magnet in which such a rare earth magnetic powder is fixed with a synthetic resin binder has a problem that the magnetic characteristics are deteriorated due to oxidation when the usage environment is a high humidity atmosphere.

On the other hand, it is well known that the electroplating method is frequently used as one of the methods for applying a metal coating treatment to a material having a conductive surface so as to prevent cracking and chipping and to give an aesthetic appearance. Is. Furthermore, it is also common to carry out plating for the purpose of imparting oxidation resistance and corrosion resistance. Here, the electroplating method means that the object to be treated is a cathode (cathode), a reduction reaction is caused on this to deposit a metal on the object to be treated, and at the time of the anode, it is deposited on the object to be treated on the cathode. It refers to a method for forming a metal coating based on the mechanism of metal dissolution to supplement the metal.

The present inventors have previously tried to apply the electroplating method to bonded magnets, and have aimed at improving the effect of imparting corrosion resistance. The present inventors are not limited to Nd-Fe-B based magnets, and R-T-B (R is Nd or a part thereof substituted with a rare earth element, T is Fe or a part thereof is a transition metal element). The entire research target is a bonded magnet (hereinafter, referred to as an RTB-based magnet) in which a magnetic powder represented by (substituted) and a binder are main components. For example, Japanese Patent Application Hei 1
No. 147380 proposed to provide corrosion resistance by electroplating, and JP-A-4-276095 proposed a method of dramatically increasing corrosion resistance. Japanese Unexamined Patent Publication No. 4-276095 solves the problems inherent in the technique disclosed in Japanese Patent Application No. 1-147380. That is, JP-A-4-276095
In No. 6, when electroplating the bonded magnet base material directly, the cause of the small pinholes that frequently appear on the surface of the plated coating is that the surface of the bonded magnet base material, which is the base of the plated coating, is a synthetic resin part with low conductivity. It was found that the problem was caused by the fact that the exposure was exposed, and the methods listed below were proposed as a method for solving this problem. A method of electroless plating after electroless plating on the surface of the RTB magnet. A method of applying a mixture of a resin and a conductive material powder on the surface of an RTB-based magnet and then performing electroplating. A method in which an RTB-based magnetic powder is molded using a mixture of a resin and a conductive material powder resin as a binder, and then electroplating is performed. A method in which R-T-B based magnetic powder is molded using a metal powder as a binder and then electroplated. All of these are characterized by imparting conductivity to the surface of the bond magnet prior to electroplating in order to facilitate electroplating on the surface of the bond magnet. Can be formed, and it can be applied to, for example, magnets for automobile motors, which are used in severe environments. In particular, the above method is industrially extremely useful because it can be realized by a simple method of spray coating a mixture of resin and conductive material powder (hereinafter referred to as conductive paste).

The method (1) will be described with reference to the schematic diagrams of FIGS. FIG. 5 is a schematic diagram showing a cross-sectional structure near the surface of the bonded magnet base material. In the figure, 1 is a magnetic powder and 2 is a synthetic resin 2 for binding the magnetic powder 1. The bonded magnet base material is pre-polished to adjust the outer dimensions to the product dimensions, but the magnetic powder 1 and the synthetic resin 2 have different hardness, and the magnetic powder 1 may fall off during polishing. Microscopically, therefore, the magnetic powder 1 is partially projected or the resin layer is exposed on the surface of the bonded magnet base material as shown in the figure. Since the portion where the resin layer is exposed has low conductivity, the growth of the plated coating at that portion is slow when electroplating, which causes pinholes. In this method, as shown in FIG. 6, the surface of the bonded magnet base material A is coated with the conductive paste 6 to form the conductive coating layer B, which is then electroplated to form the plating coating as shown in FIG. Layer C is layered. Since a simple method such as spray coating can be used as the coating method of the conductive paste 6, the work of forming the conductive coating layer B is easy, and the surface of the bond magnet after the formation of the conductive coating layer B is Since good conductivity is exhibited over the entire area, it is possible to stably form the plating film layer C having a substantially constant film thickness.

Another method has been proposed as a method for imparting conductivity to the surface of a bonded magnet, for example, Japanese Patent Laid-Open No. 5-3.
There is a technique disclosed in No. 02176. Here, when forming a plating film on the surface of the bonded magnet, after forming a resin layer having adhesiveness on the surface of the bonded magnet base material, it is sprinkled with metal powder etc. A method has been proposed in which a metal powder is fixed to the surface of a bonded magnet by vibrating or stirring a magnet or hitting a medium such as a steel ball on the surface to give a striking force to impart conductivity.

This method is illustrated by the schematic diagrams shown in FIGS. In this method, as shown in FIG. 9, a resin layer D containing 100% of a resin component having excellent adhesiveness is formed on the upper layer of the bonded magnet base material A, and a metal powder as shown in FIG. As shown in FIG. 11, by sprinkling 3 onto the bonded magnet, and then vibrating or stirring the bonded magnet in such a state in the container, or by hitting a metal medium such as a steel ball or a soft medium such as soft plastic onto the bonded magnet. Then, a part of the metal powder 3 is caused to enter the surface layer portion of the resin layer D to fix the metal powder 3 inside and outside the resin layer. Further, the surplus amount of the metal powder 3 which exceeds the capturing ability of the resin layer D is removed. Through such a procedure, the resin Rich resin layer D on the bonded magnet base material A, and the transition layer D ′ in which the metal powder 3 is mixed in the resin layer in a state in which the content thereof is gradually changed. , The Rich conductive coating layer E of the metal powder 3 is laminated, the plating coating layer C is formed on the conductive coating layer E, and a bond magnet having a plating coating without pinholes is produced. It

As a typical example of the method for producing the bonded magnet having the plating film layer having no pinhole, the above-mentioned 2 is used.
There are different types. All of these have various shapes, and there is no need for dimensional adjustment or final finishing by re-polishing after forming the plating film layer C due to the fact that they have curved surfaces and uneven surfaces and are disadvantageous in terms of cost. A finished product is obtained when the plating film layer C is formed.

[0009]

Although it is possible to obtain a bonded magnet having a plating film layer without pinholes by the above-mentioned two methods, there are still problems to be solved in these plating methods.

First, as for the former, as shown in FIG. 7, the surface of the plating film layer C reflects the surface undulation state of the conductive film layer B, so that the surface of the plating film layer C cannot be made a uniform smooth surface. There's a problem. The surface undulations of the plating film layer C do not reflect the surface undulations of the conductive film layer B as they are, but the difference in height of the undulations is reflected in a slightly relaxed form. However, there is a concern that this surface undulation may adversely affect the uniformity of the surface magnetic property of the product and the aesthetics. Further, since the conductive coating layer B is merely spray-painted and the conductive coating layer B only covers the bond magnet base material A due to its wettability, the bond coating of the conductive coating layer B is not limited. The adhesiveness to the material A tends to be slightly insufficient. Further, when the conductive paste is applied, the packing density of the conductive material powder cannot be increased so much in order to improve the wettability and the adhesion, and therefore even if the conductive paste is applied, There is a limit to the effect of improving conductivity. Further, as described above, the shape immediately after the formation of the plating film layer C becomes the shape of the final product without performing the final finishing process after forming the plating film layer C. However, in the present technology, the conductive paste is simply spray coated. Since the plating film layer C is formed on top of the above, the average thickness of the total film thickness of the conductive film layer B and the plating film layer C is relatively large, and the deviation from the outer dimensions of the bonded magnet base material A is relatively large. As the size increases, the distance from the external dimensions of the final product designed on the assumption that the external dimensions of the bonded magnet base material A are substantially the same tends to increase.

On the other hand, the technique disclosed in Japanese Patent Laid-Open No. 5-302176 also has a problem to be solved. First, in this technique, in order to vibrate or agitate the bond magnet having the metal powder 3 adhered on the surface in the container, or to hit a metal medium such as a steel ball onto the bond magnet,
The surface undulation (see FIG. 11) after deposition of the metal powder 3 is the conductive coating layer B in the above-mentioned JP-A-4-276095.
Although it is slightly gentler than the surface undulation immediately after formation (see FIG. 7), the purpose of vibrating, stirring, and hitting with a metal medium is to attach the metal powder 3 to the adhesive resin layer D. Therefore, the pressure applied to the surface on which the metal powder is adhered is relatively low, and therefore the surface undulation cannot be smoothed. Further, in this technique, since the resin layer D is formed on the bonded magnet base material A, the metal powder 3 is accumulated and the conductive coating layer E is laminated.
It is essential that the metal powder 3 be present over the entire surface. Therefore, also from this point of view, it is not assumed that a strong pressure is exerted such that the bonded magnet base material A is partially exposed. It is impossible to smooth the surface. Therefore, even with this technique, the surface of the plating film layer C cannot be smoothed as shown in FIG. Moreover, since the two-layer structure of the resin layer D and the conductive coating layer E is always formed on the upper layer of the bonded magnet base material A, and the plating coating layer C is formed thereon, the resin layer D and the conductive coating layer E are formed.
The average thickness of the total thickness of the three layers of the plating film layer C and the plating film layer C is considerably large, and the gap between the external dimensions of the plated film forming product as a finished product and the external dimensions of the bonded magnet base material A is large, and dimensional accuracy is ensured. There is a problem that becomes difficult. Further, in this technique, there is a transition layer D ′ between the resin layer D and the conductive coating layer E in which the blending amount of the metal powder 3 is gradually increased, but between the resin layer D and the plating coating layer C. There is an aggregated layer of the metal powder 3 which is different from the resin layer D and the plating layer C, and the aggregated layer of the metal powder 3 is fixed only by the adhesive force of the resin layer D. Therefore, there is also a problem that the plating film layer C is easily peeled off at the boundary of the agglomerated layer of the metal powder 3. Furthermore, the bonded magnet base material A
Has a deep recess, and assuming that the plating film layer C needs to be formed in this recess as well, the resin should be wettable by adjusting the viscosity to reach the deep inside of the recess. However, it is difficult for the metal powder 3 to reach such a part uniformly, and as a result,
There is a possibility that a non-existing portion of the plating film may be partially formed. This means that the technology is difficult to apply to bonded magnets having a complicated shape, and leaves a problem in that the variety of products is limited. Further, according to the present technology, the resin for forming the resin layer D and the metal powder 3 are separately handled, and the conductive coating layer E made of the metal powder 3 is formed on the resin layer D. There is also the problem that there is. Further, in this technique, a metal medium such as a steel ball or a soft medium such as a soft plastic can be used as a medium for hitting the metal powder 3 sprinkled on the surface of the resin layer D, but the publication describes that it is practical. However, since the conductive coating layer formed by the formed metal powder is conversely damaged, only soft media can be used, and there is a problem that the selection range of media is limited.

The present invention has been made in view of the present situation, and the problems inherent in both of the above techniques are disclosed in JP-A-4-27.
It is an attempt to overcome it by improving it based on the technology proposed in No. 6095, and it is excellent not only in corrosion resistance and aesthetics but also in dimensional accuracy and capable of handling complicated shapes. The manufacturing procedure is also to provide a bonded magnet having a simple plated coating and a method for manufacturing the bonded magnet.

[0013]

MEANS TO SOLVE THE PROBLEMS The present inventors have made diligent studies in order to solve such problems, and as a result, have come up with the idea of smoothing the surface of the conductive coating layer formed on the surface of the bonded magnet base material. The bonded magnet having the plating film of the present invention completed based on such an idea is R-T-B.
(R is Nd or a part thereof substituted with a rare earth element,
T is Fe or part of it replaced by a transition metal element)
Is a single layer in which a magnetic powder and a binder are mainly composed of a magnetic powder and a binder, and a conductive material powder is uniformly dispersed in a resin, the surface of which has a reference length of 25 mm.
And a conductive coating layer whose surface roughness is set so that the maximum height (R _max ) is 400 μm or less and an electroplating layer formed on the conductive coating layer. It is characterized by having.

The method of manufacturing the bonded magnet is RT-T-
A magnetic powder represented by B (R is Nd or a part thereof is replaced with a rare earth element, T is Fe or a part thereof is replaced with a transition metal element) and a binder are main components. In the bonded magnet, after coating a mixture of resin and conductive material powder to form a conductive coating layer on the surface of the bond magnet base material, the conductive coating layer is subjected to a surface smoothing treatment to smooth the conductive coating. It is characterized in that the surface of the layer is electroplated.

The method of manufacturing the bonded magnet of the present invention will be described as follows with reference to the schematic diagrams shown in FIGS. First, a conductive paste 6 which is a mixture of a resin 4 and a conductive material powder 5 is applied on the surface of the bonded magnet base material A. Various coating methods can be applied, but spray coating and dip coating are particularly preferable from the viewpoint of simplicity. Conductive paste 6
Owing to its fluidity, it penetrates into the holes and pinholes on the surface of the bonded magnet base material, but if the viscosity of the conductive paste is high, all the holes and pinholes may not be blocked by just painting. . For example, if the amount of conductive material powder contained in the conductive paste is increased in order to lower the surface resistance of the conductive coating layer formed by coating, the viscosity of the conductive paste will increase, and the mere coating will cause the inside of the pores to become It is difficult to penetrate deep inside. Also, if the surface of the bonded magnet base material is extremely complicated or if the surface of the bonded magnet base material is water-soluble due to the adhesion of oil etc., the conductive paste islands are isolated. In some cases, discontinuous parts such as parts and resin balls are generated, and the conductive coating layer is interrupted. Further, if the coating is simple, the surface of the conductive coating layer B becomes a non-uniform layer due to the traces of the undulations on the surface of the bonded magnet base material being reflected on the coating surface although the coating surface is slightly relaxed. This tendency is remarkable especially when the conductive paste 6 has a high viscosity.

In the present invention, the surface smoothing treatment is applied to the conductive coating layer B to smooth the surface of the bonded magnet base material A and at the same time to the unfilled portion of the conductive paste 6 on the surface of the bonded magnet base material A. And the island-shaped isolated portions of the conductive paste 6 are eliminated. Although there are various specific methods for the surface smoothing treatment, the important point is that this surface smoothing treatment is a surface smoothing treatment involving surface pressing and does not include cutting or grinding. That is, the conductive paste 6 excessively adhered to a specific portion on the surface of the bonded magnet base material A is not removed from the surface of the bonded magnet base material A, but the excess portion is pressed and pushed into the concave portion of the surface of the bonded magnet base material A. That is, the coating surface is leveled by moving it to an adjacent part. The surface smoothing treatment is, specifically, a hitting treatment in which a metal medium or a ceramics medium is struck on a coated surface of a conductive paste so that the surface undulations are leveled and the surface is flattened. It is possible to employ a method in which the paste is put into a container together with the coated bond magnet, and a smoothing process is performed by applying a stirring operation, a rotating operation, or a vibrating operation.

The state after the surface smoothing treatment is shown in FIG.
As a result of the surface smoothing treatment, the conductive paste 6 in the portion that is raised from the surroundings moves to the adjacent portion and is leveled low,
On the other hand, the conductive paste 6 that has moved from the adjacent portion is replenished to the portion that is recessed from the surroundings and is leveled high. In this way, the surface height of the conductive coating layer surface is made uniform, and the surface of the conductive coating layer B is made uniform (flat). What is important here is that in the present invention, the maximum height of surface roughness (R _max ) indicating the degree of surface undulation after surface smoothing is the maximum height of surface roughness of the bonded magnet base material A ( R _max ). As in the technique disclosed in JP-A-5-302176, after forming a resin layer having an adhesive property on the surface of the bonded magnet base material, it is sprinkled with a metal powder or the like, and then the adhesion of the metal powder to the surface is enhanced. When a slight impact force is applied only for the purpose of partially infiltrating and fixing the metal powder into the resin, the maximum height (R _max ) of the surface roughness after the impact treatment is the same as that of the bonded magnet base material A. It is not always lower than the maximum height of surface roughness (R _max ). For the surface roughness after the surface smoothing treatment, for example, the reference length is 2
Maximum height of conductive coating layer (R _max ) when 5 mm
Is set to be 400 μm or less. When the maximum height (R _max ) of the conductive coating layer exceeds 400 μm, the plating coating is concentratedly formed on the protrusions, which is not preferable in terms of appearance and dimensional accuracy.

In the present invention, it is important that the surface after the formation of the conductive coating layer is smooth, and it is not always necessary that the smoothed surface is completely covered with the conductive coating layer. For example, as shown in FIG. 3, the magnetic powder 1 may be partially exposed as a result of the surface smoothing treatment. Usually, the electric resistance of one grain of Nd-Fe-B type magnetic powder is in the order of 10 ^{-8 in} the case of the quenched powder, and it has sufficient conductivity. The problem is the exposure of the binder in the bonded magnet base material. If there is an exposed portion of the resin that is the binder, this portion has a low conductivity, and thus the growth of the plating layer becomes somewhat defective. Battering treatment in which metal media or ceramics media is struck on the surface of the conductive paste to even out the surface unevenness to make the surface flat, or a container with metal or ceramic media together with a bond magnet coated with the conductive paste. The binder resin that is softer than the magnetic powder 1 remains on the surface after the smoothing treatment as long as the smoothing treatment is performed by throwing it into the container and applying a stirring operation, a rotation operation, or a vibration operation. Is almost impossible. Even if the binder resin is exposed, the surface resistance after smoothing is 0.05 to 10
The present inventors have confirmed that there is no hindrance to the formation of the plating layer as long as it is in the range of 0 Ω / sq (or Ω / □).
In reality, the surface resistance value after the smoothing treatment almost satisfies the above range.

Although it is a rare case, there is a case in which a recess is present on the surface after the surface smoothing treatment, and the magnetic powder 1 is exposed at the bottom of this recess. At this time, there is a possibility that the acidic plating solution may stay in this recess, which may lead to rusting. Therefore, in the surface smoothing treatment of the present invention,
Care has been taken to prevent such a recessed portion where the magnetic powder 1 is exposed at the bottom, and from this viewpoint, the specific method of the surface smoothing treatment is selected. According to the above-described surface smoothing method, the conductive paste is preferentially filled in the recessed portion on the surface of the bonded magnet base material, so that the exposed portion of the bonded magnet base material is rarely located in the recessed portion.

On the upper surface of the conductive coating layer B smoothed by the surface smoothing treatment, a plating coating layer C is formed as shown in FIG. Since the plating film layer C is formed by electroplating, it is relatively thick and firm. Plating coating layer C
The smooth surface of the conductive coating layer B is reflected in the surface shape of, and a bonded magnet having a plated coating with a smooth surface is obtained. Further, the conductive paste is pressed into the surface undulations of the bonded magnet base material by the surface smoothing treatment, and since the packing density of the conductive material powder is high and the conductivity is excellent, the plating film layer C and the underlying conductive film are The adhesiveness with the layer B is extremely high, and it does not peel off even when an external stress or the like acts. Since the conductive coating layer B is thinned by the surface smoothing treatment, the average thickness of the total thickness of the conductive coating layer B and the plating coating layer C is the surface smoothing treatment of the conductive coating layer B. It is thinner than a conventional magnet that is not subjected to the heat treatment, and the gap between the outer dimensions of the magnet and the bonded magnet base material is small, so that it is easy to secure dimensional accuracy.

[0021]

EXAMPLES Next, details of the present invention will be described with reference to examples. The rare-earth bonded magnet targeted by the present invention is RT
A magnetic powder represented by -B (R is Nd or a part thereof is replaced with a rare earth element, T is Fe or a part thereof is replaced with a transition metal element) and a synthetic resin as a binder. It refers to what can be obtained by molding the compound. The above-mentioned resin is appropriately selected from commonly used thermoplastic resins, thermosetting resins or rubber in consideration of the molding method. Examples of the thermoplastic resin used in the present invention include phenol resin, epoxy resin, and melamine resin, and examples of the thermoplastic resin include polyamide such as nylon 6 and nylon 12, polyolefin such as polyethylene and polypropylene, polyvinyl chloride, and the like. Examples thereof include polyester and polyphenylene sulfide. Also, an ultraviolet curable resin or the like may be used. The purpose of the present invention is to promote the growth of the plated coating by electroplating by forming a uniform conductive coating layer on the surface of the base material of the bonded magnet. Therefore, it is fundamental to use a resin as the binder. The present invention can also be applied when a metal having a relatively low melting point is used as a binder. In this case, the formation of the conductive coating layer has the function of equalizing the variation in conductivity between the magnetic powder and the binder metal.

Z is a metal powder that can be used as a binder.
Although n, Sn, Pb powder and the like can be exemplified, the molding method when a metal is used as the binder is limited to the compression molding method.
It is important that the binder used in the compression molding method is deformed during compression molding in order to improve the density of the molded body, and in this sense, the metal is preferably relatively soft,
Low melting point metals are generally preferred. Examples of the low melting point metal include Rose alloy, Newton alloy, Wood alloy, Povits alloy and the like.

As a molding method for obtaining the bonded magnet base material from the mixture of the magnetic powder and the binder resin used in the present invention, compression molding, injection molding, extrusion molding, calender molding and the like can be exemplified.

The metal species for electroplating used in the present invention include Ni, Cu, Cr, Fe, Zn, Cd, Sn, and
Pb, Al, Au, Ag, Pd, Pt, Rh and the like can be exemplified, but Ni is particularly preferable. In electroplating, generally, Cu, Ni, Zn, Sn, and A as described above are used.
Metal coating treatment of g, Au, Pt metals and their alloys is possible. When the purpose is to protect the material to be treated by sacrificial corrosion of the plating layer, such as structural materials, Zn, Sn plating, etc. will also exhibit sufficient effects, but especially for electronic parts. If oxidation and corrosion of both the plating layer and the material to be treated cannot be tolerated, it is necessary to apply resin coating, inorganic material coating, etc. after plating.
It is not efficient. In this respect, Cu is also the same, and has a defect that black copper oxide or patina is likely to be generated on the surface even though it is a noble metal. On the other hand, Au, A
Although g and Pt plating are extremely effective in preventing corrosion, they are expensive and often industrially useful. From the above points, it is clear that Ni and its alloy plating are the most effective means, which is one of the preferable embodiments of the present invention.

The aqueous solution for electroplating used in the present invention can be appropriately selected depending on the metal species and the anode metal species. Copper cyanide bath, copper pyrophosphate bath, copper sulfate bath, matte Ni bath, Watt bath, sulfamine Acid bath, wood strike bath, immersion Ni bath, hexavalent Cr low concentration bath, hexavalent Cr sergent bath, hexavalent Cr fluoride-containing bath, high cyanide alkali Zn plating bath, medium cyanide alkali Zn plating bath,
Low cyanide alkali Zn plating bath, zincate bath, cyanide Cd plating bath, borofluoride Cd plating bath, sulfuric acid Sn plating bath, borofluoric acid Sn plating bath, borofluoric acid Pb plating bath, sulfamic acid Pb plating bath, Methanesulfonic acid Pb plating bath, borofluoric acid solder plating bath, phenolsulfonic acid solder plating bath, alkanolsulfonic acid solder plating bath, chloride Fe plating bath, sulfate F
e plating bath, borofluoride Fe plating bath, sulfamate Fe plating bath, Sn-Co alloy stannate bath, Sn
-Co alloy pyrophosphoric acid bath, Sn-Co alloy fluoride bath,
Examples include Sn-Ni alloy pyrophosphoric acid baths, Sn-Ni alloy fluoride baths, and the like, and further additives such as brighteners, levelers, pit inhibitors, satin-forming agents, anode dissolving agents, PH buffers, stabilizers, etc. Can also be added. Further, a washing step, a surface activation treatment step, etc. as a pretreatment and a water washing, hot water washing, sealing treatment step etc. as a post step can be added depending on the purpose.

The rare earth bonded magnet, which is the object to be treated in the present invention, has the property of easily rusting, but since the conductive paste is applied to the surface of the base material of the bonded magnet, it is necessary to avoid the acidic plating bath. However, in consideration of the possibility that the surface of the bonded magnet base material is exposed to a part of the conductive coating layer after the surface smoothing treatment, the closer the PH is to the neutral region of the plating bath, and the chlorine content is higher. Needless to say, it is preferable to reduce the amount.

A pretreatment step and a posttreatment step may be provided in the electroplating treatment, and examples of the pretreatment include immersion degreasing, electrolytic degreasing, bath agent degreasing, acid treatment, alkali treatment, palladium treatment, and water washing. The post-treatment process can be exemplified by chromate treatment, water washing, hot water washing and the like.

Next, the conductive paste, which is a mixture of resin and conductive material powder, will be described. Examples of the resin contained in the conductive paste include the same as the binder resin of the bond magnet. The conductive material powder contains A
Examples thereof include metal powders such as g, Ni, and Cu powders, carbon powders, alloy powders, and powders of conductive metal oxides. Considering the dispersibility and the conductivity of the conductive paste to be obtained. The material, grain shape, and grain size are appropriately selected. Further, in order to disperse these conductive powders in the resin, the conductive material powder may be subjected to a coupling agent treatment or a surface activation treatment, or a component capable of improving dispersibility may be added to the resin.

As the surface smoothing treatment, a hitting treatment using a metal medium, a ceramics medium, or a soft medium such as a rubber material, a smoothing action by a stirring operation, a rotation operation, or a vibration operation involving these media can be adopted. . Shot peening is a specific example of the hitting process, and a rotary barrel and a vibrating barrel are specific examples of the smooth polishing action by the stirring operation, the rotating operation, or the vibrating operation.

Examples of the metal media include metal balls such as zinc lumps and cast iron balls, and examples of the ceramic media include glass balls and various other ceramic balls. Besides being spherical, these media may be cubic, polygonal, or irregular. Further, powder having a relatively large particle size is also included. Also, media other than metal media and ceramic media are available,
Organic matter such as shavings, sawdust, chaff, bran, fruit shells, felt scraps, nylon scraps, corn shafts and polishing stones are appropriately selected according to the object to be processed.

The object to be processed used in the present invention is a bond magnet, and is a part utilizing its magnetic force. Therefore,
It is unavoidable that the available magnetic force decreases as the coating film thickness increases. The thinner the coating film thickness, the more effectively the magnetic force can be used, but on the other hand, the corrosion resistance, which is the object of the present invention, decreases, so the coating film thickness must be adjusted according to the purpose. In this sense, the total of the electroconductive coating layer + electroplating film thickness applied in the present invention is preferably 5 μm or more and 100 μm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Examples and Comparative Examples) NdFeB passed 32 mesh
System isotropic magnetic powder (MQP-B manufactured by General Motors) 9
A magnetic powder compound consisting of 7 wt% and an epoxy adhesive 3 wt% was press-molded at a molding pressure of 5 t / cm ² and cured under argon atmosphere at 180 ° C. for 1 hour, φ8 mm ×
A 9 mm cylindrical bonded magnet (sample) was obtained. Next, as a pretreatment for coating the conductive paste, a pre-barrel polishing treatment of the bonded magnet base material was performed. The preliminary barrel polishing treatment was carried out by introducing φ3.2 mm steel balls (apparent volume 2.0 liter) into a small oscillating barrel having a volume of 3 liters, and introducing 300 samples for 10 minutes. The small vibrating barrel has an amplitude of 5 mm / cycle and a frequency of 60 Hz. The following tests were performed on the samples that had undergone the preliminary barrel polishing process.

First, the following materials (1) to (3) were prepared as conductive pastes, and each of them was used as Examples 1, 2 and 3. (Example 1) <Phenol resin + silver powder> Phenolic resin component 5 wt% Silver powder (particle size 0.5 μm or less) 15 wt% MEK (methyl ethyl ketone) 80 wt% (Example 2) <Epoxy resin + nickel powder> Epoxy resin component (commodity) Name: Epicoat 1001-B80) 7 wt% Curing agent (Brand name: BMI-12) 0.5 wt% Nickel powder (particle size 0.7 μm or less) 15 wt% BGE (Butyl glycidyl ether) 77.5 wt% (Example 3) <Acrylic resin + zinc> Acrylic resin component 30 wt% Zinc powder (particle size 0.5 μm or less) 20 wt% Water 50 wt%

After adjusting and mixing the respective liquids described in 1 to 3, the samples were immersed by stirring for 30 minutes or more. The immersion time is 5 minutes. After the immersion, the solution was drained with a basket and immediately subjected to barrel polishing treatment as surface smoothing treatment for the conductive coating layer. The thickness of the conductive coating layer is about 12 μm
Is.

The barrel polishing treatment was carried out by introducing 300 balls of steel balls (apparent volume of 2.0 liters) having a particle diameter of 2.5 mm into a small vibration barrel having a volume of 3 liters, and introducing 300 samples for 20 minutes. The small vibrating barrel has an amplitude of 5 mm / cycle and a frequency of 60 Hz. The following tests were performed on the samples that had undergone the preliminary barrel polishing process. After the barrel polishing, the steel balls as the medium were separated from the sample to cure the sample. The curing conditions are as follows. (Example 1) <Phenol resin + silver powder> 150 ° C 30 minutes (Example 2) <Epoxy resin + nickel powder> 150 ° C 30 minutes (Example 3) <Acrylic resin + zinc> 100 ° C 10 minutes

Examples 1, 2, 3 in which a conductive coating layer is formed
The surface resistance value of the bonded magnet and the surface resistance value of the bonded magnet at each treatment step were measured. The results are shown in "Table 1". The number of samples in each example was 500, and the average value is shown in the table.

[0037]

[Table 1]

In addition, as a comparative example, a small vibrating barrel was used in the above-mentioned embodiment, in which 300 samples, each of which had a phenol resin layer formed on the surface of a bonded magnet base material by dip coating and sprinkled with silver powder (particle size: 0.5 μm or less) It was put into a machine and barrel polishing was performed under the same conditions using the same media as those used in the examples. The results are shown in "Table 2".

[0039]

[Table 2]

Compared to Comparative Example 1 shown in "Table 2", all of Examples 1, 2 and 3 shown in "Table 1" had a remarkably smaller surface resistance value after curing, and had excellent conductivity. It was confirmed to have.

In addition, Example 1 thus obtained
After washing a few samples and comparative samples with a 1% potassium pyrophosphate aqueous solution, electroplating was performed by a conventional method to form a nickel plating film. Regarding the film thickness, the electrocoating film thickness was adjusted so that the conductive material-containing resin coating was about 5 μm and the total coating film thickness was 30 μm for all samples. After washing and drying after plating, the bonded magnet having the completed plating film was observed. As a result, the sample surfaces of Examples 1, 2, and 3 were extremely smooth and free from pinholes. On the other hand, the sample of Comparative Example 1 was relatively inferior to the sample surfaces of Examples 1, 2, and 3, but was relatively smooth and free of pinholes. The reason why the comparative example 1 obtained relatively good results in terms of surface smoothness is considered to be because the content of the barrel polishing treatment was the same as that of the present invention for the purpose of surface smoothing.

Further, when a sample of Comparative Example 2 which is different from Example 1 only in that the surface smoothing treatment (barrel polishing treatment) is not performed and the surface after the plating film formation was observed, Examples 1 and 2 were obtained. , 3 and Comparative Example 1 were confirmed to be inferior in smoothness.

Next, the samples of Examples 1, 2 and 3 and the samples of Comparative Examples 1 and 2 were cut and their cross-sectional structures were observed. As a result, in each of Examples 1, 2, and 3, the average film thickness from the surface of the bonded magnet base material to the surface of the plating film was 2
It was confirmed to be 31 μm in Comparative Example 1 and 39 μm in Comparative Example 2 while it was 3 μm. From this, it was confirmed that in Examples 1, 2 and 3, there was a small gap between the outer dimensions of the sample after the plating film was formed and the outer dimensions of the bonded magnet base material, and excellent dimensional accuracy was ensured. .

Then, a peeling test of the plating film was conducted. The peeling test method was the "peeling test method". As a result, it is necessary to remove the plating film in Examples 1, 2 and 3 by 2
A peeling force of 9 Kgf was required, whereas a peeling force of 17 Kgf was used in Comparative Example 1 and 11 K in Comparative Example 2.
It has been found that the peeling force of about gf can be relatively easily peeled. It was also confirmed that the cross-sectional structure of Comparative Example 1 had a three-layer structure of a resin layer, a metal powder layer, and a plating film layer on the bonded magnet base material. The weak peel strength of Comparative Example 1 is presumed to be due to this three-layer structure.

Further, the samples of Examples 1, 2 and 3 and Comparative Examples 1 and 2 were subjected to a moisture resistance test under the conditions of 80 ° C. × 90% RH × 600 hours, and the rusting condition was visually observed. All samples did not rust, and it was confirmed that all samples were acceptable products in terms of corrosion resistance.

Finally, the time of each step required for producing the works of Examples 1, 2 and 3 will be shown. Preliminary barrel polishing treatment (10 minutes) → immersion in conductive paste solution (5 minutes) → barrel polishing treatment (20 minutes) → cure (~ 3)
Washing with water, washing with potassium pyrophosphate aqueous solution (potassium pyrophosphate aqueous solution: 1 minute, washing with water: 2 minutes) → nickel electroplating treatment (up to 3 hours) → washing with water (washing with water: washing with 3 minutes 3 times, drying) : 10 minutes at 50 ° C)

[0047]

According to the present invention, it is possible to obtain a bonded magnet having a plated film having a smooth surface and excellent corrosion resistance and aesthetics. Moreover, this bond magnet has excellent separation accuracy between the outer dimensions of the bond magnet base material and the outer dimensions of the bond magnet base material, and is capable of handling complex shapes, and also has excellent adhesion of the plating coating. ing. Further, since the manufacturing procedure is simple, it is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method for producing a bonded magnet having a plated coating of the present invention, showing a state before forming a conductive coating layer.

FIG. 2 is a schematic diagram showing a method for producing a bonded magnet having a plated coating of the present invention, showing a state in which a conductive coating layer is formed.

FIG. 3 is a schematic diagram showing a method for producing a bonded magnet having a plated coating of the present invention, showing a state in which a conductive coating layer is subjected to surface smoothing treatment.

FIG. 4 is a schematic diagram showing a method for producing a bonded magnet having a plating film of the present invention, showing a state in which a plating film layer is formed.

FIG. 5 is a schematic diagram showing a conventional method for manufacturing a bonded magnet having a plated coating, showing a state before forming a conductive coating layer.

FIG. 6 is a schematic diagram showing a conventional method for producing a bonded magnet having a plated coating, showing a state in which a conductive coating layer is formed.

FIG. 7 is a schematic diagram showing a conventional method for producing a bonded magnet having a plating film, showing a state in which a plating film layer is formed.

FIG. 8 is a schematic diagram showing a conventional method for producing a bonded magnet having a plated coating, showing a state before forming a conductive coating layer.

FIG. 9 is a schematic diagram showing a conventional method for producing a bonded magnet having a plated coating, showing a state in which a resin layer is formed.

FIG. 10 is a schematic diagram showing a conventional method for manufacturing a bonded magnet having a plated coating, showing a state in which a metal powder is sprinkled on a resin layer.

FIG. 11 is a schematic diagram showing a conventional method for producing a bonded magnet having a plated coating, showing a state in which a metal powder is partially infiltrated into a resin layer.

FIG. 12 is a schematic diagram showing a conventional method for producing a bonded magnet having a plating film, showing a state in which a plating film layer is formed.

[Explanation of symbols]

A Bonded magnet base material B Conductive coating layer C Plating coating layer D Resin layer D'Transition layer E Conductive coating layer 1 Magnetic powder 2 Synthetic resin 3 Metal powder 4 Resin 5 Conductive material powder 6 Conductive paste

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01F 41/02 G

Claims (9)

[Claims] 1. A magnetic powder represented by RTB (where R is Nd or a part thereof is replaced by a rare earth element, and T is Fe or a part thereof is replaced by a transition metal element). A bonded magnet base material mainly composed of a binder and a single layer in which a conductive material powder is uniformly dispersed in a resin, the surface of which has a maximum height (R _max ) when the reference length is 25 mm. A bonded magnet having a plated coating film comprising a conductive coating layer having a surface roughness of 400 μm or less and an electroplating layer formed on the conductive coating layer. 2. A magnetic powder represented by R-T-B (R is Nd or a part thereof is replaced with a rare earth element, and T is Fe or a part thereof is replaced with a transition metal element). In a bond magnet having a binder as a main component, a mixture of resin and conductive material powder is applied to form a conductive coating layer on the surface of the bond magnet base material, and then the surface of the conductive coating layer is smoothed. A method for producing a bonded magnet having a plated coating, which comprises performing electroplating on the surface of the smoothed conductive coating layer. 3. The method for producing a bonded magnet having a plated coating according to claim 2, wherein the surface resistance of the conductive coating layer after the surface smoothing treatment is 0.05 to 100 Ω / sq. 4. The maximum height (R _max ) of surface undulations after the surface smoothing treatment is lower than the maximum height (R _max ) of surface undulations of the bonded magnet base material. A method for producing a bonded magnet having a plating film according to claim 1. 5. The maximum height (R _max ) of the conductive coating layer after the surface smoothing when the reference length is 25 mm is 40.
The surface roughness is set so as to be 0 μm or less.
5. A method for manufacturing a bonded magnet having the plating film according to any one of 4 to 4. 6. Production of a bonded magnet having a plating film according to any one of claims 2 to 5, wherein spray coating or dip coating is adopted as a method for coating the mixture of resin and conductive material powder. Method. 7. The method for producing a bonded magnet having a plated coating according to claim 2, wherein the surface smoothing treatment is a hitting treatment using a metal medium or a ceramic medium. 8. The surface smoothing treatment is performed by a smooth polishing action by a stirring action, a rotating action, or a vibrating action involving a metal medium or a ceramic medium, according to any one of claims 2 to 7. A method for producing a bonded magnet having a plating film according to claim 1. 9. The method for producing a bonded magnet having a plated coating according to claim 2, wherein the exposed portion of the base material is present in a part of the conductive coating layer after the surface smoothing treatment.