CN102800456A - Ferrite core and electric parts - Google Patents
Ferrite core and electric parts Download PDFInfo
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- CN102800456A CN102800456A CN2012101577642A CN201210157764A CN102800456A CN 102800456 A CN102800456 A CN 102800456A CN 2012101577642 A CN2012101577642 A CN 2012101577642A CN 201210157764 A CN201210157764 A CN 201210157764A CN 102800456 A CN102800456 A CN 102800456A
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Abstract
The ferrite core of the invention comprises a magnetic core part composed of a ferrite composition and at least part of coated layer formed on the surface of the magnetic core part. The principal component of the ferrite composition comprises, by mall, 63.3%-65.5% of Fe2O3, 11.6%-15.8% OF ZnO, and the balance Mn3O4; relative to the 100 wt% principal component, the oxidation silicon content is 60-250 ppm, the calcium oxide content is 360-1000 ppm, the Pb content is below 7 ppm, and the Cd content is below 7ppm; the Tsp of the above ferrite composition is in the range of 0-50 DEG C, and the thermal expansion coefficient of the coated layer is less than the thermal expansion coefficient of the magnetic core part.
Description
Technical field
The present invention relates to ferrite core and electronic component; In more detail; Relate to serviceability temperature near room temperature or near outdoor temperature; In high-frequency region (for example more than the 1MHz), can either reduce power loss (Pcv) and can realize high saturation magnetic flux density (Bs), the result can improve the ferrite core of factor of merit (Pcv/Bs) and the electronic component that uses this ferrite core.
Background technology
In recent years, miniaturization, the lightweight of various electronic equipments such as portable set develop rapidly, and for corresponding with it, the electronic component that more and more requires to use on the electric wiring of various electronic equipments is realized miniaturization, high efficiency, high frequencyization.
For example, the coil magnetic core used of the DC-DC converter of portable set etc. always adopts the Ni-Zn ferrite.But Ni-Zn ferrite power loss is bigger, therefore is difficult to tackle miniaturization, high efficiency, the high frequency requirement of parts such as coil magnetic core.
For such problem, consider to adopt the Mn-Zn ferrite to replace the Ni-Zn ferrite.Always, the Mn-Zn ferrite is used in power transformer etc., in the environment of low frequency and highfield, uses.
Usually the ferrite that the magnetic core as transformer etc. is used requires to have and is reaching minimum temperature characterisitic than the high temperature province magnetic loss in actual serviceability temperature zone.This is that the temperature of transformer itself rises because transformer can generate heat because of magnetic loss in use, and the result further increases magnetic loss, and the transformer heating becomes big, and such process again and again has the danger of rapid heating.Under the situation of power transformer, the serviceability temperature zone is generally near the temperature province the working temperature (for example 80 ℃).
But, to use in recent years under the situation that for example fluorine-containing torpescence liquid etc. cools off transformer, its ambient temperature or serviceability temperature can be below the room temperature, can also be arbitrary temps.In this case, making magnetic loss is the minimum not special restriction of temperature, only requires that the absolute value of magnetic loss is little.
On the other hand, under the situation that the coil magnetic core of using as the DC-DC converter of portable set etc. uses, ambient temperature or serviceability temperature are near the room temperature or near the temperature the outdoor temperature, compare with transformer, and voltage is also low, and heating is dangerous little rapidly.Again, such portable set more and more requires driving frequency high frequencyization (for example more than the 1MHz), requires little in the loss of high-frequency region.
Again, for the part of the transformer portable set such with being used in the DC-DC converter, all more and more requirement can be tackled big electric current.Therefore to being used in the magnetic core in such part, even also require the dc superposition characteristic of the excellence that inductance does not also reduce under big electric current.In order to realize excellent dc superposition characteristic, high saturation magnetic flux density is necessary, particularly under its ambient temperature or serviceability temperature, must have high saturation magnetic flux density.
Thereby requiring ambient temperature or serviceability temperature is near the temperature room temperature or the external air temperature, and the magnetic loss at high-frequency region is reduced, and has the ferrite composition of high saturation magnetic flux density.
As low-loss and have the ferritic example of Mn-Zn of high saturation magnetic flux density, for example in the patent documentation 1 Fe by 52.4～53.7 moles of % is being proposed
2O
3, the ZnO of 7.0～11.5 moles of %, the MnO of surplus constitute principal component, the CaO of certain content, V
2O
5, Nb
2O
5, Al
2O
3Or Bi
2O
3Constitute the Mn-Zn ferrite of accessory ingredient.
But above-mentioned Mn-Zn ferrite is also of patent documentation 1, and the magnetic loss that promptly is set in low frequency region in the actual actuation temperature of transformer more than 60 ℃ is minimum temperature (Pcv
Min), be not suitable near the temperature of room temperature and be to use in the high-frequency region.
To the ferrite core of various uses, research forms glass by the technology of overlay film on magnetic core portion surface again.But, think that always glass is had the influences such as deterioration in characteristics that make the ferrite script by the stress of overlay film, is considered to unfavorable.
Patent documentation 1: the spy opens the 2003-128458 communique
Patent documentation 2: the spy opens the 2001-237135 communique
The present invention makes in view of above-mentioned actual state; Its purpose is; Provide serviceability temperature or ambient temperature near room temperature or outdoor temperature; Can either reduce power loss (Pcv) and can realize high saturation magnetic flux density (Bs) at high-frequency region (for example more than the 1MHz), the result can improve the ferrite core of factor of merit (Pcv/Bs) and the electronic component with this ferrite core.
Summary of the invention
The inventor is through conscientiously research; Discovery with the MnZn based ferrite composition of specific composition as magnetic core portion; At least a portion on magnetic core portion surface forms the lining rete with thermal coefficient of expansion lower than ferrite core; Can not only reduce power loss (Pcv) but also realize high saturation magnetic flux density (Bs) at high-frequency region (for example more than the 1MHz), the result can improve factor of merit (Pcv/Bs), thereby has accomplished the present invention.
Be that ferrite core of the present invention is to have the magnetic core portion that constitutes with ferrite composition and the ferrite core of the coating that at least a portion on said magnetic core portion surface, forms, it is characterized in that,
Said ferrite composition is by with Fe
2O
3The content that converts is that the iron oxide of 63.3～65.5 moles of %, the content that converts with ZnO are that the zinc oxide of 11.6～15.8 moles of %, the manganese oxide of surplus constitute principal component, with respect to said principal component 100 weight %, with SiO
2The conversion silica content is 60～250ppm, is 360～1000ppm with CaO conversion calcium oxide content, is below the 7ppm with element conversion Pb content, is below the 7ppm with element conversion Cd content;
The magnetic loss of said ferrite composition be minimum temperature T sp in 0～50 ℃ of scope, the thermal coefficient of expansion of said coating is lower than the thermal coefficient of expansion of said magnetic core portion.
The present invention considers using near room temperature or under near the temperature conditions of external air temperature; Magnetic loss is that minimum temperature (Tsp) is in 0～50 ℃ of scope; With the composition of above-mentioned main component, also have the content of accessory ingredients such as silica and calcium oxide to confirm in above-mentioned particular range.Through using such ferric oxide composite, can keep high saturation magnetic flux density Bs and also can reduce power loss (Pev) at high-frequency region (for example more than the 1MHz), the result can improve factor of merit (Pcv/Bs).
Again, in the present invention, be set at relation as stated, can improve power loss (Pcv) through thermal coefficient of expansion with magnetic core portion and coating.And coating also has the effect as the protective layer of the defective that suppresses magnetic core portion etc., can enhance productivity.
Preferably said coating is made up of glass composition.If do like this, can form coating easily on the surface of magnetic core portion.Also have, form under the situation of glass composition, can improve the insulating properties of the lead etc. of magnetic core portion and coiling with insulating properties on magnetic core portion surface.
Electronic component of the present invention has by aforesaid ferrite composition and constitutes, and controls the ferrite core of the thermal coefficient of expansion of magnetic core portion and coating as stated, is used in the zone of 1MHz with upper frequency.
Electronic component of the present invention is because the Tsp of ferrite composition in 0～50 ℃ temperature range, therefore can reduce magnetic loss as serviceability temperature or ambient temperature under the situation that near near the part the room temperature or the outdoor temperature uses.And ferrite composition of the present invention can reduce export license and simultaneously also can realize high saturation magnetic flux density, therefore can make the electronic component with the ferrite core that is made up of this ferrite composition save electric power.
As electronic component of the present invention, be not particularly limited, can enumerate the coil component of the DC-DC converter that portable set for example etc. uses etc.As coil component for example inductance and choking-winding etc. are arranged.Again, through transformer being cooled to represent also can electronic component of the present invention to be used in transformer suitably near the temperature of Tsp.For example there is switch power transformer etc. such as use as the transformer part with, inverter.
Adopt the present invention, can either saturation flux density (Bs) be maintained at high saturation magnetic flux density, and also can reduce power loss (Pcv) at high-frequency region (for example more than the 1MHz), the result can improve factor of merit (Pcv/Bs).
Because coating is made up of glass composition, can form coating easily on the surface of magnetic core portion so again.Also having, is under the situation of insulating properties at glass composition, even there is conductivity in magnetic core portion, also can guarantee the insulating properties with the lead of reeling etc.
Description of drawings
Fig. 1 is the summary section of the ferrite core of the present invention's one example.
Fig. 2 is the summary section of the drum apparatus that uses in the manufacturing of ferrite core of the present invention's one example.
Fig. 3 is the profile of the drum-shaped magnetic core behind the coiling coil.
Embodiment
It is following that the present invention will be described according to example shown in the drawings.
Ferrite core
The shape of ferrite core of the present invention except cydariform shown in Figure 1, also has for example FT type, ET type, EI type, UU type, EE type, EER type, UI type, annular (Toroidal), pot (pot) type, cup type etc.In this example, as shown in Figure 1, ferrite core 1 has the shape of drum-shaped magnetic core, has the structure that forms coating 10 on the whole surface of magnetic core portion 2.
Magnetic core portion
The size of magnetic core 2 is not special to be limited; In this example; The external diameter of winding hub 4 is 0.6～1.2mm, and the axial width of winding hub 4 is 0.3～1.0mm, and the external diameter of blade of a sword portion 5 is 2.0～3.0mm; The thickness of blade of a sword portion 5 is 0.2～0.3mm, and the degree of depth from the outer surface of blade of a sword portion 5 to the outer surface of winding hub 4 is 0.5～1.0mm.Again, the shape of blade of a sword portion 5 also can be quadrangle, octangle etc. except circle.
The ferrite composition of this example is the Mn-Zn based ferrite, and principal component comprises iron oxide, manganese oxide and zinc oxide.Again, the magnetic loss of the ferrite composition of this example is that minimizing temperature (Tsp) is in 0～50 ℃ of scope.
Always, in the Mn-Zn based ferrite, the temperature of expression Tsp is by the explanation of crystallization magnetic anisotropy.That is to say, the symbol of crystallization magnetic anisotropy constant K1 along with the rising of temperature from negative value become on the occasion of the temperature of K1=0, magnetic loss has minimum.
Known again this temperature and magnetic permeability are that so-called magnetic permeability second peak of maximum is consistent.Above-mentioned K1 is dull increasing along with the rising of temperature, but because Fe
2+Has positive K1, Fe
2+Amount (Fe when increasing
2O
3When amount increases), the temperature at second peak moves to low temperature side.
" electronic material series ferrite " (" electronic material シ リ one ズ Off エ ラ イ ト ", the distribution of the kind Co., Ltd. of Japanese ball, clear and 63 years) the 79th page put down in writing the formula of asking Tsp as described below, promptly at Fe
2O
3Amount is X mole %, and the ZnO amount is under the situation of Z mole %, Tsp=-45.5 (X+0.2Z)+2620
Known to again making Fe
2O
3The amount increase obtains high saturation magnetic flux density easily.But, Fe
2O
3When increasing, saturation flux density not only receives Fe
2O
3The influence of amount, and receive Fe
2O
3The influence of amount and the ratio of ZnO amount.
The Tsp of the ferrite composition of this example is in 0～50 ℃ scope.Such ferrite composition is considered to through making Fe
2O
3Amount increases, and can make Tsp in above-mentioned scope, improves saturation flux density.Therefore want to utilize above-mentioned formula, confirm Fe
2O
3Amount and ZnO amount for example make Fe
2O
3Amount is 64.4 moles of %, and the ZnO amount is 13.7 moles of %, and when surplus was MnO, making Tsp was below-400 ℃, and this is unpractical.
Therefore think that the formula of the above-mentioned Tsp of asking is at Fe
2O
3Be false under the situation of amount big (for example 63 moles more than the %).But, at Fe
2O
3Measure under the big situation, the thing that becomes the index of asking Tsp does not exist, therefore at Fe
2O
3Measure under the big situation, the high-frequency region more than 1MHz has no understanding for the ferrite composition with high saturation magnetic flux density.
Therefore, inventor of the present invention etc. experimentize with keen determination, and under the discovery situation that iron oxide content is bigger in ferrite composition, Tsp and iron oxide and zinc oxide have the relation that is different from following formula.Just principal component comprises with Fe
2O
3The content that converts is the iron oxide of 63.3～65.5 moles of %; Preferably comprise the iron oxide of 63.9～65.0 moles of %, the content that converts with ZnO is the zinc oxide of 11.6～15.8 moles of %; Preferably under the situation of the manganese oxide of the zinc oxide of 12.0～15.8 moles of %, surplus, Tsp is in 0～50 ℃ scope.
Under the poor situation of iron oxide or zinc oxide, magnetic loss be minimizing temperature (Tsp) less than 0 ℃, and content when too much above 50 ℃.
The ferrite composition of this example contains silica and calcium oxide as accessory ingredient except the principal component of above-mentioned compositing range.Through making it contain such accessory ingredient, can reduce the absolute value of power loss, and can access high saturation magnetic flux density.
With respect to principal component 100 weight %, with SiO
2The silica content that converts is 60～250ppm, preferably 60～200ppm.The content of silica is many or very few, and the power loss of high-frequency region all has the tendency of deterioration.
With respect to principal component 100 weight %, the calcium oxide content that converts with CaO is 360～1000ppm, preferably 630～830ppm.The content of calcium oxide is many or very few, and the power loss of high-frequency region all has the tendency of deterioration.
Again, the ferrite composition of this example also contains Pb and Cd except containing above-mentioned principal component and accessory ingredient.Through with such Composition Control in the regulation scope in, can prevent power loss deterioration at high-frequency region.
With respect to principal component 100 weight %, the Pb content that converts with element is below the 7ppm, and that better is 2～7ppm, it would be desirable 5～7ppm.With respect to principal component 100 weight %, when its content converts above 7ppm with element, the tendency of deterioration is arranged in the power loss of high-frequency region.
With respect to principal component 100 weight %, the Cd content that converts with element is below the 7ppm, and that better is 2～7ppm, preferably 5～7ppm.With respect to principal component 100 weight %, when its content converts above 7ppm with element, the tendency of deterioration is arranged in the power loss of high-frequency region.
Pb and Cd are contained in iron oxide as principal component, zinc oxide, the manganese oxide.When the present inventor finds that the content of Pb and Cd surpasses the scope of regulation, the tendency of deterioration is arranged in the power loss of high-frequency region.Therefore in the present invention, the content of Pb and Cd is carried out strict control, it is controlled in the above-mentioned scope.Also have, the content of Pb and Cd is controlled at not special qualification of method in the prescribed limit, the oxide etc. that also can be used in interpolation Pb and Cd in the principal component is controlled at the method in the prescribed limit with it.
In addition, can comprise the oxide of the impurity element that unavoidably contains in the raw material in the ferrite composition of this example, its content is in number ppm～hundreds of ppm scopes.
Specifically, for example comprise transition metals such as typical metal element such as B, C, S, Cl, As, Se, Br, Te, I and Li, Na, Mg, Al, K, Ga, Ge, Sr, In, Sn, Sb, Ba, Bi and Sc, Ti, V, Cr, Y, Nb, Mo, Pd, Ag, Hf, Ta.
Again, the thermal coefficient of expansion of magnetic core portion 2 changes because of the composition of ferrite composition, roughly 9 * 10
-6/ ℃～10 * 10
-6/ ℃ about.
Coating
The material of coating 10 does not limit as long as adopt the material of thermal coefficient of expansion under the thermal coefficient of expansion of magnetic core portion 2 especially, for example, and glass composition, SiO
2, B
2O
3, ZrO
2Deng.Also have, coating 10 can be made up of multiple material, also can have the stromatolithic structure that is formed by multilayer.
The thermal coefficient of expansion of glass composition changes because of the composition of the composition that contains in the glass composition and the content of each composition etc.Thereby, being necessary composition and content of suitable set component etc., the thermal coefficient of expansion that makes glass composition is under the thermal coefficient of expansion of magnetic core portion 2.
As long as coating 10 covers the degree that can obtain the effect of improving power consumption; Be not particularly limited; As long as be formed at least a portion on the surface of magnetic core portion 2; Surface area with respect to magnetic core portion 2; The ratio (lining rate) that forms coating is a surname with 50～100%, preferably 90～100%.The high more then effect as the protective layer of the defective etc. that prevents magnetic core portion 2 of lining rate is also big more.
Also have, Fig. 1 representes that the lining rate is 100% situation.In magnetic core portion 2, when near the part (recess 6 in this example) of coiling lead etc., forming coating 10, obtain better effect easily again.
The thickness of coating 10 is not so long as the thickness of the effect of the power loss that can improve limits especially, and to be advisable below the 50 μ m more than the 0 μ m, better is below the above 25 μ m of 5 μ m.If form coating 10, can improve power loss, but coating is little to the contribution that improves power loss when blocked up, and the tendency that increases manufacturing cost is arranged again.When coating has thickness to a certain degree, also can work as the protective layer of magnetic core portion again.Therefore, the thickness of coating 10 is preferably in the above-mentioned scope.
And, if coating 10 has insulating properties,, also can guarantee insulation with the lead of reeling even there is conductivity in magnetic core portion 2.
Down in the face of as the ferrite core of this example, an example of the manufacturing approach of the ferrite core that coating 10 is made up of glass composition describes.
At first, for the raw material of the ferrite composition of preparing to constitute magnetic core portion 2, ratio of components weighing initiation material according to the rules (raw material of principal component and the raw material of accessory ingredient) mixes, and obtains raw mix.Mixed method for example has wet mixed of carrying out with ball mill and the dry mixed of carrying out with dry blender.Also have, preferably using average grain diameter is 0.1～3 micron initiation material.
The raw material of principal component can adopt iron oxide (α-Fe
2O
3), zinc oxide (ZnO), manganese oxide (Mn
3O
4) or composite oxides etc.And can adopt all cpds that can be through being fired into above-mentioned oxide or composite oxides etc. in addition.As can for example metal monomer, carbonate, oxalates, nitrate, hydroxide, halide, organo-metallic compound etc. being arranged through being fired into the material of above-mentioned oxide.Also have, the manganese oxide content in the principal component is used the MnO Conversion Calculation, but preferably uses Mn as the raw material of principal component
3O
4
As the raw material of accessory ingredient, identical with the situation of the raw material of principal component, be not only the employing oxide, as long as adopt composite oxides or burn till the compound that the back forms oxide, at silica (SiO
2) situation under, preferably use SiO
2And under the situation of calcium oxide (CaO), preferably use calcium carbonate (CaCO
3).
Pb and Cd sometimes are contained in iron oxide, zinc oxide and the manganese oxide as principal component.The use amount of raw material that therefore can be through the content of adjustment Pb and Cd different various iron oxide, zinc oxide and manganese oxide is adjusted the content of Pb and Cd.Also have, the content of Pb and Cd is controlled at not special qualification of method in the prescribed limit, oxide that also can be through in principal component, adding Pb and Cd etc. is controlled at it in prescribed limit.
Then, raw mix is calcined, obtained calcined materials.Calcining is for the homogenizing of the thermal decomposition that realizes raw material, composition, ferritic generation, utilizes sintering that the ultra micro powder is disappeared, and generates the particle of suitable particle size, raw mix is transformed to the form that is suitable for subsequent handling carries out.Such calcining is preferably carried out under 800～1100 ℃ temperature, carries out about 1～3 hour usually.Calcining can be carried out in atmosphere (air), also can or carry out in the pure oxygen atmosphere in the partial pressure of oxygen atmosphere higher than atmosphere.Also have, the raw material of principal component can carry out before calcining with mixing of the raw material of accessory ingredient, also can after calcining, carry out.
Then calcined materials is pulverized, obtained comminution of material.Pulverizing is in order to smash the aggegation of agglomerated material, and the powder that obtains having the agglutinating property of appropriateness carries out.When agglomerated material forms big agglomerate, carry out carrying out case of wet attrition with ball mill or pulverizing mill etc. again after the coarse crushing.Preferably case of wet attrition is about 1～2 μ m to the average grain diameter of agglomerated material.
Then carry out the granulation (particle) of comminution of material, obtain granule.Granulation is in order comminution of material to be formed the agglutinating particle of modest size, to be transformed to the form that is suitable for moulding and to carry out.Such prilling process has for example pressurize comminution granulation and spray drying process etc.Spray drying process is after in comminution of material, adding normally used bonding agent such as polyvinyl alcohol, the method for atomizing, low temperature drying in spray-drying process.
Then granule is shaped to the shape of regulation, obtains formed body.Methods such as that the forming method of granule has is for example dry formed, wet type moulding, extrusion modling.Dry formed method is the forming method that the granule filling is pressurizeed in mould and compressed.The shape of formed body is not special to be limited, as long as according to suitably decision of purposes, in this example, form bulging core pattern.
Then carry out formally burning till of formed body, obtain sintered body (magnetic core portion 2).Formally burning till is between the powder particle of the formed body that contains many spaces, makes its sintering that powder aggegation takes place with the temperature below the fusing point, to obtain fine and close sintered body.Formally burning till preferably like this carried out under 900～1300 ℃ temperature, carries out about 2～5 hours usually.Formally burn till and in atmosphere (air), to carry out, also can in the partial pressure of oxygen atmosphere higher, carry out than atmosphere.
Then the magnetic core portion 2 that obtains is used drum apparatus shown in Figure 2, the coating 10a before the surface of magnetic core portion 2 forms the heat treatment that is made up of glass composition, adhesive resin etc.
On the inner axle core position of drum container 22, nozzle 25 is along the direction of principal axis configuration, can be from nozzle 25 to a plurality of magnetic core portion 2 spraying slurries 26 that store in drum container 22 inside.Drum container 22 is owing to rotate on the arrow A direction, and magnetic core portion 2 exists with the state shown in Fig. 2, stirs by means of the rotation of drum container 22.
Form a plurality of holes that are communicated with outside and inside on the wall of drum container 22, the slurries 26 that below cylinder sleeve 20a, store also can get into the inside of drum container 22, can magnetic core portion 2 be immersed in these slurries 26.Again, oven dry is passed through cylinder sleeve 20a with gas when outlet 24 flows from inlet tube 23, also can flow to drum container 22 inside.
In order to form the coating 10a before the heat treatment, at first many magnetic cores portion 2 is contained in the inside of drum container shown in Figure 2 22.Make drum container 22 rotations then, on one side the set of magnetic core portion 2 is stirred, from nozzle 25 it is sprayed slurries 26 on one side, the coating 10a before the formation heat treatment.
The resin glue that is contained in slurries 26 is the modification body of polyvinyl alcohol (PVA), polyvinyl alcohol resin or their mixture preferably.Through such operation, the coating 10a before the heat treatment of formation can with 2 fine being close to of magnetic core portion.
Solvent is preferably moisture.Can solvent only be water also, but when the contact angle of the surface of glass powder and water was big, preferably ethanol, isopropyl alcohol (IPA), isobutanol water-soluble alcohols such as (IBA) mix with certain proportion, can suppress the aggegation and the sedimentation of glass powder so well.
Be sprayed on the surface of slurries 26 each the magnetic core portion 2 of covering in the magnetic core portion 2, form the coating 10a before burning till.At this moment, remaining slurries 26 are discharged through not shown discharge pipe.From not special qualification of the processing time of nozzle 25 spraying slurries 26, for example can be about 30～180 minutes.Again, though the temperature of slurries 26 is relevant with the composition of solvent during injection, preferably more than 40 ℃, below 100 ℃.Under the situation of using low-boiling solvent, preferably in the said temperature scope, make temperature on the low side.
Then, Yi Bian spray slurries 26, Yi Bian simultaneously the coating 10a before the heat treatment is dried processing.When oven dry is handled, oven dry is flowed in the cylinder sleeve 20a with gas from inlet tube 23, discharge from outlet 24.Be used in oven dry that this oven dry handles and use the air of gas for 50～100 ℃ of temperature for example.The oven dry that also can after inject process, carry out again 5～30 minutes is handled.
After oven dry is handled, the magnetic core portion 2 that forms the coating 10a before the heat treatment is taken out from drum container 22, carry out thermal softening and handle.The decisions such as softening point of the glass powder that contains among the coating 10a of heat-treat condition before according to heat treatment.Specifically, preferably 600～800 ℃ of heat treatment temperatures, heat treatment time is 5～120 minutes.
Under the ferritic situation of Mn-Zn, heat treatment is preferably in the nitrogen atmosphere of partial pressure of oxygen below 0.1% and burns till.Because the oxidation of magnetic core portion 2 is reasons of deterioration in characteristics, therefore can be through reducing the anti-oxidation of partial pressure of oxygen.
After the heat treatment, form vitrified coating 10, obtain ferrite core shown in Figure 11 on the surface of magnetic core portion 2.Also have, in this example, so-called vitrifying is defined as with the body thin film formation of continuous amorphous state has the state with the rigidity of crystallization same degree.
Thereafter, as shown in Figure 3, on the end face of a blade of a sword portion 5 of each magnetic core portion 2 with print, duplicate, methods such as dipping, sputter, galvanoplastic form the pair of terminal electrode 32 that silver, titanium, nickel, chromium, copper etc. constitute.Even there is conductivity in magnetic core portion 2, terminal electrode 32 is also owing to the existence of coating 10 is able to insulation.
Thereafter, the lead 30 of around winding hub 4, reeling is distinguished hot pressing on terminal electrode 32 with the two ends of this lead, utilizes methods such as ultrasonic bonding, laser welding, soldering to connect, and accomplishes the coil component of example of the present invention.
The ferrite core of this example can either be kept high saturation magnetic flux density (Bs), and also can reduce power loss (Pcv) at high-frequency region (for example more than the 1MHz), and the result can improve factor of merit (Pcv/Bs).Again, particularly constitute coating, can easily form coating on the surface of magnetic core portion with glass composition.Again, have at glass composition under the situation of insulating properties,, also can guarantee insulating properties with the lead of reeling etc. even there is conductivity in magnetic core portion.
In the ferrite core of this example, the relevant reason that can improve factor of merit (Pcv/Bs) may not be clear and definite, but can be described below consideration.
Sometimes in ferrite core, there be applied interior in compression stress as residual stress.The stress that the evaporation of composition, particularly ZnO composition in the ferrite composition when such residual stress is considered to its reason and is the stress that causes of the contraction of burning till when cooling of ferrite composition or sintering cooling etc. produces etc.
Therefore; On at least a portion on the surface of magnetic core portion 2, form coating 10 with thermal coefficient of expansion lower than the thermal coefficient of expansion of magnetic core portion 2; In the process of heating, cooling; Therefore the thermal expansion of coating 10 takes place on coating 10 because the tensile stress that the thermal expansion of magnetic core portion 2 causes less than the thermal expansion of magnetic core portion 2.And, consider that this tensile stress is not that the residual stress of having offset magnetic core portion 2 (compression stress), not the power loss Pcv that can improve ferrite core therefore.
Again, the invention is not restricted to above-mentioned example, can implement various changes within the scope of the invention.
For example, in the above-mentioned example,, form the coating before the heat treatment, it is heat-treated the formation coating, but also can carry out the heat treatment with coating of burning till of this magnetic core portion simultaneously for the magnetic core portion of burning till.Carry out like this and can simplify working process.
In taking off the bonding agent operation, also can the particle diameter of glass powder be chosen in the particular range, so that the organic principle of the adhesive resin that contains in the slurries volatilizees easily again.By means of this, can improve the intensity of the coating self before the heat treatment, in the time of can preventing that coating before the heat treatment from forming in magnetic core portion defective etc. takes place.
Again, form in the operation of the coating before the heat treatment, through for example changing the amount of the adhesive resin that contains in the slurries, also can make the intensity of the near surface of the coating before the heat treatment become than the intensity of the boundary vicinity of this coating and magnetic core portion more a little less than.Through such operation, the near surface of this coating plays a part expendable film (sacrificial film), can prevent effectively that magnetic core portion from defective etc. taking place.
And can the coating before the heat treatment be formed multilayer, the soft softening point that changes the glass composition that contains in the layer of a ratio near magnetic core portion that makes the glass composition that contains in the layer of face side of this coating is high.And, in heat treatment step, make heat treatment temperature, and the softening point of the glass composition that contains in the layer than the face side of coating is low than high near the softening point of the glass composition that contains in the layer of magnetic core portion.Through doing like this, can prevent effectively that magnetic core portion from defective etc. taking place with the layer of the face side of coating as expendable film.
Embodiment
Further the present invention will be described according to specific embodiment below, but the invention is not restricted to these embodiment.
Embodiment 1
At first, prepare Fe
2O
3, ZnO and Mn
3O
4Raw material as principal component.Prepare SiO
2And CaCO
3Raw material as accessory ingredient.
Also have, Pb and Cd are contained in as in the iron oxide of the raw material of principal component, zinc oxide and the manganese oxide.Therefore, prepare Cd various iron oxide, zinc oxide and the manganese oxide raw material different, adjust its use amount, so that the sample that finally obtains contains Cd amount and Pb amount that table 1～table 3 is put down in writing with Pb content.
The then material powder of the principal component prepared of weighing again behind the material powder according to the amount weighing accessory ingredient shown in the table 1, carries out 5 hours wet mixed with ball mill, obtains raw mix.
Then the raw mix that obtains is carried out 950 ℃, 2 hours calcining in air, carry out 20 hours case of wet attrition then with ball mill, obtain the comminution of material of average grain diameter 1.5 μ m.
Then, after this comminution of material oven dry, the polyvinyl alcohol that in this comminution of material of 100 weight %, adds 1.0 weight % carries out granulation as bonding agent, carries out whole grain with 20 purpose sieves and obtains particle, with (2 tons/cm of 196MPa
2) pressure this particle is carried out extrusion forming, obtain the formed body of annular (size=external diameter 22mm * internal diameter 12mm * height 6mm).
Formed body to obtaining carries out x-ray fluorescence analysis, measures the composition of ferrite core, confirms consistent with the amount that is shown in table 1.
Then, these formed bodys suitably calcining 2.5 hours with 1270 ℃ of temperature in the control partial pressure of oxygen, are obtained the magnetic core portion as sintered body.
Then prepare to form the powder of the glass composition that coating uses.Using Si-B as glass composition is glass.Si-B is that glass is that chilling manufactures then with the raw materials such as oxide that constitute glass ingredient mixed melting in addition.
In the present embodiment, the composition of the composition of change Si-B glass, amount etc. use the glass composition A～D that lets thermal coefficient of expansion change.The thermal coefficient of expansion of glass composition A is 6 * 10
-6/ ℃, the thermal coefficient of expansion of glass composition B is 11 * 10
-6/ ℃, the thermal coefficient of expansion of glass composition C is 8 * 10
-6/ ℃, the thermal coefficient of expansion of glass composition G is 10 * 10
-6/ ℃.
Again, the thermal coefficient of expansion of magnetic core portion and glass composition utilizes TMA to measure.
Then, make the slurries that are used to form the preceding coating of heat treatment.At first, with the weight ratio of regulation the powder of the glass composition that obtains is mixed with PVA.Also have, with the weight ratio of regulation the solid constituent that obtains (mixture of glass powder and PVA) is mixed with solvent, with ball mill mixing preparation slurries.Use is with 8: 2 the mixed water and the solvent of ethanol.With respect to the glass powder in the slurries, the content of resin glue is 10%.
Then, magnetic core portion is dropped in the drum container of drum apparatus, the whole surface in magnetic core portion is used above-mentioned slurries to carry out inject process and is formed coating.When spraying, dry processing with 70 ℃ of temperature of temperature again with warm braw.
Thereafter, the magnetic core portion of the coating from drum container before the taking-up formation heat treatment carries out 1 hour heat treatment with 750 ℃ of temperature to this magnetic core portion, obtains the ferrite core (ring-type) that vitrified coating is formed at the whole surface of magnetic core portion.
Coating thickness is about 3～25 μ m.Again, the size before and after coating thickness is formed by coating calculates.
Again, lining rate is 98～100%.Also have, the lining rate is that 20 samples are carried out visualization, and coating is formed incomplete sample, and the lining planimeter calculates through measuring.
< power loss (Pcv) >
The elementary winding of coiling and each three circle of secondary winding on the ferrite core behind magnetic core portion sample that obtains and the formation coating; Under the condition of 1MHz-50mT, measure-10～60 ℃ power loss; Ask the minimum temperature (Tsp) of loss, calculate the power loss Pcv (unit: kW/m under the Tsp
3).Measure with B-H analyzer (the system SY-8217 of the rugged communication of rock Co., Ltd.) and carry out.The results are shown in table 1～table 3.
< saturation flux density (Bs) >
Behind the 60 circle windings of reeling on the ferrite core behind magnetic core portion sample that obtains and the formation coating; With B-H waveform meter (the system Model BHS40 of Riken Densi K. K.), under Tsp, measure the saturation flux density Bs (unit: mT) when applying 2kA/m magnetic field.The result is shown in table 1 and 2.
Express the magnetic core portion of high-frequency region (1MHz) and the factor of merit Pcv/Bs of the ferrite core behind the formation coating at table 1 and table 2 again.Pcv is more little or Bs is big more, and then this Pcv/Bs is more little.Thereby the minimizing and the high saturation magnetic flux density of the more little then power loss of the value of Pcv/Bs can be realized simultaneously.
In table 2, express the raising rate (rate of change) that coating that the value of the power loss (Pcv) of the ferrite core after forming with coating from the value of the power loss (Pcv) of the magnetic core portion sample of coating before forming calculates forms the power loss (Pcv) of front and back again.Also have, in the present embodiment, raising rate (rate of change) is good 15% above person, is more preferably the raising rate more than 20%.
Again, in the table 2, the Pcv/Bs of the ferrite core after coating forms is good less than 1.0, and better is less than 0.9.
Table 2
Can confirm from table 1, sample 2～6 and sample 9～11, its Tsp is in 0～50 ℃ scope.Can also confirm, sample 2～6 and sample 9～11, with Tsp not the sample in 0～50 ℃ scope 1,7,8 compare with 12, at power loss (Pcv) step-down of high-frequency region (1MHz).
Sample 2a～the 6a and the 9a～11a of table 2 are magnetic core portion with Tsp sample 2～6 and 9～11 of (Tsp is in 0～50 ℃ of scope) in the application's scope of invention, utilize to possess the thermal coefficient of expansion (10 * 10 than this magnetic core portion
-6/ ℃) little thermal coefficient of expansion (6 * 10
-6) glass A cover the surface of this magnetic core portion.
Also have; Before and after magnetic core portion surface forms the coating that is made up of glass A, keeping high saturation magnetic flux density (Bs), consequently; (under the situation of sample 2a～6a and 9a～11a), the factor of merit of representing with Pcv/Bs has improved at the ferrite core that forms the coating be made up of glass A.
But; Under with the Tsp situation that sample 1,7,8 in the scope of invention in the application and 12 does not use as magnetic core portion; Even the surface in magnetic core portion forms the coating that is made up of glass A; Also can confirm the front and back that form at coating, the power loss (Pcv) of high-frequency region (1MHz) effect (sample 1a, 7a, 8a and 12a) that is not fully improved.
Can confirm according to these results; The Tsp of ferrite composite that forms magnetic core portion is in the application's scope of invention under the situation of (Tsp is in 0～50 ℃ of scope); Surface through in magnetic core portion forms the coating with thermal coefficient of expansion lower than magnetic core portion; Can keep higher saturation flux density, and also can reduce power loss (Pcv) at high-frequency region (for example more than the 1MHz), the result can improve factor of merit (Pcv/Bs).
Particularly, to improve effect be significant under the situation of (Tsp is in 0～50 ℃ of scope) in the Tsp of the ferrite composition that forms magnetic core portion is in the application's scope of invention for such power loss.
The thermal coefficient of expansion (11 * 10 that the sample 1b～12b of table 2 is bigger than magnetic core portion except use has
-6/ ℃) the glass B glass A that replaces in sample 1a～12a, using outside, make ferrite core with sample 1a～12a the samely, carry out same evaluation.
Under the situation of sample 1b～12b; Can confirm before and after the coating that forms glass B; The power loss of high-frequency region (1MHz) does not all improve; But worsened more, and this, and this and form the Tsp of ferrite composition of magnetic core portion whether it doesn't matter in the application's scope of invention.
Confirm that promptly the coating that has the thermal coefficient of expansion bigger than magnetic core portion in utilization covers under the situation of magnetic core portion, power losss (Pcv) all do not improve before and after coating forms, and this scope with Tsp has nothing to do.
Again, the sample 4c and the 4d of table 2 are except use has the thermal coefficient of expansion (8 * 10 littler than magnetic core portion
-6/ ℃) glass C or have the thermal coefficient of expansion (10 * 10 identical with magnetic core portion
-6/ ℃) glass D, replace making ferrite core with sample 4a outside the glass A that sample 4a uses the samely, carry out same evaluation.
Sample 4c and 4d; The Tsp that adopt to form the ferrite composition of magnetic core portion is in the magnetic core portion sample of the sample 4 in the application's the scope of invention; The coating that utilization has the thermal coefficient of expansion littler than the thermal coefficient of expansion of magnetic core portion covers magnetic core portion; Therefore can confirm equally with 4a, the power loss (Pcv) of high-frequency regions (1MHz) is improved before and after coating forms.
Except making the accessory ingredient SiO in the ferrite composition that forms magnetic core portion
2Outside the change as described in Table 3 of the content of CaO, make the sample that forms magnetic core portion with the sample 4 (Tsp is 25 ℃) of embodiment 1 the samely, carry out identical evaluation (sample 13～21).The result is shown in table 3.
Then, form magnetic core portion, obtain utilizing glass A or glass B to form the ferrite core (annular) of coating on the surface of magnetic core portion with ferrite composition shown in Figure 3.To the ferrite core sample that obtains, carry out the evaluation the same (sample 13a～21a and sample 13b～21b) with embodiment 1.The result is shown in table 4.
Table 4
Can confirm the accessory ingredient SiO in the ferrite composition according to table 3
2And the sample 4,14,15 of content in the application's scope of invention of CaO with 18～20 with the content of accessory ingredient not the sample in the application's scope of invention 13,16,17,21 compare, the power loss (Pcv) of high-frequency region (1MHz) is little.
Sample 4a, 14a, 15a and the 18a～20a of table 4 are with the accessory ingredient SiO in the ferrite composition
2The sample 4,14,15 and 18～20 of content in the application's scope of invention that reaches CaO forms magnetic core portion, utilizes the glass A with thermal coefficient of expansion littler than this magnetic core portion to cover the surface of this magnetic core portion.
Can confirm, such sample 4a, 14a, 15a and 18a～20a with form coating before sample 4,14,15 compare with 18～20, reduced in the power loss (Pcv) of high-frequency region (1MHz).Promptly can confirm to compare with magnetic core portion sample (sample 4,14,15 and 18～20); (sample 4a, 14a, 15a and 18a～20a) power loss (Pcv) at high-frequency region (1MHz) has reduced about 20～22% the ferrite core of the coating that formation is made up of glass A, and performance has improved.
Can also confirm; Before and after magnetic core portion surface forms the coating that is made up of glass A, keeping high saturation magnetic flux density (Bs), consequently; (sample 4a, 14a, 15a and 18a～20a), it has improved with the factor of merit that Pcv/Bs representes the ferrite core of the coating that formation is made up of glass A.
But, the accessory ingredient SiO in using ferrite composition
2With the content of CaO not under the sample in the application's scope of invention 13,16,17,21 the situation as magnetic core; Even form the coating that constitutes by glass A, the power loss (Pcv) that also can confirm high-frequency regions (1MHz) before and after coating forms be not fully improved (sample 13a, 16a, 17a and 21a).
Can confirm the accessory ingredient SiO in the ferrite composition of formation magnetic core portion according to these results
2Under the situation of content in the application's scope of invention of CaO; Through forming the coating that thermal coefficient of expansion is lower than magnetic core portion on magnetic core portion surface; Can keep high saturation magnetic flux density (Bs) and power loss is reduced, consequently can improve factor of merit (Pcv/Bs) at high-frequency region (for example more than the 1MHz).
Can confirm sample 13b～21b before and after the coating that forms glass B, the power loss (Pcv) of high-frequency region (1MHz) does not improve, and has worsened more, and this with the ferrite composition of formation magnetic core portion in accessory ingredient SiO
2Whether it doesn't matter in the application's scope of invention with the content of CaO.
Can confirm that promptly the coating that has the thermal coefficient of expansion bigger than magnetic core portion in utilization covers under the situation of magnetic core portion, power losss (Pcv) do not improve before and after coating forms, and accessory ingredient SiO in this and the ferrite composition
2Irrelevant with the content of CaO.
Embodiment 3
Cd in the ferrite composition of formation magnetic core portion and the content of Pb are adjusted according to the amount that contains in principal component raw material iron oxide, zinc oxide and the manganese oxide as ferrite composition; Except as table 5, changing; Make the sample that forms magnetic core portion with the sample 4 (Tsp is 25 ℃) of embodiment 1 the samely, carry out identical evaluation (sample 22～31).The result is shown in table 5.
Then, form magnetic core portion, obtain utilizing glass A or glass B to form the ferrite core (annular) of coating on the surface of magnetic core portion with the ferrite composition shown in the table 5.The ferrite core sample that obtains is carried out the evaluation identical with embodiment 1 and embodiment 2 (sample 22a～31a and sample 22b～31b).The result is shown in table 6.
Table 6
According to table 5; Can confirm Cd and the sample 4,22～25 and 27～30 of content in the application's scope of invention of Pb in the ferrite composition; With accessory ingredient content not the sample in the application's scope of invention 26 compare with 31, the power loss (Pcv) of high-frequency region (1MHz) is low.
Sample 4a, 22a～25a and the 27a of table 4,30a; The sample 4,22～25,27～30 of content in the application's scope of invention with Cd in the ferrite composition and Pb forms magnetic core portion, utilizes the glass A with thermal coefficient of expansion littler than this magnetic core portion to cover the surface of this magnetic core portion.
Can confirm such sample 4a, 22a～25a and 27a～30a, compare with 27～30, reduce in the power loss (Pcv) of high-frequency region (1MHz) with the sample 4,22～25 before forming coating.Promptly can confirm to compare with magnetic core portion sample ( sample 4,22～25 and 27～30); (sample 4a, 22a～25a and 27a～30a) power loss (Pcv) at high-frequency region (1MHz) has reduced 20～24% to the ferrite core of the coating that formation is made up of glass A, and performance has improved.
Also confirm before and after the surface of magnetic core portion forms the coating that is made up of glass A; High saturation magnetic flux density remains unchanged; Consequently, (sample 4a, 22～25a and 27a～30a), it is improved with the factor of merit that Pcv/Bs representes to form the ferrite core of the coating that is made up of glass A.
But; Under with the content of Cd in the ferrite composition and the Pb situation that sample 26 and 31 in the scope of invention in the application does not use as magnetic core portion; Even can confirm to form the coating that constitutes by glass A; Forming before and after the coating, at the power loss (Pcv) of high-frequency region (1MHz) be not fully improved (sample 26a and 31a).
According to these results; The content that can confirm Cd and Pb in forming the ferrite composition of magnetic core is under the situation in the application's the scope of invention; Surface through in magnetic core portion forms the coating with thermal coefficient of expansion lower than magnetic core portion; Can keep high saturation magnetic flux density Bs, and also can reduce power loss, consequently can improve factor of merit (Pcv/Bs) at high-frequency region (for example 1MHz).
Can confirm that sample 22b～31b is before and after the coating of glass B forms; The power loss of high-frequency region (1MHz) does not improve; And worsen more, and whether this has nothing to do in the application's scope of invention with Cd and the content of Pb in the ferrite composition that forms magnetic core portion.
Can confirm that promptly the coating that has the thermal coefficient of expansion bigger than magnetic core portion in utilization covers under the situation of magnetic core portion, power losss (Pcv) did not improve before and after coating formed, and this has nothing to do with Cd and the content of Pb in the ferrite composition.
Claims (3)
1. ferrite core, the coating that has the magnetic core portion that is made up of ferrite composition and be formed at least a portion on said magnetic core portion surface is characterized in that,
Said ferrite composition is by with Fe
2O
3The content that converts is that the iron oxide of 63.3～65.5 moles of %, the content that converts with ZnO are that the zinc oxide of 11.6～15.8 moles of %, the manganese oxide of surplus constitute principal component, with respect to said principal component 100 weight %, with SiO
2The silica content that converts is 60～250ppm, and the calcium oxide content that converts with CaO is 360～1000ppm, and the Pb content that converts with element is below the 7ppm, and the Cd content that converts with element is below the 7ppm,
The minimum temperature T sp of the magnetic loss of said ferrite composition is in 0～50 ℃ of scope, and the thermal coefficient of expansion of said coating is under the thermal coefficient of expansion of said magnetic core portion.
2. ferrite core according to claim 1 is characterized in that said coating is made up of glass composition.
3. an electronic component is characterized in that, has claim 1 or 2 described ferrite cores.
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| CN103382106A (en) * | 2013-06-27 | 2013-11-06 | 电子科技大学 | High-conductive and high-loss NiCuZn ferrite material, magnetic sheets and preparation method thereof |
| CN103943321A (en) * | 2013-01-23 | 2014-07-23 | Tdk株式会社 | Magnetic core and coil-type electronic element |
| CN107077948A (en) * | 2014-11-06 | 2017-08-18 | 株式会社村田制作所 | Multilayer coil component |
| CN107077949A (en) * | 2014-11-06 | 2017-08-18 | 株式会社村田制作所 | Multilayer coil component |
| CN111435618A (en) * | 2019-01-11 | 2020-07-21 | 京瓷株式会社 | Core member, method of manufacturing core member, and inductor |
| CN112321160A (en) * | 2020-10-22 | 2021-02-05 | 标旗磁电产品(佛冈)有限公司 | Method for improving thermal shock resistance of magnetic core |
| US11915854B2 (en) * | 2018-03-13 | 2024-02-27 | Murata Manufacturing Co., Ltd. | Wire coil component and method for producing wire coil component |
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| JP2012244064A (en) | 2012-12-10 |
| JP5786454B2 (en) | 2015-09-30 |
| CN102800456B (en) | 2016-01-13 |
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