CN1193960C - Low-temp sintered material - Google Patents

Abstract

The present invention relates to a low temperature sintered material, particularly to a low temperature sintered material which is made from 48 to 75 wt% of Fe2O3, 5 to 15 wt% of ZnO, 15 to 25 wt% of NiO, 1 to 5 wt% of CuO, 0.05 to 0.5 wt% of Co3O4, 0.5 to 5 wt% of Bi2O3 and 0.5 to 2 wt% of PbO. The present invention has the advantages of good flow-casting film property, low sintering temperature, broad sintered range (880 (+/-)5 DEG C), good co-sintering accordance with a pure silver internal conductor, compact porcelain body structure, consistent crystal size, uniform distribution (1 to 5 mum), good electromagnetic property, etc.

Description

A kind of low-temp sintered material and preparation method thereof

Technical field

The present invention relates to a kind of low-temp sintered material, the invention still further relates to the preparation method of this kind low-temp sintered material.

Background technology

Since the late nineteen eighties, with robot calculator and communication etc. is that the electronics and information industry of representative has obtained fast development, electronics is advanced by leaps and bounds towards miniaturization, lightweight, high performance direction, the high density surface field engineering more and more comes into one's own, and has promoted microminiaturization, the chip type, integrated of all kinds of electronic devices and components greatly.Enter the nineties, the chip type rate of Global Electronics Components is near 50%.Because chip inductor with high content of technology, the production difficulty is big, so its developmental level lags behind the chip Resistor-Capacitor Unit, and however, according to Japanese printed wiring association statistics, the early 1990s, oneself surpasses 35% the chip type rate of Japanese inductive element.Chip inductor has been widely used in electronicss such as pocket computer, cordless telephone, TV, sound equipment, Video Camera.Present global chip inductor annual requirement is about 10,000,000,000, and will increase progressively to be higher than 30% annual growth every year.

The main flow and the developing direction of current chip inductor are the lamellar inductors with monolithic structure, it is compared with the sense of Wound-rotor type sheet and to have size little, help the miniaturization of circuit: magnetic circuit closed, can not disturb components and parts on every side, can not be subjected to the interference of contiguous components and parts yet, help the high-density installation of components and parts; Integral structure, the reliability height; Thermotolerance, weldability are good: regular shape is suitable for the automatization surface and installs and produce.

The process technology key of lamellar inductor is the common burning coupling of Ferrite Material and inner wire.This not only needs Ferrite Material can satisfy the requirement of high magnetic permeability μ i, high quality factor Q, high-temperature stability α μ r, and requires Ferrite Material to have low sintering temperature, and promptly high-performance and low-temperature sintering have both.And high-performance low-temperature sintered chip inductor does not also occur on the society in recent years with Ferrite Material.

Summary of the invention

Order of the present invention is to provide a kind of curtain coating formula film properties good, and sintering temperature is low, firing range is wide (880 ± 5 ℃) can well burn coupling altogether with the fine silver inner wire; The ceramic structure densification, grain size consistent and be evenly distributed (1-5 μ m); A kind of low-temp sintered material that electromagnetic performance is good.

Another object of the present invention provides a kind of preparation method of above-mentioned low-temp sintered material.

The object of the present invention is achieved like this: a kind of low-temp sintered material, it comprises Fe by weight percentage ₂O ₃48-75%, ZnO5-15%, NiO15-25%, CuO1-5%, Co ₃O ₄0.05-0.5%, Bi ₂O ₃0.5-5%, PbO0.5-2%.

A kind of low-temp sintered material, it comprises Fe by weight percentage ₂O348-75%, ZnO5-15%, Ni ₂O ₃14-30%, CuO1-5%, Co ₃O ₄0.05-0.5%, Bi ₂O ₃0.5-5%, PbO0.5-2%.

Described low-temp sintered material is that sintering forms in 860～900 ℃ temperature range, and preferred temperature is 860 ℃ and 880 ℃.

A kind of preparation method of above-mentioned low-temp sintered material, it comprises following processing step: behind the mix → grinding → drying → pre-burning → regrind → mix slurry → drying.

After the described drying step, the powder or the step of sieving of beating can also be arranged.

Description of drawings

Fig. 1 is a lamellar inductor structure iron of the present invention;

Fig. 2 is the equivalent-circuit diagram of lamellar inductor of the present invention;

Fig. 3 is the dielectric frequency spectrum of Ferrite Material of the present invention;

Fig. 4 is the resistivity binary pattern of Pd-Ag electrode slurry of the present invention;

Fig. 5 is the highest sintering temperature curve of Pd-Ag electrode slurry of the present invention;

Fig. 6 is Ni of the present invention _0.3Zn _0.7Fe ₂+ xO ₄In x and the relation of electricalresistivity v;

Fig. 7 is CuO content x of the present invention influence to sintering temperature;

Fig. 8 is the influence of CuO content x of the present invention to μ i:

Fig. 9 is the influence of CuO content x of the present invention to μ r;

Figure 10 is the influence of Ni content x of the present invention to μ i;

Figure 11 is the TEMPERATURE SPECTROSCOPY curve under the different Ni content x of the present invention,

Figure 12 is that several low melting point oxide of the present invention and glass are to (Ni _0.557Zn _0.270Cu _0.170CO _0.003) Fe _1.90O _3.85The cooling-down effect of material:

Figure 13 is the relation of ferritic volume density dV of the present invention and sintering temperature Ts:

Figure 14 is the SEM photo of material porcelain body section under the different sintering temperature of the present invention;

Figure 15 is the SEM photo of lamellar inductor porcelain body section under the different sintering temperature of the present invention:

Figure 16 is the variation of sheet sense magnetic bead RDC under the different sintering temperature of the present invention.

Table 1 is the size-grade distribution of four kinds of main raw material(s)s of the present invention;

Table 2 is that cooling agent of the present invention is to (Ni _0.557Zn _0.270Cu _0.170CO _0.003) Fe _1.90O _3.85The influence of ferrite μ i, Q value:

Table 3 is calcined temperature of the present invention influences to material μ i value.

Embodiment

Fig. 1 is the lamellar inductor structural representation.From Fig. 1 as seen, interior electrode is that coil is entirely the ferrite porcelain body and wraps up in the shape of a spiral, has only two end electrodes to link to each other with interior electrode.Ferrite Material also is a dielectric, has distributed capacity between interior electrode, and lamellar inductor can be represented with the equivalent electrical circuit of Fig. 2.

$Q=\frac{\mathrm{\ωL}}{r}-\mathrm{\ωCr}---\left(2\right)$

Here, ${{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C0011753700181.png"\; state="\{\{state\}\}">r</figure-callout>}}}^2=\frac{1}{\mathrm{LC}}$ Be the parallel resonance frequency of equivalent electrical circuit, be called self-resonant frequency again;

ω is the operating frequency of device;

R is the direct current resistance of lamellar inductor;

L, C are respectively inductance value and the distributed capacity relevant with material;

Q is the quality factor of device.

When the operating frequency ω of lamellar inductor＜＜ω _rThe time, formula (1), (2) can be reduced to:

$L^{\&prime;}=\frac{L-{\mathrm{<figure-callout\; id="2"\; label="Cr"\; filenames="C0011753700181.png"\; state="\{\{state\}\}">Cr</figure-callout>}}^2}{1+{\left(\mathrm{\&omega;Cr}\right)}^2}(1-j\frac{1}{Q})---\left(3\right)$

$Q=\frac{\mathrm{\&omega;L}}{r}-\mathrm{\&omega;Cr}---\left(4\right)$

Draw from formula (3) (4), L and L, C, r have confidential relation, and L and Q reduce with the increase of C, r, wherein are subjected to the influence of r the most remarkable with Q, therefore, make high-quality lamellar inductor and just must take following measure:

(1) reduces distributed capacity C

Distributed capacity C between inner electrode layer directly influences lamellar inductor self-resonant frequency w and inductance value L ' and quality factor q.C is bigger, and self-resonant frequency w is lower, simultaneously inductance value L and quality factor q is also corresponding reduces.Because being the interfloor distance t with the interior utmost point, distributed capacity C is inverse relation, i.e. CL '/t (5)

And the less (see figure 2) of the specific inductivity of Ferrite Material itself, the interlamellar spacing of electrode in choosing just can make the self-resonant frequency of lamellar inductor, far above or approach ferritic limiting frequency fr.

(2) selection of inner electrode

From formula (3), (4) as seen, the direct current resistance of interior electrode has very big influence to the electromagnetic property of lamellar inductor, select the little material of resistivity to make interior electrode and promptly can help to increase inductance value, can guarantee that again device has higher quality factor q value.

As seen from Figure 4, the resistivity minimum of fine silver, Pd: Ag=2: the resistivity maximum at 3 places.Fig. 5 is different palladiums---the highest sintering temperature change curve of silver-colored ratio electrode size.

(3) high performance Ferrite Material

Lamellar inductor has monolithic structure, is burnt altogether by Ferrite Material and inner wire to form, and wherein the internal layer body coil is not only long but also thin, and resistance is very big, is the main restricting factor of lamellar inductor Q value.Realize the common burning of Ferrite Material and fine silver internal layer body, then require the sintering temperature of Ferrite Material should be lower than the fusing point (961 ℃) of fine silver, general requirement about 900 ℃ to prevent the silver diffusion in the sintering process.NiCuZn Ferrite Material high frequency performance is good, and the sintering temperature of system is generally about 1000 ℃.Make NiCuZn ferrite and fine silver inner wire burn coupling altogether, still need further to reduce its sintering temperature.Reducing the ferrite sintered method of temperature of NiCuZn mainly contains: (1) is introduced low melting point or can be formed the additive of eutectoid point with some composition in the NiCuZn base-material, so that form liquid phase or transiting liquid phase sintering at a lower temperature.Additive commonly used has low melting glass, low melting point oxide etc.(2) the ultra-fine grain method utilizes the high surface active that ultrafine particle has to realize low-temperature sintering as the sintering impellent one by one.The main method that obtains ultra-fine grain has mechanical ultra-fine mill method and chemical powdering method.The technology for preparing NiCuZn ferrite superfine powder with chemical methods such as chemical coprecipitations is still not mature enough at present, is difficult to accurately control desired chemical constitution, and technology stability is poor, the cost height.The ultra-fine mill technology of machinery can both make the various stupalith powders of mean particle size less than 1 μ m at present usually.Therefore adopt the synthetic in advance NiCuZn ferrite base-material of traditional pyroprocess, will burn piece with mechanical ultra-fine mill then and be milled to mean particle size and reach about 1 μ m, an amount of sintering aids of cooperation interpolation drops to about 900 ℃ the sintering temperature of Ferrite Material, adopts Co simultaneously ₂O ₃, MgO, PbO, Sb ₂O ₃, Nb ₂O ₅Deng properties-correcting agent, thereby the high-performance and the low-temperature sintering that realize material have both.

Preparation NiCuZn ferritic main raw material(s) has: four kinds of ferric oxide, nickel oxide, zinc oxide and cupric oxide, they generally account for more than 95% of total amount of prescription, play a leading role in prescription.

As seen from Table 1, all about 2 μ m, size-grade distribution is preferable for the median size of four kinds of main raw material(s)s.From the SEM shape appearance figure of four kinds of main raw material(s)s as can be known, their form is sphere, and does not have tangible agglomeration.The physical and chemical performance of main raw material(s) is quite desirable.With the base side that they are prepared burden and are studied, sintering temperature can be reduced in 1000 ℃, and electromagnetic performance is good.

The principal constituent of NiCuZn Ferrite Material is a spinel solid solution, and it is the key component of decision material property.Proportion research between each is formed in this sosoloid is called the research of base side mainly comprise Ni/Zn ratio, Cu content and iron deficiency amount.

1, the iron deficiency amount chooses

Chip inductor uses its resistivity of Ferrite Material general requirement greater than 10 ⁸Ω.Concerning the NiZn ferrite, adopt the iron deficiency prescription, i.e. Fe in the prescription ₂O ₃, content can suppress Fe effectively a little less than 50%mol ²⁺Appearance, resistivity is obviously risen, see Fig. 6.But the iron deficiency amount is too much, and μ i value is reduced greatly, so lack Fe ₂O ₃Amount x generally is chosen between-0.04 to-0.1.

2, CuO content determines

The main purpose of introducing CuO is the sintering temperature of reduction system, but also can influence the electromagnetic performance of material.And select (Ni for use _0.32Zn _0.68) _1-XCu _ZFe _1.90O _3.85The prescription formula experimentizes, and promptly fix N i/Zn changes CuO content x than under the constant prerequisite.Choose Ni/Zn=1/2.125 and consider that mainly material should have suitable μ i value.Experimental result is seen Fig. 7, Fig. 8, Fig. 9.

From Fig. 7 as seen, CuO has the obvious cooling effect.When x increased to 0.18, sintering temperature was reduced to about 970 ℃, and x increases again, and Ts no longer descends.Fig. 8 has provided the curve that μ i changes with x.Maximum value appears in μ i about x=0.17, descend rapidly then.Fig. 9 is than the change curve of temperature factor α μ r with x.Maximum value appears in α μ r about X=0.13, sharply descend then.The change of CuO content causes that the Changing Pattern of μ i and α μ r is subjected to the domination of metal ion regularity of distribution in the spinel lattice.According to above experimental result, the content of choosing CuO is between x=0.15 to 0.25.

3, the influence of Ni/Zn ratio

Concerning the NiZn ferrite, Ni/Zn is than being the principal element that influences Ferrite Material initial permeability μ i.Equally, the NiCuZn Ferrite Material also is like this.Choose (Ni _XZn _0.83-XCu _0.17) Fe _1.90O _3.85The prescription formula is tested, and the results are shown in Figure 10 and Figure 11.From Figure 10 as seen, when Ni/Zn when identical, the ferritic μ i of NiZn value is more much higher than NiCuZn ferrite.Obviously, this is that introducing owing to CuO causes.According to metal ion occupy-place trend analysis in spinel A, B position, though Cu ²⁺Ion can occupy A position and B position simultaneously, but by contrast, Cu ²⁺Occupy-place trend away from Zn ²⁺And near Ni ²⁺, that is to say Cu ²⁺The trend ratio that occupies the B position occupies the A position more by force.Promptly to a certain extent, be equivalent to B position Ni content increase is arranged.In addition, Cu ²⁺The ion magnetic moment compare Ni ²⁺Little, thereby total specific magnetising moment can reduce, and causes the μ i value of material to descend.In addition, the logarithmic value of NiCuZn ferrite μ i and the relation of Ni content x are close to and are a straight line, help the selection of the Ni/Zn ratio of base side.

The low sintering main means of NiCuZn ferrite are to adopt ultra-fine powder-grinding method will burn piece to be milled to granularity and to reach about 1 μ m, add suitable sintering aids again and make sintering temperature reduce to needed about 900 ℃.Bi ₂O ₃, V ₂O ₅, PbO, B ₂O ₃Deng low melting point oxide and by them is the main low melting glass that constitutes, and can reduce the ferritic sintering temperature of NiCuZn effectively.Figure 12 and table 2 have provided the experimental result to material.From Figure 12 as seen, V ₂O ₅Cooling-down effect best, consumption is minimum; Bi ₂O ₃Few with the weak effect of boron lead-silica glass, they can both make sintering temperature reduce in 900 ℃, even can reduce to 860 ℃.But be not difficult to find V from table 2 ₂O ₅Can significantly reduce the Q value of material, not satisfy high performance requirement.Adopt the cooling of boron lead-silica glass, then will increase the operation of fusion cast glass.Bi ₂O ₃It is a kind of good cooling sintering aids.Figure 13 provides different B i ₂O ₃Relation curve under the content between ferritic volume density dv and the sintering temperature Ts.From Figure 13 as seen, work as Bi ₂O ₃Content is during greater than 1.0wt%, and sample can be at sintering below 900 ℃, and its volume density is greater than 5.0 gram per centimeters.

Low-temp sintered material is the high μ value material in the Ferrite Material series used of present middle and high frequency lamellar inductor, be used to make the lamellar inductor of big inductance quantity, test frequency is 1MHz, its main performance index requires: Ts=890 ± 20 ℃, μ i=250 ± 20%, α μ i＜10 * 10 ^-6/ ℃, ρ v＞10 ⁷Ω cm, Tc＞120 ℃, the base side's prescription that obtains material from base side is: Fe ₂O ₃=48.5～49.5mol%, NiO=13-14mol%, ZnO=27～28mol%, CuO=9-10mol% is by introducing The addition of C o ₂O ₃, basic side's salient features of developing is: Ts=1000 ℃/2hr, and μ i=515, Q _4MHz＞120, α _{μ r}=12 * 10 ^-6/ ℃, ρ v＞10 ⁸Ω .cm, Tc＞180 ℃.

From research Bi ₂O ₃, find during to the cooling-down effect of low-temp sintered material base side that the height of calcined temperature is to the μ i value influence of material greatly (seeing Table 3).Calcined temperature is appropriate, and burn piece and be brown-black, and levigate easily.Calcined temperature is on the low side, and burning piece color is red partially, and the μ i value of material will be on the low side greatly; Calcined temperature is too high, burns the very hard of agllutination, is difficult to levigate.Figure 14 is 960 ℃ of X-Ray diffractograms of 4 hours synthetic base sides of insulation burning piece down.

Adopt the synthetic in advance base-material of higher calcined temperature (950-980 ℃), after will burning piece and being milled to granularity＜1 μ m, use less than 2wt%Bi ₂O ₃The realization low-temperature sintering, obtained high performance low-temp sintered material, its salient features sees Table 4, from this table as seen, sintering temperature is when 870 ℃ are increased to 910 ℃, the variation of μ i is less than ± 6%; Sintering temperature is 890 ℃/2hr, and same stove burns the sample μ i that to be changed within ± 3%.Under the different sintering temperatures, the SEM pattern of low-temperature sintering material porcelain body fracture is seen Figure 15.Contrast under the different sintering temperatures the SEM photo as seen, sintering temperature is increased to 920 ℃/2hr from 860 ℃/2hr, promptly sintering temperature is wide reaches in 60 ℃ the scope, grain-size changes little, the grain size consistent performance almost can not found the excrescent phenomenon of crystal grain about 1-3 μ m.The porcelain body knot. the structure densification, pore is few and little.

Low-temp sintered material has the favorable manufacturability energy: not only the casting film-forming performance is good, and sintering temperature is low, firing range wide (860-890 ℃), can mate well with silver-colored inner wire, and simultaneously, low-temp sintered material also has good electric property; The lamellar inductor sensibility reciprocal of being done is stable, the Q value is high, self-resonant frequency is high, direct current resistance is little; The impedance of magnetic bead [Z] value stabilization is concentrated (under corresponding test condition), the R20 value is little, through-current capacity is big, weather resistance is strong.

The 2012 type lamellar inductors that made by low-temp sintered material are in 860～890 ℃ of nearly sintering ranges of 30 ℃, in the broad frequency range of 1MHz-50MHz, the Ls phase mutual deviations that cause owing to sintering temperature is different and since the Ls phase mutual deviation that frequency change causes respectively just between 2% and 5%, the Q value assigns 31 at test frequency 1MHz, self-resonant frequency 41MHz, direct current resistance 0.46 Ω.

Figure 15 is the section SEM photo of the lamellar inductor porcelain body made by low-temp sintered material under the different sintering temperatures.As seen from the figure: the grain size in each photo is distributed between 1～5 μ m, and the ceramic structure densification, and void content is low.Illustrating that sintering temperature changes between 860-890 ℃ does not all significantly influence the crystal grain of this kind porcelain body and pore opening, distribution.

Figure 16 has provided lamellar inductor and the magnetic bead direct current resistance R that low-temp sintered material is made under the different sintering temperatures _DCChanging conditions.As seen from the figure, along with the variation of burning temperature, the direct current resistance R of lamellar inductor and magnetic bead _DCVelocity of variation all in 2%.This shows inner wire pattern dimensional stabilizing, and silver does not participate in reaction or diffusion, and this point can also further be confirmed (seeing Figure 15) from the section photo of lamellar inductor.15 as seen by, silver-colored inner wire is clear clearly demarcated; Good with the ferrite material coupling, layering and hole do not appear each other, there are not tangible diffusion phenomena yet.

The present invention has compared to existing technology: (a) the casting film-forming performance is good; (b) sintering temperature is low, firing range is wide (880 ± 20 ℃), can well burn coupling altogether with the fine silver inner wire; (c) ceramic structure densification, grain size consistent and be evenly distributed (1～5 μ m); (d) electromagnetic performance is good.

Embodiment 1: a kind of low-temp sintered material comprises by weight percentage: Fe ₂O ₃75%, ZnO5%, Ni ₂O ₃14%, CuO1%, Co ₃O ₄0.5%, Bi ₂O ₃4%, PbO0.5%, it is to form at 860 ℃ of sintering.The preparation method of this kind low-temp sintered material comprises following processing step: behind the mix → grinding → drying → pre-burning → regrind → mix slurry → drying to get final product.

Embodiment 2: a kind of low-temp sintered material comprises by weight percentage: Fe ₂O ₃65%, ZnO10%, NiO15%, CuO3%, Co ₃O ₄0.5%, Bi ₂O ₃5%, PbO1.5%, it is to form at 860 ℃ of sintering.The preparation method of this kind low-temp sintered material comprises following processing step: behind the mix → grinding → drying → pre-burning → regrind → mixed slurry → drying → sieve.

Table 1.

Table 2.

Cooling agent	V 2O 5(0.7wt％) Bi 2O 3(3wt%) boron lead-silica glass (2wt%)
		T s(℃) μ 1 Q	870 870 870 67 58 44 70 240 220

Table 3.

Calcined temperature (℃/hr)	Sintering condition (℃/hr)	μ 1	Q 1MHz	dv (g/cm 3)
					850/4	900/2	187	205	5.24
900/4	900/2	195	203	5.21
					960/4	900/2	252	222	5.20

Claims (4)

1, a kind of low-temp sintered material, it comprises by weight percentage: Fe ₂O ₃48-75%, ZnO 5-15%, NiO 15-25%, CuO 1-5%, Co ₃O ₄0.05-0.5%, Bi ₂O ₃0.5-5%, PbO 0.5-2%.

2, a kind of low-temp sintered material, it comprises by weight percentage: Fe ₂O ₃48-75%, ZnO 5-15%, Ni ₂O ₃14-30%, CuO 1-5%, Co ₃O ₄0.05-0.5%, Bi ₂O ₃0.5-5%, PbO 0.5-2%.

3, the preparation method of low-temp sintered material as claimed in claim 1 or 2, it may further comprise the steps: behind the mix → grinding → drying → pre-burning → regrind → mixed slurry → drying.

4, the preparation method of a kind of low-temp sintered material according to claim 3 is characterized in that: beat the powder step or the step of sieving after drying step in addition.

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