JP2004217477A - Ferrite and inductance element - Google Patents
Ferrite and inductance element Download PDFInfo
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- JP2004217477A JP2004217477A JP2003007417A JP2003007417A JP2004217477A JP 2004217477 A JP2004217477 A JP 2004217477A JP 2003007417 A JP2003007417 A JP 2003007417A JP 2003007417 A JP2003007417 A JP 2003007417A JP 2004217477 A JP2004217477 A JP 2004217477A
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【0001】
【発明の属する技術分野】
本発明は、インダクタンス素子のコア材として使用され、特に樹脂モールドタイプのチップインダクタのコア材として使用されるフェライトと、このフェライトをコア材に用いたインダクタンス素子に関する。
【0002】
【従来の技術】
電子機器に多数使用されているインダクタンス素子のコア材としては鉛を含むフェライトが多く使用されてきている。しかし、電子機器はいずれは廃棄物として環境中に廃棄されることになるので、インダクタンス素子のコア材中に含まれている鉛は環境中に拡散し、人間を含めた生物に悪影響を及ぼすおそれがある。従って、インダクタンス素子のコア材としては鉛を含まないフェライトを使用するのが望ましい。そこで、近年、鉛を含まないコア材及びインダクタンス素子が種々提案されている。
【0003】
例えば、特開平11−087126号公報には、Fe,Ni,Cu及びZnの酸化物を主成分とし、これに第1副成分(酸化ビスマス、酸化バナジウム、酸化リンおよび酸化ホウ素の1種または2種以上と酸化シリコン)及び第2副成分(酸化マグネシウム、酸化カルシウムおよび酸化ストロンチウムの1種または2種以上)を添加したものが開示されている。
【0004】
ここで、第1副成分は0.1〜10.0wt%、第2副成分は0.1〜10.0wt%、第1副成分+第2副成分の添加物の比率は主成分の0.5〜15wt%である。そして、このフェライトは、1t/cm2(98MPa)の圧力で加圧したときのインダクタンスの変化率は−5%〜+5%以内となっている。
【0005】
また、特開2002−134312号公報には、Fe,Ni,Cu,Mg及びZnの酸化物を主成分とし、Co、Bi及びSiの酸化物を副成分として含むフェライトが開示されている。
【0006】
ここで、主成分は、鉄の酸化物がFeO換算で45.0〜51.0モル%、銅の酸化物がCuO換算で0.5〜15.0モル%、亜鉛の酸化物がZnO換算で0〜33.0モル%、マグネシウムの酸化物がMgO換算で0.1〜5.0モル%、及び残部酸化ニッケルとなっている。
【0007】
また、副成分は、この主成分に対してコバルト酸化物がCoO換算で0.05〜1.0重量%の範囲、ビスマス酸化物がBiO換算で0.5〜7.0重量%の範囲、ケイ素酸化物がSiO換算で0〜5.0重量%の範囲で添加されている。
【0008】
そして、このフェライトは樹脂モールド型のインダクタンス素子に使用されるものであり、インダクタンスの加圧変化特性として49MPaの圧力で加圧したときのインダクタンスの変化率が種々記載されている。
【0009】
【発明が解決しようとする課題】
ところで、近年における技術の進歩はとどまるところがなく、フェライト及びインダクタンス素子についても、鉛を含まず、電気的特性が優れ、信頼性が高くかつ安価なものが望まれている。
【0010】
また、一定形状・大きさのインダクタンス素子についてインダクタンス値を大きくするためには、コアの芯径を細くし、巻数を多くする必要がある。しかし、このようにすると、モールドした樹脂による外部応力が強くかかるため、安定したインダクタンス値を有するインダクタンス素子を作るために高圧下(2t/cm2=196MPa)での応力特性が重要となってくる。
【0011】
本発明は、鉛を含まず、初透磁率が高く、安価で、2t/cm2(196MPa)の圧力で加圧したときのインダクタンスの抗応力特性に優れ、また、狭交差および高信頼性を備えたフェライト及びこのフェライトをコアとして使用したインダクタンス素子を提供することである。
【0012】
【課題を解決するための手段】
この発明に係るフェライトは、Fe,Ni,Cu,Mg及びZnの酸化物を主成分とし、Co、Bi及びSiの酸化物を副成分として含み、含まれているBi及びSiの酸化物の重量比がBi2O3/SiO2として1.29〜1.82、Bi及びSiの酸化物の合計重量がBi2O3+SiO2として4.99〜6.13重量%である。
【0013】
ここで、Bi及びSiの酸化物の重量比をBi2O3/SiO2として1.29〜1.82、Bi及びSiの酸化物の合計重量をBi2O3+SiO2として4.99〜6.13重量%の範囲としたのは、Bi2O3/SiO2が1.82を超えかつBi2O3+SiO2が6.13を超えると98MPaの変化率ΔL1/L、196MPaの変化率ΔL2/Lが悪くなり、Bi2O3/SiO2が1.29未満かつBi2O3+SiO2が4.99未満では98MPaの変化率ΔL1/L、196MPaの変化率ΔL2/Lが悪くなり、Q値が低くなるが、上記範囲であれば所望の特性のものが得られるからである。
【0014】
また、この発明に係るフェライトは、Fe,Ni,Cu,Mg及びZnの酸化物を主成分とし、Co、Bi及びSiの酸化物を副成分として含み、Bi及びSiの酸化物を、Bi2O3及びSiO2の重量%で示すグラフ(図1)において、Bi2O3が2.81wt%、SiO2が2.18wt%の組成を示す第1の点Aと、Bi2O3が3.45wt%、SiO2が2.68wt%の組成を示す第2の点Bと、Bi2O3が3.96wt%、SiO2が2.17wt%の組成を示す第3の点Cと、Bi2O3が3.22wt%、SiO2が1.77wt%の組成を示す第4の点Dとをこの順に結ぶ4本の直線で囲まれた領域内にある。
【0015】
ここで、Bi及びSiの酸化物を、Bi2O3及びSiO2の重量%で示すグラフの第1〜第4の点A〜点Dをこの順に結ぶ4本の直線で囲まれた領域内としたのは、Bi及びSiの酸化物をこの領域内とすれば、所望の特性を有するフェライトを得ることができるが、Bi及びSiの酸化物をこの範囲外とすれば所望の特性を有するフェライトを得ることができないからである。
【0016】
また、この発明に係るフェライトは、1t/cm2の圧力で加圧したときのインダクタンスの変化率が−5%〜+5%以内であり、2t/cm2の圧力で加圧したときのインダクタンスの変化率が−10%〜+10%以内である。
【0017】
また、この発明に係るインダクタンス素子は、上記フェライトがコアとして使用され、このコアにコイルが巻回され、これらが合成樹脂でモールドされているものである。
【0018】
【実施例】
主成分の原料粉末として、Fe2O3を47.4モル%、NiOを31.0モル%、ZnOを16.9モル%、MgOを3.1モル%、CuOを3.6モル%の割合で秤量した。また、副成分の原料粉末として、Co3O4を主成分の重量の0.08重量%、Bi2O3、SiO2を表1に示す割合(主成分に対する重量%)で秤量した。
【0019】
【表1】
【0020】
次に、これら主成分及び副成分の原料粉末をボールミルに入れ、2時間混合し、得られた混合物を空気中において900℃で2時間仮焼した。
【0021】
次に、この仮焼粉をボールミルに入れ、比表面積が3m2/gとなるように湿式で混合・粉砕し、磁性材料(試料1〜3、比較試料1〜2)を得た。ここで、比表面積は、株式会社島津製作所製の比表面積測定装置フローソーブII 2300形でBET一点法により測定した。
【0022】
次に、粉砕後の混合物を乾燥させ、ポリビニルアルコールを1.0wt%加えて混合し、2t/cm2の圧力で加圧成形して、寸法が7mmφ×15mmの円柱状の成形体を得、この成形体を、空気中において1050℃で2時間焼成し、フェライトからなる円柱状のコアサンプルを得た。
【0023】
次に、コアサンプルの中央部にワイヤを20回巻回し、このコアサンプルの両端面に一定圧力で一軸圧縮力を印加し、このときのインダクタンス値をLCRメータにて連続的に測定し、得られた測定値からインダクタンス変化率を算出した。表2に、1t/cm2(98MPa)、2t/cm2(196MPa)の一軸圧縮力を印加したときのインダクタンス変化率ΔL/Lを示す。
【0024】
【表2】
【0025】
焼結密度(見かけ密度)は、焼結体の焼結性の良し悪しを判断するためのものである。焼結密度が低い場合は焼結体の内部の空孔が多くなり、素子化した場合、高い温湿度で使用するとこの空孔が原因となって、ショート不良等を生じ、信頼性に影響を及ぼしたり、物理的強度が脆弱となる。このような問題を生じさせない焼結密度は、一般に5g/cm3以上である。
【0026】
Q(25MHz)は上記コアサンプルをJISコイル6φ用に入れ、LCRメーター4285A、42851Aで25MHzのQ値を測定した。
【0027】
試料1〜3は、Bi2O3、SiO2含有量を本発明の規定範囲内で変化させ、比較試料1,2はBi2O3、SiO2含有量が本発明から外れるものとした。
【0028】
焼結密度は全て5g/cm3程度である。また試料1〜3、比較例1は、充分なQ値をもつ。また、比較例1,2は外部応力に対するインダクタンスの変化率が98MPaで−5%〜+5%の範囲を超え、196MPaで−10%〜+10%の範囲を超えるものであった。
【0029】
表1、表2から、重量比Bi2O3/SiO2が1.82を超えかつ合計重量Bi2O3+SiO2が6.13を超えると98MPa、196MPaの加圧変化率ΔL1/L、ΔL2/Lが悪くなることがわかる。
【0030】
また、表1、表2から、重量比Bi2O3/SiO2が1.29未満かつ合計重量Bi2O3+SiO2が4.99未満になると98MPa、196MPaの変化率ΔL1/L、ΔL2/Lが悪くなり、また、Q値も低くなることがわかる。
【0031】
【発明の効果】
この発明は、高周波領域におけるQ値が充分に高く、かつ圧縮応力に対するインダクタンス変化率が小さいフェライトを得ることができ、その結果、高周波領域において高い信頼性と優れた性能を備えたインダクタンス素子を得ることができるという効果がある。
【0032】
また、この発明は、圧縮応力に対するインダクタンス変化率が小さいフェライトを得ることができるので、インダクタンス素子の設計においてインダクタンス値のねらいが絞り易くなり、インダクタンス素子の設計がし易くなるという効果がある。
【図面の簡単な説明】
【図1】本発明に係るフェライトに含まれるSiO2とBi2O3の範囲を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ferrite used as a core material of an inductance element, particularly a ferrite used as a core material of a resin-molded chip inductor, and an inductance element using the ferrite as a core material.
[0002]
[Prior art]
Ferrite containing lead has been frequently used as a core material of an inductance element used in many electronic devices. However, electronic devices will eventually be discarded into the environment as waste, so lead contained in the core material of the inductance element may diffuse into the environment and adversely affect living organisms including humans. There is. Therefore, it is desirable to use lead-free ferrite as the core material of the inductance element. Therefore, various types of lead-free core materials and inductance elements have recently been proposed.
[0003]
For example, Japanese Patent Application Laid-Open No. H11-087126 discloses that an oxide of Fe, Ni, Cu and Zn is used as a main component and a first subcomponent (one or two of bismuth oxide, vanadium oxide, phosphorus oxide and boron oxide) is added. There is disclosed an addition of at least one species and silicon oxide) and a second auxiliary component (one or more of magnesium oxide, calcium oxide, and strontium oxide).
[0004]
Here, the first subcomponent is 0.1 to 10.0 wt%, the second subcomponent is 0.1 to 10.0 wt%, and the ratio of the first subcomponent + the second subcomponent additive is 0% of the main component. 0.5 to 15 wt%. The rate of change in inductance of this ferrite when pressed at a pressure of 1 t / cm 2 (98 MPa) is within -5% to + 5%.
[0005]
Japanese Patent Application Laid-Open No. 2002-134312 discloses a ferrite containing oxides of Fe, Ni, Cu, Mg, and Zn as main components and oxides of Co, Bi, and Si as subcomponents.
[0006]
Here, the main components are 45.0 to 51.0 mol% of iron oxide in terms of FeO, 0.5 to 15.0 mol% of copper oxide in terms of CuO, and zinc oxide in terms of ZnO. 0 to 33.0 mol%, the oxide of magnesium is 0.1 to 5.0 mol% in terms of MgO, and the balance is nickel oxide.
[0007]
The sub-components are such that cobalt oxide is in the range of 0.05 to 1.0% by weight in terms of CoO, bismuth oxide is in the range of 0.5 to 7.0% by weight in terms of BiO, and Silicon oxide is added in the range of 0 to 5.0% by weight in terms of SiO.
[0008]
This ferrite is used for a resin mold type inductance element, and various changes in inductance when pressurized at a pressure of 49 MPa are described as inductance change characteristics.
[0009]
[Problems to be solved by the invention]
By the way, the technical progress in recent years has not stopped, and ferrite and inductance elements that do not contain lead, have excellent electrical characteristics, high reliability, and are inexpensive are desired.
[0010]
Also, in order to increase the inductance value of an inductance element having a fixed shape and size, it is necessary to reduce the core diameter of the core and increase the number of turns. However, in this case, since an external stress due to the molded resin is strongly applied, stress characteristics under high pressure (2 t / cm 2 = 196 MPa) are important in order to produce an inductance element having a stable inductance value. .
[0011]
The present invention contains no lead, has a high initial permeability, is inexpensive, has excellent inductance stress resistance when pressed at a pressure of 2 t / cm 2 (196 MPa), and has a narrow crossing and high reliability. An object of the present invention is to provide a ferrite provided and an inductance element using the ferrite as a core.
[0012]
[Means for Solving the Problems]
The ferrite according to the present invention contains oxides of Fe, Ni, Cu, Mg, and Zn as main components and oxides of Co, Bi, and Si as subcomponents, and the weight of the contained Bi and Si oxides.
[0013]
Here, the weight ratio of Bi and Si oxides is 1.29 to 1.82 as Bi 2 O 3 / SiO 2 , and the total weight of Bi and Si oxides is 4.99 to Bi 2 O 3 + SiO 2 . The range of 6.13% by weight is that when the ratio of Bi 2 O 3 / SiO 2 exceeds 1.82 and the ratio of Bi 2 O 3 + SiO 2 exceeds 6.13, the rate of change ΔL 1 / L of 98 MPa is 196 MPa. When the rate of change ΔL 2 / L deteriorates, and when Bi 2 O 3 / SiO 2 is less than 1.29 and Bi 2 O 3 + SiO 2 is less than 4.99, the rate of change ΔL 1 / L of 98 MPa and the rate of change ΔL 2 of 196 MPa This is because / L becomes worse and the Q value becomes lower, but within the above range, desired characteristics can be obtained.
[0014]
The ferrite according to the present invention contains oxides of Fe, Ni, Cu, Mg, and Zn as main components, oxides of Co, Bi, and Si as subcomponents, and oxides of Bi and Si, formed of Bi 2. In a graph (% by weight) of O 3 and SiO 2 (FIG. 1), a first point A indicating a composition of Bi 2 O 3 of 2.81 wt% and SiO 2 of 2.18 wt%, and Bi 2 O 3 3.45wt%, and B second point SiO 2 shows a composition of 2.68wt%, Bi 2 O 3 is 3.96wt%, and C a third point where SiO 2 is the composition of 2.17Wt% , Bi 2 O 3 of 3.22 wt% and SiO 2 of 1.77 wt% in a region surrounded by four straight lines connecting in this order a fourth point D.
[0015]
Here, a region surrounded by four straight lines connecting the first to fourth points A to D in the graph in which the oxides of Bi and Si are represented by the weight% of Bi 2 O 3 and SiO 2 in this order. The reason is that if the oxides of Bi and Si are in this range, a ferrite having desired characteristics can be obtained, but if the oxides of Bi and Si are out of this range, the desired characteristics can be obtained. This is because ferrite cannot be obtained.
[0016]
Further, in the ferrite according to the present invention, the rate of change of the inductance when pressed at a pressure of 1 t / cm 2 is within -5% to + 5%, and the inductance of the ferrite when pressed at a pressure of 2 t / cm 2 . The rate of change is within -10% to + 10%.
[0017]
In the inductance element according to the present invention, the ferrite is used as a core, a coil is wound around the core, and these are molded with a synthetic resin.
[0018]
【Example】
As the raw material powder of the main component, 47.4 mol% of Fe 2 O 3 , 31.0 mol% of NiO, 16.9 mol% of ZnO, 3.1 mol% of MgO, and 3.6 mol% of CuO were used. Weighed in proportions. Further, as raw material powders of the auxiliary components, Co 3 O 4 was weighed at 0.08% by weight of the weight of the main component, and Bi 2 O 3 and SiO 2 were weighed at the ratios shown in Table 1 (% by weight based on the main component).
[0019]
[Table 1]
[0020]
Next, the raw material powders of these main components and subcomponents were put into a ball mill and mixed for 2 hours, and the obtained mixture was calcined in air at 900 ° C. for 2 hours.
[0021]
Next, the calcined powder was put into a ball mill, mixed and pulverized by a wet method so that the specific surface area became 3 m 2 / g, to obtain magnetic materials (samples 1 to 3 and comparative samples 1 to 2). Here, the specific surface area was measured by a BET one-point method using a specific surface area measuring apparatus Flowsorb II 2300 manufactured by Shimadzu Corporation.
[0022]
Next, the mixture after the pulverization was dried, 1.0 wt% of polyvinyl alcohol was added and mixed, and the mixture was molded under pressure at a pressure of 2 t / cm 2 to obtain a cylindrical molded body having a size of 7 mmφ × 15 mm. The molded body was fired in air at 1050 ° C. for 2 hours to obtain a columnar core sample made of ferrite.
[0023]
Next, a wire is wound 20 times around the center of the core sample, a uniaxial compressive force is applied to both end surfaces of the core sample at a constant pressure, and the inductance value at this time is continuously measured by an LCR meter to obtain The inductance change rate was calculated from the measured values. Table 2 shows the inductance change rate ΔL / L when a uniaxial compressive force of 1 t / cm 2 (98 MPa) and 2 t / cm 2 (196 MPa) is applied.
[0024]
[Table 2]
[0025]
The sintering density (apparent density) is used to determine whether the sinterability of the sintered body is good or bad. When the sintering density is low, the number of pores inside the sintered body increases, and when the element is used, when used at high temperature and humidity, these pores cause short-circuit failure and affect the reliability. Or weak physical strength. The sintering density that does not cause such a problem is generally 5 g / cm 3 or more.
[0026]
As for Q (25 MHz), the above core sample was put in a 6φ JIS coil, and the Q value at 25 MHz was measured with an LCR meter 4285A, 42885A.
[0027]
In Samples 1 to 3 , the contents of Bi 2 O 3 and SiO 2 were changed within the range specified in the present invention, and in Comparative Samples 1 and 2, the contents of Bi 2 O 3 and SiO 2 deviated from the present invention.
[0028]
The sintering densities are all about 5 g / cm 3 . Samples 1 to 3 and Comparative Example 1 have sufficient Q values. In Comparative Examples 1 and 2, the rate of change of the inductance with respect to the external stress was more than -5% to + 5% at 98 MPa, and more than -10% to + 10% at 196 MPa.
[0029]
From Tables 1 and 2, it can be seen that when the weight ratio Bi 2 O 3 / SiO 2 exceeds 1.82 and the total weight Bi 2 O 3 + SiO 2 exceeds 6.13, the pressure change rate ΔL 1 / L of 98 MPa and 196 MPa. , ΔL 2 / L become worse.
[0030]
Also, from Tables 1 and 2, when the weight ratio Bi 2 O 3 / SiO 2 is less than 1.29 and the total weight Bi 2 O 3 + SiO 2 is less than 4.99, the change rate ΔL 1 / L of 98 MPa and 196 MPa, It can be seen that ΔL 2 / L becomes worse and the Q value also becomes lower.
[0031]
【The invention's effect】
According to the present invention, it is possible to obtain a ferrite having a sufficiently high Q value in a high frequency region and a small inductance change rate with respect to a compressive stress, and as a result, obtain an inductance element having high reliability and excellent performance in a high frequency region. There is an effect that can be.
[0032]
Further, according to the present invention, it is possible to obtain a ferrite having a small inductance change rate with respect to a compressive stress, so that the aim of the inductance value can be easily narrowed in the design of the inductance element, and the design of the inductance element can be easily performed.
[Brief description of the drawings]
FIG. 1 is a graph showing a range of SiO 2 and Bi 2 O 3 contained in a ferrite according to the present invention.
Claims (8)
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006206347A (en) * | 2005-01-25 | 2006-08-10 | Taiyo Yuden Co Ltd | Oxide magnetic material |
JP2006273608A (en) * | 2005-03-28 | 2006-10-12 | Neomax Co Ltd | Oxide magnetic material and lamination type inductor using the same |
CN110540421A (en) * | 2018-05-28 | 2019-12-06 | Tdk株式会社 | Ferrite composition and laminated electronic device |
-
2003
- 2003-01-15 JP JP2003007417A patent/JP4102673B2/en not_active Expired - Lifetime
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006206347A (en) * | 2005-01-25 | 2006-08-10 | Taiyo Yuden Co Ltd | Oxide magnetic material |
JP2006273608A (en) * | 2005-03-28 | 2006-10-12 | Neomax Co Ltd | Oxide magnetic material and lamination type inductor using the same |
CN110540421A (en) * | 2018-05-28 | 2019-12-06 | Tdk株式会社 | Ferrite composition and laminated electronic device |
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