Compositions – Magnetic – Iron-oxygen compound containing
Reexamination Certificate
2002-01-14
2004-02-24
Koslow, C. Melissa (Department: 1755)
Compositions
Magnetic
Iron-oxygen compound containing
C252S062600, C252S062620
Reexamination Certificate
active
06695972
ABSTRACT:
This invention relates to the formula and preparation method for low-temperature sintering, multi-layer chip inductor material of high performance used in very high frequencies. This invention is classified into the field of new material technologies.
Multi-layer chip inductors or multi-layer ferrite inductors (MLCI or MLFI for short) are of monolithic structure sintered together by ferrite material and internal screw type serial electrodes. The key of the process technology lies in the sintering together of ceramic medium material (soft magnetic ferrite) and internal conducting material (in consideration of conductivity, cost, and other respects, silver is the best selection). This requires that the soft magnetic ferrite possess a lower sintering temperature and a high permeability as well as high factor of quality. At present, the multi-layer chip inductor materials at home and abroad are mainly NiZnCu ferrite of low sintering temperature and low dielectric ceramics. The working frequencies of NiZnCu low sintering temperature ferrite and its device are generally less than 200 MHz. When Zn is not included in its compositions, its working frequencies are maximized to 300 MHz. The permeability of the low dielectric ceramics is usually 1, therefore can only be used in the frequencies above ultra-high frequency (800 MHz), where less inductance is required. In the very high frequencies of 300 MHz-800 MHz, which are commonly used in mobile telecommunication, IT techniques, television and defense field, there is no ferrite material of high performance and low sintering temperature yet up till now. Only low dielectric ceramics can be used as medium to manufacture multi-layer chip inductors of low inductance as substitutes.
Planar hexagonal ferrite of anisotropic Z-type, Ba
3
Co
2
Fe
24
O
41
(Co
2
Z), was discovered by Holland's Philips Lab in the late 50s. It has natural resonance frequencies between 1.3-3.4 GHz, possessing superior electric-magnetic properties, therefor, it is widely used in very high frequencies and microwave section. However, because of the complex crystal structure of Z-type ferrite, its phase-forming and sintering temperature is up to about 1300 ° C. In order to use it as material for multi-layer chip inductors, its sintering temperature must be reduced to about 900° C. so as to be able to sinter together with silver internal electrodes. Current technologies have been able to prepare low temperature sintering multi-layer chip inductor material of Co
2
Z series of planar hexagonal ferrite. The low temperature for sintering can be lower than 900° C., and permeability is 4-8. However, this kind of chemical powder preparation method is complex in process, relatively higher in cost.
The purpose of this invention is to provide a formula and preparation method for a material used in multi-layer chip inductors for very high frequencies, and to realize low temperature sintering below 900° C. by adopting solid-phase synthetic method so as to obtain the material and to meet the requirement on multi-layer material used in 300 MHz-800 MHz very high frequencies with a simple preparation process, low cost, and high performances.
The composition of the material of very high frequency multi-layer chip inductors provided by this invention are as follows: The main composition is planar hexagonal soft magnetic ferrite, of which the molecular formula is Ba
3−x
Sr
x
Co
2−y−z
Zn
y
Cu
z
Mn
w
Fe
24−w−v
O
41
, in which 0 ≦X≦2, 0≦Y≦2, 0≦Z≦2.0, 0≦W≦1.0, 0≦V≦1.0. Ingredient is low temperature sintering aid consisting of one or more than one composition of bismuth oxide, vanadium oxide, cadmium oxide, calcium oxide, silicon oxide, lead-oxide, boron oxide, lead fluoride, lithium fluoride, calcium fluoride, boron-lead glass, lithium carbonate or lithium borate. The percentage of main composition in the total weight of this material is 99-88%. The secondary doping in the ingredient accounts 1-12% of the total weight of the material.
The inductor material with the above formula can be prepared through the following synthetic method of solid phase reaction, of which the steps are:
(1) Synthesizing of main composition, planar hexagonal soft magnetic ferrite: On the basis of the molecular formula, select raw material from Fe
2
O
3
, SrCO
3
or SrO, BaCO
3
or BaO, Co
3
O
4
or CoO, ZnO, CuO, Mn
2
O
3
or MnO
2
or MnCO
3
; Weigh according to molecular formula stoichiometry ratio; Ball grind for 2-48 hr after mixing, taking water as the medium;
(2) Bake dry the slurry obtained by ball grinding in step (1), and pre-calcining at 1000-1300° C., resulting in main composition type Z: planar hexagonal soft magnetic ferrite;
(3) Mixing secondary doped sintering aid with the main composition according to formula and ball-grind for 2-48 hr with water as medium;
(4) Bake dry the slurry obtained in step (3), sieve with 100-200 mesh size, granulate, and moulding;
(5) Sintering at 860-920° C. for 1-10 hr.
By the use of the formula and preparation process of this invention, preparation can be made of pure Co
2
Z and doped Z type soft magnetic ferrite of planar hexagonal series, and 900° C. low temperature sintering can be realized. Adjusting formula and process, materials for multi-layer chip inductors can be obtained of high performance used in very high frequencies. Compared with current techniques, the advantages of this material are that the formula is adjustable; the sintering temperature is low and temperature range is wide; the process is simple; the cost is low; the properties are stable and reliable; the electromagnetic properties are superior with permeability being 10 when sintering below 900° C.
REFERENCES:
patent: 5954992 (1999-09-01), Onizuka et al.
patent: 2002/0108677 (2002-08-01), Wang et al.
Gui Zhilun
Li Longtu
Ma Zhenwei
Su Shuiyuan
Wang Xiao-hui
Koslow C. Melissa
Merchant & Gould P.C.
Tsinghua Tongfang Co., Ltd.
LandOfFree
Formula and preparation method for multi-layer chip inductor... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Formula and preparation method for multi-layer chip inductor..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Formula and preparation method for multi-layer chip inductor... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3307823