Low temperature cofirable MnZn ferrite for power electronic applications

Abstract

A new MnZn ferrite tape material for sintering at 900°C and its performance in power electronic embedded multilayer inductors of several μH inductance are described. The low sintering temperature is achieved by optimizing powder processing and sintering additives. The material is suited for processing within the low temperature cofired ceramics (LTCC) technology and it is particularly compatible with low loss Ag metallization. Although reduced by a factor of two compared to high-temperature sintered material, its relative amplitude permeability of 700 allows for numerous device applications below the Curie temperature of 260°C. Volumetric losses are not affected by the new material formulation since increased hysteresis losses are compensated by reduced eddy current losses. Power line filters with ceramic integrated inductors and surface mounted capacitors exhibit a current capacity of up to 10 A and a shift in cutoff frequency compatible with the measured B-H curve of the material. By integration of these inductors with conventional dielectric LTCC tapes a strain-induced permeability quenching is revealed and attributed to magnetostriction. Therefore good thermal matching between tape materials is needed, but the effect also permits construction of variometers and pressure sensors without moving mechanical parts.

CaF2–AlF3–SiO2 glass-ceramic with low dielectric constant for LTCC application

“…T g of this glass system is identified as about 550 • C from the base line changing in the DSC traces. Compared with the common borosilicate glass and aluminosilicate glass for LTCCs [1,7,[10][11][12][13][14][15], the T g of present oxyfluoride glass is much lower, which is mainly due to the increase in non-bridging bonds caused by the fact that fluoride ions penetrate into the glass network and one Si-O bond is replaced by two Si-F bonds [16,17]. In addition, as marked with arrows in the DSC trace of S1, two exothermic peaks appear which is caused by the crystallization and can be identified as about 750 and 805 • C, respectively.…”

“…In this case, the transition temperature (T g ) of glass plays an important role in the reduction of sintering temperature. However, T g of current crystallized glass or glass fillers, such as borosilicate glass and aluminosilicate glass, is usually at a relative high level (about 700-800 • C) [1,7,[10][11][12][13][14][15]. Even though the BaO-B 2 O 3 -SiO 2 system with large B 2 O 3 content could exhibit a T g of 619 • C, the microstructure will be destroyed and the dielectric loss increases due to the large amount of B 2 O 3 [14].…”

Ceramic Multilayer Integration of Power Electronic Inductors

“…As an established soft ferrite for power transformers and inductors with high permeability and magnetic saturation, MnZn ferrite has been recently adapted to LTCC technology [15]. As compared to NiZn-based ferrites, its drawbacks like low specific resistivity, high permittivity and sensitivity to excess oxygen during sintering can be overcome by device design and process control.…”

Effect of oxygen partial pressure on co-firing behavior and magnetic properties of LTCC modules with integrated NiCuZn ferrite layers

“…Significant progress in the low-temperature sinterability of NiCuZn ferrites was reported in the last few years and the successful development of such low-fired ferrite materials was demonstrated in various papers [5][6][7][8][9][10]. Alternatively, MnZn ferrites were suggested as lowtemperature co-firable magnetics [11,12]. However, their operating frequency is limited to few MHz and sintering has to be performed in atmospheres with reduced partial pressure of oxygen.…”