Common mode filter

The common mode filter of the instant disclosure includes a non-magnetic insulating substrate, a stacked-layer structure, an insulating layer, and a magnetic layer. The stacked-layer structure is arranged on the non-magnetic insulating substrate. The magnetic layer is covered on the stacked-layer structure by the insulating layer arranged therebetween. The stacked-layer structure comprises a first coil and second coil, wherein the first coil is coupled to the second coil to suppress the common mode noise. Specially, a width W (mm) and a length L (mm) of at least one coil in the first and second coils satisfy the relational expression of:[(14.1−fc)/6.5]2<L/W<[(16.7−fc)/4.5]2 Where fc (MHz) is the cutoff frequency of a differential-mode signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The instant disclosure relates to a common mode filter; in particular, to a thin-film common mode filter for a portable electric device.

2. Description of Related Art

Common mode filter is a component used to suppress common mode current that causes electromagnetic interference (EMI) conducted on parallel lines in the same direction as a source of the noise in electronic circuit. To address the miniaturizing requirement of portable electronic apparatuses, thin-film common mode filters have been developed.

Japanese Patent Application Laid-Open NO. 2000-173824A discloses one type of electronic component, which includes an insulating substrate, a multi-layer structure, and a plurality of external electrode terminals. The multi-layer structure is arranged on the insulating substrate and comprises a plurality of conducting patterns and a plurality of insulating layers, wherein two of the conducting patterns are laminated with one insulating layer interposed therebetween for electrically insulating the conducting patterns. The external electrode terminals are surroundingly arranged on the insulating substrate and the multi-layer structure for establishing an external electrical connection. Moreover, the electronic component further comprises a plurality of magnetic layer or sheet to cover at least part of the conducting patterns.

For such structural design, the electronic component needs to modify the conducting patterns of the multi-layer structure to adjust the common mode impedance. However, more improvements may cause the large volume of the electronic component and affect the process variables due to the complex structure of the electronic component.

To address the above issues, the inventors strive via industrial experience and academic research to present the instant disclosure, which can effectively improve the limitations described above.

SUMMARY OF THE INVENTION

The object of the instant disclosure is to provide a common mode filter having simple structural configuration to achieve the purpose of miniaturization.

In order to achieve the aforementioned objects, according to an embodiment of the instant disclosure, the common mode filter includes a non-magnetic insulating substrate, a first coil body, a first electric insulating layer, a coil leading layer, a second electric insulating layer, a second coil body, an insulating layer, and a magnetic layer.

The first coil body is arranged on the non-magnetic insulating substrate and comprises a first spiral coil. The coil leading layer is stacked above the first coil body. The first electric insulating layer is arranged between the first coil body and the coil leading layer and has a first conducting structure formed thereon, wherein the first coil body and the coil leading layer are respective electrically coupled to the first conducting structure. The second coil body is stacked above the coil leading layer and comprises a second spiral coil. The second electric insulating layer is arranged between the coil leading layer and the second coil body and has a second conducting structure formed thereon, wherein the coil leading layer and the second coil body are respective electrically coupled to the second conducting structure. The insulating layer is arranged on the second coil body.

Specially, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils satisfy the relational expression of:
[(14.1−fc)/6.5]2<L/W<[(16.7−fc)/4.5]2
where fc (MHz) is the cutoff frequency of a differential-mode signal.

According to another embodiment of the instant disclosure, the common mode filter includes a non-magnetic insulating substrate, a lower leading layer, a first electric insulating layer, a first coil body, a second electric insulating layer, a second coil body, a third electric insulating layer, an upper leading layer, an insulating layer, and a magnetic layer.

The lower leading layer is arranged on the non-magnetic insulating substrate. The first coil body is stacked above the lower leading layer and comprises a first spiral coil. The first electric insulating layer is arranged between the lower leading layer and the first coil body and has a first conducting structure formed thereon, wherein the lower leading layer and the first coil body are respective electrically coupled to the first conducting structure. The second coil body is stacked above the first coil body and comprises a second spiral coil. The second electric insulating layer is arranged between the first coil body and the second coil body.

The upper leading layer is stacked above the second coil body. The third electric insulating layer is arranged between the second coil body and the upper leading layer and has a second conducting structure formed thereon, wherein the second coil body and the upper leading layer are respective electrically coupled to the second conducting structure. Specially, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils satisfy the relational expression of:
[(15.4−fc)/14.3]2<L/W<[(18.2−fc)/12.0]2
where fc (MHz) is the cutoff frequency of a differential-mode signal.

Base on above, the first and second spiral coils can be magnetically coupled to be used in common to eliminate common mode noise. In addition, the common mode filter is effective in maintaining range of the cutoff frequency by stacking the first and second spiral coils above the non-magnetic insulating substrate to accurately control the common mode impedance and achieve the purpose of miniaturization.

In order to further appreciate the characteristics and technical contents of the instant disclosure, references are hereunder made to the detailed descriptions and appended drawings in connection with the instant disclosure. However, the appended drawings are merely shown for exemplary purposes, rather than being used to restrict the scope of the instant disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless stated otherwise, all mentioned quantities are not intended to be limiting.

The First Embodiment

Please refer toFIG. 1, The thin-film common mode filter1includes a non-magnetic insulating substrate10, a stacked-layer structure20, an insulating layer30, and a magnetic layer40.

The stacked-layer structure20is arranged on the non-magnetic insulating substrate10and includes a first coil body21, a first electric insulating layer22, a coil leading layer23, a second electric insulating layer24, and a second coil body25in sequential order. The magnetic layer40covering the stacked-layer structure20by the insulating layer30interposed therebetween to increase inductance effect of the common mode filter1. In this embodiment, the insulating layer30can be, but not limited to, an adhesive layer.

The specific features of the stacked-layer structure20are described as follows. The first coil body21includes a first spiral coil211, a first electrode212, a second electrode213, a third electrode214, and a fourth electrode215. Moreover, the first spiral coil211has an inner end portion2111and an outer end portion2112formed thereon, wherein the outer end portion2112is electrically connected to the first electrode212.

The coil leading layer23is stacked above the first coil body21and includes a pair of L-shaped coils231, a first electrode232, a second electrode233, a third electrode234, and a fourth electrode235. Moreover, each of the L-shaped coil231has an inner end portion2311and an outer end portion2312formed thereon, and the outer end portions2312are respective electrically connected to the third electrode234and the fourth electrode235.

The first electric insulating layer22has an upper surface and a lower surface, the first coil body21and the coil leading layer23are arranged on the upper surface and the lower surface respectively. Moreover, the first electric insulating layer22has a first conducting structure221formed thereon, the inner end portion2111of the first spiral coil211and the inner end portion2311of one of the L-shaped coils231are respective electrically connected to the first conducting structure221to achieve electrical connection between the first coil body21and the coil leading layer23.

The second coil body25is stacked above the coil leading layer23and includes a second spiral coil251, a first electrode252, a second electrode253, a third electrode254, and a fourth electrode255. Moreover, the second spiral coil251has an inner end portion2511and an outer end portion2512formed thereon, wherein the outer end portion2512is electrically connected to the second electrode253. Specially, the first and second spiral coils211,251can be magnetically coupled to be utilized in common to eliminate common mode noise.

The second electric insulating layer24has an upper surface and a lower surface, the second coil body25and the coil leading layer23are arranged on the upper surface and the lower surface respectively. Moreover, the second electric insulating layer24has a second conducting structure241formed thereon, the inner end portion2311of another one of the L-shaped coils231and the inner end portion2511of the second spiral coil251are respective electrically connected to the second conducting structure241to achieve electrical connection between the coil leading layer23and the second coil body25. In this embodiment, the first and second conducting structures221,241can be, but not limited to, via holes or connecting pillars.

Preferably, the first spiral coil211and the second spiral251may be in the form of a rectangular spiral as shown. Alternatively, they may have other spiral shapes such as a shape of circular spiral. The first spiral coil211and the second spiral251may have the same of the coil windings, and they may be substantially overlapped in the direction which is perpendicular to the non-magnetic insulating substrate10.

Please refer toFIG. 2, which is a graph showing the relationship between a total length L (mm) divided by a width W (mm) and a cutoff frequency. So as you can see, the cutoff frequency of the common mode filter1can satisfy the following relationship by stacking the first and second spiral coils211,251above the non-magnetic insulating substrate10.
[(14.1−fc)/6.5]2<L/W<[(16.7−fc)/4.5]2
where fc (MHz) is the cutoff frequency of a differential-mode signal.

Concretely speaking, every node point of the cutoff frequency in correspondence with the total length L (mm) divided by a width W (mm) falls into the scope of the first trend line G1and the second trend line G2. In other words, the cutoff frequency generated by the thin-film common mode filter1is about 4 to 10 MHz such that the thin-film common mode filter1can meet the requirement of the specific portable electronic devices.

In this embodiment, the first coil body21, the coil leading layer23, and the second coil body25may made of conducting material of Ag, Pd, Al, Cr, Ni, Ti, Au, Cu, or Pt and can be formed by a depositing process, a lithography process, and a etching process in sequential order. The first electric insulating layer22and the second electric insulating layer24may be made of electrical insulating material of polyimide, epoxy, or benzocyclobutene (BCB) and can be formed by a spin-coating process, a dipping process, a spraying process, a screen-printing process, or a thin film process, wherein Said electrical insulating material has better electrical and mechanical property.

The magnetic layer40may be a magnetic substrate or a colloid comprising magnetic powder, wherein the colloid can be made by mixing the magnetic powder with the material comprising polyimide, epoxy, or benzocyclobutene (BCB). Similarly, the magnetic layer40can be formed by a spin-coating process, a dipping process, a spraying process, a screen-printing process, or a thin film process.

The Second Embodiment

Please refer toFIG. 3A, which shows a common mode filter in accordance to the second embodiment of the instant disclosure. The difference in the second embodiment is that the common mode filter1A further comprises another magnetic layer40. Said another magnetic layer40is arranged between the non-magnetic insulating substrate10and the stacked-layer structure20.

Concretely speaking, said another magnetic layer40is arranged between the non-magnetic insulating substrate10and the first coil body21to achieve better eliminating efficiency of the common mode noise. Similarly, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils211,251satisfy the relational expression of:
[(14.1−fc)/6.5]2<L/W<[(16.7−fc)/4.5]2
where fc (MHz) is the cutoff frequency of a differential-mode signal. Thereby, the cutoff frequency generated by the thin-film common mode filter1A is about 4 to 10 MHz such that the thin-film common mode filter1A can meet the requirement of the specific portable electronic devices.

The Third Embodiment

Please refer toFIG. 3B, which shows a common mode filter in accordance to the third embodiment of the instant disclosure. The difference in the third embodiment is that the common mode filter1B comprises a plurality of magnetic members50having the advantages of high resistance and low eddy current loss in a wild range of frequencies. In this embodiment, the magnetic members50can be, but not limited to ferrite cores.

In addition, each of the first and second electric insulating layers22,24has a through-hole222,242formed thereon near the first and the second conducting structures221,241respectively. The magnetic members50respectively arranged inside the first, second spiral coils211,251and near one end of the L-shaped coils231through the through-holes222,242to increase the magnetic field intensity between the first and the second coil body21,25(means that cross magnetic field intensity between the first and the second spiral coils211,251) to further increase the common mode impedance and the stability of the common mode filter1B.

Similarly, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils211,251satisfy the relational expression of:
[(15.4−fc)/14.3]2<L/W<[(18.2−fc)/12.0]2
Where fc (MHz) is the cutoff frequency of a differential-mode signal. Thereby, the cutoff frequency generated by the thin-film common mode filter1B is about 4 to 10 MHz such that the thin-film common mode filter1B can meet the requirement of the specific portable electronic devices.

The Fourth Embodiment

Please refer toFIG. 4, which shows a common mode filter1C in accordance to the fourth embodiment of the instant disclosure. The common mode filter1C includes a non-magnetic insulating substrate10′, a stacked-layer coil20′, an insulating layer30′, and a magnetic layer40′.

Concretely speaking, the common mode filter1C includes a lower leading layer21′, a first electric insulating layer22′, a first coil body23′, a second electric insulating layer24′, a second coil body25′, a third electric insulating layer26′, and an upper leading layer27′ in sequential order to generate a wide-ranged cutoff frequency.

The lower leading layer21′ is arranged on the non-magnetic insulating substrate10′ and includes a L-shaped coil211′, a first electrode212′, a second electrode213′, a third electrode214′, and a fourth electrode215′. Moreover, the L-shaped coil211′ has an inner end portion2111′ and an outer end portion2112′ formed thereon, wherein the outer end portion2112′ is electrically connected to the first electrode212′.

The first coil body23′ is stacked above the lower leading layer21′ and includes a first spiral coil231′, a first electrode232′, a second electrode233′, a third electrode234′, and a fourth electrode235′. Moreover, the first spiral coil231′ has an inner end portion2311′ and an outer end portion2312′ formed thereon, wherein the outer end portion2312′ is electrically connected to the third electrode234′.

The first electric insulating layer22′ has an upper surface and a lower surface, the lower leading layer21′ and the first coil body23′ are arranged on the upper surface and the lower surface respectively. Moreover, the first electric insulating layer22′ has a first conducting structure221′ formed thereon, the inner end portion2111′ of the L-shaped coil211′ and the inner end portion2311′ of the first spiral coil231′ are respective electrically connected to the first conducting structure221′ to achieve the electrical connection between the lower leading layer21′ and the first coil body23′.

The second coil body25′ is stacked above the first coil body23′ and includes a second spiral coil251′, a first spiral coil251′, a first electrode252′, a second electrode253′, a third electrode254′, and a fourth electrode255′. Moreover, the second spiral coil251′ has an inner end portion2511′ and an outer end portion2512′ formed thereon, wherein the outer end portion2512′ is electrically connected to the fourth electrode255′.

The second electric insulating layer24′ has an upper surface and a lower surface, the first coil body23′ and the second coil body25′ are arranged on the upper surface and the lower surface respectively such that the first and second spiral coils231′,251′ can be magnetically coupled to be utilized in common to eliminate common mode noise.

The upper leading layer27′ is stacked above the second coil body25′ and includes a L-shaped coil271′, a first electrode272′, a second electrode273′, a third electrode274′, and a fourth electrode275′. Moreover, the L-shaped coil271′ has an inner end portion2711′ and an outer end portion2712′ formed thereon, wherein the outer end portion2712′ is electrically connected to the second electrode273′.

The third electric insulating layer26′ has an upper surface and a lower surface, the upper leading layer27′ and the second coil body25′ are arranged on the upper surface and the lower surface respectively. Moreover, the third electric insulating layer26′ has a second conducting structure261′ formed thereon, the inner end portion2711′ of the L-shaped coil271′ and the inner end portion2511′ of the second spiral coil251′ are respective electrically connected to the second conducting structure261′ to achieve the electrical connection between the upper leading layer27′ and the second coil body25′. In this embodiment, the first and second conducting structures221′,261′ can be, but not limited to, via holes or connecting pillars.

Preferably, the first spiral coil231′ and the second spiral251′ may be in the form of a rectangular spiral. Alternatively, they may have other spiral shapes such as a shape of circular spiral. The first spiral coil231′ and the second spiral251′ may have the same of the coil windings, and they may be substantially overlapped in the direction which is perpendicular to the non-magnetic insulating substrate10′.

Please refer toFIG. 5, which is a graph showing the relationship between a total length L (mm) divided by a width W (mm) and a cutoff frequency. So as you can see, the cutoff frequency of the common mode filter1C can satisfy the following relationship by stacking the first and second spiral coils231′,251′ above the non-magnetic insulating substrate10′.
[(15.4−fc)/14.3]2<L/W<[(18.2−fc)/12.0]2
where fc (MHz) is the cutoff frequency of a differential-mode signal.

Concretely speaking, every node point of the cutoff frequency in correspondence with the total length L (mm) divided by a width W (mm) falls into the scope of the first trend line G1and the second trend line G2. In other words, the cutoff frequency generated by the common mode filter1C is about 2 to 10 MHz such that the common mode filter1C can meet the requirement of the specific portable electronic devices.

The Fifth Embodiment

Please refer toFIG. 6A, which shows a common mode filter1D in accordance to the fifth embodiment of the instant disclosure. The difference in the fifth embodiment is that the common mode filter1D further comprises another magnetic layer40′. Said another magnetic layer40is arranged between the non-magnetic insulating substrate10′ and the stacked-layer structure20′.

Concretely speaking, said another magnetic layer40′ is arranged between the non-magnetic insulating substrate10′ and the lower leading layer21′ to achieve better eliminating efficiency of the common mode noise. Similarly, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils231′,251′ satisfy the relational expression of:
[(15.4−fc)/14.3]2<L/W<[(18.2−fc)/12.0]2
where fc (MHz) is the cutoff frequency of a differential-mode signal. Thereby, the cutoff frequency generated by the thin-film common mode filter1A is about 2 to 10 MHz such that the thin-film common mode filter1D can meet the requirement of the specific portable electronic devices.

The Sixth Embodiment

Please refer toFIG. 6B, which shows a common mode filter1E in accordance to the fifth embodiment of the instant disclosure. The difference in the fifth embodiment is that the common mode filter1D comprises a plurality of magnetic members50′ having the advantages of high resistance and low eddy current loss in a wild range of frequencies. In this embodiment, the magnetic members50′ can be, but not limited to ferrite cores.

In addition, each of the first and third electric insulating layers22′,26′ has a through-hole222′,262′ formed thereon near the first and the second conducting structure respectively221′,261′. The second electric insulating layers24′ has a through-hole241′ formed thereon in correspondence with the through-hole222′ of the second insulating layers22′ and the through-hole262′ of the third insulating layers26′. The magnetic members50′ respectively arranged inside the first, second spiral coils231′,251′ and near one end of the L-shaped coils211′,231′ through the through-holes222′,241′,262′ to increase the stability of the common mode filter1D. Similarly, a width W (mm) and a length L (mm) of at least one spiral coil in the first and second spiral coils231′,251′ satisfy the relational expression of:
[(15.4−fc)/14.3]2<L/W<[(18.2−fc)/12.0]2
Where fc (MHz) is the cutoff frequency of a differential-mode signal. Thereby, the cutoff frequency generated by the common mode filter1D is about 2 to 10 MHz such that the common mode filter1D can meet the requirement of the specific portable electronic devices.

Base on above, the first and second spiral coils can be magnetically coupled to be used in common to eliminate common mode noise. In addition, the common mode filter is effective in maintaining range of the cutoff frequency by stacking the first and second spiral coils above the non-magnetic insulating substrate to accurately control the common mode impedance and achieve the purpose of miniaturization.