Transformer

This application claims the priority benefit of Taiwan application serial no. 97125135, filed on Jul. 3, 2008. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.

1. Field of the Invention

The present invention generally relates to a transformer, and more particularly, to transformer configured with an inner wiring inside a wiring substrate.

2. Description of Related Art

In a balance/unbalance filter, mutual inductance can be obtained by mutual coupling magnetic field between two inductors of a transformer, for single end transmission of differential signals. According to the trend of developing miniaturized electronic products, many electronic components have been integrated into a wiring substrate, such as passive components including capacitors, inductors, and resistors.

FIG. 1 illustrates a layout of a conventional transformer. Referring to FIG. 1 , a conventional transformer 100 includes two plane coils 110 and 120 , substantially positioned at a same plane. Each of the two plane coils 110 and 120 includes a plurality of loops. The loops of the two plane coils 110 and 120 are sequentially arranged one's across another's. With a specific circuit design, mutual inductance between these two plane coils 110 and 120 can be adjusted by adjusting sizes of these two coils. However, such an adjustment also varies self-inductances of the two plane coils 110 and 120 . Therefore, the transformer layout employing such a design lacks design flexibility.

FIG. 2 illustrates a layout of another conventional transformer. Referring to FIG. 2 , a conventional transformer 200 includes two plane coils 210 and 220 , substantially positioned in a same plane and adjacent to one another. The transformer 200 is capable of adjusting mutual inductance between these two plane coils 210 and 220 by adjusting a distance between the two parties. However, even though the change of the distance between the two parties does not vary self-inductances of thereof, this design requires a larger layout area of the transformer 200 .

Accordingly, the present invention is directed to a transformer having an improved design flexibility.

The present invention is also directed to a method for adjusting a mutual inductance, which is adapted for adjusting the mutual inductance without affecting a self-inductance.

The present invention provides a transformer adapted for being configured in a wiring substrate. The transformer includes a first plane coil and a second plane coil. The first plane coil includes a plurality of first loops. The second plane coil includes a plurality of second loops. A first bundle constituted by at least two adjacent first loops and a second bundle constituted by at least two adjacent second loops are stridden one over another.

According to an embodiment of the present invention, a first segment of the first loops is positioned between two adjacent second loops.

According to an embodiment of the present invention, a second segment of the second loops is positioned between two adjacent first loops.

According to an embodiment of the present invention, the wiring substrate includes an insulation layer. Each of the first loops of the first plane coil includes a first general segment, a first crossing segment, and a first conductive via. The first general segment and the first crossing segment of the first loop are positioned at two sides of the insulation layer. The first conductive via is configured passing through the insulation layer for connecting the first general segment and the first crossing segment.

Each of the second loops of the second plane coil includes a second general segment, a second crossing segment, and a second conductive via. The second general segment and the first general segment are positioned substantially in a same plane. The second general segment and the second crossing segment of the second loop are positioned at two sides of the insulation layer. The second conductive via is configured passing through the insulation layer for connecting the second general segment and the second crossing segment.

Projections of the first crossing segments of the first bundle at the plane are crossed with the second general segments of the second bundle, and projections of the second crossing segments of the second bundle at the plane are crossed with the first general segments of the first bundle.

According to an embodiment of the present invention, the first general segment of at least one first loop is crossed with a projection of the first crossing segment of at least another first loop at the plane. The insulation layer is positioned between the first general segment of the at least one first loop and the first crossing segment of the at least another one first loop.

According to an embodiment of the present invention, the second general segment of at least one second loop is crossed with a projection of the second crossing segment of at least another second loop at the plane. The insulation layer is positioned between the second general segment of the at least one second loop and the second crossing segment of the at least another second loop.

The present invention further provides a method for adjusting a mutual inductance for adjusting a mutual inductance between a first plane coil and a second plane coil of a transformer. The first plane coil includes a plurality of first loops, and the second coil includes a plurality of second loops. Each of the first loops includes at least one first inner loop and at least one first outer loop. Each of the second loops includes at least one second inner loop and at least one second outer loop. The first inner loop and the second inner loop are stridden one over another.

The method includes adjusting positions of the first inner loops and the second inner loops for varying an overlapping area between the first inner loops and the second inner loops, while maintaining positions of the first outer loops and the second outer loops unchanged.

According to an embodiment of the present invention, when one of the first inner loops is positioned between two second loops, positions of the first inner loop and the two second loops are adjusted.

According to an embodiment of the present invention, when one of the second inner loops is positioned between two first loops, positions of the second inner loop and the two first loops are adjusted.

Accordingly, while maintaining positions of the first outer loops and the second outer loops unchanged, the present invention is capable of adjusting positions of the first inner loops and the second inner loops for varying an overlapping area between the first inner loops and the second inner loops, so as to adjust the mutual inductance of the transformer. As such, when adjusting the mutual inductance between the first plane coil and the second plane coil, the present invention does not affect self-inductances of the first plane coil and the second plane coil, and won't increase a layout area of the transformer too much.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates a layout of a conventional transformer.

FIG. 2 illustrates a layout of another conventional transformer.

FIG. 3 illustrates a layout of a transformer according to an embodiment of the present invention.

FIG. 4 is a cross-section view of FIG. 3 along line I-I.

FIG. 5 is a cross-section view of FIG. 3 along line II-II.

FIG. 6 is a cross-section view of FIG. 3 along line III-III.

FIG. 7 is a cross-section view of FIG. 3 along line IV-IV.

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference counting numbers are used in the drawings and the description to refer to the same or like parts.

FIG. 3 illustrates a layout of a transformer according to an embodiment of the present invention. Referring to FIG. 3 , it shows a transformer 300 for being configured in a wiring substrate 400 . The wiring substrate 400 , for example, is a printed circuit board (PCB) or an electronic package carrier. The layout of the transformer 300 includes a first plane coil 310 and a second plane coil 320 , both of which are constituted by inner wirings of the wiring substrate 400 . The wiring substrate 400 includes a plurality of wiring layers, a plurality of insulation layers alternately overlaying with the wiring layers, and a plurality of conductive vias passing through the insulation layers for connecting the wiring layers. The inner wirings of the wiring substrate 400 include the wiring layers and the conductive vias.

The first plane coil 310 includes a plurality of sequentially connected first loops 312 (three first loops 312 a to 312 c are exemplified in FIG. 3 for illustration). The second plane coil 320 includes a plurality of sequentially connected second loops 322 (three first loops 322 a to 322 c are exemplified in FIG. 3 for illustration). In the current embodiment, a plurality of adjacent first loops 312 constitute a first bundle B 1 , and a plurality of adjacent second loops 322 constitute a second bundle B 2 . The first bundle B 1 and the second bundle B 2 are stridden one over another.

In the present embodiment, sizes of the first bundle B 1 and the second bundle B 2 can be adjusted within a range defined by the outmost first loop 312 a and the outmost second loop 322 a , so as to adjust a mutual inductance between the first bundle B 1 and the second bundle B 2 . It should be noted that the adjustment of the mutual inductance between the first bundle B 1 and the second bundle B 2 does not affect self-inductances of the first bundle B 1 and the second bundle B 2 , and won't increase the layout area of the transformer 300 too much. As such, compared to the conventional transformer 100 as shown in FIG. 1 , the transformer 300 according to the embodiment of the present invention has an improved design flexibility.

Referring to a region A 1 shown in FIG. 3 , in the present embodiment, the first loop 312 c has a first segment L 1 positioned between two adjacent second loops 322 b and 322 c . Similarly, referring to a region A 2 shown in FIG. 3 , in the present embodiment, the second loop 322 c has a second segment L 2 positioned between two adjacent first loops 312 b and 312 c.

FIG. 4 is a cross-section view of FIG. 3 along line I-I. Referring to FIGS. 3 and 4 together, in the present embodiment, the wiring substrate 400 includes an insulation layer 410 . Each of the first loop 312 of the first plane coil 310 includes a first general segment G 1 , a first crossing segment C 1 , and a first conductive via V 1 . The first crossing segment C 1 and the first general segment G 1 are respectively positioned at two sides of the insulation layer 410 . The first conductive via V 1 is configured passing through the insulation layer 410 for connecting the first general segment G 1 and the first crossing segment C 1 .

FIG. 5 is a cross-section view of FIG. 3 along line II-II. Referring to FIGS. 3 and 5 together, in the present embodiment, each of the second loops 322 of the second plane coil 320 includes a second general segment G 2 , a second crossing segment C 2 , and a second conductive via V 2 . The second general segment G 2 and the first general segment G 1 are substantially positioned in a same plane. The second crossing segment C 2 and the second general segment G 2 are respectively positioned at two sides of the insulation layer 410 . The second conductive via V 2 is configured passing through the insulation layer 410 for connecting the second general segment G 2 and the second crossing segment C 2 .

Referring to FIGS. 3 and 4 again, in the current embodiment, projections of the first crossing segments C 1 of the first bundle B 1 at the plane are crossed with the second general segments G 2 of the second bundle B 2 . Further, in the present embodiment, the first crossing segments C 1 of the first bundle B 1 and the second general segments G 2 of the second bundle B 2 are positioned at two sides of the insulation layer 410 .

Referring to FIGS. 3 and 5 again, in the current embodiment, projections of the second crossing segments C 2 of the second bundle B 2 at the plane are crossed with the first general segments G 1 of the first bundle B 1 . Further, in the current embodiment, the second crossing segments C 2 of the second bundle B 2 and the first general segments G 1 of the first bundle B 1 are positioned at two sides of the insulation layer 410 .

FIG. 6 is a cross-section view of FIG. 3 along line III-III. Referring to FIGS. 3 and 6 together, in the current embodiment, first general segments G 1 of two first loops 312 a and 312 b are crossed with a projection of a first crossing segment C 1 of another first loop 312 c at the plane. The insulation layer 410 is positioned between the first general segments G 1 of the two first loops 312 a and 312 b , and the first crossing segment C 1 of the another first loop 312 c . It should be noted that the quantities of the first loops crossing at the projection plane are not restricted by the present invention. For example, it may be three first general segments G 1 of three first loops crossing with a projection of one first crossing segment C 1 of another one first loop at the plane.

FIG. 7 is a cross-section view of FIG. 3 along line IV-IV. Referring to FIGS. 3 and 7 together, in the current embodiment, second general segments G 2 of two second loops 322 a and 322 b are crossed with a second crossing segment C 2 of another second loop 322 c at a projection plane. The insulation layer 410 is positioned between the two second general segments G 2 of the two second loops 322 a and 322 b , and the second crossing segment C 2 of the another second loop 322 c . It should be noted that the quantities of the second loops crossing at the projection plane are not restricted by the present invention. For example, it may be three second general segments G 2 of three second loops crossing with a projection of one second crossing segment C 2 of another one second loop at the plane.

Further, referring to FIG. 3 again, according to the current embodiment, in the first loops 312 a to 312 c , the first loop 312 c is more adjacent to a center portion of the first plane coil 310 , and thus is attributed as a first inner loop, and the first loops 312 a and 312 b are more adjacent to a peripheral of the first plane coil 310 , and thus are attributed as first outer loops. Similarly, in the second loops 322 a to 322 c , the second loop 322 c is more adjacent to a center portion of the second plane coil 320 , and thus is attributed as a second inner loop, and the second loops 322 a and 322 b are more adjacent to a peripheral of the second plane coil 320 , and thus are attributed as second outer loops. Further, the self-inductance of the first plane coil 310 can be adjusted by adjusting the first outer loops (i.e., the first loops 312 a , 312 b here), and the self-inductance of the second plane coil 320 can be adjusted by adjusting the second outer loops (i.e., the second loops 322 a , 322 b here).

According to a method for adjusting the mutual inductance of the transformer 300 , the mutual inductance of the transformer 300 can be adjusted by varying an overlapping area O between the first inner loops and the second inner loops by adjusting positions of the first inner loops and the second inner loops, while maintaining positions of the first outer loops and the second outer loops unchanged. As such, the embodiment of the present invention is adapted for adjusting the mutual inductance between the first plane coil 310 and the second plane coil 320 without affecting the self-inductances of the first plane coil 310 and the second plane coil 320 .

Referring to a region A 1 shown in FIG. 3 , in the current embodiment, when the first inner loop is positioned between two second loops 322 , the mutual inductance of the transformer 300 can be adjusted by adjusting the positions of the first inner loop and the two second loops 322 . Similarly, referring to a region A 2 shown in FIG. 3 , in the present embodiment, when the second inner loop is positioned between two first loops 312 , the mutual inductance of the transformer 300 can be adjusted by adjusting the positions of the second inner loop and the two first loops 312 .

In summary, while maintaining positions of the first outer loops and the second outer loops unchanged, the present invention is capable of adjusting positions of the first inner loops and the second inner loops for varying an overlapping area between the first inner loops and the second inner loops, so as to adjust the mutual inductance of the transformer. As such, when adjusting the mutual inductance between the first plane coil and the second plane coil, the present invention does not affect self-inductances of the first plane coil and the second plane coil, and won't increase a layout area of the transformer too much. In such a way, the transformer according to the present invention has an improved design flexibility compared to the conventional art.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.