WO2024070406A1

WO2024070406A1 - Coil component

Info

Publication number: WO2024070406A1
Application number: PCT/JP2023/031164
Authority: WO
Inventors: 和弘吉川; 啓吾東田; 晃一角田
Original assignee: Tdk株式会社
Priority date: 2022-09-30
Filing date: 2023-08-29
Publication date: 2024-04-04

Abstract

[Problem] To reduce connection resistance between a coil part and a terminal electrode. [Solution] A coil component 100 comprises: a coil part C1 in which a coil shaft is embedded in a base body so as to lie parallel to terminal formation surfaces 161, 162; and terminal electrodes 131, 132. A conductor layer 110 included in the coil part C1 includes: a coil pattern 111, a connection pattern 112 that connects the coil pattern 111 to the terminal electrode 131, and an auxiliary pattern 113 connected to the terminal electrode 132. A conductor layer 120 included in the coil part C1 includes: a coil pattern 121 and a connection pattern 122 that connects the coil pattern 121 to the terminal electrode 132. The coil patterns 111, 121 are connected to one another via a via conductor 151. The auxiliary pattern 113 is connected to the connection pattern 122 via a via conductor 152.

Description

Coil parts

This disclosure relates to coil components, and in particular to a type of coil component in which both ends of a coil portion embedded in a base body are exposed on a terminal forming surface that is parallel to the coil axis.

Patent document 1 discloses a type of coil component in which both ends of the coil portion embedded in the base body are exposed on the terminal formation surface parallel to the coil axis.

JP 2019-165169 A

However, the coil component described in Patent Document 1 had a problem in that the connection resistance between the coil portion and the terminal electrodes was high.

This disclosure describes a technology for reducing the connection resistance between a coil section and a terminal electrode in a coil component in which both ends of the coil section embedded in the base body are exposed on a terminal forming surface parallel to the coil axis.

A coil component according to one aspect of the present disclosure comprises a base body having a terminal forming surface, a first coil portion embedded in the base body such that the coil axis is parallel to the terminal forming surface, and first and second terminal electrodes provided on the terminal forming surface and connected to one end and the other end of the first coil portion, respectively, the first coil portion including a first conductor layer and a second conductor layer stacked via an interlayer insulating film, the first conductor layer including a first coil pattern having a loop shape, a first connection pattern exposed on the terminal forming surface and connecting the first coil pattern and the first terminal electrode, and a first connection pattern exposed on the terminal forming surface, The first conductor layer includes a first auxiliary pattern that is connected to the second terminal electrode and is provided independently of the first coil pattern and the first connection pattern, and the second conductor layer includes a loop-shaped second coil pattern and a second connection pattern that is exposed on the terminal forming surface and connects the second coil pattern and the second terminal electrode, the first and second coil patterns are connected to each other through a first via conductor that is provided through the interlayer insulating film, and the first auxiliary pattern is connected to the second connection pattern through a second via conductor that is provided through the interlayer insulating film.

This disclosure provides a technology for reducing the connection resistance between a coil section and a terminal electrode in a coil component in which both ends of the coil section embedded in the base body are exposed on a terminal forming surface parallel to the coil axis.

FIG. 1 is a schematic perspective view showing the appearance of a coil device 100 according to a first embodiment of the present disclosure. 2A and 2B are plan views for explaining the configuration of the coil portion C1, in which FIG. 2A shows the pattern shape of the conductor layer 110 and FIG. 2B shows the pattern shape of the conductor layer 120. As shown in FIG. FIG. 3 is a schematic cross-sectional view taken along line AA shown in FIG. 4A and 4B are plan views for illustrating the configuration of a coil portion C1 according to a first modified example, in which (a) shows the pattern shape of a conductor layer 110 and (b) shows the pattern shape of a conductor layer 120. FIG. FIG. 5 is a schematic cross-sectional view taken along line AA shown in FIG. 6A and 6B are plan views for illustrating the configuration of a coil portion C1 according to a second modified example, in which (a) shows the pattern shape of a conductor layer 110 and (b) shows the pattern shape of a conductor layer 120. FIG. FIG. 7 is a schematic cross-sectional view taken along line AA shown in FIG. FIG. 8 is a schematic perspective view showing the appearance of a coil device 200 according to the second embodiment of the present disclosure. 9A and 9B are plan views for explaining the configuration of the coil portion C2, in which (a) shows the pattern shape of the conductor layer 210 and (b) shows the pattern shape of the conductor layer 220. FIG. FIG. 10 is a schematic perspective view showing the appearance of a coil device 300 according to the third embodiment of the present disclosure. FIG. 11 is a schematic perspective view showing the appearance of a coil device 400 according to the fourth embodiment of the present disclosure.

Below, an embodiment of the present disclosure will be described in detail with reference to the attached drawings.

FIG. 1 is a schematic perspective view showing the appearance of a coil component 100 according to a first embodiment of the present disclosure.

As shown in FIG. 1, the coil component 100 according to the first embodiment includes a base body 101, a coil portion C1 embedded in the base body 101, and a pair of

terminal electrodes

131, 132 provided on the surface of the base body 101. The base body 101 may be made of a composite magnetic material in which magnetic particles made of a high magnetic permeability material such as ferrite or permalloy are solidified with a resin binder. The coil axis of the coil portion C1 embedded in the base body 101 is in the Z direction. The XY surface of the base body 101 is the mounting surface, and the

terminal electrodes

131, 132 are formed on the terminal formation surface constituting the XZ surface. Therefore, the coil axis of the coil portion C1 is parallel to the terminal formation surface. The

terminal electrodes

131, 132 are so-called five-sided electrodes, and some of them wrap around the XY and YZ surfaces. The terminal electrode 131 is connected to one end of the coil portion C1, and the terminal electrode 132 is connected to the other end of the coil portion C1. As explained below, the coil section C1 has a structure in which two conductor layers are stacked.

FIG. 2 is a plan view for explaining the configuration of the coil portion C1, where (a) shows the pattern shape of the conductor layer 110 and (b) shows the pattern shape of the conductor layer 120. Also, FIG. 3 is a schematic cross-sectional view taken along line A-A shown in FIG. 2.

As shown in FIG. 2(a), the conductor layer 110 includes a loop-shaped coil pattern 111, a connection pattern 112 that connects one end of the coil pattern 111 to a terminal electrode 131, and

auxiliary patterns

113 and 114 that are provided independently of the coil pattern 111 and the connection pattern 112 in the same layer as the conductor layer 110. Also, as shown in FIG. 2(b), the conductor layer 120 includes a loop-shaped coil pattern 121, a connection pattern 122 that connects one end of the coil pattern 121 to a terminal electrode 132, and

auxiliary patterns

123 and 124 that are provided independently of the coil pattern 121 and the connection pattern 122 in the same layer as the conductor layer 120.

The coil pattern 111 and the connection pattern 112 are integral, and the boundary position between them is not particularly limited, but it may be configured to wrap around in a loop of about 0.5 turns, with the portion that does not overlap with the auxiliary pattern 123 defined as the coil pattern 111, and the portion that overlaps with the auxiliary pattern 123 defined as the connection pattern 112. Similarly, the coil pattern 121 and the connection pattern 122 are integral, and the boundary position between them is not particularly limited, but it may be configured to wrap around in a loop of about 0.5 turns, with the portion that does not overlap with the auxiliary pattern 113 defined as the coil pattern 121, and the portion that overlaps with the auxiliary pattern 113 defined as the connection pattern 122.

The

conductor layers

110 and 120 and the element body 101 are separated from each other by an interlayer insulating film 140. The interlayer insulating film 140 includes an interlayer insulating film 141 located between the element body 101 and the conductor layer 110, an interlayer insulating film 142 located between the

conductor layers

110 and 120, and an interlayer insulating film 143 located between the element body 101 and the conductor layer 120. Here, reference numerals 151 to 155 shown in FIG. 2 are via conductors provided to penetrate the interlayer insulating film 142. The planar shape of the via conductors 151 to 155 may be circular.

The other end of coil pattern 111 is connected to the other end of coil pattern 121 through via conductor 151. As a result, a coil of approximately one turn consisting of the two

coil patterns

111 and 121 is connected between

terminal electrodes

131 and 132.

The connection pattern 112 and the auxiliary pattern 123 are connected to each other through the via conductor 153, and are exposed to the terminal forming surface 161 of the element body 101, thereby contacting the terminal electrode 131. Similarly, the connection pattern 122 and the auxiliary pattern 113 are connected to each other through the via conductor 152, and are exposed to the terminal forming surface 162 of the element body 101, thereby contacting the terminal electrode 132. The

terminal forming surfaces

161, 162 are XZ surfaces located on opposite sides of the element body 101. In the example shown in Figures 2 and 3, two via

conductors

152, 153 are provided, but the number of

via conductors

152, 153 is not particularly limited.

The auxiliary pattern 114 is provided at a position overlapping the coil pattern 121, and the two are connected to each other via a plurality of via conductors 154 arranged along the circumferential direction of the coil pattern 121. Similarly, the auxiliary pattern 124 is provided at a position overlapping the coil pattern 111, and the two are connected to each other via a plurality of via conductors 155 arranged along the circumferential direction of the coil pattern 111. The

auxiliary patterns

114, 124 may be integral with the

coil patterns

111, 121, respectively.

With this configuration, the terminal electrode 131 not only contacts the connection pattern 112 located on the conductor layer 110, but also contacts the auxiliary pattern 123 located on the conductor layer 120, so the contact area between the terminal electrode 131 and the coil portion C1 is increased, thereby reducing the connection resistance. Similarly, the terminal electrode 132 not only contacts the connection pattern 122 located on the conductor layer 120, but also contacts the auxiliary pattern 113 located on the conductor layer 110, so the contact area between the terminal electrode 132 and the coil portion C1 is increased, thereby reducing the connection resistance. Moreover, as shown in Figures 1 and 2, the connection pattern 112 and the auxiliary pattern 123 have planar shapes whose pattern widths become wider as they approach the terminal electrode 131, and the connection pattern 122 and the auxiliary pattern 113 have planar shapes whose pattern widths become wider as they approach the terminal electrode 132, so the contact area between the coil portion C1 and the

terminal electrodes

131 and 132 is further increased, and the connection resistance between them is further reduced.

In addition, since the connection pattern 112 and the auxiliary pattern 123 are connected in parallel, the connection pattern 122 and the auxiliary pattern 113 are connected in parallel, the coil pattern 111 and the auxiliary pattern 124 are connected in parallel, and the coil pattern 121 and the auxiliary pattern 114 are connected in parallel, the resistance value of the coil portion C1 itself is also reduced.

FIG. 4 is a plan view for explaining the configuration of the coil portion C1 according to the first modified example, where (a) shows the pattern shape of the conductor layer 110, and (b) shows the pattern shape of the conductor layer 120. FIG. 5 is a schematic cross-sectional view taken along line A-A shown in FIG. 4.

In the first modified example shown in Figures 4 and 5, there is one via

conductor

152, 153 each, and both have a shape with their longitudinal direction aligned with the Y direction, which is the current direction. In this way, by making the

via conductors

152, 153 extend along the

connection patterns

122, 112, it is possible to further reduce the connection resistance between the connection pattern 122 and the auxiliary pattern 113, and the connection resistance between the connection pattern 112 and the auxiliary pattern 123.

FIG. 6 is a plan view for explaining the configuration of the coil portion C1 according to the second modified example, where (a) shows the pattern shape of the conductor layer 110, and (b) shows the pattern shape of the conductor layer 120. Also, FIG. 7 is a schematic cross-sectional view taken along line A-A shown in FIG. 6.

In the second modified example shown in Figures 6 and 7, the

via conductors

152, 153 are exposed on the

terminal forming surfaces

162, 161, respectively. This further increases the contact area between the coil portion C1 and the

terminal electrodes

131, 132, making it possible to further reduce the connection resistance between the coil portion C1 and the

terminal electrodes

131, 132.

FIG. 8 is a schematic perspective view showing the appearance of a coil component 200 according to a second embodiment of the present disclosure.

As shown in FIG. 8, the coil component 200 according to the second embodiment includes a base body 201, a coil portion C2 embedded in the base body 201, and a pair of

terminal electrodes

231, 232 provided on the surface of the base body 201. The base body 201 may be made of a composite magnetic material in which magnetic particles made of a high magnetic permeability material such as ferrite or permalloy are bound by a resin binder, as in the first embodiment. The coil axis of the coil portion C2 embedded in the base body 201 is in the Z direction. The XZ surface of the base body 201 is the terminal forming surface 260, and the

terminal electrodes

231, 232 are formed on the pair of terminal forming surfaces 260. In this embodiment, the terminal forming surface 260 is a single surface, and this terminal forming surface 260 also serves as the mounting surface. The

terminal electrodes

231, 232 are so-called bottom electrodes, but they may be L-shaped electrodes by wrapping around the side surfaces that form the YZ surface.

FIG. 9 is a plan view for explaining the configuration of coil portion C2, where (a) shows the pattern shape of conductor layer 210 and (b) shows the pattern shape of conductor layer 220.

As shown in FIG. 9(a), the conductor layer 210 includes a loop-shaped coil pattern 211, a connection pattern 212 that connects one end of the coil pattern 211 to a terminal electrode 231, and an auxiliary pattern 213 that is provided independently of the coil pattern 211 and the connection pattern 212 in the same layer as the conductor layer 210. The conductor layer 210 and the element body 201 are separated from each other by an interlayer insulating film 240. As shown in FIG. 9(b), the conductor layer 220 includes a loop-shaped coil pattern 221, a connection pattern 222 that connects one end of the coil pattern 221 to a terminal electrode 232, and an auxiliary pattern 223 that is provided independently of the coil pattern 221 and the connection pattern 222 in the same layer as the conductor layer 220. The conductor layer 220 and the element body 201 are separated from each other by an interlayer insulating film 240.

The coil pattern 211 and the connection pattern 212 are integral, and the boundary position between them is not particularly limited, but it is also possible to define the portion that does not overlap with the auxiliary pattern 223 as coil pattern 211 by wrapping around in a loop for about one turn, and the portion that overlaps with the auxiliary pattern 223 as connection pattern 212. Similarly, the coil pattern 221 and the connection pattern 222 are integral, and the boundary position between them is not particularly limited, but it is also possible to define the portion that does not overlap with the auxiliary pattern 213 as coil pattern 221 by wrapping around in a loop for about one turn, and the portion that overlaps with the auxiliary pattern 213 as connection pattern 222.

The

coil patterns

211 and 221 partially overlap. A via conductor 251 is provided in the overlapping portion of the

coil patterns

211 and 221, thereby connecting the two

coil patterns

211, 221. In the example shown in FIG. 9, the via conductor 251 has a shape that extends along the circumferential direction of the

coil patterns

211, 221.

The connection pattern 212 and the auxiliary pattern 223 are connected to each other through the via conductor 253, and are exposed to the terminal forming surface 260 of the element body 201, thereby contacting the terminal electrode 231. Similarly, the connection pattern 222 and the auxiliary pattern 213 are connected to each other through the via conductor 252, and are exposed to the terminal forming surface 260 of the element body 201, thereby contacting the terminal electrode 232. In the example shown in FIG. 9, the via

conductors

252 and 253 have shapes that follow the extension direction of the

connection patterns

222 and 212, respectively.

With this configuration, the terminal electrode 231 is in contact not only with the connection pattern 212 located on the conductor layer 210, but also with the auxiliary pattern 223 located on the conductor layer 220, thereby reducing the connection resistance between the terminal electrode 231 and the coil portion C2. Similarly, the terminal electrode 232 is in contact not only with the connection pattern 222 located on the conductor layer 220, but also with the auxiliary pattern 213 located on the conductor layer 210, thereby reducing the connection resistance between the terminal electrode 232 and the coil portion C2.

Furthermore, since the connection pattern 212 and the auxiliary pattern 223 are connected in parallel, the connection pattern 222 and the auxiliary pattern 213 are connected in parallel, and a part of the coil pattern 211 and a part of the coil pattern 212 are connected in parallel, the resistance value of the coil portion C2 itself is also reduced.

As exemplified by the coil component 200 according to the second embodiment, both ends of the coil portion may be exposed from the same surface of the body.

FIG. 10 is a schematic perspective view showing the appearance of a coil component 300 according to a third embodiment of the present disclosure.

As shown in FIG. 10, the coil component 300 according to the third embodiment includes a base body 301, two coil sections C3 and C4 embedded in the base body 301, and terminal electrodes 331-334 provided on the surface of the base body 301. The coil sections C3 and C4 have the same structure as the coil section C1 included in the coil component 100 according to the first embodiment. In other words, the coil component 300 according to the third embodiment has a structure in which two coil components 100 according to the first embodiment are stacked in the Z direction. The base body 301 may be made of a composite magnetic material in which magnetic particles made of a high magnetic permeability material such as ferrite or permalloy are bound by a resin binder, as in the first embodiment.

The element body 301 has

terminal forming surfaces

361, 362 that form the XZ plane. Two

terminal electrodes

331, 333 are formed on the terminal forming surface 361, and two

terminal electrodes

332, 334 are formed on the terminal forming surface 362. One end and the other end of the coil portion C3 are connected to the

terminal electrodes

331, 332, respectively, and one end and the other end of the coil portion C4 are connected to the

terminal electrodes

333, 334, respectively.

In this way, the coil component 300 according to this embodiment has the same mounting area as the coil component 100 according to the first embodiment, and it is possible to provide an array product with two built-in coils.

FIG. 11 is a schematic perspective view showing the appearance of a coil component 400 according to a fourth embodiment of the present disclosure.

As shown in FIG. 11, the coil component 400 according to the fourth embodiment has a structure in which three coil components 300 according to the third embodiment are arranged in the X direction. The coil component 400 according to this embodiment makes it possible to provide an array of six coils.

　Although the above describes embodiments of the technology disclosed herein, the technology disclosed herein is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the technology disclosed herein, and it goes without saying that these modifications are also included within the scope of the technology disclosed herein.

For example, in the first embodiment described above, a configuration in which

auxiliary patterns

113, 114, 123, and 124 are formed is exemplified, but it is sufficient that one or more of these auxiliary patterns are formed. As an example,

auxiliary patterns

113 and 123 may be formed while

auxiliary patterns

114 and 124 may be omitted. Similarly, for example, in the second embodiment described above, a configuration in which

auxiliary patterns

213 and 223 are formed is exemplified, but it is sufficient that one or more of these auxiliary patterns are formed.

The technology disclosed herein includes, but is not limited to, the following configuration examples.

According to the present disclosure, the second terminal electrode contacts not only the second connection pattern located on the second conductor layer, but also the first auxiliary pattern located on the first conductor layer, increasing the contact area between the coil portion and the second terminal electrode, thereby making it possible to reduce the connection resistance between the two.

In the present disclosure, the second conductor layer is connected to the first terminal electrode by being exposed on the terminal formation surface, and further includes a second auxiliary pattern provided within the second conductor layer independently from the second coil pattern and the second connection pattern, and the second auxiliary pattern may be connected to the first connection pattern through a third via conductor provided through the interlayer insulating film. In this way, the first terminal electrode contacts not only the first connection pattern located on the first conductor layer, but also the second auxiliary pattern located on the second conductor layer, thereby increasing the contact area between the coil portion and the first terminal electrode, thereby making it possible to reduce the connection resistance between them.

In the present disclosure, the first conductor layer may further include a third auxiliary pattern that overlaps with the second coil pattern, and the third auxiliary pattern may be connected to the second coil pattern through a fourth via conductor that penetrates the interlayer insulating film. This makes it possible to reduce the resistance value of the coil portion itself.

In the present disclosure, the second conductor layer may further include a fourth auxiliary pattern that overlaps with the first coil pattern, and the fourth auxiliary pattern may be connected to the first coil pattern through a fifth via conductor that penetrates the interlayer insulating film. This makes it possible to further reduce the resistance value of the coil portion itself.

In the present disclosure, the second connection pattern and the first auxiliary pattern may have a pattern width that increases as they approach the second terminal electrode. This increases the contact area between the coil portion and the second terminal electrode, making it possible to further reduce the connection resistance between the two.

In the present disclosure, the second via conductor may be in contact with the second terminal electrode. This increases the contact area between the coil portion and the second terminal electrode, making it possible to further reduce the connection resistance between the two.

In the present disclosure, the terminal forming surface may have first and second terminal forming surfaces located on opposite sides of the element body, the first terminal electrode may be formed on the first terminal forming surface, the second terminal electrode may be formed on the second terminal forming surface, the first connection pattern may be exposed on the first terminal forming surface to contact the first terminal electrode, and the first auxiliary pattern and the second connection pattern may be exposed on the second terminal forming surface to contact the second terminal electrode. This makes it possible to form a pair of terminal electrodes on surfaces located on opposite sides of the element body.

The coil component according to the present disclosure further comprises a second coil portion embedded in the base body so as to be coaxially stacked on the first coil portion, a third terminal electrode formed on the first terminal forming surface and connected to one end of the second coil portion, and a fourth terminal electrode formed on the second terminal forming surface and connected to the other end of the second coil portion, and the second coil portion may include third and fourth conductor layers having the same configurations as the first and second conductor layers, respectively. This makes it possible to provide an array product incorporating two coils.

The coil component according to the present disclosure may have a single terminal forming surface. This makes it possible to use the terminal forming surface as a mounting surface.

This application claims the benefit of Japanese Patent Application No. 2022-158363, filed on September 30, 2022, the entire disclosure of which is incorporated herein by reference.

100, 200, 300, 400

Coil component

101, 201, 301

Base body

110, 120, 210, 220

Conductor layer

111, 121, 211, 221

Coil pattern

112, 122, 212, 222

Connection pattern

113, 114, 123, 124, 213, 223

Auxiliary pattern

131, 132, 231, 232, 331 to 334 Terminal electrode 140 to 143, 240 Interlayer insulating film 151 to 155, 251 to 253

Via conductor

161, 162, 260, 361, 362 Terminal formation surface C1 to C4 Coil section

Claims

an element body having a terminal forming surface;
a first coil portion embedded in the element body such that a coil axis is parallel to the terminal forming surface;
a first terminal electrode and a second terminal electrode provided on the terminal forming surface and connected to one end and the other end of the first coil portion,
the first coil portion includes a first conductor layer and a second conductor layer stacked with an interlayer insulating film therebetween,
the first conductor layer includes a first coil pattern having a loop shape, a first connection pattern exposed on the terminal forming surface and connecting the first coil pattern and the first terminal electrode, and a first auxiliary pattern exposed on the terminal forming surface and connected to the second terminal electrode, the first auxiliary pattern being provided in the first conductor layer independently of the first coil pattern and the first connection pattern,
the second conductor layer includes a second coil pattern having a loop shape, and a second connection pattern exposed on the terminal forming surface and connecting the second coil pattern and the second terminal electrode,
the first and second coil patterns are connected to each other through a first via conductor provided to penetrate the interlayer insulating film;
the first auxiliary pattern is connected to the second connection pattern through a second via conductor provided to penetrate the interlayer insulating film.
the second conductor layer is connected to the first terminal electrode by being exposed on the terminal forming surface, and further includes a second auxiliary pattern provided in the second conductor layer independently of the second coil pattern and the second connection pattern;
The coil component according to claim 1 , wherein the second auxiliary pattern is connected to the first connection pattern through a third via conductor provided to penetrate the interlayer insulating film.
the first conductor layer further includes a third auxiliary pattern overlapping the second coil pattern,
The coil component according to claim 2 , wherein the third auxiliary pattern is connected to the second coil pattern through a fourth via conductor provided to penetrate the interlayer insulating film.
the second conductor layer further includes a fourth auxiliary pattern overlapping the first coil pattern,
The coil component according to claim 3 , wherein the fourth auxiliary pattern is connected to the first coil pattern through a fifth via conductor provided to penetrate the interlayer insulating film.
The coil component according to claim 1, wherein the second connection pattern and the first auxiliary pattern have pattern widths that increase as they approach the second terminal electrode.
The coil component of claim 1, wherein the second via conductor is in contact with the second terminal electrode.
the terminal forming surface includes first and second terminal forming surfaces located on opposite sides of the body,
the first terminal electrode is formed on the first terminal forming surface,
the second terminal electrode is formed on the second terminal forming surface,
the first connection pattern is exposed on the first terminal forming surface and is in contact with the first terminal electrode;
The coil component according to claim 1 , wherein the first auxiliary pattern and the second connection pattern are exposed on the second terminal forming surface and are in contact with the second terminal electrode.
a second coil portion embedded in the element body so as to be coaxially stacked on the first coil portion;
a third terminal electrode formed on the first terminal forming surface and connected to one end of the second coil portion;
a fourth terminal electrode formed on the second terminal forming surface and connected to the other end of the second coil portion,
The coil component according to claim 7 , wherein the second coil portion includes third and fourth conductor layers having the same configurations as the first and second conductor layers, respectively.
The coil component according to claim 1 or 2, wherein the terminal forming surface is a single surface.