Coil device and pulse transformer

A coil device having high bonding strength and bonding reliability has a core member including a winding core and a flange, wires wound around the winding core and one end being positioned at the flange, and terminal electrodes provided to the flange. Each of the terminal electrodes has a wire connecting part where one ends of the wires are connected, and a mounting part continuously formed with the wire connecting part at the side close to the winding core with respect to the wire connecting part along the axis direction of the winding core. The wire connecting part is provided at a position lower than the mounting part along the height direction of the flange.

BACKGROUND OF THE INVENTION

The present invention relates to a coil device used for example as a pulse transformer.

As a coil device used as a pulse transformer and the like, a coil device shown in Patent document 1 is known. In this conventional coil device, an end part of a wire forming a coil is connected by thermocompression to a terminal electrode having a mounting face.

However, the conventional coil device described in Patent document 1 had part of a coating film covering the wire remained on the mounting face of the terminal electrode as a residue of coating film. As a result, when the coil device is mounted on a substrate, voids and the like are formed at a connecting member such as a solder and the like which connects the mounting face of the terminal electrode and the substrate. Cracks may be formed from the voids, and in some case a connection reliability may be compromised.

Also, due to the influence from heat when the wire is connected by thermocompression, Sn layer melts and diminishes on the mounting face of the terminal electrode, as a result, adhesiveness between the terminal electrode and the connecting member such as solder and the like is deteriorated, and in some case a bonding strength may decrease.

Patent document 1: JP Patent Application Publication No. 2018-78155

BRIEF SUMMARY OF THE INVENTION

The present invention is attained in view of such circumstances, and the object is to provide a coil device and a pulse transformer having high bonding strength and bonding reliability.

In order to attain the above object, the coil device according to the present invention has

a core member having a winding core and a flange,

a wire wound around the winding core and one end of the wire being positioned on the flange, and

a terminal electrode provided on the flange, in which

the terminal electrode has

a wire connecting part connecting one end of the wire with the terminal electrode, and

a mounting part formed continuously with the wire connecting part at a side away from the winding core with respect to the wire connecting part along an axis direction of the wire connecting part.

In the coil device according to the present invention, the wire connecting part and the mounting part are separate parts on outer surface of the terminal electrode, thus when one end of the wire is connected by thermocompression to the wire connecting part of the terminal electrode, a residue of coating film which may be formed at the wire connecting part and adheres on the mounting part is decreased. As a result, when the coil device is mounted on the substrate, voids are less likely to be generated at the connecting member such as a solder and the like when the substrate and the mounting face of the terminal electrode are connected, thus cracks are suppressed from forming and a connection reliability is improved.

Also, since the mounting part and the connecting part are provided as separate parts at the outermost surface of the terminal electrode, the mounting part is less likely to be influenced by heat when the wire is connected by thermocompression, and Sn layer of the surface of the mounting part (the outermost surface layer which improves the adhesiveness with the connecting member such as a solder and the like) is unlikely to melt. As a result, when the coil device is mounted on the substrate, the adhesiveness between the mounting part of the terminal electrode and the connecting member such as a solder and the like is enhanced, and the bonding strength is improved.

Also, the mounting part is formed continuously with the wire connecting part and at a side away from the winding core with respect to the wire connecting part along the axis direction of the winding core, thus the wire connecting part becomes closer to the winding core, and a length of the wire from the wire connecting part to the winding core can be shortened. Thus, DC internal resistance of the coil device can be lowered (low DCR).

Further, the mounting part is formed continuously with the wire connecting part and at a side away from the winding core with respect to the wire connecting part along the axis direction of the winding core, thus the wire connecting part does not protrude out towards a width direction of the flange of the coil device (does not protrude out towards the side away from a center axis of the winding core). Therefore, the coil device can be made compact, also it becomes easy to transport and handle the coil device, and a handling property improves when the coil device is mounted.

Preferably, the wire connecting part is placed at a position lower than the mounting part along a height direction of the flange. By constituting as such, residue of coating film which may be formed at the wire connecting part and adheres on the mounting part is further decreased. Also, the mounting part is more unlikely to be influenced by heat when the wire is connected by thermocompression. Further, when the coil device is mounted on the substrate and the like, the wire connecting part is not connected to the terminal electrode but the mounting part of the terminal electrode contacts with connecting parts of the substrate, thus the connection strength of the substrate and the mounting part of the terminal electrode is improved and also the connection reliability improves.

Preferably, a step part is formed between the wire connecting part and the mounting part. By forming the step part, the wire connecting part can be easily provided at a position lower than the mounting part while providing the wire connecting part and the mounting part close to each other. Also, by having the step part, a residue of coating film which may be formed at the wire connecting part and adheres on the mounting part is further decreased.

Preferably, the outermost surface released part is formed between the wire connecting part and the mounting part. At an outermost surface of a metal member constituting the terminal electrode, a layer, for example Sn layer and the like is formed which is highly adhesive with the connecting member such as a solder and the like. Therefore, when the wire wound around the winding core is cut at an edge of the wire connecting part, due to the heat of thermocompression for connecting the wire, a portion of wire which is cut and supposed to be removed from the wire may be bonded to the terminal electrode, and in some case the wire cannot be cut appropriately.

By forming the outermost surface released part in which the outermost surface of the terminal electrode is released and removed between the wire connecting part and the mounting part, an unnecessary portion of wire is unlikely to bond with the terminal electrode when the wire is cut at the edge of the wire connecting part. As a result, the wire can be cut appropriately at the edge of the wire connecting part and the unnecessary portion of wire can be securely removed.

Also, because the outermost surface released part is formed between the wire connecting part and the mounting part, the mounting part and the wire connecting part become separate parts at the outermost surface, thus a residue of coating film which may be formed at the wire connecting part and adheres on the mounting part is further decreased. Also, the mounting part is even more unlikely to be influenced by heat when the wire is connected by thermocompression.

Preferably, the step part is formed between the wire connecting part and the mounting part, and the outermost surface released part is formed between the step part and the wire connecting part. In this case, the outermost surface released part is provided at a position lower than the mounting part along the height direction of the flange. By constituting as such, when the wire wound around the winding core is cut, the wire can be provided as a straight line on the surface of wire connecting part and outermost surface released part, thus the wire can be cut appropriately at the edge of the wire connecting part. Also, a residue of coating film which may be formed at the wire connecting part and adheres on the mounting part is further decreased. Also, the mounting part is even more unlikely to be influenced by heat when the wire is connected by thermocompression.

The flange may have a first area where the wire connecting part is provided and a second area where the mounting part is provided. A step part having a shape which corresponds to the shape of the step part formed to the terminal electrode may be formed between the first area and the second area. Alternatively, a large space which is larger than the space formed between the first area and the wire connecting part of the terminal electrode may be formed between the second area and the mounting part of the terminal electrode. Note that, the first area and the wire connecting part is preferably not adhered, and the second area and the mounting part is preferably not adhered.

Preferably, the terminal electrode further has an installation part formed continuously with the mounting part at a different position from a connecting part of the wire connecting part and the mounting part. The installation part is fixed to an outer surface of the flange by an adhesive and the like. By constituting as such, the wire connecting part and the mounting part of the terminal electrode do not need to be fixed to the flange, and a heat and impact resistance of the coil device after it has been mounted is improved.

Preferably, in the terminal electrode, an area of the wire connecting part is smaller than an area of the mounting part. By constituting as such, a heat capacity of the wire connecting part can be made small in relativity, and the influence of heat to the mounting part when the wire is connected by thermocompression can be made small.

The width of the wire connection part along the axis direction of the winding core is narrower than the width of the mounting part. By constituting as such, the area of the wire connecting part can be made smaller than the area of the mounting part.

Preferably, an exposed surface where the outer circumference face of the flange is exposed is formed between the edge of the wire connecting part at the side closer to the winding core side and the inner face of the flange at the side closer to the winding core. Further preferably, the exposed surface is chamfered. By constituting as such, an angle of the end of the wire contacting the edge of the wire connecting part at the side closer to the winding core can be enlarged, and damage to the end of the wire can be reduced.

One terminal electrode among plurality of terminal electrodes provided to the flange has a wide wire connecting part having wider width than the wire connecting part of other terminal electrodes of the flange. In the wide wire connecting part, ends of two or more wires may be connected by aligning along outer circumference direction of the flange.

The pulse transformer according to the present invention has any one of the coil device mentioned in above.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described based on embodiments shown in the figures.

As shown inFIG.1, the coil device1is a coil component of a surface mounting type used for example as a pulse transformer. The coil device1has a drum core10as a core member of a drum shape, a coil part30, and terminal electrodes51to56.

In the coil device1, an upper face in Z axis direction ofFIG.1is a mounting face when the coil device1is mounted on a substrate and the like. Note that, in the below description, an axis parallel to a coil axis of the coil part30of the coil device1is defined as X-axis, an axis parallel to a height direction of the coil device1is defined as Z-axis, and an axis approximately perpendicular to X-axis and Z-axis is defined as Y-axis.

An external dimension of the coil device1is not particularly limited, and for example it may be X-axis length of 3.0 to 6.0 mm, Y-axis width of 3.0 to 6.0 mm, and Z-axis height of 1.5 to 4.0 mm.

The drum core10has a rod shape portion (a winding core11shown by broken line ofFIG.3andFIG.4) to which the coil part30is wound around, and a pair of flanges12,12provided to both ends of the winding core11in X-axis direction. A cross section shape of the winding core11is approximately square shape in the present embodiment, but it is not particularly limited and it may be other polygonal shape, a circular shape, or an oval shape. As shown inFIG.1, the outer shape of the two flanges12,12are both approximately rectangular parallelepiped shape, but these may have different shape and size against each other.

The drum core10is constituted by a magnetic member, and for example a magnetic material having a relatively high magnetic permeability such as Ni—Zn based ferrite, Mn—Zn based ferrite, or magnetic powder including metal magnetic material and the like.

Two flanges12,12are provided so that these are approximately parallel to each other and predetermined space in X-axis direction is provided between the two flanges12,12. Both ends of the winding core11in X-axis direction are connected to a center part in Y-axis direction of an inner faces13,13of opposing pair of flanges12,12as shown inFIG.3andFIG.4.

As shown inFIG.1, regarding the flanges12,12, first to third terminal electrodes51to53are formed to the mounting face20of one flange12; and fourth to sixth terminal electrodes54to56are formed to the mounting face20of other flange12.

The coil part30is formed to the winding core11of the drum core10. In the present embodiment, the coil part30is constituted by four wires31to34which are wound around the winding core11. The first wire31and the second wire32constitute a primary coil as a pulse transformer, and the third wire33and the fourth wire34constitute a secondary coil. The first wire31and the second wire32forming the primary coil are wound around in opposite direction, and the third wire33and the fourth wire34forming the secondary coil are wound around in opposite direction.

Each end31ato34aand31bto34bof four wires31to34wound around in such manner are connected to the respective terminal electrodes51to56provided to the flanges12,12of the drum core10by thermocompression.

Specifically, one end31aof the first wire31is connected to the first terminal electrode51, one end32aof the second wire32is connected to the second terminal electrode52, and ends33aand34aof the third wire33and the fourth wire34are both connected to the third terminal electrode53.

Also, the other ends31band32bof the first wire31and the second wire32are both connected to the sixth terminal electrode56, and the other end33bof the third wire33is connected to the fifth terminal electrode55, and the other end34bof the fourth terminal electrode34is connected to the fourth terminal electrode54.

The wires31to34are wound around in such manner, and connected to the terminal electrodes51to56. Thereby, the first terminal electrode51and the second terminal electrode52form a primary coil terminal electrode (input terminal); and the fourth terminal electrode54and the fifth terminal electrode55form the secondary coil terminal (output terminal). Also, the third terminal electrode53and the sixth terminal electrode56respectively form a center tap of the primary coil (input) and the secondary coil (output).

Each wire31to34is constituted by a coated conductive wire, and for example a core material made of a conductor having high conductivity such as copper (Cu) and the like is coated with an insulating material made of imide-modified polyurethane and the like, and the outermost surface is further coated with a thin film of resin such as polyester and the like. Note that, the core material and the coating material of the wires31to34are not limited thereto.

Also, a wire size, a number of winding, a method of winding a wire, and a number of layers of wire wound around the coil part30regarding each wire31to34may be determined per each wire depending on demanded properties of the coil device1. In the present embodiment, the wire size and the number of winding of each wire31to34are same, and the wires are wound by forming a pair of wires31and34(or32and34) which are wound around in the same direction, and for example four wires are wound around to form two layers.

As shown inFIG.5, the terminal electrodes51to56are respectively formed by bending the terminal member61of a metal board. The terminal member61is a metal for example copper, copper alloy, and the like, or it is constituted by other conductive board.

As shown inFIG.5, in the present embodiment, each of the terminal electrodes51to56has same size and shape, and each of them has the wire connecting part63, the mounting part65, and the installation part66. Note that, the wire connecting part63provided respectively to the terminal electrodes53and56where ends of two wires are connected may have wider width in Y-axis direction compared to the wire connecting part63of other terminal electrodes51,52,54, and55.

Each of the terminal electrode51to56is formed with the step part64between the wire connecting part63and the mounting part65. The outermost surface released part68is formed between the step part64and the wire connecting part63. The wire connecting part63, the outermost surface released part68, the step part64, and the mounting part65are formed continuously with respective terminal electrodes51to56in X-axis direction in this order which is the order of closer ones from the winding core11. Also, the installation part66is formed continuously by bending the opposite side in X-axis direction of the wire connecting part63from other end of the mounting part65in X-axis direction down along Z-axis direction.

The outermost surface released part (gap)68is a part where Sn layer as the outermost surface of the terminal member61has been released. Sn layer has a high adhesiveness with a solder, thus Sn layer is formed at the outermost surface of the metal material constituting the terminal member61. The outermost surface released part68does not have Sn layer, thus the wire barely bonds with the outermost surface released part68. By providing this outermost surface released part68at the position where the wire being cut and removed could possibly be in contact, the unnecessary wire being cut and removed can be prevented from bonding with the terminal member61.

Therefore, the outermost surface released part68is preferably provided adjacent to the wire connecting part63and along an extending direction of the wire, and in the present embodiment, the outermost surface released part68is formed between the wire connecting part63and the step part64. Note that, in the present embodiment, the outermost surface released part68is formed by releasing the outermost surface of the terminal member61by a mechanical processing, a laser processing, a solvent processing, and the like; and for example, the outermost surface released part68may be formed by not forming Sn layer to the area which becomes the outermost surface released part68of the metal material constituting the terminal member61from the beginning.

A height z1in Z-axis direction of the installation part66is preferably shorter than or same as a height z0in Z-axis direction of the flange12as shown inFIG.4; and z1/z0is preferably 0.2 to 1. As shown inFIG.5, the width in Y-axis direction of the installation part66is preferably wider than or equal to the width y2in axis direction of the mounting part65, and it may be smaller. The width y1in Y-axis direction of the wire connecting part63is about the same as the width y2of the mounting part65in Y-axis direction, and it may be different, and preferably y1/y2is within the range of 0.5 to 2.

Also, the width x2in X-axis direction of the wire connecting part63is shorter than or equal to the width x1in X-axis direction of the mounting part65; and x2/x1is preferably 1/4 to 4/4 and more preferably 1/3 to 3/4. Moreover, the area s1 (not shown in figure) of the wire connecting part63is preferably equal to or less than the area s2 (not shown in figure) of the mounting part65; and s1/s2 is preferably 1/4 to 4/4 and more preferably 1/3 to 3/4.

The X-axis direction length x1of the mounting part65is preferably shorter than the X-axis direction width x0of the mounting face20of the flange12shown inFIG.4; and x1/x0is preferably 1/3 to 2/3. The width x3in X-axis direction of the outermost surface released part68is preferably shorter than the width x2in X-axis direction of the wire connecting part63; and x3/x2is preferably 1/10 to 1/2 and more preferably 2/10 to 4/10.

The wire connecting part63is provided at a higher position by a step height z2in Z-axis direction than the wire connecting part63due to the step part64. The outermost surface released part68is provided at a position lower than the wire connecting part63in Z-axis direction because Sn layer as the outermost surface layer is removed. Since Sn layer is a thin layer of 0.1 to 10 μm or so, the outermost surface released part68is provided at substantially about the same height as the wire connecting part63.

As shown inFIG.5, the width x4in X-axis direction of the step part64is about the same height as the thickness t1of the terminal member61of a metal board, and preferably the width t1is about 1.0 times to 2 times of the thickness t1. As the step part64is formed between the wire connecting part63and the mounting part65, the mounting part65is provided at a position higher than the wire connecting part63in Z-axis direction by a step height z2in Z-axis direction of the step part64. The step height z2of the step part64in Z-axis direction is about the same as the thickness t1of the terminal member61, and preferably the step height z2is about 1.0 times to 2.0 times of the thickness t1. The thickness t1is not particularly limited, and preferably it is 50 to 150 μm.

A total length x5which is the total length of the mounting part65, the step part64, the outermost surface released part68, and the wire connecting part63in X-axis direction is determined in relation with the width x0of the flange12in X-axis direction shown inFIG.4. That is, the total length x5shown inFIG.5is determined so that the exposed surfaces23ato23cwhich expose part of the mounting face20(part of the outer circumference face of the flange12) are formed between the edge67of the wire connecting part63of the terminal electrode at a side closer to the winding core and the inner face of the flange12as shown inFIG.3.

As shown inFIG.1, the mounting face20of the flange12is a flat and smooth surface. Therefore, as shown inFIG.2andFIG.4, a space is formed between the mounting part65of the terminal electrode53and the second area22cof the mounting face20which corresponds to the mounting part65.

As shown inFIG.4, the wire connecting part63is provided by closely contacting against the first area21cof the mounting face20of the flange12. The end34a(33a) of the wire34(33) is connected by thermocompression to the wire connecting part63in later step, thus the wire connecting part63is preferably closely contacting the mounting face20, but it does not necessarily have to be adhered and some degree of space may be formed. A space is preferably formed between the mounting part65and the mounting face20, and by having the space, the mounting part65can be resiliently deformed and the heat and impact resistance can be improved after the coil device1is mounted on the substrate and the like. Also, by having the space, coplanarity of the mounting face of the coil device1can be improved. Note that, the above mentioned description regarding the terminal electrode53usingFIG.2andFIG.4can be applied to other terminal electrodes51to56shown inFIG.1.

As shown inFIG.1, the installation part66of the terminal member61constituting each terminal electrode51to56is bonded to the outer surface14of the flange12by means of adhesion and the like. The mounting part65, the step part64, the outermost surface released part68, and the wire connecting part63of the terminal member61shown inFIG.1are preferably not adhered on the mounting face20and these are movable on the mounting face20which is the upper face of the flange12in Z-axis direction shown inFIG.1.

The wire connecting part63, the outermost surface released part68, and the mounting part68of each terminal electrode51to56is not adhered to the mounting face20of the flange12, thereby coplanarity of the mounting face of the coil device1can be improved. The coil device1can have improved resistance against strain or vibration of the substrate when the coil device1is mounted on the substrate and the like, thus a mounting reliability can be improved.

As shown inFIG.3, when the terminal member61is installed to the flange12, the wire connecting part63and the mounting part65are provided along the coil axis direction (X-axis direction in the present embodiment) of the winding core11; and also the wire connecting part63is provided at a position closer to the winding core11than the mounting part65. That is, the terminal electrodes51to53(54to56) which are all provided along the flange12have the wire connecting part63at a position towards inner side (towards the side closer to the winding core11) of each mounting part65.

When producing the coil device1having such constitution, first the terminal electrodes51to56are provided to the drum core10. Each terminal electrode51to56has the wire connecting part63, the outermost surface released part68, the step face64, and the mounting part65of the terminal member61corresponding to the terminal electrode are provided on the mounting face20; and the installation part66is adhered to the outer face14of the flange12; thereby each terminal electrode51to56is formed.

Note that, a method of forming the terminal electrodes51to56is not limited to a method of installing the terminal member61, and the terminal electrodes51to56may be formed by a baking process, a plating process, and the like of a printed or coated conductive film. Even by such method, the terminal electrode having the wire connecting part63, the step part64, the mounting part64, and the outermost surface released part68can be formed to the mounting face20, and also the exposed surfaces23ato23ccan be formed to the mounting face20.

After the terminal electrodes51to53and54to56are respectively mounted to the flange of the drum core10, then the drum core10is set to a winding machine, and the wires31to34are wound around the winding core11of the drum core10in a predetermined order.

When the wire is wound, the ends31ato34aand31bto34bof the wires31to34are fixed by thermocompressing to the wire connecting part63of each terminal electrode51to56. For example, in order to connect the ends33aand34aof the third wire33and the fourth wire34to the wire connecting part63of the third terminal electrode53, as shown inFIG.6A, while wires33and34are stretched from the winding machine not shown in the figure and placed on the wire connecting part of the third terminal electrode53, a heater H is pressed over the wires33and34and the wire connecting part63, then heated. Note that, a thermocompression of the wire33to the wire connecting part63and a thermocompression of the wire34to the wire connecting part63may be carried out in a separate step.

By carrying out the thermocompression, the coating material of the wires33and34is melted or removed, and the core material of wires33and34as a conductor is exposed, then by thermocompression, the wires33and34are electrically connected to the terminal electrode53. Here, since the outermost surface released part68adjacent to the wire connecting art63is an area where Sn layer on the surface is released, it is unlikely that the wires33and34are bonded to the outermost surface released part68due to heat of the thermocompression. Therefore, the wires33and34are appropriately compressed only to the wire connecting part63of the terminal electrode53.

In the coil device1of the present embodiment, the wire connecting part63of each terminal electrode51to56is provided closer to the coil part30than the mounting part65. At the flange12provided with three terminal electrodes51to53or54to56, the wires may be thermocompressed using one wide heater H to one flange12, or the four wires31to34may be thermocompressed using a single heater and by changing the position of thermocompression.

Also, by using one wide heater, the ends of wires32and34which are wound in the same direction can be thermocompressed at a same time. Therefore, in the coil device1, a step of thermocompressing the ends31ato34aand31bto34bof the wires31to34to the terminal electrodes51to56can be done easily, and also the production machine can be simplified.

After the ends31ato34aand31bto34bof the wires31to34are thermocompressed to the terminal electrodes51to56, the ends31ato34aand31bto34bare cut off at the wire connecting portion. For example, for the third wire33and the fourth wire34thermocompressed to the wire connecting part63of the third terminal electrode53, as shown inFIG.6B, the wires33and34are cut using a wire cutter C which is lowered to the boundary between the wire connecting part63and the outermost surface released part68.

When the wires are cut by a wire cutter, the ends33aand34aof the wires33and34positioned towards inside of the cut portion (towards the side closer to the inner face13of the flange12) is kept thermocompressed to the wire connecting part63of the terminal electrode53. On the other hand, the unnecessary portions33cand34cof the wires which are the portions towards outside from the cut portion are positioned on the outermost surface released part68, thus these are not thermocompressed to the terminal electrode53and appropriately removed.

In the coil device1of the present embodiment, the wire connecting part63and the mounting part65are separate parts at the outermost surface of the terminal electrode, thus when one end of each wire31to34is thermocompressed to the wire connecting part63of respective terminal electrodes51to56, a residue of coating film which may be formed at the wire connecting part63and adheres on the mounting part65is decreased. As a result, when the coil device1is mounted on the circuit board (not shown in figure) and the like, voids and the like in the connecting member such as a solder and the like connecting the substrate and the mounting face63of each of terminal electrodes51to56are decreased, thus cracks are suppressed from forming and a connection reliability improves.

Also, the wire connecting part63and the mounting part65are separate parts of the terminal electrodes51to56at the outermost surface, therefore the mounting part65is unlikely to be influenced by heat when the wire is connected by thermocompression, and Sn layer on the surface of the mounting part65(the layer improving the adhesiveness with the connecting member such as a solder and the like) is unlikely to melt. As a result, when the coil device1is mounted on the substrate and the like, the adhesiveness between the mounting part of each terminal electrode51to56and the connecting member such as a solder and the like is enhanced, thus the bonding strength improves.

Also, the mounting part65is formed continuously to the wire connecting part63at a side away from the winding core11along X-axis direction with respect to the wire connecting part63, thus the wire connecting part63becomes closer to the winding core11, and the length of the wire stretched from the wire connecting part63to the winding core11can be shortened, hence DC internal resistance of the coil device can be lowered (low DCR).

Further, the mounting part65is formed continuously at a side away from the winding core11with respect to the wire connecting part63, thus the wire connecting part63does not protrude out of the flange12in Y-axis direction. Therefore, the coil device1can be made more compact, and also transport and handling of the coil device1becomes easier, and also the handling property can be improved when the coil device1is mounted.

Also, since the mounting part65is formed close to the wire connecting part63via the step part64, even lower DCR can be attained. Further, the wire connecting part63is provided at a position lower than the mounting part65along the height direction (Z-axis direction) of the flange12. Thus, a residue of coating film which may be formed at the wire connecting part63and adheres on the mounting part65is further decreased. Also, the mounting part65is even more unlikely to be influenced by heat when the wire is connected by thermocompression. Further, when the coil device1is mounted on the substrate and the like, it is not the wire connecting part63of the terminal electrode but the mounting part65of the terminal electrode first contacts to the connection part of the substrate, thus the connection strength between the substrate and the mounting part65of each terminal electrode51to56further improves and the connection reliability improves.

Also, the step part64is formed between the wire connecting part63and the mounting part65, thus the step part64has a function to determine the position of the wires31to34when the wires start to wind or to determine the position of cut of the wires31to34after the winding is finished and thermocompression is done, hence the ends of the wires31to34can be cut appropriately. Also, since the step part64is formed, a residue of coating film which may be formed at the wire connecting part63and adheres on the mounting part65is further decreased.

Also, in each of the terminal electrodes51to56, the outermost surface released part68of which Sn layer at the outermost surface of the terminal member61is released is formed between the wire connecting part63and the mounting part65. Thus, when the ends of the wires31to34are thermocompressed and cut at the wire connecting part63, the unnecessary portions of wires (for example,33cand34cshown inFIG.6B) being cut and removed are unlikely to bond with the terminal electrodes51to56which may be caused by heat when the wire is thermocompressed. As a result, the wires31to34are cut appropriately and the unnecessary portions can be removed.

Also, by forming the outermost surface released part68between the wire connecting part63and the mounting part65, the mounting part65is separated from the wire connecting part63at the outermost surface, hence a residue of coating film which may be formed at the wire connecting part63and adheres on the mounting part65is further decreased. Also, the mounting part is even less influenced by heat of connecting the wire by thermocompression.

Also, the outermost surface released part68is provided at a position lower than the mounting part65along the height direction (Z-axis direction) of the flange12, hence when the wires31to34wound around the winding core are cut, the wires31to34can be provided in a straight line at the surface of the wire connecting part63and the outermost surface released part68, the wires31to34can be cut appropriately at end of the wire connecting part63. Also, a residue of coating film which may be formed at the wire connecting part and adheres on the mounting part65is even more decreased. Also, the mounting part is even less influenced from heat when the wire is connected by thermocompression.

Furthermore, in the present embodiment, the exposed surfaces23ato23cexposing the outer circumference face of the flange12are formed between the edge67of the wire connecting part63at a side closer to the winding core and the inner face13of the flange12. The exposed surfaces23ato23care chamfered. By constituting as such, the ends of the wires31to34can contact in a larger angle with the edge67of the wire connecting part63at a side closer to the winding core11(see for exampleFIG.2), thereby damages to the lead ends (leads) of the wires31to34can be reduced.

Note that, the present invention is not limited to the above mentioned embodiments, and various modifications can be done within the scope of the present invention.

For example, in the above mentioned embodiment, the mounting faces20is constituted by a flat and smooth face, however for the first areas21ato21cwhere the wire connecting part63is respectively provided and the second areas22ato22cwhere the mounting part65is respectively provided, the second areas22ato22chaving higher height than the first areas21ato21cmay be formed to the mounting face20. The core step parts are formed between the first areas21ato21cand the second areas22ato22c, and the second areas22ato22care provided at higher position in Z-axis than the first areas21ato21c. The height of the core step parts are about the same as the step height z2of the step part64shown inFIG.5, or it may be even smaller.

In such constitution, the wire connecting part63shown inFIG.5is provided by closely contacting the first area21c(21ato21c), and the mounting part65shown inFIG.5, the mounting part65shown inFIG.5is provided by closely contacting the second area22c(22ato22c). Also, the step part64shown inFIG.5is provided on the core step part.

Note that, even in this constitution, the wire connecting part63does not necessarily have to be adhered on the first area21c(21ato21c), and some degree of space may exist. Also, the mounting part65does not necessarily have to be adhered on the second area22c(22ato22c), and some degree of space may exist.

Preferably, the space between the mounting part65and the second area22cis wider than the space between the wire connecting part63and the first area21cshown inFIG.4. The ends of the wires33and34are thermocompressed to the wire connecting part63in a subsequent step, thus the wire connecting part63and the first area21care preferably in close contact, but it is not a problem if a space exist between the mounting part65and the second area22c. By having a space, the mounting part65can be deformed more resiliently, thus the heat and impact resistance and the like can be improved after the coil device1is mounted on the substrate and the like.

Further, in the above mentioned embodiment, a board shaped core which magnetically connect a pair of flanges12,12is not provided to an opposite face of the mounting face20of the pair of flanges12,12; however a board shaped core may be bonded by adhesion and the like.

Also, in the above mentioned embodiment, the third terminal electrode53and the sixth terminal electrode56are formed as a center tap for input and output respectively, but the center tap may be omitted depending on use. In such case, the third terminal electrode53and the sixth terminal electrode56are not needed and the coil device (pulse transformer) can be constituted by two wires.

Also, in the above mentioned embodiment, the present invention is described as preferable device as a pulse transformer which is used to transfer pulse signal via LAN cable and the like, but the use of the present invention is not limited thereto. For example, the present invention can be used as other coil device such as common mode filter and the like, and also the present invention can be used as any type of electronic component which connects leads of wire to the terminal electrode by thermocompression or method other than thermocompression.

NUMERICAL REFERENCES