GB2525692A - Differential current transformer - Google Patents

Abstract

A differential current transformer comprises a sensor coil 4 having a substantially cylindrical form, and a pair of current conductors having opposite current directions. Said current conductors, when powered, give a substantially balanced magnetic configuration relative to a magnetic neutral axis within the sensor coil core. Said conductors comprise conductive layers in a printed circuit board 61. Each conductor comprises at least a pair of conductive layers. The layers of the conductors are arranged parallel to each other, with both an upper and a lower layer. Layers having identical current flow direction are connected through vias.

Description

DIFFERENTIAL CURRENT TRANSFORMER

The present invention is related to a differential current transformer in accordance with the preamble of claim 1.

S

As widely known differential transformers are commonly used for measuring leakage current. The principle of such measurement is shown in FIGURE 1, giving a transformer which comprises two primary windings, most frequently just a single turn each. The signal developed across a secondary winding is proportional to the difference between the before said single turn primaries, thus giving the differential' reference.

To explain and to illustrate the well-known principles and basics of dividing current flow and differential current transformer functions as mentioned above there is referred to FIGURES 1, 2, 3 and 4. In these FIGURES the same numbers present the same issues or parts.

In FIGURE 1 schematically a usual differential current transformer is shown, with a load or appliance 1 under test, a power source 2, and the measuring differential transformer 3 with schematically coil and inside core 4, and the curent wires 5 a, b, c for respectively live current Sa, for neutral current Sb, and for earth Sc. It might be clear to those skilled in the art that this view is taken at a certain moment in time and thus presents opposite current directions for live 5a and neutral Sb, presented by according arrows. In this schematic FIGURE 1 the plane of the coil with inside core is thought perpendicular to the wires 5, whereas the wires are thought to be parallel to the coil axis, and thus to be considered an axis of a cylinder.

In FIGURE 2A a view along the wires 5a, b upon the coil plane, and in FIGURE 2B a suchlike view of a coaxial cable 50, are presented.

As shown in particular in FIGURE 2A the wires Sa, b are not positioned symmetrical so that resulting magnetic field lines 40 accordingly are divided not equally in the coil with inside core 4.

In FIGURE 2B the coaxial cable 50 on the contrary gives a highly equally divided magnetic field lines 41, even when cable 50 is not positioned in the cylinder center of the coil.

In FIGURES 3A, B schematically electrics for measurement situation within such differential current transformer coil core are presented. In FIGURE 3A the 5a, b current wires are shown in most schematic form, giving load 1 and current wire resistances respectively RI and R2 which resistances are positioned within said coil 4. The situation confronted with almost always comprises a system of sub-conductors, for example because of slightly different connection situation, as there are amounts of solder, location of connection spots, etcetera, which is immediately clear to those skilled in the art. Therefore in FIGURE 3B a first approximation is shown with parallel split up of Ri and R2, giving respectively RI 1, R12, and R21, R22, and thus providing a balanced situationwithRll Ri2 andR2I R22.

This type of measurement provides a high resolution differential measurement of AC currents. However, its performance is highly dependent on the position of the turns or wires when passing the secondary winding. To have a suitable positioning is difficult and expensive to achieve, As generally known in the past good quality magnetic secondary core material and/or coaxial primaries have appeared advantageous.

The above shows that positioning of the primaries is of high interest to have a zero' -difference, i.e. the effect that the magnetic fields originating from each primary cancel to a large degree.

As to improving accuracy of measurement the following references might be of interest.

In US6184672 specific measures have been taken as regards the secondary winding whereas a symmetrical positioning of the primaries is arranged, n US6400130 shown a common setup with primary windings having opposite current directions. The primary windings are positioned within the secondary winding functioning as sensor coil in a symmetrical way.

S For arriving at reliable measurements in low current electronic devices for the primary winding output connections V -shaped configurations are shown.

Hereinafter amongst other things the application of PCB layers is explained, In order to employ its features as dear as possible reference is made to FIGURE 4 thereby defining and setting geometrical and electrical characteristics of conductor layers as arranged on such PCB.

In FIGURE 4 schematically an isometric view of a part of a PCB layer P is shown as a dotted block. In particular by using such doffing the block as shown should be considered a part of such a PCB layer. For ease, as may be clear from this FIGURE 4, said PCB layer P is designed as a block, having all rectangles between its planes, In this FIGURE 4 on'y layer P is shown, according'y having an upper plane PlO and a lower plane P1 i, More in particular conductor layers or strips SlO, SI], S20, S21, S30, S31 have been shown, As clearly shown in FIGURE 4 said strips are presented as couples or pairs, a first couple SI 0-Si, a second couple S20-S2], and a third couple S30-S3], The geometrical structure of each couple or pair is such that they form a cuboid C, in FIGURE 4 specifically CI, CII, and CIII, More in detail cuboid CI has vertices d -c4 for the upper strip Sb, and has vertices cS -c8 for the lower strip Sli.

As shown the conductor layers are hatched with dotted lines at their distal end to illustrate again that it is schematic and is considered to give only a part of each such strip.

Generally for such conductor layers or strips S, Cu as conductor material is applied.

Furthermore for the cuboids CII and CIII directions of currents I have been shown. For two cuboids CII and CIII specific current directions in their corresponding conductor layers, respectively the pairs S20-S21 and S30-S3I, are shown.

As can be seen, for the cuboid CII the currents 120 and 121 are parallel, having between their directions an angle of 00, whereas for the cuboid CIII the respective currents 130 and 131 are mutually opposite, having between their directions an angle of 180°.

Hereinafter having such 0-angle combination there is referred to as 0-layers of aD-cuboid, whereas for an 180 -angle combination there is referred to as 180 -layers of a 180-cuboid, In further explanatory drawings instead of I -arrows and/or shading are applied.

Consequently a black couple or a grey couple represent a 0 -cuboid whereas a black -grey couple is considered a 180 -cuboid.

As well known to those skilled in the art all such strips on such a PCB layer are connected through very little holes in said layer, so-called vias. Consequently 180 -layers are connected through 180 -vias and 0 -layers are connected through 0 -vias.

In order to substantially improve and simplify manufacturing of the differential transformer, the transformer of the present invention is characterized in that, said conductors are flat layered and are conductive layers in a printed circuit board (PCB) which are connected through vias, each said conductor comprises at least a pair of PCB current conductors, thereby obtaining pairs of opposite current direction layers (i80 -layers) and pairs of same current direction layers (0 -layers), wherein each layer of said pair of current conductors is arranged as an upper and as a lower layer of mainly a cuboid, wherein all said layers and said directions are parallel both with each other and with said central cylinder axis, and wherein at either side of said coil said 180 -layers are electrically connected through -vias and said 0 -layers are electrically connected through 0 -vias, thereby obtaining a mainly symmetrical current sharing for each of said current directions resulting in said balanced configuration.

It has appeared very suitable to have such configuration, guided by the principle of dividing current flow of primaries, the live and the neutral, in such a way that highly equal current sharing is obtained, and consequently highly reliable measurements result.

More in particular both current division within the PCB and connections of layer currents at the PCB interface is achieved by the present invention.

In some more detail it is observed that by replacing the primary wires by PCB layered conductors positioning of such layers in a PCB can be made highly similar to coaxial positioning.

Moreover processing PCB's result in low cost parts manufacturing. In view of the wide application now days, and to be expected for the future in communication devices and house hold apparatus, costs can be reduced substantially.

With the present highly accurate measurement device comprising such PCB configurations suitable size reduction is obtained as well.

Further embodiments of the present invention are characterized in that, said cuboid comprises at least a pair of 180 -layers and at least a pair of 0 -layers, giving respectively a 180 -cuboid and a 0-cuboid; at least two 180 -cuboids are arranged on top of each other thereby obtaining a 0 -cuboid in between; said cuboids are arranged in at least a four layer PCB; said PCB comprises at least two 0 -cuboids layers, with each layer having an odd number of 0 -cuboids, and with per layer having 0 -cuboids with different current direction arranged side by side and every other one; said PCB comprises at least two 0 -cuboids, with one 0 -cuboid enveloping the at least one second 0 -cuboid and having different current directions; said PCB comprises a second 0 -cuboid, enveloping said at least one second 0 -cuboid and having conductor layers perpendicular to the at least two 0 -cuboid conductor layers; said vias provide parallel electrical connections from and to said PCB, respectively from and to a load and from and to a power supply; said PCB comprises electrical connecting pads arranged at distal ends of said PCB; and said connecting pads comprise a substantial width thereby lowering electrical connection resistance.

In view of all the above the differential current transformer of the present invention will be explained in more detail, thereby referring to the above FIGURES 1, 2, 3, and 4 as a first reference of principles and basics, and to further FIGURES 5 -10, with FIGURES 5 giving all together real situation views of an embodiment of the invention, both as applied and used for experiments, with in more detail for FIGURE SA as a schematic isometric view on an embodiment ofa PCB as applied in accordance with the present invention, and the FIGURES SB, C presenting schematic views along a coil transformer cylinder axis of two different PCB layer embodiments, with FIGURE 6 giving in detail a cross section through and thus an along view of a suchlike FIGURE SB PCB embodiment, with FIGURE 7 giving in detail a cross section through and thus an along view of a suchlike FIGURE SC PCB embodiment, with FIGURE 8 giving in detail a further embodiment of a cross section through and thus an along view which is very similar to the FIGURE SB PCB embodiment, with FIGURES 9A, B giving yet further embodiments ofthe present invention and close to the embodiment of FIGURE 7, with FIGURES IOA, B embodiments of similar current sharing circuitry as already shown in FIGURES 3A, B, and S with FIGURES 1 1A, B showing an embodiment of a PCB, more in particular showing the spatial structure of layers and their connections of said PCB.

Also for these FIGURES the same numbers represent the same issues and parts.

In FIGURE SA a schematic isometric view of a differential current transformer in accordance with the present invention is shown. More in particular a PCB 6 having an extension 6a is arranged with the core 4 with coil 4a. Thus this extension 6a together with the core -coil 4-4a form the differential transformer 3. In this embodiment vias are guided such that the current wires for life Sa, fore neutral Sb, and for earth Sc are all connected with electrical connection holes, respectively for live 7a, for neutral 7b, and for earth 7c. Hereinafter such connections will be explained in more detail thereby referring to specific PCB layers with PCB layer conductors.

In FIGURES SB, C schematic views along a coil transformer cylinder axis of two different PCB layer embodiments are shown. It is noted that these views are positioned in a section plane which is perpendicular to the cylinder axis and through the coil -core 4a -4 combination.

In FIGURE SB a digital presentation of a PCB 61, when powered, in accordance with the present invention is shown. In particular 3 groups of pairs of conductor layers which will be specified hereinafter as to FIGURE 6 are applied. Obviously magnetic field lines 62 in the core 4 resulting from this arrangement are far more suitable than those as shown hereinabove as to FIGURE 2A. It is striking that, although this PCB 61 is not positioned exactly in the middle of the core -coil 4-4a, this arrangement already gives a far more equal pattern in the core 4.

In FIGURE SC a suchlike digital presentation of a PCB 63, when powered, in accordance with the present invention is shown. In particular 2 pairs of conductor layers which will be specified hereinafter as to FIGURE 7 are applied. Obviously field lines 64 in the core 4 resulting from this arrangement are far more suitable than those as shown hereinabove as to FIGURE 2K It is even more striking that, although also this PCB 63 is not positioned exactly in the middle of the core -coil 4-4a, this arrangement S gives an almost ideal pattern of fully equally positioned field lines 64 in the core 4, In FIGURE 6 in detail the PCB 61 as mentioned before is shown in detail in cross section, thus having a view along the cylinder axis of the surrounding transformer 3 which for ease of explanation is not shown. For having for all the FIGURES 6 -9 showing PCB's in detail the same terminology, the foflowing is applied.

Three PCB layers are presented in light grey shading. As known to those skilled in the art such PCB layers are made of so-called FR4' matter, which is very usual in this field of technology. The outer layer planes are usually used for depositing copper layers as conductors, whereas such layers are stacked and connected by means of so-called pre-preg' material which is very usual as well, in the drawings being unshaded.

In this FIGURE 6 in total six 0-cuboids 600, 601,610, 611, 620, 621 are applied. More in particular by means of shading it is expressed that these cuboids each have layers with currents in the same direction, i.e. the four dark grey cuboids 600, 601, 620, 621, and the two black cuboids 610,611. Furthermore the current directions between these two groups, i.e. the grey ones and the black ones, are opposite, and thus the grey versus the black.

The way of application of materials as referred to above, i.e. the FR4 and the pre-preg is self-evident. For this FIGURE 6 one can say that three PCB layers are stocked and connected, whereas only four PCB planes are applied for depositing conductor layers.

As well known to those skilled in the art it might be clear that distances between copper layers, both within plane (in this FIGURE 6 horizontal') and between planes (in this FIGTJRE 6 vertical') are applied and predetermined in accordance with specific use of such a differential current transformer, More in detail and as well known to those skilled in the art such specific use depends on voltages and currents applied and considered to be processed by such device.

Having the set-up of this FIGURE 6 there will be referred as to this set-up as having S two 0 -cuboid layers, with each layer having all odd number of 0 -cuboids, i.e. the one layer having the 0 -cuboids 600, 610, 620, and the other layer having the 0 -cuboids 601, 611, 621. As regards current directions, the above-mentioned grey and black, in each layer the side 0-cuboids 600, 620, 601, 621 have the opposite current direction of the middle 0-cuboids 610, 6L1, thus obtaining so-called alternating 0-cuboids in each cuboid layer.

As referred to hereinabove the pattern of field lines of this set-up is the one of FIGURE 5B.

Having this set-up, for a skilled person it might be clear that different designs are possible as well, thus for example, and not limited thereto, having per layer of conductors an odd number of layers, and/or choosing different widths, and or applying well determined ratio's for the widths between neighbouring cuboids, thereby obtaining advantageous symmetry.

In FIGURE 7 another embodiment for a three layer PCB in accordance with the present invention is shown, The choice of materials, presented in shading as was done in FIGURE 6, is the same as shown in FIGURE 6.

However the way of arranging 180-layers and according 180-cuboids at the one side, and arranging 0 -layers and according 0-cuboids, is very different from the previous embodiments. Whereas in FIGURE 6 only four PCB planes were deposited with conductor layers, in this embodiment six planes were deposited, having no in-between distances within such a conductor layer, being the layers of three cuboids 700a, b, 710, and7ii.

In particular it can be seen by the shading that two 0 -cuboids were arranged in-between the third 0 -cuboid, thus giving a "180" structure as well. Furthermore the widths of the in-between cuboids 7102 711 is slightly smaller than the width of the layers of the third cuboid 700a, b.

As referred to hereinabove this FIGURE 7 has appeared to have a pattern of field lines as shown in FIGURE SC. It might be clear that this field is very close to the field pattern of a coaxial cable which in this field of technology is considered almost ideal, Also for this set-up sizes might be chosen in accordance with the application aimed at.

In FIGURE 8 another embodiment is shown which looks to some extent similar to the one of FIGURE 6, However, whereas also 6 cuboids 800, 810, 820, 830, 840, 850, are arranged now only two PCB layers are applied, thus 3 cuboids per layer, whereas such layers are stocked and connected in a different way thereby having the pre-preg in the middle and at both sides. Electrically each said cuboid is a 0 -cuboid as defined hereinabove, whereas the dark grey and black alternate per layer and between layers, As can be seen in this FIGURE 8, in the upper layer cuboids 800 and 820 are at the sides are presented in grey, whereas in-between a black one 810 is arranged, and in the lower layer the reversed arrangement is applied with two black cuboids 830, 850 at the sides, and a grey cuboid 840 in-between, Furthermore in this design the widths of the middle ones 810, 840 is wider than the side ones 800, 820, 830, 850, As explained with reference to FIGURE 6 also in FIGURE 8 two 0 -cuboid layers are comprised, each having an odd number of 0-cuboids, the one layer with 0 -cuboids 800, 810, 820, and the other layer with 0-cuboids 830, 840, 850. Also in this set-up in each layer an alternating sequence is obtained, side by side and every other one, however now having the alternating effect also between the layers.

In FIGURES 9A, B yet another embodiment is shown, closely related to the one as described with reference to FIGURE 7. Whereas in this FIGURE 9A design again three ii layers with three cuboids 900-901, 920, 930 are applied, additional to that the PCB sides are connected and covered with conductor layers 910, 911, thereby obtaining a fourth 0-cuboid 910-911.

This design having such 0 -cuboids 900-901, 910-9iiwith both the same current direction, presented as red, and the 0-cuboids 920, 930 arranged in the middle and thereby having been enveloped, is very similar to the coaxial cable set-up. As shown in this FIGURE 9A the layers 910, 911 are perpendicular to all other layers 900, 901, and those of the cuboids 920, 930. It might be clear to those skilled in the art that the field line pattern resulting from this FIGURE 9A set-up is a further advantageous improvement over the FIGURE 7 set-up.

In FIGURE 9B a highly similar set-up is applied, having the same enveloping 0 -cuboids 900-90 1, 910-911, with middle cuboids 940, 950, now having slightly modified conductor layer widths, thereby obtaining further similarity with the coaxial cable set-up as described hereinabove with regard to FIGURE 2B. As shown in this FIGURE 9B the layers 910, 911 are perpendicular to all other layers 900, 9W, and those of the cuboids 940, 950. It might be clear to those skilled in the art that the field line pattern resulting from this FIGURE 9B set-up, being a further advantageous improvement over the FIGURE 7 set-up, is a yet further improvement.

In FIGURES bA, B further details as to current sharing are shown, In particular these FIGURES refer to the set-up somewhat similar with the set-up for example FIGURE 7 having two 0 -cuboids sandwiched between a third 0 -cuboid with upper and lower conductor layers. As shown in FIGURE bOA the side current live wire Sa is divided over two resistances RI I and RU, whereas in-between neutral current wire Sb is divided over layers having resistances R21, R22. In FIGURE lOB the FIGURE bOA scheme is simplified thereby replacing the R2i-R22 parallel resistance by R2.

It might be clear to those skilled in the art that in each RI I, R12, R2 I, and R22 branch further series resistances representing the vias resistances can be comprised, thereby giving a further advantageous parallel resistance replacement calculation effect. This means that further distribution of currents will improve the field patterns substantially towards the coaxial cable design.

In order to explain arrangements and functions of said vias in more detail, in FIGURES t IA, B an embodiment of a PCB having a spatial structure of layers and connections is shown. Especially in FIGURES hA, B isometric views of a part of a PCB 60 are shown, a real picture of such PCB 60 in FIGURE 1 IA, whereas FIGURE 1 lB shows only an arrangement of conductor layers of said PCB 60, highly schematically in detail, i.e. digitized and enlarged. More in particular, for reason of clarity vertical distances in FIGURE 1 lB are enlarged substantially compared to real ones in the PCB 60 of FIGURE 1 IA. The part of the PCB 60 as shown in these FIGURES t tA, B is quite comparable with the part as shown in FIGURE 5A. Where in FIGURE SA the extension 6a has the function of carrying conductor layers for electrically connection and for mechanically supporting the coil 4a with core 4, a suchlike extension 16 is shown in FIGURE 11A.

In FIGURE HA only details of an upper conductor layer 16] are shown, comprising from left to right three parts 161 a, b, c. Said parts are electrically separated and resulting from manufacture by etching as well known in this field of technology.

Accordingly in FIGURE 1 lB further four conductor layers inside said PCB 60 are numbered 162, 163, 64, 165, with a further outer conductor layer 166 underneath, For the layers 162 -t65 geometrically only two separate parts are comprised, accordingly numbered 162 a, b, 163 a, b, 164 a, b, and 165 a, b.

For said plurality of conductor layers 161 -166 said conductor layer parts are connected in such a way that the main conductor layer parts 161 b, 166 b ofthe two outer conductor layers 161, 166 form for example the live in this differential current transformer device, whereas the main conductor layer parts t 62 a, t 63 a, 164 a, 165 a, of the conductor layers 162 -165, in-between the conductor layers 161, 166, consequently form the neutral of this differential current transformer device, As can be recognized easily this set-up corresponds with the conductor layer arrangement of FIGURE 7. In I 3

In accordance with FIGURES 3A, B showing live and neutral divided in such a way that electrical circuitry results comprising both a parallel split up, in the same way conductor layers 161, 166 at the one side, and 162-165 at the other side, are split up and mutually connected. In particular such connections are accomplished through so-called vias, in this field of technology defined as plated connecting holes arranged in a corresponding conductor layer.

In order to connect the upper and lower conductor layers 161, 166, holes are arranged in the conductor layers 161 -166, which holes are numbered 1620-1650. Within said holes 1620 -1650 conductor layer parts 162 b -165 b, like islands within said holes, are arranged, resulting again from etching.

As can be seen, for connecting purposes little holes and big holes are arranged at mainly the ends of the live conductor layers 161, 166, and the ends of the neutral conductor layers 162-165. In accordance with their left-right locations said holes are numbered, fortheouterconductorlayers 1611, 1612, 1613, 1614, 1661, 1662, 1663, 1664,andfor the conductorlayers in-between 1621,1622,1624,1631, 632, 1634, Th41, 1642,1644, 1651, 1652, 1654. Because each group of holes has small holes and one large hole, said holes are typified accordingly 1621 a, 1621 b, etcetera.

In FIGURE II B vertically extending thin connecting wires are shown, numbered from left to right, 171, 172, 173, 174, Referring to FIGURE 5A where the large or thick wires 5a -Sc are shown to be connected to such PCB 6, whereas in FIGURE JIB only large holes 1611b-1661b, 1612a-1662b, 1613b-1663b, 1614b-l664bareshown.Itwill be clear to those skilled in the art that small wires and thick wires are connecting the conductor layers they are aimed for and guided to, wherein such electrically connecting is accomplished by well-known via connecting technology. In particular this means that in a suchlike group of thin wires 171 each wire is electrically connected to each layer, and the same is said for a thick wire.

For a skilled person it will be clear that live and neutral may be reversed in this explanation.

Furthermore specific choices of materials and sizes are mentioned although they will be clear to those skilled in the art. For example an advantageous material for a core is ferrite which is applied in the embodiments of the present invention as well. As regards widths for example the via connection holes may vary suitable between 0.01 and 10 mm for their diameters.

For every skilled person it will be clear that minor variations and modifications as to the embodiments described hereinabove are considered to be comprised in the scope of the appending claims.

Claims (9)

1. Claims 1. Differential current transformer, comprising, -a sensor coil and core of mainly cylindrical form and having a central cylinder axis, -a pair of current conductors mainly parallel to said axis and having opposite current directions, wherein said pair of conductors and said coil are arranged respectively as first primary coil conductor and as secondary coil conductor, and wherein said pair of conductors, when powered, give a substantially balanced magnetic configuration relative to a magnetic neutral axis within said sensor coil core, characterized in that, said conductors are flat layered and are conductive layers in a printed circuit board (PCB) which are connected through vias, each said conductor comprises at least a pair of PCB current conductors, thereby obtaining pairs of opposite current direction layers (180 -layers) and pairs of same current direction layers (0 -layers), wherein each layer of said pair of current conductors is arranged as an upper and as a lower layer of mainly a cuboid, wherein all said layers and said directions are parallel both with each other and with said central cylinder axis, and wherein at either side of said coil said 180 -layers are electrically connected through 180-vias and said 0-layers are electrically connected through 0 -vias, thereby obtaining a mainly symmetrical current sharing for each of said current directions resulting in said balanced configuration.
2. 2. Differential current transformer of claim I, characterized in that, said cuboid comprises at least a pair of 180-layers and at least a pair of 0-layers, giving respectively a t80 -cuboid and a 0 -cuboid.
3. 3. Differential current transformer of claim t, characterized in that, at least two 180 -cuboids are arranged on top of each other thereby obtaining a 0 -cuboid in between.
4. 4. Differential current transformer of claim 2 or 3, characterized in that, said cuboids are arranged in at least a four layer PCB.
5. 5. Differential current transformer of claims 2 and 4, characterized in that, said PCB comprises at least two 0 -cuboids layers, with each layer having an odd number of 0 -cuboids, and with per layer having 0 -cuboids with different current direction arranged side by side and every other one.
6. 6. Differential current transformer of claim 2 and 4, characterized in that, said PCB comprises at least two 0 -cuboids, with one 0 -cuboid enveloping the at least one second 0 -cuboid and having different current directions.
7. 7. Differential current transformer of claim 6, characterized in that, said PCB comprises a second 0-cuboid, enveloping said at least one second 0 -cuboid and having conductor layers perpendicular to the at least two 0 -cuboid conductor layers.
8. 8. Differential current transformer in accordance with anyone of the claims -7, characterized in that, said vias provide parallel electrical connections from and to said PCB, respectively from and to a load and from and to a power supply.
9. 9. Differential current transformer of claim 8, characterized in that, said PCB comprises electrical connecting pads arranged at distal ends of said PCB.tO. Differential current transformer of claim 9, characterized in that, said connecting pads comprise a substantial width thereby lowering electrical connection resistance.