SE2230148A1 - Flexible PCB adapted for catheter with preferred direction of bending - Google Patents

Abstract

The invention relates to an elongated FPC (1) comprising a set of conductors (s2a1-2, 2b1-2) extending in the direction of the elongated FPC (1). The set of conductors (s2a1-2, 2b1-2) is divided into four consecutive subsets of conductors (s2a1-2, 2b1-2). The total degree of adaptation to bending in the plane of the flat FPC (1) of the first and third subsets of conductors (s2a1-2, 2b 1-2) is different from the total degree of adaptation to bending in the plane of the flat FPC (1) of the second and fourth subsets of conductors (s2a1-2, 2b1-2). This gives a catheter comprising such an FPC rolled into a tubular shape an adaptation to a preferred bending direction.In an embodiment of the invention, at least one of the conductors (s2a1-2, 2b1-2) is meandering. The average meandering amplitude of the first and third subsets of conductors (2b1-2) is different from average meandering amplitude of the second and fourth subsets of conductors (s2a1-2).In a further embodiment of the invention, the total width of the first and third subsets of conductors (2b1-2) is different from the total width of the second and fourth subsets of conductors (s2a1-2).

Description

The present invention relates to a flexible and stretchable PCB (FPC) for arranging in a tubular shape adapted for a catheter having a preferred direction of bending according to the introductory portion of the independent claím. Background of the invention Catheters are commonly nearly fully circularly symmetrical and may bend in any direction. For certain applications, it may be advantageous if catheters and catheter like component have a preferred bending direction, such that it naturally does not tend to bend in a direction opposite the preferred bending direction. This is in catheters known in the art achieved by adding mechanical elements to the catheter that gives it a preferred bending direction. Using an FPC for arranging in a tubular shape with such a catheter will preferably put strain on conductors in the FPC arranged in the bending plane of the catheter, so these conductors suffer an elevated risk of breaking.

US2019l51616Al, US5304l3lA and US6102886A all disclose catheters with additional elements comprising a set of slits, giving the catheter a preferred bending direction.

EP3653254Al discloses a catheter With an additional central plane element, giving the catheter a preferred bending direction out of the plane of theplane element An object of the invention is therefore to provide an FPC for arranging in a tubular shape having an adaptation to a preferred direction of bending. The adaptation may be constituted by a tolerance to bending in a given bending direction, reducing the risk of conductors breaking. The adaptation may also be constituted by a preferred direction of bending which require no additional elements for achieving this preferred direction of bending. The adaptation may further be constituted by both a tolerance to bending in a given bending direction and by a preference for a preferred direction of bending.

These and other objects are attained by an FPC for arranging in a tubular shape and adapted for an adaptation to a preferred direction of bending according to the characterising portions of the independent claims.

Summary of the ínvention The invention relates to an elongated FPC (1) formed into a tubular shape, where the elongated FPC (1) at least comprises a set of conductors s2al-2, 2bl-2 primarily extending in the direction of the elongated FPC 1. The conductors s2a1-2, 2bl-2 have a resistance to bending in the plane of the flat FPC 1. The set of conductors s2a1-2, 2b1-2 is divided into four consecutive subsets of conductors s2a1-2, 2b1-2. The first and third subsets of conductors (2b1-2) are arranged on opposite sides of the tubularly shaped FPC (1) and the second and fourth subsets of conductors (s2a1-2) are arranged on opposite sides of the tubularly shaped FPC (1). The total resistance to bending in the plane of the flat FPC 1 of the first and third subsets of conductors 2b1-2 is different from the total resistance to bending in the plane of the flat FPC 1 of the second and fourth subsets of conductors s2a1-2. This advantageously gives a catheter comprising such an FPC rolled into a tubular shape an adaptation to a preferred bending direction.

In an advantageous embodiment of the ínvention, at least one of the conductors s2a1-2, 2b1-2 is meandering. The average meandering amplitude of the first and third subsets of conductors 2b1- 2 is different from average meandering amplitude of the second and fourth subsets of conductors s2al-2.This advantageously primarily gives a catheter comprising such an FPC an adaptation to bending in a given bending direction, which obviously should be equivalent to a preferred bending direction.

In a further advantageous embodiment of the ínvention, the total width of the first and third subsets of conductors 2b1-2 is different from the total width of the second and fourth subsets of conductors s2al-2. This advantageously primarily gives a catheter comprising such an FPC a preferred bending direction.

Brief description of the drawings Fig. 1 shows a first embodiment of an FPC according to the ínvention rolled into a tubular shape Fig. 2 shows the first embodiment of the FPC according to the ínvention in a flat state Fig. 3 shows a second embodiment of an FPC according to the inventionin a flat state Fig. 4 shows a third embodiment of an FPC according to the inventionin a flat state Fig. 5 shows a fourth embodiment of an FPC according to the inventionin a flat state Description of preferred embodiments Catheters are commonly nearly fully circularly symmetrical and may bend in any direction. For certain applications, it may be advantageous if catheters and catheter like component have a preferred bending direction, such that it naturally does not tend to bend in a direction opposite the preferred bending direction. This is in catheters known in the art typically achieved by adding mechanical elements to the catheter that gives it a preferred bending direction. Adding an additional component increases the cost and size of the catheter, so achieving the same result by designing electrical conductors in the catheter in such a manner that it gives the catheter a preferred bending direction is advantageous, reducing the need for additional mechanical components and not adding to the size. Using an FPC for arranging in a tubular shape with such a catheter will preferably put strain on conductors in the FPC arranged in the bending plane of the catheter, so these conductors suffer an elevated risk of breaking.

The embodiments demonstrate an adaptation to a preferred bending direction and/or a tolerance to a preferred bending direction, where each embodiment has a degree of preference for a preferred bending direction and a degree of tolerance to a given bending direction. The proportions between the degree of preference and the degree of tolerance varies from embodiment to embodiment, so generally the degree of preference and the degree of tolerance is here jointly denoted adaptation to a preferred bending direction. In an extreme case, the adaptation may be constituted exclusively by a degree of tolerance to a preferred bending direction, and then the preferred bending direction is generated by other elements in the catheter, extemal to the FPC itself.

A good way of achieving a tolerance to a preferred bending direction and/or a preference for preferred bending direction is by producing elongated rectangular flexible and stretchable circuit boards, FBCs, with a set of conductors extending along the long axis of the FPC and rolling the FPC into a tubular shape. Fig. l shows such an FPC primarily with a preferred bending direction rolled into a tubular shape. The conductors can be arranged in a number of different ways, achieving the preferred bending direction in the FPC rolled into a tubular shape, and figs 2-5 illustrates four examples of how the conductors may be arranged. 3 Obviously, the FPC rolled into a tubular shape would have to be fixed into such a tubular shape, using reheating the FPC, using an adhesive or in some other way. The FPC may of course in addition to the conductors extending along the long axis of the FPC comprise other conductor components such as electrodes or active electronic components, but these or not illustrated. The FPC fixed in a tubular shape may itself constitute a catheter, but it may alternatively constitute only a component in a catheter and be affixed to other elongate elements in the catheter, but this is not illustrated here.

Fig. 1 shows a first embodiment of an FPC 1 according to the invention rolled into a tubular shape, forming a tube. The FPC 1 is provided with a set of conductors 2a1-2, 2b1 of varying widths. The widest conductors are arranged on what in the figure is the top and the bottom of the tube, that is the furthest from the centre of the tube in the direction of the x-axis illustrated. The narrowest conductors are arranged on what in the figure is side of the tube facing the viewer and on the opposite side, not seen in the figure, that is the furthest from the centre of the tube in the direction of the y-axis illustrated.

The conductors are typically thinner than their width, and this is more pronounced for the wider conductors. They are therefore easier to bend out of the plane in which they extend that in the plane they extend, and this is more pronounced the wider they are. With the widest conductors on the top and bottom of the tube, the tube may much more easily be bent upwards and downward, that is along the x-axis, than sideways, that is along the y-axis. The preferred bending direction of the tube is thus along the x-axis.

Fig. 2 shows the first embodiment of the FPC1 according to the invention in a flat state. Here, it is clearly seen that the set of conductors 2a1-2, 2b1-2 can be subdivided into four bands with a first set of narrower conductors 2b1, followed by a first set of wider conductors 2a1, followed by a second set of narrower conductors 2b2, finally followed by a second set of wider conductors 2a2. On a more detailed level, the distribution of widths nearly adheres to a continuous periodical curve with a wavelength corresponding to half the width of the FPC, in tum corresponding to the circumference of the FPC rolled into a tubular form.

As the FPC is rolled into a tubular form, the two sets of conductors 2a1-2 with the largest width end up on opposite sides of the tube, while two sets of conductors 2bl-2 with the narrowest width end up on opposite sides of the tube, with each two consecutive sets of narrow and wide conductors shifted 90 degrees apart.

Fig. 3 shows a second embodiment of an FPC primarily with a preferred bending direction according to the invention in a flat state. Here, instead of conductors of varying widths as in the first embodiment, each conductor is of equal width, but they are instead arranged with a varying density, so nearer or more distantly to the adjacent conductors.

The figure clearly shows that the set of conductors 2a1-Z, 2bl-2 can be subdivided into four bands with a first set of conductors Zblspaced apartmore distantly, followed by a first set of conductors 2a1 densely spaced, followed by a second set of conductors 2b2 spaced apart more distantly, finally followed by a second set of conductors 2a2 densely spaced. Like in the first embodiment, the distribution of conductor density nearly adheres to a continuous periodical curve with a wavelength corresponding to half the width of the FPC, in tum corresponding to the circumference of the FPC rolled into a tubular form.

Fig. 4 shows a third embodiment of an FPC primarily with a preferred bending direction according to the invention in a flat state. Here, contrary to the first and second embodiments, the conductors are meandering. As the catheter is bent, conductors on one side of the catheter is drawn out while conductors on the opposite side are contracted, and this may cause conductors to break. Meandering conductors are more tolerant to this contraction or expansion, so using meandering conductors a catheter which allows a higher degree of bending than what is possible for catheters with straight conductors is achieved.

All conductors are of the same width and meanders with the same amplitude. The meanders occur in phase, such that the troughs of adj acent conductors are aligned and the peaks of adjacent conductors are aligned. This advantageously means that conductors may be arranged as densely as conductors with straight conductors, such as in the second embodiment.

Just like in the second embodiment, the figure clearly shows that the set of meandering conductors 2a1-2, 2bl-2 can be subdivided into four bands with a first set of meandering conductors 2bl spaced apart more distantly, followed by a first set of meandering conductors 2a1 densely spaced, followed by a second set of meandering conductors 2b2 spaced apart more distantly, finally followed by a second set of meandering conductors 2a2 densely spaced. Like in the second embodiment, the distribution of conductor density nearly adheres to a continuous periodical curve with a wavelength corresponding to half the width of the FPC, in tum corresponding to the circumference of the FPC rolled into a tubular form.

Fig. 5 shows a fourth embodiment of an FPC with primarily with a particular tolerance to bending in the preferred bending direction coinciding with a preferred bending direction according to the invention in a flat state. Here, just like the third embodiment, the conductors are meandering, but they are meandering with varying amplitude.

While meandering conductors meandering with a low amplitude have a lower tolerance against lengthwise extension of the conductors, meandering conductors meandering with a higher amplitude have a higher tolerance against lengthwise extension of the conductors. This in turn gives a corresponding higher and lower tolerance to bending, as bending generates such an extension of the conductors that varies radially. The reason for the varying tolerance to bending of a meandering conductor is its varying effective length, conductors meandering with a higher amplitude giving opportunity for more slack.This is what gives the fourth embodiment a particular tolerance to bending in the preferred bending direction While meandering conductors meandering with a low amplitude act less against bending in the plane of the conductors, meandering conductors meandering with a higher amplitude acts more strongly against bending in the plane of the conductors. The reason for this is of course that a meandering conductor has a distribution component directed orthogonally to the conductor's longitudinal direction, and this orthogonal component becomes larger as the amplitude of the meandering increases. It is as if the meandering conductor has an effective width corresponding to the varying widths of the straight conductors in the first embodiment.This is what in addition gives the fourth embodiment a preference for bending in the preferred bending direction All conductors are of the same width and meanders with the same frequency but with varying amplitude. The meanders occur in phase, such that the troughs of adjacent conductors are aligned and the peaks of adj acent conductors are aligned. This advantageously means that conductors may be arranged more densely than conductors with straight conductors of varying width, such as in the first embodiment, although less densely than conductors with meandering conductors with varying meandering amplitude, such as in the third embodiment.

Just like in third embodiment, the figure clearly shows that the set of meandering conductors 2al-2, 2bl-2 can be subdivided into four bands with a first set of meandering conductors 2bl meandering with a lower meandering amplitude, followed by a first set of meandering 6 conductors 2al meandering with a higher meandering amplitude, followed by a second set of meandering conductors 2b2 meandering with a lower meandering amplitude, finally followed by a second set of meandering conductors 2a2 meandering with a higher meandering amplitude. Like in the third embodiment, the distribution of meandering amplitude nearly adheres to a continuous periodical curve with a wavelength corresponding to half the width of the FPC, in tum corresponding to the circumference of the FPC rolled into a tubular form.

Alternative embodiments In the presented embodiments the width, density and meandering amplitude of the conductors changes from side to side of the flat FPC corresponding to a variation around the periphery of the tubular FPC. Obviously, other alternative ways of arranging such a variation in resistance to bending and tolerance to bending in the plane of the flat FPC are possible, such as varying thickness of the conductors. In addition, these methods of causing a variation in resistance to bending and tolerance of bending in the plane of the flat FPC can be combined in many different ways, such as a concurrent conductor to conductor variation in width in combination with meandering amplitude or variation in density in combination with meandering amplitude.

In the four illustrated embodiments, the distribution of resistance to bending and tolerance of bending in the plane of the flat FPC nearly adheres to a continuous periodical curve with a wavelength corresponding to half the width of the FPC. As the conductors are discrete elements, the distribution of resistance to bending and tolerance to bending is not fully continuous but occurs in a step-wise fashion. The continuous periodical curve to which distribution of resistance to bending adheres may itself be alranged with discontinuous steps. In an extreme case, the set of conductors 2al-2, 2b1-2 can be subdivided into four bands with a first set of narrower conductors 2b1 identical to each other, followed by a first set of wider conductors 2al identical to each other, followed by a second set of narrower conductors 2b2 identical to each other, finally followed by a second set of wider conductors 2a2 all identical to each other. This could for example be suitable for the fourth embodiments, as identical meandering conductors in each set fit together in a space saving fashion.

In the four illustrated embodiments, the resistance to bending and tolerance to bending in the plane of the flat FPC is identical for the first and third sets of conductors, while the resistance to bending in the plane of the flat FPC is identical for the second and fourth sets of conductors.

Obviously, this does not have to be the case. Instead the total resistance to bending and tolerance to bending in the plane of the flat FPC must be higher for the first and third sets of conductors and lower for the second and fourth sets of conductors or oppositely the total resistance to bending in the plane of the flat FPC may be lower for the first and third sets of conductors and lower for the second and fourth sets of conductors.

Claims (6)

1.Claíms l Anelongated PPC (l) at least comprising a set of conductors (s2al-2, 2bl-2) primarily extending in the direction of the elongated PPC (l), the conductors (s2al-2, 2bl-2) having an adaptation to bending in the plane of the flat PPC (l),characterised in that theset of conductors (s2al-2, 2bl-2) is divided into four consecutive subsets of conductors (s2al-2, 2bl-2), Where the total degree of adaptation to bending in the plane of the flat PPC (l) of the first and third subsets of conductors (s2al-2, 2bl-2) is different from the total degree of adaptation to bending in the plane of the flat PPC (l) of the second and fourthsubsets of conductors (s2al-2, 2bl-2)

2. An elongated PPC (l) according to claims l, characterised in that at least one of the conductors (s2al-2, 2bl-2) is meandering.

3. An elongated PPC (l) according to claim 2, characterised in that theaverage meandering amplitude of the first and third subsets of conductors (2bl-2) is different from average meandering amplitude of the second and fourthsubsets of conductors (s2al-2).

4. An elongated PPC (l) according to claim l, characterised in that the total Width of the first and third subsets of conductors (2bl-2) is different from the total Width of the second and fourthsubsets of conductors (s2al-2).

5.An elongated PPC (l) according to any one of the preceding claims, characterised in that the elongated PPC (l) is formed into a tubular shape.

6. An elongated PPC (l) according to claim 5, characterised in that the first and third subsets of conductors (2bl-2) are arranged on opposite sides of the tubularly shaped PPC (l) and in that the second and fourthsubsets of conductors (s2al-2)are arranged on opposite sides of the tubularly shaped PPC (l).