Flexible printed circuit board for sensor arrangement, sensor arrangement with such a flexible printed circuit board, and method

Abstract

In some embodiments, a flexible printed circuit board (1') for a sensor arrangement is provided, wherein the flexible printed circuit board (1') comprises a strip-shaped base substrate (3) with a plurality of contact pads (5) and a plurality of conductive tracks (7a, 7b). The plurality of contact pads (5) and the plurality of conductive tracks (7a, 7b) comprise a first set of contact pads interconnected with two first contact pads (5a1, 5a2) and two second contact pads (5b1, 5b2). Each of the first contact pads (5a1, 5a2) is interconnected with one of the corresponding second contact pads (5b1, 5b2) via a corresponding conductive track of a first pattern of conductive tracks (7a) routed in a meander or zigzag pattern (7a1). The strip-shaped base substrate (3) further includes a pattern of cutting lines (15) provided in the strip-shaped base substrate (3).(Fig. 2).

Description

Title of the invention: Flexible printed circuit board for a sensor arrangement, sensor arrangement with such a flexible printed circuit board, and method

[0001] Scope of disclosure This disclosure relates to a flexible printed circuit board for a sensor arrangement, a sensor arrangement with such a flexible printed circuit board, and a method for forming such a sensor arrangement. For example, this disclosure may relate to a flexible printed circuit board for an optical sensor arrangement, such as an oximeter, and an optical sensor arrangement with such a flexible printed circuit board, such as an oximeter with such a flexible printed circuit board. Technological background

[0002] A wide variety of sensor arrangements with flexible circuits are known to monitor vital parameters of a patient, such as heart rate and blood oxygen, among a variety of additional biometric parameters to be monitored for health reasons and for medical purposes.

[0003] In the field of medicine, it is particularly important to monitor the condition of tissues, organs, or systems undergoing treatment, especially if this information is collected in real time during treatment. Many types of treatments are still routinely performed without the use of sensor data collection. Instead, such treatments rely on visual inspection by a caregiver or other limited means rather than on collected sensor data.

[0004] It is often necessary to adapt wearable devices to the shape of the body part on which the device is to be positioned in order to avoid discomfort or irritation of the corresponding body part. Therefore, it may be desirable to provide a flexible printed circuit board for an intelligent wearable arrangement in which user discomfort is minimized, if not completely avoided, due to the presence of the sensor system, and in which the manufacturing of such a sensor system and intelligent wearable arrangement is optimized.

[0005] US patent 5,390,670 A discloses a flexible printed circuit sensor assembly for detecting optical pulses. This known sensor assembly comprises a flexible sheet containing a set of conductive circuits attached to it. On this assembly, the conductive circuit comprises a first pair of conductive strips insulated from each other and extending at one end to provide a first set of terminals and at the other end to provide a second set of terminals. The conductive circuit further comprises a second pair of conductive strips insulated from each other and from the first pair of conductive strips, extending at one end to provide a first set of terminals and at the other end to provide a second set of terminals, the second set of terminals being spaced apart from the second set of terminals of the first pair of conductive strips. At least one photodetector is mounted through and physically and electrically fixed by a conductive fastener to the first set of terminals of the first pair of conductive strips.At least one LED is mounted across the first set of terminals of the second pair of conductive strips. Insulating tape is attached to the photodetector, the LED, and the circuit assembly at least as far as the second set of terminals of the first and second pairs of conductive strips. The flexible sensor assembly can be bent so that the photodetector can be spaced and positioned above the LED.

[0006] It is desirable to provide a flexible printed circuit board for a sensor arrangement and a sensor arrangement with such a flexible printed circuit board of a compact format having a size that can be adjusted to the shape of the part of the body on which the device is to be positioned. Disclosure Summary

[0007] The disadvantages of the prior art are overcome by means of a flexible printed circuit board as defined in independent claim 1, and a sensor arrangement as defined in claim 10. Advantageous embodiments are defined in dependent claims 2 to 9 and 11.

[0008] In the various aspects of the disclosure, a flexible printed circuit board for a sensor arrangement is provided, wherein the flexible printed circuit board comprises a strip-shaped base substrate with a plurality of contact pads and a plurality of conductive tracks. The plurality of contact pads and the plurality of conductive tracks comprise a first set of interconnected contact pads with two first contact pads and two second contact pads. Each of the first contact pads is interconnected with one of the corresponding second contact pads via a corresponding conductive track of a first pattern of conductive tracks routed in a meander or zigzag pattern. The strip-shaped base substrate further comprises a pattern of cut lines provided in the strip-shaped base substrate.

[0009] According to a first aspect of this disclosure, a flexible printed circuit board for a sensor arrangement is provided. In the illustrative embodiments of the first aspect, the flexible printed circuit board for a sensor arrangement comprises a strip-shaped base substrate with a plurality of contact pads and a plurality of conductive tracks, wherein the plurality of contact pads and the plurality of conductive tracks are formed in a principal surface of the strip-shaped base substrate. The strip-shaped base substrate may be formed of a thin, heat-resistant material, which may consist of polymers such as polyimide and polyethylene terephthalate (PET). In some illustrative embodiments of various aspects disclosed herein, a strip-shaped base substrate may be provided as flexible thin-film printed circuit board (PCB) type functional substrates.

[0010] The contact pads may be portions of a conductive surface of the flexible printed circuit board, for example, a portion of a main surface of the base substrate covered by a portion of conductive material, each contact pad being electrically and physically connected to at least one conductive track, the contact pad having at least one dimension, among two orthogonal directions, greater than at least one corresponding dimension of the connected conductive track. Here, a main surface of the base substrate is a surface of the base substrate surrounded by edges of the base substrate and having a larger area than at least one other surface of the base substrate.

[0011] Here, the plurality of contact pads and the plurality of conductive tracks form interconnected sets of interconnected contact pads, each set of interconnected contact pads comprising at least two contact pads interconnected by at least one conductive track routed between the interconnected contact pads of each set in the main surface. The sets of interconnected contact pads comprise a first set of interconnected contact pads, the first set comprising two first contact pads located at a first end portion of the strip-shaped base substrate, and two second contact pads located at a second end portion of the strip-shaped base substrate opposite the first end portion along a length of the strip-shaped base substrate.Each of the first contact pads is interconnected to one of the corresponding second contact pads via a corresponding conductive track of a first pattern of conductive tracks routed in an intermediate portion of the base substrate in the form of a strip between the first and second end portions in the main surface.

[0012] The conductive tracks of the first pattern of conductive tracks are partially routed in a meander or zigzag pattern in the portion intermediate. The strip-shaped base substrate further includes a pattern of cutting lines provided in the strip-shaped base substrate, the pattern of cutting lines having cutting lines which are at least partially interlocked with the meander or zigzag pattern.

[0013] The plurality of contact pads and the plurality of conductive tracks can be formed on the strip-shaped base substrate in the form of a wiring pattern created by depositing a coating of conductive material on at least one surface of the flexible base substrate, followed by pattern formation in the deposited conductive material, for example, by etching, laser etching, and the like, to produce a desired pattern with conductive tracks and contact pads. In laser pattern formation, for example, sections of a conductive layer are removed to create a pattern for electrical circuits on the strip-shaped base substrate. Compared to photolithography, laser pattern formation allows for greater flexibility in customization for specific applications and reduces the need for consumable materials during the circuit board production process.Preventing substrate breakage is a challenge in laser pattern formation, but the use of processes such as front and back processing can reduce the risk. Alternatively, the conductive material can be printed onto at least one surface of the strip-like base substrate in a desired pattern of contact pads and conductive tracks. For example, the conductive material can be at least one of the following: aluminum, silver, gold, copper, indium oxide and tin, and carbon. Substrate materials used to provide the strip-like base substrate, or a rigid base substrate if desired, can include, for example, at least one of the following: quartz, glass, ceramics, organic materials, thermoplastics, PI, PET, PEEK, and FR-4, without limitation.In some examples, a PCB style known as a "rigid-flexible" PCB, incorporating both flexible and non-flexible circuits to create a hybrid design solution, can be provided in a modification to replace the flexible base substrate with a rigid-flexible base substrate only in portions outside the meander or zigzag pattern.

[0014] The flexible printed circuit board of the first aspect can be compact with a small footprint, while the flexible printed circuit board can be enlarged to accommodate larger length dimensions. These flexible printed circuit boards can reduce waste during production by more efficiently utilizing the available space on a fabrication sheet, providing a flexible printed circuit board for a sensor arrangement, while the possibility of enlargement along a dimension of aThe length of the flexible printed circuit board allows for adjustments to its compactness to conform to the required length dimension when cutting along the cutting lines. In other words, the flexible printed circuit board can be designed compactly with high flexibility (in terms of function and / or mechanical characteristics) to maximize product density, thereby minimizing base material consumption and offering optimal cost.Routing in a meander or zigzag pattern in the intermediate portion, along with a cutting line pattern featuring lines that are at least partially interlocked with the meander or zigzag pattern, allows for the production of a flexible printed circuit board (PCB) for a sensor arrangement (and therefore a sensor arrangement with such a flexible PCB) in a condensed manner. This is achieved by extending the flexible PCB to a desired length after separation during at least a partial cut in the cutting pattern. This allows the flexible PCB to expand and achieve a functional bending area over a greater distance than that initially formed during production. In this way, space and material can be saved, a higher unit production rate (UPH) can be achieved, and the overall cost can be reduced.

[0015] In certain embodiments illustrating the first aspect, the pattern of cutting lines provided in the strip-shaped base substrate may have cutting lines that are at least partially interlocked with the meander or zigzag pattern and / or the cutting lines may be aligned with the meander or zigzag pattern in the intermediate portion such that the cutting lines in the intermediate portion exhibit a meander or zigzag pattern following the meander or zigzag pattern. The cutting lines outside the meander or zigzag pattern surround the plurality of contact pads.

[0016] For example, the cutting lines of the cutting line pattern may be formed from lines along which the strip-shaped base substrate is mechanically cut or may be cut in a separate cutting process. The cutting lines of the cutting line pattern may include lines indicating lines along which the strip-shaped base substrate is to be subjected to a mechanical cutting or punching process, or they may indicate a line along which the strip-shaped base substrate is subjected to a cutting or punching process. A cutting line may be provided by material at least partially cut, hollowed out, or serrated from the strip-shaped base substrate so that the strip-shaped base substrate is mechanically weakened along the cutting line. Alternatively, the mechanical integrity and The stability of the strip-shaped base substrate along the cutting line may not be affected unless it is subjected to a mechanical cutting or punching process. In still other variations, a cutting line may represent a line along which the material of the strip-shaped base substrate is at least partially removed in a pattern of broken or continuous lines.

[0017] In certain embodiments illustrating the first aspect, the flexible printed circuit board may further comprise at least one LED and at least one photodiode arranged on the main surface of the strip-shaped base substrate, the at least one LED and the at least one photodiode being electrically connected to associated contact pads. Here, the LED(s) and the photodiode(s) may be arranged on the flexible printed circuit board where the meander or zigzag pattern allows for adjusting the separation of the LED(s) and the photodiode(s) independently of the size of the base substrate.

[0018] In other embodiments illustrating the first aspect, the flexible printed circuit board may further comprise at least one LED and at least one photodiode arranged on a second main surface of the base substrate in the form of a strip opposite the main surface and electrically interconnected with contact pads associated by a via interconnecting the main surface and the second main surface. Here, the LED(s) and the photodiode(s) may be arranged on the flexible printed circuit board where the meander or zigzag pattern allows for adjusting the separation of the LED(s) and the photodiode(s) independently of the size of the base substrate.

[0019] In certain embodiments illustrating the first aspect, the meander or zigzag pattern may include U-shaped bending routing portions and linear track portions extending between two U-shaped bending routing portions, the U-shaped bending routing portions and the linear track portions being routed between cutting lines of the pattern of cutting lines extending laterally close together along each of the U-shaped bending routing portions and linear track portions such that adjacent linear track portions are completely separated by at least one cutting line extending completely between each of two adjacent linear track portions. Consequently, the meander or zigzag pattern can be provided in a very compact design.

[0020] In certain special illustrative examples, the meandering or zigzag pattern may extend almost over the entire width of the strip-shaped base substrate. The meandering or zigzag pattern may include portions of U-shaped flex routing and portions of linear tracks extending between two U-shaped bending routing portions. In some examples here, the linear track portions can be aligned with the width direction of the strip-like base substrate so that a length of the meander or zigzag pattern can be adjusted by appropriately choosing a number of linear track portions so as to be substantially determined by the number of linear track parts multiplied by the length of the linear track portions along the width direction which can substantially or approximately correspond to the width dimension of the strip-like base substrate.In some alternative examples here, the linear track portions can be aligned with the length direction of the strip-like base substrate such that a length of the meander or zigzag pattern can be adjusted by appropriately choosing a number of linear track portions so as to be substantially determined by the number of linear track parts multiplied by the length of the linear track portions along the length direction which can be freely chosen or approximately determined by the length dimension of the strip-like base substrate.In both cases, the length of the meander or zigzag pattern can be determined independently of the specific geometric dimensions of the strip-shaped base substrate, but over a number of U-bend portions and a number and length of linear track portions, thus providing a compact overall design of the strip-shaped base substrate.

[0021] In certain embodiments illustrating the first aspect, the meander or zigzag pattern may extend between the first and second end portions of the strip-shaped base substrate to electrically connect contact pads arranged at or near the first and second end portions. The U-shaped bending routing portions may be understood as routing portions of the meander or zigzag pattern that include bending portions resulting in bending sections where the routings at the ends of each of the bending portions have an orientation relative to each other equal to or less than 90°, such that each of the U-shaped bending routing portions has a U-shape. For example, linear routing segments extending between U-shaped flex routing segments can be arranged directly adjacent to each other in a meander or zigzag pattern. In the illustrative examples shown here, adjacent linear routing segments are separated by at least one cut line extending completely between each pair of adjacent linear routing segments. For example, the cut line extends toward the U-shaped flex routing segment between the first and second segments. portion, where conductive interconnect lines are routed between an antenna pattern and the U-bending routing portion, and electrically connecting the antenna pattern and the U-bending routing portion.

[0022] For example, the cutting line may start at an edge of the flexible base substrate in an undeployed state of the sensor tag and / or the cutting line may extend substantially parallel to the conductive interconnect lines routed between the antenna pattern and the U-bending routing portion, and / or it may extend at least partially to the U-bending routing portion.

[0023] In some illustrative examples, the meander or zigzag pattern can be mechanically folded at the U-shaped bending routing portions and / or the linear track portions adjacent to the cutting lines so as to fold or bend the meander or zigzag pattern at least once. The base substrate can be at least flexible at the U-shaped bending routing portions and / or the linear track portions adjacent to the cutting lines, and / or the base substrate can be cut at least partially along the cutting lines. For example, at least one of the linear track portions can be folded or bent. The base substrate can be cut along the cutting lines in such a way that the meander or zigzag pattern can be enlarged in a substantially linear fashion when at least one of the linear track portions is folded or bent.

[0024] In certain illustrative examples, the meander or zigzag pattern has at least one linear track portion oriented so as to face the opposite side of the main surface. For example, when folding or unfolding the meander or zigzag pattern at the end of one or more linear track portions.

[0025] In certain embodiments illustrating the first aspect, the pattern of cutting lines may include cutting lines along which the strip-shaped base substrate can be mechanically cut to completely separate adjacent portions of material from the strip-shaped base substrate between which cutting lines are defined. For example, the cutting lines may form exposed edges of the strip-shaped base substrate in each of the primary and secondary surfaces. Consequently, the pattern of cutting lines allows the conductive tracks to be extended to a greater length.

[0026] In certain embodiments illustrating the first aspect, the interconnected contact pad assemblies may comprise a second interconnected contact pad assemblies, the second assembly comprising two third contact pads located in the intermediate portion of the strip-shaped base substrate and Fourth contact pads are located at the first end portion of the strip-shaped base substrate adjacent to the second contact pads. Third contact pads can be located in the main surface between the first end portion and the meander or zigzag pattern. Each third contact pad can be interconnected with one of the respective fourth contact pads via a corresponding conductive track from a second pattern of conductive tracks routed between the third and fourth contact pads. Consequently, a separation of the second set of interconnected contact pads can be independent of a separation of the first set of interconnected contact pads.For example, the separation of the first set of interconnected contact pads can be extended via the meander or zigzag pattern and can be greater than the separation of the second set of interconnected contact pads.

[0027] In a second aspect of the disclosure, a sensor arrangement may be provided. In the illustrative embodiments of the second aspect, the sensor arrangement comprises the flexible printed circuit board of the first aspect, a sensor structure provided on at least one principal surface of opposite principal surfaces of the flexible printed circuit board and electrically connected to some of the contact pads, and electronic communication lines connected to some of the other contact pads. Accordingly, an expandable sensor arrangement may be provided.

[0028] In certain illustrative embodiments of the second aspect, the flexible printed circuit board can be provided by the flexible printed circuit board of the first aspect according to embodiments having the second set of interconnected contact pads. The sensor structure can include two LEDs connected to the third contact pads of the second set and a photodiode electrically connected to the first contact pads of the first set.

[0029] In certain illustrative embodiments of the first aspect and the second aspect, a flexible printed circuit board design based on the flexible printed circuit board of the first aspect or on the sensor arrangement of the second aspect can be obtained.Here, the flexible printed circuit board design can be achieved by cutting the flexible printed circuit board along the pattern of cutting lines and enlarging the flexible printed circuit board by enlarging the meander or zigzag pattern into an enlarged intermediate routing portion spanning a separation between end portions and the strip-shaped base substrate of the flexible printed circuit board so that interconnected contact pads of the first set of interconnected contact pads are separated from each other along a longitudinal extension of the strip-shaped base substrate via an enlarged strip-shaped base substrate.

[0030] In some examples here, the meander or zigzag pattern can be successively enlarged by folding down portions of linear track in an alternating arrangement of linear track portions. For example, a first linear track portion can be arranged near the first end portion, and a second linear track portion following the first linear track portion after a first U-bend portion separating the first and second linear track portions in the meander or zigzag pattern can be flipped or folded down at the end of the first U-bend portion opposite an end of the first U-bend portion interfacing with the first linear track portion.To prevent a short circuit of conductive tracks in the second linear track routing in the event that the conductive tracks are not covered by an insulating coating, the second portion of linear track is folded down so that the conductive tracks formed in the main surface of the second portion of linear track are turned towards the second main surface opposite the main surface.

[0031] In another iteration of the enlargement, the meander or zigzag pattern can be further enlarged by folding down a third linear track portion following the second linear track portion after a second U-shaped bend at the end of the second U-shaped bend portion opposite one end of the second U-shaped bend portion interfacing with the second linear track portion. In order to prevent a short circuit of conductive tracks in the third linear track routing 55c in the case where the conductive tracks are not covered by an insulating coating, the third linear track portion can be folded down so that the conductive tracks formed in the main surface of the third linear track portion face the main surface.The main surface of the third linear track portion, exhibiting conductive tracks formed within it, is exposed when viewed from above the main surface of the flexible printed circuit board.

[0032] In another iteration, the meander or zigzag pattern can be further enlarged by folding down a fourth linear track portion following the third linear track portion after a third U-bend portion at the end of the third U-bend portion opposite one end of the third U-bend portion interfacing with the third linear track portion. In order to prevent a short circuit of conductive tracks in the fourth linear track routing in a case where the conductive tracks are not covered by an insulating coating, the fourth linear track portion can be folded down such that the conductive tracks formed in the main surface of the fourth linear track portion face the second main surface. The second main surface of the fourth linear track portion can be exposed in the top view on the main surface of the flexible printed circuit board.

[0033] In another iteration, the meander or zigzag pattern can be further enlarged by folding a fifth linear track segment following the fourth linear track segment after a fourth U-shaped bend segment at the end of the fourth U-shaped bend segment opposite one end of the fourth U-shaped bend segment interfacing with the fourth linear track segment. To prevent short-circuiting of conductive tracks in the fifth linear track routing in a case where the conductive tracks are not covered by an insulating coating, the fifth linear track segment can be folded such that the conductive tracks formed in the main surface of the fifth linear track segment face the main surface of the flexible printed circuit board.The main surface of the fifth linear track segment, exhibiting conductive tracks formed within it, can be exposed in the top view on the main surface of the flexible printed circuit board.

[0034] This folding can be iterated accordingly up to a maximum enlargement in which all linear track portions are folded. This means that the enlarged intermediate routing portion has a maximum number of folds or creases depending on the number of linear track portions, such that all possible linear track portions can be folded alternately to achieve the maximum separation. However, a discretely offset separation between the end portions of less than the maximum separation can be obtained by folding only a subset of linear tracks starting with the second linear track in the iteration disclosed above.

[0035] In a third aspect of this disclosure, a method for forming a sensor arrangement may be provided. In the illustrative embodiments, the method may include providing the sensor arrangement of one of the first to second aspects, cutting along the pattern of cutting lines, and enlarging the meander or zigzag pattern into an enlarged meander or zigzag pattern. In particular, the enlargement may be as disclosed in the immediately preceding paragraphs.

[0036] In certain embodiments illustrating at least one of the first to third aspects, the flexible printed circuit board includes an electromagnetic interference (EMI) metallic film covering metallic lines. The EMI metallic film can be arranged to bend over a component at its end to reduce electromagnetic interference in a very low current measured during the operation of a sensor arrangement. In illustrative but not limiting examples, the EMI metallic film may include a conductive layer attached to opposing principal surfaces by means of an adhesive, for example, double-sided adhesive. The adhesive may include a portion of anisotropic conductive film (ACF). For example, the ACF portion may be in contact with wiring to impose a protective potential, for example, coupling the conductive layer to ground. For example, in the case where the component corresponds to a photodiode in a sensor arrangement, the EMI metallic film shields the photodiode to reduce electromagnetic interference in current measurements provided by the sensor arrangement. In other illustrative examples, the EMI metallic film may have an opening or a suitable window portion (not shown) allowing electromagnetic radiation to be received and / or emitted by the component during the operation of the sensor arrangement.In the case of using a portion of a window instead of an opening, the window portion may be a portion of transparent material, where the portion of transparent material is transparent with respect to the electromagnetic radiation received and / or emitted by the component. The transparent window portion can protect the component from environmental degradation such as the ingress of liquid, dirt, etc.

[0037] In certain embodiments illustrating the second aspect, the EMI metallic film may be formed only above the sensor arrangement at one of the end portions of the sensor arrangement corresponding to one of the end portions. Alternatively, the EMI metallic film may be formed only above the sensor arrangement at both end portions of the sensor arrangement corresponding to the end portions without being formed above an intermediate portion between the end portions.

[0038] The first through third aspects as described above are not necessarily understood as distinct and unrelated, but may be understood as interdependent. Consequently, the disclosure explicitly presented above in the context of one aspect of the first through third aspects may also apply to the other of the first through third aspects. In particular, various embodiments and examples as described with respect to one of the first through third aspects may be combined at least partially with at least one other embodiment and / or another example of the other of the first through third aspects.

[0039] Other features and aspects of the disclosure will become evident from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features according to various embodiments. The summary is not intended to limit the scope of the invention, which is defined solely by the attached claims. Brief description of the drawings

[0040] Various illustrative embodiments and other advantages of the various aspects of this disclosure will become apparent from the detailed description of the accompanying figures as presented below.

[0041] Fig. 1 is a schematic top view of a flexible printed circuit board at early stages during manufacturing in accordance with certain illustrative embodiments of this disclosure.

[0042] Fig. 2 is a schematic top view of a flexible printed circuit board at later stages during manufacturing in accordance with certain illustrative embodiments of this disclosure.

[0043] Fig. 3 is a schematic top view of a flexible printed circuit board at early stages during manufacturing in accordance with certain other embodiments illustrative of this disclosure.

[0044] Fig. 4 is a schematic top view of a flexible printed circuit board at later stages during manufacturing in accordance with other illustrative embodiments of this disclosure.

[0045] Fig. 5 is a schematic top view of enlarged flexible printed circuit boards according to various embodiments illustrating the present disclosure in comparison with a conventional flexible printed circuit board design.

[0046] Fig. 6 is an enlarged schematic cross-sectional view of a sensor arrangement at the level of a component of the sensor arrangement in accordance with certain illustrative embodiments of this disclosure.

[0047] Fig. 7 schematically represents an enlarged cross-sectional view of a sensor arrangement during its operation in accordance with certain embodiments illustrative of this disclosure.

[0048] The figures accompanying this disclosure are provided only to schematically show certain concepts and aspects of this disclosure without showing all possible details of certain embodiments and without necessarily being actually to scale. Detailed description of preferred embodiments

[0049] The illustrative embodiments described below relate to a flexible printed circuit board and a sensor arrangement in various aspects of this disclosure. Although the embodiments below are described as a specific design and application of a flexible printed circuit board in illustrative embodiments, this does not impose any limitations, and another design and / or application of the flexible printed circuit board may be considered.

[0050] In medical applications, sensor arrangements can be integrated into intelligent wearable arrangements, for example, for digital health monitoring in hospitals or remotely at home via telemedicine. For instance, a fully integrated wearable electronic system that more effectively monitors a patient's physiological conditions can be provided by mechanically flexible and stretchable wearable arrangements. By adjusting wearable electronic systems to a patient's anatomy, the level of comfort can be improved when worn, as skin irritation can be reduced by appropriately fitting the wearable electronic system to the location where it is placed.

[0051] In some examples, the portable electronic system may include a sensor arrangement comprising various sensors that can monitor various patient characteristics, including oxygen level, temperature, pH, ammonium, glucose, lactate, UA, and other biomarkers of a patient to be monitored. In various embodiments, the sensor arrangement can monitor, in real time or at discrete intervals, the biomarkers or patient characteristics.

[0052] In addition to the sensor arrangement, the portable electronic system can be equipped with an electro-reactive drug delivery and on-demand antimicrobial agent delivery system loaded with an antimicrobial and / or anti-inflammatory peptide. The delivery system can release the drugs or antimicrobial agents under an applied positive voltage, such that when a positive voltage is applied, the electroactive hydrogels can release the dual-function peptide, or another drug, which can increase the elimination of bacteria (or other pathogens) and modulate inflammatory responses in the wound bed during various stages of wound healing.In various embodiments, the on-demand delivery system can be modified with different electroactive hydrogels to deliver other drugs (including positively and negatively charged drugs and biomolecules, e.g., proteins, peptides, and growth factors). Similarly, the integration of an electrical stimulation therapeutic module can facilitate cell motility and proliferation, as well as ECM deposition and remodeling in the wound regeneration process, resulting in enhanced wound healing.

[0053] With regard to [Fig. 1], a flexible printed circuit board 1 for a sensor arrangement is provided at an early stage during its operation. Here, the flexible printed circuit board 1 comprises a strip-shaped base substrate 3 with a plurality of contact pads 5 and a plurality of conductive tracks 7a and 7b. The plurality of contact pads 5 and the plurality of conductive tracks 7a and 7b can be formed in a main surface 3a of the basic substrate in the form of a strip 3. The length and width dimensions are shown on [Fig.l] with respect to the orthogonal directions L and W as shown by a Cartesian coordinate system with the L axis and the W axis on the illustration of [Fig.l].

[0054] The plurality of contact pads 5 and the plurality of conductive tracks 7a and 7b form interconnected sets of interconnected contact pads, each set of interconnected contact pads comprising at least two contact pads. As shown in [Fig. 1], one set of interconnected contact pads can be provided by the contact pads 5a1 and 5b1. Another set of interconnected contact pads can be provided by the contact pads 5a2 and 5b2. Another set of interconnected contact pads can be provided by the contact pads 5c1 and 5d1. Another set of interconnected contact pads can be provided by the contact pads 5c2 and 5d2. Another set of interconnected contact pads can be provided by the contact pads 5f and 5g.The contact pads in each of these assemblies are interconnected by at least one conductive trace routed between the interconnected contact pads, such as one or more conductive traces between contact pads 5a1 and 5b1, one or more conductive traces between contact pads 5a2 and 5b2, one or more conductive traces between contact pads 5c1 and 5d1, one or more conductive traces between contact pads 5c2 and 5d2, and one or more conductive traces between contact pads 5f and 5g. Therefore, the contact pads in each assembly are interconnected by one or more conductive traces in the main surface 3a. Contact pad 5c1 can be connected to an auxiliary pad 5e1, and contact pad 5c2 can be connected to an auxiliary pad 5e2. An additional auxiliary pin 5e3 can be connected to the contact pin 5e1. As shown in the [Fig.l], the contact pads 5c1, 5c2 are located in the main surface 3a between the first end portion 9a and the meander or zigzag pattern 7al, and each of the contact pads 5c1, 5c2 is interconnected with one of the corresponding contact pads 5dl, 5d2 via a corresponding conductive track of the pattern of conductive tracks 7b routed between the contact pads 5c1, 5c2, 5b1, 5b2. .

[0055] In the following description, the contact pads 5a may refer to the contact pads 5a 1 and 5a2, the contact pads 5b may refer to the contact pads 5b 1 and 5b2, the contact pads 5c may refer to the contact pads 5c 1 and 5c2, the contact pads 5d may refer to the contact pads 5dl and 5d2, and the contact pads 5e may refer to the contact pads 5el, 5e2 and 5e3.

[0056] According to some illustrative embodiments, the contact pads 5b, 5d and 5f may be oval pads. These pads may be used to connect to communication lines (not shown), for example by soldering one or more cables (not shown) to the contact pads which are in communication with a medical device (not shown).

[0057] According to some illustrative embodiments, the contact pads 5c2 can be L-shaped pads. These pads can be used to attach and wire two LEDs (not shown) such as a red LED and an infrared LED, for application to the tip of a patient's fingertip (not shown).

[0058] The interconnected contact pad assemblies comprise a first set of interconnected contact pads, the first set comprising two first contact pads 5a1 and 5a2 located at a first end portion 9a of the strip-shaped base substrate 3 and two second contact pads 5b1, 5b2 located at a second end portion 9b of the strip-shaped base substrate 3 opposite to the first end portion 9a along a direction of length L of the strip-shaped base substrate 3. Each of the first contact pads 5a1, 5a2 is interconnected to one of the corresponding second contact pads 5b1, 5b2 via a corresponding conductive track of a first pattern of conductive tracks 7a routed in an intermediate portion 9c of the strip-shaped base substrate 3 between the first and second end portions 9a in the main surface 3a.The conductive tracks of the first pattern of conductive tracks 7a are partially routed in a meander or zigzag pattern 7a 1 in the intermediate portion 9c. .

[0059] As shown in [Fig. 1], the meander or zigzag pattern 7al has a conductive track 7a 11 connected to the contact pad 5al and a conductive track 7a 12 connected to the contact pad 5a2 at the first end portion 9a. At the second end portion 9b, the conductive track 7al 1 is connected to the contact pad 5bl and the conductive track 7al2 is connected to the contact pad 5b2. The conductive tracks 7al and 7al2 are routed in the first pattern of conductive tracks 7a between the meander or zigzag pattern 7al and the contact pads 5b1, 5b2 along a linear routing portion 7a2. The meander or zigzag pattern 7a 1 can extend almost across a full width W of the band-shaped base substrate 3.Contact pads 5al and 5a2 can be connected to an LED (not shown) or a photodiode (not shown), while contact pads 5b1 and 5b2 can allow connection to a control circuit (not shown) for the LED (not shown) or the photodiode (not shown).

[0060] In certain illustrative embodiments, the contact pads 5c1 and 5c2 can be connected to an LED (not shown) or a photodiode (not shown), while the contact pads 5d1 and 5d2 can allow connection to a driver circuit (not shown) of the LED (not shown) or the photodiode (not shown). (illustrated). Via the additional contact pads 5e 1, 5e2, 5e3, one or more additional LEDs (not illustrated) or one or more photodiodes (not illustrated) can be connected in parallel with the contact pads 5c 1, 5c2. For example, when connecting one or more LEDs to the flexible printed circuit board 1 via the contact pads 5c and / or 5e, a photodiode can be connected to the flexible printed circuit board 1 via the contact pads 5a, the photodiode being able to be spatially arranged relative to the LED(s).

[0061] At the first end portion 9a, the strip-shaped basic substrate 3 may further comprise a test circuit arrangement 11b with test pads interconnected with the contact pads 5a2 and 5g via conductive tracks 13b. At the second end portion 9b, a test circuit arrangement with test pads may be interconnected with some of the contact pads 5 via conductive tracks 13a.

[0062] With continuous reference to [Fig. 1], the meander or zigzag pattern 7a1 comprises U-shaped bending routing portions (with the U-shaped bending routing portion 7a3 shown as an example in [Fig. 1]) and linear track portions extending between two U-shaped bending routing portions. The linear track portions can be aligned with the width direction W of the strip-shaped base substrate 3. Accordingly, a length of the meander or zigzag pattern 7a1 can be adjusted by appropriately selecting a number of linear track portions so as to be substantially determined by the number of linear track portions multiplied by the length of the linear track portions along the width direction W, which can substantially or approximately correspond to the width dimension W of the strip-shaped base substrate 3.

[0063] With reference to [Fig. 2], a flexible printed circuit board 1' is shown, the flexible printed circuit board 1' corresponding to the flexible printed circuit board 1 shown in [Fig. 1], however, the flexible printed circuit board 1' corresponding to a later stage during manufacturing. Accordingly, the description in [Fig. 1] applies to the flexible printed circuit board 1' with respect to identical numerical references, the repetition of the description given above with respect to [Fig. 1] being avoided for the sake of brevity, and the disclosure given with respect to [Fig. 1] being incorporated by reference in its entirety.

[0064] In the flexible printed circuit board 1', the strip-shaped base substrate 3 further comprises a pattern of cutting lines 15 provided in the strip-shaped base substrate 3, the pattern of cutting lines 15 having cutting lines 15a and 15b which are at least partially intertwined with the meander or zigzag pattern 7a1. The cutting lines 15a are aligned with the pattern in In the intermediate portion 9c, the cutting lines 15a in the intermediate portion 9c have a meander or zigzag pattern following the meander or zigzag pattern 7al. The cutting lines 15b outside the meander or zigzag pattern 7a surround the plurality of contact pads. In some examples, the cutting lines 15a and 15b of the cutting line pattern 15 may completely surround the plurality of contact pads 15 as well as the plurality of conductive tracks 7a, 7b. In an unenlarged state of the flexible printed circuit board 1', the cutting lines 15a and 15b may extend substantially parallel to conductive tracks 7a interconnecting contact pads 5a and 5b.During a complete cut along the cut lines 15a, the meander or zigzag pattern 7al, the flexible printed circuit board 1' can be flexed or bent in the intermediate portion 9c at least once along the meander or zigzag pattern 7al so that the flexible printed circuit board 1' can be enlarged along the cut line, for example, the flexible printed circuit board 1' being enlarged or folded open in a state in which the meander or zigzag pattern 7al is enlarged and a separation between the contact pads 5a and 5b is increased.

[0065] For example, the cutting lines 15a, 15b of the cutting line pattern 15 may be formed from lines along which the strip-shaped base substrate 3 is mechanically cut or may be cut in a separate cutting process. The cutting lines 15a, 15b of the cutting line pattern 15 may include lines indicating lines along which the strip-shaped base substrate 3 is to be subjected to a mechanical cutting or punching process, or they may indicate a line along which the strip-shaped base substrate 3 is subjected to a cutting or punching process. A cutting line may be provided by a material at least partially cut, hollowed out, or serrated from the strip-shaped base substrate 3 such that the strip-shaped base substrate 3 is mechanically weakened along the cutting line.Alternatively, the mechanical integrity and stability of the strip-shaped base substrate 3 along the cut line may not be affected unless it is subjected to a mechanical cutting or punching process. In still other variants, a cut line may represent a line along which the material of the strip-shaped base substrate 3 is at least partially removed in a pattern of interrupted or continuous lines.

[0066] With reference to [Fig. 2] and as will be described below in more detail with respect to [Fig. 5], the meander or zigzag pattern 7a1 can be mechanically bent at one or more U-shaped bending routing portions. Furthermore, or alternatively, the meander or zigzag pattern 7a1 can be Mechanically folded or bent at one or more linear track segments adjacent to the cut line 15a so as to fold or bend the meander or zigzag pattern 7al at least once. Here, at least one of the linear track segments may be folded or bent as described below in more detail in the context of [Fig. 5]. The meander or zigzag pattern 7al may have at least one linear track segment oriented to face away from the main surface 3a.

[0067] In certain illustrative embodiments and as described above, the pattern of cutting lines 15 may include cutting lines 15a, 15b along which the strip-shaped base substrate 3 is mechanically cut to completely separate adjacent portions of material from the strip-shaped base substrate 3, between which cutting lines are defined. Once cut, the cutting lines 15a, 15b may then form exposed edges of the strip-shaped base substrate 3 in each of the main surface 3a and a second main surface 3b opposite the first main surface 3a.

[0068] With reference to either of Figures 1 and 2, that is, with respect to each of the flexible printed circuit boards 1 and 1', a sensor arrangement comprising such a flexible printed circuit board can be provided. The sensor arrangement may further include a sensor structure (not shown) provided on at least one of the opposing principal surfaces 3a, 3b of the flexible printed circuit board 1 or 1' and electrically connected to some of the contact pads 5a, 5c, 5e, 5g. The sensor arrangement may further include electronic communication lines (not shown) connected to some of the other contact pads 5b, 5d, 5f. Here, the sensor arrangement may be an oximeter and include two LEDs (not shown) connected to the contact pads 5c, 5e and a photodiode (not shown) connected to the contact pads 5a.

[0069] With regard to [Fig. 3], a flexible printed circuit board 20 for a sensor arrangement is provided at an early stage during its operation. Here, the flexible printed circuit board 20 comprises a strip-shaped base substrate 23 with a plurality of contact pads 25 and a plurality of conductive tracks 27a and 27b. The plurality of contact pads 25 and the plurality of conductive tracks 27a and 27b can be formed in a principal surface 23a of the strip-shaped base substrate 23. The length and width dimensions are shown in [Fig. 3] with respect to the orthogonal directions L and W as indicated by a Cartesian coordinate system with the L-axis and W-axis in the illustration of [Fig. 3].

[0070] The plurality of contact pads 25 and the plurality of conductive tracks 27a and 27b form interconnected sets of interconnected contact pads, each set of interconnected contact pads comprising at least two Contact pads. As shown in [Fig. 3], one set of interconnected contact pads can be provided by contact pads 25a1 and 25b1. Another set of interconnected contact pads can be provided by contact pads 25a2 and 25b2. Another set of interconnected contact pads can be provided by contact pads 25c1 and 25d1. Another set of interconnected contact pads can be provided by contact pads 25c2 and 25d2. Another set of interconnected contact pads can be provided by contact pads 25f and 25g.The contact pads in each of these assemblies are interconnected by at least one conductive track routed between the interconnected contact pads, such as one or more conductive tracks between contact pads 25a1 and 25b1, one or more conductive tracks between contact pads 25a2 and 25b2, one or more conductive tracks between contact pads 25c1 and 25d1, one or more conductive tracks between contact pads 25c2 and 25d2, and one or more conductive tracks between contact pads 25f and 25g. Therefore, the contact pads in each assembly are interconnected by one or more conductive tracks in the main surface 23a. Contact pad 25c1 can be connected to an auxiliary pad 25e1, and contact pad 25c2 can be connected to an auxiliary pad 25e2. An additional auxiliary pin 25e3 can be connected to the contact pin 25e 1. As shown in the [Fig.3], the contact pads 25c1, 25c2 are located in the main surface 23a between the first end portion 29a and the meander or zigzag pattern 27al, and each of the contact pads 25cl, 25c2 is interconnected with one of the corresponding contact pads 25dl, 25d2 via a corresponding conductive track of the pattern of conductive tracks 27b routed between the contact pads 25c1, 25c2, 25b1, 25b2. .

[0071] In the following description, the contact pads 25a may refer to the contact pads 25al and 25a2, the contact pads 25b may refer to the contact pads 25b 1 and 25b2, the contact pads 25c may refer to the contact pads 25c 1 and 25c2, the contact pads 25d may refer to the contact pads 25dl and 25d2, and the contact pads 25e may refer to the contact pads 25el, 25e2 and 25e3.

[0072] According to some illustrative embodiments, the contact pads 25b, 25d and 25f may be oval pads. These pads may be used to connect to communication lines (not shown), for example by soldering one or more cables (not shown) to the contact pads that are in communication with a medical device (not shown).

[0073] According to some illustrative embodiments, the contact pads 25c2 can be L-shaped pads. These pads can be used to fix and wire two LEDs (not shown) such as a red LED and an infrared LED, for application to the tip of a finger (not shown) of a patient (not shown).

[0074] The interconnected contact pad assemblies comprise a first set of interconnected contact pads, the first set comprising two first contact pads 25a1 and 25a2 located at a first end portion 29a of the strip-shaped base substrate 23 and two second contact pads 25b1, 25b2 located at a second end portion 29b of the strip-shaped base substrate 23 opposite the first end portion 29a along a direction of length L of the strip-shaped base substrate 23. Each of the first contact pads 25a1, 25a2 is interconnected to one of the corresponding second contact pads 25b1, 25b2 via a corresponding conductive track of a first pattern of conductive tracks 27a routed in an intermediate portion 29c of the strip-shaped base substrate 23 between the first and second portions of ends 29a in the main surface 23a.The conductive tracks of the first pattern of conductive tracks 27a are partially routed in a meander or zigzag pattern 27a 1 in the intermediate portion 29c. .

[0075] As shown in [Fig. 3], the meander or zigzag pattern 27al has a conductive track 27a 11 connected to the contact pad 25al and a conductive track 27a 12 connected to the contact pad 25a2 at the first end portion 29a. At the second end portion 29b, the conductive track 27al 1 is connected to the contact pad 25bl and the conductive track 27al2 is connected to the contact pad 25b2. The conductive tracks 27a 11 and 27a 12 are routed in the first pattern of conductive tracks 27a between the meander or zigzag pattern 27al and the contact pads 25b 1, 25b2 along a linear routing portion 27a2. The meander or zigzag pattern 27al can extend almost across a full width W of the band-shaped base substrate 23.Contact pads 25al and 25a2 can be connected to an LED (not shown) or a photodiode (not shown), while contact pads 25b1 and 25b2 can allow connection to a control circuit (not shown) for the LED (not shown) or the photodiode (not shown).

[0076] In certain illustrative embodiments, the contact pads 25c1 and 25c2 can be connected to an LED (not shown) or a photodiode (not shown), while the contact pads 25d1 and 25d2 can allow connection to a control circuit (not shown) for the LED (not shown) or the photodiode (not shown). Via the additional contact pads 25e1, 25e2, 25e3, one or more additional LEDs (not shown) or one or more photodiodes (not shown) can be connected in parallel with the contact pads 25c1, 25c2. For example, when connecting one or more LEDs to the flexible printed circuit board 20 via the contact pads 25c and / or 25e, a photodiode can be connected to the flexible printed circuit board 20 via the contact pads 25a, the photodiode can be spatially arranged in relation to the LED(s).

[0077] At the first end portion 29a, the strip-shaped base substrate 23 may further comprise a test circuit arrangement 21b with test pads interconnected with the contact pads 25a2 and 25g via conductive tracks 33b. At the second end portion 29b, a test circuit arrangement 21a with test pads may be interconnected with some of the contact pads 25 via conductive tracks 33a.

[0078] With continuous reference to [Fig. 3], the meander or zigzag pattern 27al comprises U-shaped bending routing portions interconnecting linear track portions (a linear track portion 27a3 shown as an example in [Fig. 3]) such that linear track portions extend between two U-shaped bending routing portions. The linear track portions can be aligned with the direction of the length L of the strip-shaped base substrate 23.Consequently, a length of the meander or zigzag pattern 27al can be adjusted by appropriately choosing a number of linear track portions so as to be substantially determined by the number of linear track portions multiplied by the length of the linear track portions along the direction of length L which can be freely chosen or determined approximately by the length dimension la L of the strip-like basic substrate 23.

[0079] With reference to [Fig. 4], a 20' flexible printed circuit board is shown, the 20' flexible printed circuit board corresponding to the 20' flexible printed circuit board shown in [Fig. 3], however, the 20' flexible printed circuit board corresponds to a later stage during manufacturing. Accordingly, the description in [Fig. 3] applies to the 20' flexible printed circuit board with respect to identical numerical references, the repetition of the description presented above with respect to [Fig. 3] being avoided for the sake of brevity and the disclosure presented with respect to [Fig. 3] being incorporated by reference in its entirety.

[0080] In the flexible printed circuit board 20', the strip-shaped base substrate 23 further comprises a pattern of cutting lines 35 provided in the strip-shaped base substrate 23, the pattern of cutting lines 35 having cutting lines 35a and 35b that are at least partially intertwined with the meander or zigzag pattern 27al. The cutting lines 35a are aligned with the meander or zigzag pattern 27al in the intermediate portion 29c, the cutting lines 35a in the intermediate portion 29c having a meander or zigzag pattern following the meander or zigzag pattern 27a. The cutting lines 35b outside the meander or zigzag pattern 27al surround the plurality of contact pads. 35. In some examples, The cutting lines 35a and 35b of the cutting line pattern 35 can completely surround the plurality of contact pads 35 as well as the plurality of conductive tracks 27a, 27b. In an unenlarged state of the flexible printed circuit board 20', the cutting lines 35a and 35b can extend substantially in parallel with conductive tracks 27a interconnecting contact pads 25a and 25b.During a complete cut along the cut lines 35a, the meander or zigzag pattern 27al, the flexible printed circuit board 20' can be flexed or bent in the intermediate portion 29c at least once along the meander or zigzag pattern 27al so that the flexible printed circuit board 20' can be enlarged along the cut line, for example, the flexible printed circuit board 20' being enlarged or folded open in a state in which the meander or zigzag pattern 27al is enlarged and a separation between the contact pads 25a and 25b is increased.

[0081] For example, the cutting lines 35a, 35b of the cutting line pattern 35 may be formed from lines along which the strip-shaped base substrate 23 is mechanically cut or may be cut in a separate cutting process. The cutting lines 35a, 35b of the cutting line pattern 35 may include lines indicating lines along which the strip-shaped base substrate 23 is to be subjected to a mechanical cutting or punching process, or they may indicate a line along which the strip-shaped base substrate 23 is subjected to a cutting or punching process. A cutting line may be provided by a material at least partially cut, hollowed out, or serrated from the strip-shaped base substrate 23 such that the strip-shaped base substrate 23 is mechanically weakened along the cutting line.Alternatively, the mechanical integrity and stability of the strip-shaped base substrate 23 along the cutting line may not be affected unless it is subjected to a mechanical cutting or punching process. In still other variants, a cutting line may represent a line along which the material of the strip-shaped base substrate 23 is at least partially removed in a pattern of interrupted or continuous lines.

[0082] With reference to [Fig. 4] and as will be described in more detail below with respect to [Fig. 5], the meander or zigzag pattern 27al can be mechanically bent at one or more portions of the U-shaped bending path. Alternatively, the meander or zigzag pattern 27al can be mechanically bent or folded back at one or more portions of the linear track adjacent to the cutting line 35a so as to fold or fold the meander or zigzag pattern 27al at least once. Here, at least one of the linear track portions can be bent or folded back as described below in the context of the [Fig.5] in more detail. The meander or zigzag pattern 27al may have at least one linear track portion oriented to face the opposite of the main surface 23a.

[0083] At the first end portion 29a, the strip-shaped base substrate 23 may further comprise a test circuit arrangement 31b (according to the test circuit arrangement 21b of [Fig. 3]) with test pads interconnected with the contact pads 25a2 and 25g via conductive tracks 33b. At the second end portion 29b, a test circuit arrangement 31a (according to the test circuit arrangement 31a of [Fig. 3]) with test pads may be interconnected with some of the contact pads 25 via conductive tracks 33a.

[0084] In certain illustrative embodiments and as described above, the pattern of cutting lines 35 may include cutting lines 35a, 35b along which the strip-shaped base substrate 23 is mechanically cut to completely separate adjacent portions of material from the strip-shaped base substrate 23, between which cutting lines are defined. Once cut, the cutting lines 35a, 35b may then form exposed edges of the strip-shaped base substrate 23 in each of the main surface 23a and a second main surface 23b opposite the first main surface 23a.

[0085] With reference to either of Figures 3 and 4, that is, with respect to each of the flexible printed circuit boards 20 and 20', a sensor arrangement comprising such a flexible printed circuit board can be provided. The sensor arrangement may further include a sensor structure (not shown) provided on at least one of the opposing principal surfaces 23a, 23b of the flexible printed circuit board 20 or 20' and electrically connected to some of the contact pads 25a, 25c, 25e, 25g. The sensor arrangement may further include electronic communication lines (not shown) connected to some of the other contact pads 25b, 25d, 25f. Here, the sensor arrangement may be an oximeter and include two LEDs (not shown) connected to contact pads 25c, 25e and a photodiode (not shown) connected to contact pads 25a.

[0086] Now, reference is made to [Fig. 5], showing in a schematic top view a design of a conventional flexible printed circuit board in comparison with a design of a flexible printed circuit board 50 according to certain illustrative embodiments of this disclosure and a design of a flexible printed circuit board 60 according to certain other illustrative embodiments of this disclosure.

[0087] The design of the conventional flexible printed circuit board 40 shows contact pads arranged with a separation dimension L1 on a flexible substrate strip. In the case of a larger separation L2, a correspondingly increased length of the flexible substrate strip is required. The conventional flexible printed circuit board 40 has a fixed footprint, and the design of the conventional flexible printed circuit board 40 is determined by the dimensions of the flexible substrate strip.

[0088] The flexible printed circuit board design 50 is based on the flexible printed circuit board 20' as disclosed above in the context of Figures 3 and 4, the description of the flexible printed circuit board 20' applying directly to the flexible printed circuit board design 50 and the disclosure of the flexible printed circuit board 20' being incorporated by reference in its entirety. In particular, the flexible printed circuit board design 50 is obtained from the flexible printed circuit board 20' after cutting the flexible printed circuit board 20' and enlarging the flexible printed circuit board 20' by enlarging the meander or zigzag pattern 27al on the [Fig.4] in an enlarged intermediate routing portion 55 spanning a separation L2 between EPI and EP2 end portions of the flexible printed circuit board design 50 such that the contact pads 57al and 57a2 at the EPI end portion are separated from the interconnected contact pads 57b1 and 57b2 of a strip-shaped base substrate enlarged 54 by dimension L2. .

[0089] The meander or zigzag pattern 27al of [Fig. 4] is enlarged, as shown in the flexible printed circuit board design 50 of [Fig. 5], by folding down portions of linear track such as the linear track portion 55b following the linear track portion 55a (indicated by portion 27a3 of [Fig. 4]) after a U-bend at the end of the U-bend portion opposite one end of the U-bend portion interfacing with the linear track portion 55a. In order to prevent a short circuit of conductive tracks in the routing of linear track 55b in the case where the conductive tracks are not covered by an insulating coating, the folded-down portion of linear track is folded down so that the conductive tracks formed in a main surface (indicated by the main surface 23a in [Fig. 4]) are not covered by an insulating coating.4]) of the linear track portion 55b are turned towards a second main surface 56 (indicated by the main surface 23b on [Fig.4]). The main surface 56 of the linear track portion 55b is exposed in the top view shown on [Fig.5], i.e. in the top view on the main surface of the base substrate 54.

[0090] The meander or zigzag pattern 27al on [Fig. 4] is further enlarged by folding the linear track portion 55c along the linear track portion 55b After a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing with the linear track section 55b. To prevent a short circuit of conductive tracks in the linear track routing 55c in the event that the conductive tracks are not covered by an insulating coating, the folded linear track section 55c is folded so that the conductive tracks formed in a main surface (indicated by the main surface 23a in [Fig. 4]) of the linear track section 55c face towards the main surface (indicated by the main surface 23a in [Fig. 4]). The main surface of the linear track section 55c, with conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0091] The meander or zigzag pattern 27al in [Fig. 4] is further enlarged by folding the linear track portion 55d following the linear track portion 55c after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 55c. In order to prevent a short circuit of conductive tracks in the routing of linear track 55d in the case where the conductive tracks are not covered by an insulating coating, the folded linear track portion 55d is folded so that the conductive tracks formed in a main surface (indicated by the main surface 23a in [Fig. 4]) of the linear track portion 55d are turned towards a second main surface 56 (indicated by the main surface 23b in [Fig. 4]). The main surface 56 of the linear track portion 55d is exposed in the top view shown in the [Fig.5]. .

[0092] The meander or zigzag pattern 27al on [Fig. 4] is further enlarged by folding the linear track portion 55e following the linear track portion 55d after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 55d. In order to prevent a short circuit of conductive tracks in the routing of linear track 55e in the case where the conductive tracks are not covered by an insulating coating, the folded linear track portion 55e is folded so that the conductive tracks formed in a main surface (indicated by the main surface 23a on [Fig. 4]) of the linear track portion 55e are turned towards the main surface (indicated by the main surface 23a on [Fig. 4]).The main surface of the linear track portion 55e, which has conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0093] The meander or zigzag pattern 27al on [Fig. 4] is further enlarged by folding the linear track portion 55f following the linear track portion 55e after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the track portion linear 55e. To prevent a short circuit of conductive tracks in the routing of linear track 55f in the event that the conductive tracks are not covered by an insulating coating, the folded portion of linear track 55f is folded so that the conductive tracks formed in a main surface (indicated by the main surface 23a in [Fig. 4]) of the linear track portion 55f face a second main surface 56 (indicated by the main surface 23b in [Fig. 4]). The main surface 56 of the linear track portion 55f is shown in the top view shown in [Fig. 5].

[0094] The meander or zigzag pattern 27al in [Fig. 4] is further enlarged by folding the linear track portion 55g following the linear track portion 55f after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 55f. In order to prevent a short circuit of conductive tracks in the routing of linear track 55g in the event that the conductive tracks are not covered by an insulating coating, the folded linear track portion 55g is folded so that the conductive tracks formed in a main surface (indicated by the main surface 23a in [Fig. 4]) of the linear track portion 55g face the main surface (indicated by the main surface 23a in [Fig. 4]).The main surface of the linear track portion 55g, which has conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0095] The enlarged intermediate routing portion 55 has a maximum number of folds or creases so that all possible linear track portions are folded alternately to achieve the maximum separation characterized by dimension L2. However, a discretely stepped separation between the end portions EPI and EP2 of less than L2, as by dimension L1, can be obtained by omitting any folding of the linear track portions 55f and following, folding back only up to the linear track portion 55e.In this way, offset separations smaller than dimension L2 can be made by only folding the linear portion 55b or by folding only the linear portions 55a, 55b or by folding only the linear portions 55a, 55b, 55c or by folding only the linear portions 55a, 55b, 55c, 55d or by folding only the linear portions 55a, 55b, 55c, 55d, 55e.

[0096] With reference to the flexible printed circuit board design 60, this design is based on the flexible printed circuit board 1' as disclosed above in the context of Figures 1 and 2, the description of the flexible printed circuit board 1' applying directly to the flexible printed circuit board design 60 and the flexible printed circuit board 1' being incorporated by reference in its entirety. In particular, the flexible printed circuit board design 60 is obtained from the flexible printed circuit board 1' after cutting the flexible printed circuit board 1' and enlarging the flexible printed circuit board by enlarging the meander or zigzag pattern 7al on the [Fig.2] into an enlarged intermediate routing portion 65 spanning a separation L2 between EPI and EP2 end portions of the flexible printed circuit board 60 such that the contact pads 67a 1 and 67a2 at the EPI end portion are separated from the interconnected contact pads 67b 1 and 67b2 of a strip-shaped base substrate enlarged 64 by dimension L2.

[0097] The meander or zigzag pattern 7al of [Fig. 2] is enlarged, as shown in the flexible printed circuit board 60 of [Fig. 5], by folding down portions of linear track such as the linear track portion 65b following the linear track portion 65a after a U-bend portion (indicated by portion 7a3 of [Fig. 2]) at the end of the U-bend portion opposite one end of the U-bend portion interfacing with the linear track portion 65a. In order to prevent a short circuit of conductive tracks in the routing of linear track 65b in the case where the conductive tracks are not covered by an insulating coating, the folded-down portion of linear track is folded down so that the conductive tracks formed in a main surface (indicated by the main surface 3a in [Fig. 5]) are not covered by an insulating coating.2]) of the linear track portion 65b are oriented towards a second main surface 66 (indicated by the main surface 3b in [Fig.2]). The main surface 66 of the linear track portion 65b is exposed in the top view shown in [Fig.5], i.e. in the top view of the main surface of the base substrate 64.

[0098] The meander or zigzag pattern 7al on [Fig.2] is further enlarged by folding the linear track portion 65c following the linear track portion 65b after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 65b. In order to prevent a short circuit of conductive tracks in the routing of linear track 65c in the event that the conductive tracks are not covered by an insulating coating, the folded linear track portion 65c is folded so that the conductive tracks formed in a main surface (indicated by the main surface 3a on [Fig.2]) of the linear track portion 65c are oriented towards the main surface (indicated by the main surface 3a on [Fig.2]).The main surface of the linear track portion 65c, which has conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0099] The meander or zigzag pattern 7al on [Fig. 2] is further enlarged by folding the linear track portion 65d following the linear track portion 65c after a U-shaped bend at the end of the bend. U opposite one end of the U-shaped bend interfacing portion of linear track 65c. To prevent short circuits of conductive tracks in the linear track 65d routing in cases where the conductive tracks are not covered by an insulating coating, the folded-down portion of linear track 65d is folded down so that the conductive tracks formed in a main surface (indicated by main surface 3a in [Fig. 2]) of the linear track portion 65d face a second main surface 66 (indicated by main surface 3b in [Fig. 2]). The main surface 66 of the linear track portion 65d is shown in the top view depicted in [Fig. 5].

[0100] The meander or zigzag pattern 7al on [Fig.2] is further enlarged by folding the linear track portion 65e following the linear track portion 65d after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 65d. In order to prevent a short circuit of conductive tracks in the routing of linear track 65e in the case where the conductive tracks are not covered by an insulating coating, the folded linear track portion 65e is folded so that the conductive tracks formed in a main surface (indicated by the main surface 3a on [Fig.2]) of the linear track portion 65e are turned towards the main surface (indicated by the main surface 3a on [Fig.2]).The main surface of the linear track portion 65e, which has conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0101] The meander or zigzag pattern 7al on [Fig.2] is further enlarged by folding down the linear track portion 65f following the linear track portion 65e after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 65e. In order to prevent a short circuit of conductive tracks in the routing of linear track 65f in the case where the conductive tracks are not covered by an insulating coating, the folded linear track portion 65f is folded down so that the conductive tracks formed in a main surface (indicated by the main surface 3a on [Fig.2]) of the linear track portion 65f are oriented towards a second main surface 66 (indicated by the main surface 3b on [Fig.2]). The main surface 66 of the linear track portion 65f is exposed in the top view shown in the [Fig.5].

[0102] The meander or zigzag pattern 7al on [Fig. 2] is further enlarged by folding the linear track portion 65g following the linear track portion 65f after a U-shaped bend at the end of the U-shaped bend opposite one end of the U-shaped bend interfacing the linear track portion 65f. In order to avoid a short circuit of conductive tracks in the routing In the case where the conductive tracks of linear track 65g are not covered by an insulating coating, the folded portion of linear track 65g is folded so that the conductive tracks formed in a main surface (indicated by main surface 3a in [Fig. 2]) of the linear track portion 65g are oriented towards the main surface (indicated by main surface 3a in [Fig. 2]). The main surface of the linear track portion 65g, including the conductive tracks formed within it, is shown in the top view shown in [Fig. 5].

[0103] The enlarged intermediate routing portion 65 has a maximum number of folds or creases so that all possible linear track portions are folded alternately to achieve the maximum separation by dimension L2. However, a discretely stepped separation between the end portions EPI and EP2 of less than L2, as characterized by dimension L1, can be obtained by omitting any folding of the linear track portions 65f and following, folding back only up to the linear track portion 65e.In this way, offset separations smaller than dimension L2 can be made by folding only the linear portion 65b or by folding only the linear portions 65a, 65b or by folding only the linear portions 65a, 65b, 65c or by folding only the linear portions 65a, 65b, 65c, 65d or by folding only the linear portions 65a, 65b, 65c, 65d, 65e.

[0104] Figure 6 is an enlarged schematic cross-sectional view of a sensor arrangement 70 at a component 93 of the sensor arrangement 70 according to certain illustrative embodiments of this disclosure. The component 93 may be an LED component or a photodiode component.

[0105] As illustrated in [Fig.6], a portion of a substrate 87 in accordance with certain special illustrative embodiments is shown without implying any limitation on the specifically disclosed sensor arrangement 70.

[0106] In some illustrative embodiments, the substrate 87 may be a flexible, strip-shaped substrate as described above.

[0107] In certain special illustrative examples, the substrate 87 may be, for example, an epoxy glass material. The substrate 87 may have a thickness in a range from about 50 µm to about 150 µm. For example, the substrate 87 may have a thickness of 110 µm.

[0108] In certain special illustrative examples, the substrate 87 may have a contact pad formed on one SI side of the substrate (e.g., a principal surface of the substrate 87 on the SI side). For example, the contact area includes gold 78, nickel 81, and copper 83. In certain illustrative examples, the gold may have a thickness of less than 1 pm, for example, a few nanometers, and the nickel may have with a thickness of about 1 to 4 pm, copper can have a thickness of about 35 pm.

[0109] As shown in [Fig. 6], the contact area on the SI side can be made contact through the substrate 87 by component 93 through an opening in the substrate 87 such that component 93 can be arranged on an S2 side opposite the SI side. This construction allows for further cost savings by using a single layer of metal (for the contact pad and / or the conductive track) accessible from both sides of the substrate 87, where the S2 side can be for the component assembly and the SI side for metallic lines in wiring, such as conductive line tracks.

[0110] With continued reference to [Fig. 6], the component 93 in the opening can make contact with the contact pad and be assembled in the opening by means of a conductive adhesive 89 to make contact with a contact pad 82 in the opening. For example, a first electrode contact 78a in the opening can provide a portion of via 82 extending through the substrate 87. Another electrode contact 78b can be provided by an adjacent via for a wire connection with the component 93 via a wire 95, for example, an upper contact of the component 93.

[0111] According to some illustrative embodiments, the contact pad can be formed on the SI side by an adhesive 85, for example with a thickness of approximately 10 µm to approximately 30 µm, for example approximately 18 µm. However, this does not imply any limitations, and alternatives to assembling the contact pad by adhesive are possible.

[0112] As shown in [Fig. 6], the sensor arrangement 70 may further include the addition of an electromagnetic interference (EMI) metallic film covering metallic lines and flexing over the top of the component 93 at the end to reduce electromagnetic interference in the very low current measured by the sensor arrangement 90. In the illustrative but not limiting example shown in [Fig. 6], the EMI metallic film may include a conductive layer 72 attached to the sides S1 and S2 by means of an adhesive, for example, a double-sided adhesive. The adhesive may include a portion of anisotropic conductive film (ACF) 74, the ACF portion 74 being in contact with wiring to impose a protective potential, for example, coupling the conductive layer 72 to earth.For example, in the case where component 93 corresponds to a photodiode in the sensor arrangement 70, the EMI metallic film protects the photodiode to reduce electromagnetic interference in current measurements provided by the sensor arrangement 70. As shown in [Fig. 6], the EMI metallic film may have an opening or a suitable window portion (not shown) allowing electromagnetic radiation to be received and / or emitted by component 93 during the operation of the sensor arrangement. In the case of use. instead of an opening, the window portion may be a portion of transparent material, where the portion of transparent material is transparent to the electromagnetic radiation received and / or emitted by component 93. The transparent window portion may protect component 93 against an environmental influence of deterioration such as the ingress of liquid, dirt, etc.

[0113] According to some illustrative embodiments, the conductive layer 72 may have a thickness of approximately 10 µm to approximately 50 µm, for example, approximately 30 µm. The adhesive and the ACF portion 74 may have a thickness of approximately 5 µm to approximately 20 µm, for example, approximately 10 µm.

[0114] In certain illustrative embodiments, the EMI metallic film may be formed only above the sensor arrangement 70 at certain end portions of the sensor arrangement 70 corresponding to certain end portions 1a, 11b, 21a, 21b, 31a, 31b, EPI, EP2 when applied in the context of the embodiments disclosed above with respect to Figures 1 to 5. Alternatively, the EMI metallic film may be formed only on the sensor arrangement 70 at both end portions of the sensor arrangement 70 corresponding to end portions 1a, 11b, 21a, 21b, 31a, 31b, EPI, EP2 when applied in the context of the embodiments disclosed above with respect to Figures 1 to 5 without being formed above a intermediate portion between the end portions.

[0115] When applying the sensor arrangement 70 of [Fig.6] to one of the embodiments of Figures 1 to 5, the contact pad of the sensor arrangement 70 can be connected to an enlarged meander or zigzag pattern of conductive tracks connecting the contact pad to counter contact pads.

[0116] With reference to [Fig. 7], an implementation of a sensor arrangement 90 as an oxygen sensor element is schematically illustrated. The sensor arrangement 90 comprises a sensor structure provided by a light detector LD and light sources L1 and L2. The light detector is electrically coupled via an interconnect 82 through a connection routing 86 connected to contact pads (not shown). However, this does not impose any limitations on the present disclosure, and those skilled in the art will understand that the sensor arrangement 90 can be implemented as an electrostimulation electrode or any other suitable sensor element.

[0117] In the schematic illustration of the sensor arrangement 90, the sensor arrangement further comprises a flexible printed circuit board 80 corresponding to any one of the flexible printed circuit boards as disclosed above, as in the context of Figures 1 to 6 above. The circuit board The flexible printed circuit board 80 can be electrically coupled to a module (not shown) via communication lines (not shown) or wirelessly. The module (not shown) may include a set of electrical circuits to control the sensor arrangement 90, i.e., the photodiode LD on the flexible printed circuit board 80 and the light sources L1 and L2. The light sources L1 and L2 can provide optical signals to be detected by the photodiode LD, which, in response, generates electrical signals. During operation, as shown in [Fig. 7], the sensor arrangement 90 can be arranged on a patient's finger F such that the photodiode LD is positioned opposite the light sources L1 and L2 by appropriately positioning the photodiode LD relative to the light sources L1 and L2 on the finger F, i.e., at fixed spatial locations on the finger F.The sensor arrangement 90 can correspond at the level of a region of the photodiode LD or of one of the light sources L1 and L2 to the sensor arrangement 70 disclosed in the context of [Fig.6].

[0118] Summarizing the disclosure with respect to Figures 1 to 7, a flexible printed circuit board for a sensor arrangement is provided, wherein the flexible printed circuit board comprises a strip-shaped base substrate with a plurality of contact pads and a plurality of conductive tracks. The plurality of contact pads and the plurality of conductive tracks comprise a first set of interconnected contact pads with two first contact pads and two second contact pads. Each of the first contact pads is interconnected with one of the corresponding second contact pads via a corresponding conductive track of a first pattern of conductive tracks routed in a meander or zigzag pattern. The strip-shaped base substrate further comprises a pattern of cut lines provided in the strip-shaped base substrate.

[0119] The terminology used herein is solely for the purpose of describing particular embodiments and is not intended to limit disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "includes" and / or "comprising," when used in this description, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. "Optional" or "facultatively" means that the event or circumstance described later may or may not occur, and that the description includes cases where the event does and cases where it does not.

[0120] An approximation language, as used herein throughout the description and claims, can be applied to modify any quantitative representation that might vary permissibleally without causing a change in the basic function to which it relates. Accordingly, a value modified by one or more terms, such as "about," "approximately," and "substantially," need not be limited to the precise value specified. In at least some cases, the approximation language may correspond to the precision of an instrument for measuring the value. Herein and throughout the description and claims, range limitations may be combined and / or interchanged; these ranges are identified and include all subranges contained therein, unless otherwise indicated by the context or the language."Approximately" or "significantly", applied to a particular value in a range applies to both values, and unless it depends on the accuracy of the instrument measuring the value, may indicate + / - 10% of the value(s) indicated.

[0121] The descriptions of the various embodiments of the present invention have been given for illustrative purposes only, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used here has been chosen to better explain the principles of the embodiments, their practical application or technical improvement over commercially available technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. Demands Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) for a sensor arrangement, wherein the flexible printed circuit board (1; 1'; 20; 20'; 50; 60) comprises a strip-shaped base substrate (3; 23) with a plurality of contact pads (5; 25) and a plurality of conductive tracks (7a, 7b; 27a, 27b), in which the plurality of contact pads (5; 25) and the plurality of conductive tracks (7a, 7b; 27a, 27b) are formed in a principal surface (3a; 23a; 54; 64; SI) of the strip-shaped basic substrate (3; 23), in which the plurality of contact pads (5; 25) and the plurality of conductive tracks (7a, 7b; 27a, 27b) form interconnected sets of interconnected contact pads, each set of interconnected contact pads comprising at least two contact pads (5a1, 5b1; 5a2, 5b2; 5c1, 5d1; 5c2, 5d2; 5f, 5g; 25a1, 25b1; 25a2, 25b2; 25c1, 25d1; 25c2, 25d2; 25f, 25g; 57a1, 57b1; 57a2, 57b2; 67a1, 67b1; 67a2, 67b2) interconnected by at least one conductive track routed between the contact pads interconnected (5al, 5b 1; 5a2, 5b2; 5cl, 5dl; 5c2, 5d2; 5f, 5g; 25al, 25b 1; 25a2, 25b2; 25c 1, 25dl; 25c2, 25d2; 25f, 25g; 57al, 57b 1; 67b2) of each set in the main surface (3a; 54a; 23b2; 64; SI) wherein the interconnected contact pad assemblies comprise a first set of interconnected contact pads, the first set comprising two first contact pads (5a1, 5a2; 25a1, 25a2; 57a1, 57a2; 67a1, 67a2) located at a first end portion (9a; 29a; EP1) of the strip-shaped base substrate (3; 23) and two second contact pads (5b1, 5b2; 25b1, 25b2; 57b1, 57b2; 67b1, 67b2) located at a second end portion (9b; 29b; EP2) of the strip-shaped base substrate (3; 23) opposite the first end portion (9a; 29a; EP1) along a direction of length (L) of the strip-shaped base substrate (3; 23), each of the first contact pads (5al, 5a2; 25al, 25a2; 57al, 57a2; 67al, 67a2) being interconnected with one of the corresponding second contact pads (5b1, 5b2; 25b1, 25b2; 57b1, 57b2; 67b1, 67b2) via a corresponding conductive track of a first pattern of conductive tracks (7a; 27a) routed in an intermediate portion (9c; 29c; MP) of the strip-shaped base substrate (3; 23) between the first and second end portions (9a; 29a, EPI; 9b, 29b), EP2) in the main surface (3a; 23a; 54; 64; SI), wherein the conductive tracks of the first pattern of conductive tracks (7a; 27a) are partially routed in a meander or zigzag pattern (7al; 27al) in the intermediate portion (9c; 29c; MP), and wherein the strip-shaped base substrate (3; 23) further comprises a pattern of cutting lines (15; 35) provided in the strip-shaped base substrate (3; 23), the pattern of cutting lines (15; 35) having cutting lines (15a, 15b;35a, 35b) which are at least partially interlocked with the meander or zigzag pattern (7al; 27al).;

2. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to claim 1, further comprising at least one LED and at least one photodiode arranged on a second principal surface (3b; 23b; 56; 66; S2) of the strip-shaped base substrate (3; 23) opposite the principal surface (3a; 23a; 54; 64; SI) and electrically interconnected with associated contact pads via a via (82) interconnecting the principal surface (3a; 23a; 54; 64; SI) and the second principal surface (3b; 23b; 56; 66; S2).

3. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to claim 1, further comprising at least one LED and at least one photodiode arranged on the main surface (3a; 23a; 54; 64; SI) of the strip-shaped base substrate (3, 23), the at least one LED and the at least one photodiode being electrically connected with associated contact pads.

4. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to any one of claims 1 to 3, wherein the meander or zigzag pattern (7a1; 27a1) comprises U-shaped bending routing portions and linear track portions extending between two U-shaped bending routing portions, wherein the U-shaped bending routing portions and the linear track portions are routed between cutting lines of the pattern of cutting lines (15; 35) extending laterally close along each of the U-shaped bending routing portions and the linear track portions such that adjacent linear track portions are completely separated by at least one cutting line extending completely between each pair of adjacent linear track portions.

5. Flexible circuit board (1; 1'; 20; 20'; 50; 60) according to claim 4, wherein the meander or zigzag pattern (7al; 27al) can be mechanically bent at the U-bending routing portions and / or linear track portions adjacent to the cut lines so as to fold or bend the meander or zigzag pattern (7al; 27a1) at least once.

6. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to claim 5, wherein at least one of the linear track portions is folded or bent.

7. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to any one of claims 4 to 6, wherein the meander or zigzag pattern (7al; 27al) has at least one linear track portion oriented so as to face the opposite of the main surface (3a; 23a; 54; 64; SI).

8. Flexible circuit board (1; 1'; 20; 20'; 50; 60) according to any one of claims 1 to 7, wherein the pattern of cutting lines (15; 35) comprises cutting lines along which the strip-shaped base substrate (3; 23) is mechanically cut to mechanically completely separate adjacent portions of material from the strip-shaped base substrate (3; 23) between which cutting lines are defined, preferably the cutting lines forming exposed edges of the strip-shaped base substrate (3; 23a; 54; 64; SI) in each of the primary surface (3a; 23a; 54; 64; SI) and the second primary surface (3b; 23b; 56; 66; S2).

9. Flexible printed circuit board (1; 1'; 20; 20'; 50; 60) according to any one of claims 1 to 8, wherein the interconnected contact pad assemblies comprise a second pad assemblies of interconnected contact points, the second set comprising two third contact points (5c1, 5c2; 25c1, 25c2; 57c1, 57c2; 67c1, 67c2) located in the intermediate portion (9c; 29c; MP) of the strip-shaped base substrate (3; 23) and fourth contact points (5dl, 5d2; 25dl, 25d2; 57dl, 57d2; 67dl, 67d2) located at the first end portion (9a; 29a; EPI) of the strip-shaped base substrate (3; 23) adjacent to the second contact points (5b1, 5b2; 25b1, 25b2; 57b1, 57b2; 67b1, 67b2), in which the third contact pads (5c 1, 5c2; 25c 1, 25c2; 57c 1, 57c2; 67c 1, 67c2) are located in the main surface (3a; 23a; 54; 64; SI) between the first end portion (9a; 29a, EPI) and the meander or zigzag pattern (7al; 27al), wherein each of the third contact pads (5c1, 5c2; 25c1, 25c2; 57c1, 57c2; 67c1, 67c2) is interconnected with one of the corresponding fourth contact pads (5dl, 5d2; 25dl, 25d2; 57dl, 57d2; 67dl, 67d2) via a corresponding conductive track of a second pattern of conductive tracks (7b; 27b) routed between the third and fourth contact pads (5c1, 5c2; 25c1, 25c2; 57c1, 57c2; 67c 1, 67c2; 5bl, 5b2; 25b 1, 25b2; 57b 1, 57b2; 67b 1, 67b2).

10. Sensor arrangement (90), comprising: the flexible printed circuit board (1; 1'; 20; 20'; 50; 60; 80) of any one of claims 1 to 9; a sensor structure (LD) provided on at least one principal surface of the opposite principal surfaces of the flexible printed circuit board and electrically connected to some of the contact pads; and electronic communication lines connected to some of the other contact points.

11. Sensor arrangement according to claim 9, wherein the flexible printed circuit board (1; 1'; 20; 20'; 50; 60) is provided by the flexible printed circuit board (1; 1'; 20; 20'; 50; 60) of claim 9, and wherein the sensor structure comprises two LEDs connected to the third contact pads of the second assembly and a photodiode electrically connected to the first contact pads of the first assembly.

12. Method of forming a sensor arrangement, comprising the steps of: providing the sensor arrangement of claim 10 or 11; cutting along the pattern of cutting lines; and enlarging the meander or zigzag pattern into an enlarged meander or zigzag pattern.

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