WO2011135153A1

WO2011135153A1 - Method for manufacturing an antenna component by etching

Info

Publication number: WO2011135153A1
Application number: PCT/FI2010/050349
Authority: WO
Inventors: Antti Manninen
Original assignee: Upm Raflatac Oy
Priority date: 2010-04-29
Filing date: 2010-04-29
Publication date: 2011-11-03
Also published as: CN103081101B; KR101644493B1; CN103081101A; KR20130098164A

Abstract

A method for manufacturing an antenna component (2) by etching, the component comprising a substrate (3) and an electrically conductive line configuration (4) supported by the substrate (3). The electrically conductive line configuration (4) is formed by etching away locally by etchant an electrically conductive coating supported by the substrate (3). An extent of etching of the antenna component (2) is indicated by an etching indicator (10), the etching indicator (10) being located at the antenna component (2) to be etched or in proximity to the antenna component (2) to be etched and consisting of the same electrically conductive coating supported by the substrate (3) of the component (2) and being exposed to the etchant during etching. Further an antenna component (2) or a group (15) of antenna components (2) comprising an etching indicator (10) and an etching mask (12) for manufacturing an antenna component (2) by etching are introduced.

Description

METHOD FOR MANUFACTURING AN ANTENNA COMPONENT BY ETCHING

FIELD OF THE INVENTION

The invention relates to a method for manufacturing an antenna component by etching, the component comprising a substrate and an electrically conductive line configuration supported by the substrate, and in which method the electrically conductive line configuration is formed by etching away locally by etchant an electrically conductive coating supported by the substrate.

Further the invention relates to an antenna component or a group of antenna components, the component comprising a substrate and an electrically conductive line configuration supported by the substrate.

Further the invention relates to an etching mask for manufacturing an antenna component by etching, the component comprising a substrate and an electrically conductive line configuration supported by the substrate, the electrically conductive line configuration being formed by etching away locally by etchant an electrically conductive coating supported by the substrate, the etching mask determining the electrically conductive line configuration of the component.

BACKGROUND OF THE INVENTION

Typically in the etching of printed circuit boards or other corresponding electronic components or products etching process variations may cause significant deviation of electrical characteristics of the electric circuits between successively etched similar etched circuits. This is especially true when etching radio frequency structures such as antenna structures. In the etching of antennas for radio frequency identification tags or RFID tags, for example, the process variations in the etching may cause frequency behaviour variation in the etched antennas which further affects the electrical matching of the antenna with the other parts of RFID circuitry.

Figure 1 discloses a prior art radio frequency identification tag 1 or RFID tag 1 , the RFID tag 1 being one example of a product which may comprise an antenna component comprising an electrically conductive line configuration formed by etching. The RFID tag 1 comprises an antenna component 2 comprising a substrate 3 and an antenna 4, the antenna 4 being an electrically conductive line configuration of the antenna component 2 and the substrate 3 supporting one or more layers of electrically conductive coating which is partly removed during etching of the antenna 4. The antenna component 2 thus forms a part of the RFID tag 1 , which may be used in many different kind of applications. RFID tags may, for example, be attached to different kind of items sold in department stores, for storing specific information relating to the items they are attached to. The antenna 4 provides means to transfer information between the RFID tag 1 and a device for reading the information stored in the tag 1 or a device for sending information to be stored in the tag 1 .

The RFID tag 1 comprises further an integrated circuit 5 or chip 5 arranged in connection with the electrically conductive line configuration or the antenna 4, in order to store specific information relating to the item the RFID tag 1 is attached to. The antenna component 2 and the integrated circuit 5 attached to the antenna component 2 may be further attached to a pressure sensitive adhesive, i.e. a sticker 6 or some other kind of attachment element, thus providing a finished RFID tag 1 ready to be attached to the items to be sold in the department store, for example. In Figure 1 , the sticker 6 has been schematically shown by a box surrounding the antenna component 2. In addition to the basic elements shown in Figure 1 , the RFID tag 1 may also contain other layers laminated or otherwise attached to the structure.

The antenna 4 may comprise two resonant circuits, i.e. a radiating element 4' and a separate impedance matching element 4", which are electromagnetically coupled together to achieve a desired frequency response of the antenna 4 together with the integrated circuit 5. The frequency response of the impedance matching element 4" is affected by the inductance of the impedance matching element 4" and the input resistance and the input capacitance of the integrated circuit 5 connected to the impedance matching element 4". The frequency response of the radiating element 4' is affected by the inductance, capacitance and radiation resistance of the radiating element 4'. Basically, the impedances of the antenna 4 and the integrated circuit 5 needs to be suitably matched in order the circuitry to have a proper performance and frequency response.

Especially in UHF frequency range operating RFID tags the impedance matching element 4" and the radiating element 4' may be physically connected to each other by a coupling part 4"' but practically the impedance matching element 4" and the radiating element 4' are coupled to each other via mutual inductance, i.e. the impedance matching element 4" having a certain resonance frequency is inductively coupled to the radiating element 4' having a certain resonance frequency. A coupling distance D between the impedance matching element 4" and the radiating element 4', i.e. the shortest distance between the impedance matching loop 4" and the radiating element 4' affects the frequency response of the antenna 4.

It should be noted that the specific antenna structure shown in Figure 1 is given as an example only. The separate impedance matching loop 4" in addition to the radiating element 4' is typical for RFID tag antennas designed for UHF range. For example, in near field operating UHF tags (UHF NF) the loop structure of the impedance matching loop 4" may perform as the antenna without any additional radiating element.

For the invention described later the main importance is to understand that the etching process variations in antenna manufacturing may alter physical dimensions of the antenna 4. The variations of the physical dimensions of the antenna 4 means that the antenna pattern dimensions have some offset from the initial design target, which design target depends on the frequency range and type of the RFID tag in question. The etching process variations may result for example from the variations of the temperature and composition of the etchant or the time the etchant has an influence on the electrically conductive coating to be etched away. The variations in the physical dimensions of the antenna 4 cause electrical parameters of the antenna 4 to change, changing the antenna frequency tuning and impedance matching with the integrated circuit 5. This frequency tuning change can be further seen as shifts in performance so that the optimum performance of the antenna starts to degrade.

One rather typical factor of the frequency tuning changes is a change in the coupling distance D between the impedance matching element 4" and the radiating element 4'. Changes in the coupling distance D alter further the impedance match and the frequency response of the antenna 4 together with the integrated circuit 5. With some antenna designs the change in the coupling distance D after etching may be as high ± 10%. This kind of changes in the coupling distance D may have a significant effect on the performance of the antenna, the performance of the antenna starting to degrade for example such that the frequency response of the antenna becomes distinctively distorted. This may be observed in practice for example by some loss in reading distance of the RFID tag. US-publication 2007/0069037 A1 discloses a noncontact RFID tag comprising an antenna unit having an antenna as a radiating element and an impedance matching wiring portion. The impedance matching wiring portion comprises several mounting positions for the integrated circuit module such that when the integrated circuit module is mounted at different mounting positions, the frequency characteristics of the antenna unit are different. With this kind of solution a single antenna unit construction may be used as a basic antenna unit for RFID tag manufacturing and the final frequency response of the antenna unit is selected by mounting the integrated circuit module to the specific mounting position in the antenna unit. This makes it possible to manufacture several types of RFID tags having different frequency bands on the basis of only one kind of antenna unit in cases, where the allowable frequency bands for RFID tags are different in different countries. The RFID tag according to US-publication 2007/0069037 further comprises specific marker positions formed to the corresponding mounting positions of the integrated circuit module such that for example the country to which the manufactured RFID tag is intended to can be easily determined at a glance.

With the solution disclosed in US-publication 2007/0069037 RFID tags having different frequency response characteristics may be manufactured by using only one type of antenna unit construction. However, RFID tags disclosed in US-publication 2007/0069037 still suffer from the changes or variations in the coupling distance between the actual radiating element and the impedance matching wiring portion, the changes or variations originating from the etching process variations in antenna manufacturing. Further, it should be noted that the mounting positions therein are designed to cause a rather big change in the RFID tag operating frequency corresponding to the frequency requirements in different geographic areas. These changes are much bigger than the changes caused by any etching variations discussed in relation to the current invention. BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is thus to provide a solution by which the effects of the changes or variations originating from the etching process variations may be taken into account in the further use of the antenna component comprising the etched electrically conductive line configuration providing the antenna of the antenna component. The invention aims to help to eliminate the effect of the etching variations in the electrical performance of the final product such as in a RFID tag.

A method according to the invention is characterized by indicating by an etching indicator an extent of etching of the antenna component, the etching indicator being located at the antenna component to be etched or in proximity to the antenna component to be etched and consisting of the same electrically conductive coating supported by the substrate of the antenna component and being exposed to the etchant during etching.

An antenna component or a group of antenna components is characterized in that at least at some manufacturing stage of the at least one antenna component there is at least one etching indicator at the antenna component or in proximity to at least one antenna component, the etching indicator providing information about the extent of etching of the at least one antenna component and consisting of the same electrically conductive coating supported by the substrate.

An etching mask according to the invention is characterized in that the etching mask comprises barrier material on at least one main area corresponding to the electrically conductive line configuration to be maintained during etching and that the etching mask further comprises barrier material on at least one sub-area for forming an etching indicator consisting of the same electrically conductive coating supported by the substrate, the etching indicator being arranged to indicate the extent of etching of the antenna component.

In a method for manufacturing an antenna component by etching, the component comprising a substrate and an electrically conductive line configuration supported by the substrate, the electrically conductive line configuration of the component is formed by etching away locally by etchant an electrically conductive coating supported by the substrate. An extent of etching of the antenna component is indicated by an etching indicator, the etching indicator being located at the antenna component to be etched or in proximity to the antenna component to be etched and consisting of the same electrically conductive coating supported by the substrate of the component and being exposed to the etchant during etching.

The etching indicator can be used to indicate the extent of the effect of the etchant on the electrically conductive coating, the effect of the etchant on the electrically conductive coating providing information about the extent to which the electrically conductive line configuration was etched during etching process. By inspecting the etching indicator it is possible to determine if the electrically conductive line configuration of the antenna component was etched too much (over-etching), too less (under-etching) or exactly corresponding to the designed target line configuration. Thereby the usability of the antenna component in the electromagnetic sense in further manufacturing stages may be determined before any integrated circuits or other similar parts are attached to the etched antenna component. This is an important factor for reducing manufacturing costs.

According to an embodiment the etching indicator comprises a number of parallel lines having different width relative to each other, the etching indicator thus having a simple form or shape.

According to one embodiment the antenna component is intended to form a part of a radio frequency identification tag or RFID tag comprising an integrated circuit, whereby the electrically conductive line configuration is intended to form at least a part of an antenna of the RFID tag. The antenna may comprise one or more elements, for example, a radiating element and an impedance matching element. When the component to be manufactured is intended to form a part of the RFID tag, the electrically conductive line configuration of the component being intended to form at least part of the antenna of the RFID tag, the etching indicator may be used to indicate the frequency tuning characteristics of the actual etched antenna pattern relative to the design target antenna, and thereby to indicate the usability of the antenna component in the further manufacturing stages of the RFID tag.

According to a further embodiment the antenna or the impedance matching element of the antenna for the RFID tag comprises a number of possible attachment points for attaching the integrated circuit and that the specific attachment point for the integrated circuit is determined by inspecting the etching indicator. By inspecting the etching indicator it is possible to determine the frequency tuning characteristics of the actual etched antenna pattern relative to the design target antenna, and then, by selecting the proper attachment point for the integrated circuit in the antenna or in the impedance matching element of the antenna it is possible to compensate the changes of the frequency tuning characteristics of the antenna, the changes originating from the variations in the etching process ("over" or "under" etching), in order to provide a workable RFID tag despite of the process variations in the etching process of the antenna pattern. According to a further embodiment the antenna or antenna conductor structure may be altered after etching of the antenna or the antenna conductor structure on the basis of extent of etching indicated by the etching indicator. The antenna conductor structure may be altered locally by removing conductive material for example by laser tuning or die cutting away form the antenna structure and/or by adding conductive material on the antenna structure to affect the radio frequency behaviour of the etched antenna. The antenna conductor structure may also be altered by adding a separate, possibly laminated, tuning structure at the antenna component to affect the radio frequency behaviour of the etched antenna. Thereby the information provided by the etching indicator may also be used for altering the antenna conductor structure after etching in addition to or instead of the selection of proper attachment point for the integrated circuit at the antenna component.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figure 1 shows schematically a top view of a prior art radio frequency identification tag;

Figure 2 shows schematically a top view of an antenna component comprising an electrically conductive line configuration and an etching indicator;

Figure 3 shows schematically a top view of a detail of the antenna component according to Figure 2;

Figure 4 shows schematically a top view of an etching indicator;

Figure 5 shows schematically a top view of a second etching indicator;

Figure 6 shows schematically a top view of an etching mask which can be used in the manufacturing of the antenna component according to Figure 2 and

Figure 7 shows schematically a group of antenna components comprising one etching indicator for each group of components.

DETAILED DESCRIPTION OF THE INVENTION

Figure 2 is a top view of an antenna component 2 comprising an electrically conductive line configuration on a substrate 3. The antenna component 2 of Figure 2 forms part of a basic radio frequency identification tag, lacking only an integrated circuit 5 and a sticker 6 when compared to a finished radio frequency identification tag or RFID tag. The electrically conductive line configuration of the component 2 according to Figure 2 forms an antenna 4 for the RFID tag. The antenna 4 according to Figure 2 comprises a radiating element 4', an impedance matching element 4" and a coupling element 4"'. The antenna may be designed for UHF frequency range, for example.

The impedance matching element 4" shown in Figure 2 further comprises a number of attachment points for attaching the integrated circuit 5 in connection with the impedance matching element 4". The impedance matching element 4" shown in Figure 2 is shown more clearly in Figure 3. The impedance matching element 4" according to Figures 2 and 3 comprises five attachment points, i.e. attachment points 7a, 7b, 7c, 7d and 7e, for attaching the integrated circuit 5 in connection with the impedance matching element 4". The attachment points 7a - 7e are formed during etching of the antenna 4 of the same electrically conductive coating as the antenna 4, the electrically conductive coating being supported by the substrate 3. The attachment point configuration comprises two projections 8, one projection 8 on both sides of the attachment points 7a - 7e. The projections 8 are perpendicular to the line configuration of the impedance matching element 4" and in the embodiment of Figures 2 and 3 the projections 8 are directed inwards of the loop structure of the impedance matching element 4" but they could naturally be directed into the opposite direction too. Both projections 8 comprise five side projections 9, the side projections 9 being in physical connection with the corresponding projection 8 and perpendicular to the projection 8, the side projections 9 being directed towards that other projection 8 with which they are not in physical connection. The side projections 9 connected to the opposite projections 8 are facing to each other but they do not have any straight physical connection with each other before attaching the integrated circuit 5 at the specific attachment point 7a, 7b, 7c, 7d or 7e. Each of the attachment points 7a to 7e forms a different physical loop length of the impedance matching element 4" and thus each of the attachment points 7a to 7e provides different frequency tuning characteristics for the impedance matching element 4" after the integrated circuit has been attached at the specific attachment point 7a to 7e.

The attachment points and connection area can be designed in several ways and therefore the design shown in Figures 2 and 3 should be understood only as an example. Further it should be noted although in the embodiment shown in Figures 2 and 3 the attachment points 7a to 7e are arranged in connection with the impedance matching element 4", the attachment points 7a to 7e could be arranged in connection with some other part of the antenna 4 depending for example on the antenna structure.

The antenna component 2 according to Figure 2 further comprises an etching indicator 10, which is shown in more details in Figure 4. The etching indicator 10 or etching indicator pattern 10 according to Figure 4 comprises five parallel lines 1 1 a, 1 1 b, 1 1 c, 1 1 d and 1 1 of different widths, whereby these five parallel lines 1 1 a to 1 1 e form a pattern comprising five portions, i.e. lines 1 1 a to 1 1 e, having different dimensions of same characteristic, i.e. width of the line, relative to each other. The etching indicator 10 is used to indicate an extent of the etching of the component 2 or an extent of the effect of the etchant on the electrically conductive coating supported by the substrate 3 of the component 2. The lines 1 1 a to 1 1 e consists of the electrically conductive coating supported by the substrate 3, whereby the etching indicator 10 is to be formed during etching of the electrically conductive line configuration of the component 2. In Figure 4 the etching indicator 10 is shown in its basic form or shape before the etchant has had any effect on the etching indicator 10 and in Figure 2 the etching indicator 10 is shown in a form or shape, wherein the etchant has removed lines 1 1 c to 1 1 e away from the etching indicator 10 during the etching of the antenna 4.

During etching of the antenna 4 the antenna component 2 comprising the substrate 3 is exposed to the effect of the etchant for forming the antenna 4 configuration, i.e. the radiating element 4', the impedance matching element 4" and the coupling element 4"', and in the case of the embodiment according to Figure 2, also for forming the projections 8 and the side projections 9 for providing the attachment points 7a to 7e. During etching the etchant removes the electrically conductive coating from the substrate 3 of the antenna component 2 on those parts of the substrate 3 not protected by the etching mask used. The etching mask comprises barrier material on those parts of the substrate 3 wherein the designed electrically conductive line configuration is desired to be maintained. The basic principle of the etching process itself is generally known by a person skilled in the art and therefore it is not described more detailed here. However, as already described above, the etching process variations in antenna manufacturing for RFID tags may alter physical dimensions of the antenna 4. The variations of the physical dimensions of the antenna 4 caused by over- or under-etching give rise to the antenna pattern dimensions to have some offset from the initial design target. The etching process variations may result for example from the variations of the temperature and composition of the etchant or the time the etchant has an influence on the electrically conductive coating to be etched away. The variations in the physical dimensions of the antenna cause electrical parameters of the antenna 4 to change, changing the antenna frequency tuning characteristics. This frequency tuning change can be further seen as shifts in performance so that the optimum performance of the antenna starts to degrade.

By using the above described etching indicator 10 this frequency tuning change may be estimated. This estimation may be based on theoretical calculations or simulations or it may be based on empirical etching tests, where a range of over- and under-etching tests are performed and the effect of those on the frequency characteristics of the antennas are afterwards measured.

During etching process the etchant removes the electrically conductive coating not only on those portions of the electrically conductive coating which are to be removed in order to obtain the designed target antenna pattern, but also from the portions forming the electrically conductive line configuration corresponding to the antenna 4 and the etching indicator 10. Thereby the etchant removes also material away from the lines 1 1 a to 1 1 e during etching. This can schematically be seen in the embodiment of Figure 2, wherein the lines 1 1 c to 1 1 e of the etching indicator 10 have completely disappeared during etching of the antenna 4, when it is assumed that Figure 2 shows the antenna component 2 after the etching process is completed. However, for the sake of clarity, the lines 1 1 c to 1 1 e disappeared during etching is shown by broken lines in Figure 2. The number of lines of the etching indicator 10 disappeared during etching or the amount or measure of the etching indicator material disappeared during etching, if any of the lines 1 1 a to 1 1 e has not totally disappeared during etching, provides the information about the frequency tuning change of the antenna 4 as explained as follows. By inspecting the remaining etching indicator 10 in Figure 2 it can be seen that only lines 1 1 a and 1 1 b are left, lines 1 1 c to 1 1 e being removed during etching. If it has been determined that the middlemost line 1 1 c forms a reference portion of the etching indicator 10 such that when the middlemost line 1 1 c having a certain width and the lines 1 1 d and 1 1 e having smaller width, i.e. smaller corresponding characteristic than the reference portion, have all disappeared, this means that the electrically conductive line configuration corresponding to antenna 4 has been etched to the extent corresponding to the desired extent of effect of the etchant, i.e. to the design target of the antenna 4. This means that the physical dimensions of the antenna and thereby the frequency tuning characteristics of the antenna 4 shown in Figure 2 corresponds exactly the physical dimensions and the frequency tuning characteristics of the designed target antenna 4 and that there is no frequency tuning change in the antenna 4 according to Figure 2. This, in turn, means, for example, that the integrated circuit 5 may be attached at the attachment point 7c in the impedance matching element 4", the attachment point 7c corresponding in this example to that loop length of the impedance matching element 4", which is intended for the impedance matching element 4" in a case wherein the etched antenna 4 has the designed target frequency tuning characteristics or the designed target operating frequency.

However, if, for example, only line 1 1 e has disappeared during etching, the inspection of the etching indicator 10 indicates that the effect of the etchant on the electrically conductive coating has been too low. This means that the physical dimensions of the antenna 4 are too large when compared to the physical dimensions of the designed target antenna 4, this meaning that the frequency tuning characteristics of the actual etched antenna 4 do not correspond to the frequency tuning characteristics of the designed target antenna 4, i.e there is a change in the frequency tuning characteristics. However, this change in the frequency tuning characteristics may now be compensated by attaching the integrated circuit 5 for example at the attachment point 7e in the impedance matching element 4", the attachment point 7e corresponding in this example to that loop length of the impedance matching element 4", which is intended for the impedance matching element 4" in a case wherein the etched antenna 4 has the physical dimensions which are much larger than the physical dimensions of the designed target antenna, leading, without any compensation, to incorrect frequency tuning characteristics the frequency tuning characteristics compared to the designed target antenna.

However, if, for example, all the lines 1 1 a to 1 1 e have disappeared during etching, the inspection of the etching indicator 10 indicates that the effect of the etchant on the electrically conductive coating has been too strong. This means that the physical dimensions of the antenna 4 are too small when compared to the physical dimensions of the designed target antenna 4, this meaning that the frequency tuning characteristics of the actual etched antenna 4 do not correspond to the frequency tuning characteristics of the designed target antenna 4. However, this change in the frequency tuning characteristics may now be compensated by attaching the integrated circuit 5 for example at the attachment point 7a in the impedance matching element 4", the attachment point 7a corresponding in this example to that loop length of the impedance matching element 4", which is intended for the impedance matching element 4" in a case wherein the etched antenna 4 has the physical dimensions which are much smaller than the physical dimensions of the designed target antenna, leading, without any compensation, to frequency tuning characteristics which deviate from the operating frequency of the designed target antenna.

After the etching process and after the etchant being on the top of the substrate 3 of the component 2 has been flushed away it can be determined by inspecting the etching indicator 10 the extent of the effect of the etchant on the electrically conductive coating, the effect of the etchant on the electrically conductive coating providing information about the extent to which the electrically conductive line configuration, in the example above the antenna pattern 4 for the RFID tag 1 , was etched during etching process. The changes in the etching indicator 10, when compared to the basic form or shape of the etching indicator shown for example in Figure 4, indicate the degree how well the actual etched antenna pattern corresponds to the designed target antenna. On the basis of the inspection of those changes in the etching indicator 10 it can be determined the changes in the dimensions of the antenna pattern and the changes in the frequency tuning characteristics of the antenna 4. If, for example, the etching indicator 10 indicates, as explained above, that the effect of the etchant has been too low so that the designed target antenna construction has not been achieved, this causes a difference in the frequency tuning characteristics between the actual antenna 4 and the designed target antenna 4. However, this change in the frequency tuning characteristics may be compensated by attaching the integrated circuit 5 into that attachment point 7a, 7b, 7c, 7d or 7e corresponding to the change in the frequency tuning characteristics of the antenna 4. The attachment of the integrated circuit 5 into different attachment points 7a to 7e in the impedance matching loop 4" of the antenna 4 provides different frequency tuning characteristics for the antenna 4. Thereby, by using the etching indicator 10, it is possible to determine the extent of the effect of the etchant on the electrically conductive coating and thereby the possible changes in the frequency tuning characteristics when compared to the designed target antenna 4, and then, by selecting the proper attachment point for the integrated circuit 5, it is possible to compensate the frequency tuning changes in the antenna, originating from the etching process, closer to or exactly at the designed target values and thus provide a workable RFID tag. Therefore the variations in the etching process may be corrected later in the RFID tag manufacturing process by inserting the integrated circuit 5 at appropriate attachment point in the impedance matching element 4", for example. This means that despite of the variations in the etching process also the RFID tag antenna components 2 comprising lower quality antennas 4 in terms of frequency tuning characteristics may also be utilized in RFID tag manufacturing. This reduces manufacturing costs by either reducing or totally preventing appearances of rejected antenna billets because of etching process variations. The inspection of the etching indicator 10 may be provided for example by using camera technology and image recognition technologies.

In the embodiment according to Figure 2, the etching indicator 10 is located inside the area confined by the radiating element 4' of the antenna 4 but the etching indicator 10 may be located at any suitable position in the component 2, at which position the remaining part of the etching indicator 10 after the etching process does not interfere the operation of the antenna 4.

In the example above the etching indicator 10 was used with an antenna 4 comprising impedance matching element 4" comprising several different attachment points 7a to 7e for the integrated circuit 5. However, the etching indicator 10 may be used also with antenna patterns having only one possible attachment point for the integrated circuit 5. In this case the inspection of the etching indicator 10 may be used to indicate the frequency tuning properties of the etched antennas 4 before attaching any integrated circuits at the antennas 4. By this way it is possible to reject all the defective antenna components in terms of frequency tuning characteristics before completing the structure of the RFID tag by attaching the integrated circuit 5 and the sticker 6 with the antenna component 2.

Please note that the size of the etching indicator 10 shown in Figures 2 and 4 to 7 are not to scale but the size of the etching indicator 10 has been greatly exaggerated for illustration purposes only. In practice the etching indicator dimensions are much smaller that in the Figures in order to be able to be more sensitive for antenna over- or under-etching situations. In practice, depending for example on the shape and dimensions of the impedance matching element 4" in an UHF antenna, the etching indicator 10 is designed and dimensioned accordingly to be sensitive to indicate the etching status of such an antenna component. Further, the attachment points 7a to 7e for the integrated circuit are also designed to have a suitable tuning range to be able to compensate typical etching variations. The design of the etching indicator 10 aims to optimise its sensitivity for typical etching variations and the design of the attachment points 7a to 7e aims to be able to accurately compensate the tuning range and effect of such variations when the integrated circuit is attached to a proper attachment point.

It should also be noted that the antenna structures shown here are only examples and therefore the practical antenna design may omit a separate radiating element and be based only on loop-like element similar to the impedance matching element 4", or it may omit the galvanic coupling part 4"' between the radiating element 4' and the impedance matching element 4" and be based on inductive/capacitive coupling instead. The examples included in the Figures are intended to highlight only certain typical areas of antenna structures sensitive for etching variations.

In addition to or instead of using the etching indicator for selecting any attachment point for the integrated circuit 5 of the RFID tag 1 , or any other measures to affect the tuning of the RFID tag after antenna etching phase, the condition or state of the etching indicator may also be used to control the etching process, for example the duration of the etching process or the composition of the etchant. This control can be arranged to take place using visual inspection of the etching indicator by the etching process operator or it may also be arranged to take place automatically using machine vision or similar techniques.

Also other measures instead of or in addition to the selection of proper attachment point for the integrated circuit may be provided on the basis of the etching indicator after etching of the antenna structure. These include, but are not limited to the alteration of the antenna conductor structure locally after etching for example by removing conductive material for example by laser tuning or die cutting and/or by adding conductive material, or by adding a separate, possibly laminated, tuning structure at the antenna component 2 to affect the radio frequency behaviour of the etched antenna. Such an additional tuning structure, which may have a form of a loop, for example, may be selected for example from a range of different sizes and may be attached to a range of different areas and it may become inductively or capacitively coupled with the etched antenna structure.

In the above example the etching indicator 10 was used in the RFID tag manufacturing. However, similar kind of etching indicator 10 may be used in manufacturing of any other electrical antenna component comprising an electrically conductive line configuration for indicating the effect of the etchant on the electrically conductive coating and thereby to determine electrical characteristics of the electrically conductive line configuration, i.e. the antenna or part of the antenna, of the antenna component with respect to the designed target antenna component. By this way it is for example possible to determine if the component is competent to be used as a part of an electrical equipment before any integrated circuits are set on that component.

Figure 5 is a top view of a second etching indicator 10 or a second etching indicator pattern 10. The etching indicator 10 according to Figure 5 comprises also a number of portions of pattern, i.e. lines 1 1 a, 1 1 b, 1 1 c, 1 1 d and 1 1 e, which are arranged to be successive lines with respect to each other. In Figure 5 the end of the lines 1 1 a to 1 1 e are arranged to be in contact with each other but the lines 1 1 a to 1 1 e may also be arranged such that there is a small gap between the ends of the lines. Similarly, as already explained above, it is possible to establish that the middlemost line 1 1 c forms a reference portion of the etching indicator pattern 10 such that the disappearance of the line 1 1 c during etching process indicates that the electrically conductive line configuration has achieved the designed target configuration or dimensions.

When the etching indicator 10 comprises a number of parallel or successive lines having different width relative to each other, the etching indicator 10 can be realized and detected very easily. The etching indicator form and size may be designed especially for easy interpretation using machine vision or other automated analysis methods. Such automated analysis results can further be arranged to control integrated circuit positioning on the manufacturing line or to control any other measures that are based on the analysis result.

Figures 4 and 5 show two different embodiments for the etching indicator 10 but other kind of embodiments for the etching indicator 10 are naturally possible. Other possible geometric arrangements may include, for example, concentric rings, rectangles or other shapes.

Figure 6 shows a top view of an etching mask 12 which can be used in the manufacturing of the antenna component 2 according to Figure 2. The etching mask is used to control locally removal and maintenance of the electrically conductive coating by using etchant. When starting the etching of the antenna 4 in the component 2, the etching mask 12 according to Figure 6 is arranged on top of the substrate 3 comprising electrically conductive coating. The etching mask 12 comprises etching mask material or barrier material on a first main area 13 and on the second main area 13' and on the third main area 13" of the etching mask 12, the shape of the first main area 13 corresponding to the shape of the radiating element 4' of the antenna 4 to be maintained during etching, the shape of the second main area 13' corresponding to the shape of the impedance matching element 4" of the antenna 4 to be maintained during etching and the shape of the third main area 13" corresponding to the shape of the coupling element 4"' of the antenna 4 to be maintained during etching. The etching mask further comprises barrier material on the sub-area 14 being located inside the area confined by the first main area 13. The sub-area 14 comprises five lines of barrier material having different widths with respect to each other, for forming lines of electrically conductive coating corresponding lines 1 1 a to 1 1 e of the etching indicator 10 shown in Figure 4.

Typically, the etching mask 12 is arranged on top of the electrically conductive coating supported by the substrate 3 such that in the first phase the whole substrate is coated by mask material or resist material. After that the mask pattern is exposed in the mask material and then either the exposed or un-exposed part of the mask material is removed by etchant, depending whether positive or negative photoresistive mask material is used. In the etching of antennas typically negative photoresistive mask material is used. Also other kind of ways generally known for the person skilled in the art are available for arranging the etching mask 12 on top of the substrate 3, such as the use of different kind of etchant resistive protective materials, such as paint, for example. However, the above explained method being based on the photolithography is the most used in the etching of fine patterns or line configurations.

After the etching mask 12 according to Figure 6 has been arranged on top of the component 2 comprising a substrate 3 comprising electrically conductive coating, etchant is applied on the component 2. The etchant removes the electrically conductive coating on the parts of the coating not protected by the barrier material, such that the electrically conductive coating remains in the areas corresponding to the first 13, second 13' and third 13" main areas and the sub-area 14 of the etching mask 12. Thus, at some point of etching of the component 2, the component 2 comprises the electrically conductive line configuration corresponding to at least to some extent the designed target antenna pattern 4. Similarly, at some point of etching, the component 2 further comprises, depending on the effect of the etchant on the etching indicator 10, no lines 1 1 a to 1 1 e at all, at least partly at least some lines 1 1 a to 1 1 e or all the lines 1 1 a to 1 1 e completely. Other parts of the electrically conductive coating have been removed by etchant away from the component 2.

The reason why at least some lines 1 1 a to 1 1 e have possibly been removed at least partly during etching process despite of the protective layer of barrier material originates from the fact that etchant removes electrically conductive coating away also sideways under the protective barrier material. Therefore the dimensions of the barrier material in the etching mask is selected to take into account the sideways advance of the etchant under barrier material such that the dimensions of the electrically conductive line configuration after etching correspond as well as possible the designed target dimensions of the antenna 4.

Figure 2 shows a single antenna component 2 comprising an etching indicator 10 intended to indicate the effect of the etchant only on that specific component 2. Figure 7 is a top view of three groups 15 of antenna components 2, wherein, in the embodiment shown in Figure 7, each group 15 comprises three antenna components 2 next to each other. However, several groups of components, for example thousands of groups of components, wherein one group of component may comprise any reasonable number of components next to each other, may be placed to form a long banded structure 16, which is continuously moved forward in the etching process such that each group 15 of components 2 is exposed to the effect of the etchant in an etching machine for specific period of time. In the embodiment of Figure 7 there is arranged only one etching indicator 10 for each group 15, the etching indicator 10 being located at the edge part 17 of the band, i.e. in the proximity of the antenna components 2. In this embodiment this single etching indicator 10 is used to indicate the effect of the etchant on the electrically conductive coating in each of the components 2 belonging to the same specific group 15. In Figure 7 the components 2 have been shown in the form they have after etching process, i.e. comprising the antenna pattern 4, but, for clarity reasons, the etching indicators 10 have been shown in their originally designed shape or form. Again, the etching indicators are not shown in their correct scale compared to the antenna components but have been enlarged for clarity.

In the embodiment according to Figure 7 a single etching indicator 10 intended to indicate the effect of the etchant on the electrically conductive coating in each of the components 2 belonging to the same specific group 15 may also be placed inside one antenna component 2 in the group 15 instead of the edge 17 of the band structure 16. However, it is also possible that every component 2 in the group 15 comprises an etching indicator 10 or that there is only one etching indicator 10 intended to indicate the effect of the etchant on the components 2 in several successive groups 15.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A method for manufacturing an antenna component (2) by etching, the component comprising a substrate (3) and an electrically conductive line configuration (4) supported by the substrate (3), and in which method the electrically conductive line configuration (4) is formed by etching away locally by etchant an electrically conductive coating supported by the substrate (3), characterized by indicating by an etching indicator (10) an extent of etching of the antenna component (2), the etching indicator (10) being located at the antenna component (2) to be etched or in proximity to the antenna component (2) to be etched and consisting of the same electrically conductive coating supported by the substrate (3) of the antenna component (2) and being exposed to the etchant during etching.

2. A method according to claim 1, characterized by indicating by the etching indicator (10) an extent of the effect of the etchant on the electrically conductive coating supported by the substrate (3), the extent of the effect of the etchant on the electrically conductive coating providing information about the extent of etching of the electrically conductive line configuration (4) of the antenna component (2).

3. A method according to claim 1 or 2, characterized in that the etching indicator (10) comprises a number of portions of pattern, the portions having different dimensions of same characteristic relative to each other.

4. A method according to claim 3, characterized by indicating by the number of portions of pattern disappeared during etching the extent of etching of the electrically conductive line configuration (4) of the antenna component (2).

5. A method according to claim 3 or 4, characterized in that the portions of pattern are a number of parallel or successive lines (11a, 11b, 11c, 11d, 11 e) having different width relative to each other.

6. A method according to any one of previous claims, characterized in that the etching indicator (10) comprises a reference portion (11c) of the etching indicator (10) and that the disappearance of only the reference portion (11c) and the portions (11d, 11 e) of pattern of the etching indicator (10) having smaller characteristic than the corresponding characteristic of the reference portion (11c) during etching indicates that the electrically conductive line configuration (4) of the antenna component (2) has been etched to the extent corresponding to the desired extent of etching.

7. A method according to any one of previous claims, characterized by adjusting the etching process on the basis of extent of etching of the etching indicator (10).

8. A method according to any one of previous claims, characterized in that the antenna component (2) is intended to form a part of a radio frequency identification tag (1) or RFID tag (1) comprising an integrated circuit (5), whereby the electrically conductive line configuration (4) is intended to form at least a part of an antenna (4) of the RFID tag (1 ).

9. A method according to claim 8, characterized in that the antenna (4) comprises at least a radiating element (4') and an impedance matching element (4").

10. A method according to claim 9, characterized in that the impedance matching element (4") of the antenna (4) comprises a number of possible attachment points (7a, 7b, 7c, 7d, 7e) for attaching the integrated circuit (5) in connection with the impedance matching element (4") and that the specific attachment point (7a, 7b, 7c, 7d, 7e) for the integrated circuit (5) is determined on the basis of extent of etching of the etching indicator (10).

11. A method according to any one of previous claims, characterized by, on the basis of extent of etching of the etching indicator (10) after etching of the antenna (4), altering of the antenna conductor structure locally by removing or adding conductive material or by adding a separate tuning structure at the antenna component (2) to affect the radio frequency behaviour of the antenna (4).

12. An antenna component (2) or a group (15) of antenna components (2), the component (2) comprising a substrate (3) and an electrically conductive line configuration (4) supported by the substrate (3), characterized in that at least at some manufacturing stage of the at least one antenna component (2) there is at least one etching indicator (10) at the antenna component (2) or in proximity to at least one antenna component (2), the etching indicator (10) providing information about the extent of etching of the at least one antenna component (2) and consisting of the same electrically conductive coating supported by the substrate (3).

13. An antenna component (2) or a group (15) of antenna components (2) according to claim 12, characterized in that the etching indicator (10) is arranged to indicate an extent of the effect of the etchant on the electrically conductive coating supported by the substrate (3), the extent of the effect of the etchant on the electrically conductive coating providing information about the extent of etching of the electrically conductive line configuration (4) of the antenna component (2).

14. An antenna component (2) or a group (15) of antenna components (2) according to claim 12 or 13, characterized in that the etching indicator (10) comprises a number of portions of pattern, the portions having different dimensions of same characteristic relative to each other.

15. An antenna component (2) or a group (15) of antenna components (2) according to claim 14, characterized in that the number of portions of pattern disappeared during etching of at least one antenna component (2) is arranged to indicate the extent of etching of the electrically conductive line configuration (4) of the at least one antenna component (2).

16. An antenna component (2) or a group (15) of antenna components (2) according to claim 14 or 15, characterized in that the portions of pattern are a number of parallel or successive lines (11a, 11b, 11c, 11d, 11 e) having different width relative to each other.

17. An antenna component (2) or a group (15) of antenna components (2) according to any one of claims 12 - 16, characterized in that the etching indicator (10) comprises a reference portion (11c) of the etching indicator (10) and that the disappearance of only the reference portion (11 c) and the portions (11 d, 11 e) of pattern of the etching indicator (10) having smaller characteristic than the corresponding characteristic of the reference portion (11c) during etching indicates that the electrically conductive line configuration (4) of the at least one antenna component (2) has been etched to the extent corresponding to the desired extent of etching.

18. An antenna component (2) or a group (15) of antenna components (2) according to any one of claims 12 - 17, characterized in that the antenna component (2) is intended to form a part of a radio frequency identification tag (1) or RFID tag (1) comprising an integrated circuit (5), whereby the electrically conductive line configuration (4) is intended to form an antenna (4) of the RFID tag (1 ).

19. An antenna component (2) or a group (15) of antenna components (2) according to claim 18, characterized in that the antenna (4) comprises at least a radiating element (4') and an impedance matching element (4"), the impedance matching element (4") of the antenna (4) comprising a number of possible attachment points (7a, 7b, 7c, 7d, 7e) for attaching the integrated circuit (5) in connection with the impedance matching element (4").

20. An etching mask (12) for manufacturing an antenna component (2) by etching, the component (2) comprising a substrate (3) and an electrically conductive line configuration (4) supported by the substrate (3), the electrically conductive line configuration (4) being formed by etching away locally by etchant an electrically conductive coating supported by the substrate (3), the etching mask (12) determining the electrically conductive line configuration (4) of the component (2), characterized in that the etching mask (12) comprises barrier material on at least one main area (13, 13') corresponding to the electrically conductive line configuration (4) to be maintained during etching and that the etching mask (12) further comprises barrier material on at least one sub-area (14) for forming an etching indicator (10) consisting of the same electrically conductive coating supported by the substrate (3), the etching indicator (10) being arranged to indicate the extent of etching of the antenna component (2).

21. An etching mask (12) according to claim 20, characterized in that the sub-area (14) comprising barrier material for forming an etching indicator (10) is located in the etching mask (12) at the antenna component (2) to be etched or in proximity to the antenna component (2) to be etched.

22. An etching mask (12) according to claim 20 or 21, characterized in that the sub-area (14) comprising barrier material for forming an etching indicator (10) comprises a number of portions of pattern, the portions having different dimensions of same characteristic relative to each other.

23. An etching mask (12) according to claim 22, characterized in that the portions of pattern correspond to a number of parallel or successive lines (11a, 11b, 11c, 11d, 11 e) having different width relative to each other.

24. An etching mask (12) according to any one of claims 20 - 23, characterized in that the antenna component (2) is intended to form a part of a radio frequency identification tag (1) or RFID tag (1) comprising an integrated circuit (5), whereby the electrically conductive line configuration (4) is intended to form an antenna (4) of the RFID tag (1).

25. An etching mask (12) according to claim 24, characterized in that the antenna (4) comprises at least a radiating element (4') and an impedance matching element (4"), whereby the etching mask (12) comprises at least a first main area (13) of barrier material corresponding to the radiating element (4') of the antenna (4) and a second main area (13') of barrier material corresponding to the impedance matching element (4") of the antenna (4).

26. An etching mask (12) according to claim 25, characterized in that the second main area (13') of barrier material comprises barrier material for providing a number of possible attachment points (7a, 7b, 7c, 7d, 7e) for attaching the integrated circuit (5) in connection with the impedance matching element (4") of the antenna (4).