Through-contacting of a carrier film printed on both sides with fill printing and a method for producing such a through-contacting

Description

Subject of the invention

[0001] The present invention relates to a method for producing a through-hole plating in a carrier film printed on both sides and to a carrier film printed on both sides with a through-hole plating. Background of the invention

[0002] Carrier foils printed with conductor tracks are known in the prior art, for example, from WO2014 / 095232. For example, RFID labels ("radio frequency identification" labels or labels for identification using electromagnetic waves) comprise an antenna in the form of a conductor track printed on a foil, which is connected to an RFID chip and serves both as a power supply and for communication with an RFID reader.

[0003] The conductor track is often spiral-shaped and is connected to two antenna taps located at a distance from each other with corresponding contacts of the RFID chip.

[0004] With sufficiently large RFID chips, it is possible to connect the two antenna taps directly to the RFID chip by placing the RFID chip directly onto the spiral conductor, thereby connecting two distantly located contacts of the RFID chip to the antenna taps. The RFID chip acts as a bridge between the two antenna taps via the additional antenna windings located between the antenna taps.

[0005] DE 10 2015 005 690 A1 describes a via in which a first conductive layer is contacted with a second conductive layer via a via, wherein the via can additionally be assigned a plating.

[0006] EP 1 096 842 A2 describes a method for producing a multilayer printed circuit board, in which a filling step is carried out by introducing an ink to produce the through-hole.

[0007] US 2011 / 0 180 310 A1 describes a structure for a printed circuit board in which an electrically conductive plate is embedded between two vias.

[0008] EP 0 595 752 A1 describes the production of a through-hole plating in which two or more electrically insulating layers are penetrated with an electrically conductive material

[0009] WO 2013 / 139 470 A2 describes a substrate for a portable data carrier, in particular a chip card, which has a first antenna part on one side and a second antenna part on the other side, wherein the two antenna parts can be electrically connected to one another via the through-contact areas.

[0010] US 5,203,078 A describes an identity card which is provided with an integrated circuit (IC), which also has a through-hole connection.

[0011] WO 2005 / 117096 A1 describes a chip module that is fixed to a substrate via an electrical through-hole with an antenna. A through-hole is first created in the substrate and filled with a first filler material, and the antenna is then applied to the substrate by electrochemical deposition. Description of the invention

[0012] Against the background described, it is the object of the present invention to provide an improved method for producing a carrier film printed on both sides, wherein in particular the conductivity in the area of ​​the through-hole is further improved.

[0013] This object is achieved by a method for producing a through-hole in a carrier film printed on both sides with conductor tracks according to claim 1, a carrier film according to claim 7, an RFID inlay according to claim 10, and a valuable or security document according to claim 11. The dependent claims contain further advantageous embodiments of the invention.

[0014] The invention is based on and includes the finding that due to the progressive miniaturization of RFID chips, bridging the antenna windings is becoming increasingly difficult, since the distance between the contacts of the RFID chips is often smaller than the minimum distance between the two antenna taps of the conductor track that can be achieved with reasonable effort.

[0015] The method according to the invention for producing a through-hole in a carrier film printed on both sides with conductor tracks, wherein the carrier film comprises a first side and a second side, comprises several steps.

[0016] The first side of the carrier film is printed with electrically conductive material, covering the area of ​​the intended via. A through-hole is then made in the carrier film. The second side of the carrier film is printed, preferably partially printed, with electrically conductive material. The through-hole is filled with electrically conductive material, preferably completely covered. The second side of the carrier film is printed at least once more with electrically conductive material. The through-hole and the previously printed electrically conductive material are filled, preferably completely covered.

[0017] In the context of the present invention, filling is to be understood as creating a material connection between the electrically conductive material printed on the first side and the second side over the entire area or cross-sectional area of ​​the through-hole. Completely filling the through-hole or the volume removed in this context with electrically conductive material up to the surface of the second side is advantageous but not absolutely necessary.

[0018] The first side of the carrier film is preferably partially printed with electrically conductive material, namely in the area of ​​the intended through-hole connection. Preferably, the area of ​​the intended through-hole connection is completely covered with electrically conductive material.

[0019] The method according to the invention has the advantage that an additional printing step applies a filling pressure, which results in more conductive material being present in the via. At the same time, increased stability against lateral constrictions in subsequent lamination is achieved. Furthermore, conductivity is increased and electrical resistance is reduced. "Breaks" in the filling pressure on the flanks of the through-hole are compensated for by the additional pressure, which also acts as an antenna pressure. This results in higher yields and greater tolerance to unfavorable through-hole geometries. Holes with a larger aspect ratio can be filled, for example, when using thicker substrates if the hole diameter cannot be increased due to the sensitivity of the exposed "membrane."

[0020] The first side of the carrier film is printed with electrically conductive material before the through hole is made in the carrier film.

[0021] According to the invention, the through-hole is created after printing the first side, while the already applied electrically conductive material remains intact. The material from the first printing step thus forms an electrically conductive seal for the through-hole, ensuring a good electrical connection with the electrically conductive material applied to the through-hole in the second printing step. These variants allow the process to be flexibly integrated into existing processes.

[0022] For example, in a first printing step, conductor tracks can first be applied to the first side of the carrier film, before the fill print and conductor tracks, in accordance with the invention as antenna print, are applied to the second side of the carrier film in a second and third printing step after completion of the first printing step. However, it is also possible for several printing steps to be carried out simultaneously or at an overlap in time. If the through-hole is created before the first printing step, or if the through-hole, when created after the first printing step, also extends through the already applied electrically conductive material, which does not fall within the scope of protection of the claims, it is preferred if the through-hole is dimensioned such that the electrically conductive material applied in the subsequent printing steps, in particular the first and second printing steps, does not shoot through the through-hole.In other words, the electrically conductive material printed on one side of the carrier film should not essentially pass through the through-hole and freely exit on the other side; rather, it should remain in the through-hole to fill it. This can usually be achieved by a sufficiently small cross-section of the through-hole overall or at least on the other side, adapted to the flow properties of the electrically conductive material during the printing process. For example, the through-hole can be shaped like a truncated cone with a cross-section that decreases toward the other side.

[0023] Printing, especially the first printing on the second side, can be done using screen printing or a jet printing process. However, other technologies suitable for increasing the amount of conductive material applied are also conceivable.

[0024] The diameter of the through-hole can be between 50 micrometers and 5,000 micrometers. Particularly when the through-hole is created after the first printing step while preserving the electrically conductive material applied during the printing step, it is preferred for the diameter of the through-hole to be between 100 micrometers and 500 micrometers. A suitable diameter ensures secure through-plating with high electrical conductivity. In this case, there is no risk of the material applied in the second printing step being shot through. Particularly in cases where shooting through is generally possible, the diameter of the through-hole is preferably between 50 micrometers and 200 micrometers. With electrically conductive materials commonly used for printing processes, this prevents the material from being shot through.The thickness of the carrier film is preferably 20 micrometers to 250 micrometers, more preferably 50 micrometers to 100 micrometers, ensuring that the through-hole is filled as far as possible, or even completely, by the electrically conductive material applied in a single printing step. The thickness of the carrier film and the diameter of the through-hole are typically selected interdependently, with a thicker carrier film resulting in a larger through-hole diameter.

[0025] Although dimensions for the diameter of the through-hole are specified above, the shape of the through-hole is not limited to the preferred circular configuration. In the case of a non-circular through-hole, the cross-sectional area of ​​the through-hole, which is directly related to the diameter specifications, applies, i.e., preferably 0.002 square millimeters to 20.0 square millimeters, more preferably 0.008 square millimeters to 0.2 square millimeters, or 0.002 square millimeters to 0.03 square millimeters.

[0026] The through-hole can be created, for example, by punching, drilling, or lasering, preferably with CO2 lasers. Especially if the electrically conductive material applied during the first printing step or when printing the first side is to be preserved as much as possible, the through-hole is preferably created by lasering, as this allows the required precision to be easily maintained.

[0027] It is preferred if the electrically conductive material comprises or consists of silver conductive paste. Silver conductive paste is well suited for printing circuit tracks. The carrier film preferably comprises or consists of polycarbonate. A carrier film made of polycarbonate can be laminated to additional layers of polycarbonate to form a multilayer RFID security document, without increasing the risk of delamination due to incompatible materials in the layers of the multilayer composite.

[0028] The carrier film according to the invention, printed on both sides with conductor tracks, has at least one via produced according to the invention. For further explanation, reference is made to the above statements. Since the electrical conductivity of a via may be too low for a intended use due to the dimensioning of the through-hole required for the inventive method, it is possible to electrically connect a conductor track on different sides of the carrier film by means of an array of at least two vias. The vias, which are preferably arranged closely adjacent to one another, thus establish parallel connections between the two conductor tracks, resulting in an increased cumulative electrical conductivity between the two conductor tracks.In addition, there is a redundancy of the vias, whereby an insufficient contact in one via is compensated by a successful contact in another via.

[0029] It is further preferred if two conductor tracks connected by at least one via on the carrier film comprise contact points for testing the via(s). Test probes of a measuring device can be applied to the contact points, thus verifying the basic existence of an electrical connection via the via(s) and / or the electrical resistance or electrical conductivity of the via(s).

[0030] The RFID inlay according to the invention comprises a carrier film according to the invention and an RFID chip connected to the conductor tracks. The valuable or security document according to the invention comprises such an inventive RFID inlay. The RFID inlay according to the invention and the valuable or security document according to the invention have the features and advantages already mentioned above in connection with the method according to the invention and the carrier film according to the invention. Typical examples of a valuable or security document according to the present invention are identity cards, passports, driver's licenses, company ID cards, credit cards, encryption cards, and the like. Description of implementation examples

[0031] Further features, characteristics and advantages of the present invention are described in more detail below using embodiments with reference to the attached figures.

[0032] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed herein are not to be interpreted in a limiting sense, but merely as an illustrative basis for teaching one skilled in the art how to variously employ the present invention.

[0033] As used herein, the term "and / or," when used in a series of two or more elements, means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described as containing components A, B, and / or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Fig. 1 shows a schematic representation of an embodiment of an RFID inlay with a carrier film according to the invention. Fig. 2a shows a schematic detailed representation of the carrier film from Figure 1 . Fig. 2b shows a schematic detailed representation of a variant of Figure 2aFig. 3 schematically shows the first steps of an embodiment of the inventive method for creating a through-hole plating in a carrier film printed with conductor tracks on both sides. Fig. 4 schematically shows a further step of this embodiment of the inventive method. Fig. 5 schematically shows a final step of this embodiment of the inventive method.

[0034] In Figure 1 An RFID inlay 1, such as is used in security documents (e.g., passports), is shown. The RFID inlay 1 comprises a carrier film 10 according to the invention, which is printed on both sides with conductor tracks 11. In Figure 1The conductor tracks 11 on the directly visible front side of the carrier film 10 are shown in solid lines, while the conductor tracks 11 on the back side of the carrier film 10 are shown in dashed lines. The RFID inlay 1 further comprises the RFID chip 2, indicated only by a dash-dotted line, which is arranged on the back side of the carrier film 10.

[0035] The RFID chip 2 of the RFID inlay 1 is connected via supply lines 3 to antenna taps 4 of an antenna 5, the latter serving not only for communication purposes but also for power supply. The supply lines 3, the antenna taps 4 and the antenna 5 itself are formed by the conductor tracks 11 printed on the carrier film 10. On the front side of the carrier film 10, the conductor track 11 is spirally designed to form the antenna 3 and is extended at the antenna taps 4 to form merely exemplary circular fields. On the back side, the conductor tracks 11 are designed as two separate supply lines 3, each of which is connected at one end (in Figure 1by the antenna taps 4 concealed), for example, have circular fields analogous to the antenna taps 4 on the front. In the exemplary embodiment shown, the two supply lines 3 are designed to converge on each other at their other ends on a common axis. This optional but preferred embodiment allows the carrier film 10 to be flexibly equipped with various RFID chips 2, since the layout of the conductor tracks 11 does not prescribe a spacing for the contacts of the RFID chip 2, but rather RFID chips 2 with different contact spacings can be arranged on the carrier film 10 such that one contact is connected to each supply line 3.

[0036] To connect the conductor tracks 11 on the front and back of the carrier film 10, fields of through-contacts 12 are provided in the area of ​​the antenna taps 4, with which the antenna taps 4 are electrically connected to the supply lines 3 and thus the antenna 5 to the RFID chip 2.

[0037] In Figures 2a and b Two different design variants for the field of vias 12 are shown in schematic detail views, whereby the variant from Figure 2a the representation from Figure 1 The through-contacts 12, which are actually concealed by the conductor track 11 on the front, are indicated by dotted lines.

[0038] In the version according to Figure 2a In the area of ​​each antenna tap 4, 21 vias 12 are provided, each via 12 having a diameter of approximately 140 micrometers. In the embodiment according to Figure 2bOnly five vias 12 are provided in the area of ​​each antenna tap 4. However, since these each have a diameter of approximately 285 micrometers, the cumulative electrical conductivity of a respective array of vias 12 is practically identical in both embodiments, assuming identical materials and thickness of the carrier foil 10. The invention is not limited to the number of vias 12 shown and can be implemented with different configurations in individual cases.

[0039] The vias 12 of the carrier foil 10 of the RFID chip made of Figures 1 and 2a, b have been produced using a method according to the invention. A variant of the method according to the invention is described below with reference to Figures 3 to 5 explained in more detail. The Figures 3 to 5The carrier film 10 shown comprises a first side 21 and a second side 22. This can be a top side or bottom side or front side or back side.

[0040] In the present variant, as in the Figure 3 As shown schematically in a sectional view, first, the first side 21 of the carrier film 10 is printed with electrically conductive material 13, for example, silver conductive paste, in the area of ​​the intended through-hole. The printing can, for example, include the printing of conductor tracks 11. Subsequently, a through-hole 14 is introduced into the carrier film 10 from the second side 22. This can be done using a laser 24, preferably a CO2 laser, but also by punching or drilling.

[0041] In a subsequent step, which is described in the Figure 4As shown schematically in a sectional view, the second side 22 of the carrier film 10 is printed with electrically conductive material 13, for example, silver conductive paste, whereby the through-hole 14 is filled—preferably completely. The filling pressure thus generated is designated by reference numeral 23. The filling pressure 23 ensures that the side surfaces and edges of the through-hole 14 are completely covered with conductive material.

[0042] Afterwards, in the Figure 5 In the schematically shown step, the second side 22 of the carrier film 10 is reprinted with electrically conductive material 13, for example, silver conductive paste, whereby the through-hole 14 and the fill print are covered—preferably completely. The antenna print thus generated is designated by reference numeral 25.

[0043] The filling pressure 23 causes more conductive material to be placed in the through-hole 14 or the through-plating 12. This results in greater mechanical stability and lower electrical resistance.

[0044] In a variant that does not fall within the scope of the claims, the through-hole 14 can also be first introduced into the carrier film 10, for example by means of a laser 24. Subsequently, the first side 21 can be printed with conductive material, for example in the context of printing conductor tracks 11. Subsequently, the filling print 23 can be applied and finally the antenna print 25.

[0045] Several filling pressure steps can also be carried out in order to further increase the amount of conductive material 13 present in the through-hole 14.

[0046] The printing on the first side 21 can also involve the antenna printing, and the final printing on the second side 22, which covers the filler printing, can involve the printing of the conductor tracks. This latter embodiment is not covered by the subject matter of the protection sought. List of reference symbols-

[0047] 1RFID inlay 2RFID chip 3Feed line 4Antenna tap 5Antenna 6Contact points 10Carrier foil 11Conductor track 12Through-hole 13Electrically conductive material 14Through-hole 21First side 22Second side 23Fill print layer 24Laser 25Antenna print layer

Claims

1. A method for producing a through-contact plating (12) in a carrier film (10) printed on both sides with conductor tracks (11) and having a first and a second side (21, 22), wherein the method comprises the following steps: - printing of the first side (21) of the carrier film (10) with electrically conductive material (13), whereby the area of the prospective through-contact plating (12) is covered, - after printing the first side (21), a through hole (14) is made in the carrier film (10), wherein the already applied electrically conductive material (13) is retained, - printing of the second side (22) of the carrier film (10) with electrically conductive material (13), wherein the through hole (14) being filled with a filling print (23), and - at least one further printing of the second side (22) of the carrier film (10) with electrically conductive material (13), wherein the through hole (14) and the already printed electrically conductive material of the filling print (23) are at least partially covered, and wherein during the further printing of the second side (22) of the carrier film (10) an antenna print (25) of the electrically conductive material (13) is applied at the same time.

2. The method according to claim 1, characterized in that the printing is carried out by means of screen printing or by means of a jet printing process.

3. The method according to one of the preceding claims, characterized in that the diameter of the through hole (14) is 50 micrometers to 5000 micrometers, preferably 50 micrometers to 200 micrometers or 100 micrometers to 500 micrometers, and / or the thickness of the carrier film (10) is 20 micrometers to 250 micrometers, preferably 75 micrometers to 125 micrometers.

4. The method according to one of the preceding claims, characterized in that the through hole (14) is introduced by punching, drilling or lasering (24), preferably CO2 lasering.

5. The method according to one of the preceding claims, characterized in that the electrically conductive material (13) comprises silver conductive paste.

6. The method according to one of the preceding claims, characterized in that the carrier film (10) comprises polycarbonate.

7. A carrier film (10), which is printed on both sides with conductor tracks (11) and has at least one through-contact plating (12) produced in accordance with one of the preceding claims.

8. The carrier film (10) according to claim 7, characterized in that in each case one conductor track (11) on different sides of the carrier film (10) is electrically connected to one another by an array of at least two through-contact platings (12).

9. The carrier film according to claim 7 or 8, characterized in that two conductor tracks (11) connected by at least one through-contact plating (12) comprise contact points (6) for checking the through-contact plating (12).

10. A RFID inlay (1) with a carrier film (10) according to one of claims 7 to 9 and an RFID chip (2) connected to the conductor tracks (11).

11. A value or security document with an RFID inlay according to the preceding claim.