Technical field

The technical field of the present invention regards the assembly methods of RFID assembly.

State of the art

RFID assembly comprises some electrical contacts made of a small metal deposition layer and some re-passivation layer, which are present below the electrical contact.

Indeed, in standard assembly of electrical contact, anisotropic glue is deposited at a location of contact between the electrical contact and inlay. The chip with electrical contact is assembled onto a PET substrate with metallization traces, typically aluminum, sometimes copper, silver or other conductive material, the glue creates the electrical contact between the chip electrical contact and the metal traces on the inlay.

Thermo-compression occurs in order to ensure both mechanical stability and reliable electrical contact between inlay substrate and the electrical contacted silicon chip. During the assembly compression, it has been observed that the PET inlay substrate is distorted by the assembly pressure.

Due to flexibility of the PET inlay and of the re-passivation layer, the thermo-compression applied during the film assembly process generates variability in the distance between the inlay aluminum traces and metal connections within the integrated circuit as the inlay flexes. Curing pressure, temperature, duration act upon the distance between the metals and the resulting assembly capacitance. It is necessary to control the assembly capacitances between the antenna terminal and the input of the integrated circuit in order to ensure that the impedance matching and RFID tag performance remains within specification. Too high variation of the input capacitances will induce a critical loss of UHF power sensitivity.

Summary of the invention

The present invention relates to an assembly method for an RFID assembly comprising:

- Providing at least one integrated circuit; said at least one integrated circuit comprising at least one IC contact and at least one dielectric layer;

- Deposition of at least one electrical contact directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer; and,

- Re-passivation of said at least one integrated circuit by depositing at least one re-passivation layer directly on and in contact with said at least one integrated circuit, preferably by deposition of said at least one re-passivation layer directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer.

Thus, the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer.

According to an embodiment, said at least one electrical contact is deposited on at least one first portion and/or said at least one re-passivation layer is deposited one at least on second portion; said at least one first portion is distinct of said at least one second portion. Thus, said at least one electrical contact does not overlap said at least one re-passivation layer or vice versa, and the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer

According to an embodiment, at least one electrical contact is deposited with at least one primary dimension and said at least one repassivation layer is deposited with at least one secondary dimension; a dimension ratio of said at least one primary dimension to said at least one secondary dimension is comprised between 0.5 and 2, preferably between 0.9 and 1.11.

Thus, said at least one electrical contact has substantially the same dimension, rather thickness as said at least one re-passivation layer, and when the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer.

According to an embodiment, said at least one electrical contact comprises at least one first electrical contact surface and at least one second electrical contact surface opposite to said at least one first electrical contact surface and/or wherein said at least one re-passivation layer comprises at least one first re-passivation layer surface and at least one second repassivation layer surface opposite to said at least one first re-passivation layer surface; said at least one primary dimension is comprised between said at least one first electrical contact surface and said at least one second electrical contact surface and/or said at least one secondary dimension is comprised between said at least one first re-passivation layer surface and said at least one second re-passivation layer surface. Thus, said at least one electrical contact has substantially the same thickness as said at least one re-passivation layer, and when the thermocompression applied during the film assembly method generates a constant thickness between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer.

According to an embodiment, said at least one first electrical contact surface is directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer and/or said at least one first repassivation layer surface is directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer.

Thus, said at least one electrical contact does not overlap said at least one re-passivation layer or vice versa, and the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer

According to an embodiment, said assembly method comprises an RFID Tag forming by superimposing at least one film directly on and in contact with said at least one electrical contact and said at least one repassivation layer.

Thus, the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer such as the antenna terminal and the input of said at least one integrated circuit match and the RFID assembly performance remains within specification.

According to an embodiment, said at least one first electrical contact surface and at least one second electrical contact surface are linked via at least one intermediate electrical contact surface and said at least one first re- passivation layer surface and said at least one second re-passivation layer surface are linked via at least one intermediate re-passivation layer surface; said at least one intermediate electrical contact surface is configured to be directly on or under and in contact with said at least one intermediate repassivation layer surface.

Thus, said at least one electrical contact does not overlap said at least one re-passivation layer or vice versa, and the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer.

According to an embodiment, said at least one film comprises at least one antenna terminal and said RFID Tag forming comprises contact forming by contacting said at least one antenna terminal to said at least one electrical contact.

Thus, the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer such as the antenna terminal and the input of said at least one integrated circuit match and the RFID assembly performance remains within specification.

The present invention relates to an RFID assembly comprising at least one:

- integrated circuit; said at least one integrated circuit including at least one IC contact and at least one dielectric layer;

- electrical contact; said at least one electrical contact is directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer; and, - re-passivation layer; said at least one re-passivation layer is directly on and in contact with said at least one integrated circuit.

Thus, the constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer allows ensuring an impedance matching between the antenna terminal and the input of said at least one integrated circuit such that said RFID assembly performance remains within specification.

According to an embodiment, said at least one electrical contact is deposited on at least one first portion and/or said at least one re-passivation layer is deposited one at least on second portion; said at least one first portion is distinct of said at least one second portion.

Thus, said at least one electrical contact does not overlap said at least one re-passivation layer or vice versa, and the thermo-compression applied during the film assembly method generates a constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer

According to an embodiment, said at least one electrical contact comprising at least one primary dimension and said at least one repassivation layer comprising at least one secondary dimension; a dimension ratio of said at least one primary dimension to said at least one secondary dimension is comprised between 0.5 and 2, preferably between 0.9 and 1.11.

Thus, the constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer allows ensuring an impedance matching between the antenna terminal and the input of said at least one integrated circuit such that said RFID assembly performance remains within specification. According to an embodiment, said at least one electrical contact comprises at least one first electrical contact surface and at least one second electrical contact surface opposite to said at least one first electrical contact surface and/or wherein said at least one re-passivation layer comprises at least one first re-passivation layer surface and at least one second repassivation layer surface opposite to said at least one first re-passivation layer surface; said at least one primary dimension is comprised between said at least one first electrical contact surface and said at least one second electrical contact surface and/or said at least one secondary dimension is comprised between said at least one first re-passivation layer surface and said at least one second re-passivation layer surface.

Thus, the constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer allows ensuring an impedance matching between the antenna terminal and the input of said at least one integrated circuit such that said RFID assembly performance remains within specification.

According to an embodiment, said at least one first electrical contact surface is directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer and/or said at least one first repassivation layer surface is directly on and in contact with said at least one IC contact and/or with said at least one dielectric layer.

Thus, the constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer allows ensuring an impedance matching between the antenna terminal and the input of said at least one integrated circuit such that said RFID assembly performance remains within specification.

According to an embodiment, said at least one first electrical contact surface and at least one second electrical contact surface are linked via at least one intermediate electrical contact surface and said at least one first repassivation layer surface and said at least one second re-passivation layer surface are linked via at least one intermediate re-passivation layer surface; said at least one intermediate electrical contact surface is configured to be directly on or under and in contact with said at least one intermediate repassivation layer surface.

According to an embodiment, said RFID assembly comprises at least one film including at least one antenna terminal directly connected to said at least one electrical contact.

Thus, the constant distance, rather thickness, between said at least one integrated circuit and the top of said at least one electrical contact and the top of said at least one re-passivation layer allows ensuring an impedance matching between the antenna terminal and the input of said at least one integrated circuit such that said RFID assembly performance remains within specification.

Brief description of the drawings

The foregoing and other purposes, features, aspects and advantages of the invention will become apparent from the following detailed description of the embodiments, given by way of illustration and not limitation with reference to the accompanying drawings, in which:

- figure 1 represents a step of providing at least one integrated circuit 110 according to an embodiment;

- figures 2A and 2B represent a step of delimitation of at least one first portion 129 and at least on second portion 139;

- figures 3A-3D represent a step of deposition 530 of at least one electrical contact 120 on said at least one integrated circuit 110 according to an embodiment; - figures 4A-4D represent a step of re-passivation 550 of said at least one integrated circuit 110 on said at least one integrated circuit 110 according to an embodiment;

- figures 5A and 5B represent a top view of said at least one integrated circuit 110 after said step of deposition 530 and said step of re-passivation 550 according to an embodiment; and,

- figures 6A-6D and 7 represent a step of an RFID Tag forming 570 by superimposing at least one film 140 on said at least one integrated circuit 110 according to an embodiment.

Description of the invention

As early mentioned, it is necessary to control the assembly capacitances between the antenna terminal and the input of the integrated circuit in order to ensure that the impedance matching and RFID tag performance remains within specification. Too high variation of the input capacitances will induce a critical loss of UHF power sensitivity.

Therefore, the applicant proposes an assembly method 500 for an RFID assembly 100. Said RFID assembly 100 comprises at least one integrated circuit 110 including at least one IC contact 111 and at least one dielectric layer 112. Said at least one integrated circuit 110 is provided 510 and at least one electrical contact 120 is deposited 530 directly on and in contact with said at least one IC contact 111 and/or with said at least one dielectric layer 112, figure 1.

Said at least one IC contact 111 may be an electric layer realized during the manufacturing process of said at least one integrated circuit 110 and said at least one IC contact 111 is integrated in said at least one integrated circuit 110. Said at least one IC contact 111 may be used for test purposes.

As illustrated in fig. 1 , said at least one dielectric layer 112 may be deposited after said at least one IC contact 111 and at the end of the manufacturing process of said at least one integrated circuit 110 and said at least one dielectric layer 112 may comprise an opening configured to let appear said at least one IC contact 111 such as to avoid undesired contact and/or oxydation when said at least one IC contact 111 may be used for test purposes, and said at least one dielectric layer 112 may cover said at least one integrated circuit 110, preferably may cover integrally said at least one integrated circuit 110 excepted said at least one IC contact 111.

A delimitation 520 of at least one first portion 129 and at least one second portion 139 is realized on said at least one integrated circuit 110, as shown in figures 2A and 2B, and said at least one first portion 129 is distinct of said at least one second portion 139.

Figures 3A-3D illustrate how said at least one electrical contact 120 is deposited 530 directly on and in contact with said at least one IC contact 111 and/or with said at least one dielectric layer 112 in said at least one first portion 129. Said at least one IC contact 111, illustrated in figs. 3A-3C, may be larger than usual and may be called large pad for example, and said at least one IC contact 111 may support said at least one electrical contact 120 all over the pad surface.

A re-passivation 550 of said at least one integrated circuit 110 is done by depositing at least one re-passivation layer 130 directly on and in contact with said at least one integrated circuit 110, preferably by deposition of said at least one re-passivation layer 130 directly on and in contact with said at least one IC contact 111 and/or with said at least one dielectric layer 112, as shown in figures 4A-4D, in said at least one second portion 139. It is unnecessary to specify that said deposition step 530 and re-passivation 550 step might be done in consecutively, simultaneously or in a different order. Thus, said at least one electrical contact 120 does not overlap said at least one re-passivation layer 130 or vice versa, and the thermo-compression applied during the film assembly 570 method generates a constant distance, rather thickness, between said at least one integrated circuit 110 and the top of said at least one electrical contact 120 and the top of said at least one repassivation layer 130.

Indeed, said at least one electrical contact 120 is deposited 530 with at least one primary dimension 123 and said at least one re-passivation layer 130 is deposited with at least one secondary dimension 133; a dimension ratio of said at least one primary dimension 123 to said at least one secondary dimension 133 may be comprised between 0.5 and 2, preferably between 0.9 and 1.11 , and may be measured via a high Resolution Scanning Electron Microscope, HR-SEM for short, like Hitachi S-4800.

Said at least one electrical contact 120 comprises at least one first electrical contact surface 121 and at least one second electrical contact surface 122 opposite to said at least one first electrical contact surface 121 , as shown in figures 4A-4D, said at least one primary dimension 123 may be defined as being comprised between said at least one first electrical contact surface 121 and said at least one second electrical contact surface 122.

Regarding said at least one secondary dimension 133, said at least one secondary dimension 133 may be comprised between at least one first re-passivation layer surface 131 of said at least one re-passivation layer 130 and at least one second re-passivation layer surface 132 of said at least one re-passivation layer 130 opposite to said at least one first re-passivation layer surface 131. In other words, said at least one primary dimension 123 and/or said at least one secondary dimension 133 may be considered as being the thickness of said at least one electrical contact 120 and/or of said at least one re-passivation layer 130 respectively. As early mentioned, said at least one primary dimension 123 and/or said at least one secondary dimension 133 may be measured via HR-SEM. Further, in order to form 570 an RFID Tag, at least one film 140 is deposited directly on said at least one re-passivation layer 130, and said at least one film 140, comprising at least one antenna terminal 145, may forms an electrical contact by contacting said at least one antenna terminal 145 to said at least one electrical contact 120. Said at least one film 140 is also called inlay and may be, for example, a paper substrate and/or a PET substrate with metallization traces, like aluminum, copper, silver, a conductive material or an alloy thereof, forming an antenna. Said at least one film 140 may be able to be applied on top of said at least one electrical contact 120, as illustrated in figs. 6A-6C, and the mechanical and electrical properties previously mentioned may be also applicable in this case.

Thus, as depicted in figures 6A-6D and 7, the thermo-compression applied during the film assembly 570 method generates a constant distance, rather thickness measureable via HR-SEM, between said at least one integrated circuit 110 and the top of said at least one electrical contact 120 and the top of said at least one re-passivation layer 130 such as the antenna terminal 145 and the input of said at least one integrated circuit 110 match and the RFID assembly performance remains within specification.

Further, during the thermo-compression applied during the film assembly 570, it may be possible that said at least one electrical contact 120 and/or said at least one re-passivation layer 130 may go over of said at least one first portion 129 and/or of said at least one second portion 139.

As depicted in figure 6A-6D and 7, said at least one electrical contact 120 may comprise at least one intermediate electrical contact surface 124, typically at least one peripheral electrical contact surface 124. In other word, said at least one first electrical contact surface 121 and at least one second electrical contact surface 122 are linked via said at least one intermediate electrical contact surface 124.

Said at least one re-passivation layer 130 may comprise at least one intermediate re-passivation layer surface 134, typically at least one peripheral re-passivation layer surface 134. In other word, said at least one first repassivation layer surface 131 and said at least one second re-passivation layer surface 132 are linked via at least one intermediate re-passivation layer surface 134.

And when the thermo-compression applied during the film assembly 570, said at least one intermediate electrical contact surface 124 may be directly on or under and in contact with said at least one intermediate re-passivation layer surface 134. However, said at least one electrical contact 120 does not overlap said at least one re-passivation layer 130 or vice versa, since said at least one first electrical contact surface 121 is not on said at least one second re-passivation layer surface 132 or said at least one first re-passivation layer surface 131 is not on said at least one second electrical contact surface 122.

According to some thermo-compression parameters or according to the dimension of said at least one primary dimension 123 and said at least one secondary dimension 133, said at least one first electrical contact surface 121 may be on said at least one second re-passivation layer surface 132 or said at least one first re-passivation layer surface 131 may be on at least one second electrical contact surface 122, but said at least one first electrical contact surface 121 never covers totally said at least one second re-passivation layer surface 132 and or said at least one first repassivation layer surface 131 never covers totally said at least one second electrical contact surface 122. Thus, thanks a cross-sectional view of said RFID assembly 100 and measured via HR-SEM, said at least one electrical contact 120 has substantially the same dimension, rather thickness as said at least one re-passivation layer 130, and when the thermo-compression applied during the film assembly 570 method generates a constant distance, rather thickness, between said at least one integrated circuit 110 and the top of said at least one electrical contact 120 and the top of said at least one repassivation layer 130.