Method and device for assembling a sensor on a substrate

Abstract

The invention relates to a method for bonding a miniature sensor (110) of the type comprising an assembly of nanoparticles, to the surface of a substrate (101), by a pressure-sensitive adhesive film (330), comprising bonding to the sensor by a rigid adhesive, of a thin stiffener (310), extending under the active part (410) of the miniature sensor (110), between the pressure-sensitive adhesive film (330) and the miniature sensor (110).

Description

Title of the invention: Method and device for assembling a sensor on a substrate Technical field

[0001] The invention belongs to the field of miniature sensors, used in particular to measure an applied force.

[0002] The invention is more particularly intended for so-called force sensors using an assembly of nanoparticles and measuring, during the application of this force, the variation of an electrical property of this assembly, proportional to the modification of a distance between the nanoparticles constituting the assembly.

[0003] This type of sensor is for example described in document EP2 601 491, the content of which is incorporated here by reference. Prior art

[0004] The sensors described above have a very high sensitivity and, due to their operation, can be attached to the surface of any substrate, rigid or flexible, in order to functionalize this surface.

[0005] By way of non-limiting example, such a sensor can be stuck on an automobile accessory, such as an armrest, a dashboard or a console, directly on the surface exposed to touch or on an opposite surface (below) the surface exposed to touch, pressure on the area where the sensor is located making it possible to control an action, such as the lowering or raising of an electric window, the activation of the windshield wipers, etc., thus avoiding the mechanical installation of any switch or commutator.

[0006] In addition, these sensors have a variable response depending on the force applied; this information can be used directly to control the targeted device; for example, a stronger pressure results in a higher windshield wiper speed.

[0007] In order to functionalize the surface, said miniature sensors are glued to a surface of the substrate using a polymerizable liquid glue of the cyanoacrylate or epoxy type. This type of rigid glue ensures firm support and excellent mechanical coupling of the sensor to the surface of the substrate,

[0008] [Fig-1] relating to the prior art shows this type of bonding, between a substrate (101), the sensor (110) and the adhesive layer (120).

[0009] However, the application of these liquid adhesives, which must be applied on a small surface and with precision, is not suitable for a large-scale manufacturing process, such as in the automotive industry, which prefers to use pressure-sensitive adhesives (PSA) in film form.

[0010] [Fig.2], however, if the adhesive layer (120) of [Fig.l] is replaced by a film pressure-sensitive adhesive, on the one hand the system's ability to detect a force is reduced, which results in an apparent drop in the sensitivity of the sensor, on the other hand, relaxation phenomena occur and modify the response of the device. Thus [Fig.2] shows an example of time response (210) of a sensor glued with a rigid glue at stress levels and an example of time response (220) of the same sensor, but glued using a pressure-sensitive adhesive film, at similar stress levels. Summary of the invention

[0011] The invention aims to resolve the drawbacks of the prior art and relates to this end to a method for bonding a miniature sensor of the type comprising an assembly of nanoparticles, to the surface of a substrate, by a pressure-sensitive adhesive film, comprising bonding by a rigid glue, of a thin stiffener, at the active part of the miniature sensor, between the pressure-sensitive adhesive film and the miniature sensor. Brief description of the drawings

[0012] The invention is implemented according to the preferred, non-limiting embodiments described below with reference to [Fig.1] to [Fig.5]. Fig.l

[0013] [Fig.l] relating to the prior art represents in a sectional view the installation of a miniature sensor on a substrate; Fig.2

[0014] [Fig.2] relating to the prior art shows the comparative temporal responses of a sensor subjected to stress levels in the case of a sensor glued to a substrate with a rigid glue and in the case of a sensor glued to a substrate with a pressure-sensitive adhesive film; Fig.3

[0015] [Fig.3] shows in a sectional view a sensor bonded to a substrate by a film pressure-sensitive adhesive implementing the method which is the subject of the invention; Fig.4

[0016] [Fig.4] shows from below an example of the embodiment of a sensor miniature incorporating a thin stiffener; Fig.5

[0017] [Fig.5] shows the comparative time responses of a sensor subjected to stress levels in the case of a sensor bonded to a substrate with a rigid glue and in the case of a sensor bonded to a substrate with a pressure-sensitive adhesive film but implementing the bonding method of the invention, Description of the embodiments

[0018] [Fig.3] the miniature sensor (110) is glued at the time of its manufacture onto a thin stiffener (310) for example made of a polycarbonate with a thickness of 0.2 mm.

[0019] The sensor and stiffener assembly is then attached to the substrate (101) by means of a pressure-sensitive adhesive film (330).

[0020] [Fig.4] the stiffener (310) must extend at least under the active part (410) of the sensor. According to one embodiment, said stiffener only extends under the active zone (410) of the sensor (110), i.e. the one which comprises the assembly of nanoparticles.

[0021] [Fig.5] the presence of this stiffener eliminates the relaxation phenomena in the time response (520) of the sensor.

Claims

Claims

1. Method for bonding a miniature sensor (110) of the type comprising an assembly of nanoparticles, to the surface of a substrate (101), by a pressure-sensitive adhesive film (330), comprising bonding to the sensor by a rigid glue, a thin stiffener (310), extending under the active part (410) of the miniature sensor (110), between the pressure-sensitive adhesive film (330) and the miniature sensor (110).

2. The method of claim 1 wherein the thin stiffener (310) is made of a polycarbonate with a thickness of 0.2 mm.

Images