SECURITY ELEMENT, ELECTRONIC CARD, ELECTRONIC PAYMENT TERMINAL AND CORRESPONDING ASSEMBLY METHOD

Abstract

The technique proposes a security element (1), called security dome, intended to be adhesively bonded to an electronic card (20), the security element comprising at least: - a metal portion (11) intended to be in contact with at least one electric circuit of said electronic card; - a protective portion (12) covering said metal portion (11) and having a first face (121) comprising an adhesive section intended to adhesively bond said security element (1) to said electronic card through an automatic assembly process comprising at least one remelting step, said metal portion (11) and protective portion (12) being resistant to the temperatures used during said remelting step.

Description

[0001] DESCRIPTION

[0002] TITLE: Security element, electronic card, electronic payment terminal and corresponding assembly process.

[0003] Scope of the invention

[0004] The field of the invention is that of electronic devices comprising at least one electronic board on which electronic components are implanted.

[0005] More specifically, the invention relates to securing and improving the performance of such an electronic card.

[0006] The use of such electronic cards is widespread in industry. Furthermore, many fields require high levels of security in terms of the confidentiality of electrical signals transmitted through equipment. The invention thus has numerous applications, notably, but not exclusively, in the fields of electronic payment terminals, payment card readers, etc.

[0007] Prior art and its drawbacks

[0008] Therefore, in the remainder of this document, we focus more specifically on describing an existing problem in the field of electronic payment terminals which the inventors of this patent application have faced, relating to the particular components which are the security domes classically used in electronic payment terminals.

[0009] These specific components are implemented primarily to detect intrusions within an electronic payment terminal, as part of a broader security system for such a device. A security dome is strategically positioned on an electronic card within the terminal. This dome closes an electrical circuit when the terminal is closed, due to a pressure applied to the dome. When the terminal is subjected to an attempted opening or intrusion, the security dome is released from this pressure, opening the electrical circuit. This circuit is connected to an intrusion detection module, which then triggers security measures for the terminal (such as erasing all sensitive data or rendering the terminal unusable).

[0010] Currently, there are two main techniques for attaching these safety domes to a circuit board: gluing and soldering. With the first technique, the safety domes are glued to the circuit board manually by an operator after the other components have been attached and soldered. These safety domes typically consist of several elements, including a metal part for the electrical connection and one or more adhesive pads that allow the dome to be glued in place and protect the metal part.

[0011] This adhesive application technique leads to difficulties in precisely positioning the security domes on the circuit board and can subsequently cause problems during the operation of the electronic payment terminal, for example, by triggering false intrusion detection if one or more domes are incorrectly positioned within their security zone. Indeed, positioning a security dome requires not only very high precision but can also be challenging depending on its location on the circuit board. Components already positioned (by soldering) on ​​the board can either obscure the dome's location or interfere with its placement. Finally, this manual technique has drawbacks in terms of application efficiency, which is directly linked to the operator's skill in performing this operation.This adhesive application technique can therefore generate low productivity and thus increase the manufacturing costs of the electronic boards on which safety domes are placed.

[0012] According to the second technique, the safety domes are automatically soldered onto an electronic board.

[0013] The main drawback of this technique lies in reliability issues during use, due to the fact that the brazing / welding joint is constantly subjected to mechanical stress, or strain, on the safety dome. Furthermore, since the brazed joint cannot be reproduced in shape, it is difficult to define reliability rules for installation and use with this technique.

[0014] Therefore, there is a need for a technique for installing safety domes on an electronic board that allows for optimal installation reliability and optimal reliability in use.

[0015] Description of the invention

[0016] The present technique proposes a safety element, called a safety dome, intended to be glued onto an electronic board, the safety element comprising at least: a metallic part intended to be in contact with at least one electrical circuit of the electronic board; a protective part covering the metallic part and having a first face comprising an adhesive portion intended to ensure the bonding of the safety element to the electronic board by an automatic assembly process comprising at least one reflow step, said metallic part and protective part being resistant to the temperatures used during said reflow step.

[0017] Thus, the present technique offers a new and inventive solution to improve the performance of safety domes implanted on an electronic board, by allowing their implantation by bonding and automatically during the assembly process used to assemble so-called "SMT" components, including a reflow soldering step, on the electronic board.

[0018] The desired technical effects are achieved on the one hand through the automatic placement of such safety domes, allowing for optimal reliability and efficiency in terms of assembly, compared to manual placement, and on the other hand through the choice of materials for manufacturing the domes which allow the use of a bonding technique resistant to reflow temperatures and thus obtain greater robustness over time, compared to a welding technique.

[0019] To achieve this, such a safety dome includes, in particular, a metallic part that performs the dome's actual safety function, as well as a protective part that covers the metallic part and allows the dome to be bonded to the electronic board, either directly or via another part of the dome, depending on the specific design. The materials used to manufacture these metallic and protective parts are therefore chosen for their resistance to the reflow temperatures used during the assembly process.In one embodiment, the safety element also includes a first part, called a spacer, having: a first face comprising an adhesive portion intended to be bonded to the electronic board by an automated assembly process including at least one reflow step; and a second face onto which the adhesive portion of the first face of the protective part is bonded, the first part being resistant to the temperatures used during the reflow step. Thus, in this embodiment, the safety dome, consisting of a metallic part to ensure electrical conductivity and a protective part covering the metallic part, also includes an adhesive part (spacer) for bonding it to the electronic board. This spacer has the same temperature resistance characteristics as the other two parts.This spacer also allows for the creation of a "pre-assembled" dome, comprising the three parts, which can be positioned on a support for integration into the automated assembly process. The safety dome produced according to this technique is therefore suitable for bonding during an automated component assembly process on a circuit board that includes a reflow soldering step.

[0020] According to one particular aspect, the first part has a central hollowed-out portion and the metallic part is movable relative to the first part and the protective part.

[0021] Thus, according to this embodiment, the safety dome consists of a spacer with an adhesive side for bonding to the electronic board and a central hollowed-out section allowing a metallic part, the dome itself, to make contact with an electrical circuit on the electronic board, as well as a third protective part. This third part corresponds, for example, to a plastic film also having an adhesive side for attaching it to the other side of the spacer and thus "enclosing" the free-moving metallic dome between the electronic board and the protective film.

[0022] This assembly of the three parts of the safety dome results in a reliable and high-performance safety element, both in terms of precise bonding to the circuit board and in terms of securing the electronic device in which the circuit board is installed. The mobility of the metal part, in particular, allows for greater robustness during use. As a specific characteristic, the safety element is composed of temperature-resistant materials belonging to the group comprising:

[0023] Polyimides;

[0024] Liquid crystal polymers;

[0025] Silicones;

[0026] Polyepoxides: Acrylic.

[0027] Thus, the proposed solution relies on a choice of temperature-resistant materials for each of the parts composing a safety dome, allowing it to be glued onto an electronic board during a classic automatic assembly process of components on the electronic board, including in particular a reflow soldering step.

[0028] The present technique also relates to an electronic card comprising at least one security element as described above, according to the different embodiments.

[0029] This technique also relates to an electronic payment terminal comprising at least one electronic card as described above, according to the different embodiments.

[0030] This technique also relates to a method for the automatic assembly of at least one safety element, as described above, according to various embodiments, onto an electronic board. According to this technique, the method comprises the following automatic steps: obtaining said at least one safety dome; positioning said at least one safety dome by bonding said adhesive portion of said first face of said first part or of said adhesive portion of said first face of said protective part onto said electronic board at a predetermined location; and reflow soldering of said electronic board.

[0031] Thus, the present technique also relates to a method of assembling one or more safety domes on an electronic board, automatically and by gluing, making it possible to obtain the desired technical effects in terms of reliability, precision and efficiency of implantation and robustness in use.

[0032] To achieve this, the bonding of the safety dome(s) is integrated into the reflow process during which the so-called "SMT" components to be soldered to the electronic board are brazed, this bonding being possible thanks to the specificities of the materials composing the dome, chosen for their resistance to the temperatures used during reflow.

[0033] According to one particular aspect, the assembly process also includes the following two steps, prior to the soldering step: screen printing of the electronic board; placement of electronic components to be soldered, and the obtaining step consists of removing by aspiration said at least one safety dome previously positioned on a support.

[0034] The different embodiments mentioned above can be combined with each other for the implementation of the proposed technique.

[0035] List of figures

[0036] Other objects, features and advantages of the invention will become more apparent upon reading the following description, given by way of simple illustration and not limitation, in relation to the figures, among which:

[0037] [Fig la] illustrates an exploded view of the underside of a security dome, according to one embodiment of the invention;

[0038] [Fig lb] illustrates an exploded view of the underside of a security dome, according to a second embodiment of the invention;

[0039] [Fig. 1] illustrates an exploded view of the top of the safety dome shown in Figure 1b, according to a second embodiment of the invention; [Fig. 2] illustrates an example of the positioning location of a safety dome on an electronic board according to an embodiment of the invention; and

[0040] [Fig 3] illustrates the main steps of an automatic assembly process for an electronic board comprising the positioning of at least one safety dome as illustrated in Figure 1a, according to an embodiment of the invention.

[0041] Detailed description of embodiments of the invention

[0042] As previously stated, the inventors of this patent application sought to solve various technical problems related to different methods of placing safety elements, or safety domes, on an electronic board.

[0043] Thus, the well-known soldering technique has the major drawback of poor robustness in use, due in particular to the high stresses and movements experienced by the domes soldered onto a circuit board, itself integrated into an electronic device such as an electronic payment terminal, for example. Since this robustness problem is not, or only rarely, observed with domes manually glued onto a circuit board, the inventors therefore favored a technique for gluing the domes onto a circuit board. However, current manual dome gluing techniques have two main drawbacks: low placement accuracy and low gluing efficiency. The inventors therefore sought to integrate a gluing technique into the existing automated process for assembling components onto a circuit board using soldering (for example, by reflow soldering).This assembly process is notably used for assembling surface-mount components, known as SMDs (Surface Mount Devices). During SMD assembly, the circuit boards pass through a reflow oven to solder the components, which have been pre-positioned in predetermined locations on the boards. Reflow soldering is used, for example, for circuit boards containing only SMD components, or components that can only be soldered using this technique, such as ball grid array (BGA) components. SMD components are preferred for mounting on a circuit board because it is faster, simpler, and more reliable than through-hole components, which require drilling into the circuit board for installation.

[0044] However, the inventors encountered other problems related to using an adhesive mounting technique during a soldering process, namely maintaining the temperature of the domes during the soldering stage of the assembly process and ensuring the dome's positioning on its support (e.g., a reel, a tape, a film) before being placed on the circuit board. Indeed, if the domes are misaligned on their support before placement, their positioning on the circuit board may be inaccurate, leading to reliability issues with their safety function.

[0045] To overcome these difficulties, the proposed technique is based on a modification of the safety dome to allow for its automatic integration into the assembly process of other components on the electronic board. Indeed, component placement machines enable the optimized, rapid, and precise positioning of components on electronic boards.

[0046] The general principle of the invention is therefore based on the modification of the materials which make up the safety domes themselves, so that they can withstand the temperature profile recorded during the brazing stage(s) and so that they can be placed during the automatic assembly process of the components of an electronic board (for example an SMT assembly process).

[0047] We now describe a method of implementing the proposed technique, in relation to figures Fig 1a to Fig 3.

[0048] Figure 1a illustrates an exploded view of the underside of an example of a safety dome 1, according to a first embodiment, in which the safety dome 1 comprises a metallic part 11 intended to be in contact with at least one electrical circuit of the electronic board (not shown in Figure 1a). The safety dome 1 also comprises a protective part 12 covering the metallic part 11 and having a first face 121 comprising an adhesive portion intended to ensure the bonding of the dome to the electronic board by an automated assembly process comprising at least one reflow step.

[0049] For example, according to this first embodiment, the adhesive portion of the first face 121 of the protective part 12 is intended to be glued directly onto the electronic board, thus allowing the safety dome 1 to be glued, the metallic part 11 being "enclosed" between the board and the protective part 12.

[0050] According to the second embodiment described below, the adhesive portion of the first face 121 of the protective part 12 is intended to be glued onto another part of the dome, called a spacer, which is itself glued directly onto the electronic board

[0051] Furthermore, according to this embodiment, the two parts 11 and 12 are resistant to the temperatures used during the reflow step implemented to assemble the safety dome 1 onto a circuit board. To achieve this, the materials chosen for these parts 11 and 12 must be compatible with the temperatures used during a reflow step, while also ensuring the functions necessary for the use of a safety dome, namely, mechanical robustness and the dimensions required for such a dome. Indeed, these safety elements are implemented on circuit boards comprising a large number of components and at strategic locations on the board, sometimes requiring relatively small sizes for these safety elements. These characteristics are described in more detail below, in relation to the second embodiment.

[0052] Figure Fig lb illustrates an exploded view of the underside of an example of a safety dome 1. According to this second embodiment of the invention, such a safety dome 1 comprises at least a first part 10, called a spacer, having a first face comprising an adhesive portion 101 intended to be glued onto the electronic board (not shown in Fig lb), and a second metallic part 11 intended to be in contact with at least one electrical circuit of the electronic board.

[0053] According to this embodiment, these two parts 10 and 11 are resistant to the temperatures used during the reflow step implemented to assemble the safety dome 1 onto an electronic board.

[0054] As previously mentioned, the materials chosen for these first and second parts 10 and 11 must be compatible with the temperatures used during a reflow step, while also ensuring the functions necessary for the use of a safety dome, namely mechanical robustness and the dimensions required for such a dome. Indeed, these safety features are implemented on electronic boards containing a large number of components and at strategic locations on the board, sometimes requiring relatively small sizes for these safety features.

[0055] For example, the spacer 10 measures approximately 25 to 100 micrometers in thickness and has a cut-out shape allowing the metal part 11 to make electrical contact with a circuit present on the electronic board.

[0056] Furthermore, this spacer 10 is made of a temperature-resistant material such as polyimides, liquid crystal polymers, or silicones (in film form). For face 101, the material used is, for example, an adhesive such as polyepoxides, polyimides, or acrylic. The choice of one or another of these materials to achieve the desired technical effect, namely temperature resistance, may be dictated, for example, by considerations of cost, supply, or manufacturing process.

[0057] The metallic part 11 has a substantially circular shape, for example with a diameter of about 3 to 5 millimeters (plus or minus 0.03 millimeters), with a thickness of 1.18 millimeters (plus or minus 0.03 millimeters), and about 30 to 150 gram-force.

[0058] According to this embodiment, the safety dome 1 also includes a third protective part 12, having temperature resistance properties used during the reflow step and covering the first and second parts 10, 11. This third protective part 12 is, for example, in the form of a plastic film approximately 25 to 100 micrometers thick, with at least one adhesive face 121 intended to be bonded to the first part 10 (on the face 102 opposite the face 101), so as to form a housing for the metal part 11, while protecting it. In this second embodiment, the third protective part 12 is therefore not directly bonded to the electronic board, but is bonded to the spacer 10, which allows the dome to be formed in such a way that it can subsequently be bonded to an electronic board, as described below in relation to the assembly process.

[0059] To achieve the desired technical effects, namely temperature resistance during one or more reflow stages, this third protective section 12 has characteristics similar to the spacer 10 in that it is made of a temperature-resistant material such as polyimides, liquid crystal polymers, or silicones (in film form). The portion of the face 121 is made of an adhesive material such as polyepoxides, polyimides, or acrylic. Again, the same selection criteria for one or the other of the aforementioned materials, or an equivalent material, lie in optimizing the achievement of the desired technical effect. Figure Fig le illustrates an exploded view from the top of the example security dome as described above in relation to Figure Fig lb, with faces 101 of the strut 10 and 121 of the third protective part 12 no longer visible, face 102 of the strut being shown.

[0060] As already mentioned, the proposed solution relies not only on safety elements, or domes, featuring specific materials that can withstand temperatures used during one or more reflow stages, but also on integrating the bonding of these domes into an automated component assembly process on an electronic board.

[0061] To do this, it is first necessary to recall how a security dome works: the periphery of the dome's metallic part rests on a conductive track on the electronic card. Then, when the dome is under stress (for example, when the two covers of an electronic payment terminal are assembled), the central part of the dome's metallic section rests on another conductive track, thus closing an electrical circuit. Consequently, when the stress is no longer applied to the dome (for example, when the electronic payment terminal is subjected to an attempted opening), the electrical circuit opens. This opening is detected and then analyzed, for example, as representing an intrusion into the device in which the electronic card is integrated (for example, an electronic payment terminal).Figure 2 illustrates a portion of an electronic circuit board 20 before the assembly of electronic components. This portion consists, for example, of a copper plate covering a substrate 21 (most often made of epoxy resin), the copper plate itself being coated with a varnish. Figure 2 more specifically illustrates a location for the installation of a safety dome. This location is defined by a set of electrical traces 22a, 22b, enabling the dome to function as described above. A central trace 22a allows the electrical circuit to close when the dome is compressed, thanks also to the other trace 22b, on which the periphery of the dome (via its spacer 10 described above) rests.

[0062] Secondly, it is appropriate to describe the main steps of such an automatic assembly process, for example an SMT process, according to an embodiment of the present technique, in relation to the figure Fig 3.

[0063] The first, classic and well-known step (not shown in Fig. 2) in such an automated SMT assembly process consists of screen-printing the circuit board with solder paste, that is, applying solder paste to predetermined areas intended to later receive components to be soldered. This screen-printing step is, for example, carried out using a metal stencil (called a "stencil"), which allows solder paste to be applied only to the locations of the component leads.

[0064] An automated component placement phase is then implemented, using a machine that picks up the components and places them in predetermined locations ("Pick & Place"). Typically, the components that feed the placement machine are packaged in strips and are picked from this strip to be positioned on the board.

[0065] This automated placement phase includes not only obtaining and placing solderable electronic components, of the SMD type, but also, during an E30 step, obtaining at least one safety element, or dome, as described previously.

[0066] In an automated SMT assembly application of an electronic card in an electronic payment terminal, the domes are deposited / glued onto a support (a reel, a film or a strip), from which they are picked up by suction by a nozzle of the placement machine, during a step E30. The picked-up domes are then positioned, by gluing (using the adhesive face 101 of their spacers 10), at the predetermined locations on the electronic card, during a step E31.

[0067] At the end of this automated placement phase, the components to be soldered are placed in their designated locations (previously screen-printed with solder paste), and the safety domes are glued to their designated locations. The gluing of the safety domes is therefore fully automated, as it is integrated into the automated process of assembling electronic components onto a circuit board.

[0068] Next, the circuit board is placed in an oven during at least one E32 reflow soldering step to solder the components. During this E32 step, the temperature rises, for example, according to a known temperature profile, up to a peak of 260°C for a period of 5 to 6 minutes. This heat remelts the solder paste applied during the screen printing step to form the solder without risk of overheating the electronic components. The materials that make up the dome must withstand this temperature profile, as described above. Typically, an automated inspection step to verify the correct placement of the components is then implemented, as well as an electrical test of the circuit board.

[0069] Thus, the proposed technical solution improves the assembly of security domes on electronic cards and, consequently, the manufacturing quality of electronic payment terminals using such cards, thanks to reproducible positioning on the card achieved through process automation. Furthermore, the automation of this process also leads to productivity gains. This technical solution is therefore easily transferable to a range of electronic payment terminals using electronic cards assembled in this way, and readily scalable for industrial production.

[0070] The proposed technical assembly solution therefore also increases the manufacturing quality of payment terminals while improving security. Indeed, through this bonding assembly process integrated into the automated SMT process, the security domes, compatible with the temperatures used during reflow taps thanks to the careful selection of materials, are automatically placed onto electronic boards, optimizing the reliability of their positioning as well as their reliability in use.

Claims

DEMANDS 1. Safety element (1), called a safety dome, intended to be glued onto an electronic card (20), said safety element being characterized in that it comprises at least: a metallic part (11) intended to be in contact with at least one electrical circuit of said electronic card; a protective part (12) covering said metallic part (11) and having a first face (121) comprising an adhesive portion intended to ensure the bonding of said safety element (1) onto said electronic card by an automatic assembly process comprising at least one reflow step, said metallic part (11) and protective part (12) being resistant to the temperatures used during said reflow step.

2. Safety element (1) according to claim 1, characterized in that it also comprises a first part, called a spacer (10), having: a first face (101) comprising an adhesive portion intended to be glued onto said electronic board by an automatic assembly process comprising at least one reflow step, a second face (102) on which is glued said adhesive portion of said first face (121) of said protective part (12), said first part (10) being resistant to the temperatures used during said reflow step.

3. Safety element (1) according to any one of claims 1 and 2, characterized in that said first part (10) has a central hollow portion and said metal part (11) is movable relative to the first part (10) and the protective part (12).

4. Safety element according to any one of claims 1 to 3, characterized in that it is composed of temperature-resistant materials belonging to the group comprising: Polyimides; Liquid crystal polymers; Silicones; Polyepoxides and acrylic.

5. Electronic card comprising at least one security element according to any one of claims 1 to 4.

6. Electronic payment terminal comprising at least one electronic card according to claim 5.

7. Method for automatically assembling at least one safety element according to any one of claims 1 to 4, on an electronic board, characterized in that said method comprises the following automatic steps: - obtaining said at least one safety dome; positioning said at least one safety dome by gluing said adhesive portion of said first face of said first part or of said adhesive portion of said first face of said protective part on said electronic board at a predetermined location; - reflow soldering of said electronic board.

8. Automatic assembly method according to claim 7, characterized in that it also comprises the following two steps, prior to said soldering step: screen printing of said electronic board; - placement of electronic components to be soldered, and in that said obtaining step consists of removing by aspiration said at least one safety dome previously positioned on a support.