METHOD FOR LOCALIZED DEPOSITION OF A MATERIAL ON AN ELEMENT

Abstract

Method for localized deposition of a material on an element (110), comprising: - deposition of a portion (108) of the material on a part of a surface (101) of a support (102); - positioning of a part (112) of the element against the portion of the material; - thermal and / or chemical treatment of the portion of material increasing, at the end of the treatment, the adhesion force of the material against the part of the element, the materials of the part of the element and of the part of the surface of the support being chosen such that the adhesion of the material against the part of the element is, at the end of the treatment, greater than that of the material against the part of the surface of the support; - separation of the element and the support at the interface between the material and the part of the surface of the support, the material remaining integral with the part of the element. Figure for abstract: Figure 6.

Description

Title of the invention: METHOD FOR LOCALIZED DEPOSITION OF A MATERIAL ON AN ELEMENT Technical field

[0001] The invention relates to a method for localized deposition of at least one material on at least one element, applied in particular for:

[0002] - the production of electrical and / or mechanical interconnections, for example me fusible ball or microbead type metallizations, or solder balls or microbeads, on at least one electronic chip,

[0003] - the production of at least one sealing bead on at least one layer of protection or a cover intended to close at least one cavity in which there is, for example, at least one MEMS (“MicroElectroMechanical System” or microelectromechanical system) type component,

[0004] - the production of at least one functionalization layer for at least one sensor or test device used in the field of biology and / or chemistry. STATE OF THE PRIOR ART

[0005] Electronic chips, such as ASICs or "Application-Specific Integrated Circuits", memory chips, etc., marketed are generally intended to be connected by wire bonding, or "wire-bonding", and are not provided with solder bump type metallizations, or "solder bumps", on their connection pads. Due to their small lateral dimensions (generally a few millimeters) and / or their small thickness (generally a few tens of microns), it is very difficult to manufacture, on each electronic chip taken individually, solder bump type metallizations. Such metallizations make it possible to secure the electronic chip by "flip-chip", or turning over, on an interposition element, or "interposer", or a substrate to which the electronic chip is intended to be mechanically and / or electrically coupled.

[0006] To form fusible bead type metallizations on an electronic chip, these are generally carried out collectively for several electronic chips simultaneously, at the scale of a wafer or substrate containing the electronic chips. Screen printing is the most commonly used technique to produce fusible beads, because it is the least costly technique for processing the chips at the wafer scale.

[0007] An example of a process for the collective production of fusible bead type metallizations by screen printing is described below in connection with Figures 1 to 4.

[0008] As shown in [fig. 1], solder paste 10 comprising fusible material, or metallic solder material, is spread on a substrate 12 in or on which the chips have been previously made, on the side where the fusible balls are intended to be made. The solder paste 10 is spread for example by a doctor blade 11 through a screen printing screen 14 or screen printing mask. Openings formed through the screen printing screen 14 define locations of the substrate 12 on which the solder paste 10 is deposited in the form of small portions 15 spaced from each other.

[0009] The screen printing screen 14 is then removed and then annealing is carried out at a temperature greater than or equal to the melting temperature of the fusible material so that the portions 15 pass into the liquid state and then form, at the end of this annealing and after the fusible material has returned to the solid state, balls 16 of fusible material ([fig.2]).

[0010] A cut of the substrate 12 is then made to form separate electronic chips 18, each provided with fusible beads 16 ([fig-3]).

[0011] In [fig.4], an electronic chip 18 ready to be transferred by "flip-chip" onto a support is shown.

[0012] This implementation of the fusible beads 16 by depositing the fusible material by screen printing is not feasible for individual chips, that is, at the scale of an already cut electronic chip on which the screen printing screen would be placed, because it would significantly increase the manufacturing cost of the electronic chips.

[0013] Furthermore, this method of producing the fusible balls is not suitable when the surface on which the fusible balls are to be produced is irregular and has hollows because when spreading the paste 10, the latter is not deposited correctly in the hollows. Furthermore, because the screen printing screen 14 must be pressed against the surface on which the fusible balls are produced when depositing the paste 10, the irregularities of this surface pose a problem of flatness.

[0014] Similar constraints also exist in other applications, such as for example when producing sealing beads intended for securing covers or protective layers for MEMS devices, or even when producing functionalization layers for sensors and test devices used in the field of biology and / or chemistry. Statement of the invention

[0015] An aim of the present invention is to propose a method for localized deposition of at least one material on at least one element which does not have the drawbacks of the prior art previously described, that is to say which makes it possible to locally deposit the material onto a small individual element such as an electronic chip, and / or to deposit the material onto an irregular surface having hollows.

[0016] For this, the present invention proposes a method for localized deposition of at least one material on at least one element, comprising the implementation of the following steps:

[0017] - depositing at least a portion of the material on at least part of a surface of a support;

[0018] - positioning at least a portion of the element against the portion of the material;

[0019] - thermal and / or chemical treatment of the portion of material increasing, at the end of the heat and / or chemical treatment, the adhesive strength of the material against the part of the element, the materials of the part of the element and of the part of the surface of the support being chosen such that the adhesion of the material against the part of the element is, at the end of the heat and / or chemical treatment, greater than that of the material against the part of the surface of the support;

[0020] - separation of the element and the support at the interface between the material and the part of the surface of the support, the material remaining integral with the part of the element.

[0021] In this method, the material to be deposited locally is first deposited on a support which does not correspond to the element on which the material is intended to be deposited and which serves as a temporary support. The part of the element on which the material is intended to be deposited is then positioned in contact with the material. A heat and / or chemical treatment is then implemented in order to increase the adhesion strength of the material against the part of the element. At the end of the heat and / or chemical treatment, the adhesion of the material against the part of the element is greater than that of the material against the part of the surface of the support. This property is obtained by judiciously choosing the materials forming the part of the surface of the support and the part of the element against which the material is arranged.Thus, the separation which is then carried out between the element and the support causes a rupture at the interface between the material and the part of the surface of the support, with the material which remains attached to the element. The material is therefore found to be deposited locally on the element.

[0022] This method is particularly well suited to be implemented with small individual elements, for example electronic chips, which are independent of each other. This method can be implemented simultaneously for several individual elements. This method is also well suited to locally depositing a material on elements having irregular material receiving surfaces comprising hollows since no screen printing is directly implemented on these receiving surfaces.

[0023] This process can be implemented for numerous applications: production of fusible ball type metallizations on one or more individual electronic chips individual, production of sealing cords intended for the securing of covers or protective layers for MEMS devices, production of electrical and / or mechanical interconnections, production of functionalization layers for sensors and test devices used in the field of biology and / or chemistry.

[0024] Throughout the document, the term “bead” is used to designate microbeads of micrometric dimensions, or beads of larger dimensions.

[0025] The thermal and / or chemical treatment may correspond to at least one of the following treatments: annealing at a temperature greater than or equal to the melting temperature of the material, dehydration, quenching, freezing, polymerization,

[0026] The deposition of the portion of the material on the part of the surface of the support can be carried out by screen printing through a screen comprising at least one opening determining, when positioning the screen on the surface of the support, the location of the part of the surface of the support.

[0027] The portion of the element may form a hollow relative to the remainder of a surface of the element at which said portion of the element is located.

[0028] The part of the surface of the support may include a raised marking. Thus, when the deposited material and the part of the surface of the support are separated, a pattern opposite to that of the marking is transferred to the surface of the material which is detached from the support. This marking may be used to produce logos or punches making it possible to identify or authenticate the element.

[0029] The method may be such that:

[0030] - the thermal and / or chemical treatment corresponds to a thermal treatment carried out works at a temperature greater than or equal to the melting temperature of the material;

[0031] - the part of the surface of the support is such that a contact angle between the material to the liquid state and the part of the surface of the support has a value 0Ci;

[0032] - the part of the element is such that a contact angle between the material in the state liquid and the part of the element has a value 0C2 < 0ci-

[0033] In this case, during the heat treatment, the treated material changes phase and passes into the liquid state. These values ​​of the contact angles 0Ci and 0C2 are obtained by judiciously choosing the materials forming the part of the surface of the support and the part of the element and which are in contact with the material in the liquid state. With such contact angles, after the material returns to the solid state, the adhesion of the material against the part of the element is much greater than that of the material against the part of the surface of the support.

[0034] In an advantageous configuration, the method may be such that:

[0035] - the material is a metallic brazing material, and

[0036] - the heat treatment implemented is annealing.

[0037] In addition, the metallic brazing material may comprise at least one of the following metals: tin, indium, silver, and the part of the surface of the support may comprise a metal oxide and the part of the element may comprise at least one of the following metals: aluminum, copper, gold. Such materials make it possible to obtain, on the side of the element, a material said to be "wettable" by the metallic brazing material and, on the side of the support, a material said to be "non-wettable" by the metallic brazing material.

[0038] The method may further comprise, between the deposition of the portion of the material on the part of the surface of the support and the positioning of the part of the element against the portion of the material, the implementation of an initial annealing of the portion of material. This initial annealing makes it possible to remove a portion of the solvents present in the material deposited on the part of the surface of the support.

[0039] According to a first embodiment, the element may correspond to an electronic chip.

[0040] In addition, the method may be such that:

[0041] - several portions of material are deposited on the support,

[0042] - the parts of the electronic chip arranged against the portions of cor material correspond to electrical contact pads, and

[0043] - after the implementation of the heat treatment, the portions of material form fusible ball type metallizations.

[0044] According to a second embodiment, the method can be such that:

[0045] - the element corresponds to a protective layer or a cover adapted to enclose or protect at least one MEMS type device in a cavity, and

[0046] - after the implementation of the heat treatment, the portion of material forms a sealing cord secured to the protective layer or cover.

[0047] Throughout this document, the expression "MEMS device" is used to designate MEMS or NEMS ("NanoElectroMechanical System" or nanoelectromechanical system) or MOEMS ("Micro-Opto-ElectroMechanical System" or microopto-electromechanical system) or NOEMS ("Nano-Opto-ElectroMechanical System" or nanoopto-electromechanical system) devices or any other electronic or microelectronic device intended to be enclosed or protected in a cavity.

[0048] According to a third embodiment, the method can be such that:

[0049] - the material is an organic material, and

[0050] - the thermal and / or chemical treatment comprises the implementation of a dehydration treatment and / or heat treatment such as quenching and / or freezing.

[0051] In this case, the element may correspond to a test device or a sensor intended for biological and / or chemical applications, and the portion of material forms, at the end thermal and / or chemical treatment, a functionalization layer.

[0052] According to a fourth embodiment, the method can be such that:

[0053] - the material is a polymer, and

[0054] - the thermal and / or chemical treatment corresponds to a polymerization comprising the implementation of illumination by a laser beam and / or exposure by UV or infrared radiation of the material.

[0055] Generally, the method can be implemented simultaneously for several elements.

[0056] In addition, the elements may have different thicknesses. Brief description of the drawings

[0057] The present invention will be better understood upon reading the description of exemplary embodiments given purely for informational purposes and in no way limiting, with reference to the appended drawings in which:

[0058] [fig.l]

[0059] [fig.2]

[0060] [fig.3] and

[0061] [fig.4]

[0062] represent an example of a method for producing fusible ball type metallizations according to the prior art;

[0063] [fig.5]

[0064] [fig.6]

[0065] [fig.7]

[0066] [fig.8]

[0067] [fig.9] and

[0068] [fig.10]

[0069] represent an example of a method for localized deposition of at least one material on at least one element according to a first embodiment;

[0070] [fig.ll]

[0071] [fig.12]

[0072] [fig.13]

[0073] [fig.14] and

[0074] [fig.15]

[0075] represent an example of a method for localized deposition of at least one material on at least one element according to a second embodiment.

[0076] Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the transition from one figure to another.

[0077] The different parts represented in the figures are not necessarily on a uniform scale, in order to make the figures more readable.

[0078] The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other.

[0079] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0080] A method for localized deposition of at least one material on at least one element according to a first embodiment is described below in connection with figures 5 to 10. In this first particular embodiment, this deposition method is implemented to produce fusible ball type metallizations on electronic chips.

[0081] As shown in [fig.5], solder paste 100 comprising material to be deposited locally, here fusible material, or metallic solder material, is spread over at least a portion of a surface 101 of a support 102. The material to be deposited corresponds for example to tin or indium or silver or an alloy comprising at least one of these metals. The support 102 corresponds for example to a semiconductor substrate, or any other support suitable for receiving the deposition of the material 100.

[0082] The solder paste 100 is spread for example with a doctor blade 104 through a screen printing screen 106. Openings formed through the screen printing screen 106 determine, when positioning the screen printing screen 106 on the surface 101 of the support 102, the location of the parts of the surface 101 of the support 102 on which solder paste 100 is deposited. The reference 108 designates the portions of material deposited on the support 102. The thickness “e” of the mask 106, which corresponds to the thickness of the portions 108 of material deposited, is for example between approximately 40 μm and 500 μm.

[0083] The parts of the surface 101 of the support 102 on which the portions 108 of material are deposited comprise a material such that when the material of the portions 108 is in the liquid state, the contact angle between the material in the liquid state and the parts of the surface 101 of the support 102 on which the portions 108 are deposited has a value 0Ci. It is possible for the entire surface 101 of the support 102 at which the material is deposited, i.e. the entire face of the support 102 on the side on which the material is deposited, to comprise such a material.

[0084] This material of the parts of the surface 101 of the support 102 on which the portions 108 are deposited is chosen such that it is less “wetting”, or has a lower wettability, than that of the element(s) (corresponding to electronic chips in the first embodiment described here) on which the portions 108 are intended to be deposited locally at the end of the method. Thus, the material of said part(s) of the surface 101 of the support 102 may be such that a contact angle between the material of the portions 108 in the liquid state and said part(s) of the surface 101 of the support 102 has a value 0Ci, and the material of the part or parts of the elements on which the portions 108 are intended to be deposited locally at the end of the process may be such that a contact angle between the material of the portions 108 in the liquid state and said part or parts of these elements has a value 0C2 < 0ci-

[0085] When the deposited material corresponds to one of the previously mentioned brazing materials, the material of the part or parts of the surface 101 of the support 102 may correspond to a metal oxide such as copper oxide. For example, in the exemplary embodiment described here, the surface 101 of the support 102 is formed from a layer of metal oxide. When the metallic material corresponds to a metal oxide, its wettability may be adjusted via the parameters for implementing the oxidation forming this material, for example by adjusting the baking time or the plasma treatment of this oxidation.

[0086] Optionally, an initial annealing of the portions 108 of material at a temperature causing the material 100 to pass into the liquid state, i.e. at a temperature greater than or equal to the melting temperature of the material of the portions 108, is implemented. This initial annealing makes it possible to remove a portion of the solvents present in the deposited material, and is implemented for example at a temperature between approximately 220°C and 260°C when the deposited material corresponds to one of the previously mentioned brazing materials, and for a duration between approximately 5 and 15 minutes.

[0087] The screen 106 is removed and one or more elements 110 are then arranged against the portions 108. In the first embodiment described here, several elements referenced 110.1 and 110.2, corresponding to electronic chips, are arranged against the portions 108 (see figures 6 and 7).

[0088] The chips 110.1 and 110.2 each comprise, on one of their faces, connection pads 112 forming the parts against which the fusible ball type metallizations are intended to be produced. These connection pads 112 comprise a material such that when the fusible material is in the liquid state, the contact angle between the fusible material in the liquid state and the connection pads 112 has a value 0C2 < 0ci-When the material 100 corresponds to one of the previously mentioned soldering materials, such a material may correspond to aluminum, copper or gold or an alloy comprising at least one of these metals. Furthermore, the connection pads 112 present on the electronic chips 110.1 and 110.2 are arranged in an arrangement compatible with that of the portions 108, that is to say such as when the electronic chips 110.1 and 110.2 are placed against the portions 108, these portions 108 are in contact with the connection pads 112.

[0089] As shown in [fig.8], a thermal and / or chemical treatment of the portions 108 of material is then implemented in order to generate at the end of this treatment, an increase in the adhesion of the material against the connection pads 112. In the first embodiment described here, this treatment corresponds to a heat treatment, and more particularly an annealing carried out in a furnace at a temperature greater than or equal to the melting temperature of the material of the portions 108. This heat treatment is carried out for example at a temperature between approximately 220°C and 260°C when the material of the portions 108 corresponds to one of the previously mentioned soldering materials, and for a duration of between approximately 5 min. and 15 min (complete duration including the rise and fall in temperature). During this heat treatment, the portions 108 can be exposed to a temperature between approximately 220°C and 260°C for a duration of the order of one minute. The portions of material obtained at the end of the annealing, after solidification of the deposited material, bear the reference 114.

[0090] The materials of the part or parts of the element or elements on which the material is intended to be deposited locally, i.e. the material of the connection pads 112 in the embodiment described in connection with FIGS. 5 to 10, and of the part or parts of the surface 101 of the support 102 on which the material is initially deposited are chosen such that during the annealing carried out, the contact angles 0Ci and 0C2 are such that 0C2 < Oci- These contact angles are visible in [fig.8]. With such contact angles, at the end of the annealing, the adhesion of the material of the portions 114 against the connection pads 112 is greater than that of the material of the portions 114 against the parts of the surface 101 of the support 102 due in particular to the larger contact surface obtained between the material of the portions 114 and the connection pads 112 compared to that between the material of the portions 114 and the surface 101 of the support 102.

[0091] By way of example, when the material to be deposited corresponds to a solder comprising a tin alloy (tin composition greater than 96%), the material of the portion(s) of the surface 101 of the support 102 on which the material is initially deposited may be chosen such that the adhesion between the material of the portions 114 and the portions of the surface 101 of the support 102 is less than approximately 3 kg / mm2 when this value is measured in a shear test, after the implementation of the annealing, according to the methodology described in the following publications: “Effect of inter-metallic compound thickness on shear strength of 25 qm diameter Cu-pillars” by Julien Bertheau et al., Intermetallics, vol. 51, August 2014, pages 37-47, and “Effects of bump size on deformation and fracture behavior of Sn3.0Ag0.5Cu / Cu solder joints during shear testing” by Yanhong Tian and al., Materials Science and Engineering: A, vol. 529, November 25, 2011, pages 468-478.

[0092] In the first embodiment described here, the portions 114 obtained correspond to metallizations of the fusible ball type. The diameter of these balls is by example between about 40 pm and 500 pm.

[0093] As shown in [fig.9], the electronic chips 110.1 and 110.2 are removed and separated from the support 102, advantageously collectively. Since the adhesion of the portions 114 against the connection pads 112 is greater than that of the portions 114 against the support 102, the portions 114 remain integral with the electronic chips 110.1 and 110.2 and are detached from the support 102.

[0094] The electronic chips 110.1 and 110.2 obtained and represented in [fig. 10] are ready to be transferred by “flip-chip” onto another support.

[0095] Advantageously, the parts of the support 102 on which the portions 108 are deposited comprise a raised marking. Thus, when the portions 114 are separated from the support 102, this marking is found (in an inverted pattern) on the surface of the material of the portions 114 which was in contact with the support 102. This marking can be used, for example, to produce logos or punches making it possible to identify or authenticate the element(s) 110.

[0096] The method described above advantageously applies for a localized deposition of the material 100 on one or more parts of one or more elements 110, corresponding for example to electronic chips, forming one or more hollows relative to the rest of the surface of the element(s) 100 at the level of which this or these parts are located. Given that the screen printing of the material to be deposited is not carried out directly on this irregular surface and that the material is “transferred” from the support 102 to the element(s) 110 via the implementation of the thermal and / or chemical treatment, this transfer takes place without difficulty on this irregular surface.

[0097] The localized deposition method described above can be implemented for applications other than the production of fusible ball type metallizations.

[0098] A method for localized deposition of at least one material on at least one element according to a second embodiment is described below in connection with figures 11 to 15. In this second embodiment, this deposition method is implemented to produce a sealing bead for a cover or a protective layer of a MEMS type device.

[0099] In Figures 11 and 12, as in the first embodiment, the material is deposited by screen printing on the support 102. In this second embodiment, the material 100 is deposited in the form of a portion 108 comprising for example a closed contour pattern and intended to form a sealing bead. The material 100 here corresponds to a fusible material for example similar to that previously described for the first embodiment. In addition, at least the part or parts of the surface 101 of the support 102 (possibly the entire surface 101 of the support 102) on which the material of the portion 108 is deposited comprises a so-called “non-wettable” material, corresponding for example to one of the examples of materials previously described for the first embodiment.

[0100] As in the first embodiment, optionally, an initial annealing may be carried out at a temperature greater than or equal to the melting temperature of the material 100 in order to remove the solvents present in the deposited material.

[0101] The screen 106 is removed and an element 110 corresponding to a protective layer or a cover is positioned against the portion 108 ([fig.13]). As for the electronic chips previously described in the first embodiment, the element 110 forming the cover or the protective layer comprises, on the face intended to receive the portion 108, a “wettable” material corresponding for example to one of the examples of materials previously mentioned in the first embodiment. The element 110 may therefore comprise a region 112 of material similar to that of the contact pads 112 and whose shape and dimensions correspond to those of the sealing bead intended to be produced.

[0102] Annealing is then carried out at a temperature greater than or equal to the melting temperature of the material of the portion 108. During this annealing, the material of the portion 108 passes into the liquid state, forming, as in the first embodiment, contact angles 0Ci and 0C2 such that 0C2 < Oci- The portion 114 obtained at the end of the annealing forms a sealing bead whose adhesion against the element 110 is greater than that against the support 102.

[0103] The element 110 is removed, which separates the portion 114 from the support 102 (figures 14 and 15). The cover 110 obtained is ready to be attached to close, for example, a cavity in which a MEMS device is arranged.

[0104] As in the first embodiment, the support 102 may include a raised marking, the pattern of which is then found on the surface of the material of the portion 114 which was in contact with the support 102.

[0105] According to a third embodiment, the method can be implemented to carry out a localized deposition of at least one organic material, corresponding for example to a compound comprising organic binders. In this case, the thermal and / or chemical treatment implemented corresponds to a step of drying and / or dehydration of the material. After having carried out the separation between the element(s) 110 (for example chips) on which the material has been deposited locally and the support 102, the elements 110 can be subjected to a subsequent thermal treatment making it possible to stabilize the locally deposited material and / or obtain the desired compound.

[0106] This third embodiment is advantageously implemented to functionalize a sensor, as described in the document “Optimization of the screen printing process for the production of thick-layer gas sensors”, doctoral thesis defended by Béatrice Rivière in Saint-Etienne on February 4, 2004, p34, part B. 1.1 “Principle of screen printing”.

[0107] According to a fourth embodiment, the method can be implemented to produce a localized deposition of at least one polymer material. Such polymer materials correspond for example to epoxy-based encapsulation or coating resins, called “Glob Top”, which are notably used to protect components, for example electronic components, from the external environment. In this case, the thermal and / or chemical treatment implemented corresponds to a polymerization obtained for example by implementing UV exposure through the support 102 which must be transparent to the radiation used for the polymerization. This polymerization makes it possible to stiffen and fix the chemical composition of the deposited material. The support 102 is then separated from the component(s) on which the polymerized resin has been deposited and which remains integral with the component(s).Alternatively, depending on the nature of the polymer to be deposited, the polymerization can also be carried out by a laser beam and / or exposure by infrared radiation.

[0108] According to a fifth embodiment, the method can be implemented to produce test devices intended for biological and / or chemical applications. For example, this method can be used to locally deposit, on elements corresponding to microfluidic chips, for example based on polydimethylsiloxane or PDMS, a material in the form of a gel or liquid, comprising for example proteins, to be analyzed. This material can be deposited on the support 102 by screen printing or by another method (pipette, syringe). Then, one or more microfluidic chips 110, comprising specific areas so that the material in the form of a gel or liquid adheres after a thermal and / or chemical treatment such as freezing and / or quenching, are positioned on the support 102, in the areas where the dispensing of the material has been carried out. The thermal and / or chemical treatment is then implemented, which makes it possible to adhere the material to the chips 110.The support 102 is then removed, and the chips 110 are removed. At the end of the process, to carry out the analyses of the material deposited on the chips 110, a heat treatment is for example implemented so that the material returns to its gel or liquid state, which makes it possible to produce a of the material, for example proteins contained in the liquid or gel. List of cited documents

[0109] Julien Bertheau et al., “Effect of intermetallic compound thickness on shear strength of 25 qm diameter Cu-pillars” by Julien Bertheau et al., Intermetallics, vol.51, August 2014, pages 37-47.

[0110] Yanhong Tian et al., “Effects of bump size on deformation and fracture behavior of Sn3.0Ag0.5Cu / Cu solder joints during shear testing”, Materials Science and En- gineering: A, vol. 529, November 25, 2011, pages 468-478.

[0111] Béatrice Rivière, doctoral thesis entitled “Optimization of the screen printing process for the production of thick-film gas sensors”, Saint-Etienne, February 4, 2004, p.34, part B. 1.1 “Principle of screen printing”.

Claims

Claims

1. Method for localized deposition of at least one material on at least one element (110), comprising the implementation of the following steps: - deposition of at least one portion (108) of the material on at least one part of a surface (101) of a support (102); - positioning at least a portion (112) of the element (110) against the portion (108) of the material; - heat treatment, corresponding to an annealing carried out at a temperature greater than or equal to the melting temperature of the material, of the portion (108) of material increasing, at the end of the heat treatment, the adhesion force of the material against the part (112) of the element (110), the materials of the part (112) of the element (110) and of the part of the surface (101) of the support (102) being chosen such that the adhesion of the material against the part (112) of the element (110) is, at the end of the heat treatment, greater than that of the material against the part of the surface (101) of the support (102); - separation of the element (110) and the support (102) at the interface between the material and the part of the surface (101) of the support (102), the material remaining integral with the part (112) of the element (110), and in which: - the part of the surface (101) of the support (102) is such that a contact angle between the material in the liquid state and the part of the surface (101) of the support (102) has a value 0Ci; - the part (112) of the element (110) is such that a contact angle between the material in the liquid state and the part (112) of the element (110) has a value 0C2 < 0"; - the material corresponds to a metallic brazing material comprising at least one of the following metals: tin, indium, silver, and - the part of the surface (101) of the support (102) comprises a metal oxide and the part (112) of the element (110) comprises at least one of the following metals: aluminum, copper, gold.

2. Method according to claim 1, in which the deposition of the portion (108) of the material on the part of the surface (101) of the support (102) is carried out by screen printing through a screen (106) comprising at least one opening determining, when positioning the screen (106) on the surface (101) of the support (102), the location of the part of the surface (101) of the support (102).

3. A method according to any preceding claim, wherein the portion (112) of the element (110) forms a recess relative to the remainder of a surface of the element (110) at which said portion (112) of the element (110) is located.

4. Method according to one of the preceding claims, in which the part of the surface (101) of the support (102) comprises a raised marking.

5. Method according to one of the preceding claims, further comprising, between the deposition of the portion (108) of the material on the part of the surface (101) of the support (102) and the positioning of the part (112) of the element (110) against the portion (108) of the material, the implementation of an initial annealing of the portion (108) of material.

6. Method according to one of the preceding claims, in which the material has an adhesion on the surface (101) of the support (102) of less than 3 kg / mm2.

7. Method according to one of the preceding claims, in which the element (110) corresponds to an electronic chip.

8. Method according to claim 7, in which: - several portions (108) of material are deposited on the support (102), - the parts (112) of the electronic chip (110) arranged against the portions (108) of material correspond to electrical contact pads, and - after the implementation of the heat treatment, the portions (114) of material form metallizations of the fusible ball type.

9. Method according to one of claims 1 to 6, in which: - the element (110) corresponds to a protective layer or a cover adapted to enclose or protect at least one MEMS type device in a cavity, and - after the implementation of the heat treatment, the portion (114) of material forms a sealing bead secured to the protective layer or to the cover.

10. Method according to one of the preceding claims, in which the method is implemented simultaneously for several elements (110.1, 110.2).

11. A method according to claim 10, wherein the elements (110.1, 110.2) have different thicknesses.

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