Electronic circuit including connection pads

Abstract

Electronic circuit comprising connecting pads. This description relates to an electronic circuit (10) comprising an electrically insulating layer (16) having a face (17), and electrically conductive connecting pads (20) arranged on the face (17), each connecting pad (20) comprising a trunk (22) projecting from the face (17) and extended by protrusions (28) each extending into the electrically insulating layer (16) from the trunk (22) to a depth greater than 0.1 µm, the protrusions (28) being completely surrounded by the electrically insulating layer (16) except on the side of the trunk (22). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Electronic circuit comprising connection pads. Technical field

[0001] The present invention relates to the field of electrical connection of an electronic circuit to an external element, and more particularly to the connection pads of the electronic circuit. Previous technique

[0002] In an electronic circuit, the connections between the electronic components of the circuit are made by an internal interconnection structure. To connect the electronic circuit to an external element, for example a printed circuit board or an integrated circuit chip, the interconnection structure is connected to connection pads, generally arranged protruding from one face of the electronic circuit. Thus, it is possible to make contact between the connection pads and conductive areas or connection traces located on this other external element, or with conductive wires connected to this other external element.

[0003] The connection pads arranged on the face of the electronic circuit are generally formed directly on the face of the electronic circuit or via an adhesive layer. During post-processing steps, the connection pads formed on the face of the electronic circuit are subjected to shear forces that can lead to their deterioration. For example, the manufacturing process of the electronic circuit may include steps in which the electronic circuit is temporarily attached to an adhesive strip, fixed for some steps on the side of the connection pads and / or for other steps on the side opposite the connection pads, this adhesive strip being subsequently removed. This step of removing the adhesive strip can lead to deterioration of the connection pads, in particular partial or total detachment of the connection pads from the electronic circuit.Furthermore, during the heating process of fixing the connection pads to another component, such as a printed circuit board, the different components to be fixed generally have different coefficients of thermal expansion. Therefore, expansion phenomena can occur during heating and then cooling, inducing mechanical stress on the connection pads relative to the electronic circuit or the component to which the connection pads are to be fixed. This heating process can also lead to deterioration of the connection pads. It would thus be advisable to reinforce the mechanical resistance of the connection pads to the electronic circuit. Summary of the invention

[0004] An embodiment overcomes all or part of the disadvantages of known electronic circuits comprising connection pads.

[0005] An object of an embodiment is that the pull-out resistance of the connecting pads is increased.

[0006] One embodiment provides an electronic circuit comprising an electrically insulating layer having one face, and electrically conductive connection pads arranged on the face, each connection pad comprising a trunk projecting from the face and extended by protrusions each embedded in the electrically insulating layer from the trunk to a depth greater than 0.1 µm, the protrusions being completely surrounded by the electrically insulating layer except on the side of the trunk. Advantageously, the presence of the protrusions connected to the trunk provides improved resistance to the connection pads arranged on the face by a kind of anchoring or force absorption parallel to the face, or by the formation of reliefs / topography under the trunk that serve as anchors and improve grip.Advantageously, the structure of the connecting studs allows for good resistance to pull-out of the connecting studs relative to the insulating layer.

[0007] According to one embodiment, the electronic circuit further comprises an interconnection structure including, for each connection pad, an electrically conductive track. The electronic circuit further comprises, for each connection pad, at least one electrically conductive via, flush with the face, passing through the electrically insulating layer and a portion of the interconnection structure, and connecting the connection pad to the electrically conductive track. Advantageously, the protrusions connected to the trunk do not participate in the electrical connection between each connection pad and the electrically conductive track.

[0008] According to one embodiment, each connecting pad comprises a bonding and / or priming layer between the trunk and the electrically insulating layer, and between the protrusions and the electrically insulating layer. The bonding and / or priming layer also covers the via, in direct physical contact with the via. Advantageously, the bonding and / or priming layer ensures good adhesion between the trunk and the face. This also advantageously provides continuity of the material composing the protrusions and the trunk.

[0009] According to one embodiment, at least one of the protuberances comprises at least a first straight portion extending along a first axis parallel to the face.

[0010] According to one embodiment, the first straight portion has a length along the first axis greater than 3 pm. A large anchoring surface is advantageously obtained in this way.

[0011] According to one embodiment, at least one of the protrusions comprises at least a second straight portion extending along a second axis parallel to the face, and connected to the first straight portion, the first axis being inclined with respect to the second axis. Advantageously, this provides resistance to pull-out in all directions of pull-out.

[0012] According to one embodiment, the trunks of the connecting studs and the protrusions are made of the same material. This allows for continuity of the material composing the protrusions and the trunk.

[0013] According to one embodiment, the trunk of each connection pad is made of copper.

[0014] According to an added embodiment, the electronic circuit comprises electronic components, at least one of which is electrically connected to the electrically conductive track.

[0015] One embodiment also provides a method for manufacturing an electronic circuit comprising an electrically insulating layer having one face, the method comprising the following steps: - formation of a plate comprising several copies of the electronic circuit, each electronic circuit comprising an electrically insulating layer having one face, and electrically conductive connection pads arranged on the face, each connection pad comprising a trunk projecting from the face and extended by protrusions each penetrating the electrically insulating layer from the trunk to a depth greater than 100 nm, the protrusions being completely surrounded by the electrically insulating layer except on the side of the trunk; and - separation of electronic circuits. The protrusions are advantageously made at the same stage as the trunk of the connection pad, which allows for continuity of the material composing the protrusions and the trunk.

[0016] According to one embodiment, the method further comprises in order a step of fixing the plate to a first adhesive strip on the side of the connection pads, the separation of the electronic circuits, and a step of peeling the connection pads from the adhesive strip.

[0017] According to one embodiment, step a) comprises the following steps, in order: c) formation of grooves each penetrating the electrically insulating layer; d) formation of a tack coat and / or primer coat covering the face and in particular each groove; and e) formation of electrically conductive connection pads on the tack and / or primer layer.

[0018] According to one embodiment, step a) further comprises the formation, for each connection pad, of at least one electrically conductive via, flush with the face, passing through the electrically insulating layer and part of the interconnection structure, the tack and / or primer layer covering, in step d) further the via, in direct physical contact with the via, and the via connecting, in step e), the connection pad to the electrically conductive track.

[0019] According to one embodiment, the formation of each connecting pad includes an electrochemical deposition step of the material composing the trunk and the protuberances of the connecting pad. Brief description of the drawings

[0020] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0021] [Fig.1] is a partial and schematic cross-sectional view of an electronic circuit comprising a connection pad;

[0022] [Fig. 2] is a cross-sectional view of [Fig. 1] along plane II-II; and

[0023] [Fig.3], [Fig.4], [Fig.5], [Fig.6], [Fig.7], [Fig.8], [Fig.9], [Fig. 10], [Fig.11], [Fig.12], [Fig.13], [Fig.14], [Fig.15], [Fig.16], [Fig.17], and [Fig.18] are partial and schematic cross-sectional views of structures obtained at successive stages of an embodiment of a manufacturing process for the electronic circuit of [Fig.1]. Description of the implementation methods

[0024] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0025] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0026] Unless otherwise specified, when referring to two interconnected elements, this means directly connected without any intervening elements other than conductors, and when referring to two coupled elements, this means that these two elements can be connected or linked via one or more other elements. Furthermore, the terms "insulator" and "conductor" are taken to mean "electrically insulating" and "electrically conductive," respectively.

[0027] In the following description, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative, such as the terms "above", "below", "superior", "inferior", etc., or to orienting qualifiers, such as the terms "horizontal", "vertical", etc., it refers, unless otherwise specified, to the orientation of the figures.

[0028] Unless otherwise specified, the expressions "approximately", "roughly", and "on the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0029] Fig. 1 is a partial, schematic cross-sectional view of an electronic circuit 10. Fig. 2 is a cross-sectional view of Fig. 1 along plane II-II.

[0030] The electronic circuit 10 comprises a substrate 11 having an upper face 12 and a lower face 13, opposite the upper face 12. The upper face 12 is covered with an interconnection structure 14. The interconnection structure 14 comprises a stack of insulating layers, conductive tracks 15 extending between the insulating layers, and through-conductive vias 40 extending through the insulating layers, a single conductive track 15 being shown in [Fig. 1]. The interconnection structure 14 is covered with an insulating layer 16. The insulating layer 16 comprises an upper face 17. The electronic circuit 10 may include electronic components in and / or on the substrate 11, for example, insulated-gate field-effect transistors more commonly known as MOSFETs (metal-oxide-semiconductor field-effect transistors).

[0031] The electronic circuit 10 comprises connection pads 20 made of a conductive material. Although only one connection pad 20 is shown in [Fig. 1], the electronic circuit 10 comprises as many connection pads 20 as there are electrical connections to be made. Depending on the intended application, from two to six connection pads 20, preferably four connection pads 20, may be present.

[0032] Each connection pad 20 comprises: - an adhesion layer 21, also called a primer layer, resting on the upper face 17 and in direct physical contact with the upper face 17; - a trunk 22 comprising a base 23, an end face 24 opposite the base 23, and a side wall 25 connecting the base 23 to the end face 24, the base 23 resting on the tack layer 21 and in direct physical contact with the tack layer 21; and - a finishing layer 26, when present, covering the end face 24 and in direct physical contact with the end face 24, and comprising a top face 27 opposite the end face 24.

[0033] When assembling the electronic circuit 10 to another element, a fixing material, not shown, for example solder paste, brazing paste, or sintering paste, is deposited on the upper face 27 of each connection pad 20.

[0034] The upper face 17 of the insulating layer 16 is substantially flat in the part covered by the connecting stud 20, with the exception of grooves 18. The layer The bonding layer 21 extends into each groove 18. The connecting block 20 includes protrusions 28 that extend from the shaft 22 and fill the grooves 18, the bonding layer 21 being interposed between the insulating layer 16 and each protrusion 28. In this embodiment, each protrusion 28 is shaped like a bar 28. According to one embodiment, each bar 28 includes at least one straight portion 29. By way of example, three grooves 18 and three bars 28 are shown in Figures 1 and 2. However, the number of bars 28 depends on the intended application. In particular, only one bar 28 may be present. According to one embodiment, the number of bars 28 is greater than 2, preferably greater than 3. In reality, the maximum number of bars 28 will depend on the design rules and the size of the protrusions. As an example, as illustrated in [Fig.2], each bar 28 comprises first and second straight portions 29.The first straight section 29 extends along a first axis A1 parallel to the face 17. The second straight section 29 extends along a second axis A2 parallel to the face 17, and can be connected to the first straight section 29, the first axis A1 being inclined with respect to the second axis A2, for example orthogonal to the second axis A2. As an alternative, shapes other than straight bars 28 can be considered. Thus, the protrusions 28 can correspond to studs, in particular with a circular, square, rectangular, or cross-section, or to annular elements.

[0035] The electronic circuit 10 further includes through-conductive vias 40, also called TSVs (Through Silicon Vias), which extend through the insulating layer 16 from the upper face 17 and through the insulating layers of the interconnect structure 14 to the conductive track 15. Each TSV 40 is flush with the upper face 17 and is in direct physical contact with the connection pad 20 at one end and in direct physical contact with the conductive track 15 at the opposite end. By way of example, three TSV 40s are visible in [Fig. 1] and nine TSV 40s are visible in [Fig. 2]. However, the number of TSV 40s depends on the intended application, in particular the maximum current density to be transmitted. In particular, only one TSV 40 may be present. According to one embodiment, the number of TSV 40 varies from 1 to 50, preferably between 1 and 10.When several TSV 40s are present, at least some TSV 40s are located near the grooves 18. Each TSV 40 is situated in an opening 41 extending through the insulating layer 16, from the upper face 17, and through the insulating layers of the interconnecting structure 14. In one embodiment, each TSV 40 comprises a tack layer 42, also called a starter layer, covering the walls of the opening 41 and a conductive core 43 filling the remainder of the opening 41. The interconnecting structure 14 may include conductive layers. The layer. The tack layer 42 can then be insulating. Alternatively, the tack layer 42 is conductive and an insulating layer is provided between the opening 41 and the tack layer 42 to electrically isolate the TSV 40 from the interconnection structure 14. In one embodiment, the tack layer 21 covers the flush end of the TSV 40 and is in direct physical contact with the TSV 40.

[0036] According to one embodiment, the total thickness of the connecting portion 20, measured from the flat portion of the upper face 17, is between 1 µm and 50 µm, for example, approximately 5 µm. In a top view, the end face 24 of each connecting portion 20 may have a circular, oval, square, rectangular, etc. shape. According to one embodiment, the diameter of the circle inscribed in the end face 24 is between 5 µm and 100 µm.

[0037] According to one embodiment, the depth of each groove 18, measured from the flat portion of the upper face 17, is between 0.1 pm and 2 pm, for example, approximately 0.5 pm. According to one embodiment, the length of the straight portion 29 is between 3 pm and 80 pm. According to one embodiment, the width of each groove 18 is between 0.5 pm and 5 pm, for example, approximately 2 pm. According to one embodiment, the minimum gap between two adjacent grooves 18 is between 0.5 pm and 10 pm, for example, approximately 2 pm.

[0038] The adhesion layer 21 improves the adhesion between the core 22 and the insulating layer 16. According to the method for forming the core 22, the adhesion layer 21 also allows the growth of the material composing the core 22. Similarly, the adhesion layer 42 improves the adhesion between the conductive core 43 and the insulating layer 16 and the insulating layers of the interconnecting structure 14. According to the method for forming the core 22, the adhesion layer 42 also allows the growth of the material composing the conductive core 43. In one embodiment, the adhesion layer 21 and / or the adhesion layer 42 comprises a stack of an adhesion sublayer, one or more barrier layers, and / or one or more germination layers. In one embodiment, the adhesion sublayer is made of titanium (Ti) or tantalum nitride (TaN).In one embodiment, the barrier layer is made of titanium (Ti), tantalum (Ta), titanium nitride (TiN), tantalum nitride (TaN), or a mixture of these compounds. For example, when the bonding sublayer is titanium, the barrier layer may be titanium nitride, and when the bonding sublayer is tantalum nitride, the barrier layer may be titanium. In one embodiment, the thickness of the bonding sublayer and / or the barrier layer is between 10 nm and 200 nm. In one embodiment, the germination layer is made of the same material as the stem 22 of the connecting pad 20 or the conductive core 43 of the TSV 40. In one embodiment, the germination layer is copper. In one embodiment, . The thickness of the germination layer is between 10 nm and 600 nm. According to one embodiment, the total thickness of the adhesion layer 21 is between 20 nm and 800 nm, and is for example equal to about 50 nm.

[0039] According to one embodiment, the trunk 22 and / or the core 43 is made of metal, for example copper, nickel, silver, gold, or an alloy of these metals. Preferably, the trunk 22 and / or the conducting core 43 is made of copper.

[0040] According to one embodiment, the length of each TSV 40, measured from the flat portion of the upper face 17 to the conductive track 15, is between 0.5 pm and 20 pm, for example, approximately 5 pm. In a top view, each TSV 40 may have a circular, oval, square, rectangular, etc. shape. According to one embodiment, the diameter of the circle inscribed in the cross-section of the TSV 40 is between 0.5 pm and 100 pm, in particular between 0.5 pm and 15 pm.

[0041] In one embodiment, the topcoat 26 is made of a conductive material that improves the adhesion of the fixing material used to attach the connecting pad 20 to another element. The topcoat 26 is, for example, made of metal, in particular gold, and optionally includes one or more bonding layers and / or one or more barrier layers, comprising, for example, platinum (Pt), palladium (Pd), nickel (Ni), titanium (Ti), chromium (Cr), and / or tantalum (Ta), between the trunk material 22 and the fixing material. The topcoat 26 also prevents oxidation of the trunk 22 if the electronic circuit 10 is not stored and / or the assembly process is not carried out under a neutral or reducing atmosphere. In one embodiment, the thickness of the topcoat 26 is between 20 nm and 1 µm, and is, for example, approximately 50 nm.

[0042] A block, not shown, of a fixing material, for example a solder bead, is intended to be deposited on the upper face 27 of the finishing layer 26 of each connection pad 20 for assembling the electronic circuit 10 to another element. Depending on the assembly process used, the blocks may be made of solder paste, solder paste, or sintering paste. In one embodiment, the paste includes, in particular, an active filler comprising particles of a metallic material, for example tin, silver, copper, or an alloy of at least two of these elements.

[0043] The substrate 11 is, for example, a substrate made of silicon, silicon carbide (SiC), III-V compounds, in particular gallium nitride (GaN), or diamond. The substrate 11 may have a monolayer or multilayer structure, for example, a silicon-on-insulator (SOI) structure, and comprise a semiconductor layer on an insulating support, for example, a glass support. According to one embodiment, the thickness of the substrate 11 of the electronic circuit 10 at the The end of the manufacturing process is between 100 pm and 900 pm, and is for example equal to 200 pm.

[0044] The insulating layer 16 is, for example, a layer of silicon oxide, silicon nitride, or silicon oxynitride. In one embodiment, the thickness of the insulating layer 16 is between 100 nm and 5 pm, in particular between 0.5 pm and 5 pm, and is, for example, equal to 2.5 pm. The conductive track 15 comprises, for example, a stack of metallic layers. In one embodiment, the metallic track 15 can be formed by depositing full-plate metallic layers and etching the metallic layers to form the metallic track 15. In one embodiment, the thickness of the metallic track 15 is between 200 nm and 2 pm, and is, for example, equal to 500 nm. The metallic layers of the metallic track 15 are for example made of materials selected from aluminium, an aluminium alloy, copper, a copper alloy, titanium, a titanium alloy, titanium nitride, platinum, and a platinum alloy.As an alternative, the insulating layer 16 is part of the interconnection structure 14 and corresponds to the insulating layer of the interconnection structure 14 furthest from the substrate 11.

[0045] Advantageously, the structure of the connecting studs 20 provides good pull-out resistance of the connecting studs 20 relative to the insulating layer 16. This is due, at least in part, to the continuity of the grains of the material composing the trunk 22 from the protrusions 28 and the rest of the trunk 22 outside the protrusions 28. According to one embodiment, the shear strength of each connecting stud 20 in the presence of the protrusions 28 is greater than the shear strength of the connecting stud 20 in the absence of the protrusions 28. The shear strength test includes applying a point to the connecting stud 20, which pushes the connecting stud 20 until it is pulled out.

[0046] Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13, Fig. 14, Fig. 15, Fig. 16, Fig. 17, and Fig. 18 are partial and schematic cross-sectional views of structures obtained at successive stages of an embodiment of a manufacturing process for the electronic circuit 10 of Fig. 1.

[0047] The steps shown in figures 3 to 11 illustrate an embodiment of a method for making a plate 50 comprising several electronic circuits 10.

[0048] Figure 3 represents the structure obtained after the formation of a plate 50 comprising several copies of the electronic circuit to be produced before the formation of the TSVs 40 and the connection pads 20, only one copy of the electronic circuit being partially shown in Figures 3 to 11. In particular, the plate 50 comprises the substrate 11, the interconnection structure 14 and the insulating layer 16. several copies. According to one embodiment, the upper face 17 of the insulating layer 16 is substantially flat.

[0049] Figure 4 shows the structure obtained after the formation of the aperture 41 for each TSV 40. For each instance of the electronic circuit, each aperture 41 opens onto the conductive track 15 at one end and onto the upper surface 17 at the opposite end. Three apertures 41 are shown by way of example in Figure 4. According to one embodiment, the formation of the apertures 41 may include photolithography steps.

[0050] Figure 5 shows the structure obtained after the deposition, over the entire structure, of the tack coat 42 and a layer 51 of the material composing the conductive core 43 of each TSV 40, such that the layer 51 completely fills the openings 4L. In one embodiment, the tack coat 42 is deposited by physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD). In one embodiment, the layer 51 is deposited by PVD, CVD, ALD, or preferably by electrochemical deposition (ECD).Electrochemical deposition, also called electroplating or electrodeposition, uses an electrolysis reaction to apply a metallic coating to the surface of an object using a direct electric current. The metal is initially in the form of cations in solution in a solvent (usually water). Electrochemical deposition offers the advantage of rapidly depositing a metallic layer with a precisely controlled, uniform thickness.

[0051] Fig. 6 represents the structure obtained after a planarization step, for example by CMP (Chemical Mechanical Planarization) to remove the parts of the layer 51 and the tack layer 42 located outside the openings 41 and expose the upper face 17 of the insulating layer 16. The TSV 40 are thus completely defined.

[0052] Figure 7 shows the structure obtained after the formation of the grooves 18 in the upper face 17. According to one embodiment, the formation of the grooves 18 may include photolithography steps. Four grooves 18 are shown by way of example in Figure 7.

[0053] Figure 8 shows the structure obtained after the formation of the bonding layer 21 on the upper surface 17. In one embodiment, the bonding layer 21 is formed by PVD or CVD. In one embodiment, the formation of the bonding layer 21 is preceded by a cleaning step of the upper surface 17, for example, an ion etching step of the upper surface 17. In one embodiment, In implementation, the ion stripping step includes ion bombardment of the upper face 17, for example by argon ions.

[0054] Figure 9 shows the structure obtained after a step of depositing a layer of photosensitive resin 52 onto the tack layer 21 and a step of forming openings 53 in the resin layer 52 at the desired locations of the connecting pads 20, a single opening 53 being shown as an example in Figure 9. According to one embodiment, the thickness of the resin layer 52 is greater than or equal to 1 µm. The formation of the openings 53 may include photolithography steps.

[0055] Figure 10 shows the structure obtained after a forming step, in each opening 53, of the trunk 22 of the connecting stud 20, and then of the finishing layer 26. According to one embodiment, the trunks 22 and the finishing layers 26 are formed by electroplating. The tack coat 21 advantageously ensures good adhesion between the trunk 22 and the upper surface 17. In particular, a continuity of the grains of the material composing the trunk 22 is observed from the protrusions 28 and the rest of the trunk 22 outside the protrusions 28.

[0056] Figure 11 shows the structure obtained after a step of removing the resin layer 52 and a step of etching parts of the tack layer 21 around the connecting pads 20 to expose the upper surface 17 around the connecting pads 20. The connecting pads 20 are then completely defined. The stems 22 of the connecting pads 20 can act as etching masks during the etching of the tack layer 21. Etching of a part of the tack layer 21 located under the stem 22 from the sides of the connecting pad 20 can occur.

[0057] According to another embodiment, in the step described above in relation to [Fig. 10], a stack of a layer of the material composing the trunks 22 and the finishing layer 26 is deposited over the entire structure, i.e., over the resin layer 52 and over the bonding layer 21 in the openings 53. In one embodiment, the layer of material composing the trunk 22 and / or the finishing layer 26 are formed by physical vapor deposition. In the step described above in relation to [Fig. 11], during the removal of the resin layer 52, the portions of the layer of material composing the trunks 22 and the finishing layer 26 that covered the resin layer 52 are removed, leaving only the portions of the layer of material composing the trunks 22 and the finishing layer 26 present in the openings 53.

[0058] The steps shown in figures 12 to 18 illustrate one embodiment of a method for separating electronic circuits 10.

[0059] Figure 12 represents the structure obtained after a step of fixing the plate 50 to a handling tool, for example an adhesive strip 54, on the side of the face 13 of the plate 50 opposite the connection pads 20. Two electronic circuits 10 to be separated and two connection pads 20 per electronic circuit 10 are shown as an example in [Fig. 12]. Furthermore, the internal structure of the electronic circuits 10, in particular the connection pads 20, is not illustrated in Figures 12 to 18.

[0060] Figure 13 shows the structure obtained after a groove-forming step 55, creating pre-cuts, in the plate 50 between the electronic circuits 10 to be separated, a single groove 55 being shown in Figure 13. The grooves 55 can be made by plasma etching, sawing, or laser cutting. The depth of each groove 55, measured from the face 17, is such that the remaining thickness of the plate 50 is greater than 100 nm.

[0061] Fig. 14 represents the structure obtained after a step of fixing the plate 50 to another handling tool, for example another adhesive strip 56, on the side of the connecting studs 20, the plate 50 being otherwise still fixed to the adhesive strip 54.

[0062] Fig. 15 represents the structure obtained after a step of removing the adhesive strip 54 to expose the face 13 of the plate 50. The removal of the adhesive strip 54 can be carried out by tearing off the adhesive strip 54.

[0063] Figure 16 shows the structure obtained after a thinning step of the plate 50 on the side of face 13 until the pre-cuts 55 are reached. The thinning step can be carried out by grinding or by CMP. The electronic circuits 10 are then separated from each other. All the electronic circuits 10 are still attached to the adhesive strip 56.

[0064] Fig. 17 represents the structure obtained after a step of fixing the electronic circuits 10, now separated from each other but still fixed to the adhesive strip 56, to another handling tool, for example another adhesive strip 57, on the side of the face 13 of each electronic circuit 10 opposite the connection pads 20. All the electronic circuits 10 are then fixed to the adhesive strip 56 and to the adhesive strip 57.

[0065] Figure 18 shows the structure obtained after removing the adhesive strip 56 to release the connecting studs 20. The adhesive strip 56 can be removed by peeling it off. Advantageously, the structure of the connecting studs 20 provides good pull-out resistance during the removal of the adhesive strip 56. Such a structure, having a trunk 22 and protrusions 28 (not visible in Figure 18), advantageously improves the mechanical pull-out resistance of the connecting studs 20 by means of a kind of anchoring, compared to a structure without a trunk and protrusions. The anchoring provided by the protrusions 28 does not play a role. in the electrical connection, and is arranged near the 40 elements used for the electrical connection.

[0066] According to one embodiment, the method may include further steps of forming a block of solder, brazing, or sintering paste on each connection pad 20, and fixing the electronic circuits 10 onto another element.

[0067] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0068] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Electronic circuit (10) comprising an electrically insulating layer (16) having a face (17), and electrically conductive connecting pads (20) arranged on the face (17), each connecting pad (20) comprising a trunk (22) projecting from the face (17) and extended by protrusions (28) each extending into the electrically insulating layer (16) from the trunk (22) to a depth greater than 0.1 pm, the protrusions (28) being completely surrounded by the electrically insulating layer (16) except on the side of the trunk (22).

2. Electronic circuit (10) according to claim 1, further comprising an interconnection structure (14) comprising, for each connection pad (20), an electrically conductive track (15), the electronic circuit (10) further comprising, for each connection pad (20), at least one electrically conductive via (40), flush with the face (17), passing through the electrically insulating layer (16) and a portion of the interconnection structure (14), and connecting the connection pad (20) to the electrically conductive track (15).

3. Electronic circuit (10) according to claim 2, wherein each connection pad (20) comprises an anchoring and / or priming layer (21) between the trunk (22) and the electrically insulating layer (16) and between the protrusions (28) and the electrically insulating layer (16), the anchoring and / or priming layer (21) further covering the via (40), in direct physical contact with the via (40).

4. Electronic circuit (10) according to any one of claims 1 to 3, wherein at least one of the protrusions (28) comprises at least a first straight portion (29) extending along a first axis (Al) parallel to the face (17).

5. Electronic circuit (10) according to claim 4, wherein the first straight portion (29) has a length along the first axis greater than 3 pm.

6. Electronic circuit (10) according to claim 4 or 5, wherein at least one of the protrusions (28) comprises at least a second straight portion (29) extending along a second axis (A2) parallel to the face (17), and connected to the first portion rectilinear (29), the first axis (Al) being inclined with respect to the second axis (A2).

7. Electronic circuit (10) according to any one of claims 1 to 6, wherein the trunks (22) of the connecting pads (20) and the protrusions (28) are in the same material.

8. Electronic circuit (10) according to any one of claims 1 to 7, wherein the trunk (22) of each connecting pad (20) is made of copper.

9. Electronic circuit (10) according to any one of claims 1 to 8, comprising electronic components of which at least one is electrically connected to the electrically conductive track (15).

10. A method for manufacturing an electronic circuit (10) comprising an electrically insulating layer (16) having a face (17), the method comprising the following steps: a) forming a plate (50) comprising several copies of the electronic circuit (10), each electronic circuit (10) comprising an electrically insulating layer (16) having a face (17), and electrically conductive connecting pads (20) arranged on the face (17), each connecting pad (20) comprising a trunk (22) projecting from the face (17) and extended by protrusions (28) each extending into the electrically insulating layer (16) from the trunk (22) to a depth greater than 100 nm, the protrusions (28) being completely surrounded by the electrically insulating layer except on the side of the trunk (22); and b) separating the electronic circuits (10).

11. A method according to claim 10, further comprising in order a step of fixing the plate (50) to a first adhesive strip (56) on the side of the connection pads (20), the separation of the electronic circuits (10), and a step of peeling the connection pads (20) from the adhesive strip (56).

12. A method according to claim 10 or 11, wherein step a) comprises the following steps, in order: c) formation of grooves (18) each embedded in the electrically insulating layer (16); d) formation of a tack and / or primer layer (21) covering the face (17) and in particular each groove (18); and e) formation of electrically conductive connecting pads (20) on the tack and / or primer layer (21).

13. A method according to claim 12, wherein step a) further comprises the formation, for each connecting pad (20), of at least one electrically conductive via (40), flush with the face (17), passing through the electrically insulating layer (16) and a portion of the interconnecting structure (14), the tack and / or primer layer (21) covering, in step d) further the via (40), in direct physical contact with the via (40), and the via (40) connecting, in step e), the connecting pad (20) to the electrically conductive track (15).

14. A method according to any one of claims 10 to 13, wherein the formation of each connecting pad (20) comprises an electrochemical deposition step of the material composing the trunk (22) and the protrusions (28) of the connecting pad (20).

Images