Method for manufacturing electronic components with wettable flanks

Abstract

Method for manufacturing electronic components with wettable sides. Method for manufacturing electronic components with wettable sides from a substrate (301) covered by connection pads (107) and in which chips (103) are formed, the method comprising the following steps: a) soldering connection pads onto the connection pads (107), b) coating the connection pads with a layer of insulating resin (121), c) thinning the layer of insulating resin (121) until the connection pads are reached, d) forming cavities by removing a portion of the connection pads and a portion of the insulating resin layer (121), so as to make a portion of the component sides accessible, e) depositing a layer of conductive material (122) on the component sides and on the connection pads, f) separating the chips (103). Figure for the abstract: Fig. 2E

Description

Title of the invention: Method for manufacturing electronic components with wettable flanks. Technical field

[0001] This description relates to the manufacture of electronic components. More particularly, it relates to the manufacture of so-called surface-mount components, that is, components having, on at least one side, one or more metallized connection pads intended to be soldered to corresponding connection pads of an external device, for example, a printed circuit board or another component. Prior art

[0002] In certain applications, there is a need for surface-mount components in which metallizations for connections intended to be soldered to an external device extend to the component flanks. These are referred to as wettable flank components. When the component is mounted in its environment (for example, on a printed circuit board), the metallizations for connections (also called electrical contacts) are soldered or brazed to corresponding metallic tracks or elements on the printed circuit board side. Some of the solder material then extends up the component flanks, allowing for visual inspection of the connection quality.

[0003] This need exists, for example, in the automotive or medical fields and, more generally, in fields where it is necessary to guarantee the reliability of electrical connections once the circuits have been installed in their environment. Summary of the invention

[0004] There is a need to improve at least in part certain aspects of known processes for manufacturing electronic components with wettable flanks.

[0005] This objective is achieved by a method for manufacturing electronic components with wettable flanks from a substrate covered by connection pads and in which chips are formed, the method comprising the following steps: a) solder connection pads onto the chip connection pads, b) coat the connection pads with a layer of insulating resin, c) thin the insulating resin layer until it reaches the connection pads, d) create cavities by removing part of the connection pads and part of the insulating resin layer, so as to make part of the sides of the components accessible, e) deposit a layer of conductive material on the sides of the components and on the connection pads, f) separate the chips at the level of the cavities.

[0006] According to one embodiment, the connection pads comprise an electrically conductive core, covered by a layer of brazable material.

[0007] According to one embodiment, the brazable material is Sn or a tin alloy such as SnAg or SnAgCu.

[0008] According to one embodiment the electrically conductive core is made of copper.

[0009] According to one embodiment, the conductive material and the brazeable material are identical.

[0010] According to one embodiment, step e) is carried out by printing.

[0011] This goal is also achieved by an electronic component with wettable sides comprising a chip having connection pages protected by a housing comprising a first main face, sides and a second main face, a layer of conductive material covering a part of the sides and extending over the first main face, the layer of conductive material being electrically connected to the electrical connection areas of the chip by means of connection pads brazed onto the connection areas.

[0012] According to one embodiment, the connection pads comprise an electrically conductive core covered at least partially by a layer of material brazed onto the connection pads.

[0013] According to one embodiment, the conductive material layer is Sn or a tin alloy, such as SnAg or SnAgCu.

[0014] According to one embodiment, a layer of insulating resin covers the first main face of the chip between the connection pads. Brief description of the drawings

[0015] 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:

[0016] [Fig.1] represents, schematically and in cross-section, an electronic component with wettable sides according to a particular embodiment;

[0017] [Fig.2A], [Fig.2B], [Fig.2C], [Fig.2D], [Fig.2E] and [Fig.2F] represent cross-sectional views illustrating steps in a manufacturing process for a wettable-sided electronic component according to a particular embodiment;

[0018] [Fig.3] represents a wettable sidewall electronic component, top view, obtained by the process of figures 2A to 2F;

[0019] [Fig.4A] and [Fig.4B] represent cross-sectional views illustrating steps in a manufacturing process for a wettable flank electronic component according to another particular embodiment;

[0020] [Fig.5] represents a wettable sidewall electronic component, top view, obtained by the process of figures 4A and 4B;

[0021] [Fig.6] is a scanning electron microscope (SEM) image representing a spherical connection point with a core-shell structure according to a particular embodiment. Description of the implementation methods

[0022] 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.

[0023] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0024] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0025] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or to a ... in a normal position of use.

[0026] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0027] Electronic components find applications in many industrial fields, and in particular, in the automotive or medical fields.

[0028] Fig. 1 illustrates, by a partial and schematic cross-sectional view, an electronic component 100.

[0029] The electronic component 100 consists of an electronic chip 103 and a package 109. By way of example, the electronic chip 103 is formed from a semiconductor substrate, for example silicon. It could also be SiC. Alternatively, the substrate could be glass or sapphire.

[0030] The chip comprises a front face 105 (also called the first face or front face), a rear face 104 (also called the second face or rear face), and sides 106 (also called lateral faces). The lower face 104 is opposite the upper face 105.

[0031] One or more connection areas 107 (also called electrical contacts) are formed on the upper face 105 of the electronic chip 103 and allow it to be connected to other elements (chips or electronic devices).

[0032] The electrical connection pads 107 are also called "UBM" (for the English term "Under Bump Metallization"). The electrical connection pads 107 are made of a conductive material specifically adapted to receive the connection pads 117, and exhibiting, in particular, good adhesion to the pads 177. The electrical connection pads 107 comprise at least one of the following elements: gold, titanium, nickel, copper, silver, tin, or tungsten. Preferably, they comprise gold or copper. The connection pads 107 may be coated with a metallic layer ("plating").

[0033] The electrical connection pads 107 are, for example, at a distance of 10 to 50 pm, or even 10 to 30 pm, from the side wall of the chip. The distance will depend on the size of the connection pads 117. The electrical connection pads 107 can be positioned on the top face 105 of the chip 103 or be flush with the top face (i.e., level with the top face 105 of the chip 103).

[0034] The chip 103 may comprise one or more discrete components. The discrete component(s) may be chosen, for example, from transistors, diodes, thyristors, triacs, filters, etc. The chip 103 may comprise one or more electronic circuits. The chip 103 allows the implementation of various electronic functions.

[0035] Component 100 is a so-called integrated component.

[0036] The chip 103 is protected by the housing 109. More particularly, the housing 109 covers at least the upper face 105. Preferably, as shown in [Fig.1], it can also cover the sides 106 of the chip 103 and / or the lower face 105 of the chip 103.

[0037] The housing 109 is made of an electrically insulating material.

[0038] To enable the connection of component 100 to other electronic components and / or circuits, the housing 109 further includes connection pads 117 (also called housing contacts or contact points). The connection pads 117 are positioned on the upper surface 105 of the chip 103. Each connection pad 117 is connected to an electrical connection range 107 of the chip 103.

[0039] The connecting pads 117 can be metallic elements.

[0040] The connecting pads 117 are, for example, metal balls. They may be balls made of copper, nickel or any other non-fusible material.

[0041] The connection pads 117 can be elements comprising an electrically conductive core 118 covered by a layer 116 (also called shell) of brazable material.

[0042] Preferably, the electrically conductive core 118 is made of copper.

[0043] Preferably, the brazable material is tin or one of its alloys, such as SnAgCu or SnAg. Layer 116 acts as an oxidation barrier layer.

[0044] The electrical connection areas 107 of the chip 103 and the connection pads 117 are positioned in openings in a layer of insulating resin 121 covering the chip 103.

[0045] Component 100 is a component with a wettable side, that is to say that at least part of its sides is covered by a layer of a wettable and / or weldable material, that is to say a material on which it is possible to braze or to carry out another method of mechanical fixing (conductive glue, sintering for example).

[0046] The layer 122 of wettable material covers part of the sides 119 of the component 100 and extends over the first main face 115 of the component 100. This layer forms a continuous layer of which a first part 122A covers part of the first face 115 of the component 100 and of which a second part 122B covers part of the sides 119 of the component 100.

[0047] The wettable material is in direct contact with the connecting studs 117. Direct contact means that there is no element between the connecting studs 117 and the wettable material. It is in direct contact at the sides 119 and at the first main face 115.

[0048] The wettable material is preferably a brazable material, such as Sn, SnAg or SnAgCu, or another material with a higher melting point.

[0049] We will now describe in more detail the manufacturing process of such a component 100 with reference to figures 2A to 2F.

[0050] The process is carried out from a substrate 301 covered by connection areas 107 and in which chips 103 are formed.

[0051] The process comprises the following steps: a) brazing connection pads 117 onto connection pads 107, the connection pads 117 preferably comprising an electrically conductive core 118, covered by a coating layer 116 of a brazable material ([Fig.2A]), b) depositing a layer of insulating resin 121 onto the substrate 301, the insulating resin layer 121 encasing the connection pads 117 and the connection pads 107 ([Fig.2B]), c) thin the insulating resin layer 121 until reaching the connection pads 117, and where applicable, the core 118 of the connection pads 117 ([Fig.2C]), d) form cavities 311 between the chips 103 by locally removing part of the connection pads 117 and part of the insulating resin layer 121, so as to make accessible part of the sides 119 of the components 100 ([Fig.2D]), e) deposit a layer of conductive material 122 on the sides 119 of the components 100 and on the connection pads ([Fig.2E]), f) separate the chips 103 by cutting in the cavities 311 ([Fig.2F]), thereby obtaining components 100 with wettable sides.

[0052] In step a), the fabrication of the discrete component(s) and / or integrated circuit(s) forming the components 100 is completed. The components 100 are formed from a single substrate 301 and have not yet been individualized. The chips 103 are delimited by a dotted line in the substrate 301. The substrate 301 comprises a first face 305 (top face or front face) and a second face 303 (or back face).

[0053] The substrate 301 is, for example, a semiconductor substrate, for example made of silicon, or of SiC.

[0054] The substrate 301 has, for example, a thickness between 300 and 900 pm, for example a thickness of about 725 pm.

[0055] In addition, electrical connection areas 107, described in relation to [Fig.1], were formed on an upper face 305 of the substrate 301 ([Fig.2A]).

[0056] During step a), the connection pads 117 are brazed onto the connection pads 107.

[0057] As shown in Figures 2A to 2F and 3, the connecting pads 117 can be balls (i.e., spherical in shape). It is evident that the drawings are schematic representations and that, in reality, the connecting pads 117 and the connecting areas 107 have a contact surface larger than a simple point of contact when welded to each other.

[0058] Alternatively, as shown in Figures 4A, 4B and 5, the connecting blocks can be columns. These can be pillars with a square, circular or rectangular cross-section.

[0059] Preferably, the connecting pads 117 comprise a core 116 of a first material and a shell (or coating) 118 of a second material.

[0060] The shell 118 preferably covers the core continuously. The shell has, for example, a thickness of between 10 and 20 µm.

[0061] The electrically conductive core 116 is preferably made of copper.

[0062] The shell 118 or coating is made of a material that can be brazed onto the connection surfaces. In particular, it is tin or a tin alloy, such as SnAg or SnAgCu.

[0063] Fig. 6 represents, by way of illustration and not limitation, a SEM image of a spherical connection pad 117 having a copper core and a shell made of a tin-based alloy.

[0064] In an unshown variant, the connecting pads are metal balls. The balls are not covered by a shell. They may be copper balls, in nickel.

[0065] During step b), a layer of insulating resin 121 is deposited on the substrate 301.

[0066] More specifically, the insulating resin layer 121 is deposited on the first face 305 of the substrate 301 and on the pads 117. Thus, the pads 117 are arranged within the resin. The insulating resin layer 121 forms a first part of the component housing 100. For example, the layer 121 can be deposited by screen printing, compression molding, or injection molding. This first part of the housing therefore protects the upper face of the components 100.

[0067] The resin is an electrically insulating resin. More specifically, the resin comprises at least one base material to which electrically insulating particles are added. The base material is selected from the group including: epoxy resins, phenolic resins, and acrylic resins. Preferably, it is an epoxy resin. The particles are, for example, oxide particles, and in particular alumina or silica particles.

[0068] Polymerization is, for example, carried out under ultraviolet (UV) radiation or by thermal activation. Annealing may be carried out before step c).

[0069] During step c), a thinning step is carried out from the front face in order to remove the part of the insulating resin 121 covering the connection pads 117 and the upper part of the connection pads 117 until reaching the core 116 of the connection pads 117.

[0070] The thinning step on the front face can be carried out by polishing ('grinding'). Mechanical polishing is preferably chosen.

[0071] During step d), the cavities 311 are formed between the chips 103 in order to remove part of the resin layer 121 and part of the connecting pads 117. The core 116 of the connecting pads 117 is thus also accessible laterally.

[0072] The cavities 311 obtained extend from the front face to a depth corresponding at least to the height of the conductive material layer 122 covering the sides of the components 100 described below. The height of the cavity 311 is less than the thickness of the insulating resin layer 121 in order to isolate the wettable sides from the substrate 301.

[0073] Step d) is carried out using a cutting device. The cutting device is, for example, a mechanical cutting tool such as a saw, or a laser engraving tool. In a preferred embodiment, the cutting device is a laser. Furthermore, when the cutting device is a laser, the cutting technique used may be a laser direct structuring (LDS) technique.

[0074] During step e), a layer 122 of conductive material is deposited so as to cover at least part of the flanks 119 of the components 100 and the pads of connection 117.

[0075] The 122 layer of conductive material can be deposited by a printing method, an additive deposition method, or by immersion in a bath. For example, it is possible to deposit an anti-oxidant material onto metallic surfaces. The deposition is selective.

[0076] The 122 layer of conductive material is advantageously deposited locally by a dispensing technique, and preferably by screen printing, in particular through a mask.

[0077] Alternatively, it can be deposited as a full plate.

[0078] At the end of step e), the cavities 311 are filled with the conductive material and the core 116 of the connecting pads 117 is covered by the layer 122 of conductive material. The core 116 is thus completely covered by a protective layer formed partly by the shell 118 and partly by the layer 122. The core is thus protected from the external environment, and in particular from oxidation, which is especially advantageous in the case of a copper core 116.

[0079] During step f), the components 100 are individualized by making a cut at the level of the cavities 311. The components 100 are thus separated from each other.

[0080] It is also possible to carry out the steps in the following order: a), b), c), d), f), and e). After the formation of the cavities 311, it is possible to proceed with a complete cutting (step f)) and then to deposit the layer of conductive material 122 (step e)). The deposited layer is advantageously an organic layer. It also serves as a protective layer against oxidation.

[0081] The process may also include a thinning step on the rear face. For this, the structure is turned over and fixed by its front face, i.e., face 305, onto a support. The support is, for example, a strip of adhesive tape. The structure is then thinned by its rear face 303 so that the substrate 301 has its final thickness.

[0082] The method may advantageously include a step in which an additional insulating layer is deposited on the rear face 303 of the structure to form the rear face of the housing 111 and / or on the side faces 106 of the chip 103.

[0083] The additional insulating layer is a layer made of an electrically insulating material, for example a resin, for example a resin of the same type as the resin of layer 121. According to another example, the materials of the layers are different.

[0084] At the end of the process, the components 100 obtained are surface-mount devices (or SMDs for "surface mounting device") of the "flip-chip" type, that is to say, they can be fixed to an external device, for example, a printed circuit board or another component, by their upper face, that is to say the face on which are the contacts 117 of the housing 109 arranged.

[0085] For this purpose, a soldering material is positioned between the component 100 and the external device. During soldering, the soldering material rises along the sides 119 of the components 100, which makes it possible to verify that the soldering has been carried out correctly.

[0086] Such components 100 are particularly interesting for ensuring the reliability of electrical connections, once the circuits have been mounted in their environment.

[0087] 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.

[0088] 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. A method for manufacturing wettable-sided electronic components (100) from a substrate (301) covered by connection pads (107) and in which chips (103) are formed, the method comprising the following steps: a) soldering connection pads (117) onto the connection pads (107) of the chips (103), b) coating the connection pads (117) with a layer of insulating resin (121), the insulating resin layer (121) forming a first part of a housing protecting the chip (103), c) thinning the insulating resin layer (121) until the connection pads (117) are reached, d) forming cavities (311) by removing a portion of the connection pads (117) and a portion of the insulating resin layer (121), so as to make a portion of the sides (119) of the components accessible (100), e) deposit a layer of conductive material (122) on the sides (119) of the components (100) and on the connection pads (117),f) separate the chips (103) at the level of the cavities (311).

2. Method according to claim 1, wherein the connecting pads (117) comprise an electrically conductive core (116), covered by a layer of brazable material (118).

3. Method according to the preceding claim, wherein the brazable material is Sn or a tin alloy such as SnAg or SnAgCu.

4. A method according to any one of claims 2 and 3, wherein the electrically conductive core (116) is made of copper.

5. A method according to any one of claims 2 to 4, wherein the conductive material and the brazable material are identical.

6. A method according to any one of the preceding claims, wherein step e) is carried out by printing.

7. Electronic component (100) with wettable sides comprising a chip (103) having connection pages (107), the chip (103) being protected by a housing (109) comprising a first main face (115), sides (119) and a second main face, a layer of conductive material (122) covering a portion of the sides (119) and extending over the first main face (115), the layer of conductive material (122) being electrically connected to the electrical connection areas (107) of the chip (103) by means of pads connection (117) brazed onto the connection pads (107), a layer of insulating resin (121) covering the chip (103) between the connection pads (117) and forming a first part of the housing (109).

8. Component according to claim 7, wherein the connection pads (117) comprise an electrically conductive core (116) covered at least partially by a layer of material (118) brazed onto the connection pads (107).

9. Electronic component (100) according to claim 7 or 8, wherein the conductive material layer (122) is Sn or a tin alloy, such as SnAg or SnAgCu.

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