METHOD OF MANUFACTURING ELECTRONIC COMPONENTS HAVING WETTABLE flanks

Abstract

The invention relates to a method of manufacturing an electronic assembly having wettable flanks. A process for manufacturing an electronic component having wettable flanks from a substrate covered by connection terminals and in which a chip is formed, the process comprising the steps of: a) soldering connection pads to the connection terminals, b) coating the connection pads with an insulating resin layer, c) thinning the insulating resin layer until it reaches the core of the connection pads, and d) removing the insulating resin layer from the substrate. D) forming a cavity by removing portions of the connection pads and portions of the insulating resin layer so that portions of the flanks of the component are accessible, e) depositing a layer of conductive material on the flanks of the component and the connection pads, f) separating the chips.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATION(S)

[0002] This application claims the benefit of priority to French patent application No. 2312922, filed on November 23, 2023, entitled “Procédé de fabrication decomposants électroniques”, which is hereby incorporated by reference to the fullest extent permitted by law. Technical Field

[0003] The present specification relates to the manufacture of electronic components. More specifically, it applies to the manufacture of so-called surface mount components, i.e., components having one or more connection metallizations on at least one side, which are designed to be soldered to corresponding connection pads on an external device, such as a printed circuit board or another component. Background Art

[0004] In some applications, one use of surface mount components is where the connection metallization designed to be soldered to an external device extends to the side of the component. These are called "wettable flank" components. When the component is mounted in its environment (e.g., on a printed circuit board), the connection metallization (also called electrical contacts) is soldered or brazed to the corresponding metal track or component on the PCB side. Some of the solder material then rises to the side of the component, enabling visual inspection of the connection quality.

[0005] Such uses exist, for example, in the automotive or medical fields and more generally in all fields where the reliability of the electrical connections must be guaranteed once a circuit has been installed in its environment. Summary of the invention

[0006] There is a need for improving at least some aspects of known processes for making electronic components having wettable flanks.

[0007] This is achieved by a process for producing an electronic component with wettable flanks from a substrate covered with connection terminals and in which a chip is formed, the process comprising the following steps:

[0008] a) Solder the connection pads to the connection terminals of the chip,

[0009] b) coating the connection pads with an insulating resin layer,

[0010] c) thinning the insulating resin layer until it reaches the core of the connection pad,

[0011] d) forming a cavity by removing portions of the connection pads and portions of the insulating resin layer so as to make portions of the flanks of the component accessible,

[0012] e) depositing a layer of conductive material on the flanks of the component and on the core of the connection pads,

[0013] f) Separate the chips through the cavity.

[0014] According to an embodiment, the connection pad comprises an electrically conductive core covered by a layer of solderable material.

[0015] According to an embodiment, the solderable material is Sn or a tin alloy, such as SnAg or SnAgCu.

[0016] Advantageously, the electrically conductive core is made of copper.

[0017] According to an embodiment, the electrically conductive material and the solderable material are the same.

[0018] According to an embodiment, step e) is performed by screen printing.

[0019] This is achieved by an electronic component with wettable flanks, which comprises: a chip with connection terminals protected by a housing, the housing comprising a first main surface, a flank and a second main surface; a layer of conductive material covering part of the flank and extending above the first main surface, the conductive material layer being electrically connected to the connection terminals of the chip by means of connection pads soldered to the connection terminals.

[0020] According to an embodiment, the connection pad comprises an electrically conductive core at least partially covered by a layer of material which is soldered to the connection terminal.

[0021] According to an embodiment, the conductive material layer is a Sn layer or a tin alloy (such as SnAg or SnAgCu) layer.

[0022] According to an embodiment, the insulating resin layer covers the first main face of the chip between the connection pads. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The foregoing features and advantages, as well as other features and advantages, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation, with reference to the accompanying drawings, in which:

[0024] Figure 1 shows a schematic cross-section of an electronic component having wettable flanks according to certain embodiments;

[0025] Figure 2A , Figure 2B , Figure 2C , Figure 2D , Figure 2E and Figure 2F is a cross-sectional view illustrating steps in a process for making an electronic component having wettable flanks according to certain embodiments;

[0026] Figure 3 Shown by Figures 2A to 2F Top view of an electronic component with wettable flanks obtained by the process described in;

[0027] Figure 4A and Figure 4B is a cross-sectional view illustrating steps in a process for making an electronic component having wettable flanks according to another specific embodiment;

[0028] Figure 5 Shown by Figure 4A and 4B Top view of an electronic component with wettable flanks obtained by the process described in;

[0029] Figure 6 is a scanning electron microscope (SEM) image of a spherical core shell connection pad in a particular embodiment. DETAILED DESCRIPTION

[0030] Similar features in the various figures are represented by similar reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals and may have the same structure, dimensions, and material properties.

[0031] For clarity, only operations and elements useful for understanding the embodiments described herein are illustrated and described in detail.

[0032] Unless otherwise specified, when referring to two elements being connected together, this means a direct connection without any intermediate elements except conductors, and when referring to two elements being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0033] In the following disclosure, unless otherwise stated, when absolute position qualifiers, such as terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as terms "above", "below", "higher", "lower", etc., or orientation qualifiers, such as "horizontal", "vertical", etc., are mentioned, they all refer to the orientation shown in the figures.

[0034] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "approximately" mean within 10%, preferably within 5%.

[0035] Electronic components are used in a wide range of industrial sectors, especially in the automotive and medical fields.

[0036] Figure 1 A schematic cross section of an electronic assembly 100 is shown.

[0037] The electronic component 100 consists of an electronic chip 103 and a housing 109. In one example, the chip 103 is formed of a semiconductor substrate such as silicon. It can also be SiC. Alternatively, the substrate can be glass or sapphire.

[0038] The chip comprises a front side 105 (also referred to as a first side or front face), a back side 104 (also referred to as a second side or rear face) and sidewalls 106 (also referred to as side faces). The lower side 104 is opposite to the upper side 105 .

[0039] One or more connection terminals 107 (also called electrical contacts) are formed on the top surface 105 of the microchip 103 so that it can be connected to other elements (microchips or electronic devices).

[0040] The electrical connection terminals 107 are also referred to as "UBM" (under bump metallization). The electrical connection terminals 107 are made of a conductive material specifically designed to receive the connection pads 117 (particularly designed to adhere well to the pads 117). The electrical connection terminals 107 include at least one of the following elements: gold, titanium, nickel, copper, silver, tin or tungsten. Preferably, they include gold or copper. The connection terminals 107 may be electroplated.

[0041] The electrical connection terminals 107 are, for example, 10 to 50 μm, or even 10 to 30 μm away from the chip sidewalls. This distance will depend on the size of the connection pads 117. The electrical connection terminals 107 can be positioned on the top surface 105 of the chip 103 or flush with the top surface (i.e., at the same level as the top surface 105 of the chip 103).

[0042] The chip 103 may include one or more discrete components. The (one or more) discrete components are selected, for example, from transistors, diodes, thyristors, triacs, filters, etc. The chip 103 may include one or more electronic circuits. The chip 103 may be used to implement various electronic functions.

[0043] The assembly 100 is an integrated assembly.

[0044] The chip 103 is protected by the housing 109. More specifically, the housing 109 covers at least the front side 105. Figure 1 As shown in , it may also cover side faces 106 of chip 103 and / or back side 104 of chip 103 .

[0045] The housing 109 is made of an electrically insulating material.

[0046] To connect assembly 100 to other electronic components and / or circuits, housing 109 also includes connection pads 117 (also referred to as housing contacts or contact covers). Connection pads 117 are positioned on top surface 105 of chip 103. Each pad 117 is connected to an electrical terminal 107 on chip 103.

[0047] The connection pad 117 may be a metal element.

[0048] The connection pads 117 are, for example, metal balls, which can be made of copper, nickel or any other non-fusible material.

[0049] The connection pad 117 may be an element including a conductive core 116 covered by a layer 118 of solderable material (also referred to as a shell).

[0050] Preferably, the conductive core 116 is made of copper.

[0051] Preferably, the solderable material is tin or one of its alloys, such as SnAgCu or SnAg. Layer 118 acts as an oxidation barrier.

[0052] The electrical connection terminals 107 and the connection pads 117 on the chip 103 are positioned in holes in the insulating resin layer 121 covering the chip 103 .

[0053] The component 100 is a component with wettable flanks, ie, at least part of its sidewalls are covered by a layer 122 of wettable and / or solderable material (ie, material that can be soldered or otherwise mechanically attached (eg, conductive adhesive, sintering)).

[0054] The wettable material layer 122 covers a portion of the flank 119 of the component 100 and extends over the first major surface 115 of the component 100 to form a continuous layer having a first portion 122A covering a portion of the first major surface 115 of the component 100 and a second portion 122B covering a portion of the flank 119 of the component 100 .

[0055] The wettable material is in direct contact with the connection pad 117. There are no components between the connection pad 117 and the wettable material. It is in direct contact on the flank 119 and the first main face 115.

[0056] The wettable material is preferably a solderable material such as Sn, SnAg or SnAgCu or another material with a higher melting point.

[0057] Now we will refer to Figures 2A to 2F The manufacturing process of such an assembly 100 is described in more detail.

[0058] The process is based on a substrate 301 which is covered by connection terminals 107 and in which the chip 103 is formed.

[0059] The process includes the following steps:

[0060] a) Soldering a connection pad 117 to the connection terminal 107, the connection pad 117 preferably comprising a conductive core 116 covered by a coating 118 of solderable material ( Figure 2A ),

[0061] b) depositing an insulating resin layer 121 on the substrate 301, the insulating resin layer 121 encapsulating the connection pads 117 and the connection terminals 107 ( Figure 2B ),

[0062] c) Thinning the insulating resin layer 121 until it reaches the connection pad 117 and, if applicable, the core 116 of the connection pad 117 ( Figure 2C ),

[0063] d) forming a cavity 311 between the chips 103 by partially removing a portion of the connection pads 117 and a portion of the insulating resin layer 121 so that a portion of the flank 119 of the component 100 is accessible ( Figure 2D ),

[0064] e) Applying a layer of conductive material 122 on the flanks of the component 100 and the connection pads 117 ( Figure 2E ),

[0065] f) Separating the chip 103 by cutting into the cavity 311 ( Figure 2F ), thereby obtaining a component 100 with wettable flanks.

[0066] In step a), the manufacture of (one or more) discrete components and / or (one or more) integrated circuits forming the assembly 100 is completed. The assembly 100 is formed by a single substrate 301 and has not yet been singulated. In the figures, the chips 103 are bounded by the dotted lines in the substrate 301. The substrate 301 has a first face 305 (top or front) and a second face 303 (back or back). Adjacent chips 103 are separated from each other by a portion of the substrate 301. In other words, a portion of the substrate 301 separates adjacent chips 103.

[0067] The substrate 301 is, for example, a semiconductor substrate such as silicon or SiC.

[0068] The thickness of the substrate 301 is between 300 and 900 μm, for example, about 725 μm.

[0069] In addition, regarding Figure 1 The electrical connection terminals 107 are formed on the upper surface 305 of the substrate 301 ( Figure 2A ).

[0070] In step a), the connection pad 117 is soldered to the connection terminal 107 .

[0071] like FIG. 2A to FIG. 2F and Figure 3 As shown in , the connection pad 117 may be a ball (ie, spherical in shape). Obviously, these figures are schematic representations, and in reality the solder connection pad 117 and the connection terminal 107 have a larger contact surface than a single contact point when they are soldered to each other.

[0072] Alternatively, if Figure 4A , Figure 4B and Figure 5 As shown in , the connecting studs can be columns. These can be columns with square, circular or rectangular cross-sections.

[0073] Preferably, the connection pad 117 includes a core 116 made of a first material and a shell (or coating) 118 made of a second material.

[0074] The shell 118 preferably covers the core continuously. The thickness of the shell is, for example, between 10 and 20 μm.

[0075] The conductive core 116 is preferably made of copper.

[0076] The housing 118 or coating is made of a material that can be soldered to the terminal pads. In particular, it is tin or a tin alloy, such as SnAg or SnAgCu.

[0077] Figure 6 An SEM image of a ball-shaped connection pad 117 having a copper core and a tin-based alloy shell is shown by way of illustration and not limitation.

[0078] In a variant not shown, the connection pads are metal balls. These balls are not covered by the housing. They can be copper balls or nickel balls.

[0079] In step b), an insulating resin layer 121 is deposited on the substrate 301 .

[0080] More specifically, an insulating resin layer 121 is deposited on the first face 305 of the substrate 301 and on the pads 117. In this way, the pads 117 are arranged within the resin. The insulating resin layer 121 forms a first portion of the component housing 100. As an example, the layer 121 can be deposited by screen printing, compression or injection molding. Thus, this first portion of the case protects the upper side of the component 100.

[0081] The resin is an electrically insulating resin. More particularly, the resin comprises at least one substrate to which electrically insulating particles are added. The substrate is selected from the group comprising: epoxy resins, phenolic resins, acrylic resins. Preferably, the resin is an epoxy resin. The particles are, for example, oxide particles, in particular aluminum oxide or silicon dioxide particles.

[0082] The polymerization is performed, for example, under ultraviolet (UV) radiation or by thermal activation. Annealing may be performed before step c).

[0083] In step c), a thinning step is performed from the front side to remove the portion of the insulating resin 121 covering the connection pad 117 and the upper portion of the connection pad 117 until the core 116 of the connection pad 117 is reached.

[0084] The thinning step on the front side can be performed by grinding. Mechanical polishing is preferred.

[0085] In step d), a cavity 311 is formed between the chips 103 so as to remove parts of the resin layer 121 and parts of the connection pads 117. Thus, the core 116 of the connection pads 117 can also be reached from the side.

[0086] The resulting cavity 311 extends from the front side and to a depth corresponding at least to the height of the conductive material layer 122 described below covering the sidewalls of the assembly 100. The height of the cavity 311 is less than the thickness of the insulating resin layer 121 so as to insulate the wettable flank from the substrate 301.

[0087] Step d) is performed using a cutting device. The cutting device is, for example, a mechanical engraving tool, such as a saw, or a laser engraving tool. In a preferred embodiment, the cutting device is a laser. In addition, when the cutting device is a laser, the cutting technology used can be a laser direct structuring (LDS) technology.

[0088] In step e), a layer 122 of electrically conductive material is deposited so as to cover the connection pads 117 and at least part of the side faces 119 of the component 100 .

[0089] The conductive material layer 122 may be deposited by a printing method, an additive deposition method or by immersion in a bath. For example, an oxidation resistant material may be deposited on a metal surface. The deposition is selective.

[0090] Advantageously, the layer of electrically conductive material 122 is deposited locally by a dispensing technique, preferably by screen printing, in particular through a mask.

[0091] Alternatively, it can be a full plate deposition.

[0092] At the end of step e), the cavity 311 is filled with the conductive material and the core 116 of the connection pads 117 is covered by the layer of conductive material 122. The core 116 is thus completely covered by the protective layer formed partly by the shell 118 and partly by the layer 122. The core is thus protected from the external environment, in particular from oxidation, which is particularly advantageous in the case of a copper core 116.

[0093] In step f), the components 100 are separated by cutting through the cavities 311. Thus, the components 100 are separated from each other. In some embodiments, cutting includes cutting through the portion of the substrate 301 separating adjacent chips 103.

[0094] Alternatively, the steps can be performed in the following order: a), b), c), d), f) and e). Once the cavity 311 is formed, it is possible to proceed with full cutting (step f)) and then deposit the conductive material layer 122 (step e)). Advantageously, the deposited layer is an organic layer. It also serves as a protective layer against oxidation.

[0095] The process may also include a backside thinning step. To this end, the structure is turned over and attached to a support via its front side (i.e., face 305). The support is, for example, an adhesive tape. The structure is then thinned on its back side 303 so that the substrate 301 has its final thickness.

[0096] The process may advantageously include steps during 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 an additional insulating layer is deposited on the side faces 106 of the chip 103 .

[0097] The additional insulating layer is made of an electrically insulating material, for example the same type of resin as in layer 121. In another example, the materials of the layers are different.

[0098] At the end of this process, the components 100 obtained are surface mount devices (SMDs) of the “flip chip” type, i.e. they can be attached via their front side (i.e. the side on which the pads 117 of the housing 109 are arranged) to an external device such as a printed circuit board or another component.

[0099] To achieve this, a brazing material is positioned between the assembly 100 and the external device. During welding, the brazing material rises to the sides 119 of the assembly 100, allowing verification that the welding has been performed correctly.

[0100] Such an assembly 100 is particularly useful for ensuring the reliability of electrical connections once the circuit has been installed in its environment.

[0101] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these embodiments may be combined, and those skilled in the art will readily conceive of other variations.

[0102] Finally, actual implementation of the embodiments and variations described herein are within the capabilities of those skilled in the art based on the functional description provided above.

[0103] A process for manufacturing an electronic component (100) with wettable flanks from a substrate (301) covered by connection terminals (107) and in which a chip (103) is formed, the process being summarized as comprising the following steps: a) soldering connection pads (117) to the connection terminals (107) of the chip (103), b) coating the connection pads (117) with an insulating resin layer (121), c) thinning the insulating resin layer (121) until it reaches the core (116) of the connection pads (117), d) forming a cavity (311) by removing parts of the connection pads (117) and parts of the insulating resin layer (121) so as to make parts of the flanks (119) of the component (100) accessible, e) depositing a layer of conductive material (122) on the flanks (119) of the component (100) and the core of the connection pads (117), and f) separating the chip (103) through the cavity (311).

[0104] The connection pad (117) includes a conductive core (116) covered by a layer (118) of solderable material.

[0105] The solderable material is Sn or a tin alloy such as SnAg or SnAgCu.

[0106] The conductive core (116) is made of copper.

[0107] The conductive material and the solderable material are the same.

[0108] Step e) is performed by screen printing.

[0109] An electronic component (100) with wettable flanks is summarized as comprising: a chip (103) with connection terminals (107), the chip (103) being protected by a housing (109), the housing (109) comprising a first main surface (115), flanks (119) and a second main surface; a conductive material layer (122) covering a portion of the flanks (119) and extending above the first main surface (115), the conductive material layer (122) being electrically connected to the connection terminals (107) of the chip (103) by means of connection pads (117) soldered to the connection terminals (107).

[0110] The connection pad (117) includes a conductive core (116) at least partially covered by a layer of material (118) that is soldered to the connection terminal (107).

[0111] The conductive material layer (122) is a Sn layer or a tin alloy layer, such as SnAg or SnAgCu.

[0112] The insulating resin layer (121) covers the first main surface (105) of the chip (103) between the connection pads (117).

[0113] The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications, and publications to provide further embodiments.

[0114] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full range of equivalents to which these claims are entitled. Therefore, the claims are not limited by the present disclosure.

Claims

1. A method for manufacturing an electronic component, comprising: forming a connection pad on each of a plurality of connection terminals on the plurality of chips; coating each connection pad with a layer of insulating resin; thinning the insulating resin layer until it reaches the core of each connection pad; forming a cavity by removing a portion of one of the connection pads and a portion of the insulating resin layer, thereby exposing a side wall of the electronic component; depositing a layer of conductive material on the sidewalls of the electronic component and on the core of the connection pad; as well as Each chip of the plurality of chips is separated by a cavity. 2 . The method of claim 1 , wherein the core of each connection pad is a conductive core covered by a layer of solderable material.

3. The method of claim 2, wherein the solderable material is a tin alloy.

4. The method of claim 2, wherein the conductive core is copper. The method of claim 2 , wherein the conductive material and the solderable material are the same material. The method of claim 1 , wherein depositing the layer of conductive material is performed by screen printing.

7. An electronic component comprising: chip; Multiple connection terminals on the chip; a plurality of connection pads, each connection pad being coupled to one of the plurality of connection terminals; a housing surrounding the plurality of connection terminals on the chip, the housing comprising a first surface opposite to the second surface and a plurality of side walls; as well as A conductive material layer covers a portion of the sidewall and extends over the first face, the conductive material layer being electrically coupled to the connection terminals of the chip through connection pads soldered to the connection terminals. 8 . The electronic assembly of claim 7 , wherein the connection pad comprises a conductive core at least partially covered by a layer of solderable material coupled to the connection terminal.

9. The electronic assembly of claim 7, wherein the conductive material layer is an alloy of tin.

10. The electronic component according to claim 7, wherein the insulating resin layer covers the first side of the chip between the connection pads.

11. A device comprising: A chip having a first surface opposite to the second surface and a plurality of side walls extending from the first surface to the second surface along a first direction; a plurality of connection terminals on the first side; an insulating housing covering the first surface and having a plurality of side walls extending along a first direction; a plurality of connection pads, each connection pad being coupled to one of the plurality of connection terminals; as well as A first wettable material layer partially covers a sidewall of the plurality of sidewalls of the insulating housing, and the first wettable material layer is directly coupled to a first connection pad of the plurality of connection pads. 12 . The device of claim 11 , wherein each of the plurality of connection terminals is separated from a sidewall of the chip by a first distance in a range of 10 μm to 50 μm.

13. The device of claim 11, wherein the housing completely covers the first side, the second side, and the plurality of side walls of the chip.

14. The apparatus of claim 11, wherein each connection pad comprises a conductive core covered by a layer of solderable material.

15. The apparatus of claim 14, wherein the insulating housing has a first face that is transverse to the plurality of side walls of the insulating housing.

16. The apparatus of claim 15, wherein the wettable material layer is L-shaped having a first portion covering a sidewall of the plurality of sidewalls of the insulating housing and a second portion located on the first face of the insulating housing.

17. The apparatus of claim 16, wherein the second portion of the layer of wettable material is coplanar with the first side of the insulating housing.

18. The apparatus of claim 16, wherein the first portion and the second portion of the layer of wettable material are each directly coupled to the conductive core of a first connection pad of the plurality of connection pads.

19. The apparatus of claim 16, further comprising a second layer of wettable material directly coupled to a second one of the plurality of connection pads, the second layer of wettable material being coplanar with the first side of the insulating housing.

20. The device of claim 11, further comprising an insulating resin layer completely covering the chip.

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