Electronic component manufacturing process

Abstract

Method for manufacturing electronic components. This description relates to a method for manufacturing wettable-sided electronic components from a substrate (301) in which chips are formed, the chips being separated by cavities. The method comprises a first step in which a layer of insulating material (121) is deposited, followed by a second step in which a layer of conductive material (122) is deposited on the insulating material layer (121) to form wettable sides. Figure for the abstract: Fig. 2F

Description

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

[0001] This description relates to the manufacture of electronic components. More specifically, it relates to the manufacture of so-called surface-mount, or "leadless," components, meaning components with no visible connections once assembled on the electronic board. These components have, 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. Previous technique

[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 ensure the correct assembly of components whose connections are not visible (the connections are under the component) and to guarantee the reliability of electrical connections, once the circuits are mounted 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 goal is achieved by a process for manufacturing electronic components with wettable flanks from a substrate in which chips are formed, the chips being separated by cavities, the process comprising a first step in which a layer of insulating material is deposited in the cavities and then a second step in which a layer of conductive material is deposited on the layer of insulating material in order to form wettable flanks.

[0006] According to one embodiment, the chips comprise at least two connection areas, covered by connection pads and arranged on a first main face of the substrate, and, in the first step, the layer of insulating material is deposited in the cavities, on the metal pads and on the first face of the substrate.

[0007] According to one embodiment, the process includes, before the second step, a step in which part of the insulating resin present in the cavities is removed, so as to form trenches whose bottom and walls are made of insulating resin and, in the second step, the layer of conductive material is deposited in the trenches.

[0008] According to one embodiment, the process further comprises the following steps: - Thinning the layer of insulating material to make the metal pads accessible, - Separating the electronic components by cutting the substrate through the layer of conductive material.

[0009] This goal is also achieved by an electronic component with wettable sides comprising a chip protected by a housing whose sides successively comprise a layer of insulating material and a layer of conductive material.

[0010] According to one embodiment, the electronic component comprises a first main face including at least two connection pads, a second main face and sides, the layer of conductive material being electrically insulated from the connection pads by the layer of insulating material, the layer of conductive material extending over a portion of the sides from the first main face.

[0011] According to one embodiment, the layer of insulating material covers the first main face of the chip between the connection pads.

[0012] According to one embodiment, the insulating material layer is a layer of epoxy or phenolic resin in which electrically insulating charges are dispersed, for example alumina particles.

[0013] According to one embodiment, the conductive material layer is a layer of epoxy or phenolic resin in which electrically conductive charges are dispersed, for example, particles of silver, copper, or carbon black. Brief description of the drawings

[0014] 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:

[0015] [Fig.1] represents, schematically and in cross-section, an electronic component with wettable sides according to a particular embodiment;

[0016] the [Fig.2A], the [Fig.2B], the [Fig.2C], the [Fig.2D], the [Fig.2E], the [Fig.2F] and the [Fig. 2G] represent cross-sectional views illustrating steps in a process of manufacturing of a wettable sidewall electronic component according to a particular embodiment;

[0017] Fig. 3A and Fig. 3B represent cross-sectional views illustrating steps of a process for assembling a wettable-flank electronic component with an external device according to a particular embodiment. Description of the implementation methods

[0018] 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.

[0019] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0020] 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.

[0021] 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.

[0022] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0023] Electronic components find applications in many industrial fields, and in particular, in the automotive or medical fields.

[0024] Fig. 1 illustrates, by a partial and schematic cross-sectional view, an electronic component 100 with non-through connections.

[0025] 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.

[0026] The chip comprises a front face 105 (also called the first face, front face, or top face), a rear face 104 (also called the second face, rear face, or bottom face), and sides 106 (also called lateral faces). The bottom face 104 is opposite the top face 105.

[0027] 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).

[0028] The electrical connection pads 107 are, for example, at a distance of 10 to 30 pm from the side wall of the chip. The electrical connection pads 107 can be positioned on the upper face 105 of the chip 103 or be flush with the upper face (i.e., reach the level of the upper face 105 of the chip 103).

[0029] The electrical connection pads 107 are also called "UBM" (for the Anglo-Saxon expression "Under Bump Metallization") or "bumping pads". The electrical connection pads 107 are made of a conductive material specifically adapted to receive connection pads 117, and in particular exhibiting good adhesion to the connection pads 117. The electrical connection pads 107 comprise at least one of the following elements: gold, titanium, nickel, copper, or tungsten. Preferably, they comprise gold.

[0030] 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.

[0031] Component 100 is a so-called integrated component.

[0032] The chip 103 is protected by the housing 109. More particularly, the housing 109 covers at least the upper face 105 and the sides 106 of the chip 103. According to an unrepresented variant, the housing 109 may also cover the lower face 104 of the chip 103.

[0033] The housing 109 is made of an electrically insulating material.

[0034] 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.

[0035] The connection pads 117 are formed from an electrically conductive and "wettable" (i.e. brazable) material, that is to say, a material on which it is possible to carry out brazing.

[0036] The electrical connection areas 107 of the chip 103 and the contact points 117 are positioned in openings in a layer of insulating material 121 covering the chip 103. The layer 121 is preferably an insulating resin layer.

[0037] The component is a wettable side component, that is to say that at least a part of the sides 119 of the housing 109 is covered by a layer of material conductor 122 in a wettable material, that is to say a material on which it is possible to braze.

[0038] The layer 122 partially covers the sides 119 of the housing 109 from the top face.

[0039] Layer 122 is preferably a conductive resin layer.

[0040] The conductive layer 122 partially covers the insulating layer 121. It is electrically insulated from the contact points 117 by the insulating material layer 121.

[0041] The wettable side device makes it easy to see if the soldering of the component onto another device has been done correctly.

[0042] We will now describe the process for manufacturing electronic components with wettable sides. This process includes a step in which a layer of insulating material 121 is deposited on the sides of the electronic components 100 and then a step in which a layer of conductive material 122 is deposited on the layer of insulating material 121.

[0043] More specifically, the process comprises the following steps: a) Provide a substrate 301 in which chips 103 are formed, the chips 103 comprising at least two connection areas 107, covered by connection pads 117, and arranged on a first main face 305 of the substrate 301 ([Fig.2A]), b) Partially cut the substrate 301 between the chips 103 so as to form cavities 307, the walls of the cavities 307 corresponding to the lateral walls of the chips 103 ([Fig.2B]), c) Deposit a layer of insulating material 121, whereby the insulating material 121 covers the metal studs 117, covers the first face 305 of the substrate 301 between the metal studs 107 and fills the cavities 307 ([Fig.2C]), d) Remove some of the insulating material present in the cavities 307 so as to form trenches 311 ([Fig.2D]), e) Deposit a layer of conductive material 122 on the layer of insulating material 121, the conductive material filling the trenches 311 ([Fig.2E]), f) Thin the device to make the connection pads 117 accessible ([Fig.2F]), g) Separate the components 100 by cutting the substrate 301 through the conductive material, thereby obtaining components with wettable flanks 100 ([Fig.2G]).

[0044] 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 the same 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 (back face or bottom face).

[0045] The substrate 301 is, for example, a semiconductor substrate, for example made of silicon.

[0046] The substrate 301 has, for example, a thickness between 300 and 900 pm, for example a thickness of about 725 pm.

[0047] 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]).

[0048] The electrical connection areas 107 are covered by a metal stud 117, which may in particular have the shape of a ball (or "bump"). Alternatively, it may be a conductive element having another shape, such as a pillar or a cube.

[0049] The metal studs 117 allow direct resumption of contact on the front face 115 of the housing 119.

[0050] The metal pads 117 are advantageously brazed onto the electrical connection areas 107. For example, the metal pads are made of a tin-based brazable material, typically SnAgCu.

[0051] In the figures, the chips 103 are shown with similar dimensions. However, according to one variant, they may have different dimensions. An electrical connection range 107 is shown for better readability, but each chip 103 comprises at least two connection pads 107. A person skilled in the art will be able to adapt the manufacturing process described here in this case.

[0052] In step b), a partial cutting step of the components 100 is performed, for example by a mechanical cutting process, such as a sawing process. This forms cavities 307 defining the lateral contours of the chips 103 of the components 100 in the substrate 301. More specifically, the cavities 307 extend from the upper face 305 of the substrate 301. For example, the depth of the cavities 307 corresponds to the desired thickness of the chips of the components 100. For example, the depth of the cavities 307 is on the order of 100 or 300 µm. The depth can be modified according to the intended application.

[0053] The cavities 307 formed in step b) preferably have a thickness of between 50 and 80 µm and a depth of between 100 and 150 µm. The thickness can be modified according to the intended application.

[0054] This step b) is carried out 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.

[0055] In step c), the walls of the cavities 307 are covered with an insulating material. For this purpose, a layer 121 of insulating material is deposited in the cavities 307, on the first face 305 of the substrate 301, and on the pads 117. Thus, the pads 117 are arranged within the insulating material. The layer 121 forms a first part of the housing 109 of the components 100. This first part of the housing therefore protects the upper face of the components 100, and at least a portion of the sides of the components 100.

[0056] During step c), the insulating material can be deposited using a press or by vacuum molding.

[0057] The insulating material may include an electrically insulating resin. This may be a thermosetting resin or a thermoplastic resin. The material will be chosen so as not to be fusible within the operating temperature range of the electronic components. The resin may be chosen from the group comprising: epoxy resins, phenolic resins, and acrylic resins.

[0058] The insulating material may also include electrically insulating particles. The particles are, for example, oxide particles, and in particular alumina or silica particles.

[0059] Polymerization is, for example, a UV polymerization step or a thermal activation polymerization.

[0060] Annealing can be carried out before step d).

[0061] In step d), a cutting step is performed to form trenches 311 in the insulating material layer 121. The trenches 311 are formed at the cavities 307. A portion of the insulating material remains in the cavities. This portion covers the bottom and side walls of the cavities 307. It protects and electrically insulates the sides of the components 100. By way of example, the thickness of insulating material remaining on the side walls of the cavities 307 is between 5 and 20 µm, preferably between 5 and 10 µm. The bottom of the cavities 307 can be covered by a thickness of 1 to 10 µm of insulating material.

[0062] The trenches 311 are made 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.

[0063] During step e), a layer of conductive material 122 is deposited on the layer of insulating material 121. The layer of conductive material 122 is deposited at least in the trenches 311 so as to cover the layer of insulating material 121. It can be deposited as a full sheet.

[0064] The conductive material is preferably an electrically conductive resin. More particularly, the resin of layer 122 comprises at least one material of base to which metallic particles covered with an electrically insulating protective layer are added.

[0065] The base material ensures the adhesion of layer 122 to material 121 and the particles ensure the final wettability of layer 122.

[0066] The base material is selected from the group comprising: epoxy resins, phenolic resins, and acrylic resins. The metallic particles are, for example, metallic particles whose material is selected from the group comprising: copper, a copper alloy, titanium, a titanium alloy, nickel, a nickel alloy, silver, and a silver alloy.

[0067] According to one embodiment, the conductive resin layer 122 can be deposited by printing (“screen printing”) or by vacuum molding.

[0068] Polymerization is, for example, a step of UV polymerization or by thermal activation.

[0069] Annealing can be carried out after step e) and before step f).

[0070] The process includes a front-face thinning step f) to make the conductive pads 117 accessible. The contacts of the housing 109 of the components 100 are then completely formed. The front-face thinning step can be carried out by polishing ('grinding').

[0071] The process may also include a step of thinning the substrate 301 on its rear face 303. For this, the structure is turned over and fixed by its front face, i.e., face 305. 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. In one example, the structure 301 is thinned until it reaches the bottom of the cavities 307.

[0072] The method may advantageously include a step between step f) and step g) in which an additional insulating layer is deposited on the rear face 303 of the structure to form the rear 111 of the component housing 100. Thus, all faces of the substrate 301 are protected either by the layer 121 or by the additional insulating layer.

[0073] 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.

[0074] During step g), the components are individualized by making a cut through the conductive resin 122. The components 100 are thus separated from each other.

[0075] The metallic particles of the conductive material 122 are then exposed, ensuring the wettability function of the flanks 119 of the electronic components 100.

[0076] The components 100 obtained are surface mount devices (or SMDs for "surface mounting device") of the "flip-chip" type, that is to say that they can be fixed on a support, for example, a printed circuit board, by their upper face, that is to say the face on which the contacts 117 of the housing 109 are arranged.

[0077] The components could also be DFN (“dual fiat no-lead”) or QFN (“quad fiat no-lead”) type components. These components have no through connections (“leads”). These leads do not protrude from the resin body of the housing.

[0078] Such components are particularly interesting for ensuring the reliability of electrical connections, once the circuits have been mounted in their environment.

[0079] Figures 3A and 3B represent steps in a process for assembling a component 100 onto an external device, for example a printed circuit board or other component.

[0080] The external device comprises a substrate 401 covered by tracks 402.

[0081] A soldering material 500 is positioned between the component 100 and the tracks 402 of the external device 400 ([Fig. 3A]). During soldering, the soldering material 500 rises along the wettable flanks 122 of the components, which allows verification that the soldering has been carried out correctly.

[0082] Various embodiments and variants have been described. A person skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will become apparent to a person skilled in the art.

[0083] 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) comprising a chip (103) and a package (109) from a substrate (301) in which chips (103) are formed, the chips (103) comprising at least two connection areas (107), covered by connection pads (117), and arranged on a first main face (305) of the substrate (301), the chips (103) being separated by cavities (307), the method comprising the following steps: - depositing a layer of insulating material (121) in the cavities, - depositing a layer of conductive material (122) on the layer of insulating material (121) in order to form wettable sides, - separating the electronic components (100) from each other by cutting the substrate (301) through the layer of conductive material (122),whereby the electronic components (100) comprise a chip (103) protected by a housing (109) the sides of which comprise successively a layer of insulating material (121) and a layer of conductive material (122), the layer of conductive material (122) being electrically insulated from the contact points (117) by the layer of insulating material (121).

2. A method according to claim 1, wherein, in the first step, the layer of insulating material (121) is deposited in the cavities (307), on the connecting pads (117) and on the first face of the substrate (305).

3. The method according to claim 2, the method comprising, prior to the second step, a step in which a portion of the insulating material present in the cavities (307) is removed, so as to form trenches (311) whose bottom and walls are made of insulating resin and in which, during the second step, the layer of conductive material (122) is deposited in the trenches (311).

4. A method according to claims 2 and 3, the method further comprising the following steps: - Thinning the layer of insulating material (121) to make the metal pads (117) accessible, - Separating the electronic components (100) by cutting the substrate (301) through the layer of conductive material (122).

5. Electronic component (100) with wettable sides comprising a chip (103) protected by a housing (109) whose sides successively comprise a layer of insulating material (121) and a layer of conductive material (122).

6. Electronic component (100) according to claim 5, comprising a first main face (115) comprising at least two connection pads (117), a second main face (111) and flanks (119), the layer of conductive material (122) being electrically insulated from the connection pads (117) by the layer of insulating material (121), the layer of conductive material (122) extending over a portion of the flanks (119) from the first main face (115).

7. Electronic component according to any one of claims 5 and 6, wherein the insulating material layer (121) covers a first main face (105) of the chip (103) between the connection pads (117).

8. Electronic component according to any one of claims 5 to 7, wherein the insulating material layer (121) is an epoxy or phenolic resin layer in which electrically insulating charges, for example alumina particles, are dispersed.

9. Electronic component according to any one of claims 5 to 8, wherein the conductive material layer (122) is an epoxy or phenolic resin layer in which electrically conductive charges are dispersed, for example particles of silver, copper or carbon black.