Electronic component manufacturing process

Abstract

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

Description

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

[0001] The present description relates to the manufacture of electronic components. It relates more particularly to the manufacture of so-called surface-mount components, so-called "leadless", that is to say without visible connections once assembled on the electronic card. These components comprise, on at least one side, one or more connection metallizations intended to be soldered to corresponding connection pads of an external device, for example a printed circuit card or another component. Prior art

[0002] In some applications, there is a need for surface-mount components in which connection metallizations intended to be soldered to an external device extend to the sides of the components. These are referred to as wettable flank components. When mounting the component in its environment (for example, on a printed circuit board), the connection metallizations (also called electrical contacts) are soldered or welded to corresponding metal tracks or elements on the printed circuit side. A portion of the solder material then rises up the sides of the components, which allows for a visual inspection of the quality of the connections.

[0003] This need exists for example in the automotive or medical fields and, more generally, in fields where it is desired to ensure the correct assembly of components whose connections are not visible (the connections are under the component) and to guarantee the reliability of the 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 methods for manufacturing electronic components with wettable sides.

[0005] This aim is achieved by a method of manufacturing electronic components with wettable sides from a substrate in which chips are formed, the chips being separated by cavities, the method comprising a first step during which a layer of insulating material is deposited in the cavities and then a second step during which a layer of conductive material is deposited on the layer of insulating material in order to form wettable sides.

[0006] According to one embodiment, the chips comprise at least two connection pads, covered by connection pads and arranged on a first main face of the substrate, and, during 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 method comprises, before the second step, a step during which a portion 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, during the second step, the layer of conductive material is deposited in the trenches.

[0008] According to one embodiment, the method 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 aim is also achieved by an electronic component with wettable sides comprising a chip protected by a package 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 comprising at least two connection pads, a second main face and flanks, 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 flanks 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 layer of insulating material is a layer of epoxy or phenolic resin in which electrically insulating fillers, for example alumina particles, are dispersed.

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

[0014] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

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

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

[0017] [Fig.3A] and [Fig.3B] represent sectional views illustrating steps of a method of assembling a wettable edge electronic component with an external device according to a particular embodiment. Description of the embodiments

[0018] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

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

[0020] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of 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", "upper", "lower", 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 "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

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

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

[0025] The electronic component 100 is formed from an electronic chip 103 and a housing 109. According to one example, the electronic chip 103 is formed from a semiconductor substrate, for example made of silicon. It may also be SiC.

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

[0027] One or more connection pads 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 English 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 having good adhesion with 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) are, for example, chosen from transistors, diodes, thyristors, triacs, filters, etc. The chip 103 may comprise one or more electronic circuits. The chip 103 makes it possible to implement different 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 a variant not shown, the housing 109 can also cover the lower face 104 of the chip 103.

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

[0034] In order to be able to connect the component 100 to other components and / or electronic circuits, the housing 109 further comprises connection pads 117 (also called housing contacts or contact connections). The connection pads 117 are positioned on the upper face 105 of the chip 103. Each connection pad 117 is connected to an electrical connection pad 107 of the chip 103.

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

[0036] The electrical connection pads 107 of the chip 103 and the contact connections 117 are positioned in openings of a layer of insulating material 121 coating the chip 103. The layer 121 is, preferably, a layer of insulating resin.

[0037] The component is a wettable sidewall component, i.e. at least part of the sides 119 of the housing 109 is covered by a layer of material conductor 122 made of a wettable material, i.e. a material on which it is possible to solder.

[0038] The layer 122 partially covers the sides 119 of the housing 109 from the upper 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 layer of insulating material 121.

[0041] The wettable flank device makes it easy to see whether the soldering of the component to another device has been carried out correctly.

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

[0043] More particularly, the method comprises the following steps: a) Providing a substrate 301 in which chips 103 are formed, the chips 103 comprising at least two connection pads 107, covered by connection pads 117, and arranged on a first main face 305 of the substrate 301 ([Fig.2A]), b) Partially cutting the substrate 301 between the chips 103 so as to form cavities 307, the walls of the cavities 307 corresponding to the side walls of the chips 103 ([Fig.2B]), c) Depositing a layer of insulating material 121, whereby the insulating material 121 covers the metal pads 117, covers the first face 305 of the substrate 301 between the metal pads 107 and fills the cavities 307 ([Fig.2C]), d) Removing part of the insulating material present in the cavities 307 so as to form trenches 311 ([Fig.2D]), e) Depositing a layer of conductive material 122 on the layer of insulating material 121, the conductive material filling the trenches 311 ([Fig.2E]), f) Thinning the device to make the connection pads 117 accessible ([Fig.2F]), g) Separating the components 100 by cutting the substrate 301 through the conductive material, whereby wettable sidewall components 100 are obtained ([Fig.2G]).

[0044] In step a), the manufacture of the discrete component(s) and / or integrated circuits 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 of between 300 and 900 μm, for example a thickness of approximately 725 μm.

[0047] In addition, electrical connection pads 107, described in relation to [Fig. 1], have been formed on an upper face 305 of the substrate 301 ([Fig. 2A]).

[0048] The electrical connection pads 107 are covered by a metal pad 117, which may in particular have the shape of a ball (“bump” in English terms). Alternatively, it may be a conductive element having another shape, such as for example a pillar or a cube.

[0049] The metal pads 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 pads 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. But according to a variant, they can have different dimensions. An electrical connection pad 107 is shown for better readability, but each chip 103 comprises at least two connection pads 107. The person skilled in the art will know how to adapt the manufacturing method described here in this case.

[0052] During step b), a step of partial cutting of the components 100 is carried out, for example by a mechanical cutting method, such as a sawing method. Thus, cavities 307 defining the lateral contours of the chips 103 of the components 100 are formed in the substrate 301. More particularly, the cavities 307 extend from the upper face 305 of the substrate 301. According to one example, the depth of the cavities 307 corresponds to the desired thickness of the chips of the components 100. According to one example, the depth of the cavities 307 is of the order of 100 or 300 μm. The depth can be modified depending on the desired 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 depending on the desired application.

[0054] This step b) is carried out by means of a cutting device. The cutting device is, for example, a mechanical engraving tool such as a saw, or a laser engraving tool. According to a preferred embodiment, the cutting device is a laser.

[0055] During step c), the walls of the cavities 307 are covered with an insulating material. For this, 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 part of the sides of the components 100.

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

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

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

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

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

[0061] During step d), a cutting step is implemented to form trenches 311 in the layer of insulating material 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 the side walls of the cavities 307. It protects and electrically insulates the side of the components 100. According to one 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 may be covered by a thickness of 1 to 10 μm of insulating material.

[0062] The trenches 311 are made by means of a cutting device. The cutting device is, for example, a mechanical engraving tool such as a saw, or a laser engraving tool. According to 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 plate.

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

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

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

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

[0068] The polymerization is, for example, a UV or thermal activation polymerization step.

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

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

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

[0072] The method can advantageously comprise a step between step f) and step g) during which an additional insulating layer is deposited on the rear face 303 of the structure to form the rear 111 of the component package 100. Thus, all the 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 metal particles of the conductive material 122 are then exposed, ensuring the wettability function of the sides 119 of the electronic components 100.

[0076] The components 100 obtained are surface-mount components (or SMD for “surface-mounting device”) of the “flip-chip” type, that is to say 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 are components that do not have through connections ("leads"). The latter do not protrude from the resin body of the package.

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

[0079] Figures 3A and 3B show steps of a method for assembling a component 100 on an external device, for example a printed circuit board or another 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 sides 122 of the components, which makes it possible to verify that the soldering has been carried out correctly.

[0082] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0083] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. Method for manufacturing electronic components (100) with wettable sides from a substrate (301) in which chips (103) are formed, the chips (103) being separated by cavities (307), the method comprising a first step during which a layer of insulating material (121) is deposited in the cavities and then a second step during which a layer of conductive material (122) is deposited on the layer of insulating material (121) in order to form wettable sides.

2. Method according to claim 1, in which the chips (103) comprise at least two connection pads (107), covered by connection pads (117) and arranged on a first main face (305) of the substrate (301), and in which, during the first step, the layer of insulating material (121) is deposited in the cavities (307), on the connection pads (117) and on the first face of the substrate (305).

3. A method according to claim 2, the method comprising, before the second step, a step during 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. 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 package (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 sides (119) from the first main face (115).

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

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

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

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