Electronic circuit and electromagnetic shielding cap for an electronic circuit

Abstract

An electronic circuit and an electromagnetic shielding cap for the electronic circuit are disclosed. The electromagnetic shielding cap includes: a main surface; four side surfaces; a first side surface of the four side surfaces including a recessed portion formed by an open cavity located in and at the base of the first side surface; the height of the first side surface is less than the height of the other side surfaces of the four side surfaces. The electronic circuit includes: a substrate having a first main surface including at least one metal pad; a chip bonded to the first main surface of the substrate; a first cap forming the electromagnetic shielding cap; and a second cap stacked and disposed on the first main surface of the substrate; the first cap includes a main surface and four side surfaces; the first side surface of the four side surfaces includes a recessed portion formed by an open cavity located in and at the base of the first side surface; solder joints disposed in the recessed portion, which are soldered to the metal pads and to at least one wall of the recessed portion, the solder joints being configured to assemble the first cap and the substrate to each other.

Description

[0001] Priority requirements

[0002] This application claims priority to French patent application serial number FR2405584, filed on May 30, 2024, the contents of which are incorporated herein by reference in their entirety to the fullest extent permitted by law. Technical Field

[0003] This disclosure generally relates to the field of electronic circuits, and more particularly to electromagnetic shielding caps designed to protect electronic circuits (especially electronic circuits including light radiation emitters and / or light radiation receivers). Background Technology

[0004] Some electronic circuits include an integrated circuit (IC) chip housed in a package. This package often includes a support portion to which the chip is bonded, and a cover portion that covers the chip. The cover is mounted on the support portion. The cover is, for example, made of resin.

[0005] When the electronic chip includes optical signal transmitting and receiving areas, the cover portion includes an element that is transparent to the wavelength of the optical signal and is opposite to the transmitting / receiving areas, and an inner wall that defines two cavities, one for the transmitting area and the other for the receiving area.

[0006] Such electronic circuits are used, for example, to create time-of-flight (TOF) proximity sensors to detect the presence or absence of an object located in front of the package cover.

[0007] Because such electronic circuits are sensitive to electromagnetic waves, electromagnetic shielding must be added. For this purpose, a metal cap can be placed on the cover. The metal cap can be bonded to the supporting substrate using adhesive beads.

[0008] However, several drawbacks exist due to the difficulty in calibrating the liquid droplets. There is a risk that the bonding material between the wall and the receiver chip may flow into the cap through capillary action, which could hinder the normal operation of electronic components. Furthermore, the strength of the cap bond is uncertain.

[0009] There is a need to provide an electronic circuit that includes an electromagnetic shielding cap with good mechanical strength. Utility Model Content

[0010] In one embodiment, an electronic circuit (particularly an optical transmitting and / or receiving device) includes: a chip bonded to a first main surface of a substrate, the first main surface of the substrate including at least one metal pad; a first electromagnetic shielding cap (preferably made of metal) and a second cap (preferably made of polymer material), stacked and disposed on the first main surface of the substrate; the first cap includes a main surface and four side surfaces, a recessed portion is formed at the base of the first side surface, the first cap and the substrate are assembled to each other by means of solder joints disposed in the recessed portion, soldered to the metal pads and soldered to at least one wall of the wall of the recessed portion.

[0011] According to one embodiment, at least one of the other side surfaces of the cap covers one of the sides (flanks) of the substrate.

[0012] According to one specific embodiment, the other three side surfaces each cover one of the sides of the substrate.

[0013] According to one specific embodiment, the second cap is disposed between the chip and the first cap.

[0014] According to one specific embodiment, the second cap is mechanically assembled to the first cap by means of a layer of glue or adhesive.

[0015] According to one specific embodiment, the second cap is overmolded onto the first cap.

[0016] According to one embodiment, the substrate includes a plurality of metal pads, for each metal pad a solder joint is soldered, and the solder joint is soldered to at least one of the walls of the recessed portion.

[0017] According to one specific embodiment, the cap covers at least 80%, preferably at least 90%, and even more preferably at least 95% of the surface area of ​​the first surface of the substrate.

[0018] In one embodiment, a method of manufacturing an electronic circuit includes: disposing a first electromagnetic shielding cap on a first main surface of a substrate; and assembling the first cap and the substrate together by means of one or more solder points, each solder point being disposed in a recess and soldered to a metal pad and to at least one wall of the recess.

[0019] According to one embodiment, the method further includes the steps of assembling a second cap (preferably made of a polymer material) onto a first main surface of a first substrate via glue beads, and assembling the first cap onto the second cap by means of a layer of glue or adhesive.

[0020] According to one specific embodiment, before setting the first electromagnetic shielding cap, a second cap made of polymer material is overmolded onto the first cap.

[0021] According to one specific embodiment, the assembly is performed via solder projection.

[0022] In one embodiment, an electromagnetic shielding cap for electronic circuits (e.g., made of a metal selected from stainless steel or copper) includes a main surface and four side surfaces, with a recessed portion formed at the base of a first side surface, preferably with the height of the first side surface being less than the height of the other side surfaces.

[0023] According to one aspect, an electronic circuit is provided, comprising: a substrate having a first main surface including at least one metal pad; a chip bonded to the first main surface of the substrate; a first cap forming an electromagnetic shielding cap; and a second cap stacked and disposed on the first main surface of the substrate; wherein the first cap includes a main surface and four side surfaces; wherein the first side surface of the four side surfaces includes a recessed portion formed by an open cavity located in and at a base of the first side surface; and solder joints disposed in the recessed portion, which are soldered to the metal pads and to at least one wall of the recessed portion, the solder joints being configured to assemble the first cap and the substrate to each other.

[0024] According to one embodiment, the electronic circuit includes optical transmitting and / or receiving devices.

[0025] According to one embodiment, the first cap is made of metal and the second cap is made of polymer material.

[0026] According to one embodiment, at least one of the four side surfaces of the cap has a greater height than the first side surface and is configured to cover one side of the substrate.

[0027] According to one embodiment, the other three of the four side surfaces have a greater height than the first side surface and are configured to cover the corresponding side surfaces of the substrate.

[0028] According to one embodiment, the second cap is disposed between the chip and the first cap.

[0029] According to one embodiment, the second cap is mechanically assembled to the first cap by a layer of glue or adhesive.

[0030] According to one embodiment, the second cap is overmolded onto the first cap.

[0031] According to one embodiment, the substrate includes a plurality of metal pads, wherein a solder joint is soldered to each metal pad, and the solder joint is soldered to at least one wall of the recessed portion.

[0032] According to one embodiment, the cap covers at least 80% of the surface area of ​​the first surface of the substrate.

[0033] According to another aspect, an electromagnetic shielding cap for electronic circuits is provided, comprising: a main surface; and four side surfaces; wherein a first side surface of the four side surfaces includes a recessed portion formed by an open cavity located in and at the base of the first side surface; and wherein the height of the first side surface is less than the height of the other side surfaces of the four side surfaces.

[0034] According to one embodiment, the electromagnetic shielding cap is made of a metal selected from stainless steel and copper. Attached Figure Description

[0035] The foregoing features and advantages, as well as other features and advantages, will be described in detail with reference to the accompanying drawings in the remainder of the disclosure of specific embodiments given by way of illustration and not limitation, wherein:

[0036] Figure 1 A schematic cross-section and top view of the electronic circuit are shown.

[0037] Figure 2 A schematic cross-sectional and side view of the electronic circuit are shown.

[0038] Figure 3 A schematic cross-sectional and side view of the electronic circuit are shown.

[0039] Figure 4 A schematic cross-sectional and side view of the electronic circuit are shown.

[0040] Figure 5 A portion of an electronic circuit is schematically shown in three dimensions; and

[0041] Figure 6 and Figure 7 These are photographic views of a portion of the substrate and a portion of the recessed portion of the electronic circuit cap, before and after jet soldering, respectively. Detailed Implementation

[0042] To make the accompanying drawings more readable, the various components are not necessarily drawn to the same scale.

[0043] Similar features are indicated by similar reference numerals in the various figures. In particular, common structural and / or functional features among the various embodiments may have the same reference numerals and may have the same structure, dimensions, and material properties.

[0044] For clarity, only the steps and elements useful for understanding the described embodiments are shown and described in detail.

[0045] Unless otherwise stated, when referring to two elements connected together, it means a direct connection without any intermediate elements other than the conductor, while when referring to two elements coupled together, it means that the two elements can be connected or they can be coupled via one or more other elements.

[0046] In the following description, when referring to absolute position qualifiers (such as “front,” “back,” “top,” “bottom,” “left,” “right,” etc.) or relative position qualifiers (such as “top,” “bottom,” “up,” “down,” etc.) or orientation qualifiers (such as “horizontal,” “vertical,” etc.), the orientation of the accompanying drawings shall be indicated unless otherwise stated.

[0047] Unless otherwise stated, the expressions “approximately,” “around,” “substantially,” and “around” indicate addition or subtraction of 10% or 10°, preferably 5% or 5°.

[0048] Between X and Y, it means that the limits X and Y are included in the range of values.

[0049] Radio frequency waves refer to electromagnetic waves with frequencies between 3 kHz and 3000 GHz, more specifically between 3 kHz and 6 GHz, and even more specifically between 100 kHz and 6 GHz.

[0050] Reference Figures 1 to 5 Describe in detail the various components of an electronic circuit.

[0051] The electronic circuit includes a support substrate 300 on which an electronic chip 350 is disposed, a first electromagnetic shielding cap 100, and a second cap 200 made of polymer material. Both the first cap 100 and the second cap 200 are disposed on the support substrate 300 to protect the chip 350.

[0052] The first cap 100 and the second cap 200 are stacked on top of each other. The first cap 100 can be positioned above or below the second cap 200.

[0053] The support substrate 300 (also referred to as a substrate or support member) includes a first main surface 301 (front surface), a second main surface 302 (rear surface) substantially parallel to the first main surface 301, and side flanks 303. The side flanks 303 extend from the first main surface 301 to the second main surface 302. The outline of the support substrate is, for example, square or rectangular.

[0054] The peripheral region of the first surface 301 of the support substrate 300 is covered by at least one pad 310. Preferably, the peripheral region is covered by multiple pads 310.

[0055] The metal pad 310 can be set back from the edge of the substrate 300. Figure 1) or arranged on the edge of the substrate ( Figures 1 to 5 ).

[0056] To bond the cap 100 to both sides of the substrate 300, metal pads 310 may be arranged on both sides of the first surface. Preferably, the metal pads 310 are arranged on the same side of the first surface 301.

[0057] The pads 310 are made of components that can be wetted with solder material to assemble the substrate 300 to the first cap 100. The pads 310 are made of metal or metal alloy. Metal pads 310 are made of copper, for example.

[0058] The support substrate 300 is made of a dielectric material. It includes electrical connections (not shown) extending from the first main surface 301 to the second main surface 302.

[0059] The substrate 300 is an interconnect substrate that enables electronic circuits to be connected to external devices or to a PCB (printed circuit board) type substrate.

[0060] The rear surface 302 of the support substrate 300 may be provided with electrical connection pads to connect electronic circuits to external components.

[0061] An electronic integrated circuit (IC) chip 350 (referred to as chip) 350 is disposed on a support 300 and more specifically mounted on a first main surface 301 of the support substrate 300. For example, it is mounted on the central portion of the substrate 300.

[0062] Chip 350 is electrically coupled to the electrical connection network of support substrate 300 via elements such as wires or balls that ensure electrical connection. An adhesive layer (not shown) may be placed between the front surface 301 of support substrate 300 and the rear surface of electronic chip 350.

[0063] According to one embodiment, chip 350 includes an optical transmitting (light emitting) portion 357 and an optical receiving (light receiving) portion 358.

[0064] The light emitting section 357 is configured to transmit an optical signal, while the light receiving section 358 is configured to detect the incident optical signal. The light emitting section 357 and the light receiving section 358 are designed to cooperate in such a way that distance is measured by the time of flight of the optical signal after it is transmitted, reflected, and then incident.

[0065] Alternatively, two chips can be used: one is a light-emitting chip configured to transmit light signals, and the other is a light-receiving chip configured to detect incident light signals.

[0066] The first cap 100 serves as electromagnetic shielding, particularly radio frequency shielding. The first cap 100 is preferably a metal cap, for example, made of stainless steel or copper. Stainless steel, for example, is SUS430 or SUS 316L stainless steel. The first cap 100 may be nickel-plated (i.e., stainless steel or copper coated with nickel).

[0067] The first cap 100 includes a main surface 101 (also called the front surface or upper surface) and four side surfaces (first side surface 102, second side surface 103, third side surface 104, and fourth side surface 105). The third side surface 104 of the cap is opposite to the first side surface 102.

[0068] Side surfaces 102, 103, 104, and 105 each have a base (also called a foot) and a vertex. The vertex is located on one side of the main surface 101. The base is positioned opposite the vertex.

[0069] The first side surface 102 has a recessed portion 110 at its base. This portion 110 is recessed relative to the first side surface 102.

[0070] The recessed portion 110 includes a first wall 111 (or main wall) parallel to the first side surface 102 of the first cap 100, two side walls 112 and 113, and a top wall 114. The side walls 112 and 113 of the recessed portion 110 may be perpendicular to the first wall 111 or inclined relative to the first wall 111. When the first cap 100 is assembled to the substrate 300, the first surface 301 of the substrate 300 forms the bottom wall of the cavity 110. The base of the first side surface 102 is pressed against the substrate 300.

[0071] The recessed portion 110 forms an open cavity having an opening at the first side surface 102. The recessed portion 110 is a portion recessed into the cap 100; the recessed portion 110 does not form a through hole extending through the first side surface 102 of the first cap 100.

[0072] The first cap 100 may have two recessed portions, one on the first side surface 102 and one on the third side surface 104, for example, as shown in portion 110.

[0073] The shape and size of the recess 110 depend on the shape and size of one or more solder joints 400. The recess 110 is configured to accommodate one or more solder joints 400. Each pad 310 has one solder joint 400. For example, there are two solder joints 400 in the recess 110.

[0074] By placing the solder joint 400 in the recessed portion 110, the bending effect of the substrate 300 is limited or even eliminated, which would affect the mechanical strength of the solder joint 400 (and in particular may cause the solder joint 400 to break).

[0075] At least a portion of the surface of each pad 310 is disposed in the recessed portion 110. According to a first variant, only a portion of the surface of each pad 310 is disposed in the recessed portion 110. Figure 1 According to the second variant, the entire surface of each pad 310 ( Figures 2 to 5 It is set in the recessed portion 110.

[0076] Once assembled, at least 80%, preferably at least 90%, and even more preferably at least 95% of the surface area of ​​the first surface 301 of the substrate 300 is covered by the first cap 100. Therefore, the portion of the substrate 300 not covered by electromagnetic shielding is very small, which improves the performance of the electronic circuit. This electronic circuit exhibits good mechanical strength not only during the final testing performed at the end of manufacturing but also during its operation.

[0077] The first side surface 102 has a first height. The second side surface 103, the third side surface 104, and the fourth side surface 105 have second, third, and fourth heights, respectively. The first height is less than at least one of the second, third, and fourth heights. Preferably, the first height is less than the second, third, and fourth heights. Therefore, during the placement of the cap 100 on the substrate 300, the second side surface 103, the third side surface 104, and the fourth side surface 105 cover the side surface 303 of the supporting substrate 300. The resulting electromagnetic shielding is particularly efficient.

[0078] Preferably, the side surfaces 103, 104, 105 cover at least 50%, more preferably at least 80%, and even more preferably the entire height of the side surface 303 of the substrate 300.

[0079] The first cap 100 may include transparent elements, such as those made of glass, like lenses or filters, positioned opposite the light transmitting / receiving regions 357 and 358 of the chip 350. The transparent elements of the inner cap are stacked onto the transparent elements of the outer cap 200.

[0080] Optical filters can be configured to be selectively transparent for a given wavelength range, typically including the wavelengths of signals transmitted by the light-emitting section 357, such as infrared.

[0081] The first cap 100 can be manufactured by stamping.

[0082] In addition to the first cap 100a, the electronic circuit also includes a second cap 200.

[0083] according to Figures 1 to 3 In the first embodiment shown, the second cap 200 is disposed between the chip 350 and the first cap 100. The first cap 100 covers the second cap 200.

[0084] According to this first embodiment, the first cap 100 is an outer cap and the second cap 200 is an inner cap.

[0085] The first cap 200 forms a cavity to accommodate the chip 350.

[0086] The inner cap 200 includes a main surface 201 (also called the front surface or upper surface) and a side surface.

[0087] The inner cap 200 has a profile lower than that of the supporting substrate 300. The feet on the side surface of the second cap 200 are mechanically assembled to the first surface 301 of the substrate 300. This assembly can be performed by means of a bead of glue.

[0088] The inner cap 200 may include one or more inner walls 206 in the form of plates (e.g., such as...). Figure 3 (As shown in the diagram). The inner wall 206 is opaque.

[0089] One or more walls 206 separate the optical transmission / reception areas 357, 358 from the chip 350.

[0090] The upper surface of the inner cap 200 is mechanically assembled to the outer cap 100 by a layer 500, such as glue or adhesive (e.g., ...). Figures 1 to 3 (as shown in the image).

[0091] According to this embodiment, the second cap 200 can be made of epoxy resin.

[0092] According to the second embodiment, such as Figures 4 to 6 As shown, the first cap 100 is disposed between the second cap 200 and the chip 350.

[0093] According to this second embodiment, the first cap 100 is an inner cap and the second cap 200 is an outer cap.

[0094] The second cap 200 covers the first cap 100, except for the recessed portion 110. Therefore, the recessed portion 110 is free. The recessed portion 110 is accessible to enable assembly of the first cap 100 with the substrate 100. The second cap 200 has a through opening at the recessed portion 110 of the first cap 100.

[0095] The second cap 200 can be overmolded onto the first cap 100. It is made of, for example, a thermosetting resin. For example, it can be epoxy resin. The first cap 100 and the second cap 200 form a monoblock.

[0096] According to these two embodiments, the second cap 200 may include transparent elements, such as those made of glass, such as lenses or filters, positioned opposite the optical transmitting / receiving areas 357, 358 of the chip 350.

[0097] Optical filters can be configured to be selectively transparent for a given wavelength range, typically including the wavelengths of signals transmitted by the light-emitting section 357, such as infrared.

[0098] For these different variations and embodiments, the support substrate 300 and the first cap 100 are mechanically assembled by means of solder joints 400.

[0099] More specifically, the assembly stage includes: a first step of placing the first cap 100 in contact with the support substrate 300, and more specifically in contact with the first surface 301 of the support substrate 300, which is used as a bearing surface; and a second step of bonding the first cap 100 to the support substrate 300.

[0100] The bonding is performed by means of a soldering step. Solder material can be deposited using any solder paste dispensing technique. Preferably, the soldering is performed by jet soldering, during which solder balls are sprayed.

[0101] To bond the cap 100 to the substrate 300, a ball made of (molten) solder material is projected onto the surface to be assembled (in this case, the contact area between the connecting pad 310 supporting the substrate 300 and one of the walls of the recessed portion 110), and a solder joint 400 is formed during the cooling of the solder material. The pad 310 is disposed on the substrate 300, thereby contacting the base of the main wall 111.

[0102] During welding, the main wall 111 is wetted by welding balls.

[0103] The recess allows for the restriction of solder propagation. The first surface of the first side surface 102 is not wetted by the solder joint 400. The resulting solder joint 400 has a good volume to surface area ratio. The mechanical strength of the solder joint 400 is improved over time.

[0104] On one side of the support substrate 300, the extension of the solder joint 400 is defined by the surface of the solder pad 310, which is accessible from the recessed portion 110.

[0105] For example, for a connection pad with a surface area of ​​250μm×180μm or 250μm×250μm, the ball diameter is 250μm.

[0106] The ball is made of solder material (or solderable material), preferably selected from tin and tin alloys, such as SnAg, SnAgCu (SAC), for example.

[0107] As a non-limiting illustration, Figure 6The electronic circuitry of the outer cap 200 is shown. The cap 200 has an opening that allows for soldering between the underlying metal and the metal pads 310 of the substrate 300. Soldering is performed by solder projection. The resulting solder joint 400 exhibits good mechanical strength. Figure 7 ).

[0108] Using this method, there is no need to perform an additional thermal annealing step.

[0109] This method is simple to implement and inexpensive.

[0110] The obtained electronic circuit has good mechanical strength and efficient electromagnetic shielding.

[0111] Specifically, the electronic circuit is a light transmitting and / or receiving electronic circuit, and more specifically, a time-of-flight (TOF) measuring device. The light emitting section 357 is configured to transmit a light signal. The signal exits from the inner cap 200 and the outer cap 100. The photosensitive reference surface of the light receiving section 358 immediately detects the emitted signal transmitted by the light emitting section 357, thereby defining the signal transmission time. The emitted signal is intended to be reflected or scattered on elements outside the outer cap 100. The reflected or scattered signal is directed to the photosensitive detection section 358. Therefore, the light receiving section 358 detects the reception time of the reflected signal, and the time elapsed between the transmission time and the reception time is proportional to the distance between the TOF device and an external object.

[0112] This type of electronic circuit is particularly useful in the field of mobile phones. It also has applications in other industrial sectors.

[0113] For example, this device is designed for use in the automotive industry.

[0114] This device can be used, for example, in industrial applications.

[0115] This device can also be used in the Internet of Things and smart home fields.

[0116] It can be used in Near Field Communication (NFC).

[0117] The device can also be used in the implementation of 5G networks, data centers, and servers.

[0118] For example, the device is intended for use in personal electronic devices, 5G connected devices, or more generally connected devices.

[0119] For example, the device is intended for use in communication equipment or computers and peripherals.

[0120] Various embodiments and variations have been described above. Those skilled in the art will understand that certain features of these various embodiments and variations can be combined, and other variations will become apparent to them.

[0121] Finally, based on the instructions given above, the actual implementation of the described embodiments and variations is within the capabilities of those skilled in the art.

Claims

1. An electronic circuit, comprising: A substrate having a first main surface including at least one metal pad; The chip is bonded to the first main surface of the substrate; The first cap forms an electromagnetic shielding cap; as well as The second cap is stacked and disposed on the first main surface of the substrate; The first cap includes a main surface and four side surfaces; The first of the four side surfaces includes a recessed portion formed by an open cavity located in and at the base of the first side surface; Solder joints, disposed in the recessed portion, are soldered to metal pads and to at least one wall of the recessed portion, said solder joints being configured to assemble the first cap and the substrate to each other.

2. The electronic circuit according to claim 1, wherein the electronic circuit includes optical transmitting and / or receiving devices.

3. The electronic circuit of claim 1, wherein the first cap is made of metal and the second cap is made of polymer material.

4. The electronic circuit of claim 1, wherein at least one of the four side surfaces of the cap has a height greater than that of the first side surface and is configured to cover one side of the substrate.

5. The electronic circuit of claim 1, wherein the other three of the four side surfaces have a greater height than the first side surface and are configured to cover the respective sides of the substrate.

6. The electronic circuit according to claim 1, wherein the second cap is disposed between the chip and the first cap.

7. The electronic circuit of claim 6, wherein the second cap is mechanically assembled to the first cap by a layer of glue or adhesive.

8. The electronic circuit of claim 1, wherein the second cap is overmolded onto the first cap.

9. The electronic circuit of claim 1, wherein the substrate comprises a plurality of metal pads, and wherein a solder joint is soldered to each metal pad, and the solder joint is soldered to at least one wall of the recessed portion.

10. The electronic circuit of claim 1, wherein the cap covers at least 80% of the surface area of ​​the first surface of the substrate.

11. An electromagnetic shielding cap for electronic circuits, comprising: Main surface; as well as Four side surfaces; The first of the four side surfaces includes a recessed portion formed by an open cavity located in and at the base of the first side surface; and The height of the first side surface is less than the height of the other four side surfaces.

12. The electromagnetic shielding cap according to claim 11, wherein the electromagnetic shielding cap is made of a metal selected from the group consisting of stainless steel and copper.

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