Electromagnetic shielding cap for electronic circuit and electronic circuit

Abstract

This disclosure relates to an electromagnetic shielding cap for electronic circuits and the electronic circuit itself. An electromagnetic shielding cap for an electronic circuit includes: a main surface and four side surfaces; wherein a first side surface of the four side surfaces has at least one solder area at its base; and wherein each solder area is defined by a plurality of openings in the first side surface. An electronic circuit includes: a substrate; a chip bonded to a first main surface of the substrate; and an electromagnetic shielding cap including: a main surface and four side surfaces; wherein a first side surface of the four side surfaces has at least one solder area at its base; and wherein each solder area is defined by a plurality of openings; wherein the first main surface of the substrate is partially covered by metal pads; wherein the cap and the substrate are assembled to each other by solder joints; and wherein each solder joint is soldered to one of the metal pads of the substrate and to one of the solder areas of the cap.

Description

[0001] Priority requirements

[0002] This application claims priority to French patent application No. FR2405583, 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 electronic chips housed in a package. This package typically includes a support portion to which the chip is bonded, and a cover portion to which the chip is covered. 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 elements that are transparent to the optical signal wavelength and are opposite to the transmitting / receiving areas, and inner walls that define two cavities, one for the transmitting area and the other for the receiving area.

[0006] Such electronic circuits are used, for example, to form 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 support substrate via a bead of glue.

[0008] However, several drawbacks exist due to the difficulty in calibrating the adhesive beads. For the bonding material, there is a risk of it flowing inside the cap via 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 for an electromagnetic shielding cap that can be easily assembled into an electronic circuit to protect it from electromagnetic waves, and a method for assembling the electronic circuit that implements the cap, wherein the resulting cap exhibits good mechanical strength. Utility Model Content

[0010] In one embodiment, an electromagnetic shielding cap for electronic circuits includes a main surface and four side surfaces, the first side surface having a soldering area at its base, each soldering area being defined by a plurality of openings.

[0011] According to one embodiment, each welding area is defined by three openings, which are formed by a top opening and two side openings, the side openings being perpendicular to the top opening and perpendicular to the base of the first side surface.

[0012] According to one specific embodiment, the height of the first side surface is less than the height of the other side surfaces.

[0013] According to one embodiment, the cap is made of metal, preferably stainless steel or copper.

[0014] In one embodiment, a method of manufacturing an electromagnetic shielding cap (such as those previously defined) for electronic circuits includes forming an opening in the cap by stamping.

[0015] In one embodiment, an electronic circuit (particularly an optical transmitting and / or receiving circuit) includes a chip attached to a first main surface of a substrate and an electromagnetic shielding cap (such as as defined above), the first main surface of the substrate being partially covered by metal pads, the cap being assembled to the substrate by means of solder joints, each solder joint being soldered to one of the metal pads of the substrate and to one of the solder areas of the cap.

[0016] According to one embodiment, at least one of the other side surfaces of the cap covers one of the side surfaces of the substrate, preferably, wherein each of the other three side surfaces covers one of the side surfaces of the substrate.

[0017] According to one embodiment, an additional cap made of polymer material is disposed on a first surface of a substrate and covered by an electromagnetic shielding cap, the additional cap defining a cavity in which a chip is disposed, and the electromagnetic shielding cap being bonded to the additional cap by means of an adhesive layer.

[0018] According to one specific embodiment, the surface area ratio between the welded areas and the metal pads is approximately 1.

[0019] According to one specific embodiment, the cap covers at least 80%, preferably at least 90%, of the surface area of ​​the first main surface of the substrate.

[0020] In one embodiment, a method of manufacturing an electronic circuit (such as, as previously defined) includes: disposing an electromagnetic shielding cap (such as, as previously defined) for the electronic circuit on a first main surface of a substrate, arranging a chip on the first main surface of the substrate, the periphery of the first main surface of the substrate being partially covered by metal pads, the cap being configured such that a soldering area is arranged at the level of the metal pads of the substrate; and performing soldering to form solder joints, each solder joint being soldered to one of the metal pads of the substrate and to one of the soldering areas of the cap.

[0021] According to one specific embodiment, the welding step is performed by solder ball spraying.

[0022] According to one aspect of this disclosure, 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 has at least one soldering area at its base; and wherein each soldering area is defined by a plurality of openings in the first side surface.

[0023] According to one embodiment, each welding area is defined by three openings, including a top opening located above the welding area and two lateral openings located on opposite sides of the welding area, wherein the two lateral openings have a length perpendicular to the length of the top opening and extending perpendicularly to the base of the first side surface, and wherein the length of the top opening extends parallel to the base of the first side surface.

[0024] According to one specific embodiment, the height of the first side surface is less than the height of the other side surfaces among the four side surfaces.

[0025] According to one specific embodiment, the cap is made of metal.

[0026] According to one specific embodiment, the metal used for the cap is stainless steel.

[0027] According to one specific embodiment, the metal used for the cap is copper.

[0028] According to another aspect of this disclosure, an electronic circuit is provided, comprising: a substrate; a chip bonded to a first main surface of the substrate; and an electromagnetic shielding cap including: a main surface and four side surfaces; wherein the first side surface of the four side surfaces has at least one solder area at its base; and wherein each solder area is defined by a plurality of openings; wherein the first main surface of the substrate is partially covered by metal pads; wherein the cap and the substrate are assembled to each other by solder joints; and wherein each solder joint is soldered to one of the metal pads of the substrate and to one of the solder areas of the cap.

[0029] According to one specific embodiment, the electronic circuit is an optical transmitting and / or receiving circuit.

[0030] According to one embodiment, at least one of the four side surfaces of the cap covers one side of the substrate.

[0031] According to one specific embodiment, three of the other three side surfaces of the cap cover three corresponding side surfaces of the substrate.

[0032] According to one embodiment, the electronic circuit further includes an additional cap made of polymer material disposed on a first surface of the substrate, wherein the additional cap is covered by an electromagnetic shielding cap, the additional cap defining a cavity in which the chip is disposed, and wherein the electromagnetic shielding cap is configured to be bonded to the additional cap by an adhesive layer.

[0033] According to one specific embodiment, the surface area ratio between the welded areas and the metal pads is approximately 1.

[0034] According to one specific embodiment, the cap covers at least 80% of the surface area of ​​the first main surface of the substrate.

[0035] According to one embodiment, each welding area is defined by three openings, including a top opening located above the welding area and two lateral openings located on opposite sides of the welding area, wherein the two lateral openings have a length perpendicular to the length of the top opening and extending perpendicularly to the base of the first side surface, and wherein the length of the top opening extends parallel to the base of the first side surface. Attached Figure Description

[0036] The foregoing features and advantages, as well as other features and advantages, will be described in detail with reference to the accompanying drawings, which are given by way of illustration and not limitation:

[0037] Figure 1 The electronic circuit is shown in an exploded diagram;

[0038] Figure 2 A portion of the electronic circuit is shown in three dimensions;

[0039] Figure 3 A portion of the electronic device is shown in a front view; and

[0040] Figure 4A and Figure 4B The solder joints of the electronic circuit are shown schematically and in a front view. Detailed Implementation

[0041] To make the accompanying drawings more readable, the various components are not necessarily drawn to the same scale.

[0042] 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.

[0043] For clarity, only the steps and elements useful for understanding the described embodiments are shown and described in detail.

[0044] 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.

[0045] 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.

[0046] Unless otherwise stated, the expressions “approximately,” “around,” “substantially,” and “around” indicate addition or subtraction of 10% or 10°, preferably 5% or 5°.

[0047] Between X and Y, it means that the limits X and Y are included in the range of values.

[0048] 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.

[0049] Reference Figure 1 , Figure 2 and Figure 3 Describe in detail the various components of an electronic circuit.

[0050] The electronic circuit includes a support substrate 300 on which an electronic chip 350 is disposed, a first cap (referred to as the outer cap) 100, and a second cap (referred to as the inner cap) 200. The outer cap 100 covers the inner cap 200. The outer cap 100 serves as electromagnetic shielding, particularly radio frequency shielding.

[0051] 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, 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.

[0052] A portion of the periphery of the first surface 301 of the support substrate 300 is covered by metal pads 310, which are intended for assembly with the outer cap 100. The metal pads 310 may be arranged on both sides of the first surface 301 to bond the cap 100 to both sides of the substrate 300. Preferably, the metal pads 310 are arranged on the same side of the first surface 301.

[0053] The metal pad 310 is made of metal or a metal alloy. For example, the metal pad 310 is made of copper.

[0054] 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.

[0055] Substrate 300 is an interconnect substrate that enables electronic circuitry to be coupled to external devices or to a printed circuit board (PCB) type substrate.

[0056] The rear surface 302 of the support substrate 300 may be provided with electrical metal pads to connect the electronic package to external components.

[0057] An electronic integrated circuit (IC) chip 350 (referred to as chip) 350 is disposed on a substrate 300 and more specifically mounted on a first main surface 301 of the supporting substrate 300. For example, it is mounted on the central portion of the support 300.

[0058] 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.

[0059] According to one embodiment, chip 350 includes an optical transmitting (light emitting) portion 357 and an optical receiving (light receiving) portion 358.

[0060] 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 transmitted and then incident optical signal after reflection.

[0061] 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.

[0062] The electronic circuit includes an inner cap 200, which is located above and positioned at a distance from the chip 350, parallel to the support substrate 300. The inner cap 200 includes a main surface (also referred to as the front surface or top surface) and side surfaces. The chip is housed within the inner cap 200.

[0063] The inner cap 200 has a profile lower than that of the supporting substrate 300. Feet on its side surface are mechanically assembled to the first surface 301 of the substrate 300. Assembly can be performed by means of adhesives or glue.

[0064] The inner cap 200 includes one or more inner walls in the form of plates. These walls are opaque.

[0065] One or more inner walls separate the optical transmitting / receiving areas 357, 358 from the chip 350.

[0066] The inner 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.

[0067] 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.

[0068] The inner cap 200 is made of a polymer material, for example, a thermosetting resin. For example, it is epoxy resin.

[0069] The upper surface of the inner cap 200 is mechanically assembled to the outer cap 100, for example, by a layer 500 of glue or adhesive disposed between the two caps 100, 200.

[0070] The outer 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).

[0071] The outer cap 100 includes a chamber that defines free space to accommodate the inner cap 200.

[0072] The outer cap 100 may include transparent elements, such as those made of glass, like lenses or filters, positioned opposite the light transmitting / receiving regions 357, 358 of the chip 350. The transparent elements of the inner cap 100 are stacked on top of the transparent elements of the outer cap 200.

[0073] 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.

[0074] The outer cap 100 is a metal cap. For example, it is made of stainless steel or copper. Stainless steel can be made of SUS 430 or SUS 316L. The stainless steel or copper outer cap 100 can be nickel-plated (i.e., coated with nickel).

[0075] In one embodiment, the welding area 110 is a region located in the side surface of the cap 100.

[0076] The first side surface 102 has a welding area 110 at its base (also referred to as the foot). Each welding area is defined by a plurality of openings 120. There are at least two openings, for example, three openings in a preferred embodiment.

[0077] An opening means a through-hole. In other words, the opening extends through the entire thickness of the first side surface 102.

[0078] The opening preferably has an elongated shape, that is, a length / width ratio greater than 2 and preferably greater than 4.

[0079] like Figure 4A and Figure 4B As shown, the openings 120 can have different shapes. For example, they can be rectangular. Figure 4A ) or oval ( Figure 4B ).

[0080] The openings 120 can have the same or different shapes. Preferably, they are exactly the same.

[0081] Preferably, each weld area 110 is defined by three openings 120: two lateral openings and a top opening. The lateral openings may be shared by two weld areas 110 and have a length perpendicular to the base of the first surface 102. The two lateral openings of the weld area 110 are parallel to each other. The top opening has a length perpendicular to the length of the lateral openings and is parallel to the base of the first surface 102.

[0082] The outer cap 100 has at least one welding area 110, preferably at least two welding areas 110. For example, it has four welding areas.

[0083] The welding zones 110 are preferably formed on a single side surface of the cap 100. They can be provided on two opposing side surfaces, particularly on the first surface 102 and the third surface 104.

[0084] The surface area of ​​the welding area 110 is preferably the same as the surface area of ​​the metal pad 310 on the support substrate 300.

[0085] 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 outer cap 100.

[0086] 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 lower than at least one of the second, third, and fourth heights. Preferably, the first height is lower 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 electromagnetic shielding thus obtained has particularly high performance.

[0087] Preferably, the side surfaces 103, 104, and 105 cover at least 50% of the height of the side surface 303 of the substrate 300, more preferably at least 80% of the height, and even more preferably the entire height.

[0088] This electromagnetic shielding cap can be manufactured by a method including a stamping step, during which an opening 120 is formed by perforating the cap 100.

[0089] The support substrate 300 and the outer cap 100 are mechanically assembled via solder joints 400.

[0090] More specifically, the assembly stage includes: placing the cap 100 in contact with the support substrate 300, more specifically in contact with a first surface 301 of the support substrate 300, the first surface serving as a bearing surface, and attaching the cap 100 to the support substrate 300.

[0091] The joining is performed by means of a welding step. Preferably, the welding is spray welding, in which solder ball spraying is performed. In order to join the cap 100 to the substrate 300, balls made of solder material (in a molten state) are sprayed onto the surface to be assembled (here, at the contact area between the metal pads 310 supporting the substrate 300 and the welding area 110), and solder joints 400 are formed during the cooling of the solder material.

[0092] After soldering, each solder joint 400 contacts the soldering area 110 and the cap 100 on one hand, and the metal pad 310 of the substrate 300 on the other hand.

[0093] During soldering, the soldering area 110 of the outer cap 100 is wetted by solder balls. Lateral openings 310 allow for lateral limitation of solder material propagation (and prevent short circuits between solder joints). Top opening 310 limits the propagation of solder material 400 towards the top of the outer cap 300. The resulting solder joint 400 has a good surface area to volume ratio of the soldered area 110 covered by the solder joint. The resulting solder joint 400 has a good surface area to volume ratio of the pads 310 of the support substrate 300 covered by the solder joint. The mechanical strength of the solder joint 400 over time is improved.

[0094] On this side of the support substrate 300, the extension of the solder joint 400 is defined by the solder pad 310.

[0095] For example, for a metal pad with a surface area of ​​250μm×180μm or 250μm×250μm, the ball diameter is 250μm.

[0096] The ball is made of solder material (or solderable material), preferably selected from tin and tin alloys, such as SnAg, SnAgCu (denoted as SAC).

[0097] Using this method, no additional heat annealing step is required.

[0098] This method is simple to implement and inexpensive.

[0099] The resulting electronic circuit has good mechanical strength and efficient electromagnetic shielding.

[0100] Specifically, this electronic circuit is a light transmitting and / or receiving electronic circuit, and particularly a Time-of-Flight (TOF) measurement 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.

[0101] This electronic circuit is particularly used in the mobile phone industry. It also has applications in other industrial sectors.

[0102] For example, this device is designed for use in the automotive industry.

[0103] This device can be used, for example, in industrial applications.

[0104] This device can also be used in the Internet of Things and smart home fields.

[0105] It can be used in Near Field Communication (NFC).

[0106] The device can also be used in the implementation of 5G networks, data centers, and servers.

[0107] For example, the device is intended for use in personal electronic devices, 5G-connected devices, or more generally connected devices.

[0108] For example, the device is intended for use in communication equipment or computers and peripherals.

[0109] 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.

[0110] 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 electromagnetic shielding cap for electronic circuits, comprising: Main surface and four side surfaces; The first of the four side surfaces has at least one welded area at its base; as well as Each weld zone is defined by multiple openings in the first side surface.

2. The cap of claim 1, wherein each welding area is defined by three openings, including a top opening above the welding area and two lateral openings on opposite sides of the welding area, wherein the two lateral openings have a length perpendicular to the length of the top opening and extending perpendicularly to the base of the first side surface, and wherein the length of the top opening extends parallel to the base of the first side surface.

3. The electromagnetic shielding cap according to claim 1, wherein the height of the first side surface is less than the height of the other side surfaces among the four side surfaces.

4. The electromagnetic shielding cap according to claim 1, wherein the cap is made of metal.

5. The electromagnetic shielding cap according to claim 4, wherein the metal used for the cap is stainless steel.

6. The electromagnetic shielding cap according to claim 4, wherein the metal used for the cap is copper.

7. An electronic circuit, comprising: substrate; The chip is bonded to the first main surface of the substrate; as well as Electromagnetic shielding cap, the electromagnetic shielding cap comprising: Main surface and four side surfaces; The first of the four side surfaces has at least one welded area at its base; and Each welding zone is defined by multiple openings; The first main surface of the substrate is partially covered by metal pads; The cap and the substrate are assembled together by solder joints; and Each solder joint is soldered to one of the metal pads on the substrate and to one of the soldering areas on the cap.

8. The electronic circuit according to claim 7, wherein the electronic circuit is an optical transmitting and / or receiving circuit.

9. The electronic circuit of claim 7, wherein at least one of the other side surfaces of the cap covers one side of the substrate.

10. The electronic circuit of claim 7, wherein three of the other side surfaces of the cap cover three corresponding side surfaces of the substrate.

11. The electronic circuit of claim 7, further comprising an additional cap made of polymer material disposed on a first surface of the substrate, wherein the additional cap is covered by an electromagnetic shielding cap, the additional cap defining a cavity in which the chip is disposed, and wherein the electromagnetic shielding cap is configured to be bonded to the additional cap by an adhesive layer.

12. The electronic circuit of claim 7, wherein the surface area ratio between the soldered areas and the metal pads is approximately 1.

13. The electronic circuit of claim 7, wherein the cap covers at least 80% of the surface area of ​​the first main surface of the substrate.

14. The electronic circuit of claim 7, wherein each soldering area is defined by three openings, including a top opening above the soldering area and two lateral openings on opposite sides of the soldering area, wherein the two lateral openings have a length perpendicular to the length of the top opening and extending perpendicularly to the base of the first side surface, and wherein the length of the top opening extends parallel to the base of the first side surface.

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