Metal perimeter EMC and ENV frame between pcbs

Abstract

An electronic assembly includes a first printed circuit board (PCB) with a first ground layer and a second PCB with a second ground layer, separated by a gap. A metal frame resides in the gap, featuring an upper surface facing the first PCB and a lower surface facing the second PCB. The assembly incorporates a first electrically-conductive seal on the upper surface contacting the first ground layer and a second electrically-conductive seal on the lower surface contacting the second ground layer. In some embodiments, the metal frame extends about or adjacent to the perimeters of the two PCBs. In other embodiments, the metal frame is a local metal frame, partially surrounding a connector.

Description

METAL PERIMETER EMC AND ENV FRAME BETWEEN PCBSTECHNICAL FIELD

[0001] The present disclosure relates to an electromagnetic compatibility (EMC) frame disposed between, and connected to, two printed circuit boards (PCBs).BACKGROUND OF THE INVENTION

[0002] Electronic systems often require effective shielding and environmental protection to ensure reliable operation. Traditional methods for shielding multiple components can present challenges, particularly when using certain housings. These housings may not guarantee consistent contact between elements, leading to potential interference and environmental vulnerabilities.

[0003] Existing solutions typically involve various shields and housings to establish contact between different sides. These approaches may not provide adequate protection or flexibility in design, especially in applications requiring reduced packaging, and enhanced thermal performance and tolerance.SUMMARY OF THE INVENTION

[0004] According to an embodiment, an electronic assembly comprises: a first printed circuit board (PCB) having a first ground layer; a second PCB having a second ground layer, wherein the second PCB is spaced from the first PCB defining a gap therebetween; and a metal frame positioned between the first PCB and the second PCB in the gap, the metal frame having an upper surface facing the first PCB and a lower surface facing the second PCB; a first electrically-conductive seal on the upper surface of the frame and contacting the first ground layer; and a second electrically-conductive seal on the lower surface of the frame and contacting the second ground layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a perspective view of an electronic assembly according to a first embodiment.

[0006] FIG. 2 is an exploded perspective view of the electronic assembly of FIG. 1, from a reversed perspective compared to FIG. 1.

[0007] FIG. 3 is a perspective view of the electronic assembly of FIG. 1 with a first housing removed.

[0008] FIG. 4 is a perspective view of the electronic assembly of FIGS. 1-2 with a first printed circuit board (PCB) removed.

[0009] FIG. 5 is a perspective view of a metal frame (also referred to as a metal perimeter frame) of the electronic assembly of FIGS. 1-4, according to an embodiment.

[0010] FIG. 6 is a perspective cross-sectional view of a region of the electronic assembly of FIG. 1.

[0011] FIG. 7 is a perspective view of the metal frame of FIG. 5 with an attached electromagnetic compatibility (EMC) shield, according to an embodiment.

[0012] FIG. 8 is a perspective view of the metal frame of FIG. 5 with an attached spring frame element, according to an embodiment.

[0013] FIG. 9 is a cross-sectional view of another region of the electronic assembly of FIG. 1, according to an embodiment.

[0014] FIG. 10 is a perspective view of an electronic assembly according to a second embodiment.

[0015] FIG. 11 is a perspective view of the electronic assembly of FIG. 10 with a first housing removed.

[0016] FIG. 12 is a perspective view of the electronic assembly of FIGS. 10-11 with a first PCB removed.

[0017] FIGS. 13-14 are perspective views of a metal frame (here referred to as a local metal frame) of the electronic assembly of FIG. 10, according to an embodiment.

[0018] FIG. 15 is a perspective cross-sectional view of a region of the electronic assembly of FIG. 10, according to an embodiment.DETAILED DESCRIPTION OF THE INVENTION

[0019] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.

[0020] Electronic assemblies often require effective shielding and environmental protection to ensure reliable operation. In electronic assemblies, including those with printed circuit boards (PCBs) and connectors, Electromagnet Compatibility (EMC) shielding is crucial for ensuring that electronic devices operate reliably without interfering with one another. EMC shielding refers to protective measures that prevent electromagnetic interference (EMI) from affecting sensitive electronic components or systems. It involves enclosing components, connectors, or entire devices in materials that block electromagnetic waves from entering or leaving the system.

[0021] Traditional shielding methods face several challenges that can limit their effectiveness in modem electronics. One major issue is the bulk and weight of metal shields, which are not suitable for compact, lightweight devices, and can complicate design flexibility. Cost is another significant factor, as high-quality shielding materials and the added complexity of integrating them into the assembly drive up manufacturing expenses. Ensuring consistent contact between shielded components can also be problematic; improper contact or grounding can cause gaps that allow EMI to leak through, reducing shielding effectiveness. Additionally, these gaps can make the systemmore vulnerable to environmental factors like moisture, dust, or corrosion, which could compromise both the shield and the overall system reliability.

[0022] Shielding an electronic assembly having two or more PCBs and connectors can be challenging, especially if the housing of the electrical system is made of aluminum diecast. One particular problem that may arise is galvanic corrosion when the aluminum comes into contact with other metals, especially in the presence of moisture. Galvanic corrosion occurs when two dissimilar metals (e.g., aluminum and steel or copper) are in electrical contact, creating a galvanic cell where the aluminum can corrode over time. This can weaken the housing, compromise its structural integrity, and reduce its ability to provide consistent EMC shielding. Additionally, aluminum’s oxide layer can create challenges with grounding and maintaining consistent electrical contact between components, which is essential for effective shielding. This oxide layer is non- conductive, so if the grounding or contact points are not properly treated or maintained, it can result in poor conductivity, allowing EMI to penetrate the shield or cause grounding issues.

[0023] Therefore according to embodiments described herein, an electronic assembly includes a metal frame (e.g., metal perimeter frame or local metal frame, described more below) sandwiched between two PCBs. The metal frame has electrically-conductive seals that contact ground layers (e.g., exposed copper) on both PCBs. In embodiments, the ground layer can be located about or near a perimeter of the PCBs, and the seals of the metal frame can contact this ground layer about its perimeter, thus providing an EMC shield to prevent emissions between the PCBs from escaping. This metal frame can also provide environmental protection to electronic components between the two PCBs. In other embodiments, the metal frame is local to a connector, and at least partially surrounds the connector, while being sandwiched between the two PCBs. This local metal frame can have its electrically-conductive seals contact corresponding ground layers located at areas of the PCBs surrounding the connector.

[0024] Turning to the Figures, FIGS. 1-9 illustrate an electronic assembly according to a first embodiment, and FIGS. 10-15 illustrate an electronic assembly according to a second embodiment. As will be described, in the first embodiment, the metal frame canbe referred to as a metal perimeter frame in that it defines a perimeter that is located at or near the corresponding perimeters of the two PCBs. In the second embodiment, the metal frame can be referred to as a local metal frame in that it is in a localized region of the electronic assembly, for example surrounding just the connector rather than extending about the perimeters of the PCBs. Unless stated otherwise, it should be understood that characteristics and qualities of the metal frame of one embodiment equally apply to the other embodiment.

[0025] First, referring to the first embodiment illustrated in FIGS. 1-10, an electronics assembly 100 is provided. As shown in FIGS. 1-2, in which FIG. 1 shows the electronics assembly 100 in perspective and FIG. 2 shows the electronics assembly 100 in an exploded perspective view from a reverse perspective, the electronics assembly 100 can include the following general components: a first housing 102, a first PCB 104, a metal frame 106, a second PCB 108, and a second housing 110. FIG. 3 illustrates the electronics assembly 100 with the first housing 102 removed to reveal the first PCB 104 underneath. FIG. 4 illustrates the electronics assembly 100 with the first PCB 104 removed, revealing the metal frame 106 underneath.

[0026] Referring to FIGS. 1-4, the first and second housings 102, 110 can be joined together to encapsulate or otherwise contain the first and second PCBs 104, 108, and the metal frame 106 can be sandwiched between the two PCBs 104, 108. The first housing 102 may be referred to as an upper housing, and the second housing 110 may be referred to as a lower housing, although these housings are not restricted in such an orientation. The first and second housings 102, 110 can be joined together with a plurality of fasteners 112, such as screws, bolts, snap-fit or clip mechanisms, tabs and slots, or the like. These fasteners 112 can be located about the perimeter of the housings 102, 110 and are not limited to the number or location shown in the Figures. Additionally, the first and second housings 102, 110 can be joined together via a rubber or silicone seal 114. Such a seal can provide environmental protection (e.g. against moisture, dust, or EMI).

[0027] The first and second housings 102, 110 can also be formed with various openings to enable various connectors to establish electrical communication with the electrical components contained within the housings. For example, either one or both of the PCBs104, 108 may include or be connected with one or more connectors, some of which are shown generally at 116, 118, and 120. One or more of these connectors can be configured to electrically connect one or more external devices to one or more of the PCBs, or to electrically connect the two PCBs together. The connectors can include, for example, an Ethernet connector (e.g., RJ45) used for network communication, a camera connector (e.g., MIPI / CSI or FFC / FPC) used for interfacing with cameras, a USB connector (Type- A, Type-B, or Type-C) used for USB connection to provide power and data transfer capabilities, a power connector (e.g., barrel jack or Molex) for supplying power to the PCB and / or other components in the assembly, a pin header for connecting the two PCBs together, bus bars, or the like. Of course, the present disclosure is not limited to these types of connectors; others may be used depending on the configuration of the electronic assembly 100. The connectors can also include a power terminal 122 for connecting power sources to the PCB or distributing power between components within the electronic assembly 100.

[0028] The first PCB 104 and the second PCB 108 can be spaced apart vertically by a gap therebetween. As such, the first PCB 104 may be referred to as an upper PCB, and the second PCB 108 may be referred to as a lower PCB. Positioned between these two PCBs in the gap therebetween is the metal frame 106. It can therefore be said that the metal frame 106 is sandwiched between the two PCBs, in that an upper surface of the metal frame 106 is disposed on or supports a lower surface of the first PCB 104, and a lower surface of the metal frame 106 is disposed on or supports an upper surface of the second PCB 108.

[0029] In this embodiment, the metal frame 106 can be referred to as a metal perimeter frame. This is because the metal frame 106 can be shaped such that its perimeter takes the general shape of the perimeters of either or both of the first and second PCBs 104, 108. In other words, the perimeter of the metal frame 106 is generally aligned with or adjacent to the perimeters of the first and second PCBs 104, 108. Said another way, the perimeter of the metal frame 106 substantially traces the perimeters of the PCBs 104, 108. As shown in FIG. 2, the perimeter of the metal frame 106 may not be identical tothe perimeters of the PCBs 104, 108; there may be portions of the metal perimeter frame 106 that are either inboard or outboard of the PCBs 104, 108 to which it connects.

[0030] The metal perimeter frame 106 is shown in isolation in FIG. 5. The metal perimeter frame 106 may include a first sealing layer or first seal 124 located on an upper surface or edge of the metal perimeter frame 106. Likewise, the metal perimeter frame 106 may include a second sealing layer or second seal 126 located on a lower surface or edge of the metal perimeter frame. The first and second seals 124, 126 can each be a conductive elastomer gasket, for example. These gaskets can be made from a silicone or other elastomeric material embedded with conductive particles, such as silver, nickel, or copper. The silicone provides elasticity, while the metallic particles allow for electrical conductivity, making these seals ideal for EMI shielding and grounding. They can be dispensed as a liquid or paste for precise application. In embodiments, these conductive elastomers can be dispensed in a liquid form, referred to as a dispensable conductive elastomer gasket or form-in-place (FIP) conductive gasket. In other embodiments not shown, the first and second seals can be or include EMC springs assembled to the PCB boards and attached to the first and second housings 102, 110.

[0031] FIG. 6 shows a cross-sectional view of the electronic assembly 110 at a region near connectors 118, showing the metal perimeter frame 106 located in the gap between the first PCB 104 and the second PCB 108. As shown, the metal perimeter frame 106 is sandwiched between the first and second PCBs 104, 108, with the first seal 124 contacting the first PCB 104, and the second seal 126 contacting the second PCB 108. In embodiments, the first PCB 104 can include a trace of exposed ground (e.g., copper) that traces the shape of the first seal 124 so that the first seal 124 can be in direct contact with the ground. Likewise, the second PCB 108 can include a trace of exposed ground that traces the shape of the second seal 126 so that the second seal 126 can be in direct contact with the ground.

[0032] Referring back to FIG. 5, the metal perimeter frame 106 can have one or more interior frame ribs 128, also referred to as interior lips or support frame members. These interior frame ribs 128 provide support to the perimeter wall 130 of the metal perimeter frame 106, inhibiting inward flexing of the perimeter wall 130 and providing generalstructural support. Additionally, the interior frame ribs 128 segregate the interior of the metal perimeter frame 106 into a plurality of sections or regions 132. These regions 132 can be gaps or voids within the interior of the metal perimeter frame 106. However, in embodiments, one or more of these regions can include additional structure therein, as described below with reference to FIGS. 7-8.

[0033] For example, referring to FIG. 7, the metal perimeter frame 106 may include an EMC shield 134 in one of the regions 132. Additional EMC shields can be located in other segregated regions 132 of the metal perimeter frame. As shown in this embodiment, the EMC shield 134 can be bound by (and attached to, e.g. via fasteners or adhesion) a plurality of the interior frame ribs 128 as well as at least a portion of the perimeter wall 130 of the metal perimeter frame 106. The EMC shield 134 can be configured to prevent EMI from affecting sensitive electronic components or systems. It achieves this by blocking electromagnetic waves from entering or leaving the system, thus ensuring reliable operation of the electronic assembly. The shield helps maintain the integrity of the signals within the PCBs and protects against external electromagnetic disturbances.

[0034] In embodiments, the EMC shield 134 has a plurality of apertures 136. These apertures are strategically designed to allow for ventilation and weight reduction while maintaining effective EMI shielding. The apertures 136 can vary in size and distribution, representing a specific percentage of the total surface area of the EMC shield.

[0035] The range of the apertures’ surface area can be configured to represent up to 75% of the total surface area of the EMC shield. In embodiments, the plurality of apertures represent up to 50% of the total surface area of the EMC shield, and in yet other embodiments, the apertures represent up to 25% of the surface area of the EMC shield 134. These ranges allow for flexibility in balancing the need for EMI shielding with other design considerations, such as thermal management and structural integrity. In embodiments, the apertures are no larger than 1 / 1 Oth of the wavelength of the electromagnetic waves being shielded, ensuring that the shield remains effective in blocking unwanted interference.

[0036] In another example, referring to FIG. 8, the metal perimeter frame 106 may include a spring frame element, also referred to as frame springs 140, in one of the regions 132. More frame springs 140 can be provided in more of the regions 132, and only one frame spring 140 is shown here. The frame spring 140 can include a plurality of lateral spring elements 142, each connecting to either the perimeter wall 130 and / or one of the interior frame ribs 128. These lateral spring elements 142 extend toward the center of the region 132 whereupon they connect to a diagonal spring element 144. Each diagonal spring element is oriented diagonally relative to the interior frame rib 128, for example. A frame spring 140 with four lateral spring elements 142 can have four corresponding diagonal spring elements 144, with each diagonal spring element 144 interconnecting two adjacent lateral spring elements 142. This can leave a central void, shown in the embodiment of FIG. 8 as a diamond shape in the center of the region 132. This center diamond shape can rest below, and be suspended by, the lateral spring elements, as shown in FIG. 9.

[0037] Referring to FIGS. 8-9, in embodiments, the frame springs 140 are designed to apply pressure to the PCBs. This element is strategically positioned within the metal perimeter frame to ensure consistent contact between the PCBs and the housing, enhancing both electrical and thermal conductivity. A purpose of the frame springs 140 is to maintain a secure and stable connection between the PCBs and the housings 102, 110. By applying pressure, the frame springs 140 ensure that the PCBs remain in contact with the thermal interface, which can be important for effective heat dissipation from semiconductor chips to the housing. This helps in maintaining optimal operating temperatures and preventing overheating. Additionally, the frame springs 140 aid in maintaining the structural integrity of the assembly by reducing the risk of movement or misalignment of the PCBs, which could otherwise lead to electrical connectivity issues or mechanical failures.

[0038] FIGS. 10-15 illustrate an electronic assembly 200 according to a second embodiment, in which similar components are shown with a reference number that increases by 100 relative to the first embodiment. It should be understood that in this embodiment, the various components of the electronic assembly 200 can include similarstructure and purpose as the electronic assembly 100 of the first embodiment unless context dictates elsewise. In other words, in the avoidance of duplication, several components of the electronic assembly 200 will not be as thoroughly described as above, yet should be understood to include the features explained above unless otherwise indicated.

[0039] Referring to FIGS. 10-15, the electronic assembly 200 can include the following general components: a first housing 202, a first PCB 204, a metal frame 206, a second PCB 208, and a second housing 210. FIG. 10 illustrates the electronics assembly 200 with the first housing 202 attached, FIG. 11 illustrates the electronic assembly 200 with the first housing 202 removed to reveal the first PCB 204 underneath, and FIG. 12 illustrates the electronic assembly 200 with the first PCB 204 removed, revealing the metal frame 206 and second PCB 208 underneath.

[0040] In this embodiment, the metal frame 206 can be referred to as a local metal frame. The local metal frame 206 does not extend about a periphery or perimeter of the PCBs. Instead, the local metal frame 206 is situated and in a localized region to protect a particular component of the electronic assembly 200. For example, in the illustrated embodiment, the local metal frame 206 can be located at or near connectors 218 so as to protect those connectors 218 from electrical interference. Of course, the local metal frame 206 can be located at or near other connectors or components, and the present disclosure is not limited to the illustrated embodiment.

[0041] The local metal frame 206 can have a first sidewall 209, a second sidewall 211, and an inner wall 213 (also referred to as a third sidewall) to provide shielding from multiple sides of the connectors 218. The sidewalls 209, 211, and inner wall 213 can cooperate (along with the first and second PCBs 204, 208) to define a receptacle or container for at least partially surrounding the connectors 218. The first and second sidewalls 209, 211 can extend inward toward a central area of the gap between the PCBs, and the inner wall 213 connects the two sidewalls 209, 211. The first sidewall 209 extends along a first side of the connectors 218, and the second sidewall 211 extends along a second side of the connectors 218. The local metal frame 206 can have an open top and an open bottom such that the local metal frame 206 does not surround the top orbottom of the connectors 218. Underneath the local metal frame 206 can be an upper surface of the second PCB 208, and above the local metal frame 206 can be the lower surface of the first PCB 204. The local metal frame 206 provides shielding from multiple sides of the connectors 218.

[0042] As best shown in FIG. 15, the local metal frame 206 can be sandwiched between the first PCB 204 and the second PCB 208. Similar to the first embodiment, a first sealing layer or first seal 224 can be located on an upper surface or edge of the local metal frame 206. Likewise, the local metal frame 206 may include a second sealing layer or second seal 226 on a lower surface or edge of the local metal frame 206. The first and second seals 224, 226 can each be a conductive elastomer gasket, for example, and provide the advantages as described in the first embodiment above.

[0043] In embodiments, the local metal frame 206 has attachment flanges 217 with corresponding apertures 215 for receiving a fastener (e.g., screw, bolt, etc.) to mount the local metal frame 206 to the second housing 210.

[0044] It should be understood that the metal frames disclosed herein can be made of metal throughout. Alternatively, the metal frames can have a plastic (or other non- conductive) core, with a metal conductive coating around the core. In general, the metal frame does not need to be entirely metal.

[0045] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength,durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.

Claims

WHAT IS CLAIMED IS:

1. An electronic assembly, comprising: a first printed circuit board (PCB) having a first ground layer; a second PCB having a second ground layer, wherein the second PCB is spaced from the first PCB defining a gap therebetween; a metal frame positioned between the first PCB and the second PCB in the gap, the metal frame having an upper surface facing the first PCB and a lower surface facing the second PCB; a first electrically-conductive seal on the upper surface of the metal frame and contacting the first ground layer; and a second electrically-conductive seal on the lower surface of the metal frame and contacting the second ground layer.

2. The electronic assembly of claim 1, wherein the metal frame is a metal perimeter frame that defines a closed perimeter that extends adjacent a perimeter of both the first PCB and the second PCB.

3. The electronic assembly of claim 2, wherein the metal perimeter frame includes interior frame ribs segregating a plurality of regions, wherein at least one of the regions includes an electromagnetic compatibility (EMC) shield therein.

4. The electronic assembly of claim 3, further comprising a frame spring within at least one of the regions and interconnecting at least two of the interior frame ribs.

5. The electronic assembly of claim 3, wherein the interior frame ribs are positioned between the upper surface and the lower surface of the metal perimeter frame, wherein the interior frame ribs have a thickness that is less than a thickness of the metal perimeter frame.

6. The electronic assembly of claim 1, wherein the electronic assembly includes at least one connector located in the gap and configured to electrically connect to the second PCB,wherein the metal frame is a local metal frame that partially surrounds the at least one connector.

7. The electronic assembly of claim 6, wherein the local metal frame comprises a first wall and a second wall that extend inward toward a central area of the gap, and a third wall that connects the first and second walls, wherein the at least one connector is located between the first and second walls and outboard of the third wall.

8. The electronic assembly of claim 7, wherein the at least one connector is surrounded by the first PCB, the second PCB, the first and second walls, and the third wall.

9. The electronic assembly of any of claims 2 through 8, wherein the first and second electrically-conductive seals include a conductive elastomer gasket.

10. The electronic assembly of any of claims 2 through 9, wherein the metal frame provides environmental protection to electronic components between the first and second PCBs.

11. The electronic assembly of any of claims 2 through 10, wherein the metal frame includes an aluminum alloy to enhance thermal conductivity and structural integrity.

12. The electronic assembly of any of claims 6 through 8, wherein the local metal frame includes a mounting flange having a corresponding aperture that receives a fastener to mount the local metal frame to a housing.

Images