Strain relief system for flexbile circuit board assembly

Abstract

An electronic device may include a printed circuit board (PCB) configured to maintain a sensor on a first surface of the PCB in a sensor area; and a substrate arranged on a second side of the PCB, opposite the first side, the substrate defined by a perimeter including at least one edge, the substrate defining at least one strain relief element positioned inboard of the at least one edge to redistribute strain induced in the printed circuit board.

Description

STRAIN RELIEF SYSTEM FOR FLEXBILE CIRCUIT BOARD ASSEMBLYCROSS-REFERENCE TO RELATED APPLICATIONS[00011 This application claims priority to U.S. application Serial No. 63 / 736,631 filed December 20, 2024, the disclosure of which is hereby incorporated in its entirety by reference herein.TECHNICAL FIELD

[0002] Aspects of the disclosure generally relate to systems and methods for strain relief of a flexible circuit board assembly.BACKGROUND[0003J Printed circuit boards (“PCBs”) are used in wide range of vehicle applications for mounting sensors, such as image sensor, rain sensors, proximity sensors, light sensors, etc., used to assist operation of the vehicle. The sensor can be secured the PCB with electrically conductive solder. The PCBs can be connected to another PCB, motherboard or other component or substrate by fasteners, adhesive and / or compression between enclosure components. The interface between the connection and the PCB can experience high levels of strain.SUMMARY[0004| An electronic device may include a printed circuit board (PCB) configured to maintain a sensor on a first surface of the PCB in a sensor area; and a substrate arranged on a second side of the PCB, opposite the first side, the substrate defined by a perimeter including at least one edge, the substrate defining at least one strain relief element positioned inboard of the at least one edge to redistribute strain induced in the printed circuit board.[0005J An electronic device, may include a flexible printed circuit board (PCB) having a first surface and a second surface, a sensor mounted to the first surface within a sensor area and asubstrate disposed adjacent the second surface and defining a plurality of strain relief elements inboard of a perimeter edge of the substrate, each strain relief element defining a slot having a curved portion that encircles at least a portion of the sensor area, the plurality of strain relief elements cooperating to reduce strain transmitted to the PCB during thermal or mechanical loading.

[0006] An electronic device may include a printed circuit board (PCB), a sensor electrically and mechanically coupled to the PCB, and a composite substrate defining at least one strain relief element formed through the substrate, the at least one strain relief element positioned inboard of an edge of the composite substrate to redistribute strain and limit out-of-plane movement of the sensor with respect to the PCB.BRIEF DESCRIPTION OF THE DRAWINGS[OO(I7| The exemplary arrangements of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various exemplary arrangements will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompanying drawings herein.

[0008] FIG. 1 is a schematic plan view of an example electronic device having a flexible printed circuit board (PCB) and a substrate having a strain relief arrangement;

[0009] FIG. 2 is a side view of the assembly of FIG. 1;

[0010] FIG. 3 is a plan view of the example substrate of FIG. 1;

[0011] FIG. 4 is a plan view of the example PCB of FIG. 1;

[0012] FIG. 5 is a schematic plan view of another example electronic device having a flexible PCB and a substrate having a strain relief arrangement;[0013[ FIG. 6 is a side view of the assembly of FIG. 5;[0014| FIG. 7 is a plan view of the example substrate of FIG. 5;

[0015] FIG. 8 is a plan view of the example PCB of FIG. 5;

[0016] FIG. 9 is a schematic plan view illustration of another example electronic device having a flexible PCT and a substrate having a strain relief arrangement; and

[0017] FIG. 10 is a schematic plan view of another example electronic device having a flexible PCT and a substrate having a strain relief arrangement.DETAILED DESCRIPTION

[0018] Referring now to the discussion that follows, and to the drawings, illustrative approaches to the disclosed systems and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further, the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description.

[0019] As explained, printed circuit boards (“PCBs”) are used in wide range of vehicle applications for mounting sensors, such as image sensor, rain sensors, proximity sensors, light sensors, etc., used to assist operation of the vehicle. The sensor can be secured the PCB with electrically conductive solder. The PCBs can be connected to another PCB, motherboard or other component or substrate by fasteners, adhesive and / or compression between enclosure components. The interface between the connection and the PCB can experience high levels of strain. Existing strain relief techniques may include adhesive bonding, rigid stiffeners, flexible connectors. However, these mechanisms often increase weight, reduce flexibility, have higher manufacturing costs, etc.

[0020] Disclosed herein is an electronic device featuring a flexible printed circuit board (PCB) and a rigid substrate designed to provide strain relief. A sensor is mounted on the first surface of the PCB, while the substrate is positioned on the opposite side. The substrate includes one or more strain relief elements, such as slots or curved features, located inboard of its perimeter edges. Theseelements redistribute mechanical and thermal strain, reducing stress on the PCB and minimizing z-axis movement of the sensor during thermal events. This design improves sensor alignment, enhances optical performance, and increases durability under vibration and temperature fluctuations, making it suitable for automotive, consumer electronics, and other high-reliability applications.[00211 The present disclosure relates generally to electronics, and more specifically, to a strain relief arrangement for an electronic device. FIGs. 1 and 2 illustrate one example electronic device 100. FIG. 3 illustrates an example substrate 140 and FIG. 4 illustrates an example PCB 102. The electronic device 100 includes a printed circuit board (“PCB”) 102 having a first surface 104 and a second surface (not visible), opposite the first surface 104. The PCB 102 can be polygonal (square, rectangular, etc.) or round (not shown). In the example shown in FIG. 1, the PCB 102 has four corners 106, but at least one irregular shaped edge 108.

[0022] As shown in FIG. 1, the PCB 102 is rectangular and includes a pair of first edges 108 extending generally parallel to each other and a pair of second edges 110 perpendicular to the first edges 108. The first and second edges 108, 110 collectively define the perimeter of the PCB 12.[0023J A sensor may be secured to the first PCB surface 104 of the PCB 12 in a sensor area 122. The sensor may be, for example, an image sensor, rain sensor, proximity sensor, light sensor or pressure senor. The sensor may be used for advance driver-assistance systems (ADAS) in vehicles. Alternatively, the sensor can be omitted (not shown). The sensor can be secured to the PCB 102 by, for example, solder formed as a ball grid array (BGA) or a pin grid array (not shown) that is heated to undergo reflow in order to secure the sensor 122 to the PCB 102. The solder is formed from an electrically conductive material. The sensor area 122 may be generally at the center of the first PCB surface 104.

[0024] The PCB 102 may define at least one PCB opening 124 extending through the PCB from the first PCB surface 104 to the second surface of the PCB. The PCB openings 124 may be configured to receive attachment mechanisms. In the example shown, four openings 124 are defined, though more or less may be contemplated. Each opening 124 may be circular.

[0025] A substrate 130 is arranged adjacent and touching the second side of the PCB 102. The substrate 130, as also best shown in FIG. 3, has a first substrate surface 132 and a second substrate surface (not visible), opposite the first substrate surface 132. Similar to the PCB, the substrate 130 may be generally polygonal (square, rectangular, etc.) or round (not shown). In the example shown in FIG. 1, the substrate 132 has four comers 136, but at least one irregular shaped first substrate edge 138. The substrate 130 includes a pair of first substrate edges 138 extending generally parallel to each other and a pair of second substrate edges 140 perpendicular the first edges 138. The first and second edges 138, 140 collectively define the perimeter of the substrate 130.

[0026] The substrate 130 may be made of metal such as aluminum. Other metals may also be contemplated such as Magnesium, Titanium, Carbon Fiber. Other materials such as plastics, polymers and ceramics may also be considered, as well as composites such as carbon fiber reinforced polymer, or high performance plastics (PEEK, PTFE).

[0027] The substrate 130 may define at least one substrate opening 144 extending through the substrate from the first substrate surface 132 to the second substrate surface. The substrate openings 144 may be configured to align with the PCB openings 124 to receive attachment mechanisms. In the example shown, four openings 144 are defined, though more or less may be contemplated. Each opening 144 may be circular.

[0028] At least one strain relief element 146 is defined by the substrate 130. In one example, a strain relief element 146 may be associated with each substrate opening 144 for helping to reduce or alleviate strain on the PCB 102 during / when connected to another component. Each opening 144, is configured to receive a fastener to secure the PCB 102 to an electronic component. In the exemplary arrangement shown in FIGs. 1 and 3, there are four strain relief elements 146. The strain relief elements 146 are positioned inboard of the first and second edges 138, 140 of the substrate 130.

[0029] Each strain relief element 146 may be formed as a slot. In one exemplary arrangement, the strain relief element 146 may form a concave curve extending around the sensor area 122. In the example shown in FIG. 3, a first strain relief element 146a, a second strain relief element 146b, and a third strain relief element 146c all have similar curvatures. The first and third elements 146a,146c may have ends arranged just within the ends of the second element 146b. A fourth strain relief element 146d may also have a curved shape, but may include a combination of concave and convex portions. In the example shown in FIG. 3, the fourth element 146d may include a concave portion on each side of a convex portion. The concave portions may be adjacent an opposite end of the first and third elements 146a, 146c.[0030| The width of the elements 146 may be generally consistent across the cross-sections thereof, and the width of each element 146 may be generally similar to the other elements 146. While a concave shaped element 146 is shown, other shapes may be appreciated, including but not limited to zig zag shapes, lattice, honeycomb, etc. The slots may also have variable widths. Also, the substrate may include multiple layers of composite materials.[00311 The substrate 130 may be manufactured by one or more methods. In one example, the substrate 130 may formed from a metal substrate via a CNC machine. In another example, the substrate 130 may be laser cut from polymer substrates. Further, overmolding techniques for integrate strain relief may be used.|0032] Referring to FIGs. 5-8, a second exemplary arrangement of an electronic device 100 is illustrated. The electronic device 100 is similar to that shown in FIG. 1, having a PCB 102, except that instead of irregular first PCB edges 108, the first PCB edges 108 are straight, as well as the first substrate edges 138. Further, the example in FIGs. 5-8 does not include PCB openings 124 or substrate openings 144. The strain relief elements 146 are all generally curved, overlapping slightly around the sensor area 122.

[0033] FIG. 9 is a schematic plan view of another example electronic device having a flexible PCB and a substrate having a strain relief arrangement similar to the example in FIG. 5. However, this example includes PCB openings 124 and substrate openings 144.[0034| FIG. 10 is a schematic plan view of another example electronic device having a flexible PCT and a substrate having a strain relief arrangement. In this example, the PCB 102 and substrate 130 may be bonded together via glue along a glue line 150. The substrate 130 may also be bonded to another item or device via glue.

[0035] Accordingly, described herein is an electrical component having a flexible PCB and a rigid substrate where the substrate defines stress relief slots to help isolate an image sensor from thermal events, all while maximizing the space needed to fit electrical components on the PCB. By minimizing z-axis movement of an image sensor on the PCB during a thermal event, optical performance is maximized. The sensor may further benefit from calibration stability, durability under vibration, and resistance to thermal cycling.

[0036] While the disclosure may reference application in a vehicle setting, other applications may be appreciated, including consumer electronics, including smartphones, cameras, wearables. The disclosure may also be applicable in other areas where flexible PCBs experience thermal or mechanical stress, the aerospace and medical fields, industrial and robotic systems., etc.

[0037] What have been described above are examples of the present disclosure. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. While certain novel features of this disclosure shown and described below are pointed out in the annexed claims, the disclosure is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the disclosure illustrated and in its operation may be made without departing in any way from the spirit of the present disclosure. Accordingly, the present disclosure is intended to embrace all such alterations, modifications, and variations that fall within the scope of the appended claims. As used herein, the term "includes" means includes but not limited to, the term "including" means including but not limited to. The term "based on" means based at least in part on. Additionally, where the disclosure or claims recite "a," "an," "a first," or "another" element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements. No feature of the disclosure is critical or essential unless it is expressly stated as being “critical” or “essential.”

Claims

WHAT IS CLAIMED IS:

1. An electronic device, comprising: a printed circuit board (PCB) configured to maintain a sensor on a first surface of the PCB in a sensor area; and a substrate arranged on a second side of the PCB, opposite the first surface, the substrate defined by a perimeter including at least one edge, the substrate defining at least one strain relief element positioned inboard of the at least one edge to redistribute strain induced in the printed circuit board.

2. The electronic device recited in claim 1, wherein the at least one edge includes first and second edges extending transverse to one another.

3. The electronic device recited in claim 1, wherein each strain relief element defines a slot between a first substrate side and a second opposite substrate side.

4. The electronic device recited in claim 3, wherein each strain relief element forms at least one curve.

5. The electronic device of claim 1, wherein the at least one strain relief element comprises a plurality of slots arranged to partially surround the sensor area in an arcuate pattern.

6. The electronic device of claim 1, wherein each strain relief element has a substantially uniform width along its length.

7. The electronic device recited in claim 3, further comprising at least one opening extending through the printed circuit board, the opening being configured to receive a fastener to secure the printed circuit board to an electronic component.

8. The electronic device recited in claim 5, wherein each strain relief element is positioned between one of the edges and the sensor area of the printed circuit board when the substrate is attached to the PCB.

9. The electronic device of claim 1, wherein the PCB and substrate are attached via glue.

10. The electronic device of claim 1, wherein the strain relief element includes four strain relief elements, each surrounding a portion of the sensor area.

11. An electronic device, comprising: a flexible printed circuit board (PCB) having a first surface and a second surface; a sensor mounted to the first surface within a sensor area; and a substrate disposed adjacent the second surface and defining a plurality of strain relief elements inboard of a perimeter edge of the substrate, each strain relief element defining a slot having a curved portion that encircles at least a portion of the sensor area, the plurality of strain relief elements cooperating to reduce strain transmitted to the PCB during thermal or mechanical loading.

12. The electronic device of claim 11, wherein the substrate is stiffer than the PCB and the plurality of strain relief elements locally reduces the effective bending stiffness of the substrate between the perimeter edge and the sensor area.

13. An electronic device, comprising: a printed circuit board (PCB); a sensor electrically and mechanically coupled to the PCB; and a composite substrate defining at least one strain relief element formed through the substrate, the at least one strain relief element positioned inboard of an edge of the composite substrate to redistribute strain and limit out-of-plane movement of the sensor with respect to the PCB.

14. The electronic device of claim 11, wherein the at least one strain relief element includes a first strain relief element having a concave curvature oriented toward the sensor area and a second strain relief element has a convex curvature oriented away from the sensor area.

15. The electronic device of claim 14, wherein the at least one strain relief element includes an adjacent strain relief element that overlaps the first strain relief element to define a nested curvature pattern.

16. The electronic device of claim 11, wherein each strain relief element has a substantially uniform width along its length.

17. The electronic device of claim 11, wherein the strain relief element extends along a chord connecting two points located inboard of the first and second edges of the substrate.

18. The electronic device of claim 11, wherein the substrate defines four strain relief elements disposed at quadrants around the sensor area.

19. The electronic device of claim 11, wherein the substrate defines six or more strain relief elements arranged in pairs on opposing sides of the sensor area.

20. The electronic device of claim 11, wherein the substrate comprises aluminum, magnesium, titanium, carbon fiber composite, or a ceramic.

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