A locking device and a circuit board arrangement

Abstract

A locking device (100) configured to lock a secondary circuit board in a fixed position on a primary circuit board (1), comprising: - a base portion (101) configured to be inserted into a hole (5) formed in the primary circuit board, - a head portion (102) configured to protrude from the primary circuit board, comprising an actuation interface configured to enable rotation of the locking device from an unlocking to a locking position, - at least one axial interlock member and a rotational interlock mechanism (130) configured to engage with the primary circuit board in the locking position, wherein the head portion further comprises a board locking structure (140) configured to engage with an edge portion of the secondary circuit board in the locking position, and to disengage from the secondary circuit board in the unlocking position.

Description

[0001] A LOCKING DEVICE AND A CIRCUIT BOARD ARRANGEMENT

[0002] TECHNICAL FIELD

[0003] The technology disclosed herein relates generally to circuit boards for electronic devices, and in particular to a locking device for locking a secondary circuit board in a fixed position on a primary circuit board. It further relates to a circuit board arrangement comprising the locking device.

[0004] BACKGROUND

[0005] An electronic device, such as a smartphone, tablet, desktop computer, or similar, can be assembled from separate electronic modules connected via electrical connectors. A common design includes a circuit board, often referred to as a motherboard, which hosts various electronic components. Additional components, like solid-state storage devices (SSD), are frequently mounted on a secondary circuit board, also referred to as an add-in card, which is positioned apart from the motherboard and electrically connected thereto.

[0006] When such add-in cards are mounted to a motherboard, a first end of the add-in card is usually pivotably connected to the motherboard by a connector, providing mechanical as well as electrical connection to the motherboard. The add-in card is pivoted into its desired position and locked in this position by a locking device engaging with an edge portion of a second end of the add-in card. The locking of the second end of the add-in card to the motherboard may typically be realized by a metallic stand-off attached to the motherboard, and a screw clamping the edge portion to the stand-off. These screws are small and prone to being dropped during mounting. If a screw later becomes loose, it poses a risk of creating a short circuit on the motherboard.

[0007] An alternative to screws is to use a specifically designed locking device that is on one hand attached to the motherboard, and on the other hand clamps the edge portion of the circuit board in its desired position. However, known such locking devices are typically made of several small intricate parts that need to be precisely assembled, hence making them complex to manufacture. Furthermore, known locking devices usually require a first operation to attach the locking device to the motherboard, and a second operation to lock the add-in card to the locking device.

[0008] In view of the above, there is a need for an improved locking device for locking a circuit board in a fixed position on a motherboard.

[0009] SUMMARY

[0010] A primary objective of embodiments herein is to provide for an in at least some aspects improved locking of a secondary circuit board in a fixed position on a primary circuit board. In particular, it is an objective to provide a locking device which maybe used to lock a secondary circuit board to a primary circuit board without the use of tools and which securely holds the secondary circuit board in its position. Another objective is to provide a locking device that facilitates locking of the secondary circuit board to the primary circuit board. Yet another objective is to provide a circuit board arrangement in which a secure locking of a secondary circuit board to a primary circuit board may be achieved in a cost-efficient manner and with a low risk of short circuits during usage.

[0011] According to a first aspect of embodiments herein, at least the primary objective is accomplished by a locking device according to claim i. The locking device is configured to lock a secondary circuit board in a fixed position on a first side of a primary circuit board. The locking device extends along a longitudinal axis and comprises: a base portion configured to be longitudinally inserted into a hole formed in the primary circuit board, a head portion fixed to a first end of the base portion, the head portion being configured to protrude from the first side of the primary circuit board when the base portion is received in the hole, the head portion comprising an abutment surface configured to abut the first side of the primary circuit board, and an actuation interface configured to enable rotation of the locking device about the longitudinal axis when the base portion is received in the hole, from an unlocking position to a locking position, at least one axial interlock member protruding transversely from the base portion at a second end of the base portion, the axial interlock member being configured to engage with a second side of the primary circuit board in the locking position, and a rotational interlock mechanism configured to engage with the first side of the primary circuit board in the locking position.

[0012] The head portion further comprises a board locking structure configured to engage with an edge portion of the secondary circuit board in the locking position, and to disengage from the secondary circuit board in the unlocking position, the board locking structure being longitudinally spaced apart from the abutment surface.

[0013] According to a second aspect of embodiments herein, at least the primary objective is further achieved by a circuit board arrangement according to claim 17. The circuit board arrangement comprises a secondary circuit board and a primary circuit board comprising a hole extending from a first side to a second side of the primary circuit board. A first end of the secondary circuit board is pivotably connected to the first side of the primary circuit board via a connector, and a second end of the secondary circuit board comprises an edge portion. The circuit board arrangement further comprises a locking device according to the first aspect, wherein the locking device is configured to, in its locking position, lock the secondary circuit board in a fixed position relative to the primary circuit board.

[0014] The locking device as proposed herein is rotatable from an unlocking position, in which it can be disengaged from both the primary circuit board and the secondary circuit board, and a locking position, in which it is rotationally and axially locked to the primary circuit board and in which it also fixes the secondary circuit board relative to the primary circuit board. Thus, in a single operation, the locking device can be secured to the primary circuit board and the secondary circuit board can be secured to the locking device. A facilitated assembly of a primary and a secondary circuit board may thereby be achieved in comparison with locking devices requiring more than one operation to lock the components with respect to one another. The rotational and axial interlocks and the board locking structure provide a lock which is stable over time, hence preventing short circuits of the primary circuit board during usage. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0015] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, device, member, component, means, etc." are to be interpreted openly as referring to at least one instance of the element, device, member, component, means, etc., unless explicitly stated otherwise.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Examples of embodiments herein are described in more detail with reference to attached drawings, in which:

[0018] FIG. 1 is a schematic illustration of a primary circuit board and a locking device according to an embodiment;

[0019] FIG. 2 is a schematic illustration of a circuit board arrangement according to an embodiment;

[0020] FIG. 3 is an illustration of the circuit board arrangement with the locking device in an unlocking position;

[0021] FIG. 4 is an illustration of the circuit board arrangement with the locking device in a locking position;

[0022] FIG. 5 is a perspective view of the locking device according to an embodiment;

[0023] FIG. 6 is a side view of the locking device illustrated in FIG. 5;

[0024] FIG. 7 is another perspective view of the locking device illustrated in FIG. 5;

[0025] FIG. 8 is a top view of the locking device illustrated in FIG. 5;

[0026] FIG. 9 is a sectional view of the circuit board arrangement illustrated in FIG. 4; and

[0027] FIG. 10 is a bottom view of the circuit board arrangement illustrated in FIG. 4. The illustrations are schematic and not necessarily drawn to scale. Like reference numbers refer to like elements throughout the description, unless expressed otherwise.

[0028] DETAILED DESCRIPTION

[0029] A motherboard of an electronic device or system, such as a computer, server, laptop, smartphone, base station, etc., typically hosts various electronic components. For instance, in a server, the motherboard may house a processor and associated chips. Additional components are frequently mounted on the motherboard in the form of add-in cards, which are positioned apart from the motherboard. The add-in card may, by way of example, be a Wi-Fi card, a Bluetooth card, a Global Navigation Satellite System (GNSS) card, a Near Field Communication (NFC) card, a wireless adapter card, a Wireless Wide Area Network (WWAN) card, an SSD card, a Hybrid Digital Radio (HDR) card, a hardware accelerator card, etc.

[0030] The add-in card connects to the motherboard through a slot in an electrical connector. To ensure a stable connection, the opposite end of the add-in card must also be securely fixed relative to the motherboard. Without this support, the connection to the electrical connector may loosen, leading to an unstable interface between the add-in card and the motherboard. This instability can degrade the transmission of signals or power, negatively impacting system performance.

[0031] The present disclosure relates to circuit board arrangements for electronic devices and systems, in which a secondary circuit board, such as an add-in card as exemplified above, is mounted to a primary circuit board, such as a motherboard, and locked thereto by means of a locking device.

[0032] FIG. i illustrates a primary circuit board i and an electrical connector 15 attached to an upper surface 4 thereof. The primary circuit board 1 comprises a hole 5, extending from a first side 2, comprising the upper surface 4, to a second side 3 of the primary circuit board 1. Hence, the hole 5 is a through-hole. The connector 15 comprises a slot 16. As further illustrated in FIG. 2, showing a circuit board arrangement 200, the slot 16 is configured to receive a first end 12 of a secondary circuit board 10, thereby achieving an electrical and mechanical connection of the secondary circuit board 10 to the primary circuit board 1. The secondary circuit board 10 is configured to be mounted to the primary circuit board 1 with a lower surface 14 of the secondary circuit board 10 being spaced apart from, and facing, the upper surface 4 of the primary circuit board 1. Various components are mounted on an upper surface 16 of the secondary circuit board 10.

[0033] At a second end 13 of the secondary circuit board 10, a semicircular notch delimited by an edge portion 11 is formed. The secondary circuit board 10 is configured to be locked in a desired position relative to the primary circuit board 1 by means of a locking device 100 according to an embodiment of the disclosure, which is configured to engage with the secondary circuit board 10 at the edge portion 11. The edge portion 11 is herein to be understood as including surface portions of the upper 16 and lower 14 surfaces of the secondary circuit board 10 being adjacent to the semicircular notch.

[0034] The locking device 100 extends along a longitudinal axis Z, defining a longitudinal direction perpendicular to the upper surface 4 of the primary circuit board 1. It comprises a base portion 101 configured to be inserted into the hole 5, and a head portion 102 configured to protrude from the hole 5 at the first side 2 of the primary circuit board 1. Once received in the hole 5, the locking device is configured to be rotated about the longitudinal axis Z from an unlocking position A, illustrated in FIG. 3, to a locking position B, illustrated in FIG. 4. In the unlocking position A, the locking device 100 is movable along the longitudinal axis Z relative to the primary circuit board 1, and it is not lockingly engaged with the secondary circuit board 10. In the locking position B, the locking device 100 is locked against rotation about the longitudinal axis Z as well as against movement along the longitudinal axis Z. It is further in locking engagement with the edge portion 11 of the secondary circuit board 10, holding the secondary circuit board 10 in a fixed position parallel with and spaced apart from the primary circuit board 1. Hence, transition from the unlocking position A, in which the locking device 100 as well as the secondary circuit board 10 are movable relative to the primary circuit board 1, to the locking position B, in which the locking device 100 and the secondary circuit board 10 are both fixed relative to the primary circuit board 1, is achieved in a single operation by rotating the locking device 100 about the longitudinal axis Z. In the illustrated embodiment, this is achieved by a clockwise rotation of 90° about the longitudinal axis Z.

[0035] Reference is now made to FIGS. 5-8, illustrating the locking device 100 in further detail. When the base portion 101 is received in the hole 5 of the primary circuit board i, the longitudinal axis Z extends perpendicularly to the upper surface 4 of the primary circuit board 1. The base portion 101 is hence configured to be longitudinally inserted into the hole 5. The head portion 102 is fixed to a first end 111 of the base portion 101. It comprises an abutment surface 121 configured to abut the first side 2 of the primary circuit board 1, i.e., the upper surface 4. It further comprises an actuation interface 122, in the illustrated embodiment a lever 122, configured to enable rotation of the locking device 100 about the longitudinal axis Z when the base portion 101 is received in the hole 5. The actuation interface 122 enables the rotation of the locking device 100 from the unlocking position A to the locking position B.

[0036] Two axial interlock members 113 protrude transversely from the base portion 101 at a second end 112 of the base portion 101, corresponding to a lower end of the locking device 100. The axial interlock members 113 are configured to, in a first orientation corresponding to the unlocking position A of the locking device 100, fit into the hole 5 of the primary circuit board 1 such that the base portion 101 can be longitudinally inserted into the hole 5. In a second orientation of the locking device 100, corresponding to the locking position B, the axial interlock members 113 are configured to engage with the second side 3 of the primary circuit board 1 and prevent relative longitudinal movement of the locking device 100 and the primary circuit board 1. For this purpose, each axial interlock member 113 comprises a stopping surface 114 configured to abut a lower surface of the primary circuit board 1 in the locking position B. Hence, the second end 112 of the base portion 101 will protrude from the hole 5 at the second side 3 of the primary circuit board 1.

[0037] A rotational interlock mechanism 130 is further provided, which is configured to engage with the first side 2 of the primary circuit board 1 in the locking position B of the locking device 100 and prevent relative rotational movement of the locking device 100 and the primary circuit board 1 in the locking position. In the illustrated embodiment, the rotational interlock mechanism 130 comprises a first engagement member 131, in the form of a peg, configured to engage with a second engagement member 6, in the form of a recess or hole, disposed on the first side 2 of the primary circuit board 1. The first engagement member 131 is offset from the longitudinal axis Z and disposed on a distal end portion 133 of a first arm 132. In other embodiments, the rotational interlock mechanism may comprise a hole or recess provided on the locking device, configured to engage with a peg or similar formed on the primary circuit board.

[0038] The head portion 102 further comprises a board locking structure 140 configured to engage with the edge portion 11 of the secondary circuit board 10 in the locking position, and to disengage from the secondary circuit board 10 in the unlocking position. The board locking structure 140 is longitudinally spaced apart from the abutment surface 121. In other words, as measured along the longitudinal axis Z, a non-zero distance is provided between the abutment surface 121, configured to abut the upper surface 4 of the primary circuit board 1, and the board locking structure 140 configured to hold and lock the secondary circuit board 10. A clearance is thereby provided between the primary circuit board 1 and the secondary circuit board 10 when the locking device 100 holds the secondary circuit board 10 in the fixed position.

[0039] The head portion 102 also comprises a seating surface 141, which is opposite to the abutment surface 121. In the illustrated embodiment, the abutment surface 121 is directed downwards, toward the upper surface 4 of the primary circuit board 1, whereas the seating surface 141 is directed upwards, toward the lower surface 14 of the secondary circuit board 10. The seating surface 141 is configured to support a portion of the lower surface 14 of the secondary circuit board 10 along the edge portion 11. For this purpose, the seating surface 141 has an arc shape. For example, the seating surface 141 may have the shape of a first annulus sector centred on the longitudinal axis Z. However, it may also be shaped as a non-circular arc, as long as it is able to support the edge portion 11 at least in the locking position, and preferably also in the unlocking position.

[0040] The seating surface 141 may extend over an angular range of more than 90°, preferably over an angular range of at least 18 o° around the longitudinal axis Z. In the illustrated embodiment, the seating surface 141 extends over an angular range of about 270°. Hereby, it is able to support secondary circuit board 10 both in the locking position B and in the unlocking position A.

[0041] The board locking structure 140 comprises a locking surface 145 formed opposite to a first portion 142 of the seating surface 141. A pocket for receiving the edge portion 11 of the secondary circuit board io is provided between the locking surface 145 and the first portion 142 of the seating surface 141. Hence, the locking surface 145 is, in the locking position, configured to overlap with a portion of the upper surface 16 of the secondary circuit board 10, along the edge portion 11. In the unlocking position A, the locking surface 145 does not overlap with the edge portion 11, hence enabling tilting of the secondary circuit board 10 relative to the primary circuit board 1. The locking surface 145 has an arc shape and extends over a smaller angular range than the seating surface 141. In the illustrated embodiment, the locking surface 145 extends over an angular range of about 90°. The locking surface 145 may, byway of example, be shaped as a second annulus sector centred on the longitudinal axis Z. However, in other embodiments, the locking surface may have other shapes, as long as it is able to overlap with the edge portion 11 and thereby lock the secondary circuit board 10 in the locking position of the locking device, but not in the unlocking position.

[0042] The head portion 102 comprises an upper side surface 146 extending perpendicularly or essentially perpendicularly to the seating surface 141, from the seating surface 141 and to an upper end 103 of the locking device 100. The upper side surface 146 is a convex surface configured to face the concave part of the edge portion 11 that connects the upper 16 and lower 14 surfaces of the secondary circuit board 10.

[0043] In the illustrated embodiment, the head portion 102 comprises a central part 104 centred on the longitudinal axis Z. In a top view, as in FIG. 8, the central part 104 has the basic shape of a circle. The first arm 132, a second arm 150, and the lever 122, all extend from the central part 104 in different directions. The first arm 132 extends outwards / downwards from a first side 104a of the central part 104. The first engagement member 131 of the rotational interlock mechanism 130 is disposed on the distal end portion 133 of the first arm 132. The second arm 150 extends outwards / downwards from a second side 104b of the central part 104, opposite to the first side 104a. It is configured to abut the first side 2 of the primary circuit board 1, i.e., the upper surface 4. As best seen in FIG. 8, the first and second arms 132, 150 are both centred on a central longitudinal first plane Pi of the locking device 100. The lever 122 is offset from a central longitudinal second plane P2 of the locking device 100, wherein Pi and P2 are orthogonal planes. In the locking position B, the second plane P2 will be parallel or essentially parallel with the second end 13 of the secondary circuit board 10, as maybe gleaned from FIG. 4. The offset between the lever 122 and the plane P2 ensures that a clearance maybe provided between the second end 13 of the secondary circuit board 10 and a first side surface 123 of the lever 122.

[0044] The first side surface 123 of the lever 122 delimits the board locking structure 140 in a circumferential direction of the locking device 100, as can be seen in FIG. 5. The first side surface 123 is offset from the plane P2 and comprises an innermost portion 123a extending between the locking surface 145 and the first portion 142 of the seating surface 141.

[0045] The first arm 132 and the second arm 150 maybe resilient members configured to, in the locking position B, press the locking device 100 against the primary circuit board 1. The resilient members exert a spring force that pushes the second side 3 of the primary circuit board 1 against the axial interlock members 113, thereby pressing the locking device 100 against the primary circuit board 1 in the locking position B. To move from the unlocking position A to the locking position B, the locking device 100 is pushed downwards along the longitudinal axis Z against the spring force until the axial interlock members 113 protrude from the hole 5 and rotation of the locking device 100 is enabled.

[0046] In the illustrated embodiment, the actuation interface 122 is in the form of a lever 122 configured to be manually gripped. The lever 122 enables manual manipulation of the locking device 100, without the use of tools. In other embodiments, the actuation interface may comprise another type of lever or handle, or an interface for rotating the locking device between the unlocking and locking positions by using a tool, such as a screwdriver or similar.

[0047] The locking device 100 maybe formed by a single piece of material, such as from a plastic material or from a metal material. It maybe formed by moulding, additive manufacturing, and / or machining. Typically, the locking device 100 may be formed by injection moulding of a plastic material. In other embodiments, the locking device may comprise more than one piece of materials, wherein for example one or both arms maybe formed of spring steel, aluminium, copper, or similar, and attached to the central part of the head portion, which may be made of a plastic material. The base portion 101 is in the illustrated embodiment shaped as a right circular cylinder defining the longitudinal axis Z. The hole 5 is a bore shaped to fit the base portion 101 and the axial interlock members 113 in the orientation of the locking device 100 corresponding to the unlocking position B. The circle cylindrical shape of the base portion 101 enables a sidewall of the base portion 101 to be supported by a sidewall of the hole 5 in the unlocking as well as in the locking position.

[0048] Although the base portion 101 is in the illustrated embodiment shaped as a right circular cylinder, it may in other embodiments have a different shape as long as it can fit in a hole of the primary circuit board and be rotated therein between an unlocking and a locking position. For example, the base portion maybe shaped as a truncated cone.

[0049] FIG. 9 shows a section along the plane Pi, with the locking device 100 provided in the locking position B in locking engagement with the primary circuit board 1 and the secondary circuit board 10. FIG. 10 is a bottom view, illustrating the locking device 100 in the locking position B as seen from the second side 3 of the primary circuit board 1. The first engagement member 131 is received in the second engagement member 6, preventing rotational movement of the locking device 100 about the longitudinal axis Z. To release the first engagement member 131, the distal end portion 133 of the first arm 132 is provided with a phase 134 under which a screwdriver or similar can be introduced to force the first arm 132 upwards, thereby enabling rotation of the locking device 100 to the unlocking position A. The resilient second arm 150 presses against the upper surface 4 of the primary circuit board 1. The edge portion 11 of the secondary circuit board 10 is received between the first portion 142 of the seating surface 141 and the locking surface 145. The axial interlock members 113 abut the second side 3 of the primary circuit board 1 in the vicinity of the hole 5, preventing relative axial movement of the locking device 100 and the primary circuit board 1. Portions of the abutment surface 121, provided on opposite sides of the longitudinal axis Z, abut the upper surface 4 of the primary circuit board 1. The abutment surface 121 is in the illustrated embodiment an annular surface.

[0050] As can be seen from FIG. 10, if the first engagement member 131 is released from the second engagement member 6 and the locking device 100 is rotated to the unlocking position A, the axial interlock members 113 will fit in the hole 5 and the locking device 100 can be removed from the primary circuit board 1. Relative terms such as "below" or "above" or "upper" or "lower" maybe used herein to describe a relationship of one element to another element as illustrated in the figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientations depicted in the figures.

[0051] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A locking device (ioo) configured to lock a secondary circuit board (io) in a fixed position on a first side (2) of a primary circuit board (1), the locking device (100) extending along a longitudinal axis (Z), the locking device (100) comprising:- a base portion (101) configured to be longitudinally inserted into a hole (5) formed in the primary circuit board (1),- a head portion (102) fixed to a first end (111) of the base portion (101), the head portion (102) being configured to protrude from the first side (2) of the primary circuit board (1) when the base portion (101) is received in the hole (5), the head portion (102) comprising an abutment surface (121) configured to abut the first side (2) of the primary circuit board (1), and an actuation interface (122) configured to enable rotation of the locking device (100) about the longitudinal axis (Z) when the base portion (101) is received in the hole (5), from an unlocking position (A) to a locking position (B),- at least one axial interlock member (113) protruding transversely from the base portion (101) at a second end (112) of the base portion (101), the axial interlock member (113) being configured to engage with a second side (3) of the primary circuit board (1) in the locking position (B),- a rotational interlock mechanism (130) configured to engage with the first side (2) of the primary circuit board (1) in the locking position (B), wherein the head portion further comprises a board locking structure (140) configured to engage with an edge portion (11) of the secondary circuit board (10) in the locking position (B), and to disengage from the secondary circuit board (10) in the unlocking position (A), the board locking structure (140) being longitudinally spaced apart from the abutment surface (121).

2. The locking device of claim 1, wherein the head portion (102) comprises a seating surface (141) opposite to the abutment surface (121) and longitudinally spaced apart from the abutment surface (121), the seating surface (141) being configured to support the edge portion (11) of the secondary circuit board (10).

3. The locking device of claim 2, wherein the seating surface (141) is shaped as a first arc, such as a first annulus sector centred on the longitudinal axis (Z).

4. The locking device of claim 3, wherein the seating surface (141) extends over an angular range of more than 90°, preferably over an angular range of at least 180°.

5. The locking device of any one of claims 2-4, wherein the board locking structure (140) comprises a locking surface (145) opposite to a first portion (142) of the seating surface (141), wherein a pocket for receiving the edge portion (11) of the secondary circuit board (10) is provided between the locking surface (145) and the first portion (142) of the seating surface (141).

6. The locking device of claim 5, wherein the locking surface (145) is shaped as a second arc, such as a second annulus sector centred on the longitudinal axis (Z) and extending over a smaller angular range than the seating surface (141).

7. The locking device of any one of the preceding claims, wherein the actuation interface (122) comprises a lever (122) configured to be manually gripped.

8. The locking device of claim 7, wherein the lever (122) comprises a first side surface (123) delimiting the board locking structure (140) in a circumferential direction of the locking device (100).

9. The locking device of any one of the preceding claims, wherein the locking device (100) is configured to be moved from the unlocking position (A) to the locking position (B) by rotating it 90° about the longitudinal axis (Z).

10. The locking device of any one of the preceding claims, wherein, in the unlocking position (A), the at least one axial interlock member (113) is configured to be disengaged from the second side (3) of the primary circuit board (1).

11. The locking device of any one of the preceding claims, wherein the base portion (101) is shaped as a right circular cylinder defining the longitudinal axis (Z).

12. The locking device of any one of the preceding claims, wherein the locking device (100) is formed by a single piece of material.

13. The locking device of any one of the preceding claims, wherein the rotational interlock mechanism (130) comprises a first engagement member (131) configured to engage with a second engagement member (6) disposed on the first side (2) of the primary circuit board (1).14- The locking device of claim 13, further comprising a first arm (132) extending from a central part (104) of the head portion (102), the first engagement member (131) being disposed on a distal end portion (133) of the first arm (132).

15. The locking device of claim 14, further comprising a second arm (150) extending from the central part (104) of the head portion (102), the second arm (150) being configured to abut the first side (2) of the primary circuit board (1), the first and second arms (132, 150) extending from opposite sides (104a, 104b) of the central part (104).

16. The locking device of claim 14 or 15, wherein the first arm (132) and the second arm (150) are resilient members configured to, in the locking position (B), press the locking device (100) against the primary circuit board (1).

17. A circuit board arrangement (200) comprising:- a secondary circuit board (10),- a primary circuit board (1) comprising a hole (5) extending from a first side (2) to a second side (3) of the primary circuit board (1), wherein a first end (12) of the secondary circuit board (10) is pivotably connected to the first side (2) of the primary circuit board (1) via a connector (15), and a second end (13) of the secondary circuit board (10) comprises an edge portion (n), the circuit board arrangement (200) further comprising a locking device (100) according to any one of the preceding claims, wherein the locking device (100) is configured to, in its locking position (B), lock the secondary circuit board (10) in a fixed position relative to the primary circuit board (1).

18. The circuit board arrangement of claim 17, wherein the primary circuit board (1) is a motherboard, and the secondary circuit board (10) is an add-in card.

19. The circuit board arrangement of claim 17 or 18, wherein the edge portion (11) delimits a semi-circular notch formed in the second end (13) of the secondary circuit board (10).

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