Fasteners for mounting printed circuit boards

Abstract

A fastener includes: a head; a first pin extending from the head along a longitudinal axis, the first pin including a surface feature configured to engage a first circuit board assembly; and a second pin extending from the head in a direction opposite the first pin, the second pin including a stop wall and a plurality of deflectable arms configured to deflect in the direction of the longitudinal axis when inserted into a second circuit board assembly to couple the second pin to the second circuit board assembly. The stop wall extends from at least one of the plurality of deflectable arms away from the longitudinal axis and is configured to contact the second circuit board assembly when the plurality of deflectable arms are coupled to the second circuit board assembly.

Description

TECHNICAL FIELDThe present description relates generally to fasteners, and more particularly to fasteners for attaching circuit board assemblies to metal castings.BACKGROUNDScrews are used in various manufacturing processes to attach one component to another. Manufacturing using screws requires controlling torque values when the components are fastened together. Controlling torque may be difficult to reproduce and increases the time required for manufacturing. Moreover, too much tightening of the screws can result in damage to the attached components. Accordingly, there is a need for alternative fasteners to attach two components to each other.SUMMARYIn one embodiment, it is a fastener for attaching circuit board assemblies, the fastener including: a head having a first radius; a first pin having a second radius less than the first radius, the first pin extending from the head along a longitudinal axis, the first pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface between the head and a tip of the pin, the surface feature configured to engage a first circuit board assembly; A second pin extending from the head along the longitudinal axis in a direction opposite the first pin, the second pin including a stop wall and a plurality of deflectable arms configured to deflect in the direction of the longitudinal axis when inserted into a second circuit board assembly to couple the second pin to the second circuit board assembly, and the stop wall extending from at least one of the plurality of deflectable arms away from the longitudinal axis, the stop wall configured to contact the second circuit board assembly when the plurality of deflectable arms are coupled to the second circuit board assembly.Another embodiment is a fastener for fastening circuit board assemblies, the fastener including: a head having a first radius; a first pin having a second radius less than the first radius, the first pin extending from the head along a longitudinal axis, the first pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head toward a tip of the pin, the surface feature including at least one of: a plurality of barbs, a helical knurl, and a plurality of threads, and the surface feature configured to engage a first circuit board assembly; and a second pin extending from the head along the longitudinal axis in a direction opposite the first pin, the second pin including a plurality of deflectable arms configured to deflect in the direction of the longitudinal axis when inserted into a second circuit board assembly to couple the second pin to the second circuit board assembly.These and other features provided by the embodiments described herein will be more fully understood from the following detailed description taken in conjunction with the drawings.BRIEF DESCRIPTION OF THE DRAWINGSThe embodiments set forth in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments will be understood when read in conjunction with the following drawings, in which like structures are denoted by like reference numerals and in which: FIG. 1 depicts a perspective view of a fastener coupling a pair of circuit board assemblies and a circuit board housing according to one or more embodiments shown and described herein; FIG. 2A depicts a perspective view of an example fastener according to one or more embodiments shown and described herein, FIG. 2B depicts a cross-sectional side view of an example fastener inserted into a circuit board housing according to one or more embodiments shown and described herein; FIG. 3 depicts a perspective view of another exemplary fastener according to one or more embodiments shown and described herein; and FIG. 4 depicts a perspective view of yet another example fastener according to one or more embodiments shown and described herein.DETAILED DESCRIPTIONReferring initially to Fig. 1, a pair of circuit board assemblies secured together are pictorially illustrated. A first printed circuit board assembly 24 is fastened to a second printed circuit board assembly 26 by means of a fastening element 10 by means of an interference fit. The first circuit board assembly 24 includes a first attachment aperture 25 and the second circuit board assembly 26 includes a second attachment aperture 27, each for receiving a portion of the fastener 10. Alternatively, the first attachment aperture 25 may have an aperture radius that is greater than a radius of the pin 14, where the first circuit board assembly 24 is attached to a circuit board housing 11 by being positioned between the head 12 of the fastener 10 and the circuit board housing 11. Each circuit board assembly may include a printed circuit board (PCB) and electronic components such as capacitors, transistors, inductors, or the like on the PCB. The pair of circuit board assemblies can be mounted to the circuit board housing 11 by inserting the pin of the fastener 10 into an opening in the circuit board housing 11. The pair of circuit board assemblies may be a power supply card for supplying power to a device and a control card for controlling an operation of the device. The circuit board housing 11 may be formed of any suitable material such as plastic or metal, wherein the circuit board housing 11 may be a metal casting. In some embodiments, the circuit board housing 11 may be a housing for an electric motor, such as an electric vehicle motor. In other embodiments, the circuit board housing 11 may be a plastic housing such as for use with a steering column, for use with smaller circuit board assemblies than metal castings. The above examples are merely examples and do not limit the component materials or uses.The fastener 10 extends into the first attachment aperture 25 of the first circuit board assembly 24, the second attachment aperture 27 of the second circuit board assembly 26, and the aperture of the circuit board housing 11 to couple the circuit board assemblies to the circuit board housing 11, wherein the fastener 10 completes the ground path between the pair of circuit board assemblies and the circuit board housing 11 thereby connecting the circuit board assemblies to ground. As shown in phantom, the fastener 10 can be inserted into the circuit board assemblies and the circuit board housing 11 along an insertion axis I that extends through a center of the first attachment opening 25, the second attachment opening 27, and the opening in the circuit board housing 11.Referring now to Fig. 2A, there is illustrated a first embodiment of the fastener 10 of Fig. 1. The fastener 10 includes a head 12, a first pin 14 extending from the head 12 along a longitudinal axis 30, and a second pin 16 extending from the head 12 along the longitudinal axis 30 in a direction opposite the first pin 14. The head 12 has a first radius, the first pin 14 has a second radius that is less than the first radius, and the second pin 16 has a third radius that is less than the first radius. The first pin 14 includes an outer surface 18 circumferentially surrounding the longitudinal axis 30 and a surface feature 20 extending on the outer surface 18 from the head 12 toward a tip 22 of the pin 14. The surface feature 20 may be at least one of a plurality of barbs, a helical knurl, and a plurality of threads configured to engage the first circuit board assembly 24 and the circuit board housing 11. The pictorially illustrated fastener 10 of Fig. 2A includes the helical knurl 60. The helical knurl 60 includes a plurality of knurls extending from the head 12 to the tip 22 of the first pin 12, the plurality of knurls forming a spiral, and each of the plurality of knurls at least partially circumferentially surrounding the longitudinal axis 30. When the fastener 10 is inserted into the attachment openings, the helical knurl 60 can rotate the fastener 10 as the fastener 10 moves into the attachment openings. The helical knurl 60 similarly causes the fastener 10 to rotate as the fastener 10 is removed from the attachment openings. However, a tool such as a claw hammer applies a normal force to the head 12 of the fastener 10 during removal, thereby resisting rotation of the fastener 10 and increasing the force required to remove the fastener 10 as compared to insertion. The helical knurl 60 may include any operable number of knurls such as 1, 20, between 1 and 20, or more than 20 knurls. Each knurl may be disposed at an angle relative to the longitudinal axis 30 when viewed in a side view. The angle may be between 10° and 80°, more specifically between 25° and 40°, including the endpoints, in some embodiments.The fastener 10 may include a chamfer 42 at the tip 22 of the first pin 14 having an angle between 25° and 40° relative to the longitudinal axis 30. The fastener 10 may further include a length of the pin 14 that does not include the surface feature 20 positioned between the surface feature 20 and a tip 22 of the pin 14, wherein the length of the pin 14 without the surface feature 20 extends from the surface feature 20 to the chamfer 42. The fastener 10 may include a zinc coating (or other coating that allows for a ground connection) to prevent corrosion.The second pin 16 of the fastener 10 may include a stop wall 32, a plurality of deflectable arms 36, and a base 44 from which the deflectable arms 36 extend. The plurality of deflectable arms 36 may be configured to deflect in the direction of the longitudinal axis 30 upon insertion into the second circuit board assembly 26 to press fit the second pin 16 to the second circuit board assembly 26. The stop wall 32 may extend from at least one of the plurality of deflectable arms 36 and may extend from each of the deflectable arms 36 away from the longitudinal axis 30 to radially describe the longitudinal axis 30. The stop wall 32 is configured to contact the second circuit board assembly 26 when the plurality of deflectable arms 36 are coupled to the second circuit board assembly 26 to space the second circuit board assembly 26 a predetermined distance from the first circuit board assembly 24.The plurality of deflectable arms 36 may each include an outer surface 37 having an outwardly tapered section 38 whose distance from the longitudinal axis 30 increases as the outer surface 37 moves from the stop wall 32 toward the tip 22, and an inwardly tapered section 40 whose distance from the longitudinal axis 30 decreases as the outer surface 37 moves from the outwardly tapered section 38 toward the tip 22. The inwardly tapered section 40 can engage the second attachment aperture 27 in the second circuit board assembly 26 to couple the fastener 10 to the second circuit board assembly 26. The plurality of deflectable arms 36 may each include a chamfer 42 at the tip 22 at an inner edge of the deflectable arms 36 closest to the longitudinal axis 30. The plurality of deflectable arms 36 may include any number of deflectable arms 36, such as four deflectable arms 36.Referring to FIG. 2B, an insertion tool 50 may be used for inserting the fastener 10 into the circuit board housing 11. The insertion tool 50 may include a body 52 defining a cavity 54 having a first inner section 56 having a first radius and a second inner section 58 having a second radius greater than the first radius, the second inner section 58 positioned between the first inner section 56 and an open end 57 of the cavity 54. The cavity 54 of the insertion tool 50 may further include a tapered section 59 between the first inner section 56 and the second inner section 58 to contact and engage an insertion section 46 of the second pin 16. The second pin 16 may include an insertion section 46 at an end of the base 44 from which the plurality of deflectable arms 36 extend, the insertion section 46 including a tapered surface 48.Referring now to Fig. 3, another embodiment of the fastener 10' is illustrated. The fastener 10' may include any of the features described above with reference to FIG. 2A, except for the surface feature 20'. Accordingly, similar features will not be described again for brevity. The surface feature 20' of the fastener 10' may be a plurality of barbs 62, each of the plurality of barbs 62 encircling the longitudinal axis 30 in the circumferential direction, and the plurality of barbs 62 spaced apart from one another along the longitudinal axis 30. The plurality of barbs 62 are arranged sequentially along the longitudinal axis 30. The plurality of barbs 62 may include any operable number of barbs including 1, 20, or any number therebetween, and more particularly 12 barbs. The barbs may each have a uniform thickness (e.g., distance along the longitudinal axis 30) and a uniform distance between the barbs along the longitudinal axis 30.Referring now to Fig. 4, there is illustrated yet another embodiment of the fastener 10''. The fastener 10'' may include any of the features described above with reference to FIGS. 2A and 3 except for the surface feature 20''. Accordingly, similar features will not be described again for brevity. The surface feature 20 of the fastener 10 may be a threaded surface 64 similar to a screw or bolt such that the fastener 10 may be screwed into the circuit board housing 11 to be coupled to the circuit board housing 11. In such embodiments, the head 12 of the fastener 10'' may be hexagonal or other shape that allows a tool to grasp the head 12 and rotate the fastener 10''.It should be appreciated that the terms "substantially" and "about" may be used herein to represent the inherent level of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also used herein to represent the degree to which a quantitative representation may deviate from a specified reference without changing the basic function of the subject matter in question.While specific embodiments are illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. While various aspects of the claimed subject matter have been described herein, such aspects need not be used in combination. It is therefore intended that the appended claims cover all such changes and modifications as fall within the scope of the claimed subject matter.

Claims

A fastener for fastening circuit board assemblies, the fastener comprising: a head having a first radius; a first pin having a second radius less than the first radius, the first pin extending from the head along a longitudinal axis, the first pin comprising an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface between the head and a tip of the pin, the surface feature configured to engage a first circuit board assembly; A second pin extending from the head along the longitudinal axis in a direction opposite the first pin, the second pin comprising a stop wall and a plurality of deflectable arms configured to deflect toward the longitudinal axis when inserted into a second circuit board assembly to couple the second pin to the second circuit board assembly, and the stop wall extending from at least one of the plurality of deflectable arms away from the longitudinal axis, the stop wall configured to contact the second circuit board assembly when the plurality of deflectable arms are coupled to the second circuit board assembly.The fastener of claim 1, wherein the plurality of deflectable arms each include an outer surface having an outwardly tapered section whose distance from the longitudinal axis increases as the outer surface moves from the stop wall toward the tip and an inwardly tapered section whose distance from the longitudinal axis decreases as the outer surface moves from the outwardly tapered section toward the tip.The fastener of claim 1, wherein the plurality of deflectable arms each include a chamfer at the tip of an inner edge of the deflectable arms that is closest to the longitudinal axis.The fastener of claim 1, wherein the plurality of deflectable arms comprises four deflectable arms.The fastener of claim 1, wherein the stop wall extends from each of the plurality of deflectable arms to radially encircle the longitudinal axis.The fastener of claim 1, wherein the second pin further comprises a base from which the plurality of deflectable arms extend.The fastener of claim 6, wherein the base comprises an insertion section at an end of the base from which the plurality of deflectable arms extend, the insertion section comprising a tapered surface.The insertion tool for inserting the fastener of claim 1, wherein the insertion tool comprises a body defining a cavity having a first interior section having a first radius and a second interior section having a second radius greater than the first radius, the first interior section positioned between the first interior section and an open end of the cavity.The fastener of claim 8, wherein the cavity of the insertion tool further comprises a tapered section between the first inner section and the second inner section to contact and engage an insertion section of the second pin, and the second pin comprises a base from which the plurality of deflectable arms extend and an insertion section at an end of the base from which the plurality of deflectable arms extend, the insertion section comprising a tapered surface.A fastener for fastening circuit board assemblies, the fastener comprising: a head having a first radius; a first pin having a second radius less than the first radius, the first pin extending from the head along a longitudinal axis, the first pin comprising an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head toward a tip of the pin, the surface feature comprising at least one of: a plurality of barbs, a helical knurl, and a plurality of threads, and the surface feature configured to engage a first circuit board assembly; and a second pin extending from the head along the longitudinal axis in a direction opposite the first pin, the second pin comprising a plurality of deflectable arms configured to deflect in the direction of the longitudinal axis when inserted into a second circuit board assembly to couple the second pin to the second circuit board assembly.The fastener of claim 10, wherein the plurality of deflectable arms each include an outer surface having an outwardly tapered section whose distance from the longitudinal axis increases as the outer surface moves from the stop wall toward the tip and an inwardly tapered section whose distance from the longitudinal axis decreases as the outer surface moves from the outwardly tapered section toward the tip.The fastener of claim 10, wherein the plurality of deflectable arms comprises four deflectable arms.The fastener of claim 10, wherein the stop wall extends from each of the plurality of deflectable arms to radially encircle the longitudinal axis.The fastener of claim 10, wherein the second pin further comprises a base from which the plurality of deflectable arms extend.The fastener of claim 14, wherein the base comprises an insertion section at an end of the base from which the plurality of deflectable arms extend, the insertion section comprising a tapered surface.The fastener of claim 10, wherein the plurality of barbs are arranged sequentially along the longitudinal axis.The fastener of claim 10, further comprising a chamfer at a tip of the pin having an angle between 25° and 40° relative to the longitudinal axis.The fastener of claim 10, further comprising a length of the pin that does not include the surface feature positioned between the surface feature and a tip of the pin.The fastener of claim 10, wherein the surface feature is the plurality of barbs and each of the plurality of barbs circumferentially surrounds the longitudinal axis and the plurality of barbs are spaced apart from one another along the longitudinal axis.The fastener of claim 10, wherein the surface feature is the helical knurl having a plurality of knurls extending from the head to the tip of the pin, the plurality of knurls forming a helix, each of the plurality of knurls surrounding the longitudinal axis at least partially circumferentially.

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