Apparatus for holding a printed circuit board

An apparatus for holding a printed circuit board when mounting components thereon, said apparatus comprising a base plate, a mounting device for mounting a printed circuit board spaced from and substantially parallel to the base plate, a plurality of elongate support pins extending through respective holes within the base plate to extend transversely from the base plate, the support pins being independently positionable in height with respect to the base plate to define a configurable support surface for supporting components mounted on the printed circuit board during soldering, wherein the height that each pin extends from the base plate can be adjusted such that the support surface defined by the support pins can correspond to the topography of the circuit board and the components mounted thereon, a locking mechanism being provided for selectively locking the position of each support pin with respect to the base plate, wherein said locking mechanism comprises at least one elongate flexible member arranged to extend around a plurality of said support pins in convolute manner, tensioning device being associated with said at least one flexible member, whereby said tensioning device is adapted to selectively apply tension to said at least one flexible member to grip the pins around which said flexible member extends to lock the position of said pins with respect to the base plate.

FIELD OF THE INVENTION

This invention relates to an apparatus for holding a printed circuit board (PCB) and in particular to an apparatus for holding a printed circuit board to facilitate the soldering of components onto the PCB.

BACKGROUND OF THE INVENTION

When attaching components to a printed circuit board, after inserting the pins of the components through holes in the board and locating the components in place on the board, it is necessary to invert the board to provide access to the pins of the components on the underside of the board for soldering to the electrically conductive tracks of the board. During such operation it is necessary to support the components on the upper side of the board so that they do not move or fall out of the board before the pins have been soldered. However, due to the different dimensions of the components the topography of the components on the upper side of the board varies and therefore the support surface must typically be exchanged or altered for each PCB arrangement to be assembled.

It is known to provide a support surface defined by a plurality of spring loaded pins, whereby the pins can be individually displaced against a spring biasing force so that the support surface conforms to the topography of the PCB and the components mounted thereon. Such arrangement is disclosed in U.S. Pat. No. 5,984,293. However, the provision of individually spring loaded pins exert a variable force on the components and board dependent upon how far the pins are displaced. Such variable force may damage or dislodge the components from their desired position. Also, the force applied to the PCB by the spring loaded pins may distort the board.

SUMMARY OF THE INVENTION

According to the present invention there is provided an apparatus for holding a printed circuit board when mounting components thereon as claimed in claim1.

In one embodiment said at least one flexible member may extend around a plurality of said support pins in convolute manner, wherein said at least one flexible member grips said plurality of support pins to lock the position of said support pins when in its tensioned configuration.

In a preferred embodiment said plurality of support pins are arranged in an array of rows and columns, a respective flexible member being arranged to extend around each row of support pins in convolute manner to grip the pins in a respective row when tension is applied to the respective flexible member by the tensioning device.

Preferably a plurality of said elongate flexible members are arranged in a plurality of parallel rows corresponding to said rows of said array of support pins, said tensioning device comprising a pair of opposed anchor members between which the elongate flexible members extend, at least one of said anchor members being displaceable away from the other of said anchor members by an actuating device to define said tensioning device, whereby operation of said actuating device displaces at least one anchor member away from the other to apply tension to the elongate flexible members, thereby locking the support pins in position within their apertures.

Said actuating device may comprise a cam having a cam surface arranged to act upon the at least one anchor member to displace said at least one anchor member away from the other when moved to an operative configuration, thus applying tension to said elongate flexible members, and to release tension on said elongate flexible members when the cam is moved to an inoperative configuration. Said cam may include an actuating lever for moving said cam between its operative and inoperative configurations. Alternatively the actuating device may comprise a nut or knob threadedly engaged on a cooperating portion of at least one of the anchor member, whereby the nut or knob can be screwed onto said cooperating portion of the anchor member to displace the anchor members away from each other, thus applying tension to the elongate flexible members.

In one embodiment each elongate flexible member may be attached to and extends between a pair of transversely extending anchor members extending parallel to the ends of the base plate, each anchor member being associated with a respective actuating device, whereby operation of the actuating device displaces said anchor members away from one another to apply tension to the flexible members extending therebetween. Each actuating device may comprise a lever operated cam having a cam surface arranged to act upon the respective anchor member to displace said anchor members away from one another when the cams are moved to an operative configuration, thus applying tension to said elongate flexible members, and to release tension on said elongate flexible members when the cams are moved to an inoperative configuration.

Said mounting device may comprise a pair of opposed clamp members spaced from and extending parallel to said base plate, whereby said clamp members are adapted to engage opposite sides of a PCB to hold the PCB spaced from and parallel to said base plate at a position whereby a first end of said support pins can act against the PCB and any components mounted thereon. Said clamp members may be mounted on the base plate via respective carriers, each carrier being slideably mounted on the base plate for movement in a direction parallel to the base plate to permit the clamp members to be moved towards and away from one another. In one embodiment said carriers may be slideably mounted on parallel guide rails or tracks arranged on either side of said base plate. Said carriers may be provided with a biasing device biasing said clamp members towards one another. Said biasing device may comprise springs mounted on said guide rails or tracks acting between a respective end of the guide rail or track and a mounting portion of the respective carrier.

The clamp members may be mounted on said carriers via respective slides whereby each clamp member can be slid laterally with respect to the base plate between a loading position located to one side of the base plate and an operative position facing said base plate.

Support device may be provided on the base plate extending from the base plate to allow the apparatus to rest upon a surface upon said support device in a first configuration with said mounting device beneath said base plate and a second configuration with said mounting device above the base plate, the apparatus being moveable between said first and second configurations by inverting the apparatus, said pins are adapted to fall under gravity into contact with a populated side of a printed circuit board assembly when the PCB is mounted is said mounting device with the apparatus in its first configuration and when said locking mechanism is operated to release said pins to slide freely within the apertures in the base plate, the underside of the PCB being exposed to facilitate soldering of the pins when the apparatus is in its second configuration, with the locking mechanism operated to lock the support pins in their apertures such that the pins provide a support surface for the populated side of the PCB.

Preferably said support pins are provided with enlarged ends to prevent the support pins from falling out of the apertures.

Preferably the pins are formed from a rigid metallic or plastic material. The pins may be coated with an electrically and/or thermally insulating coating to provide protection to components in contact therewith from electrostatic discharge and/or to prevent heat transfer to the pins from the components during soldering.

In an alternative embodiment said at least one flexible member may be formed from an elastic material, and wherein said at least one flexible member is located between adjacent rows of support pins, wherein said at least one flexible member, when in its relaxed configuration, is dimensioned to engage and grip the sides of the support pins in said adjacent rows to lock the position of said pins with respect to the base plate, and wherein, when the at least one flexible member is elastically stretched when in its tensioned configuration such that the width of the at least one flexible member is reduced to the extent that the at least one flexible member no longer grips the sides of the support pins in said adjacent rows, allowing the pins to move freely with respect to the base plate.

DETAILED DESCRIPTION OF THE DRAWINGS

As illustrated inFIGS. 1 to 11, an apparatus for holding a printed circuit board (PCB) in accordance with an embodiment of the present invention comprises a planar base plate2having a pair of vertical end plates4,6extending perpendicularly from either end of the base plate2defining legs upon which the apparatus may rest, as shown inFIG. 1. The end plates4,6may be provided with fittings and apertures for enable the attachment of additional components, as will be described below in more detail. The end plates4,6may also be provided with angled side faces upon which the apparatus may be placed to arrange the apparatus in different positions/orientations to facilitate operations on a PCB100mounted thereon.

The base plate2has a plurality of apertures8formed therein within which are mounted a rectangular array of rigid support pins10, formed from a metal or suitable plastic material, arranged in a plurality of rows and columns. Each support pin10extends transversely from the base plate2and is slideable within the respective aperture to be displaceable with respect to the base plate2along the axis of the pin10. Each support pin10has a first end12, the first ends12of the array of support pins10defining a reconfigurable support surface for supporting components mounted on a PCB100, as best shown inFIGS. 2 and 3. Each pin10may have a flattened and enlarged second end14, opposite said first end12, peened over or otherwise formed to prevent the pin10from falling out of its aperture8in the base plate2. Each pin may be coated with an electrically and/or thermally insulating material, such as polyphenylene sulphide (PPS) or polyetheretherketone (PEEK) to reduce the risk of electrical discharge between the pins10and any electrical components in contact therewith and to reduce thermal conduction between the pins and the components in contact therewith, for example during soldering.

The support pins10are independently positionable with respect to the base plate2to adjust the height at which each pin extends from the base plate2, such that the first ends12of the array of pins10define a reconfigurable support surface for supporting components102mounted on the PCB100during soldering, wherein the height of the first end12of each pin10from the base plate2can be adjusted such that the support surface defined by the first ends12of the support pins10can correspond to the topography of the PCB100and the components102mounted thereon.

A locking mechanism is provided for selectively locking the position of each support pin10with respect to the base plate2. In the embodiment shown in the drawings, as best illustrated inFIGS. 5 and 6, the locking mechanism comprises parallel rows of parallel flexible elongate members16extending across the base plate2, each flexible elongate member16being arranged to extend around the pins10in a respective row thereof in convolute manner.

A tensioning device is associated with the flexible members16, whereby the tensioning device is adapted to selectively apply tension the flexible members16, such that each flexible member16grips the row of pins10around which it extends to lock the position of said pins10with respect to the base plate2.

The flexible members16may comprise elongate webs, tapes, threads, wires or cords and may be formed from a plastic web, polymeric or natural fibre or metal wire. The flexible members16may extend around the pins10in a respective row in zig zag fashion. Preferably each flexible member16is wrapped around each support pin10in the respective row, as illustrated inFIG. 7.

In the embodiment shown in the drawings, each flexible member is attached to and extends between a pair of transversely extending anchor members18,20, extending parallel to the ends of the base plate2. Each anchor member18,20is coupled to a respective operating device, such as a cam22,24, whereby the anchor members18,20can be displaced away from one another to apply tension to the flexible members16extending therebetween by displacing the cams22,24to respective release positions (shown inFIG. 5) and locking positions (shown inFIG. 6). It is envisaged that a first anchor member may be fixed with respect to the base plate while a second anchor member may be displaceable away from the first anchor member by means of a cam or similar operating device.

Parallel spaced apart clamp members26,28are mounted on the base plate2via carriers30,32, whereby said clamp members26,28can hold a PCB100therebetween such that the PCB100is spaced from and parallel to the base plate. The clamp member carriers26,28are slideably mounted on guide rails34,36located or defined on either side of the base plate2. The clamp members26,28may be provided with opposed “V” shaped slots for receiving opposite sides of the PCB100therein.

Handle portions33may be provided on each carrier30,32to enable the carriers30,32to be moved towards and away from one another, to facilitate placement and removal of a PCB100therebetween. The handle portions33may have angled outer sides, as shown inFIGS. 1 and 4, upon which the apparatus may be placed to facilitate placement of the PCB100for soldering.

In the embodiment shown inFIG. 3, screw locking members35may be provided for locking the carriers30,32in position on the guide rails34,36. Such locking members may not be required wherein the clamp members26,28are spring biased towards on another, as shown inFIGS. 9 and 10, although may be preferred to prevent excessive force being applied to the PCB via the springs or to more securely hold the PCB.

A best shown inFIG. 3, the clamp members26,28may be mounted on the carriers30,32via slides42,44to enable the clamp members26,28to be transversely slid outwards, in a direction parallel to the base plate2, to a loading position to one side of the base plate2, as shown inFIG. 2, and returned to an operative position adjacent the base plate2, to facilitate loading of a PCB between the clamp members26,28.

The end plates4,6preferably have a height extending from the base plate2greater than the distance between the clamp members26,28and the base plate2such that the apparatus can rest upon the end plates4,6, and optionally on the lower faces of the clamp members26,28, when loading a PCB into the clamp members26,28, as shown inFIG. 1.

A support plate46may be mounted on the base plate2to extend parallel to the base plate2via a plurality of support legs48extending transverse to the base plate2on an opposite side of the base plate2to the clamp members26,28. The apparatus may be arranged to rest on the support plate46, or on the ends of the support legs48, when the apparatus is arranged with the clamp members26,28uppermost, as shown inFIG. 3. The support plate46may also serve to retain the pins10within the apertures8in the base plate2by limiting the distance that the pins10can move out of the base plate2, as shown inFIG. 1.

In an alternative embodiment, as illustrated inFIG. 8, the first ends12of the pins10may be enlarged to provide a greater contact area between the pins10and the PCB100and any components102mounted thereon. The enlarged end of each pin10, or possible the entire pin, may be formed from a rigid plastic material, such as a Vespel®, a polyimide engineering plastic manufactured by Dupont®.

In use, firstly the apparatus is placed in a loading configuration, with the support plate46uppermost, resting on the end plates4,6, with the cams22,24in their locking positions to retain the support pins10in a fully retracted position with respect to the base plate2, abutting the support plate46, as shown inFIG. 1. The clamp members26,28may be slid out to their loading position to facilitate insertion of the PCB100. The carriers30,32are pushed away from one another using the handle portions33, and a PCB100having components102mounted thereon is located between the clamp members26,28.

With the PCB100beneath the base plate2, the cams22,24are moved to their release position, releasing the tension on the elongate members16, thus allowing the support pins10to fall under the action of gravity until the first end12of each pin10abuts the PCB100or components mounted thereon102located therebeneath, as shown inFIG. 2. The cams22,24may then be moved to their locking position, tensioning the elongate members16and thereby locking each pin100in position.

The apparatus can then rotated or inverted to a working configuration, as shown inFIGS. 3 and 4, to rest upon the support plate46and/or support legs48or the handle portions33, with the PCB located between the clamp members26,28and the components102mounted thereon supported and retained in position by the support surface defined by the first ends12of the support pins10.

In such configuration, the pins of the components102can be soldered to the PCB100, as illustrated inFIG. 4.

As shown inFIGS. 9 and 10, in an alternative embodiment springs138,140may be mounted on guide rails134,136upon which the carriers130,132of the clamp members126,128are slideably mounted to bias the carriers130,132, and thus the clamp members126,128, towards one another to engage and hold opposite sides of the PCB100when located between the clamp members126,128.

In the embodiment shown inFIGS. 9 and 10, the cams22,24have been replaced by nuts or control knobs122,124threadedly engaged on threaded projections125extending from the anchor members through apertures in side walls of the base plate2, whereby the control knobs122,124may be rotated or tightened to pull the anchor members away from one another and apply tension to the flexible members16to lock the pins10in position.

The apparatus may be adapted to facilitate other operations on the PCB100. For example, support posts50,52may be provided on either side of the base plate2, extending from the base plate2beside each end plate4,6, whereby additional components may be mounted on the support posts50,52. In the example shown inFIG. 11, a support frame54may be mounted on the support posts50,52, upon which may be mounted other components, as a fan56, light58and clips60,62for facilitating placement of the components102onto the PCB100and/or for testing the assembled circuit. In such case, the PCB100may be mounted between the clamp members26,28with the components uppermost, if required.

It is envisaged that the apparatus may be mounted in a chassis, whereby the base plate2may be rotated about a horizontal axis between the loading configuration and working configurations described above.

The present invention provides an apparatus for holding a PCB to facilitate the assembly and soldering of components onto the PCB whereby the support pins10provide a reconfigurable support surface that can readily conform to the topography of the PCB and components, wherein the pins can be readily and reliably locked in position by virtue of the tensioned elongate members to support the components during soldering without placing any stress on the PCB. The apparatus can also facilitate other operations on the PCB, during both assembly and testing, by reliably and stably supporting the PCB while permitting full access to either side of the PCB as required.

A locking mechanism for selectively locking the position of each support pin210with respect to the base plate202in accordance with a further embodiment of the invention is shown inFIGS. 12 and 13. The locking mechanism comprises s plurality of parallel elongate flexible members216formed from an elastic material extending across the base plate202, each elongate member216being arranged to extend between adjacent rows of support pins210. The thickness of each flexible member216is greater than the distance between the adjacent rows of pins210between which it extends, such that, when in a relaxed state, the sides of the flexible member216engage and grip the pins to lock the pins210in place with respect to the base plate202, as shown inFIG. 12.

A tensioning device is associated with the flexible members216, whereby the tensioning device is adapted to selectively apply tension to the flexible members216, such that each elastic flexible member216stretches, causing a reduction in the thickness of the flexible members such that the pins210are free to move with respect to the base plate2.

Each flexible member216is attached to and extends between a pair of transversely extending anchor members218,220, extending parallel to the ends of the base plate202. Each anchor member218,220is coupled to a operating device, such as a cam122,124, whereby the anchor members218,220can be displaced away from one another to apply tension to the flexible members216extending therebetween by displacing the cams222,224from respective release positions (shown inFIG. 12) to tensioning positions (shown inFIG. 13), to stretch the flexible members216and release the pins210. When it is desired to lock the position of the pins210with respect to the base plate202, the cams122,124, can be operated to displace the anchor members218,220towards one another, releasing or relaxing the tension on the flexible members216such that they once again expand to their original thickness and grip the pins210therebetween.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.