A printed circuit board component mounting device

Abstract: A printed circuit board component mounting device characterised in that it comprises: a sheet-metal member having a head portion formed to be locatable in a slot of a component to be mounted by the device on a printed circuit board; and a base portion formed to be locatable in an aperture in the board and partially extend therethrough to be soldered to a reverse surface of the board to retain said member on the board for locating a component thereon.

Description: The present invention relates to printed circuit board (pcb) component mounting devices and more particularly to such devices for mounting semiconductor heatsinks on pcbs. Semiconductor heatsinks are mounted on pcbs to be in contact with certain components (normally electronic) to dissipate heat from said components. In some cases a heatsink is relatively massive when compared to the component contacting with it. The component can, with other components, be soldered to the pcb by firstly locating the components on the pcb by inserting their contact pins (terminals) in ready formed apertures in the pcb and then passing the pcb over a solder bath to solder said pins to a reverse surface of the pcb thus forming electrical circuit connections. However, whilst relatively small heatsinks can also be mounted in this way simultaneously with the components, larger heatsinks must subsequently be separately screwed to the pcb or separately soldered thereto thus complicating and increasing the cost of the pcb circuit assembly process. In the case of separate soldering of massive heatsinks, the sinks are provided with large solder pins which locate through relatively large preformed apertures in the pcb. Heat required for separately soldering such a large component to the pcb can damage already formed solder joints thus jeopardising the integrity of the circuit assembled on the pcb. It can be economically worthwhile to recover relatively massive heatsinks from discarded or defective pcbs but recovery of such heatsinks secured to the pcbs by the methods mentioned above is labour intensive and therefore not always cost effective. DE-U-84 23 052 discloses a retaining device for an electrical component such as a relay. The device generally comprises a sheet-metal member having a slightly bent head portion formed with a projecting spade-form member and a base portion in the form of a conventional spring clamp. In use, the head portion of the device locates in an opening of the component, but the spade-form member locates outside the opening and acts as a stop to prevent the device from being removed from the component. The purpose of the retaining device is to secure the electrical component on a bracket or other fixing device. It is one object of the present invention to obviate or mitigate the above problems in order to provide a less expensive pcb circuit assembly process. It is another object of the present invention to provide a device and method for mounting relatively massive components, particularly semiconductor heatsinks, on a pcb whereby the mounting device can be mounted on the pcb simultaneously with electronic components by the solder bath or other suitable method, the device being such that a large component to be mounted to the pcb thereby can be push fitted onto the device by locating a head portion of the device in a pre-formed slot in the component. It is yet another aspect of the present invention to provide a device for mounting relatively large components on a pcb whereby said large components can be easily recovered from defective or discarded pcbs. According to the present invention, there is provided a sheet-metal member having a head portion and a base portion; said head portion having at least one spade-form member which depends or projects at an angle from the plane of the head portion and is directed generally downwards towards the base portion such that, in use, said head portion locates within a slot of a component to be mounted by the device on a printed circuit board and said spade-form member engages a side wall of the slot; and said base portion is locatable, in use, in an aperture in the board to partially extend therethrough to be soldered to a reverse surface of the board in order to retain said member on the board for locating the component thereon. Further features of the present invention are defined in the appended claims. The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments, by way of example thereof, by reference to the accompanying drawings, of which: Figure 1a shows a front elevational view of a first embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 1b shows a cross-sectional side view of the device of figure 1a; Figure 2a shows a front elevational view of a second embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 2b shows a cross-sectional side view of the device of figure 2a; Figure 3a shows a front elevational view of a third embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 3b shows a cross-sectional side view of the device of figure 3a; Figure 4a shows a front elevational view of a fourth embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 4b shows a cross-sectional side view of the device of figure 4a; Figure 5a shows on larger scale a front elevational view of a fifth embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 5b shows a cross-sectional side view of the device of figure 5a; Figure 6a shows a front elevational view of a sixth embodiment of a component mounting device according to the present invention mounted on a printed circuit board; Figure 6b shows a cross-sectional side view of the device of figure 6a; Figure 7a shows a front elevational view of a seventh embodiment of a component mounting device according to the present invention mounted on a printed circuit board; and Figure 7b shows a cross-sectional side view of the device of figure 7a. Figures 1 to 7 show various embodiments of an integrally formed sheet-metal device 10 for mounting relatively large components, particularly semiconductor heatsinks, to a printed circuit board 12 (pcb). Each of the figures (a) and (b) shows a front elevational and a side sectional view respectively of an embodiment of the mounting device 10 mounted on a pcb 12. In the following description like numerals are used to denote like parts. Each device includes a sheet-metal member 14 having a head portion 16 for locating in a slot 18 of a component 20 (partially shown in the side views of the figures) to be mounted by the device 10 to a pcb 12. Each device 10 also includes a base portion 22 which extends through an aperture 24 formed in the pcb. The aperture 24 in the pcb is intended to be generally of standard size as employed for directly mounting normal size components such as integrated circuit chips, transistors or resistors, for example, to the pcb 14 to thus avoid complicating the pcb circuit assembly process. The head portion 16 of the device is either formed with a stamped out spade-form member 30 and/or a rolled over spade-form member 32, each of which act in an identical manner to engage in a slot 18 of a component 20. Similarly, the base portion 22 is formed with a stamped out spade-form member 30 and/or a rolled over spade-form member 32. In use, the spade-form member (30, 32) of the base portion 22 engages a side wall 28 of an aperture 24 of the pcb 12 and a pull-out force applied to the device 10 causes the spade-form member (30, 32) to imbed firmly into the material of the pcb 12. The base portion 22 of the device 10 extends through the aperture 24 and can be soldered by normal techniques, such as the solder bath method, to a reverse surface 36 of the pcb simultaneously with the soldering of other components on the pcb 12. The degree to which the spade-form member (30, 32) extends away from the base portion 22 is chosen such that the base portion and spade-form member combination forms a friction fit in an aperture 24 in a pcb 12 thus holding the device 10 in a stable position until the soldering process is complete. The spade-form member (30, 32) of the base portion is generally flat across its width. This provides a greater surface area between the spade-form member and aperture surfaces for contact with solder (not shown) than in the conventional case where a component is mounted on a pcb by means of wire-like terminals. The base portion 22 may, however, comprise a spade-form member 38 of arcuate form extending in the plane of the sheet-metal member, as shown in figure 3. It will be understood that the base portion can comprise a spade-form member of any suitable shape for securing the device by soldering to a pcb. A component 20 such as a semiconductor heatsink can be mounted on a pcb 12 by mounting on the device 10 subsequent to the device having been soldered to the pcb. It is intended that components such as heatsinks are mounted onto the head portion 16 of the device 10 having firstly been formed with a suitably shaped slot in a base part thereof. In use, the component 20 can be push-fitted onto the head portion 16 of a mounting device 10 such that the spade-form member (30, 32) of the head portion engages a side wall 26 of the slot in the component. The side wall 26 of the slot 18 may have serrations 40 to improve the grip of the head portion in the slot and to increase its resistance to being forcably extracted. However, since the device 10 is formed of sheet-metal material, the spade-form member (30, 32) will possess some resilience which improves the fitting grip and assists in more easily retrieving the component 20 from the device 10. Further features of the various embodiments of the invention will be described with reference to specific figures. Figure 1 shows a first embodiment of the invention. This is of simple form, the head portion 16 having two integrally formed spade-form members 30 stamped from widthwise extending side edge portions 50, both of said spade-form members 30 depending in the same direction away from a face 52 of the head portion 16. The base portion 22 of the device has a single integrally formed spade-form member 30, also formed by stamping, which depends outwardly in the same direction as the spade-form members of the head portion. The base portion is of lesser width than a central portion 54 of the sheet-metal member extending between the head and base portions. Accordingly, at sides of a line defining the junction between the central and base portions 54, 22), there are provided shoulders 56 which assist in the accurate location of the device 10 on a pcb 12. These shoulders contact with an upper surface 58 of the pcb and thus ensure that the base portion projects through an aperture in the pcb such that an outer edge of the spade-form member engages a side wall of the aperture. The device can be positioned ready for soldering on the pcb simultaneously with other components (normally electronic) and by similar methods. Once all components, including component mounting devices, are positioned on the pcb, they can then be secured thereto by passing over a solder bath or by some other suitable soldering method. The embodiment of figure 2 is similar to that of figure 1 insofar that it also has a head portion 16 including two spade-form members 32 and a base portion 22 with a single spade-form member 32. Indeed, in this embodiment the width of the base portion 16 is also less than that of the central portion 54. However, in this embodiment the spade-form members 32 of the head portion are formed by bending over top edge portions of side portions of the head portion. Similarly, the spade-form member of the base portion is formed by bending an edge portion but the spade-form members 32 act in identical manner to those of the first embodiment. The embodiment of figure 3 is also similar to that of figure 1 but differs in that the base portion 22 has been formed by pressing to provide a single arcuate spade-form member 38 which is adapted to fit in a generally circular aperture in a pcb. The shape of the spade-form member 38 is such that it provides a friction fit in the aperture 24 of the pcb 12 with its outer curved surface in contact with a portion of a side wall 28 of said aperture 24. Figure 4 illustrates an embodiment of the device in which the head portion 16 has a number of spade-form members 30 arranged in rows. The spade-form members are integrally formed by stamping but are arranged such that alternate spade-form members depend from oppositely facing faces of said head portion. In use, when the head portion is inserted in a slot 18 of a component 20, the oppositely directed spade-form members 30 engage opposing side walls 26 of said slot. Such an arrangement can improve the grip between the device and component particularly where both side walls of the slot and the component have serrations 40. The embodiment of figure 5 is similar to that of figure 4 insofar that it also has a head portion 16 having a number of rows of spade-form members 30. These also are arranged to depend alternately from oppositely facing faces of the head portion. In this embodiment, however, a top edge portion 60 of the head portion is bent over to lie in a plane substantially at right-angles to the plane of the head portion. This portion 60 acts to provide a contact zone for manually applying pressure to the device 10 when inserting it on a pcb 12. Experience has shown that, where this feature is absent, the top edge of the device 10 can be sharp and cause injury when manual pressure is applied on this edge during insertion of the device on the board. In addition, the bent edge portion 60 provides rigidity in the device in a transverse direction across its width. In addition to the bent over top portion 60, side edge portions 62 of the head portion 16 are bent to lie in a plane at right-angles to the plane of the head portion. The bent side edge portions 62 provide rigidity to the device in a depth-wise direction and also improve the stability of the device when inserted on a pcb. The bent side edge portions contact on an upper surface 58 of the pcb and act to prevent rotational movement of the device in a direction normal to the plane of the device 10 when a component 20 is being push fitted onto the device. It can be seen from the embodiments of 1 to 5 that the base portion 22 of the device 10 is shown as having or comprising only one spade-form member (30, 32, 38). It will be clearly understood that this portion 22 of the device may be formed with a number of such spade-form members suitably arranged for contact, in use, with a side wall 28 of an aperture 24 on a pcb 12. In addition, in figures 1 to 5, the base portion is shown to be located in an aperture which is generally elongate in shape. It will be understood that the width of the base portion 22 can be reduced in order that the base portion might locate in a standard circular aperture on a pcb. Figure 6 shows a sixth embodiment of the invention which has a configuration generally similar to that of the embodiment of figure 5. However, in this embodiment the device has two base portions (22a,b) each formed with a spade-form member 30. The spade-form member of the first base portion 22a extends in a direction generally opposite to that of the spade-form member of the second base portion 22b. Therefore, in use, this embodiment of the device can be mounted on a pcb 12 by locating said base portions (22a,b) in separate apertures 24, or alternatively, by locating said base portions in a single elongate aperture whereby said spade-form members each contact with respective opposing side walls of said aperture. Figure 7 shows a seventh embodiment of the invention which is generally similar to the embodiment of figure 6. However, this embodiment includes support members 70 extending generally outwardly from the plane of the sheet-metal member 14. Each of said support members 70 comprises a first portion 70a extending in a direction normal to the plane of the sheet-metal member 14 and a second portion 70b depending from the first portion in a downward direction generally at right-angles thereto. In use, the distal ends 70c of the support members 70 contact with an upper surface 58 of a pcb 12. The support members 70 extend from the plane of the sheet-metal member 14 for a distance sufficient to allow a component 20 mounted on the device 10 to rest with its base on the first portions 70a of said support members 70 such that the component is mounted to the pcb spaced above the upper surface 58 thereof. The support members facilitate washing of the pcb. The support members are integrally formed from the sheet-metal member 14 by stamping from edge portions of said member.

Claims: A printed circuit board component mounting device comprising: a sheet-metal member (14) having a head portion (16) and a base portion (22); said head portion (16) having at least one spade-form member (30; 32) which depends or projects at an angle from the plane of the head portion (16) and is directed generally downwards towards the base portion (22) such that, in use, said head portion (16) locates within a slot of a component to be mounted by the device on a printed circuit board and said spade-form member (30; 32) engages a side wall of the slot; and said base portion (22) is locatable, in use, in an aperture in the board to partially extend therethrough to be soldered to a reverse surface of the board in order to retain said member (14) on the board for locating the component thereon. A device as claimed in claim 1, wherein the base portion (22) is locatable, in use, in an aperture in the board by means of at least one spade-form member (30; 32) which depends or projects at an angle from the plane of the base portion (22) and is directed generally upwards towards said head portion (16) such that, in use, said base portion (22) locates through an aperture in the board and said spade-form member (30; 32) engages a side wall of the aperture. A device as claimed in claim 1 or claim 2, wherein the head portion (16) has two spade-form members (30; 32) which depend or project outwardly from respective oppositely facing faces of said portion to engage, in use, respective opposing side walls of a slot in a component. A device as claimed in claim 2 or claim 3, wherein the base portion (22) has two spade-form members (30; 32) which depend or project outwardly from respective oppositely facing faces of said portion to engage, in use, the side wall of an aperture of a printed circuit board. A device as claimed in any one of claims 1 to 4, wherein a top edge portion (60) of the head portion (16) is bent over to generally lie in a plane at an angle to the plane of the head portion (16). A device as claimed in any preceding claim, wherein at least one side edge portion (62) of the sheet-metal member (14) is bent to generally lie in a plane at an angle to the plane of said sheet-metal member (14). A device as claimed in claim 1, wherein the base portion (22) comprises a spade-form member (38) of arcuate form extending in the plane of the sheet-metal member (14). A device as claimed in any preceding claim, wherein the width of the base portion (22) is less than that of the sheet-metal member (14). A device as claimed in any preceding claim, wherein the device has two or more base portions (22) . A device as claimed in any preceding claim, wherein the device includes an integrally formed support member (70) depending generally away from the plane of the sheet-metal member (14) such that, in use, a distal end (70c) of the support member (70) rests upon an upper surface of a printed circuit board to hold a component mounted on the device with its base resting on the support member (70) spaced from said upper surface of the board. A device as claimed in claim 10, wherein the support member (70) comprises a first portion (70a) depending generally away from the plane of the sheet-metal member (14) in a direction normal thereto, and a second portion (70b) depending generally downwardly from said first portion (70a) such that, in use, the base of a component mounted on the device rests only on the first portion (70a) of the support member (70). A device as claimed in claim 10, wherein the support member (70) is formed by stamping said member from the sheet-metal member (14). A device as claimed in claim 12, wherein the support member (70) is formed by stamping from a side edge portion of the sheet-metal member (14). A device as claimed in claims 11 to 13, wherein the device includes two support members (70) which depend outwardly from respective oppositely facing faces of the sheet-metal member (14). A printed circuit board having a device in accordance with any of the preceding claims fixed thereto by soldering. A combination comprising: a printed circuit board; a circuit board component; and a device in accordance with any one of claims 1 to 14, wherein the base portion of the device is soldered to the printed circuit board and the head portion of the device is located in a slot of the component to mount it on the board. A method of mounting a component to a printed circuit board using a device according to any one of claims 1 to 14, wherein it comprises the steps of: mounting a device on a printed circuit board such that a base portion (22) of the device locates through an aperture in the board; soldering a base portion (22) of the device to a reverse surface of the board to that upon which the device is mounted; and mounting a component having a slot therein on the board by placing said component on the device such that the head portion (16) of the device locates within the slot of the component such that a spade-form member (30; 32) of the head portion engages a side wall of the slot.

Inventors: FISHER FRANCIS EDWARD, JOHNSON ROBIN DOUGLAS, JORDAN WILLIAM D, FISHER, FRANCIS EDWARD, JOHNSON, ROBIN DOUGLAS, JORDAN, WILLIAM D
Applicants: REDPOINT THERMALLOY LTD, REDPOINT THERMALLOY LIMITED
Application year: 1993
Main classification: H05K7
IPC codes: H05K7, H05K3