Fixing apparatus for mounting a heat sink to a printed circuit board

1. Field

The present invention generally relates to a fixing apparatus, and particularly relates to a fixing apparatus having a retention module and a back plate engaged with the retention module so that the retention module and the back plate are both secured on a printed circuit board whereby a heat sink attached to the retention module can be securely mounted on the printed circuit board.

2. Related Art

With advancement of computer technology, electronic devices operate with high speeds. It is well known that the more rapidly the electronic devices operate, the more heat they generate. If the heat is not dissipated duly, the stability of the operation of the electronic devices will be impacted severely.

Generally, in order to ensure the electronic device to run normally, a heat sink is used to dissipate the heat generated by the electronic device. And in order to facilitate installation of the heat sink to the electronic device, a retention module is employed. Commonly, the retention module is mounted onto a printed circuit board and is around the electronic device. One the other hand, to enhance the strength of the printed circuit board, a back plate is applied underneath the printed circuit board. An example of a combination comprising a retention module and a back plate both secured to a printed circuit board, is taught in U.S. Pat. No. 6,549,412B1. In this patent, the retention module forms four downward posts adjacent four corners thereof. A heat sink (not shown) is to be fixed to the retention module. Each post defines a through hole therein. The back plate comprises four poles corresponding to the through holes of the retention module. In assembly, the poles extend through the printed circuit board and the through holes of the retention module, and further protrude from a top surface of the retention module. The protruded portions of the poles are stamped to thereby form rivet joints between the retention module and the back plate. Thus, the retention module and the back plate are attached on opposite sides of the printed circuit board, whereby the heat sink fixed on the retention module is secured to the printed circuit board to thermally contact with a CPU (not shown) mounted on the printed circuit board and surrounded by the retention module.

Free ends of the poles of the '412 patent are stamped after the retention module and the back plate are placed to the printed circuit board. That is to say, the printed circuit board is placed in a situation subjected to stamping procedure, with the retention module and the back plate. The printed circuit board is thus at the risk of being damaged under stamping force or huge vibration during stamping the poles. Additionally, stamping the free ends of the poles increases the assembly cost.

It is strongly desired to provide an improved heat sink fixing apparatus which overcomes the above problem.

What is needed is a fixing apparatus having a retention module and a back plate wherein the retention module and the back plate are mounted to a printed circuit board simultaneously and expediently by an engagement of the retention module and the back plate. The retention module is for carrying a heat sink so that when the retention module and the back plate are mounted to the printed circuit board, the heat sink carried by the retention module can have an intimate contact with a heat-generating electronic device mounted on the printed circuit board and surrounded by the retention module.

A fixing apparatus in accordance with a preferred embodiment of the present invention comprises a retention module and a back plate. The retention module is attached on a printed circuit board that defines a plurality of through apertures therein. The retention module comprises a plurality of posts depending therefrom. Each post is aligned with a corresponding through aperture and defines a pair of support portions on an inner wall thereof. The back plate is attached on an underside of the printed circuit board, for reinforcing the printed circuit board and securing the retention module on the printed circuit board. The back plate comprises a plurality of poles extending upwardly from a periphery thereof. The poles are extended through the through apertures and inserted in the posts. Each pole locks in a corresponding post by engaging with the support portions to render the retention module and the back plate to be mounted to the printed circuit board.

Other advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded, isometric view of a heat sink fixing apparatus in accordance with a preferred embodiment of the present invention and a printed circuit board, the fixing apparatus comprising a retention module with posts thereon and a back plate;

FIG. 2 is an assembled view of the fixing apparatus of FIG. 1 without the printed circuit board;

FIG. 3 is an enlarged bottom view of the retention module of the fixing apparatus of FIG. 1 , with a part being cut away;

FIG. 4 is an enlarged view of an indicated portion IV of FIG. 3 ;

FIG. 5 is an enlarged view of the back plate of the fixing apparatus of FIG. 1 ;

FIG. 6 is an enlarged view of an indicated portion VI of FIG. 5 ;

FIG. 7 is an enlarged view of the retention module of the fixing apparatus of FIG. 1 , with a part being cut away to more clearly show an inner configuration of one of the posts;

FIG. 8 is an enlarged view of an indicated portion VIII of FIG. 7 ;

FIG. 9 is a view similar to FIG. 1 , but with a part of the retention module being cut away and an arrow being added to indicate a direction that the back plate is moved to attach on a bottom surface of the printed circuit board;

FIG. 10 is an assembled view of FIG. 9 ; and

FIG. 11 is an enlarged view of an indicated portion XI of FIG. 10 .

Reference will now be made to the drawings to describe embodiment of the present invention in detail.

FIG. 1 illustrates a heat sink fixing apparatus in accordance with a preferred embodiment of the present invention, together with a printed circuit board 20 . The printed circuit board 20 defines four through apertures 22 therein. The fixing apparatus comprises a retention module 10 and a back plate 30 . The retention module 10 cooperates with the back plate 30 to sandwich the printed circuit board 20 therebetween. Referring to FIG. 2 , the back plate 30 is engaged with the retention module 10 so that the retention module 10 and the back plate 30 are secured together.

The retention module 10 is for attaching on a top surface of the printed circuit board 20 and thereby enabling a heat sink (not shown) retained by the retention module 10 to contact with an electronic component (not shown) mounted on the top surface of the printed circuit board 20 and surrounded by the retention module 10 . Referring to FIGS. 3–4 , the retention module 10 comprises a base 11 , an opening 13 and four posts 12 . The base 11 and the opening 13 each have a rectangular configuration. The opening 13 is defined in a center of the base 11 . The four posts 12 respectively depend from four corners of the retention module 10 , corresponding to the through apertures 22 of the printed circuit board 20 . The posts 12 are hollow. A pair of support portions 124 is formed on an inner wall of each post 12 . Each support portion 124 is configured as a triangle-shaped tab. The support portions 124 are spaced from and parallel to each other. Each support portion 124 comprises an inclined plane 1240 and a horizontal platform 1242 as clearly shown in FIGS. 7–8 . The platform 1242 is located at a top of the support portion 124 . The inclined plane 1240 inclines outwardly along a direction from a bottom to the top of the support portion 124 .

The back plate 30 is for attaching on a bottom surface of the printed circuit board 20 thereby reinforcing the printed circuit board 20 . Referring to FIGS. 5–6 , the back plate 30 comprises four poles 32 extending upwardly from four corners of a periphery of the back plate 30 , corresponding to the through apertures 22 of the printed circuit board 20 and the posts 12 . Each pole 32 comprises a seat 320 extending from an edge of the back plate 30 , a shaft 322 extending from the seat 320 and a hook 324 extending from the shaft 322 . The hook 324 further comprises a pair of arms 3240 formed at opposite ends of the hook 324 .

Referring to FIGS. 9–11 , in assembly, the back plate 30 is attached onto the bottom surface of the printed circuit board 20 . The poles 32 of the back plate 30 are extended through the through apertures 22 of the printed circuit board 20 . The seats 320 are received in the through apertures 22 of the printed circuit board 20 and the shafts 322 and the hooks 324 are extended upwardly beyond the printed circuit board 20 . The retention module 10 is then attached to the top surface of the printed circuit board 20 . The posts 12 are aligned with the through apertures 22 of the printed circuit board 20 to allow the hooks 324 of the poles 32 inserted insides of the posts 12 . The retention module 10 is pressed toward the printed circuit board 20 . The arms 3240 of the hooks 324 are rendered to slide along the inclined planes 1240 and the shafts 322 moves upwardly between the support portions 124 , respectively, until the arms 3240 of the hooks 324 reach a position engaging the platforms 1242 so that the poles 32 of the back plate 30 are locked in the posts 12 of the retention module 10 , as particularly clearly shown in FIGS. 10–11 . The shaft 322 of each pole 32 is thus received between the support portions 124 of the corresponding post 12 . The posts 12 are engagingly rested on the printed circuit board 20 . The retention module 10 and the back plate 30 therefore are attached on opposite sides of the printed circuit board 20 .

In this invention, the retention module 10 and the back plate 30 are simultaneously secured to the printed circuit board 20 by the poles 32 locked inside of the posts 12 . This is a very fast and simple operation.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.