Apparatus for mounting a printed circuit board

A circuit board mounting arrangement is provided including a circuit board and a press fit mounting bushing including a cylindrical inner piece and an outer piece secured to the inner piece. The outer piece has a plurality of radially projecting, deformable elements and the circuit board has a cylindrical opening having a diameter less than an outer diameter of the radially projecting deformable elements. The deformable elements deform when the mounting bushing is pushed into the cylindrical opening of the circuit board so as to hold the mounting bushing to the circuit board. The circuit board and press fit bushing are then overmolded.

FIELD OF THE INVENTION

The present invention is directed to an apparatus for mounting a printed circuit board (“PCB”) to a structure and is particularly directed to a press fit bushing for a PCB used for mounting the PCB to a structure.

BACKGROUND OF THE INVENTION

PCB's are substrates that hold and interconnect electrical circuit components as part of a larger electrical system. PCB's are often mounted into a housing structure designed to hold and protect the PCB and associated circuitry. Various ways of mounting the PCB in the house are known such as by using screws or other attachment means. In such mounting arrangements, the screws are directly received through a mounting hole in the PCB and secured to associated screw support structure of the housing. The housing is then, in turn, typically secured to another structure such as a mounting location within a vehicle.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a circuit board mounting arrangement is provided including a circuit board and a press fit mounting bushing including a cylindrical inner piece and an outer piece secured to the inner piece. The outer piece has a plurality of radially projecting, deformable elements and the circuit board has a cylindrical opening having a diameter less than an outer diameter of the radially projecting deformable elements. The deformable elements deform when the mounting bushing is pushed into the cylindrical opening of the circuit board so as to hold the mounting bushing to the circuit board. The circuit board and press fit bushing are then overmolded.

DETAILED DESCRIPTION

Referring toFIGS. 1-6, a two piece press fit mounting bushing20is shown used for mounting a printed circuit board (“PCB”)22to a structure. The two piece mounting bushing20includes an inner cylindrical piece26having a through bore28. In accordance with one example embodiment of the present invention, the inner cylindrical piece26is made from metal. A portion30of the outer wall32of the inner piece26has a knurled surface or, at least, a surface that has a rough texture. The inner piece26could be formed through machining, cold forming, or other metal forming processes with the knurled surface.

The two piece mounting bushing20further includes an outer piece36that circumferentially covers at least an axial portion of the inner cylindrical piece26commensurate with the knurled surface. In accordance with one example embodiment of the present invention, the outer piece36is made from plastic and is molded to the outer wall32and in contact with the knurled portion30so as to be adhered and fixed to the inner piece26. The knurled surface, or otherwise textured surface of the inner piece, provides mechanical retention between the outer piece36and the inner piece26. The outer piece being plastic electrically isolates the inner piece from the printed circuit board22.

The outer piece36of the two piece bushing20includes a main body portion40and a plurality of radially extending retaining members42circumferentially and equally spaced around the main body portion40. The radially extending retaining members42are substantially V-shaped in cross section but could take other forms. The retaining ring50radially extends outward from the main body portion40.

A first end52of the two piece mounting bushing20is inserted, i.e., press fit, into an opening56of the PCB22. The outside radial diameter of the radially extending retaining members42is slightly greater than the diameter of the opening56of the PCB22such that the bushing20must be press fit into the opening with sufficient force applied against end58. Force would be continuously applied until the retaining ring50contacts the PCB22. During the process of inserting the bushing20into the PCB22, the radially extending retaining members42deform slightly and form a tight press fit engagement, i.e., interference fit, with the PCB22. A bolt may then be inserted through the opening28so as to secure the PCB22to a mounting structure via a nut on the end of the bolt.

If the press fit mounting bushing were made entirely of metal, such a bushing would cause stress in the PCB board when inserted into the PCB. Also, if the PCB would include a plurality of all metal bushings, the accumulated stress caused by the metal bushings could result in a bowing of the PCB.

Referring toFIG. 7, a completed mounting arrangement60for a PCB22in accordance with one embodiment of the present invention is shown. The PCB22includes circuitry64mounted to the PCB22. In a vehicle application, the circuitry64could include vehicle crash sensors such as an accelerometer or a pressure sensor. The bushing20is mounted to the PCB22as described above with regard toFIGS. 1-6. The two piece bushing20is press fit into the circuit board22as described above prior to an overmolding process. First, a soft plastic material68is molded over the circuitry64and a portion of the PCB22. A hard plastic material72is then overmolded the soft plastic material68, the exposed portions of the PCB22and the two piece bushing20. The hard plastic material forms a rigid mounting case74that is formed, i.e., molded, into any desired shape. The rigid mounting case78is then, in turn, secured to a mounting structure80, such as a mounting beam in a vehicle, using a bolt82and associated nut84through the two piece bushing20.

An overmolding process showing the soft inner layer and hard outer layer for a vehicle crash sensor arrangement is shown and described in U.S. Pat. No. 8,966,975 which is hereby fully incorporated herein by reference.

Referring toFIG. 8, another example embodiment is shown of the present invention using a modified two piece press fit bushing20′ for mounting to a PCB22. The bushing20′ has an inner member26′ made of metal and outer plastic member36′ secured to a knurled portion of the inner member in a similar manner as described above. With this embodiment, the inner member26′ includes a stepped flange portion90that provides an additional contact surface to enhance the retention characteristics between the inner member26′ and the outer member36′ of the two piece bushing20′.

From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, the retention members have been described, in accordance with one example embodiment, as being V-shaped in cross section. Other shapes or patterns could also be used. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.