Patent Application
20080220665
Not Applicable
Not Applicable
Not Applicable
1. Field of Invention
This invention relates in general to compliant pins, and more specifically, to utilizing compliant pins in relays.
2. Background of Related Art
The electronics manufacturing industry is facing a change in its assembly processes. Soldering has been used world wide in the electronic industry for electrically coupling electronic devices to one another such as wiring and terminals to circuit boards (PCBs). Lead based solder has been used almost exclusively in the electronics industry for attaching components of various electronic devices to PCBs. Solders have been primarily used because they are inexpensive and are primarily reliable under various operating conditions. Soldering also possesses highly favorable characteristics such as high strength ductility, high thermal cycling, high strength durability and joint integrity.
However, concerns have been increasingly growing due to the contamination of heavy metals such as lead ending up in landfills. As a result, there has been a worldwide movement to utilize environmentally friendly soldering methods and ban the use of heavy metals such as lead in solders.
Lead-free soldering materials have been tested and utilized with some success. However, issues remain with high temperature compatibility. Lead-free materials require a high temperature for reflow. The high temperature required for reflow may cause damage to the components being soldered together. This includes the plastic encapsulated devices such as capacitors, LEDs, connectors and electromechanical components, in addition to delaminating circuit boards. Therefore, there is a need for providing a reliable and durable electrical connection between two devices such as a relay and a printed circuit board without utilizing a soldering operation.
The present invention provides an advantage of eliminating soldering for the electrical coupling of a relay to a printed circuit board by using a press fit connection between a relay and a printed circuit board. The relay includes terminals having a compliance feature which assist is securing the relay to a printed circuit board or like device.
In one aspect of the present invention, a self-contained power distribution device is provided having compliant pins for attachment to mating receptacles of a printed circuit board for use in a vehicle electrical system. An insulative body forms a housing. An electrical switching element is disposed within the housing. A plurality of non-coaxial terminal contacts extends from a lower planar surface of the housing. The lower planer surface is substantially perpendicular to the plurality of terminal contacts. Each of the plurality of terminal contacts is substantially parallel to one another having exposed portions adapted to be received by the mating receptacles of a printed circuit board. The plurality of terminal contacts is in electrical communication with the switching element. The exposed portion of the plurality of terminal contacts each has a compliance feature. The compliance feature is resilient to deformation when received by the mating receptacles of the printed circuit board. An interference condition occurs between the compliance feature of the plurality of terminal contacts and the mating receptacles of the printed circuit board.
In yet another aspect of the present invention, a printed circuit board assembly is provided for use in a vehicle electrical system. The printed circuit board assembly includes a printed circuit board having mating receptacles extending through the printed circuit board. A self-contained power distribution device is releasably attachable to the mating receptacles of a printed circuit board. The self-contained power distribution device includes a housing and an electrical switching element disposed within the housing. The self-contained power distribution device further includes a plurality of non-coaxial terminal contacts extending from a lower planar surface of the housing. The lower planar surface being substantially perpendicular to the plurality of terminal contacts. Each of the plurality of terminal contacts is substantially parallel to one another and includes exposed portions adapted to be received by the mating receptacles of a printed circuit board. The plurality of terminal contacts are in electrical communication with the switching element. The exposed portion of the plurality of terminal contacts each includes a compliance feature. The compliance feature being resilient to deformation when received by the mating receptacles of the printed circuit board for creating an interference condition between the compliance feature and the mating receptacles of the printed circuit board.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
There is shown in
A switching element 22 is disposed within the interior region 20. The switching element 22 includes contacts (not shown) that are moveable between an open position (i.e., open circuit) and a closed position (i.e., closed circuit). The switching element 22 also includes an electromagnetic coil (not shown) for generating an electromagnetic field for switching the contacts between the open and closed position. Alternatively, the switching element 22 may include other electrical elements for making and breaking the electrical circuit.
The switching element 22 is electrically coupled to a plurality of terminal contacts 23 extending through the housing for electrically providing an electrical connection with the PCB 14 disposed exterior of the housing 16. The plurality of terminals contacts 23 typically include a first terminal contact 24 and a second terminal contact 26 which are electrically coupled to the open and closeable contacts of the switching element 22. The third terminal contact 28 and fourth terminal contact 30 provide power to the electromagnetic element (not shown) for generating the electromagnetic field that opens and closes the contacts.
Each of the plurality of terminal contacts 23 protrude through respective through-holes, shown generally at 32, formed in the PCB 14 for making an electrical connection to traces of the PCB 14. The mechanical connection, as well as the electrical connection, is provided by a soldering operation. Solder 36 is applied at the through-holes 32 for forming an electrical and mechanical bond between the plurality of terminal contacts 23 and the PCB 14. The solder 36 not only forms an electrical connection to the PCB 14, but provides structural support for the relay 12 via the plurality of terminal contacts 23. The soldering operation is typically performed by heating the solder 36 to an elevated temperature for reflowing the solder to form a continuous bond between the PCB 14 and the terminal contacts 23. The solder 36 cools to a hardened state for forming the mechanical and electrical connection between the PCB 14 and the plurality of terminal contacts 23.
The relay 40 includes the plurality of planar members 18a-f formed perpendicular to one another thereby enclosing the switching element 22 within the interior region 20. A plurality of terminal contacts 44 extends from the lower surface 18f of the relay 40 and is in electrical contact with the switching element 22.
The plurality of terminal contacts 44 includes an exposed portion having substantially straight edges 46 with a compliance feature 48 formed on a contacting region of each respective terminal contact. The compliance feature 48 includes an enlarged section 50, such as a bowed section, having an aperture 52 formed substantially concentric to the enlarged section 50. Preferably, the enlarged section 50 is substantially circular-shaped that extend beyond a width of the straight edges 46 of a respective terminal contact for creating an interference condition with the mating through-hole 43 of the PCB 14. The through-holes 43 are typically plated with a conductive material 47 that provides an electrical connection between the plurality of traces 45 and the associated enlarged sections 50 of the plurality of terminal contacts 23 when the relay 40 is secured to the PCB 42. As the compliance feature 48 is inserted within the through-hole 43, the conductive material 47 lining the interior of the through-hole 43 contacts the enlarged section 50 for making an electrical connection with the respective terminal contact. In addition, the plated through-hole 43, being smaller in diameter than the enlarged section 50 of the respective terminal, exerts a resistant force against the enlarged section 50 as the enlarged section 50 is inserted through the through-hole 43. The aperture 52 formed in the enlarged section 50 allows the enlarged section 50 to deform radially inward so that the enlarged section 50 may be press-fit within the through-hole 43. The compliance feature 48 is resilient to deformation when received by the through-hole 43 so that an interference condition may be created for seating the plurality of terminals contacts 44 within the respective through-holes 43 of the PCB 42 for providing a mechanical supporting connection and an electrical connection. The interference condition between the relay 42 and the PCB 42 eliminates any requirement for soldering or a socket. In addition, the compliance feature 48 allows the relay 40 to be releasably attachable (i.e., serviceable) to the PCB 42.
The enlarged section 50 may include other shapes including, but not limited to, diamond-shapes and oval-shapes, as shown in
In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope. For example, the enlarged section may include a resilient section (e.g., thin-wall section) that does not utilize an aperture or slot but is capable of compressing and expanding to maintain the interference condition between the terminal contact and the printed circuit board.
