Patent Application
20060223349
This invention relates to electrical or electronic connectors, and more particularly to connectors having an array of pins secured to a housing.
Connectors having a two-dimensional array of conductive pins in an insulative housing often include solder balls disposed on an underside of the housing. The solder balls are connected to or disposed on ends of the pins to enable electrical connection to a printed wiring board.
Often, pins are held in place in the array by press fitting them into openings in the connector housing. A planar shield is often disposed between rows of pins to inhibit crosstalk and like drawbacks. Shields are especially useful in tightly packed or high speed connectors but may be employed in other circumstances. In some arrays of pins, such as pins retained by press fitting, residual stresses can build up such that stress and/or strain is transmitted from one portion of the housing (proximate a pin) to an adjacent portion. In this way, stresses can build up or accumulate, which diminish the planarity of the contacts and/or solder balls or having other drawbacks.
A connector is provided that comprises a housing having plural apertures in which plural pins are disposed. At least one of the pins includes a longitudinal groove formed therein and at least one of the apertures includes a gap at least partly defined by a rib. The rib in an as-molded state has a cross-sectional profile that is different from a cross-sectional profile of the corresponding longitudinal groove. Accordingly, upon insertion of the pin into said aperture the profile of the rib conforms to match at least a portion of the groove profile.
The aperture may have a pair of opposing ribs that are disposed in and contact a pair of opposing grooves in each pin. Alternatively, the aperture may have a single rib that is disposed in and contacts a groove in the pin; opposite the single rib, the housing may be flat or have another shape that does not constitute a rib. Preferably, the gap has a dimension less than a width of the pin measured at the groove or between the pair of grooves, wherein the apex of the rib deforms against the bottom of the groove so as to form an interference fit. The conformation of the rib to the groove diminishes stress transmitted to parts of the housing adjacent to the rib and diminishes strain in parts of the housing adjacent the rib.
The pins may have a contact portion extending upwardly from the housing and a solder ball is disposed in a depression on the underside of the housing. and is coupled to the pin opposite the contact portion. The pins may include at least one embossment formed in the groove for enhancing engagement between the pin and the corresponding rib. Also, the rib may include at least one embossment formed thereon for enhancing engagement between the rib and the corresponding pin.
The aperture preferably includes an elongate portion extending approximately perpendicular to a centerline of the corresponding ribs or perpendicular to a plane defined by the centerlines of corresponding ribs. A contact beam is disposed the aperture elongate portion and contact a corresponding pin. Preferably, a shield is disposed along a row of pins, the shield being coupled to the contact beam.
Also provided is a ball grid array connector that includes an array of pins, a housing, an array of solder balls, and a plurality of contact beams. The pins, which are disposed in a corresponding array of apertures in the housing, include opposing longitudinal grooves.
The housing has an upper side, an underside, and the array of apertures. At least a portion of the apertures include an elongate portion that opens onto the upper side of the housing. The apertures include a gap at least partly defined by a pair of opposing ribs, which are conformable in response to insertion of the pin into the aperture to secure the pin. The solder balls disposed on the housing underside proximate ends of said pins. The contact beams disposed are at least partly in the elongate portions of the apertures such that the contact beams are insertable into the aperture from the upper side of the housing.
The ribs in an as-molded state preferably have a cross-sectional profile different from a cross-sectional profile of the corresponding pin groove such that upon insertion of the pin into said pin aperture the profile of the ribs conforms to match at least a portion of groove profile. Preferably, the ribs engage the pins in interference fits. The connector may also include a slot that opens onto an upper surface of the housing and a shielding bar disposed in the slot. The shielding bar is in contact with at least a portion of said contact beams.
Referring to the figures to illustrate an embodiment of the present invention, a ball grid array connector 10 includes an insulative housing 12, plural pins 14 retained in or by housing 12, and solder balls 16. Housing 12 preferably includes a pair of opposing sidewalls 20 connected by a base 22 that has an upper surface or upper side 23a and an opposing lower side or underside 23b. A coordinate system is shown on some figures to aid in the understanding of the orientation of the parts.
Housing 12 includes arrays of apertures 24 from upper side 23a to lower side 23b. Pins 14 are disposed parallel to the z-axis in apertures 24 such that a pin is disposed in each aperture in a one-to-one relationship. As best shown in
An elongate shielding bar 26 is disposed in an elongate recess 27 formed in the upper surface 23a of housing 12. Preferably, shielding bar 26 is planar to provide shielding between adjacent rows of pins 14. A contact beam 28 is coupled to shielding bar 26 and disposed at least partly in the extended portion 38. Shielding bar 26 and contact beam 28 may be formed from a unitary piece of a conductive sheet such the contact beam is bent so as to extend from shielding bar 26.
Preferably, contact beam 28 extends outwardly from shielding bar 26 at an oblique angle and includes a distal bent to form a bent our rounded contact surface 29 that contacts pin 14, as more fully explained below. As recess 27 and aperture extended portion 38 open upwardly onto housing upper surface 23a, in the illustrated embodiment disclosed in the figures, shield 26 and contact beam 28 can be inserted from the upper side of housing 12, opposite the solder balls 16.
A contact beam 28 may be employed at each of pins 14 that serve as a power or ground contact. Often, for convenience, power contacts and/or ground contacts are arranged in one or more rows. Accordingly, some shielding bars may be equipped with contact beams at each pin 14 of a row of power or contact pins and other shielding bars may be without contact beams to diminish cross-talk and like drawbacks along rows of signal pins.
As shown in
Pin 14 includes a contact portion 48, a base 50, and a stake portion 52, which preferably are integrally formed. Each pin 14 includes a pair of longitudinal grooves 54 formed on opposing sides of pin 14. Preferably, grooves 54 are formed in stake portion 52 and/or a portion of base 50. The present invention, however, is not limited to the extent or length of grooves 54 shown in the figures and the present invention encompasses grooves extending the length of the pin (not shown in the figures) or along any portion thereof. Preferably, grooves 54 extend substantially to or nearly to a terminal end of pin 14. Pin 14 includes a pair of ungrooved sides 55a adjacent to sides 55b having grooves 54.
Pin 14 preferably includes one or more embossments or protrusions 60 formed in the grooves 54, or none at all.
A width W1 of pin 14 is measured between the bottom dead centers of the main portions of the grooves such that W1 is measured parallel to the x direction. As shown in
Ungrooved side 55a may also be tapered at tip 56. The figures show pin stake portion 54 as un-tapered except for the portion near tip 56. But the present invention encompasses pins having a tapered section and other changes to its cross sectional shape and/or size along its length.
In this regard, the portion between cavity floor 23c and ball pocket 36 may be considered to constitute an aperture lower portion, which is un-numbered in the figures. A through aperture or narrow gap 25 preferably exists between pin stake portion 52 and each of the innermost edges of cavity floor 23c, aperture lower portion, and the innermost edges of ball pocket 36 all the way around pin stake portion 52. Alternatively, aperture lowermost portion could contact pin stake portion 52 to enhance rigidity of pin 14 in housing 12.
During insertion of pin 14 into aperture 24 after pin tapered tip 56 and rib lead-in portions 42 have helped to locate pin grooves 54 relative to ribs 30, pin 14 is pressed downwardly into aperture 24. In some circumstances, pin 14 could be inserted into aperture 24 while eliminating or diminishing burrs created from the rib material by the metallic pin 14. Rib 30 extends into groove 54. The transverse cross-sectional shape of rib 30 does not match the transverse cross sectional shape of groove 54.
The surface of rib 30 at its base is slightly more narrow than the corresponding dimension of groove 54. Gap G between rib tips 44 is less than pin width W1 between the grooves.
The precise dimensions of groove 54, ribs 30, and like structure will depend upon the materials chosen, the desired overall dimension of pin contact portion 48, the desired mechanical properties such as insertion force, resistance to deflection in the x-y plane, and like parameters. Generally, pin 14 may be formed of any conventional, conductive material commonly employed for such pins and may be formed by an technique, including conventional techniques such as swaging and/or coining.
Housing 12 may be formed of a conventional liquid crystal polymer or like engineering plastic generally suitable for embodiments employing solder balls 16 and for use with reflow temperatures. The hardness, yield point, modulus of elasticity and like properties of the material of housing 12 may particularly take into account the desired interference between ribs 30 and grooves 54 and the corresponding magnitude of the conformance. Based on the material and structure of pin 14, it is expected that pin 14 would like be relatively inflexible. Preferably, in order to provide adequate stability of pin 14 in the x-y plane, the portion of rib tip 44 in groove 54 is expected to be roughly in the range of 0.060 to 0.080 inches (that is, in the z-direction).
Upon assembly, contact portion 48 extends upwardly from housing base 22. Housing 12 may be affixed to a printed wiring board 9 (
The conformance of ribs 30 within grooves 54 diminishes the compressive stress that would be transmitted to adjacent cells or areas of the housing. Because of the conformance of the ribs, stresses to not accumulate throughout a row or array of pins. In this regard, the structure and/or function disclosed herein isolates the stress and strain caused by the press fit or interference fit of pins 14 locally near the particular pin or, as the term is sometimes used, within a cell.
The phrases “upper,” “lower,” and “bottom” and the like are used herein merely to provide relative orientation to aid in the explanation of the illustrative embodiment and are not intended to limit the scope of the embodiment of the invention to any particular orientation. Further, the present invention is not limited to any particular configuration. For example, the term pin encompasses not only the single, linear contact shown herein, but also encompasses the corresponding female contact, forked receptacles, and the like. The pins are described as having groove 54 disposed in stake portion 52, and the present invention encompasses any configuration, including for example opposing grooves formed throughout the length of the pin, which in some circumstances may foster manufacturing simplicity. The housing may be formed with a pair of extended side openings formed on opposing sides of pin 14. Similarly, the present invention is not limited to the particular type of connector shown herein; for example, the present invention encompasses male and female connectors, those with and those without solder balls, and connectors regardless of their purpose, as of course limited by the language of the claims. And the present invention is not limited to solving any particular problem; for example, the background section discusses stress build-up among rows or an array of pins, yet the present invention is not limited to structure or circumstances in which stress build-up occurs. According to the foregoing, the claims should be read to define the scope of the present invention.
