Patent Application
20170162964
The present invention relates generally to the field of electrical connectors, and more particularly to card edge connectors.
Card edge connectors are used to receive a circuit card such as a memory module or I/O device and provide electrical connectivity to components on the circuit board on which the card edge connector is mounted. Consequently, the signal bandwidth provided by card edge connectors may be a limiting factor in system performance.
An apparatus includes a connector housing having a card edge channel and a connector pin channel formed therein, the connector pin channel comprising a front portion that is immediately adjacent to the card edge channel and a back portion that is proximate to a back wall of the connector pin channel, and a connector pin disposed within the connector pin channel. The connector pin includes a rising portion disposed within the back portion of the connector pin channel, and a curved portion that connects the rising portion to a deflectable descending portion. The deflectable descending portion may comprise a contacting portion that protrudes outside of the connector pin channel when a card is not inserted into the card edge channel.
A corresponding system includes the above apparatus and one or more elements of a computing system such as a processor, a memory, and an I/O device.
The embodiments disclosed herein recognize that the electrical and electromagnetic characteristics of card edge connectors (e.g., PCIe and DIMM) are a limiting factor for data throughput in computing systems. For example, as shown in
The embodiments disclosed herein also recognize that the point of contact on the connector pins of existing card edge connectors may result in “pin stubs” that are ancillary to the signal propagation path of card edge connectors. Such stubs may provide parasitic inductance and capacitance as well as unwanted signal reflections.
Various embodiments of the present invention will now be described in reference to the Figures. The embodiments disclosed herein address at least some of the above issues.
For example,
The card edge channel 220 enables insertion of a card edge of a circuit card (not shown) into the housing 210 in order to provide physical contact and an electrical connection between connection pads (e.g., fingers) on the inserted circuit card and a contacting portion 241 of the connector pins 240. As shown in
Referring at least to
The mounting portion 244 enables mounting the card edge connector 200 on a printed circuit board, or the like, and providing an electrical connection thereto. In the embodiment depicted in
Each depicted connector pin 240 (i.e., 240A and 240B) also includes a curved portion 245 that connects the rising portion 243 to a deflectable descending portion 246. The rising portion 243, the curved portion 245, and the deflectable descending portion 246 form a hook-like shape for the connector pins 240.
The deflectable descending portion 246 of each depicted connector pin 240 includes the contacting portion 241 that protrudes outside of the connector pin channel 230 when a card is not present in the card edge channel 220. The depicting contacting portion 241 is not as wide as the rest of the depicted connector pin 240 resulting in a reduced insertion force for the card edge connector 200. Furthermore, the depicting contacting portion 241 is proximate to one end of the connector pin 240 and thereby substantially eliminates the ill effects of a pin stub that is present in many conventional card edge connectors.
In addition to the “pin-stub” resonance removal, signal loss through the card edge connector 200 may be further reduced by tuning the dielectric constant of the connector housing 210 so that each connector pin 240 disposed within a connector pin channel 230 provides a selected constant impedance to a signal. Impedances from less than 10 ohms to greater that 300 ohms are attainable. As signal waves propagate along the connector pins 240 and through the connector pin channels 230, a constant impedance minimizes reflections (return loss), which not only helps retain waveform integrity but also reduces insertion loss. The reflection coefficient is given by:
R=(ZL−ZS)/(ZL+ZS) (1)
where ZL and ZS are load and source impedances. Reflections may be substantially eliminated when ZL and ZS are matched (ZL=ZS). Source impedance is usually defined and fixed with system designs, and load (connector) impedance can be expressed as:
For a given connector structure, by adjusting the dielectric constant of the housing 210, the shunt capacitance C may be increased/decreased to achieve the desired impedance. In case of conventional PCIe and DIMM connectors, single-ended/differential impedance is usually higher than normal system impedance of 50 to 100 ohm, in its original form, which tends to introduce additional insertion and return losses. Therefore, since the impedance is inversely related to the capacitance C, the dielectric constant of the housing 210 may be increased in order to increase shunt capacitance C and reduce the impedance to match a 10 to 300 ohm system including the normal system impedance of 50 to 100 ohm.
Dielectric constant adjustment of the housing 210 can be achieved by the addition of high dielectric constant ceramic particles into the connector housing material which varies the effective dielectric constant of the housing. The increase in dielectric constant of the connector housing helps bring down the pin-to-pin impedance into the 50 to 100 ohm system impedance range, and therefore helps reduce insertion and return losses.
The dielectric constant of the particle-resin compound in the housing 210 may be determined using Looyenga's formula:
∈=[∈11/3+ν2(∈21/3−∈11/3)]3 (3)
where, ∈1 is the dielectric constant of the carrier material, and ∈2 and ν2 are the dielectric constant and volume fraction of the ceramic particles. As an example, SrTiO3 powder has a dielectric constant of 300, and a K=16 dielectric compound may be obtained by adding 20% SrTiO3 powder into the connector housing carrier material. The particle size may range from nanometers to micrometers. Generally, smaller particle size allows greater particle volume fraction as well as better compound stability. In some instances, a bi-modal (two particle sizes) or multi-modal powder may be used for maximum particle volume fraction. The mechanical properties and stability of the resulting housing should be similar to its original form, since it is a common process to add particles (normally silica) and pigment into connector housing for desired mechanical properties.
It should be noted that this description is not intended to limit the invention. On the contrary, the embodiments presented are intended to cover some of the alternatives, modifications, and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the disclosed embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the embodiments disclosed herein are described in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.
