Circuit board including hybrid via structures

A circuit board may include hybrid via structures configured to connect to components, such as connectors and electronic components, mounted on the circuit board. A hybrid via structure may include one or more micro-vias configured to provide an electrical connection to a signal trace in the circuit board and one or more through-vias configured to provide a ground connection to at least one reference plane in the circuit board. In one embodiment, a plurality of circuit boards including the hybrid via structures and signal traces may be connected to establish a channel supporting differential signaling and data transfer rates of at least about 5 Gb/s. Of course, many alternatives, variations, and modifications are possible without departing from this embodiment.

FIELD

The present disclosure relates to circuit boards including via structures, and more particularly, relates to circuit boards including hybrid via structures with through-vias for grounding and micro-vias for signals.

BACKGROUND

In a computer system, a plurality of circuit boards may be connected to establish one or more communication channels. In an Advanced Telecommunications Computer Architecture (ATCA) system, for example, a plurality of circuit boards (also referred to as blades) may be coupled to and interconnected via a common backplane within a shelf or chassis. Electronic components (e.g., chip packages) and connectors may be mounted to the circuit boards. The circuit boards may include conductive paths that electrically connect the electronic components and/or connectors. The conductive paths may include traces that extend along the circuit board and vias that connect the traces to the electronic components and/or connectors mounted on the circuit board. The traces may include signal traces that carry data signals between the electronic components.

Modern communications systems may establish high-speed channels having data rates that approach several gigabits per second (Gb/s) using differential signaling techniques. In such systems, the existing via structures in the circuit boards (e.g., in an 18 layer ATCA backplane) may degrade the high-speed channel performance. This degradation may cause a high-speed channel to fail despite the use of signaling techniques that improve signaling performance, such as de-emphasis in a transmitter buffer and/or equalization in a receiver buffer. The degradation is especially problematic when vias extending through the circuit board (referred to as through-vias) are connected to traces in top signal layers of the circuit board, leaving an unused portion of the via (referred to as a stub) that adversely affects signal integrity. To recover signal quality caused by discontinuity in the vias, an equalization technique may be applied at the circuit level but may be complicated and expensive to implement. One technique for removing the stub includes back drilling the via, which requires an additional manufacturing step and is expensive.

Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly.

DETAILED DESCRIPTION

Referring toFIG. 1, a computer system100may include circuit boards102,104,106connected to establish one or more communication channels, such as a high speed channel in a high speed communication system. To establish the channel(s), the circuit boards102,104,106may include conductive paths such as traces122,142,162and via structures120,124,140,144,160,164. Via structures120,124,140,144,160,164may extend into the circuit boards102,104,106and electrically connect the traces122,142,162to components coupled to the circuit boards102,104,106. One or more of the, via structures120,124,140,144,160,164may be hybrid via structures including one or more through-vias that provide a ground connection and one or more micro-vias that provide a signal connection, as will be described in greater detail below. Although one trace and two via structures are shown schematically in each of the circuit boards102,104,106to establish a single channel, those skilled in the art will recognize the circuit boards102,104,106may include any number of traces and via structures to establish multiple channels.

One or more electronic components110,170may be mounted to one or more of the circuit boards102,106and electrically connected to via structures120,164. The electronic components110,170may transmit and receive signals over the communication channel. One or more connectors130,150may be coupled to one or more of the circuit boards102,104,106and electrically connected to via structures124,140,144,160. The connectors130,150may connect the circuit boards102,104,106to each other and may include connector conductive paths132,152that provide an electrical connection between the circuit boards102,104,106. Those skilled in the art will recognize that other components or devices may also be coupled to the circuit boards102,104,106and electrically connected to via structures.

In one embodiment, at least one circuit board104may be a motherboard or backplane connected to other circuit boards102,106, such as line cards that interface with telecommunications lines. The connectors130,150may include mating connectors, such as data transport connectors, mounted on each of the circuit boards102,104,106, for example, such that the line cards may be connected to the backplane. In one example, the traces122,162may extend at least about two (2) inches in the circuit boards102,106and the trace142may extend at least about twenty (20) inches in the backplane circuit board104. The electronic components110,170may be chip packages including, for example, a transmitter chip112and a receiver chip172. Signals may be transmitted over the channel (e.g., between the transmitter chip112and receiver chip172) using differential signaling such as low voltage differential signaling (LVDS). In one embodiment, the channel may support 5 Gb/s PCI Express Gen. 2 signaling that is compatible with or complies with Peripheral Component Interconnect (PCI) Express Base Specification Revision 1.1a, published on Apr. 15, 2003 (the “PCI Express Specification”).

The computer system100may be implemented in an advanced telecommunications computing architecture (Advanced TCA or ATCA) complying with or compatible with, at least in part, PCI Industrial Computer Manufacturers Group (PICMG), Advanced Telecommunications Computing Architecture (ATCA) Base Specification, PICMG 3.0 Rev. 2.0, published Mar. 18, 2005, and/or later versions of the specification (“the ATCA specification”). According to such an embodiment, the circuit boards102,106may be ATCA blades and the circuit board104may be an ATCA backplane complying with or compatible with, at least in part, the ATCA Specification.

Various other embodiments consistent with the present disclosure may include circuit boards complying with and/or compatible with technical specifications other than and/or in addition to the ATCA Specification. Circuit boards may be used, for example, in other types of chassis or systems such as a VME chassis, a CompactPCI chassis, or an IBM BladeCenter®. The scope of the present disclosure should not, therefore, be construed as being limited to any particular computer system or form factor.

FIG. 2is a diagrammatic illustration of the passive components of a channel200in the computer system100inFIG. 1, which uses differential signaling. The channel200may include a transmitter210to transmit a differential signal and a receiver270to receive the differential signal. The channel200may include a first via structure220, a first line card trace222, a second via structure224, a first connector path232, a third via structure240, a backplane trace242, a fourth via structure244, a second connector path252, a fifth via structure260, a second line card trace262, and a sixth via structure264. In this exemplary embodiment, therefore, six (6) via structures220,224,240,244,260,264are used to establish the channel200. To carry differential signals, the traces222,242,262may include differential pairs of traces and the via structures220,224,240,244,260,264may be hybrid via structures including differential pairs of micro-vias.

Referring toFIGS. 3A-3C, a hybrid via structure300may be used in a circuit board310to establish a connection to components, such as connectors and/or electronic components (not shown), mounted on the circuit board310. The circuit board310may include a plurality of circuit board layers312,314. An ATCA backplane, for example, may include eighteen (18) layers. In one embodiment, circuit board layers may include signal layers312and reference layers314, as is known to those skilled in the art. The signal layers312may include a dielectric material and a conductive material (e.g., copper) embedded within the dielectric material to form signal traces. The reference layers314may include a plane of conductive material (e.g., copper) extending between the dielectric material of the signal layers312to provide power or ground paths. Those skilled in the art will recognize that various multi-layer circuit board designs may be used.

The hybrid via structure300may include a combination of one or more micro-vias320,322for connecting to signal traces330,332and one or more through-vias340,342for connecting to one or more reference layers314. In an embodiment using differential signaling, each hybrid via structure300may include a pair of micro-vias320,322connected to a pair of signal traces330,332(e.g., copper traces in a signal layer312). As used herein, a micro-via is a conductive path that extends through one or more circuit board layers to the target signal layer including the signal trace to which the micro-via is connected but does not extend beyond the target signal layer. As used herein, a through-via is a conductive path extending through the circuit board layers from one side to another side of a circuit board (e.g., a plated through hole).

In the illustrated embodiment, the signal traces330,332are located in the top second signal layer312of the circuit board310. The micro-via structures320,322may also extend further into the circuit board310to connect with signal traces in other signal layers of the circuit board310. The through-vias340,342may be connected to one or more of the reference layers314, for example, to provide a ground connection.

As shown inFIG. 3C, a plurality of hybrid via structures300may form a connection region350on a circuit board, which is configured to be connected to a component such as an electronic component or a connector. The connection region350may include single rows352a-dof through-vias340,342located between two rows354a-d,356a-dof micro-vias320,322. The rows354a-d,356a-dof micro-vias320,322and the rows352a-dof through-vias340are arranged to connect with connection pads and pins on a component, such as a connector, as described in greater detail below.

Referring toFIGS. 4 and 5, embodiments of micro-vias and the construction thereof are described in greater detail.FIG. 4shows a micro-via400between two neighboring metal layers402,404in a circuit board layer410. The micro-via400may include a side portion420extending through the circuit board layer410, a top portion422, and a bottom portion424. The micro-via400thus provides conductivity between the neighboring metal layers402,404. The micro-via400may thus connect to a trace or to another micro-via in stacked configuration, as described below.

The micro-via400may be manufactured using processes known to those skilled in the art. In one embodiment, the micro-via400may be constructed by forming a hole426in the circuit board layer410, for example, using a UV or CO2laser drilling process. The hole426may be plated with a conductive material, such as copper or another conductive metal, to form the side portion420, top portion422and bottom portion424of the micro-via400. The micro-via400may then be filled, for example, with a conductive material.

FIG. 5shows a stacked micro-via500formed by a plurality of micro-vias520a-din a plurality of circuit board layers510a-d. The stacked micro-via500may provide conductivity from a metal layer502(e.g., at the top of a circuit board) through the plurality of circuit board layers510a-dto another metal layer504(e.g., a trace) within a circuit board.

The stacked micro-via500may be constructed layer-by-layer from a core layer (e.g., layer510d) up to a top layer (e.g., layer510a) or down to a bottom layer (not shown). According to one embodiment, the individual micro-vias520a-dmay be constructed by metal plating holes formed in each of the layers510a-d, for example, as described above, and by filling the metal plated holes with metal. The micro-vias520a-dare aligned and constructed such that portions522a-cof micro-vias520a-din adjacent layers are connected. The stacked micro-via500may include micro-vias520a-dstacked generally in an “in-line” configuration, for example, as shown inFIG. 5. Alternatively, a stacked micro-via may include micro-vias stacked in a staggered configuration, for example, as shown inFIG. 3A. Those skilled in the art will recognize that other configurations may be constructed and other manufacturing processes may be used.

FIGS. 6A and 6Bshow one embodiment of a connector600that may be coupled to a connection region including a group of hybrid via structures on a circuit board. The connector600may include a connector body602having a front side604and a rear side606. A plurality of signal pins612and grounding contacts614may extend from the front side604of the connector body602. A plurality of signal pads620and grounding pins640may extend from the rear side606of the connector body602. The rear side606of the connector600is configured to be mounted on a circuit board (e.g., on a backplane) and the front side604of the connector600is configured to be coupled to a mating connector (e.g., on a circuit board to be coupled to the backplane).

The signal pads620may be connected to the micro-vias in the hybrid via structures (e.g., micro-vias320,322shown inFIG. 3C). In one embodiment, the signal pads620are solderable pads that are soldered to the micro-vias. The grounding pins640may be received in and connected to the through-vias in the hybrid via structures (e.g., the through-vias340,342shown inFIG. 3C). In one embodiment, the grounding pins are press fit into the through-vias to provide mechanical strength to the connector600coupled to the circuit board.

According to one embodiment, the connector body602, signal pins604and grounding contacts606may be configured similar to high speed data transport connectors known to those skilled in the art. Those skilled in the art will recognize that other types of connectors configured for use with a circuit board may also include contact pads and grounding pins configured to be connected to hybrid via structures. Other components (e.g., chip packages or other electronic components) may also include solderable pads and grounding pins for connecting to hybrid via structures on a circuit board.

The hybrid via-structure thus allows the elimination of long stubs that may adversely affect signal integrity, while maintaining a secure mechanical connection to a component or connector.FIG. 7illustrates one example of a corresponding eye pattern at the receiver side for a 5.0 Gb/s PCI Express Gen2 signal on a channel using hybrid via structures (e.g., as shown inFIG. 3A). As shown, the eye pattern is sufficiently open to comply with the PCI Express Specification.

Referring toFIG. 8, a system800may include a frame or cabinet806that accommodates and electrically couples a plurality of shelves or chassis802a,802b,802c. According to one example, a cabinet806may be provided by a telecommunications equipment manufacturer (TEM) to house telecommunications equipment. One or more of the chassis802a,802b,802cmay include circuit boards including hybrid via structures consistent with any of the embodiments described herein. The cabinet806may include, for example, a power supply for providing power to each of the individual chassis802a,802b,802cand other equipment804(e.g., alarms, power distribution units, etc.) disposed in the cabinet806. Additionally, as mentioned above, the cabinet806may electrically couple one or more of the chassis802a,802b,802cto at least one other chassis.

According to an alternative embodiment, rather than being disposed in a common cabinet, a system consistent with the present disclosure may include a plurality of chassis that may be individually hardwired to one another without a cabinet. One or more of the plurality of chassis may include circuit boards including hybrid via structures consistent with any embodiment described herein. Additionally, each of the plurality of chassis may be powered by an individual power supply and/or may be separately powered by a common power supply. Such a system may, therefore, provide a greater freedom in the physical arrangement and interrelation of the plurality of chassis.

Consistent with one embodiment, an apparatus includes a plurality of circuit board layers including a plurality of signal layers and at least one reference layer, at least one signal trace located within at least one of the signal layers, and at least one hybrid via structure located in the circuit board and associated with the at least one signal trace. The hybrid via structure may be configured to connect to a component and may include at least one through-via electrically connected to the at least one reference layer and configured to be connected to a pin of the component. The hybrid via structure may also include at least one micro-via electrically connected to the signal trace and configured to be connected to a conductive pad of the component.

Consistent with another embodiment, an apparatus includes at least one circuit board including a plurality of circuit board layers including a plurality of signal layers and at least one reference layer, at least one signal trace located within the at least one of the signal layers, and at least one hybrid via structure located in the circuit board. The hybrid via structure may include at least one through-via electrically connected to the at least one reference layer and at least one micro-via electrically connected to the signal trace. At least one component connected to the circuit board includes at least one grounding pin extending into and electrically connected with the at least one through-via and at least one signal pad contacting and electrically connected to the at least one micro-via.

Consistent with a further embodiment, a system includes a plurality of circuit boards configured to be connected to establish a communication channel. The circuit boards include a plurality of signal layers and at least one reference layer, at least one signal trace located within at least one of the signal layers, and hybrid via structures associated with the signal trace. Each of the hybrid via structures may include at least one through-via electrically connected to the at least one reference layer and at least one micro via electrically connected to the signal trace. At least first and second electronic components are mounted to at least first and second of the circuit boards. The first and second electronic components include at least one grounding pin extending into and electrically connected with the at least one through-via in one of the hybrid via structures and at least one signal pad contacting and electrically connected with the at least one micro-via in one of the hybrid via structures. A plurality of connectors may be mounted to the circuit boards and configured to connect the circuit boards together. The connectors include at least one grounding pin extending into and electrically connected with the at least one through-via and at least one signal pad contacting and electrically connected with the at least one micro-via.