Methods and apparatus for providing a signal to a circuit board component

A circuit board is configured to exchange data signals with a circuit board component through data signal contacts located between the circuit board and a primary surface of the circuit board component. The circuit board has power supply signal contacts that are configured to carry power supply signals to the circuit board component through a secondary surface of the circuit board component. A signal carrier connects the power supply signal contacts of the circuit board with the circuit board component through the secondary surface of the circuit board component. Such a configuration allows the circuit board component to receive a relatively large amount of power while maintaining the number of data signal contacts dedicated for transmission of data signals between the circuit board and circuit board component.

BACKGROUND

A conventional circuit board includes circuit board components, such as an Application Specific Integrated Circuit (ASIC), mounted to the circuit board. Such mounting secures the circuit board components to the circuit board and provides electrical contact between the circuit board components and the circuit board. Certain conventional circuit board components, such as ball grid array (BGA) devices) have an array of solder balls located on an attachment surface of the circuit board component (e.g., a surface of the circuit board component that attaches to the circuit board). The array of solder balls of the circuit board component attaches to contact pads, for example, located on the circuit board.

A conventional ASIC has an attachment surface having a relatively small surface area (e.g., 2025 mm2). The conventional ASIC utilizes an array of solder balls having a ball diameter of 1 mm, thereby allowing placement of a relatively large number of solder balls on the attachment surface of the ASIC. In the array, the solder balls are distributed across the attachment surface of the ASIC in an array pattern of 50 columns having 50 solder balls per column. Such an array or grid configuration (50×50) results in 2500 solder balls in the array for mechanical attachment of the ASIC to the circuit board (e.g., attachment to the contact pads of the circuit board) and for electrical contact between the ASIC and the circuit board.

In a typical solder ball array, the solder balls of the ASIC allow transmission of data signals between the circuit board and the ASIC and allow transmission of power supply signals from the circuit board to the ASIC in order to power the ASIC during operation. Approximately 40–50% of the solder balls (e.g., 1000–1250 solder balls) of the conventional solder ball array are configured for carrying power supply signals from the circuit board to the ASIC. Approximately 50–60% of the remaining solder balls (e.g., 1250–1500 solder balls) of the conventional solder ball array, therefore, are configured to carry data signals between the circuit board and the ASIC.

SUMMARY

Conventional techniques for exchanging power supply signals and data signals between a circuit board component and a circuit board suffer from a variety of deficiencies.

As described above, the solder ball array of a conventional ASIC carries data signals between the circuit board and the ASIC and power supply signals from the circuit board to the ASIC in order to power the ASIC during operation. Approximately 40–50% of the solder balls (e.g., 1000–1250 solder balls) of the solder ball array are configured for carrying (e.g., transmitting and grounding) power supply signals between the circuit board and ASIC. Trends in ASIC design and application, however, indicate an increase in the power consumption (e.g., in excess of 50 W/ASIC) for ASIC's, thereby requiring an increase in the current required by such ASIC's during operation.

One method to increase the amount of power received by an ASIC involves increasing the number of solder balls of a 50×50 array dedicated to carrying power signals to the ASIC. For example, as the power consumption increases for a conventional ASIC having 2500 solder balls in a solder ball array, an increased number of the 2500 solder balls of the array (e.g., greater than 40–50% of the solder balls of the array) can be configured to carry power supply signals from the circuit board to the ASIC. As a result, however, the number of remaining solder balls of the array dedicated to carry data signals between the ASIC and the circuit board decreases. Such a configuration can reduce the overall performance (e.g., relative processing speed) of the ASIC.

Another method to increase the amount of power received by an ASIC involves increasing the number of solder balls of the ASIC solder ball array while maintaining the conventional package size (45 mm×45 mm) for the ASIC. For example, solder balls of a conventional array have a diameter of approximately 1 mm. To maintain the package size of the ASIC and increase the number of solder balls associated with the ASIC solder ball array requires a manufacturer to decrease the diameter and pitch of the solder balls of the array. For example, reducing the pitch of the solder balls to 0.8 mm allows a manufacturer to place a greater number of solder balls on a conventional ASIC attachment surface (e.g., an ASIC having a surface area of 2025 mm2). Increasing the number of solder balls of the array allows a manufacturer to utilize the additional solder balls to carry power supply signals from the circuit board to the ASIC while maintaining the number of solder balls carrying data signals between the circuit board and ASIC.

Decreasing the pitch of the solder balls of the ASIC, however, decreases the strength of the solder ball array and increases the risk of fracture of the solder balls of the array. A conventional ASIC package is formed from a material (e.g., substrate) having a coefficient of thermal expansion that is different than the coefficient of thermal expansion of the circuit board material (e.g., fiberglass). Because of the differences in the coefficients of thermal expansion between the ASIC package and the circuit board, the ASIC package and the circuit board expand and contract at different rates when exposed to variations in temperature. During thermal expansion or contraction of the ASIC and the circuit board, such differences in the coefficients of thermal expansion of the ASIC package and the circuit board generate a stress on the solder balls of the array. In the case where the pitch of the solder balls of the array decreases below 1 mm, the stresses induced on the solder balls, as caused by the differences in the expansion rates of the ASIC and the circuit board, can be higher than the failure strength of the solder balls, thereby leading to potential fracturing or failure of the solder balls of the array.

Another method to increase the amount of power received by an ASIC involves increasing the number of solder balls of the ASIC while increasing the size of the ASIC packaging. Increasing the size of the ASIC packaging allows a manufacturer to add solder balls to the array and configure the additional solder balls to carry power supply signals from the circuit board to the ASIC. Such a configuration allows the manufacturer to maintain the number of solder balls of the array carrying data signals between the circuit board and ASIC.

Increasing the size of the ASIC package, however, decreases the amount of real estate available on the circuit board for other circuit board components and electrical traces. Increasing the size of the ASIC package also increases the differences in the overall expansion between the ASIC package and the circuit board. During thermal expansion or contraction of the ASIC and the circuit board the differences in the coefficients of thermal expansion of the ASIC package and the circuit board generate a stress on the solder ball array that can be higher than the failure strength of the solder balls of the array, thereby leading to potential fracturing or failure of the solder balls. To compensate for the differences in the coefficient of thermal expansion of the ASIC package and the circuit board, manufacturers can use mounting sockets in the circuit board for the solder balls to absorb the coefficient of thermal expansion mismatch. Use of the sockets, however, increases the costs associated with manufacturing the circuit board.

By contrast, embodiments of the present invention significantly overcome the described deficiencies and provide mechanisms for transmitting power supply signals and data signals between a circuit board component and a circuit board. A circuit board is configured to exchange data signals with a circuit board component through data signal contacts located between the circuit board and a primary surface of the circuit board component. The circuit board has power supply signal contacts that are configured to carry power supply signals to the circuit board component through a secondary surface of the circuit board component. A signal carrier connects the power supply signal contacts of the circuit board with the circuit board component through the secondary surface of the circuit board component. Such a configuration allows the circuit board component to receive a relatively large amount of power while maintaining the number of data signal contacts dedicated for transmission of data signals between the circuit board and circuit board component. The configuration of the circuit board, circuit board component, and the signal carrier also allows the circuit board component to receive relatively large amount of power while maintaining the package size of the circuit board component, thereby minimizing manufacturing costs associated with the circuit board.

In one arrangement, a signal carrier has a support member having a first surface and a second surface. The signal carrier has a first carrier contact coupled to the first surface of the support member that are configured to electrically communicate with a signal carrier contact of a circuit board. The circuit board has a circuit board component, where the circuit board component has a primary surface having a primary contact configured to electrically communicate with a component contact of the circuit board. The signal carrier has a second carrier contact coupled to the second surface of the support member and in electrical communication with the first carrier contact. The second carrier contact is configured to electrically communicate with a secondary contact of a secondary surface of the circuit board component. The signal carrier carries a signal, such as a power supply signal, from the circuit board to the circuit board device, thereby bypassing the interface between the circuit board and the circuit board component. In such a configuration, the signal carrier allows the circuit board component to receive a relatively larger amount of power than conventional circuit board components without modification to the size of the circuit board component.

In one arrangement, the support member of the signal carrier has a first support member portion defining a first opening having a first perimeter configured to encompass a boundary of the circuit board component where the first support member portion is configured to retain the first carrier contacts. The support member also has a second support member portion in communication with the first support member portion, the second support member portion defining a second opening having a second perimeter where the second perimeter is configured to retain the second carrier contacts. Such geometry of the support member allows the support member to surround and attach to the circuit board component during operation, thereby minimizing the amount of real estate on the circuit board used by the signal carrier.

In one arrangement, the second carrier contact of the signal carrier defines a substantially semicircular plated opening engaging the second set of contacts of the circuit board component. The semicircular plated opening allows a manufacturer to use a reflow soldering technique to electrically couple the plated opening to the contact of the circuit board component to form a relatively robust electrical connection.

In one arrangement, the first carrier contacts of the signal carrier have at least one solder ball having a diameter of at least approximately 1.0 mm. In the case where the diameter of the solder balls is at least approximately 1 mm, the solder balls absorb a stress generated between the signal carrier and the circuit board as caused by a coefficient of thermal expansion mismatch between the signal carrier and the circuit board. Use of solder balls having a diameter of at least approximately 1.0 mm, therefore, minimizes a fracture risk of the solder balls and minimizes a risk of failure of the signal carrier.

In one arrangement, the signal carrier has a power regulation device coupled to the support member and in electrical communication with the first set of terminals and the second set of terminals. Placement of the power regulation devices on the signal carrier minimizes the use of real estate or surface area of the circuit board by the power regulation devices.

The features of the invention, as described above, may be employed in electronic equipment and methods such as those of Cisco Systems of San Jose, Calif.

DETAILED DESCRIPTION

Embodiments of the present invention provide mechanisms for transmitting power supply signals and data signals between a circuit board component and a circuit board. A circuit board is configured to exchange data signals with a circuit board component through data signal contacts located between the circuit board and a primary surface of the circuit board component. The circuit board has power supply signal contacts that are configured to carry power supply signals to the circuit board component through a secondary surface of the circuit board component. A signal carrier connects the power supply signal contacts of the circuit board with the circuit board component through the secondary surface of the circuit board component. Such a configuration allows the circuit board component to receive a relatively large amount of power while maintaining the number of data signal contacts dedicated for transmission of data signals between the circuit board and circuit board component. The configuration of the circuit board, circuit board component, and the signal carrier also allows the circuit board component to receive relatively large amount of power while maintaining the package size of the circuit board component, thereby minimizing manufacturing costs associated with the circuit board.

FIG. 1illustrates an arrangement of a circuit board assembly20having a circuit board22, a circuit board component24, and a signal carrier26.

The circuit board22, such as formed from a fiberglass material having electrically conductive traces, has a mounting surface23having a set28of component contacts29and a second set30of signal carrier contacts31. In one arrangement, the component contacts29are electrically conductive pads defined by the circuit board22. The component contacts29, in one arrangement, are data signal contacts29configured to carry data signals between the circuit board22and the circuit board component24. In one arrangement, the signal carrier contacts31are electrically conductive pads defined by the circuit board22. The signal carrier contacts31, in one arrangement, are power supply signal contacts31configured to carry a D.C. current from the circuit board22to the circuit board component24to power the circuit board component24during operation.

The circuit board component24, such as an ASIC, has a primary surface32and a secondary surface34. The primary surface32of the circuit board component24faces or is directed toward the mounting surface23of the circuit board22and has a set36of primary contacts37configured electrically and mechanically couple to the component contacts29of the circuit board22. For example, the primary contacts37are solder balls of a solder ball array. The primary contacts37, in one arrangement, carry data signals between the circuit board22(e.g., via the component contacts29of the circuit board22) and the circuit board component24. Attachment of the primary contacts37of the circuit board component24to the component contacts29of the circuit board22, therefore, allows data exchange or data signal transmission between the circuit board component24and the circuit board22.

The secondary surface34of the circuit board component24faces away or is directed away from the mounting surface23of the circuit board22(e.g., in one arrangement, the secondary surface34opposes the primary surface32). The second surface34of the circuit board component24has a set38of secondary contacts39formed from an electrically conductive material, such as a copper material. For example the secondary contacts39are electrically conductive pads. In one arrangement, the secondary contacts39are configured to receive a power supply signal from the circuit board22and provide grounding of the power supply signal, via the signal carrier26. In one arrangement the secondary contacts39are located on the secondary surface34of the circuit board component24at a distance of approximately 1.0 mm–1.5 mm from a boundary or edge54of the circuit board component24.

The signal carrier26has a support member40, such as formed from a circuit board material (e.g. fiberglass material having electrically conductive traces), having a first surface42and a second surface44. The signal carrier26has a set46first carrier contacts47coupled to the first surface42of the support member40. The signal carrier26also has a set48of second carrier contacts49coupled to the second surface44of the support member40. The second carrier contacts49electrically couple with the first carrier contacts47by way of electrical couplers or electrical traces50within the support member40, such as illustrated inFIG. 3.

Returning toFIG. 1, the first carrier contacts47, in one arrangement, are formed as solder balls configured to mechanically and electrically couple with the signal carrier contacts31(e.g., the power supply signal contacts) of the circuit board22. The second carrier contacts49, in one arrangement, are formed of an electrically conductive material and are configured to electrically communicate with the secondary contacts39of the circuit board component24. In one arrangement, the second carrier contacts49are configured to transmit a D.C. current from the circuit board22to the circuit board component24to the circuit board component24during operation. In one arrangement, the signal carrier26and the circuit board component24form a circuit board component assembly52.

During operation, for example, the circuit board component24both exchanges data signals with the circuit board22and receives power supply signals from the circuit board22. In one arrangement, the circuit board component24exchanges data signals with the circuit board22through the primary contacts37located on the primary surface32(e.g., bottom surface) of the circuit board component24. The circuit board component24also receives power supply signals from the circuit board22, via the signal carrier26, through the secondary contacts39located on the secondary surface34(e.g., top surface) of the circuit board component24.

The configuration of the circuit board22, the circuit board component24, and the signal carrier26allows the circuit board component24to receive different types of signals (e.g., data signal and power supply signal) at separate locations (e.g., primary surface32and secondary surface34) of the circuit board component24, relative to the circuit board22, where each location is configured to receive a particular signal type. For example, the circuit board component24receives data signals through the primary contacts37located on the primary surface32of the circuit board component24. Furthermore, the circuit board component24receives power supply signals through the secondary contacts39located on the secondary surface34of the circuit board component24. Each surface32,34of the circuit board component24receives either data signals or power supply signals, respectively, from the circuit board component22. In such a configuration, therefore, a manufacturer can increase the amount of power received by the circuit board component24without modifying the size of the circuit board component24or increasing the number of contacts on a single surface of the circuit board component to receive additional power supply signals.

For example, as described above, a conventional circuit board component (e.g., ASIC's) typically has a 45 mm×45 mm attachment surface area with a 2500 solder ball array. The solder ball array of the conventional circuit board component carries both data signals between the circuit board and the ASIC and power supply signals from the circuit board to the ASIC. To increase the amount of power received by a conventional circuit board component, in one arrangement, a manufacturer can increase the attachment surface area (e.g., package size) of the conventional circuit board components, thereby allowing an increase in the number of solder balls of the array. Such an increase in the array size of the solder ball array, in turn, allows an increase in the number of solder ball contacts in the array dedicated to carrying power to the circuit board component (e.g., configured to provide power to the circuit board component). Increasing the size conventional circuit board component to accommodate a greater number of solder balls of the array, however, increases the amount of circuit board surface area or real estate required to mount the modified circuit board component to the circuit board. Such an increase thereby decreases the amount of real estate available for other circuit board components and traces on the circuit board. Increasing the size conventional circuit board component, furthermore, increases the probability of a coefficient of thermal expansion mismatch between the circuit board component and the circuit board, thereby increasing the risk of failure of the solder balls.

The present circuit board component24, by contrast, receives power supply signals through the secondary contacts39located on the secondary surface34of the circuit board component24. To increase the amount of power received by the circuit board component24, in one arrangement, a manufacturer increases the number of the secondary contacts39located on the secondary surface34of the circuit board component24. Such a configuration does not require an increase in the package size of the circuit board component24(e.g., increase in the attachment surface area) to accommodate additional secondary contacts39. In one arrangement, the manufacturer increases the size or gauge of the secondary contacts39to increase the amount of power received by the circuit board component24. Such a configuration also does not require an increase in the package size of the circuit board component24to accommodate larger secondary contacts39. By maintaining the package size of the circuit board component24, the configuration of the circuit board assembly20minimizes the use of additional real estate on the circuit board22to support a larger circuit board component. The configuration of the circuit board assembly20, furthermore, minimizes a potential coefficient of thermal expansion mismatch between the circuit board component24and the circuit board22by maintaining the size of the package of the circuit board component24. Use of the circuit board assembly20, therefore minimizes potential fracture or failure of the primary contacts37(e.g., solder balls) of the circuit board component24.

As described above, the signal carrier26carries a signal, such as a power supply signal, from the circuit board22to the secondary surface34of the circuit board component24. The signal carrier26, therefore, transmits the signal to the circuit board component24while bypassing a connection between the component contacts29of the circuit board22and the primary contacts37of the circuit board component24.

FIGS. 2 and 3illustrate a bottom view and a side sectional view, respectively, of an arrangement of the signal carrier26. The support member40of the signal carrier26has a first support member portion60defining a first opening64and a second support member portion62defining a second opening66. In one arrangement, the first support member portion60and the second support member portion62are formed from a circuit board material (e.g., fiberglass) having traces or electrical couplers50that couple the first carrier contacts47of the first support member portion60with the second carrier contacts49of the second support member portion62. As illustrated inFIGS. 2 and 3, the first support member portion60retains or carries the first carrier contacts47and the second support member portion60retains or carries the second carrier contacts49.

The first opening64of the first support member portion60has a first perimeter68configured to encompass a boundary of the circuit board component24. For example, in the case where the circuit board component24is an ASIC having a 45 mm×45 mm package size, each side65of the first opening64has a length greater than approximately 45 mm (e.g., the perimeter68of the first opening64is greater than the perimeter of the circuit board component24). Such geometry of the first support member portion60allows the circuit board component24to fit within the first support member portion60during attachment of the signal carrier26to the circuit board22. The first support member portion60, therefore, surrounds the circuit board component24and minimizes the amount of real estate on the circuit board22used by the signal carrier26.

The second opening66of the second support member portion62has a second perimeter70configured to retain the second carrier contacts49. For example, second opening66positions or spaces the second carrier contacts49along the second perimeter70to correspond with the locations of the secondary contacts on the secondary surface34of the circuit board component24. In such a configuration, during attachment of the signal carrier26to the circuit board22, the second carrier contacts49of the second perimeter70are positioned in relative proximity to the secondary contacts39on the secondary surface34of the circuit board component24. Such positioning allows a manufacturer to form an electrical connection between the secondary contacts39and the second carrier contacts49, thereby allowing the circuit board component24to receive a power supply signal from the circuit board22.

FIG. 3shows an arrangement of the first carrier contacts47of the signal carrier26. As illustrated the first carrier contacts47are configured as solder balls having a diameter72of at least approximately 1 mm. Such a configuration of the first carrier contacts47allows the first carrier contacts47to absorb stresses generated by a coefficient of thermal expansion mismatch between the signal carrier26and the circuit board22. For example, assume the signal carrier26is formed of a material having a coefficient of thermal expansion different than the coefficient of thermal expansion of the material forming the circuit board22(e.g., a coefficient of thermal expansion mismatch). Because of the differences in the coefficients of thermal expansion, the signal carrier26and the circuit board22expand and contract at different rates when exposed to variations in temperature. During thermal expansion or contraction of the signal carrier26and the circuit board22, such differences in expansion rates of the signal carrier26and the circuit board22generate a stress on the first carrier contacts47. In the case where the diameter72of the first carrier contacts (e.g., solder balls)47is at least approximately 1 mm, the first carrier contacts47absorb the generated stresses, thereby minimizing a risk of fracture or failure of the contacts47.

FIG. 4illustrates, in one arrangement, the signal carrier26defining the second carrier contacts49as substantially semicircular plated openings80. Each semicircular plated opening80has a plated coating82, such as an electrically conductive or metallic coating, that electrically contacts an electrical coupler50of the support member40to form an electrical contact with a first carrier contact47of the signal carrier26.

Use of the semicircular plated openings80, in one arrangement, allows a manufacturer to use a reflow soldering technique to electrically couple the signal carrier26to the contacts39of the circuit board component24. The reflow soldering technique provides a relatively robust connection between the semicircular plated openings80and the secondary contacts39of the circuit board component24.

In one arrangement, the semicircular plated openings80of the signal carrier26the semicircular plated openings80each have a perimeter84that absorbs stresses generated on a solder connection86between the secondary contacts39of the circuit board component24and the signal carrier26. For example, in one arrangement, the solder connection86experiences a stress caused as a result of a coefficient of thermal expansion mismatch between the material forming the signal carrier26and the material forming the circuit board component24. The perimeter84expands or contracts as a result of the stresses placed on the solder connection86, thereby reducing the stress on the solder connection86and minimizing a risk of fracture of the solder connection86.

FIG. 5illustrates, in one arrangement, the signal carrier26having power regulation devices90coupled to the support member40. For example, the power regulation devices90include charge to digital converters (CDC's), voltage regulators, capacitors, or DC—DC converters. In certain cases the circuit board component24requires a power signal having a particular voltage. The power regulation devices90electrically connect between the first carrier contact47and the second carrier contact49of the signal carrier26and provide a power supply signal having an appropriate voltage (e.g., a required voltage) to the circuit board component24. Placement of the power regulation devices90on the signal carrier26minimizes the amount of real estate or surface area of the circuit board22as required by the power regulation devices90.

FIG. 6illustrates a method100for assembling a circuit board assembly20, according to one embodiment of the invention. Such a method can be performed either manually (e.g., by a technician on an assembly line) or automatically (e.g., by automated equipment).

In step102, an assembler electrically couples a primary contact37of a primary surface32of a circuit board component24with a component contact29of a circuit board22. For example, in one arrangement, the assembler attaches a solder ball array37of the primary surface32of the circuit board component24with contact pads29of the circuit board22. Attachment of the primary contacts37with the component contacts29provides data signal transmission between the circuit board22and the circuit board component24, for example.

In step104, the assembler electrically couples a first carrier contact47of a first surface42of a support member40, with a signal carrier contact31of the circuit board22. For example, in one arrangement, the assembler attaches solder balls47of the support member40to contact pads31of the circuit board22.

In step106, an assembler electrically couples a second carrier contact49of a second surface44of the support member40with a secondary contact39of a secondary surface34of the circuit board component24where the second carrier contact49is in electrical communication with the first carrier contact47. For example, in one arrangement, attachment of the first carrier contacts47of the support member40with the signal carrier contacts31of the circuit board22provides power supply signal transmission between the signal carrier contacts31of the circuit board22and the second carrier contacts49of the support member40. Further attachment of the second carrier contact49of the support member40with the secondary contacts39of the circuit board component24provides power supply signal transmission between the signal carrier contacts31of the circuit board22and the secondary contacts39of the circuit board component24. Such a configuration allows an assembler to increase the amount of power provided to the circuit board component24without requiring alteration or modification to the size of the circuit board component24.

Those skilled in the art will understand that there can be many variations made to the embodiments explained above while still achieving the same objective of those embodiments and the invention in general.

FIGS. 1 and 4show the secondary contacts39of the circuit board component24as electrically conductive pads extending from the second surface34of the circuit board component24. Such a configuration is by way of example only. In one arrangement, the secondary contacts39of the circuit board component24are formed as cylindrical protrusions located on the second surface34of the circuit board component24.

With respect toFIG. 1, as described, the circuit board component24is configured with a primary surface32having primary contacts37that carry a data signal between the circuit board22and the circuit board component24. Also as described, the circuit board component24is configured with a secondary surface34having secondary contacts39that carry a power supply signal, transmitted by the signal carrier24, from the circuit board22. Such a configuration is by way of example only. In one arrangement, the circuit board component24is configured with the primary surface32having primary contacts37that carry a power supply signal from the circuit board22to the circuit board component24. Furthermore, in such an arrangement, the circuit board component24is configured with the secondary surface34having secondary contacts39that carry a data signal between the circuit board22and the circuit board component24, via the signal carrier26. In such an arrangement, therefore, the signal carrier26carries the data signal between the circuit board22and the circuit board component24.

Such variations are intended to be covered by the scope of this invention. As such, the foregoing description of embodiments of the invention is not intended to be limiting. Rather, any limitations to the invention are presented in the following claims.