Surface mount technology (SMT) pad design with differential contact strips having converging narrowing distal ends that facilitate high speed communication
An Information handling system (IHS) includes a circuit board assembly with surface mount technology (SMT) pad structure. Landing pad(s) attached to circuit board substrate have a mounting area that receive an SMT connector pin onto adjacent pair of differential contact strips plated to nonconductive surface and extending longitudinally in parallel alignment. A return current strip is longitudinally aligned, adjacent to the differential contact strips on a first lateral side. The return current strip is connected to a ground plane of the circuit board substrate. Converging narrowing of the adjacent differential contact strip increases separation from a distal end of the return current strip. The separation improves signal integrity by reducing fringe effects, increasing impedance, and quenching resonance. A surface mount device (SMD) has one or more connector pins that are attached to the one or more landing pads to conduct the high-speed communication signal.
1. A circuit board assembly of an information handling system (IHS), the circuit board assembly comprising:
a circuit board substrate having a nonconductive surface;
a surface mount technology (SMT) pad structure comprising:
one or more landing pads formed on an exposed surface of the circuit board substrate and having a mounting area that is longitudinally sized to receive an SMT connector pin of a surface mount device (SMD) within a placement tolerance, each landing pad comprising:
an adjacent pair of differential contact strips plated to the nonconductive surface and longitudinally extending in parallel alignment, the differential contact strips having converging narrowing of each strip at a distal end and having a proximal signal trace for conducting a high-speed communication signal to another functional component attached to the circuit board substrate, wherein a longitudinal length of a converging narrowing portion of each strip of the pair of differential contact strips is within a range of 30-50% of a total longitudinal length of the respective landing pad; and
a return current strip that is longitudinally aligned adjacent to the pair of differential contact strips and connected to a ground plane of the circuit board substrate, the converging narrowing of the adjacent differential contact strip increasing separation of a distal end of the adjacent differential contact strip from the return current strip, the increased separation reducing coupling with the return current strip and consequently improving signal integrity by reducing fringe effects, increasing impedance, and quenching resonance to support high speed communication signals passing through the SMT landing pad at next generation speeds of greater than 12 Gigabytes per second; and
the surface mount device (SMD) having one or more connector pins that correspond to and are attached to the one or more landing pads to conduct high-speed communication signals.
2. The circuit board assembly of claim 1 , wherein the converging narrowing of each strip comprises a tapered end that provides an increased impedance, which quenches any resonance by the converging, narrowing distal ends of the strip.
3. The circuit board assembly of claim 2 , wherein the converging narrowing to provide the tapered end provides a removal at the distal end of 14% of a contact area of each strip.
4. The circuit board assembly of claim 1 , wherein the converging narrowing of each strip comprises a rounded end that provides an increased impedance, which quenches any resonance by the converging, narrowing distal ends of the strip.
5. The circuit board assembly of claim 4 , wherein the converging narrowing to provide the rounded end provides a removal at the distal end of 8% of a contact area of each strip.
6. The circuit board assembly of claim 4 , wherein the converging narrowing provides a greater length of curved surface which reduces charge accumulation at each strip.
7. The circuit board assembly of claim 1 , further comprising a next return current strip that is longitudinally aligned adjacent to the pair of differential contact strips and on an opposite side to the return current strip, the next return current strip connected to the ground plane of the circuit board substrate, the return current strip and next return current strip extending on lateral sides of the pair of differential contact strips that are electrically connected as positive and negative values to a high communication speed functional component of the IHS.
8. The circuit board assembly of claim 1 , wherein the SMT landing pad is formed by:
attaching a metallic layer onto a surface of the circuit board substrate;
etching the metallic layer to leave the adjacent pair of differential contact strips;
attaching a return current strip; and
attaching a raised rectangular ridge around the adjacent pair of differential contact strips to form the landing pad to guide the SMT connector pin of the SMD.
9. The IHS of claim 1 , further comprising a next return current strip that is longitudinally aligned adjacent to the pair of differential contact strips and on an opposite side to the return current strip, the next return current strip connected to the ground plane of the circuit board substrate, the return current strip and next return current strip extending on lateral sides of the pair of differential contact strips that are electrically connected as positive and negative values to a high communication speed functional component of the IHS.
10. The IHS of claim 9 , wherein the SMT landing pad is form by:
attaching a metallic layer onto a surface of the circuit board substrate;
etching the metallic layer to leave the adjacent pair of differential contact strips;
attaching a return current strip; and
attaching a raised rectangular ridge around the adjacent pair of differential contact strips to form the landing pad to guide the SMT connector pin of the SMD.
11. The circuit board assembly of claim 1 , wherein the converging narrowing of the adjacent differential contact strip ensures superior electrical performance for next generation speeds, while maintaining mechanical stability of the strip, decreases capacitive effect by the landing pads resulting in improved impedance, achieves better return loss and insertion loss, and mitigates crosstalk because of a differential property maintained at edges of the landing pads, and reduces electrical field density and results in superior electrical performance of the landing pads.
12. An information handling system (IHS) comprising:
a circuit board assembly comprising:
a circuit board substrate having a nonconductive surface;
a surface mount technology (SMT) pad structure comprising:
one or more landing pads formed on an exposed surface of the circuit board substrate and having a mounting area that is longitudinally sized to receive an SMT connector pin of a surface mount device (SMD) within a longitudinal mounting displacement tolerance value, each landing pad comprising:
an adjacent pair of differential contact strips plated to the nonconductive surface and longitudinally extending in parallel alignment, the differential contact strips having converging narrowing of each strip at a distal end and having a proximal signal trace for conducting a high-speed communication signal to another functional component attached to the circuit board substrate, wherein a longitudinal length of a converging narrowing portion of each strip of the pair of differential contact strips is within a range of 30-50% of a total longitudinal length of the respective landing pad; and
a return current strip that is longitudinally aligned adjacent to the pair of differential contact strips and connected to a ground plane of the circuit board substrate, the converging narrowing of the adjacent differential contact strip increasing separation of a distal end of the adjacent differential contact strip from the return current strip, the increased separation improving signal integrity by reducing fringe effects, increasing impedance, and quenching resonance to support high speed communication signals at next generation speeds of greater than 12 Gigabytes per second; and
a surface mount device (SMD) having one or more connector pins that correspond to and are attached to the one or more landing pads to conduct high-speed communication signals.
13. The IHS of claim 12 , wherein the converging narrowing of each strip comprises a tapered end that provides an increased impedance, which quenches any resonance by the converging, narrowing distal ends of the strip.
14. The IHS of claim 12 , wherein the converging narrowing of each strip comprises a rounded end that provides an increased impedance, which quenches any resonance by the converging, narrowing distal ends of the strip.