Surface mount pads for next generation speeds
A high-speed transmission circuit comprises, as part of a signal path, a connector pin disposed on a pad that comprises an unused pad region. The unused pad region is not considered part of the signal path but is part of a resonant sub-circuit. In various embodiments, by properly adjusting the dimensions of the pad region and other structures in the high-speed transmission circuit, resonant frequencies of the sub-circuit are shifted to a frequency range that is outside of the frequency range of interest in the signal path, thereby, reducing insertion loss and increasing signal integrity without compromising mechanical stability.
1. A high-speed transmission circuit comprising: a first connector pin that serves as part of a signal path for a high-speed signal, the first connector pin coupled to a first signal trace that extends toward a first end of a printed circuit board (PCB); a pad coupled to the first connector pin, the pad comprising a first pad region that is not considered part of the signal path; a connector pin leg coupled to the first connector pin, the connector pin leg being disposed on the pad; a resonant sub-circuit formed at least by the first pad region, the resonant sub-circuit comprising one or more dimensions chosen to more closely match an impedance of the signal path to the impedance of the resonant sub-circuit such as to reduce an insertion loss in the signal path, which comprises the first signal trace, the first pad region extending from the first connector pin towards a second end of the PCB, the second end being opposite to the first end; and a second connector pin coupled to a second signal trace and to a second pad region that extend from the second connector pin toward a second end of the PCB.
2. The high-speed transmission circuit of claim 1 , further comprising a low-speed structure having least one dimension that is greater than the one or more dimensions of the resonant sub-circuit to increase mechanical stability or to compensate for a potential loss in mechanical stability.
3. The high-speed transmission circuit of claim 2 , wherein the low-speed structure is designed to assume a ground potential.
4. The high-speed transmission circuit of claim 1 , wherein the first connector pin is associated with a first impedance at a frequency of operation, and wherein the connector pin leg is associated with a second impedance at the frequency of operation.
5. The high-speed transmission circuit of claim 4 , wherein the second impedance represents an impedance discontinuity at the frequency of operation.
6. The high-speed transmission circuit of claim 5 , wherein the impedance discontinuity causes a signal at the frequency of operation to be reflected into the signal path.
7. The high-speed transmission circuit of claim 1 , wherein the resonant sub-circuit causes a transmission line effect at a resonant frequency.
8. The high-speed transmission circuit of claim 1 , wherein the circuit carries a signal having one or more high frequency components that flow on an outer layer of the first connector pin.
9. A lead frame comprising: a first connector pin coupled to a first signal trace that serves as part of a signal path in a circuit; a connector pin leg coupled to the first connector pin and to a first pad that comprises a first pad region that is not considered part of the signal path that extends toward a first end of a printed circuit board (PCB), the connector pin leg and
at least a portion of the first pad forming a resonant sub-circuit that is coupled to the signal path, at least one dimension of the portion of the resonant sub-circuit being chosen to more closely match an impedance of the signal path to the impedance of the resonant sub-circuit such as to cause a reduction in insertion loss in the signal path, which comprises the first signal trace, the first pad region extending from the first connector pin toward a second end of the PCB, the second end being opposite to the first end; and a second connector pin coupled to a second signal trace and to a second pad region that extend from the second connector pin toward a second end of the PCB.
10. The lead frame of claim 9 , wherein a reduction in mechanical stability that is caused by the at least one dimension is compensated by increasing at least one dimension of a physical structure in the circuit.
11. The lead frame of claim 10 , wherein the physical structure is designed to carry signals that have relatively lower speeds or rise times than the resonant sub-circuit.
12. The lead frame of claim 9 , wherein the first connector pin is associated with a first impedance at a frequency of operation, and wherein the connector pin leg is associated with a second impedance at the frequency of operation.
13. The lead frame of claim 12 , wherein the second impedance represents an impedance discontinuity at the frequency of operation.
14. The lead frame of claim 13 , wherein the impedance discontinuity causes a signal at the frequency of operation to be reflected into the signal path.
15. The lead frame of claim 9 , wherein a current that flows on an outer layer of the first connector pin has one or more high frequency components.
16. A printed circuit board (PCB) comprising:
a first connector pin coupled to a first signal trace that extends toward a first end of the PCB;
a pad coupled to the first connector pin, the pad comprising a first pad region that has one or more dimensions chosen to at least partially match an impedance of a first signal path such as to reduce an insertion loss in the first signal path, which comprises the first signal trace, the first pad region extending from the first connector pin toward a second end of the PCB, the second end being opposite to the first end; and
a second connector pin coupled to a second signal trace and to a second pad region that extend from the second connector pin toward the second end of the PCB.
17. The PCB of claim 16 , further comprising a first connector pin leg that is coupled to the first connector pin and is disposed on the pad.
18. The PCB of claim 17 , wherein at least one of the one or more dimensions of the first pad region is smaller than a largest dimension of the first connector pin leg.
19. The PCB of claim 17 , further comprising a second connector pin leg that is coupled to the second connector pin and is disposed on a second pad region that has one or more dimensions chosen to at least partially match an impedance of a second signal path that comprises the second signal trace.