Plated pads and leads for surface mount technology connections
A high-speed transmission circuit comprises a connector pin that serves as part of a signal path, has a first conductivity, and has a connector pin leg that is coupled to a pad that has a second conductivity lower than the first conductivity. The connector pin leg and at least a portion of the pad form a resonant sub-circuit coupled to the signal path. The second conductivity causes a reduction in insertion loss in the signal path by damping a current in the resonant sub-circuit.
1. A high-speed transmission circuit comprising:
a connector pin that serves as part of a signal path, the connector pin having a first conductivity;
a connector pin leg coupled to the connector pin and having the first conductivity; and
a pad coupled to the connector pin leg and comprising a second conductivity that is lower than the first conductivity, the connector pin leg and at least a portion of the pad forming a resonant sub-circuit that is coupled to the signal path, the second conductivity causing a reduction in insertion loss in the signal path, when compared to an insertion loss in the signal path if the pad had only the first conductivity, by damping a current in the resonant sub-circuit.
2. The high-speed transmission circuit of claim 1 , wherein the resonant sub-circuit causes a transmission line effect at one or more frequencies, the resonant sub-circuit being coupled to a ground connection that is capacitively coupled to at least the connector pin leg.
3. The high-speed transmission circuit of claim 2 , wherein the ground connection has a different conductivity than the first conductivity.
4. The high-speed transmission circuit of claim 1 , wherein the connector pin is associated with a first impedance at a frequency of interest, and wherein the connector pin leg is associated with a second impedance at the frequency of interest.
5. The high-speed transmission circuit of claim 4 , wherein the second impedance represents an impedance discontinuity at the frequency of interest.
6. The high-speed transmission circuit of claim 5 , wherein the impedance discontinuity causes a signal at the frequency of interest to be reflected into the signal path.
7. The high-speed transmission circuit of claim 1 , wherein the current in the resonant sub-circuit is damped proportional to a ratio between the second conductivity and the first conductivity, the pad having been plated with a material that has the second conductivity.
8. The high-speed transmission circuit of claim 1 , wherein the current has one or more high frequency components that flow on an outer layer of the connector pin.
9. A lead frame comprising:
a connector pin that serves as part of a signal path, the connector pin having a first conductivity; and
a connector pin leg coupled to the connector pin and to a pad that comprises a second conductivity lower than the first conductivity, the connector pin leg and at least a portion of the pad forming a resonant sub-circuit that is coupled to the signal path, the second conductivity causing a reduction in insertion loss in the signal path, when compared to an insertion loss in the signal path if the pad had only the first conductivity, by damping a current in the resonant sub-circuit.
10. The lead frame of claim 9 , wherein the resonant sub-circuit causes a transmission line effect at one or more frequencies.
11. The lead frame of claim 9 , wherein the connector pin is associated with a first impedance at a frequency of interest, and wherein the connector pin leg is associated with a second impedance at the frequency of interest.
12. The lead frame of claim 11 , wherein the second impedance represents an impedance discontinuity at the frequency of interest.
13. The lead frame of claim 12 , wherein the impedance discontinuity causes a signal at the frequency of interest to be reflected into the signal path.
14. The lead frame of claim 9 , wherein the current in the resonant sub-circuit is damped proportional to a ratio between the second conductivity and the first conductivity.
15. The lead frame of claim 9 , wherein the current has one or more high frequency components that flow on an outer layer of the connector pin.
16. A method for reducing insertion loss in a high-speed transmission circuit, the method comprising:
applying a voltage to a signal path that comprises a connector pin; and
driving a current through the connector pin that has a first conductivity and a connector pin leg coupled to a pad, the pad comprising a second conductivity that is lower than the first conductivity and causing a reduction in insertion loss in the signal path, when compared to an insertion loss in the signal path if the pad had only the first conductivity, by damping a current in a resonant sub-circuit that is formed by the connector pin leg and at least a portion of the pad.
17. The method of claim 16 , wherein the resonant sub-circuit causes a transmission line effect at one or more frequencies, the resonant sub-circuit being coupled to a ground connection that is capacitively coupled to at least the connector pin leg, the ground connection having a different conductivity than the first conductivity.
18. The method of claim 16 , wherein the connector pin is associated with a first impedance at a frequency of interest, and wherein the connector pin leg is associated with a second impedance at the frequency of interest.
19. The method of claim 18 , wherein, at the frequency of interest, the second impedance represents an impedance discontinuity that causes a signal to be reflected into the signal path.
20. The method of claim 19 , wherein the current in the resonant sub-circuit is damped proportional to a ratio between the second conductivity and the first conductivity, the pad having been plated with a material that has the second conductivity.