Printed circuit board trace for galvanic effect reduction
Devices and methods are described for reducing etching due to galvanic effect within a printed circuit board that may be used, for example, in a data storage device, such as a card-type data storage device. Specifically, a contact trace is coupled to a contact finger that has a substantially larger surface area than the contact trance, and that is configured to couple the data storage device to a host device. The contact trace is electrically isolated from the rest of the circuitry during a fabrication process. The contact finger and an exposed portion of the contact trace are plated with a common material to reduce galvanic etching of the contact trace during fabrication. The contact trace is then connected to an impedance trace though at least one of a component and a bond wire.
1. A printed circuit board for an electronic device, comprising:
a substrate having a first side and a second side opposite to the first side;
a contact finger disposed on the first side of the substrate configured to interface with an external electronic device;
a contact trace coupled to the contact finger and extending from the first side of the substrate to the second side of the substrate, wherein the contact trace has an exposed portion disposed on the second side of the substrate; and
an impedance trace disposed on the second side of the substrate and configured to be coupled to one or more components of the electronic device;
wherein the contact finger and the exposed portion of the contact trace are plated with a common material to reduce galvanic etching of the contact trace; and
wherein the exposed portion of the contact trace is electrically connected to the impedance trace by way of at least one of a component and a bond wire.
2. The printed circuit board of claim 1 , wherein the exposed portion of the contact trace is electrically connected to the impedance trace with a bond wire.
3. The printed circuit board of claim 1 , wherein the component is a resistor.
4. The printed circuit board of claim 1 , wherein the component is a capacitor.
5. The printed circuit board of claim 1 , wherein the surface area of the contact finger is up to twenty times larger than the exposed portion of the contact trace.
6. The printed circuit board of claim 1 , wherein the common material is gold.
7. The printed circuit board of claim 1 , wherein the common material is nickel-gold.
8. The printed circuit board of claim 1 , wherein the impedance trace includes a plated portion plated with the common material, and wherein the plated portion of the impedance trace is coupled to the component.
9. A method for reducing etching due to galvanic effect in a printed circuit board, the method comprising:
determining a ratio of a surface area of a contact finger to a surface area of an exposed portion of a contact trace electrically connected to the contact finger, wherein the contact finger is configured to provide an electrical connection to an external electronic device;
determining whether the ratio exceeds a predetermined threshold;
responsive to determining that the ratio exceeds the predetermined threshold, separating the exposed portion of the contact trace into a contact trace portion and an impedance trace, wherein the contact trace portion and the impedance trace are electrically isolated;
plating the contact finger and the contact trace portion with a common material; and
electrically connecting the contact trace portion and the impedance trace with one of a component or a bond wire.
10. The method of claim 9 , wherein the contact trace portion and the impedance trace are electrically connected with the bond wire.
11. The method of claim 9 , wherein the component is a resistor having a resistance value of less than fifty ohms.
12. The method of claim 9 , wherein the component is a capacitor.
13. The method of claim 9 , wherein the common material is gold.
14. The method of claim 9 , further comprising plating a first portion of the impedance trace with the common material.
15. A card-type data storage device, comprising:
a substrate having a first side and a second side opposite to the first side;
a contact finger disposed on the first side of the substrate configured to interface with a host device and plated with a plating material;
a first trace coupled to the first contact finger and extending from the first side of the substrate to the second side of the substrate, wherein the first trace has an exposed portion disposed on the second side of the substrate, the exposed portion being plated with the plating material; and
a second trace disposed on the second side of the substrate, wherein a portion of the second trace is plated with the plating material; and
wherein the exposed portion of the first contact trace is electrically connected to the second trace through a connection device, the connection device connected between the plated portion of the first trace and the plated portion of the second trace.
16. The card-type data storage device of claim 15 , wherein the connection device is a bond wire.
17. The card-type data storage device of claim 15 , wherein the connection device is a resistor.
18. The card-type data storage device of claim 15 , wherein the connection device is a capacitor.
19. The card-type data storage device of claim 15 , wherein the surface area of the contact finger is up to twenty times larger than the exposed portion of the first trace.
20. The card-type data storage device of claim 15 , wherein the plating material is at least one of gold or nickel-gold.