Electrolytic capacitor assembly and method with recessed leadframe channel
A solid electrolytic capacitor has a capacitor body formed from a pressed anode, a dielectric layer and a solid electrolyte layer. An anode lead extends from anode pellet and is electrically connected to an anode termination. The outer surface of the capacitor body forms a cathode that is electrically connected to a cathode termination. Base anode and cathode termination portions are coplanar and connected with a recessed leadframe channel. A capacitor element is attached to the anode and cathode termination portions and encapsulated. The recessed leadframe channel is removed to isolate the anode and cathode terminations on a single mounting surface, leaving a surface groove formed between the anode and cathode terminations.
1. A method for forming a solid electrolytic capacitor, comprising:
attaching a capacitor element having a capacitor body and an anode lead to a leadframe, wherein the leadframe comprises an anode termination having at least a base anode termination portion for supporting part of the capacitor body and an upstanding anode termination portion for connecting to the anode lead, a cathode termination having at least a base cathode termination portion for supporting part of the capacitor body, and a recessed leadframe channel formed between and connecting the base anode termination portion and the base cathode termination portion;
encapsulating the capacitor element in a casing such that at least a portion of the base anode termination portion, base cathode termination portion and recessed leadframe channel remain exposed; and
removing the recessed leadframe channel to isolate the anode and cathode terminations.
2. The method of claim 1 , further comprising applying an insulating material between the base anode termination portion and the capacitor body.
3. The method of claim 1 , wherein attaching a capacitor element to a leadframe comprises:
applying an insulating material between the base anode termination portion and the capacitor body;
applying a conductive material between the base cathode termination portion and the capacitor body;
welding the anode lead to the upstanding anode termination portion.
4. The method of claim 1 , further comprising forming a capacitor element.
5. The method of claim 4 , wherein forming a capacitor element comprises;
pressing an anode body;
anodically oxidizing at least a portion of the anode body to form a dielectric layer; and
forming a solid electrolyte over at least a portion of the dielectric layer.
6. The method of claim 5 , wherein the anode body includes tantalum, niobium, or an electrically conductive oxide thereof.
7. The method of claim 5 , wherein the solid electrolyte includes manganese dioxide or a conductive polymer.
8. The method of claim 1 , wherein removing the recessed leadframe channel comprises one of cutting, grinding or sawing the recessed leadframe channel.
9. The method of claim 1 , wherein the base anode termination portion and base cathode termination portion are generally coplanar.
10. The method of claim 1 , further comprising forming a groove on the surface of the capacitor between the base anode termination portion and the base cathode termination portion.
11. The method of claim 1 , further comprising forming a first external termination over the base anode termination portion and forming a second external termination over the base cathode termination portion.
12. A capacitor formed by one of the methods set forth in claims 1 through 11 .