Patent Application
20150357097
1. Field of the Invention
The present invention relates to a chip resistor, and in particular, to a sulfur resistant chip resistor.
2. Description of the Related Art
Thick-film and thin-film chip resistors of the conventional surface mount components usually includes resistors, conductors, glass, insulating overcoats and electro-plated terminals. Generally, silver-containing materials are often used as conductor materials, so as to be electrically connected with resistive materials and serve as first electrodes, second electrodes or side electrodes.
The present disclosure provides a chip resistor. In an embodiment, the chip resistor includes: a substrate, two first electrodes, two second electrodes, a resistive layer, at least one protection layer and at least one coating layer. The substrate has a first surface and a second surface, and the second surface is opposite to the first surface. The two first electrodes are disposed on the first surface. The two second electrodes are disposed on the second surface. The resistive layer is disposed on the first surface and covers part of the two first electrodes. The at least one protection layer is disposed on the resistive layer and covers part of the two first electrodes. The at least one protection layer includes at least two overlay sides and at least one overlay plane. The at least one coating layer covers the at least two overlay sides, the at least one overlay plane, and part of the two first electrodes and the two second electrodes.
The present disclosure provides a chip resistor. In an embodiment, the chip resistor includes: a substrate, two first electrodes, two second electrodes, a resistive layer, at least one protection layer and at least one coating layer. The substrate has a first surface and a second surface, and the second surface is opposite to the first surface. The two first electrodes are disposed on the first surface. The two second electrodes are disposed on the second surface. The resistive layer is disposed on the first surface and covers part of the two first electrodes. The at least one protection layer is disposed on the resistive layer and completely covers the other part of the two first electrodes on the plane. The at least one protection layer includes at least tone overlay side. The at least one coating layer covers the at least one overlay side, and the sides of the two first electrodes and the two second electrodes.
The chip resistor of the present invention uses the two overlay sides and the overplay plane to extend a distance between the two first electrodes and the outside. Therefore, it is difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the two first electrodes. Thus, the chip resistor of the present invention can resist corrosion of harmful substances such as sulfur, sulfides and sulfur-containing compounds or halogens on the electrodes.
The invention will be described according to the appended drawings in which:
Reference numerals may be repeated throughout the embodiments, but this does not necessarily require that feature(s) of one embodiment apply to another embodiment, even if they share the same reference numeral.
The resistive layer 14 is disposed on the first surface 111 and covers part of the two first electrodes 12, so as to be electrically connected with the two first electrodes 12. The protection layers 15 and 16 are disposed on the resistive layer 14 and cover part of the two first electrodes 12. The at least one protection layer includes at least two overlay sides and at least one overlay plane. In an embodiment, the at least one protection layer includes a first protection layer 15 and a second protection layer 16. The first protection layer 15 is disposed on the resistive layer 14, and the second protection layer 16 is disposed on the first protection layer 15 and covers part of the two first electrodes 12. The second protection layer 16 includes at least two overlay sides 161 and 162 and at least one overlay plane 163. The overlay plane 163 is disposed between the two overlay sides 161 and 162. Corresponding to the overlay plane 163, the two overlay sides 161 and 162 have a tilt angle.
The second protection layer 16 further includes an exposed plane 164, and a thickness H2 from the exposed plane 164 to a bottom 165 of the second protection layer 16 is greater than a thickness H1 from the overlay plane 163 to the bottom 165, to form a convex structure.
In an embodiment, the second protection layer 16 is manufactured with two steps: the first step is that the overlay plane 163 and the overlay side 161 are formed, and the second step is that the exposed plane 164 and the overlay side 162 are formed, and the exposed plane 164 and the overlay side 162 cover part of the overlay plane 163, to form a convex structure.
In another embodiment, the second protection layer 16 is manufactured in a stack manner: first, the overlay plane 163 and the overlay side 161 are manufactured to serve as one layer of the second protection layer 16, and the exposed plane 164 and the overlay side 162 are manufactured to serve as the other layer of the second protection layer 16, and then the layer of the exposed plane 164 and the overlay side 162 is stacked on part of the overlay plane 163, to form a convex structure.
The coating layers 17, 18 and 19 cover the at least two overlay sides 161 and 162, the at least one overlay plane 163, and part of the two first electrodes 12 and the two second electrodes 13. In an embodiment, the at least one coating layer includes a first coating layer 17, a second coating layer 18 and a third coating layer 19. The first coating layer 17 covers the at least two overlay sides 161 and 162, the at least one overlay plane 163, and part of the two first electrodes 12 and the two second electrodes 13. The first coating layer 17 completely covers sides of the two first electrodes 12 and sides of the two second electrodes 13, so as to be electrically connected with the first electrodes 12 and the second electrodes 13. The first coating layer 17 is a conductive material, and preferably, the material is selected from a group including nickel, palladium, platinum, gold, nickel-chromium, nickel-boron, nickel-phosphorus and combinations thereof. The second coating layer 18 covers the first coating layer 17, and preferably, the second coating layer 18 is nickel (Ni). The third coating layer 19 covers the second coating layer 18, and preferably, the third coating layer 19 is tin (Sn).
When the chip resistor is used in harsh environments such as sulfur or halogen-containing atmosphere, because the electrode materials contain silver or copper, under particular temperature and humidity, the silver or copper may have an electrochemical reaction with airborne sulfur, sulfide and sulfur-containing compounds or halogens, so that silver sulfide, copper sulfide, silver bromide, or other products may be produced. The airborne sulfur, sulfides, and sulfur-containing compounds such as hydrogen sulfide, by using diffusion of itself gas, may have an electrochemical reaction at a boundary between an organic protection layer and electrodes. Since a diffusion coefficient of a gas is much greater than that of a solid, sulfur-containing species are diffused inward, and the silver or copper are diffused outward. During the electrochemical reaction, sulfur gas may gradually corrode the silver or copper, causing an increase of a resistance value, and over time, the resistance value is eventually infinite and becomes open-circuited. Flower-like products may be observed from the appearance of the components, which are commonly known as flower of sulfur (FOS).
Generally, the airborne sulfur, sulfides and sulfur-containing compounds are diffused inward from a contact junction between heterogeneous metals, and hence, for example, are usually diffused inward from between the first coating layer 17 and the second protection layer 16. To prevent the chip resistor from being damaged by the FOS or even becoming unusable, a distance between the electrodes and the outside may be increased, so that it is difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the electrodes. The chip resistor 10 of the present invention uses the two overlay sides 161 and 162 and the overplay plane 163, so that the coating layers 17, 18, and 19 cover the two overlay sides 161 and 162 and the overplay plane 163, to extend a distance between the two first electrodes 12 and the outside. Therefore, it is difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the two first electrodes 12. In an embodiment, the length of the two overlay sides 161 and 162 and the overplay plane 163 is ½ (L2-L1), which is about 0.1 mm. Moreover, the convex structure formed by the two overlay sides 161 and 162 and the overplay plane 163 generates a height difference, so that it is further difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the electrodes. Thus, the chip resistor 10 of the present invention can resist corrosion of harmful substances such as sulfur, sulfides and sulfur-containing compounds or halogens on the electrodes.
Furthermore, the chip resistor 10 of the present invention uses the convex structure formed by the two overlay sides 161 and 162 and the overplay plane 163, which has highly compatible in the process, is conducive to mass production and can reduce the manufacturing cost.
The coating layers 37, 38, and 39 of the chip resistor 30 cover the at least one overlay side 361, the sides of the two first electrodes 12, and the two second electrodes 13. The at least one coating layer includes a first coating layer 37, a second coating layer 38 and a third coating layer 39. The first coating layer 37 covers part of the exposed plane 362, the at least one overlay side 361, the sides of the two first electrodes 12, sides of the two second electrodes 13, and part of the two second electrodes 13. The second coating layer 38 covers the first coating layer 37 and part of the two second electrodes 13. The third coating layer 39 covers the second coating layer 38.
The chip resistor 30 of the present invention uses the second protection layer 36 to completely cover the other part of the two first electrodes 12 on the plane, and the coating layers 37, 38, and 39 cover the overlay side 361 and the sides of the two first electrodes 12, so that it is difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the electrodes. Hence, the chip resistor 30 of the present invention can resist corrosion of harmful substances such as sulfur, sulfides and sulfur-containing compounds or halogens on the electrodes.
The at least one coating layer covers the at least one overlay side and the at least one overlay plane of the second protection layer, and the at least one overlay side of the third protection layer. In an embodiment, the at least one coating layer includes a first coating layer 47, a second coating layer 48, and a third coating layer 49. The first coating layer 47 covers the overlay side 411 of the third protection layer 41, the overlay plane 462 and the at least one overlay side 461 of the second protection layer 46, sides of the two first electrodes 12, and the two second electrodes 13. The second coating layer 48 covers the first coating layer 47. The third coating layer 49 covers the second coating layer 48.
The third protection layer 41 further includes an exposed plane 412, and a thickness from the exposed plane 412 to a bottom 463 of the second protection layer 46 is greater than a thickness from the overlay plane 462 of the second protection layer 46 to the bottom 463 of the second protection layer 46, thereby also forming a convex structure.
Therefore, the chip resistor 40 of the present invention uses the overlay side 411 of the third protection layer 41 and the overlay side 461 and the overlay plane 462 of the second protection layer 46, to extend a distance between the two first electrodes 12 and the outside, so that it is difficult for the airborne sulfur, sulfides and sulfur-containing compounds to enter and react with the two first electrodes 12. Hence, the chip resistor 40 of the present invention can resist corrosion of harmful substances such as sulfur, sulfides and sulfur-containing compounds or halogens on the electrodes.
While several embodiments of the present disclosure have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present disclosure are therefore described in an illustrative but not in a restrictive sense. It is intended that the present disclosure should not be limited to the particular forms as illustrated and that all modifications which maintain the spirit and scope of the present disclosure are within the scope defined in the appended claims.
