Chip resistor and method for manufacturing the same

A chip resistor comprising:

• an insulating substrate;
• a pair of main electrodes formed on a surface of the insulating substrate and spaced from each other;
• a resistor film formed on the surface of the insulating substrate to bridge between the main electrodes, the resistor film being provided with a trimming groove for resistance adjustment;
• a protective coating formed to cover the resistor film;
• and
• a metal plating formed in electrical conduction with each of the main electrodes;
• wherein the protective coating includes an undercoat layer of glass formed on the resistor film, a middle-coat layer of glass formed on the undercoat layer, and an overcoat layer formed on the middle-coat layer, the trimming groove being formed through the undercoat layer and the resistor film;
• and
• wherein the middle-coat layer has a thickness of 5-10 .mu.m.

A method of making a chip resistor comprising the steps of:

• forming a pair of main electrodes on a surface of an insulating substrate to be spaced from each other;
• forming a resistor film on the surface of the insulating substrate to bridge between the main electrodes;
• forming an undercoat layer of glass to cover the resistor film;
• forming a trimming groove through the undercoat layer and the resistor film for resistance adjustment;
• forming a middle-coat layer of glass to cover the undercoat layer;
• forming an overcoat layer to cover the middle-coat layer;
• and
• forming a metal plating in electrical conduction with each of the main electrodes;
• wherein the step of forming the trimming groove is performed so that the trimming groove has a width which is no less than 80 .mu.m but smaller than an interval between the main electrodes, the trimming groove being inverted-trapezoidal in cross section, the trimming groove having a pair of inclined side surfaces, each of the inclined side surfaces having an inclination angle of 20-45 degrees.

A method of making a chip resistor comprising the steps of:

• forming a pair of main electrodes on a surface of an insulating substrate to be spaced from each other;
• forming a resistor film on the surface of the insulating substrate to bridge between the main electrodes;
• forming an undercoat layer of glass to cover the resistor film;
• forming a trimming groove through the undercoat layer and the resistor film for resistance adjustment;
• forming a middle-coat layer of glass to cover the undercoat layer;
• forming an overcoat layer to cover the middle-coat layer;
• and
• forming a metal plating in electrical conduction with each of the main electrodes;
• wherein the step of forming the middle-coat layer is performed so that the middle-coat layer has a thickness of 5-10 .mu.m.

A chip resistor comprising:

• an insulating substrate;
• a pair of main electrodes formed on a surface of the insulating substrate and spaced from each other;
• a resistor film formed on the surface of the insulating substrate to bridge between the main electrodes, the resistor film being provided with a trimming groove for resistance adjustment;
• a protective coating formed to cover the resistor film;
• and
• a metal plating formed in electrical conduction with each of the main electrodes;
• wherein the trimming groove is inverted-trapezoidal in cross section;
• and
• wherein the trimming groove has a pair of inclined side surfaces, each of the inclined side surfaces has an inclination angle of 20-45 degrees.

A method of making a chip resistor comprising the steps of:

• forming a pair of main electrodes on a surface of an insulating substrate to be spaced from each other;
• forming a resistor film on the surface of the insulating substrate to bridge between the main electrodes;
• forming an undercoat layer of glass to cover the resistor film;
• forming a trimming groove through the undercoat layer and the resistor film for resistance adjustment;
• forming a middle-coat layer of glass to cover the undercoat layer;
• forming a overcoat layer to cover the middle-coat layer;
• and
• forming a metal plating in electrical conduction with each of the main electrodes;
• wherein the step of forming the trimming groove is performed so that the trimming groove is inverted-trapezoidal in cross section, the trimming groove having a pair of inclined side surfaces, each of the inclined side surfaces having an inclination angle of 20-45 degrees.