Thick film fuse and method for its manufacture

• US 5,367,280 A
• Filed: 07/07/1993
• Issued: 11/22/1994
• Est. Priority Date: 07/07/1992
• Status: Expired due to Fees

• Current Assignee: Roederstein Spezialfabriken FUER Bauelemente Der Elektronik und Kondensatoren Der Starkstromtechnik GmbH
• Original Assignee: Roederstein Spezialfabriken FUER Bauelemente Der Elektronik und Kondensatoren Der Starkstromtechnik GmbH
• Inventors: Grieb, Theo, Walch, Konrad, Thiel, Egon
• Primary Examiner(s): DONOVAN, LINCOLN D
• Application Number:
  US08/088,542
• Time in Patent Office: 503 Days
• Field of Search: 337/297, 29/623
• US Class Current: 337/297
• CPC Class Codes: H01C 17/242 by laser trimming by laser in general B23K26/351
• CPC Class Codes: H01C 7/13 current responsive
• CPC Class Codes: H01H 2069/025 using lasers
• CPC Class Codes: H01H 85/046 Fuses formed as printed circuits
• CPC Class Codes: H01H 85/048 Fuse resistors
• CPC Class Codes: Y10T 29/49107 Fuse making

Abstract

An electrical thick-layer fuse 10 and a method of manufacturing such a fuse is described. Here a conductive paste is printed onto a substrate 12 for the manufacture of a resistive layer 24. A dielectric layer 22 is however expediently first applied to the substrate in the manner of a podium to which the resistive layer 24 is then applied in overlapping manner. Two electrodes 14, 16 having a spacing d from one another are then applied onto this resistive layer 24, with a web of the resistive layer 24 forming a thick-film fuse being left between the two electrodes. The web width is set by laser treatment.

Claims

1. Method of manufacturing electrical thick-layer fuses having:

providing a supporting substrate;

placing a thick-layer fusible conductor on said substrate generated on the substrate by printing on a conductive paste;

placing two electrodes supported on said substrate extending over said thick-layer fusible conductor, said two electrodes applied with a spacing from one another preferably onto said thick-layer fusible conductor;

the improvement to said process including the step of;

forming the width of the thick-layer fusible conductor relative to said electrodes by laser ablation of said thick-layer fusible conductor to form a resistive path under said electrodes whereby a fuse of known tolerance to current flow is formed.

2. Method in accordance with claim 1, including the steps of:

applying a dielectric layer to the substrate in a flat elevated podium like layer; and

forming the thick-layer fusible conductor to overlap said dielectric layer.

3. Method in accordance with claim 1, including the steps of:

applying said thick-layer fusible conductor by the screen-printing process.

4. Method in accordance with claim 2, including the steps of:

applying said dielectric layer by the screen-printing process.

5. Method in accordance with claim 1, including the steps of:

selecting the web length to be at least substantially the same as the electrode spacing.

6. Method in accordance with claim 1, including the steps of:

selecting the web width obtained by laser ablation of the thick-layer fusible conductor is directly set to a predetermined width value.

7. Method in accordance with claim 1, including the steps of:

calibrating the thick-layer fuse individually for each fuse; and

,

setting of the web width obtained by laser ablation of the thick-layer fusible conductor is set to a value determined by said calibration.

8. Method in accordance with claim 1, including the steps of:

determining the surface resistance for the thick-layer region between the electrodes; and

,

setting the web width dependent upon said determined surface resistance.

9. Method in accordance with claim 1, including the steps of:

measuring the surface resistance resulting from different initial web widths; and

,

determining the surface resistance of the resistive path remaining between the electrodes from said measured initial web widths.

10. Method in accordance with claim 1, including the steps of:

choosing the initial width of the applied thick-layer fusible conductor in accordance with the width of the electrodes; and

,

providing to said electrodes the same geometrical form as said fusible conductor.

11. A thick-layer fuse with a thick-layer fusible conductor arranged between two electrodes with the thick-layer fuse being applied onto a substrate together with the electrodes comprising:

at least one dielectric layer is applied to the substrate with the uppermost layer in each case being built-up in podium-like manner;

said thick layer fusible conductor being arranged in overlapping manner on this upper most layer;

said electrodes having confronting edges overlying said dielectric layer with a constant a spacing from one another;

said thick layer fusible conductor being formed with a web of controlled width forming the thick-layer fusible conductor between said electrodes for obtaining precision tolerance of current flow restriction.