Method of protecting a surface-mount fuse device

• US 5,844,477 A
• Filed: 10/23/1995
• Issued: 12/01/1998
• Est. Priority Date: 05/27/1994
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Onken, Daniel B., Blecha, Vladmir, McGuire, Katherine M., Neuhalfen, Andrew J.
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Gandhi, Jayprakash N.
• Application Number:
  US08/551,900
• Time in Patent Office: 1,135 Days
• Field of Search: 337/152, 337/160, 337/297, 337/227, 29/623
• US Class Current: 337/297
• CPC Class Codes: H01C 17/08 by vapour deposition
• CPC Class Codes: H01C 7/006 Thin film resistors
• CPC Class Codes: H01C 7/1013 Thin film varistors
• CPC Class Codes: H01C 7/12 Overvoltage protection resistors series resistors structurally associated with spark gaps H01T1/16
• CPC Class Codes: H01H 2085/0414 Surface mounted fuses
• CPC Class Codes: H01H 69/022 of printed circuit fuses
• CPC Class Codes: H01H 85/0411 Miniature fuses
• CPC Class Codes: H01H 85/046 Fuses formed as printed circuits
• CPC Class Codes: H01H 85/11 with applied local area of a metal which, on melting, forms a eutectic with the main material of the fusible member, i.e. M-effect devices
• CPC Class Codes: Y10T 29/49101 Applying terminal
• CPC Class Codes: Y10T 29/49107 Fuse making
• CPC Class Codes: Y10T 29/49204 Contact or terminal manufacturing

Abstract

A thin film surface-mount fuse having two material subassemblies. The first subassembly includes a fusible link, its supporting substrate and terminal pads. The second subassembly includes a protective layer which overlies the fusible link so as to provide protection from impacts and oxidation. The protective layer is preferably made of a polymeric material. The most preferred polymeric material is a polycarbonate adhesive. In addition, the most preferred supporting substrate is an FR-4 epoxy or a polyimide.

Claims

1. A thin film surface-mount fuse, said fuse comprising:

a. a substrate having an upper surface;

b. a fusible link made of a first conductive metal deposited on the upper surface of the substrate;

c. a second conductive metal, other than the first conductive metal, deposited on the surface of the fusible link;

d. terminal pads electrically connected to the fusible link, the terminal pads having a plurality of conductive layers, wherein a first of the plurality of conductive layers and the fusible link form a single continuous film.

2. The device of claim 1, wherein a second of the plurality of conductive layers is deposited on the first of the plurality of conductive layers and consists of the same metal as the first conductive metal.

3. The device of claim 2, wherein a third of the plurality of conductive layers is deposited on the second of the plurality of conductive layers and consists of nickel.

4. The device of claim 3, wherein a fourth of the plurality of conductive layers is deposited on the third of the plurality of conductive layers and consists of tin.

5. The surface-mount fuse of claim 4, wherein the first conductive metal is selected from the group including copper, silver, nickel, titanium, aluminum or alloys thereof.

6. The surface-mount fuse of claim 5, wherein the second conductive metal is tin.

7. The surface-mount fuse of claim 6, wherein the second conductive metal is deposited onto the fusible link in the form of a rectangle.

8. The surface-mount fuse of claim 7, wherein the fusible link has a central portion and the rectangle is deposited along the central portion of said fusible link.