Preformed thermal fuse

• US 6,373,371 B1
• Filed: 08/17/1999
• Issued: 04/16/2002
• Est. Priority Date: 08/29/1997
• Status: Expired due to Fees

• Current Assignee: MMC Bidding, Inc.
• Original Assignee: Microelectronic Modules Corporation (Bourns Incorporated)
• Inventors: Krachenfels, Kurt M., Doerrwaechter, Bernhard E., Pathammavong, Keck C.
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Vortman, Anatoly
• Application Number:
  US09/376,726
• Time in Patent Office: 973 Days
• Field of Search: 337/297, 337/158, 337/159, 337/268, 337/290, 337/401, 337/413, 337/416, 337/152, 337/232
• US Class Current: 337/297
• CPC Class Codes: H01H 2037/046 being soldered on the printed circuit to be protected
• CPC Class Codes: H01H 2037/768 characterised by the composition of the fusible material
• CPC Class Codes: H01H 37/761 with a fusible element forming part of the switched circuit H01H37/767 takes precedence
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device
• CPC Class Codes: H05K 1/0293 Individual printed conductors which are adapted for modification, e.g. fusable or breakable conductors, printed switches
• CPC Class Codes: H05K 1/092 Dispersed materials, e.g. conductive pastes or inks
• CPC Class Codes: H05K 2201/0305 Solder used for other purposes than connections between PCB or components, e.g. for filling vias or for programmable patterns
• CPC Class Codes: H05K 2201/10181 Fuse
• CPC Class Codes: H05K 2201/10992 Using different connection materials, e.g. different solders, for the same connection
• CPC Class Codes: H05K 3/3463 Solder compositions in relation to features of the printed circuit board or the mounting process
• CPC Class Codes: Y10T 29/49107 Fuse making

Abstract

A preformed thermal fuse comprising two electrodes, at least one layer of solder, and a conductive bridge comprising a non-paste solder material is disclosed. The conductive bridge has a melting temperature which is substantially equivalent to the predetermined actuation temperature of the fuse.

Claims

1. An apparatus comprising a heat actuated fuse which opens at a predetermined temperature, said fuse comprising:

an electrically insulating substrate;

first and second electrodes disposed on a surface of said substrate in a spaced apart relationship to define a gap there between, each of said electrodes comprising a layer of electrically conductive material;

a layer of solder disposed on each of the first and second electrodes; and

a conductive chip comprising a non-paste solder material having a melting temperature, said chip substantially corresponding to said predetermined actuation temperature extending across said gap and disposed on said portion of each of said first and second electrodes, wherein the solder layer couples the conductive link to the electrodes, and wherein said layer comprises a solder material having a melting temperature selected from the group consisting of a temperature substantially the same as the melting temperature of said chip and a temperature less than the melting temperature of said chip.

2. The apparatus of claim 1, further comprising a protective layer.

3. The apparatus as defined in claim 2, wherein the protective layer is an electrically insulating material with a melting temperature