Lead-free, high tin ternary solder alloy of tin, silver, and indium

• US 5,874,043 A
• Filed: 12/17/1996
• Issued: 02/23/1999
• Est. Priority Date: 06/12/1996
• Status: Expired due to Term

• Current Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Original Assignee: International Business Machines Corporation
• Inventors: Woychik, Charles G., Sarkhel, Amit Kumar
• Primary Examiner(s): Ip, Sikyin
• Application Number:
  US08/768,907
• Time in Patent Office: 798 Days
• Field of Search: 420/557, 420/560, 420/561, 420/562
• US Class Current: 420/557
• CPC Class Codes: B23K 35/025 Pastes, creams, slurries
• CPC Class Codes: B23K 35/262 Sn as the principal constituent
• CPC Class Codes: C22C 13/00 Alloys based on tin
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/01327 Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H05K 3/3463 Solder compositions in relation to features of the printed circuit board or the mounting process

Abstract

A high solidus temperature, high service temperature, high strength ternary solder alloy, solder paste and method. The alloy contains a major proportion of tin of at least about 70% by weight, a selectively limited amount of silver from about 6.5 to about 7.5% by weight, balance indium.

Claims

1. A lead free ternary solder alloy for use in microelectronic application consisting essentially of from 70.5 to 73.5 weight percent tin, from 6.5 to 7.5% by weight silver, balance indium.

2. A ternary solder alloy as defined in claim 1 consisting essentially of 73.2 weight percent tin, 6.5 weight percent silver, balance indium.

3. A microelectronic structure comprising at least two microelectronic components bonded to one another by means of a solder alloy with the solder alloy consisting essentially of from 70.5 to 73.5 weight percent tin, from 6.5 to 7.5% by weight silver, balance indium.

4. A microelectronic structure as defined in claim 3 wherein said microelectronic components are selected from the group consisting of:

chip carriers, IC chips and circuit boards.

5. A solder paste comprising a flux, an organic vehicle and particles of metal having a composition consisting essentially of from 70.5 to 73.5 weight percent tin, from 6.5 to 7.5% by weight silver, balance indium.