Method for enhancing fatigue life of ball grid arrays

• US 6,283,359 B1
• Filed: 08/23/2000
• Issued: 09/04/2001
• Est. Priority Date: 04/30/1998
• Status: Expired due to Term

• Current Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Original Assignee: International Business Machines Corporation
• Inventors: Martin, Gregory B., Jackson, Raymond A., Ray, Sudipta K., Brofman, Peter J., Interrante, Mario J., Sablinski, William E., Farooq, Shaji, Stalter, Kathleen A., Courtney, Mark G.
• Primary Examiner(s): Dunn, Tom
• Assistant Examiner(s): JOHNSON, JONATHAN J
• Application Number:
  US09/644,486
• Time in Patent Office: 377 Days
• Field of Search: 228/180.22, 228/208, 228/180.21, 228/56.3, 228/189, 438/613-617, 257/737, 257/738, 361/767, 361/768, 428/403, 428/209, 428/643, 428/644, 428/570, 106/286.2, 106/287.19
• US Class Current: 228/180.22
• CPC Class Codes: B23K 35/0222 for use in soldering, brazing B23K35/0205 takes precedence
• CPC Class Codes: B23K 35/0244 Powders, particles or spheres; Preforms made therefrom
• CPC Class Codes: H01L 2224/1184 involving a mechanical process, e.g. planarising the bump connector
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/29099 Material
• CPC Class Codes: H01L 23/49811 Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads H01L23/49827 takes precedence
• CPC Class Codes: H01L 24/11 Manufacturing methods for bumps on insulating substrates H01L21/4853
• CPC Class Codes: H01L 24/12 Structure, shape, material or disposition of the bump connectors prior to the connecting process
• CPC Class Codes: H01L 24/16 of an individual bump connector
• 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 2924/00013 Fully indexed content
• CPC Class Codes: H01L 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 Solder alloys
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H05K 2201/10992 : Using different connection materials, e.g. different solders, for the same connection
• CPC Class Codes: H05K 2203/041 : Solder preforms in the shape of solder balls
• CPC Class Codes: H05K 2203/0415 : Small preforms other than balls, e.g. discs, cylinders or pillars
• CPC Class Codes: H05K 2203/0435 : Metal coated solder, e.g. for passivation of solder balls
• CPC Class Codes: H05K 3/3436 : having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/12687 : Pb- and Sn-base components: alternative to or next to each other
• CPC Class Codes: Y10T 428/2991 : Coated

Abstract

This invention relates to a solder structure which provides enhanced fatigue life properties when used to bond substrates particularly at the second level such as BGA and CGA interconnections. The solder structure is preferably a sphere or column and has a metal layer wettable by solder and the structure is used to make solder connections in electronic components such as joining an electronic module such as a chip connected to a MLC which module is connected to a circuit board. The solder structure preferably has an overcoat of solder on the metal layer to provide a passivation coating to the metal layer to keep it clean from oxidation and corrosion and also provide a wettable surface for attachment of the solder structure to solder on the pads of the substrate being bonded.

Claims

1. A method for making solder electrical interconnections in an electronic component assembly comprising the steps of:

applying a first solder having a first melting point to first pads on the surface of a first substrate of an electronic component assembly;

forming a solder structure comprising;

an inner core of a second solder having a second melting point which is higher than the melting point of the first solder to which the structure is to be bonded;

a layer of a metal wettable by the first solder and having a melting point higher than the second melting point of the second solder of the inner core;

an outer layer of a third solder having a third melting point which provides a wettable surface for attachment of the solder structure and passivates the layer of metal from oxidation and corrosion, the third melting point being lower than the second melting point;

bonding the solder structure to the first pad by reflowing the first and third solders;

applying a fourth solder to second pads on the surface of a second substrate of the electronic component assembly;

positioning the second pads on the surface of the second substrate electronic component assembly to be joined proximate to the corresponding solder structure containing pads on the first substrate;

heating the substrates to a temperature sufficient to form a bond between the solder structure and the pads of the second substrate; and

cooling the bonded interconnected assembly.

2. The method of claim 1 wherein the structure is in the form of a sphere.

3. The method of claim 1 wherein the structure is in the form of a column.

4. The method of claim 1 wherein the metal layer is copper or nickel.

5. The method of claim 1 wherein the free end of the solder structure is shaved to expose the inner core of solder and to provide a desired height of the solder structure which shaved end of the structure is then bonded to the pads on the second substrate.