US 6,283,359 B1Granted

Method for enhancing fatigue life of ball grid arrays

AssigneeInternational Business Machines Corporation

InventorsPeter J. Brofman, Mark G. Courtney, Shaji Farooq, Mario J. Interrante, Raymond A. Jackson, Gregory B. Martin, Sudipta K. Ray, William E. Sablinski, Kathleen A. Stalter

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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.

Claims5

Dependent claims

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.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/644,486Filed 23 Aug 2000 · division
Priority: 30 Apr 1998
Granted: 4 Sep 2001
Term ends: Not estimatedThe source records don’t support an estimate.

Classification19 codes

H10W 72/20
Interconnections or connectors in packages: bump connectors, e.g. solder bumps or copper pillars; Dummy bumps; Thermal bumps
B23K 35/0222
Characterised by mechanical features, e.g. shape: for use in soldering or brazing
H05K 3/3436
Leadless components: having an array of bottom contacts, e.g. pad grid array or ball grid array components
H10W 90/701
Package configurations: characterised by the relative positions of pads or connectors relative to package parts