US 7,070,088 B2Granted

Method of semiconductor device assembly including fatigue-resistant ternary solder alloy

AssigneeTexas Instruments Incorporated

InventorKejun Zeng

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Abstract

Method for assembling a semiconductor device having fatigue-resistant interconnection fillet provides a semiconductor chip with at least one solder bump comprising an alloy of tin and lead with a melting temperature higher than the solder paste used. Further, a solder paste (preferably binary) is provided, which comprises tin and about 2.5 weight percent silver, and has a melting temperature of about 221° C. The solder bump is brought in contact with the solder paste, the bump is partially immersed in the paste, and thermal energy is supplied to reflow the solder paste at about 235° C. The amount of energy and time after the reflow of the paste is controlled so that the molten paste dissolves a pre-determined amount of the solder bump (lead and tin) to form a ternary alloy of about eutectic composition (about 1.62 weight % Ag, 36.95 weight % Pb, 61.43 weight % Sn) without melting the solder bump.

Claims8

Dependent claims

A method for the assembly of a semiconductor device having fatigue-resistant interconnection elements, comprising the steps of:

providing a semiconductor chip having at least one solder bump comprising an alloy of about ten weight percent tin and about ninety weight percent lead;
providing a solder paste comprising tin and silver, said solder paste having a reflow temperature of about 221° C., said bump alloy having a melting temperature higher than said paste reflow temperature;
bringing said solder bump in contact with said solder paste and immersing said bump partially in said paste;
supplying thermal energy to reflow said solder paste at about 235° C.;
controlling the amount of energy and time after said melting of said solder paste so that the molten paste dissolves a pre-determined amount of said solder bump to form a tin/lead/silver ternary alloy of about eutectic composition without melting said solder bump;
and
removing said thermal energy to cool said ternary alloy fillet and said bump.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/797,779Filed 9 Mar 2004
Published: US 2005/0199684 A115 Sep 2005
Granted: 4 Jul 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

H05K 3/346
By soldering: solder materials or compositions specially adapted therefor
B23K 35/025
Powders, particles or spheres; Preforms made therefrom: pastes, creams or slurries
B23K 35/262
With the principal constituent melting at less than 400°C: sn as the principal constituent
H05K 3/3436
Leadless components: having an array of bottom contacts, e.g. pad grid array or ball grid array components