Lucent Technologies Inc.

At+t Corp.

Ho S Chen

Sungho Jin

Mark T McCormack

King Lien Tai

Avishay Katz

Cheng-Hsuan Chen

Donald D Bacon

According to the present invention, an article of manufacture is provided having at least one region which includes a lead-free solder composition. The lead-free solder composition comprises an alloy of at least 50 wt. % tin and 7-30 wt. % zinc. An effective amount of silver is added to increase the ductility of the resultant alloy at least 25% over the ductility of the binary eutectic tin-zinc alloy. In a further embodiment, the present invention provides alloys useful in articles comprising lead-free solder compositions. The alloys include at least (8.0+y) wt. % zinc, 0.25 y to 0.5 y wt. % silver and at least 50 wt. % tin where y is from 0.2 to 22.

Lead-free alloys for use in solder bonding

A method for bonding one body to another, such as a laser device to a submount, uses a metallic layer composed of a Group VB metal, such as niobium, sandwiched between a non-metallic layer and solder layer formed by an approximate Au-Sn eutectic layer. Advantageously the Group VB layer is formed at a submount temperature of less than approximately 201.degree. C., advantageously less than approximately 125.degree. C., and preferably less than approximately 101.degree. C.--advantageously to a thickness in the approximate range 0.05 .mu.m to 0.2 .mu.m, or even thinner if pinholes do not develop. The non-metallic layer is located on one of the bodies, and the other body has a metallic coating advantageously capped with an Au layer.

Bonding scheme using group VB metallic layer

We have made the surprising discovery that small amounts of Ag below 1% by weight are effective in making Bi--Sn alloys less strain-rate sensitive without deleteriously affecting the melting character of the alloy. A Pb-free solder composition comprising at least 40% by weight Bi, between 40% and 60% Sn, and between 0.05 and 1% Ag is effective to increase the total elongation of the solder by at least 20% under the same processing conditions. Moreover the solder is free of undesirable Ag-containing phases with a melting point in excess of the 183.degree. C. melting point of the Pb--Sn binary eutectic alloy. In a preferred embodiment, the composition comprises 54.75% Bi, 45% Sn, and 0.25 % Ag.

Lead-free low melting solder with improved mechanical properties

Pb-free solder alloys based on the Sn-In-Zn system (exemplarily 86:5:9 weight %) are disclosed. Compositions can have a melting temperature in the range 183.degree. C..+-.10.degree. C. and thus can be readily substituted for conventional 40 Pb-60 Sn solder. The novel compositions also can possess superior mechanical properties, compared to the 40/60 Pb-Sn composition, and readily wets copper. Bi and/or Sb may be added to the Sn-In-Zn base to reduce the tendency for the formation of lower temperature phases.

Growing community of inventors

Lebanon, NJ, United States of America

Ho S Chen