Compositions, methods and devices for high temperature lead-free solder

Abstract

A lead-free solder (130) comprises an alloy that includes Ag in an amount of 2 wt % to 18 wt %, Bi in an amount of 98 wt % to 82 wt %, and a third element in an amount of 0.1 wt % to 5.0 wt %. The third element is selected from the group consisting of Au, Cu, Pt, Sb, Zn, In, Sn, Ni and Ge. Contemplated alloys have a solidus of no lower than 230°C and a liquidus of no higher than 400°C.

Description

technical field [0001] The invention relates to the field of lead-free solder. Background technique [0002] Most known die connection methods use high-lead solder to connect the semiconductor chip in the integrated circuit to the lead frame to form a mechanical connection and enable thermal and electrical conduction between the chip and the lead frame. Although most high-lead solders are relatively inexpensive and exhibit a variety of good physical and chemical properties, the use of lead in attaching chips and other solders has been more studied from environmental and occupational health perspectives. Therefore, various measures have been taken to replace lead-containing solders with lead-free die attach compositions. [0003] For example, one approach is to use a polymeric adhesive such as epoxy or cyanate resin to attach the chip to the substrate as described in US Pat. As described in U.S. Patent No. 5,612,403, at a temperature lower than 200°C, the polymer adhesive w...

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Problems solved by technology

But the solidus line of J alloy is 228 ℃, and its mechanical properties are also poor

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