Lead-Free Soldering

Posted by Alphaassembly on August 29th, 2017

Environmental crises and outcries are leading to innovations across all industries, seeking reforms that are environmentally friendlier. In the electronics industry, this has led to lead-free soldering. Why the objection to using lead? In the ‘90s, in a spell of acid rain, the lead from the electronic waste dissolved and seeped down to the ground waters, polluting it all. Widespread grievance pushed the industry into seeking solutions that did not contain this harmful metal, leading to the creation of lead-free solder bars. In this blog, you shall get to know some points about lead-free soldering.

Point #1: Temperature

Standard Sn-Pb 40/60 alloy used for soldering usually works at an operating temperature (or melting point) of 361° F. The most commonly used lead-free alloys require a melting point of 422° F in order to create an effective intermetallic bond. This increase in temperature generates some benefits and some disadvantages. The overall finished look of the product is altered from conventional because of higher temperatures. The time required for soldering may also be greatly reduced, owing to high temperature soldering. However, higher temperature may create greater fume nuisance than lower temperatures, even for lead-free soldering alloys.

Point #2: Flux

Lead-free solders have much more active fluxes as compared to solder alloys with lead. There is still a requirement of added fluxes with lead-free solder alloys, which is still better than rosin fluxes. However, owing to high operating temperatures and high activity, fluxing lead-free alloy jobs create excessive fumes, which can turn into a health hazard if not properly ventilated.

Point #3: Tin whiskers

The purpose of adding lead to soldering alloys was to prevent tin whiskers from popping up. While the reason for whisker formation remains unknown, we do know these crystalline structures of tin sometimes grow from surfaces where tin, especially electroplated tin, is used as a final finish. It is also suggested that voltage and soldering temperature have something to do with tin whisker growth.

Point #4: Reliability

Soldering professionals all agree that that for critical applications where reliability is paramount, such as in military and aerospace electronics, the use of lead-bearing solders is the wiser choice. Lead-free solders have a tendency of failing earlier as compared to lead-bearing solders. For reliable electronic components that have sound circuits, lead-bearing solder alloys are better; they ensure the electrical properties are preserved over a longer time period.

Lead-free soldering is continually evolving.  In the future, you might find that lead-free solder alloys can compete better with lead-bearing alloys in terms of reliability.

About the Author:

Alpha Assembly Solutions, Inc. is the global leader in the development, manufacturing and sales of innovative specialty materials used in a wide range of industry segments, including electronics assembly, power electronics, die attach, LED lighting, photovoltaics, semiconductor packaging, automotive and others. Since its founding in 1872, Alpha has been committed to developing and manufacturing the highest quality specialty materials.