Electronics Assembly Knowledge, Vision & Wisdom
Copper-Tin Intermetallics: Their Importance, Growth Rate and Nature
Copper-Tin Intermetallics: Their Importance, Growth Rate and Nature
This paper will review the formation of copper-tin intermetallics, their growth rate, their effect on thermal cycle life, and drop shock performance.
Analysis Lab

Analysis Lab programs cover topics including:
Corrosion, Contamination, Data Acquisition, ESD and EOS, Inspection, Measurement, Profiling, Reliability, R&D, RFID, Solder Defects, Test, Tombstoning, X-ray and more.
Submit A Comment
Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name

Your Company

Your E-mail

Your Country

Your Comment

Authored By:
Ronald C. Lasky, Ph.D., P.E.
Indium Corporation

The formation of copper-tin intermetallics is fundamental to a functional solder joint. In creating most solder joints, two pieces of copper, which melt at 1085oC, are bonded together with solder, at less than 230oC. Most of us, with years of experience in electronic assembly, don’t usually think of this technological “miracle” of soldering. We are able to bond two pieces of copper together at a temperature low enough where the bonding can be performed in the presence of polymer material. Without this low-temperature formation of copper-tin intermetallics, the electronic industry might not exist. However, contemporary wisdom is that these intermetallics are brittle and can result in poor thermal cycle or drop shock performance.

This paper will review the formation of copper-tin intermetallics, their growth rate, their effect on thermal cycle life, and drop shock performance. The brittle nature of copper-tin intermetallics will also be discussed. In addition, several graphs of intermetallic growth rate will be presented. Some of the additional ancillary effects of copper-tin intermetallic growth, such as tin whiskers, will also be discussed.

Intermetallics are a miracle of soldering, enabling the bonding of copper to copper at less than 250oC in the presence of polymeric insulators. Without this feature of copper-tin intermetallics, the electronics industry as we know it would not exist.

Intermetallics form immediately during the soldering process, typically at a thickness of one to two micrometers. The intermetallics increase in thickness very slowly over time at temperatures below 100oC. However, intermetallic thickness increases vary rapidly at temperatures above the melting point of solder. Therefore, multiple solder reworks can dramatically increase intermetallic thickness. Most studies show that increasing intermetallic thickness reduces thermal cycle life, but dramatically reduces drop shock life. Considering this information, it is best to minimize the number of reworks and the times of rework soldering.

Initially Published in the SMTA Proceedings

No comments have been submitted to date.
Free Newsletter Subscription
Every issue of the Circuit Insight email newsletter will bring you the latest information on the issues affecting you and your company.

Insert Your Email Address

Directory Search

Program Search
Related Programs
bullet Hand Soldering Reliability
bullet Opens With Assembled QFN Components
bullet EOS Exposure of Components in the Soldering Process
bullet Wettable-Flanks On Bottom-Termination Components in Mass Production
bullet Effects of Composition and Isothermal Aging on Microstructure Performance
bullet Causes of Blowholes
bullet Controlling Voiding Mechanisms in the Reflow Soldering Process
bullet Transient Solder Separation of BGA Solder Joint During Second Reflow Cycle
bullet Evaluation of Stencil Technology for Miniaturization
bullet Simple Test for Flux Penetration
More Related Programs