Electronics Assembly Knowledge, Vision & Wisdom
Overcoming Solder Icicling and Copper Wire Dissolution
Overcoming Solder Icicling and Copper Wire Dissolution
Dip soldering remains a common attachment method due to its simplicity, robustness, uniformity and low cost for a number of applications.
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:
Showalter, Chad; Sibell, Susan; Jean, Denis; Klimah, Paul; Biggs, Joe
Kester Inc.
Itasca, IL, USA

Solder icicling and copper dissolution are anything but new phenomena in the soldering industry since the switch from lead to lead-free solder. However, in these common defects there are still industry unknowns in understanding how to correctly plan and execute a Design of Experiment (DoE) to optimize a lead-free process to its full operating potential. In order to increase efficiency and quality of your process and product it is essential that a DoE be conducted when switching from a lead to lead-free alloy. By utilizing common industry solder analysis methods, in conjunction with a robust design of experiments, we have been able to provide three process improvements to a dip soldering application. We were able to show scientific results with data. This allowed us to correlate the results with actual process conditions to bring awareness of how final product quality may change if any of the parameters were increased or decreased from the determined setting.

Complete wetting of the terminal, including the exposed base metal on the stamped edges, is required for the elimination of the solder icicles. Any oxides on the surface of the base metal of the terminal to be soldered will act as a barrier and will prevent wetting and adherence of the solder to the terminal. The oxide need to react chemically with the compound material in the liquid flux. Using the wetting balance test, the solderability of the 2 terminal finishes was determined and found to be solderable when sufficient dwell time is allowed.

The copper dissolution was found to be a function of solder temperature, solder dwell time, and solder alloy. A solder dwell time of three seconds of the copper wire in SnCu-LD solder bath alloy at 390oC had the same cross sectional area than the Sn5Pb93.5Ag1.5 solder alloy (16% reduction for both) but the SAC305 under the same conditions dissolved 50% of the cross sectional area of the copper wire. At increased temperatures (430 Celsius) the benefit of the SnCu-LD wire was less due to the temperature being an exponential factor to the dissolution rate.

The terminal base alloy, the solder alloy, the interaction between the solder alloy and the terminal base alloy, and the interaction between the solder alloy and the solder dwell time were statistically significant factors in the formation of solder icicling. The SAC 305 alloy exhibited solder icicling on both terminal materials when subjected to a solder pot temperature of 430 Celsius. The optimum settings for minimizing the solder icicles and copper wire dissolution for this application were found to be:

1. Solder alloy: SnCu-LD
2. Dip solder pot temperature: 390oC
3. Solder dwell time: 3 seconds
4. ROM1 rosin based alcohol flux

Phosphor-Bronze terminal alloy

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 Impact of Lead-Free Components for High Reliability
bullet Solder Column Attachment for Absorbing Large CTE Mismatch
bullet Reliability Improvements by the Creation of Intermetallic Connections
bullet TOF SIMS Analysis for SnO Determination
bullet What Causes Solder Balls During Hand Soldering?
bullet Position Accuracy Machines for Selective Soldering Fine Pitch
bullet Dross Contamination After Selective Soldering
bullet A Control-Chart Based Method for Solder Joint Crack Detection
bullet The Versatile Preform
bullet What Causes Solder Icicles During Wave Soldering
More Related Programs