Embedded Components from Concept-To-Manufacturing
Copper Foil Elements Affecting Transmission Loss with High Speed Circuits
pH neutral Cleaning Agents - Market Expectation & Field Performance
Reducing Dust Deposition on Electronic Equipment
New Requirements for Sir Measurement
Effects of Mixing Solder Sphere Alloys with Bismuth-Based Pastes
The Development of a 0.3 mm Pitch CSP Assembly Process
Generalizations About Component Flatness at Elevated Temperature
Latest Industry News
iPhone 12 Production Could Be Delayed
Acer sees PC component shortages
Bio-Ink for 3-D Printing Inside the Body
Covid Seen Driving the Security Sector
U.S. Eases Restrictions on Private Remote-Sensing Satellites
EMS Manufacturing quote complexity drives OEMs to look behind EMS curtain
U.S. Manufacturing Rebounds to 14-Month High
IBM's New AI Tool Parses A Tidal Wave of Coronavirus Research

Uni-Directional Growth of CU SN in Microbumps

Uni-Directional Growth of CU SN in Microbumps
The growth of CuSn has been proven as a preferential growth behavior on single crystal copper. However, a layer of single crystal copper is not possible.
Analysis Lab


Authored By:

Han-wen Lin, Jia-ling Lu, Chien-min Liu, Chih Chen, King-ning Tu, Delphic Chen, and Jui-Chao Kuo
Department of Materials Science & Engineering, National Chiao Tung University
Hsinchu, Taiwan, R.O.C.
Department of Materials Science and Engineering, University of California Los Angeles
Los Angeles, CA, USA
Department of Materials Science & Engineering, National Cheng Kung University
Tainan, Taiwan, R.O.C.


The growth of CuSn has been proven as a preferential growth behavior on single crystal copper. However, a layer of single crystal copper is not possible to be electroplated. It can not be utilized in the electronic industry.

In this paper, we electroplated an array of (111) uni-directional Cu pad followed by electroplating SnAg2.3. After being reflowed at 260 degrees C for 1 minute, the CuSn showed a referential growth to (0001) plane. As reflow time extended, the preferential growth behavior would change. It means the preferential growth of CuSn would change during reflow. Eventually, the preferred orientation of CuSn changed after 5 minutes of reflowing. It is also found that this preferential growth behavior of CuSn would be affected by the quality of (111) uni-directional Cu.


The uni-directional Cu with surface covered by (111) plane can be made by electroplating. The shape of Cu grain was columnar. The diameters of these columnar grains were 2 - 5 im. After electroplating SnAg2.3 on the Cu pad and then reflowed at 260 degrees C, the CuSn have shown a preferential growth relationship on the unidirectional Cu.

At the early stage of reflowing, the orientations of CuSn were preferred at (0001). As the time of reflow extended. Since the unidirectional Cu was still poly-crystal metal, the coherence must be achieved by Cu-Sn bonding at the interface between Cu pads and the intermetallics. Electroplating parameters would affect the quality of uni-directional Cu and therefore affecting the preferential behavior of CuSn. With the technique of electroplating (111) unidirectional Cu, it is possible to control the orientations of intermetallics in the solder joints.

Initially Published in the SMTA Proceedings


No comments have been submitted to date.

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 Comments

Board Talk
Solder Paste Beyond The Shelf Life?
Issues With Fillets on Via Holes?
Can Tape Residue Contaminate a Clean Tank?
Suggested Stencil Wipe Frequency?
Reflow Oven Zone Separation Challenges
When To Use Adhesive To Bond SMT Components
How To Clean a Vintage Circuit Board Assembly?
PCBA Inspection Concerns
Ask the Experts
Lifted Lead on SOT Component
Allowable Bow and Twist on Round PC Fab
Mixed MSL Baking
Step Stencil Squeegee Angle
Solder Balling Splash After Reflow
Application Using No-Clean and Water Soluble Fluxes
IPC SOIC Defect Question
Mixed Process Solder Joint Appearance, Smooth or Grainy?