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March 7, 2016

Solder Paste Mixing

How can we confirm that our centrifuge machine is properly mixing jars of solder paste to give us the results as per the standard requirement?

S.R.

Experts Comments

We have no recommended technique for verifying machine paste mixing as we do not recommend the use of paste mixing equipment.
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Eric Bastow
Senior Technical Support Engineer
Indium Corporation
Eric is an SMTA-certified process engineer (CSMTPE) and has earned his Six Sigma Green Belt from the Thayer School of Engineering at Dartmouth College. He is also a certified IPC-A-600 and 610D Specialist. He has an associate's degree in Engineering Science from the State University of New York and has authored several technical papers and articles.

Mixing solder paste in a centrifuge can cause flux and other ingredients to separate from powder particles and is not recommended by many solder paste manufacturers.

Testing viscosity at multiple shear rates is the only method to confirm if the centrifugal mixing had an adverse effect on the paste.

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Mitch Holtzer
Global Director of Customer Technical Support
Alpha Assembly Solutions
As the Global Director of Customer Technical Service (CTS) for Alpha, Mitch sets direction and provides coordination for the Alpha CTS group in a global capacity. A major focus of this position is to provide strategic support to OEM, CEM and Automotive customers and target accounts. Mitch joined Alpha in 1998 and has progressed through positions of increasing responsibilities in Marketing, Product Management and R&D. He is a graduate of Purdue University with a degree in Chemistry and holds an MBA from Temple University.
If the vendor's requirements for handling and storage of solder paste are followed mixing it with a plastic spatula should be enough to maintain its properties. Some solder paste manufacturers do not recommend the use of mechanical equipment. If you still prefer to use the centrifuge, the goal will be to obtain a nice smooth homogenous mixture without flux separation. A capability study on the mixer can determine if changes in paste's tack & viscosity have occurred.
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Edithel Marietti
Senior Manufacturing Engineer
iDirect
Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.
The use of a mechanical (automated) mixing process is recommended to be done in conjunction with a viscometer to understand if the paste viscosity is within the values that the manufacturer recommends for optimal results.
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Georgian Simion
Engineering and Operations Management
Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.
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