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June 12, 2017

Options for Reballing BGA Components

Which of the following do you recommend when reballing BGA components? Reballing with solder paste and solder spheres, or with solder spheres only? Would you change the process depending on the size of the BGA component or number of balls?

J.J.

Experts Comments

The appropriate re-balling process to follow is dependent on the BGA package. If you are re-balling a eutectic or lead-free BGA package then using a tacky flux along with the specified alloy solder sphere is the most common approach.

However if the BGA package requires a  high temperature solder sphere then applying eutectic solder paste through the use of a stencil, and then placing the high temperature solder sphere may be recommended. The re-balling profile temperature will allow the eutectic solder to reflow and attach the high temperature sphere to the component pad.

We have been successfully reballing BGA devices for years in accordance with IPC 7711 procedure 5.7.3 BGA Reballing Procedure, Fixture Method Flux Only. Our experience would indicate there is no need to change the process with a change in ball size or ball count.
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Peter Vigneau
Vice President
Circuit Technology Center
Mr. Vigneau has been a key member of the team at Circuit Technology Center since 2008. He has vast expertise, experience and understanding of complex circuit board rework, repair and modification operations. He is one of the most knowledgeable experts in this area across the globe.
I would re-ball using spheres and tacky flux. I would not use paste. There are two main reasons for this:
  1. The variability in paste volume will contribute to variability in the final sphere volume, and therefore in size.
  2. The paste will create additional voiding by incorporating flux volatiles into the final sphere. A tacky-flux based process will not do so
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Fritz Byle
Process Engineer
Astronautics
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
I would recommend re-balling by applying flux first then solder balls. No need to change process depending on ball size.
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Bill Coleman
Vice President Technology
Photo Stencil
For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.
IPC-7711 "Rework, Modification, and Repair of Electronic Assemblies" has several procedures which all indicate that you should use flux and solder spheres to reball the BGA.

Take a look at the latest BGA reballing procedure to be added to the document, procedure 5.7.6 (attached). You'll see that this procedure uses a polyimide ball carrier that matches the layout of the BGA. Simply clean the BGA, Flux the component, align the polyimide carrier and then reflow.

There are several other methods in the guidelines which would be helpful in your situation.

See: http://www.circuitnet.com/pdf/BGA_Reballing_5_7_6.pdf
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Kris Roberson
Manager of Assembly Technology
IPC
Kris Roberson has experience as a machine operator, machine and engineering technician and process engineer for companies including Motorola, and US Robotics. Kris is certified as an Master Instructor in IPC-7711 / 7721, IPC A-610 and IPC J-STD 001.
There are a number of viable methods available for reballing BGAs and other area array devices. Ball count, pitch, diameter, alloy and package size are all considerations.

One preferred method that satisfies most reballing applications is the use of flux with a mask (stencil) to accurately position replacement solder spheres onto a package and then reflow in a controlled environment, such as a stand-alone MiniOven.

Typically an air environment is used, however reballing with an inert environment is gaining popularity, especially reballing smaller devices. Occasionally solder paste is used instead of flux when criteria necessitates increased interconnect solder volumes.
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Al Cabral
Regional Sales Manager
Finetech
Al Cabral is Regional Sales Manager for Finetech and Martin rework products. His expertise includes through-hole, surface mount and semiconductor packaging with an emphasis on soldering and heat transfer. Al has been a significant contributor to the development and optimization of reflow and rework processes and systems, particularly lead-free transitions and microelectronic applications.
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