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iNEMI Members Call for Unique Part Numbers for Ball Metallurgies on Lead-Free Components
Written by Tracy Heffner
Wednesday, 09 May 2007
HERNDON, Va – The International Electronics Manufacturing Initiative (iNEMI) reported that a majority of its OEM and EMS members strongly support unique part numbers for BGA components to differentiate any lead-free ball metallurgies other than SAC 305 or SAC 405, including low silver, added dopants such as nickel, and other SAC (or non-SAC) alloy compositions.
iNEMI members supporting this position include: 3M, Agilent Technologies Inc., Alcatel-Lucent, Analogic, Celestica Inc., Delphi Electronics & Safety, Hewlett-Packard Co., Huawei Technologies Co. Ltd., Intel Corp., Jabil Circuit Inc., Microsoft Corp., Micro Systems Engineering Inc., Plexus Corp., Sanmina-SCI Corp., Solectron Corp. and Tyco Electronics Corp.
Many suppliers are moving away from SAC 305/405 ball metallurgies in order to improve the ability to survive mechanical shock (e.g. drop test of portable products). Changes include reductions in silver down to as low as 0.3% and addition of other metals, such as nickel. Concerns about these changes in metallurgies prompted iNEMI to release the following statement:
While variations in alloy metallurgy may improve mechanical shock performance, they can also impact the manufacturing process in a number of ways. Since these changes can affect form, fit and function of the device, they should be documented by the issuance of a part change notice (PCN) and should be associated with a change in manufacturing part number (MPN). In this way, the manufacturing assembly process can be properly controlled and optimized prior to actual assembly to ensure repeatable and reliable attachment of the BGA to the next higher assembly and to help minimize ship holds due to unknown parts. While JEDEC identifies BGA solder ball material composition as an example of a major change (see JESD46C), we recognize that some further guidelines may need to be developed around triggering the PCN and/or change to MPN.
“It is inevitable that solder ball metallurgies will change as industry learns more about the performance of lead-free technologies,” said Jim McElroy, CEO of iNEMI. “However, use of these different compositions will most likely require changes in reflow profiles and corresponding adjustments to the assembly process. The lower-silver compositions have a higher melting point than SAC 305/405 alloys, which moves the melting range higher. Based on assembly process margins (especially for large complex boards), low-silver compositions could also impact the MSL rating. In order to maintain reliable assembly processes manufacturers must know the metallurgical characteristics of the components they are using and be able to differentiate parts.”
In 2004, iNEMI called for the use of unique part numbers for RoHS-compliant components, as defined by JEDEC/IPC standards. The consortium is also calling for continued availability of SnPb BGAs for use in high-reliability products, which are currently exempt from, or out of scope of, the EU RoHS Directive. Manufacturers of these high-reliability products will continue to use SnPb processes until long-life reliability concerns regarding lead-free are resolved, and lead-free BGAs are not compatible with these processes.
For additional information and further discussion about transitioning to alternate metallurgies, see the EMS Forum’s recently published “Guidelines for Suppliers Transitioning to RoHS Compliant Ball Grid Array (BGA) Packages with Low-Ag SAC Alloys.” http://thor.inemi.org/webdownload/projects/ese/EMSF_Guidelines_BGA_metallurgy.pdf
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