The next generation lead-free alloys have been developed as solutions to finding the perfect balance between being strong and flexible. However, developing the ideal combination to meet all of the desired properties has proven to have limitations within the Pb-free space. Different compositions of these elements added into a tin-silver-copper matrix can improve thermal fatigue and strength. SAC305 has proven itself a worthy replacement for Sn63, although requirements in the automotive, aerospace, and military industries have driven further research for alloys with even higher reliability expectations.Įlemental additions of indium, bismuth, antimony, and nickel have been candidates for the next generation Pb-free alloys. SAC305 (96.5% Sn, 3.0% Ag, and 0.5% Cu) has emerged as the go-to lead-free alloy by popular choice. The introduction of RoHS regulations in the electronics industry has prompted extensive research into the development of Pb-free soldering alloys with the reliability the industry came to expect from SnPb alloys.
#Solder reflow temperatures how to#
This experiment focused on developing the best profile for next generation SAC alloys and how to best modify the reflow process when a new material is chosen.
#Solder reflow temperatures software#
To keep up with these industry needs, reflow profiling software and best practices have continued to develop. New materials and process constraints have also limited process windows, making assemblies that much more sensitive to profile. Companies with a high mix of assembly designs and materials are even more challenged with using the best reflow process for each one. The reflow process is at the top of the list for optimization. Process development and continuous improvement are critical to success in PCB assembly. KEY WORDS: high-reliability, SAC alloys, reflow profiling, reflow process window In addition, as high-temperature applications that traditionally used high-Pb alloys for high operating temperatures come close to losing RoHS exemptions, new alloys are emerging to achieve the high performance expectations associated with applications in this range. There will also be a discussion on the critical points of successful reflow profiling for the wider range of Pb-free alloys now on the market. This paper will review common profile shapes and recipes, showing data for how they differ in the resulting solder joints. These choices really expand the playbook of possible reflow profiles. More than a decade later, a large segment of the industry is moving to adopt modified SAC alloys, as well as new Pb-free alloys for higher reliability, or even low melting point alloys. MB Allen, KIC San Diego, CA, Sloan, Kim Flanagan, Brook Sandy-Smith, Indium Corporation Clinton, NY, the Pb-free transition, most of the industry settled on using predominantly SAC305 solders. Hot air reflow is used for faster profiles, especially desirous when there is a great volume of BGA rework to be accomplished.Reflow Profiling for Next-Generation Solder Alloys IR reflow is preferred for micro miniature devices as the lack of air flow prevent the component from being disturbed during reflow. If the PCB is bowed or warped, they might not be able to properly fit into the final assembly or opens may be formed.īGA rework reflow sources commonly used include both hot air as well as infrared heat sources. The bowing can be exacerbated by the proximity of other components such as pin-in-hole connectors that may anchor the PCB, thereby enhancing the localized bowing under the BGA. This can be a serious problem in the case of very thin PCBs or boards with an uneven thermal mass distribution. PCB warping and bowing should be minimized by the BGA rework process. Cleaning parameters should those be used in the original assembly process. If a water-soluble paste is used, the reworked area needs to be cleaned. The solder joint between the ball and the PCB pad should be similar in size and shape to the ball/part joint. Care should also be taken to not overheat any internal thermal grease if the BGA is capped.Īfter successfully attaching the BGA to the PCB, and allowing the board to be cooled down, the perimeter row of solder joints should be visually examined. This care must be extended to components with low melting points such as connectors or standoffs or adjacent moisture-sensitive devices. In addition, care must be taken to ensure that adjacent components are not damaged during the reflow process.
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