Wave soldering is the widely-used method in high volume production of PCBs (printed circuit boards.) Traditionally, a wave soldering process depended upon the tin/lead eutectic Sn63/Pb37 alloy, but the new environmental safety requirements and regulations have changed this norm resulting in the introduction of environmentally friendly, lead-free alloys to enable a lead-free wave soldering process.
There are various lead-free alloys available for the wave soldering process. To choose the right one, consider the following factors:
• The criteria for selection – Examine the process yield DPMO (defects per million opportunities), board and component compatibility, total cost of ownership, in-service reliability, and process maintenance.
• Initial screening – Analyze the selection of available alloys and create a short list of prospective products.
• Process yield examination – Consider the optimized process settings and the DoE (design of experiment) setup.
• Testing reliability – Test the lead-free alloy to see how it performs under thermal cycles and soldering performance.
Process yield can be examined using DoE, with the variables such as the pad finish, Sn/Cu/Ni and alloy type SACX, solder-pot temperature, conveyor speed, the preheat temperature, and the flux. Reliability for every alloy can be determined by making the boards go through thermal shock cycling in 300 cycles with temperatures ranging from -25°C to +85°C.
Choosing a lead-free soldering alloy may be challenging. Keep in mind that the lead-free wave solder alloys have different properties. Hence, conducting extensive in-house testing can help in making an informed decision. Some of the best lead-free alloys are suitable replacements for Sn63. They can stabilize and minimize copper content in the solder bath, if process conditions call for it.
There are various lead-free alloys available for the wave soldering process. To choose the right one, consider the following factors:
• The criteria for selection – Examine the process yield DPMO (defects per million opportunities), board and component compatibility, total cost of ownership, in-service reliability, and process maintenance.
• Initial screening – Analyze the selection of available alloys and create a short list of prospective products.
• Process yield examination – Consider the optimized process settings and the DoE (design of experiment) setup.
• Testing reliability – Test the lead-free alloy to see how it performs under thermal cycles and soldering performance.
Process yield can be examined using DoE, with the variables such as the pad finish, Sn/Cu/Ni and alloy type SACX, solder-pot temperature, conveyor speed, the preheat temperature, and the flux. Reliability for every alloy can be determined by making the boards go through thermal shock cycling in 300 cycles with temperatures ranging from -25°C to +85°C.
Choosing a lead-free soldering alloy may be challenging. Keep in mind that the lead-free wave solder alloys have different properties. Hence, conducting extensive in-house testing can help in making an informed decision. Some of the best lead-free alloys are suitable replacements for Sn63. They can stabilize and minimize copper content in the solder bath, if process conditions call for it.
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