Tin alloys are a lead-free soldering option, however, soldering can exhibit the appearance of "whiskers" - small bumps of metal that protrude beyond the solder joint or pad. This kind of whisker can grow very long, so that the current of the two welding areas is too large, a short circuit occurs, and the equipment malfunctions. This problem can be easily found using tin alloys in-circuit test, but it can take time for tin whiskers to grow, and it can be a long-standing reliability problem.
In order to optimize the reflow technology of lead-free soldering, we have increased the amount of flux used. In a non-clean environment, as the contact resistance increases, the probe head may be polluted and the performance of the device will be damaged. Therefore, it is necessary to strengthen the protection of the equipment, or change the probe head to a sharper type. However, sharper probe tips can conflict with the brittleness of lead-free solder, causing damage. Due to the brittleness of lead-free solder, extra care must be taken when limiting the flex characteristics of the components in the test setup.
Rework and Correction Questions
A final question to consider is the impact of lead-free soldering on rework and correction operations. The melting of lead-free alloys requires higher temperatures. If the components on the assembly are large in size, there will be high heat dissipation, so the components should be preheated. Due to the use of lead-free soldering and the removal of certain flame retardants from the bare PCB, the high temperatures required for repairs can damage components or assemblies.
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Notes on the Transportation of Exported Tin Ingots
