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April 8, 2014

Minimum Component Lead to Lead Spacing for Wave Soldering

What is the recommended minimum lead to lead spacing for through hole components run through a wave soldering system? Would the spacing be different for lead-fee solder compared to leaded solder?

V.P.

Experts Comments

The minimum practical pitch for multi-lead components such as connectors is about 1.27mm (0.050); I have not personally dealt with any with smaller pitches. It is in theory possible to do smaller pitches, but the required hole diameter, and thus the maximum lead size, becomes very small. Pad sizes are also severely limited, which will affect soldering performance. The small hole also represents a problem for getting flux penetration and hole fill.

The minimum pitch should not be different for Pb-free vs. SnPb. In either case, it is necessary to tightly control lead protrusion to reduce shorting risk. It is potentially more critical with Pb-free due to the higher solder surface tension.
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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.
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