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Wave Soldering Defects - Incomplete
Joints
The incomplete solder fillet is often seen on
single-sided boards after wave soldering.
In Figure 1, the lead-to-hole ratio is
excessive, which has made soldering difficult. There is also evidence
of resin
smear on the edge of the pad. It
may be possible, even on this design, to improve the soldering
performance by decreasing the conveyor angle from 6 to 4°. This
reduces the drainage
performance of the wave but can lead to the incidence of shorting.
Reducing wave temperature has also been seen to overcome the problem.
As a guide, the hole-to-lead ratio is normally the
lead diameter plus 0.010", which is the normal guideline for automatic insertion.  |
| Figure 1: The lead-to-hole ratio here was excessive. |
Incomplete solder fillets are caused by poor
hole-to-lead ratio, steep conveyor angles, excessive wave temperature
and contamination on the edge of the pads.
The example shown in Figure 1 is a result
of burring on the copper pads. During either drilling
or punching, the copper on the surface of the board was deflected
in some areas, making soldering difficult. The same thing can
occur if resin is smeared onto the edge of the pads.  |
| Figure 2: Burring on the copper pads caused this defect. |
Wave Soldering Defects:
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Incomplete Joint | | | | |
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