Hello Pete,
Thank you for the information below.
BTW, did you do any test to improve wetting contact angle for the lead PTH
connected with copper plane with thermal relief? At the lead free wave
soldering process in our facility, the wetting contact angle exceed 90°
and the surface appearance of the solder joint looks as follows. Any
thoughts on this? Thanks a lot.
__
| | <--------------- Component Lead
| |
/ \
/ \ <-------------- Surface Appearance
of Solder Joint
/ \
/ \
| | <------------ 90° wetting
contact angle
_________|__________|________ The surface of copper plane
Best Regards
Charming Chan
PCBA Engineer
Pete Houwen <[log in to unmask]>
发件人： TechNet <[log in to unmask]>
2008-10-29 21:06
请答复 给 TechNet E-Mail Forum; 请答复 给 Pete Houwen
收件人： [log in to unmask]
抄送：
主题： Re: [TN] How to improve solder filling and wetting contact
angles for thermal vias at wave soldering process.
We did some testing of design parameters when we switched to lead-free,
and
found that the lead-hole ratio is more critical. We also found that top
side
pad size is irrelevant for hole fill, but large bottom side pads can
adversly
affect hole fill. Using this chart, we are able to achieve 75% with
regularity
(and we do not have the best process controls in our plant):
Lead Range Pad Size Hole Size
.000-.017 0.05 0.026
.018-.022 0.06 0.035
.023-.027 0.07 0.04
.028-.032 0.07 0.046
.033-.042 0.08 0.052
.043-.052 0.09 0.062
.053-.063 0.1 0.073
.064-.076 0.11 0.086
.077-.086 0.12 0.096
.087-.106 0.14 0.116
.107-.115 0.15 0.125
(dimensions in inches)
standard plane connects are thermal relief, using (4) .008" spokes.
This testing was done only to establish design parameters, there are
plenty of
process parameters that will affect hole fill. But if your design
parameters
aren't good, all the process tweaks in the world won't fix trhe problem.
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