normally, the eutectic sj oxide surface is Sn rich.  however, for what
ever the reason - subsequent process, such as solvent clean, or DI clean,
you might end up with Pb rich surface (not as shining as the Sn rich one
with some roughness). it is not as stable as the Sn rich surface under
85/85/5 condition.  based on the old memory.  my 2 cents.
             jk
> Hi Dick - sometimes tin/lead solder surfaces get "texture" due to the
> solidification behavior of the solder joints. Years ago "grainy" solder
> was
> "bad" because the specifications required "bright and shiny" solder
> joints.
> Industry data has shown that solder joint appearance is not the best
> assessment of solder joint quality. There are many situations solder
> joints
> having "texture" is not an issue. For example, if you have a hot reflow
> profile which allows the solder joint microstructure to form large lead
> (Pb) dendrites then the solder joint surface can look rough as the
> dendrites cause topography differences. Once Steve posts the picture,
> TechNet should be able to provide a more detailed assessment.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Mon, Aug 31, 2015 at 11:14 AM, Richard Krug <[log in to unmask]> wrote:
>
>> I've got something I haven't seen before.  We wave soldered boards with
>> Sn63Pb37 and found a "textured" surface after soldering.
>> We seem to have good wetting, but it looks like we have "lumps"  under
>> the
>> solder surface.  The lumps are most visible where the solder is thin,
>> but
>> can also be found on thicker solder joints as well.
>> The application is class 3.  We do monthly solder analysis on the pot so
>> I
>> don't think it is contamination in the solder.
>> Any insights would be appreciated
>>
>> I know the picture will be stripped out of the message, but I'm copying
>> Steve Gregory directly in hopes he can post the picture.
>>
>> Steve - Please post this picture to go with my question for the TechNet
>> forum.  Thanks in advance.
>>
>> Dick Krug, CSSBB, CSMTPE
>> Lead Process Engineer
>> Sparton Brooksville, LLC
>> 30167 Power Line Road
>> Brooksville, FL  34602-8299
>> (352) 540-4012
>> [log in to unmask]
>>
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