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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