Thanks for the info.
  ----- Original Message ----- 
  From: Jeffrey Bush<mailto:[log in to unmask]> 
  To: [log in to unmask]<mailto:[log in to unmask]> 
  Sent: Monday, September 13, 2004 7:41 AM
  Subject: Re: [TN] PWB Conductive Contamination Under Solder Mask; What Can ...


  I can also see from the micrograph that the plating surface to hole
  ratio is skewed - the PTH appears to have adequate copper ~ .0012" while
  the surface plating appears to be 2-3X the PTH.  This would indicate an
  issue in plating distribution and current density.  I also see that the
  process was possible a panel plate followed by a pattern plate, further
  contributing to the overhang.



  Jeffrey Bush
  Director, Quality Assurance and Technical Support

                            76 Technology Drive - POB 1890
                               Brattleboro, Vermont 05302-1890
                                  Tel. 802.257.4571.21 Fax. 802.257.0011
                                      [log in to unmask]<mailto:[log in to unmask]>
                                http://www.vtcircuits.com<http://www.vtcircuits.com/> 



  -----Original Message-----
  From: Susan Mansilla [mailto:[log in to unmask]] 
  Sent: Sunday, September 12, 2004 6:26 PM
  To: [log in to unmask]<mailto:[log in to unmask]>
  Subject: Re: [TN] PWB Conductive Contamination Under Solder Mask; What
  Can ...


  I received the photo - I realize Technet did not.  The one surface land
  does show over hang, but the one on the bottom from another coupon shows
  NO overhang.

  The one with overhang also shows severe UNDERCUT of the solder mask next
  to the land.

  I am puzzled by the "scotch brite" comment as I can think of no reason
  for using this in a SMOBC product.  Any and all tinlead plating should
  have been stripped off prior to cleaning and solder mask application,
  The overhang of copper that was present on the top coupon would not have
  been removed by an abrasion process.

  The real proof would be seeing what the sample looked like in the "as
  plated" tin/lead condition and finding out why an abrasion process was
  used.  The few times I have used an abrasion process only caused the
  overhang to become splinters that then came loose later on and caused
  problems.

  The undercut of the solder mask is also a potential threat for trapping
  contamination later on during HASL or assembly processing.

  Susan Mansilla
  Technical Director
  Robisan Laboratory, Inc.
  6502 E 21st Street
  Indianapolis, IN  461219
  www.robisan.com<http://www.robisan.com/>
  317-353-6249


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