Tony

  This is easy to see in the screen printer machine, just load the board and
do the align without printing ( most of screen printers has this
capabilities ) , go into the machine and see if all stencil apertures are
aligned with the board pads, from there you have the final conclusion ...

Jorge Santana

  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]]On Behalf Of tony steinke
  Sent: Friday, March 29, 2002 12:49 PM
  To: [log in to unmask]
  Subject: [TN] solder paste registration


  Ladies and Gentlemen,

  We are having a major problem with an assembly house with registering
  the solder paste to surface mount features prior to pick and place. They
  are claiming that the boards are growing/shrinking some 15-20 mils.
  We have done extensive measuring on unpopulated boards in-house
  and cannot see more than 3-5 mils misregistration. The panel size
  is approximately 14.00 x 16.00 inches, 20-24 mil pitch, and 15 BGA's
  throughout the panel. Overall thickness .080. Is it possible that the mesh
  screen that they are using can expand/contract over time? has anyone
  heard of this experienced this situation before. Any information would be
  greatly appreciated.

  Thanks
  Tony Steinke
  AIT-Atlanta