This is a very big question.  You will receive a lot of pro's and con's 
      for each process.  (I know I have my opinions) The best thing you can do 
      is decide what you are looking for in a finished etched trace geometry.  
      Process samples of different line widths and take many cross sections.  
      When you take your cross sections you will want to cross section both top 
      and bottom (horizontal) / left or right (vertical) of the substrate as it 
      was processed as well as traces that are processed in parallel and 
      perpendicular and at 45 degree angle to the direction of travel of the 
      substrate as it was processed.  When you read these cross sections you 
      will be focused on what the sidewall characteristic is of the left and 
      right side of each trace and how they relate to each other based on 
      direction and position.  With the these cross sections you must also look 
      at the position on the conveyor top center bottom on vertical or left 
      center right of a horizontal
     unit.  Once you gather this data you can then determine which process 
     will meet YOUR expectations.  Include in this decision controlled 
     impedance and very fine lines if this is part of your goal. 
      When you measure the line widths make sure you compare the 
     measurement to the exact location on the A/W that was used to image 
     the test panel.  Line widths on A/W vary and you want to remove this 
     variation from your comparison.  Because each shop's expectations are 
     different each process finds it's own niche.
     
     Guy Willingham
     Zycon
     [log in to unmask]
     
     
______________________________ Reply Separator _________________________________
Subject: FAB: Horizontal versus vertical etching 
Author:  [log in to unmask] at corp
Date:    1/29/97 3:16 AM
     
     
We would like to receive input on the positive and negative aspects 
of horizontal etching with oscillating spray bars, versus vertical 
etching of inner layers and outer layers using an alkaline etchant.
     
We would like to hear of experiences as to which method provides 
the best results in terms of line width uniformity, top to bottom 
consistency, and conveying of cores as thin as .004 with half ounce 
copper on both sides. 
     
Panel sizes vary from 12 X 12 to 21 X 30. Line and spaces down to 
.004 X .004 for the smaller panels, .008 X .008 on the larger panels. 
     
Please presume that equipment of either type is well maintained and 
that the chemistry is under good control. 
     
Many thanks,
     
Luis Rivera
CompuRoute, Inc.
Dallas, TX
[log in to unmask]
(214) 340-0543
     
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