Joe;

  From a laser drilling standpoint, we prefer to use a minimum of half
ounce copper for capture pad foil thickness. We have laser drilled a few
parts with quarter ounce capture pad foil, but it is tricky to do so as
the thin coppers buckle and damage easily from the localized heat of a
laser beam. We have also produced blind vias on plated up sub assemblies
that start with half ounce foil. We also routinely laser drill boards
for power management devices that utilize one and two ounce copper
foils. The thick foils are really hard to damage. 

Dave Simonik
Laser Process Technician
Sanmina SCI Corp.
Owego NY Division

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US
SSA)
Sent: Tuesday, December 04, 2007 11:54 AM
To: [log in to unmask]
Subject: Blind Via Question

For HDI vias, what minimum target pad foil thickness is allowed after 
hole preparation, prior to deposition and copper plating?  IPC-6016 
does not provide any requirements similar to those in 
IPC-6012 Table 3-7 for HDI applications.
 
Joe Kane
BAE Systems
Johnson City, NY


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