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Mon, 17 Jul 2006 09:32:14 -0400 |
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No, it should be bigger!
If a blind via is made by a laser as a controlled depth job, the target
pad acts a bit like a "backstop" for the laser. For this case
"breakout" has the most horrendous consequences: The dielectric
adjacent to the pad is damaged (perhaps even carbonized) and may plate
during the plating step. It may be detectable as a short right away, or
may have to wait a while to show up. I use minimum of 3 mil annular
ring for laser blinds, and other pcb fabricators appear to be in the
same ballpark.
Wayne Thayer
>>> [log in to unmask] 7/16/2006 2:39 am >>>
IPC-6012, Class 3 requires 1 mil minimum internal annular ring for
plated through holes. Is the internal layer of a blind via bound by
these requirements?
Jay Otts
Raytheon
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