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October 2012

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From:
"Thayer, Wayne - IS" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Thayer, Wayne - IS
Date:
Sat, 27 Oct 2012 02:58:50 +0000
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Hi Victor-

I was offline for awhile.

The most common problem with laser ablated vias is debris/residue left in the bottom of the hole.  Usually it is clear and thin and VERY tough.  We use the graphite-based Shadow process for direct plate, so the residue becomes obvious after the panel goes through the Shadow line.  Next is the problem of trying to get nice conical sidewalls to make it easy for the plating to go around the bottom edge between the wall and the floor of the via.  It is very common to have an acute angle at this juncture, creating something that looks like a crack when it plates.  If using a UV laser, you can become over-aggressive in trying to expose lower layer copper, ablating more of the copper than optimal.  In this case the base foil could become over-weakened, or you could damage dielectric beneath the foil.

If the via needs to be filled by plating, you will have the usual problems with that:  Trying to minimize yet maintain a lap plate so you can get high resolution during the next etching process.  Most shops still sand by hand with a block.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Friday, October 19, 2012 3:04 PM
To: [log in to unmask]
Subject: [TN] PCB/PWB laminate laser abolition

Fellow TechNetters:

   Searching for Industry Standards/Guideline for HDI micro vias on the above stated process.   The anatomy of a micro via after laser abolition.   What are some common anomalies/defects?

Victor,

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