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April 2008

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Subject:
From:
"Terry L. Munson" <[log in to unmask]>
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Date:
Tue, 22 Apr 2008 23:58:08 +0000
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Ryan

The photo appears the same as other failures we have tested. Has any analysis been done on the amount of sulfuric acid in the barrel. The etch residue if not properly rinsed can also corrode open a via during reflow.

Terry Munson
Foresite
765457-8095
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Dwight Mattix <[log in to unmask]>

Date: Tue, 22 Apr 2008 16:08:21
To:[log in to unmask]
Subject: Re: [TN] Via barrel cracks


gee, was that hole drilled or punched? ;^)


At 03:53 PM 4/22/2008, stephengregory5849 wrote:
>Hi Ryan!
>
>Have your pics up! They're at:
>
>http://stevezeva.homestead.com/files/Via_Barrel.jpg
>
>http://stevezeva.homestead.com/files/Via_Barrel_2.jpg
>
>http://stevezeva.homestead.com/files/Via_Barrel_3.jpg
>
>Steve
>
>----- Original Message -----
>From: "Ryan Grant" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Tuesday, April 22, 2008 5:08 PM
>Subject: Re: [TN] Via barrel cracks
>
>
>Steve,
>
>I would much appreciate your help with posting these pictures.
>
>Thanks,
>Ryan
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
>Sent: Tuesday, April 22, 2008 3:55 PM
>To: [log in to unmask]
>Subject: Re: [TN] Via barrel cracks
>
>Would you have an image for posting?
>
>
>===================
>Hi Technetters,
>
>I have a case of via barrel cracks (E crack) and I would like to know
>possible causes.
>
>The crack is circumferential and occurs at the center of the via. The
>hole appears smooth, i.e., no glass nodules or tearout and there is
>neither positive nor negative etchback. Of course there is some
>wicking, but only about 25um max. The copper thickness is 20um at the
>crack and roughly 35-40um at the knee. Although, at the initiation
>point of the crack, the copper thickness is only 10um, but that could be
>due to stretching and subsequent thinning of the copper. Around the
>periphery of the crack are micro-voids in the resin about 30um. It is
>triangular shaped, so I can't tell if it is resin recession or a
>laminate crack.
>
>In other words, this via pretty much looks normal, except for one thing,
>which might be an artifact of stretching and cracking of the via. For a
>span of about 60um on the vertical of the via, at the crack, there is a
>roughness that slightly reduces the copper thickness. The surface of
>the copper at this point appears both rough and black in color.
>
>This board has seen two reflows and a hot functional test before final
>failure.
>
>The board shop's initial response was speculation of the OSP soft etch
>attacking the copper, but this particular via has solder mask plugging
>both sides of the via; therefore chemicals after solder mask cure can
>not get into the via.
>
>In case it matters, at one time, we have had occurrences of this board
>shop "re-working" panels after copper plating by placing the panel in a
>tank of etchant, then re-running the board through copper plating.
>(They do panel plating).
>
>I'm a little suspicious of their FA, so I would like some independent
>opinions and places for me to dig into.
>
>Thanks for any help,
>Ryan
>
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