Ryan-
Picture http://stevezeva.homestead.com/files/Via_Barrel_2.jpg shows
walls that appear to thin considerably wherever the solder mask is not.
Is this true, or is it just a trick of the lighting?
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dwight Mattix
Sent: Tuesday, April 22, 2008 7:08 PM
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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