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April 2005

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Subject:
From:
paul reid <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, paul reid <[log in to unmask]>
Date:
Thu, 21 Apr 2005 11:52:07 -0400
Content-Type:
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We have found that it is possible to gain insight on peeling trace failure
modes by microsectioning peeling traces.  We are examining our microsections
up to about 1000X magnification (according to our objective and eye pieces).
At that power you can easily see a electroless copper deposition layer but
cannot visualize a direct metalization layer.  Separation above, through, or
below the electroless copper will give good insight on where in the process
to focus your investigation. On occasion we will be able to see a
contaminate that is causing separation (particularly ash at the bottom of
laser ablated microvias) but usually we can only determine at which level of
copper the separation occurs.

I have used a solution of Sulfonated Potash (which is toxic) to oxidize bare
and imaged panels.  The potash oxidizes exposed copper turning it dark blue
or black.  Areas with a contaminate like resist residue, that is otherwise
invisible, will resist the oxidation and remain pink.  Resist residues and
other surface contaminates can be visualized in this way.  You might be able
to do the same thing with other, safer chemistries, that mildly oxidize
exposed copper without attacking the surface contaminate.

Paul Reid
PWB Interconnect Solutions



-----Original Message-----
From: Franklin D Asbell [mailto:[log in to unmask]]
Sent: Thursday, April 21, 2005 9:35 AM
To: [log in to unmask]
Subject: Re: [TN] Peeling Copper traces


I would think his comment "pulling away from the foil" would rule out the
need for peel strength test. I've never seen conditions that have caused
plated copper peeling show up in microsection, of course I've never viewed
them over 200X...and it's been my experience angstroms thick passivation
contaminates are not viewable in most in-house labs.

Where I would begin is water break on the foil panels before and after
electroless copper, perhaps experiments involving cleaning and microetch to
determine where (on raw foil surface, or during/post electroless copper) the
condition is occuring.

Franklin



----- Original Message -----
From: "Jeffrey Bush" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, April 21, 2005 7:51 AM
Subject: Re: [TN] Peeling Copper traces


If the failure is plating to foil you will need to do a microsection to
identify the failure mechanism - foil to dep, dep to plate, etc.  If the
failure is foil to base material you will need to assess that raw
material lot for peel-strength.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com


-----Original Message-----
From: Rich Olsen [mailto:[log in to unmask]]
Sent: Wednesday, April 20, 2005 4:51 PM
To: [log in to unmask]
Subject: [TN] Peeling Copper traces

Hello,

        What are some likely causes of peeling copper traces?
        It is plated copper pulling away from the foil copper?

thanks,
Rich

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