Yo Moonman,

I am on this committee at the IPC and with the IEC and working with the
NPL who are presently doing even more research work in this area. What
do you want to know about CAF testing?

For the un-initiated - CAF = Conductive Anodic Filamentation or Cathodic
Anodic Filamentation.....or sub-surface dendrites.

Regards Graham Naisbitt

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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Earl Moon
> Sent: Friday, August 09, 2002 05:30
> To: [log in to unmask]
> Subject: [TN] CAF
>
>
> Folks,
>
> I really am a rookie. I can't get over how much I don't know
> but want to know. I need one more lifetime to get even a
> little more knowledgeable. Our good friend David Douthit
> provided some very important input as the following sample as
> it pertains to cleanliness etc:
>
> Test Method 2.6.25
> Title: Conductive Anodic Filament (CAF) Resistance Test
> Stage: Working Draft
> Date: May 2002
> Originating Task Group: Electrochemical Migration Task Group (5-32e)
>
> 1.0 Scope  This test method provides a means to assess the
> propensity for conductive anodic filament (CAF) growth, a
> form of electrochemical migration within a printed wiring
> board (PWB). Conductive anodic filaments may be primarily
> composed of conductive salts rather than cationic metal ions.
> This test method can be used to assess PWB laminate
> materials, PWB design and application parameters, PWB
> manufacturing process changes and press-fit connector applications.
>
> 2.0 Applicable Documents
>
> 2.1 IPC
> XXX-YYYY-04 CAF Test Board
> IPC-6012 Qualification and Performance Specification for
> Rigid Printed Boards IPC-9201 Surface Insulation Resistance
> Handbook ICP-TM-650, Section 2.6.14.1 Electrochemical
> Migration Resistance Test
> (note: covers only surface electrochemical migration)
> TR-476A - Electrochemical Migration: Electrically Induced
> Failures in Printed Wiring Assemblies
>
> 2.2 American Society for Testing and Materials (ASTM)
> ASTM D-257-93 Standard Test Methods for DC Resistance or
> Conductance of Insulating Materials
>
>
> 3 Test Specimens
>
> 3.1 IPC XXX-YYYY-04
> The IPC XXX-YYYY-04 has 10 layers and dimensions are about 5
> x 7 inches. Test board designs for evaluating CAF resistance
> shall have varying drilled hole wall to drilled hole wall
> distances for plated holes. These distances can range from as
> low as 0.006 inches separation for alternate laminate
> materials expected to have very high CAF resistance and
> minimal copper wicking out from the plated-through hole
> (PTH), to as high as 0.035 inches separation for evaluating
> press-fit connector applications. The drilled hole size,
> rather than the finished hole size, is specified in the chart
> on the bare board fabrication drawing to ensure consistent
> spacing. Internal layer thieving may be added to plane layers
> around the perimeter. Test boards should be manufactured so
> that the machine direction of the woven fiber reinforcement
> is perpendicular to the rows of same-net daisy chain vias for
> A1-A4 (machine direction tends to fail first). Test board
> designs shall have sufficient minimum spacings on outer
> layers to ensure that surface insulation resistance failures
> do not occur. Layout of the IPC XXX-YYYY-04 test board
> structure (CAF Test Board) is shown below (Figure 1).
>
> I know David knows about this. Is anyone else on this forum
> aware or involved. Jeez, I got lost on the QFP coplanarity
> issue thinking that was way past history and learned a whole bunch.
>
> MoonMan
>
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