have a look at article written by Bob Neves in April 2002 PCFab available on-line Dougal Stewart email: [log in to unmask] phone: +44 1896 822204 mob: +44 7984 629667 ----- Original Message ----- From: "Earl Moon" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, August 09, 2002 5:29 AM 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 > > -------------------------------------------------------------------------- ------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8e > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > -------------------------------------------------------------------------- ------- > --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------