Jeff, The number you are looking for is 1000 volts per mill.. this is a reference number.. you can ask your board supplier to send the tech data sheet for the laminate you are running and that will give you the materials insulation characteristic..tested to a standard method..at 1 ply of 1080 (.0025 usually) you probably are yielding a thinner in a 1 ply sistuation may be even as low as .002 or .0018" depending on fill and press setup.. Doug Jeffery You wrote: > >I have a .062" thick, 10 layer PCB that I am working with. My first = >round of prototypes came back a bit thin at .052" thick. Between each = >of the inner layers of copper is only one sheet of prepreg, .0025" = >thick. I have a couple of long runs that are on separate inner layers, = >but they run right on top of each other. The runs are about 5" long, = >1oz. copper, .04" thick. The only separation between these runs is = >through the prepreg layer. Usually, we do not have a problem with doing = >this, but we usually have more than one layer of prepreg between = >conductor layers. =20 > >My problem is this: during testing of the assembly, somewhere during = >surge, eft, or isolation verification, a few of the runs that run on top = >of each other, but on different inner layers have shorted together = >internally in the PCB. I don't know if it was during surge, eft, or = >isolation testing. Is there a way to quantify, calculate, or is there a = >general rule of thumb for determining the isolation characteristics = >between inner layers of a PCB? We are ready to do a second production = >run of the board where the prepreg thickness between the inner layers is = >doubled compared to the first prototypes, but I would like to get a good = >feeling if it will pass my testing before we sign off to produce the = >boards. I would appreciate anyone's comments or insight. I have listed = >some of the test requirements below: > >Surge Testing: 3kV peak voltage (IEC waveform of 50usec duration) >EFT Testing: 2kV peak voltage (IEC waveform of 2.5kHz frequency) >Isolation Testing: 2kV ACrms, 60Hz, no more than 1mA conduction, = >sustained for at least 1 minute > >Thank you for your time, >Jeff Fries >Design Engineer >Harmon Industries, Inc. >[log in to unmask] > >------=_NextPart_000_000C_01BD3D6F.7548A040 >Content-Type: text/html; > charset="iso-8859-1" >Content-Transfer-Encoding: quoted-printable > ><!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> ><HTML> ><HEAD> > ><META content=3Dtext/html;charset=3Diso-8859-1 = >http-equiv=3DContent-Type> ><META content=3D'"MSHTML 4.72.2106.6"' name=3DGENERATOR> ></HEAD> ><BODY bgColor=3D#d8d0c8> ><DIV><FONT color=3D#000000 face=3DArial size=3D2>I have a .062" = >thick, 10 layer=20 >PCB that I am working with. My first round of prototypes came back = >a bit=20 >thin at .052" thick. Between each of the inner layers of = >copper is=20 >only one sheet of prepreg, .0025" thick. I have a couple of = >long runs=20 >that are on separate inner layers, but they run right on top of each=20 >other. The runs are about 5" long, 1oz. copper, .04"=20 >thick. The only separation between these runs is through the = >prepreg=20 >layer. Usually, we do not have a problem with doing this, but we = >usually=20 >have more than one layer of prepreg between conductor layers. =20 ></FONT></DIV> ><DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV> ><DIV><FONT face=3DArial size=3D2>My problem is this: during = >testing of the=20 >assembly, somewhere during surge, eft, or isolation verification, a few = >of the=20 >runs that run on top of each other, but on different inner layers have = >shorted=20 >together internally in the PCB. I don't know if it was during = >surge, eft,=20 >or isolation testing. Is there a way to quantify, calculate, or is = >there a=20 >general rule of thumb for determining the isolation characteristics = >between=20 >inner layers of a PCB? We are ready to do a second production run = >of the=20 >board where the prepreg thickness between the inner layers is doubled = >compared=20 >to the first prototypes, but I would like to get a good feeling if it = >will pass=20 >my testing before we sign off to produce the boards. I would = >appreciate=20 >anyone's comments or insight. I have listed some of the test = >requirements=20 >below:</FONT></DIV> ><DIV><FONT face=3DArial size=3D2></FONT> </DIV> ><DIV><FONT face=3DArial size=3D2>Surge Testing: 3kV peak voltage = >(IEC waveform=20 >of 50usec duration)</FONT></DIV> ><DIV><FONT face=3DArial size=3D2>EFT Testing: 2kV peak voltage (IEC = >waveform of=20 >2.5kHz frequency)</FONT></DIV> ><DIV><FONT face=3DArial size=3D2>Isolation Testing: 2kV ACrms, 60Hz, no = >more than=20 >1mA conduction, sustained for at least 1 minute</FONT></DIV> ><DIV><FONT face=3DArial size=3D2></FONT> </DIV> ><DIV><FONT face=3DArial size=3D2>Thank you for your time,</FONT></DIV> ><DIV><FONT face=3DArial size=3D2>Jeff Fries</FONT></DIV> ><DIV><FONT face=3DArial size=3D2>Design Engineer</FONT></DIV> ><DIV><FONT face=3DArial size=3D2>Harmon Industries, Inc.</FONT></DIV> ><DIV><FONT face=3DArial = >size=3D2>[log in to unmask]</FONT></DIV></BODY></HTML> > >------=_NextPart_000_000C_01BD3D6F.7548A040-- > >################################################################ >TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >################################################################ >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: >To subscribe: SUBSCRIBE TechNet <your full name> >To unsubscribe: SIGNOFF TechNet >################################################################ >Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. >For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 >################################################################ > > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. 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