James, I would be most concerned about the minimum electrical spacing between the trace and the external component lead/termination. IPC-A-610C, Appendix A, gives guidelines for minimum electrical conductor spacing that are taken from IPC-2221 (2/98), paragraph 6.3. I suggest looking at Table 6-1 and paragraphs 6.3.6 and 6.3.7 Also consider the Note in Section 9.2 of IPC-A-610C, that solder resist coatings should not be considered as an "insulator or insulative material". Charles Lawson Product Assurance General Dynamics Advanced Technology Systems >Date: Thu, 7 Jun 2001 15:09:01 -0400 >From: "Riling, James J" <[log in to unmask]> >Subject: Separation Guidelines For PCB Traces Running Under Components >MIME-Version: 1.0 >Content-Type: text/plain > >Several of my companies PCB's have traces running under components. For >Horizontal and Vertical Axial Leaded Components IPC-A-610 specifies a >minimum distance for the components to be above the board surface. Are >there any other "separation" guidelines for Traces Running Under Leaded >Components? In addition, we also have PCB's w/ traces running under surface >mount chip resistors and capacitors. Are there any "separation" guidelines >for surface mount? In particular, is there a guideline for the minimum >width of the ceramic substrate for a SM Chip Resistor or the insulation >characteristics of the substrate? > >Any help would be greatly appreciated. > >James J. Riling >Hardware Validation Engineer >Union Switch & Signal Inc. >Phone: (412)688-2926 Fax: (412)688-2398 >Email: [log in to unmask] --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------