The term "dentritic growth" is becoming more synonymous with 85 C /85 RH electrical testing. Some refer to it as "hydrolytic stability" as well. This results in basically "shorts" in systems with tight spacings and high voltages. The limiting factors really become the substrate and covercoat types, as the minimum spacing at 100 volts to be acceptable will depend on which combinations of materials are used. Not all materials are equivalent!!! See recent proceedings from May '96 IPC meeting in Phoenix. ______________________________ Reply Separator _________________________________ Subject: DES: Track spacing for 100V on internal layers -Reply Author: "Dennis Ostendorf" <[log in to unmask]> at -FABRIK/Internet Date: 6/2/97 8:50 AM From: Dennis Ostendorf Date: Mon, Jun 2, 1997 8:50 AM Subject: DES: Track spacing for 100V on internal layers -Reply To: Duane B. Mahnke; TechNet Cc: Gary_Willard-G10982 Gary, You should not have a problem with .015 inch spacing for 100V (unless you have contaminant(s) between the traces). In fact, I believe the spacing is conservative & could be reduced. Dennis Ostendorf aaeee2o @snds.com >>> Gary Willard-G10982 <[log in to unmask]> 06/02/97 06:15am >>> Hello All I am in need of some input on a design issue relating to track spacing for 100V operation for the internal layers of a 4-layer PCB. This PCB is 2.0mm thick with a 1mm core and 35um copper. This design has to withstand 85% humidity / 85deg temperature testing for 500 Hours some of which is under 'power-up' conditions. The current design has an epoxy based solder mask and conformal coating and has an internal spacing of .015", which I believe should be adequate as IPC-D-275 suggests a spacing of only .004-.008" for class 3 assemblies, this figure of .015" has been put to question so I am seeking further input. my questions are:- 1) What does class 3 mean in terms of general environmental testing and in particular 85/85 testing. 2) Does any body have practical knowledge of what a 'better spacing' may be. Any input would be most appreciated. Regards Gary Willard - Substrate Design Engineer Motorola (UK) *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** ---------- Received: from vanness6.fabrik.com by post.fabrik.com with SMTP (Fabrik F07.0-000) id [log in to unmask] ; Mon, 2 Jun 1997 08:54:48 -0700 Received: from kani.wwa.com ([198.49.174.58]) by vanness6.fabrik.com (post.office MTA v2.0 0813 ID# 0-0U10) with SMTP id AAA84 for <[log in to unmask]>; Mon, 2 Jun 1997 08:54:14 -0700 Received: from ipc.org/ipc.ipc.org [209.42.29.23] by kani.wwa.com with smtp (Smail3.2.WWA) id m0wYZPb-003rjdC; Mon, 2 Jun 1997 10:53:54 -0500 (CDT) Received: by ipc.org (Smail3.1.28.1 #2) id m0wYZG4-000BjbC; Mon, 2 Jun 97 10:42 CDT Resent-Sender: TechNet-request Old-Return-Path: <[log in to unmask]> Message-Id: <[log in to unmask]> X-Mailer: Novell GroupWise 4.1 Date: Mon, 02 Jun 1997 10:50:55 -0500 From: Dennis Ostendorf <[log in to unmask]> To: [log in to unmask] Cc: [log in to unmask] Subject: DES: Track spacing for 100V on internal layers -Reply Mime-Version: 1.0 Content-Type: text/plain Content-Disposition: inline Resent-Message-ID: <"XNnt-.0.XQI.pdkap"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/13095 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] ---------- *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************