Jason, We have a military program with rather large assemblies where the PWB's are at least .093" thick impedance control boards (14-16 layers, lots of plane layers) and external aluminum heat sinks bonded to the PWB. When rework is required, we first bake the board, and then work with it hot on the plates. This greatly improves the ability to solder & desolder. If we don't there has always been problems where damage to the board or component would occur. Cindy Kemp Lockheed Martin Orlando, FL (407) 306-6873 email: [log in to unmask] ******************************************************************************** Resent-Date: Thu, 10 Oct 1996 09:55:40 -0700 Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> date: Thu, 10 Oct 96 9:48:05 message-id: <[log in to unmask]> From: [log in to unmask] ("Jason Spera Production Eng.") Sender: [log in to unmask] ("Jason Spera Production Eng.") to: [log in to unmask] Subject: Preheating of Ceramic Chip Capacitors MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-description: Message Body Content-transfer-encoding: 7BIT Resent-Message-ID: <"sdBrd3.0.pDM.eQGNo"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/6784 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] Dear Technet, We are a military assembly house that employs preheating plates for ceramic chip rework to reduce the risk of internal chip delamination from thermal shock. This has been done per IPC recommendations. However, this step in the rework process is time consuming and cumbersome. We have done minor and informal tests to determine the real value of this practice and found that it really is not needed if the operators take care in their soldering. If the tip size and heating time is controlled, there doesn't seem to be an immediate effect or a temperature cycling effect on the chips. I am interested to see how widespread the use of preheating plates actually is. I would like to hear from anyone having any experience indicating that the process is actually necessary. (or not necessary) Thank you in advance for any input. Jason Spera Manufacturing Engineering General Atronics Corporation *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************