Scott, Preheating can serve a couple of purposes; 1. To activate the flux should that be a part of the processes, as in attachment of the component. 2. To prevent thermal shock of the elements being exposed to the localized wave/fountain. Much of the criteria that is appropriate for wave soldering would apply here since the process is quite similar, and as with wave soldering there is not a single recipe that fits all situations. We should never profile the machine but should always profile the product for the machine. Profiling is efficiently accomplished with the application of thermal couples if the production resources warrant that effort. Otherwise a surface probe can suffice to achieve adequate results for occasional use. Variation within the machine supporting the process can vary from a partial contact to just maintaining the board position over the solder resource. Where? I would recommend on the top side near the component leads of the component. How fast? Deals with capability to a great extent. Component manufacturers sometime recommend 2 degrees C per sec for sensitive components such as Chip caps. Mel Parrish Soldering Technology International 102 Tribble Drive Madison, AL 35758 256 705 5530 256 705 5538 Fax [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Rougeux, Scott Sent: Wednesday, September 26, 2001 12:21 PM To: [log in to unmask] Subject: [TN] FW: preheating assemblies prior to rework Importance: High > Your input is requested on this issue. > In regards to preheating assemblies prior to reworking them on the Solder > Fountain/solderpot. > We have been asked to look into preheating components or boards during > rework. This opens many questions: > * What is the desirable preheat temperature? > * How is it measured? > * Where is it measured? > * How quickly can the assembly be heated? > Thanks. > ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------