Hello All, I have to agree with Werner with regard to the combined use of IR and Forced Convection. I am also interested in why Eddie is prejudiced against the combination of IR and Convection. At Heraeus, we commisioned a study at Fraunhofer Institute in Berlin on the effects of various percentage combinations of forced convection and IR. As a result of the study we have modified our full forced convection oven design. (Yes, Heraeus also manufactures reflow and curing ovens in addition to solder paste and glues) Without going into a lot of detail, the report showed that a percentage combination of IR and Forced Convection helped the reflow process especially when it came to large mass components. The critical part however is that the IR must be well controlled. If the IR system drifts over the course of a day then the process will be non-repeatable. If anyone has any questions about the report or the Heraeus Ovens, please contact me directly. Douglas Bennett Sales Engineer Heraeus Amersil, Inc. Atlanta, GA, USA [log in to unmask] 770-623-5630 ext 4225 At 09:04 AM 1/9/98 EST, you wrote: >Hi Rainer & Eddie, >There is no practical way to avoid mixing infrared with forced convection, nor >is there a need to do so, nor is it desirable. By the very nature of having an >oven consisting of surfaces hotter than the PCB assemblies running through it, >you will get heat transfer by mid-range infrared radiation. Depending on the >convection gas, flow velocity and flow volume, and delta-T between oven and >assembly, the ratio heat transfer by convection and IR will vary. The so- >called Full Forced Convection ovens, have IR heat transfer contents of15 to >25%; conversely, with the so-called IR reflow ovens you get heat transfer from >convection as high as about 50%. >Having different heat transfer modes present actually contributes to more >uniform heating of your assemblies, because they have different shadowing and >therefore complement each other. > >Werner Engelmaier >Engelmaier Associates, L.C. >Electronic Packaging, Interconnection and Reliability Consulting >7 Jasmine Run >Ormond Beach, FL 32174 USA >Phone: 904-437-8747, Fax: 904-437-8737 >E-mail: [log in to unmask] > >############################################################## >TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. >For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 >############################################################## > ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################