I have used board supports from Transition Automation very successfully in the past also. Their "BoardLok" system is a "vacuum-formed" rubber-like material which conforms to the entire backside, components and all, so you have 95%+ support from the backside during printing. I believe they are at www.transitionautomation.com Jeff Hempton United Technology Electronic Controls Ken, Just to ad more info, the second side may need a special support on screen printer in order to have acceptable board support, mainly if you have fine pitch device on second side. This support is called " dedicated workholder" by MPM guys, but you can built yourself using your toolshop. Try MPM web site to see what a dedicated workholder looks like. When we did double side reflow no problem were found using eutetic solder paste. Jorge Santana Process Engr Microtec - Brazil > -----Original Message----- > From: Stephen R. Gregory [SMTP:[log in to unmask]] > Sent: 13 de Abril de 1999 12:20 > To: [log in to unmask] > Subject: Re: [TN] Double sided reflow > > In a message dated 4/13/99 12:27:46 AM Pacific Daylight Time, > [log in to unmask] writes: > > << Can someone help with the processing of a heavily populated SM PCB, > SM top and bottom which has to be reflowed both sides and has through > holes parts ( no wave solder ). > > Any guidelines on how this should be processed would be of great > help ie what side is the high temp solder used on, most densly least > densly populated etc etc. > > Regards, > ken Robertson > Telspec >> > > Hi Ken! > > I'm assuming that the reason you must do double sided reflow is > because the > board either has fine pitch or BGA's on both sides, am I correct? As > far as > using different melting point solders, I know there's some info out > there > that discusses that, but I really don't think that's a good thing to > do. Just > say for instance; what if somebody screws up and prints the wrong > paste on > the wrong side? You really don't need to do that anyway. Just about > any > component I can think of (as long as IPC guidlelines have been > followed as > far as pad layout and footprint) has enough surface tension to stay > put when > solder goes liquidous on the bottom...(provided your board isn't > bowing and > the reflow oven conveyer is smooth running). > > The exceptions to that are extremely heavy parts like ceramic or metal > bodied > QFP's and PLCC's, or parts with attached heatsinks. Sometimes Melfs > will give > you problems, or I've had problems with 4-leaded plastic body > oscillators and > certain filters too. Basically, suspect the parts that don't have much > lead > area to 'em. The figure I remember, and many people say this is pretty > conservative, is that you'll have 30-grams of surface tension for > every > square inch of lead surface. > > As far as what side to do first, I usually leave the side that has the > finest > pitch on it for the last side. If ya got any other specific questions, > let us > know... > > -Steve Greory- > > ################################################################ > TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################