Hi Peter Thanks God it's not a civil-aero , than I'd be worried . Something must be forcing you to the epoxy (I wouldn't) . And if you really insist on dragging SMD's through the wave : I am sure Bob (is on copy) will tell you where you stand . He's the author of the outrageous title : "Wavesoldering Surface Mount PCB's With Zero Defect" , so blame him if you won't achieve the 100% pass : [log in to unmask] See you (wish you luck[you'll need more than that on class3]) Paul Klasek http://www.resmed.com PS If you can not follow recommended manufacturers profile (may be difficult on wave) , you know you're in the reliability gray zone . The controlled cooling would help you on grain . Details with Werner Engelmaier (he may be on the road) : [log in to unmask] > ---------- > From: mudbugz[SMTP:[log in to unmask]] > Sent: Wednesday, 12 August 1998 12:37 > To: [log in to unmask] > Subject: [TN] DFM guidelines > > I have a customer who is transitioning from 100% thru hole boards to > designing boards with smt components. > > We gave them our basic DFM guidelines and they have laid out 2 boards > following these guidelines. When I saw the result of their first > pass, I > thought of two things. 1) we need to review our guidelines and 2) I > need > some advice from Technetters. > > The product is mil-aero building to IPC Class 3 using mil spec > components. > > The assemblies are all laid out for a process flow of > 1) reflow topside smt > 2) epoxy bottomside smt > 3) stuff thruhole > 4) wave solder > > I have 2 questions: > > 1) They have placed smt resistors as large as 2512's and capacitors > up to > 1812 on the bottomside. I recall reading about problems with wave > soldering large capacitors and having reliability problems. Would > this > also apply to resistors? What about the 1812 caps? > > 2) They have also place 1206 resistors between the pins of .300 dips > on > the secondary side. We had them orient the resistors parallel to the > wave > but unfortunately the dips are also oriented parallel to the wave (I > need > to check our DFM doc). With this, they have positioned 6 1206's > between > the leads of a dip16 component and place 3 dip components in a row > with 3 > 1206s between them. ASCII art to follow. > > o - reps a dip lead > > [] - reps a 1206 > [] > > <----- conveyor direction > > o [] [] o [] > o [] [] o [] > o o > o [] [] o [] repeated 3 times in this direction > o [] [] o [] > o o > o [] [] o [] > o [] [] o [] > > Is anyone building anything like this successfully? Volumes are less > than > 100/mo. > > Any input is appreciated. > > Peter Wong > [log in to unmask] > > ################################################################ > 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 ################################################################