If you reflow top side parts during wavesolder, your solder wave profile is WRONG. I have been doing this for years without ever reflowing parts. If you attempt to meet chip cap specifications with less than 5 feet of preheat, you may be forced to solder at less than 4.5 (5.0 for some wave designs) fpm and dwell time at the wave will result in high temperatures. You must either cool the wave (and reduce preheating accordingly), heat sink top side SMD, get a machine with more preheat, or all of these suggestions. If you are using a burn-off no clean in air, 4.8 fpm is the minimum conveyor speed to keep sufficient flux on the foil side for proper yield. If you have blowholes in plated through boards, check age, storage or have your supplier provide sufficient plating. Baking all panels masks procurement/storage problems. Aric Parr United Technologies Electronic Controls [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: FW: wavesoldering mixed tech boards Author: [log in to unmask] at internet Date: 11/12/96 12:46 AM -----Mark, I tend to agree with the PTH board moisture and poor copper theory. we pre-bake our bare pwb's @ 220 deg f for 4 hours to remove any moisture prior to build and solder. Check with your board vendor to have him check his platting process. As to the reflow of SMT components on the component side I have found that as the assy crosses the wave, the top side temp will reach 181 deg c for approx. 2-3 seconds this can be enough to send the solder into a partial reflow. we use fiberglass bags filled with steel shotgun shot. These are put on the assy to act as a heat sink and also helps to hold hand installed components from floating during the wave solder process.. - Ray Volk Tel 612-957-4075 e-mail: [log in to unmask] ---------- From: [log in to unmask] To: [log in to unmask] Cc: [log in to unmask] Subject: Re: wavesoldering mixed tech boards Date: Monday, November 11, 1996 4:07PM MR MARK A WARYCKA wrote: > > Good Day, > > This is a request for some assistance on a wavesoldering > problem that we are currently experiencing on some mixed technology > boards that we process. The boards have surface mount top and bottom > and when the process is set to wave the bottom side with no defects > we are experiencing a problem with some top side surface mount IC's > de-soldering! I have tried using soldering pallets set at > approximately a 30 degree angle with some success but it slows down > the processing time and the top side components still come loose. > Initial profiling indicates that the top side of the board is showing > temperatures below the eutectic point of the solder paste being used. > When the boards are processed without the pallets the defect rate > increases dramatically but the incidence of topside component des- > soldering decreases! The wavesolder machine is a T/D Nu-Era with > dancer wave and the flux being used is Kester 2331-ZX. Topside > preheat temperatures just prior to wave entry are around 185 degrees > F. > > Another question is in regard to voids and blowholes occurring > on a PTH board that is auto-inserted. Just can't seem to get rid of > them. The boards are inspected at incoming for voids in the plated > thru holes. Profiling indicates that all process parameters are > correct. Any ideas? > From: Mark A. Warycka > Process Engineering Manager > Electronic Systems, Inc. > Sioux Falls, SD > > *************************************************************************** > * 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. * > *************************************************************************** Mark, blowholes and voids in PTH boards are due to two main reasons: 1. PCB laminate moisture 2. Poor quality copper plating in barrel ( rough drilling, thin copper, pin holes, plating voids etc) Two factors when present together can affect blowholing and solder voids in PTH joint. Examine your as received boards for plating defects in barrel and try drying your PCBs before soldering. As regards your reflow of SMT component on top surface during wave solder, I have a question. Are there vias in the SMT pads? Many times the wave will reflow the solder in the pad via and suck the sodler out of SMT joint on top. -- Pratap Singh Tel./Fax: 512-255-6820 e-mail: [log in to unmask] *************************************************************************** * 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. * *************************************************************************** *************************************************************************** * 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. * ***************************************************************************