Bob- For what its worth, I've seen this same problem with 2 scenarios: 1. Lack of fluxing action in the paste caused by long hot ramp or long ambient exposure combined with reduced part or pad solderability. 2. Tiny amounts of contaminant (residual conformal coat or adhesive) on pads "floats" to surface of paste during reflow, an instant before the pad solder joins with ball solder. > Larry Jindra > TRW/Avionics Systems Division > mailto:[log in to unmask] ph (858) 592-3424 fax (858) 592-3606 -----Original Message----- From: bbarr [mailto:[log in to unmask]] Sent: Wednesday, November 15, 2000 6:45 AM To: [log in to unmask] Subject: [TN] BGA Soldering Problem I have a PBGA357 that is exhibiting a strange (to me) soldering condition. Two to three balls (not necessarily adjacent, but usually along an edge) do not appear to be wetting to the solder paste on the land. This is what it looks like after reflow: The paste on the land has reflowed to a mound, the ball on the BGA is compressed in shape but not wetted to the mound on the land (so the ball must have reached reflow temperature to get compressed.) A clear line of demarcation between the compressed ball and the mound of solder on the land is visible. The component fails in test, but sometimes pressing on it can get it to work. In most cases the balls on either side of the one not wetted look fine. Process is OA flux with convection reflow. Profile run several months ago with thermocouples imbedded in one center ball and one edge ball showed max. temp. of 217 (center) and 220 (edge) degrees C with time above 183 of 56 seconds. Max slope is 2 (center) and 2.8 (edge) degrees C. I am going to go run a verification profile, but in the mean time your thoughts are much appreciated. Bob Robert Barr Manufacturing Engineering Formation, Inc. Voice: 856-234-5020 x3035 Fax: 856-234-6679 email: [log in to unmask] --------------------------------------------------------------------------------- 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 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 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 ---------------------------------------------------------------------------------