Lon, I think the other technetters have hit it on the nose as far as what is going on. You have some CTE mismatch problems that induce more stress than the bond can withstand. SMT adhesive in the cured state has high tensile strength, and is brittle, when you actually need it to be more ductile. What I have done in the past to overcome this problem is this. Rather than putting all of the adhesive dots under the component, I would put a few large dots at the edge of the component. Rather than bonding the underside of the package, I am now bonded to the side and underside (especially if I can get adhesive past the mold line at mid package). This gives you much more shear strength on the bond, and also a heck of a lot more tact (green) strength during placement equipment handling. This is why most folks use the double dots for small actives. A single dot is usually hidden, whereas the unsightly double dot provides much more shear strength due to the structure that secures the part from the sides. Steve Abrahamson > -----Original Message----- > From: Lon Weffers [SMTP:[log in to unmask]] > Sent: Thursday,June 21,2001 6:50 AM > To: [log in to unmask] > Subject: [TN] FW: dispensing glue > > Dear technetters, > > One of my colleges has a problem with glueing a plcc on the solderside of > the pcb. > They glue with a Hereaus glue and when they check the joint directly after > the oven it is stuck. > When the pcb's are cooled down the component falls of the board. The glue > spot is on the board. > What causes this problem?? > > > Lon Weffers > Matas Electronics bv > www.matas.nl > > -------------------------------------------------------------------------- > ------- > 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 > To temporarily halt delivery of Technet send the following message: SET > Technet NOMAIL > 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 To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------