Hi Gabi, Acceptable tombstoning defects for 0603's should be in the single digit PPM's. That's by component, not solder joint. 0402 are ten times that. We have found 0603's are particularly difficult to tombstone, so I you are having difficulty, solderability of the component could certainly be suspect. When we have had difficulty with 0603's, it has been because the pads were spaced too far apart, allowing molten solder on one side to pull the component off the other pad. Once one side of the component is off the other pad, its an open, and it doesn't matter if the component goes one step farther and tombstones. With 0402's, we have found that they are VERY sensitive to placement alignment. We try to keep the centroid of the component better than 0.002" of where it should be. (Not exactly easy with the Fuji CP6) Sensitivity is not so much side to side or even skewing, but end to end makes the biggest difference. In other words, if the component is on one pad more than the other, it is more prone to tombstone. Further, the side that is more on the pad will also be the side that ends up in the air. This means, you can predict the direction the placement machine must be adjusted if there is a trend in the direction of tombstoning. The screen print must be centered as well, for similar reasons, but I see you already check that. If you beat this problem, let us know how you did it. Thanks Ryan Grant Advanced Technology Engineer MCMS (208) 898-1145 [log in to unmask] > -----Original Message----- > From: Bogdan Gabi [SMTP:[log in to unmask]] > Sent: Monday, February 05, 2001 7:58 AM > To: [log in to unmask] > Subject: [TN] Tombstoning > > Hi, Technetters > > As we moved to smaller ceramic multilayer capacitors and > resistors,(0603)we encounter an increase of tombstoning . > > We checked our process-printing, reflow, layout, and did not find any > other clues but the component solderablity- so it seems. > > Due to very populated boards, the defect is seen quite often per board, > but usually only one component /board. > > Could you please tell me what is the acceptable number of this kind of > defect, and how you record it, per board or per solder joints? > > Thank you, > > Gaby > --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------