Jonathan, There are basically a few things going on with the solder paste. A higher activity paste will attack more aggresively and create more of a chemical reaction, and thus more outgassing. This outgassing creates more turbulence in the reflowing solder, and thus improves self alignmnet. The outgassing also can become entrapped and cause voiding. Some fluxes that are lower in activity create less voiding, but also there is reflow speed (according to some solder paste chemists). Reflow speed could be thought of as the time that the powder begins to reflow, until the entire mass is liquidous (typically between 1/2 to 2 seconds for eutectic SnPb). Most no-clean formulas do not create too many voids (especially if your O2 ppm levels are under 200). I know of some slow reflowing OA formulas that I can refer you to if you want to e-mail me off line. I would get voiding to an acceptable level, and then work on misplacement/self alignment. Smaller passives seem to perform well on smaller pads. Additional solder paste will increase the overall surface tension of the joint, and help pull the part into position. Type 3 paste is generally better than type 4 if you want to reduce voiding. Unfortunately the optimum parameters are up to you- at least once you are sure your pad design is not too loose). I assume you might be using a 96% metals by weight solder paste. My experience has been with the 90% +/- 1% solder pastes, so while the principles might still apply, one can only check and see with the 91.5Sn8.5Sb formula. Hope some of this helps.. Steve A > -----Original Message----- > From: Jonathan A Noquil [SMTP:[log in to unmask]] > Sent: Monday,October 01,2001 11:14 PM > To: [log in to unmask] > Subject: [TN] Component skewing > > Hello Guys, > I have been experiencing component skewing after reflow. > However, when i used type 6 paste (no clean flux), there is no skewing > or movement of the component but a lot of voids. > When i used type 3 paste, the voids were reduced but there is much skewing > of the components. Seems voiding and skewing were in contrast. > Does anybody had experienced the same problem. Had they gotten the > optimum parameter? (Less voids, no skewing?). > My process is solder paste dispensing, then attach the component and > reflow > in an N2 Blanketed oven. > Paste is leadfree (alloy : 91.5Sn8.5Sb). > > Appreciate any help > > God Bless > > > thanks > > -------------------------------------------------------------------------- > ------- > 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 ---------------------------------------------------------------------------------