Hi Rudolph, What's your mean and std dev? With 5 mils thickness for 50% tolerance, the USL would be 7.5 mils and LSL is 2.5 mils. This tolerance is a bit too high. I think 25% is a more reasonable tolerance, unless there are no-loads that you're taping with tape on the stencil. This will create a larger gap, and thus much thicker deposits. Even with 25%, you should be able to get process cap index of 1.66 across 6 std deviations. Andy > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Rudolph yu > Sent: Monday, December 01, 2008 3:52 PM > To: [log in to unmask] > Subject: [TN] What are the industrial standards for Solder paste printing > limits? > > Hi Technetees: > > One of our customers had asked us to show that our solder paste despoisition > process is capable to acheive Cpk at 1.66 (6 sigma). We just built a > thousands of pilot boards, and the SPC report I got from the TRI's SPI > machine indicated that the process is able to reach that goal.......however > the software sets the upper limit and lower limits for height, area and > volumn to about +/-50%. Is this reasonable to have such a high variance in > the printing process? (We use 5 mil stencil with 0201 and fine picthc > aperature). If I change the limits to +/- 25%, the Cpk will become around > 1.33 ( 4 sigma)...should I claims that we can acheive 1.66, and point out > that the wide tolerence was set by the machine expert, or should I limit > the tolerance spread, and hope that customer will accept lower Cpk. > > > I guess my quesiton is " Is +/- 50% tolerance a resonable limits for paste > printing process?" > > > > BTW the AOI and AXI yield is in the high 98 and low 99 range for this > design. > > Thanks > Rudolph > > > _________________________________________________________________ > Proud to be a PC? Show the world. Download the "I'm a PC" Messenger > themepack now. > hthttp://clk.atdmt.com/MRT/go/119642558/direct/01/ > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at [log in to unmask] or > 847-615-7100 ext.2815 > ----------------------------------------------------- > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site > http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional > information, or contact Keach Sasamori at [log in to unmask] or > 847-615-7100 ext.2815 > ----------------------------------------------------- > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------