Glenn I agree that using the die area would give a larger value, but are you sure that you can discount the PCB area. Have you measured the PCB, by itself, before attaching the die, and, with no die/flux but after cleaning? Remember the fact that putting the flux only on the die is meaningless because it will spread over the PCB well beyond the condines of the die area during reflow. Brian Glenn Pelkey wrote: > Hi Technetters, > > My buddy and I have a disagreement on using Resistivity of > Solvent Extract (ROSE) for measuring cleanliness on a Flip Chip board. > So, we're throwing it to league of experts on this forum for feedback > > Here's the story: The board and assembly are very simple. One > flip chip die at about 0.002 square inches and one board about 0.490 > square inches. Flux is applied only to the flip chip die, reflowed, and > DI inline washed. > > Here's the disagreement: I say use 2X the surface area of the > die for the calculation. My good friend says use 2X the board surface. > Of course, you can see one number is much higher than the other in ug/sq > inch NaCl equiv. My logic for using only the die area is to understand > the process cleanliness at that location only, but I recognize the > entire board surface could be cross contaminated in some manner. We > also loaded the machine with 32 of these units to get something > measurable. When we only put 4 in, nothing showed up, but the smallest > entry for surface area is 0.1 square inches. > > Thanks for your input! > > Glenn > > --------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8e > 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/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 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------