Hi Steve: Here are my replies to your questions: 1. What would be considered a significant variation in the cleanliness level? a. What variation should I see board to board of the same part number coming off the same process? b. What variation should I see board to board of different part numbers, but using similar parameters in the soldering process ? c. Has anybody studied their flux and soldering parameters to determine when they see large increases in residues due to adverse affects on the cleanibility of the flux caused by excessive heat and dwell ??? The significant variation in cleanliness level will become evident as part of your statistical analysis. Have you done or do you have access to a statistical terrorist, for the setting up of a design of experiment (DOE). The use of a balanced DOE with controllable factors will tell a great deal about your process. You will need to "fix" some of the process variables - not necessarily lock up the process variables you are not investigating at one level but understand how these "other" process variables change while you conduct your DOE. Things such as cleaning system load, type of pwb materials that are being processed, operator induced changes, etc., need to be understood. You may want to break up your process variables of interest into smaller chunks and do sequential DOEs to keep your sample sizes small. 2. What test methodologies would be best used to determine cleanliness level for this effort? A DOE is only as good as the response measure used. Many of the studies I am familiar with have used the Omegameter, SIR coupons, HPLC, spectrophotometry, or some combination of these tests. I would recommend using the Omegameter to get an understanding of how your DOE results relate to an every day process control check, and HPLC to get a very detailed view of what chemicals are not being removed in the cleaning cycle. The combination of the science and the practical should give you a good idea of which set of process parameters give you the best cleaning. It will also give your statistical terrorist variables data to analyze and cut down the number of samples you need to process. 3. Has anyone done a gage R & R on their test methods? The gauge R&R on HPLC is very good and the same can probably be said for most analytical tests but I don't know if the Omegameter falls into that category (I suspect not). The IPC specification PC-90 on SPC has some good information on DOE methodology. Also email Doug Pauls at CSL ([log in to unmask]) for a lively discussion on possible test methods. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Assy:SPC of cleaning process Author: [log in to unmask] at ccmgw1 Date: 6/2/96 8:57 We are reviewing our alternative cleaning process for application of SPC methodologies. The first system to be subjected to the microscope will be an in-line water cleaner using a water miscible solvent in the wash. During the course of our evaluation we will attempt to determine the variation in the temperature, spray pressure, bath concentration, bath loading, belt speed, and incoming water quality. We also intend to attempt to determine the impact of the variation of each process element as well as determine any significant interactions. We have the following questions for comment: 1. What would be considered a significant variation in the cleanliness level? a. What variation should I see board to board of the same part number coming off the same process? b. What variation should I see board to board of different part numbers, but using similiar parameters in the soldering process ? c. Has anybody studied their flux and soldering parameters to determine when they see large increases in residues due to adverse affects on the cleanibility of the flux caused by excessive heat and dwell ??? 2. What test methodologies would be best used to determine cleanliness level for this effort? 3. Has anyone done a gage R & R on their test methods? I would also appreciate hearing from anyone who has conducted such a study, with information on the engineered limits you established. Your responses are appreciated Steve Mikell SCI Systems, Huntsville, ALA [log in to unmask] Steve Mikell, Process Engineer, Soldering & cleaning processes SCI Systems Plant 13 [log in to unmask]