A good wave profiler can be made of Durostone CAS 760, with TCs in the far corners of the fixture (flush to the bottom of the fixture, exposed to the wave) to measure lag between corner 1 and corner 2, for the purpose of establishing coplanarity of the wave to the board. There should not be a significant time lag between the spike seen by TC1 and TC2 when they hit the pot. Then put TC3 in the center of the fixture (mounted the same way, the same distance from the leading edge as TC1 and TC2) to measure dwell time in the pot all the way across. TC1 and 2 can also be used for this, but TC3 ensures the time in the solder is the same across the bottom of the fixture. Realize that with larger pwbs the sag can cause differences in the total immersion time at different locations. Three lug-terminal TCs (www.omega.com) should be clamped to the bottom to measure the pre-heat temps from the bottom preheater, and three on the topside for measuring the topside temps. This fixture is not intended to measure the temperatures that a pwb would see, it is only intended to be used as a process control fixture for the sake of verifying the machine is producing a repeatable profile for dwell time, co-planarity, solder peak temp, etc.. It should be run and checked each day that the machine is used for production, and compared with a benchmark profile. Over time, as the preheater and pot temps drop (normal) the machine settings will need to be adjusted to get the profile back in the required range. Measurements should be made based on a trigger, ie, phase-adjusted to the point in time that the profile hits 50 deg. C. to accomodate small changes in climate. The reflow temp just prior to the spike when the TC hits the pot, the peak solder temp, the ramp rate, the time lag between TC1,2,3 (coplanarity) and the time lag between the average of TC1,2,3 and the average of TC5,6,7 (belt speed repeatability) should be monitored and tracked with MINITAB or other process control software and the CpK established and monitored. This is what the minimum process control is for a wave solder machine. But you can do better than that. To determine an optimum profile for a particular pwb, you should use a pwb (scrap solder coupon). But don't use a pwb for a daily process control check fixture, as a pwb will not hold up very long for this purpose and the readings will change drastically over time, even from one run to the next. Having to remove busted thermocouples invalidates the medium used to measure the temps, as every time you need to replace one, it reads differently than the last. That is why a good fixture with TCs embedded in the material so that only the business end (the weld) is exposed, or with lug-terminal TCs that remain very robust over time will work well. Have fun. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dominic Boudreau Sent: Wednesday, December 20, 2006 12:46 PM To: [log in to unmask] Subject: [TN] Wave soldering profiling Hi Technet! My question is simple: Where should I put the thermocouples to do an accurate wave soldering profile? We have different points of view in this matter, some say that I should put the probes on top of PTH and some inside PTH. Anyone have any suggestions? Is there any literature which should help? Thank you Dominic Boudreau Digico Fabrication --------------------------------------------------- Technet Mail List provided as a 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/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 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------