| Has anyone had any experience or data using vibration during the reflow process. | We introduced a vibration device attached to the fixed rail on a Vitronics reflow oven. The reason was to prevent skewing on large PLCC devices. The process worked very well. | I'm looking for comments. | | Thank you | | John Eramo | 915-780-5521 | Hey John, You don't say what pitch leads you are dealing with, but..... Did some testing along these lines with a vibratory feeder base attached to the edge rails of an oven back in the late 80's, early 90's. I was running 20 mil parts back then. It worked, but the other folks are right about cold joints. I never did perfect it. Now, be aware that my process rates at that time were 70 inches a minute, and I was using quartz IR tube technology in my ovens. Yes, that's right--65 to 70 IPM! The quartz tube lamp ovens were the only ones responsive enough to reflow the products at those rates; and we had to keep up with the placement at the front end. In those days, turning a board to toast was not uncommon at project startup.....
HOWEVER, Also worked with a company in the early 90's--think it was Yamaha or Panasonic. We were developing a volume 11 mil TAB process. We had to excise the TAB device out of a lead carrier, place it on the boards, and reflow. One of the issues at 11 mils is to keep the pads flat. In addition, back in the early 90's, we didn't have the process windows cranked down on printing like today. So, we tried deep gold, OSP, funky apertures, etc. Couldn't eliminate bridging. Ended up with eliminating paste deposition, and very TIGHT controls on plating / leveling / thickness. Gets fairly expensive. Today, I'd try SiPad for this process..... Anyway, the equipment was prototype. One of a kind; a lab machine someone cooked up in their mind. It had underside preheat, a wide area focused xenon beam (a custom aperture was developed for this device, and it's leadframe outline), a flux dispenser, and a vibrating table. As I remember it, we dispensed flux along the length of the pads (a run perpendicular to the leads), placed the TAB device down directly on the pads / flux, and as the xenon beam fired up, the table vibrated a bit at a pre-determined frequency (can't remember what that was....)and time interval. VERY tricky process, but it worked! We eliminated bridging. Key point here is that we had the PLACEMENT down. We weren't fighting skewing; just bridging. We never bought the machine, because the job went away (SOJ's replaced the TAB devices; it was a SIMM type product--but with LOTS of memory). That process was a nightmare, because you had to tightly define and understand the Xenon reflow parameters, and then program the vibration based upon that information, and turn off the vibration before you turned the Xenon lamp off.
Overall, I don't think the vibration idea is a good one. I'm with the other guys; tighten up the print windows......
Scott Cook
reply »
Has anyone had any experience or data using vibration duri...
- May 21, 1999
by
