Brad Velander wrote:
>Hi Guys, > Well I guess a little more info would be helpful. Seems everybody is > typically mentioning cheaper little stations. Maybe they are fine but I > suspect they don't go far enough for what we are looking for. I have never > used any of these things so pardon my ignorance. > > What we will typically be using it for reworking your regular > assortment of QFPs, QFNs, SOIC, TQFP, PLCC and TSOP devices. A fair number of > devices that give us the greatest difficulties are the ones containing a > central Tab pad under the device (and there are becoming more of these each > day). There would/could be some attempts to use it for BGAs but they are not > the largest concern because we have no way to inspect BGAs anyway. Most > devices don't give our people much trouble until it comes to those with the > central thermal pad. So we believe that what we are looking for would > probably best include a hotplate to assist heating the board from > underneath, then the regular assortment of air nozzles/hoods with some form > of vacuum nozzle to pick the device off the board as it is freed. > > I do a LOT of rework, partly for design changes, partly for repair. We have our own custom ASIC in a 128-lead rectangular thermal flatpack. We don't have anything with a thermal pad on the bottom of the chip. We use an old Pace rework/desoldering station. We have a Bausch & Lomb stereo-zoom microscope at work, and I have a very old Olympus stereo-zoom at home. I still can't say which one I prefer. We do most of our small chip rework with desoldering braid, tweezers and a standard temp-controlled iron. We got some chip desoldering tips for the Pace, but ended up making some ourselves that fit our specific chips better. Machined them out of solid copper. For the small chips, I remove as much solder as possible with the braid, then use an Xacto knife and the soldering iron to lift pins on one side of the chip, one at a time. When one side is all lifted, the chip usually will just flip off the board, pulling the other side's pins free without heat. For the QFPs, we add solder and/or flux first, then apply our custom-made tool, and lift the chip off. For passives, we have a two-point tip for the Pace, but I usually just heat one end for a few seconds, then quickly move the regular soldering iron to the other side of the part and flick it off. We are staying away from BGAs due to the inspection problem. Jon ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
