We assemble prototypes by hand-soldering down to 0.5mm pitch. Just apply a lot of solder with the tip of the iron, short-circuiting all the pads, then with a solder wick remove the excess. Sometimes there are shorts that don't want to go, then scratch it with a steel brush or add more solder and remove with the wick again. Isaac Em 18/04/2013 02:53, Perry Curling-Hope escreveu: > it's very much a prototype.? > > Then why are you attempting assembly by board reflow, which is very much = a > production technique? > > Hand soldering directly onto the HASL surface is practical given the > following considerations: > > The land pattern is designed with hand soldering in mind > The PCB has been produced for this purpose ( lead solder tinned ) > A compatible liquid flux is applied > The board is assembled promptly after manufacture ( oxidation minimized) > > This is workable with consistent results down to a pitch of 0.8mm (e.g. > TQFP ) without any special equipment or skills. > > Prototyping with 0,65mm pitch (e.g. SSOP) packages is possible if one has > an assembly stereo microscope, a micro tipped solder iron, a steady hand > and a lot of patience,,,,i.e. "very much a prototype" technique. > > The pads need to be longer than than that typically recommended, in order > to afford access to the pad beyond the package pin. > The solder tip is touched here to reflow the HASL tinning, slid up to the > pin and then on top of it, pressing the pin down into the molten > hot leveled solder, and immediately withdrawn. > > > > > > On Thu, Apr 18, 2013 at 1:45 AM, Jesse Lackey = wrote: > >> Hi Josh, my 2c... >> >> 1) use a syringe with a fine tip and dab a little solder on each pcb pad >> that way, instead of a stencil. >> >> 2) use iron to melt a little solder on each pcb pad, then to reflow >> either with oven or (better) hot air gun. Or use iron to reflow one pin >> at a time. So you'll be melting the solder per pin twice, not >> recommended in general, but these are prototypes. >> >> 3) metal stencils, I gave up on mylar long ago. If it is worth the >> effort to get a stencil made etc., it is worth getting metal. I use >> stencilsunlimited.com and have their prototype frame holder thingy, >> recommended. The stencils are in the $125 range. >> >> 4) give up on being overly cautious about bridges; this is what the fine >> solder wick (0.025" wide, mg chemicals cat #423, for example) is for. >> >> Have a few extra pcbs and chips, and don't be in a hurry, try different >> techniques. If you don't have a hot air gun, now is definitely the time >> to invest. >> >> Making the pads on the pcb a bit longer to be hand-assemble-friendly is >> a good idea. >> >> And of course have fun...! >> J >> >> >> Josh Koffman wrote: >>> On Tue, Apr 16, 2013 at 10:31 PM, Marc Nicholas >> wrote: >>>> What package is the component in question? I have success without a >> stencil on just about any part that has exposed pads/pins=85a fine line = of >> solder paste across the pins is one trick, followed by a quick visit to = the >> toaster over. >>> Interesting. I'm currently designing a project for myself that will >>> use an LFSCP package (reference here: >>> >> http://www.analog.com/en/technical-library/packages/csp-chip-scale-packa= ge/lfcsp/index.html >>> ), which will be the first time I'm using such a fine pitch, lead free >>> device. I'm currently planning on making the pads a bit longer than >>> usual, so I can try to touch an iron to them if things don't go well >>> during reflow. I currently use laser cut mylar stencils, but the >>> separation between the pads on fine pitch devices usually ends up a >>> bit wonky, so I'm not sure what to do. I'm definitely afraid of too >>> much paste causing a bridge. >>> >>> Josh >>> -- >>> A common mistake that people make when trying to design something >>> completely foolproof is to underestimate the ingenuity of complete >>> fools. >>> -Douglas Adams >>> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .