RE: [AVR-Chat] One of >46 pin project
2006-06-05 by Tim Mitchell
AVR-Chat@yahoogroups.com wrote: >> Ryan wrote: >> > >> If you've never seen it before, check out this video: >> >> http://region.bdmicro.com/smt1.mov >> > > I had not seen that before, very tempting. > > If there was any sound on the video, I couldn' t hear it, so > does anyone know what the 'pen' was? > > It looks like a highlighter, but clearly thats not the case. > I assume it wasn't solder paste, as this regular solder was used. > > I assume therefore that it was flux, but then the iron was > used to 'glue' the chip into place. > I guess that must have relied upon the tinning on the PCB, > > Anyone any experience of this? > > What sort of thickness of solder is required. It looked about > the same width as the pitch of the pins (or at least thicker than the > width of a pin). > If the board is roller tinned there is normally enough solder to tack the corner pins of the chip without needing to add any more. The flux pen just helps to make the solder flow between the chip and the pad. If it is a new board you don't normally need it. The solder thickness is not important really... You can usually drag off any shorts with the iron, or get them off with braid or a solder sucker. Having the smallest pointiest iron tip is an advantage though. We're in big trouble in Europe at the moment because lead in solder (and all components) has just been banned under the rohs directive, so boards are not roller tinned any more, they are now plated with a special coating. The new lead free solder does not flow the same as the old stuff, and it seems to bridge across pins much more easily. Plus the iron has to be much hotter which makes the pads come off the board very easily. -- Tim Mitchell tim@sabretechnology.co.uk http://www.sabretechnology.co.uk