DiscFerret PCBs for sale

On 14/11/10 16:42, Dave wrote: A slightly modified Argos "Cookworks" mini-oven. 2100 Watts at 230V, fairly close to the limits of a 13A mains plug. At the moment I'm using an Agilent digital multimeter and a K-type thermocouple for monitoring, and have the bimetal thermostat locked in the "on" position. At some point I intend to replace this with a proper temperature controller, though ones that can handle sequencing seem to be unbelievably expensive. That's basically what I've got. 852A+ hot-air workstation, and the mini preheater (not the Quartz-IR one, the one below it). Turn the airflow down, or stick them down with epoxy. Once the solder paste gets above ~150C, the flux tends to drain off and the solder balls bunch up around the pad. If you're lucky, this sticks the part down. Once the solder melts, surface tension holds the part in place. On an 852A+, you want to have the airflow at around 30% for really small parts, or about 50% (the startup default) for larger parts like ICs. The ovens are based on convection, not forced-air. They heat the air around the board (although the IR from the heating elements helps to heat the board directly, too). The board absorbs heat from the air, temperature goes up, and everything heats up at roughly the same rate. If you're using cheap solder paste, you can have issues with tombstoning, where one end of a part melts first, but this is *rare* with modern pastes. I've just got my paws on a full SMD paste kit -- just need to find a slab of melamine or similar to use as a base board for applying the paste. There's some info about this method on PCB-Pool's SMT stencil site. -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/