[EE]: Flux Kills ??? [a monday morning story] by Dan Michaels .

Funny thing happened on the way to monday. In the past we have always used rosin-flux solder to hand solder pcbs. But I have 3 new pcbs here that were soldered last week using "water-clean" solder. The boards use a 766x type switched capacitor negative voltage converter chip, with 10+ Khz oscillator, that happily decided not to run on any of the 3 boards. [I just love mondays]. So, scratch head, check with scope, input voltage ok, nothing out. Hmmmm, measurements of inter-pin resistances with DMM all >1 Mohm. Start snipping capacitors, v-regs, etc. Still doesn't work. Hmmmm, scratch head. Maybe try cleaning up the new weird flux with distilled water. Bingo, instant success - all 766x chips start oscillating fine. Whew, new pcb layout ok - stop sweating, go for cappucino. [Hmmm, maybe better clean all the other solder joints too before any more tests]. Hmmm, in the past many people have mentioned problems getting PIC oscillators to run properly. Hmmm, wonder could this have to do with flux leakage - water-cleanable or otherwise? Any comments? cheers, - DanM -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]: PIC only [EE]: engineering [OT]: off topic [AD]: advertisements